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/delay.h>
30 #include <linux/smp.h>
31 #include <linux/security.h>
32 #include <linux/bootmem.h>
33 #include <linux/memblock.h>
34 #include <linux/syscalls.h>
35 #include <linux/kexec.h>
36 #include <linux/kdb.h>
37 #include <linux/ratelimit.h>
38 #include <linux/kmsg_dump.h>
39 #include <linux/syslog.h>
40 #include <linux/cpu.h>
41 #include <linux/notifier.h>
42 #include <linux/rculist.h>
43 #include <linux/poll.h>
44 #include <linux/irq_work.h>
45 #include <linux/utsname.h>
46 #include <linux/ctype.h>
47 #include <linux/uio.h>
49 #include <asm/uaccess.h>
50 #include <asm/sections.h>
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/printk.h>
55 #include "console_cmdline.h"
59 int console_printk[4] = {
60 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
61 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
62 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
63 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
67 * Low level drivers may need that to know if they can schedule in
68 * their unblank() callback or not. So let's export it.
71 EXPORT_SYMBOL(oops_in_progress);
74 * console_sem protects the console_drivers list, and also
75 * provides serialisation for access to the entire console
78 static DEFINE_SEMAPHORE(console_sem);
79 struct console *console_drivers;
80 EXPORT_SYMBOL_GPL(console_drivers);
83 static struct lockdep_map console_lock_dep_map = {
84 .name = "console_lock"
88 enum devkmsg_log_bits {
89 __DEVKMSG_LOG_BIT_ON = 0,
90 __DEVKMSG_LOG_BIT_OFF,
91 __DEVKMSG_LOG_BIT_LOCK,
94 enum devkmsg_log_masks {
95 DEVKMSG_LOG_MASK_ON = BIT(__DEVKMSG_LOG_BIT_ON),
96 DEVKMSG_LOG_MASK_OFF = BIT(__DEVKMSG_LOG_BIT_OFF),
97 DEVKMSG_LOG_MASK_LOCK = BIT(__DEVKMSG_LOG_BIT_LOCK),
100 /* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
101 #define DEVKMSG_LOG_MASK_DEFAULT 0
103 static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
105 static int __control_devkmsg(char *str)
110 if (!strncmp(str, "on", 2)) {
111 devkmsg_log = DEVKMSG_LOG_MASK_ON;
113 } else if (!strncmp(str, "off", 3)) {
114 devkmsg_log = DEVKMSG_LOG_MASK_OFF;
116 } else if (!strncmp(str, "ratelimit", 9)) {
117 devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
123 static int __init control_devkmsg(char *str)
125 if (__control_devkmsg(str) < 0) {
126 pr_warn("printk.devkmsg: bad option string '%s'\n", str);
131 * Set sysctl string accordingly:
133 if (devkmsg_log == DEVKMSG_LOG_MASK_ON) {
134 memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE);
135 strncpy(devkmsg_log_str, "on", 2);
136 } else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) {
137 memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE);
138 strncpy(devkmsg_log_str, "off", 3);
140 /* else "ratelimit" which is set by default. */
143 * Sysctl cannot change it anymore. The kernel command line setting of
144 * this parameter is to force the setting to be permanent throughout the
145 * runtime of the system. This is a precation measure against userspace
146 * trying to be a smarta** and attempting to change it up on us.
148 devkmsg_log |= DEVKMSG_LOG_MASK_LOCK;
152 __setup("printk.devkmsg=", control_devkmsg);
154 char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit";
156 int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
157 void __user *buffer, size_t *lenp, loff_t *ppos)
159 char old_str[DEVKMSG_STR_MAX_SIZE];
164 if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK)
168 strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE);
171 err = proc_dostring(table, write, buffer, lenp, ppos);
176 err = __control_devkmsg(devkmsg_log_str);
179 * Do not accept an unknown string OR a known string with
182 if (err < 0 || (err + 1 != *lenp)) {
184 /* ... and restore old setting. */
186 strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE);
196 * Number of registered extended console drivers.
198 * If extended consoles are present, in-kernel cont reassembly is disabled
199 * and each fragment is stored as a separate log entry with proper
200 * continuation flag so that every emitted message has full metadata. This
201 * doesn't change the result for regular consoles or /proc/kmsg. For
202 * /dev/kmsg, as long as the reader concatenates messages according to
203 * consecutive continuation flags, the end result should be the same too.
205 static int nr_ext_console_drivers;
208 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
209 * macros instead of functions so that _RET_IP_ contains useful information.
211 #define down_console_sem() do { \
213 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
216 static int __down_trylock_console_sem(unsigned long ip)
218 if (down_trylock(&console_sem))
220 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
223 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
225 #define up_console_sem() do { \
226 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
231 * This is used for debugging the mess that is the VT code by
232 * keeping track if we have the console semaphore held. It's
233 * definitely not the perfect debug tool (we don't know if _WE_
234 * hold it and are racing, but it helps tracking those weird code
235 * paths in the console code where we end up in places I want
236 * locked without the console sempahore held).
238 static int console_locked, console_suspended;
241 * If exclusive_console is non-NULL then only this console is to be printed to.
243 static struct console *exclusive_console;
246 * Array of consoles built from command line options (console=)
249 #define MAX_CMDLINECONSOLES 8
251 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
253 static int selected_console = -1;
254 static int preferred_console = -1;
255 int console_set_on_cmdline;
256 EXPORT_SYMBOL(console_set_on_cmdline);
258 /* Flag: console code may call schedule() */
259 static int console_may_schedule;
262 * The printk log buffer consists of a chain of concatenated variable
263 * length records. Every record starts with a record header, containing
264 * the overall length of the record.
266 * The heads to the first and last entry in the buffer, as well as the
267 * sequence numbers of these entries are maintained when messages are
270 * If the heads indicate available messages, the length in the header
271 * tells the start next message. A length == 0 for the next message
272 * indicates a wrap-around to the beginning of the buffer.
274 * Every record carries the monotonic timestamp in microseconds, as well as
275 * the standard userspace syslog level and syslog facility. The usual
276 * kernel messages use LOG_KERN; userspace-injected messages always carry
277 * a matching syslog facility, by default LOG_USER. The origin of every
278 * message can be reliably determined that way.
280 * The human readable log message directly follows the message header. The
281 * length of the message text is stored in the header, the stored message
284 * Optionally, a message can carry a dictionary of properties (key/value pairs),
285 * to provide userspace with a machine-readable message context.
287 * Examples for well-defined, commonly used property names are:
288 * DEVICE=b12:8 device identifier
292 * +sound:card0 subsystem:devname
293 * SUBSYSTEM=pci driver-core subsystem name
295 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
296 * follows directly after a '=' character. Every property is terminated by
297 * a '\0' character. The last property is not terminated.
299 * Example of a message structure:
300 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
301 * 0008 34 00 record is 52 bytes long
302 * 000a 0b 00 text is 11 bytes long
303 * 000c 1f 00 dictionary is 23 bytes long
304 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
305 * 0010 69 74 27 73 20 61 20 6c "it's a l"
307 * 001b 44 45 56 49 43 "DEVIC"
308 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
309 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
311 * 0032 00 00 00 padding to next message header
313 * The 'struct printk_log' buffer header must never be directly exported to
314 * userspace, it is a kernel-private implementation detail that might
315 * need to be changed in the future, when the requirements change.
317 * /dev/kmsg exports the structured data in the following line format:
318 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
320 * Users of the export format should ignore possible additional values
321 * separated by ',', and find the message after the ';' character.
323 * The optional key/value pairs are attached as continuation lines starting
324 * with a space character and terminated by a newline. All possible
325 * non-prinatable characters are escaped in the "\xff" notation.
329 LOG_NOCONS = 1, /* already flushed, do not print to console */
330 LOG_NEWLINE = 2, /* text ended with a newline */
331 LOG_PREFIX = 4, /* text started with a prefix */
332 LOG_CONT = 8, /* text is a fragment of a continuation line */
336 u64 ts_nsec; /* timestamp in nanoseconds */
337 u16 len; /* length of entire record */
338 u16 text_len; /* length of text buffer */
339 u16 dict_len; /* length of dictionary buffer */
340 u8 facility; /* syslog facility */
341 u8 flags:5; /* internal record flags */
342 u8 level:3; /* syslog level */
344 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
345 __packed __aligned(4)
350 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
351 * within the scheduler's rq lock. It must be released before calling
352 * console_unlock() or anything else that might wake up a process.
354 DEFINE_RAW_SPINLOCK(logbuf_lock);
357 DECLARE_WAIT_QUEUE_HEAD(log_wait);
358 /* the next printk record to read by syslog(READ) or /proc/kmsg */
359 static u64 syslog_seq;
360 static u32 syslog_idx;
361 static size_t syslog_partial;
363 /* index and sequence number of the first record stored in the buffer */
364 static u64 log_first_seq;
365 static u32 log_first_idx;
367 /* index and sequence number of the next record to store in the buffer */
368 static u64 log_next_seq;
369 static u32 log_next_idx;
371 /* the next printk record to write to the console */
372 static u64 console_seq;
373 static u32 console_idx;
375 /* the next printk record to read after the last 'clear' command */
376 static u64 clear_seq;
377 static u32 clear_idx;
379 #define PREFIX_MAX 32
380 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
382 #define LOG_LEVEL(v) ((v) & 0x07)
383 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
386 #define LOG_ALIGN __alignof__(struct printk_log)
387 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
388 #define LOG_BUF_LEN_MAX (u32)(1 << 31)
389 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
390 static char *log_buf = __log_buf;
391 static u32 log_buf_len = __LOG_BUF_LEN;
393 /* Return log buffer address */
394 char *log_buf_addr_get(void)
399 /* Return log buffer size */
400 u32 log_buf_len_get(void)
405 /* human readable text of the record */
406 static char *log_text(const struct printk_log *msg)
408 return (char *)msg + sizeof(struct printk_log);
411 /* optional key/value pair dictionary attached to the record */
412 static char *log_dict(const struct printk_log *msg)
414 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
417 /* get record by index; idx must point to valid msg */
418 static struct printk_log *log_from_idx(u32 idx)
420 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
423 * A length == 0 record is the end of buffer marker. Wrap around and
424 * read the message at the start of the buffer.
427 return (struct printk_log *)log_buf;
431 /* get next record; idx must point to valid msg */
432 static u32 log_next(u32 idx)
434 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
436 /* length == 0 indicates the end of the buffer; wrap */
438 * A length == 0 record is the end of buffer marker. Wrap around and
439 * read the message at the start of the buffer as *this* one, and
440 * return the one after that.
443 msg = (struct printk_log *)log_buf;
446 return idx + msg->len;
450 * Check whether there is enough free space for the given message.
452 * The same values of first_idx and next_idx mean that the buffer
453 * is either empty or full.
455 * If the buffer is empty, we must respect the position of the indexes.
456 * They cannot be reset to the beginning of the buffer.
458 static int logbuf_has_space(u32 msg_size, bool empty)
462 if (log_next_idx > log_first_idx || empty)
463 free = max(log_buf_len - log_next_idx, log_first_idx);
465 free = log_first_idx - log_next_idx;
468 * We need space also for an empty header that signalizes wrapping
471 return free >= msg_size + sizeof(struct printk_log);
474 static int log_make_free_space(u32 msg_size)
476 while (log_first_seq < log_next_seq &&
477 !logbuf_has_space(msg_size, false)) {
478 /* drop old messages until we have enough contiguous space */
479 log_first_idx = log_next(log_first_idx);
483 if (clear_seq < log_first_seq) {
484 clear_seq = log_first_seq;
485 clear_idx = log_first_idx;
488 /* sequence numbers are equal, so the log buffer is empty */
489 if (logbuf_has_space(msg_size, log_first_seq == log_next_seq))
495 /* compute the message size including the padding bytes */
496 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
500 size = sizeof(struct printk_log) + text_len + dict_len;
501 *pad_len = (-size) & (LOG_ALIGN - 1);
508 * Define how much of the log buffer we could take at maximum. The value
509 * must be greater than two. Note that only half of the buffer is available
510 * when the index points to the middle.
512 #define MAX_LOG_TAKE_PART 4
513 static const char trunc_msg[] = "<truncated>";
515 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
516 u16 *dict_len, u32 *pad_len)
519 * The message should not take the whole buffer. Otherwise, it might
520 * get removed too soon.
522 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
523 if (*text_len > max_text_len)
524 *text_len = max_text_len;
525 /* enable the warning message */
526 *trunc_msg_len = strlen(trunc_msg);
527 /* disable the "dict" completely */
529 /* compute the size again, count also the warning message */
530 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
533 /* insert record into the buffer, discard old ones, update heads */
534 static int log_store(int facility, int level,
535 enum log_flags flags, u64 ts_nsec,
536 const char *dict, u16 dict_len,
537 const char *text, u16 text_len)
539 struct printk_log *msg;
541 u16 trunc_msg_len = 0;
543 /* number of '\0' padding bytes to next message */
544 size = msg_used_size(text_len, dict_len, &pad_len);
546 if (log_make_free_space(size)) {
547 /* truncate the message if it is too long for empty buffer */
548 size = truncate_msg(&text_len, &trunc_msg_len,
549 &dict_len, &pad_len);
550 /* survive when the log buffer is too small for trunc_msg */
551 if (log_make_free_space(size))
555 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
557 * This message + an additional empty header does not fit
558 * at the end of the buffer. Add an empty header with len == 0
559 * to signify a wrap around.
561 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
566 msg = (struct printk_log *)(log_buf + log_next_idx);
567 memcpy(log_text(msg), text, text_len);
568 msg->text_len = text_len;
570 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
571 msg->text_len += trunc_msg_len;
573 memcpy(log_dict(msg), dict, dict_len);
574 msg->dict_len = dict_len;
575 msg->facility = facility;
576 msg->level = level & 7;
577 msg->flags = flags & 0x1f;
579 msg->ts_nsec = ts_nsec;
581 msg->ts_nsec = local_clock();
582 memset(log_dict(msg) + dict_len, 0, pad_len);
586 log_next_idx += msg->len;
589 return msg->text_len;
592 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
594 static int syslog_action_restricted(int type)
599 * Unless restricted, we allow "read all" and "get buffer size"
602 return type != SYSLOG_ACTION_READ_ALL &&
603 type != SYSLOG_ACTION_SIZE_BUFFER;
606 int check_syslog_permissions(int type, int source)
609 * If this is from /proc/kmsg and we've already opened it, then we've
610 * already done the capabilities checks at open time.
612 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
615 if (syslog_action_restricted(type)) {
616 if (capable(CAP_SYSLOG))
619 * For historical reasons, accept CAP_SYS_ADMIN too, with
622 if (capable(CAP_SYS_ADMIN)) {
623 pr_warn_once("%s (%d): Attempt to access syslog with "
624 "CAP_SYS_ADMIN but no CAP_SYSLOG "
626 current->comm, task_pid_nr(current));
632 return security_syslog(type);
634 EXPORT_SYMBOL_GPL(check_syslog_permissions);
636 static void append_char(char **pp, char *e, char c)
642 static ssize_t msg_print_ext_header(char *buf, size_t size,
643 struct printk_log *msg, u64 seq)
645 u64 ts_usec = msg->ts_nsec;
647 do_div(ts_usec, 1000);
649 return scnprintf(buf, size, "%u,%llu,%llu,%c;",
650 (msg->facility << 3) | msg->level, seq, ts_usec,
651 msg->flags & LOG_CONT ? 'c' : '-');
654 static ssize_t msg_print_ext_body(char *buf, size_t size,
655 char *dict, size_t dict_len,
656 char *text, size_t text_len)
658 char *p = buf, *e = buf + size;
661 /* escape non-printable characters */
662 for (i = 0; i < text_len; i++) {
663 unsigned char c = text[i];
665 if (c < ' ' || c >= 127 || c == '\\')
666 p += scnprintf(p, e - p, "\\x%02x", c);
668 append_char(&p, e, c);
670 append_char(&p, e, '\n');
675 for (i = 0; i < dict_len; i++) {
676 unsigned char c = dict[i];
679 append_char(&p, e, ' ');
684 append_char(&p, e, '\n');
689 if (c < ' ' || c >= 127 || c == '\\') {
690 p += scnprintf(p, e - p, "\\x%02x", c);
694 append_char(&p, e, c);
696 append_char(&p, e, '\n');
702 /* /dev/kmsg - userspace message inject/listen interface */
703 struct devkmsg_user {
706 struct ratelimit_state rs;
708 char buf[CONSOLE_EXT_LOG_MAX];
711 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
714 int level = default_message_loglevel;
715 int facility = 1; /* LOG_USER */
716 struct file *file = iocb->ki_filp;
717 struct devkmsg_user *user = file->private_data;
718 size_t len = iov_iter_count(from);
721 if (!user || len > LOG_LINE_MAX)
724 /* Ignore when user logging is disabled. */
725 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
728 /* Ratelimit when not explicitly enabled. */
729 if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) {
730 if (!___ratelimit(&user->rs, current->comm))
734 buf = kmalloc(len+1, GFP_KERNEL);
739 if (copy_from_iter(buf, len, from) != len) {
745 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
746 * the decimal value represents 32bit, the lower 3 bit are the log
747 * level, the rest are the log facility.
749 * If no prefix or no userspace facility is specified, we
750 * enforce LOG_USER, to be able to reliably distinguish
751 * kernel-generated messages from userspace-injected ones.
754 if (line[0] == '<') {
758 u = simple_strtoul(line + 1, &endp, 10);
759 if (endp && endp[0] == '>') {
760 level = LOG_LEVEL(u);
761 if (LOG_FACILITY(u) != 0)
762 facility = LOG_FACILITY(u);
769 printk_emit(facility, level, NULL, 0, "%s", line);
774 static ssize_t devkmsg_read(struct file *file, char __user *buf,
775 size_t count, loff_t *ppos)
777 struct devkmsg_user *user = file->private_data;
778 struct printk_log *msg;
785 ret = mutex_lock_interruptible(&user->lock);
788 raw_spin_lock_irq(&logbuf_lock);
789 while (user->seq == log_next_seq) {
790 if (file->f_flags & O_NONBLOCK) {
792 raw_spin_unlock_irq(&logbuf_lock);
796 raw_spin_unlock_irq(&logbuf_lock);
797 ret = wait_event_interruptible(log_wait,
798 user->seq != log_next_seq);
801 raw_spin_lock_irq(&logbuf_lock);
804 if (user->seq < log_first_seq) {
805 /* our last seen message is gone, return error and reset */
806 user->idx = log_first_idx;
807 user->seq = log_first_seq;
809 raw_spin_unlock_irq(&logbuf_lock);
813 msg = log_from_idx(user->idx);
814 len = msg_print_ext_header(user->buf, sizeof(user->buf),
816 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
817 log_dict(msg), msg->dict_len,
818 log_text(msg), msg->text_len);
820 user->idx = log_next(user->idx);
822 raw_spin_unlock_irq(&logbuf_lock);
829 if (copy_to_user(buf, user->buf, len)) {
835 mutex_unlock(&user->lock);
839 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
841 struct devkmsg_user *user = file->private_data;
849 raw_spin_lock_irq(&logbuf_lock);
852 /* the first record */
853 user->idx = log_first_idx;
854 user->seq = log_first_seq;
858 * The first record after the last SYSLOG_ACTION_CLEAR,
859 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
860 * changes no global state, and does not clear anything.
862 user->idx = clear_idx;
863 user->seq = clear_seq;
866 /* after the last record */
867 user->idx = log_next_idx;
868 user->seq = log_next_seq;
873 raw_spin_unlock_irq(&logbuf_lock);
877 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
879 struct devkmsg_user *user = file->private_data;
883 return POLLERR|POLLNVAL;
885 poll_wait(file, &log_wait, wait);
887 raw_spin_lock_irq(&logbuf_lock);
888 if (user->seq < log_next_seq) {
889 /* return error when data has vanished underneath us */
890 if (user->seq < log_first_seq)
891 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
893 ret = POLLIN|POLLRDNORM;
895 raw_spin_unlock_irq(&logbuf_lock);
900 static int devkmsg_open(struct inode *inode, struct file *file)
902 struct devkmsg_user *user;
905 if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
908 /* write-only does not need any file context */
909 if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
910 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
916 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
920 ratelimit_default_init(&user->rs);
921 ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
923 mutex_init(&user->lock);
925 raw_spin_lock_irq(&logbuf_lock);
926 user->idx = log_first_idx;
927 user->seq = log_first_seq;
928 raw_spin_unlock_irq(&logbuf_lock);
930 file->private_data = user;
934 static int devkmsg_release(struct inode *inode, struct file *file)
936 struct devkmsg_user *user = file->private_data;
941 ratelimit_state_exit(&user->rs);
943 mutex_destroy(&user->lock);
948 const struct file_operations kmsg_fops = {
949 .open = devkmsg_open,
950 .read = devkmsg_read,
951 .write_iter = devkmsg_write,
952 .llseek = devkmsg_llseek,
953 .poll = devkmsg_poll,
954 .release = devkmsg_release,
957 #ifdef CONFIG_KEXEC_CORE
959 * This appends the listed symbols to /proc/vmcore
961 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
962 * obtain access to symbols that are otherwise very difficult to locate. These
963 * symbols are specifically used so that utilities can access and extract the
964 * dmesg log from a vmcore file after a crash.
966 void log_buf_kexec_setup(void)
968 VMCOREINFO_SYMBOL(log_buf);
969 VMCOREINFO_SYMBOL(log_buf_len);
970 VMCOREINFO_SYMBOL(log_first_idx);
971 VMCOREINFO_SYMBOL(clear_idx);
972 VMCOREINFO_SYMBOL(log_next_idx);
974 * Export struct printk_log size and field offsets. User space tools can
975 * parse it and detect any changes to structure down the line.
977 VMCOREINFO_STRUCT_SIZE(printk_log);
978 VMCOREINFO_OFFSET(printk_log, ts_nsec);
979 VMCOREINFO_OFFSET(printk_log, len);
980 VMCOREINFO_OFFSET(printk_log, text_len);
981 VMCOREINFO_OFFSET(printk_log, dict_len);
985 /* requested log_buf_len from kernel cmdline */
986 static unsigned long __initdata new_log_buf_len;
988 /* we practice scaling the ring buffer by powers of 2 */
989 static void __init log_buf_len_update(u64 size)
991 if (size > (u64)LOG_BUF_LEN_MAX) {
992 size = (u64)LOG_BUF_LEN_MAX;
993 pr_err("log_buf over 2G is not supported.\n");
997 size = roundup_pow_of_two(size);
998 if (size > log_buf_len)
999 new_log_buf_len = (unsigned long)size;
1002 /* save requested log_buf_len since it's too early to process it */
1003 static int __init log_buf_len_setup(char *str)
1010 size = memparse(str, &str);
1012 log_buf_len_update(size);
1016 early_param("log_buf_len", log_buf_len_setup);
1019 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1021 static void __init log_buf_add_cpu(void)
1023 unsigned int cpu_extra;
1026 * archs should set up cpu_possible_bits properly with
1027 * set_cpu_possible() after setup_arch() but just in
1028 * case lets ensure this is valid.
1030 if (num_possible_cpus() == 1)
1033 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
1035 /* by default this will only continue through for large > 64 CPUs */
1036 if (cpu_extra <= __LOG_BUF_LEN / 2)
1039 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1040 __LOG_CPU_MAX_BUF_LEN);
1041 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1043 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
1045 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
1047 #else /* !CONFIG_SMP */
1048 static inline void log_buf_add_cpu(void) {}
1049 #endif /* CONFIG_SMP */
1051 void __init setup_log_buf(int early)
1053 unsigned long flags;
1057 if (log_buf != __log_buf)
1060 if (!early && !new_log_buf_len)
1063 if (!new_log_buf_len)
1068 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
1070 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
1074 if (unlikely(!new_log_buf)) {
1075 pr_err("log_buf_len: %lu bytes not available\n",
1080 raw_spin_lock_irqsave(&logbuf_lock, flags);
1081 log_buf_len = new_log_buf_len;
1082 log_buf = new_log_buf;
1083 new_log_buf_len = 0;
1084 free = __LOG_BUF_LEN - log_next_idx;
1085 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
1086 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
1088 pr_info("log_buf_len: %u bytes\n", log_buf_len);
1089 pr_info("early log buf free: %u(%u%%)\n",
1090 free, (free * 100) / __LOG_BUF_LEN);
1093 static bool __read_mostly ignore_loglevel;
1095 static int __init ignore_loglevel_setup(char *str)
1097 ignore_loglevel = true;
1098 pr_info("debug: ignoring loglevel setting.\n");
1103 early_param("ignore_loglevel", ignore_loglevel_setup);
1104 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1105 MODULE_PARM_DESC(ignore_loglevel,
1106 "ignore loglevel setting (prints all kernel messages to the console)");
1108 static bool suppress_message_printing(int level)
1110 return (level >= console_loglevel && !ignore_loglevel);
1113 #ifdef CONFIG_BOOT_PRINTK_DELAY
1115 static int boot_delay; /* msecs delay after each printk during bootup */
1116 static unsigned long long loops_per_msec; /* based on boot_delay */
1118 static int __init boot_delay_setup(char *str)
1122 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
1123 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
1125 get_option(&str, &boot_delay);
1126 if (boot_delay > 10 * 1000)
1129 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1130 "HZ: %d, loops_per_msec: %llu\n",
1131 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1134 early_param("boot_delay", boot_delay_setup);
1136 static void boot_delay_msec(int level)
1138 unsigned long long k;
1139 unsigned long timeout;
1141 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
1142 || suppress_message_printing(level)) {
1146 k = (unsigned long long)loops_per_msec * boot_delay;
1148 timeout = jiffies + msecs_to_jiffies(boot_delay);
1153 * use (volatile) jiffies to prevent
1154 * compiler reduction; loop termination via jiffies
1155 * is secondary and may or may not happen.
1157 if (time_after(jiffies, timeout))
1159 touch_nmi_watchdog();
1163 static inline void boot_delay_msec(int level)
1168 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1169 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1171 static size_t print_time(u64 ts, char *buf)
1173 unsigned long rem_nsec;
1178 rem_nsec = do_div(ts, 1000000000);
1181 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1183 return sprintf(buf, "[%5lu.%06lu] ",
1184 (unsigned long)ts, rem_nsec / 1000);
1187 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1190 unsigned int prefix = (msg->facility << 3) | msg->level;
1194 len += sprintf(buf, "<%u>", prefix);
1199 else if (prefix > 99)
1201 else if (prefix > 9)
1206 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1210 static size_t msg_print_text(const struct printk_log *msg, bool syslog, char *buf, size_t size)
1212 const char *text = log_text(msg);
1213 size_t text_size = msg->text_len;
1217 const char *next = memchr(text, '\n', text_size);
1221 text_len = next - text;
1223 text_size -= next - text;
1225 text_len = text_size;
1229 if (print_prefix(msg, syslog, NULL) +
1230 text_len + 1 >= size - len)
1233 len += print_prefix(msg, syslog, buf + len);
1234 memcpy(buf + len, text, text_len);
1238 /* SYSLOG_ACTION_* buffer size only calculation */
1239 len += print_prefix(msg, syslog, NULL);
1250 static int syslog_print(char __user *buf, int size)
1253 struct printk_log *msg;
1256 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1264 raw_spin_lock_irq(&logbuf_lock);
1265 if (syslog_seq < log_first_seq) {
1266 /* messages are gone, move to first one */
1267 syslog_seq = log_first_seq;
1268 syslog_idx = log_first_idx;
1271 if (syslog_seq == log_next_seq) {
1272 raw_spin_unlock_irq(&logbuf_lock);
1276 skip = syslog_partial;
1277 msg = log_from_idx(syslog_idx);
1278 n = msg_print_text(msg, true, text, LOG_LINE_MAX + PREFIX_MAX);
1279 if (n - syslog_partial <= size) {
1280 /* message fits into buffer, move forward */
1281 syslog_idx = log_next(syslog_idx);
1283 n -= syslog_partial;
1286 /* partial read(), remember position */
1288 syslog_partial += n;
1291 raw_spin_unlock_irq(&logbuf_lock);
1296 if (copy_to_user(buf, text + skip, n)) {
1311 static int syslog_print_all(char __user *buf, int size, bool clear)
1316 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1320 raw_spin_lock_irq(&logbuf_lock);
1327 * Find first record that fits, including all following records,
1328 * into the user-provided buffer for this dump.
1332 while (seq < log_next_seq) {
1333 struct printk_log *msg = log_from_idx(idx);
1335 len += msg_print_text(msg, true, NULL, 0);
1336 idx = log_next(idx);
1340 /* move first record forward until length fits into the buffer */
1343 while (len > size && seq < log_next_seq) {
1344 struct printk_log *msg = log_from_idx(idx);
1346 len -= msg_print_text(msg, true, NULL, 0);
1347 idx = log_next(idx);
1351 /* last message fitting into this dump */
1352 next_seq = log_next_seq;
1355 while (len >= 0 && seq < next_seq) {
1356 struct printk_log *msg = log_from_idx(idx);
1359 textlen = msg_print_text(msg, true, text,
1360 LOG_LINE_MAX + PREFIX_MAX);
1365 idx = log_next(idx);
1368 raw_spin_unlock_irq(&logbuf_lock);
1369 if (copy_to_user(buf + len, text, textlen))
1373 raw_spin_lock_irq(&logbuf_lock);
1375 if (seq < log_first_seq) {
1376 /* messages are gone, move to next one */
1377 seq = log_first_seq;
1378 idx = log_first_idx;
1384 clear_seq = log_next_seq;
1385 clear_idx = log_next_idx;
1387 raw_spin_unlock_irq(&logbuf_lock);
1393 int do_syslog(int type, char __user *buf, int len, int source)
1396 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1399 error = check_syslog_permissions(type, source);
1404 case SYSLOG_ACTION_CLOSE: /* Close log */
1406 case SYSLOG_ACTION_OPEN: /* Open log */
1408 case SYSLOG_ACTION_READ: /* Read from log */
1410 if (!buf || len < 0)
1415 if (!access_ok(VERIFY_WRITE, buf, len)) {
1419 error = wait_event_interruptible(log_wait,
1420 syslog_seq != log_next_seq);
1423 error = syslog_print(buf, len);
1425 /* Read/clear last kernel messages */
1426 case SYSLOG_ACTION_READ_CLEAR:
1429 /* Read last kernel messages */
1430 case SYSLOG_ACTION_READ_ALL:
1432 if (!buf || len < 0)
1437 if (!access_ok(VERIFY_WRITE, buf, len)) {
1441 error = syslog_print_all(buf, len, clear);
1443 /* Clear ring buffer */
1444 case SYSLOG_ACTION_CLEAR:
1445 syslog_print_all(NULL, 0, true);
1447 /* Disable logging to console */
1448 case SYSLOG_ACTION_CONSOLE_OFF:
1449 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1450 saved_console_loglevel = console_loglevel;
1451 console_loglevel = minimum_console_loglevel;
1453 /* Enable logging to console */
1454 case SYSLOG_ACTION_CONSOLE_ON:
1455 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1456 console_loglevel = saved_console_loglevel;
1457 saved_console_loglevel = LOGLEVEL_DEFAULT;
1460 /* Set level of messages printed to console */
1461 case SYSLOG_ACTION_CONSOLE_LEVEL:
1463 if (len < 1 || len > 8)
1465 if (len < minimum_console_loglevel)
1466 len = minimum_console_loglevel;
1467 console_loglevel = len;
1468 /* Implicitly re-enable logging to console */
1469 saved_console_loglevel = LOGLEVEL_DEFAULT;
1472 /* Number of chars in the log buffer */
1473 case SYSLOG_ACTION_SIZE_UNREAD:
1474 raw_spin_lock_irq(&logbuf_lock);
1475 if (syslog_seq < log_first_seq) {
1476 /* messages are gone, move to first one */
1477 syslog_seq = log_first_seq;
1478 syslog_idx = log_first_idx;
1481 if (source == SYSLOG_FROM_PROC) {
1483 * Short-cut for poll(/"proc/kmsg") which simply checks
1484 * for pending data, not the size; return the count of
1485 * records, not the length.
1487 error = log_next_seq - syslog_seq;
1489 u64 seq = syslog_seq;
1490 u32 idx = syslog_idx;
1493 while (seq < log_next_seq) {
1494 struct printk_log *msg = log_from_idx(idx);
1496 error += msg_print_text(msg, true, NULL, 0);
1497 idx = log_next(idx);
1500 error -= syslog_partial;
1502 raw_spin_unlock_irq(&logbuf_lock);
1504 /* Size of the log buffer */
1505 case SYSLOG_ACTION_SIZE_BUFFER:
1506 error = log_buf_len;
1516 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1518 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1522 * Call the console drivers, asking them to write out
1523 * log_buf[start] to log_buf[end - 1].
1524 * The console_lock must be held.
1526 static void call_console_drivers(int level,
1527 const char *ext_text, size_t ext_len,
1528 const char *text, size_t len)
1530 struct console *con;
1532 trace_console_rcuidle(text, len);
1534 if (!console_drivers)
1537 for_each_console(con) {
1538 if (exclusive_console && con != exclusive_console)
1540 if (!(con->flags & CON_ENABLED))
1544 if (!cpu_online(smp_processor_id()) &&
1545 !(con->flags & CON_ANYTIME))
1547 if (con->flags & CON_EXTENDED)
1548 con->write(con, ext_text, ext_len);
1550 con->write(con, text, len);
1555 * Zap console related locks when oopsing.
1556 * To leave time for slow consoles to print a full oops,
1557 * only zap at most once every 30 seconds.
1559 static void zap_locks(void)
1561 static unsigned long oops_timestamp;
1563 if (time_after_eq(jiffies, oops_timestamp) &&
1564 !time_after(jiffies, oops_timestamp + 30 * HZ))
1567 oops_timestamp = jiffies;
1570 /* If a crash is occurring, make sure we can't deadlock */
1571 raw_spin_lock_init(&logbuf_lock);
1572 /* And make sure that we print immediately */
1573 sema_init(&console_sem, 1);
1576 int printk_delay_msec __read_mostly;
1578 static inline void printk_delay(void)
1580 if (unlikely(printk_delay_msec)) {
1581 int m = printk_delay_msec;
1585 touch_nmi_watchdog();
1591 * Continuation lines are buffered, and not committed to the record buffer
1592 * until the line is complete, or a race forces it. The line fragments
1593 * though, are printed immediately to the consoles to ensure everything has
1594 * reached the console in case of a kernel crash.
1596 static struct cont {
1597 char buf[LOG_LINE_MAX];
1598 size_t len; /* length == 0 means unused buffer */
1599 size_t cons; /* bytes written to console */
1600 struct task_struct *owner; /* task of first print*/
1601 u64 ts_nsec; /* time of first print */
1602 u8 level; /* log level of first message */
1603 u8 facility; /* log facility of first message */
1604 enum log_flags flags; /* prefix, newline flags */
1605 bool flushed:1; /* buffer sealed and committed */
1608 static void cont_flush(void)
1616 * If a fragment of this line was directly flushed to the
1617 * console; wait for the console to pick up the rest of the
1618 * line. LOG_NOCONS suppresses a duplicated output.
1620 log_store(cont.facility, cont.level, cont.flags | LOG_NOCONS,
1621 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1622 cont.flushed = true;
1625 * If no fragment of this line ever reached the console,
1626 * just submit it to the store and free the buffer.
1628 log_store(cont.facility, cont.level, cont.flags, 0,
1629 NULL, 0, cont.buf, cont.len);
1634 static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len)
1636 if (cont.len && cont.flushed)
1640 * If ext consoles are present, flush and skip in-kernel
1641 * continuation. See nr_ext_console_drivers definition. Also, if
1642 * the line gets too long, split it up in separate records.
1644 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
1650 cont.facility = facility;
1652 cont.owner = current;
1653 cont.ts_nsec = local_clock();
1656 cont.flushed = false;
1659 memcpy(cont.buf + cont.len, text, len);
1662 // The original flags come from the first line,
1663 // but later continuations can add a newline.
1664 if (flags & LOG_NEWLINE) {
1665 cont.flags |= LOG_NEWLINE;
1669 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1675 static size_t cont_print_text(char *text, size_t size)
1680 if (cont.cons == 0) {
1681 textlen += print_time(cont.ts_nsec, text);
1685 len = cont.len - cont.cons;
1689 memcpy(text + textlen, cont.buf + cont.cons, len);
1691 cont.cons = cont.len;
1695 if (cont.flags & LOG_NEWLINE)
1696 text[textlen++] = '\n';
1697 /* got everything, release buffer */
1703 static size_t log_output(int facility, int level, enum log_flags lflags, const char *dict, size_t dictlen, char *text, size_t text_len)
1706 * If an earlier line was buffered, and we're a continuation
1707 * write from the same process, try to add it to the buffer.
1710 if (cont.owner == current && (lflags & LOG_CONT)) {
1711 if (cont_add(facility, level, lflags, text, text_len))
1714 /* Otherwise, make sure it's flushed */
1718 /* Skip empty continuation lines that couldn't be added - they just flush */
1719 if (!text_len && (lflags & LOG_CONT))
1722 /* If it doesn't end in a newline, try to buffer the current line */
1723 if (!(lflags & LOG_NEWLINE)) {
1724 if (cont_add(facility, level, lflags, text, text_len))
1728 /* Store it in the record log */
1729 return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len);
1732 asmlinkage int vprintk_emit(int facility, int level,
1733 const char *dict, size_t dictlen,
1734 const char *fmt, va_list args)
1736 static bool recursion_bug;
1737 static char textbuf[LOG_LINE_MAX];
1738 char *text = textbuf;
1739 size_t text_len = 0;
1740 enum log_flags lflags = 0;
1741 unsigned long flags;
1743 int printed_len = 0;
1744 int nmi_message_lost;
1745 bool in_sched = false;
1746 /* cpu currently holding logbuf_lock in this function */
1747 static unsigned int logbuf_cpu = UINT_MAX;
1749 if (level == LOGLEVEL_SCHED) {
1750 level = LOGLEVEL_DEFAULT;
1754 boot_delay_msec(level);
1757 local_irq_save(flags);
1758 this_cpu = smp_processor_id();
1761 * Ouch, printk recursed into itself!
1763 if (unlikely(logbuf_cpu == this_cpu)) {
1765 * If a crash is occurring during printk() on this CPU,
1766 * then try to get the crash message out but make sure
1767 * we can't deadlock. Otherwise just return to avoid the
1768 * recursion and return - but flag the recursion so that
1769 * it can be printed at the next appropriate moment:
1771 if (!oops_in_progress && !lockdep_recursing(current)) {
1772 recursion_bug = true;
1773 local_irq_restore(flags);
1780 /* This stops the holder of console_sem just where we want him */
1781 raw_spin_lock(&logbuf_lock);
1782 logbuf_cpu = this_cpu;
1784 if (unlikely(recursion_bug)) {
1785 static const char recursion_msg[] =
1786 "BUG: recent printk recursion!";
1788 recursion_bug = false;
1789 /* emit KERN_CRIT message */
1790 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1791 NULL, 0, recursion_msg,
1792 strlen(recursion_msg));
1795 nmi_message_lost = get_nmi_message_lost();
1796 if (unlikely(nmi_message_lost)) {
1797 text_len = scnprintf(textbuf, sizeof(textbuf),
1798 "BAD LUCK: lost %d message(s) from NMI context!",
1800 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1801 NULL, 0, textbuf, text_len);
1805 * The printf needs to come first; we need the syslog
1806 * prefix which might be passed-in as a parameter.
1808 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1810 /* mark and strip a trailing newline */
1811 if (text_len && text[text_len-1] == '\n') {
1813 lflags |= LOG_NEWLINE;
1816 /* strip kernel syslog prefix and extract log level or control flags */
1817 if (facility == 0) {
1820 while ((kern_level = printk_get_level(text)) != 0) {
1821 switch (kern_level) {
1823 if (level == LOGLEVEL_DEFAULT)
1824 level = kern_level - '0';
1826 case 'd': /* KERN_DEFAULT */
1827 lflags |= LOG_PREFIX;
1829 case 'c': /* KERN_CONT */
1838 if (level == LOGLEVEL_DEFAULT)
1839 level = default_message_loglevel;
1842 lflags |= LOG_PREFIX|LOG_NEWLINE;
1844 printed_len += log_output(facility, level, lflags, dict, dictlen, text, text_len);
1846 logbuf_cpu = UINT_MAX;
1847 raw_spin_unlock(&logbuf_lock);
1849 local_irq_restore(flags);
1851 /* If called from the scheduler, we can not call up(). */
1855 * Try to acquire and then immediately release the console
1856 * semaphore. The release will print out buffers and wake up
1857 * /dev/kmsg and syslog() users.
1859 if (console_trylock())
1866 EXPORT_SYMBOL(vprintk_emit);
1868 asmlinkage int vprintk(const char *fmt, va_list args)
1870 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1872 EXPORT_SYMBOL(vprintk);
1874 asmlinkage int printk_emit(int facility, int level,
1875 const char *dict, size_t dictlen,
1876 const char *fmt, ...)
1881 va_start(args, fmt);
1882 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1887 EXPORT_SYMBOL(printk_emit);
1889 int vprintk_default(const char *fmt, va_list args)
1893 #ifdef CONFIG_KGDB_KDB
1894 if (unlikely(kdb_trap_printk)) {
1895 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1899 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1903 EXPORT_SYMBOL_GPL(vprintk_default);
1906 * printk - print a kernel message
1907 * @fmt: format string
1909 * This is printk(). It can be called from any context. We want it to work.
1911 * We try to grab the console_lock. If we succeed, it's easy - we log the
1912 * output and call the console drivers. If we fail to get the semaphore, we
1913 * place the output into the log buffer and return. The current holder of
1914 * the console_sem will notice the new output in console_unlock(); and will
1915 * send it to the consoles before releasing the lock.
1917 * One effect of this deferred printing is that code which calls printk() and
1918 * then changes console_loglevel may break. This is because console_loglevel
1919 * is inspected when the actual printing occurs.
1924 * See the vsnprintf() documentation for format string extensions over C99.
1926 asmlinkage __visible int printk(const char *fmt, ...)
1931 va_start(args, fmt);
1932 r = vprintk_func(fmt, args);
1937 EXPORT_SYMBOL(printk);
1939 #else /* CONFIG_PRINTK */
1941 #define LOG_LINE_MAX 0
1942 #define PREFIX_MAX 0
1944 static u64 syslog_seq;
1945 static u32 syslog_idx;
1946 static u64 console_seq;
1947 static u32 console_idx;
1948 static u64 log_first_seq;
1949 static u32 log_first_idx;
1950 static u64 log_next_seq;
1951 static struct cont {
1957 static char *log_text(const struct printk_log *msg) { return NULL; }
1958 static char *log_dict(const struct printk_log *msg) { return NULL; }
1959 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
1960 static u32 log_next(u32 idx) { return 0; }
1961 static ssize_t msg_print_ext_header(char *buf, size_t size,
1962 struct printk_log *msg,
1963 u64 seq) { return 0; }
1964 static ssize_t msg_print_ext_body(char *buf, size_t size,
1965 char *dict, size_t dict_len,
1966 char *text, size_t text_len) { return 0; }
1967 static void call_console_drivers(int level,
1968 const char *ext_text, size_t ext_len,
1969 const char *text, size_t len) {}
1970 static size_t msg_print_text(const struct printk_log *msg,
1971 bool syslog, char *buf, size_t size) { return 0; }
1972 static size_t cont_print_text(char *text, size_t size) { return 0; }
1973 static bool suppress_message_printing(int level) { return false; }
1975 /* Still needs to be defined for users */
1976 DEFINE_PER_CPU(printk_func_t, printk_func);
1978 #endif /* CONFIG_PRINTK */
1980 #ifdef CONFIG_EARLY_PRINTK
1981 struct console *early_console;
1983 asmlinkage __visible void early_printk(const char *fmt, ...)
1993 n = vscnprintf(buf, sizeof(buf), fmt, ap);
1996 early_console->write(early_console, buf, n);
2000 static int __add_preferred_console(char *name, int idx, char *options,
2003 struct console_cmdline *c;
2007 * See if this tty is not yet registered, and
2008 * if we have a slot free.
2010 for (i = 0, c = console_cmdline;
2011 i < MAX_CMDLINECONSOLES && c->name[0];
2013 if (strcmp(c->name, name) == 0 && c->index == idx) {
2015 selected_console = i;
2019 if (i == MAX_CMDLINECONSOLES)
2022 selected_console = i;
2023 strlcpy(c->name, name, sizeof(c->name));
2024 c->options = options;
2025 braille_set_options(c, brl_options);
2031 * Set up a console. Called via do_early_param() in init/main.c
2032 * for each "console=" parameter in the boot command line.
2034 static int __init console_setup(char *str)
2036 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2037 char *s, *options, *brl_options = NULL;
2041 * console="" or console=null have been suggested as a way to
2042 * disable console output. Use ttynull that has been created
2043 * for exacly this purpose.
2045 if (str[0] == 0 || strcmp(str, "null") == 0) {
2046 __add_preferred_console("ttynull", 0, NULL, NULL);
2050 if (_braille_console_setup(&str, &brl_options))
2054 * Decode str into name, index, options.
2056 if (str[0] >= '0' && str[0] <= '9') {
2057 strcpy(buf, "ttyS");
2058 strncpy(buf + 4, str, sizeof(buf) - 5);
2060 strncpy(buf, str, sizeof(buf) - 1);
2062 buf[sizeof(buf) - 1] = 0;
2063 options = strchr(str, ',');
2067 if (!strcmp(str, "ttya"))
2068 strcpy(buf, "ttyS0");
2069 if (!strcmp(str, "ttyb"))
2070 strcpy(buf, "ttyS1");
2072 for (s = buf; *s; s++)
2073 if (isdigit(*s) || *s == ',')
2075 idx = simple_strtoul(s, NULL, 10);
2078 __add_preferred_console(buf, idx, options, brl_options);
2079 console_set_on_cmdline = 1;
2082 __setup("console=", console_setup);
2085 * add_preferred_console - add a device to the list of preferred consoles.
2086 * @name: device name
2087 * @idx: device index
2088 * @options: options for this console
2090 * The last preferred console added will be used for kernel messages
2091 * and stdin/out/err for init. Normally this is used by console_setup
2092 * above to handle user-supplied console arguments; however it can also
2093 * be used by arch-specific code either to override the user or more
2094 * commonly to provide a default console (ie from PROM variables) when
2095 * the user has not supplied one.
2097 int add_preferred_console(char *name, int idx, char *options)
2099 return __add_preferred_console(name, idx, options, NULL);
2102 bool console_suspend_enabled = true;
2103 EXPORT_SYMBOL(console_suspend_enabled);
2105 static int __init console_suspend_disable(char *str)
2107 console_suspend_enabled = false;
2110 __setup("no_console_suspend", console_suspend_disable);
2111 module_param_named(console_suspend, console_suspend_enabled,
2112 bool, S_IRUGO | S_IWUSR);
2113 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2114 " and hibernate operations");
2117 * suspend_console - suspend the console subsystem
2119 * This disables printk() while we go into suspend states
2121 void suspend_console(void)
2123 if (!console_suspend_enabled)
2125 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2127 console_suspended = 1;
2131 void resume_console(void)
2133 if (!console_suspend_enabled)
2136 console_suspended = 0;
2141 * console_cpu_notify - print deferred console messages after CPU hotplug
2142 * @self: notifier struct
2143 * @action: CPU hotplug event
2146 * If printk() is called from a CPU that is not online yet, the messages
2147 * will be spooled but will not show up on the console. This function is
2148 * called when a new CPU comes online (or fails to come up), and ensures
2149 * that any such output gets printed.
2151 static int console_cpu_notify(struct notifier_block *self,
2152 unsigned long action, void *hcpu)
2157 case CPU_DOWN_FAILED:
2158 case CPU_UP_CANCELED:
2166 * console_lock - lock the console system for exclusive use.
2168 * Acquires a lock which guarantees that the caller has
2169 * exclusive access to the console system and the console_drivers list.
2171 * Can sleep, returns nothing.
2173 void console_lock(void)
2178 if (console_suspended)
2181 console_may_schedule = 1;
2183 EXPORT_SYMBOL(console_lock);
2186 * console_trylock - try to lock the console system for exclusive use.
2188 * Try to acquire a lock which guarantees that the caller has exclusive
2189 * access to the console system and the console_drivers list.
2191 * returns 1 on success, and 0 on failure to acquire the lock.
2193 int console_trylock(void)
2195 if (down_trylock_console_sem())
2197 if (console_suspended) {
2203 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2204 * safe to schedule (e.g. calling printk while holding a spin_lock),
2205 * because preempt_disable()/preempt_enable() are just barriers there
2206 * and preempt_count() is always 0.
2208 * RCU read sections have a separate preemption counter when
2209 * PREEMPT_RCU enabled thus we must take extra care and check
2210 * rcu_preempt_depth(), otherwise RCU read sections modify
2213 console_may_schedule = !oops_in_progress &&
2215 !rcu_preempt_depth();
2218 EXPORT_SYMBOL(console_trylock);
2220 int is_console_locked(void)
2222 return console_locked;
2226 * Check if we have any console that is capable of printing while cpu is
2227 * booting or shutting down. Requires console_sem.
2229 static int have_callable_console(void)
2231 struct console *con;
2233 for_each_console(con)
2234 if ((con->flags & CON_ENABLED) &&
2235 (con->flags & CON_ANYTIME))
2242 * Can we actually use the console at this time on this cpu?
2244 * Console drivers may assume that per-cpu resources have been allocated. So
2245 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2246 * call them until this CPU is officially up.
2248 static inline int can_use_console(void)
2250 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2253 static void console_cont_flush(char *text, size_t size)
2255 unsigned long flags;
2258 raw_spin_lock_irqsave(&logbuf_lock, flags);
2263 if (suppress_message_printing(cont.level)) {
2264 cont.cons = cont.len;
2271 * We still queue earlier records, likely because the console was
2272 * busy. The earlier ones need to be printed before this one, we
2273 * did not flush any fragment so far, so just let it queue up.
2275 if (console_seq < log_next_seq && !cont.cons)
2278 len = cont_print_text(text, size);
2279 raw_spin_unlock(&logbuf_lock);
2280 stop_critical_timings();
2281 call_console_drivers(cont.level, NULL, 0, text, len);
2282 start_critical_timings();
2283 local_irq_restore(flags);
2286 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2290 * console_unlock - unlock the console system
2292 * Releases the console_lock which the caller holds on the console system
2293 * and the console driver list.
2295 * While the console_lock was held, console output may have been buffered
2296 * by printk(). If this is the case, console_unlock(); emits
2297 * the output prior to releasing the lock.
2299 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2301 * console_unlock(); may be called from any context.
2303 void console_unlock(void)
2305 static char ext_text[CONSOLE_EXT_LOG_MAX];
2306 static char text[LOG_LINE_MAX + PREFIX_MAX];
2307 static u64 seen_seq;
2308 unsigned long flags;
2309 bool wake_klogd = false;
2310 bool do_cond_resched, retry;
2312 if (console_suspended) {
2318 * Console drivers are called with interrupts disabled, so
2319 * @console_may_schedule should be cleared before; however, we may
2320 * end up dumping a lot of lines, for example, if called from
2321 * console registration path, and should invoke cond_resched()
2322 * between lines if allowable. Not doing so can cause a very long
2323 * scheduling stall on a slow console leading to RCU stall and
2324 * softlockup warnings which exacerbate the issue with more
2325 * messages practically incapacitating the system.
2327 * console_trylock() is not able to detect the preemptive
2328 * context reliably. Therefore the value must be stored before
2329 * and cleared after the the "again" goto label.
2331 do_cond_resched = console_may_schedule;
2333 console_may_schedule = 0;
2336 * We released the console_sem lock, so we need to recheck if
2337 * cpu is online and (if not) is there at least one CON_ANYTIME
2340 if (!can_use_console()) {
2346 /* flush buffered message fragment immediately to console */
2347 console_cont_flush(text, sizeof(text));
2350 struct printk_log *msg;
2355 raw_spin_lock_irqsave(&logbuf_lock, flags);
2356 if (seen_seq != log_next_seq) {
2358 seen_seq = log_next_seq;
2361 if (console_seq < log_first_seq) {
2362 len = sprintf(text, "** %u printk messages dropped ** ",
2363 (unsigned)(log_first_seq - console_seq));
2365 /* messages are gone, move to first one */
2366 console_seq = log_first_seq;
2367 console_idx = log_first_idx;
2372 if (console_seq == log_next_seq)
2375 msg = log_from_idx(console_idx);
2377 if ((msg->flags & LOG_NOCONS) ||
2378 suppress_message_printing(level)) {
2380 * Skip record we have buffered and already printed
2381 * directly to the console when we received it, and
2382 * record that has level above the console loglevel.
2384 console_idx = log_next(console_idx);
2387 * We will get here again when we register a new
2388 * CON_PRINTBUFFER console. Clear the flag so we
2389 * will properly dump everything later.
2391 msg->flags &= ~LOG_NOCONS;
2395 len += msg_print_text(msg, false, text + len, sizeof(text) - len);
2396 if (nr_ext_console_drivers) {
2397 ext_len = msg_print_ext_header(ext_text,
2400 ext_len += msg_print_ext_body(ext_text + ext_len,
2401 sizeof(ext_text) - ext_len,
2402 log_dict(msg), msg->dict_len,
2403 log_text(msg), msg->text_len);
2405 console_idx = log_next(console_idx);
2407 raw_spin_unlock(&logbuf_lock);
2409 stop_critical_timings(); /* don't trace print latency */
2410 call_console_drivers(level, ext_text, ext_len, text, len);
2411 start_critical_timings();
2412 local_irq_restore(flags);
2414 if (do_cond_resched)
2419 /* Release the exclusive_console once it is used */
2420 if (unlikely(exclusive_console))
2421 exclusive_console = NULL;
2423 raw_spin_unlock(&logbuf_lock);
2428 * Someone could have filled up the buffer again, so re-check if there's
2429 * something to flush. In case we cannot trylock the console_sem again,
2430 * there's a new owner and the console_unlock() from them will do the
2431 * flush, no worries.
2433 raw_spin_lock(&logbuf_lock);
2434 retry = console_seq != log_next_seq;
2435 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2437 if (retry && console_trylock())
2443 EXPORT_SYMBOL(console_unlock);
2446 * console_conditional_schedule - yield the CPU if required
2448 * If the console code is currently allowed to sleep, and
2449 * if this CPU should yield the CPU to another task, do
2452 * Must be called within console_lock();.
2454 void __sched console_conditional_schedule(void)
2456 if (console_may_schedule)
2459 EXPORT_SYMBOL(console_conditional_schedule);
2461 void console_unblank(void)
2466 * console_unblank can no longer be called in interrupt context unless
2467 * oops_in_progress is set to 1..
2469 if (oops_in_progress) {
2470 if (down_trylock_console_sem() != 0)
2476 console_may_schedule = 0;
2478 if ((c->flags & CON_ENABLED) && c->unblank)
2484 * console_flush_on_panic - flush console content on panic
2486 * Immediately output all pending messages no matter what.
2488 void console_flush_on_panic(void)
2491 * If someone else is holding the console lock, trylock will fail
2492 * and may_schedule may be set. Ignore and proceed to unlock so
2493 * that messages are flushed out. As this can be called from any
2494 * context and we don't want to get preempted while flushing,
2495 * ensure may_schedule is cleared.
2498 console_may_schedule = 0;
2503 * Return the console tty driver structure and its associated index
2505 struct tty_driver *console_device(int *index)
2508 struct tty_driver *driver = NULL;
2511 for_each_console(c) {
2514 driver = c->device(c, index);
2523 * Prevent further output on the passed console device so that (for example)
2524 * serial drivers can disable console output before suspending a port, and can
2525 * re-enable output afterwards.
2527 void console_stop(struct console *console)
2530 console->flags &= ~CON_ENABLED;
2533 EXPORT_SYMBOL(console_stop);
2535 void console_start(struct console *console)
2538 console->flags |= CON_ENABLED;
2541 EXPORT_SYMBOL(console_start);
2543 static int __read_mostly keep_bootcon;
2545 static int __init keep_bootcon_setup(char *str)
2548 pr_info("debug: skip boot console de-registration.\n");
2553 early_param("keep_bootcon", keep_bootcon_setup);
2556 * The console driver calls this routine during kernel initialization
2557 * to register the console printing procedure with printk() and to
2558 * print any messages that were printed by the kernel before the
2559 * console driver was initialized.
2561 * This can happen pretty early during the boot process (because of
2562 * early_printk) - sometimes before setup_arch() completes - be careful
2563 * of what kernel features are used - they may not be initialised yet.
2565 * There are two types of consoles - bootconsoles (early_printk) and
2566 * "real" consoles (everything which is not a bootconsole) which are
2567 * handled differently.
2568 * - Any number of bootconsoles can be registered at any time.
2569 * - As soon as a "real" console is registered, all bootconsoles
2570 * will be unregistered automatically.
2571 * - Once a "real" console is registered, any attempt to register a
2572 * bootconsoles will be rejected
2574 void register_console(struct console *newcon)
2577 unsigned long flags;
2578 struct console *bcon = NULL;
2579 struct console_cmdline *c;
2581 if (console_drivers)
2582 for_each_console(bcon)
2583 if (WARN(bcon == newcon,
2584 "console '%s%d' already registered\n",
2585 bcon->name, bcon->index))
2589 * before we register a new CON_BOOT console, make sure we don't
2590 * already have a valid console
2592 if (console_drivers && newcon->flags & CON_BOOT) {
2593 /* find the last or real console */
2594 for_each_console(bcon) {
2595 if (!(bcon->flags & CON_BOOT)) {
2596 pr_info("Too late to register bootconsole %s%d\n",
2597 newcon->name, newcon->index);
2603 if (console_drivers && console_drivers->flags & CON_BOOT)
2604 bcon = console_drivers;
2606 if (preferred_console < 0 || bcon || !console_drivers)
2607 preferred_console = selected_console;
2610 * See if we want to use this console driver. If we
2611 * didn't select a console we take the first one
2612 * that registers here.
2614 if (preferred_console < 0) {
2615 if (newcon->index < 0)
2617 if (newcon->setup == NULL ||
2618 newcon->setup(newcon, NULL) == 0) {
2619 newcon->flags |= CON_ENABLED;
2620 if (newcon->device) {
2621 newcon->flags |= CON_CONSDEV;
2622 preferred_console = 0;
2628 * See if this console matches one we selected on
2631 for (i = 0, c = console_cmdline;
2632 i < MAX_CMDLINECONSOLES && c->name[0];
2634 if (!newcon->match ||
2635 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2636 /* default matching */
2637 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2638 if (strcmp(c->name, newcon->name) != 0)
2640 if (newcon->index >= 0 &&
2641 newcon->index != c->index)
2643 if (newcon->index < 0)
2644 newcon->index = c->index;
2646 if (_braille_register_console(newcon, c))
2649 if (newcon->setup &&
2650 newcon->setup(newcon, c->options) != 0)
2654 newcon->flags |= CON_ENABLED;
2655 if (i == selected_console) {
2656 newcon->flags |= CON_CONSDEV;
2657 preferred_console = selected_console;
2662 if (!(newcon->flags & CON_ENABLED))
2666 * If we have a bootconsole, and are switching to a real console,
2667 * don't print everything out again, since when the boot console, and
2668 * the real console are the same physical device, it's annoying to
2669 * see the beginning boot messages twice
2671 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2672 newcon->flags &= ~CON_PRINTBUFFER;
2675 * Put this console in the list - keep the
2676 * preferred driver at the head of the list.
2679 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2680 newcon->next = console_drivers;
2681 console_drivers = newcon;
2683 newcon->next->flags &= ~CON_CONSDEV;
2685 newcon->next = console_drivers->next;
2686 console_drivers->next = newcon;
2689 if (newcon->flags & CON_EXTENDED)
2690 if (!nr_ext_console_drivers++)
2691 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2693 if (newcon->flags & CON_PRINTBUFFER) {
2695 * console_unlock(); will print out the buffered messages
2698 raw_spin_lock_irqsave(&logbuf_lock, flags);
2699 console_seq = syslog_seq;
2700 console_idx = syslog_idx;
2701 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2703 * We're about to replay the log buffer. Only do this to the
2704 * just-registered console to avoid excessive message spam to
2705 * the already-registered consoles.
2707 exclusive_console = newcon;
2710 console_sysfs_notify();
2713 * By unregistering the bootconsoles after we enable the real console
2714 * we get the "console xxx enabled" message on all the consoles -
2715 * boot consoles, real consoles, etc - this is to ensure that end
2716 * users know there might be something in the kernel's log buffer that
2717 * went to the bootconsole (that they do not see on the real console)
2719 pr_info("%sconsole [%s%d] enabled\n",
2720 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2721 newcon->name, newcon->index);
2723 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2725 /* We need to iterate through all boot consoles, to make
2726 * sure we print everything out, before we unregister them.
2728 for_each_console(bcon)
2729 if (bcon->flags & CON_BOOT)
2730 unregister_console(bcon);
2733 EXPORT_SYMBOL(register_console);
2735 int unregister_console(struct console *console)
2737 struct console *a, *b;
2740 pr_info("%sconsole [%s%d] disabled\n",
2741 (console->flags & CON_BOOT) ? "boot" : "" ,
2742 console->name, console->index);
2744 res = _braille_unregister_console(console);
2750 if (console_drivers == console) {
2751 console_drivers=console->next;
2753 } else if (console_drivers) {
2754 for (a=console_drivers->next, b=console_drivers ;
2755 a; b=a, a=b->next) {
2764 if (!res && (console->flags & CON_EXTENDED))
2765 nr_ext_console_drivers--;
2768 * If this isn't the last console and it has CON_CONSDEV set, we
2769 * need to set it on the next preferred console.
2771 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2772 console_drivers->flags |= CON_CONSDEV;
2774 console->flags &= ~CON_ENABLED;
2776 console_sysfs_notify();
2779 EXPORT_SYMBOL(unregister_console);
2782 * Some boot consoles access data that is in the init section and which will
2783 * be discarded after the initcalls have been run. To make sure that no code
2784 * will access this data, unregister the boot consoles in a late initcall.
2786 * If for some reason, such as deferred probe or the driver being a loadable
2787 * module, the real console hasn't registered yet at this point, there will
2788 * be a brief interval in which no messages are logged to the console, which
2789 * makes it difficult to diagnose problems that occur during this time.
2791 * To mitigate this problem somewhat, only unregister consoles whose memory
2792 * intersects with the init section. Note that code exists elsewhere to get
2793 * rid of the boot console as soon as the proper console shows up, so there
2794 * won't be side-effects from postponing the removal.
2796 static int __init printk_late_init(void)
2798 struct console *con;
2800 for_each_console(con) {
2801 if (!keep_bootcon && con->flags & CON_BOOT) {
2803 * Make sure to unregister boot consoles whose data
2804 * resides in the init section before the init section
2805 * is discarded. Boot consoles whose data will stick
2806 * around will automatically be unregistered when the
2807 * proper console replaces them.
2809 if (init_section_intersects(con, sizeof(*con)))
2810 unregister_console(con);
2813 hotcpu_notifier(console_cpu_notify, 0);
2816 late_initcall(printk_late_init);
2818 #if defined CONFIG_PRINTK
2820 * Delayed printk version, for scheduler-internal messages:
2822 #define PRINTK_PENDING_WAKEUP 0x01
2823 #define PRINTK_PENDING_OUTPUT 0x02
2825 static DEFINE_PER_CPU(int, printk_pending);
2827 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2829 int pending = __this_cpu_xchg(printk_pending, 0);
2831 if (pending & PRINTK_PENDING_OUTPUT) {
2832 /* If trylock fails, someone else is doing the printing */
2833 if (console_trylock())
2837 if (pending & PRINTK_PENDING_WAKEUP)
2838 wake_up_interruptible(&log_wait);
2841 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2842 .func = wake_up_klogd_work_func,
2843 .flags = IRQ_WORK_LAZY,
2846 void wake_up_klogd(void)
2849 if (waitqueue_active(&log_wait)) {
2850 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2851 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2856 int printk_deferred(const char *fmt, ...)
2862 va_start(args, fmt);
2863 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2866 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2867 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2874 * printk rate limiting, lifted from the networking subsystem.
2876 * This enforces a rate limit: not more than 10 kernel messages
2877 * every 5s to make a denial-of-service attack impossible.
2879 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2881 int __printk_ratelimit(const char *func)
2883 return ___ratelimit(&printk_ratelimit_state, func);
2885 EXPORT_SYMBOL(__printk_ratelimit);
2888 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2889 * @caller_jiffies: pointer to caller's state
2890 * @interval_msecs: minimum interval between prints
2892 * printk_timed_ratelimit() returns true if more than @interval_msecs
2893 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2896 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2897 unsigned int interval_msecs)
2899 unsigned long elapsed = jiffies - *caller_jiffies;
2901 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2904 *caller_jiffies = jiffies;
2907 EXPORT_SYMBOL(printk_timed_ratelimit);
2909 static DEFINE_SPINLOCK(dump_list_lock);
2910 static LIST_HEAD(dump_list);
2913 * kmsg_dump_register - register a kernel log dumper.
2914 * @dumper: pointer to the kmsg_dumper structure
2916 * Adds a kernel log dumper to the system. The dump callback in the
2917 * structure will be called when the kernel oopses or panics and must be
2918 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2920 int kmsg_dump_register(struct kmsg_dumper *dumper)
2922 unsigned long flags;
2925 /* The dump callback needs to be set */
2929 spin_lock_irqsave(&dump_list_lock, flags);
2930 /* Don't allow registering multiple times */
2931 if (!dumper->registered) {
2932 dumper->registered = 1;
2933 list_add_tail_rcu(&dumper->list, &dump_list);
2936 spin_unlock_irqrestore(&dump_list_lock, flags);
2940 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2943 * kmsg_dump_unregister - unregister a kmsg dumper.
2944 * @dumper: pointer to the kmsg_dumper structure
2946 * Removes a dump device from the system. Returns zero on success and
2947 * %-EINVAL otherwise.
2949 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2951 unsigned long flags;
2954 spin_lock_irqsave(&dump_list_lock, flags);
2955 if (dumper->registered) {
2956 dumper->registered = 0;
2957 list_del_rcu(&dumper->list);
2960 spin_unlock_irqrestore(&dump_list_lock, flags);
2965 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2967 static bool always_kmsg_dump;
2968 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2971 * kmsg_dump - dump kernel log to kernel message dumpers.
2972 * @reason: the reason (oops, panic etc) for dumping
2974 * Call each of the registered dumper's dump() callback, which can
2975 * retrieve the kmsg records with kmsg_dump_get_line() or
2976 * kmsg_dump_get_buffer().
2978 void kmsg_dump(enum kmsg_dump_reason reason)
2980 struct kmsg_dumper *dumper;
2981 unsigned long flags;
2983 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2987 list_for_each_entry_rcu(dumper, &dump_list, list) {
2988 if (dumper->max_reason && reason > dumper->max_reason)
2991 /* initialize iterator with data about the stored records */
2992 dumper->active = true;
2994 raw_spin_lock_irqsave(&logbuf_lock, flags);
2995 dumper->cur_seq = clear_seq;
2996 dumper->cur_idx = clear_idx;
2997 dumper->next_seq = log_next_seq;
2998 dumper->next_idx = log_next_idx;
2999 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3001 /* invoke dumper which will iterate over records */
3002 dumper->dump(dumper, reason);
3004 /* reset iterator */
3005 dumper->active = false;
3011 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
3012 * @dumper: registered kmsg dumper
3013 * @syslog: include the "<4>" prefixes
3014 * @line: buffer to copy the line to
3015 * @size: maximum size of the buffer
3016 * @len: length of line placed into buffer
3018 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3019 * record, and copy one record into the provided buffer.
3021 * Consecutive calls will return the next available record moving
3022 * towards the end of the buffer with the youngest messages.
3024 * A return value of FALSE indicates that there are no more records to
3027 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
3029 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
3030 char *line, size_t size, size_t *len)
3032 struct printk_log *msg;
3036 if (!dumper->active)
3039 if (dumper->cur_seq < log_first_seq) {
3040 /* messages are gone, move to first available one */
3041 dumper->cur_seq = log_first_seq;
3042 dumper->cur_idx = log_first_idx;
3046 if (dumper->cur_seq >= log_next_seq)
3049 msg = log_from_idx(dumper->cur_idx);
3050 l = msg_print_text(msg, syslog, line, size);
3052 dumper->cur_idx = log_next(dumper->cur_idx);
3062 * kmsg_dump_get_line - retrieve one kmsg log line
3063 * @dumper: registered kmsg dumper
3064 * @syslog: include the "<4>" prefixes
3065 * @line: buffer to copy the line to
3066 * @size: maximum size of the buffer
3067 * @len: length of line placed into buffer
3069 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3070 * record, and copy one record into the provided buffer.
3072 * Consecutive calls will return the next available record moving
3073 * towards the end of the buffer with the youngest messages.
3075 * A return value of FALSE indicates that there are no more records to
3078 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
3079 char *line, size_t size, size_t *len)
3081 unsigned long flags;
3084 raw_spin_lock_irqsave(&logbuf_lock, flags);
3085 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
3086 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3090 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
3093 * kmsg_dump_get_buffer - copy kmsg log lines
3094 * @dumper: registered kmsg dumper
3095 * @syslog: include the "<4>" prefixes
3096 * @buf: buffer to copy the line to
3097 * @size: maximum size of the buffer
3098 * @len: length of line placed into buffer
3100 * Start at the end of the kmsg buffer and fill the provided buffer
3101 * with as many of the the *youngest* kmsg records that fit into it.
3102 * If the buffer is large enough, all available kmsg records will be
3103 * copied with a single call.
3105 * Consecutive calls will fill the buffer with the next block of
3106 * available older records, not including the earlier retrieved ones.
3108 * A return value of FALSE indicates that there are no more records to
3111 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
3112 char *buf, size_t size, size_t *len)
3114 unsigned long flags;
3122 if (!dumper->active)
3125 raw_spin_lock_irqsave(&logbuf_lock, flags);
3126 if (dumper->cur_seq < log_first_seq) {
3127 /* messages are gone, move to first available one */
3128 dumper->cur_seq = log_first_seq;
3129 dumper->cur_idx = log_first_idx;
3133 if (dumper->cur_seq >= dumper->next_seq) {
3134 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3138 /* calculate length of entire buffer */
3139 seq = dumper->cur_seq;
3140 idx = dumper->cur_idx;
3141 while (seq < dumper->next_seq) {
3142 struct printk_log *msg = log_from_idx(idx);
3144 l += msg_print_text(msg, true, NULL, 0);
3145 idx = log_next(idx);
3149 /* move first record forward until length fits into the buffer */
3150 seq = dumper->cur_seq;
3151 idx = dumper->cur_idx;
3152 while (l >= size && seq < dumper->next_seq) {
3153 struct printk_log *msg = log_from_idx(idx);
3155 l -= msg_print_text(msg, true, NULL, 0);
3156 idx = log_next(idx);
3160 /* last message in next interation */
3165 while (seq < dumper->next_seq) {
3166 struct printk_log *msg = log_from_idx(idx);
3168 l += msg_print_text(msg, syslog, buf + l, size - l);
3169 idx = log_next(idx);
3173 dumper->next_seq = next_seq;
3174 dumper->next_idx = next_idx;
3176 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3182 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3185 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3186 * @dumper: registered kmsg dumper
3188 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3189 * kmsg_dump_get_buffer() can be called again and used multiple
3190 * times within the same dumper.dump() callback.
3192 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3194 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3196 dumper->cur_seq = clear_seq;
3197 dumper->cur_idx = clear_idx;
3198 dumper->next_seq = log_next_seq;
3199 dumper->next_idx = log_next_idx;
3203 * kmsg_dump_rewind - reset the interator
3204 * @dumper: registered kmsg dumper
3206 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3207 * kmsg_dump_get_buffer() can be called again and used multiple
3208 * times within the same dumper.dump() callback.
3210 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3212 unsigned long flags;
3214 raw_spin_lock_irqsave(&logbuf_lock, flags);
3215 kmsg_dump_rewind_nolock(dumper);
3216 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3218 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3220 static char dump_stack_arch_desc_str[128];
3223 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3224 * @fmt: printf-style format string
3225 * @...: arguments for the format string
3227 * The configured string will be printed right after utsname during task
3228 * dumps. Usually used to add arch-specific system identifiers. If an
3229 * arch wants to make use of such an ID string, it should initialize this
3230 * as soon as possible during boot.
3232 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3236 va_start(args, fmt);
3237 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3243 * dump_stack_print_info - print generic debug info for dump_stack()
3244 * @log_lvl: log level
3246 * Arch-specific dump_stack() implementations can use this function to
3247 * print out the same debug information as the generic dump_stack().
3249 void dump_stack_print_info(const char *log_lvl)
3251 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3252 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3253 print_tainted(), init_utsname()->release,
3254 (int)strcspn(init_utsname()->version, " "),
3255 init_utsname()->version);
3257 if (dump_stack_arch_desc_str[0] != '\0')
3258 printk("%sHardware name: %s\n",
3259 log_lvl, dump_stack_arch_desc_str);
3261 print_worker_info(log_lvl, current);
3265 * show_regs_print_info - print generic debug info for show_regs()
3266 * @log_lvl: log level
3268 * show_regs() implementations can use this function to print out generic
3269 * debug information.
3271 void show_regs_print_info(const char *log_lvl)
3273 dump_stack_print_info(log_lvl);
3275 printk("%stask: %p task.stack: %p\n",
3276 log_lvl, current, task_stack_page(current));