--- /dev/null
+/* Copyright (C) 2002, 2003 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+ Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <mntent.h>
+#include <paths.h>
+#include <pthread.h>
+#include <search.h>
+#include <semaphore.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/statfs.h>
+#include <linux_fsinfo.h>
+#include "semaphoreP.h"
+
+
+/* Compatibility defines. */
+#define __endmntent endmntent
+#define __fxstat64(vers, fd, buf) fstat64(fd, buf)
+#define __getmntent_r getmntent_r
+#define __setmntent setmntent
+#define __statfs statfs
+#define __libc_close close
+#define __libc_open open
+#define __libc_write write
+
+/* Information about the mount point. */
+struct mountpoint_info mountpoint attribute_hidden;
+
+/* This is the default mount point. */
+static const char defaultmount[] = "/dev/shm";
+/* This is the default directory. */
+static const char defaultdir[] = "/dev/shm/sem.";
+
+/* Protect the `mountpoint' variable above. */
+pthread_once_t __namedsem_once attribute_hidden = PTHREAD_ONCE_INIT;
+
+
+/* Determine where the shmfs is mounted (if at all). */
+void
+attribute_hidden
+__where_is_shmfs (void)
+{
+ char buf[512];
+ struct statfs f;
+ struct mntent resmem;
+ struct mntent *mp;
+ FILE *fp;
+
+ /* The canonical place is /dev/shm. This is at least what the
+ documentation tells everybody to do. */
+ if (__statfs (defaultmount, &f) == 0 && f.f_type == SHMFS_SUPER_MAGIC)
+ {
+ /* It is in the normal place. */
+ mountpoint.dir = (char *) defaultdir;
+ mountpoint.dirlen = sizeof (defaultdir) - 1;
+
+ return;
+ }
+
+ /* OK, do it the hard way. Look through the /proc/mounts file and if
+ this does not exist through /etc/fstab to find the mount point. */
+ fp = __setmntent ("/proc/mounts", "r");
+ if (__builtin_expect (fp == NULL, 0))
+ {
+ fp = __setmntent (_PATH_MNTTAB, "r");
+ if (__builtin_expect (fp == NULL, 0))
+ /* There is nothing we can do. Blind guesses are not helpful. */
+ return;
+ }
+
+ /* Now read the entries. */
+ while ((mp = __getmntent_r (fp, &resmem, buf, sizeof buf)) != NULL)
+ /* The original name is "shm" but this got changed in early Linux
+ 2.4.x to "tmpfs". */
+ if (strcmp (mp->mnt_type, "tmpfs") == 0
+ || strcmp (mp->mnt_type, "shm") == 0)
+ {
+ /* Found it. There might be more than one place where the
+ filesystem is mounted but one is enough for us. */
+ size_t namelen;
+
+ /* First make sure this really is the correct entry. At least
+ some versions of the kernel give wrong information because
+ of the implicit mount of the shmfs for SysV IPC. */
+ if (__statfs (mp->mnt_dir, &f) != 0 || f.f_type != SHMFS_SUPER_MAGIC)
+ continue;
+
+ namelen = strlen (mp->mnt_dir);
+
+ if (namelen == 0)
+ /* Hum, maybe some crippled entry. Keep on searching. */
+ continue;
+
+ mountpoint.dir = (char *) malloc (namelen + 4 + 2);
+ if (mountpoint.dir != NULL)
+ {
+ char *cp = mempcpy (mountpoint.dir, mp->mnt_dir, namelen);
+ if (cp[-1] != '/')
+ *cp++ = '/';
+ cp = stpcpy (cp, "sem.");
+ mountpoint.dirlen = cp - mountpoint.dir;
+ }
+
+ break;
+ }
+
+ /* Close the stream. */
+ __endmntent (fp);
+}
+
+
+/* Comparison function for search of existing mapping. */
+int
+attribute_hidden
+__sem_search (const void *a, const void *b)
+{
+ const struct inuse_sem *as = (const struct inuse_sem *) a;
+ const struct inuse_sem *bs = (const struct inuse_sem *) b;
+
+ if (as->ino != bs->ino)
+ /* Cannot return the difference the type is larger than int. */
+ return as->ino < bs->ino ? -1 : (as->ino == bs->ino ? 0 : 1);
+
+ if (as->dev != bs->dev)
+ /* Cannot return the difference the type is larger than int. */
+ return as->dev < bs->dev ? -1 : (as->dev == bs->dev ? 0 : 1);
+
+ return strcmp (as->name, bs->name);
+}
+
+
+/* The search tree for existing mappings. */
+void *__sem_mappings attribute_hidden;
+
+/* Lock to protect the search tree. */
+lll_lock_t __sem_mappings_lock = LLL_LOCK_INITIALIZER;
+
+
+/* Search for existing mapping and if possible add the one provided. */
+static sem_t *
+check_add_mapping (const char *name, size_t namelen, int fd, sem_t *existing)
+{
+ sem_t *result = SEM_FAILED;
+
+ /* Get the information about the file. */
+#ifdef __UCLIBC_HAS_LFS__
+ struct stat64 st;
+ if (__fxstat64 (_STAT_VER, fd, &st) == 0)
+#else
+ struct stat st;
+ if (fstat (fd, &st) == 0)
+#endif
+ {
+ /* Get the lock. */
+ lll_lock (__sem_mappings_lock);
+
+ /* Search for an existing mapping given the information we have. */
+ struct inuse_sem *fake;
+ fake = (struct inuse_sem *) alloca (sizeof (*fake) + namelen);
+ memcpy (fake->name, name, namelen);
+ fake->dev = st.st_dev;
+ fake->ino = st.st_ino;
+
+ struct inuse_sem **foundp = tfind (fake, &__sem_mappings, __sem_search);
+ if (foundp != NULL)
+ {
+ /* There is already a mapping. Use it. */
+ result = (*foundp)->sem;
+ ++(*foundp)->refcnt;
+ }
+ else
+ {
+ /* We haven't found a mapping. Install ione. */
+ struct inuse_sem *newp;
+
+ newp = (struct inuse_sem *) malloc (sizeof (*newp) + namelen);
+ if (newp != NULL)
+ {
+ /* If the caller hasn't provided any map it now. */
+ if (existing == SEM_FAILED)
+ existing = (sem_t *) mmap (NULL, sizeof (sem_t),
+ PROT_READ | PROT_WRITE, MAP_SHARED,
+ fd, 0);
+
+ newp->dev = st.st_dev;
+ newp->ino = st.st_ino;
+ newp->refcnt = 1;
+ newp->sem = existing;
+ memcpy (newp->name, name, namelen);
+
+ /* Insert the new value. */
+ if (existing != MAP_FAILED
+ && tsearch (newp, &__sem_mappings, __sem_search) != NULL)
+ /* Successful. */
+ result = existing;
+ else
+ /* Something went wrong while inserting the new
+ value. We fail completely. */
+ free (newp);
+ }
+ }
+
+ /* Release the lock. */
+ lll_unlock (__sem_mappings_lock);
+ }
+
+ if (result != existing && existing != SEM_FAILED && existing != MAP_FAILED)
+ {
+ /* Do not disturb errno. */
+ INTERNAL_SYSCALL_DECL (err);
+ INTERNAL_SYSCALL (munmap, err, 2, existing, sizeof (sem_t));
+ }
+
+ return result;
+}
+
+
+sem_t *
+sem_open (const char *name, int oflag, ...)
+{
+ char *finalname;
+ sem_t *result = SEM_FAILED;
+ int fd;
+
+ /* Determine where the shmfs is mounted. */
+ __pthread_once (&__namedsem_once, __where_is_shmfs);
+
+ /* If we don't know the mount points there is nothing we can do. Ever. */
+ if (mountpoint.dir == NULL)
+ {
+ __set_errno (ENOSYS);
+ return SEM_FAILED;
+ }
+
+ /* Construct the filename. */
+ while (name[0] == '/')
+ ++name;
+
+ if (name[0] == '\0')
+ {
+ /* The name "/" is not supported. */
+ __set_errno (EINVAL);
+ return SEM_FAILED;
+ }
+ size_t namelen = strlen (name) + 1;
+
+ /* Create the name of the final file. */
+ finalname = (char *) alloca (mountpoint.dirlen + namelen);
+ mempcpy (mempcpy (finalname, mountpoint.dir, mountpoint.dirlen),
+ name, namelen);
+
+ /* If the semaphore object has to exist simply open it. */
+ if ((oflag & O_CREAT) == 0 || (oflag & O_EXCL) == 0)
+ {
+ try_again:
+ fd = __libc_open (finalname,
+ (oflag & ~(O_CREAT|O_ACCMODE)) | O_NOFOLLOW | O_RDWR);
+
+ if (fd == -1)
+ {
+ /* If we are supposed to create the file try this next. */
+ if ((oflag & O_CREAT) != 0 && errno == ENOENT)
+ goto try_create;
+
+ /* Return. errno is already set. */
+ }
+ else
+ /* Check whether we already have this semaphore mapped and
+ create one if necessary. */
+ result = check_add_mapping (name, namelen, fd, SEM_FAILED);
+ }
+ else
+ {
+ /* We have to open a temporary file first since it must have the
+ correct form before we can start using it. */
+ char *tmpfname;
+ mode_t mode;
+ unsigned int value;
+ va_list ap;
+
+ try_create:
+ va_start (ap, oflag);
+
+ mode = va_arg (ap, mode_t);
+ value = va_arg (ap, unsigned int);
+
+ va_end (ap);
+
+ if (value > SEM_VALUE_MAX)
+ {
+ __set_errno (EINVAL);
+ return SEM_FAILED;
+ }
+
+ /* Create the initial file content. */
+ sem_t initsem;
+
+ struct sem *iinitsem = (struct sem *) &initsem;
+ iinitsem->count = value;
+
+ /* Initialize the remaining bytes as well. */
+ memset ((char *) &initsem + sizeof (struct sem), '\0',
+ sizeof (sem_t) - sizeof (struct sem));
+
+ tmpfname = (char *) alloca (mountpoint.dirlen + 6 + 1);
+ char *xxxxxx = mempcpy (tmpfname, mountpoint.dir, mountpoint.dirlen);
+
+ int retries = 0;
+#define NRETRIES 50
+ while (1)
+ {
+ /* Add the suffix for mktemp. */
+ strcpy (xxxxxx, "XXXXXX");
+
+ /* We really want to use mktemp here. We cannot use mkstemp
+ since the file must be opened with a specific mode. The
+ mode cannot later be set since then we cannot apply the
+ file create mask. */
+ if (mktemp (tmpfname) == NULL)
+ return SEM_FAILED;
+
+ /* Open the file. Make sure we do not overwrite anything. */
+ fd = __libc_open (tmpfname, O_RDWR | O_CREAT | O_EXCL, mode);
+ if (fd == -1)
+ {
+ if (errno == EEXIST)
+ {
+ if (++retries < NRETRIES)
+ continue;
+
+ __set_errno (EAGAIN);
+ }
+
+ return SEM_FAILED;
+ }
+
+ /* We got a file. */
+ break;
+ }
+
+ if (TEMP_FAILURE_RETRY (__libc_write (fd, &initsem, sizeof (sem_t)))
+ == sizeof (sem_t)
+ /* Map the sem_t structure from the file. */
+ && (result = (sem_t *) mmap (NULL, sizeof (sem_t),
+ PROT_READ | PROT_WRITE, MAP_SHARED,
+ fd, 0)) != MAP_FAILED)
+ {
+ /* Create the file. Don't overwrite an existing file. */
+ if (link (tmpfname, finalname) != 0)
+ {
+ /* Undo the mapping. */
+ (void) munmap (result, sizeof (sem_t));
+
+ /* Reinitialize 'result'. */
+ result = SEM_FAILED;
+
+ /* This failed. If O_EXCL is not set and the problem was
+ that the file exists, try again. */
+ if ((oflag & O_EXCL) == 0 && errno == EEXIST)
+ {
+ /* Remove the file. */
+ (void) unlink (tmpfname);
+
+ /* Close the file. */
+ (void) __libc_close (fd);
+
+ goto try_again;
+ }
+ }
+ else
+ /* Insert the mapping into the search tree. This also
+ determines whether another thread sneaked by and already
+ added such a mapping despite the fact that we created it. */
+ result = check_add_mapping (name, namelen, fd, result);
+ }
+
+ /* Now remove the temporary name. This should never fail. If
+ it fails we leak a file name. Better fix the kernel. */
+ (void) unlink (tmpfname);
+ }
+
+ /* Map the mmap error to the error we need. */
+ if (MAP_FAILED != (void *) SEM_FAILED && result == MAP_FAILED)
+ result = SEM_FAILED;
+
+ /* We don't need the file descriptor anymore. */
+ if (fd != -1)
+ {
+ /* Do not disturb errno. */
+ INTERNAL_SYSCALL_DECL (err);
+ INTERNAL_SYSCALL (close, err, 1, fd);
+ }
+
+ return result;
+}
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