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 int console_printk[4] = {
59 CONSOLE_LOGLEVEL_DEFAULT, /* console_loglevel */
60 MESSAGE_LOGLEVEL_DEFAULT, /* default_message_loglevel */
61 CONSOLE_LOGLEVEL_MIN, /* minimum_console_loglevel */
62 CONSOLE_LOGLEVEL_DEFAULT, /* default_console_loglevel */
66 * Low level drivers may need that to know if they can schedule in
67 * their unblank() callback or not. So let's export it.
70 EXPORT_SYMBOL(oops_in_progress);
73 * console_sem protects the console_drivers list, and also
74 * provides serialisation for access to the entire console
77 static DEFINE_SEMAPHORE(console_sem);
78 struct console *console_drivers;
79 EXPORT_SYMBOL_GPL(console_drivers);
82 static struct lockdep_map console_lock_dep_map = {
83 .name = "console_lock"
88 * Number of registered extended console drivers.
90 * If extended consoles are present, in-kernel cont reassembly is disabled
91 * and each fragment is stored as a separate log entry with proper
92 * continuation flag so that every emitted message has full metadata. This
93 * doesn't change the result for regular consoles or /proc/kmsg. For
94 * /dev/kmsg, as long as the reader concatenates messages according to
95 * consecutive continuation flags, the end result should be the same too.
97 static int nr_ext_console_drivers;
100 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
101 * macros instead of functions so that _RET_IP_ contains useful information.
103 #define down_console_sem() do { \
105 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
108 static int __down_trylock_console_sem(unsigned long ip)
110 if (down_trylock(&console_sem))
112 mutex_acquire(&console_lock_dep_map, 0, 1, ip);
115 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
117 #define up_console_sem() do { \
118 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
123 * This is used for debugging the mess that is the VT code by
124 * keeping track if we have the console semaphore held. It's
125 * definitely not the perfect debug tool (we don't know if _WE_
126 * hold it and are racing, but it helps tracking those weird code
127 * paths in the console code where we end up in places I want
128 * locked without the console sempahore held).
130 static int console_locked, console_suspended;
133 * If exclusive_console is non-NULL then only this console is to be printed to.
135 static struct console *exclusive_console;
138 * Array of consoles built from command line options (console=)
141 #define MAX_CMDLINECONSOLES 8
143 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
145 static int selected_console = -1;
146 static int preferred_console = -1;
147 int console_set_on_cmdline;
148 EXPORT_SYMBOL(console_set_on_cmdline);
150 /* Flag: console code may call schedule() */
151 static int console_may_schedule;
154 * The printk log buffer consists of a chain of concatenated variable
155 * length records. Every record starts with a record header, containing
156 * the overall length of the record.
158 * The heads to the first and last entry in the buffer, as well as the
159 * sequence numbers of these entries are maintained when messages are
162 * If the heads indicate available messages, the length in the header
163 * tells the start next message. A length == 0 for the next message
164 * indicates a wrap-around to the beginning of the buffer.
166 * Every record carries the monotonic timestamp in microseconds, as well as
167 * the standard userspace syslog level and syslog facility. The usual
168 * kernel messages use LOG_KERN; userspace-injected messages always carry
169 * a matching syslog facility, by default LOG_USER. The origin of every
170 * message can be reliably determined that way.
172 * The human readable log message directly follows the message header. The
173 * length of the message text is stored in the header, the stored message
176 * Optionally, a message can carry a dictionary of properties (key/value pairs),
177 * to provide userspace with a machine-readable message context.
179 * Examples for well-defined, commonly used property names are:
180 * DEVICE=b12:8 device identifier
184 * +sound:card0 subsystem:devname
185 * SUBSYSTEM=pci driver-core subsystem name
187 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
188 * follows directly after a '=' character. Every property is terminated by
189 * a '\0' character. The last property is not terminated.
191 * Example of a message structure:
192 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
193 * 0008 34 00 record is 52 bytes long
194 * 000a 0b 00 text is 11 bytes long
195 * 000c 1f 00 dictionary is 23 bytes long
196 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
197 * 0010 69 74 27 73 20 61 20 6c "it's a l"
199 * 001b 44 45 56 49 43 "DEVIC"
200 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
201 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
203 * 0032 00 00 00 padding to next message header
205 * The 'struct printk_log' buffer header must never be directly exported to
206 * userspace, it is a kernel-private implementation detail that might
207 * need to be changed in the future, when the requirements change.
209 * /dev/kmsg exports the structured data in the following line format:
210 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
212 * Users of the export format should ignore possible additional values
213 * separated by ',', and find the message after the ';' character.
215 * The optional key/value pairs are attached as continuation lines starting
216 * with a space character and terminated by a newline. All possible
217 * non-prinatable characters are escaped in the "\xff" notation.
221 LOG_NOCONS = 1, /* already flushed, do not print to console */
222 LOG_NEWLINE = 2, /* text ended with a newline */
223 LOG_PREFIX = 4, /* text started with a prefix */
224 LOG_CONT = 8, /* text is a fragment of a continuation line */
228 u64 ts_nsec; /* timestamp in nanoseconds */
229 u16 len; /* length of entire record */
230 u16 text_len; /* length of text buffer */
231 u16 dict_len; /* length of dictionary buffer */
232 u8 facility; /* syslog facility */
233 u8 flags:5; /* internal record flags */
234 u8 level:3; /* syslog level */
238 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
239 * within the scheduler's rq lock. It must be released before calling
240 * console_unlock() or anything else that might wake up a process.
242 static DEFINE_RAW_SPINLOCK(logbuf_lock);
244 #ifdef CONFIG_EARLY_PRINTK
245 struct console *early_console;
247 static void early_vprintk(const char *fmt, va_list ap)
251 int n = vscnprintf(buf, sizeof(buf), fmt, ap);
253 early_console->write(early_console, buf, n);
257 asmlinkage void early_printk(const char *fmt, ...)
262 early_vprintk(fmt, ap);
267 * This is independent of any log levels - a global
268 * kill switch that turns off all of printk.
270 * Used by the NMI watchdog if early-printk is enabled.
272 static bool __read_mostly printk_killswitch;
274 static int __init force_early_printk_setup(char *str)
276 printk_killswitch = true;
279 early_param("force_early_printk", force_early_printk_setup);
281 void printk_kill(void)
283 printk_killswitch = true;
287 static int forced_early_printk(const char *fmt, va_list ap)
289 if (!printk_killswitch)
291 early_vprintk(fmt, ap);
297 static inline int forced_early_printk(const char *fmt, va_list ap)
304 DECLARE_WAIT_QUEUE_HEAD(log_wait);
305 /* the next printk record to read by syslog(READ) or /proc/kmsg */
306 static u64 syslog_seq;
307 static u32 syslog_idx;
308 static enum log_flags syslog_prev;
309 static size_t syslog_partial;
311 /* index and sequence number of the first record stored in the buffer */
312 static u64 log_first_seq;
313 static u32 log_first_idx;
315 /* index and sequence number of the next record to store in the buffer */
316 static u64 log_next_seq;
317 static u32 log_next_idx;
319 /* the next printk record to write to the console */
320 static u64 console_seq;
321 static u32 console_idx;
322 static enum log_flags console_prev;
324 /* the next printk record to read after the last 'clear' command */
325 static u64 clear_seq;
326 static u32 clear_idx;
328 #define PREFIX_MAX 32
329 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
331 #define LOG_LEVEL(v) ((v) & 0x07)
332 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
335 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
338 #define LOG_ALIGN __alignof__(struct printk_log)
340 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
341 static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
342 static char *log_buf = __log_buf;
343 static u32 log_buf_len = __LOG_BUF_LEN;
345 /* Return log buffer address */
346 char *log_buf_addr_get(void)
351 /* Return log buffer size */
352 u32 log_buf_len_get(void)
357 /* human readable text of the record */
358 static char *log_text(const struct printk_log *msg)
360 return (char *)msg + sizeof(struct printk_log);
363 /* optional key/value pair dictionary attached to the record */
364 static char *log_dict(const struct printk_log *msg)
366 return (char *)msg + sizeof(struct printk_log) + msg->text_len;
369 /* get record by index; idx must point to valid msg */
370 static struct printk_log *log_from_idx(u32 idx)
372 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
375 * A length == 0 record is the end of buffer marker. Wrap around and
376 * read the message at the start of the buffer.
379 return (struct printk_log *)log_buf;
383 /* get next record; idx must point to valid msg */
384 static u32 log_next(u32 idx)
386 struct printk_log *msg = (struct printk_log *)(log_buf + idx);
388 /* length == 0 indicates the end of the buffer; wrap */
390 * A length == 0 record is the end of buffer marker. Wrap around and
391 * read the message at the start of the buffer as *this* one, and
392 * return the one after that.
395 msg = (struct printk_log *)log_buf;
398 return idx + msg->len;
402 * Check whether there is enough free space for the given message.
404 * The same values of first_idx and next_idx mean that the buffer
405 * is either empty or full.
407 * If the buffer is empty, we must respect the position of the indexes.
408 * They cannot be reset to the beginning of the buffer.
410 static int logbuf_has_space(u32 msg_size, bool empty)
414 if (log_next_idx > log_first_idx || empty)
415 free = max(log_buf_len - log_next_idx, log_first_idx);
417 free = log_first_idx - log_next_idx;
420 * We need space also for an empty header that signalizes wrapping
423 return free >= msg_size + sizeof(struct printk_log);
426 static int log_make_free_space(u32 msg_size)
428 while (log_first_seq < log_next_seq) {
429 if (logbuf_has_space(msg_size, false))
431 /* drop old messages until we have enough contiguous space */
432 log_first_idx = log_next(log_first_idx);
436 /* sequence numbers are equal, so the log buffer is empty */
437 if (logbuf_has_space(msg_size, true))
443 /* compute the message size including the padding bytes */
444 static u32 msg_used_size(u16 text_len, u16 dict_len, u32 *pad_len)
448 size = sizeof(struct printk_log) + text_len + dict_len;
449 *pad_len = (-size) & (LOG_ALIGN - 1);
456 * Define how much of the log buffer we could take at maximum. The value
457 * must be greater than two. Note that only half of the buffer is available
458 * when the index points to the middle.
460 #define MAX_LOG_TAKE_PART 4
461 static const char trunc_msg[] = "<truncated>";
463 static u32 truncate_msg(u16 *text_len, u16 *trunc_msg_len,
464 u16 *dict_len, u32 *pad_len)
467 * The message should not take the whole buffer. Otherwise, it might
468 * get removed too soon.
470 u32 max_text_len = log_buf_len / MAX_LOG_TAKE_PART;
471 if (*text_len > max_text_len)
472 *text_len = max_text_len;
473 /* enable the warning message */
474 *trunc_msg_len = strlen(trunc_msg);
475 /* disable the "dict" completely */
477 /* compute the size again, count also the warning message */
478 return msg_used_size(*text_len + *trunc_msg_len, 0, pad_len);
481 /* insert record into the buffer, discard old ones, update heads */
482 static int log_store(int facility, int level,
483 enum log_flags flags, u64 ts_nsec,
484 const char *dict, u16 dict_len,
485 const char *text, u16 text_len)
487 struct printk_log *msg;
489 u16 trunc_msg_len = 0;
491 /* number of '\0' padding bytes to next message */
492 size = msg_used_size(text_len, dict_len, &pad_len);
494 if (log_make_free_space(size)) {
495 /* truncate the message if it is too long for empty buffer */
496 size = truncate_msg(&text_len, &trunc_msg_len,
497 &dict_len, &pad_len);
498 /* survive when the log buffer is too small for trunc_msg */
499 if (log_make_free_space(size))
503 if (log_next_idx + size + sizeof(struct printk_log) > log_buf_len) {
505 * This message + an additional empty header does not fit
506 * at the end of the buffer. Add an empty header with len == 0
507 * to signify a wrap around.
509 memset(log_buf + log_next_idx, 0, sizeof(struct printk_log));
514 msg = (struct printk_log *)(log_buf + log_next_idx);
515 memcpy(log_text(msg), text, text_len);
516 msg->text_len = text_len;
518 memcpy(log_text(msg) + text_len, trunc_msg, trunc_msg_len);
519 msg->text_len += trunc_msg_len;
521 memcpy(log_dict(msg), dict, dict_len);
522 msg->dict_len = dict_len;
523 msg->facility = facility;
524 msg->level = level & 7;
525 msg->flags = flags & 0x1f;
527 msg->ts_nsec = ts_nsec;
529 msg->ts_nsec = local_clock();
530 memset(log_dict(msg) + dict_len, 0, pad_len);
534 log_next_idx += msg->len;
537 return msg->text_len;
540 int dmesg_restrict = IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT);
542 static int syslog_action_restricted(int type)
547 * Unless restricted, we allow "read all" and "get buffer size"
550 return type != SYSLOG_ACTION_READ_ALL &&
551 type != SYSLOG_ACTION_SIZE_BUFFER;
554 int check_syslog_permissions(int type, int source)
557 * If this is from /proc/kmsg and we've already opened it, then we've
558 * already done the capabilities checks at open time.
560 if (source == SYSLOG_FROM_PROC && type != SYSLOG_ACTION_OPEN)
563 if (syslog_action_restricted(type)) {
564 if (capable(CAP_SYSLOG))
567 * For historical reasons, accept CAP_SYS_ADMIN too, with
570 if (capable(CAP_SYS_ADMIN)) {
571 pr_warn_once("%s (%d): Attempt to access syslog with "
572 "CAP_SYS_ADMIN but no CAP_SYSLOG "
574 current->comm, task_pid_nr(current));
580 return security_syslog(type);
582 EXPORT_SYMBOL_GPL(check_syslog_permissions);
584 static void append_char(char **pp, char *e, char c)
590 static ssize_t msg_print_ext_header(char *buf, size_t size,
591 struct printk_log *msg, u64 seq,
592 enum log_flags prev_flags)
594 u64 ts_usec = msg->ts_nsec;
597 do_div(ts_usec, 1000);
600 * If we couldn't merge continuation line fragments during the print,
601 * export the stored flags to allow an optional external merge of the
602 * records. Merging the records isn't always neccessarily correct, like
603 * when we hit a race during printing. In most cases though, it produces
604 * better readable output. 'c' in the record flags mark the first
605 * fragment of a line, '+' the following.
607 if (msg->flags & LOG_CONT && !(prev_flags & LOG_CONT))
609 else if ((msg->flags & LOG_CONT) ||
610 ((prev_flags & LOG_CONT) && !(msg->flags & LOG_PREFIX)))
613 return scnprintf(buf, size, "%u,%llu,%llu,%c;",
614 (msg->facility << 3) | msg->level, seq, ts_usec, cont);
617 static ssize_t msg_print_ext_body(char *buf, size_t size,
618 char *dict, size_t dict_len,
619 char *text, size_t text_len)
621 char *p = buf, *e = buf + size;
624 /* escape non-printable characters */
625 for (i = 0; i < text_len; i++) {
626 unsigned char c = text[i];
628 if (c < ' ' || c >= 127 || c == '\\')
629 p += scnprintf(p, e - p, "\\x%02x", c);
631 append_char(&p, e, c);
633 append_char(&p, e, '\n');
638 for (i = 0; i < dict_len; i++) {
639 unsigned char c = dict[i];
642 append_char(&p, e, ' ');
647 append_char(&p, e, '\n');
652 if (c < ' ' || c >= 127 || c == '\\') {
653 p += scnprintf(p, e - p, "\\x%02x", c);
657 append_char(&p, e, c);
659 append_char(&p, e, '\n');
665 /* /dev/kmsg - userspace message inject/listen interface */
666 struct devkmsg_user {
671 char buf[CONSOLE_EXT_LOG_MAX];
674 static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
677 int level = default_message_loglevel;
678 int facility = 1; /* LOG_USER */
679 size_t len = iov_iter_count(from);
682 if (len > LOG_LINE_MAX)
684 buf = kmalloc(len+1, GFP_KERNEL);
689 if (copy_from_iter(buf, len, from) != len) {
695 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
696 * the decimal value represents 32bit, the lower 3 bit are the log
697 * level, the rest are the log facility.
699 * If no prefix or no userspace facility is specified, we
700 * enforce LOG_USER, to be able to reliably distinguish
701 * kernel-generated messages from userspace-injected ones.
704 if (line[0] == '<') {
708 u = simple_strtoul(line + 1, &endp, 10);
709 if (endp && endp[0] == '>') {
710 level = LOG_LEVEL(u);
711 if (LOG_FACILITY(u) != 0)
712 facility = LOG_FACILITY(u);
719 printk_emit(facility, level, NULL, 0, "%s", line);
724 static ssize_t devkmsg_read(struct file *file, char __user *buf,
725 size_t count, loff_t *ppos)
727 struct devkmsg_user *user = file->private_data;
728 struct printk_log *msg;
735 ret = mutex_lock_interruptible(&user->lock);
738 raw_spin_lock_irq(&logbuf_lock);
739 while (user->seq == log_next_seq) {
740 if (file->f_flags & O_NONBLOCK) {
742 raw_spin_unlock_irq(&logbuf_lock);
746 raw_spin_unlock_irq(&logbuf_lock);
747 ret = wait_event_interruptible(log_wait,
748 user->seq != log_next_seq);
751 raw_spin_lock_irq(&logbuf_lock);
754 if (user->seq < log_first_seq) {
755 /* our last seen message is gone, return error and reset */
756 user->idx = log_first_idx;
757 user->seq = log_first_seq;
759 raw_spin_unlock_irq(&logbuf_lock);
763 msg = log_from_idx(user->idx);
764 len = msg_print_ext_header(user->buf, sizeof(user->buf),
765 msg, user->seq, user->prev);
766 len += msg_print_ext_body(user->buf + len, sizeof(user->buf) - len,
767 log_dict(msg), msg->dict_len,
768 log_text(msg), msg->text_len);
770 user->prev = msg->flags;
771 user->idx = log_next(user->idx);
773 raw_spin_unlock_irq(&logbuf_lock);
780 if (copy_to_user(buf, user->buf, len)) {
786 mutex_unlock(&user->lock);
790 static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence)
792 struct devkmsg_user *user = file->private_data;
800 raw_spin_lock_irq(&logbuf_lock);
803 /* the first record */
804 user->idx = log_first_idx;
805 user->seq = log_first_seq;
809 * The first record after the last SYSLOG_ACTION_CLEAR,
810 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
811 * changes no global state, and does not clear anything.
813 user->idx = clear_idx;
814 user->seq = clear_seq;
817 /* after the last record */
818 user->idx = log_next_idx;
819 user->seq = log_next_seq;
824 raw_spin_unlock_irq(&logbuf_lock);
828 static unsigned int devkmsg_poll(struct file *file, poll_table *wait)
830 struct devkmsg_user *user = file->private_data;
834 return POLLERR|POLLNVAL;
836 poll_wait(file, &log_wait, wait);
838 raw_spin_lock_irq(&logbuf_lock);
839 if (user->seq < log_next_seq) {
840 /* return error when data has vanished underneath us */
841 if (user->seq < log_first_seq)
842 ret = POLLIN|POLLRDNORM|POLLERR|POLLPRI;
844 ret = POLLIN|POLLRDNORM;
846 raw_spin_unlock_irq(&logbuf_lock);
851 static int devkmsg_open(struct inode *inode, struct file *file)
853 struct devkmsg_user *user;
856 /* write-only does not need any file context */
857 if ((file->f_flags & O_ACCMODE) == O_WRONLY)
860 err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
865 user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
869 mutex_init(&user->lock);
871 raw_spin_lock_irq(&logbuf_lock);
872 user->idx = log_first_idx;
873 user->seq = log_first_seq;
874 raw_spin_unlock_irq(&logbuf_lock);
876 file->private_data = user;
880 static int devkmsg_release(struct inode *inode, struct file *file)
882 struct devkmsg_user *user = file->private_data;
887 mutex_destroy(&user->lock);
892 const struct file_operations kmsg_fops = {
893 .open = devkmsg_open,
894 .read = devkmsg_read,
895 .write_iter = devkmsg_write,
896 .llseek = devkmsg_llseek,
897 .poll = devkmsg_poll,
898 .release = devkmsg_release,
901 #ifdef CONFIG_KEXEC_CORE
903 * This appends the listed symbols to /proc/vmcore
905 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
906 * obtain access to symbols that are otherwise very difficult to locate. These
907 * symbols are specifically used so that utilities can access and extract the
908 * dmesg log from a vmcore file after a crash.
910 void log_buf_kexec_setup(void)
912 VMCOREINFO_SYMBOL(log_buf);
913 VMCOREINFO_SYMBOL(log_buf_len);
914 VMCOREINFO_SYMBOL(log_first_idx);
915 VMCOREINFO_SYMBOL(log_next_idx);
917 * Export struct printk_log size and field offsets. User space tools can
918 * parse it and detect any changes to structure down the line.
920 VMCOREINFO_STRUCT_SIZE(printk_log);
921 VMCOREINFO_OFFSET(printk_log, ts_nsec);
922 VMCOREINFO_OFFSET(printk_log, len);
923 VMCOREINFO_OFFSET(printk_log, text_len);
924 VMCOREINFO_OFFSET(printk_log, dict_len);
928 /* requested log_buf_len from kernel cmdline */
929 static unsigned long __initdata new_log_buf_len;
931 /* we practice scaling the ring buffer by powers of 2 */
932 static void __init log_buf_len_update(unsigned size)
935 size = roundup_pow_of_two(size);
936 if (size > log_buf_len)
937 new_log_buf_len = size;
940 /* save requested log_buf_len since it's too early to process it */
941 static int __init log_buf_len_setup(char *str)
943 unsigned size = memparse(str, &str);
945 log_buf_len_update(size);
949 early_param("log_buf_len", log_buf_len_setup);
952 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
954 static void __init log_buf_add_cpu(void)
956 unsigned int cpu_extra;
959 * archs should set up cpu_possible_bits properly with
960 * set_cpu_possible() after setup_arch() but just in
961 * case lets ensure this is valid.
963 if (num_possible_cpus() == 1)
966 cpu_extra = (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN;
968 /* by default this will only continue through for large > 64 CPUs */
969 if (cpu_extra <= __LOG_BUF_LEN / 2)
972 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
973 __LOG_CPU_MAX_BUF_LEN);
974 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
976 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN);
978 log_buf_len_update(cpu_extra + __LOG_BUF_LEN);
980 #else /* !CONFIG_SMP */
981 static inline void log_buf_add_cpu(void) {}
982 #endif /* CONFIG_SMP */
984 void __init setup_log_buf(int early)
990 if (log_buf != __log_buf)
993 if (!early && !new_log_buf_len)
996 if (!new_log_buf_len)
1001 memblock_virt_alloc(new_log_buf_len, LOG_ALIGN);
1003 new_log_buf = memblock_virt_alloc_nopanic(new_log_buf_len,
1007 if (unlikely(!new_log_buf)) {
1008 pr_err("log_buf_len: %ld bytes not available\n",
1013 raw_spin_lock_irqsave(&logbuf_lock, flags);
1014 log_buf_len = new_log_buf_len;
1015 log_buf = new_log_buf;
1016 new_log_buf_len = 0;
1017 free = __LOG_BUF_LEN - log_next_idx;
1018 memcpy(log_buf, __log_buf, __LOG_BUF_LEN);
1019 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
1021 pr_info("log_buf_len: %d bytes\n", log_buf_len);
1022 pr_info("early log buf free: %d(%d%%)\n",
1023 free, (free * 100) / __LOG_BUF_LEN);
1026 static bool __read_mostly ignore_loglevel;
1028 static int __init ignore_loglevel_setup(char *str)
1030 ignore_loglevel = true;
1031 pr_info("debug: ignoring loglevel setting.\n");
1036 early_param("ignore_loglevel", ignore_loglevel_setup);
1037 module_param(ignore_loglevel, bool, S_IRUGO | S_IWUSR);
1038 MODULE_PARM_DESC(ignore_loglevel,
1039 "ignore loglevel setting (prints all kernel messages to the console)");
1041 #ifdef CONFIG_BOOT_PRINTK_DELAY
1043 static int boot_delay; /* msecs delay after each printk during bootup */
1044 static unsigned long long loops_per_msec; /* based on boot_delay */
1046 static int __init boot_delay_setup(char *str)
1050 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
1051 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
1053 get_option(&str, &boot_delay);
1054 if (boot_delay > 10 * 1000)
1057 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1058 "HZ: %d, loops_per_msec: %llu\n",
1059 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
1062 early_param("boot_delay", boot_delay_setup);
1064 static void boot_delay_msec(int level)
1066 unsigned long long k;
1067 unsigned long timeout;
1069 if ((boot_delay == 0 || system_state != SYSTEM_BOOTING)
1070 || (level >= console_loglevel && !ignore_loglevel)) {
1074 k = (unsigned long long)loops_per_msec * boot_delay;
1076 timeout = jiffies + msecs_to_jiffies(boot_delay);
1081 * use (volatile) jiffies to prevent
1082 * compiler reduction; loop termination via jiffies
1083 * is secondary and may or may not happen.
1085 if (time_after(jiffies, timeout))
1087 touch_nmi_watchdog();
1091 static inline void boot_delay_msec(int level)
1096 static bool printk_time = IS_ENABLED(CONFIG_PRINTK_TIME);
1097 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
1099 static size_t print_time(u64 ts, char *buf)
1101 unsigned long rem_nsec;
1106 rem_nsec = do_div(ts, 1000000000);
1109 return snprintf(NULL, 0, "[%5lu.000000] ", (unsigned long)ts);
1111 return sprintf(buf, "[%5lu.%06lu] ",
1112 (unsigned long)ts, rem_nsec / 1000);
1115 static size_t print_prefix(const struct printk_log *msg, bool syslog, char *buf)
1118 unsigned int prefix = (msg->facility << 3) | msg->level;
1122 len += sprintf(buf, "<%u>", prefix);
1127 else if (prefix > 99)
1129 else if (prefix > 9)
1134 len += print_time(msg->ts_nsec, buf ? buf + len : NULL);
1138 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
1139 bool syslog, char *buf, size_t size)
1141 const char *text = log_text(msg);
1142 size_t text_size = msg->text_len;
1144 bool newline = true;
1147 if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX))
1150 if (msg->flags & LOG_CONT) {
1151 if ((prev & LOG_CONT) && !(prev & LOG_NEWLINE))
1154 if (!(msg->flags & LOG_NEWLINE))
1159 const char *next = memchr(text, '\n', text_size);
1163 text_len = next - text;
1165 text_size -= next - text;
1167 text_len = text_size;
1171 if (print_prefix(msg, syslog, NULL) +
1172 text_len + 1 >= size - len)
1176 len += print_prefix(msg, syslog, buf + len);
1177 memcpy(buf + len, text, text_len);
1179 if (next || newline)
1182 /* SYSLOG_ACTION_* buffer size only calculation */
1184 len += print_prefix(msg, syslog, NULL);
1186 if (next || newline)
1197 static int syslog_print(char __user *buf, int size)
1200 struct printk_log *msg;
1203 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1211 raw_spin_lock_irq(&logbuf_lock);
1212 if (syslog_seq < log_first_seq) {
1213 /* messages are gone, move to first one */
1214 syslog_seq = log_first_seq;
1215 syslog_idx = log_first_idx;
1219 if (syslog_seq == log_next_seq) {
1220 raw_spin_unlock_irq(&logbuf_lock);
1224 skip = syslog_partial;
1225 msg = log_from_idx(syslog_idx);
1226 n = msg_print_text(msg, syslog_prev, true, text,
1227 LOG_LINE_MAX + PREFIX_MAX);
1228 if (n - syslog_partial <= size) {
1229 /* message fits into buffer, move forward */
1230 syslog_idx = log_next(syslog_idx);
1232 syslog_prev = msg->flags;
1233 n -= syslog_partial;
1236 /* partial read(), remember position */
1238 syslog_partial += n;
1241 raw_spin_unlock_irq(&logbuf_lock);
1246 if (copy_to_user(buf, text + skip, n)) {
1261 static int syslog_print_all(char __user *buf, int size, bool clear)
1267 text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL);
1271 raw_spin_lock_irq(&logbuf_lock);
1276 enum log_flags prev;
1280 if (attempts > 10) {
1285 if (clear_seq < log_first_seq) {
1286 /* messages are gone, move to first available one */
1287 clear_seq = log_first_seq;
1288 clear_idx = log_first_idx;
1292 * Find first record that fits, including all following records,
1293 * into the user-provided buffer for this dump.
1298 while (seq < log_next_seq) {
1299 struct printk_log *msg = log_from_idx(idx);
1301 len += msg_print_text(msg, prev, true, NULL, 0);
1303 idx = log_next(idx);
1308 raw_spin_unlock_irq(&logbuf_lock);
1309 raw_spin_lock_irq(&logbuf_lock);
1310 if (clear_seq < log_first_seq)
1315 /* move first record forward until length fits into the buffer */
1319 while (len > size && seq < log_next_seq) {
1320 struct printk_log *msg = log_from_idx(idx);
1322 len -= msg_print_text(msg, prev, true, NULL, 0);
1324 idx = log_next(idx);
1329 raw_spin_unlock_irq(&logbuf_lock);
1330 raw_spin_lock_irq(&logbuf_lock);
1331 if (clear_seq < log_first_seq)
1336 /* last message fitting into this dump */
1337 next_seq = log_next_seq;
1340 while (len >= 0 && seq < next_seq) {
1341 struct printk_log *msg = log_from_idx(idx);
1344 textlen = msg_print_text(msg, prev, true, text,
1345 LOG_LINE_MAX + PREFIX_MAX);
1350 idx = log_next(idx);
1354 raw_spin_unlock_irq(&logbuf_lock);
1355 if (copy_to_user(buf + len, text, textlen))
1359 raw_spin_lock_irq(&logbuf_lock);
1361 if (seq < log_first_seq) {
1362 /* messages are gone, move to next one */
1363 seq = log_first_seq;
1364 idx = log_first_idx;
1371 clear_seq = log_next_seq;
1372 clear_idx = log_next_idx;
1375 raw_spin_unlock_irq(&logbuf_lock);
1381 int do_syslog(int type, char __user *buf, int len, int source)
1384 static int saved_console_loglevel = LOGLEVEL_DEFAULT;
1387 error = check_syslog_permissions(type, source);
1392 case SYSLOG_ACTION_CLOSE: /* Close log */
1394 case SYSLOG_ACTION_OPEN: /* Open log */
1396 case SYSLOG_ACTION_READ: /* Read from log */
1398 if (!buf || len < 0)
1403 if (!access_ok(VERIFY_WRITE, buf, len)) {
1407 error = wait_event_interruptible(log_wait,
1408 syslog_seq != log_next_seq);
1411 error = syslog_print(buf, len);
1413 /* Read/clear last kernel messages */
1414 case SYSLOG_ACTION_READ_CLEAR:
1417 /* Read last kernel messages */
1418 case SYSLOG_ACTION_READ_ALL:
1420 if (!buf || len < 0)
1425 if (!access_ok(VERIFY_WRITE, buf, len)) {
1429 error = syslog_print_all(buf, len, clear);
1431 /* Clear ring buffer */
1432 case SYSLOG_ACTION_CLEAR:
1433 syslog_print_all(NULL, 0, true);
1435 /* Disable logging to console */
1436 case SYSLOG_ACTION_CONSOLE_OFF:
1437 if (saved_console_loglevel == LOGLEVEL_DEFAULT)
1438 saved_console_loglevel = console_loglevel;
1439 console_loglevel = minimum_console_loglevel;
1441 /* Enable logging to console */
1442 case SYSLOG_ACTION_CONSOLE_ON:
1443 if (saved_console_loglevel != LOGLEVEL_DEFAULT) {
1444 console_loglevel = saved_console_loglevel;
1445 saved_console_loglevel = LOGLEVEL_DEFAULT;
1448 /* Set level of messages printed to console */
1449 case SYSLOG_ACTION_CONSOLE_LEVEL:
1451 if (len < 1 || len > 8)
1453 if (len < minimum_console_loglevel)
1454 len = minimum_console_loglevel;
1455 console_loglevel = len;
1456 /* Implicitly re-enable logging to console */
1457 saved_console_loglevel = LOGLEVEL_DEFAULT;
1460 /* Number of chars in the log buffer */
1461 case SYSLOG_ACTION_SIZE_UNREAD:
1462 raw_spin_lock_irq(&logbuf_lock);
1463 if (syslog_seq < log_first_seq) {
1464 /* messages are gone, move to first one */
1465 syslog_seq = log_first_seq;
1466 syslog_idx = log_first_idx;
1470 if (source == SYSLOG_FROM_PROC) {
1472 * Short-cut for poll(/"proc/kmsg") which simply checks
1473 * for pending data, not the size; return the count of
1474 * records, not the length.
1476 error = log_next_seq - syslog_seq;
1478 u64 seq = syslog_seq;
1479 u32 idx = syslog_idx;
1480 enum log_flags prev = syslog_prev;
1483 while (seq < log_next_seq) {
1484 struct printk_log *msg = log_from_idx(idx);
1486 error += msg_print_text(msg, prev, true, NULL, 0);
1487 idx = log_next(idx);
1491 error -= syslog_partial;
1493 raw_spin_unlock_irq(&logbuf_lock);
1495 /* Size of the log buffer */
1496 case SYSLOG_ACTION_SIZE_BUFFER:
1497 error = log_buf_len;
1507 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
1509 return do_syslog(type, buf, len, SYSLOG_FROM_READER);
1513 * Call the console drivers, asking them to write out
1514 * log_buf[start] to log_buf[end - 1].
1515 * The console_lock must be held.
1517 static void call_console_drivers(int level,
1518 const char *ext_text, size_t ext_len,
1519 const char *text, size_t len)
1521 struct console *con;
1523 trace_console(text, len);
1525 if (level >= console_loglevel && !ignore_loglevel)
1527 if (!console_drivers)
1530 if (IS_ENABLED(CONFIG_PREEMPT_RT_BASE)) {
1531 if (in_irq() || in_nmi())
1536 for_each_console(con) {
1537 if (exclusive_console && con != exclusive_console)
1539 if (!(con->flags & CON_ENABLED))
1543 if (!cpu_online(smp_processor_id()) &&
1544 !(con->flags & CON_ANYTIME))
1546 if (con->flags & CON_EXTENDED)
1547 con->write(con, ext_text, ext_len);
1549 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);
1577 * Check if we have any console that is capable of printing while cpu is
1578 * booting or shutting down. Requires console_sem.
1580 static int have_callable_console(void)
1582 struct console *con;
1584 for_each_console(con)
1585 if (con->flags & CON_ANYTIME)
1592 * Can we actually use the console at this time on this cpu?
1594 * Console drivers may assume that per-cpu resources have been allocated. So
1595 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1596 * call them until this CPU is officially up.
1598 static inline int can_use_console(unsigned int cpu)
1600 return cpu_online(cpu) || have_callable_console();
1604 * Try to get console ownership to actually show the kernel
1605 * messages from a 'printk'. Return true (and with the
1606 * console_lock held, and 'console_locked' set) if it
1607 * is successful, false otherwise.
1609 static int console_trylock_for_printk(void)
1611 unsigned int cpu = smp_processor_id();
1612 #ifdef CONFIG_PREEMPT_RT_FULL
1613 int lock = !early_boot_irqs_disabled && (preempt_count() == 0) &&
1622 if (!console_trylock())
1625 * If we can't use the console, we need to release the console
1626 * semaphore by hand to avoid flushing the buffer. We need to hold the
1627 * console semaphore in order to do this test safely.
1629 if (!can_use_console(cpu)) {
1637 int printk_delay_msec __read_mostly;
1639 static inline void printk_delay(void)
1641 if (unlikely(printk_delay_msec)) {
1642 int m = printk_delay_msec;
1646 touch_nmi_watchdog();
1652 * Continuation lines are buffered, and not committed to the record buffer
1653 * until the line is complete, or a race forces it. The line fragments
1654 * though, are printed immediately to the consoles to ensure everything has
1655 * reached the console in case of a kernel crash.
1657 static struct cont {
1658 char buf[LOG_LINE_MAX];
1659 size_t len; /* length == 0 means unused buffer */
1660 size_t cons; /* bytes written to console */
1661 struct task_struct *owner; /* task of first print*/
1662 u64 ts_nsec; /* time of first print */
1663 u8 level; /* log level of first message */
1664 u8 facility; /* log facility of first message */
1665 enum log_flags flags; /* prefix, newline flags */
1666 bool flushed:1; /* buffer sealed and committed */
1669 static void cont_flush(enum log_flags flags)
1678 * If a fragment of this line was directly flushed to the
1679 * console; wait for the console to pick up the rest of the
1680 * line. LOG_NOCONS suppresses a duplicated output.
1682 log_store(cont.facility, cont.level, flags | LOG_NOCONS,
1683 cont.ts_nsec, NULL, 0, cont.buf, cont.len);
1685 cont.flushed = true;
1688 * If no fragment of this line ever reached the console,
1689 * just submit it to the store and free the buffer.
1691 log_store(cont.facility, cont.level, flags, 0,
1692 NULL, 0, cont.buf, cont.len);
1697 static bool cont_add(int facility, int level, const char *text, size_t len)
1699 if (cont.len && cont.flushed)
1703 * If ext consoles are present, flush and skip in-kernel
1704 * continuation. See nr_ext_console_drivers definition. Also, if
1705 * the line gets too long, split it up in separate records.
1707 if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
1708 cont_flush(LOG_CONT);
1713 cont.facility = facility;
1715 cont.owner = current;
1716 cont.ts_nsec = local_clock();
1719 cont.flushed = false;
1722 memcpy(cont.buf + cont.len, text, len);
1725 if (cont.len > (sizeof(cont.buf) * 80) / 100)
1726 cont_flush(LOG_CONT);
1731 static size_t cont_print_text(char *text, size_t size)
1736 if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
1737 textlen += print_time(cont.ts_nsec, text);
1741 len = cont.len - cont.cons;
1745 memcpy(text + textlen, cont.buf + cont.cons, len);
1747 cont.cons = cont.len;
1751 if (cont.flags & LOG_NEWLINE)
1752 text[textlen++] = '\n';
1753 /* got everything, release buffer */
1759 asmlinkage int vprintk_emit(int facility, int level,
1760 const char *dict, size_t dictlen,
1761 const char *fmt, va_list args)
1763 static int recursion_bug;
1764 static char textbuf[LOG_LINE_MAX];
1765 char *text = textbuf;
1766 size_t text_len = 0;
1767 enum log_flags lflags = 0;
1768 unsigned long flags;
1770 int printed_len = 0;
1771 bool in_sched = false;
1772 /* cpu currently holding logbuf_lock in this function */
1773 static unsigned int logbuf_cpu = UINT_MAX;
1776 * Fall back to early_printk if a debugging subsystem has
1777 * killed printk output
1779 if (unlikely(forced_early_printk(fmt, args)))
1782 if (level == LOGLEVEL_SCHED) {
1783 level = LOGLEVEL_DEFAULT;
1787 boot_delay_msec(level);
1790 /* This stops the holder of console_sem just where we want him */
1791 local_irq_save(flags);
1792 this_cpu = smp_processor_id();
1795 * Ouch, printk recursed into itself!
1797 if (unlikely(logbuf_cpu == this_cpu)) {
1799 * If a crash is occurring during printk() on this CPU,
1800 * then try to get the crash message out but make sure
1801 * we can't deadlock. Otherwise just return to avoid the
1802 * recursion and return - but flag the recursion so that
1803 * it can be printed at the next appropriate moment:
1805 if (!oops_in_progress && !lockdep_recursing(current)) {
1807 local_irq_restore(flags);
1814 raw_spin_lock(&logbuf_lock);
1815 logbuf_cpu = this_cpu;
1817 if (unlikely(recursion_bug)) {
1818 static const char recursion_msg[] =
1819 "BUG: recent printk recursion!";
1822 /* emit KERN_CRIT message */
1823 printed_len += log_store(0, 2, LOG_PREFIX|LOG_NEWLINE, 0,
1824 NULL, 0, recursion_msg,
1825 strlen(recursion_msg));
1829 * The printf needs to come first; we need the syslog
1830 * prefix which might be passed-in as a parameter.
1832 text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
1834 /* mark and strip a trailing newline */
1835 if (text_len && text[text_len-1] == '\n') {
1837 lflags |= LOG_NEWLINE;
1840 /* strip kernel syslog prefix and extract log level or control flags */
1841 if (facility == 0) {
1842 int kern_level = printk_get_level(text);
1845 const char *end_of_header = printk_skip_level(text);
1846 switch (kern_level) {
1848 if (level == LOGLEVEL_DEFAULT)
1849 level = kern_level - '0';
1851 case 'd': /* KERN_DEFAULT */
1852 lflags |= LOG_PREFIX;
1855 * No need to check length here because vscnprintf
1856 * put '\0' at the end of the string. Only valid and
1857 * newly printed level is detected.
1859 text_len -= end_of_header - text;
1860 text = (char *)end_of_header;
1864 if (level == LOGLEVEL_DEFAULT)
1865 level = default_message_loglevel;
1868 lflags |= LOG_PREFIX|LOG_NEWLINE;
1870 if (!(lflags & LOG_NEWLINE)) {
1872 * Flush the conflicting buffer. An earlier newline was missing,
1873 * or another task also prints continuation lines.
1875 if (cont.len && (lflags & LOG_PREFIX || cont.owner != current))
1876 cont_flush(LOG_NEWLINE);
1878 /* buffer line if possible, otherwise store it right away */
1879 if (cont_add(facility, level, text, text_len))
1880 printed_len += text_len;
1882 printed_len += log_store(facility, level,
1883 lflags | LOG_CONT, 0,
1884 dict, dictlen, text, text_len);
1886 bool stored = false;
1889 * If an earlier newline was missing and it was the same task,
1890 * either merge it with the current buffer and flush, or if
1891 * there was a race with interrupts (prefix == true) then just
1892 * flush it out and store this line separately.
1893 * If the preceding printk was from a different task and missed
1894 * a newline, flush and append the newline.
1897 if (cont.owner == current && !(lflags & LOG_PREFIX))
1898 stored = cont_add(facility, level, text,
1900 cont_flush(LOG_NEWLINE);
1904 printed_len += text_len;
1906 printed_len += log_store(facility, level, lflags, 0,
1907 dict, dictlen, text, text_len);
1910 logbuf_cpu = UINT_MAX;
1911 raw_spin_unlock(&logbuf_lock);
1913 local_irq_restore(flags);
1915 /* If called from the scheduler, we can not call up(). */
1919 * Disable preemption to avoid being preempted while holding
1920 * console_sem which would prevent anyone from printing to
1925 * Try to acquire and then immediately release the console
1926 * semaphore. The release will print out buffers and wake up
1927 * /dev/kmsg and syslog() users.
1929 if (console_trylock_for_printk())
1937 EXPORT_SYMBOL(vprintk_emit);
1939 asmlinkage int vprintk(const char *fmt, va_list args)
1941 return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1943 EXPORT_SYMBOL(vprintk);
1945 asmlinkage int printk_emit(int facility, int level,
1946 const char *dict, size_t dictlen,
1947 const char *fmt, ...)
1952 va_start(args, fmt);
1953 r = vprintk_emit(facility, level, dict, dictlen, fmt, args);
1958 EXPORT_SYMBOL(printk_emit);
1960 int vprintk_default(const char *fmt, va_list args)
1964 #ifdef CONFIG_KGDB_KDB
1965 if (unlikely(kdb_trap_printk)) {
1966 r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
1970 r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
1974 EXPORT_SYMBOL_GPL(vprintk_default);
1977 * This allows printk to be diverted to another function per cpu.
1978 * This is useful for calling printk functions from within NMI
1979 * without worrying about race conditions that can lock up the
1982 DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
1985 * printk - print a kernel message
1986 * @fmt: format string
1988 * This is printk(). It can be called from any context. We want it to work.
1990 * We try to grab the console_lock. If we succeed, it's easy - we log the
1991 * output and call the console drivers. If we fail to get the semaphore, we
1992 * place the output into the log buffer and return. The current holder of
1993 * the console_sem will notice the new output in console_unlock(); and will
1994 * send it to the consoles before releasing the lock.
1996 * One effect of this deferred printing is that code which calls printk() and
1997 * then changes console_loglevel may break. This is because console_loglevel
1998 * is inspected when the actual printing occurs.
2003 * See the vsnprintf() documentation for format string extensions over C99.
2005 asmlinkage __visible int printk(const char *fmt, ...)
2007 printk_func_t vprintk_func;
2011 va_start(args, fmt);
2014 * If a caller overrides the per_cpu printk_func, then it needs
2015 * to disable preemption when calling printk(). Otherwise
2016 * the printk_func should be set to the default. No need to
2017 * disable preemption here.
2019 vprintk_func = this_cpu_read(printk_func);
2020 r = vprintk_func(fmt, args);
2026 EXPORT_SYMBOL(printk);
2028 #else /* CONFIG_PRINTK */
2030 #define LOG_LINE_MAX 0
2031 #define PREFIX_MAX 0
2033 static u64 syslog_seq;
2034 static u32 syslog_idx;
2035 static u64 console_seq;
2036 static u32 console_idx;
2037 static enum log_flags syslog_prev;
2038 static u64 log_first_seq;
2039 static u32 log_first_idx;
2040 static u64 log_next_seq;
2041 static enum log_flags console_prev;
2042 static struct cont {
2048 static char *log_text(const struct printk_log *msg) { return NULL; }
2049 static char *log_dict(const struct printk_log *msg) { return NULL; }
2050 static struct printk_log *log_from_idx(u32 idx) { return NULL; }
2051 static u32 log_next(u32 idx) { return 0; }
2052 static ssize_t msg_print_ext_header(char *buf, size_t size,
2053 struct printk_log *msg, u64 seq,
2054 enum log_flags prev_flags) { return 0; }
2055 static ssize_t msg_print_ext_body(char *buf, size_t size,
2056 char *dict, size_t dict_len,
2057 char *text, size_t text_len) { return 0; }
2058 static void call_console_drivers(int level,
2059 const char *ext_text, size_t ext_len,
2060 const char *text, size_t len) {}
2061 static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
2062 bool syslog, char *buf, size_t size) { return 0; }
2063 static size_t cont_print_text(char *text, size_t size) { return 0; }
2065 /* Still needs to be defined for users */
2066 DEFINE_PER_CPU(printk_func_t, printk_func);
2068 #endif /* CONFIG_PRINTK */
2070 static int __add_preferred_console(char *name, int idx, char *options,
2073 struct console_cmdline *c;
2077 * See if this tty is not yet registered, and
2078 * if we have a slot free.
2080 for (i = 0, c = console_cmdline;
2081 i < MAX_CMDLINECONSOLES && c->name[0];
2083 if (strcmp(c->name, name) == 0 && c->index == idx) {
2085 selected_console = i;
2089 if (i == MAX_CMDLINECONSOLES)
2092 selected_console = i;
2093 strlcpy(c->name, name, sizeof(c->name));
2094 c->options = options;
2095 braille_set_options(c, brl_options);
2101 * Set up a console. Called via do_early_param() in init/main.c
2102 * for each "console=" parameter in the boot command line.
2104 static int __init console_setup(char *str)
2106 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
2107 char *s, *options, *brl_options = NULL;
2110 if (_braille_console_setup(&str, &brl_options))
2114 * Decode str into name, index, options.
2116 if (str[0] >= '0' && str[0] <= '9') {
2117 strcpy(buf, "ttyS");
2118 strncpy(buf + 4, str, sizeof(buf) - 5);
2120 strncpy(buf, str, sizeof(buf) - 1);
2122 buf[sizeof(buf) - 1] = 0;
2123 options = strchr(str, ',');
2127 if (!strcmp(str, "ttya"))
2128 strcpy(buf, "ttyS0");
2129 if (!strcmp(str, "ttyb"))
2130 strcpy(buf, "ttyS1");
2132 for (s = buf; *s; s++)
2133 if (isdigit(*s) || *s == ',')
2135 idx = simple_strtoul(s, NULL, 10);
2138 __add_preferred_console(buf, idx, options, brl_options);
2139 console_set_on_cmdline = 1;
2142 __setup("console=", console_setup);
2145 * add_preferred_console - add a device to the list of preferred consoles.
2146 * @name: device name
2147 * @idx: device index
2148 * @options: options for this console
2150 * The last preferred console added will be used for kernel messages
2151 * and stdin/out/err for init. Normally this is used by console_setup
2152 * above to handle user-supplied console arguments; however it can also
2153 * be used by arch-specific code either to override the user or more
2154 * commonly to provide a default console (ie from PROM variables) when
2155 * the user has not supplied one.
2157 int add_preferred_console(char *name, int idx, char *options)
2159 return __add_preferred_console(name, idx, options, NULL);
2162 bool console_suspend_enabled = true;
2163 EXPORT_SYMBOL(console_suspend_enabled);
2165 static int __init console_suspend_disable(char *str)
2167 console_suspend_enabled = false;
2170 __setup("no_console_suspend", console_suspend_disable);
2171 module_param_named(console_suspend, console_suspend_enabled,
2172 bool, S_IRUGO | S_IWUSR);
2173 MODULE_PARM_DESC(console_suspend, "suspend console during suspend"
2174 " and hibernate operations");
2177 * suspend_console - suspend the console subsystem
2179 * This disables printk() while we go into suspend states
2181 void suspend_console(void)
2183 if (!console_suspend_enabled)
2185 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2187 console_suspended = 1;
2191 void resume_console(void)
2193 if (!console_suspend_enabled)
2196 console_suspended = 0;
2201 * console_cpu_notify - print deferred console messages after CPU hotplug
2202 * @self: notifier struct
2203 * @action: CPU hotplug event
2206 * If printk() is called from a CPU that is not online yet, the messages
2207 * will be spooled but will not show up on the console. This function is
2208 * called when a new CPU comes online (or fails to come up), and ensures
2209 * that any such output gets printed.
2211 static int console_cpu_notify(struct notifier_block *self,
2212 unsigned long action, void *hcpu)
2217 case CPU_DOWN_FAILED:
2218 case CPU_UP_CANCELED:
2226 * console_lock - lock the console system for exclusive use.
2228 * Acquires a lock which guarantees that the caller has
2229 * exclusive access to the console system and the console_drivers list.
2231 * Can sleep, returns nothing.
2233 void console_lock(void)
2238 if (console_suspended)
2241 console_may_schedule = 1;
2243 EXPORT_SYMBOL(console_lock);
2246 * console_trylock - try to lock the console system for exclusive use.
2248 * Try to acquire a lock which guarantees that the caller has exclusive
2249 * access to the console system and the console_drivers list.
2251 * returns 1 on success, and 0 on failure to acquire the lock.
2253 int console_trylock(void)
2255 if (down_trylock_console_sem())
2257 if (console_suspended) {
2262 console_may_schedule = 0;
2265 EXPORT_SYMBOL(console_trylock);
2267 int is_console_locked(void)
2269 return console_locked;
2272 static void console_cont_flush(char *text, size_t size)
2274 unsigned long flags;
2277 raw_spin_lock_irqsave(&logbuf_lock, flags);
2283 * We still queue earlier records, likely because the console was
2284 * busy. The earlier ones need to be printed before this one, we
2285 * did not flush any fragment so far, so just let it queue up.
2287 if (console_seq < log_next_seq && !cont.cons)
2290 len = cont_print_text(text, size);
2291 #ifdef CONFIG_PREEMPT_RT_FULL
2292 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2293 call_console_drivers(cont.level, NULL, 0, text, len);
2295 raw_spin_unlock(&logbuf_lock);
2296 stop_critical_timings();
2297 call_console_drivers(cont.level, NULL, 0, text, len);
2298 start_critical_timings();
2299 local_irq_restore(flags);
2303 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2307 * console_unlock - unlock the console system
2309 * Releases the console_lock which the caller holds on the console system
2310 * and the console driver list.
2312 * While the console_lock was held, console output may have been buffered
2313 * by printk(). If this is the case, console_unlock(); emits
2314 * the output prior to releasing the lock.
2316 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2318 * console_unlock(); may be called from any context.
2320 void console_unlock(void)
2322 static char ext_text[CONSOLE_EXT_LOG_MAX];
2323 static char text[LOG_LINE_MAX + PREFIX_MAX];
2324 static u64 seen_seq;
2325 unsigned long flags;
2326 bool wake_klogd = false;
2327 bool do_cond_resched, retry;
2329 if (console_suspended) {
2335 * Console drivers are called under logbuf_lock, so
2336 * @console_may_schedule should be cleared before; however, we may
2337 * end up dumping a lot of lines, for example, if called from
2338 * console registration path, and should invoke cond_resched()
2339 * between lines if allowable. Not doing so can cause a very long
2340 * scheduling stall on a slow console leading to RCU stall and
2341 * softlockup warnings which exacerbate the issue with more
2342 * messages practically incapacitating the system.
2344 do_cond_resched = console_may_schedule;
2345 console_may_schedule = 0;
2347 /* flush buffered message fragment immediately to console */
2348 console_cont_flush(text, sizeof(text));
2351 struct printk_log *msg;
2356 raw_spin_lock_irqsave(&logbuf_lock, flags);
2357 if (seen_seq != log_next_seq) {
2359 seen_seq = log_next_seq;
2362 if (console_seq < log_first_seq) {
2363 len = sprintf(text, "** %u printk messages dropped ** ",
2364 (unsigned)(log_first_seq - console_seq));
2366 /* messages are gone, move to first one */
2367 console_seq = log_first_seq;
2368 console_idx = log_first_idx;
2374 if (console_seq == log_next_seq)
2377 msg = log_from_idx(console_idx);
2378 if (msg->flags & LOG_NOCONS) {
2380 * Skip record we have buffered and already printed
2381 * directly to the console when we received it.
2383 console_idx = log_next(console_idx);
2386 * We will get here again when we register a new
2387 * CON_PRINTBUFFER console. Clear the flag so we
2388 * will properly dump everything later.
2390 msg->flags &= ~LOG_NOCONS;
2391 console_prev = msg->flags;
2396 len += msg_print_text(msg, console_prev, false,
2397 text + len, sizeof(text) - len);
2398 if (nr_ext_console_drivers) {
2399 ext_len = msg_print_ext_header(ext_text,
2401 msg, console_seq, console_prev);
2402 ext_len += msg_print_ext_body(ext_text + ext_len,
2403 sizeof(ext_text) - ext_len,
2404 log_dict(msg), msg->dict_len,
2405 log_text(msg), msg->text_len);
2407 console_idx = log_next(console_idx);
2409 console_prev = msg->flags;
2410 #ifdef CONFIG_PREEMPT_RT_FULL
2411 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2412 call_console_drivers(level, ext_text, ext_len, text, len);
2414 raw_spin_unlock(&logbuf_lock);
2416 stop_critical_timings(); /* don't trace print latency */
2417 call_console_drivers(level, ext_text, ext_len, text, len);
2418 start_critical_timings();
2419 local_irq_restore(flags);
2421 if (do_cond_resched)
2426 /* Release the exclusive_console once it is used */
2427 if (unlikely(exclusive_console))
2428 exclusive_console = NULL;
2430 raw_spin_unlock(&logbuf_lock);
2435 * Someone could have filled up the buffer again, so re-check if there's
2436 * something to flush. In case we cannot trylock the console_sem again,
2437 * there's a new owner and the console_unlock() from them will do the
2438 * flush, no worries.
2440 raw_spin_lock(&logbuf_lock);
2441 retry = console_seq != log_next_seq;
2442 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2444 if (retry && console_trylock())
2450 EXPORT_SYMBOL(console_unlock);
2453 * console_conditional_schedule - yield the CPU if required
2455 * If the console code is currently allowed to sleep, and
2456 * if this CPU should yield the CPU to another task, do
2459 * Must be called within console_lock();.
2461 void __sched console_conditional_schedule(void)
2463 if (console_may_schedule)
2466 EXPORT_SYMBOL(console_conditional_schedule);
2468 void console_unblank(void)
2472 if (IS_ENABLED(CONFIG_PREEMPT_RT_BASE)) {
2473 if (in_irq() || in_nmi())
2478 * console_unblank can no longer be called in interrupt context unless
2479 * oops_in_progress is set to 1..
2481 if (oops_in_progress) {
2482 if (down_trylock_console_sem() != 0)
2488 console_may_schedule = 0;
2490 if ((c->flags & CON_ENABLED) && c->unblank)
2496 * console_flush_on_panic - flush console content on panic
2498 * Immediately output all pending messages no matter what.
2500 void console_flush_on_panic(void)
2503 * If someone else is holding the console lock, trylock will fail
2504 * and may_schedule may be set. Ignore and proceed to unlock so
2505 * that messages are flushed out. As this can be called from any
2506 * context and we don't want to get preempted while flushing,
2507 * ensure may_schedule is cleared.
2510 console_may_schedule = 0;
2515 * Return the console tty driver structure and its associated index
2517 struct tty_driver *console_device(int *index)
2520 struct tty_driver *driver = NULL;
2523 for_each_console(c) {
2526 driver = c->device(c, index);
2535 * Prevent further output on the passed console device so that (for example)
2536 * serial drivers can disable console output before suspending a port, and can
2537 * re-enable output afterwards.
2539 void console_stop(struct console *console)
2542 console->flags &= ~CON_ENABLED;
2545 EXPORT_SYMBOL(console_stop);
2547 void console_start(struct console *console)
2550 console->flags |= CON_ENABLED;
2553 EXPORT_SYMBOL(console_start);
2555 static int __read_mostly keep_bootcon;
2557 static int __init keep_bootcon_setup(char *str)
2560 pr_info("debug: skip boot console de-registration.\n");
2565 early_param("keep_bootcon", keep_bootcon_setup);
2568 * The console driver calls this routine during kernel initialization
2569 * to register the console printing procedure with printk() and to
2570 * print any messages that were printed by the kernel before the
2571 * console driver was initialized.
2573 * This can happen pretty early during the boot process (because of
2574 * early_printk) - sometimes before setup_arch() completes - be careful
2575 * of what kernel features are used - they may not be initialised yet.
2577 * There are two types of consoles - bootconsoles (early_printk) and
2578 * "real" consoles (everything which is not a bootconsole) which are
2579 * handled differently.
2580 * - Any number of bootconsoles can be registered at any time.
2581 * - As soon as a "real" console is registered, all bootconsoles
2582 * will be unregistered automatically.
2583 * - Once a "real" console is registered, any attempt to register a
2584 * bootconsoles will be rejected
2586 void register_console(struct console *newcon)
2589 unsigned long flags;
2590 struct console *bcon = NULL;
2591 struct console_cmdline *c;
2593 if (console_drivers)
2594 for_each_console(bcon)
2595 if (WARN(bcon == newcon,
2596 "console '%s%d' already registered\n",
2597 bcon->name, bcon->index))
2601 * before we register a new CON_BOOT console, make sure we don't
2602 * already have a valid console
2604 if (console_drivers && newcon->flags & CON_BOOT) {
2605 /* find the last or real console */
2606 for_each_console(bcon) {
2607 if (!(bcon->flags & CON_BOOT)) {
2608 pr_info("Too late to register bootconsole %s%d\n",
2609 newcon->name, newcon->index);
2615 if (console_drivers && console_drivers->flags & CON_BOOT)
2616 bcon = console_drivers;
2618 if (preferred_console < 0 || bcon || !console_drivers)
2619 preferred_console = selected_console;
2622 * See if we want to use this console driver. If we
2623 * didn't select a console we take the first one
2624 * that registers here.
2626 if (preferred_console < 0) {
2627 if (newcon->index < 0)
2629 if (newcon->setup == NULL ||
2630 newcon->setup(newcon, NULL) == 0) {
2631 newcon->flags |= CON_ENABLED;
2632 if (newcon->device) {
2633 newcon->flags |= CON_CONSDEV;
2634 preferred_console = 0;
2640 * See if this console matches one we selected on
2643 for (i = 0, c = console_cmdline;
2644 i < MAX_CMDLINECONSOLES && c->name[0];
2646 if (!newcon->match ||
2647 newcon->match(newcon, c->name, c->index, c->options) != 0) {
2648 /* default matching */
2649 BUILD_BUG_ON(sizeof(c->name) != sizeof(newcon->name));
2650 if (strcmp(c->name, newcon->name) != 0)
2652 if (newcon->index >= 0 &&
2653 newcon->index != c->index)
2655 if (newcon->index < 0)
2656 newcon->index = c->index;
2658 if (_braille_register_console(newcon, c))
2661 if (newcon->setup &&
2662 newcon->setup(newcon, c->options) != 0)
2666 newcon->flags |= CON_ENABLED;
2667 if (i == selected_console) {
2668 newcon->flags |= CON_CONSDEV;
2669 preferred_console = selected_console;
2674 if (!(newcon->flags & CON_ENABLED))
2678 * If we have a bootconsole, and are switching to a real console,
2679 * don't print everything out again, since when the boot console, and
2680 * the real console are the same physical device, it's annoying to
2681 * see the beginning boot messages twice
2683 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
2684 newcon->flags &= ~CON_PRINTBUFFER;
2687 * Put this console in the list - keep the
2688 * preferred driver at the head of the list.
2691 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
2692 newcon->next = console_drivers;
2693 console_drivers = newcon;
2695 newcon->next->flags &= ~CON_CONSDEV;
2697 newcon->next = console_drivers->next;
2698 console_drivers->next = newcon;
2701 if (newcon->flags & CON_EXTENDED)
2702 if (!nr_ext_console_drivers++)
2703 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2705 if (newcon->flags & CON_PRINTBUFFER) {
2707 * console_unlock(); will print out the buffered messages
2710 raw_spin_lock_irqsave(&logbuf_lock, flags);
2711 console_seq = syslog_seq;
2712 console_idx = syslog_idx;
2713 console_prev = syslog_prev;
2714 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2716 * We're about to replay the log buffer. Only do this to the
2717 * just-registered console to avoid excessive message spam to
2718 * the already-registered consoles.
2720 exclusive_console = newcon;
2723 console_sysfs_notify();
2726 * By unregistering the bootconsoles after we enable the real console
2727 * we get the "console xxx enabled" message on all the consoles -
2728 * boot consoles, real consoles, etc - this is to ensure that end
2729 * users know there might be something in the kernel's log buffer that
2730 * went to the bootconsole (that they do not see on the real console)
2732 pr_info("%sconsole [%s%d] enabled\n",
2733 (newcon->flags & CON_BOOT) ? "boot" : "" ,
2734 newcon->name, newcon->index);
2736 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
2738 /* We need to iterate through all boot consoles, to make
2739 * sure we print everything out, before we unregister them.
2741 for_each_console(bcon)
2742 if (bcon->flags & CON_BOOT)
2743 unregister_console(bcon);
2746 EXPORT_SYMBOL(register_console);
2748 int unregister_console(struct console *console)
2750 struct console *a, *b;
2753 pr_info("%sconsole [%s%d] disabled\n",
2754 (console->flags & CON_BOOT) ? "boot" : "" ,
2755 console->name, console->index);
2757 res = _braille_unregister_console(console);
2763 if (console_drivers == console) {
2764 console_drivers=console->next;
2766 } else if (console_drivers) {
2767 for (a=console_drivers->next, b=console_drivers ;
2768 a; b=a, a=b->next) {
2777 if (!res && (console->flags & CON_EXTENDED))
2778 nr_ext_console_drivers--;
2781 * If this isn't the last console and it has CON_CONSDEV set, we
2782 * need to set it on the next preferred console.
2784 if (console_drivers != NULL && console->flags & CON_CONSDEV)
2785 console_drivers->flags |= CON_CONSDEV;
2787 console->flags &= ~CON_ENABLED;
2789 console_sysfs_notify();
2792 EXPORT_SYMBOL(unregister_console);
2794 static int __init printk_late_init(void)
2796 struct console *con;
2798 for_each_console(con) {
2799 if (!keep_bootcon && con->flags & CON_BOOT) {
2800 unregister_console(con);
2803 hotcpu_notifier(console_cpu_notify, 0);
2806 late_initcall(printk_late_init);
2808 #if defined CONFIG_PRINTK
2810 * Delayed printk version, for scheduler-internal messages:
2812 #define PRINTK_PENDING_WAKEUP 0x01
2813 #define PRINTK_PENDING_OUTPUT 0x02
2815 static DEFINE_PER_CPU(int, printk_pending);
2817 static void wake_up_klogd_work_func(struct irq_work *irq_work)
2819 int pending = __this_cpu_xchg(printk_pending, 0);
2821 if (pending & PRINTK_PENDING_OUTPUT) {
2822 /* If trylock fails, someone else is doing the printing */
2823 if (console_trylock())
2827 if (pending & PRINTK_PENDING_WAKEUP)
2828 wake_up_interruptible(&log_wait);
2831 static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
2832 .func = wake_up_klogd_work_func,
2833 .flags = IRQ_WORK_LAZY,
2836 void wake_up_klogd(void)
2839 if (waitqueue_active(&log_wait)) {
2840 this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
2841 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2846 int printk_deferred(const char *fmt, ...)
2852 va_start(args, fmt);
2853 r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
2856 __this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
2857 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
2864 * printk rate limiting, lifted from the networking subsystem.
2866 * This enforces a rate limit: not more than 10 kernel messages
2867 * every 5s to make a denial-of-service attack impossible.
2869 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
2871 int __printk_ratelimit(const char *func)
2873 return ___ratelimit(&printk_ratelimit_state, func);
2875 EXPORT_SYMBOL(__printk_ratelimit);
2878 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2879 * @caller_jiffies: pointer to caller's state
2880 * @interval_msecs: minimum interval between prints
2882 * printk_timed_ratelimit() returns true if more than @interval_msecs
2883 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2886 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
2887 unsigned int interval_msecs)
2889 unsigned long elapsed = jiffies - *caller_jiffies;
2891 if (*caller_jiffies && elapsed <= msecs_to_jiffies(interval_msecs))
2894 *caller_jiffies = jiffies;
2897 EXPORT_SYMBOL(printk_timed_ratelimit);
2899 static DEFINE_SPINLOCK(dump_list_lock);
2900 static LIST_HEAD(dump_list);
2903 * kmsg_dump_register - register a kernel log dumper.
2904 * @dumper: pointer to the kmsg_dumper structure
2906 * Adds a kernel log dumper to the system. The dump callback in the
2907 * structure will be called when the kernel oopses or panics and must be
2908 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2910 int kmsg_dump_register(struct kmsg_dumper *dumper)
2912 unsigned long flags;
2915 /* The dump callback needs to be set */
2919 spin_lock_irqsave(&dump_list_lock, flags);
2920 /* Don't allow registering multiple times */
2921 if (!dumper->registered) {
2922 dumper->registered = 1;
2923 list_add_tail_rcu(&dumper->list, &dump_list);
2926 spin_unlock_irqrestore(&dump_list_lock, flags);
2930 EXPORT_SYMBOL_GPL(kmsg_dump_register);
2933 * kmsg_dump_unregister - unregister a kmsg dumper.
2934 * @dumper: pointer to the kmsg_dumper structure
2936 * Removes a dump device from the system. Returns zero on success and
2937 * %-EINVAL otherwise.
2939 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
2941 unsigned long flags;
2944 spin_lock_irqsave(&dump_list_lock, flags);
2945 if (dumper->registered) {
2946 dumper->registered = 0;
2947 list_del_rcu(&dumper->list);
2950 spin_unlock_irqrestore(&dump_list_lock, flags);
2955 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
2957 static bool always_kmsg_dump;
2958 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
2961 * kmsg_dump - dump kernel log to kernel message dumpers.
2962 * @reason: the reason (oops, panic etc) for dumping
2964 * Call each of the registered dumper's dump() callback, which can
2965 * retrieve the kmsg records with kmsg_dump_get_line() or
2966 * kmsg_dump_get_buffer().
2968 void kmsg_dump(enum kmsg_dump_reason reason)
2970 struct kmsg_dumper *dumper;
2971 unsigned long flags;
2973 if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
2977 list_for_each_entry_rcu(dumper, &dump_list, list) {
2978 if (dumper->max_reason && reason > dumper->max_reason)
2981 /* initialize iterator with data about the stored records */
2982 dumper->active = true;
2984 raw_spin_lock_irqsave(&logbuf_lock, flags);
2985 dumper->cur_seq = clear_seq;
2986 dumper->cur_idx = clear_idx;
2987 dumper->next_seq = log_next_seq;
2988 dumper->next_idx = log_next_idx;
2989 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
2991 /* invoke dumper which will iterate over records */
2992 dumper->dump(dumper, reason);
2994 /* reset iterator */
2995 dumper->active = false;
3001 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
3002 * @dumper: registered kmsg dumper
3003 * @syslog: include the "<4>" prefixes
3004 * @line: buffer to copy the line to
3005 * @size: maximum size of the buffer
3006 * @len: length of line placed into buffer
3008 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3009 * record, and copy one record into the provided buffer.
3011 * Consecutive calls will return the next available record moving
3012 * towards the end of the buffer with the youngest messages.
3014 * A return value of FALSE indicates that there are no more records to
3017 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
3019 bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
3020 char *line, size_t size, size_t *len)
3022 struct printk_log *msg;
3026 if (!dumper->active)
3029 if (dumper->cur_seq < log_first_seq) {
3030 /* messages are gone, move to first available one */
3031 dumper->cur_seq = log_first_seq;
3032 dumper->cur_idx = log_first_idx;
3036 if (dumper->cur_seq >= log_next_seq)
3039 msg = log_from_idx(dumper->cur_idx);
3040 l = msg_print_text(msg, 0, syslog, line, size);
3042 dumper->cur_idx = log_next(dumper->cur_idx);
3052 * kmsg_dump_get_line - retrieve one kmsg log line
3053 * @dumper: registered kmsg dumper
3054 * @syslog: include the "<4>" prefixes
3055 * @line: buffer to copy the line to
3056 * @size: maximum size of the buffer
3057 * @len: length of line placed into buffer
3059 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3060 * record, and copy one record into the provided buffer.
3062 * Consecutive calls will return the next available record moving
3063 * towards the end of the buffer with the youngest messages.
3065 * A return value of FALSE indicates that there are no more records to
3068 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
3069 char *line, size_t size, size_t *len)
3071 unsigned long flags;
3074 raw_spin_lock_irqsave(&logbuf_lock, flags);
3075 ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len);
3076 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3080 EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
3083 * kmsg_dump_get_buffer - copy kmsg log lines
3084 * @dumper: registered kmsg dumper
3085 * @syslog: include the "<4>" prefixes
3086 * @buf: buffer to copy the line to
3087 * @size: maximum size of the buffer
3088 * @len: length of line placed into buffer
3090 * Start at the end of the kmsg buffer and fill the provided buffer
3091 * with as many of the the *youngest* kmsg records that fit into it.
3092 * If the buffer is large enough, all available kmsg records will be
3093 * copied with a single call.
3095 * Consecutive calls will fill the buffer with the next block of
3096 * available older records, not including the earlier retrieved ones.
3098 * A return value of FALSE indicates that there are no more records to
3101 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
3102 char *buf, size_t size, size_t *len)
3104 unsigned long flags;
3109 enum log_flags prev;
3113 if (!dumper->active)
3116 raw_spin_lock_irqsave(&logbuf_lock, flags);
3117 if (dumper->cur_seq < log_first_seq) {
3118 /* messages are gone, move to first available one */
3119 dumper->cur_seq = log_first_seq;
3120 dumper->cur_idx = log_first_idx;
3124 if (dumper->cur_seq >= dumper->next_seq) {
3125 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3129 /* calculate length of entire buffer */
3130 seq = dumper->cur_seq;
3131 idx = dumper->cur_idx;
3133 while (seq < dumper->next_seq) {
3134 struct printk_log *msg = log_from_idx(idx);
3136 l += msg_print_text(msg, prev, true, NULL, 0);
3137 idx = log_next(idx);
3142 /* move first record forward until length fits into the buffer */
3143 seq = dumper->cur_seq;
3144 idx = dumper->cur_idx;
3146 while (l > size && seq < dumper->next_seq) {
3147 struct printk_log *msg = log_from_idx(idx);
3149 l -= msg_print_text(msg, prev, true, NULL, 0);
3150 idx = log_next(idx);
3155 /* last message in next interation */
3160 while (seq < dumper->next_seq) {
3161 struct printk_log *msg = log_from_idx(idx);
3163 l += msg_print_text(msg, prev, syslog, buf + l, size - l);
3164 idx = log_next(idx);
3169 dumper->next_seq = next_seq;
3170 dumper->next_idx = next_idx;
3172 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3178 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);
3181 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3182 * @dumper: registered kmsg dumper
3184 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3185 * kmsg_dump_get_buffer() can be called again and used multiple
3186 * times within the same dumper.dump() callback.
3188 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3190 void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
3192 dumper->cur_seq = clear_seq;
3193 dumper->cur_idx = clear_idx;
3194 dumper->next_seq = log_next_seq;
3195 dumper->next_idx = log_next_idx;
3199 * kmsg_dump_rewind - reset the interator
3200 * @dumper: registered kmsg dumper
3202 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3203 * kmsg_dump_get_buffer() can be called again and used multiple
3204 * times within the same dumper.dump() callback.
3206 void kmsg_dump_rewind(struct kmsg_dumper *dumper)
3208 unsigned long flags;
3210 raw_spin_lock_irqsave(&logbuf_lock, flags);
3211 kmsg_dump_rewind_nolock(dumper);
3212 raw_spin_unlock_irqrestore(&logbuf_lock, flags);
3214 EXPORT_SYMBOL_GPL(kmsg_dump_rewind);
3216 static char dump_stack_arch_desc_str[128];
3219 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3220 * @fmt: printf-style format string
3221 * @...: arguments for the format string
3223 * The configured string will be printed right after utsname during task
3224 * dumps. Usually used to add arch-specific system identifiers. If an
3225 * arch wants to make use of such an ID string, it should initialize this
3226 * as soon as possible during boot.
3228 void __init dump_stack_set_arch_desc(const char *fmt, ...)
3232 va_start(args, fmt);
3233 vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
3239 * dump_stack_print_info - print generic debug info for dump_stack()
3240 * @log_lvl: log level
3242 * Arch-specific dump_stack() implementations can use this function to
3243 * print out the same debug information as the generic dump_stack().
3245 void dump_stack_print_info(const char *log_lvl)
3247 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3248 log_lvl, raw_smp_processor_id(), current->pid, current->comm,
3249 print_tainted(), init_utsname()->release,
3250 (int)strcspn(init_utsname()->version, " "),
3251 init_utsname()->version);
3253 if (dump_stack_arch_desc_str[0] != '\0')
3254 printk("%sHardware name: %s\n",
3255 log_lvl, dump_stack_arch_desc_str);
3257 print_worker_info(log_lvl, current);
3261 * show_regs_print_info - print generic debug info for show_regs()
3262 * @log_lvl: log level
3264 * show_regs() implementations can use this function to print out generic
3265 * debug information.
3267 void show_regs_print_info(const char *log_lvl)
3269 dump_stack_print_info(log_lvl);
3271 printk("%stask: %p ti: %p task.ti: %p\n",
3272 log_lvl, current, current_thread_info(),
3273 task_thread_info(current));