2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/memblock.h>
35 #include <linux/syscalls.h>
36 #include <linux/kexec.h>
37 #include <linux/kdb.h>
38 #include <linux/ratelimit.h>
39 #include <linux/kmsg_dump.h>
40 #include <linux/syslog.h>
41 #include <linux/cpu.h>
42 #include <linux/notifier.h>
43 #include <linux/rculist.h>
44 #include <linux/poll.h>
45 #include <linux/irq_work.h>
46 #include <linux/utsname.h>
47 #include <linux/ctype.h>
48 #include <linux/uio.h>
50 #include <asm/uaccess.h>
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/printk.h>
55 #include "console_cmdline.h"
58 #ifdef CONFIG_EARLY_PRINTK_DIRECT
59 extern void printascii(char *);
62 int console_printk[4] = {
63 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
64 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
65 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
66 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
70 * Low level drivers may need that to know if they can schedule in
71 * their unblank() callback or not. So let's export it.
74 EXPORT_SYMBOL(oops_in_progress);
77 * console_sem protects the console_drivers list, and also
78 * provides serialisation for access to the entire console
81 static DEFINE_SEMAPHORE(console_sem);
82 struct console *console_drivers;
83 EXPORT_SYMBOL_GPL(console_drivers);
86 static struct lockdep_map console_lock_dep_map = {
87 .name = "console_lock"
92 * Number of registered extended console drivers.
94 * If extended consoles are present, in-kernel cont reassembly is disabled
95 * and each fragment is stored as a separate log entry with proper
96 * continuation flag so that every emitted message has full metadata. This
97 * doesn't change the result for regular consoles or /proc/kmsg. For
98 * /dev/kmsg, as long as the reader concatenates messages according to
99 * consecutive continuation flags, the end result should be the same too.
101 static int nr_ext_console_drivers;
104 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
105 * macros instead of functions so that _RET_IP_ contains useful information.
107 #define down_console_sem() do { \
109 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
112 static int __down_trylock_console_sem(unsigned long ip)
114 if (down_trylock(&console_sem))
116 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
119 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
121 #define up_console_sem() do { \
122 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
127 * This is used for debugging the mess that is the VT code by
128 * keeping track if we have the console semaphore held. It's
129 * definitely not the perfect debug tool (we don't know if _WE_
130 * hold it and are racing, but it helps tracking those weird code
131 * paths in the console code where we end up in places I want
132 * locked without the console sempahore held).
134 static int console_locked, console_suspended;
137 * If exclusive_console is non-NULL then only this console is to be printed to.
139 static struct console *exclusive_console;
142 * Array of consoles built from command line options (console=)
145 #define MAX_CMDLINECONSOLES 8
147 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
149 static int selected_console = -1;
150 static int preferred_console = -1;
151 int console_set_on_cmdline;
152 EXPORT_SYMBOL(console_set_on_cmdline);
154 /* Flag: console code may call schedule() */
155 static int console_may_schedule;
158 * The printk log buffer consists of a chain of concatenated variable
159 * length records. Every record starts with a record header, containing
160 * the overall length of the record.
162 * The heads to the first and last entry in the buffer, as well as the
163 * sequence numbers of these entries are maintained when messages are
166 * If the heads indicate available messages, the length in the header
167 * tells the start next message. A length == 0 for the next message
168 * indicates a wrap-around to the beginning of the buffer.
170 * Every record carries the monotonic timestamp in microseconds, as well as
171 * the standard userspace syslog level and syslog facility. The usual
172 * kernel messages use LOG_KERN; userspace-injected messages always carry
173 * a matching syslog facility, by default LOG_USER. The origin of every
174 * message can be reliably determined that way.
176 * The human readable log message directly follows the message header. The
177 * length of the message text is stored in the header, the stored message
180 * Optionally, a message can carry a dictionary of properties (key/value pairs),
181 * to provide userspace with a machine-readable message context.
183 * Examples for well-defined, commonly used property names are:
184 * DEVICE=b12:8 device identifier
188 * +sound:card0 subsystem:devname
189 * SUBSYSTEM=pci driver-core subsystem name
191 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
192 * follows directly after a '=' character. Every property is terminated by
193 * a '\0' character. The last property is not terminated.
195 * Example of a message structure:
196 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
197 * 0008 34 00 record is 52 bytes long
198 * 000a 0b 00 text is 11 bytes long
199 * 000c 1f 00 dictionary is 23 bytes long
200 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
201 * 0010 69 74 27 73 20 61 20 6c "it's a l"
203 * 001b 44 45 56 49 43 "DEVIC"
204 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
205 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
207 * 0032 00 00 00 padding to next message header
209 * The 'struct printk_log' buffer header must never be directly exported to
210 * userspace, it is a kernel-private implementation detail that might
211 * need to be changed in the future, when the requirements change.
213 * /dev/kmsg exports the structured data in the following line format:
214 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
216 * Users of the export format should ignore possible additional values
217 * separated by ',', and find the message after the ';' character.
219 * The optional key/value pairs are attached as continuation lines starting
220 * with a space character and terminated by a newline. All possible
221 * non-prinatable characters are escaped in the "\xff" notation.
225 LOG_NOCONS = 1, /* already flushed, do not print to console */
226 LOG_NEWLINE = 2, /* text ended with a newline */
227 LOG_PREFIX = 4, /* text started with a prefix */
228 LOG_CONT = 8, /* text is a fragment of a continuation line */
232 u64 ts_nsec; /* timestamp in nanoseconds */
233 u16 len; /* length of entire record */
234 u16 text_len; /* length of text buffer */
235 u16 dict_len; /* length of dictionary buffer */
236 u8 facility; /* syslog facility */
237 u8 flags:5; /* internal record flags */
238 u8 level:3; /* syslog level */
240 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
241 __packed __aligned(4)
246 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
247 * within the scheduler's rq lock. It must be released before calling
248 * console_unlock() or anything else that might wake up a process.
250 static DEFINE_RAW_SPINLOCK(logbuf_lock);
253 DECLARE_WAIT_QUEUE_HEAD(log_wait);
254 /* the next printk record to read by syslog(READ) or /proc/kmsg */
255 static u64 syslog_seq;
256 static u32 syslog_idx;
257 static enum log_flags syslog_prev;
258 static size_t syslog_partial;
260 /* index and sequence number of the first record stored in the buffer */
261 static u64 log_first_seq;
262 static u32 log_first_idx;
264 /* index and sequence number of the next record to store in the buffer */
265 static u64 log_next_seq;
266 static u32 log_next_idx;
268 /* the next printk record to write to the console */
269 static u64 console_seq;
270 static u32 console_idx;
271 static enum log_flags console_prev;
273 /* the next printk record to read after the last 'clear' command */
274 static u64 clear_seq;
275 static u32 clear_idx;
277 #define PREFIX_MAX 32
278 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
280 #define LOG_LEVEL(v) ((v) & 0x07)
281 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
284 #define LOG_ALIGN __alignof__(struct printk_log)
285 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
286 #define LOG_BUF_LEN_MAX (u32)(1 << 31)
287 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
288 static char *log_buf = __log_buf;
289 static u32 log_buf_len = __LOG_BUF_LEN;
291 /* Return log buffer address */
292 char *log_buf_addr_get(void)
297 /* Return log buffer size */
298 u32 log_buf_len_get(void)
303 /* human readable text of the record */
304 static char *log_text(const struct printk_log *msg)
306 return (char *)msg + sizeof(struct printk_log);
309 /* optional key/value pair dictionary attached to the record */
310 static char *log_dict(const struct printk_log *msg)
312 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
315 /* get record by index; idx must point to valid msg */
316 static struct printk_log *log_from_idx(u32 idx)
318 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
321 * A length == 0 record is the end of buffer marker. Wrap around and
322 * read the message at the start of the buffer.
325 return (struct printk_log *)log_buf;
329 /* get next record; idx must point to valid msg */
330 static u32 log_next(u32 idx)
332 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
334 /* length == 0 indicates the end of the buffer; wrap */
336 * A length == 0 record is the end of buffer marker. Wrap around and
337 * read the message at the start of the buffer as *this* one, and
338 * return the one after that.
341 msg = (struct printk_log *)log_buf;
344 return idx + msg->len;
348 * Check whether there is enough free space for the given message.
350 * The same values of first_idx and next_idx mean that the buffer
351 * is either empty or full.
353 * If the buffer is empty, we must respect the position of the indexes.
354 * They cannot be reset to the beginning of the buffer.
356 static int logbuf_has_space(u32 msg_size, bool empty)
360 if (log_next_idx > log_first_idx || empty)
361 free = max(log_buf_len - log_next_idx, log_first_idx);
363 free = log_first_idx - log_next_idx;
366 * We need space also for an empty header that signalizes wrapping
369 return free >= msg_size + sizeof(struct printk_log);
372 static int log_make_free_space(u32 msg_size)
374 while (log_first_seq < log_next_seq) {
375 if (logbuf_has_space(msg_size, false))
377 /* drop old messages until we have enough contiguous space */
378 log_first_idx = log_next(log_first_idx);
382 /* sequence numbers are equal, so the log buffer is empty */
383 if (logbuf_has_space(msg_size, true))
389 /* compute the message size including the padding bytes */
390 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
394 size = sizeof(struct printk_log) + text_len + dict_len;
395 *pad_len = (-size) & (LOG_ALIGN - 1);
402 * Define how much of the log buffer we could take at maximum. The value
403 * must be greater than two. Note that only half of the buffer is available
404 * when the index points to the middle.
406 #define MAX_LOG_TAKE_PART 4
407 static const char trunc_msg[] = "<truncated>";
409 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
410 u16 *dict_len, u32 *pad_len)
413 * The message should not take the whole buffer. Otherwise, it might
414 * get removed too soon.
416 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
417 if (*text_len > max_text_len)
418 *text_len = max_text_len;
419 /* enable the warning message */
420 *trunc_msg_len = strlen(trunc_msg);
421 /* disable the "dict" completely */
423 /* compute the size again, count also the warning message */
424 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
427 /* insert record into the buffer, discard old ones, update heads */
428 static int log_store(int facility, int level,
429 enum log_flags flags, u64 ts_nsec,
430 const char *dict, u16 dict_len,
431 const char *text, u16 text_len)
433 struct printk_log *msg;
435 u16 trunc_msg_len = 0;
437 /* number of '\0' padding bytes to next message */
438 size = msg_used_size(text_len, dict_len, &pad_len);
440 if (log_make_free_space(size)) {
441 /* truncate the message if it is too long for empty buffer */
442 size = truncate_msg(&text_len, &trunc_msg_len,
443 &dict_len, &pad_len);
444 /* survive when the log buffer is too small for trunc_msg */
445 if (log_make_free_space(size))
449 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
451 * This message + an additional empty header does not fit
452 * at the end of the buffer. Add an empty header with len == 0
453 * to signify a wrap around.
455 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
460 msg = (struct printk_log *)(log_buf + log_next_idx);
461 memcpy(log_text(msg), text, text_len);
462 msg->text_len = text_len;
464 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
465 msg->text_len += trunc_msg_len;
467 memcpy(log_dict(msg), dict, dict_len);
468 msg->dict_len = dict_len;
469 msg->facility = facility;
470 msg->level = level & 7;
471 msg->flags = flags & 0x1f;
473 msg->ts_nsec = ts_nsec;
475 msg->ts_nsec = local_clock();
476 memset(log_dict(msg) + dict_len, 0, pad_len);
480 log_next_idx += msg->len;
483 return msg->text_len;
486 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
488 static int syslog_action_restricted(int type)
493 * Unless restricted, we allow "read all" and "get buffer size"
496 return type != SYSLOG_ACTION_READ_ALL &&
497 type != SYSLOG_ACTION_SIZE_BUFFER;
500 int check_syslog_permissions(int type, int source)
503 * If this is from /proc/kmsg and we've already opened it, then we've
504 * already done the capabilities checks at open time.
506 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
509 if (syslog_action_restricted(type)) {
510 if (capable(CAP_SYSLOG))
513 * For historical reasons, accept CAP_SYS_ADMIN too, with
516 if (capable(CAP_SYS_ADMIN)) {
517 pr_warn_once("%s (%d): Attempt to access syslog with "
518 "CAP_SYS_ADMIN but no CAP_SYSLOG "
520 current->comm, task_pid_nr(current));
526 return security_syslog(type);
528 EXPORT_SYMBOL_GPL(check_syslog_permissions);
530 static void append_char(char **pp, char *e, char c)
536 static ssize_t msg_print_ext_header(char *buf, size_t size,
537 struct printk_log *msg, u64 seq,
538 enum log_flags prev_flags)
540 u64 ts_usec = msg->ts_nsec;
543 do_div(ts_usec, 1000);
546 * If we couldn't merge continuation line fragments during the print,
547 * export the stored flags to allow an optional external merge of the
548 * records. Merging the records isn't always neccessarily correct, like
549 * when we hit a race during printing. In most cases though, it produces
550 * better readable output. 'c' in the record flags mark the first
551 * fragment of a line, '+' the following.
553 if (msg->flags & LOG_CONT && !(prev_flags & LOG_CONT))
555 else if ((msg->flags & LOG_CONT) ||
556 ((prev_flags & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
559 return scnprintf(buf, size, "%u,%llu,%llu,%c;",
560 (msg->facility << 3) | msg->level, seq, ts_usec, cont);
563 static ssize_t msg_print_ext_body(char *buf, size_t size,
564 char *dict, size_t dict_len,
565 char *text, size_t text_len)
567 char *p = buf, *e = buf + size;
570 /* escape non-printable characters */
571 for (i = 0; i < text_len; i++) {
572 unsigned char c = text[i];
574 if (c < ' ' || c >= 127 || c == '\\')
575 p += scnprintf(p, e - p, "\\x%02x", c);
577 append_char(&p, e, c);
579 append_char(&p, e, '\n');
584 for (i = 0; i < dict_len; i++) {
585 unsigned char c = dict[i];
588 append_char(&p, e, ' ');
593 append_char(&p, e, '\n');
598 if (c < ' ' || c >= 127 || c == '\\') {
599 p += scnprintf(p, e - p, "\\x%02x", c);
603 append_char(&p, e, c);
605 append_char(&p, e, '\n');
611 /* /dev/kmsg - userspace message inject/listen interface */
612 struct devkmsg_user {
617 char buf[CONSOLE_EXT_LOG_MAX];
620 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
623 int level = default_message_loglevel;
624 int facility = 1; /* LOG_USER */
625 size_t len = iov_iter_count(from);
628 if (len > LOG_LINE_MAX)
630 buf = kmalloc(len+1, GFP_KERNEL);
635 if (copy_from_iter(buf, len, from) != len) {
641 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
642 * the decimal value represents 32bit, the lower 3 bit are the log
643 * level, the rest are the log facility.
645 * If no prefix or no userspace facility is specified, we
646 * enforce LOG_USER, to be able to reliably distinguish
647 * kernel-generated messages from userspace-injected ones.
650 if (line[0] == '<') {
654 u = simple_strtoul(line + 1, &endp, 10);
655 if (endp && endp[0] == '>') {
656 level = LOG_LEVEL(u);
657 if (LOG_FACILITY(u) != 0)
658 facility = LOG_FACILITY(u);
665 printk_emit(facility, level, NULL, 0, "%s", line);
670 static ssize_t devkmsg_read(struct file *file, char __user *buf,
671 size_t count, loff_t *ppos)
673 struct devkmsg_user *user = file->private_data;
674 struct printk_log *msg;
681 ret = mutex_lock_interruptible(&user->lock);
684 raw_spin_lock_irq(&logbuf_lock);
685 while (user->seq == log_next_seq) {
686 if (file->f_flags & O_NONBLOCK) {
688 raw_spin_unlock_irq(&logbuf_lock);
692 raw_spin_unlock_irq(&logbuf_lock);
693 ret = wait_event_interruptible(log_wait,
694 user->seq != log_next_seq);
697 raw_spin_lock_irq(&logbuf_lock);
700 if (user->seq < log_first_seq) {
701 /* our last seen message is gone, return error and reset */
702 user->idx = log_first_idx;
703 user->seq = log_first_seq;
705 raw_spin_unlock_irq(&logbuf_lock);
709 msg = log_from_idx(user->idx);
710 len = msg_print_ext_header(user->buf, sizeof(user->buf),
711 msg, user->seq, user->prev);
712 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
713 log_dict(msg), msg->dict_len,
714 log_text(msg), msg->text_len);
716 user->prev = msg->flags;
717 user->idx = log_next(user->idx);
719 raw_spin_unlock_irq(&logbuf_lock);
726 if (copy_to_user(buf, user->buf, len)) {
732 mutex_unlock(&user->lock);
736 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
738 struct devkmsg_user *user = file->private_data;
746 raw_spin_lock_irq(&logbuf_lock);
749 /* the first record */
750 user->idx = log_first_idx;
751 user->seq = log_first_seq;
755 * The first record after the last SYSLOG_ACTION_CLEAR,
756 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
757 * changes no global state, and does not clear anything.
759 user->idx = clear_idx;
760 user->seq = clear_seq;
763 /* after the last record */
764 user->idx = log_next_idx;
765 user->seq = log_next_seq;
770 raw_spin_unlock_irq(&logbuf_lock);
774 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
776 struct devkmsg_user *user = file->private_data;
780 return POLLERR|POLLNVAL;
782 poll_wait(file, &log_wait, wait);
784 raw_spin_lock_irq(&logbuf_lock);
785 if (user->seq < log_next_seq) {
786 /* return error when data has vanished underneath us */
787 if (user->seq < log_first_seq)
788 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
790 ret = POLLIN|POLLRDNORM;
792 raw_spin_unlock_irq(&logbuf_lock);
797 static int devkmsg_open(struct inode *inode, struct file *file)
799 struct devkmsg_user *user;
802 /* write-only does not need any file context */
803 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
806 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
811 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
815 mutex_init(&user->lock);
817 raw_spin_lock_irq(&logbuf_lock);
818 user->idx = log_first_idx;
819 user->seq = log_first_seq;
820 raw_spin_unlock_irq(&logbuf_lock);
822 file->private_data = user;
826 static int devkmsg_release(struct inode *inode, struct file *file)
828 struct devkmsg_user *user = file->private_data;
833 mutex_destroy(&user->lock);
838 const struct file_operations kmsg_fops = {
839 .open = devkmsg_open,
840 .read = devkmsg_read,
841 .write_iter = devkmsg_write,
842 .llseek = devkmsg_llseek,
843 .poll = devkmsg_poll,
844 .release = devkmsg_release,
847 #ifdef CONFIG_KEXEC_CORE
849 * This appends the listed symbols to /proc/vmcore
851 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
852 * obtain access to symbols that are otherwise very difficult to locate. These
853 * symbols are specifically used so that utilities can access and extract the
854 * dmesg log from a vmcore file after a crash.
856 void log_buf_kexec_setup(void)
858 VMCOREINFO_SYMBOL(log_buf);
859 VMCOREINFO_SYMBOL(log_buf_len);
860 VMCOREINFO_SYMBOL(log_first_idx);
861 VMCOREINFO_SYMBOL(log_next_idx);
863 * Export struct printk_log size and field offsets. User space tools can
864 * parse it and detect any changes to structure down the line.
866 VMCOREINFO_STRUCT_SIZE(printk_log);
867 VMCOREINFO_OFFSET(printk_log, ts_nsec);
868 VMCOREINFO_OFFSET(printk_log, len);
869 VMCOREINFO_OFFSET(printk_log, text_len);
870 VMCOREINFO_OFFSET(printk_log, dict_len);
874 /* requested log_buf_len from kernel cmdline */
875 static unsigned long __initdata new_log_buf_len;
877 /* we practice scaling the ring buffer by powers of 2 */
878 static void __init log_buf_len_update(u64 size)
880 if (size > (u64)LOG_BUF_LEN_MAX) {
881 size = (u64)LOG_BUF_LEN_MAX;
882 pr_err("log_buf over 2G is not supported.\n");
886 size = roundup_pow_of_two(size);
887 if (size > log_buf_len)
888 new_log_buf_len = (unsigned long)size;
891 /* save requested log_buf_len since it's too early to process it */
892 static int __init log_buf_len_setup(char *str)
899 size = memparse(str, &str);
901 log_buf_len_update(size);
905 early_param("log_buf_len", log_buf_len_setup);
908 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
910 static void __init log_buf_add_cpu(void)
912 unsigned int cpu_extra;
915 * archs should set up cpu_possible_bits properly with
916 * set_cpu_possible() after setup_arch() but just in
917 * case lets ensure this is valid.
919 if (num_possible_cpus() == 1)
922 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
924 /* by default this will only continue through for large > 64 CPUs */
925 if (cpu_extra <= __LOG_BUF_LEN / 2)
928 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
929 __LOG_CPU_MAX_BUF_LEN);
930 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
932 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
934 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
936 #else /* !CONFIG_SMP */
937 static inline void log_buf_add_cpu(void) {}
938 #endif /* CONFIG_SMP */
940 void __init setup_log_buf(int early)
946 if (log_buf != __log_buf)
949 if (!early && !new_log_buf_len)
952 if (!new_log_buf_len)
957 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
959 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
963 if (unlikely(!new_log_buf)) {
964 pr_err("log_buf_len: %lu bytes not available\n",
969 raw_spin_lock_irqsave(&logbuf_lock, flags);
970 log_buf_len = new_log_buf_len;
971 log_buf = new_log_buf;
973 free = __LOG_BUF_LEN - log_next_idx;
974 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
975 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
977 pr_info("log_buf_len: %u bytes\n", log_buf_len);
978 pr_info("early log buf free: %u(%u%%)\n",
979 free, (free * 100) / __LOG_BUF_LEN);
982 static bool __read_mostly ignore_loglevel;
984 static int __init ignore_loglevel_setup(char *str)
986 ignore_loglevel = true;
987 pr_info("debug: ignoring loglevel setting.\n");
992 early_param("ignore_loglevel", ignore_loglevel_setup);
993 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
994 MODULE_PARM_DESC(ignore_loglevel,
995 "ignore loglevel setting (prints all kernel messages to the console)");
997 #ifdef CONFIG_BOOT_PRINTK_DELAY
999 static int boot_delay; /* msecs delay after each printk during bootup */
1000 static unsigned long long loops_per_msec; /* based on boot_delay */
1002 static int __init boot_delay_setup(char *str)
1006 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
1007 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
1009 get_option(&str, &boot_delay);
1010 if (boot_delay > 10 * 1000)
1013 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1014 "HZ: %d, loops_per_msec: %llu\n",
1015 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1018 early_param("boot_delay", boot_delay_setup);
1020 static void boot_delay_msec(int level)
1022 unsigned long long k;
1023 unsigned long timeout;
1025 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
1026 || (level >= console_loglevel && !ignore_loglevel)) {
1030 k = (unsigned long long)loops_per_msec * boot_delay;
1032 timeout = jiffies + msecs_to_jiffies(boot_delay);
1037 * use (volatile) jiffies to prevent
1038 * compiler reduction; loop termination via jiffies
1039 * is secondary and may or may not happen.
1041 if (time_after(jiffies, timeout))
1043 touch_nmi_watchdog();
1047 static inline void boot_delay_msec(int level)
1052 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1053 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1055 static size_t print_time(u64 ts, char *buf)
1057 unsigned long rem_nsec;
1062 rem_nsec = do_div(ts, 1000000000);
1065 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1067 return sprintf(buf, "[%5lu.%06lu] ",
1068 (unsigned long)ts, rem_nsec / 1000);
1071 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1074 unsigned int prefix = (msg->facility << 3) | msg->level;
1078 len += sprintf(buf, "<%u>", prefix);
1083 else if (prefix > 99)
1085 else if (prefix > 9)
1090 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1094 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1095 bool syslog, char *buf, size_t size)
1097 const char *text = log_text(msg);
1098 size_t text_size = msg->text_len;
1100 bool newline = true;
1103 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1106 if (msg->flags & LOG_CONT) {
1107 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1110 if (!(msg->flags & LOG_NEWLINE))
1115 const char *next = memchr(text, '\n', text_size);
1119 text_len = next - text;
1121 text_size -= next - text;
1123 text_len = text_size;
1127 if (print_prefix(msg, syslog, NULL) +
1128 text_len + 1 >= size - len)
1132 len += print_prefix(msg, syslog, buf + len);
1133 memcpy(buf + len, text, text_len);
1135 if (next || newline)
1138 /* SYSLOG_ACTION_* buffer size only calculation */
1140 len += print_prefix(msg, syslog, NULL);
1142 if (next || newline)
1153 static int syslog_print(char __user *buf, int size)
1156 struct printk_log *msg;
1159 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1167 raw_spin_lock_irq(&logbuf_lock);
1168 if (syslog_seq < log_first_seq) {
1169 /* messages are gone, move to first one */
1170 syslog_seq = log_first_seq;
1171 syslog_idx = log_first_idx;
1175 if (syslog_seq == log_next_seq) {
1176 raw_spin_unlock_irq(&logbuf_lock);
1180 skip = syslog_partial;
1181 msg = log_from_idx(syslog_idx);
1182 n = msg_print_text(msg, syslog_prev, true, text,
1183 LOG_LINE_MAX + PREFIX_MAX);
1184 if (n - syslog_partial <= size) {
1185 /* message fits into buffer, move forward */
1186 syslog_idx = log_next(syslog_idx);
1188 syslog_prev = msg->flags;
1189 n -= syslog_partial;
1192 /* partial read(), remember position */
1194 syslog_partial += n;
1197 raw_spin_unlock_irq(&logbuf_lock);
1202 if (copy_to_user(buf, text + skip, n)) {
1217 static int syslog_print_all(char __user *buf, int size, bool clear)
1222 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1226 raw_spin_lock_irq(&logbuf_lock);
1231 enum log_flags prev;
1233 if (clear_seq < log_first_seq) {
1234 /* messages are gone, move to first available one */
1235 clear_seq = log_first_seq;
1236 clear_idx = log_first_idx;
1240 * Find first record that fits, including all following records,
1241 * into the user-provided buffer for this dump.
1246 while (seq < log_next_seq) {
1247 struct printk_log *msg = log_from_idx(idx);
1249 len += msg_print_text(msg, prev, true, NULL, 0);
1251 idx = log_next(idx);
1255 /* move first record forward until length fits into the buffer */
1259 while (len > size && seq < log_next_seq) {
1260 struct printk_log *msg = log_from_idx(idx);
1262 len -= msg_print_text(msg, prev, true, NULL, 0);
1264 idx = log_next(idx);
1268 /* last message fitting into this dump */
1269 next_seq = log_next_seq;
1272 while (len >= 0 && seq < next_seq) {
1273 struct printk_log *msg = log_from_idx(idx);
1276 textlen = msg_print_text(msg, prev, true, text,
1277 LOG_LINE_MAX + PREFIX_MAX);
1282 idx = log_next(idx);
1286 raw_spin_unlock_irq(&logbuf_lock);
1287 if (copy_to_user(buf + len, text, textlen))
1291 raw_spin_lock_irq(&logbuf_lock);
1293 if (seq < log_first_seq) {
1294 /* messages are gone, move to next one */
1295 seq = log_first_seq;
1296 idx = log_first_idx;
1303 clear_seq = log_next_seq;
1304 clear_idx = log_next_idx;
1306 raw_spin_unlock_irq(&logbuf_lock);
1312 int do_syslog(int type, char __user *buf, int len, int source)
1315 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1318 error = check_syslog_permissions(type, source);
1323 case SYSLOG_ACTION_CLOSE: /* Close log */
1325 case SYSLOG_ACTION_OPEN: /* Open log */
1327 case SYSLOG_ACTION_READ: /* Read from log */
1329 if (!buf || len < 0)
1334 if (!access_ok(VERIFY_WRITE, buf, len)) {
1338 error = wait_event_interruptible(log_wait,
1339 syslog_seq != log_next_seq);
1342 error = syslog_print(buf, len);
1344 /* Read/clear last kernel messages */
1345 case SYSLOG_ACTION_READ_CLEAR:
1348 /* Read last kernel messages */
1349 case SYSLOG_ACTION_READ_ALL:
1351 if (!buf || len < 0)
1356 if (!access_ok(VERIFY_WRITE, buf, len)) {
1360 error = syslog_print_all(buf, len, clear);
1362 /* Clear ring buffer */
1363 case SYSLOG_ACTION_CLEAR:
1364 syslog_print_all(NULL, 0, true);
1366 /* Disable logging to console */
1367 case SYSLOG_ACTION_CONSOLE_OFF:
1368 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1369 saved_console_loglevel = console_loglevel;
1370 console_loglevel = minimum_console_loglevel;
1372 /* Enable logging to console */
1373 case SYSLOG_ACTION_CONSOLE_ON:
1374 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1375 console_loglevel = saved_console_loglevel;
1376 saved_console_loglevel = LOGLEVEL_DEFAULT;
1379 /* Set level of messages printed to console */
1380 case SYSLOG_ACTION_CONSOLE_LEVEL:
1382 if (len < 1 || len > 8)
1384 if (len < minimum_console_loglevel)
1385 len = minimum_console_loglevel;
1386 console_loglevel = len;
1387 /* Implicitly re-enable logging to console */
1388 saved_console_loglevel = LOGLEVEL_DEFAULT;
1391 /* Number of chars in the log buffer */
1392 case SYSLOG_ACTION_SIZE_UNREAD:
1393 raw_spin_lock_irq(&logbuf_lock);
1394 if (syslog_seq < log_first_seq) {
1395 /* messages are gone, move to first one */
1396 syslog_seq = log_first_seq;
1397 syslog_idx = log_first_idx;
1401 if (source == SYSLOG_FROM_PROC) {
1403 * Short-cut for poll(/"proc/kmsg") which simply checks
1404 * for pending data, not the size; return the count of
1405 * records, not the length.
1407 error = log_next_seq - syslog_seq;
1409 u64 seq = syslog_seq;
1410 u32 idx = syslog_idx;
1411 enum log_flags prev = syslog_prev;
1414 while (seq < log_next_seq) {
1415 struct printk_log *msg = log_from_idx(idx);
1417 error += msg_print_text(msg, prev, true, NULL, 0);
1418 idx = log_next(idx);
1422 error -= syslog_partial;
1424 raw_spin_unlock_irq(&logbuf_lock);
1426 /* Size of the log buffer */
1427 case SYSLOG_ACTION_SIZE_BUFFER:
1428 error = log_buf_len;
1438 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1440 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1444 * Call the console drivers, asking them to write out
1445 * log_buf[start] to log_buf[end - 1].
1446 * The console_lock must be held.
1448 static void call_console_drivers(int level,
1449 const char *ext_text, size_t ext_len,
1450 const char *text, size_t len)
1452 struct console *con;
1454 trace_console_rcuidle(text, len);
1456 if (level >= console_loglevel && !ignore_loglevel)
1458 if (!console_drivers)
1461 for_each_console(con) {
1462 if (exclusive_console && con != exclusive_console)
1464 if (!(con->flags & CON_ENABLED))
1468 if (!cpu_online(smp_processor_id()) &&
1469 !(con->flags & CON_ANYTIME))
1471 if (con->flags & CON_EXTENDED)
1472 con->write(con, ext_text, ext_len);
1474 con->write(con, text, len);
1479 * Zap console related locks when oopsing.
1480 * To leave time for slow consoles to print a full oops,
1481 * only zap at most once every 30 seconds.
1483 static void zap_locks(void)
1485 static unsigned long oops_timestamp;
1487 if (time_after_eq(jiffies, oops_timestamp) &&
1488 !time_after(jiffies, oops_timestamp + 30 * HZ))
1491 oops_timestamp = jiffies;
1494 /* If a crash is occurring, make sure we can't deadlock */
1495 raw_spin_lock_init(&logbuf_lock);
1496 /* And make sure that we print immediately */
1497 sema_init(&console_sem, 1);
1501 * Check if we have any console that is capable of printing while cpu is
1502 * booting or shutting down. Requires console_sem.
1504 static int have_callable_console(void)
1506 struct console *con;
1508 for_each_console(con)
1509 if (con->flags & CON_ANYTIME)
1516 * Can we actually use the console at this time on this cpu?
1518 * Console drivers may assume that per-cpu resources have been allocated. So
1519 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1520 * call them until this CPU is officially up.
1522 static inline int can_use_console(unsigned int cpu)
1524 return cpu_online(cpu) || have_callable_console();
1528 * Try to get console ownership to actually show the kernel
1529 * messages from a 'printk'. Return true (and with the
1530 * console_lock held, and 'console_locked' set) if it
1531 * is successful, false otherwise.
1533 static int console_trylock_for_printk(void)
1535 unsigned int cpu = smp_processor_id();
1537 if (!console_trylock())
1540 * If we can't use the console, we need to release the console
1541 * semaphore by hand to avoid flushing the buffer. We need to hold the
1542 * console semaphore in order to do this test safely.
1544 if (!can_use_console(cpu)) {
1552 int printk_delay_msec __read_mostly;
1554 static inline void printk_delay(void)
1556 if (unlikely(printk_delay_msec)) {
1557 int m = printk_delay_msec;
1561 touch_nmi_watchdog();
1567 * Continuation lines are buffered, and not committed to the record buffer
1568 * until the line is complete, or a race forces it. The line fragments
1569 * though, are printed immediately to the consoles to ensure everything has
1570 * reached the console in case of a kernel crash.
1572 static struct cont {
1573 char buf[LOG_LINE_MAX];
1574 size_t len; /* length == 0 means unused buffer */
1575 size_t cons; /* bytes written to console */
1576 struct task_struct *owner; /* task of first print*/
1577 u64 ts_nsec; /* time of first print */
1578 u8 level; /* log level of first message */
1579 u8 facility; /* log facility of first message */
1580 enum log_flags flags; /* prefix, newline flags */
1581 bool flushed:1; /* buffer sealed and committed */
1584 static void cont_flush(enum log_flags flags)
1593 * If a fragment of this line was directly flushed to the
1594 * console; wait for the console to pick up the rest of the
1595 * line. LOG_NOCONS suppresses a duplicated output.
1597 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1598 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1600 cont.flushed = true;
1603 * If no fragment of this line ever reached the console,
1604 * just submit it to the store and free the buffer.
1606 log_store(cont.facility, cont.level, flags, 0,
1607 NULL, 0, cont.buf, cont.len);
1612 static bool cont_add(int facility, int level, const char *text, size_t len)
1614 if (cont.len && cont.flushed)
1618 * If ext consoles are present, flush and skip in-kernel
1619 * continuation. See nr_ext_console_drivers definition. Also, if
1620 * the line gets too long, split it up in separate records.
1622 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
1623 cont_flush(LOG_CONT);
1628 cont.facility = facility;
1630 cont.owner = current;
1631 cont.ts_nsec = local_clock();
1634 cont.flushed = false;
1637 memcpy(cont.buf + cont.len, text, len);
1640 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1641 cont_flush(LOG_CONT);
1646 static size_t cont_print_text(char *text, size_t size)
1651 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1652 textlen += print_time(cont.ts_nsec, text);
1656 len = cont.len - cont.cons;
1660 memcpy(text + textlen, cont.buf + cont.cons, len);
1662 cont.cons = cont.len;
1666 if (cont.flags & LOG_NEWLINE)
1667 text[textlen++] = '\n';
1668 /* got everything, release buffer */
1674 asmlinkage int vprintk_emit(int facility, int level,
1675 const char *dict, size_t dictlen,
1676 const char *fmt, va_list args)
1678 static int recursion_bug;
1679 static char textbuf[LOG_LINE_MAX];
1680 char *text = textbuf;
1681 size_t text_len = 0;
1682 enum log_flags lflags = 0;
1683 unsigned long flags;
1685 int printed_len = 0;
1686 bool in_sched = false;
1687 /* cpu currently holding logbuf_lock in this function */
1688 static unsigned int logbuf_cpu = UINT_MAX;
1690 if (level == LOGLEVEL_SCHED) {
1691 level = LOGLEVEL_DEFAULT;
1695 boot_delay_msec(level);
1698 /* This stops the holder of console_sem just where we want him */
1699 local_irq_save(flags);
1700 this_cpu = smp_processor_id();
1703 * Ouch, printk recursed into itself!
1705 if (unlikely(logbuf_cpu == this_cpu)) {
1707 * If a crash is occurring during printk() on this CPU,
1708 * then try to get the crash message out but make sure
1709 * we can't deadlock. Otherwise just return to avoid the
1710 * recursion and return - but flag the recursion so that
1711 * it can be printed at the next appropriate moment:
1713 if (!oops_in_progress && !lockdep_recursing(current)) {
1715 local_irq_restore(flags);
1722 raw_spin_lock(&logbuf_lock);
1723 logbuf_cpu = this_cpu;
1725 if (unlikely(recursion_bug)) {
1726 static const char recursion_msg[] =
1727 "BUG: recent printk recursion!";
1730 /* emit KERN_CRIT message */
1731 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1732 NULL, 0, recursion_msg,
1733 strlen(recursion_msg));
1737 * The printf needs to come first; we need the syslog
1738 * prefix which might be passed-in as a parameter.
1740 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1742 /* mark and strip a trailing newline */
1743 if (text_len && text[text_len-1] == '\n') {
1745 lflags |= LOG_NEWLINE;
1748 /* strip kernel syslog prefix and extract log level or control flags */
1749 if (facility == 0) {
1750 int kern_level = printk_get_level(text);
1753 const char *end_of_header = printk_skip_level(text);
1754 switch (kern_level) {
1756 if (level == LOGLEVEL_DEFAULT)
1757 level = kern_level - '0';
1759 case 'd': /* KERN_DEFAULT */
1760 lflags |= LOG_PREFIX;
1763 * No need to check length here because vscnprintf
1764 * put '\0' at the end of the string. Only valid and
1765 * newly printed level is detected.
1767 text_len -= end_of_header - text;
1768 text = (char *)end_of_header;
1772 #ifdef CONFIG_EARLY_PRINTK_DIRECT
1776 if (level == LOGLEVEL_DEFAULT)
1777 level = default_message_loglevel;
1780 lflags |= LOG_PREFIX|LOG_NEWLINE;
1782 if (!(lflags & LOG_NEWLINE)) {
1784 * Flush the conflicting buffer. An earlier newline was missing,
1785 * or another task also prints continuation lines.
1787 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1788 cont_flush(LOG_NEWLINE);
1790 /* buffer line if possible, otherwise store it right away */
1791 if (cont_add(facility, level, text, text_len))
1792 printed_len += text_len;
1794 printed_len += log_store(facility, level,
1795 lflags | LOG_CONT, 0,
1796 dict, dictlen, text, text_len);
1798 bool stored = false;
1801 * If an earlier newline was missing and it was the same task,
1802 * either merge it with the current buffer and flush, or if
1803 * there was a race with interrupts (prefix == true) then just
1804 * flush it out and store this line separately.
1805 * If the preceding printk was from a different task and missed
1806 * a newline, flush and append the newline.
1809 if (cont.owner == current && !(lflags & LOG_PREFIX))
1810 stored = cont_add(facility, level, text,
1812 cont_flush(LOG_NEWLINE);
1816 printed_len += text_len;
1818 printed_len += log_store(facility, level, lflags, 0,
1819 dict, dictlen, text, text_len);
1822 logbuf_cpu = UINT_MAX;
1823 raw_spin_unlock(&logbuf_lock);
1825 local_irq_restore(flags);
1827 /* If called from the scheduler, we can not call up(). */
1831 * Disable preemption to avoid being preempted while holding
1832 * console_sem which would prevent anyone from printing to
1838 * Try to acquire and then immediately release the console
1839 * semaphore. The release will print out buffers and wake up
1840 * /dev/kmsg and syslog() users.
1842 if (console_trylock_for_printk())
1850 EXPORT_SYMBOL(vprintk_emit);
1852 asmlinkage int vprintk(const char *fmt, va_list args)
1854 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1856 EXPORT_SYMBOL(vprintk);
1858 asmlinkage int printk_emit(int facility, int level,
1859 const char *dict, size_t dictlen,
1860 const char *fmt, ...)
1865 va_start(args, fmt);
1866 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1871 EXPORT_SYMBOL(printk_emit);
1873 int vprintk_default(const char *fmt, va_list args)
1877 #ifdef CONFIG_KGDB_KDB
1878 if (unlikely(kdb_trap_printk)) {
1879 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1883 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1887 EXPORT_SYMBOL_GPL(vprintk_default);
1890 * This allows printk to be diverted to another function per cpu.
1891 * This is useful for calling printk functions from within NMI
1892 * without worrying about race conditions that can lock up the
1895 DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
1898 * printk - print a kernel message
1899 * @fmt: format string
1901 * This is printk(). It can be called from any context. We want it to work.
1903 * We try to grab the console_lock. If we succeed, it's easy - we log the
1904 * output and call the console drivers. If we fail to get the semaphore, we
1905 * place the output into the log buffer and return. The current holder of
1906 * the console_sem will notice the new output in console_unlock(); and will
1907 * send it to the consoles before releasing the lock.
1909 * One effect of this deferred printing is that code which calls printk() and
1910 * then changes console_loglevel may break. This is because console_loglevel
1911 * is inspected when the actual printing occurs.
1916 * See the vsnprintf() documentation for format string extensions over C99.
1918 asmlinkage __visible int printk(const char *fmt, ...)
1920 printk_func_t vprintk_func;
1924 va_start(args, fmt);
1927 * If a caller overrides the per_cpu printk_func, then it needs
1928 * to disable preemption when calling printk(). Otherwise
1929 * the printk_func should be set to the default. No need to
1930 * disable preemption here.
1932 vprintk_func = this_cpu_read(printk_func);
1933 r = vprintk_func(fmt, args);
1939 EXPORT_SYMBOL(printk);
1941 #else /* CONFIG_PRINTK */
1943 #define LOG_LINE_MAX 0
1944 #define PREFIX_MAX 0
1946 static u64 syslog_seq;
1947 static u32 syslog_idx;
1948 static u64 console_seq;
1949 static u32 console_idx;
1950 static enum log_flags syslog_prev;
1951 static u64 log_first_seq;
1952 static u32 log_first_idx;
1953 static u64 log_next_seq;
1954 static enum log_flags console_prev;
1955 static struct cont {
1961 static char *log_text(const struct printk_log *msg) { return NULL; }
1962 static char *log_dict(const struct printk_log *msg) { return NULL; }
1963 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1964 static u32 log_next(u32 idx) { return 0; }
1965 static ssize_t msg_print_ext_header(char *buf, size_t size,
1966 struct printk_log *msg, u64 seq,
1967 enum log_flags prev_flags) { return 0; }
1968 static ssize_t msg_print_ext_body(char *buf, size_t size,
1969 char *dict, size_t dict_len,
1970 char *text, size_t text_len) { return 0; }
1971 static void call_console_drivers(int level,
1972 const char *ext_text, size_t ext_len,
1973 const char *text, size_t len) {}
1974 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1975 bool syslog, char *buf, size_t size) { return 0; }
1976 static size_t cont_print_text(char *text, size_t size) { return 0; }
1978 /* Still needs to be defined for users */
1979 DEFINE_PER_CPU(printk_func_t, printk_func);
1981 #endif /* CONFIG_PRINTK */
1983 #ifdef CONFIG_EARLY_PRINTK
1984 struct console *early_console;
1986 asmlinkage __visible void early_printk(const char *fmt, ...)
1996 n = vscnprintf(buf, sizeof(buf), fmt, ap);
1999 early_console->write(early_console, buf, n);
2003 static int __add_preferred_console(char *name, int idx, char *options,
2006 struct console_cmdline *c;
2010 * See if this tty is not yet registered, and
2011 * if we have a slot free.
2013 for (i = 0, c = console_cmdline;
2014 i < MAX_CMDLINECONSOLES && c->name[0];
2016 if (strcmp(c->name, name) == 0 && c->index == idx) {
2018 selected_console = i;
2022 if (i == MAX_CMDLINECONSOLES)
2025 selected_console = i;
2026 strlcpy(c->name, name, sizeof(c->name));
2027 c->options = options;
2028 braille_set_options(c, brl_options);
2034 * Set up a console. Called via do_early_param() in init/main.c
2035 * for each "console=" parameter in the boot command line.
2037 static int __init console_setup(char *str)
2039 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2040 char *s, *options, *brl_options = NULL;
2043 if (_braille_console_setup(&str, &brl_options))
2047 * Decode str into name, index, options.
2049 if (str[0] >= '0' && str[0] <= '9') {
2050 strcpy(buf, "ttyS");
2051 strncpy(buf + 4, str, sizeof(buf) - 5);
2053 strncpy(buf, str, sizeof(buf) - 1);
2055 buf[sizeof(buf) - 1] = 0;
2056 options = strchr(str, ',');
2060 if (!strcmp(str, "ttya"))
2061 strcpy(buf, "ttyS0");
2062 if (!strcmp(str, "ttyb"))
2063 strcpy(buf, "ttyS1");
2065 for (s = buf; *s; s++)
2066 if (isdigit(*s) || *s == ',')
2068 idx = simple_strtoul(s, NULL, 10);
2071 __add_preferred_console(buf, idx, options, brl_options);
2072 console_set_on_cmdline = 1;
2075 __setup("console=", console_setup);
2078 * add_preferred_console - add a device to the list of preferred consoles.
2079 * @name: device name
2080 * @idx: device index
2081 * @options: options for this console
2083 * The last preferred console added will be used for kernel messages
2084 * and stdin/out/err for init. Normally this is used by console_setup
2085 * above to handle user-supplied console arguments; however it can also
2086 * be used by arch-specific code either to override the user or more
2087 * commonly to provide a default console (ie from PROM variables) when
2088 * the user has not supplied one.
2090 int add_preferred_console(char *name, int idx, char *options)
2092 return __add_preferred_console(name, idx, options, NULL);
2095 bool console_suspend_enabled = true;
2096 EXPORT_SYMBOL(console_suspend_enabled);
2098 static int __init console_suspend_disable(char *str)
2100 console_suspend_enabled = false;
2103 __setup("no_console_suspend", console_suspend_disable);
2104 module_param_named(console_suspend, console_suspend_enabled,
2105 bool, S_IRUGO | S_IWUSR);
2106 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2107 " and hibernate operations");
2110 * suspend_console - suspend the console subsystem
2112 * This disables printk() while we go into suspend states
2114 void suspend_console(void)
2116 if (!console_suspend_enabled)
2118 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2120 console_suspended = 1;
2124 void resume_console(void)
2126 if (!console_suspend_enabled)
2129 console_suspended = 0;
2133 #ifdef CONFIG_CONSOLE_FLUSH_ON_HOTPLUG
2136 * console_cpu_notify - print deferred console messages after CPU hotplug
2137 * @self: notifier struct
2138 * @action: CPU hotplug event
2141 * If printk() is called from a CPU that is not online yet, the messages
2142 * will be spooled but will not show up on the console. This function is
2143 * called when a new CPU comes online (or fails to come up), and ensures
2144 * that any such output gets printed.
2146 static int console_cpu_notify(struct notifier_block *self,
2147 unsigned long action, void *hcpu)
2152 case CPU_DOWN_FAILED:
2153 case CPU_UP_CANCELED:
2155 #ifdef CONFIG_CONSOLE_FLUSH_ON_HOTPLUG
2167 * console_lock - lock the console system for exclusive use.
2169 * Acquires a lock which guarantees that the caller has
2170 * exclusive access to the console system and the console_drivers list.
2172 * Can sleep, returns nothing.
2174 void console_lock(void)
2179 if (console_suspended)
2182 console_may_schedule = 1;
2184 EXPORT_SYMBOL(console_lock);
2187 * console_trylock - try to lock the console system for exclusive use.
2189 * Try to acquire a lock which guarantees that the caller has exclusive
2190 * access to the console system and the console_drivers list.
2192 * returns 1 on success, and 0 on failure to acquire the lock.
2194 int console_trylock(void)
2196 if (down_trylock_console_sem())
2198 if (console_suspended) {
2203 console_may_schedule = 0;
2206 EXPORT_SYMBOL(console_trylock);
2208 int is_console_locked(void)
2210 return console_locked;
2213 static void console_cont_flush(char *text, size_t size)
2215 unsigned long flags;
2218 raw_spin_lock_irqsave(&logbuf_lock, flags);
2224 * We still queue earlier records, likely because the console was
2225 * busy. The earlier ones need to be printed before this one, we
2226 * did not flush any fragment so far, so just let it queue up.
2228 if (console_seq < log_next_seq && !cont.cons)
2231 len = cont_print_text(text, size);
2232 raw_spin_unlock(&logbuf_lock);
2233 stop_critical_timings();
2234 call_console_drivers(cont.level, NULL, 0, text, len);
2235 start_critical_timings();
2236 local_irq_restore(flags);
2239 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2243 * console_unlock - unlock the console system
2245 * Releases the console_lock which the caller holds on the console system
2246 * and the console driver list.
2248 * While the console_lock was held, console output may have been buffered
2249 * by printk(). If this is the case, console_unlock(); emits
2250 * the output prior to releasing the lock.
2252 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2254 * console_unlock(); may be called from any context.
2256 void console_unlock(void)
2258 static char ext_text[CONSOLE_EXT_LOG_MAX];
2259 static char text[LOG_LINE_MAX + PREFIX_MAX];
2260 static u64 seen_seq;
2261 unsigned long flags;
2262 bool wake_klogd = false;
2263 bool do_cond_resched, retry;
2265 if (console_suspended) {
2271 * Console drivers are called under logbuf_lock, so
2272 * @console_may_schedule should be cleared before; however, we may
2273 * end up dumping a lot of lines, for example, if called from
2274 * console registration path, and should invoke cond_resched()
2275 * between lines if allowable. Not doing so can cause a very long
2276 * scheduling stall on a slow console leading to RCU stall and
2277 * softlockup warnings which exacerbate the issue with more
2278 * messages practically incapacitating the system.
2280 do_cond_resched = console_may_schedule;
2281 console_may_schedule = 0;
2283 /* flush buffered message fragment immediately to console */
2284 console_cont_flush(text, sizeof(text));
2287 struct printk_log *msg;
2292 raw_spin_lock_irqsave(&logbuf_lock, flags);
2293 if (seen_seq != log_next_seq) {
2295 seen_seq = log_next_seq;
2298 if (console_seq < log_first_seq) {
2299 len = sprintf(text, "** %u printk messages dropped ** ",
2300 (unsigned)(log_first_seq - console_seq));
2302 /* messages are gone, move to first one */
2303 console_seq = log_first_seq;
2304 console_idx = log_first_idx;
2310 if (console_seq == log_next_seq)
2313 msg = log_from_idx(console_idx);
2314 if (msg->flags & LOG_NOCONS) {
2316 * Skip record we have buffered and already printed
2317 * directly to the console when we received it.
2319 console_idx = log_next(console_idx);
2322 * We will get here again when we register a new
2323 * CON_PRINTBUFFER console. Clear the flag so we
2324 * will properly dump everything later.
2326 msg->flags &= ~LOG_NOCONS;
2327 console_prev = msg->flags;
2332 len += msg_print_text(msg, console_prev, false,
2333 text + len, sizeof(text) - len);
2334 if (nr_ext_console_drivers) {
2335 ext_len = msg_print_ext_header(ext_text,
2337 msg, console_seq, console_prev);
2338 ext_len += msg_print_ext_body(ext_text + ext_len,
2339 sizeof(ext_text) - ext_len,
2340 log_dict(msg), msg->dict_len,
2341 log_text(msg), msg->text_len);
2343 console_idx = log_next(console_idx);
2345 console_prev = msg->flags;
2346 raw_spin_unlock(&logbuf_lock);
2348 stop_critical_timings(); /* don't trace print latency */
2349 call_console_drivers(level, ext_text, ext_len, text, len);
2350 start_critical_timings();
2351 local_irq_restore(flags);
2353 if (do_cond_resched)
2358 /* Release the exclusive_console once it is used */
2359 if (unlikely(exclusive_console))
2360 exclusive_console = NULL;
2362 raw_spin_unlock(&logbuf_lock);
2367 * Someone could have filled up the buffer again, so re-check if there's
2368 * something to flush. In case we cannot trylock the console_sem again,
2369 * there's a new owner and the console_unlock() from them will do the
2370 * flush, no worries.
2372 raw_spin_lock(&logbuf_lock);
2373 retry = console_seq != log_next_seq;
2374 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2376 if (retry && console_trylock())
2382 EXPORT_SYMBOL(console_unlock);
2385 * console_conditional_schedule - yield the CPU if required
2387 * If the console code is currently allowed to sleep, and
2388 * if this CPU should yield the CPU to another task, do
2391 * Must be called within console_lock();.
2393 void __sched console_conditional_schedule(void)
2395 if (console_may_schedule)
2398 EXPORT_SYMBOL(console_conditional_schedule);
2400 void console_unblank(void)
2405 * console_unblank can no longer be called in interrupt context unless
2406 * oops_in_progress is set to 1..
2408 if (oops_in_progress) {
2409 if (down_trylock_console_sem() != 0)
2415 console_may_schedule = 0;
2417 if ((c->flags & CON_ENABLED) && c->unblank)
2423 * console_flush_on_panic - flush console content on panic
2425 * Immediately output all pending messages no matter what.
2427 void console_flush_on_panic(void)
2430 * If someone else is holding the console lock, trylock will fail
2431 * and may_schedule may be set. Ignore and proceed to unlock so
2432 * that messages are flushed out. As this can be called from any
2433 * context and we don't want to get preempted while flushing,
2434 * ensure may_schedule is cleared.
2437 console_may_schedule = 0;
2442 * Return the console tty driver structure and its associated index
2444 struct tty_driver *console_device(int *index)
2447 struct tty_driver *driver = NULL;
2450 for_each_console(c) {
2453 driver = c->device(c, index);
2462 * Prevent further output on the passed console device so that (for example)
2463 * serial drivers can disable console output before suspending a port, and can
2464 * re-enable output afterwards.
2466 void console_stop(struct console *console)
2469 console->flags &= ~CON_ENABLED;
2472 EXPORT_SYMBOL(console_stop);
2474 void console_start(struct console *console)
2477 console->flags |= CON_ENABLED;
2480 EXPORT_SYMBOL(console_start);
2482 static int __read_mostly keep_bootcon;
2484 static int __init keep_bootcon_setup(char *str)
2487 pr_info("debug: skip boot console de-registration.\n");
2492 early_param("keep_bootcon", keep_bootcon_setup);
2495 * The console driver calls this routine during kernel initialization
2496 * to register the console printing procedure with printk() and to
2497 * print any messages that were printed by the kernel before the
2498 * console driver was initialized.
2500 * This can happen pretty early during the boot process (because of
2501 * early_printk) - sometimes before setup_arch() completes - be careful
2502 * of what kernel features are used - they may not be initialised yet.
2504 * There are two types of consoles - bootconsoles (early_printk) and
2505 * "real" consoles (everything which is not a bootconsole) which are
2506 * handled differently.
2507 * - Any number of bootconsoles can be registered at any time.
2508 * - As soon as a "real" console is registered, all bootconsoles
2509 * will be unregistered automatically.
2510 * - Once a "real" console is registered, any attempt to register a
2511 * bootconsoles will be rejected
2513 void register_console(struct console *newcon)
2516 unsigned long flags;
2517 struct console *bcon = NULL;
2518 struct console_cmdline *c;
2520 if (console_drivers)
2521 for_each_console(bcon)
2522 if (WARN(bcon == newcon,
2523 "console '%s%d' already registered\n",
2524 bcon->name, bcon->index))
2528 * before we register a new CON_BOOT console, make sure we don't
2529 * already have a valid console
2531 if (console_drivers && newcon->flags & CON_BOOT) {
2532 /* find the last or real console */
2533 for_each_console(bcon) {
2534 if (!(bcon->flags & CON_BOOT)) {
2535 pr_info("Too late to register bootconsole %s%d\n",
2536 newcon->name, newcon->index);
2542 if (console_drivers && console_drivers->flags & CON_BOOT)
2543 bcon = console_drivers;
2545 if (preferred_console < 0 || bcon || !console_drivers)
2546 preferred_console = selected_console;
2549 * See if we want to use this console driver. If we
2550 * didn't select a console we take the first one
2551 * that registers here.
2553 if (preferred_console < 0) {
2554 if (newcon->index < 0)
2556 if (newcon->setup == NULL ||
2557 newcon->setup(newcon, NULL) == 0) {
2558 newcon->flags |= CON_ENABLED;
2559 if (newcon->device) {
2560 newcon->flags |= CON_CONSDEV;
2561 preferred_console = 0;
2567 * See if this console matches one we selected on
2570 for (i = 0, c = console_cmdline;
2571 i < MAX_CMDLINECONSOLES && c->name[0];
2573 if (!newcon->match ||
2574 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2575 /* default matching */
2576 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2577 if (strcmp(c->name, newcon->name) != 0)
2579 if (newcon->index >= 0 &&
2580 newcon->index != c->index)
2582 if (newcon->index < 0)
2583 newcon->index = c->index;
2585 if (_braille_register_console(newcon, c))
2588 if (newcon->setup &&
2589 newcon->setup(newcon, c->options) != 0)
2593 newcon->flags |= CON_ENABLED;
2594 if (i == selected_console) {
2595 newcon->flags |= CON_CONSDEV;
2596 preferred_console = selected_console;
2601 if (!(newcon->flags & CON_ENABLED))
2605 * If we have a bootconsole, and are switching to a real console,
2606 * don't print everything out again, since when the boot console, and
2607 * the real console are the same physical device, it's annoying to
2608 * see the beginning boot messages twice
2610 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2611 newcon->flags &= ~CON_PRINTBUFFER;
2614 * Put this console in the list - keep the
2615 * preferred driver at the head of the list.
2618 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2619 newcon->next = console_drivers;
2620 console_drivers = newcon;
2622 newcon->next->flags &= ~CON_CONSDEV;
2624 newcon->next = console_drivers->next;
2625 console_drivers->next = newcon;
2628 if (newcon->flags & CON_EXTENDED)
2629 if (!nr_ext_console_drivers++)
2630 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2632 if (newcon->flags & CON_PRINTBUFFER) {
2634 * console_unlock(); will print out the buffered messages
2637 raw_spin_lock_irqsave(&logbuf_lock, flags);
2638 console_seq = syslog_seq;
2639 console_idx = syslog_idx;
2640 console_prev = syslog_prev;
2641 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2643 * We're about to replay the log buffer. Only do this to the
2644 * just-registered console to avoid excessive message spam to
2645 * the already-registered consoles.
2647 exclusive_console = newcon;
2650 console_sysfs_notify();
2653 * By unregistering the bootconsoles after we enable the real console
2654 * we get the "console xxx enabled" message on all the consoles -
2655 * boot consoles, real consoles, etc - this is to ensure that end
2656 * users know there might be something in the kernel's log buffer that
2657 * went to the bootconsole (that they do not see on the real console)
2659 pr_info("%sconsole [%s%d] enabled\n",
2660 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2661 newcon->name, newcon->index);
2663 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2665 /* We need to iterate through all boot consoles, to make
2666 * sure we print everything out, before we unregister them.
2668 for_each_console(bcon)
2669 if (bcon->flags & CON_BOOT)
2670 unregister_console(bcon);
2673 EXPORT_SYMBOL(register_console);
2675 int unregister_console(struct console *console)
2677 struct console *a, *b;
2680 pr_info("%sconsole [%s%d] disabled\n",
2681 (console->flags & CON_BOOT) ? "boot" : "" ,
2682 console->name, console->index);
2684 res = _braille_unregister_console(console);
2690 if (console_drivers == console) {
2691 console_drivers=console->next;
2693 } else if (console_drivers) {
2694 for (a=console_drivers->next, b=console_drivers ;
2695 a; b=a, a=b->next) {
2704 if (!res && (console->flags & CON_EXTENDED))
2705 nr_ext_console_drivers--;
2708 * If this isn't the last console and it has CON_CONSDEV set, we
2709 * need to set it on the next preferred console.
2711 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2712 console_drivers->flags |= CON_CONSDEV;
2714 console->flags &= ~CON_ENABLED;
2716 console_sysfs_notify();
2719 EXPORT_SYMBOL(unregister_console);
2721 static int __init printk_late_init(void)
2723 struct console *con;
2725 for_each_console(con) {
2726 if (!keep_bootcon && con->flags & CON_BOOT) {
2727 unregister_console(con);
2730 #ifdef CONFIG_CONSOLE_FLUSH_ON_HOTPLUG
2731 hotcpu_notifier(console_cpu_notify, 0);
2735 late_initcall(printk_late_init);
2737 #if defined CONFIG_PRINTK
2739 * Delayed printk version, for scheduler-internal messages:
2741 #define PRINTK_PENDING_WAKEUP 0x01
2742 #define PRINTK_PENDING_OUTPUT 0x02
2744 static DEFINE_PER_CPU(int, printk_pending);
2746 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2748 int pending = __this_cpu_xchg(printk_pending, 0);
2750 if (pending & PRINTK_PENDING_OUTPUT) {
2751 /* If trylock fails, someone else is doing the printing */
2752 if (console_trylock())
2756 if (pending & PRINTK_PENDING_WAKEUP)
2757 wake_up_interruptible(&log_wait);
2760 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2761 .func = wake_up_klogd_work_func,
2762 .flags = IRQ_WORK_LAZY,
2765 void wake_up_klogd(void)
2768 if (waitqueue_active(&log_wait)) {
2769 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2770 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2775 int printk_deferred(const char *fmt, ...)
2781 va_start(args, fmt);
2782 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2785 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2786 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2793 * printk rate limiting, lifted from the networking subsystem.
2795 * This enforces a rate limit: not more than 10 kernel messages
2796 * every 5s to make a denial-of-service attack impossible.
2798 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2800 int __printk_ratelimit(const char *func)
2802 return ___ratelimit(&printk_ratelimit_state, func);
2804 EXPORT_SYMBOL(__printk_ratelimit);
2807 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2808 * @caller_jiffies: pointer to caller's state
2809 * @interval_msecs: minimum interval between prints
2811 * printk_timed_ratelimit() returns true if more than @interval_msecs
2812 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2815 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2816 unsigned int interval_msecs)
2818 unsigned long elapsed = jiffies - *caller_jiffies;
2820 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2823 *caller_jiffies = jiffies;
2826 EXPORT_SYMBOL(printk_timed_ratelimit);
2828 static DEFINE_SPINLOCK(dump_list_lock);
2829 static LIST_HEAD(dump_list);
2832 * kmsg_dump_register - register a kernel log dumper.
2833 * @dumper: pointer to the kmsg_dumper structure
2835 * Adds a kernel log dumper to the system. The dump callback in the
2836 * structure will be called when the kernel oopses or panics and must be
2837 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2839 int kmsg_dump_register(struct kmsg_dumper *dumper)
2841 unsigned long flags;
2844 /* The dump callback needs to be set */
2848 spin_lock_irqsave(&dump_list_lock, flags);
2849 /* Don't allow registering multiple times */
2850 if (!dumper->registered) {
2851 dumper->registered = 1;
2852 list_add_tail_rcu(&dumper->list, &dump_list);
2855 spin_unlock_irqrestore(&dump_list_lock, flags);
2859 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2862 * kmsg_dump_unregister - unregister a kmsg dumper.
2863 * @dumper: pointer to the kmsg_dumper structure
2865 * Removes a dump device from the system. Returns zero on success and
2866 * %-EINVAL otherwise.
2868 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2870 unsigned long flags;
2873 spin_lock_irqsave(&dump_list_lock, flags);
2874 if (dumper->registered) {
2875 dumper->registered = 0;
2876 list_del_rcu(&dumper->list);
2879 spin_unlock_irqrestore(&dump_list_lock, flags);
2884 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2886 static bool always_kmsg_dump;
2887 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2890 * kmsg_dump - dump kernel log to kernel message dumpers.
2891 * @reason: the reason (oops, panic etc) for dumping
2893 * Call each of the registered dumper's dump() callback, which can
2894 * retrieve the kmsg records with kmsg_dump_get_line() or
2895 * kmsg_dump_get_buffer().
2897 void kmsg_dump(enum kmsg_dump_reason reason)
2899 struct kmsg_dumper *dumper;
2900 unsigned long flags;
2902 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2906 list_for_each_entry_rcu(dumper, &dump_list, list) {
2907 if (dumper->max_reason && reason > dumper->max_reason)
2910 /* initialize iterator with data about the stored records */
2911 dumper->active = true;
2913 raw_spin_lock_irqsave(&logbuf_lock, flags);
2914 dumper->cur_seq = clear_seq;
2915 dumper->cur_idx = clear_idx;
2916 dumper->next_seq = log_next_seq;
2917 dumper->next_idx = log_next_idx;
2918 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2920 /* invoke dumper which will iterate over records */
2921 dumper->dump(dumper, reason);
2923 /* reset iterator */
2924 dumper->active = false;
2930 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2931 * @dumper: registered kmsg dumper
2932 * @syslog: include the "<4>" prefixes
2933 * @line: buffer to copy the line to
2934 * @size: maximum size of the buffer
2935 * @len: length of line placed into buffer
2937 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2938 * record, and copy one record into the provided buffer.
2940 * Consecutive calls will return the next available record moving
2941 * towards the end of the buffer with the youngest messages.
2943 * A return value of FALSE indicates that there are no more records to
2946 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2948 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
2949 char *line, size_t size, size_t *len)
2951 struct printk_log *msg;
2955 if (!dumper->active)
2958 if (dumper->cur_seq < log_first_seq) {
2959 /* messages are gone, move to first available one */
2960 dumper->cur_seq = log_first_seq;
2961 dumper->cur_idx = log_first_idx;
2965 if (dumper->cur_seq >= log_next_seq)
2968 msg = log_from_idx(dumper->cur_idx);
2969 l = msg_print_text(msg, 0, syslog, line, size);
2971 dumper->cur_idx = log_next(dumper->cur_idx);
2981 * kmsg_dump_get_line - retrieve one kmsg log line
2982 * @dumper: registered kmsg dumper
2983 * @syslog: include the "<4>" prefixes
2984 * @line: buffer to copy the line to
2985 * @size: maximum size of the buffer
2986 * @len: length of line placed into buffer
2988 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2989 * record, and copy one record into the provided buffer.
2991 * Consecutive calls will return the next available record moving
2992 * towards the end of the buffer with the youngest messages.
2994 * A return value of FALSE indicates that there are no more records to
2997 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
2998 char *line, size_t size, size_t *len)
3000 unsigned long flags;
3003 raw_spin_lock_irqsave(&logbuf_lock, flags);
3004 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
3005 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3009 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
3012 * kmsg_dump_get_buffer - copy kmsg log lines
3013 * @dumper: registered kmsg dumper
3014 * @syslog: include the "<4>" prefixes
3015 * @buf: buffer to copy the line to
3016 * @size: maximum size of the buffer
3017 * @len: length of line placed into buffer
3019 * Start at the end of the kmsg buffer and fill the provided buffer
3020 * with as many of the the *youngest* kmsg records that fit into it.
3021 * If the buffer is large enough, all available kmsg records will be
3022 * copied with a single call.
3024 * Consecutive calls will fill the buffer with the next block of
3025 * available older records, not including the earlier retrieved ones.
3027 * A return value of FALSE indicates that there are no more records to
3030 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
3031 char *buf, size_t size, size_t *len)
3033 unsigned long flags;
3038 enum log_flags prev;
3042 if (!dumper->active)
3045 raw_spin_lock_irqsave(&logbuf_lock, flags);
3046 if (dumper->cur_seq < log_first_seq) {
3047 /* messages are gone, move to first available one */
3048 dumper->cur_seq = log_first_seq;
3049 dumper->cur_idx = log_first_idx;
3053 if (dumper->cur_seq >= dumper->next_seq) {
3054 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3058 /* calculate length of entire buffer */
3059 seq = dumper->cur_seq;
3060 idx = dumper->cur_idx;
3062 while (seq < dumper->next_seq) {
3063 struct printk_log *msg = log_from_idx(idx);
3065 l += msg_print_text(msg, prev, true, NULL, 0);
3066 idx = log_next(idx);
3071 /* move first record forward until length fits into the buffer */
3072 seq = dumper->cur_seq;
3073 idx = dumper->cur_idx;
3075 while (l >= size && seq < dumper->next_seq) {
3076 struct printk_log *msg = log_from_idx(idx);
3078 l -= msg_print_text(msg, prev, true, NULL, 0);
3079 idx = log_next(idx);
3084 /* last message in next interation */
3089 while (seq < dumper->next_seq) {
3090 struct printk_log *msg = log_from_idx(idx);
3092 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
3093 idx = log_next(idx);
3098 dumper->next_seq = next_seq;
3099 dumper->next_idx = next_idx;
3101 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3107 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3110 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3111 * @dumper: registered kmsg dumper
3113 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3114 * kmsg_dump_get_buffer() can be called again and used multiple
3115 * times within the same dumper.dump() callback.
3117 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3119 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3121 dumper->cur_seq = clear_seq;
3122 dumper->cur_idx = clear_idx;
3123 dumper->next_seq = log_next_seq;
3124 dumper->next_idx = log_next_idx;
3128 * kmsg_dump_rewind - reset the interator
3129 * @dumper: registered kmsg dumper
3131 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3132 * kmsg_dump_get_buffer() can be called again and used multiple
3133 * times within the same dumper.dump() callback.
3135 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3137 unsigned long flags;
3139 raw_spin_lock_irqsave(&logbuf_lock, flags);
3140 kmsg_dump_rewind_nolock(dumper);
3141 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3143 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3145 static char dump_stack_arch_desc_str[128];
3148 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3149 * @fmt: printf-style format string
3150 * @...: arguments for the format string
3152 * The configured string will be printed right after utsname during task
3153 * dumps. Usually used to add arch-specific system identifiers. If an
3154 * arch wants to make use of such an ID string, it should initialize this
3155 * as soon as possible during boot.
3157 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3161 va_start(args, fmt);
3162 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3168 * dump_stack_print_info - print generic debug info for dump_stack()
3169 * @log_lvl: log level
3171 * Arch-specific dump_stack() implementations can use this function to
3172 * print out the same debug information as the generic dump_stack().
3174 void dump_stack_print_info(const char *log_lvl)
3176 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3177 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3178 print_tainted(), init_utsname()->release,
3179 (int)strcspn(init_utsname()->version, " "),
3180 init_utsname()->version);
3182 if (dump_stack_arch_desc_str[0] != '\0')
3183 printk("%sHardware name: %s\n",
3184 log_lvl, dump_stack_arch_desc_str);
3186 print_worker_info(log_lvl, current);
3190 * show_regs_print_info - print generic debug info for show_regs()
3191 * @log_lvl: log level
3193 * show_regs() implementations can use this function to print out generic
3194 * debug information.
3196 void show_regs_print_info(const char *log_lvl)
3198 dump_stack_print_info(log_lvl);
3200 printk("%stask: %p task.stack: %p\n",
3201 log_lvl, current, task_stack_page(current));