1 # SOME DESCRIPTIVE TITLE
2 # Copyright (C) YEAR Free Software Foundation, Inc.
3 # This file is distributed under the same license as the PACKAGE package.
4 # FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
9 "Project-Id-Version: PACKAGE VERSION\n"
10 "POT-Creation-Date: 2015-02-04 23:32+0900\n"
11 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
12 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
13 "Language-Team: LANGUAGE <LL@li.org>\n"
16 "Content-Type: text/plain; charset=UTF-8\n"
17 "Content-Transfer-Encoding: 8bit\n"
20 #: build/C/man2/alloc_hugepages.2:25
22 msgid "ALLOC_HUGEPAGES"
26 #: build/C/man2/alloc_hugepages.2:25
32 #: build/C/man2/alloc_hugepages.2:25 build/C/man2/cacheflush.2:25 build/C/man2/fallocate.2:11 build/C/man2/madvise.2:35 build/C/man3/mallinfo.3:26 build/C/man3/malloc_stats.3:26 build/C/man3/malloc_trim.3:26 build/C/man3/mallopt.3:26 build/C/man2/mlock.2:26 build/C/man2/mmap.2:40 build/C/man2/mmap2.2:29 build/C/man2/mprotect.2:39 build/C/man2/mremap.2:30 build/C/man2/msync.2:25 build/C/man2/posix_fadvise.2:28 build/C/man2/readahead.2:28 build/C/man2/remap_file_pages.2:28 build/C/man3/shm_open.3:26 build/C/man7/shm_overview.7:27 build/C/man2/shmctl.2:45 build/C/man2/shmget.2:38 build/C/man2/shmop.2:41 build/C/man2/subpage_prot.2:30 build/C/man2/sync_file_range.2:30 build/C/man2/memfd_create.2:21
38 #: build/C/man2/alloc_hugepages.2:25 build/C/man3/alloca.3:43 build/C/man2/cacheflush.2:25 build/C/man2/fallocate.2:11 build/C/man2/madvise.2:35 build/C/man3/mallinfo.3:26 build/C/man3/malloc_get_state.3:25 build/C/man3/malloc_hook.3:10 build/C/man3/malloc_info.3:25 build/C/man3/malloc_stats.3:26 build/C/man3/malloc_trim.3:26 build/C/man3/malloc_usable_size.3:25 build/C/man3/mallopt.3:26 build/C/man3/mcheck.3:25 build/C/man2/mlock.2:26 build/C/man2/mmap.2:40 build/C/man2/mmap2.2:29 build/C/man2/mprotect.2:39 build/C/man2/mremap.2:30 build/C/man2/msync.2:25 build/C/man3/mtrace.3:25 build/C/man2/posix_fadvise.2:28 build/C/man3/posix_fallocate.3:25 build/C/man3/posix_memalign.3:29 build/C/man2/readahead.2:28 build/C/man2/remap_file_pages.2:28 build/C/man3/shm_open.3:26 build/C/man7/shm_overview.7:27 build/C/man2/shmctl.2:45 build/C/man2/shmget.2:38 build/C/man2/shmop.2:41 build/C/man2/subpage_prot.2:30 build/C/man2/sync_file_range.2:30 build/C/man2/memfd_create.2:21 build/C/man2/s390_pci_mmio_write.2:25
40 msgid "Linux Programmer's Manual"
44 #: build/C/man2/alloc_hugepages.2:26 build/C/man3/alloca.3:44 build/C/man2/cacheflush.2:26 build/C/man2/fallocate.2:12 build/C/man2/madvise.2:36 build/C/man3/mallinfo.3:27 build/C/man3/malloc_get_state.3:26 build/C/man3/malloc_hook.3:11 build/C/man3/malloc_info.3:26 build/C/man3/malloc_stats.3:27 build/C/man3/malloc_trim.3:27 build/C/man3/malloc_usable_size.3:26 build/C/man3/mallopt.3:27 build/C/man3/mcheck.3:26 build/C/man2/mlock.2:27 build/C/man2/mmap.2:41 build/C/man2/mmap2.2:30 build/C/man2/mprotect.2:40 build/C/man2/mremap.2:31 build/C/man2/msync.2:26 build/C/man3/mtrace.3:26 build/C/man2/posix_fadvise.2:29 build/C/man3/posix_fallocate.3:26 build/C/man3/posix_memalign.3:30 build/C/man2/readahead.2:29 build/C/man2/remap_file_pages.2:29 build/C/man3/shm_open.3:27 build/C/man7/shm_overview.7:28 build/C/man2/shmctl.2:46 build/C/man2/shmget.2:39 build/C/man2/shmop.2:42 build/C/man2/subpage_prot.2:31 build/C/man2/sync_file_range.2:31 build/C/man2/memfd_create.2:22 build/C/man2/s390_pci_mmio_write.2:26
50 #: build/C/man2/alloc_hugepages.2:28
51 msgid "alloc_hugepages, free_hugepages - allocate or free huge pages"
55 #: build/C/man2/alloc_hugepages.2:28 build/C/man3/alloca.3:46 build/C/man2/cacheflush.2:28 build/C/man2/fallocate.2:14 build/C/man2/madvise.2:38 build/C/man3/mallinfo.3:29 build/C/man3/malloc_get_state.3:28 build/C/man3/malloc_hook.3:15 build/C/man3/malloc_info.3:28 build/C/man3/malloc_stats.3:29 build/C/man3/malloc_trim.3:29 build/C/man3/malloc_usable_size.3:28 build/C/man3/mallopt.3:29 build/C/man3/mcheck.3:28 build/C/man2/mlock.2:29 build/C/man2/mmap.2:43 build/C/man2/mmap2.2:32 build/C/man2/mprotect.2:42 build/C/man2/mremap.2:33 build/C/man2/msync.2:28 build/C/man3/mtrace.3:28 build/C/man2/posix_fadvise.2:31 build/C/man3/posix_fallocate.3:28 build/C/man3/posix_memalign.3:32 build/C/man2/readahead.2:31 build/C/man2/remap_file_pages.2:31 build/C/man3/shm_open.3:29 build/C/man2/shmctl.2:48 build/C/man2/shmget.2:41 build/C/man2/shmop.2:44 build/C/man2/subpage_prot.2:33 build/C/man2/sync_file_range.2:33 build/C/man2/memfd_create.2:24 build/C/man2/s390_pci_mmio_write.2:29
60 #. asmlinkage unsigned long sys_alloc_hugepages(int key, unsigned long addr,
61 #. unsigned long len, int prot, int flag);
63 #: build/C/man2/alloc_hugepages.2:34
66 "B<void *alloc_hugepages(int >I<key>B<, void *>I<addr>B<, size_t "
68 "B< int >I<prot>B<, int >I<flag>B<);>\n"
71 #. asmlinkage int sys_free_hugepages(unsigned long addr);
73 #: build/C/man2/alloc_hugepages.2:37
75 msgid "B<int free_hugepages(void *>I<addr>B<);>\n"
79 #: build/C/man2/alloc_hugepages.2:38 build/C/man3/alloca.3:50 build/C/man2/cacheflush.2:34 build/C/man2/fallocate.2:22 build/C/man2/madvise.2:50 build/C/man3/mallinfo.3:33 build/C/man3/malloc_get_state.3:36 build/C/man3/malloc_hook.3:33 build/C/man3/malloc_info.3:34 build/C/man3/malloc_stats.3:33 build/C/man3/malloc_trim.3:33 build/C/man3/malloc_usable_size.3:32 build/C/man3/mallopt.3:33 build/C/man3/mcheck.3:40 build/C/man2/mlock.2:39 build/C/man2/mmap.2:54 build/C/man2/mmap2.2:39 build/C/man2/mprotect.2:48 build/C/man2/mremap.2:42 build/C/man2/msync.2:32 build/C/man3/mtrace.3:34 build/C/man2/posix_fadvise.2:50 build/C/man3/posix_fallocate.3:46 build/C/man3/posix_memalign.3:84 build/C/man2/readahead.2:38 build/C/man2/remap_file_pages.2:39 build/C/man3/shm_open.3:41 build/C/man7/shm_overview.7:30 build/C/man2/shmctl.2:56 build/C/man2/shmget.2:49 build/C/man2/shmop.2:53 build/C/man2/subpage_prot.2:41 build/C/man2/sync_file_range.2:41 build/C/man2/memfd_create.2:28 build/C/man2/s390_pci_mmio_write.2:39
85 #: build/C/man2/alloc_hugepages.2:49
87 "The system calls B<alloc_hugepages>() and B<free_hugepages>() were "
88 "introduced in Linux 2.5.36 and removed again in 2.5.54. They existed only "
89 "on i386 and ia64 (when built with B<CONFIG_HUGETLB_PAGE>). In Linux 2.4.20, "
90 "the syscall numbers exist, but the calls fail with the error B<ENOSYS>."
94 #: build/C/man2/alloc_hugepages.2:57
96 "On i386 the memory management hardware knows about ordinary pages (4 KiB) "
97 "and huge pages (2 or 4 MiB). Similarly ia64 knows about huge pages of "
98 "several sizes. These system calls serve to map huge pages into the "
99 "process's memory or to free them again. Huge pages are locked into memory, "
100 "and are not swapped."
104 #: build/C/man2/alloc_hugepages.2:66
106 "The I<key> argument is an identifier. When zero the pages are private, and "
107 "not inherited by children. When positive the pages are shared with other "
108 "applications using the same I<key>, and inherited by child processes."
112 #: build/C/man2/alloc_hugepages.2:81
114 "The I<addr> argument of B<free_hugepages>() tells which page is being "
115 "freed: it was the return value of a call to B<alloc_hugepages>(). (The "
116 "memory is first actually freed when all users have released it.) The "
117 "I<addr> argument of B<alloc_hugepages>() is a hint, that the kernel may or "
118 "may not follow. Addresses must be properly aligned."
122 #: build/C/man2/alloc_hugepages.2:86
124 "The I<len> argument is the length of the required segment. It must be a "
125 "multiple of the huge page size."
129 #: build/C/man2/alloc_hugepages.2:94
131 "The I<prot> argument specifies the memory protection of the segment. It is "
132 "one of B<PROT_READ>, B<PROT_WRITE>, B<PROT_EXEC>."
136 #: build/C/man2/alloc_hugepages.2:109
138 "The I<flag> argument is ignored, unless I<key> is positive. In that case, "
139 "if I<flag> is B<IPC_CREAT>, then a new huge page segment is created when "
140 "none with the given key existed. If this flag is not set, then B<ENOENT> is "
141 "returned when no segment with the given key exists."
145 #: build/C/man2/alloc_hugepages.2:109 build/C/man3/alloca.3:60 build/C/man2/cacheflush.2:53 build/C/man2/fallocate.2:228 build/C/man2/madvise.2:268 build/C/man3/malloc_get_state.3:61 build/C/man3/malloc_info.3:48 build/C/man3/malloc_trim.3:51 build/C/man3/malloc_usable_size.3:40 build/C/man3/mallopt.3:379 build/C/man3/mcheck.3:129 build/C/man2/mlock.2:116 build/C/man2/mmap.2:375 build/C/man2/mmap2.2:54 build/C/man2/mprotect.2:77 build/C/man2/mremap.2:127 build/C/man2/msync.2:68 build/C/man2/posix_fadvise.2:87 build/C/man3/posix_fallocate.3:66 build/C/man3/posix_memalign.3:142 build/C/man2/readahead.2:66 build/C/man2/remap_file_pages.2:132 build/C/man3/shm_open.3:171 build/C/man2/shmctl.2:283 build/C/man2/shmget.2:183 build/C/man2/shmop.2:168 build/C/man2/subpage_prot.2:66 build/C/man2/sync_file_range.2:141 build/C/man2/memfd_create.2:126 build/C/man2/s390_pci_mmio_write.2:68
151 #: build/C/man2/alloc_hugepages.2:118
153 "On success, B<alloc_hugepages>() returns the allocated virtual address, and "
154 "B<free_hugepages>() returns zero. On error, -1 is returned, and I<errno> "
155 "is set appropriately."
159 #: build/C/man2/alloc_hugepages.2:118 build/C/man2/cacheflush.2:59 build/C/man2/fallocate.2:235 build/C/man2/madvise.2:275 build/C/man3/malloc_info.3:55 build/C/man3/malloc_trim.3:56 build/C/man3/mallopt.3:384 build/C/man2/mlock.2:122 build/C/man2/mmap.2:392 build/C/man2/mmap2.2:61 build/C/man2/mprotect.2:84 build/C/man2/mremap.2:135 build/C/man2/msync.2:73 build/C/man2/posix_fadvise.2:90 build/C/man3/posix_fallocate.3:72 build/C/man3/posix_memalign.3:157 build/C/man2/readahead.2:72 build/C/man2/remap_file_pages.2:139 build/C/man3/shm_open.3:180 build/C/man2/shmctl.2:305 build/C/man2/shmget.2:188 build/C/man2/shmop.2:182 build/C/man2/subpage_prot.2:71 build/C/man2/sync_file_range.2:147 build/C/man2/memfd_create.2:133 build/C/man2/s390_pci_mmio_write.2:77
165 #: build/C/man2/alloc_hugepages.2:119 build/C/man2/fallocate.2:319
171 #: build/C/man2/alloc_hugepages.2:122
172 msgid "The system call is not supported on this kernel."
176 #: build/C/man2/alloc_hugepages.2:122
182 #: build/C/man2/alloc_hugepages.2:126
184 "I</proc/sys/vm/nr_hugepages> Number of configured hugetlb pages. This can "
185 "be read and written."
189 #: build/C/man2/alloc_hugepages.2:130
191 "I</proc/meminfo> Gives info on the number of configured hugetlb pages and on "
192 "their size in the three variables HugePages_Total, HugePages_Free, "
197 #: build/C/man2/alloc_hugepages.2:130 build/C/man3/alloca.3:70 build/C/man2/cacheflush.2:75 build/C/man2/fallocate.2:375 build/C/man2/madvise.2:332 build/C/man3/mallinfo.3:110 build/C/man3/malloc_get_state.3:86 build/C/man3/malloc_hook.3:80 build/C/man3/malloc_info.3:63 build/C/man3/malloc_stats.3:55 build/C/man3/malloc_trim.3:60 build/C/man3/malloc_usable_size.3:53 build/C/man3/mallopt.3:392 build/C/man3/mcheck.3:145 build/C/man2/mlock.2:186 build/C/man2/mmap.2:499 build/C/man2/mmap2.2:77 build/C/man2/mprotect.2:112 build/C/man2/mremap.2:185 build/C/man2/msync.2:96 build/C/man3/mtrace.3:78 build/C/man2/posix_fadvise.2:122 build/C/man3/posix_fallocate.3:108 build/C/man3/posix_memalign.3:182 build/C/man2/readahead.2:88 build/C/man2/remap_file_pages.2:161 build/C/man3/shm_open.3:251 build/C/man7/shm_overview.7:101 build/C/man2/shmctl.2:377 build/C/man2/shmget.2:248 build/C/man2/shmop.2:228 build/C/man2/subpage_prot.2:96 build/C/man2/sync_file_range.2:180 build/C/man2/memfd_create.2:161 build/C/man2/s390_pci_mmio_write.2:100
199 msgid "CONFORMING TO"
203 #: build/C/man2/alloc_hugepages.2:133
205 "These calls are specific to Linux on Intel processors, and should not be "
206 "used in programs intended to be portable."
210 #: build/C/man2/alloc_hugepages.2:133 build/C/man3/alloca.3:78 build/C/man2/madvise.2:354 build/C/man3/malloc_get_state.3:88 build/C/man3/malloc_hook.3:82 build/C/man3/malloc_info.3:65 build/C/man3/malloc_stats.3:57 build/C/man3/malloc_trim.3:62 build/C/man3/malloc_usable_size.3:55 build/C/man3/mcheck.3:147 build/C/man2/mlock.2:213 build/C/man2/mmap.2:517 build/C/man2/mmap2.2:79 build/C/man2/mprotect.2:121 build/C/man2/mremap.2:191 build/C/man2/msync.2:120 build/C/man3/mtrace.3:80 build/C/man2/posix_fadvise.2:131 build/C/man3/posix_fallocate.3:133 build/C/man3/posix_memalign.3:221 build/C/man2/readahead.2:93 build/C/man2/remap_file_pages.2:165 build/C/man3/shm_open.3:257 build/C/man7/shm_overview.7:103 build/C/man2/shmctl.2:382 build/C/man2/shmget.2:256 build/C/man2/shmop.2:243 build/C/man2/subpage_prot.2:98 build/C/man2/sync_file_range.2:183 build/C/man2/memfd_create.2:165 build/C/man2/s390_pci_mmio_write.2:103
216 #: build/C/man2/alloc_hugepages.2:141
218 "These system calls are gone; they existed only in Linux 2.5.36 through to "
219 "2.5.54. Now the hugetlbfs filesystem can be used instead. Memory backed by "
220 "huge pages (if the CPU supports them) is obtained by using B<mmap>(2) to "
221 "map files in this virtual filesystem."
225 #: build/C/man2/alloc_hugepages.2:145
227 "The maximal number of huge pages can be specified using the B<hugepages=> "
232 #: build/C/man2/alloc_hugepages.2:150 build/C/man3/alloca.3:162 build/C/man2/cacheflush.2:89 build/C/man2/fallocate.2:383 build/C/man2/madvise.2:388 build/C/man3/mallinfo.3:279 build/C/man3/malloc_get_state.3:114 build/C/man3/malloc_hook.3:142 build/C/man3/malloc_info.3:262 build/C/man3/malloc_stats.3:67 build/C/man3/malloc_trim.3:82 build/C/man3/malloc_usable_size.3:69 build/C/man3/mallopt.3:568 build/C/man3/mcheck.3:208 build/C/man2/mlock.2:343 build/C/man2/mmap.2:741 build/C/man2/mmap2.2:101 build/C/man2/mprotect.2:228 build/C/man2/mremap.2:214 build/C/man2/msync.2:151 build/C/man3/mtrace.3:172 build/C/man2/posix_fadvise.2:215 build/C/man3/posix_fallocate.3:143 build/C/man3/posix_memalign.3:277 build/C/man2/readahead.2:113 build/C/man2/remap_file_pages.2:183 build/C/man3/shm_open.3:283 build/C/man7/shm_overview.7:127 build/C/man2/shmctl.2:435 build/C/man2/shmget.2:391 build/C/man2/shmop.2:301 build/C/man2/subpage_prot.2:134 build/C/man2/sync_file_range.2:227 build/C/man2/memfd_create.2:493 build/C/man2/s390_pci_mmio_write.2:109
238 #: build/C/man2/alloc_hugepages.2:158 build/C/man3/alloca.3:170 build/C/man2/cacheflush.2:97 build/C/man2/fallocate.2:391 build/C/man2/madvise.2:396 build/C/man3/mallinfo.3:287 build/C/man3/malloc_get_state.3:122 build/C/man3/malloc_hook.3:150 build/C/man3/malloc_info.3:270 build/C/man3/malloc_stats.3:75 build/C/man3/malloc_trim.3:90 build/C/man3/malloc_usable_size.3:77 build/C/man3/mallopt.3:576 build/C/man3/mcheck.3:216 build/C/man2/mlock.2:351 build/C/man2/mmap.2:749 build/C/man2/mmap2.2:109 build/C/man2/mprotect.2:236 build/C/man2/mremap.2:222 build/C/man2/msync.2:159 build/C/man3/mtrace.3:180 build/C/man2/posix_fadvise.2:223 build/C/man3/posix_fallocate.3:151 build/C/man3/posix_memalign.3:285 build/C/man2/readahead.2:121 build/C/man2/remap_file_pages.2:191 build/C/man3/shm_open.3:291 build/C/man7/shm_overview.7:135 build/C/man2/shmctl.2:443 build/C/man2/shmget.2:399 build/C/man2/shmop.2:309 build/C/man2/subpage_prot.2:142 build/C/man2/sync_file_range.2:235 build/C/man2/memfd_create.2:501 build/C/man2/s390_pci_mmio_write.2:117
240 "This page is part of release 3.79 of the Linux I<man-pages> project. A "
241 "description of the project, information about reporting bugs, and the latest "
242 "version of this page, can be found at "
243 "\\%http://www.kernel.org/doc/man-pages/."
247 #: build/C/man3/alloca.3:43
253 #: build/C/man3/alloca.3:43
259 #: build/C/man3/alloca.3:43 build/C/man3/malloc_get_state.3:25 build/C/man3/malloc_hook.3:10 build/C/man3/malloc_info.3:25 build/C/man3/malloc_usable_size.3:25 build/C/man3/mcheck.3:25 build/C/man3/mtrace.3:25 build/C/man3/posix_fallocate.3:25 build/C/man3/posix_memalign.3:29
265 #: build/C/man3/alloca.3:46
266 msgid "alloca - allocate memory that is automatically freed"
270 #: build/C/man3/alloca.3:48
271 msgid "B<#include E<lt>alloca.hE<gt>>"
275 #: build/C/man3/alloca.3:50
276 msgid "B<void *alloca(size_t >I<size>B<);>"
280 #: build/C/man3/alloca.3:60
282 "The B<alloca>() function allocates I<size> bytes of space in the stack "
283 "frame of the caller. This temporary space is automatically freed when the "
284 "function that called B<alloca>() returns to its caller."
288 #: build/C/man3/alloca.3:65
290 "The B<alloca>() function returns a pointer to the beginning of the "
291 "allocated space. If the allocation causes stack overflow, program behavior "
296 #: build/C/man3/alloca.3:65 build/C/man3/malloc_usable_size.3:48 build/C/man3/posix_fallocate.3:103
302 #: build/C/man3/alloca.3:66 build/C/man3/malloc_usable_size.3:49 build/C/man3/posix_fallocate.3:104
304 msgid "Multithreading (see pthreads(7))"
308 #: build/C/man3/alloca.3:70
309 msgid "The B<alloca>() function is thread-safe."
313 #: build/C/man3/alloca.3:72
314 msgid "This function is not in POSIX.1-2001."
318 #: build/C/man3/alloca.3:78
320 "There is evidence that the B<alloca>() function appeared in 32V, PWB, "
321 "PWB.2, 3BSD, and 4BSD. There is a man page for it in 4.3BSD. Linux uses "
326 #: build/C/man3/alloca.3:93
328 "The B<alloca>() function is machine- and compiler-dependent. For certain "
329 "applications, its use can improve efficiency compared to the use of "
330 "B<malloc>(3) plus B<free>(3). In certain cases, it can also simplify "
331 "memory deallocation in applications that use B<longjmp>(3) or "
332 "B<siglongjmp>(3). Otherwise, its use is discouraged."
336 #: build/C/man3/alloca.3:102
338 "Because the space allocated by B<alloca>() is allocated within the stack "
339 "frame, that space is automatically freed if the function return is jumped "
340 "over by a call to B<longjmp>(3) or B<siglongjmp>(3)."
344 #: build/C/man3/alloca.3:107
345 msgid "Do not attempt to B<free>(3) space allocated by B<alloca>()!"
349 #: build/C/man3/alloca.3:107
351 msgid "Notes on the GNU version"
355 #: build/C/man3/alloca.3:129
357 "Normally, B<gcc>(1) translates calls to B<alloca>() with inlined code. "
358 "This is not done when either the I<-ansi>, I<-std=c89>, I<-std=c99>, or the "
359 "I<-std=c11> option is given B<and> the header I<E<lt>alloca.hE<gt>> is not "
360 "included. Otherwise, (without an -ansi or -std=c* option) the glibc version "
361 "of I<E<lt>stdlib.hE<gt>> includes I<E<lt>alloca.hE<gt>> and that contains "
366 #: build/C/man3/alloca.3:134
370 " #define alloca(size) __builtin_alloca (size)\n"
375 #: build/C/man3/alloca.3:137
376 msgid "with messy consequences if one has a private version of this function."
380 #: build/C/man3/alloca.3:141
382 "The fact that the code is inlined means that it is impossible to take the "
383 "address of this function, or to change its behavior by linking with a "
388 #: build/C/man3/alloca.3:145
390 "The inlined code often consists of a single instruction adjusting the stack "
391 "pointer, and does not check for stack overflow. Thus, there is no NULL "
396 #: build/C/man3/alloca.3:145 build/C/man2/cacheflush.2:82 build/C/man3/mallinfo.3:114 build/C/man3/mallopt.3:406 build/C/man2/mlock.2:311 build/C/man2/mmap.2:590 build/C/man3/mtrace.3:102 build/C/man2/posix_fadvise.2:204 build/C/man2/readahead.2:98 build/C/man2/shmget.2:376
402 #: build/C/man3/alloca.3:150
404 "There is no error indication if the stack frame cannot be extended. "
405 "(However, after a failed allocation, the program is likely to receive a "
406 "B<SIGSEGV> signal if it attempts to access the unallocated space.)"
410 #: build/C/man3/alloca.3:158
412 "On many systems B<alloca>() cannot be used inside the list of arguments of "
413 "a function call, because the stack space reserved by B<alloca>() would "
414 "appear on the stack in the middle of the space for the function arguments."
418 #: build/C/man3/alloca.3:158 build/C/man2/fallocate.2:378 build/C/man2/madvise.2:379 build/C/man3/mallinfo.3:270 build/C/man3/malloc_get_state.3:111 build/C/man3/malloc_hook.3:137 build/C/man3/malloc_info.3:256 build/C/man3/malloc_stats.3:61 build/C/man3/malloc_trim.3:78 build/C/man3/malloc_usable_size.3:67 build/C/man3/mallopt.3:554 build/C/man3/mcheck.3:204 build/C/man2/mlock.2:336 build/C/man2/mmap.2:715 build/C/man2/mmap2.2:95 build/C/man2/mprotect.2:225 build/C/man2/mremap.2:199 build/C/man2/msync.2:147 build/C/man3/mtrace.3:167 build/C/man2/posix_fadvise.2:209 build/C/man3/posix_fallocate.3:138 build/C/man3/posix_memalign.3:272 build/C/man2/readahead.2:107 build/C/man2/remap_file_pages.2:176 build/C/man3/shm_open.3:271 build/C/man7/shm_overview.7:114 build/C/man2/shmctl.2:428 build/C/man2/shmget.2:382 build/C/man2/shmop.2:293 build/C/man2/subpage_prot.2:128 build/C/man2/sync_file_range.2:222 build/C/man2/memfd_create.2:487 build/C/man2/s390_pci_mmio_write.2:107
424 #: build/C/man3/alloca.3:162
425 msgid "B<brk>(2), B<longjmp>(3), B<malloc>(3)"
429 #: build/C/man2/cacheflush.2:25
435 #: build/C/man2/cacheflush.2:25
441 #: build/C/man2/cacheflush.2:28
442 msgid "cacheflush - flush contents of instruction and/or data cache"
446 #: build/C/man2/cacheflush.2:31
448 msgid "B<#include E<lt>asm/cachectl.hE<gt>>\n"
452 #: build/C/man2/cacheflush.2:33
454 msgid "B<int cacheflush(char *>I<addr>B<, int >I<nbytes>B<, int >I<cache>B<);>\n"
458 #: build/C/man2/cacheflush.2:43
460 "B<cacheflush>() flushes the contents of the indicated cache(s) for the user "
461 "addresses in the range I<addr> to I<(addr+nbytes-1)>. I<cache> may be one "
466 #: build/C/man2/cacheflush.2:43
472 #: build/C/man2/cacheflush.2:46
473 msgid "Flush the instruction cache."
477 #: build/C/man2/cacheflush.2:46
483 #: build/C/man2/cacheflush.2:49
484 msgid "Write back to memory and invalidate the affected valid cache lines."
488 #: build/C/man2/cacheflush.2:49
494 #: build/C/man2/cacheflush.2:53
495 msgid "Same as B<(ICACHE|DCACHE)>."
499 #: build/C/man2/cacheflush.2:59
501 "B<cacheflush>() returns 0 on success or -1 on error. If errors are "
502 "detected, I<errno> will indicate the error."
506 #: build/C/man2/cacheflush.2:60 build/C/man2/mmap2.2:62 build/C/man2/mremap.2:142 build/C/man2/shmctl.2:314 build/C/man2/subpage_prot.2:72 build/C/man2/memfd_create.2:134 build/C/man2/s390_pci_mmio_write.2:78 build/C/man2/s390_pci_mmio_write.2:83
512 #: build/C/man2/cacheflush.2:67
514 "Some or all of the address range I<addr> to I<(addr+nbytes-1)> is not "
519 #: build/C/man2/cacheflush.2:67 build/C/man2/fallocate.2:247 build/C/man2/fallocate.2:259 build/C/man2/fallocate.2:269 build/C/man2/fallocate.2:279 build/C/man2/fallocate.2:287 build/C/man2/madvise.2:282 build/C/man3/malloc_info.3:56 build/C/man2/mlock.2:157 build/C/man2/mlock.2:164 build/C/man2/mlock.2:176 build/C/man2/mmap.2:421 build/C/man2/mmap.2:429 build/C/man2/mmap.2:434 build/C/man2/mmap2.2:65 build/C/man2/mprotect.2:94 build/C/man2/mremap.2:151 build/C/man2/msync.2:80 build/C/man2/posix_fadvise.2:94 build/C/man3/posix_fallocate.3:81 build/C/man3/posix_memalign.3:158 build/C/man2/readahead.2:77 build/C/man2/remap_file_pages.2:140 build/C/man2/remap_file_pages.2:147 build/C/man3/shm_open.3:213 build/C/man2/shmctl.2:328 build/C/man2/shmget.2:207 build/C/man2/shmget.2:215 build/C/man2/shmop.2:197 build/C/man2/shmop.2:220 build/C/man2/subpage_prot.2:77 build/C/man2/sync_file_range.2:152 build/C/man2/memfd_create.2:139 build/C/man2/s390_pci_mmio_write.2:87
525 #: build/C/man2/cacheflush.2:75
526 msgid "I<cache> is not one of B<ICACHE>, B<DCACHE>, or B<BCACHE>."
529 #. FIXME The cacheflush() system call was only on MIPS back in 1.2 days,
530 #. but by now it is on a number of other architectures (but not i386).
531 #. Investigate the details and update this page.
532 #. Irix 6.5 appears to have a cacheflush() syscall -- mtk
534 #: build/C/man2/cacheflush.2:82
536 "This Linux-specific system call is available only on MIPS-based systems. It "
537 "should not be used in programs intended to be portable."
541 #: build/C/man2/cacheflush.2:89
543 "The current implementation ignores the I<addr> and I<nbytes> arguments. "
544 "Therefore, the whole cache is always flushed."
548 #: build/C/man2/fallocate.2:11
554 #: build/C/man2/fallocate.2:11 build/C/man3/malloc_info.3:25 build/C/man2/mmap.2:40 build/C/man3/posix_fallocate.3:25 build/C/man3/shm_open.3:26 build/C/man2/memfd_create.2:21
560 #: build/C/man2/fallocate.2:14
561 msgid "fallocate - manipulate file space"
565 #: build/C/man2/fallocate.2:18 build/C/man2/readahead.2:35
568 "B<#define _GNU_SOURCE> /* See feature_test_macros(7) */\n"
569 "B<#include E<lt>fcntl.hE<gt>>\n"
573 #: build/C/man2/fallocate.2:21
576 "B<int fallocate(int >I<fd>B<, int >I<mode>B<, off_t >I<offset>B<, off_t "
581 #: build/C/man2/fallocate.2:27
583 "This is a nonportable, Linux-specific system call. For the portable, "
584 "POSIX.1-specified method of ensuring that space is allocated for a file, see "
585 "B<posix_fallocate>(3)."
589 #: build/C/man2/fallocate.2:37
591 "B<fallocate>() allows the caller to directly manipulate the allocated disk "
592 "space for the file referred to by I<fd> for the byte range starting at "
593 "I<offset> and continuing for I<len> bytes."
597 #: build/C/man2/fallocate.2:42
599 "The I<mode> argument determines the operation to be performed on the given "
600 "range. Details of the supported operations are given in the subsections "
605 #: build/C/man2/fallocate.2:42
607 msgid "Allocating disk space"
611 #: build/C/man2/fallocate.2:65
613 "The default operation (i.e., I<mode> is zero) of B<fallocate>() allocates "
614 "the disk space within the range specified by I<offset> and I<len>. The file "
615 "size (as reported by B<stat>(2)) will be changed if I<offset>+I<len> is "
616 "greater than the file size. Any subregion within the range specified by "
617 "I<offset> and I<len> that did not contain data before the call will be "
618 "initialized to zero. This default behavior closely resembles the behavior "
619 "of the B<posix_fallocate>(3) library function, and is intended as a method "
620 "of optimally implementing that function."
624 #: build/C/man2/fallocate.2:71
626 "After a successful call, subsequent writes into the range specified by "
627 "I<offset> and I<len> are guaranteed not to fail because of lack of disk "
632 #: build/C/man2/fallocate.2:82
634 "If the B<FALLOC_FL_KEEP_SIZE> flag is specified in I<mode>, the behavior of "
635 "the call is similar, but the file size will not be changed even if "
636 "I<offset>+I<len> is greater than the file size. Preallocating zeroed blocks "
637 "beyond the end of the file in this manner is useful for optimizing append "
642 #: build/C/man2/fallocate.2:86
644 "Because allocation is done in block size chunks, B<fallocate>() may "
645 "allocate a larger range of disk space than was specified."
649 #: build/C/man2/fallocate.2:86
651 msgid "Deallocating file space"
655 #: build/C/man2/fallocate.2:101
657 "Specifying the B<FALLOC_FL_PUNCH_HOLE> flag (available since Linux 2.6.38) "
658 "in I<mode> deallocates space (i.e., creates a hole) in the byte range "
659 "starting at I<offset> and continuing for I<len> bytes. Within the specified "
660 "range, partial filesystem blocks are zeroed, and whole filesystem blocks are "
661 "removed from the file. After a successful call, subsequent reads from this "
662 "range will return zeroes."
666 #: build/C/man2/fallocate.2:112
668 "The B<FALLOC_FL_PUNCH_HOLE> flag must be ORed with B<FALLOC_FL_KEEP_SIZE> in "
669 "I<mode>; in other words, even when punching off the end of the file, the "
670 "file size (as reported by B<stat>(2)) does not change."
674 #: build/C/man2/fallocate.2:117
676 "Not all filesystems support B<FALLOC_FL_PUNCH_HOLE>; if a filesystem doesn't "
677 "support the operation, an error is returned. The operation is supported on "
678 "at least the following filesystems:"
682 #: build/C/man2/fallocate.2:117 build/C/man2/fallocate.2:119 build/C/man2/fallocate.2:122 build/C/man2/fallocate.2:124 build/C/man2/fallocate.2:222 build/C/man2/fallocate.2:225 build/C/man2/madvise.2:286 build/C/man2/madvise.2:292 build/C/man2/madvise.2:295 build/C/man2/madvise.2:298 build/C/man2/madvise.2:301 build/C/man3/mallopt.3:235 build/C/man3/mallopt.3:241 build/C/man2/shmop.2:62 build/C/man2/shmop.2:68 build/C/man2/shmop.2:80 build/C/man2/memfd_create.2:248 build/C/man2/memfd_create.2:258 build/C/man2/memfd_create.2:266
688 #: build/C/man2/fallocate.2:119
689 msgid "XFS (since Linux 2.6.38)"
692 #. commit a4bb6b64e39abc0e41ca077725f2a72c868e7622
694 #: build/C/man2/fallocate.2:122
695 msgid "ext4 (since Linux 3.0)"
699 #: build/C/man2/fallocate.2:124
700 msgid "Btrfs (since Linux 3.7)"
703 #. commit 83e4fa9c16e4af7122e31be3eca5d57881d236fe
705 #: build/C/man2/fallocate.2:127
706 msgid "tmpfs (since Linux 3.5)"
710 #: build/C/man2/fallocate.2:127
712 msgid "Collapsing file space"
715 #. commit 00f5e61998dd17f5375d9dfc01331f104b83f841
717 #: build/C/man2/fallocate.2:147
719 "Specifying the B<FALLOC_FL_COLLAPSE_RANGE> flag (available since Linux 3.15) "
720 "in I<mode> removes a byte range from a file, without leaving a hole. The "
721 "byte range to be collapsed starts at I<offset> and continues for I<len> "
722 "bytes. At the completion of the operation, the contents of the file "
723 "starting at the location I<offset+len> will be appended at the location "
724 "I<offset>, and the file will be I<len> bytes smaller."
728 #: build/C/man2/fallocate.2:161
730 "A filesystem may place limitations on the granularity of the operation, in "
731 "order to ensure efficient implementation. Typically, I<offset> and I<len> "
732 "must be a multiple of the filesystem logical block size, which varies "
733 "according to the filesystem type and configuration. If a filesystem has "
734 "such a requirement, B<fallocate>() will fail with the error B<EINVAL> if "
735 "this requirement is violated."
739 #: build/C/man2/fallocate.2:170
741 "If the region specified by I<offset> plus I<len> reaches or passes the end "
742 "of file, an error is returned; instead, use B<ftruncate>(2) to truncate a "
747 #: build/C/man2/fallocate.2:175
749 "No other flags may be specified in I<mode> in conjunction with "
750 "B<FALLOC_FL_COLLAPSE_RANGE>."
753 #. commit 9eb79482a97152930b113b51dff530aba9e28c8e
754 #. commit e1d8fb88a64c1f8094b9f6c3b6d2d9e6719c970d
756 #: build/C/man2/fallocate.2:183
758 "As at Linux 3.15, B<FALLOC_FL_COLLAPSE_RANGE> is supported by ext4 (only for "
759 "extent-based files) and XFS."
763 #: build/C/man2/fallocate.2:183
765 msgid "Zeroing file space"
768 #. commit 409332b65d3ed8cfa7a8030f1e9d52f372219642
770 #: build/C/man2/fallocate.2:199
772 "Specifying the B<FALLOC_FL_ZERO_RANGE> flag (available since Linux 3.14) in "
773 "I<mode> zeroes space in the byte range starting at I<offset> and continuing "
774 "for I<len> bytes. Within the specified range, blocks are preallocated for "
775 "the regions that span the holes in the file. After a successful call, "
776 "subsequent reads from this range will return zeroes."
780 #: build/C/man2/fallocate.2:205
782 "Zeroing is done within the filesystem preferably by converting the range "
783 "into unwritten extents. This approach means that the specified range will "
784 "not be physically zeroed out on the device (except for partial blocks at the "
785 "either end of the range), and I/O is (otherwise) required only to update "
790 #: build/C/man2/fallocate.2:217
792 "If the B<FALLOC_FL_KEEP_SIZE> flag is additionally specified in I<mode>, the "
793 "behavior of the call is similar, but the file size will not be changed even "
794 "if I<offset>+I<len> is greater than the file size. This behavior is the "
795 "same as when preallocating space with B<FALLOC_FL_KEEP_SIZE> specified."
799 #: build/C/man2/fallocate.2:222
801 "Not all filesystems support B<FALLOC_FL_ZERO_RANGE>; if a filesystem doesn't "
802 "support the operation, an error is returned. The operation is supported on "
803 "at least the following filesystems:"
806 #. commit 376ba313147b4172f3e8cf620b9fb591f3e8cdfa
808 #: build/C/man2/fallocate.2:225
809 msgid "XFS (since Linux 3.14)"
812 #. commit b8a8684502a0fc852afa0056c6bb2a9273f6fcc0
814 #: build/C/man2/fallocate.2:228
815 msgid "ext4, for extent-based files (since Linux 3.14)"
819 #: build/C/man2/fallocate.2:235
821 "On success, B<fallocate>() returns zero. On error, -1 is returned and "
822 "I<errno> is set to indicate the error."
826 #: build/C/man2/fallocate.2:236 build/C/man2/madvise.2:279 build/C/man2/mmap.2:415 build/C/man2/posix_fadvise.2:91 build/C/man3/posix_fallocate.3:73 build/C/man2/readahead.2:73 build/C/man2/sync_file_range.2:148
832 #: build/C/man2/fallocate.2:240 build/C/man3/posix_fallocate.3:77
833 msgid "I<fd> is not a valid file descriptor, or is not opened for writing."
837 #: build/C/man2/fallocate.2:240 build/C/man3/posix_fallocate.3:77
843 #: build/C/man2/fallocate.2:244
844 msgid "I<offset>+I<len> exceeds the maximum file size."
848 #: build/C/man2/fallocate.2:244
854 #: build/C/man2/fallocate.2:247
855 msgid "A signal was caught during execution."
859 #: build/C/man2/fallocate.2:259 build/C/man3/posix_fallocate.3:87
860 msgid "I<offset> was less than 0, or I<len> was less than or equal to 0."
864 #: build/C/man2/fallocate.2:269
866 "I<mode> is B<FALLOC_FL_COLLAPSE_RANGE> and the range specified by I<offset> "
867 "plus I<len> reaches or passes the end of the file."
871 #: build/C/man2/fallocate.2:279
873 "I<mode> is B<FALLOC_FL_COLLAPSE_RANGE>, but either I<offset> or I<len> is "
874 "not a multiple of the filesystem block size."
878 #: build/C/man2/fallocate.2:287
880 "I<mode> contains both B<FALLOC_FL_COLLAPSE_RANGE> and other flags; no other "
881 "flags are permitted with B<FALLOC_FL_COLLAPSE_RANGE>."
884 #. There was a inconsistency in 3.15-rc1, that should be resolved so that all
885 #. filesystems use this error for this case. (Tytso says ex4 will change.)
886 #. http://thread.gmane.org/gmane.comp.file-systems.xfs.general/60485/focus=5521
887 #. From: Michael Kerrisk (man-pages <mtk.manpages@...>
888 #. Subject: Re: [PATCH v5 10/10] manpage: update FALLOC_FL_COLLAPSE_RANGE flag in fallocate
889 #. Newsgroups: gmane.linux.man, gmane.linux.file-systems
890 #. Date: 2014-04-17 13:40:05 GMT
892 #: build/C/man2/fallocate.2:304
894 "I<mode> is B<FALLOC_FL_COLLAPSE_RANGE> or B<FALLOC_FL_ZERO_RANGE>, but the "
895 "file referred to by I<fd> is not a regular file."
899 #: build/C/man2/fallocate.2:304 build/C/man2/madvise.2:310 build/C/man2/sync_file_range.2:160
905 #: build/C/man2/fallocate.2:307
906 msgid "An I/O error occurred while reading from or writing to a filesystem."
910 #: build/C/man2/fallocate.2:307 build/C/man2/mmap.2:450 build/C/man3/posix_fallocate.3:87 build/C/man2/s390_pci_mmio_write.2:92
916 #: build/C/man2/fallocate.2:314
918 "I<fd> does not refer to a regular file or a directory. (If I<fd> is a pipe "
919 "or FIFO, a different error results.)"
923 #: build/C/man2/fallocate.2:314 build/C/man3/posix_fallocate.3:91 build/C/man2/shmget.2:233 build/C/man2/sync_file_range.2:166
929 #: build/C/man2/fallocate.2:319 build/C/man3/posix_fallocate.3:96
931 "There is not enough space left on the device containing the file referred to "
936 #: build/C/man2/fallocate.2:323
937 msgid "This kernel does not implement B<fallocate>()."
941 #: build/C/man2/fallocate.2:323
943 msgid "B<EOPNOTSUPP>"
947 #: build/C/man2/fallocate.2:332
949 "The filesystem containing the file referred to by I<fd> does not support "
950 "this operation; or the I<mode> is not supported by the filesystem containing "
951 "the file referred to by I<fd>."
955 #: build/C/man2/fallocate.2:332 build/C/man2/fallocate.2:338 build/C/man2/fallocate.2:351 build/C/man2/mlock.2:143 build/C/man2/mlock.2:182 build/C/man2/mmap.2:458 build/C/man2/mmap.2:467 build/C/man2/shmctl.2:353 build/C/man2/shmget.2:241
961 #: build/C/man2/fallocate.2:338
962 msgid "The file referred to by I<fd> is marked immutable (see B<chattr>(1))."
966 #: build/C/man2/fallocate.2:351
968 "I<mode> specifies B<FALLOC_FL_PUNCH_HOLE> or B<FALLOC_FL_COLLAPSE_RANGE> and "
969 "the file referred to by I<fd> is marked append-only (see B<chattr>(1))."
973 #: build/C/man2/fallocate.2:355 build/C/man2/mmap.2:471
974 msgid "The operation was prevented by a file seal; see B<fcntl>(2)."
978 #: build/C/man2/fallocate.2:355 build/C/man2/posix_fadvise.2:97 build/C/man3/posix_fallocate.3:96 build/C/man2/sync_file_range.2:169
984 #: build/C/man2/fallocate.2:359
985 msgid "I<fd> refers to a pipe or FIFO."
989 #: build/C/man2/fallocate.2:359 build/C/man2/mmap.2:471
995 #: build/C/man2/fallocate.2:367
997 "I<mode> specifies B<FALLOC_FL_COLLAPSE_RANGE>, but the file referred to by "
998 "I<fd> is currently being executed."
1002 #: build/C/man2/fallocate.2:367 build/C/man2/madvise.2:325 build/C/man3/malloc_info.3:60 build/C/man3/mcheck.3:134 build/C/man2/mmap2.2:74 build/C/man2/posix_fadvise.2:107 build/C/man3/posix_fallocate.3:100 build/C/man3/posix_memalign.3:167 build/C/man2/readahead.2:83 build/C/man2/remap_file_pages.2:156 build/C/man3/shm_open.3:249 build/C/man2/subpage_prot.2:90 build/C/man2/sync_file_range.2:177 build/C/man2/memfd_create.2:155 build/C/man2/s390_pci_mmio_write.2:98
1007 #. See http://sourceware.org/bugzilla/show_bug.cgi?id=14964
1009 #: build/C/man2/fallocate.2:375
1011 "B<fallocate>() is available on Linux since kernel 2.6.23. Support is "
1012 "provided by glibc since version 2.10. The B<FALLOC_FL_*> flags are defined "
1013 "in glibc headers only since version 2.18."
1017 #: build/C/man2/fallocate.2:378
1018 msgid "B<fallocate>() is Linux-specific."
1022 #: build/C/man2/fallocate.2:383
1023 msgid "B<fallocate>(1), B<ftruncate>(2), B<posix_fadvise>(3), B<posix_fallocate>(3)"
1027 #: build/C/man2/madvise.2:35
1033 #: build/C/man2/madvise.2:35 build/C/man2/posix_fadvise.2:28
1039 #: build/C/man2/madvise.2:38
1040 msgid "madvise - give advice about use of memory"
1044 #: build/C/man2/madvise.2:40 build/C/man2/msync.2:30 build/C/man3/shm_open.3:31
1045 msgid "B<#include E<lt>sys/mman.hE<gt>>"
1049 #: build/C/man2/madvise.2:42
1050 msgid "B<int madvise(void *>I<addr>B<, size_t >I<length>B<, int >I<advice>B<);>"
1054 #: build/C/man2/madvise.2:46 build/C/man2/posix_fadvise.2:43 build/C/man3/posix_fallocate.3:39 build/C/man3/posix_memalign.3:49
1055 msgid "Feature Test Macro Requirements for glibc (see B<feature_test_macros>(7)):"
1059 #: build/C/man2/madvise.2:50
1060 msgid "B<madvise>(): _BSD_SOURCE"
1064 #: build/C/man2/madvise.2:68
1066 "The B<madvise>() system call advises the kernel about how to handle paging "
1067 "input/output in the address range beginning at address I<addr> and with size "
1068 "I<length> bytes. It allows an application to tell the kernel how it expects "
1069 "to use some mapped or shared memory areas, so that the kernel can choose "
1070 "appropriate read-ahead and caching techniques. This call does not influence "
1071 "the semantics of the application (except in the case of B<MADV_DONTNEED>), "
1072 "but may influence its performance. The kernel is free to ignore the advice."
1076 #: build/C/man2/madvise.2:72
1077 msgid "The advice is indicated in the I<advice> argument which can be"
1081 #: build/C/man2/madvise.2:72
1083 msgid "B<MADV_NORMAL>"
1087 #: build/C/man2/madvise.2:76
1088 msgid "No special treatment. This is the default."
1092 #: build/C/man2/madvise.2:76
1094 msgid "B<MADV_RANDOM>"
1098 #: build/C/man2/madvise.2:80
1100 "Expect page references in random order. (Hence, read ahead may be less "
1101 "useful than normally.)"
1105 #: build/C/man2/madvise.2:80
1107 msgid "B<MADV_SEQUENTIAL>"
1111 #: build/C/man2/madvise.2:85
1113 "Expect page references in sequential order. (Hence, pages in the given "
1114 "range can be aggressively read ahead, and may be freed soon after they are "
1119 #: build/C/man2/madvise.2:85
1121 msgid "B<MADV_WILLNEED>"
1125 #: build/C/man2/madvise.2:89
1127 "Expect access in the near future. (Hence, it might be a good idea to read "
1128 "some pages ahead.)"
1132 #: build/C/man2/madvise.2:89
1134 msgid "B<MADV_DONTNEED>"
1138 #: build/C/man2/madvise.2:100
1140 "Do not expect access in the near future. (For the time being, the "
1141 "application is finished with the given range, so the kernel can free "
1142 "resources associated with it.) Subsequent accesses of pages in this range "
1143 "will succeed, but will result either in reloading of the memory contents "
1144 "from the underlying mapped file (see B<mmap>(2)) or zero-fill-on-demand "
1145 "pages for mappings without an underlying file."
1149 #: build/C/man2/madvise.2:100
1151 msgid "B<MADV_REMOVE> (since Linux 2.6.16)"
1155 #. Databases want to use this feature to drop a section of their
1156 #. bufferpool (shared memory segments) - without writing back to
1157 #. disk/swap space. This feature is also useful for supporting
1158 #. hot-plug memory on UML.
1160 #: build/C/man2/madvise.2:113
1162 "Free up a given range of pages and its associated backing store. Currently, "
1163 "only shmfs/tmpfs supports this; other filesystems return with the error "
1168 #: build/C/man2/madvise.2:113
1170 msgid "B<MADV_DONTFORK> (since Linux 2.6.16)"
1173 #. See http://lwn.net/Articles/171941/
1174 #. [PATCH] madvise MADV_DONTFORK/MADV_DOFORK
1175 #. Currently, copy-on-write may change the physical address of
1176 #. a page even if the user requested that the page is pinned in
1177 #. memory (either by mlock or by get_user_pages). This happens
1178 #. if the process forks meanwhile, and the parent writes to that
1179 #. page. As a result, the page is orphaned: in case of
1180 #. get_user_pages, the application will never see any data hardware
1181 #. DMA's into this page after the COW. In case of mlock'd memory,
1182 #. the parent is not getting the realtime/security benefits of mlock.
1184 #. In particular, this affects the Infiniband modules which do DMA from
1185 #. and into user pages all the time.
1187 #. This patch adds madvise options to control whether memory range is
1188 #. inherited across fork. Useful e.g. for when hardware is doing DMA
1189 #. from/into these pages. Could also be useful to an application
1190 #. wanting to speed up its forks by cutting large areas out of
1193 #. SEE ALSO: http://lwn.net/Articles/171941/
1194 #. "Tweaks to madvise() and posix_fadvise()", 14 Feb 2006
1196 #: build/C/man2/madvise.2:144
1198 "Do not make the pages in this range available to the child after a "
1199 "B<fork>(2). This is useful to prevent copy-on-write semantics from changing "
1200 "the physical location of a page(s) if the parent writes to it after a "
1201 "B<fork>(2). (Such page relocations cause problems for hardware that DMAs "
1202 "into the page(s).)"
1206 #: build/C/man2/madvise.2:144
1208 msgid "B<MADV_DOFORK> (since Linux 2.6.16)"
1212 #: build/C/man2/madvise.2:150
1214 "Undo the effect of B<MADV_DONTFORK>, restoring the default behavior, whereby "
1215 "a mapping is inherited across B<fork>(2)."
1219 #: build/C/man2/madvise.2:150
1221 msgid "B<MADV_HWPOISON> (since Linux 2.6.32)"
1225 #: build/C/man2/madvise.2:162
1227 "Poison a page and handle it like a hardware memory corruption. This "
1228 "operation is available only for privileged (B<CAP_SYS_ADMIN>) processes. "
1229 "This operation may result in the calling process receiving a B<SIGBUS> and "
1230 "the page being unmapped. This feature is intended for testing of memory "
1231 "error-handling code; it is available only if the kernel was configured with "
1232 "B<CONFIG_MEMORY_FAILURE>."
1236 #: build/C/man2/madvise.2:162
1238 msgid "B<MADV_SOFT_OFFLINE> (since Linux 2.6.33)"
1242 #: build/C/man2/madvise.2:180
1244 "Soft offline the pages in the range specified by I<addr> and I<length>. The "
1245 "memory of each page in the specified range is preserved (i.e., when next "
1246 "accessed, the same content will be visible, but in a new physical page "
1247 "frame), and the original page is offlined (i.e., no longer used, and taken "
1248 "out of normal memory management). The effect of the B<MADV_SOFT_OFFLINE> "
1249 "operation is invisible to (i.e., does not change the semantics of) the "
1250 "calling process. This feature is intended for testing of memory "
1251 "error-handling code; it is available only if the kernel was configured with "
1252 "B<CONFIG_MEMORY_FAILURE>."
1256 #: build/C/man2/madvise.2:180
1258 msgid "B<MADV_MERGEABLE> (since Linux 2.6.32)"
1262 #: build/C/man2/madvise.2:205
1264 "Enable Kernel Samepage Merging (KSM) for the pages in the range specified by "
1265 "I<addr> and I<length>. The kernel regularly scans those areas of user "
1266 "memory that have been marked as mergeable, looking for pages with identical "
1267 "content. These are replaced by a single write-protected page (which is "
1268 "automatically copied if a process later wants to update the content of the "
1269 "page). KSM merges only private anonymous pages (see B<mmap>(2)). The KSM "
1270 "feature is intended for applications that generate many instances of the "
1271 "same data (e.g., virtualization systems such as KVM). It can consume a lot "
1272 "of processing power; use with care. See the Linux kernel source file "
1273 "I<Documentation/vm/ksm.txt> for more details. The B<MADV_MERGEABLE> and "
1274 "B<MADV_UNMERGEABLE> operations are available only if the kernel was "
1275 "configured with B<CONFIG_KSM>."
1279 #: build/C/man2/madvise.2:205
1281 msgid "B<MADV_UNMERGEABLE> (since Linux 2.6.32)"
1285 #: build/C/man2/madvise.2:214
1287 "Undo the effect of an earlier B<MADV_MERGEABLE> operation on the specified "
1288 "address range; KSM unmerges whatever pages it had merged in the address "
1289 "range specified by I<addr> and I<length>."
1293 #: build/C/man2/madvise.2:214
1295 msgid "B<MADV_HUGEPAGE> (since Linux 2.6.38)"
1298 #. http://lwn.net/Articles/358904/
1299 #. https://lwn.net/Articles/423584/
1301 #: build/C/man2/madvise.2:243
1303 "Enables Transparent Huge Pages (THP) for pages in the range specified by "
1304 "I<addr> and I<length>. Currently, Transparent Huge Pages work only with "
1305 "private anonymous pages (see B<mmap>(2)). The kernel will regularly scan "
1306 "the areas marked as huge page candidates to replace them with huge pages. "
1307 "The kernel will also allocate huge pages directly when the region is "
1308 "naturally aligned to the huge page size (see B<posix_memalign>(2)). This "
1309 "feature is primarily aimed at applications that use large mappings of data "
1310 "and access large regions of that memory at a time (e.g., virtualization "
1311 "systems such as QEMU). It can very easily waste memory (e.g., a 2MB mapping "
1312 "that only ever accesses 1 byte will result in 2MB of wired memory instead of "
1313 "one 4KB page). See the Linux kernel source file "
1314 "I<Documentation/vm/transhuge.txt> for more details. The B<MADV_HUGEPAGE> "
1315 "and B<MADV_NOHUGEPAGE> operations are available only if the kernel was "
1316 "configured with B<CONFIG_TRANSPARENT_HUGEPAGE>."
1320 #: build/C/man2/madvise.2:243
1322 msgid "B<MADV_NOHUGEPAGE> (since Linux 2.6.38)"
1326 #: build/C/man2/madvise.2:250
1328 "Ensures that memory in the address range specified by I<addr> and I<length> "
1329 "will not be collapsed into huge pages."
1333 #: build/C/man2/madvise.2:250
1335 msgid "B<MADV_DONTDUMP> (since Linux 3.4)"
1339 #: build/C/man2/madvise.2:264
1341 "Exclude from a core dump those pages in the range specified by I<addr> and "
1342 "I<length>. This is useful in applications that have large areas of memory "
1343 "that are known not to be useful in a core dump. The effect of "
1344 "B<MADV_DONTDUMP> takes precedence over the bit mask that is set via the "
1345 "I</proc/PID/coredump_filter> file (see B<core>(5))."
1349 #: build/C/man2/madvise.2:264
1351 msgid "B<MADV_DODUMP> (since Linux 3.4)"
1355 #: build/C/man2/madvise.2:268
1356 msgid "Undo the effect of an earlier B<MADV_DONTDUMP>."
1360 #: build/C/man2/madvise.2:275
1362 "On success B<madvise>() returns zero. On error, it returns -1 and I<errno> "
1363 "is set appropriately."
1367 #: build/C/man2/madvise.2:276 build/C/man2/mlock.2:154 build/C/man2/mmap.2:411 build/C/man2/mremap.2:136
1373 #: build/C/man2/madvise.2:279
1374 msgid "A kernel resource was temporarily unavailable."
1378 #: build/C/man2/madvise.2:282
1379 msgid "The map exists, but the area maps something that isn't a file."
1383 #: build/C/man2/madvise.2:285
1384 msgid "This error can occur for the following reasons:"
1390 #: build/C/man2/madvise.2:292
1391 msgid "The value I<len> is negative."
1395 #: build/C/man2/madvise.2:295
1396 msgid "I<addr> is not page-aligned."
1400 #: build/C/man2/madvise.2:298
1401 msgid "I<advice> is not a valid value"
1405 #: build/C/man2/madvise.2:301
1407 "The application is attempting to release locked or shared pages (with "
1408 "B<MADV_DONTNEED>)."
1412 #: build/C/man2/madvise.2:309
1414 "B<MADV_MERGEABLE> or B<MADV_UNMERGEABLE> was specified in I<advice>, but the "
1415 "kernel was not configured with B<CONFIG_KSM>."
1419 #: build/C/man2/madvise.2:316
1421 "(for B<MADV_WILLNEED>) Paging in this area would exceed the process's "
1422 "maximum resident set size."
1426 #: build/C/man2/madvise.2:316 build/C/man2/madvise.2:321 build/C/man2/mlock.2:123 build/C/man2/mlock.2:131 build/C/man2/mlock.2:169 build/C/man2/mmap.2:454 build/C/man2/mprotect.2:99 build/C/man2/mprotect.2:102 build/C/man2/mremap.2:179 build/C/man2/msync.2:93 build/C/man3/posix_memalign.3:164 build/C/man2/shmctl.2:337 build/C/man2/shmget.2:230 build/C/man2/shmop.2:211 build/C/man2/subpage_prot.2:87 build/C/man2/sync_file_range.2:163 build/C/man2/memfd_create.2:152 build/C/man2/s390_pci_mmio_write.2:95
1432 #: build/C/man2/madvise.2:321
1433 msgid "(for B<MADV_WILLNEED>) Not enough memory: paging in failed."
1437 #: build/C/man2/madvise.2:325
1439 "Addresses in the specified range are not currently mapped, or are outside "
1440 "the address space of the process."
1443 #. commit d3ac21cacc24790eb45d735769f35753f5b56ceb
1445 #: build/C/man2/madvise.2:332
1447 "Since Linux 3.18, support for this system call is optional, depending on the "
1448 "setting of the B<CONFIG_ADVISE_SYSCALLS> configuration option."
1451 #. FIXME . Write a posix_madvise(3) page.
1453 #: build/C/man2/madvise.2:345
1455 "POSIX.1b. POSIX.1-2001 describes B<posix_madvise>(3) with constants "
1456 "B<POSIX_MADV_NORMAL>, B<POSIX_MADV_RANDOM>, and so on, with a behavior close "
1457 "to that described here. There is a similar B<posix_fadvise>(2) for file "
1462 #: build/C/man2/madvise.2:354
1464 "B<MADV_REMOVE>, B<MADV_DONTFORK>, B<MADV_DOFORK>, B<MADV_HWPOISON>, "
1465 "B<MADV_MERGEABLE>, and B<MADV_UNMERGEABLE> are Linux-specific."
1469 #: build/C/man2/madvise.2:355 build/C/man2/mlock.2:274 build/C/man2/shmget.2:370
1475 #: build/C/man2/madvise.2:363
1477 "The current Linux implementation (2.4.0) views this system call more as a "
1478 "command than as advice and hence may return an error when it cannot do what "
1479 "it usually would do in response to this advice. (See the ERRORS description "
1480 "above.) This is nonstandard behavior."
1486 #. function first appeared in 4.4BSD.
1488 #: build/C/man2/madvise.2:379
1490 "The Linux implementation requires that the address I<addr> be page-aligned, "
1491 "and allows I<length> to be zero. If there are some parts of the specified "
1492 "address range that are not mapped, the Linux version of B<madvise>() "
1493 "ignores them and applies the call to the rest (but returns B<ENOMEM> from "
1494 "the system call, as it should)."
1498 #: build/C/man2/madvise.2:388
1500 "B<getrlimit>(2), B<mincore>(2), B<mmap>(2), B<mprotect>(2), B<msync>(2), "
1501 "B<munmap>(2), B<prctl>(2), B<core>(5)"
1505 #: build/C/man3/mallinfo.3:26
1511 #: build/C/man3/mallinfo.3:26 build/C/man3/malloc_stats.3:26
1517 #: build/C/man3/mallinfo.3:29
1518 msgid "mallinfo - obtain memory allocation information"
1522 #: build/C/man3/mallinfo.3:31 build/C/man3/malloc_stats.3:31 build/C/man3/malloc_trim.3:31 build/C/man3/malloc_usable_size.3:30 build/C/man3/mallopt.3:31
1523 msgid "B<#include E<lt>malloc.hE<gt>>"
1527 #: build/C/man3/mallinfo.3:33
1528 msgid "B<struct mallinfo mallinfo(void);>"
1532 #: build/C/man3/mallinfo.3:41
1534 "The B<mallinfo>() function returns a copy of a structure containing "
1535 "information about memory allocations performed by B<malloc>(3) and related "
1536 "functions. This structure is defined as follows:"
1540 #: build/C/man3/mallinfo.3:56
1543 "struct mallinfo {\n"
1544 " int arena; /* Non-mmapped space allocated (bytes) */\n"
1545 " int ordblks; /* Number of free chunks */\n"
1546 " int smblks; /* Number of free fastbin blocks */\n"
1547 " int hblks; /* Number of mmapped regions */\n"
1548 " int hblkhd; /* Space allocated in mmapped regions (bytes) */\n"
1549 " int usmblks; /* Maximum total allocated space (bytes) */\n"
1550 " int fsmblks; /* Space in freed fastbin blocks (bytes) */\n"
1551 " int uordblks; /* Total allocated space (bytes) */\n"
1552 " int fordblks; /* Total free space (bytes) */\n"
1553 " int keepcost; /* Top-most, releasable space (bytes) */\n"
1558 #: build/C/man3/mallinfo.3:62
1559 msgid "The fields of the I<mallinfo> structure contain the following information:"
1563 #: build/C/man3/mallinfo.3:62
1569 #: build/C/man3/mallinfo.3:68
1571 "The total amount of memory allocated by means other than B<mmap>(2) (i.e., "
1572 "memory allocated on the heap). This figure includes both in-use blocks and "
1573 "blocks on the free list."
1577 #: build/C/man3/mallinfo.3:68
1583 #: build/C/man3/mallinfo.3:71
1584 msgid "The number of ordinary (i.e., non-fastbin) free blocks."
1588 #: build/C/man3/mallinfo.3:71
1594 #: build/C/man3/mallinfo.3:75
1595 msgid "The number of fastbin free blocks (see B<mallopt>(3))."
1599 #: build/C/man3/mallinfo.3:75
1605 #: build/C/man3/mallinfo.3:83
1607 "The number of blocks currently allocated using B<mmap>(2). (See the "
1608 "discussion of B<M_MMAP_THRESHOLD> in B<mallopt>(3).)"
1612 #: build/C/man3/mallinfo.3:83
1618 #: build/C/man3/mallinfo.3:87
1619 msgid "The number of bytes in blocks currently allocated using B<mmap>(2)."
1623 #: build/C/man3/mallinfo.3:87
1629 #: build/C/man3/mallinfo.3:92
1631 "The \"highwater mark\" for allocated space\\(emthat is, the maximum amount "
1632 "of space that was ever allocated. This field is maintained only in "
1633 "nonthreading environments."
1637 #: build/C/man3/mallinfo.3:92
1643 #: build/C/man3/mallinfo.3:95
1644 msgid "The total number of bytes in fastbin free blocks."
1648 #: build/C/man3/mallinfo.3:95
1654 #: build/C/man3/mallinfo.3:98
1655 msgid "The total number of bytes used by in-use allocations."
1659 #: build/C/man3/mallinfo.3:98
1665 #: build/C/man3/mallinfo.3:101
1666 msgid "The total number of bytes in free blocks."
1670 #: build/C/man3/mallinfo.3:101
1676 #. Available already in glibc 2.0, possibly earlier
1678 #: build/C/man3/mallinfo.3:110
1680 "The total amount of releasable free space at the top of the heap. This is "
1681 "the maximum number of bytes that could ideally (i.e., ignoring page "
1682 "alignment restrictions, and so on) be released by B<malloc_trim>(3)."
1686 #: build/C/man3/mallinfo.3:114
1688 "This function is not specified by POSIX or the C standards. A similar "
1689 "function exists on many System V derivatives, and was specified in the SVID."
1692 #. FIXME . http://sourceware.org/bugzilla/show_bug.cgi?id=208
1693 #. See the 24 Aug 2011 mail by Paul Pluzhnikov:
1694 #. "[patch] Fix mallinfo() to accumulate results for all arenas"
1695 #. on libc-alpha@sourceware.org
1697 #: build/C/man3/mallinfo.3:126
1699 "B<Information is returned for only the main memory allocation area.> "
1700 "Allocations in other arenas are excluded. See B<malloc_stats>(3) and "
1701 "B<malloc_info>(3) for alternatives that include information about other "
1706 #: build/C/man3/mallinfo.3:134
1708 "The fields of the I<mallinfo> structure are typed as I<int>. However, "
1709 "because some internal bookkeeping values may be of type I<long>, the "
1710 "reported values may wrap around zero and thus be inaccurate."
1714 #: build/C/man3/mallinfo.3:134 build/C/man3/malloc_hook.3:89 build/C/man3/malloc_info.3:84 build/C/man3/mallopt.3:454 build/C/man3/mcheck.3:159 build/C/man2/mmap.2:633 build/C/man2/mprotect.2:147 build/C/man3/mtrace.3:108 build/C/man2/memfd_create.2:293
1720 #: build/C/man3/mallinfo.3:140
1722 "The program below employs B<mallinfo>() to retrieve memory allocation "
1723 "statistics before and after allocating and freeing some blocks of memory. "
1724 "The statistics are displayed on standard output."
1728 #: build/C/man3/mallinfo.3:144
1730 "The first two command-line arguments specify the number and size of blocks "
1731 "to be allocated with B<malloc>(3)."
1735 #: build/C/man3/mallinfo.3:158
1737 "The remaining three arguments specify which of the allocated blocks should "
1738 "be freed with B<free>(3). These three arguments are optional, and specify "
1739 "(in order): the step size to be used in the loop that frees blocks (the "
1740 "default is 1, meaning free all blocks in the range); the ordinal position of "
1741 "the first block to be freed (default 0, meaning the first allocated block); "
1742 "and a number one greater than the ordinal position of the last block to be "
1743 "freed (default is one greater than the maximum block number). If these "
1744 "three arguments are omitted, then the defaults cause all allocated blocks to "
1749 #: build/C/man3/mallinfo.3:162
1751 "In the following example run of the program, 1000 allocations of 100 bytes "
1752 "are performed, and then every second allocated block is freed:"
1756 #: build/C/man3/mallinfo.3:177
1759 "$ B<./a.out 1000 100 2>\n"
1760 "============== Before allocating blocks ==============\n"
1761 "Total non-mmapped bytes (arena): 0\n"
1762 "# of free chunks (ordblks): 1\n"
1763 "# of free fastbin blocks (smblks): 0\n"
1764 "# of mapped regions (hblks): 0\n"
1765 "Bytes in mapped regions (hblkhd): 0\n"
1766 "Max. total allocated space (usmblks): 0\n"
1767 "Free bytes held in fastbins (fsmblks): 0\n"
1768 "Total allocated space (uordblks): 0\n"
1769 "Total free space (fordblks): 0\n"
1770 "Topmost releasable block (keepcost): 0\n"
1774 #: build/C/man3/mallinfo.3:189
1777 "============== After allocating blocks ==============\n"
1778 "Total non-mmapped bytes (arena): 135168\n"
1779 "# of free chunks (ordblks): 1\n"
1780 "# of free fastbin blocks (smblks): 0\n"
1781 "# of mapped regions (hblks): 0\n"
1782 "Bytes in mapped regions (hblkhd): 0\n"
1783 "Max. total allocated space (usmblks): 0\n"
1784 "Free bytes held in fastbins (fsmblks): 0\n"
1785 "Total allocated space (uordblks): 104000\n"
1786 "Total free space (fordblks): 31168\n"
1787 "Topmost releasable block (keepcost): 31168\n"
1791 #: build/C/man3/mallinfo.3:201
1794 "============== After freeing blocks ==============\n"
1795 "Total non-mmapped bytes (arena): 135168\n"
1796 "# of free chunks (ordblks): 501\n"
1797 "# of free fastbin blocks (smblks): 0\n"
1798 "# of mapped regions (hblks): 0\n"
1799 "Bytes in mapped regions (hblkhd): 0\n"
1800 "Max. total allocated space (usmblks): 0\n"
1801 "Free bytes held in fastbins (fsmblks): 0\n"
1802 "Total allocated space (uordblks): 52000\n"
1803 "Total free space (fordblks): 83168\n"
1804 "Topmost releasable block (keepcost): 31168\n"
1808 #: build/C/man3/mallinfo.3:203 build/C/man3/malloc_info.3:167 build/C/man3/mallopt.3:520 build/C/man3/mcheck.3:176 build/C/man2/mmap.2:645 build/C/man2/mprotect.2:164
1810 msgid "Program source"
1814 #: build/C/man3/mallinfo.3:208
1817 "#include E<lt>malloc.hE<gt>\n"
1818 "#include \"tlpi_hdr.h\"\n"
1822 #: build/C/man3/mallinfo.3:213
1826 "display_mallinfo(void)\n"
1828 " struct mallinfo mi;\n"
1832 #: build/C/man3/mallinfo.3:215
1834 msgid " mi = mallinfo();\n"
1838 #: build/C/man3/mallinfo.3:227
1841 " printf(\"Total non-mmapped bytes (arena): %d\\en\", mi.arena);\n"
1842 " printf(\"# of free chunks (ordblks): %d\\en\", mi.ordblks);\n"
1843 " printf(\"# of free fastbin blocks (smblks): %d\\en\", mi.smblks);\n"
1844 " printf(\"# of mapped regions (hblks): %d\\en\", mi.hblks);\n"
1845 " printf(\"Bytes in mapped regions (hblkhd): %d\\en\", mi.hblkhd);\n"
1846 " printf(\"Max. total allocated space (usmblks): %d\\en\", mi.usmblks);\n"
1847 " printf(\"Free bytes held in fastbins (fsmblks): %d\\en\", mi.fsmblks);\n"
1848 " printf(\"Total allocated space (uordblks): %d\\en\", "
1850 " printf(\"Total free space (fordblks): %d\\en\", "
1852 " printf(\"Topmost releasable block (keepcost): %d\\en\", "
1858 #: build/C/man3/mallinfo.3:235
1862 "main(int argc, char *argv[])\n"
1864 "#define MAX_ALLOCS 2000000\n"
1865 " char *alloc[MAX_ALLOCS];\n"
1866 " int numBlocks, j, freeBegin, freeEnd, freeStep;\n"
1867 " size_t blockSize;\n"
1871 #: build/C/man3/mallinfo.3:239
1874 " if (argc E<lt> 3 || strcmp(argv[1], \"--help\") == 0)\n"
1875 " usageErr(\"%s num-blocks block-size [free-step [start-free \"\n"
1876 " \"[end-free]]]\\en\", argv[0]);\n"
1880 #: build/C/man3/mallinfo.3:245
1883 " numBlocks = atoi(argv[1]);\n"
1884 " blockSize = atoi(argv[2]);\n"
1885 " freeStep = (argc E<gt> 3) ? atoi(argv[3]) : 1;\n"
1886 " freeBegin = (argc E<gt> 4) ? atoi(argv[4]) : 0;\n"
1887 " freeEnd = (argc E<gt> 5) ? atoi(argv[5]) : numBlocks;\n"
1891 #: build/C/man3/mallinfo.3:248
1894 " printf(\"============== Before allocating blocks "
1895 "==============\\en\");\n"
1896 " display_mallinfo();\n"
1900 #: build/C/man3/mallinfo.3:252
1903 " for (j = 0; j E<lt> numBlocks; j++) {\n"
1904 " if (numBlocks E<gt>= MAX_ALLOCS)\n"
1905 " fatal(\"Too many allocations\");\n"
1909 #: build/C/man3/mallinfo.3:257
1912 " alloc[j] = malloc(blockSize);\n"
1913 " if (alloc[j] == NULL)\n"
1914 " errExit(\"malloc\");\n"
1919 #: build/C/man3/mallinfo.3:260
1922 " printf(\"\\en============== After allocating blocks "
1923 "==============\\en\");\n"
1924 " display_mallinfo();\n"
1928 #: build/C/man3/mallinfo.3:263
1931 " for (j = freeBegin; j E<lt> freeEnd; j += freeStep)\n"
1932 " free(alloc[j]);\n"
1936 #: build/C/man3/mallinfo.3:266
1939 " printf(\"\\en============== After freeing blocks "
1940 "==============\\en\");\n"
1941 " display_mallinfo();\n"
1945 #: build/C/man3/mallinfo.3:269 build/C/man3/malloc_info.3:255 build/C/man3/mallopt.3:553 build/C/man3/mcheck.3:203 build/C/man2/mmap.2:714 build/C/man2/memfd_create.2:437 build/C/man2/memfd_create.2:486
1948 " exit(EXIT_SUCCESS);\n"
1953 #: build/C/man3/mallinfo.3:279
1955 "B<mmap>(2), B<malloc>(3), B<malloc_info>(3), B<malloc_stats>(3), "
1956 "B<malloc_trim>(3), B<mallopt>(3)"
1960 #: build/C/man3/malloc_get_state.3:25
1962 msgid "MALLOC_GET_STATE"
1966 #: build/C/man3/malloc_get_state.3:25 build/C/man3/malloc_usable_size.3:25
1972 #: build/C/man3/malloc_get_state.3:28
1974 "malloc_get_state, malloc_set_state - record and restore state of malloc "
1979 #: build/C/man3/malloc_get_state.3:31 build/C/man3/malloc_hook.3:18 build/C/man3/malloc_info.3:31 build/C/man3/posix_memalign.3:41
1981 msgid "B<#include E<lt>malloc.hE<gt>>\n"
1985 #: build/C/man3/malloc_get_state.3:33
1987 msgid "B<void* malloc_get_state(void);>\n"
1991 #: build/C/man3/malloc_get_state.3:35
1993 msgid "B<int malloc_set_state(void *>I<state>B<);>\n"
1997 #: build/C/man3/malloc_get_state.3:53
1999 "The B<malloc_get_state>() function records the current state of all "
2000 "B<malloc>(3) internal bookkeeping variables (but not the actual contents of "
2001 "the heap or the state of B<malloc_hook>(3) functions pointers). The state "
2002 "is recorded in a system-dependent opaque data structure dynamically "
2003 "allocated via B<malloc>(3), and a pointer to that data structure is returned "
2004 "as the function result. (It is the caller's responsibility to B<free>(3) "
2009 #: build/C/man3/malloc_get_state.3:61
2011 "The B<malloc_set_state>() function restores the state of all B<malloc>(3) "
2012 "internal bookkeeping variables to the values recorded in the opaque data "
2013 "structure pointed to by I<state>."
2017 #: build/C/man3/malloc_get_state.3:68
2019 "On success, B<malloc_get_state>() returns a pointer to a newly allocated "
2020 "opaque data structure. On error (for example, memory could not be allocated "
2021 "for the data structure), B<malloc_get_state>() returns NULL."
2024 #. if(ms->magic != MALLOC_STATE_MAGIC) return -1;
2025 #. /* Must fail if the major version is too high. */
2026 #. if((ms->version & ~0xffl) > (MALLOC_STATE_VERSION & ~0xffl)) return -2;
2028 #: build/C/man3/malloc_get_state.3:86
2030 "On success, B<malloc_set_state>() returns 0. If the implementation detects "
2031 "that I<state> does not point to a correctly formed data structure, "
2032 "B<malloc_set_state>() returns -1. If the implementation detects that the "
2033 "version of the data structure referred to by I<state> is a more recent "
2034 "version than this implementation knows about, B<malloc_set_state>() returns "
2039 #: build/C/man3/malloc_get_state.3:88 build/C/man3/malloc_hook.3:82 build/C/man3/mcheck.3:147 build/C/man3/mtrace.3:80
2040 msgid "These functions are GNU extensions."
2044 #: build/C/man3/malloc_get_state.3:94
2046 "These functions are useful when using this B<malloc>(3) implementation as "
2047 "part of a shared library, and the heap contents are saved/restored via some "
2048 "other method. This technique is used by GNU Emacs to implement its "
2049 "\"dumping\" function."
2052 #. i.e., calls __malloc_check_init()
2053 #. i.e., malloc checking is not already in use
2054 #. and the caller requested malloc checking
2056 #: build/C/man3/malloc_get_state.3:111
2058 "Hook function pointers are never saved or restored by these functions, with "
2059 "two exceptions: if malloc checking (see B<mallopt>(3)) was in use when "
2060 "B<malloc_get_state>() was called, then B<malloc_set_state>() resets malloc "
2061 "checking hooks if possible; if malloc checking was not in use in the "
2062 "recorded state, but the caller has requested malloc checking, then the hooks "
2067 #: build/C/man3/malloc_get_state.3:114
2068 msgid "B<malloc>(3), B<mallopt>(3)"
2072 #: build/C/man3/malloc_hook.3:10
2078 #: build/C/man3/malloc_hook.3:10
2084 #: build/C/man3/malloc_hook.3:15
2086 "__malloc_hook, __malloc_initialize_hook, __memalign_hook, __free_hook, "
2087 "__realloc_hook, __after_morecore_hook - malloc debugging variables"
2091 #: build/C/man3/malloc_hook.3:20
2093 msgid "B<void *(*__malloc_hook)(size_t >I<size>B<, const void *>I<caller>B<);>\n"
2097 #: build/C/man3/malloc_hook.3:23
2100 "B<void *(*__realloc_hook)(void *>I<ptr>B<, size_t >I<size>B<, const void "
2101 "*>I<caller>B<);>\n"
2105 #: build/C/man3/malloc_hook.3:26
2108 "B<void *(*__memalign_hook)(size_t >I<alignment>B<, size_t >I<size>B<,>\n"
2109 "B< const void *>I<caller>B<);>\n"
2113 #: build/C/man3/malloc_hook.3:28
2115 msgid "B<void (*__free_hook)(void *>I<ptr>B<, const void *>I<caller>B<);>\n"
2119 #: build/C/man3/malloc_hook.3:30
2121 msgid "B<void (*__malloc_initialize_hook)(void);>\n"
2125 #: build/C/man3/malloc_hook.3:32
2127 msgid "B<void (*__after_morecore_hook)(void);>\n"
2131 #: build/C/man3/malloc_hook.3:43
2133 "The GNU C library lets you modify the behavior of B<malloc>(3), "
2134 "B<realloc>(3), and B<free>(3) by specifying appropriate hook functions. "
2135 "You can use these hooks to help you debug programs that use dynamic memory "
2136 "allocation, for example."
2140 #: build/C/man3/malloc_hook.3:50
2142 "The variable B<__malloc_initialize_hook> points at a function that is called "
2143 "once when the malloc implementation is initialized. This is a weak "
2144 "variable, so it can be overridden in the application with a definition like "
2149 #: build/C/man3/malloc_hook.3:53
2151 msgid " void (*__malloc_initialize_hook)(void) = my_init_hook;\n"
2155 #: build/C/man3/malloc_hook.3:58
2156 msgid "Now the function I<my_init_hook>() can do the initialization of all hooks."
2160 #: build/C/man3/malloc_hook.3:74
2162 "The four functions pointed to by B<__malloc_hook>, B<__realloc_hook>, "
2163 "B<__memalign_hook>, B<__free_hook> have a prototype like the functions "
2164 "B<malloc>(3), B<realloc>(3), B<memalign>(3), B<free>(3), respectively, "
2165 "except that they have a final argument I<caller> that gives the address of "
2166 "the caller of B<malloc>(3), etc."
2170 #: build/C/man3/malloc_hook.3:80
2172 "The variable B<__after_morecore_hook> points at a function that is called "
2173 "each time after B<sbrk>(2) was asked for more memory."
2176 #. https://bugzilla.redhat.com/show_bug.cgi?id=450187
2177 #. http://sourceware.org/bugzilla/show_bug.cgi?id=9957
2179 #: build/C/man3/malloc_hook.3:89
2181 "The use of these hook functions is not safe in multithreaded programs, and "
2182 "they are now deprecated. Programmers should instead preempt calls to the "
2183 "relevant functions by defining and exporting functions such as \"malloc\" "
2188 #: build/C/man3/malloc_hook.3:91
2189 msgid "Here is a short example of how to use these variables."
2193 #: build/C/man3/malloc_hook.3:95
2196 "#include E<lt>stdio.hE<gt>\n"
2197 "#include E<lt>malloc.hE<gt>\n"
2201 #: build/C/man3/malloc_hook.3:99
2204 "/* Prototypes for our hooks. */\n"
2205 "static void my_init_hook(void);\n"
2206 "static void *my_malloc_hook(size_t, const void *);\n"
2210 #: build/C/man3/malloc_hook.3:102
2213 "/* Variables to save original hooks. */\n"
2214 "static void *(*old_malloc_hook)(size_t, const void *);\n"
2218 #: build/C/man3/malloc_hook.3:105
2221 "/* Override initializing hook from the C library. */\n"
2222 "void (*__malloc_initialize_hook) (void) = my_init_hook;\n"
2226 #: build/C/man3/malloc_hook.3:112
2230 "my_init_hook(void)\n"
2232 " old_malloc_hook = __malloc_hook;\n"
2233 " __malloc_hook = my_malloc_hook;\n"
2238 #: build/C/man3/malloc_hook.3:117
2242 "my_malloc_hook(size_t size, const void *caller)\n"
2248 #: build/C/man3/malloc_hook.3:120
2251 " /* Restore all old hooks */\n"
2252 " __malloc_hook = old_malloc_hook;\n"
2256 #: build/C/man3/malloc_hook.3:123
2259 " /* Call recursively */\n"
2260 " result = malloc(size);\n"
2264 #: build/C/man3/malloc_hook.3:126
2267 " /* Save underlying hooks */\n"
2268 " old_malloc_hook = __malloc_hook;\n"
2272 #: build/C/man3/malloc_hook.3:130
2275 " /* printf() might call malloc(), so protect it too. */\n"
2276 " printf(\"malloc(%u) called from %p returns %p\\en\",\n"
2277 " (unsigned int) size, caller, result);\n"
2281 #: build/C/man3/malloc_hook.3:133
2284 " /* Restore our own hooks */\n"
2285 " __malloc_hook = my_malloc_hook;\n"
2289 #: build/C/man3/malloc_hook.3:136
2297 #: build/C/man3/malloc_hook.3:142
2298 msgid "B<mallinfo>(3), B<malloc>(3), B<mcheck>(3), B<mtrace>(3)"
2302 #: build/C/man3/malloc_info.3:25
2308 #: build/C/man3/malloc_info.3:28
2309 msgid "malloc_info - export malloc state to a stream"
2313 #: build/C/man3/malloc_info.3:33
2315 msgid "B<int malloc_info(int >I<options>B<, FILE *>I<stream>B<);>\n"
2319 #: build/C/man3/malloc_info.3:44
2321 "The B<malloc_info>() function exports an XML string that describes the "
2322 "current state of the memory-allocation implementation in the caller. The "
2323 "string is printed on the file stream I<stream>. The exported string "
2324 "includes information about all arenas (see B<malloc>(3))."
2328 #: build/C/man3/malloc_info.3:48
2329 msgid "As currently implemented, I<options> must be zero."
2333 #: build/C/man3/malloc_info.3:55
2335 "On success, B<malloc_info>() returns 0; on error, it returns -1, with "
2336 "I<errno> set to indicate the cause."
2340 #: build/C/man3/malloc_info.3:60
2341 msgid "I<options> was nonzero."
2345 #: build/C/man3/malloc_info.3:63
2346 msgid "B<malloc_info>() was added to glibc in version 2.10."
2350 #: build/C/man3/malloc_info.3:65 build/C/man3/malloc_stats.3:57 build/C/man3/malloc_trim.3:62 build/C/man3/malloc_usable_size.3:55
2351 msgid "This function is a GNU extension."
2355 #: build/C/man3/malloc_info.3:71
2357 "The memory-allocation information is provided as an XML string (rather than "
2358 "a C structure) because the information may change over time (according to "
2359 "changes in the underlying implementation). The output XML string includes a "
2364 #: build/C/man3/malloc_info.3:77
2366 "The B<open_memstream>(3) function can be used to send the output of "
2367 "B<malloc_info>() directly into a buffer in memory, rather than to a file."
2371 #: build/C/man3/malloc_info.3:84
2373 "The B<malloc_info>() function is designed to address deficiencies in "
2374 "B<malloc_stats>(3) and B<mallinfo>(3)."
2378 #: build/C/man3/malloc_info.3:95
2380 "The program below takes up to four command-line arguments, of which the "
2381 "first three are mandatory. The first argument specifies the number of "
2382 "threads that the program should create. All of the threads, including the "
2383 "main thread, allocate the number of blocks of memory specified by the second "
2384 "argument. The third argument controls the size of the blocks to be "
2385 "allocated. The main thread creates blocks of this size, the second thread "
2386 "created by the program allocates blocks of twice this size, the third thread "
2387 "allocates blocks of three times this size, and so on."
2391 #: build/C/man3/malloc_info.3:102
2393 "The program calls B<malloc_info>() twice to display the memory-allocation "
2394 "state. The first call takes place before any threads are created or memory "
2395 "allocated. The second call is performed after all threads have allocated "
2400 #: build/C/man3/malloc_info.3:110
2402 "In the following example, the command-line arguments specify the creation of "
2403 "one additional thread, and both the main thread and the additional thread "
2404 "allocate 10000 blocks of memory. After the blocks of memory have been "
2405 "allocated, B<malloc_info>() shows the state of two allocation arenas."
2409 #: build/C/man3/malloc_info.3:135
2412 "$ B<getconf GNU_LIBC_VERSION>\n"
2414 "$ B<./a.out 1 10000 100>\n"
2415 "============ Before allocating blocks ============\n"
2416 "E<lt>malloc version=\"1\"E<gt>\n"
2417 "E<lt>heap nr=\"0\"E<gt>\n"
2419 "E<lt>/sizesE<gt>\n"
2420 "E<lt>total type=\"fast\" count=\"0\" size=\"0\"/E<gt>\n"
2421 "E<lt>total type=\"rest\" count=\"0\" size=\"0\"/E<gt>\n"
2422 "E<lt>system type=\"current\" size=\"135168\"/E<gt>\n"
2423 "E<lt>system type=\"max\" size=\"135168\"/E<gt>\n"
2424 "E<lt>aspace type=\"total\" size=\"135168\"/E<gt>\n"
2425 "E<lt>aspace type=\"mprotect\" size=\"135168\"/E<gt>\n"
2427 "E<lt>total type=\"fast\" count=\"0\" size=\"0\"/E<gt>\n"
2428 "E<lt>total type=\"rest\" count=\"0\" size=\"0\"/E<gt>\n"
2429 "E<lt>system type=\"current\" size=\"135168\"/E<gt>\n"
2430 "E<lt>system type=\"max\" size=\"135168\"/E<gt>\n"
2431 "E<lt>aspace type=\"total\" size=\"135168\"/E<gt>\n"
2432 "E<lt>aspace type=\"mprotect\" size=\"135168\"/E<gt>\n"
2433 "E<lt>/mallocE<gt>\n"
2437 #: build/C/man3/malloc_info.3:165
2440 "============ After allocating blocks ============\n"
2441 "E<lt>malloc version=\"1\"E<gt>\n"
2442 "E<lt>heap nr=\"0\"E<gt>\n"
2444 "E<lt>/sizesE<gt>\n"
2445 "E<lt>total type=\"fast\" count=\"0\" size=\"0\"/E<gt>\n"
2446 "E<lt>total type=\"rest\" count=\"0\" size=\"0\"/E<gt>\n"
2447 "E<lt>system type=\"current\" size=\"1081344\"/E<gt>\n"
2448 "E<lt>system type=\"max\" size=\"1081344\"/E<gt>\n"
2449 "E<lt>aspace type=\"total\" size=\"1081344\"/E<gt>\n"
2450 "E<lt>aspace type=\"mprotect\" size=\"1081344\"/E<gt>\n"
2452 "E<lt>heap nr=\"1\"E<gt>\n"
2454 "E<lt>/sizesE<gt>\n"
2455 "E<lt>total type=\"fast\" count=\"0\" size=\"0\"/E<gt>\n"
2456 "E<lt>total type=\"rest\" count=\"0\" size=\"0\"/E<gt>\n"
2457 "E<lt>system type=\"current\" size=\"1032192\"/E<gt>\n"
2458 "E<lt>system type=\"max\" size=\"1032192\"/E<gt>\n"
2459 "E<lt>aspace type=\"total\" size=\"1032192\"/E<gt>\n"
2460 "E<lt>aspace type=\"mprotect\" size=\"1032192\"/E<gt>\n"
2462 "E<lt>total type=\"fast\" count=\"0\" size=\"0\"/E<gt>\n"
2463 "E<lt>total type=\"rest\" count=\"0\" size=\"0\"/E<gt>\n"
2464 "E<lt>system type=\"current\" size=\"2113536\"/E<gt>\n"
2465 "E<lt>system type=\"max\" size=\"2113536\"/E<gt>\n"
2466 "E<lt>aspace type=\"total\" size=\"2113536\"/E<gt>\n"
2467 "E<lt>aspace type=\"mprotect\" size=\"2113536\"/E<gt>\n"
2468 "E<lt>/mallocE<gt>\n"
2472 #: build/C/man3/malloc_info.3:175
2475 "#include E<lt>unistd.hE<gt>\n"
2476 "#include E<lt>stdlib.hE<gt>\n"
2477 "#include E<lt>pthread.hE<gt>\n"
2478 "#include E<lt>malloc.hE<gt>\n"
2479 "#include E<lt>errno.hE<gt>\n"
2483 #: build/C/man3/malloc_info.3:178
2486 "static size_t blockSize;\n"
2487 "static int numThreads, numBlocks;\n"
2491 #: build/C/man3/malloc_info.3:181 build/C/man2/memfd_create.2:368 build/C/man2/memfd_create.2:450
2494 "#define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \\e\n"
2499 #: build/C/man3/malloc_info.3:187
2503 "thread_func(void *arg)\n"
2506 " int tn = (int) arg;\n"
2510 #: build/C/man3/malloc_info.3:190
2513 " /* The multiplier \\(aq(2 + tn)\\(aq ensures that each thread "
2515 " the main thread) allocates a different amount of memory */\n"
2519 #: build/C/man3/malloc_info.3:194
2522 " for (j = 0; j E<lt> numBlocks; j++)\n"
2523 " if (malloc(blockSize * (2 + tn)) == NULL)\n"
2524 " errExit(\"malloc-thread\");\n"
2528 #: build/C/man3/malloc_info.3:198
2531 " sleep(100); /* Sleep until main thread terminates */\n"
2537 #: build/C/man3/malloc_info.3:204
2541 "main(int argc, char *argv[])\n"
2543 " int j, tn, sleepTime;\n"
2544 " pthread_t *thr;\n"
2548 #: build/C/man3/malloc_info.3:211
2551 " if (argc E<lt> 4) {\n"
2552 " fprintf(stderr,\n"
2553 " \"%s num-threads num-blocks block-size [sleep-time]\\en\",\n"
2555 " exit(EXIT_FAILURE);\n"
2560 #: build/C/man3/malloc_info.3:216
2563 " numThreads = atoi(argv[1]);\n"
2564 " numBlocks = atoi(argv[2]);\n"
2565 " blockSize = atoi(argv[3]);\n"
2566 " sleepTime = (argc E<gt> 4) ? atoi(argv[4]) : 0;\n"
2570 #: build/C/man3/malloc_info.3:220
2573 " thr = calloc(numThreads, sizeof(pthread_t));\n"
2574 " if (thr == NULL)\n"
2575 " errExit(\"calloc\");\n"
2579 #: build/C/man3/malloc_info.3:223
2582 " printf(\"============ Before allocating blocks ============\\en\");\n"
2583 " malloc_info(0, stdout);\n"
2587 #: build/C/man3/malloc_info.3:225
2589 msgid " /* Create threads that allocate different amounts of memory */\n"
2593 #: build/C/man3/malloc_info.3:231
2596 " for (tn = 0; tn E<lt> numThreads; tn++) {\n"
2597 " errno = pthread_create(&thr[tn], NULL, thread_func,\n"
2599 " if (errno != 0)\n"
2600 " errExit(\"pthread_create\");\n"
2604 #: build/C/man3/malloc_info.3:236
2607 " /* If we add a sleep interval after the start-up of each\n"
2608 " thread, the threads likely won\\(aqt contend for malloc\n"
2609 " mutexes, and therefore additional arenas won\\(aqt be\n"
2610 " allocated (see malloc(3)). */\n"
2614 #: build/C/man3/malloc_info.3:240
2617 " if (sleepTime E<gt> 0)\n"
2618 " sleep(sleepTime);\n"
2623 #: build/C/man3/malloc_info.3:242
2625 msgid " /* The main thread also allocates some memory */\n"
2629 #: build/C/man3/malloc_info.3:246
2632 " for (j = 0; j E<lt> numBlocks; j++)\n"
2633 " if (malloc(blockSize) == NULL)\n"
2634 " errExit(\"malloc\");\n"
2638 #: build/C/man3/malloc_info.3:249
2641 " sleep(2); /* Give all threads a chance to\n"
2642 " complete allocations */\n"
2646 #: build/C/man3/malloc_info.3:252
2649 " printf(\"\\en============ After allocating blocks ============\\en\");\n"
2650 " malloc_info(0, stdout);\n"
2654 #: build/C/man3/malloc_info.3:262
2656 "B<mallinfo>(3), B<malloc>(3), B<malloc_stats>(3), B<mallopt>(3), "
2657 "B<open_memstream>(3)"
2661 #: build/C/man3/malloc_stats.3:26
2663 msgid "MALLOC_STATS"
2667 #: build/C/man3/malloc_stats.3:29
2668 msgid "malloc_stats - print memory allocation statistics"
2672 #: build/C/man3/malloc_stats.3:33
2673 msgid "B<void malloc_stats(void);>"
2677 #. Available already in glibc 2.0, possibly earlier
2679 #: build/C/man3/malloc_stats.3:55
2681 "The B<malloc_stats>() function prints (on standard error) statistics about "
2682 "memory allocated by B<malloc>(3) and related functions. For each arena "
2683 "(allocation area), this function prints the total amount of memory allocated "
2684 "and the total number of bytes consumed by in-use allocations. (These two "
2685 "values correspond to the I<arena> and I<uordblks> fields retrieved by "
2686 "B<mallinfo>(3).) In addition, the function prints the sum of these two "
2687 "statistics for all arenas, and the maximum number of blocks and bytes that "
2688 "were ever simultaneously allocated using B<mmap>(2)."
2692 #: build/C/man3/malloc_stats.3:61
2694 "More detailed information about memory allocations in the main arena can be "
2695 "obtained using B<mallinfo>(3)."
2699 #: build/C/man3/malloc_stats.3:67
2700 msgid "B<mmap>(2), B<mallinfo>(3), B<malloc>(3), B<malloc_info>(3), B<mallopt>(3)"
2704 #: build/C/man3/malloc_trim.3:26
2710 #: build/C/man3/malloc_trim.3:26 build/C/man2/remap_file_pages.2:28
2716 #: build/C/man3/malloc_trim.3:29
2717 msgid "malloc_trim - release free memory from the top of the heap"
2721 #: build/C/man3/malloc_trim.3:33
2722 msgid "B<int malloc_trim(size_t >I<pad>B<);>"
2726 #: build/C/man3/malloc_trim.3:40
2728 "The B<malloc_trim>() function attempts to release free memory at the top of "
2729 "the heap (by calling B<sbrk>(2) with a suitable argument)."
2733 #: build/C/man3/malloc_trim.3:51
2735 "The I<pad> argument specifies the amount of free space to leave untrimmed at "
2736 "the top of the heap. If this argument is 0, only the minimum amount of "
2737 "memory is maintained at the top of the heap (i.e., one page or less). A "
2738 "nonzero argument can be used to maintain some trailing space at the top of "
2739 "the heap in order to allow future allocations to be made without having to "
2740 "extend the heap with B<sbrk>(2)."
2744 #: build/C/man3/malloc_trim.3:56
2746 "The B<malloc_trim>() function returns 1 if memory was actually released "
2747 "back to the system, or 0 if it was not possible to release any memory."
2751 #. Available already in glibc 2.0, possibly earlier
2753 #: build/C/man3/malloc_trim.3:60
2754 msgid "No errors are defined."
2758 #: build/C/man3/malloc_trim.3:71
2760 "This function is automatically called by B<free>(3) in certain "
2761 "circumstances; see the discussion of B<M_TOP_PAD> and B<M_TRIM_THRESHOLD> in "
2766 #: build/C/man3/malloc_trim.3:74
2768 "This function cannot release free memory located at places other than the "
2772 #. malloc/malloc.c::mTRIm():
2773 #. return result | (av == &main_arena ? sYSTRIm (pad, av) : 0);
2775 #: build/C/man3/malloc_trim.3:78
2776 msgid "This function releases only memory in the main arena."
2780 #: build/C/man3/malloc_trim.3:82
2781 msgid "B<sbrk>(2), B<malloc>(3), B<mallopt>(3)"
2785 #: build/C/man3/malloc_usable_size.3:25
2787 msgid "MALLOC_USABLE_SIZE"
2791 #: build/C/man3/malloc_usable_size.3:28
2792 msgid "malloc_usable_size - obtain size of block of memory allocated from heap"
2796 #: build/C/man3/malloc_usable_size.3:32
2797 msgid "B<size_t malloc_usable_size (void *>I<ptr>B<);>"
2801 #: build/C/man3/malloc_usable_size.3:40
2803 "The B<malloc_usable_size>() function returns the number of usable bytes in "
2804 "the block pointed to by I<ptr>, a pointer to a block of memory allocated by "
2805 "B<malloc>(3) or a related function."
2809 #: build/C/man3/malloc_usable_size.3:48
2811 "B<malloc_usable_size>() returns the number of usable bytes in the block of "
2812 "allocated memory pointed to by I<ptr>. If I<ptr> is NULL, 0 is returned."
2816 #: build/C/man3/malloc_usable_size.3:53
2817 msgid "The B<malloc_usable_size>() function is thread-safe."
2821 #: build/C/man3/malloc_usable_size.3:65
2823 "The value returned by B<malloc_usable_size>() may be greater than the "
2824 "requested size of the allocation because of alignment and minimum size "
2825 "constraints. Although the excess bytes can be overwritten by the "
2826 "application without ill effects, this is not good programming practice: the "
2827 "number of excess bytes in an allocation depends on the underlying "
2832 #: build/C/man3/malloc_usable_size.3:67
2833 msgid "The main use of this function is for debugging and introspection."
2837 #: build/C/man3/malloc_usable_size.3:69
2838 msgid "B<malloc>(3)"
2842 #: build/C/man3/mallopt.3:26
2848 #: build/C/man3/mallopt.3:26 build/C/man2/shmop.2:41
2854 #: build/C/man3/mallopt.3:29
2855 msgid "mallopt - set memory allocation parameters"
2859 #: build/C/man3/mallopt.3:33
2860 msgid "B<int mallopt(int >I<param>B<, int >I<value>B<);>"
2864 #: build/C/man3/mallopt.3:44
2866 "The B<mallopt>() function adjusts parameters that control the behavior of "
2867 "the memory-allocation functions (see B<malloc>(3)). The I<param> argument "
2868 "specifies the parameter to be modified, and I<value> specifies the new value "
2869 "for that parameter."
2873 #: build/C/man3/mallopt.3:47
2874 msgid "The following values can be specified for I<param>:"
2878 #: build/C/man3/mallopt.3:47
2880 msgid "B<M_CHECK_ACTION>"
2884 #: build/C/man3/mallopt.3:53
2886 "Setting this parameter controls how glibc responds when various kinds of "
2887 "programming errors are detected (e.g., freeing the same pointer twice). The "
2888 "3 least significant bits (2, 1, and 0) of the value assigned to this "
2889 "parameter determine the glibc behavior, as follows:"
2893 #: build/C/man3/mallopt.3:54
2899 #: build/C/man3/mallopt.3:64
2901 "If this bit is set, then print a one-line message on I<stderr> that provides "
2902 "details about the error. The message starts with the string \"***\\ glibc "
2903 "detected\\ ***\", followed by the program name, the name of the "
2904 "memory-allocation function in which the error was detected, a brief "
2905 "description of the error, and the memory address where the error was "
2910 #: build/C/man3/mallopt.3:64
2916 #: build/C/man3/mallopt.3:79
2918 "If this bit is set, then, after printing any error message specified by bit "
2919 "0, the program is terminated by calling B<abort>(3). In glibc versions "
2920 "since 2.4, if bit 0 is also set, then, between printing the error message "
2921 "and aborting, the program also prints a stack trace in the manner of "
2922 "B<backtrace>(3), and prints the process's memory mapping in the style of "
2923 "I</proc/[pid]/maps> (see B<proc>(5))."
2927 #: build/C/man3/mallopt.3:79
2929 msgid "Bit 2 (since glibc 2.4)"
2933 #: build/C/man3/mallopt.3:86
2935 "This bit has an effect only if bit 0 is also set. If this bit is set, then "
2936 "the one-line message describing the error is simplified to contain just the "
2937 "name of the function where the error was detected and the brief description "
2942 #: build/C/man3/mallopt.3:91
2943 msgid "The remaining bits in I<value> are ignored."
2947 #: build/C/man3/mallopt.3:95
2949 "Combining the above details, the following numeric values are meaningful for "
2950 "B<M_CHECK_ACTION>:"
2954 #: build/C/man3/mallopt.3:96
2960 #: build/C/man3/mallopt.3:98
2961 msgid "Ignore error conditions; continue execution (with undefined results)."
2965 #: build/C/man3/mallopt.3:98
2971 #: build/C/man3/mallopt.3:100
2972 msgid "Print a detailed error message and continue execution."
2976 #: build/C/man3/mallopt.3:100
2982 #: build/C/man3/mallopt.3:102
2983 msgid "Abort the program."
2987 #: build/C/man3/mallopt.3:102
2993 #: build/C/man3/mallopt.3:105
2995 "Print detailed error message, stack trace, and memory mappings, and abort "
3000 #: build/C/man3/mallopt.3:105
3006 #: build/C/man3/mallopt.3:107
3007 msgid "Print a simple error message and continue execution."
3011 #: build/C/man3/mallopt.3:107
3017 #: build/C/man3/mallopt.3:110
3019 "Print simple error message, stack trace, and memory mappings, and abort the "
3024 #: build/C/man3/mallopt.3:116
3026 "Since glibc 2.3.4, the default value for the B<M_CHECK_ACTION> parameter is "
3027 "3. In glibc version 2.3.3 and earlier, the default value is 1."
3031 #: build/C/man3/mallopt.3:121
3033 "Using a nonzero B<M_CHECK_ACTION> value can be useful because otherwise a "
3034 "crash may happen much later, and the true cause of the problem is then very "
3035 "hard to track down."
3039 #: build/C/man3/mallopt.3:121
3041 msgid "B<M_MMAP_MAX>"
3044 #. The following text adapted from comments in the glibc source:
3046 #: build/C/man3/mallopt.3:131
3048 "This parameter specifies the maximum number of allocation requests that may "
3049 "be simultaneously serviced using B<mmap>(2). This parameter exists because "
3050 "some systems have a limited number of internal tables for use by B<mmap>(2), "
3051 "and using more than a few of them may degrade performance."
3055 #: build/C/man3/mallopt.3:138
3057 "The default value is 65,536, a value which has no special significance and "
3058 "which servers only as a safeguard. Setting this parameter to 0 disables the "
3059 "use of B<mmap>(2) for servicing large allocation requests."
3063 #: build/C/man3/mallopt.3:138
3065 msgid "B<M_MMAP_THRESHOLD>"
3069 #: build/C/man3/mallopt.3:147
3071 "For allocations greater than or equal to the limit specified (in bytes) by "
3072 "B<M_MMAP_THRESHOLD> that can't be satisfied from the free list, the "
3073 "memory-allocation functions employ B<mmap>(2) instead of increasing the "
3074 "program break using B<sbrk>(2)."
3078 #: build/C/man3/mallopt.3:167
3080 "Allocating memory using B<mmap>(2) has the significant advantage that the "
3081 "allocated memory blocks can always be independently released back to the "
3082 "system. (By contrast, the heap can be trimmed only if memory is freed at "
3083 "the top end.) On the other hand, there are some disadvantages to the use of "
3084 "B<mmap>(2): deallocated space is not placed on the free list for reuse by "
3085 "later allocations; memory may be wasted because B<mmap>(2) allocations must "
3086 "be page-aligned; and the kernel must perform the expensive task of zeroing "
3087 "out memory allocated via B<mmap>(2). Balancing these factors leads to a "
3088 "default setting of 128*1024 for the B<M_MMAP_THRESHOLD> parameter."
3092 #: build/C/man3/mallopt.3:174
3094 "The lower limit for this parameter is 0. The upper limit is "
3095 "B<DEFAULT_MMAP_THRESHOLD_MAX>: 512*1024 on 32-bit systems or "
3096 "I<4*1024*1024*sizeof(long)> on 64-bit systems."
3100 #: build/C/man3/mallopt.3:192
3102 "I<Note:> Nowadays, glibc uses a dynamic mmap threshold by default. The "
3103 "initial value of the threshold is 128*1024, but when blocks larger than the "
3104 "current threshold and less than or equal to B<DEFAULT_MMAP_THRESHOLD_MAX> "
3105 "are freed, the threshold is adjusted upward to the size of the freed block. "
3106 "When dynamic mmap thresholding is in effect, the threshold for trimming the "
3107 "heap is also dynamically adjusted to be twice the dynamic mmap threshold. "
3108 "Dynamic adjustment of the mmap threshold is disabled if any of the "
3109 "B<M_TRIM_THRESHOLD>, B<M_TOP_PAD>, B<M_MMAP_THRESHOLD>, or B<M_MMAP_MAX> "
3110 "parameters is set."
3114 #: build/C/man3/mallopt.3:192
3116 msgid "B<M_MXFAST> (since glibc 2.3)"
3119 #. The following text adapted from comments in the glibc sources:
3121 #: build/C/man3/mallopt.3:212
3123 "Set the upper limit for memory allocation requests that are satisfied using "
3124 "\"fastbins\". (The measurement unit for this parameter is bytes.) Fastbins "
3125 "are storage areas that hold deallocated blocks of memory of the same size "
3126 "without merging adjacent free blocks. Subsequent reallocation of blocks of "
3127 "the same size can be handled very quickly by allocating from the fastbin, "
3128 "although memory fragmentation and the overall memory footprint of the "
3129 "program can increase. The default value for this parameter is "
3130 "I<64*sizeof(size_t)/4> (i.e., 64 on 32-bit architectures). The range for "
3131 "this parameter is 0 to I<80*sizeof(size_t)/4>. Setting B<M_MXFAST> to 0 "
3132 "disables the use of fastbins."
3136 #: build/C/man3/mallopt.3:212
3138 msgid "B<M_PERTURB> (since glibc 2.4)"
3142 #: build/C/man3/mallopt.3:227
3144 "If this parameter is set to a nonzero value, then bytes of allocated memory "
3145 "(other than allocations via B<calloc>(3)) are initialized to the complement "
3146 "of the value in the least significant byte of I<value>, and when allocated "
3147 "memory is released using B<free>(3), the freed bytes are set to the least "
3148 "significant byte of I<value>. This can be useful for detecting errors where "
3149 "programs incorrectly rely on allocated memory being initialized to zero, or "
3150 "reuse values in memory that has already been freed."
3154 #: build/C/man3/mallopt.3:227
3156 msgid "B<M_TOP_PAD>"
3160 #: build/C/man3/mallopt.3:234
3162 "This parameter defines the amount of padding to employ when calling "
3163 "B<sbrk>(2) to modify the program break. (The measurement unit for this "
3164 "parameter is bytes.) This parameter has an effect in the following "
3169 #: build/C/man3/mallopt.3:241
3171 "When the program break is increased, then B<M_TOP_PAD> bytes are added to "
3172 "the B<sbrk>(2) request."
3176 #: build/C/man3/mallopt.3:247
3178 "When the heap is trimmed as a consequence of calling B<free>(3) (see the "
3179 "discussion of B<M_TRIM_THRESHOLD>) this much free space is preserved at the "
3184 #: build/C/man3/mallopt.3:251
3186 "In either case, the amount of padding is always rounded to a system page "
3191 #: build/C/man3/mallopt.3:258
3193 "Modifying B<M_TOP_PAD> is a trade-off between increasing the number of "
3194 "system calls (when the parameter is set low) and wasting unused memory at "
3195 "the top of the heap (when the parameter is set high)."
3198 #. DEFAULT_TOP_PAD in glibc source
3200 #: build/C/man3/mallopt.3:261
3201 msgid "The default value for this parameter is 128*1024."
3205 #: build/C/man3/mallopt.3:261
3207 msgid "B<M_TRIM_THRESHOLD>"
3211 #: build/C/man3/mallopt.3:277
3213 "When the amount of contiguous free memory at the top of the heap grows "
3214 "sufficiently large, B<free>(3) employs B<sbrk>(2) to release this memory "
3215 "back to the system. (This can be useful in programs that continue to "
3216 "execute for a long period after freeing a significant amount of memory.) "
3217 "The B<M_TRIM_THRESHOLD> parameter specifies the minimum size (in bytes) that "
3218 "this block of memory must reach before B<sbrk>(2) is used to trim the heap."
3222 #: build/C/man3/mallopt.3:282
3224 "The default value for this parameter is 128*1024. Setting "
3225 "B<M_TRIM_THRESHOLD> to -1 disables trimming completely."
3228 #. FIXME Do the arena parameters need to be documented?
3230 #. .BR M_ARENA_TEST " (since glibc 2.10)"
3232 #. .BR M_ARENA_MAX " (since glibc 2.10)"
3234 #. Environment variables
3235 #. MALLOC_ARENA_MAX_
3236 #. MALLOC_ARENA_TEST_
3238 #. http://udrepper.livejournal.com/20948.html describes some details
3239 #. of the MALLOC_ARENA_* environment variables.
3241 #. These macros aren't enabled in production releases until 2.15?
3242 #. (see glibc malloc/Makefile)
3244 #: build/C/man3/mallopt.3:305
3246 "Modifying B<M_TRIM_THRESHOLD> is a trade-off between increasing the number "
3247 "of system calls (when the parameter is set low) and wasting unused memory "
3248 "at the top of the heap (when the parameter is set high)."
3252 #: build/C/man3/mallopt.3:305
3254 msgid "Environment variables"
3258 #: build/C/man3/mallopt.3:320
3260 "A number of environment variables can be defined to modify some of the same "
3261 "parameters as are controlled by B<mallopt>(). Using these variables has the "
3262 "advantage that the source code of the program need not be changed. To be "
3263 "effective, these variables must be defined before the first call to a "
3264 "memory-allocation function. (If the same parameters are adjusted via "
3265 "B<mallopt>(), then the B<mallopt>() settings take precedence.) For "
3266 "security reasons, these variables are ignored in set-user-ID and "
3267 "set-group-ID programs."
3271 #: build/C/man3/mallopt.3:323
3273 "The environment variables are as follows (note the trailing underscore at "
3274 "the end of the name of each variable):"
3278 #: build/C/man3/mallopt.3:323
3280 msgid "B<MALLOC_CHECK_>"
3283 #. On glibc 2.12/x86, a simple malloc()+free() loop is about 70% slower
3284 #. when MALLOC_CHECK_ was set.
3286 #: build/C/man3/mallopt.3:340
3288 "This environment variable controls the same parameter as B<mallopt>() "
3289 "B<M_CHECK_ACTION>. If this variable is set to a nonzero value, then a "
3290 "special implementation of the memory-allocation functions is used. (This is "
3291 "accomplished using the B<malloc_hook>(3) feature.) This implementation "
3292 "performs additional error checking, but is slower than the standard set of "
3293 "memory-allocation functions. (This implementation does not detect all "
3294 "possible errors; memory leaks can still occur.)"
3298 #: build/C/man3/mallopt.3:345
3300 "The value assigned to this environment variable should be a single digit, "
3301 "whose meaning is as described for B<M_CHECK_ACTION>. Any characters beyond "
3302 "the initial digit are ignored."
3306 #: build/C/man3/mallopt.3:354
3308 "For security reasons, the effect of B<MALLOC_CHECK_> is disabled by default "
3309 "for set-user-ID and set-group-ID programs. However, if the file "
3310 "I</etc/suid-debug> exists (the content of the file is irrelevant), then "
3311 "B<MALLOC_CHECK_> also has an effect for set-user-ID and set-group-ID "
3316 #: build/C/man3/mallopt.3:354
3318 msgid "B<MALLOC_MMAP_MAX_>"
3322 #: build/C/man3/mallopt.3:359
3323 msgid "Controls the same parameter as B<mallopt>() B<M_MMAP_MAX>."
3327 #: build/C/man3/mallopt.3:359
3329 msgid "B<MALLOC_MMAP_THRESHOLD_>"
3333 #: build/C/man3/mallopt.3:364
3334 msgid "Controls the same parameter as B<mallopt>() B<M_MMAP_THRESHOLD>."
3338 #: build/C/man3/mallopt.3:364
3340 msgid "B<MALLOC_PERTURB_>"
3344 #: build/C/man3/mallopt.3:369
3345 msgid "Controls the same parameter as B<mallopt>() B<M_PERTURB>."
3349 #: build/C/man3/mallopt.3:369
3351 msgid "B<MALLOC_TRIM_THRESHOLD_>"
3355 #: build/C/man3/mallopt.3:374
3356 msgid "Controls the same parameter as B<mallopt>() B<M_TRIM_THRESHOLD>."
3360 #: build/C/man3/mallopt.3:374
3362 msgid "B<MALLOC_TOP_PAD_>"
3366 #: build/C/man3/mallopt.3:379
3367 msgid "Controls the same parameter as B<mallopt>() B<M_TOP_PAD>."
3371 #: build/C/man3/mallopt.3:384
3372 msgid "On success, B<mallopt>() returns 1. On error, it returns 0."
3376 #. Available already in glibc 2.0, possibly earlier
3378 #: build/C/man3/mallopt.3:392
3379 msgid "On error, I<errno> is I<not> set."
3384 #: build/C/man3/mallopt.3:406
3386 "This function is not specified by POSIX or the C standards. A similar "
3387 "function exists on many System V derivatives, but the range of values for "
3388 "I<param> varies across systems. The SVID defined options B<M_MXFAST>, "
3389 "B<M_NLBLKS>, B<M_GRAIN>, and B<M_KEEP>, but only the first of these is "
3390 "implemented in glibc."
3394 #: build/C/man3/mallopt.3:410
3395 msgid "Specifying an invalid value for I<param> does not generate an error."
3398 #. FIXME . This looks buggy:
3399 #. setting the M_MXFAST limit rounds up: (s + SIZE_SZ) & ~MALLOC_ALIGN_MASK)
3400 #. malloc requests are rounded up:
3401 #. (req) + SIZE_SZ + MALLOC_ALIGN_MASK) & ~MALLOC_ALIGN_MASK
3402 #. http://sources.redhat.com/bugzilla/show_bug.cgi?id=12129
3404 #: build/C/man3/mallopt.3:418
3406 "A calculation error within the glibc implementation means that a call of the "
3411 #: build/C/man3/mallopt.3:421
3413 msgid " mallopt(M_MXFAST, n)\n"
3416 #. Bins are multiples of 2 * sizeof(size_t) + sizeof(size_t)
3418 #: build/C/man3/mallopt.3:433
3420 "does not result in fastbins being employed for all allocations of size up to "
3421 "I<n>. To ensure desired results, I<n> should be rounded up to the next "
3422 "multiple greater than or equal to I<(2k+1)*sizeof(size_t)>, where I<k> is an "
3426 #. FIXME . http://sources.redhat.com/bugzilla/show_bug.cgi?id=12140
3428 #: build/C/man3/mallopt.3:454
3430 "If B<mallopt>() is used to set B<M_PERTURB>, then, as expected, the bytes "
3431 "of allocated memory are initialized to the complement of the byte in "
3432 "I<value>, and when that memory is freed, the bytes of the region are "
3433 "initialized to the byte specified in I<value>. However, there is an "
3434 "off-by-I<sizeof(size_t)> error in the implementation: instead of "
3435 "initializing precisely the block of memory being freed by the call "
3436 "I<free(p)>, the block starting at I<p+sizeof(size_t)> is initialized."
3440 #: build/C/man3/mallopt.3:463
3442 "The program below demonstrates the use of B<M_CHECK_ACTION>. If the program "
3443 "is supplied with an (integer) command-line argument, then that argument is "
3444 "used to set the B<M_CHECK_ACTION> parameter. The program then allocates a "
3445 "block of memory, and frees it twice (an error)."
3449 #: build/C/man3/mallopt.3:467
3451 "The following shell session shows what happens when we run this program "
3452 "under glibc, with the default value for B<M_CHECK_ACTION>:"
3456 #: build/C/man3/mallopt.3:487
3460 "main(): returned from first free() call\n"
3461 "*** glibc detected *** ./a.out: double free or corruption (top): 0x09d30008 "
3463 "======= Backtrace: =========\n"
3464 "/lib/libc.so.6(+0x6c501)[0x523501]\n"
3465 "/lib/libc.so.6(+0x6dd70)[0x524d70]\n"
3466 "/lib/libc.so.6(cfree+0x6d)[0x527e5d]\n"
3467 "\\&./a.out[0x80485db]\n"
3468 "/lib/libc.so.6(__libc_start_main+0xe7)[0x4cdce7]\n"
3469 "\\&./a.out[0x8048471]\n"
3470 "======= Memory map: ========\n"
3471 "001e4000-001fe000 r-xp 00000000 08:06 1083555 /lib/libgcc_s.so.1\n"
3472 "001fe000-001ff000 r--p 00019000 08:06 1083555 /lib/libgcc_s.so.1\n"
3473 "[some lines omitted]\n"
3474 "b7814000-b7817000 rw-p 00000000 00:00 0\n"
3475 "bff53000-bff74000 rw-p 00000000 00:00 0 [stack]\n"
3476 "Aborted (core dumped)\n"
3480 #: build/C/man3/mallopt.3:492
3482 "The following runs show the results when employing other values for "
3483 "B<M_CHECK_ACTION>:"
3487 #: build/C/man3/mallopt.3:505
3490 "$ B<./a.out 1> # Diagnose error and continue\n"
3491 "main(): returned from first free() call\n"
3492 "*** glibc detected *** ./a.out: double free or corruption (top): 0x09cbe008 "
3494 "main(): returned from second free() call\n"
3495 "$ B<./a.out 2> # Abort without error message\n"
3496 "main(): returned from first free() call\n"
3497 "Aborted (core dumped)\n"
3498 "$ B<./a.out 0> # Ignore error and continue\n"
3499 "main(): returned from first free() call\n"
3500 "main(): returned from second free() call\n"
3504 #: build/C/man3/mallopt.3:511
3506 "The next run shows how to set the same parameter using the B<MALLOC_CHECK_> "
3507 "environment variable:"
3511 #: build/C/man3/mallopt.3:518
3514 "$ B<MALLOC_CHECK_=1 ./a.out>\n"
3515 "main(): returned from first free() call\n"
3516 "*** glibc detected *** ./a.out: free(): invalid pointer: 0x092c2008 ***\n"
3517 "main(): returned from second free() call\n"
3521 #: build/C/man3/mallopt.3:526
3524 "#include E<lt>malloc.hE<gt>\n"
3525 "#include E<lt>stdio.hE<gt>\n"
3526 "#include E<lt>stdlib.hE<gt>\n"
3530 #: build/C/man3/mallopt.3:531 build/C/man3/mcheck.3:187
3534 "main(int argc, char *argv[])\n"
3540 #: build/C/man3/mallopt.3:538
3543 " if (argc E<gt> 1) {\n"
3544 " if (mallopt(M_CHECK_ACTION, atoi(argv[1])) != 1) {\n"
3545 " fprintf(stderr, \"mallopt() failed\");\n"
3546 " exit(EXIT_FAILURE);\n"
3552 #: build/C/man3/mallopt.3:544
3555 " p = malloc(1000);\n"
3556 " if (p == NULL) {\n"
3557 " fprintf(stderr, \"malloc() failed\");\n"
3558 " exit(EXIT_FAILURE);\n"
3563 #: build/C/man3/mallopt.3:547
3567 " printf(\"main(): returned from first free() call\\en\");\n"
3571 #: build/C/man3/mallopt.3:550
3575 " printf(\"main(): returned from second free() call\\en\");\n"
3579 #: build/C/man3/mallopt.3:568
3581 "B<mmap>(2), B<sbrk>(2), B<mallinfo>(3), B<malloc>(3), B<malloc_hook>(3), "
3582 "B<malloc_info>(3), B<malloc_stats>(3), B<malloc_trim>(3), B<mcheck>(3), "
3583 "B<mtrace>(3), B<posix_memalign>(3)"
3587 #: build/C/man3/mcheck.3:25
3593 #: build/C/man3/mcheck.3:25
3599 #: build/C/man3/mcheck.3:28
3601 "mcheck, mcheck_check_all, mcheck_pedantic, mprobe - heap consistency "
3606 #: build/C/man3/mcheck.3:31
3608 msgid "B<#include E<lt>mcheck.hE<gt>>\n"
3612 #: build/C/man3/mcheck.3:33
3614 msgid "B<int mcheck(void (*>I<abortfunc>B<)(enum mcheck_status >I<mstatus>B<));>\n"
3618 #: build/C/man3/mcheck.3:35
3621 "B<int mcheck_pedantic(void (*>I<abortfunc>B<)(enum mcheck_status "
3622 ">I<mstatus>B<));>\n"
3626 #: build/C/man3/mcheck.3:37
3628 msgid "B<void mcheck_check_all(void);>\n"
3632 #: build/C/man3/mcheck.3:39
3634 msgid "B<enum mcheck_status mprobe(void *>I<ptr>B<);>\n"
3638 #: build/C/man3/mcheck.3:51
3640 "The B<mcheck>() function installs a set of debugging hooks for the "
3641 "B<malloc>(3) family of memory-allocation functions. These hooks cause "
3642 "certain consistency checks to be performed on the state of the heap. The "
3643 "checks can detect application errors such as freeing a block of memory more "
3644 "than once or corrupting the bookkeeping data structures that immediately "
3645 "precede a block of allocated memory."
3649 #: build/C/man3/mcheck.3:63
3651 "To be effective, the B<mcheck>() function must be called before the first "
3652 "call to B<malloc>(3) or a related function. In cases where this is "
3653 "difficult to ensure, linking the program with I<-lmcheck> inserts an "
3654 "implicit call to B<mcheck>() (with a NULL argument) before the first call "
3655 "to a memory-allocation function."
3659 #: build/C/man3/mcheck.3:71
3661 "The B<mcheck_pedantic>() function is similar to B<mcheck>(), but performs "
3662 "checks on all allocated blocks whenever one of the memory-allocation "
3663 "functions is called. This can be very slow!"
3667 #: build/C/man3/mcheck.3:78
3669 "The B<mcheck_check_all>() function causes an immediate check on all "
3670 "allocated blocks. This call is effective only if B<mcheck>() is called "
3675 #: build/C/man3/mcheck.3:91
3677 "If the system detects an inconsistency in the heap, the caller-supplied "
3678 "function pointed to by I<abortfunc> is invoked with a single argument "
3679 "argument, I<mstatus>, that indicates what type of inconsistency was "
3680 "detected. If I<abortfunc> is NULL, a default function prints an error "
3681 "message on I<stderr> and calls B<abort>(3)."
3685 #: build/C/man3/mcheck.3:103
3687 "The B<mprobe>() function performs a consistency check on the block of "
3688 "allocated memory pointed to by I<ptr>. The B<mcheck>() function should be "
3689 "called beforehand (otherwise B<mprobe>() returns B<MCHECK_DISABLED>)."
3693 #: build/C/man3/mcheck.3:111
3695 "The following list describes the values returned by B<mprobe>() or passed "
3696 "as the I<mstatus> argument when I<abortfunc> is invoked:"
3700 #: build/C/man3/mcheck.3:111
3702 msgid "B<MCHECK_DISABLED> (B<mprobe>() only)"
3706 #: build/C/man3/mcheck.3:116
3708 "B<mcheck>() was not called before the first memory allocation function was "
3709 "called. Consistency checking is not possible."
3713 #: build/C/man3/mcheck.3:116
3715 msgid "B<MCHECK_OK> (B<mprobe>() only)"
3719 #: build/C/man3/mcheck.3:119
3720 msgid "No inconsistency detected."
3724 #: build/C/man3/mcheck.3:119
3726 msgid "B<MCHECK_HEAD>"
3730 #: build/C/man3/mcheck.3:122
3731 msgid "Memory preceding an allocated block was clobbered."
3735 #: build/C/man3/mcheck.3:122
3737 msgid "B<MCHECK_TAIL>"
3741 #: build/C/man3/mcheck.3:125
3742 msgid "Memory following an allocated block was clobbered."
3746 #: build/C/man3/mcheck.3:125
3748 msgid "B<MCHECK_FREE>"
3752 #: build/C/man3/mcheck.3:129
3753 msgid "A block of memory was freed twice."
3757 #: build/C/man3/mcheck.3:134
3758 msgid "B<mcheck>() and B<mcheck_pedantic>() return 0 on success, or -1 on error."
3762 #: build/C/man3/mcheck.3:145
3764 "The B<mcheck_pedantic>() and B<mcheck_check_all>() functions are available "
3765 "since glibc 2.2. The B<mcheck>() and B<mprobe>() functions are present "
3766 "since at least glibc 2.0"
3769 #. But is MALLOC_CHECK_ slower?
3771 #: build/C/man3/mcheck.3:159
3773 "Linking a program with I<-lmcheck> and using the B<MALLOC_CHECK_> "
3774 "environment variable (described in B<mallopt>(3)) cause the same kinds of "
3775 "errors to be detected. But, using B<MALLOC_CHECK_> does not require the "
3776 "application to be relinked."
3780 #: build/C/man3/mcheck.3:165
3782 "The program below calls B<mcheck>() with a NULL argument and then frees the "
3783 "same block of memory twice. The following shell session demonstrates what "
3784 "happens when running the program:"
3788 #: build/C/man3/mcheck.3:170
3796 #: build/C/man3/mcheck.3:174
3799 "About to free a second time\n"
3800 "block freed twice\n"
3801 "Aborted (core dumped)\n"
3805 #: build/C/man3/mcheck.3:182
3808 "#include E<lt>stdlib.hE<gt>\n"
3809 "#include E<lt>stdio.hE<gt>\n"
3810 "#include E<lt>mcheck.hE<gt>\n"
3814 #: build/C/man3/mcheck.3:190
3817 " if (mcheck(NULL) != 0) {\n"
3818 " fprintf(stderr, \"mcheck() failed\\en\");\n"
3822 #: build/C/man3/mcheck.3:193
3825 " exit(EXIT_FAILURE);\n"
3830 #: build/C/man3/mcheck.3:195
3832 msgid " p = malloc(1000);\n"
3836 #: build/C/man3/mcheck.3:200
3839 " fprintf(stderr, \"About to free\\en\");\n"
3841 " fprintf(stderr, \"\\enAbout to free a second time\\en\");\n"
3846 #: build/C/man3/mcheck.3:208
3847 msgid "B<malloc>(3), B<mallopt>(3), B<mtrace>(3)"
3851 #: build/C/man2/mlock.2:26
3857 #: build/C/man2/mlock.2:26
3863 #: build/C/man2/mlock.2:29
3864 msgid "mlock, munlock, mlockall, munlockall - lock and unlock memory"
3868 #: build/C/man2/mlock.2:32 build/C/man2/mmap.2:46 build/C/man2/mmap2.2:35 build/C/man2/mprotect.2:45 build/C/man2/mremap.2:38
3870 msgid "B<#include E<lt>sys/mman.hE<gt>>\n"
3874 #: build/C/man2/mlock.2:35
3877 "B<int mlock(const void *>I<addr>B<, size_t >I<len>B<);>\n"
3878 "B<int munlock(const void *>I<addr>B<, size_t >I<len>B<);>\n"
3882 #: build/C/man2/mlock.2:38
3885 "B<int mlockall(int >I<flags>B<);>\n"
3886 "B<int munlockall(void);>\n"
3890 #: build/C/man2/mlock.2:54
3892 "B<mlock>() and B<mlockall>() respectively lock part or all of the calling "
3893 "process's virtual address space into RAM, preventing that memory from being "
3894 "paged to the swap area. B<munlock>() and B<munlockall>() perform the "
3895 "converse operation, respectively unlocking part or all of the calling "
3896 "process's virtual address space, so that pages in the specified virtual "
3897 "address range may once more to be swapped out if required by the kernel "
3898 "memory manager. Memory locking and unlocking are performed in units of "
3903 #: build/C/man2/mlock.2:54
3905 msgid "mlock() and munlock()"
3909 #: build/C/man2/mlock.2:64
3911 "B<mlock>() locks pages in the address range starting at I<addr> and "
3912 "continuing for I<len> bytes. All pages that contain a part of the specified "
3913 "address range are guaranteed to be resident in RAM when the call returns "
3914 "successfully; the pages are guaranteed to stay in RAM until later unlocked."
3918 #: build/C/man2/mlock.2:73
3920 "B<munlock>() unlocks pages in the address range starting at I<addr> and "
3921 "continuing for I<len> bytes. After this call, all pages that contain a part "
3922 "of the specified memory range can be moved to external swap space again by "
3927 #: build/C/man2/mlock.2:73
3929 msgid "mlockall() and munlockall()"
3933 #: build/C/man2/mlock.2:83
3935 "B<mlockall>() locks all pages mapped into the address space of the calling "
3936 "process. This includes the pages of the code, data and stack segment, as "
3937 "well as shared libraries, user space kernel data, shared memory, and "
3938 "memory-mapped files. All mapped pages are guaranteed to be resident in RAM "
3939 "when the call returns successfully; the pages are guaranteed to stay in RAM "
3940 "until later unlocked."
3944 #: build/C/man2/mlock.2:88
3946 "The I<flags> argument is constructed as the bitwise OR of one or more of the "
3947 "following constants:"
3951 #: build/C/man2/mlock.2:88
3953 msgid "B<MCL_CURRENT>"
3957 #: build/C/man2/mlock.2:92
3959 "Lock all pages which are currently mapped into the address space of the "
3964 #: build/C/man2/mlock.2:92
3966 msgid "B<MCL_FUTURE>"
3970 #: build/C/man2/mlock.2:99
3972 "Lock all pages which will become mapped into the address space of the "
3973 "process in the future. These could be for instance new pages required by a "
3974 "growing heap and stack as well as new memory-mapped files or shared memory "
3979 #: build/C/man2/mlock.2:112
3981 "If B<MCL_FUTURE> has been specified, then a later system call (e.g., "
3982 "B<mmap>(2), B<sbrk>(2), B<malloc>(3)), may fail if it would cause the number "
3983 "of locked bytes to exceed the permitted maximum (see below). In the same "
3984 "circumstances, stack growth may likewise fail: the kernel will deny stack "
3985 "expansion and deliver a B<SIGSEGV> signal to the process."
3989 #: build/C/man2/mlock.2:116
3991 "B<munlockall>() unlocks all pages mapped into the address space of the "
3996 #: build/C/man2/mlock.2:122
3998 "On success these system calls return 0. On error, -1 is returned, I<errno> "
3999 "is set appropriately, and no changes are made to any locks in the address "
4000 "space of the process."
4004 #: build/C/man2/mlock.2:131
4006 "(Linux 2.6.9 and later) the caller had a nonzero B<RLIMIT_MEMLOCK> soft "
4007 "resource limit, but tried to lock more memory than the limit permitted. "
4008 "This limit is not enforced if the process is privileged (B<CAP_IPC_LOCK>)."
4011 #. In the case of mlock(), this check is somewhat buggy: it doesn't
4012 #. take into account whether the to-be-locked range overlaps with
4013 #. already locked pages. Thus, suppose we allocate
4014 #. (num_physpages / 4 + 1) of memory, and lock those pages once using
4015 #. mlock(), and then lock the *same* page range a second time.
4016 #. In the case, the second mlock() call will fail, since the check
4017 #. calculates that the process is trying to lock (num_physpages / 2 + 2)
4018 #. pages, which of course is not true. (MTK, Nov 04, kernel 2.4.28)
4020 #: build/C/man2/mlock.2:143
4022 "(Linux 2.4 and earlier) the calling process tried to lock more than half of "
4026 #. SVr4 documents an additional EAGAIN error code.
4028 #: build/C/man2/mlock.2:149
4030 "The caller is not privileged, but needs privilege (B<CAP_IPC_LOCK>) to "
4031 "perform the requested operation."
4035 #: build/C/man2/mlock.2:154
4036 msgid "For B<mlock>() and B<munlock>():"
4040 #: build/C/man2/mlock.2:157
4041 msgid "Some or all of the specified address range could not be locked."
4045 #: build/C/man2/mlock.2:164
4047 "The result of the addition I<start>+I<len> was less than I<start> (e.g., the "
4048 "addition may have resulted in an overflow)."
4052 #: build/C/man2/mlock.2:169
4053 msgid "(Not on Linux) I<addr> was not a multiple of the page size."
4057 #: build/C/man2/mlock.2:173
4059 "Some of the specified address range does not correspond to mapped pages in "
4060 "the address space of the process."
4064 #: build/C/man2/mlock.2:176
4065 msgid "For B<mlockall>():"
4069 #: build/C/man2/mlock.2:179
4070 msgid "Unknown I<flags> were specified."
4074 #: build/C/man2/mlock.2:182
4075 msgid "For B<munlockall>():"
4079 #: build/C/man2/mlock.2:186
4080 msgid "(Linux 2.6.8 and earlier) The caller was not privileged (B<CAP_IPC_LOCK>)."
4084 #: build/C/man2/mlock.2:188
4085 msgid "POSIX.1-2001, SVr4."
4089 #: build/C/man2/mlock.2:188 build/C/man2/mmap.2:503 build/C/man2/msync.2:105
4091 msgid "AVAILABILITY"
4095 #: build/C/man2/mlock.2:200
4097 "On POSIX systems on which B<mlock>() and B<munlock>() are available, "
4098 "B<_POSIX_MEMLOCK_RANGE> is defined in I<E<lt>unistd.hE<gt>> and the number "
4099 "of bytes in a page can be determined from the constant B<PAGESIZE> (if "
4100 "defined) in I<E<lt>limits.hE<gt>> or by calling I<sysconf(_SC_PAGESIZE)>."
4103 #. POSIX.1-2001: It shall be defined to -1 or 0 or 200112L.
4104 #. -1: unavailable, 0: ask using sysconf().
4105 #. glibc defines it to 1.
4107 #: build/C/man2/mlock.2:213
4109 "On POSIX systems on which B<mlockall>() and B<munlockall>() are available, "
4110 "B<_POSIX_MEMLOCK> is defined in I<E<lt>unistd.hE<gt>> to a value greater "
4111 "than 0. (See also B<sysconf>(3).)"
4115 #: build/C/man2/mlock.2:231
4117 "Memory locking has two main applications: real-time algorithms and "
4118 "high-security data processing. Real-time applications require deterministic "
4119 "timing, and, like scheduling, paging is one major cause of unexpected "
4120 "program execution delays. Real-time applications will usually also switch "
4121 "to a real-time scheduler with B<sched_setscheduler>(2). Cryptographic "
4122 "security software often handles critical bytes like passwords or secret keys "
4123 "as data structures. As a result of paging, these secrets could be "
4124 "transferred onto a persistent swap store medium, where they might be "
4125 "accessible to the enemy long after the security software has erased the "
4126 "secrets in RAM and terminated. (But be aware that the suspend mode on "
4127 "laptops and some desktop computers will save a copy of the system's RAM to "
4128 "disk, regardless of memory locks.)"
4132 #: build/C/man2/mlock.2:244
4134 "Real-time processes that are using B<mlockall>() to prevent delays on page "
4135 "faults should reserve enough locked stack pages before entering the "
4136 "time-critical section, so that no page fault can be caused by function "
4137 "calls. This can be achieved by calling a function that allocates a "
4138 "sufficiently large automatic variable (an array) and writes to the memory "
4139 "occupied by this array in order to touch these stack pages. This way, "
4140 "enough pages will be mapped for the stack and can be locked into RAM. The "
4141 "dummy writes ensure that not even copy-on-write page faults can occur in the "
4146 #: build/C/man2/mlock.2:257
4148 "Memory locks are not inherited by a child created via B<fork>(2) and are "
4149 "automatically removed (unlocked) during an B<execve>(2) or when the process "
4150 "terminates. The B<mlockall>() B<MCL_FUTURE> setting is not inherited by a "
4151 "child created via B<fork>(2) and is cleared during an B<execve>(2)."
4155 #: build/C/man2/mlock.2:261
4157 "The memory lock on an address range is automatically removed if the address "
4158 "range is unmapped via B<munmap>(2)."
4162 #: build/C/man2/mlock.2:274
4164 "Memory locks do not stack, that is, pages which have been locked several "
4165 "times by calls to B<mlock>() or B<mlockall>() will be unlocked by a single "
4166 "call to B<munlock>() for the corresponding range or by B<munlockall>(). "
4167 "Pages which are mapped to several locations or by several processes stay "
4168 "locked into RAM as long as they are locked at least at one location or by at "
4169 "least one process."
4173 #: build/C/man2/mlock.2:285
4175 "Under Linux, B<mlock>() and B<munlock>() automatically round I<addr> down "
4176 "to the nearest page boundary. However, POSIX.1-2001 allows an "
4177 "implementation to require that I<addr> is page aligned, so portable "
4178 "applications should ensure this."
4182 #: build/C/man2/mlock.2:298
4184 "The I<VmLck> field of the Linux-specific I</proc/PID/status> file shows how "
4185 "many kilobytes of memory the process with ID I<PID> has locked using "
4186 "B<mlock>(), B<mlockall>(), and B<mmap>(2) B<MAP_LOCKED>."
4190 #: build/C/man2/mlock.2:298
4192 msgid "Limits and permissions"
4196 #: build/C/man2/mlock.2:305
4198 "In Linux 2.6.8 and earlier, a process must be privileged (B<CAP_IPC_LOCK>) "
4199 "in order to lock memory and the B<RLIMIT_MEMLOCK> soft resource limit "
4200 "defines a limit on how much memory the process may lock."
4204 #: build/C/man2/mlock.2:311
4206 "Since Linux 2.6.9, no limits are placed on the amount of memory that a "
4207 "privileged process can lock and the B<RLIMIT_MEMLOCK> soft resource limit "
4208 "instead defines a limit on how much memory an unprivileged process may lock."
4212 #: build/C/man2/mlock.2:319
4214 "In the 2.4 series Linux kernels up to and including 2.4.17, a bug caused the "
4215 "B<mlockall>() B<MCL_FUTURE> flag to be inherited across a B<fork>(2). This "
4216 "was rectified in kernel 2.4.18."
4219 #. See the following LKML thread:
4220 #. http://marc.theaimsgroup.com/?l=linux-kernel&m=113801392825023&w=2
4221 #. "Rationale for RLIMIT_MEMLOCK"
4224 #: build/C/man2/mlock.2:336
4226 "Since kernel 2.6.9, if a privileged process calls I<mlockall(MCL_FUTURE)> "
4227 "and later drops privileges (loses the B<CAP_IPC_LOCK> capability by, for "
4228 "example, setting its effective UID to a nonzero value), then subsequent "
4229 "memory allocations (e.g., B<mmap>(2), B<brk>(2)) will fail if the "
4230 "B<RLIMIT_MEMLOCK> resource limit is encountered."
4234 #: build/C/man2/mlock.2:343
4236 "B<mmap>(2), B<setrlimit>(2), B<shmctl>(2), B<sysconf>(3), B<proc>(5), "
4237 "B<capabilities>(7)"
4241 #: build/C/man2/mmap.2:40
4247 #: build/C/man2/mmap.2:43
4248 msgid "mmap, munmap - map or unmap files or devices into memory"
4252 #: build/C/man2/mmap.2:51
4255 "B<void *mmap(void *>I<addr>B<, size_t >I<length>B<, int >I<prot>B<, int "
4257 "B< int >I<fd>B<, off_t >I<offset>B<);>\n"
4258 "B<int munmap(void *>I<addr>B<, size_t >I<length>B<);>\n"
4262 #: build/C/man2/mmap.2:54
4263 msgid "See NOTES for information on feature test macro requirements."
4267 #: build/C/man2/mmap.2:63
4269 "B<mmap>() creates a new mapping in the virtual address space of the calling "
4270 "process. The starting address for the new mapping is specified in I<addr>. "
4271 "The I<length> argument specifies the length of the mapping."
4274 #. Before Linux 2.6.24, the address was rounded up to the next page
4275 #. boundary; since 2.6.24, it is rounded down!
4277 #: build/C/man2/mmap.2:77
4279 "If I<addr> is NULL, then the kernel chooses the address at which to create "
4280 "the mapping; this is the most portable method of creating a new mapping. If "
4281 "I<addr> is not NULL, then the kernel takes it as a hint about where to place "
4282 "the mapping; on Linux, the mapping will be created at a nearby page "
4283 "boundary. The address of the new mapping is returned as the result of the "
4288 #: build/C/man2/mmap.2:89
4290 "The contents of a file mapping (as opposed to an anonymous mapping; see "
4291 "B<MAP_ANONYMOUS> below), are initialized using I<length> bytes starting at "
4292 "offset I<offset> in the file (or other object) referred to by the file "
4293 "descriptor I<fd>. I<offset> must be a multiple of the page size as returned "
4294 "by I<sysconf(_SC_PAGE_SIZE)>."
4298 #: build/C/man2/mmap.2:97
4300 "The I<prot> argument describes the desired memory protection of the mapping "
4301 "(and must not conflict with the open mode of the file). It is either "
4302 "B<PROT_NONE> or the bitwise OR of one or more of the following flags:"
4306 #: build/C/man2/mmap.2:97 build/C/man2/mprotect.2:74
4308 msgid "B<PROT_EXEC>"
4312 #: build/C/man2/mmap.2:100
4313 msgid "Pages may be executed."
4317 #: build/C/man2/mmap.2:100 build/C/man2/mprotect.2:68
4319 msgid "B<PROT_READ>"
4323 #: build/C/man2/mmap.2:103
4324 msgid "Pages may be read."
4328 #: build/C/man2/mmap.2:103 build/C/man2/mprotect.2:71
4330 msgid "B<PROT_WRITE>"
4334 #: build/C/man2/mmap.2:106
4335 msgid "Pages may be written."
4339 #: build/C/man2/mmap.2:106 build/C/man2/mprotect.2:65
4341 msgid "B<PROT_NONE>"
4345 #: build/C/man2/mmap.2:109
4346 msgid "Pages may not be accessed."
4350 #: build/C/man2/mmap.2:118
4352 "The I<flags> argument determines whether updates to the mapping are visible "
4353 "to other processes mapping the same region, and whether updates are carried "
4354 "through to the underlying file. This behavior is determined by including "
4355 "exactly one of the following values in I<flags>:"
4359 #: build/C/man2/mmap.2:118
4361 msgid "B<MAP_SHARED>"
4365 #: build/C/man2/mmap.2:128
4367 "Share this mapping. Updates to the mapping are visible to other processes "
4368 "that map this file, and are carried through to the underlying file. The "
4369 "file may not actually be updated until B<msync>(2) or B<munmap>() is "
4374 #: build/C/man2/mmap.2:128
4376 msgid "B<MAP_PRIVATE>"
4380 #: build/C/man2/mmap.2:137
4382 "Create a private copy-on-write mapping. Updates to the mapping are not "
4383 "visible to other processes mapping the same file, and are not carried "
4384 "through to the underlying file. It is unspecified whether changes made to "
4385 "the file after the B<mmap>() call are visible in the mapped region."
4389 #: build/C/man2/mmap.2:139
4390 msgid "Both of these flags are described in POSIX.1-2001."
4394 #: build/C/man2/mmap.2:142
4395 msgid "In addition, zero or more of the following values can be ORed in I<flags>:"
4399 #: build/C/man2/mmap.2:142
4401 msgid "B<MAP_32BIT> (since Linux 2.4.20, 2.6)"
4404 #. See http://lwn.net/Articles/294642 "Tangled up in threads", 19 Aug 08
4406 #: build/C/man2/mmap.2:158
4408 "Put the mapping into the first 2 Gigabytes of the process address space. "
4409 "This flag is supported only on x86-64, for 64-bit programs. It was added to "
4410 "allow thread stacks to be allocated somewhere in the first 2GB of memory, so "
4411 "as to improve context-switch performance on some early 64-bit processors. "
4412 "Modern x86-64 processors no longer have this performance problem, so use of "
4413 "this flag is not required on those systems. The B<MAP_32BIT> flag is "
4414 "ignored when B<MAP_FIXED> is set."
4418 #: build/C/man2/mmap.2:158
4424 #: build/C/man2/mmap.2:163
4425 msgid "Synonym for B<MAP_ANONYMOUS>. Deprecated."
4429 #: build/C/man2/mmap.2:163
4431 msgid "B<MAP_ANONYMOUS>"
4435 #: build/C/man2/mmap.2:185
4437 "The mapping is not backed by any file; its contents are initialized to "
4438 "zero. The I<fd> and I<offset> arguments are ignored; however, some "
4439 "implementations require I<fd> to be -1 if B<MAP_ANONYMOUS> (or B<MAP_ANON>) "
4440 "is specified, and portable applications should ensure this. The use of "
4441 "B<MAP_ANONYMOUS> in conjunction with B<MAP_SHARED> is supported on Linux "
4442 "only since kernel 2.4."
4446 #: build/C/man2/mmap.2:185
4448 msgid "B<MAP_DENYWRITE>"
4451 #. Introduced in 1.1.36, removed in 1.3.24.
4453 #: build/C/man2/mmap.2:193
4455 "This flag is ignored. (Long ago, it signaled that attempts to write to the "
4456 "underlying file should fail with B<ETXTBUSY>. But this was a source of "
4457 "denial-of-service attacks.)"
4461 #: build/C/man2/mmap.2:193
4463 msgid "B<MAP_EXECUTABLE>"
4466 #. Introduced in 1.1.38, removed in 1.3.24. Flag tested in proc_follow_link.
4467 #. (Long ago, it signaled that the underlying file is an executable.
4468 #. However, that information was not really used anywhere.)
4469 #. Linus talked about DOS related to MAP_EXECUTABLE, but he was thinking of
4472 #: build/C/man2/mmap.2:201
4473 msgid "This flag is ignored."
4477 #: build/C/man2/mmap.2:201
4482 #. On some systems, this was required as the opposite of
4483 #. MAP_ANONYMOUS -- mtk, 1 May 2007
4485 #: build/C/man2/mmap.2:207
4486 msgid "Compatibility flag. Ignored."
4490 #: build/C/man2/mmap.2:207
4492 msgid "B<MAP_FIXED>"
4496 #: build/C/man2/mmap.2:225
4498 "Don't interpret I<addr> as a hint: place the mapping at exactly that "
4499 "address. I<addr> must be a multiple of the page size. If the memory region "
4500 "specified by I<addr> and I<len> overlaps pages of any existing mapping(s), "
4501 "then the overlapped part of the existing mapping(s) will be discarded. If "
4502 "the specified address cannot be used, B<mmap>() will fail. Because "
4503 "requiring a fixed address for a mapping is less portable, the use of this "
4504 "option is discouraged."
4508 #: build/C/man2/mmap.2:225
4510 msgid "B<MAP_GROWSDOWN>"
4514 #: build/C/man2/mmap.2:230
4516 "Used for stacks. Indicates to the kernel virtual memory system that the "
4517 "mapping should extend downward in memory."
4521 #: build/C/man2/mmap.2:230
4523 msgid "B<MAP_HUGETLB> (since Linux 2.6.32)"
4527 #: build/C/man2/mmap.2:236
4529 "Allocate the mapping using \"huge pages.\" See the Linux kernel source file "
4530 "I<Documentation/vm/hugetlbpage.txt> for further information."
4534 #: build/C/man2/mmap.2:236
4536 msgid "B<MAP_LOCKED> (since Linux 2.5.37)"
4539 #. If set, the mapped pages will not be swapped out.
4541 #: build/C/man2/mmap.2:242
4543 "Lock the pages of the mapped region into memory in the manner of "
4544 "B<mlock>(2). This flag is ignored in older kernels."
4548 #: build/C/man2/mmap.2:242
4550 msgid "B<MAP_NONBLOCK> (since Linux 2.5.46)"
4554 #: build/C/man2/mmap.2:257
4556 "Only meaningful in conjunction with B<MAP_POPULATE>. Don't perform "
4557 "read-ahead: create page tables entries only for pages that are already "
4558 "present in RAM. Since Linux 2.6.23, this flag causes B<MAP_POPULATE> to do "
4559 "nothing. One day the combination of B<MAP_POPULATE> and B<MAP_NONBLOCK> may "
4564 #: build/C/man2/mmap.2:257
4566 msgid "B<MAP_NORESERVE>"
4570 #: build/C/man2/mmap.2:272
4572 "Do not reserve swap space for this mapping. When swap space is reserved, "
4573 "one has the guarantee that it is possible to modify the mapping. When swap "
4574 "space is not reserved one might get B<SIGSEGV> upon a write if no physical "
4575 "memory is available. See also the discussion of the file "
4576 "I</proc/sys/vm/overcommit_memory> in B<proc>(5). In kernels before 2.6, "
4577 "this flag had effect only for private writable mappings."
4581 #: build/C/man2/mmap.2:272
4583 msgid "B<MAP_POPULATE> (since Linux 2.5.46)"
4587 #: build/C/man2/mmap.2:279
4589 "Populate (prefault) page tables for a mapping. For a file mapping, this "
4590 "causes read-ahead on the file. Later accesses to the mapping will not be "
4591 "blocked by page faults. B<MAP_POPULATE> is supported for private mappings "
4592 "only since Linux 2.6.23."
4596 #: build/C/man2/mmap.2:279
4598 msgid "B<MAP_STACK> (since Linux 2.6.27)"
4601 #. See http://lwn.net/Articles/294642 "Tangled up in threads", 19 Aug 08
4602 #. commit cd98a04a59e2f94fa64d5bf1e26498d27427d5e7
4603 #. http://thread.gmane.org/gmane.linux.kernel/720412
4604 #. "pthread_create() slow for many threads; also time to revisit 64b
4605 #. context switch optimization?"
4607 #: build/C/man2/mmap.2:292
4609 "Allocate the mapping at an address suitable for a process or thread stack. "
4610 "This flag is currently a no-op, but is used in the glibc threading "
4611 "implementation so that if some architectures require special treatment for "
4612 "stack allocations, support can later be transparently implemented for glibc."
4616 #: build/C/man2/mmap.2:292
4618 msgid "B<MAP_UNINITIALIZED> (since Linux 2.6.33)"
4622 #: build/C/man2/mmap.2:302
4624 "Don't clear anonymous pages. This flag is intended to improve performance "
4625 "on embedded devices. This flag is honored only if the kernel was configured "
4626 "with the B<CONFIG_MMAP_ALLOW_UNINITIALIZED> option. Because of the security "
4627 "implications, that option is normally enabled only on embedded devices "
4628 "(i.e., devices where one has complete control of the contents of user "
4633 #: build/C/man2/mmap.2:310
4635 "Of the above flags, only B<MAP_FIXED> is specified in POSIX.1-2001. "
4636 "However, most systems also support B<MAP_ANONYMOUS> (or its synonym "
4641 #: build/C/man2/mmap.2:317
4643 "Some systems document the additional flags B<MAP_AUTOGROW>, "
4644 "B<MAP_AUTORESRV>, B<MAP_COPY>, and B<MAP_LOCAL>."
4648 #: build/C/man2/mmap.2:323
4650 "Memory mapped by B<mmap>() is preserved across B<fork>(2), with the same "
4655 #: build/C/man2/mmap.2:331
4657 "A file is mapped in multiples of the page size. For a file that is not a "
4658 "multiple of the page size, the remaining memory is zeroed when mapped, and "
4659 "writes to that region are not written out to the file. The effect of "
4660 "changing the size of the underlying file of a mapping on the pages that "
4661 "correspond to added or removed regions of the file is unspecified."
4665 #: build/C/man2/mmap.2:331
4671 #: build/C/man2/mmap.2:341
4673 "The B<munmap>() system call deletes the mappings for the specified address "
4674 "range, and causes further references to addresses within the range to "
4675 "generate invalid memory references. The region is also automatically "
4676 "unmapped when the process is terminated. On the other hand, closing the "
4677 "file descriptor does not unmap the region."
4681 #: build/C/man2/mmap.2:351
4683 "The address I<addr> must be a multiple of the page size. All pages "
4684 "containing a part of the indicated range are unmapped, and subsequent "
4685 "references to these pages will generate B<SIGSEGV>. It is not an error if "
4686 "the indicated range does not contain any mapped pages."
4690 #: build/C/man2/mmap.2:351
4692 msgid "Timestamps changes for file-backed mappings"
4696 #: build/C/man2/mmap.2:358
4698 "For file-backed mappings, the I<st_atime> field for the mapped file may be "
4699 "updated at any time between the B<mmap>() and the corresponding unmapping; "
4700 "the first reference to a mapped page will update the field if it has not "
4705 #: build/C/man2/mmap.2:375
4707 "The I<st_ctime> and I<st_mtime> field for a file mapped with B<PROT_WRITE> "
4708 "and B<MAP_SHARED> will be updated after a write to the mapped region, and "
4709 "before a subsequent B<msync>(2) with the B<MS_SYNC> or B<MS_ASYNC> flag, if "
4714 #: build/C/man2/mmap.2:392
4716 "On success, B<mmap>() returns a pointer to the mapped area. On error, the "
4717 "value B<MAP_FAILED> (that is, I<(void\\ *)\\ -1>) is returned, and I<errno> "
4718 "is set appropriately. On success, B<munmap>() returns 0, on failure -1, "
4719 "and I<errno> is set (probably to B<EINVAL>)."
4723 #: build/C/man2/mmap.2:393 build/C/man2/mprotect.2:85 build/C/man3/shm_open.3:187 build/C/man3/shm_open.3:192 build/C/man2/shmctl.2:306 build/C/man2/shmget.2:192 build/C/man2/shmop.2:188
4729 #: build/C/man2/mmap.2:411
4731 "A file descriptor refers to a non-regular file. Or a file mapping was "
4732 "requested, but I<fd> is not open for reading. Or B<MAP_SHARED> was "
4733 "requested and B<PROT_WRITE> is set, but I<fd> is not open in read/write "
4734 "(B<O_RDWR>) mode. Or B<PROT_WRITE> is set, but the file is append-only."
4738 #: build/C/man2/mmap.2:415
4740 "The file has been locked, or too much memory has been locked (see "
4745 #: build/C/man2/mmap.2:421
4746 msgid "I<fd> is not a valid file descriptor (and B<MAP_ANONYMOUS> was not set)."
4750 #: build/C/man2/mmap.2:429
4752 "We don't like I<addr>, I<length>, or I<offset> (e.g., they are too large, or "
4753 "not aligned on a page boundary)."
4757 #: build/C/man2/mmap.2:434
4758 msgid "(since Linux 2.6.12) I<length> was 0."
4762 #: build/C/man2/mmap.2:442
4764 "I<flags> contained neither B<MAP_PRIVATE> or B<MAP_SHARED>, or contained "
4765 "both of these values."
4769 #: build/C/man2/mmap.2:442 build/C/man3/shm_open.3:229 build/C/man2/shmget.2:221 build/C/man2/memfd_create.2:149
4774 #. [2.6.7] shmem_zero_setup()-->shmem_file_setup()-->get_empty_filp()
4776 #: build/C/man2/mmap.2:450 build/C/man2/shmget.2:225
4777 msgid "The system limit on the total number of open files has been reached."
4781 #: build/C/man2/mmap.2:454
4783 "The underlying filesystem of the specified file does not support memory "
4788 #: build/C/man2/mmap.2:458
4790 "No memory is available, or the process's maximum number of mappings would "
4791 "have been exceeded."
4794 #. (Since 2.4.25 / 2.6.0.)
4796 #: build/C/man2/mmap.2:467
4798 "The I<prot> argument asks for B<PROT_EXEC> but the mapped area belongs to a "
4799 "file on a filesystem that was mounted no-exec."
4803 #: build/C/man2/mmap.2:477
4805 "B<MAP_DENYWRITE> was set but the object specified by I<fd> is open for "
4810 #: build/C/man2/mmap.2:477 build/C/man2/shmctl.2:348
4812 msgid "B<EOVERFLOW>"
4816 #: build/C/man2/mmap.2:489
4818 "On 32-bit architecture together with the large file extension (i.e., using "
4819 "64-bit I<off_t>): the number of pages used for I<length> plus number of "
4820 "pages used for I<offset> would overflow I<unsigned long> (32 bits)."
4824 #: build/C/man2/mmap.2:491
4825 msgid "Use of a mapped region can result in these signals:"
4829 #: build/C/man2/mmap.2:491
4835 #: build/C/man2/mmap.2:494
4836 msgid "Attempted write into a region mapped as read-only."
4840 #: build/C/man2/mmap.2:494
4846 #: build/C/man2/mmap.2:499
4848 "Attempted access to a portion of the buffer that does not correspond to the "
4849 "file (for example, beyond the end of the file, including the case where "
4850 "another process has truncated the file)."
4853 #. SVr4 documents additional error codes ENXIO and ENODEV.
4854 #. SUSv2 documents additional error codes EMFILE and EOVERFLOW.
4856 #: build/C/man2/mmap.2:503
4857 msgid "SVr4, 4.4BSD, POSIX.1-2001."
4860 #. POSIX.1-2001: It shall be defined to -1 or 0 or 200112L.
4861 #. -1: unavailable, 0: ask using sysconf().
4862 #. glibc defines it to 1.
4864 #: build/C/man2/mmap.2:517
4866 "On POSIX systems on which B<mmap>(), B<msync>(2), and B<munmap>() are "
4867 "available, B<_POSIX_MAPPED_FILES> is defined in I<E<lt>unistd.hE<gt>> to a "
4868 "value greater than 0. (See also B<sysconf>(3).)"
4872 #: build/C/man2/mmap.2:530
4874 "On some hardware architectures (e.g., i386), B<PROT_WRITE> implies "
4875 "B<PROT_READ>. It is architecture dependent whether B<PROT_READ> implies "
4876 "B<PROT_EXEC> or not. Portable programs should always set B<PROT_EXEC> if "
4877 "they intend to execute code in the new mapping."
4881 #: build/C/man2/mmap.2:545
4883 "The portable way to create a mapping is to specify I<addr> as 0 (NULL), and "
4884 "omit B<MAP_FIXED> from I<flags>. In this case, the system chooses the "
4885 "address for the mapping; the address is chosen so as not to conflict with "
4886 "any existing mapping, and will not be 0. If the B<MAP_FIXED> flag is "
4887 "specified, and I<addr> is 0 (NULL), then the mapped address will be 0 "
4892 #: build/C/man2/mmap.2:575
4894 "Certain I<flags> constants are defined only if either B<_BSD_SOURCE> or "
4895 "B<_SVID_SOURCE> is defined. (Requiring B<_GNU_SOURCE> also suffices, and "
4896 "requiring that macro specifically would have been more logical, since these "
4897 "flags are all Linux-specific.) The relevant flags are: B<MAP_32BIT>, "
4898 "B<MAP_ANONYMOUS> (and the synonym B<MAP_ANON>), B<MAP_DENYWRITE>, "
4899 "B<MAP_EXECUTABLE>, B<MAP_FILE>, B<MAP_GROWSDOWN>, B<MAP_HUGETLB>, "
4900 "B<MAP_LOCKED>, B<MAP_NONBLOCK>, B<MAP_NORESERVE>, B<MAP_POPULATE>, and "
4905 #: build/C/man2/mmap.2:575
4907 msgid "C library/kernel ABI differences"
4910 #. Since around glibc 2.1/2.2, depending on the platform.
4912 #: build/C/man2/mmap.2:590
4914 "This page describes the interface provided by the glibc B<mmap>() wrapper "
4915 "function. Originally, this function invoked a system call of the same "
4916 "name. Since kernel 2.4, that system call has been superseded by "
4917 "B<mmap2>(2), and nowadays the glibc B<mmap>() wrapper function invokes "
4918 "B<mmap2>(2) with a suitably adjusted value for I<offset>."
4922 #: build/C/man2/mmap.2:595
4924 "On Linux there are no guarantees like those suggested above under "
4925 "B<MAP_NORESERVE>. By default, any process can be killed at any moment when "
4926 "the system runs out of memory."
4930 #: build/C/man2/mmap.2:602
4932 "In kernels before 2.6.7, the B<MAP_POPULATE> flag has effect only if I<prot> "
4933 "is specified as B<PROT_NONE>."
4937 #: build/C/man2/mmap.2:617
4939 "SUSv3 specifies that B<mmap>() should fail if I<length> is 0. However, in "
4940 "kernels before 2.6.12, B<mmap>() succeeded in this case: no mapping was "
4941 "created and the call returned I<addr>. Since kernel 2.6.12, B<mmap>() "
4942 "fails with the error B<EINVAL> for this case."
4946 #: build/C/man2/mmap.2:633
4948 "POSIX specifies that the system shall always zero fill any partial page at "
4949 "the end of the object and that system will never write any modification of "
4950 "the object beyond its end. On Linux, when you write data to such partial "
4951 "page after the end of the object, the data stays in the page cache even "
4952 "after the file is closed and unmapped and even though the data is never "
4953 "written to the file itself, subsequent mappings may see the modified "
4954 "content. In some cases, this could be fixed by calling B<msync>(2) before "
4955 "the unmap takes place; however, this doesn't work on tmpfs (for example, "
4956 "when using POSIX shared memory interface documented in B<shm_overview>(7))."
4960 #: build/C/man2/mmap.2:645
4962 "The following program prints part of the file specified in its first "
4963 "command-line argument to standard output. The range of bytes to be printed "
4964 "is specified via offset and length values in the second and third "
4965 "command-line arguments. The program creates a memory mapping of the "
4966 "required pages of the file and then uses B<write>(2) to output the desired "
4971 #: build/C/man2/mmap.2:653
4974 "#include E<lt>sys/mman.hE<gt>\n"
4975 "#include E<lt>sys/stat.hE<gt>\n"
4976 "#include E<lt>fcntl.hE<gt>\n"
4977 "#include E<lt>stdio.hE<gt>\n"
4978 "#include E<lt>stdlib.hE<gt>\n"
4979 "#include E<lt>unistd.hE<gt>\n"
4983 #: build/C/man2/mmap.2:656 build/C/man2/mprotect.2:177
4986 "#define handle_error(msg) \\e\n"
4987 " do { perror(msg); exit(EXIT_FAILURE); } while (0)\n"
4991 #: build/C/man2/mmap.2:666
4995 "main(int argc, char *argv[])\n"
4999 " struct stat sb;\n"
5000 " off_t offset, pa_offset;\n"
5006 #: build/C/man2/mmap.2:671
5009 " if (argc E<lt> 3 || argc E<gt> 4) {\n"
5010 " fprintf(stderr, \"%s file offset [length]\\en\", argv[0]);\n"
5011 " exit(EXIT_FAILURE);\n"
5016 #: build/C/man2/mmap.2:675
5019 " fd = open(argv[1], O_RDONLY);\n"
5021 " handle_error(\"open\");\n"
5025 #: build/C/man2/mmap.2:678
5028 " if (fstat(fd, &sb) == -1) /* To obtain file size */\n"
5029 " handle_error(\"fstat\");\n"
5033 #: build/C/man2/mmap.2:682
5036 " offset = atoi(argv[2]);\n"
5037 " pa_offset = offset & ~(sysconf(_SC_PAGE_SIZE) - 1);\n"
5038 " /* offset for mmap() must be page aligned */\n"
5042 #: build/C/man2/mmap.2:687
5045 " if (offset E<gt>= sb.st_size) {\n"
5046 " fprintf(stderr, \"offset is past end of file\\en\");\n"
5047 " exit(EXIT_FAILURE);\n"
5052 #: build/C/man2/mmap.2:693
5055 " if (argc == 4) {\n"
5056 " length = atoi(argv[3]);\n"
5057 " if (offset + length E<gt> sb.st_size)\n"
5058 " length = sb.st_size - offset;\n"
5059 " /* Can\\(aqt display bytes past end of file */\n"
5063 #: build/C/man2/mmap.2:697
5066 " } else { /* No length arg ==E<gt> display to end of file */\n"
5067 " length = sb.st_size - offset;\n"
5072 #: build/C/man2/mmap.2:702
5075 " addr = mmap(NULL, length + offset - pa_offset, PROT_READ,\n"
5076 " MAP_PRIVATE, fd, pa_offset);\n"
5077 " if (addr == MAP_FAILED)\n"
5078 " handle_error(\"mmap\");\n"
5082 #: build/C/man2/mmap.2:707
5085 " s = write(STDOUT_FILENO, addr + offset - pa_offset, length);\n"
5086 " if (s != length) {\n"
5088 " handle_error(\"write\");\n"
5092 #: build/C/man2/mmap.2:711
5095 " fprintf(stderr, \"partial write\");\n"
5096 " exit(EXIT_FAILURE);\n"
5101 #: build/C/man2/mmap.2:729
5103 "B<getpagesize>(2), B<memfd_create>(2), B<mincore>(2), B<mlock>(2), "
5104 "B<mmap2>(2), B<mprotect>(2), B<mremap>(2), B<msync>(2), "
5105 "B<remap_file_pages>(2), B<setrlimit>(2), B<shmat>(2), B<shm_open>(3), "
5106 "B<shm_overview>(7)"
5110 #: build/C/man2/mmap.2:736
5112 "The descriptions of the following files in B<proc>(5): I</proc/[pid]/maps>, "
5113 "I</proc/[pid]/map_files>, and I</proc/[pid]/smaps>."
5117 #: build/C/man2/mmap.2:741 build/C/man2/msync.2:151
5118 msgid "B.O. Gallmeister, POSIX.4, O'Reilly, pp. 128-129 and 389-391."
5122 #: build/C/man2/mmap2.2:29
5128 #: build/C/man2/mmap2.2:29
5134 #: build/C/man2/mmap2.2:32
5135 msgid "mmap2 - map files or devices into memory"
5139 #: build/C/man2/mmap2.2:38
5142 "B<void *mmap2(void *>I<addr>B<, size_t >I<length>B<, int >I<prot>B<,>\n"
5143 "B< int >I<flags>B<, int >I<fd>B<, off_t >I<pgoffset>B<);>\n"
5147 #: build/C/man2/mmap2.2:43
5149 "This is probably not the system call that you are interested in; instead, "
5150 "see B<mmap>(2), which describes the glibc wrapper function that invokes this "
5155 #: build/C/man2/mmap2.2:54
5157 "The B<mmap2>() system call provides the same interface as B<mmap>(2), "
5158 "except that the final argument specifies the offset into the file in "
5159 "4096-byte units (instead of bytes, as is done by B<mmap>(2)). This enables "
5160 "applications that use a 32-bit I<off_t> to map large files (up to 2^44 "
5165 #: build/C/man2/mmap2.2:61
5167 "On success, B<mmap2>() returns a pointer to the mapped area. On error, -1 "
5168 "is returned and I<errno> is set appropriately."
5172 #: build/C/man2/mmap2.2:65
5173 msgid "Problem with getting the data from user space."
5177 #: build/C/man2/mmap2.2:70
5179 "(Various platforms where the page size is not 4096 bytes.) I<offset\\ *\\ "
5180 "4096> is not a multiple of the system page size."
5184 #: build/C/man2/mmap2.2:74
5185 msgid "B<mmap2>() can also return any of the errors described in B<mmap>(2)."
5189 #: build/C/man2/mmap2.2:77
5190 msgid "B<mmap2>() is available since Linux 2.3.31."
5194 #: build/C/man2/mmap2.2:79 build/C/man2/subpage_prot.2:98
5195 msgid "This system call is Linux-specific."
5199 #: build/C/man2/mmap2.2:86
5201 "On architectures where this system call is present, the glibc B<mmap>() "
5202 "wrapper function invokes this system call rather than the B<mmap>(2) system "
5207 #: build/C/man2/mmap2.2:88
5208 msgid "This system call does not exist on x86-64."
5211 #. ia64 can have page sizes ranging from 4kB to 64kB.
5212 #. On cris, it looks like the unit might also be the page size,
5213 #. which is 8192 bytes. -- mtk, June 2007
5215 #: build/C/man2/mmap2.2:95
5217 "On ia64, the unit for I<offset> is actually the system page size, rather "
5222 #: build/C/man2/mmap2.2:101
5223 msgid "B<getpagesize>(2), B<mmap>(2), B<mremap>(2), B<msync>(2), B<shm_open>(3)"
5227 #: build/C/man2/mprotect.2:39
5233 #: build/C/man2/mprotect.2:39
5239 #: build/C/man2/mprotect.2:42
5240 msgid "mprotect - set protection on a region of memory"
5244 #: build/C/man2/mprotect.2:47
5246 msgid "B<int mprotect(void *>I<addr>B<, size_t >I<len>B<, int >I<prot>B<);>\n"
5250 #: build/C/man2/mprotect.2:55
5252 "B<mprotect>() changes protection for the calling process's memory page(s) "
5253 "containing any part of the address range in the interval [I<addr>,\\ "
5254 "I<addr>+I<len>-1]. I<addr> must be aligned to a page boundary."
5258 #: build/C/man2/mprotect.2:60
5260 "If the calling process tries to access memory in a manner that violates the "
5261 "protection, then the kernel generates a B<SIGSEGV> signal for the process."
5265 #: build/C/man2/mprotect.2:65
5267 "I<prot> is either B<PROT_NONE> or a bitwise-or of the other values in the "
5272 #: build/C/man2/mprotect.2:68
5273 msgid "The memory cannot be accessed at all."
5277 #: build/C/man2/mprotect.2:71
5278 msgid "The memory can be read."
5282 #: build/C/man2/mprotect.2:74
5283 msgid "The memory can be modified."
5287 #: build/C/man2/mprotect.2:77
5288 msgid "The memory can be executed."
5292 #: build/C/man2/mprotect.2:84
5294 "On success, B<mprotect>() returns zero. On error, -1 is returned, and "
5295 "I<errno> is set appropriately."
5299 #: build/C/man2/mprotect.2:94
5301 "The memory cannot be given the specified access. This can happen, for "
5302 "example, if you B<mmap>(2) a file to which you have read-only access, then "
5303 "ask B<mprotect>() to mark it B<PROT_WRITE>."
5306 #. Or: both PROT_GROWSUP and PROT_GROWSDOWN were specified in 'prot'.
5308 #: build/C/man2/mprotect.2:99
5309 msgid "I<addr> is not a valid pointer, or not a multiple of the system page size."
5313 #: build/C/man2/mprotect.2:102
5314 msgid "Internal kernel structures could not be allocated."
5318 #: build/C/man2/mprotect.2:112
5320 "Addresses in the range [I<addr>, I<addr>+I<len>-1] are invalid for the "
5321 "address space of the process, or specify one or more pages that are not "
5322 "mapped. (Before kernel 2.4.19, the error B<EFAULT> was incorrectly produced "
5326 #. SVr4 defines an additional error
5327 #. code EAGAIN. The SVr4 error conditions don't map neatly onto Linux's.
5329 #: build/C/man2/mprotect.2:121
5331 "SVr4, POSIX.1-2001. POSIX says that the behavior of B<mprotect>() is "
5332 "unspecified if it is applied to a region of memory that was not obtained via "
5337 #: build/C/man2/mprotect.2:128
5339 "On Linux it is always permissible to call B<mprotect>() on any address in a "
5340 "process's address space (except for the kernel vsyscall area). In "
5341 "particular it can be used to change existing code mappings to be writable."
5345 #: build/C/man2/mprotect.2:138
5347 "Whether B<PROT_EXEC> has any effect different from B<PROT_READ> is "
5348 "architecture- and kernel version-dependent. On some hardware architectures "
5349 "(e.g., i386), B<PROT_WRITE> implies B<PROT_READ>."
5353 #: build/C/man2/mprotect.2:147
5355 "POSIX.1-2001 says that an implementation may permit access other than that "
5356 "specified in I<prot>, but at a minimum can allow write access only if "
5357 "B<PROT_WRITE> has been set, and must not allow any access if B<PROT_NONE> "
5362 #: build/C/man2/mprotect.2:153
5364 "The program below allocates four pages of memory, makes the third of these "
5365 "pages read-only, and then executes a loop that walks upward through the "
5366 "allocated region modifying bytes."
5370 #: build/C/man2/mprotect.2:156
5371 msgid "An example of what we might see when running the program is the following:"
5375 #: build/C/man2/mprotect.2:162
5379 "Start of region: 0x804c000\n"
5380 "Got SIGSEGV at address: 0x804e000\n"
5384 #: build/C/man2/mprotect.2:174
5387 "#include E<lt>unistd.hE<gt>\n"
5388 "#include E<lt>signal.hE<gt>\n"
5389 "#include E<lt>stdio.hE<gt>\n"
5390 "#include E<lt>malloc.hE<gt>\n"
5391 "#include E<lt>stdlib.hE<gt>\n"
5392 "#include E<lt>errno.hE<gt>\n"
5393 "#include E<lt>sys/mman.hE<gt>\n"
5397 #: build/C/man2/mprotect.2:179
5399 msgid "static char *buffer;\n"
5403 #: build/C/man2/mprotect.2:187
5407 "handler(int sig, siginfo_t *si, void *unused)\n"
5409 " printf(\"Got SIGSEGV at address: 0x%lx\\en\",\n"
5410 " (long) si-E<gt>si_addr);\n"
5411 " exit(EXIT_FAILURE);\n"
5416 #: build/C/man2/mprotect.2:194
5420 "main(int argc, char *argv[])\n"
5424 " struct sigaction sa;\n"
5428 #: build/C/man2/mprotect.2:200
5431 " sa.sa_flags = SA_SIGINFO;\n"
5432 " sigemptyset(&sa.sa_mask);\n"
5433 " sa.sa_sigaction = handler;\n"
5434 " if (sigaction(SIGSEGV, &sa, NULL) == -1)\n"
5435 " handle_error(\"sigaction\");\n"
5439 #: build/C/man2/mprotect.2:204
5442 " pagesize = sysconf(_SC_PAGE_SIZE);\n"
5443 " if (pagesize == -1)\n"
5444 " handle_error(\"sysconf\");\n"
5448 #: build/C/man2/mprotect.2:207
5451 " /* Allocate a buffer aligned on a page boundary;\n"
5452 " initial protection is PROT_READ | PROT_WRITE */\n"
5456 #: build/C/man2/mprotect.2:211
5459 " buffer = memalign(pagesize, 4 * pagesize);\n"
5460 " if (buffer == NULL)\n"
5461 " handle_error(\"memalign\");\n"
5465 #: build/C/man2/mprotect.2:213
5467 msgid " printf(\"Start of region: 0x%lx\\en\", (long) buffer);\n"
5471 #: build/C/man2/mprotect.2:217
5474 " if (mprotect(buffer + pagesize * 2, pagesize,\n"
5475 " PROT_READ) == -1)\n"
5476 " handle_error(\"mprotect\");\n"
5480 #: build/C/man2/mprotect.2:220
5483 " for (p = buffer ; ; )\n"
5484 " *(p++) = \\(aqa\\(aq;\n"
5488 #: build/C/man2/mprotect.2:224
5491 " printf(\"Loop completed\\en\"); /* Should never happen */\n"
5492 " exit(EXIT_SUCCESS);\n"
5497 #: build/C/man2/mprotect.2:228
5498 msgid "B<mmap>(2), B<sysconf>(3)"
5502 #: build/C/man2/mremap.2:30
5508 #: build/C/man2/mremap.2:30
5514 #: build/C/man2/mremap.2:33
5515 msgid "mremap - remap a virtual memory address"
5519 #: build/C/man2/mremap.2:36
5521 msgid "B<#define _GNU_SOURCE> /* See feature_test_macros(7) */\n"
5525 #: build/C/man2/mremap.2:41
5528 "B<void *mremap(void *>I<old_address>B<, size_t >I<old_size>B<,>\n"
5529 "B< size_t >I<new_size>B<, int >I<flags>B<, ... /* void "
5530 "*>I<new_address>B< */);>\n"
5534 #: build/C/man2/mremap.2:47
5536 "B<mremap>() expands (or shrinks) an existing memory mapping, potentially "
5537 "moving it at the same time (controlled by the I<flags> argument and the "
5538 "available virtual address space)."
5542 #: build/C/man2/mremap.2:61
5544 "I<old_address> is the old address of the virtual memory block that you want "
5545 "to expand (or shrink). Note that I<old_address> has to be page aligned. "
5546 "I<old_size> is the old size of the virtual memory block. I<new_size> is the "
5547 "requested size of the virtual memory block after the resize. An optional "
5548 "fifth argument, I<new_address>, may be provided; see the description of "
5549 "B<MREMAP_FIXED> below."
5553 #: build/C/man2/mremap.2:73
5555 "In Linux the memory is divided into pages. A user process has (one or) "
5556 "several linear virtual memory segments. Each virtual memory segment has one "
5557 "or more mappings to real memory pages (in the page table). Each virtual "
5558 "memory segment has its own protection (access rights), which may cause a "
5559 "segmentation violation if the memory is accessed incorrectly (e.g., writing "
5560 "to a read-only segment). Accessing virtual memory outside of the segments "
5561 "will also cause a segmentation violation."
5565 #: build/C/man2/mremap.2:81
5567 "B<mremap>() uses the Linux page table scheme. B<mremap>() changes the "
5568 "mapping between virtual addresses and memory pages. This can be used to "
5569 "implement a very efficient B<realloc>(3)."
5573 #: build/C/man2/mremap.2:83
5574 msgid "The I<flags> bit-mask argument may be 0, or include the following flag:"
5578 #: build/C/man2/mremap.2:83
5580 msgid "B<MREMAP_MAYMOVE>"
5584 #: build/C/man2/mremap.2:95
5586 "By default, if there is not sufficient space to expand a mapping at its "
5587 "current location, then B<mremap>() fails. If this flag is specified, then "
5588 "the kernel is permitted to relocate the mapping to a new virtual address, if "
5589 "necessary. If the mapping is relocated, then absolute pointers into the old "
5590 "mapping location become invalid (offsets relative to the starting address of "
5591 "the mapping should be employed)."
5595 #: build/C/man2/mremap.2:95
5597 msgid "B<MREMAP_FIXED> (since Linux 2.3.31)"
5601 #: build/C/man2/mremap.2:117
5603 "This flag serves a similar purpose to the B<MAP_FIXED> flag of B<mmap>(2). "
5604 "If this flag is specified, then B<mremap>() accepts a fifth argument, "
5605 "I<void\\ *new_address>, which specifies a page-aligned address to which the "
5606 "mapping must be moved. Any previous mapping at the address range specified "
5607 "by I<new_address> and I<new_size> is unmapped. If B<MREMAP_FIXED> is "
5608 "specified, then B<MREMAP_MAYMOVE> must also be specified."
5612 #: build/C/man2/mremap.2:127
5614 "If the memory segment specified by I<old_address> and I<old_size> is locked "
5615 "(using B<mlock>(2) or similar), then this lock is maintained when the "
5616 "segment is resized and/or relocated. As a consequence, the amount of memory "
5617 "locked by the process may change."
5621 #: build/C/man2/mremap.2:135
5623 "On success B<mremap>() returns a pointer to the new virtual memory area. "
5624 "On error, the value B<MAP_FAILED> (that is, I<(void\\ *)\\ -1>) is returned, "
5625 "and I<errno> is set appropriately."
5629 #: build/C/man2/mremap.2:142
5631 "The caller tried to expand a memory segment that is locked, but this was not "
5632 "possible without exceeding the B<RLIMIT_MEMLOCK> resource limit."
5636 #: build/C/man2/mremap.2:151
5638 "\"Segmentation fault.\" Some address in the range I<old_address> to "
5639 "I<old_address>+I<old_size> is an invalid virtual memory address for this "
5640 "process. You can also get B<EFAULT> even if there exist mappings that cover "
5641 "the whole address space requested, but those mappings are of different "
5646 #: build/C/man2/mremap.2:179
5648 "An invalid argument was given. Possible causes are: I<old_address> was not "
5649 "page aligned; a value other than B<MREMAP_MAYMOVE> or B<MREMAP_FIXED> was "
5650 "specified in I<flags>; I<new_size> was zero; I<new_size> or I<new_address> "
5651 "was invalid; or the new address range specified by I<new_address> and "
5652 "I<new_size> overlapped the old address range specified by I<old_address> and "
5653 "I<old_size>; or B<MREMAP_FIXED> was specified without also specifying "
5654 "B<MREMAP_MAYMOVE>."
5658 #: build/C/man2/mremap.2:185
5660 "The memory area cannot be expanded at the current virtual address, and the "
5661 "B<MREMAP_MAYMOVE> flag is not set in I<flags>. Or, there is not enough "
5662 "(virtual) memory available."
5665 #. 4.2BSD had a (never actually implemented)
5667 #. call with completely different semantics.
5669 #: build/C/man2/mremap.2:191
5671 "This call is Linux-specific, and should not be used in programs intended to "
5676 #: build/C/man2/mremap.2:199
5678 "Prior to version 2.4, glibc did not expose the definition of "
5679 "B<MREMAP_FIXED>, and the prototype for B<mremap>() did not allow for the "
5680 "I<new_address> argument."
5684 #: build/C/man2/mremap.2:208
5686 "B<brk>(2), B<getpagesize>(2), B<getrlimit>(2), B<mlock>(2), B<mmap>(2), "
5687 "B<sbrk>(2), B<malloc>(3), B<realloc>(3)"
5691 #: build/C/man2/mremap.2:214
5693 "Your favorite text book on operating systems for more information on paged "
5694 "memory (e.g., I<Modern Operating Systems> by Andrew S. Tanenbaum, I<Inside "
5695 "Linux> by Randolf Bentson, I<The Design of the UNIX Operating System> by "
5700 #: build/C/man2/msync.2:25
5706 #: build/C/man2/msync.2:25
5712 #: build/C/man2/msync.2:28
5713 msgid "msync - synchronize a file with a memory map"
5717 #: build/C/man2/msync.2:32
5718 msgid "B<int msync(void *>I<addr>B<, size_t >I<length>B<, int >I<flags>B<);>"
5722 #: build/C/man2/msync.2:48
5724 "B<msync>() flushes changes made to the in-core copy of a file that was "
5725 "mapped into memory using B<mmap>(2) back to the filesystem. Without use of "
5726 "this call there is no guarantee that changes are written back before "
5727 "B<munmap>(2) is called. To be more precise, the part of the file that "
5728 "corresponds to the memory area starting at I<addr> and having length "
5729 "I<length> is updated."
5733 #: build/C/man2/msync.2:68
5735 "The I<flags> argument may have the bits B<MS_ASYNC>, B<MS_SYNC>, and "
5736 "B<MS_INVALIDATE> set, but not both B<MS_ASYNC> and B<MS_SYNC>. B<MS_ASYNC> "
5737 "specifies that an update be scheduled, but the call returns immediately. "
5738 "B<MS_SYNC> asks for an update and waits for it to complete. "
5739 "B<MS_INVALIDATE> asks to invalidate other mappings of the same file (so that "
5740 "they can be updated with the fresh values just written)."
5744 #: build/C/man2/msync.2:73
5746 "On success, zero is returned. On error, -1 is returned, and I<errno> is set "
5751 #: build/C/man2/msync.2:74
5757 #: build/C/man2/msync.2:80
5759 "B<MS_INVALIDATE> was specified in I<flags>, and a memory lock exists for the "
5760 "specified address range."
5764 #: build/C/man2/msync.2:93
5766 "I<addr> is not a multiple of PAGESIZE; or any bit other than B<MS_ASYNC> | "
5767 "B<MS_INVALIDATE> | B<MS_SYNC> is set in I<flags>; or both B<MS_SYNC> and "
5768 "B<MS_ASYNC> are set in I<flags>."
5772 #: build/C/man2/msync.2:96
5773 msgid "The indicated memory (or part of it) was not mapped."
5777 #: build/C/man2/msync.2:98 build/C/man3/posix_fallocate.3:110 build/C/man3/shm_open.3:253 build/C/man7/shm_overview.7:103
5778 msgid "POSIX.1-2001."
5782 #: build/C/man2/msync.2:105
5784 "This call was introduced in Linux 1.3.21, and then used B<EFAULT> instead of "
5785 "B<ENOMEM>. In Linux 2.4.19, this was changed to the POSIX value B<ENOMEM>."
5788 #. POSIX.1-2001: It shall be defined to -1 or 0 or 200112L.
5789 #. -1: unavailable, 0: ask using sysconf().
5790 #. glibc defines them to 1.
5792 #: build/C/man2/msync.2:120
5794 "On POSIX systems on which B<msync>() is available, both "
5795 "B<_POSIX_MAPPED_FILES> and B<_POSIX_SYNCHRONIZED_IO> are defined in "
5796 "I<E<lt>unistd.hE<gt>> to a value greater than 0. (See also B<sysconf>(3).)"
5799 #. commit 204ec841fbea3e5138168edbc3a76d46747cc987
5801 #: build/C/man2/msync.2:147
5803 "According to POSIX, either B<MS_SYNC> or B<MS_ASYNC> must be specified in "
5804 "I<flags>, and indeed failure to include one of these flags will cause "
5805 "B<msync>() to fail on some systems. However, Linux permits a call to "
5806 "B<msync>() that specifies neither of these flags, with semantics that are "
5807 "(currently) equivalent to specifying B<MS_ASYNC>. (Since Linux 2.6.19, "
5808 "B<MS_ASYNC> is in fact a no-op, since the kernel properly tracks dirty pages "
5809 "and flushes them to storage as necessary.) Notwithstanding the Linux "
5810 "behavior, portable, future-proof applications should ensure that they "
5811 "specify either B<MS_SYNC> or B<MS_ASYNC> in I<flags>."
5815 #: build/C/man2/msync.2:149 build/C/man7/shm_overview.7:46
5821 #: build/C/man3/mtrace.3:25
5827 #: build/C/man3/mtrace.3:25
5833 #: build/C/man3/mtrace.3:28
5834 msgid "mtrace, muntrace - malloc tracing"
5838 #: build/C/man3/mtrace.3:30
5839 msgid "B<#include E<lt>mcheck.hE<gt>>"
5843 #: build/C/man3/mtrace.3:32
5844 msgid "B<void mtrace(void);>"
5848 #: build/C/man3/mtrace.3:34
5849 msgid "B<void muntrace(void);>"
5853 #: build/C/man3/mtrace.3:46
5855 "The B<mtrace>() function installs hook functions for the memory-allocation "
5856 "functions (B<malloc>(3), B<realloc>(3) B<memalign>(3), B<free>(3)). These "
5857 "hook functions record tracing information about memory allocation and "
5858 "deallocation. The tracing information can be used to discover memory leaks "
5859 "and attempts to free nonallocated memory in a program."
5863 #: build/C/man3/mtrace.3:57
5865 "The B<muntrace>() function disables the hook functions installed by "
5866 "B<mtrace>(), so that tracing information is no longer recorded for the "
5867 "memory-allocation functions. If no hook functions were successfully "
5868 "installed by B<mtrace>(), B<muntrace>() does nothing."
5872 #: build/C/man3/mtrace.3:65
5874 "When B<mtrace>() is called, it checks the value of the environment variable "
5875 "B<MALLOC_TRACE>, which should contain the pathname of a file in which the "
5876 "tracing information is to be recorded. If the pathname is successfully "
5877 "opened, it is truncated to zero length."
5881 #: build/C/man3/mtrace.3:78
5883 "If B<MALLOC_TRACE> is not set, or the pathname it specifies is invalid or "
5884 "not writable, then no hook functions are installed, and B<mtrace>() has no "
5885 "effect. In set-user-ID and set-group-ID programs, B<MALLOC_TRACE> is "
5886 "ignored, and B<mtrace>() has no effect."
5890 #: build/C/man3/mtrace.3:86
5892 "In normal usage, B<mtrace>() is called once at the start of execution of a "
5893 "program, and B<muntrace>() is never called."
5897 #: build/C/man3/mtrace.3:96
5899 "The tracing output produced after a call to B<mtrace>() is textual, but not "
5900 "designed to be human readable. The GNU C library provides a Perl script, "
5901 "B<mtrace>(1), that interprets the trace log and produces human-readable "
5902 "output. For best results, the traced program should be compiled with "
5903 "debugging enabled, so that line-number information is recorded in the "
5908 #: build/C/man3/mtrace.3:102
5910 "The tracing performed by B<mtrace>() incurs a performance penalty (if "
5911 "B<MALLOC_TRACE> points to a valid, writable pathname)."
5915 #: build/C/man3/mtrace.3:108
5917 "The line-number information produced by B<mtrace>(1) is not always precise: "
5918 "the line number references may refer to the previous or following (nonblank) "
5919 "line of the source code."
5923 #: build/C/man3/mtrace.3:115
5925 "The shell session below demonstrates the use of the B<mtrace>() function "
5926 "and the B<mtrace>(1) command in a program that has memory leaks at two "
5927 "different locations. The demonstration uses the following program:"
5931 #: build/C/man3/mtrace.3:122
5934 "$ B<cat t_mtrace.c>\n"
5935 "#include E<lt>mcheck.hE<gt>\n"
5936 "#include E<lt>stdlib.hE<gt>\n"
5937 "#include E<lt>stdio.hE<gt>\n"
5941 #: build/C/man3/mtrace.3:127
5945 "main(int argc, char *argv[])\n"
5951 #: build/C/man3/mtrace.3:129
5953 msgid " mtrace();\n"
5957 #: build/C/man3/mtrace.3:132
5960 " for (j = 0; j E<lt> 2; j++)\n"
5961 " malloc(100); /* Never freed--a memory leak */\n"
5965 #: build/C/man3/mtrace.3:136
5968 " calloc(16, 16); /* Never freed--a memory leak */\n"
5969 " exit(EXIT_SUCCESS);\n"
5974 #: build/C/man3/mtrace.3:142
5976 "When we run the program as follows, we see that B<mtrace>() diagnosed "
5977 "memory leaks at two different locations in the program:"
5981 #: build/C/man3/mtrace.3:155
5984 "$ B<cc -g t_mtrace.c -o t_mtrace>\n"
5985 "$ B<export MALLOC_TRACE=/tmp/t>\n"
5987 "$ B<mtrace ./t_mtrace $MALLOC_TRACE>\n"
5988 "Memory not freed:\n"
5989 "-----------------\n"
5990 " Address Size Caller\n"
5991 "0x084c9378 0x64 at /home/cecilia/t_mtrace.c:12\n"
5992 "0x084c93e0 0x64 at /home/cecilia/t_mtrace.c:12\n"
5993 "0x084c9448 0x100 at /home/cecilia/t_mtrace.c:16\n"
5997 #: build/C/man3/mtrace.3:167
5999 "The first two messages about unfreed memory correspond to the two "
6000 "B<malloc>(3) calls inside the I<for> loop. The final message corresponds "
6001 "to the call to B<calloc>(3) (which in turn calls B<malloc>(3))."
6005 #: build/C/man3/mtrace.3:172
6006 msgid "B<mtrace>(1), B<malloc>(3), B<malloc_hook>(3), B<mcheck>(3)"
6010 #: build/C/man2/posix_fadvise.2:28
6012 msgid "POSIX_FADVISE"
6016 #: build/C/man2/posix_fadvise.2:31
6017 msgid "posix_fadvise - predeclare an access pattern for file data"
6021 #: build/C/man2/posix_fadvise.2:34 build/C/man3/posix_fallocate.3:31
6023 msgid "B<#include E<lt>fcntl.hE<gt>>\n"
6027 #: build/C/man2/posix_fadvise.2:37
6030 "B<int posix_fadvise(int >I<fd>B<, off_t >I<offset>B<, off_t >I<len>B<, int "
6035 #: build/C/man2/posix_fadvise.2:46
6036 msgid "B<posix_fadvise>():"
6040 #: build/C/man2/posix_fadvise.2:48 build/C/man3/posix_fallocate.3:44
6041 msgid "_XOPEN_SOURCE\\ E<gt>=\\ 600 || _POSIX_C_SOURCE\\ E<gt>=\\ 200112L"
6045 #: build/C/man2/posix_fadvise.2:56
6047 "Programs can use B<posix_fadvise>() to announce an intention to access file "
6048 "data in a specific pattern in the future, thus allowing the kernel to "
6049 "perform appropriate optimizations."
6053 #: build/C/man2/posix_fadvise.2:63
6055 "The I<advice> applies to a (not necessarily existent) region starting at "
6056 "I<offset> and extending for I<len> bytes (or until the end of the file if "
6057 "I<len> is 0) within the file referred to by I<fd>. The I<advice> is not "
6058 "binding; it merely constitutes an expectation on behalf of the application."
6062 #: build/C/man2/posix_fadvise.2:65
6063 msgid "Permissible values for I<advice> include:"
6067 #: build/C/man2/posix_fadvise.2:65
6069 msgid "B<POSIX_FADV_NORMAL>"
6073 #: build/C/man2/posix_fadvise.2:71
6075 "Indicates that the application has no advice to give about its access "
6076 "pattern for the specified data. If no advice is given for an open file, "
6077 "this is the default assumption."
6081 #: build/C/man2/posix_fadvise.2:71
6083 msgid "B<POSIX_FADV_SEQUENTIAL>"
6087 #: build/C/man2/posix_fadvise.2:75
6089 "The application expects to access the specified data sequentially (with "
6090 "lower offsets read before higher ones)."
6094 #: build/C/man2/posix_fadvise.2:75
6096 msgid "B<POSIX_FADV_RANDOM>"
6100 #: build/C/man2/posix_fadvise.2:78
6101 msgid "The specified data will be accessed in random order."
6105 #: build/C/man2/posix_fadvise.2:78
6107 msgid "B<POSIX_FADV_NOREUSE>"
6111 #: build/C/man2/posix_fadvise.2:81
6112 msgid "The specified data will be accessed only once."
6116 #: build/C/man2/posix_fadvise.2:81
6118 msgid "B<POSIX_FADV_WILLNEED>"
6122 #: build/C/man2/posix_fadvise.2:84
6123 msgid "The specified data will be accessed in the near future."
6127 #: build/C/man2/posix_fadvise.2:84
6129 msgid "B<POSIX_FADV_DONTNEED>"
6133 #: build/C/man2/posix_fadvise.2:87
6134 msgid "The specified data will not be accessed in the near future."
6138 #: build/C/man2/posix_fadvise.2:90
6139 msgid "On success, zero is returned. On error, an error number is returned."
6143 #: build/C/man2/posix_fadvise.2:94
6144 msgid "The I<fd> argument was not a valid file descriptor."
6148 #: build/C/man2/posix_fadvise.2:97
6149 msgid "An invalid value was specified for I<advice>."
6152 #. commit 87ba81dba431232548ce29d5d224115d0c2355ac
6154 #: build/C/man2/posix_fadvise.2:107
6156 "The specified file descriptor refers to a pipe or FIFO. (B<ESPIPE> is the "
6157 "error specified by POSIX, but before kernel version 2.16, Linux returned "
6158 "B<EINVAL> in this case.)"
6161 #. of fadvise64_64()
6163 #: build/C/man2/posix_fadvise.2:115
6165 "Kernel support first appeared in Linux 2.5.60; the underlying system call is "
6166 "called B<fadvise64>(). Library support has been provided since glibc "
6167 "version 2.2, via the wrapper function B<posix_fadvise>()."
6170 #. commit d3ac21cacc24790eb45d735769f35753f5b56ceb
6172 #: build/C/man2/posix_fadvise.2:122
6174 "Since Linux 3.18, support for the underlying system call is optional, "
6175 "depending on the setting of the B<CONFIG_ADVISE_SYSCALLS> configuration "
6180 #: build/C/man2/posix_fadvise.2:131
6182 "POSIX.1-2001. Note that the type of the I<len> argument was changed from "
6183 "I<size_t> to I<off_t> in POSIX.1-2003 TC1."
6187 #: build/C/man2/posix_fadvise.2:137
6189 "Under Linux, B<POSIX_FADV_NORMAL> sets the readahead window to the default "
6190 "size for the backing device; B<POSIX_FADV_SEQUENTIAL> doubles this size, and "
6191 "B<POSIX_FADV_RANDOM> disables file readahead entirely. These changes affect "
6192 "the entire file, not just the specified region (but other open file handles "
6193 "to the same file are unaffected)."
6197 #: build/C/man2/posix_fadvise.2:144
6199 "B<POSIX_FADV_WILLNEED> initiates a nonblocking read of the specified region "
6200 "into the page cache. The amount of data read may be decreased by the kernel "
6201 "depending on virtual memory load. (A few megabytes will usually be fully "
6202 "satisfied, and more is rarely useful.)"
6206 #: build/C/man2/posix_fadvise.2:148
6208 "In kernels before 2.6.18, B<POSIX_FADV_NOREUSE> had the same semantics as "
6209 "B<POSIX_FADV_WILLNEED>. This was probably a bug; since kernel 2.6.18, this "
6214 #: build/C/man2/posix_fadvise.2:156
6216 "B<POSIX_FADV_DONTNEED> attempts to free cached pages associated with the "
6217 "specified region. This is useful, for example, while streaming large "
6218 "files. A program may periodically request the kernel to free cached data "
6219 "that has already been used, so that more useful cached pages are not "
6220 "discarded instead."
6224 #: build/C/man2/posix_fadvise.2:164
6226 "Requests to discard partial pages are ignored. It is preferable to preserve "
6227 "needed data than discard unneeded data. If the application requires that "
6228 "data be considered for discarding then I<offset> and I<len> must be "
6233 #: build/C/man2/posix_fadvise.2:172
6235 "Pages that have not yet been written out will be unaffected, so if the "
6236 "application wishes to guarantee that pages will be released, it should call "
6237 "B<fsync>(2) or B<fdatasync>(2) first."
6241 #: build/C/man2/posix_fadvise.2:172
6243 msgid "Architecture-specific variants"
6247 #: build/C/man2/posix_fadvise.2:189
6249 "Some architectures require 64-bit arguments to be aligned in a suitable pair "
6250 "of registers (see B<syscall>(2) for further detail). On such "
6251 "architectures, the call signature of B<posix_fadvise>() shown in the "
6252 "SYNOPSIS would force a register to be wasted as padding between the I<fd> "
6253 "and I<offset> arguments. Therefore, these architectures define a version of "
6254 "the system call that orders the arguments suitably, but otherwise is "
6255 "otherwise exactly the same as B<posix_fadvise>()."
6259 #: build/C/man2/posix_fadvise.2:191
6260 msgid "For example, since Linux 2.6.14, ARM has the following system call:"
6264 #: build/C/man2/posix_fadvise.2:196
6267 "B<long arm_fadvise64_64(int >I<fd>B<, int >I<advice>B<,>\n"
6268 "B< loff_t >I<offset>B<, loff_t >I<len>B<);>\n"
6272 #: build/C/man2/posix_fadvise.2:204
6274 "These architecture-specific details are generally hidden from applications "
6275 "by the glibc B<posix_fadvise>() wrapper function, which invokes the "
6276 "appropriate architecture-specific system call."
6280 #: build/C/man2/posix_fadvise.2:209
6282 "In kernels before 2.6.6, if I<len> was specified as 0, then this was "
6283 "interpreted literally as \"zero bytes\", rather than as meaning \"all bytes "
6284 "through to the end of the file\"."
6287 #. FIXME . Write a posix_fadvise(3) page.
6289 #: build/C/man2/posix_fadvise.2:215
6291 "B<readahead>(2), B<sync_file_range>(2), B<posix_fallocate>(3), "
6292 "B<posix_madvise>(3)"
6296 #: build/C/man3/posix_fallocate.3:25
6298 msgid "POSIX_FALLOCATE"
6302 #: build/C/man3/posix_fallocate.3:28
6303 msgid "posix_fallocate - allocate file space"
6307 #: build/C/man3/posix_fallocate.3:33
6309 msgid "B<int posix_fallocate(int >I<fd>B<, off_t >I<offset>B<, off_t >I<len>B<);>\n"
6313 #: build/C/man3/posix_fallocate.3:42
6314 msgid "B<posix_fallocate>():"
6318 #: build/C/man3/posix_fallocate.3:61
6320 "The function B<posix_fallocate>() ensures that disk space is allocated for "
6321 "the file referred to by the descriptor I<fd> for the bytes in the range "
6322 "starting at I<offset> and continuing for I<len> bytes. After a successful "
6323 "call to B<posix_fallocate>(), subsequent writes to bytes in the specified "
6324 "range are guaranteed not to fail because of lack of disk space."
6328 #: build/C/man3/posix_fallocate.3:66
6330 "If the size of the file is less than I<offset>+I<len>, then the file is "
6331 "increased to this size; otherwise the file size is left unchanged."
6335 #: build/C/man3/posix_fallocate.3:72
6337 "B<posix_fallocate>() returns zero on success, or an error number on "
6338 "failure. Note that I<errno> is not set."
6342 #: build/C/man3/posix_fallocate.3:81
6343 msgid "I<offset+len> exceeds the maximum file size."
6347 #: build/C/man3/posix_fallocate.3:91
6348 msgid "I<fd> does not refer to a regular file."
6352 #: build/C/man3/posix_fallocate.3:100
6353 msgid "I<fd> refers to a pipe."
6357 #: build/C/man3/posix_fallocate.3:103
6358 msgid "B<posix_fallocate>() is available since glibc 2.1.94."
6362 #: build/C/man3/posix_fallocate.3:108
6363 msgid "The B<posix_fallocate>() function is thread-safe."
6367 #: build/C/man3/posix_fallocate.3:133
6369 "POSIX.1-2008 says that an implementation I<shall> give the B<EINVAL> error "
6370 "if I<len> was 0, or I<offset> was less than 0. POSIX.1-2001 says that an "
6371 "implementation I<shall> give the B<EINVAL> error if I<len> is less than 0, "
6372 "or I<offset> was less than 0, and I<may> give the error if I<len> equals "
6377 #: build/C/man3/posix_fallocate.3:138
6379 "In the glibc implementation, B<posix_fallocate>() is implemented using "
6384 #: build/C/man3/posix_fallocate.3:143
6385 msgid "B<fallocate>(1), B<fallocate>(2), B<lseek>(2), B<posix_fadvise>(2)"
6389 #: build/C/man3/posix_memalign.3:29
6391 msgid "POSIX_MEMALIGN"
6395 #: build/C/man3/posix_memalign.3:29
6401 #: build/C/man3/posix_memalign.3:32
6403 "posix_memalign, aligned_alloc, memalign, valloc, pvalloc - allocate aligned "
6408 #: build/C/man3/posix_memalign.3:35
6410 msgid "B<#include E<lt>stdlib.hE<gt>>\n"
6414 #: build/C/man3/posix_memalign.3:39
6417 "B<int posix_memalign(void **>I<memptr>B<, size_t >I<alignment>B<, size_t "
6419 "B<void *aligned_alloc(size_t >I<alignment>B<, size_t >I<size>B<);>\n"
6420 "B<void *valloc(size_t >I<size>B<);>\n"
6424 #: build/C/man3/posix_memalign.3:44
6427 "B<void *memalign(size_t >I<alignment>B<, size_t >I<size>B<);>\n"
6428 "B<void *pvalloc(size_t >I<size>B<);>\n"
6432 #: build/C/man3/posix_memalign.3:54
6434 "B<posix_memalign>(): _POSIX_C_SOURCE\\ E<gt>=\\ 200112L || _XOPEN_SOURCE\\ "
6439 #: build/C/man3/posix_memalign.3:57
6440 msgid "B<aligned_alloc>(): _ISOC11_SOURCE"
6444 #: build/C/man3/posix_memalign.3:59
6445 msgid "B<valloc>():"
6449 #: build/C/man3/posix_memalign.3:62
6451 msgid "Since glibc 2.12:"
6455 #: build/C/man3/posix_memalign.3:69
6459 " (_XOPEN_SOURCE\\ E<gt>=\\ 500 ||\n"
6460 " _XOPEN_SOURCE\\ &&\\ _XOPEN_SOURCE_EXTENDED) &&\n"
6461 " !(_POSIX_C_SOURCE\\ E<gt>=\\ 200112L || _XOPEN_SOURCE\\ E<gt>=\\ 600)\n"
6465 #: build/C/man3/posix_memalign.3:71
6467 msgid "Before glibc 2.12:"
6471 #: build/C/man3/posix_memalign.3:75
6473 "_BSD_SOURCE || _XOPEN_SOURCE\\ E<gt>=\\ 500 || _XOPEN_SOURCE\\ &&\\ "
6474 "_XOPEN_SOURCE_EXTENDED"
6478 #: build/C/man3/posix_memalign.3:82
6480 "(The (nonstandard) header file I<E<lt>malloc.hE<gt>> also exposes the "
6481 "declaration of B<valloc>(); no feature test macros are required.)"
6486 #: build/C/man3/posix_memalign.3:104
6488 "The function B<posix_memalign>() allocates I<size> bytes and places the "
6489 "address of the allocated memory in I<*memptr>. The address of the allocated "
6490 "memory will be a multiple of I<alignment>, which must be a power of two and "
6491 "a multiple of I<sizeof(void\\ *)>. If I<size> is 0, then the value placed "
6492 "in I<*memptr> is either NULL, or a unique pointer value that can later be "
6493 "successfully passed to B<free>(3)."
6496 #. The behavior of memalign() for size==0 is as for posix_memalign()
6497 #. but no standards govern this.
6499 #: build/C/man3/posix_memalign.3:115
6501 "The obsolete function B<memalign>() allocates I<size> bytes and returns a "
6502 "pointer to the allocated memory. The memory address will be a multiple of "
6503 "I<alignment>, which must be a power of two."
6507 #: build/C/man3/posix_memalign.3:124
6509 "The function B<aligned_alloc>() is the same as B<memalign>(), except for "
6510 "the added restriction that I<size> should be a multiple of I<alignment>."
6514 #: build/C/man3/posix_memalign.3:133
6516 "The obsolete function B<valloc>() allocates I<size> bytes and returns a "
6517 "pointer to the allocated memory. The memory address will be a multiple of "
6518 "the page size. It is equivalent to I<memalign(sysconf(_SC_PAGESIZE),size)>."
6522 #: build/C/man3/posix_memalign.3:140
6524 "The obsolete function B<pvalloc>() is similar to B<valloc>(), but rounds "
6525 "the size of the allocation up to the next multiple of the system page size."
6529 #: build/C/man3/posix_memalign.3:142
6530 msgid "For all of these functions, the memory is not zeroed."
6534 #: build/C/man3/posix_memalign.3:149
6536 "B<aligned_alloc>(), B<memalign>(), B<valloc>(), and B<pvalloc>() return a "
6537 "pointer to the allocated memory, or NULL if the request fails."
6541 #: build/C/man3/posix_memalign.3:157
6543 "B<posix_memalign>() returns zero on success, or one of the error values "
6544 "listed in the next section on failure. The value of I<errno> is "
6545 "indeterminate after a call to B<posix_memalign>()."
6549 #: build/C/man3/posix_memalign.3:164
6551 "The I<alignment> argument was not a power of two, or was not a multiple of "
6552 "I<sizeof(void\\ *)>."
6556 #: build/C/man3/posix_memalign.3:167
6557 msgid "There was insufficient memory to fulfill the allocation request."
6561 #: build/C/man3/posix_memalign.3:174
6563 "The functions B<memalign>(), B<valloc>(), and B<pvalloc>() have been "
6564 "available in all Linux libc libraries."
6568 #: build/C/man3/posix_memalign.3:178
6569 msgid "The function B<aligned_alloc>() was added to glibc in version 2.16."
6573 #: build/C/man3/posix_memalign.3:182
6574 msgid "The function B<posix_memalign>() is available since glibc 2.1.91."
6578 #: build/C/man3/posix_memalign.3:189
6580 "The function B<valloc>() appeared in 3.0BSD. It is documented as being "
6581 "obsolete in 4.3BSD, and as legacy in SUSv2. It does not appear in "
6586 #: build/C/man3/posix_memalign.3:193
6587 msgid "The function B<pvalloc>() is a GNU extension."
6591 #: build/C/man3/posix_memalign.3:197
6592 msgid "The function B<memalign>() appears in SunOS 4.1.3 but not in 4.4BSD."
6596 #: build/C/man3/posix_memalign.3:201
6597 msgid "The function B<posix_memalign>() comes from POSIX.1d."
6601 #: build/C/man3/posix_memalign.3:206
6602 msgid "The function B<aligned_alloc>() is specified in the C11 standard."
6606 #: build/C/man3/posix_memalign.3:206
6612 #: build/C/man3/posix_memalign.3:210
6614 "Everybody agrees that B<posix_memalign>() is declared in "
6615 "I<E<lt>stdlib.hE<gt>>."
6619 #: build/C/man3/posix_memalign.3:214
6621 "On some systems B<memalign>() is declared in I<E<lt>stdlib.hE<gt>> instead "
6622 "of I<E<lt>malloc.hE<gt>>."
6626 #: build/C/man3/posix_memalign.3:221
6628 "According to SUSv2, B<valloc>() is declared in I<E<lt>stdlib.hE<gt>>. "
6629 "Libc4,5 and glibc declare it in I<E<lt>malloc.hE<gt>>, and also in "
6630 "I<E<lt>stdlib.hE<gt>> if suitable feature test macros are defined (see "
6635 #: build/C/man3/posix_memalign.3:230
6637 "On many systems there are alignment restrictions, for example, on buffers "
6638 "used for direct block device I/O. POSIX specifies the "
6639 "I<pathconf(path,_PC_REC_XFER_ALIGN)> call that tells what alignment is "
6640 "needed. Now one can use B<posix_memalign>() to satisfy this requirement."
6644 #: build/C/man3/posix_memalign.3:239
6646 "B<posix_memalign>() verifies that I<alignment> matches the requirements "
6647 "detailed above. B<memalign>() may not check that the I<alignment> argument "
6651 #. Other systems allow passing the result of
6658 #: build/C/man3/posix_memalign.3:267
6660 "POSIX requires that memory obtained from B<posix_memalign>() can be freed "
6661 "using B<free>(3). Some systems provide no way to reclaim memory allocated "
6662 "with B<memalign>() or B<valloc>() (because one can pass to B<free>(3) "
6663 "only a pointer obtained from B<malloc>(3), while, for example, B<memalign>() "
6664 "would call B<malloc>(3) and then align the obtained value). The glibc "
6665 "implementation allows memory obtained from any of these functions to be "
6666 "reclaimed with B<free>(3)."
6670 #: build/C/man3/posix_memalign.3:272
6672 "The glibc B<malloc>(3) always returns 8-byte aligned memory addresses, so "
6673 "these functions are needed only if you require larger alignment values."
6677 #: build/C/man3/posix_memalign.3:277
6678 msgid "B<brk>(2), B<getpagesize>(2), B<free>(3), B<malloc>(3)"
6682 #: build/C/man2/readahead.2:28
6688 #: build/C/man2/readahead.2:28
6694 #: build/C/man2/readahead.2:31
6695 msgid "readahead - initiate file readahead into page cache"
6699 #: build/C/man2/readahead.2:37
6702 "B<ssize_t readahead(int >I<fd>B<, off64_t >I<offset>B<, size_t "
6707 #: build/C/man2/readahead.2:44
6709 "B<readahead>() initiates readahead on a file so that subsequent reads from "
6710 "that file will be satisfied from the cache, and not block on disk I/O "
6711 "(assuming the readahead was initiated early enough and that other activity "
6712 "on the system did not in the meantime flush pages from the cache)."
6716 #: build/C/man2/readahead.2:66
6718 "The I<fd> argument is a file descriptor identifying the file which is to be "
6719 "read. The I<offset> argument specifies the starting point from which data "
6720 "is to be read and I<count> specifies the number of bytes to be read. I/O is "
6721 "performed in whole pages, so that I<offset> is effectively rounded down to a "
6722 "page boundary and bytes are read up to the next page boundary greater than "
6723 "or equal to I<(offset+count)>. B<readahead>() does not read beyond the end "
6724 "of the file. The current file offset of the open file referred to by I<fd> "
6725 "is left unchanged."
6729 #: build/C/man2/readahead.2:72
6731 "On success, B<readahead>() returns 0; on failure, -1 is returned, with "
6732 "I<errno> set to indicate the cause of the error."
6736 #: build/C/man2/readahead.2:77
6737 msgid "I<fd> is not a valid file descriptor or is not open for reading."
6741 #: build/C/man2/readahead.2:83
6742 msgid "I<fd> does not refer to a file type to which B<readahead>() can be applied."
6746 #: build/C/man2/readahead.2:88
6748 "The B<readahead>() system call appeared in Linux 2.4.13; glibc support has "
6749 "been provided since version 2.3."
6753 #: build/C/man2/readahead.2:93
6755 "The B<readahead>() system call is Linux-specific, and its use should be "
6756 "avoided in portable applications."
6760 #: build/C/man2/readahead.2:98
6762 "On some 32-bit architectures, the calling signature for this system call "
6763 "differs, for the reasons described in B<syscall>(2)."
6767 #: build/C/man2/readahead.2:107
6769 "B<readahead>() attempts to schedule the reads in the background and return "
6770 "immediately. However, it may block while it reads the filesystem metadata "
6771 "needed to locate the requested blocks. This occurs frequently with ext[234] "
6772 "on large files using indirect blocks instead of extents, giving the "
6773 "appearance that the call blocks until the requested data has been read."
6777 #: build/C/man2/readahead.2:113
6778 msgid "B<lseek>(2), B<madvise>(2), B<mmap>(2), B<posix_fadvise>(2), B<read>(2)"
6782 #: build/C/man2/remap_file_pages.2:28
6784 msgid "REMAP_FILE_PAGES"
6788 #: build/C/man2/remap_file_pages.2:31
6789 msgid "remap_file_pages - create a nonlinear file mapping"
6793 #: build/C/man2/remap_file_pages.2:35
6796 "B<#define _GNU_SOURCE> /* See feature_test_macros(7) */\n"
6797 "B<#include E<lt>sys/mman.hE<gt>>\n"
6801 #: build/C/man2/remap_file_pages.2:38
6804 "B<int remap_file_pages(void *>I<addr>B<, size_t >I<size>B<, int "
6806 "B< size_t >I<pgoff>B<, int >I<flags>B<);>\n"
6809 #. commit 33041a0d76d3c3e0aff28ac95a2ffdedf1282dbc
6810 #. http://lwn.net/Articles/597632/
6812 #: build/C/man2/remap_file_pages.2:47
6814 "B<Note>: this system call is (since Linux 3.16) deprecated and will "
6815 "eventually be replaced by a slower in-kernel emulation. Those few "
6816 "applications that use this system call should consider migrating to "
6821 #: build/C/man2/remap_file_pages.2:59
6823 "The B<remap_file_pages>() system call is used to create a nonlinear "
6824 "mapping, that is, a mapping in which the pages of the file are mapped into a "
6825 "nonsequential order in memory. The advantage of using B<remap_file_pages>() "
6826 "over using repeated calls to B<mmap>(2) is that the former approach does "
6827 "not require the kernel to create additional VMA (Virtual Memory Area) data "
6832 #: build/C/man2/remap_file_pages.2:61
6833 msgid "To create a nonlinear mapping we perform the following steps:"
6837 #: build/C/man2/remap_file_pages.2:61 build/C/man2/memfd_create.2:219
6843 #: build/C/man2/remap_file_pages.2:69
6845 "Use B<mmap>(2) to create a mapping (which is initially linear). This "
6846 "mapping must be created with the B<MAP_SHARED> flag."
6850 #: build/C/man2/remap_file_pages.2:69 build/C/man2/memfd_create.2:225
6856 #: build/C/man2/remap_file_pages.2:77
6858 "Use one or more calls to B<remap_file_pages>() to rearrange the "
6859 "correspondence between the pages of the mapping and the pages of the file. "
6860 "It is possible to map the same page of a file into multiple locations within "
6861 "the mapped region."
6865 #: build/C/man2/remap_file_pages.2:88
6867 "The I<pgoff> and I<size> arguments specify the region of the file that is to "
6868 "be relocated within the mapping: I<pgoff> is a file offset in units of the "
6869 "system page size; I<size> is the length of the region in bytes."
6873 #: build/C/man2/remap_file_pages.2:106
6875 "The I<addr> argument serves two purposes. First, it identifies the mapping "
6876 "whose pages we want to rearrange. Thus, I<addr> must be an address that "
6877 "falls within a region previously mapped by a call to B<mmap>(2). Second, "
6878 "I<addr> specifies the address at which the file pages identified by I<pgoff> "
6879 "and I<size> will be placed."
6882 #. This rounding is weird, and not consistent with the treatment of
6883 #. the analogous arguments for munmap()/mprotect() and for mlock().
6886 #: build/C/man2/remap_file_pages.2:120
6888 "The values specified in I<addr> and I<size> should be multiples of the "
6889 "system page size. If they are not, then the kernel rounds I<both> values "
6890 "I<down> to the nearest multiple of the page size."
6894 #: build/C/man2/remap_file_pages.2:124
6895 msgid "The I<prot> argument must be specified as 0."
6899 #: build/C/man2/remap_file_pages.2:132
6901 "The I<flags> argument has the same meaning as for B<mmap>(2), but all flags "
6902 "other than B<MAP_NONBLOCK> are ignored."
6906 #: build/C/man2/remap_file_pages.2:139
6908 "On success, B<remap_file_pages>() returns 0. On error, -1 is returned, and "
6909 "I<errno> is set appropriately."
6913 #: build/C/man2/remap_file_pages.2:147
6915 "I<addr> does not refer to a valid mapping created with the B<MAP_SHARED> "
6919 #. And possibly others from vma->vm_ops->populate()
6921 #: build/C/man2/remap_file_pages.2:156
6922 msgid "I<addr>, I<size>, I<prot>, or I<pgoff> is invalid."
6926 #: build/C/man2/remap_file_pages.2:161
6928 "The B<remap_file_pages>() system call appeared in Linux 2.5.46; glibc "
6929 "support was added in version 2.3.3."
6933 #: build/C/man2/remap_file_pages.2:165
6934 msgid "The B<remap_file_pages>() system call is Linux-specific."
6937 #. commit 3ee6dafc677a68e461a7ddafc94a580ebab80735
6939 #: build/C/man2/remap_file_pages.2:176
6941 "Since Linux 2.6.23, B<remap_file_pages>() creates non-linear mappings only "
6942 "on in-memory file systems such as tmpfs, hugetlbfs or ramfs. On filesystems "
6943 "with a backing store, B<remap_file_pages>() is not much more efficient than "
6944 "using B<mmap>(2) to adjust which parts of the file are mapped to which "
6949 #: build/C/man2/remap_file_pages.2:183
6951 "B<getpagesize>(2), B<mmap>(2), B<mmap2>(2), B<mprotect>(2), B<mremap>(2), "
6956 #: build/C/man3/shm_open.3:26
6962 #: build/C/man3/shm_open.3:29
6963 msgid "shm_open, shm_unlink - create/open or unlink POSIX shared memory objects"
6967 #: build/C/man3/shm_open.3:33
6968 msgid "B<#include E<lt>sys/stat.hE<gt>> /* For mode constants */"
6972 #: build/C/man3/shm_open.3:35
6973 msgid "B<#include E<lt>fcntl.hE<gt>> /* For O_* constants */"
6977 #: build/C/man3/shm_open.3:37
6978 msgid "B<int shm_open(const char *>I<name>B<, int >I<oflag>B<, mode_t >I<mode>B<);>"
6982 #: build/C/man3/shm_open.3:39
6983 msgid "B<int shm_unlink(const char *>I<name>B<);>"
6987 #: build/C/man3/shm_open.3:41
6988 msgid "Link with I<-lrt>."
6992 #: build/C/man3/shm_open.3:53
6994 "B<shm_open>() creates and opens a new, or opens an existing, POSIX shared "
6995 "memory object. A POSIX shared memory object is in effect a handle which can "
6996 "be used by unrelated processes to B<mmap>(2) the same region of shared "
6997 "memory. The B<shm_unlink>() function performs the converse operation, "
6998 "removing an object previously created by B<shm_open>()."
7001 #. glibc allows the initial slash to be omitted, and makes
7002 #. multiple initial slashes equivalent to a single slash.
7003 #. This differs from the implementation of POSIX message queues.
7004 #. glibc allows subdirectory components in the name, in which
7005 #. case the subdirectory must exist under /dev/shm, and allow the
7006 #. required permissions if a user wants to create a shared memory
7007 #. object in that subdirectory.
7009 #: build/C/man3/shm_open.3:74
7011 "The operation of B<shm_open>() is analogous to that of B<open>(2). I<name> "
7012 "specifies the shared memory object to be created or opened. For portable "
7013 "use, a shared memory object should be identified by a name of the form "
7014 "I</somename>; that is, a null-terminated string of up to B<NAME_MAX> (i.e., "
7015 "255) characters consisting of an initial slash, followed by one or more "
7016 "characters, none of which are slashes."
7020 #: build/C/man3/shm_open.3:81
7022 "I<oflag> is a bit mask created by ORing together exactly one of B<O_RDONLY> "
7023 "or B<O_RDWR> and any of the other flags listed here:"
7027 #: build/C/man3/shm_open.3:81
7033 #: build/C/man3/shm_open.3:89
7035 "Open the object for read access. A shared memory object opened in this way "
7036 "can be B<mmap>(2)ed only for read (B<PROT_READ>) access."
7040 #: build/C/man3/shm_open.3:89
7046 #: build/C/man3/shm_open.3:92
7047 msgid "Open the object for read-write access."
7051 #: build/C/man3/shm_open.3:92
7056 #. In truth it is actually the filesystem IDs on Linux, but these
7057 #. are nearly always the same as the effective IDs. (MTK, Jul 05)
7059 #: build/C/man3/shm_open.3:112
7061 "Create the shared memory object if it does not exist. The user and group "
7062 "ownership of the object are taken from the corresponding effective IDs of "
7063 "the calling process, and the object's permission bits are set according to "
7064 "the low-order 9 bits of I<mode>, except that those bits set in the process "
7065 "file mode creation mask (see B<umask>(2)) are cleared for the new object. "
7066 "A set of macro constants which can be used to define I<mode> is listed in "
7067 "B<open>(2). (Symbolic definitions of these constants can be obtained by "
7068 "including I<E<lt>sys/stat.hE<gt>>.)"
7072 #: build/C/man3/shm_open.3:118
7074 "A new shared memory object initially has zero length\\(emthe size of the "
7075 "object can be set using B<ftruncate>(2). The newly allocated bytes of a "
7076 "shared memory object are automatically initialized to 0."
7080 #: build/C/man3/shm_open.3:118
7086 #: build/C/man3/shm_open.3:127
7088 "If B<O_CREAT> was also specified, and a shared memory object with the given "
7089 "I<name> already exists, return an error. The check for the existence of the "
7090 "object, and its creation if it does not exist, are performed atomically."
7094 #: build/C/man3/shm_open.3:127
7100 #: build/C/man3/shm_open.3:130
7101 msgid "If the shared memory object already exists, truncate it to zero bytes."
7105 #: build/C/man3/shm_open.3:133
7107 "Definitions of these flag values can be obtained by including "
7108 "I<E<lt>fcntl.hE<gt>>."
7112 #: build/C/man3/shm_open.3:144
7114 "On successful completion B<shm_open>() returns a new file descriptor "
7115 "referring to the shared memory object. This file descriptor is guaranteed "
7116 "to be the lowest-numbered file descriptor not previously opened within the "
7117 "process. The B<FD_CLOEXEC> flag (see B<fcntl>(2)) is set for the file "
7122 #: build/C/man3/shm_open.3:153
7124 "The file descriptor is normally used in subsequent calls to B<ftruncate>(2) "
7125 "(for a newly created object) and B<mmap>(2). After a call to B<mmap>(2) "
7126 "the file descriptor may be closed without affecting the memory mapping."
7130 #: build/C/man3/shm_open.3:171
7132 "The operation of B<shm_unlink>() is analogous to B<unlink>(2): it removes a "
7133 "shared memory object name, and, once all processes have unmapped the object, "
7134 "de-allocates and destroys the contents of the associated memory region. "
7135 "After a successful B<shm_unlink>(), attempts to B<shm_open>() an object "
7136 "with the same I<name> will fail (unless B<O_CREAT> was specified, in which "
7137 "case a new, distinct object is created)."
7141 #: build/C/man3/shm_open.3:180
7143 "On success, B<shm_open>() returns a nonnegative file descriptor. On "
7144 "failure, B<shm_open>() returns -1. B<shm_unlink>() returns 0 on success, "
7149 #: build/C/man3/shm_open.3:187
7151 "On failure, I<errno> is set to indicate the cause of the error. Values "
7152 "which may appear in I<errno> include the following:"
7156 #: build/C/man3/shm_open.3:192
7157 msgid "Permission to B<shm_unlink>() the shared memory object was denied."
7161 #: build/C/man3/shm_open.3:202
7163 "Permission was denied to B<shm_open>() I<name> in the specified I<mode>, or "
7164 "B<O_TRUNC> was specified and the caller does not have write permission on "
7169 #: build/C/man3/shm_open.3:202 build/C/man2/shmget.2:198
7175 #: build/C/man3/shm_open.3:213
7177 "Both B<O_CREAT> and B<O_EXCL> were specified to B<shm_open>() and the "
7178 "shared memory object specified by I<name> already exists."
7182 #: build/C/man3/shm_open.3:220
7183 msgid "The I<name> argument to B<shm_open>() was invalid."
7187 #: build/C/man3/shm_open.3:220 build/C/man2/memfd_create.2:146
7193 #: build/C/man3/shm_open.3:223
7194 msgid "The process already has the maximum number of files open."
7198 #: build/C/man3/shm_open.3:223
7200 msgid "B<ENAMETOOLONG>"
7204 #: build/C/man3/shm_open.3:229
7205 msgid "The length of I<name> exceeds B<PATH_MAX>."
7209 #: build/C/man3/shm_open.3:233
7210 msgid "The limit on the total number of files open on the system has been reached."
7214 #: build/C/man3/shm_open.3:233 build/C/man3/shm_open.3:242 build/C/man2/shmget.2:225
7220 #: build/C/man3/shm_open.3:242
7222 "An attempt was made to B<shm_open>() a I<name> that did not exist, and "
7223 "B<O_CREAT> was not specified."
7227 #: build/C/man3/shm_open.3:249
7228 msgid "An attempt was to made to B<shm_unlink>() a I<name> that does not exist."
7232 #: build/C/man3/shm_open.3:251
7233 msgid "These functions are provided in glibc 2.2 and later."
7237 #: build/C/man3/shm_open.3:257
7239 "POSIX.1-2001 says that the group ownership of a newly created shared memory "
7240 "object is set to either the calling process's effective group ID or \"a "
7241 "system default group ID\"."
7245 #: build/C/man3/shm_open.3:266
7247 "POSIX leaves the behavior of the combination of B<O_RDONLY> and B<O_TRUNC> "
7248 "unspecified. On Linux, this will successfully truncate an existing shared "
7249 "memory object\\(emthis may not be so on other UNIX systems."
7253 #: build/C/man3/shm_open.3:271
7255 "The POSIX shared memory object implementation on Linux 2.4 makes use of a "
7256 "dedicated filesystem, which is normally mounted under I</dev/shm>."
7260 #: build/C/man3/shm_open.3:283
7262 "B<close>(2), B<fchmod>(2), B<fchown>(2), B<fcntl>(2), B<fstat>(2), "
7263 "B<ftruncate>(2), B<memfd_create>(2), B<mmap>(2), B<open>(2), B<umask>(2), "
7264 "B<shm_overview>(7)"
7268 #: build/C/man7/shm_overview.7:27
7270 msgid "SHM_OVERVIEW"
7274 #: build/C/man7/shm_overview.7:27
7280 #: build/C/man7/shm_overview.7:30
7281 msgid "shm_overview - overview of POSIX shared memory"
7285 #: build/C/man7/shm_overview.7:33
7287 "The POSIX shared memory API allows processes to communicate information by "
7288 "sharing a region of memory."
7292 #: build/C/man7/shm_overview.7:35
7293 msgid "The interfaces employed in the API are:"
7297 #: build/C/man7/shm_overview.7:35
7299 msgid "B<shm_open>(3)"
7303 #: build/C/man7/shm_overview.7:42
7305 "Create and open a new object, or open an existing object. This is analogous "
7306 "to B<open>(2). The call returns a file descriptor for use by the other "
7307 "interfaces listed below."
7311 #: build/C/man7/shm_overview.7:42
7313 msgid "B<ftruncate>(2)"
7317 #: build/C/man7/shm_overview.7:46
7319 "Set the size of the shared memory object. (A newly created shared memory "
7320 "object has a length of zero.)"
7324 #: build/C/man7/shm_overview.7:50
7326 "Map the shared memory object into the virtual address space of the calling "
7331 #: build/C/man7/shm_overview.7:50
7333 msgid "B<munmap>(2)"
7337 #: build/C/man7/shm_overview.7:54
7339 "Unmap the shared memory object from the virtual address space of the calling "
7344 #: build/C/man7/shm_overview.7:54
7346 msgid "B<shm_unlink>(3)"
7350 #: build/C/man7/shm_overview.7:57
7351 msgid "Remove a shared memory object name."
7355 #: build/C/man7/shm_overview.7:57
7361 #: build/C/man7/shm_overview.7:62
7363 "Close the file descriptor allocated by B<shm_open>(3) when it is no longer "
7368 #: build/C/man7/shm_overview.7:62
7374 #: build/C/man7/shm_overview.7:76
7376 "Obtain a I<stat> structure that describes the shared memory object. Among "
7377 "the information returned by this call are the object's size (I<st_size>), "
7378 "permissions (I<st_mode>), owner (I<st_uid>), and group (I<st_gid>)."
7382 #: build/C/man7/shm_overview.7:76
7384 msgid "B<fchown>(2)"
7388 #: build/C/man7/shm_overview.7:79
7389 msgid "To change the ownership of a shared memory object."
7393 #: build/C/man7/shm_overview.7:79
7395 msgid "B<fchmod>(2)"
7399 #: build/C/man7/shm_overview.7:82
7400 msgid "To change the permissions of a shared memory object."
7404 #: build/C/man7/shm_overview.7:82
7410 #: build/C/man7/shm_overview.7:84
7411 msgid "POSIX shared memory is supported since Linux 2.4 and glibc 2.2."
7415 #: build/C/man7/shm_overview.7:84
7421 #: build/C/man7/shm_overview.7:89
7423 "POSIX shared memory objects have kernel persistence: a shared memory object "
7424 "will exist until the system is shut down, or until all processes have "
7425 "unmapped the object and it has been deleted with B<shm_unlink>(3)"
7429 #: build/C/man7/shm_overview.7:89
7435 #: build/C/man7/shm_overview.7:94
7437 "Programs using the POSIX shared memory API must be compiled with I<cc -lrt> "
7438 "to link against the real-time library, I<librt>."
7442 #: build/C/man7/shm_overview.7:94
7444 msgid "Accessing shared memory objects via the filesystem"
7448 #: build/C/man7/shm_overview.7:101
7450 "On Linux, shared memory objects are created in a (I<tmpfs>) virtual "
7451 "filesystem, normally mounted under I</dev/shm>. Since kernel 2.6.19, Linux "
7452 "supports the use of access control lists (ACLs) to control the permissions "
7453 "of objects in the virtual filesystem."
7457 #: build/C/man7/shm_overview.7:106
7459 "Typically, processes must synchronize their access to a shared memory "
7460 "object, using, for example, POSIX semaphores."
7464 #: build/C/man7/shm_overview.7:114
7466 "System V shared memory (B<shmget>(2), B<shmop>(2), etc.) is an older shared "
7467 "memory API. POSIX shared memory provides a simpler, and better designed "
7468 "interface; on the other hand POSIX shared memory is somewhat less widely "
7469 "available (especially on older systems) than System V shared memory."
7473 #: build/C/man7/shm_overview.7:127
7475 "B<fchmod>(2), B<fchown>(2), B<fstat>(2), B<ftruncate>(2), B<mmap>(2), "
7476 "B<mprotect>(2), B<munmap>(2), B<shmget>(2), B<shmop>(2), B<shm_open>(3), "
7477 "B<shm_unlink>(3), B<sem_overview>(7)"
7481 #: build/C/man2/shmctl.2:45
7487 #: build/C/man2/shmctl.2:45
7493 #: build/C/man2/shmctl.2:48
7494 msgid "shmctl - System V shared memory control"
7498 #: build/C/man2/shmctl.2:51 build/C/man2/shmget.2:44
7499 msgid "B<#include E<lt>sys/ipc.hE<gt>>"
7503 #: build/C/man2/shmctl.2:53 build/C/man2/shmget.2:46
7504 msgid "B<#include E<lt>sys/shm.hE<gt>>"
7508 #: build/C/man2/shmctl.2:55
7509 msgid "B<int shmctl(int >I<shmid>B<, int >I<cmd>B<, struct shmid_ds *>I<buf>B<);>"
7513 #: build/C/man2/shmctl.2:62
7515 "B<shmctl>() performs the control operation specified by I<cmd> on the "
7516 "System\\ V shared memory segment whose identifier is given in I<shmid>."
7520 #: build/C/man2/shmctl.2:67
7522 "The I<buf> argument is a pointer to a I<shmid_ds> structure, defined in "
7523 "I<E<lt>sys/shm.hE<gt>> as follows:"
7527 #: build/C/man2/shmctl.2:81
7530 "struct shmid_ds {\n"
7531 " struct ipc_perm shm_perm; /* Ownership and permissions */\n"
7532 " size_t shm_segsz; /* Size of segment (bytes) */\n"
7533 " time_t shm_atime; /* Last attach time */\n"
7534 " time_t shm_dtime; /* Last detach time */\n"
7535 " time_t shm_ctime; /* Last change time */\n"
7536 " pid_t shm_cpid; /* PID of creator */\n"
7537 " pid_t shm_lpid; /* PID of last shmat(2)/shmdt(2) */\n"
7538 " shmatt_t shm_nattch; /* No. of current attaches */\n"
7544 #: build/C/man2/shmctl.2:89
7546 "The I<ipc_perm> structure is defined as follows (the highlighted fields are "
7547 "settable using B<IPC_SET>):"
7551 #: build/C/man2/shmctl.2:102
7554 "struct ipc_perm {\n"
7555 " key_t __key; /* Key supplied to shmget(2) */\n"
7556 " uid_t B<uid>; /* Effective UID of owner */\n"
7557 " gid_t B<gid>; /* Effective GID of owner */\n"
7558 " uid_t cuid; /* Effective UID of creator */\n"
7559 " gid_t cgid; /* Effective GID of creator */\n"
7560 " unsigned short B<mode>; /* B<Permissions> + SHM_DEST and\n"
7561 " SHM_LOCKED flags */\n"
7562 " unsigned short __seq; /* Sequence number */\n"
7567 #: build/C/man2/shmctl.2:108
7568 msgid "Valid values for I<cmd> are:"
7572 #: build/C/man2/shmctl.2:109
7578 #: build/C/man2/shmctl.2:118
7580 "Copy information from the kernel data structure associated with I<shmid> "
7581 "into the I<shmid_ds> structure pointed to by I<buf>. The caller must have "
7582 "read permission on the shared memory segment."
7586 #: build/C/man2/shmctl.2:118
7592 #: build/C/man2/shmctl.2:136
7594 "Write the values of some members of the I<shmid_ds> structure pointed to by "
7595 "I<buf> to the kernel data structure associated with this shared memory "
7596 "segment, updating also its I<shm_ctime> member. The following fields can be "
7597 "changed: I<shm_perm.uid>, I<shm_perm.gid>, and (the least significant 9 bits "
7598 "of) I<shm_perm.mode>. The effective UID of the calling process must match "
7599 "the owner (I<shm_perm.uid>) or creator (I<shm_perm.cuid>) of the shared "
7600 "memory segment, or the caller must be privileged."
7604 #: build/C/man2/shmctl.2:136
7610 #: build/C/man2/shmctl.2:149
7612 "Mark the segment to be destroyed. The segment will actually be destroyed "
7613 "only after the last process detaches it (i.e., when the I<shm_nattch> member "
7614 "of the associated structure I<shmid_ds> is zero). The caller must be the "
7615 "owner or creator of the segment, or be privileged. The I<buf> argument is "
7620 #: build/C/man2/shmctl.2:157
7622 "If a segment has been marked for destruction, then the (nonstandard) "
7623 "B<SHM_DEST> flag of the I<shm_perm.mode> field in the associated data "
7624 "structure retrieved by B<IPC_STAT> will be set."
7628 #: build/C/man2/shmctl.2:160
7630 "The caller I<must> ensure that a segment is eventually destroyed; otherwise "
7631 "its pages that were faulted in will remain in memory or swap."
7635 #: build/C/man2/shmctl.2:165
7637 "See also the description of I</proc/sys/kernel/shm_rmid_forced> in "
7642 #: build/C/man2/shmctl.2:165
7644 msgid "B<IPC_INFO> (Linux-specific)"
7648 #: build/C/man2/shmctl.2:178
7650 "Return information about system-wide shared memory limits and parameters in "
7651 "the structure pointed to by I<buf>. This structure is of type I<shminfo> "
7652 "(thus, a cast is required), defined in I<E<lt>sys/shm.hE<gt>> if the "
7653 "B<_GNU_SOURCE> feature test macro is defined:"
7657 #: build/C/man2/shmctl.2:192
7660 "struct shminfo {\n"
7661 " unsigned long shmmax; /* Maximum segment size */\n"
7662 " unsigned long shmmin; /* Minimum segment size;\n"
7664 " unsigned long shmmni; /* Maximum number of segments */\n"
7665 " unsigned long shmseg; /* Maximum number of segments\n"
7666 " that a process can attach;\n"
7667 " unused within kernel */\n"
7668 " unsigned long shmall; /* Maximum number of pages of\n"
7669 " shared memory, system-wide */\n"
7674 #: build/C/man2/shmctl.2:205
7676 "The I<shmmni>, I<shmmax>, and I<shmall> settings can be changed via I</proc> "
7677 "files of the same name; see B<proc>(5) for details."
7681 #: build/C/man2/shmctl.2:205
7683 msgid "B<SHM_INFO> (Linux-specific)"
7687 #: build/C/man2/shmctl.2:216
7689 "Return a I<shm_info> structure whose fields contain information about system "
7690 "resources consumed by shared memory. This structure is defined in "
7691 "I<E<lt>sys/shm.hE<gt>> if the B<_GNU_SOURCE> feature test macro is defined:"
7695 #: build/C/man2/shmctl.2:233
7698 "struct shm_info {\n"
7699 " int used_ids; /* # of currently existing\n"
7701 " unsigned long shm_tot; /* Total number of shared\n"
7702 " memory pages */\n"
7703 " unsigned long shm_rss; /* # of resident shared\n"
7704 " memory pages */\n"
7705 " unsigned long shm_swp; /* # of swapped shared\n"
7706 " memory pages */\n"
7707 " unsigned long swap_attempts;\n"
7708 " /* Unused since Linux 2.4 */\n"
7709 " unsigned long swap_successes;\n"
7710 " /* Unused since Linux 2.4 */\n"
7715 #: build/C/man2/shmctl.2:235
7717 msgid "B<SHM_STAT> (Linux-specific)"
7721 #: build/C/man2/shmctl.2:246
7723 "Return a I<shmid_ds> structure as for B<IPC_STAT>. However, the I<shmid> "
7724 "argument is not a segment identifier, but instead an index into the kernel's "
7725 "internal array that maintains information about all shared memory segments "
7730 #: build/C/man2/shmctl.2:249
7732 "The caller can prevent or allow swapping of a shared memory segment with the "
7733 "following I<cmd> values:"
7737 #: build/C/man2/shmctl.2:250
7739 msgid "B<SHM_LOCK> (Linux-specific)"
7743 #: build/C/man2/shmctl.2:262
7745 "Prevent swapping of the shared memory segment. The caller must fault in any "
7746 "pages that are required to be present after locking is enabled. If a "
7747 "segment has been locked, then the (nonstandard) B<SHM_LOCKED> flag of the "
7748 "I<shm_perm.mode> field in the associated data structure retrieved by "
7749 "B<IPC_STAT> will be set."
7753 #: build/C/man2/shmctl.2:262
7755 msgid "B<SHM_UNLOCK> (Linux-specific)"
7759 #: build/C/man2/shmctl.2:265
7760 msgid "Unlock the segment, allowing it to be swapped out."
7763 #. There was some weirdness in 2.6.9: SHM_LOCK and SHM_UNLOCK could
7764 #. be applied to a segment, regardless of ownership of the segment.
7765 #. This was a botch-up in the move to RLIMIT_MEMLOCK, and was fixed
7766 #. in 2.6.10. MTK, May 2005
7768 #: build/C/man2/shmctl.2:283
7770 "In kernels before 2.6.10, only a privileged process could employ B<SHM_LOCK> "
7771 "and B<SHM_UNLOCK>. Since kernel 2.6.10, an unprivileged process can employ "
7772 "these operations if its effective UID matches the owner or creator UID of "
7773 "the segment, and (for B<SHM_LOCK>) the amount of memory to be locked falls "
7774 "within the B<RLIMIT_MEMLOCK> resource limit (see B<setrlimit>(2))."
7778 #: build/C/man2/shmctl.2:301
7780 "A successful B<IPC_INFO> or B<SHM_INFO> operation returns the index of the "
7781 "highest used entry in the kernel's internal array recording information "
7782 "about all shared memory segments. (This information can be used with "
7783 "repeated B<SHM_STAT> operations to obtain information about all shared "
7784 "memory segments on the system.) A successful B<SHM_STAT> operation returns "
7785 "the identifier of the shared memory segment whose index was given in "
7786 "I<shmid>. Other operations return 0 on success."
7790 #: build/C/man2/shmctl.2:305
7791 msgid "On error, -1 is returned, and I<errno> is set appropriately."
7795 #: build/C/man2/shmctl.2:314
7797 "B<IPC_STAT> or B<SHM_STAT> is requested and I<shm_perm.mode> does not allow "
7798 "read access for I<shmid>, and the calling process does not have the "
7799 "B<CAP_IPC_OWNER> capability."
7803 #: build/C/man2/shmctl.2:325
7805 "The argument I<cmd> has value B<IPC_SET> or B<IPC_STAT> but the address "
7806 "pointed to by I<buf> isn't accessible."
7810 #: build/C/man2/shmctl.2:325 build/C/man2/shmop.2:194
7816 #: build/C/man2/shmctl.2:328 build/C/man2/shmop.2:197
7817 msgid "I<shmid> points to a removed identifier."
7821 #: build/C/man2/shmctl.2:337
7823 "I<shmid> is not a valid identifier, or I<cmd> is not a valid command. Or: "
7824 "for a B<SHM_STAT> operation, the index value specified in I<shmid> referred "
7825 "to an array slot that is currently unused."
7829 #: build/C/man2/shmctl.2:348
7831 "(In kernels since 2.6.9), B<SHM_LOCK> was specified and the size of the "
7832 "to-be-locked segment would mean that the total bytes in locked shared memory "
7833 "segments would exceed the limit for the real user ID of the calling "
7834 "process. This limit is defined by the B<RLIMIT_MEMLOCK> soft resource limit "
7835 "(see B<setrlimit>(2))."
7839 #: build/C/man2/shmctl.2:353
7841 "B<IPC_STAT> is attempted, and the GID or UID value is too large to be stored "
7842 "in the structure pointed to by I<buf>."
7846 #: build/C/man2/shmctl.2:365
7848 "B<IPC_SET> or B<IPC_RMID> is attempted, and the effective user ID of the "
7849 "calling process is not that of the creator (found in I<shm_perm.cuid>), or "
7850 "the owner (found in I<shm_perm.uid>), and the process was not privileged "
7851 "(Linux: did not have the B<CAP_SYS_ADMIN> capability)."
7855 #: build/C/man2/shmctl.2:377
7857 "Or (in kernels before 2.6.9), B<SHM_LOCK> or B<SHM_UNLOCK> was specified, "
7858 "but the process was not privileged (Linux: did not have the B<CAP_IPC_LOCK> "
7859 "capability). (Since Linux 2.6.9, this error can also occur if the "
7860 "B<RLIMIT_MEMLOCK> is 0 and the caller is not privileged.)"
7863 #. SVr4 documents an additional error condition EMFILE.
7865 #: build/C/man2/shmctl.2:382 build/C/man2/shmget.2:251 build/C/man2/shmop.2:231
7866 msgid "SVr4, POSIX.1-2001."
7869 #. Like Linux, the FreeBSD man pages still document
7870 #. the inclusion of these header files.
7872 #: build/C/man2/shmctl.2:395 build/C/man2/shmget.2:269
7874 "The inclusion of I<E<lt>sys/types.hE<gt>> and I<E<lt>sys/ipc.hE<gt>> isn't "
7875 "required on Linux or by any version of POSIX. However, some old "
7876 "implementations required the inclusion of these header files, and the SVID "
7877 "also documented their inclusion. Applications intended to be portable to "
7878 "such old systems may need to include these header files."
7882 #: build/C/man2/shmctl.2:407
7884 "The B<IPC_INFO>, B<SHM_STAT> and B<SHM_INFO> operations are used by the "
7885 "B<ipcs>(1) program to provide information on allocated resources. In the "
7886 "future, these may modified or moved to a I</proc> filesystem interface."
7890 #: build/C/man2/shmctl.2:415
7892 "Linux permits a process to attach (B<shmat>(2)) a shared memory segment "
7893 "that has already been marked for deletion using I<shmctl(IPC_RMID)>. This "
7894 "feature is not available on other UNIX implementations; portable "
7895 "applications should avoid relying on it."
7899 #: build/C/man2/shmctl.2:428
7901 "Various fields in a I<struct shmid_ds> were typed as I<short> under Linux "
7902 "2.2 and have become I<long> under Linux 2.4. To take advantage of this, a "
7903 "recompilation under glibc-2.1.91 or later should suffice. (The kernel "
7904 "distinguishes old and new calls by an B<IPC_64> flag in I<cmd>.)"
7908 #: build/C/man2/shmctl.2:435
7910 "B<mlock>(2), B<setrlimit>(2), B<shmget>(2), B<shmop>(2), B<capabilities>(7), "
7915 #: build/C/man2/shmget.2:38
7921 #: build/C/man2/shmget.2:38
7927 #: build/C/man2/shmget.2:41
7928 msgid "shmget - allocates a System V shared memory segment"
7932 #: build/C/man2/shmget.2:48
7933 msgid "B<int shmget(key_t >I<key>B<, size_t >I<size>B<, int >I<shmflg>B<);>"
7937 #: build/C/man2/shmget.2:72
7939 "B<shmget>() returns the identifier of the System\\ V shared memory segment "
7940 "associated with the value of the argument I<key>. A new shared memory "
7941 "segment, with size equal to the value of I<size> rounded up to a multiple of "
7942 "B<PAGE_SIZE>, is created if I<key> has the value B<IPC_PRIVATE> or I<key> "
7943 "isn't B<IPC_PRIVATE>, no shared memory segment corresponding to I<key> "
7944 "exists, and B<IPC_CREAT> is specified in I<shmflg>."
7948 #: build/C/man2/shmget.2:91
7950 "If I<shmflg> specifies both B<IPC_CREAT> and B<IPC_EXCL> and a shared memory "
7951 "segment already exists for I<key>, then B<shmget>() fails with I<errno> set "
7952 "to B<EEXIST>. (This is analogous to the effect of the combination B<O_CREAT "
7953 "| O_EXCL> for B<open>(2).)"
7957 #: build/C/man2/shmget.2:95
7958 msgid "The value I<shmflg> is composed of:"
7962 #: build/C/man2/shmget.2:95
7964 msgid "B<IPC_CREAT>"
7968 #: build/C/man2/shmget.2:102
7970 "Create a new segment. If this flag is not used, then B<shmget>() will find "
7971 "the segment associated with I<key> and check to see if the user has "
7972 "permission to access the segment."
7976 #: build/C/man2/shmget.2:102
7982 #: build/C/man2/shmget.2:108
7984 "This flag is used with B<IPC_CREAT> to ensure that this call creates the "
7985 "segment. If the segment already exists, the call fails."
7989 #: build/C/man2/shmget.2:108
7991 msgid "B<SHM_HUGETLB> (since Linux 2.6)"
7995 #: build/C/man2/shmget.2:114
7997 "Allocate the segment using \"huge pages.\" See the Linux kernel source file "
7998 "I<Documentation/vm/hugetlbpage.txt> for further information."
8002 #: build/C/man2/shmget.2:114
8004 msgid "B<SHM_NORESERVE> (since Linux 2.6.15)"
8007 #. As at 2.6.17-rc2, this flag has no effect if SHM_HUGETLB was also
8010 #: build/C/man2/shmget.2:133
8012 "This flag serves the same purpose as the B<mmap>(2) B<MAP_NORESERVE> flag. "
8013 "Do not reserve swap space for this segment. When swap space is reserved, "
8014 "one has the guarantee that it is possible to modify the segment. When swap "
8015 "space is not reserved one might get B<SIGSEGV> upon a write if no physical "
8016 "memory is available. See also the discussion of the file "
8017 "I</proc/sys/vm/overcommit_memory> in B<proc>(5)."
8021 #: build/C/man2/shmget.2:143
8023 "In addition to the above flags, the least significant 9 bits of I<shmflg> "
8024 "specify the permissions granted to the owner, group, and others. These bits "
8025 "have the same format, and the same meaning, as the I<mode> argument of "
8026 "B<open>(2). Presently, execute permissions are not used by the system."
8030 #: build/C/man2/shmget.2:151
8032 "When a new shared memory segment is created, its contents are initialized to "
8033 "zero values, and its associated data structure, I<shmid_ds> (see "
8034 "B<shmctl>(2)), is initialized as follows:"
8038 #: build/C/man2/shmget.2:156
8040 "I<shm_perm.cuid> and I<shm_perm.uid> are set to the effective user ID of the "
8045 #: build/C/man2/shmget.2:161
8047 "I<shm_perm.cgid> and I<shm_perm.gid> are set to the effective group ID of "
8048 "the calling process."
8052 #: build/C/man2/shmget.2:166
8054 "The least significant 9 bits of I<shm_perm.mode> are set to the least "
8055 "significant 9 bit of I<shmflg>."
8059 #: build/C/man2/shmget.2:170
8060 msgid "I<shm_segsz> is set to the value of I<size>."
8064 #: build/C/man2/shmget.2:177
8065 msgid "I<shm_lpid>, I<shm_nattch>, I<shm_atime>, and I<shm_dtime> are set to 0."
8069 #: build/C/man2/shmget.2:180
8070 msgid "I<shm_ctime> is set to the current time."
8074 #: build/C/man2/shmget.2:183
8076 "If the shared memory segment already exists, the permissions are verified, "
8077 "and a check is made to see if it is marked for destruction."
8081 #: build/C/man2/shmget.2:188
8083 "On success, a valid shared memory identifier is returned. On error, -1 is "
8084 "returned, and I<errno> is set to indicate the error."
8088 #: build/C/man2/shmget.2:192
8089 msgid "On failure, I<errno> is set to one of the following:"
8093 #: build/C/man2/shmget.2:198
8095 "The user does not have permission to access the shared memory segment, and "
8096 "does not have the B<CAP_IPC_OWNER> capability."
8100 #: build/C/man2/shmget.2:207
8102 "B<IPC_CREAT> and B<IPC_EXCL> were specified in I<shmflg>, but a shared "
8103 "memory segment already exists for I<key>."
8107 #: build/C/man2/shmget.2:215
8109 "A new segment was to be created and I<size> is less than B<SHMMIN> or "
8110 "greater than B<SHMMAX>."
8114 #: build/C/man2/shmget.2:221
8116 "A segment for the given I<key> exists, but I<size> is greater than the size "
8121 #: build/C/man2/shmget.2:230
8122 msgid "No segment exists for the given I<key>, and B<IPC_CREAT> was not specified."
8126 #: build/C/man2/shmget.2:233
8127 msgid "No memory could be allocated for segment overhead."
8131 #: build/C/man2/shmget.2:241
8133 "All possible shared memory IDs have been taken (B<SHMMNI>), or allocating a "
8134 "segment of the requested I<size> would cause the system to exceed the "
8135 "system-wide limit on shared memory (B<SHMALL>)."
8139 #: build/C/man2/shmget.2:248
8141 "The B<SHM_HUGETLB> flag was specified, but the caller was not privileged "
8142 "(did not have the B<CAP_IPC_LOCK> capability)."
8146 #: build/C/man2/shmget.2:256
8147 msgid "B<SHM_HUGETLB> and B<SHM_NORESERVE> are Linux extensions."
8151 #: build/C/man2/shmget.2:280
8153 "B<IPC_PRIVATE> isn't a flag field but a I<key_t> type. If this special "
8154 "value is used for I<key>, the system call ignores all but the least "
8155 "significant 9 bits of I<shmflg> and creates a new shared memory segment."
8159 #: build/C/man2/shmget.2:280
8161 msgid "Shared memory limits"
8165 #: build/C/man2/shmget.2:284
8167 "The following limits on shared memory segment resources affect the "
8172 #: build/C/man2/shmget.2:284
8178 #: build/C/man2/shmget.2:288
8180 "System-wide limit on the total amount of shared memory, measured in units of "
8181 "the system page size."
8184 #. commit 060028bac94bf60a65415d1d55a359c3a17d5c31
8186 #: build/C/man2/shmget.2:294
8188 "On Linux, this limit can be read and modified via "
8189 "I</proc/sys/kernel/shmall>. Since Linux 3.16, the default value for this "
8194 #: build/C/man2/shmget.2:296 build/C/man2/shmget.2:331
8196 msgid " ULONG_MAX - 2^24\n"
8200 #: build/C/man2/shmget.2:307
8202 "The effect of this value (which is suitable for both 32-bit and 64-bit "
8203 "systems) is to impose no limitation on allocations. This value, rather "
8204 "than B<ULONG_MAX>, was chosen as the default to prevent some cases where "
8205 "historical applications simply raised the existing limit without first "
8206 "checking its current value. Such applications would cause the value to "
8207 "overflow if the limit was set at B<ULONG_MAX>."
8211 #: build/C/man2/shmget.2:310
8212 msgid "From Linux 2.4 up to Linux 3.15, the default value for this limit was:"
8216 #: build/C/man2/shmget.2:312
8218 msgid " SHMMAX / PAGE_SIZE * (SHMMNI / 16)\n"
8222 #: build/C/man2/shmget.2:320
8224 "If B<SHMMAX> and B<SHMMNI> were not modified, then multiplying the result of "
8225 "this formula by the page size (to get a value in bytes) yielded a value of 8 "
8226 "GB as the limit on the total memory used by all shared memory segments."
8230 #: build/C/man2/shmget.2:320
8236 #: build/C/man2/shmget.2:323
8237 msgid "Maximum size in bytes for a shared memory segment."
8240 #. commit 060028bac94bf60a65415d1d55a359c3a17d5c31
8242 #: build/C/man2/shmget.2:329
8244 "On Linux, this limit can be read and modified via "
8245 "I</proc/sys/kernel/shmmax>. Since Linux 3.16, the default value for this "
8250 #: build/C/man2/shmget.2:340
8252 "The effect of this value (which is suitable for both 32-bit and 64-bit "
8253 "systems) is to impose no limitation on allocations. See the description of "
8254 "B<SHMALL> for a discussion of why this default value (rather than "
8255 "B<ULONG_MAX>) is used."
8259 #: build/C/man2/shmget.2:343
8261 "From Linux 2.2 up to Linux 3.15, the default value of this limit was "
8266 #: build/C/man2/shmget.2:349
8268 "Because it is not possible to map just part of a shared memory segment, the "
8269 "amount of virtual memory places another limit on the maximum size of a "
8270 "usable segment: for example, on i386 the largest segments that can be mapped "
8271 "have a size of around 2.8 GB, and on x86_64 the limit is around 127 TB."
8275 #: build/C/man2/shmget.2:349
8281 #: build/C/man2/shmget.2:355
8283 "Minimum size in bytes for a shared memory segment: implementation dependent "
8284 "(currently 1 byte, though B<PAGE_SIZE> is the effective minimum size)."
8288 #: build/C/man2/shmget.2:355
8294 #: build/C/man2/shmget.2:360
8296 "System-wide limit on the number of shared memory segments. In Linux 2.2, "
8297 "the default value for this limit was 128; since Linux 2.4, the default value "
8301 #. Kernels between 2.4.x and 2.6.8 had an off-by-one error that meant
8302 #. that we could create one more segment than SHMMNI -- MTK
8303 #. This /proc file is not available in Linux 2.2 and earlier -- MTK
8305 #: build/C/man2/shmget.2:366
8307 "On Linux, this limit can be read and modified via "
8308 "I</proc/sys/kernel/shmmni>."
8312 #: build/C/man2/shmget.2:370
8314 "The implementation has no specific limits for the per-process maximum number "
8315 "of shared memory segments (B<SHMSEG>)."
8319 #: build/C/man2/shmget.2:376
8321 "Until version 2.3.30, Linux would return B<EIDRM> for a B<shmget>() on a "
8322 "shared memory segment scheduled for deletion."
8326 #: build/C/man2/shmget.2:382
8328 "The name choice B<IPC_PRIVATE> was perhaps unfortunate, B<IPC_NEW> would "
8329 "more clearly show its function."
8333 #: build/C/man2/shmget.2:391
8335 "B<memfd_create>(2), B<shmat>(2), B<shmctl>(2), B<shmdt>(2), B<ftok>(3), "
8336 "B<capabilities>(7), B<shm_overview>(7), B<svipc>(7)"
8340 #: build/C/man2/shmop.2:41
8346 #: build/C/man2/shmop.2:44
8347 msgid "shmat, shmdt - System V shared memory operations"
8351 #: build/C/man2/shmop.2:48
8354 "B<#include E<lt>sys/types.hE<gt>>\n"
8355 "B<#include E<lt>sys/shm.hE<gt>>\n"
8359 #: build/C/man2/shmop.2:50
8362 "B<void *shmat(int >I<shmid>B<, const void *>I<shmaddr>B<, int "
8367 #: build/C/man2/shmop.2:52
8369 msgid "B<int shmdt(const void *>I<shmaddr>B<);>\n"
8373 #: build/C/man2/shmop.2:54
8379 #: build/C/man2/shmop.2:62
8381 "B<shmat>() attaches the System\\ V shared memory segment identified by "
8382 "I<shmid> to the address space of the calling process. The attaching address "
8383 "is specified by I<shmaddr> with one of the following criteria:"
8387 #: build/C/man2/shmop.2:68
8389 "If I<shmaddr> is NULL, the system chooses a suitable (unused) address at "
8390 "which to attach the segment."
8394 #: build/C/man2/shmop.2:80
8396 "If I<shmaddr> isn't NULL and B<SHM_RND> is specified in I<shmflg>, the "
8397 "attach occurs at the address equal to I<shmaddr> rounded down to the nearest "
8398 "multiple of B<SHMLBA>."
8402 #: build/C/man2/shmop.2:84
8404 "Otherwise, I<shmaddr> must be a page-aligned address at which the attach "
8409 #: build/C/man2/shmop.2:90
8411 "In addition to B<SHM_RND>, the following flags may be specified in the "
8412 "I<shmflg> bit-mask argument:"
8416 #: build/C/man2/shmop.2:90
8418 msgid "B<SHM_EXEC> (Linux-specific; since Linux 2.6.9)"
8422 #: build/C/man2/shmop.2:94
8424 "Allow the contents of the segment to be executed. The caller must have "
8425 "execute permission on the segment."
8429 #: build/C/man2/shmop.2:94
8431 msgid "B<SHM_RDONLY>"
8435 #: build/C/man2/shmop.2:102
8437 "Attach the segment for read-only access. The process must have read "
8438 "permission for the segment. If this flag is not specified, the segment is "
8439 "attached for read and write access, and the process must have read and write "
8440 "permission for the segment. There is no notion of a write-only shared "
8445 #: build/C/man2/shmop.2:102
8447 msgid "B<SHM_REMAP> (Linux-specific)"
8451 #: build/C/man2/shmop.2:115
8453 "This flag specifies that the mapping of the segment should replace any "
8454 "existing mapping in the range starting at I<shmaddr> and continuing for the "
8455 "size of the segment. (Normally, an B<EINVAL> error would result if a "
8456 "mapping already exists in this address range.) In this case, I<shmaddr> "
8461 #: build/C/man2/shmop.2:122
8463 "The B<brk>(2) value of the calling process is not altered by the attach. "
8464 "The segment will automatically be detached at process exit. The same "
8465 "segment may be attached as a read and as a read-write one, and more than "
8466 "once, in the process's address space."
8470 #: build/C/man2/shmop.2:130
8472 "A successful B<shmat>() call updates the members of the I<shmid_ds> "
8473 "structure (see B<shmctl>(2)) associated with the shared memory segment as "
8478 #: build/C/man2/shmop.2:133
8479 msgid "I<shm_atime> is set to the current time."
8483 #: build/C/man2/shmop.2:136 build/C/man2/shmop.2:163
8484 msgid "I<shm_lpid> is set to the process-ID of the calling process."
8488 #: build/C/man2/shmop.2:140
8489 msgid "I<shm_nattch> is incremented by one."
8493 #: build/C/man2/shmop.2:140
8499 #: build/C/man2/shmop.2:151
8501 "B<shmdt>() detaches the shared memory segment located at the address "
8502 "specified by I<shmaddr> from the address space of the calling process. The "
8503 "to-be-detached segment must be currently attached with I<shmaddr> equal to "
8504 "the value returned by the attaching B<shmat>() call."
8508 #: build/C/man2/shmop.2:157
8510 "On a successful B<shmdt>() call, the system updates the members of the "
8511 "I<shmid_ds> structure associated with the shared memory segment as follows:"
8515 #: build/C/man2/shmop.2:160
8516 msgid "I<shm_dtime> is set to the current time."
8520 #: build/C/man2/shmop.2:168
8522 "I<shm_nattch> is decremented by one. If it becomes 0 and the segment is "
8523 "marked for deletion, the segment is deleted."
8527 #: build/C/man2/shmop.2:176
8529 "On success, B<shmat>() returns the address of the attached shared memory "
8530 "segment; on error, I<(void\\ *)\\ -1> is returned, and I<errno> is set to "
8531 "indicate the cause of the error."
8535 #: build/C/man2/shmop.2:182
8537 "On success, B<shmdt>() returns 0; on error -1 is returned, and I<errno> is "
8538 "set to indicate the cause of the error."
8542 #: build/C/man2/shmop.2:188
8543 msgid "When B<shmat>() fails, I<errno> is set to one of the following:"
8547 #: build/C/man2/shmop.2:194
8549 "The calling process does not have the required permissions for the requested "
8550 "attach type, and does not have the B<CAP_IPC_OWNER> capability."
8554 #: build/C/man2/shmop.2:211
8556 "Invalid I<shmid> value, unaligned (i.e., not page-aligned and B<SHM_RND> was "
8557 "not specified) or invalid I<shmaddr> value, or can't attach segment at "
8558 "I<shmaddr>, or B<SHM_REMAP> was specified and I<shmaddr> was NULL."
8562 #: build/C/man2/shmop.2:214
8563 msgid "Could not allocate memory for the descriptor or for the page tables."
8567 #: build/C/man2/shmop.2:220
8568 msgid "When B<shmdt>() fails, I<errno> is set as follows:"
8571 #. The following since 2.6.17-rc1:
8573 #: build/C/man2/shmop.2:228
8575 "There is no shared memory segment attached at I<shmaddr>; or, I<shmaddr> is "
8576 "not aligned on a page boundary."
8580 #: build/C/man2/shmop.2:243
8582 "In SVID 3 (or perhaps earlier), the type of the I<shmaddr> argument was "
8583 "changed from I<char\\ *> into I<const void\\ *>, and the returned type of "
8584 "B<shmat>() from I<char\\ *> into I<void\\ *>."
8588 #: build/C/man2/shmop.2:248
8589 msgid "After a B<fork>(2), the child inherits the attached shared memory segments."
8593 #: build/C/man2/shmop.2:252
8595 "After an B<execve>(2), all attached shared memory segments are detached from "
8600 #: build/C/man2/shmop.2:256
8602 "Upon B<_exit>(2), all attached shared memory segments are detached from the "
8607 #: build/C/man2/shmop.2:268
8609 "Using B<shmat>() with I<shmaddr> equal to NULL is the preferred, portable "
8610 "way of attaching a shared memory segment. Be aware that the shared memory "
8611 "segment attached in this way may be attached at different addresses in "
8612 "different processes. Therefore, any pointers maintained within the shared "
8613 "memory must be made relative (typically to the starting address of the "
8614 "segment), rather than absolute."
8618 #: build/C/man2/shmop.2:273
8620 "On Linux, it is possible to attach a shared memory segment even if it is "
8621 "already marked to be deleted. However, POSIX.1-2001 does not specify this "
8622 "behavior and many other implementations do not support it."
8626 #: build/C/man2/shmop.2:276
8627 msgid "The following system parameter affects B<shmat>():"
8631 #: build/C/man2/shmop.2:276
8637 #: build/C/man2/shmop.2:289
8639 "Segment low boundary address multiple. When explicitly specifying an attach "
8640 "address in a call to B<shmat>(), the caller should ensure that the address "
8641 "is a multiple of this value. This is necessary on some architectures, in "
8642 "order either to ensure good CPU cache performance or to ensure that "
8643 "different attaches of the same segment have consistent views within the CPU "
8644 "cache. B<SHMLBA> is normally some multiple of the system page size (on many "
8645 "Linux architectures, it is the same as the system page size)."
8649 #: build/C/man2/shmop.2:293
8651 "The implementation places no intrinsic per-process limit on the number of "
8652 "shared memory segments (B<SHMSEG>)."
8656 #: build/C/man2/shmop.2:301
8658 "B<brk>(2), B<mmap>(2), B<shmctl>(2), B<shmget>(2), B<capabilities>(7), "
8659 "B<shm_overview>(7), B<svipc>(7)"
8663 #: build/C/man2/subpage_prot.2:30
8665 msgid "SUBPAGE_PROT"
8669 #: build/C/man2/subpage_prot.2:30
8675 #: build/C/man2/subpage_prot.2:33
8676 msgid "subpage_prot - define a subpage protection for an address range"
8680 #: build/C/man2/subpage_prot.2:37
8683 "B<long subpage_prot(unsigned long >I<addr>B<, unsigned long >I<len>B<,>\n"
8684 "B< uint32_t *>I<map>B<);>\n"
8688 #: build/C/man2/subpage_prot.2:41
8689 msgid "I<Note>: There is no glibc wrapper for this system call; see NOTES."
8693 #: build/C/man2/subpage_prot.2:47
8695 "The PowerPC-specific B<subpage_prot>() system call provides the facility to "
8696 "control the access permissions on individual 4kB subpages on systems "
8697 "configured with a page size of 64kB."
8701 #: build/C/man2/subpage_prot.2:54
8703 "The protection map is applied to the memory pages in the region starting at "
8704 "I<addr> and continuing for I<len> bytes. Both of these arguments must be "
8705 "aligned to a 64-kB boundary."
8709 #: build/C/man2/subpage_prot.2:66
8711 "The protection map is specified in the buffer pointed to by I<map>. The map "
8712 "has 2 bits per 4kB subpage; thus each 32-bit word specifies the protections "
8713 "of 16 4kB subpages inside a 64kB page (so, the number of 32-bit words "
8714 "pointed to by I<map> should equate to the number of 64-kB pages specified by "
8715 "I<len>). Each 2-bit field in the protection map is either 0 to allow any "
8716 "access, 1 to prevent writes, or 2 or 3 to prevent all accesses."
8720 #: build/C/man2/subpage_prot.2:71
8722 "On success, B<subpage_prot>() returns 0. Otherwise, one of the error codes "
8723 "specified below is returned."
8727 #: build/C/man2/subpage_prot.2:77
8728 msgid "The buffer referred to by I<map> is not accessible."
8732 #: build/C/man2/subpage_prot.2:87
8734 "The I<addr> or I<len> arguments are incorrect. Both of these arguments must "
8735 "be aligned to a multiple of the system page size, and they must not refer to "
8736 "a region outside of the address space of the process or to a region that "
8737 "consists of huge pages."
8741 #: build/C/man2/subpage_prot.2:90 build/C/man2/sync_file_range.2:166
8742 msgid "Out of memory."
8746 #: build/C/man2/subpage_prot.2:96
8748 "This system call is provided on the PowerPC architecture since Linux "
8749 "2.6.25. The system call is provided only if the kernel is configured with "
8750 "B<CONFIG_PPC_64K_PAGES>. No library support is provided."
8754 #: build/C/man2/subpage_prot.2:101
8756 "Glibc does not provide a wrapper for this system call; call it using "
8761 #: build/C/man2/subpage_prot.2:106
8763 "Normal page protections (at the 64-kB page level) also apply; the subpage "
8764 "protection mechanism is an additional constraint, so putting 0 in a 2-bit "
8765 "field won't allow writes to a page that is otherwise write-protected."
8769 #: build/C/man2/subpage_prot.2:106
8774 #. In the initial implementation, it was the case that:
8775 #. In fact the whole process is switched to use 4k hardware pages when the
8776 #. subpage_prot system call is used, but this could be improved in future
8777 #. to switch only the affected segments.
8778 #. But Paul Mackerass says (Oct 2010): I'm pretty sure we now only switch
8779 #. the affected segment, not the whole process.
8781 #: build/C/man2/subpage_prot.2:128
8783 "This system call is provided to assist writing emulators that operate using "
8784 "64-kB pages on PowerPC systems. When emulating systems such as x86, which "
8785 "uses a smaller page size, the emulator can no longer use the "
8786 "memory-management unit (MMU) and normal system calls for controlling page "
8787 "protections. (The emulator could emulate the MMU by checking and possibly "
8788 "remapping the address for each memory access in software, but that is slow.) "
8789 "The idea is that the emulator supplies an array of protection masks to apply "
8790 "to a specified range of virtual addresses. These masks are applied at the "
8791 "level where hardware page-table entries (PTEs) are inserted into the "
8792 "hardware page table based on the Linux PTEs, so the Linux PTEs are not "
8793 "affected. Implicit in this is that the regions of the address space that "
8794 "are protected are switched to use 4-kB hardware pages rather than 64-kB "
8795 "hardware pages (on machines with hardware 64-kB page support)."
8799 #: build/C/man2/subpage_prot.2:131
8800 msgid "B<mprotect>(2), B<syscall>(2)"
8804 #: build/C/man2/subpage_prot.2:134
8805 msgid "I<Documentation/vm/hugetlbpage.txt> in the Linux kernel source tree"
8809 #: build/C/man2/sync_file_range.2:30
8811 msgid "SYNC_FILE_RANGE"
8815 #: build/C/man2/sync_file_range.2:30
8821 #: build/C/man2/sync_file_range.2:33
8822 msgid "sync_file_range - sync a file segment with disk"
8826 #: build/C/man2/sync_file_range.2:37
8829 "B<#define _GNU_SOURCE> /* See feature_test_macros(7) */\n"
8830 "B<#include E<lt>fcntl.hE<gt>>\n"
8834 #: build/C/man2/sync_file_range.2:40
8837 "B<int sync_file_range(int >I<fd>B<, off64_t >I<offset>B<, off64_t "
8839 "B< unsigned int >I<flags>B<);>\n"
8843 #: build/C/man2/sync_file_range.2:47
8845 "B<sync_file_range>() permits fine control when synchronizing the open file "
8846 "referred to by the file descriptor I<fd> with disk."
8850 #: build/C/man2/sync_file_range.2:61
8852 "I<offset> is the starting byte of the file range to be synchronized. "
8853 "I<nbytes> specifies the length of the range to be synchronized, in bytes; if "
8854 "I<nbytes> is zero, then all bytes from I<offset> through to the end of file "
8855 "are synchronized. Synchronization is in units of the system page size: "
8856 "I<offset> is rounded down to a page boundary; I<(offset+nbytes-1)> is "
8857 "rounded up to a page boundary."
8861 #: build/C/man2/sync_file_range.2:65
8862 msgid "The I<flags> bit-mask argument can include any of the following values:"
8866 #: build/C/man2/sync_file_range.2:65
8868 msgid "B<SYNC_FILE_RANGE_WAIT_BEFORE>"
8872 #: build/C/man2/sync_file_range.2:70
8874 "Wait upon write-out of all pages in the specified range that have already "
8875 "been submitted to the device driver for write-out before performing any "
8880 #: build/C/man2/sync_file_range.2:70 build/C/man2/sync_file_range.2:120
8882 msgid "B<SYNC_FILE_RANGE_WRITE>"
8886 #: build/C/man2/sync_file_range.2:76
8888 "Initiate write-out of all dirty pages in the specified range which are not "
8889 "presently submitted write-out. Note that even this may block if you attempt "
8890 "to write more than request queue size."
8894 #: build/C/man2/sync_file_range.2:76
8896 msgid "B<SYNC_FILE_RANGE_WAIT_AFTER>"
8900 #: build/C/man2/sync_file_range.2:80
8901 msgid "Wait upon write-out of all pages in the range after performing any write."
8905 #: build/C/man2/sync_file_range.2:84
8906 msgid "Specifying I<flags> as 0 is permitted, as a no-op."
8910 #: build/C/man2/sync_file_range.2:84
8916 #: build/C/man2/sync_file_range.2:100
8918 "This system call is extremely dangerous and should not be used in portable "
8919 "programs. None of these operations writes out the file's metadata. "
8920 "Therefore, unless the application is strictly performing overwrites of "
8921 "already-instantiated disk blocks, there are no guarantees that the data will "
8922 "be available after a crash. There is no user interface to know if a write "
8923 "is purely an overwrite. On filesystems using copy-on-write semantics (e.g., "
8924 "I<btrfs>) an overwrite of existing allocated blocks is impossible. When "
8925 "writing into preallocated space, many filesystems also require calls into "
8926 "the block allocator, which this system call does not sync out to disk. This "
8927 "system call does not flush disk write caches and thus does not provide any "
8928 "data integrity on systems with volatile disk write caches."
8932 #: build/C/man2/sync_file_range.2:100
8934 msgid "Some details"
8938 #: build/C/man2/sync_file_range.2:108
8940 "B<SYNC_FILE_RANGE_WAIT_BEFORE> and B<SYNC_FILE_RANGE_WAIT_AFTER> will detect "
8941 "any I/O errors or B<ENOSPC> conditions and will return these to the caller."
8945 #: build/C/man2/sync_file_range.2:112
8946 msgid "Useful combinations of the I<flags> bits are:"
8950 #: build/C/man2/sync_file_range.2:112
8952 msgid "B<SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE>"
8956 #: build/C/man2/sync_file_range.2:120
8958 "Ensures that all pages in the specified range which were dirty when "
8959 "B<sync_file_range>() was called are placed under write-out. This is a "
8960 "start-write-for-data-integrity operation."
8964 #: build/C/man2/sync_file_range.2:127
8966 "Start write-out of all dirty pages in the specified range which are not "
8967 "presently under write-out. This is an asynchronous flush-to-disk "
8968 "operation. This is not suitable for data integrity operations."
8972 #: build/C/man2/sync_file_range.2:127
8974 msgid "B<SYNC_FILE_RANGE_WAIT_BEFORE> (or B<SYNC_FILE_RANGE_WAIT_AFTER>)"
8978 #: build/C/man2/sync_file_range.2:134
8980 "Wait for completion of write-out of all pages in the specified range. This "
8981 "can be used after an earlier B<SYNC_FILE_RANGE_WAIT_BEFORE | "
8982 "SYNC_FILE_RANGE_WRITE> operation to wait for completion of that operation, "
8983 "and obtain its result."
8987 #: build/C/man2/sync_file_range.2:134
8990 "B<SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE | "
8991 "SYNC_FILE_RANGE_WAIT_AFTER>"
8995 #: build/C/man2/sync_file_range.2:141
8997 "This is a write-for-data-integrity operation that will ensure that all pages "
8998 "in the specified range which were dirty when B<sync_file_range>() was "
8999 "called are committed to disk."
9003 #: build/C/man2/sync_file_range.2:147
9005 "On success, B<sync_file_range>() returns 0; on failure -1 is returned and "
9006 "I<errno> is set to indicate the error."
9010 #: build/C/man2/sync_file_range.2:152
9011 msgid "I<fd> is not a valid file descriptor."
9015 #: build/C/man2/sync_file_range.2:160
9016 msgid "I<flags> specifies an invalid bit; or I<offset> or I<nbytes> is invalid."
9020 #: build/C/man2/sync_file_range.2:163
9025 #: build/C/man2/sync_file_range.2:169
9026 msgid "Out of disk space."
9029 #. FIXME . (bug?) Actually, how can 'fd' refer to a symbolic link (S_ISLNK)?
9030 #. (In user space at least) it isn't possible to obtain a file descriptor
9031 #. for a symbolic link.
9033 #: build/C/man2/sync_file_range.2:177
9035 "I<fd> refers to something other than a regular file, a block device, a "
9036 "directory, or a symbolic link."
9040 #: build/C/man2/sync_file_range.2:180
9041 msgid "B<sync_file_range>() appeared on Linux in kernel 2.6.17."
9045 #: build/C/man2/sync_file_range.2:183
9047 "This system call is Linux-specific, and should be avoided in portable "
9052 #: build/C/man2/sync_file_range.2:184
9054 msgid "sync_file_range2()"
9057 #. See kernel commit edd5cd4a9424f22b0fa08bef5e299d41befd5622
9059 #: build/C/man2/sync_file_range.2:201
9061 "Some architectures (e.g., PowerPC, ARM) need 64-bit arguments to be aligned "
9062 "in a suitable pair of registers. On such architectures, the call signature "
9063 "of B<sync_file_range>() shown in the SYNOPSIS would force a register to be "
9064 "wasted as padding between the I<fd> and I<offset> arguments. (See "
9065 "B<syscall>(2) for details.) Therefore, these architectures define a "
9066 "different system call that orders the arguments suitably:"
9070 #: build/C/man2/sync_file_range.2:206
9073 "B<int sync_file_range2(int >I<fd>B<, unsigned int >I<flags>B<,>\n"
9074 "B< off64_t >I<offset>B<, off64_t >I<nbytes>B<);>\n"
9078 #: build/C/man2/sync_file_range.2:211
9080 "The behavior of this system call is otherwise exactly the same as "
9081 "B<sync_file_range>()."
9085 #: build/C/man2/sync_file_range.2:222
9087 "A system call with this signature first appeared on the ARM architecture in "
9088 "Linux 2.6.20, with the name B<arm_sync_file_range>(). It was renamed in "
9089 "Linux 2.6.22, when the analogous system call was added for PowerPC. On "
9090 "architectures where glibc support is provided, glibc transparently wraps "
9091 "B<sync_file_range2>() under the name B<sync_file_range>()."
9095 #: build/C/man2/sync_file_range.2:227
9096 msgid "B<fdatasync>(2), B<fsync>(2), B<msync>(2), B<sync>(2)"
9100 #: build/C/man2/memfd_create.2:21
9102 msgid "MEMFD_CREATE"
9106 #: build/C/man2/memfd_create.2:24
9107 msgid "memfd_create - create an anonymous file"
9111 #: build/C/man2/memfd_create.2:26
9112 msgid "B<#include E<lt>sys/memfd.hE<gt>>"
9116 #: build/C/man2/memfd_create.2:28
9117 msgid "B<int memfd_create(const char *>I<name>B<, unsigned int >I<flags>B<);>"
9121 #. memfd uses VM_NORESERVE so each page is accounted on first access.
9122 #. This means, the overcommit-limits (see __vm_enough_memory()) and the
9123 #. memory-cgroup limits (mem_cgroup_try_charge()) are applied. Note that
9124 #. those are accounted on "current" and "current->mm", that is, the
9125 #. process doing the first page access.
9127 #: build/C/man2/memfd_create.2:51
9129 "B<memfd_create>() creates an anonymous file and returns a file descriptor "
9130 "that refers to it. The file behaves like a regular file, and so can be "
9131 "modified, truncated, memory-mapped, and so on. However, unlike a regular "
9132 "file, it lives in RAM and has a volatile backing storage. Once all "
9133 "references to the file are dropped, it is automatically released. Anonymous "
9134 "memory is used for all backing pages of the file. Therefore, files created "
9135 "by B<memfd_create>() have the same semantics as other anonymous memory "
9136 "allocations such as those allocated using B<mmap>(2) with the "
9137 "B<MAP_ANONYMOUS> flag."
9141 #: build/C/man2/memfd_create.2:58
9143 "The initial size of the file is set to 0. Following the call, the file size "
9144 "should be set using B<ftruncate>(2). (Alternatively, the file may be "
9145 "populated by calls to B<write>(2) or similar.)"
9149 #: build/C/man2/memfd_create.2:69
9151 "The name supplied in I<name> is used as a filename and will be displayed as "
9152 "the target of the corresponding symbolic link in the directory "
9153 "I</proc/self/fd/>. The displayed name is always prefixed with I<memfd:> and "
9154 "serves only for debugging purposes. Names do not affect the behavior of the "
9155 "file descriptor, and as such multiple files can have the same name without "
9160 #: build/C/man2/memfd_create.2:74
9162 "The following values may be bitwise ORed in I<flags> to change the behaviour "
9163 "of B<memfd_create>():"
9167 #: build/C/man2/memfd_create.2:74
9169 msgid "B<MFD_CLOEXEC>"
9173 #: build/C/man2/memfd_create.2:84
9175 "Set the close-on-exec (B<FD_CLOEXEC>) flag on the new file descriptor. See "
9176 "the description of the B<O_CLOEXEC> flag in B<open>(2) for reasons why this "
9181 #: build/C/man2/memfd_create.2:84
9183 msgid "B<MFD_ALLOW_SEALING>"
9186 #. FIXME Why is the MFD_ALLOW_SEALING behavior not simply the default?
9187 #. Is it worth adding some text explaining this?
9189 #: build/C/man2/memfd_create.2:100
9191 "Allow sealing operations on this file. See the discussion of the "
9192 "B<F_ADD_SEALS> and B<F_GET_SEALS> operations in B<fcntl>(2), and also NOTES, "
9193 "below. The initial set of seals is empty. If this flag is not set, the "
9194 "initial set of seals will be B<F_SEAL_SEAL>, meaning that no other seals can "
9195 "be set on the file."
9199 #: build/C/man2/memfd_create.2:104
9200 msgid "Unused bits in I<flags> must be 0."
9204 #: build/C/man2/memfd_create.2:113
9206 "As its return value, B<memfd_create>() returns a new file descriptor that "
9207 "can be used to refer to the file. This file descriptor is opened for both "
9208 "reading and writing (B<O_RDWR>) and B<O_LARGEFILE> is set for the "
9213 #: build/C/man2/memfd_create.2:126
9215 "With respect to B<fork>(2) and B<execve>(2), the usual semantics apply for "
9216 "the file descriptor created by B<memfd_create>(). A copy of the file "
9217 "descriptor is inherited by the child produced by B<fork>(2) and refers to "
9218 "the same file. The file descriptor is preserved across B<execve>(2), unless "
9219 "the close-on-exec flag has been set."
9223 #: build/C/man2/memfd_create.2:133
9225 "On success, B<memfd_create>() returns a new file descriptor. On error, -1 "
9226 "is returned and I<errno> is set to indicate the error."
9230 #: build/C/man2/memfd_create.2:139
9231 msgid "The address in I<name> points to invalid memory."
9235 #: build/C/man2/memfd_create.2:146
9237 "An unsupported value was specified in one of the arguments: I<flags> "
9238 "included unknown bits, or I<name> was too long."
9242 #: build/C/man2/memfd_create.2:149
9243 msgid "The per-process limit on open file descriptors has been reached."
9247 #: build/C/man2/memfd_create.2:152
9248 msgid "The system-wide limit on the total number of open files has been reached."
9252 #: build/C/man2/memfd_create.2:155
9253 msgid "There was insufficient memory to create a new anonymous file."
9256 #. FIXME . When glibc support appears, update the following sentence:
9258 #: build/C/man2/memfd_create.2:161
9260 "The B<memfd_create>() system call first appeared in Linux 3.17. Support in "
9261 "the GNU C library is pending."
9265 #: build/C/man2/memfd_create.2:165
9266 msgid "The B<memfd_create>() system call is Linux-specific."
9269 #. See also http://lwn.net/Articles/593918/
9270 #. and http://lwn.net/Articles/594919/ and http://lwn.net/Articles/591108/
9272 #: build/C/man2/memfd_create.2:178
9274 "The B<memfd_create>() system call provides a simple alternative to manually "
9275 "mounting a I<tmpfs> filesystem and creating and opening a file in that "
9276 "filesystem. The primary purpose of B<memfd_create>() is to create files "
9277 "and associated file descriptors that are used with the file-sealing APIs "
9278 "provided by B<fcntl>(2)."
9282 #: build/C/man2/memfd_create.2:192
9284 "The B<memfd_create>() system call also has uses without file sealing (which "
9285 "is why file-sealing is disabled, unless explicitly requested with the "
9286 "B<MFD_ALLOW_SEALING> flag). In particular, it can be used as an alternative "
9287 "to creating files in I<tmp> or as an alternative to using the B<open>(2) "
9288 "B<O_TMPFILE> in cases where there is no intention to actually link the "
9289 "resulting file into the filesystem."
9293 #: build/C/man2/memfd_create.2:192
9295 msgid "File sealing"
9299 #: build/C/man2/memfd_create.2:210
9301 "In the absence of file sealing, processes that communicate via shared memory "
9302 "must either trust each other, or take measures to deal with the possibility "
9303 "that an untrusted peer may manipulate the shared memory region in "
9304 "problematic ways. For example, an untrusted peer might modify the contents "
9305 "of the shared memory at any time, or shrink the shared memory region. The "
9306 "former possibility leaves the local process vulnerable to "
9307 "time-of-check-to-time-of-use race conditions (typically dealt with by "
9308 "copying data from the shared memory region before checking and using it). "
9309 "The latter possibility leaves the local process vulnerable to B<SIGBUS> "
9310 "signals when an attempt is made to access a now-nonexistent location in the "
9311 "shared memory region. (Dealing with this possibility necessitates the use "
9312 "of a handler for the B<SIGBUS> signal.)"
9316 #: build/C/man2/memfd_create.2:216
9318 "Dealing with untrusted peers imposes extra complexity on code that employs "
9319 "shared memory. Memory sealing enables that extra complexity to be "
9320 "eliminated, by allowing a process to operate secure in the knowledge that "
9321 "its peer can't modify the shared memory in an undesired fashion."
9325 #: build/C/man2/memfd_create.2:218
9326 msgid "An example of the usage of the sealing mechanism is as follows:"
9330 #: build/C/man2/memfd_create.2:225
9332 "The first process creates a I<tmpfs> file using B<memfd_create>(). The call "
9333 "yields a file descriptor used in subsequent steps."
9337 #: build/C/man2/memfd_create.2:232
9339 "The first process sizes the file created in the previous step using "
9340 "B<ftruncate>(2), maps it using B<mmap>(2), and populates the shared memory "
9341 "with the desired data."
9345 #: build/C/man2/memfd_create.2:232
9351 #: build/C/man2/memfd_create.2:242
9353 "The first process uses the B<fcntl>(2) B<F_ADD_SEALS> operation to place "
9354 "one or more seals on the file, in order to restrict further modifications on "
9355 "the file. (If placing the seal B<F_SEAL_WRITE>, then it will be necessary "
9356 "to first unmap the shared writable mapping created in the previous step.)"
9360 #: build/C/man2/memfd_create.2:242
9366 #: build/C/man2/memfd_create.2:247
9368 "A second process obtains a file descriptor for the I<tmpfs> file and maps "
9369 "it. Among the possible ways in which this could happen are the following:"
9373 #: build/C/man2/memfd_create.2:258
9375 "The process that called B<memfd_create>() could transfer the resulting file "
9376 "descriptor to the second process via a UNIX domain socket (see B<unix>(7) "
9377 "and B<cmsg>(3)). The second process then maps the file using B<mmap>(2)."
9381 #: build/C/man2/memfd_create.2:266
9383 "The second process is created via B<fork>(2) and thus automatically "
9384 "inherits the file descriptor and mapping. (Note that in this case and the "
9385 "next, there is a natural trust relationship between the two processes, since "
9386 "they are running under the same user ID. Therefore, file sealing would not "
9387 "normally be necessary.)"
9391 #: build/C/man2/memfd_create.2:280
9393 "The second process opens the file I</proc/E<lt>pdE<gt>/fd/E<lt>fdE<gt>>, "
9394 "where I<E<lt>pidE<gt>> is the PID of the first process (the one that called "
9395 "B<memfd_create>()), and I<E<lt>fdE<gt>> is the number of the file descriptor "
9396 "returned by the call to B<memfd_create>() in that process. The second "
9397 "process then maps the file using B<mmap>(2)."
9401 #: build/C/man2/memfd_create.2:281
9407 #: build/C/man2/memfd_create.2:293
9409 "The second process uses the B<fcntl>(2) B<F_GET_SEALS> operation to "
9410 "retrieve the bit mask of seals that has been applied to the file. This bit "
9411 "mask can be inspected in order to determine what kinds of restrictions have "
9412 "been placed on file modifications. If desired, the second process can apply "
9413 "further seals to impose additional restrictions (so long as the "
9414 "B<F_SEAL_SEAL> seal has not yet been applied)."
9418 #: build/C/man2/memfd_create.2:297
9420 "Below are shown two example programs that demonstrate the use of "
9421 "B<memfd_create>() and the file sealing API."
9425 #: build/C/man2/memfd_create.2:312
9427 "The first program, I<t_memfd_create.c>, creates a I<tmpfs> file using "
9428 "B<memfd_create>(), sets a size for the file, maps it into memory, and "
9429 "optionally places some seals on the file. The program accepts up to three "
9430 "command-line arguments, of which the first two are required. The first "
9431 "argument is the name to associate with the file, the second argument is the "
9432 "size to be set for the file, and the optional third is a string of "
9433 "characters that specify seals to be set on file."
9437 #: build/C/man2/memfd_create.2:318
9439 "The second program, I<t_get_seals.c>, can be used to open an existing file "
9440 "that was created via B<memfd_create>() and inspect the set of seals that "
9441 "have been applied to that file."
9445 #: build/C/man2/memfd_create.2:323
9447 "The following shell session demonstrates the use of these programs. First "
9448 "we create a I<tmpfs> file and set some seals on it:"
9452 #: build/C/man2/memfd_create.2:329
9455 "$ B<./t_memfd_create my_memfd_file 4096 sw &>\n"
9457 "PID: 11775; fd: 3; /proc/11775/fd/3\n"
9461 #: build/C/man2/memfd_create.2:347
9463 "At this point, the I<t_memfd_create> program continues to run in the "
9464 "background. From another program, we can obtain a file descriptor for the "
9465 "file created by B<memfd_create>() by opening the I</proc/PID/fd> file that "
9466 "corresponds to the descriptor opened by B<memfd_create>(). Using that "
9467 "pathname, we inspect the content of the I</proc/PID/fd> symbolic link, and "
9468 "use our I<t_get_seals> program to view the seals that have been placed on "
9473 #: build/C/man2/memfd_create.2:354
9476 "$ B<readlink /proc/11775/fd/3>\n"
9477 "/memfd:my_memfd_file (deleted)\n"
9478 "$ B<./t_get_seals /proc/11775/fd/3>\n"
9479 "Existing seals: WRITE SHRINK\n"
9483 #: build/C/man2/memfd_create.2:356
9485 msgid "Program source: t_memfd_create.c"
9489 #: build/C/man2/memfd_create.2:365
9492 "#include E<lt>sys/memfd.hE<gt>\n"
9493 "#include E<lt>fcntl.hE<gt>\n"
9494 "#include E<lt>stdlib.hE<gt>\n"
9495 "#include E<lt>unistd.hE<gt>\n"
9496 "#include E<lt>string.hE<gt>\n"
9497 "#include E<lt>stdio.hE<gt>\n"
9501 #: build/C/man2/memfd_create.2:377
9505 "main(int argc, char *argv[])\n"
9508 " unsigned int seals;\n"
9510 " char *name, *seals_arg;\n"
9515 #: build/C/man2/memfd_create.2:388
9518 " if (argc E<lt> 3) {\n"
9519 " fprintf(stderr, \"%s name size [seals]\\en\", argv[0]);\n"
9520 " fprintf(stderr, \"\\et\\(aqseals\\(aq can contain any of the \"\n"
9521 " \"following characters:\\en\");\n"
9522 " fprintf(stderr, \"\\et\\etg - F_SEAL_GROW\\en\");\n"
9523 " fprintf(stderr, \"\\et\\ets - F_SEAL_SHRINK\\en\");\n"
9524 " fprintf(stderr, \"\\et\\etw - F_SEAL_WRITE\\en\");\n"
9525 " fprintf(stderr, \"\\et\\etS - F_SEAL_SEAL\\en\");\n"
9526 " exit(EXIT_FAILURE);\n"
9531 #: build/C/man2/memfd_create.2:392
9534 " name = argv[1];\n"
9535 " len = atoi(argv[2]);\n"
9536 " seals_arg = argv[3];\n"
9540 #: build/C/man2/memfd_create.2:395
9543 " /* Create an anonymous file in tmpfs; allow seals to be\n"
9544 " placed on the file */\n"
9548 #: build/C/man2/memfd_create.2:399
9551 " fd = memfd_create(name, MFD_ALLOW_SEALING);\n"
9553 " errExit(\"memfd_create\");\n"
9557 #: build/C/man2/memfd_create.2:401
9559 msgid " /* Size the file as specified on the command line */\n"
9563 #: build/C/man2/memfd_create.2:404
9566 " if (ftruncate(fd, len) == -1)\n"
9567 " errExit(\"truncate\");\n"
9571 #: build/C/man2/memfd_create.2:407
9574 " printf(\"PID: %ld; fd: %d; /proc/%ld/fd/%d\\en\",\n"
9575 " (long) getpid(), fd, (long) getpid(), fd);\n"
9579 #: build/C/man2/memfd_create.2:410
9582 " /* Code to map the file and populate the mapping with data\n"
9587 #: build/C/man2/memfd_create.2:413
9590 " /* If a \\(aqseals\\(aq command-line argument was supplied, set some\n"
9591 " seals on the file */\n"
9595 #: build/C/man2/memfd_create.2:416
9598 " if (seals_arg != NULL) {\n"
9603 #: build/C/man2/memfd_create.2:425
9606 " if (strchr(seals_arg, \\(aqg\\(aq) != NULL)\n"
9607 " seals |= F_SEAL_GROW;\n"
9608 " if (strchr(seals_arg, \\(aqs\\(aq) != NULL)\n"
9609 " seals |= F_SEAL_SHRINK;\n"
9610 " if (strchr(seals_arg, \\(aqw\\(aq) != NULL)\n"
9611 " seals |= F_SEAL_WRITE;\n"
9612 " if (strchr(seals_arg, \\(aqS\\(aq) != NULL)\n"
9613 " seals |= F_SEAL_SEAL;\n"
9617 #: build/C/man2/memfd_create.2:429
9620 " if (fcntl(fd, F_ADD_SEALS, seals) == -1)\n"
9621 " errExit(\"fcntl\");\n"
9626 #: build/C/man2/memfd_create.2:432
9629 " /* Keep running, so that the file created by memfd_create()\n"
9630 " continues to exist */\n"
9634 #: build/C/man2/memfd_create.2:434
9640 #: build/C/man2/memfd_create.2:438
9642 msgid "Program source: t_get_seals.c"
9646 #: build/C/man2/memfd_create.2:447
9649 "#include E<lt>sys/memfd.hE<gt>\n"
9650 "#include E<lt>fcntl.hE<gt>\n"
9651 "#include E<lt>unistd.hE<gt>\n"
9652 "#include E<lt>stdlib.hE<gt>\n"
9653 "#include E<lt>string.hE<gt>\n"
9654 "#include E<lt>stdio.hE<gt>\n"
9658 #: build/C/man2/memfd_create.2:456
9662 "main(int argc, char *argv[])\n"
9665 " unsigned int seals;\n"
9669 #: build/C/man2/memfd_create.2:461
9672 " if (argc != 2) {\n"
9673 " fprintf(stderr, \"%s /proc/PID/fd/FD\\en\", argv[0]);\n"
9674 " exit(EXIT_FAILURE);\n"
9679 #: build/C/man2/memfd_create.2:465
9682 " fd = open(argv[1], O_RDWR);\n"
9684 " errExit(\"open\");\n"
9688 #: build/C/man2/memfd_create.2:469
9691 " seals = fcntl(fd, F_GET_SEALS);\n"
9692 " if (seals == -1)\n"
9693 " errExit(\"fcntl\");\n"
9697 #: build/C/man2/memfd_create.2:480
9700 " printf(\"Existing seals:\");\n"
9701 " if (seals & F_SEAL_SEAL)\n"
9702 " printf(\" SEAL\");\n"
9703 " if (seals & F_SEAL_GROW)\n"
9704 " printf(\" GROW\");\n"
9705 " if (seals & F_SEAL_WRITE)\n"
9706 " printf(\" WRITE\");\n"
9707 " if (seals & F_SEAL_SHRINK)\n"
9708 " printf(\" SHRINK\");\n"
9709 " printf(\"\\en\");\n"
9713 #: build/C/man2/memfd_create.2:483
9716 " /* Code to map the file and access the contents of the\n"
9717 " resulting mapping omitted */\n"
9721 #: build/C/man2/memfd_create.2:493
9722 msgid "B<fcntl>(2), B<ftruncate>(2), B<mmap>(2), B<shmget>(2), B<shm_open>(3)"
9726 #: build/C/man2/s390_pci_mmio_write.2:25
9728 msgid "S390_PCI_MMIO_WRITE"
9732 #: build/C/man2/s390_pci_mmio_write.2:25
9738 #: build/C/man2/s390_pci_mmio_write.2:29
9740 "s390_pci_mmio_write, s390_pci_mmio_read - transfer data to/from PCI MMIO "
9745 #: build/C/man2/s390_pci_mmio_write.2:32
9747 msgid "B<#include E<lt>asm/unistd.hE<gt>>\n"
9751 #: build/C/man2/s390_pci_mmio_write.2:35
9754 "B<int s390_pci_mmio_write(unsigned long >I<mmio_addr>B<,>\n"
9755 "B< void *>I<user_buffer>B<, size_t >I<length>B<);>\n"
9759 #: build/C/man2/s390_pci_mmio_write.2:38
9762 "B<int s390_pci_mmio_read(unsigned long >I<mmio_addr>B<,>\n"
9763 "B< void *>I<user_buffer>B<, size_t >I<length>B<);>\n"
9767 #: build/C/man2/s390_pci_mmio_write.2:57
9769 "The B<s390_pci_mmio_write>() system call writes I<length> bytes of data "
9770 "from the user-space buffer I<user_buffer> to the PCI MMIO memory location "
9771 "specified by I<mmio_addr>. The B<s390_pci_mmio_read>() system call reads "
9772 "I<length> bytes of data from the PCI MMIO memory location specified by "
9773 "I<mmio_addr> to the user-space buffer I<user_buffer>."
9777 #: build/C/man2/s390_pci_mmio_write.2:68
9779 "These system calls must be used instead of the simple assignment or "
9780 "data-transfer operations that are used to access the PCI MMIO memory areas "
9781 "mapped to user space on the Linux System z platform. The address specified "
9782 "by I<mmio_addr> must belong to a PCI MMIO memory page mapping in the "
9783 "caller's address space, and the data being written or read must not cross a "
9784 "page boundary. The I<length> value cannot be greater than the system page "
9789 #: build/C/man2/s390_pci_mmio_write.2:77
9791 "On success, B<s390_pci_mmio_write>() and B<s390_pci_mmio_read>() return "
9792 "0. On error, -1 is returned and I<errno> is set to one of the error codes "
9797 #: build/C/man2/s390_pci_mmio_write.2:83
9798 msgid "The address in I<mmio_addr> is invalid."
9802 #: build/C/man2/s390_pci_mmio_write.2:87
9804 "I<user_buffer> does not point to a valid location in the caller's address "
9809 #: build/C/man2/s390_pci_mmio_write.2:92
9810 msgid "Invalid I<length> argument."
9814 #: build/C/man2/s390_pci_mmio_write.2:95
9815 msgid "PCI support is not enabled."
9819 #: build/C/man2/s390_pci_mmio_write.2:98
9820 msgid "Insufficient memory."
9824 #: build/C/man2/s390_pci_mmio_write.2:100
9825 msgid "These system calls are available since Linux 3.19."
9829 #: build/C/man2/s390_pci_mmio_write.2:103
9831 "This Linux-specific system call is available only on the s390 architecture. "
9832 "The required PCI support is available beginning with System z EC12."
9836 #: build/C/man2/s390_pci_mmio_write.2:107
9838 "Glibc does not provide a wrapper for this system call, use B<syscall>(2) to "
9843 #: build/C/man2/s390_pci_mmio_write.2:109
9844 msgid "B<syscall>(2)"