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 <linux/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)
129 * Set sysctl string accordingly:
131 if (devkmsg_log
== DEVKMSG_LOG_MASK_ON
) {
132 memset(devkmsg_log_str
, 0, DEVKMSG_STR_MAX_SIZE
);
133 strncpy(devkmsg_log_str
, "on", 2);
134 } else if (devkmsg_log
== DEVKMSG_LOG_MASK_OFF
) {
135 memset(devkmsg_log_str
, 0, DEVKMSG_STR_MAX_SIZE
);
136 strncpy(devkmsg_log_str
, "off", 3);
138 /* else "ratelimit" which is set by default. */
141 * Sysctl cannot change it anymore. The kernel command line setting of
142 * this parameter is to force the setting to be permanent throughout the
143 * runtime of the system. This is a precation measure against userspace
144 * trying to be a smarta** and attempting to change it up on us.
146 devkmsg_log
|= DEVKMSG_LOG_MASK_LOCK
;
150 __setup("printk.devkmsg=", control_devkmsg
);
152 char devkmsg_log_str
[DEVKMSG_STR_MAX_SIZE
] = "ratelimit";
154 int devkmsg_sysctl_set_loglvl(struct ctl_table
*table
, int write
,
155 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
157 char old_str
[DEVKMSG_STR_MAX_SIZE
];
162 if (devkmsg_log
& DEVKMSG_LOG_MASK_LOCK
)
166 strncpy(old_str
, devkmsg_log_str
, DEVKMSG_STR_MAX_SIZE
);
169 err
= proc_dostring(table
, write
, buffer
, lenp
, ppos
);
174 err
= __control_devkmsg(devkmsg_log_str
);
177 * Do not accept an unknown string OR a known string with
180 if (err
< 0 || (err
+ 1 != *lenp
)) {
182 /* ... and restore old setting. */
184 strncpy(devkmsg_log_str
, old_str
, DEVKMSG_STR_MAX_SIZE
);
194 * Number of registered extended console drivers.
196 * If extended consoles are present, in-kernel cont reassembly is disabled
197 * and each fragment is stored as a separate log entry with proper
198 * continuation flag so that every emitted message has full metadata. This
199 * doesn't change the result for regular consoles or /proc/kmsg. For
200 * /dev/kmsg, as long as the reader concatenates messages according to
201 * consecutive continuation flags, the end result should be the same too.
203 static int nr_ext_console_drivers
;
206 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
207 * macros instead of functions so that _RET_IP_ contains useful information.
209 #define down_console_sem() do { \
211 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
214 static int __down_trylock_console_sem(unsigned long ip
)
216 if (down_trylock(&console_sem
))
218 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
221 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
223 #define up_console_sem() do { \
224 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
229 * This is used for debugging the mess that is the VT code by
230 * keeping track if we have the console semaphore held. It's
231 * definitely not the perfect debug tool (we don't know if _WE_
232 * hold it and are racing, but it helps tracking those weird code
233 * paths in the console code where we end up in places I want
234 * locked without the console sempahore held).
236 static int console_locked
, console_suspended
;
239 * If exclusive_console is non-NULL then only this console is to be printed to.
241 static struct console
*exclusive_console
;
244 * Array of consoles built from command line options (console=)
247 #define MAX_CMDLINECONSOLES 8
249 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
251 static int selected_console
= -1;
252 static int preferred_console
= -1;
253 int console_set_on_cmdline
;
254 EXPORT_SYMBOL(console_set_on_cmdline
);
256 /* Flag: console code may call schedule() */
257 static int console_may_schedule
;
260 * The printk log buffer consists of a chain of concatenated variable
261 * length records. Every record starts with a record header, containing
262 * the overall length of the record.
264 * The heads to the first and last entry in the buffer, as well as the
265 * sequence numbers of these entries are maintained when messages are
268 * If the heads indicate available messages, the length in the header
269 * tells the start next message. A length == 0 for the next message
270 * indicates a wrap-around to the beginning of the buffer.
272 * Every record carries the monotonic timestamp in microseconds, as well as
273 * the standard userspace syslog level and syslog facility. The usual
274 * kernel messages use LOG_KERN; userspace-injected messages always carry
275 * a matching syslog facility, by default LOG_USER. The origin of every
276 * message can be reliably determined that way.
278 * The human readable log message directly follows the message header. The
279 * length of the message text is stored in the header, the stored message
282 * Optionally, a message can carry a dictionary of properties (key/value pairs),
283 * to provide userspace with a machine-readable message context.
285 * Examples for well-defined, commonly used property names are:
286 * DEVICE=b12:8 device identifier
290 * +sound:card0 subsystem:devname
291 * SUBSYSTEM=pci driver-core subsystem name
293 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
294 * follows directly after a '=' character. Every property is terminated by
295 * a '\0' character. The last property is not terminated.
297 * Example of a message structure:
298 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
299 * 0008 34 00 record is 52 bytes long
300 * 000a 0b 00 text is 11 bytes long
301 * 000c 1f 00 dictionary is 23 bytes long
302 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
303 * 0010 69 74 27 73 20 61 20 6c "it's a l"
305 * 001b 44 45 56 49 43 "DEVIC"
306 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
307 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
309 * 0032 00 00 00 padding to next message header
311 * The 'struct printk_log' buffer header must never be directly exported to
312 * userspace, it is a kernel-private implementation detail that might
313 * need to be changed in the future, when the requirements change.
315 * /dev/kmsg exports the structured data in the following line format:
316 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
318 * Users of the export format should ignore possible additional values
319 * separated by ',', and find the message after the ';' character.
321 * The optional key/value pairs are attached as continuation lines starting
322 * with a space character and terminated by a newline. All possible
323 * non-prinatable characters are escaped in the "\xff" notation.
327 LOG_NOCONS
= 1, /* already flushed, do not print to console */
328 LOG_NEWLINE
= 2, /* text ended with a newline */
329 LOG_PREFIX
= 4, /* text started with a prefix */
330 LOG_CONT
= 8, /* text is a fragment of a continuation line */
334 u64 ts_nsec
; /* timestamp in nanoseconds */
335 u16 len
; /* length of entire record */
336 u16 text_len
; /* length of text buffer */
337 u16 dict_len
; /* length of dictionary buffer */
338 u8 facility
; /* syslog facility */
339 u8 flags
:5; /* internal record flags */
340 u8 level
:3; /* syslog level */
342 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
343 __packed
__aligned(4)
348 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
349 * within the scheduler's rq lock. It must be released before calling
350 * console_unlock() or anything else that might wake up a process.
352 DEFINE_RAW_SPINLOCK(logbuf_lock
);
355 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
356 /* the next printk record to read by syslog(READ) or /proc/kmsg */
357 static u64 syslog_seq
;
358 static u32 syslog_idx
;
359 static size_t syslog_partial
;
361 /* index and sequence number of the first record stored in the buffer */
362 static u64 log_first_seq
;
363 static u32 log_first_idx
;
365 /* index and sequence number of the next record to store in the buffer */
366 static u64 log_next_seq
;
367 static u32 log_next_idx
;
369 /* the next printk record to write to the console */
370 static u64 console_seq
;
371 static u32 console_idx
;
373 /* the next printk record to read after the last 'clear' command */
374 static u64 clear_seq
;
375 static u32 clear_idx
;
377 #define PREFIX_MAX 32
378 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
380 #define LOG_LEVEL(v) ((v) & 0x07)
381 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
384 #define LOG_ALIGN __alignof__(struct printk_log)
385 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
386 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
387 static char *log_buf
= __log_buf
;
388 static u32 log_buf_len
= __LOG_BUF_LEN
;
390 /* Return log buffer address */
391 char *log_buf_addr_get(void)
396 /* Return log buffer size */
397 u32
log_buf_len_get(void)
402 /* human readable text of the record */
403 static char *log_text(const struct printk_log
*msg
)
405 return (char *)msg
+ sizeof(struct printk_log
);
408 /* optional key/value pair dictionary attached to the record */
409 static char *log_dict(const struct printk_log
*msg
)
411 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
414 /* get record by index; idx must point to valid msg */
415 static struct printk_log
*log_from_idx(u32 idx
)
417 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
420 * A length == 0 record is the end of buffer marker. Wrap around and
421 * read the message at the start of the buffer.
424 return (struct printk_log
*)log_buf
;
428 /* get next record; idx must point to valid msg */
429 static u32
log_next(u32 idx
)
431 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
433 /* length == 0 indicates the end of the buffer; wrap */
435 * A length == 0 record is the end of buffer marker. Wrap around and
436 * read the message at the start of the buffer as *this* one, and
437 * return the one after that.
440 msg
= (struct printk_log
*)log_buf
;
443 return idx
+ msg
->len
;
447 * Check whether there is enough free space for the given message.
449 * The same values of first_idx and next_idx mean that the buffer
450 * is either empty or full.
452 * If the buffer is empty, we must respect the position of the indexes.
453 * They cannot be reset to the beginning of the buffer.
455 static int logbuf_has_space(u32 msg_size
, bool empty
)
459 if (log_next_idx
> log_first_idx
|| empty
)
460 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
462 free
= log_first_idx
- log_next_idx
;
465 * We need space also for an empty header that signalizes wrapping
468 return free
>= msg_size
+ sizeof(struct printk_log
);
471 static int log_make_free_space(u32 msg_size
)
473 while (log_first_seq
< log_next_seq
&&
474 !logbuf_has_space(msg_size
, false)) {
475 /* drop old messages until we have enough contiguous space */
476 log_first_idx
= log_next(log_first_idx
);
480 if (clear_seq
< log_first_seq
) {
481 clear_seq
= log_first_seq
;
482 clear_idx
= log_first_idx
;
485 /* sequence numbers are equal, so the log buffer is empty */
486 if (logbuf_has_space(msg_size
, log_first_seq
== log_next_seq
))
492 /* compute the message size including the padding bytes */
493 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
497 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
498 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
505 * Define how much of the log buffer we could take at maximum. The value
506 * must be greater than two. Note that only half of the buffer is available
507 * when the index points to the middle.
509 #define MAX_LOG_TAKE_PART 4
510 static const char trunc_msg
[] = "<truncated>";
512 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
513 u16
*dict_len
, u32
*pad_len
)
516 * The message should not take the whole buffer. Otherwise, it might
517 * get removed too soon.
519 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
520 if (*text_len
> max_text_len
)
521 *text_len
= max_text_len
;
522 /* enable the warning message */
523 *trunc_msg_len
= strlen(trunc_msg
);
524 /* disable the "dict" completely */
526 /* compute the size again, count also the warning message */
527 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
530 /* insert record into the buffer, discard old ones, update heads */
531 static int log_store(int facility
, int level
,
532 enum log_flags flags
, u64 ts_nsec
,
533 const char *dict
, u16 dict_len
,
534 const char *text
, u16 text_len
)
536 struct printk_log
*msg
;
538 u16 trunc_msg_len
= 0;
540 /* number of '\0' padding bytes to next message */
541 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
543 if (log_make_free_space(size
)) {
544 /* truncate the message if it is too long for empty buffer */
545 size
= truncate_msg(&text_len
, &trunc_msg_len
,
546 &dict_len
, &pad_len
);
547 /* survive when the log buffer is too small for trunc_msg */
548 if (log_make_free_space(size
))
552 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
554 * This message + an additional empty header does not fit
555 * at the end of the buffer. Add an empty header with len == 0
556 * to signify a wrap around.
558 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
563 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
564 memcpy(log_text(msg
), text
, text_len
);
565 msg
->text_len
= text_len
;
567 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
568 msg
->text_len
+= trunc_msg_len
;
570 memcpy(log_dict(msg
), dict
, dict_len
);
571 msg
->dict_len
= dict_len
;
572 msg
->facility
= facility
;
573 msg
->level
= level
& 7;
574 msg
->flags
= flags
& 0x1f;
576 msg
->ts_nsec
= ts_nsec
;
578 msg
->ts_nsec
= local_clock();
579 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
583 log_next_idx
+= msg
->len
;
586 return msg
->text_len
;
589 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
591 static int syslog_action_restricted(int type
)
596 * Unless restricted, we allow "read all" and "get buffer size"
599 return type
!= SYSLOG_ACTION_READ_ALL
&&
600 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
603 int check_syslog_permissions(int type
, int source
)
606 * If this is from /proc/kmsg and we've already opened it, then we've
607 * already done the capabilities checks at open time.
609 if (source
== SYSLOG_FROM_PROC
&& type
!= SYSLOG_ACTION_OPEN
)
612 if (syslog_action_restricted(type
)) {
613 if (capable(CAP_SYSLOG
))
616 * For historical reasons, accept CAP_SYS_ADMIN too, with
619 if (capable(CAP_SYS_ADMIN
)) {
620 pr_warn_once("%s (%d): Attempt to access syslog with "
621 "CAP_SYS_ADMIN but no CAP_SYSLOG "
623 current
->comm
, task_pid_nr(current
));
629 return security_syslog(type
);
631 EXPORT_SYMBOL_GPL(check_syslog_permissions
);
633 static void append_char(char **pp
, char *e
, char c
)
639 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
640 struct printk_log
*msg
, u64 seq
)
642 u64 ts_usec
= msg
->ts_nsec
;
644 do_div(ts_usec
, 1000);
646 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
647 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
,
648 msg
->flags
& LOG_CONT
? 'c' : '-');
651 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
652 char *dict
, size_t dict_len
,
653 char *text
, size_t text_len
)
655 char *p
= buf
, *e
= buf
+ size
;
658 /* escape non-printable characters */
659 for (i
= 0; i
< text_len
; i
++) {
660 unsigned char c
= text
[i
];
662 if (c
< ' ' || c
>= 127 || c
== '\\')
663 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
665 append_char(&p
, e
, c
);
667 append_char(&p
, e
, '\n');
672 for (i
= 0; i
< dict_len
; i
++) {
673 unsigned char c
= dict
[i
];
676 append_char(&p
, e
, ' ');
681 append_char(&p
, e
, '\n');
686 if (c
< ' ' || c
>= 127 || c
== '\\') {
687 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
691 append_char(&p
, e
, c
);
693 append_char(&p
, e
, '\n');
699 /* /dev/kmsg - userspace message inject/listen interface */
700 struct devkmsg_user
{
703 struct ratelimit_state rs
;
705 char buf
[CONSOLE_EXT_LOG_MAX
];
708 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
711 int level
= default_message_loglevel
;
712 int facility
= 1; /* LOG_USER */
713 struct file
*file
= iocb
->ki_filp
;
714 struct devkmsg_user
*user
= file
->private_data
;
715 size_t len
= iov_iter_count(from
);
718 if (!user
|| len
> LOG_LINE_MAX
)
721 /* Ignore when user logging is disabled. */
722 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
725 /* Ratelimit when not explicitly enabled. */
726 if (!(devkmsg_log
& DEVKMSG_LOG_MASK_ON
)) {
727 if (!___ratelimit(&user
->rs
, current
->comm
))
731 buf
= kmalloc(len
+1, GFP_KERNEL
);
736 if (!copy_from_iter_full(buf
, len
, from
)) {
742 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
743 * the decimal value represents 32bit, the lower 3 bit are the log
744 * level, the rest are the log facility.
746 * If no prefix or no userspace facility is specified, we
747 * enforce LOG_USER, to be able to reliably distinguish
748 * kernel-generated messages from userspace-injected ones.
751 if (line
[0] == '<') {
755 u
= simple_strtoul(line
+ 1, &endp
, 10);
756 if (endp
&& endp
[0] == '>') {
757 level
= LOG_LEVEL(u
);
758 if (LOG_FACILITY(u
) != 0)
759 facility
= LOG_FACILITY(u
);
766 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
771 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
772 size_t count
, loff_t
*ppos
)
774 struct devkmsg_user
*user
= file
->private_data
;
775 struct printk_log
*msg
;
782 ret
= mutex_lock_interruptible(&user
->lock
);
785 raw_spin_lock_irq(&logbuf_lock
);
786 while (user
->seq
== log_next_seq
) {
787 if (file
->f_flags
& O_NONBLOCK
) {
789 raw_spin_unlock_irq(&logbuf_lock
);
793 raw_spin_unlock_irq(&logbuf_lock
);
794 ret
= wait_event_interruptible(log_wait
,
795 user
->seq
!= log_next_seq
);
798 raw_spin_lock_irq(&logbuf_lock
);
801 if (user
->seq
< log_first_seq
) {
802 /* our last seen message is gone, return error and reset */
803 user
->idx
= log_first_idx
;
804 user
->seq
= log_first_seq
;
806 raw_spin_unlock_irq(&logbuf_lock
);
810 msg
= log_from_idx(user
->idx
);
811 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
813 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
814 log_dict(msg
), msg
->dict_len
,
815 log_text(msg
), msg
->text_len
);
817 user
->idx
= log_next(user
->idx
);
819 raw_spin_unlock_irq(&logbuf_lock
);
826 if (copy_to_user(buf
, user
->buf
, len
)) {
832 mutex_unlock(&user
->lock
);
836 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
838 struct devkmsg_user
*user
= file
->private_data
;
846 raw_spin_lock_irq(&logbuf_lock
);
849 /* the first record */
850 user
->idx
= log_first_idx
;
851 user
->seq
= log_first_seq
;
855 * The first record after the last SYSLOG_ACTION_CLEAR,
856 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
857 * changes no global state, and does not clear anything.
859 user
->idx
= clear_idx
;
860 user
->seq
= clear_seq
;
863 /* after the last record */
864 user
->idx
= log_next_idx
;
865 user
->seq
= log_next_seq
;
870 raw_spin_unlock_irq(&logbuf_lock
);
874 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
876 struct devkmsg_user
*user
= file
->private_data
;
880 return POLLERR
|POLLNVAL
;
882 poll_wait(file
, &log_wait
, wait
);
884 raw_spin_lock_irq(&logbuf_lock
);
885 if (user
->seq
< log_next_seq
) {
886 /* return error when data has vanished underneath us */
887 if (user
->seq
< log_first_seq
)
888 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
890 ret
= POLLIN
|POLLRDNORM
;
892 raw_spin_unlock_irq(&logbuf_lock
);
897 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
899 struct devkmsg_user
*user
;
902 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
905 /* write-only does not need any file context */
906 if ((file
->f_flags
& O_ACCMODE
) != O_WRONLY
) {
907 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
913 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
917 ratelimit_default_init(&user
->rs
);
918 ratelimit_set_flags(&user
->rs
, RATELIMIT_MSG_ON_RELEASE
);
920 mutex_init(&user
->lock
);
922 raw_spin_lock_irq(&logbuf_lock
);
923 user
->idx
= log_first_idx
;
924 user
->seq
= log_first_seq
;
925 raw_spin_unlock_irq(&logbuf_lock
);
927 file
->private_data
= user
;
931 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
933 struct devkmsg_user
*user
= file
->private_data
;
938 ratelimit_state_exit(&user
->rs
);
940 mutex_destroy(&user
->lock
);
945 const struct file_operations kmsg_fops
= {
946 .open
= devkmsg_open
,
947 .read
= devkmsg_read
,
948 .write_iter
= devkmsg_write
,
949 .llseek
= devkmsg_llseek
,
950 .poll
= devkmsg_poll
,
951 .release
= devkmsg_release
,
954 #ifdef CONFIG_KEXEC_CORE
956 * This appends the listed symbols to /proc/vmcore
958 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
959 * obtain access to symbols that are otherwise very difficult to locate. These
960 * symbols are specifically used so that utilities can access and extract the
961 * dmesg log from a vmcore file after a crash.
963 void log_buf_kexec_setup(void)
965 VMCOREINFO_SYMBOL(log_buf
);
966 VMCOREINFO_SYMBOL(log_buf_len
);
967 VMCOREINFO_SYMBOL(log_first_idx
);
968 VMCOREINFO_SYMBOL(clear_idx
);
969 VMCOREINFO_SYMBOL(log_next_idx
);
971 * Export struct printk_log size and field offsets. User space tools can
972 * parse it and detect any changes to structure down the line.
974 VMCOREINFO_STRUCT_SIZE(printk_log
);
975 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
976 VMCOREINFO_OFFSET(printk_log
, len
);
977 VMCOREINFO_OFFSET(printk_log
, text_len
);
978 VMCOREINFO_OFFSET(printk_log
, dict_len
);
982 /* requested log_buf_len from kernel cmdline */
983 static unsigned long __initdata new_log_buf_len
;
985 /* we practice scaling the ring buffer by powers of 2 */
986 static void __init
log_buf_len_update(unsigned size
)
989 size
= roundup_pow_of_two(size
);
990 if (size
> log_buf_len
)
991 new_log_buf_len
= size
;
994 /* save requested log_buf_len since it's too early to process it */
995 static int __init
log_buf_len_setup(char *str
)
997 unsigned size
= memparse(str
, &str
);
999 log_buf_len_update(size
);
1003 early_param("log_buf_len", log_buf_len_setup
);
1006 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1008 static void __init
log_buf_add_cpu(void)
1010 unsigned int cpu_extra
;
1013 * archs should set up cpu_possible_bits properly with
1014 * set_cpu_possible() after setup_arch() but just in
1015 * case lets ensure this is valid.
1017 if (num_possible_cpus() == 1)
1020 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
1022 /* by default this will only continue through for large > 64 CPUs */
1023 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
1026 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1027 __LOG_CPU_MAX_BUF_LEN
);
1028 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1030 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
1032 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
1034 #else /* !CONFIG_SMP */
1035 static inline void log_buf_add_cpu(void) {}
1036 #endif /* CONFIG_SMP */
1038 void __init
setup_log_buf(int early
)
1040 unsigned long flags
;
1044 if (log_buf
!= __log_buf
)
1047 if (!early
&& !new_log_buf_len
)
1050 if (!new_log_buf_len
)
1055 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
1057 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
1061 if (unlikely(!new_log_buf
)) {
1062 pr_err("log_buf_len: %ld bytes not available\n",
1067 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
1068 log_buf_len
= new_log_buf_len
;
1069 log_buf
= new_log_buf
;
1070 new_log_buf_len
= 0;
1071 free
= __LOG_BUF_LEN
- log_next_idx
;
1072 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
1073 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
1075 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
1076 pr_info("early log buf free: %d(%d%%)\n",
1077 free
, (free
* 100) / __LOG_BUF_LEN
);
1080 static bool __read_mostly ignore_loglevel
;
1082 static int __init
ignore_loglevel_setup(char *str
)
1084 ignore_loglevel
= true;
1085 pr_info("debug: ignoring loglevel setting.\n");
1090 early_param("ignore_loglevel", ignore_loglevel_setup
);
1091 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1092 MODULE_PARM_DESC(ignore_loglevel
,
1093 "ignore loglevel setting (prints all kernel messages to the console)");
1095 static bool suppress_message_printing(int level
)
1097 return (level
>= console_loglevel
&& !ignore_loglevel
);
1100 #ifdef CONFIG_BOOT_PRINTK_DELAY
1102 static int boot_delay
; /* msecs delay after each printk during bootup */
1103 static unsigned long long loops_per_msec
; /* based on boot_delay */
1105 static int __init
boot_delay_setup(char *str
)
1109 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
1110 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
1112 get_option(&str
, &boot_delay
);
1113 if (boot_delay
> 10 * 1000)
1116 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1117 "HZ: %d, loops_per_msec: %llu\n",
1118 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1121 early_param("boot_delay", boot_delay_setup
);
1123 static void boot_delay_msec(int level
)
1125 unsigned long long k
;
1126 unsigned long timeout
;
1128 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
1129 || suppress_message_printing(level
)) {
1133 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1135 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1140 * use (volatile) jiffies to prevent
1141 * compiler reduction; loop termination via jiffies
1142 * is secondary and may or may not happen.
1144 if (time_after(jiffies
, timeout
))
1146 touch_nmi_watchdog();
1150 static inline void boot_delay_msec(int level
)
1155 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1156 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1158 static size_t print_time(u64 ts
, char *buf
)
1160 unsigned long rem_nsec
;
1165 rem_nsec
= do_div(ts
, 1000000000);
1168 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1170 return sprintf(buf
, "[%5lu.%06lu] ",
1171 (unsigned long)ts
, rem_nsec
/ 1000);
1174 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1177 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1181 len
+= sprintf(buf
, "<%u>", prefix
);
1186 else if (prefix
> 99)
1188 else if (prefix
> 9)
1193 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1197 static size_t msg_print_text(const struct printk_log
*msg
, bool syslog
, char *buf
, size_t size
)
1199 const char *text
= log_text(msg
);
1200 size_t text_size
= msg
->text_len
;
1204 const char *next
= memchr(text
, '\n', text_size
);
1208 text_len
= next
- text
;
1210 text_size
-= next
- text
;
1212 text_len
= text_size
;
1216 if (print_prefix(msg
, syslog
, NULL
) +
1217 text_len
+ 1 >= size
- len
)
1220 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1221 memcpy(buf
+ len
, text
, text_len
);
1225 /* SYSLOG_ACTION_* buffer size only calculation */
1226 len
+= print_prefix(msg
, syslog
, NULL
);
1237 static int syslog_print(char __user
*buf
, int size
)
1240 struct printk_log
*msg
;
1243 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1251 raw_spin_lock_irq(&logbuf_lock
);
1252 if (syslog_seq
< log_first_seq
) {
1253 /* messages are gone, move to first one */
1254 syslog_seq
= log_first_seq
;
1255 syslog_idx
= log_first_idx
;
1258 if (syslog_seq
== log_next_seq
) {
1259 raw_spin_unlock_irq(&logbuf_lock
);
1263 skip
= syslog_partial
;
1264 msg
= log_from_idx(syslog_idx
);
1265 n
= msg_print_text(msg
, true, text
, LOG_LINE_MAX
+ PREFIX_MAX
);
1266 if (n
- syslog_partial
<= size
) {
1267 /* message fits into buffer, move forward */
1268 syslog_idx
= log_next(syslog_idx
);
1270 n
-= syslog_partial
;
1273 /* partial read(), remember position */
1275 syslog_partial
+= n
;
1278 raw_spin_unlock_irq(&logbuf_lock
);
1283 if (copy_to_user(buf
, text
+ skip
, n
)) {
1298 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1303 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1307 raw_spin_lock_irq(&logbuf_lock
);
1314 * Find first record that fits, including all following records,
1315 * into the user-provided buffer for this dump.
1319 while (seq
< log_next_seq
) {
1320 struct printk_log
*msg
= log_from_idx(idx
);
1322 len
+= msg_print_text(msg
, true, NULL
, 0);
1323 idx
= log_next(idx
);
1327 /* move first record forward until length fits into the buffer */
1330 while (len
> size
&& seq
< log_next_seq
) {
1331 struct printk_log
*msg
= log_from_idx(idx
);
1333 len
-= msg_print_text(msg
, true, NULL
, 0);
1334 idx
= log_next(idx
);
1338 /* last message fitting into this dump */
1339 next_seq
= log_next_seq
;
1342 while (len
>= 0 && seq
< next_seq
) {
1343 struct printk_log
*msg
= log_from_idx(idx
);
1346 textlen
= msg_print_text(msg
, true, text
,
1347 LOG_LINE_MAX
+ PREFIX_MAX
);
1352 idx
= log_next(idx
);
1355 raw_spin_unlock_irq(&logbuf_lock
);
1356 if (copy_to_user(buf
+ len
, text
, textlen
))
1360 raw_spin_lock_irq(&logbuf_lock
);
1362 if (seq
< log_first_seq
) {
1363 /* messages are gone, move to next one */
1364 seq
= log_first_seq
;
1365 idx
= log_first_idx
;
1371 clear_seq
= log_next_seq
;
1372 clear_idx
= log_next_idx
;
1374 raw_spin_unlock_irq(&logbuf_lock
);
1380 int do_syslog(int type
, char __user
*buf
, int len
, int source
)
1383 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1386 error
= check_syslog_permissions(type
, source
);
1391 case SYSLOG_ACTION_CLOSE
: /* Close log */
1393 case SYSLOG_ACTION_OPEN
: /* Open log */
1395 case SYSLOG_ACTION_READ
: /* Read from log */
1397 if (!buf
|| len
< 0)
1402 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1406 error
= wait_event_interruptible(log_wait
,
1407 syslog_seq
!= log_next_seq
);
1410 error
= syslog_print(buf
, len
);
1412 /* Read/clear last kernel messages */
1413 case SYSLOG_ACTION_READ_CLEAR
:
1416 /* Read last kernel messages */
1417 case SYSLOG_ACTION_READ_ALL
:
1419 if (!buf
|| len
< 0)
1424 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1428 error
= syslog_print_all(buf
, len
, clear
);
1430 /* Clear ring buffer */
1431 case SYSLOG_ACTION_CLEAR
:
1432 syslog_print_all(NULL
, 0, true);
1434 /* Disable logging to console */
1435 case SYSLOG_ACTION_CONSOLE_OFF
:
1436 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1437 saved_console_loglevel
= console_loglevel
;
1438 console_loglevel
= minimum_console_loglevel
;
1440 /* Enable logging to console */
1441 case SYSLOG_ACTION_CONSOLE_ON
:
1442 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1443 console_loglevel
= saved_console_loglevel
;
1444 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1447 /* Set level of messages printed to console */
1448 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1450 if (len
< 1 || len
> 8)
1452 if (len
< minimum_console_loglevel
)
1453 len
= minimum_console_loglevel
;
1454 console_loglevel
= len
;
1455 /* Implicitly re-enable logging to console */
1456 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1459 /* Number of chars in the log buffer */
1460 case SYSLOG_ACTION_SIZE_UNREAD
:
1461 raw_spin_lock_irq(&logbuf_lock
);
1462 if (syslog_seq
< log_first_seq
) {
1463 /* messages are gone, move to first one */
1464 syslog_seq
= log_first_seq
;
1465 syslog_idx
= log_first_idx
;
1468 if (source
== SYSLOG_FROM_PROC
) {
1470 * Short-cut for poll(/"proc/kmsg") which simply checks
1471 * for pending data, not the size; return the count of
1472 * records, not the length.
1474 error
= log_next_seq
- syslog_seq
;
1476 u64 seq
= syslog_seq
;
1477 u32 idx
= syslog_idx
;
1480 while (seq
< log_next_seq
) {
1481 struct printk_log
*msg
= log_from_idx(idx
);
1483 error
+= msg_print_text(msg
, true, NULL
, 0);
1484 idx
= log_next(idx
);
1487 error
-= syslog_partial
;
1489 raw_spin_unlock_irq(&logbuf_lock
);
1491 /* Size of the log buffer */
1492 case SYSLOG_ACTION_SIZE_BUFFER
:
1493 error
= log_buf_len
;
1503 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1505 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1509 * Call the console drivers, asking them to write out
1510 * log_buf[start] to log_buf[end - 1].
1511 * The console_lock must be held.
1513 static void call_console_drivers(int level
,
1514 const char *ext_text
, size_t ext_len
,
1515 const char *text
, size_t len
)
1517 struct console
*con
;
1519 trace_console(text
, len
);
1521 if (!console_drivers
)
1524 for_each_console(con
) {
1525 if (exclusive_console
&& con
!= exclusive_console
)
1527 if (!(con
->flags
& CON_ENABLED
))
1531 if (!cpu_online(smp_processor_id()) &&
1532 !(con
->flags
& CON_ANYTIME
))
1534 if (con
->flags
& CON_EXTENDED
)
1535 con
->write(con
, ext_text
, ext_len
);
1537 con
->write(con
, text
, len
);
1542 * Zap console related locks when oopsing.
1543 * To leave time for slow consoles to print a full oops,
1544 * only zap at most once every 30 seconds.
1546 static void zap_locks(void)
1548 static unsigned long oops_timestamp
;
1550 if (time_after_eq(jiffies
, oops_timestamp
) &&
1551 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1554 oops_timestamp
= jiffies
;
1557 /* If a crash is occurring, make sure we can't deadlock */
1558 raw_spin_lock_init(&logbuf_lock
);
1559 /* And make sure that we print immediately */
1560 sema_init(&console_sem
, 1);
1563 int printk_delay_msec __read_mostly
;
1565 static inline void printk_delay(void)
1567 if (unlikely(printk_delay_msec
)) {
1568 int m
= printk_delay_msec
;
1572 touch_nmi_watchdog();
1578 * Continuation lines are buffered, and not committed to the record buffer
1579 * until the line is complete, or a race forces it. The line fragments
1580 * though, are printed immediately to the consoles to ensure everything has
1581 * reached the console in case of a kernel crash.
1583 static struct cont
{
1584 char buf
[LOG_LINE_MAX
];
1585 size_t len
; /* length == 0 means unused buffer */
1586 struct task_struct
*owner
; /* task of first print*/
1587 u64 ts_nsec
; /* time of first print */
1588 u8 level
; /* log level of first message */
1589 u8 facility
; /* log facility of first message */
1590 enum log_flags flags
; /* prefix, newline flags */
1593 static void cont_flush(void)
1598 log_store(cont
.facility
, cont
.level
, cont
.flags
, cont
.ts_nsec
,
1599 NULL
, 0, cont
.buf
, cont
.len
);
1603 static bool cont_add(int facility
, int level
, enum log_flags flags
, const char *text
, size_t len
)
1606 * If ext consoles are present, flush and skip in-kernel
1607 * continuation. See nr_ext_console_drivers definition. Also, if
1608 * the line gets too long, split it up in separate records.
1610 if (nr_ext_console_drivers
|| cont
.len
+ len
> sizeof(cont
.buf
)) {
1616 cont
.facility
= facility
;
1618 cont
.owner
= current
;
1619 cont
.ts_nsec
= local_clock();
1623 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1626 // The original flags come from the first line,
1627 // but later continuations can add a newline.
1628 if (flags
& LOG_NEWLINE
) {
1629 cont
.flags
|= LOG_NEWLINE
;
1633 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1639 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
)
1642 * If an earlier line was buffered, and we're a continuation
1643 * write from the same process, try to add it to the buffer.
1646 if (cont
.owner
== current
&& (lflags
& LOG_CONT
)) {
1647 if (cont_add(facility
, level
, lflags
, text
, text_len
))
1650 /* Otherwise, make sure it's flushed */
1654 /* Skip empty continuation lines that couldn't be added - they just flush */
1655 if (!text_len
&& (lflags
& LOG_CONT
))
1658 /* If it doesn't end in a newline, try to buffer the current line */
1659 if (!(lflags
& LOG_NEWLINE
)) {
1660 if (cont_add(facility
, level
, lflags
, text
, text_len
))
1664 /* Store it in the record log */
1665 return log_store(facility
, level
, lflags
, 0, dict
, dictlen
, text
, text_len
);
1668 asmlinkage
int vprintk_emit(int facility
, int level
,
1669 const char *dict
, size_t dictlen
,
1670 const char *fmt
, va_list args
)
1672 static bool recursion_bug
;
1673 static char textbuf
[LOG_LINE_MAX
];
1674 char *text
= textbuf
;
1675 size_t text_len
= 0;
1676 enum log_flags lflags
= 0;
1677 unsigned long flags
;
1679 int printed_len
= 0;
1680 int nmi_message_lost
;
1681 bool in_sched
= false;
1682 /* cpu currently holding logbuf_lock in this function */
1683 static unsigned int logbuf_cpu
= UINT_MAX
;
1685 if (level
== LOGLEVEL_SCHED
) {
1686 level
= LOGLEVEL_DEFAULT
;
1690 boot_delay_msec(level
);
1693 local_irq_save(flags
);
1694 this_cpu
= smp_processor_id();
1697 * Ouch, printk recursed into itself!
1699 if (unlikely(logbuf_cpu
== this_cpu
)) {
1701 * If a crash is occurring during printk() on this CPU,
1702 * then try to get the crash message out but make sure
1703 * we can't deadlock. Otherwise just return to avoid the
1704 * recursion and return - but flag the recursion so that
1705 * it can be printed at the next appropriate moment:
1707 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1708 recursion_bug
= true;
1709 local_irq_restore(flags
);
1716 /* This stops the holder of console_sem just where we want him */
1717 raw_spin_lock(&logbuf_lock
);
1718 logbuf_cpu
= this_cpu
;
1720 if (unlikely(recursion_bug
)) {
1721 static const char recursion_msg
[] =
1722 "BUG: recent printk recursion!";
1724 recursion_bug
= false;
1725 /* emit KERN_CRIT message */
1726 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1727 NULL
, 0, recursion_msg
,
1728 strlen(recursion_msg
));
1731 nmi_message_lost
= get_nmi_message_lost();
1732 if (unlikely(nmi_message_lost
)) {
1733 text_len
= scnprintf(textbuf
, sizeof(textbuf
),
1734 "BAD LUCK: lost %d message(s) from NMI context!",
1736 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1737 NULL
, 0, textbuf
, text_len
);
1741 * The printf needs to come first; we need the syslog
1742 * prefix which might be passed-in as a parameter.
1744 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1746 /* mark and strip a trailing newline */
1747 if (text_len
&& text
[text_len
-1] == '\n') {
1749 lflags
|= LOG_NEWLINE
;
1752 /* strip kernel syslog prefix and extract log level or control flags */
1753 if (facility
== 0) {
1756 while ((kern_level
= printk_get_level(text
)) != 0) {
1757 switch (kern_level
) {
1759 if (level
== LOGLEVEL_DEFAULT
)
1760 level
= kern_level
- '0';
1762 case 'd': /* KERN_DEFAULT */
1763 lflags
|= LOG_PREFIX
;
1765 case 'c': /* KERN_CONT */
1774 if (level
== LOGLEVEL_DEFAULT
)
1775 level
= default_message_loglevel
;
1778 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1780 printed_len
+= log_output(facility
, level
, lflags
, dict
, dictlen
, text
, text_len
);
1782 logbuf_cpu
= UINT_MAX
;
1783 raw_spin_unlock(&logbuf_lock
);
1785 local_irq_restore(flags
);
1787 /* If called from the scheduler, we can not call up(). */
1791 * Try to acquire and then immediately release the console
1792 * semaphore. The release will print out buffers and wake up
1793 * /dev/kmsg and syslog() users.
1795 if (console_trylock())
1802 EXPORT_SYMBOL(vprintk_emit
);
1804 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1806 return vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1808 EXPORT_SYMBOL(vprintk
);
1810 asmlinkage
int printk_emit(int facility
, int level
,
1811 const char *dict
, size_t dictlen
,
1812 const char *fmt
, ...)
1817 va_start(args
, fmt
);
1818 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1823 EXPORT_SYMBOL(printk_emit
);
1825 int vprintk_default(const char *fmt
, va_list args
)
1829 #ifdef CONFIG_KGDB_KDB
1830 /* Allow to pass printk() to kdb but avoid a recursion. */
1831 if (unlikely(kdb_trap_printk
&& kdb_printf_cpu
< 0)) {
1832 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1836 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1840 EXPORT_SYMBOL_GPL(vprintk_default
);
1843 * printk - print a kernel message
1844 * @fmt: format string
1846 * This is printk(). It can be called from any context. We want it to work.
1848 * We try to grab the console_lock. If we succeed, it's easy - we log the
1849 * output and call the console drivers. If we fail to get the semaphore, we
1850 * place the output into the log buffer and return. The current holder of
1851 * the console_sem will notice the new output in console_unlock(); and will
1852 * send it to the consoles before releasing the lock.
1854 * One effect of this deferred printing is that code which calls printk() and
1855 * then changes console_loglevel may break. This is because console_loglevel
1856 * is inspected when the actual printing occurs.
1861 * See the vsnprintf() documentation for format string extensions over C99.
1863 asmlinkage __visible
int printk(const char *fmt
, ...)
1868 va_start(args
, fmt
);
1869 r
= vprintk_func(fmt
, args
);
1874 EXPORT_SYMBOL(printk
);
1876 #else /* CONFIG_PRINTK */
1878 #define LOG_LINE_MAX 0
1879 #define PREFIX_MAX 0
1881 static u64 syslog_seq
;
1882 static u32 syslog_idx
;
1883 static u64 console_seq
;
1884 static u32 console_idx
;
1885 static u64 log_first_seq
;
1886 static u32 log_first_idx
;
1887 static u64 log_next_seq
;
1888 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
1889 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
1890 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
1891 static u32
log_next(u32 idx
) { return 0; }
1892 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
1893 struct printk_log
*msg
,
1894 u64 seq
) { return 0; }
1895 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
1896 char *dict
, size_t dict_len
,
1897 char *text
, size_t text_len
) { return 0; }
1898 static void call_console_drivers(int level
,
1899 const char *ext_text
, size_t ext_len
,
1900 const char *text
, size_t len
) {}
1901 static size_t msg_print_text(const struct printk_log
*msg
,
1902 bool syslog
, char *buf
, size_t size
) { return 0; }
1903 static bool suppress_message_printing(int level
) { return false; }
1905 /* Still needs to be defined for users */
1906 DEFINE_PER_CPU(printk_func_t
, printk_func
);
1908 #endif /* CONFIG_PRINTK */
1910 #ifdef CONFIG_EARLY_PRINTK
1911 struct console
*early_console
;
1913 asmlinkage __visible
void early_printk(const char *fmt
, ...)
1923 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
1926 early_console
->write(early_console
, buf
, n
);
1930 static int __add_preferred_console(char *name
, int idx
, char *options
,
1933 struct console_cmdline
*c
;
1937 * See if this tty is not yet registered, and
1938 * if we have a slot free.
1940 for (i
= 0, c
= console_cmdline
;
1941 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1943 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
1945 selected_console
= i
;
1949 if (i
== MAX_CMDLINECONSOLES
)
1952 selected_console
= i
;
1953 strlcpy(c
->name
, name
, sizeof(c
->name
));
1954 c
->options
= options
;
1955 braille_set_options(c
, brl_options
);
1961 * Set up a console. Called via do_early_param() in init/main.c
1962 * for each "console=" parameter in the boot command line.
1964 static int __init
console_setup(char *str
)
1966 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
1967 char *s
, *options
, *brl_options
= NULL
;
1970 if (_braille_console_setup(&str
, &brl_options
))
1974 * Decode str into name, index, options.
1976 if (str
[0] >= '0' && str
[0] <= '9') {
1977 strcpy(buf
, "ttyS");
1978 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1980 strncpy(buf
, str
, sizeof(buf
) - 1);
1982 buf
[sizeof(buf
) - 1] = 0;
1983 options
= strchr(str
, ',');
1987 if (!strcmp(str
, "ttya"))
1988 strcpy(buf
, "ttyS0");
1989 if (!strcmp(str
, "ttyb"))
1990 strcpy(buf
, "ttyS1");
1992 for (s
= buf
; *s
; s
++)
1993 if (isdigit(*s
) || *s
== ',')
1995 idx
= simple_strtoul(s
, NULL
, 10);
1998 __add_preferred_console(buf
, idx
, options
, brl_options
);
1999 console_set_on_cmdline
= 1;
2002 __setup("console=", console_setup
);
2005 * add_preferred_console - add a device to the list of preferred consoles.
2006 * @name: device name
2007 * @idx: device index
2008 * @options: options for this console
2010 * The last preferred console added will be used for kernel messages
2011 * and stdin/out/err for init. Normally this is used by console_setup
2012 * above to handle user-supplied console arguments; however it can also
2013 * be used by arch-specific code either to override the user or more
2014 * commonly to provide a default console (ie from PROM variables) when
2015 * the user has not supplied one.
2017 int add_preferred_console(char *name
, int idx
, char *options
)
2019 return __add_preferred_console(name
, idx
, options
, NULL
);
2022 bool console_suspend_enabled
= true;
2023 EXPORT_SYMBOL(console_suspend_enabled
);
2025 static int __init
console_suspend_disable(char *str
)
2027 console_suspend_enabled
= false;
2030 __setup("no_console_suspend", console_suspend_disable
);
2031 module_param_named(console_suspend
, console_suspend_enabled
,
2032 bool, S_IRUGO
| S_IWUSR
);
2033 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2034 " and hibernate operations");
2037 * suspend_console - suspend the console subsystem
2039 * This disables printk() while we go into suspend states
2041 void suspend_console(void)
2043 if (!console_suspend_enabled
)
2045 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2047 console_suspended
= 1;
2051 void resume_console(void)
2053 if (!console_suspend_enabled
)
2056 console_suspended
= 0;
2061 * console_cpu_notify - print deferred console messages after CPU hotplug
2064 * If printk() is called from a CPU that is not online yet, the messages
2065 * will be spooled but will not show up on the console. This function is
2066 * called when a new CPU comes online (or fails to come up), and ensures
2067 * that any such output gets printed.
2069 static int console_cpu_notify(unsigned int cpu
)
2071 if (!cpuhp_tasks_frozen
) {
2079 * console_lock - lock the console system for exclusive use.
2081 * Acquires a lock which guarantees that the caller has
2082 * exclusive access to the console system and the console_drivers list.
2084 * Can sleep, returns nothing.
2086 void console_lock(void)
2091 if (console_suspended
)
2094 console_may_schedule
= 1;
2096 EXPORT_SYMBOL(console_lock
);
2099 * console_trylock - try to lock the console system for exclusive use.
2101 * Try to acquire a lock which guarantees that the caller has exclusive
2102 * access to the console system and the console_drivers list.
2104 * returns 1 on success, and 0 on failure to acquire the lock.
2106 int console_trylock(void)
2108 if (down_trylock_console_sem())
2110 if (console_suspended
) {
2116 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2117 * safe to schedule (e.g. calling printk while holding a spin_lock),
2118 * because preempt_disable()/preempt_enable() are just barriers there
2119 * and preempt_count() is always 0.
2121 * RCU read sections have a separate preemption counter when
2122 * PREEMPT_RCU enabled thus we must take extra care and check
2123 * rcu_preempt_depth(), otherwise RCU read sections modify
2126 console_may_schedule
= !oops_in_progress
&&
2128 !rcu_preempt_depth();
2131 EXPORT_SYMBOL(console_trylock
);
2133 int is_console_locked(void)
2135 return console_locked
;
2139 * Check if we have any console that is capable of printing while cpu is
2140 * booting or shutting down. Requires console_sem.
2142 static int have_callable_console(void)
2144 struct console
*con
;
2146 for_each_console(con
)
2147 if ((con
->flags
& CON_ENABLED
) &&
2148 (con
->flags
& CON_ANYTIME
))
2155 * Can we actually use the console at this time on this cpu?
2157 * Console drivers may assume that per-cpu resources have been allocated. So
2158 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2159 * call them until this CPU is officially up.
2161 static inline int can_use_console(void)
2163 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2167 * console_unlock - unlock the console system
2169 * Releases the console_lock which the caller holds on the console system
2170 * and the console driver list.
2172 * While the console_lock was held, console output may have been buffered
2173 * by printk(). If this is the case, console_unlock(); emits
2174 * the output prior to releasing the lock.
2176 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2178 * console_unlock(); may be called from any context.
2180 void console_unlock(void)
2182 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2183 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2184 static u64 seen_seq
;
2185 unsigned long flags
;
2186 bool wake_klogd
= false;
2187 bool do_cond_resched
, retry
;
2189 if (console_suspended
) {
2195 * Console drivers are called under logbuf_lock, so
2196 * @console_may_schedule should be cleared before; however, we may
2197 * end up dumping a lot of lines, for example, if called from
2198 * console registration path, and should invoke cond_resched()
2199 * between lines if allowable. Not doing so can cause a very long
2200 * scheduling stall on a slow console leading to RCU stall and
2201 * softlockup warnings which exacerbate the issue with more
2202 * messages practically incapacitating the system.
2204 do_cond_resched
= console_may_schedule
;
2205 console_may_schedule
= 0;
2209 * We released the console_sem lock, so we need to recheck if
2210 * cpu is online and (if not) is there at least one CON_ANYTIME
2213 if (!can_use_console()) {
2220 struct printk_log
*msg
;
2225 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2226 if (seen_seq
!= log_next_seq
) {
2228 seen_seq
= log_next_seq
;
2231 if (console_seq
< log_first_seq
) {
2232 len
= sprintf(text
, "** %u printk messages dropped ** ",
2233 (unsigned)(log_first_seq
- console_seq
));
2235 /* messages are gone, move to first one */
2236 console_seq
= log_first_seq
;
2237 console_idx
= log_first_idx
;
2242 if (console_seq
== log_next_seq
)
2245 msg
= log_from_idx(console_idx
);
2247 if (suppress_message_printing(level
)) {
2249 * Skip record we have buffered and already printed
2250 * directly to the console when we received it, and
2251 * record that has level above the console loglevel.
2253 console_idx
= log_next(console_idx
);
2258 len
+= msg_print_text(msg
, false, text
+ len
, sizeof(text
) - len
);
2259 if (nr_ext_console_drivers
) {
2260 ext_len
= msg_print_ext_header(ext_text
,
2263 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2264 sizeof(ext_text
) - ext_len
,
2265 log_dict(msg
), msg
->dict_len
,
2266 log_text(msg
), msg
->text_len
);
2268 console_idx
= log_next(console_idx
);
2270 raw_spin_unlock(&logbuf_lock
);
2272 stop_critical_timings(); /* don't trace print latency */
2273 call_console_drivers(level
, ext_text
, ext_len
, text
, len
);
2274 start_critical_timings();
2275 local_irq_restore(flags
);
2277 if (do_cond_resched
)
2282 /* Release the exclusive_console once it is used */
2283 if (unlikely(exclusive_console
))
2284 exclusive_console
= NULL
;
2286 raw_spin_unlock(&logbuf_lock
);
2291 * Someone could have filled up the buffer again, so re-check if there's
2292 * something to flush. In case we cannot trylock the console_sem again,
2293 * there's a new owner and the console_unlock() from them will do the
2294 * flush, no worries.
2296 raw_spin_lock(&logbuf_lock
);
2297 retry
= console_seq
!= log_next_seq
;
2298 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2300 if (retry
&& console_trylock())
2306 EXPORT_SYMBOL(console_unlock
);
2309 * console_conditional_schedule - yield the CPU if required
2311 * If the console code is currently allowed to sleep, and
2312 * if this CPU should yield the CPU to another task, do
2315 * Must be called within console_lock();.
2317 void __sched
console_conditional_schedule(void)
2319 if (console_may_schedule
)
2322 EXPORT_SYMBOL(console_conditional_schedule
);
2324 void console_unblank(void)
2329 * console_unblank can no longer be called in interrupt context unless
2330 * oops_in_progress is set to 1..
2332 if (oops_in_progress
) {
2333 if (down_trylock_console_sem() != 0)
2339 console_may_schedule
= 0;
2341 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2347 * console_flush_on_panic - flush console content on panic
2349 * Immediately output all pending messages no matter what.
2351 void console_flush_on_panic(void)
2354 * If someone else is holding the console lock, trylock will fail
2355 * and may_schedule may be set. Ignore and proceed to unlock so
2356 * that messages are flushed out. As this can be called from any
2357 * context and we don't want to get preempted while flushing,
2358 * ensure may_schedule is cleared.
2361 console_may_schedule
= 0;
2366 * Return the console tty driver structure and its associated index
2368 struct tty_driver
*console_device(int *index
)
2371 struct tty_driver
*driver
= NULL
;
2374 for_each_console(c
) {
2377 driver
= c
->device(c
, index
);
2386 * Prevent further output on the passed console device so that (for example)
2387 * serial drivers can disable console output before suspending a port, and can
2388 * re-enable output afterwards.
2390 void console_stop(struct console
*console
)
2393 console
->flags
&= ~CON_ENABLED
;
2396 EXPORT_SYMBOL(console_stop
);
2398 void console_start(struct console
*console
)
2401 console
->flags
|= CON_ENABLED
;
2404 EXPORT_SYMBOL(console_start
);
2406 static int __read_mostly keep_bootcon
;
2408 static int __init
keep_bootcon_setup(char *str
)
2411 pr_info("debug: skip boot console de-registration.\n");
2416 early_param("keep_bootcon", keep_bootcon_setup
);
2419 * The console driver calls this routine during kernel initialization
2420 * to register the console printing procedure with printk() and to
2421 * print any messages that were printed by the kernel before the
2422 * console driver was initialized.
2424 * This can happen pretty early during the boot process (because of
2425 * early_printk) - sometimes before setup_arch() completes - be careful
2426 * of what kernel features are used - they may not be initialised yet.
2428 * There are two types of consoles - bootconsoles (early_printk) and
2429 * "real" consoles (everything which is not a bootconsole) which are
2430 * handled differently.
2431 * - Any number of bootconsoles can be registered at any time.
2432 * - As soon as a "real" console is registered, all bootconsoles
2433 * will be unregistered automatically.
2434 * - Once a "real" console is registered, any attempt to register a
2435 * bootconsoles will be rejected
2437 void register_console(struct console
*newcon
)
2440 unsigned long flags
;
2441 struct console
*bcon
= NULL
;
2442 struct console_cmdline
*c
;
2444 if (console_drivers
)
2445 for_each_console(bcon
)
2446 if (WARN(bcon
== newcon
,
2447 "console '%s%d' already registered\n",
2448 bcon
->name
, bcon
->index
))
2452 * before we register a new CON_BOOT console, make sure we don't
2453 * already have a valid console
2455 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2456 /* find the last or real console */
2457 for_each_console(bcon
) {
2458 if (!(bcon
->flags
& CON_BOOT
)) {
2459 pr_info("Too late to register bootconsole %s%d\n",
2460 newcon
->name
, newcon
->index
);
2466 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2467 bcon
= console_drivers
;
2469 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2470 preferred_console
= selected_console
;
2473 * See if we want to use this console driver. If we
2474 * didn't select a console we take the first one
2475 * that registers here.
2477 if (preferred_console
< 0) {
2478 if (newcon
->index
< 0)
2480 if (newcon
->setup
== NULL
||
2481 newcon
->setup(newcon
, NULL
) == 0) {
2482 newcon
->flags
|= CON_ENABLED
;
2483 if (newcon
->device
) {
2484 newcon
->flags
|= CON_CONSDEV
;
2485 preferred_console
= 0;
2491 * See if this console matches one we selected on
2494 for (i
= 0, c
= console_cmdline
;
2495 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2497 if (!newcon
->match
||
2498 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2499 /* default matching */
2500 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2501 if (strcmp(c
->name
, newcon
->name
) != 0)
2503 if (newcon
->index
>= 0 &&
2504 newcon
->index
!= c
->index
)
2506 if (newcon
->index
< 0)
2507 newcon
->index
= c
->index
;
2509 if (_braille_register_console(newcon
, c
))
2512 if (newcon
->setup
&&
2513 newcon
->setup(newcon
, c
->options
) != 0)
2517 newcon
->flags
|= CON_ENABLED
;
2518 if (i
== selected_console
) {
2519 newcon
->flags
|= CON_CONSDEV
;
2520 preferred_console
= selected_console
;
2525 if (!(newcon
->flags
& CON_ENABLED
))
2529 * If we have a bootconsole, and are switching to a real console,
2530 * don't print everything out again, since when the boot console, and
2531 * the real console are the same physical device, it's annoying to
2532 * see the beginning boot messages twice
2534 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2535 newcon
->flags
&= ~CON_PRINTBUFFER
;
2538 * Put this console in the list - keep the
2539 * preferred driver at the head of the list.
2542 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2543 newcon
->next
= console_drivers
;
2544 console_drivers
= newcon
;
2546 newcon
->next
->flags
&= ~CON_CONSDEV
;
2548 newcon
->next
= console_drivers
->next
;
2549 console_drivers
->next
= newcon
;
2552 if (newcon
->flags
& CON_EXTENDED
)
2553 if (!nr_ext_console_drivers
++)
2554 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2556 if (newcon
->flags
& CON_PRINTBUFFER
) {
2558 * console_unlock(); will print out the buffered messages
2561 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2562 console_seq
= syslog_seq
;
2563 console_idx
= syslog_idx
;
2564 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2566 * We're about to replay the log buffer. Only do this to the
2567 * just-registered console to avoid excessive message spam to
2568 * the already-registered consoles.
2570 exclusive_console
= newcon
;
2573 console_sysfs_notify();
2576 * By unregistering the bootconsoles after we enable the real console
2577 * we get the "console xxx enabled" message on all the consoles -
2578 * boot consoles, real consoles, etc - this is to ensure that end
2579 * users know there might be something in the kernel's log buffer that
2580 * went to the bootconsole (that they do not see on the real console)
2582 pr_info("%sconsole [%s%d] enabled\n",
2583 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2584 newcon
->name
, newcon
->index
);
2586 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2588 /* We need to iterate through all boot consoles, to make
2589 * sure we print everything out, before we unregister them.
2591 for_each_console(bcon
)
2592 if (bcon
->flags
& CON_BOOT
)
2593 unregister_console(bcon
);
2596 EXPORT_SYMBOL(register_console
);
2598 int unregister_console(struct console
*console
)
2600 struct console
*a
, *b
;
2603 pr_info("%sconsole [%s%d] disabled\n",
2604 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2605 console
->name
, console
->index
);
2607 res
= _braille_unregister_console(console
);
2613 if (console_drivers
== console
) {
2614 console_drivers
=console
->next
;
2616 } else if (console_drivers
) {
2617 for (a
=console_drivers
->next
, b
=console_drivers
;
2618 a
; b
=a
, a
=b
->next
) {
2627 if (!res
&& (console
->flags
& CON_EXTENDED
))
2628 nr_ext_console_drivers
--;
2631 * If this isn't the last console and it has CON_CONSDEV set, we
2632 * need to set it on the next preferred console.
2634 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2635 console_drivers
->flags
|= CON_CONSDEV
;
2637 console
->flags
&= ~CON_ENABLED
;
2639 console_sysfs_notify();
2642 EXPORT_SYMBOL(unregister_console
);
2645 * Some boot consoles access data that is in the init section and which will
2646 * be discarded after the initcalls have been run. To make sure that no code
2647 * will access this data, unregister the boot consoles in a late initcall.
2649 * If for some reason, such as deferred probe or the driver being a loadable
2650 * module, the real console hasn't registered yet at this point, there will
2651 * be a brief interval in which no messages are logged to the console, which
2652 * makes it difficult to diagnose problems that occur during this time.
2654 * To mitigate this problem somewhat, only unregister consoles whose memory
2655 * intersects with the init section. Note that code exists elsewhere to get
2656 * rid of the boot console as soon as the proper console shows up, so there
2657 * won't be side-effects from postponing the removal.
2659 static int __init
printk_late_init(void)
2661 struct console
*con
;
2664 for_each_console(con
) {
2665 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2667 * Make sure to unregister boot consoles whose data
2668 * resides in the init section before the init section
2669 * is discarded. Boot consoles whose data will stick
2670 * around will automatically be unregistered when the
2671 * proper console replaces them.
2673 if (init_section_intersects(con
, sizeof(*con
)))
2674 unregister_console(con
);
2677 ret
= cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD
, "printk:dead", NULL
,
2678 console_cpu_notify
);
2680 ret
= cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN
, "printk:online",
2681 console_cpu_notify
, NULL
);
2685 late_initcall(printk_late_init
);
2687 #if defined CONFIG_PRINTK
2689 * Delayed printk version, for scheduler-internal messages:
2691 #define PRINTK_PENDING_WAKEUP 0x01
2692 #define PRINTK_PENDING_OUTPUT 0x02
2694 static DEFINE_PER_CPU(int, printk_pending
);
2696 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2698 int pending
= __this_cpu_xchg(printk_pending
, 0);
2700 if (pending
& PRINTK_PENDING_OUTPUT
) {
2701 /* If trylock fails, someone else is doing the printing */
2702 if (console_trylock())
2706 if (pending
& PRINTK_PENDING_WAKEUP
)
2707 wake_up_interruptible(&log_wait
);
2710 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2711 .func
= wake_up_klogd_work_func
,
2712 .flags
= IRQ_WORK_LAZY
,
2715 void wake_up_klogd(void)
2718 if (waitqueue_active(&log_wait
)) {
2719 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2720 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2725 int printk_deferred(const char *fmt
, ...)
2731 va_start(args
, fmt
);
2732 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2735 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2736 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2743 * printk rate limiting, lifted from the networking subsystem.
2745 * This enforces a rate limit: not more than 10 kernel messages
2746 * every 5s to make a denial-of-service attack impossible.
2748 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2750 int __printk_ratelimit(const char *func
)
2752 return ___ratelimit(&printk_ratelimit_state
, func
);
2754 EXPORT_SYMBOL(__printk_ratelimit
);
2757 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2758 * @caller_jiffies: pointer to caller's state
2759 * @interval_msecs: minimum interval between prints
2761 * printk_timed_ratelimit() returns true if more than @interval_msecs
2762 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2765 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2766 unsigned int interval_msecs
)
2768 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2770 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2773 *caller_jiffies
= jiffies
;
2776 EXPORT_SYMBOL(printk_timed_ratelimit
);
2778 static DEFINE_SPINLOCK(dump_list_lock
);
2779 static LIST_HEAD(dump_list
);
2782 * kmsg_dump_register - register a kernel log dumper.
2783 * @dumper: pointer to the kmsg_dumper structure
2785 * Adds a kernel log dumper to the system. The dump callback in the
2786 * structure will be called when the kernel oopses or panics and must be
2787 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2789 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2791 unsigned long flags
;
2794 /* The dump callback needs to be set */
2798 spin_lock_irqsave(&dump_list_lock
, flags
);
2799 /* Don't allow registering multiple times */
2800 if (!dumper
->registered
) {
2801 dumper
->registered
= 1;
2802 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2805 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2809 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2812 * kmsg_dump_unregister - unregister a kmsg dumper.
2813 * @dumper: pointer to the kmsg_dumper structure
2815 * Removes a dump device from the system. Returns zero on success and
2816 * %-EINVAL otherwise.
2818 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2820 unsigned long flags
;
2823 spin_lock_irqsave(&dump_list_lock
, flags
);
2824 if (dumper
->registered
) {
2825 dumper
->registered
= 0;
2826 list_del_rcu(&dumper
->list
);
2829 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2834 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2836 static bool always_kmsg_dump
;
2837 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2840 * kmsg_dump - dump kernel log to kernel message dumpers.
2841 * @reason: the reason (oops, panic etc) for dumping
2843 * Call each of the registered dumper's dump() callback, which can
2844 * retrieve the kmsg records with kmsg_dump_get_line() or
2845 * kmsg_dump_get_buffer().
2847 void kmsg_dump(enum kmsg_dump_reason reason
)
2849 struct kmsg_dumper
*dumper
;
2850 unsigned long flags
;
2852 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2856 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2857 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2860 /* initialize iterator with data about the stored records */
2861 dumper
->active
= true;
2863 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2864 dumper
->cur_seq
= clear_seq
;
2865 dumper
->cur_idx
= clear_idx
;
2866 dumper
->next_seq
= log_next_seq
;
2867 dumper
->next_idx
= log_next_idx
;
2868 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2870 /* invoke dumper which will iterate over records */
2871 dumper
->dump(dumper
, reason
);
2873 /* reset iterator */
2874 dumper
->active
= false;
2880 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2881 * @dumper: registered kmsg dumper
2882 * @syslog: include the "<4>" prefixes
2883 * @line: buffer to copy the line to
2884 * @size: maximum size of the buffer
2885 * @len: length of line placed into buffer
2887 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2888 * record, and copy one record into the provided buffer.
2890 * Consecutive calls will return the next available record moving
2891 * towards the end of the buffer with the youngest messages.
2893 * A return value of FALSE indicates that there are no more records to
2896 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2898 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
2899 char *line
, size_t size
, size_t *len
)
2901 struct printk_log
*msg
;
2905 if (!dumper
->active
)
2908 if (dumper
->cur_seq
< log_first_seq
) {
2909 /* messages are gone, move to first available one */
2910 dumper
->cur_seq
= log_first_seq
;
2911 dumper
->cur_idx
= log_first_idx
;
2915 if (dumper
->cur_seq
>= log_next_seq
)
2918 msg
= log_from_idx(dumper
->cur_idx
);
2919 l
= msg_print_text(msg
, syslog
, line
, size
);
2921 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2931 * kmsg_dump_get_line - retrieve one kmsg log line
2932 * @dumper: registered kmsg dumper
2933 * @syslog: include the "<4>" prefixes
2934 * @line: buffer to copy the line to
2935 * @size: maximum size of the buffer
2936 * @len: length of line placed into buffer
2938 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2939 * record, and copy one record into the provided buffer.
2941 * Consecutive calls will return the next available record moving
2942 * towards the end of the buffer with the youngest messages.
2944 * A return value of FALSE indicates that there are no more records to
2947 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2948 char *line
, size_t size
, size_t *len
)
2950 unsigned long flags
;
2953 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2954 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
2955 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2959 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2962 * kmsg_dump_get_buffer - copy kmsg log lines
2963 * @dumper: registered kmsg dumper
2964 * @syslog: include the "<4>" prefixes
2965 * @buf: buffer to copy the line to
2966 * @size: maximum size of the buffer
2967 * @len: length of line placed into buffer
2969 * Start at the end of the kmsg buffer and fill the provided buffer
2970 * with as many of the the *youngest* kmsg records that fit into it.
2971 * If the buffer is large enough, all available kmsg records will be
2972 * copied with a single call.
2974 * Consecutive calls will fill the buffer with the next block of
2975 * available older records, not including the earlier retrieved ones.
2977 * A return value of FALSE indicates that there are no more records to
2980 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
2981 char *buf
, size_t size
, size_t *len
)
2983 unsigned long flags
;
2991 if (!dumper
->active
)
2994 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2995 if (dumper
->cur_seq
< log_first_seq
) {
2996 /* messages are gone, move to first available one */
2997 dumper
->cur_seq
= log_first_seq
;
2998 dumper
->cur_idx
= log_first_idx
;
3002 if (dumper
->cur_seq
>= dumper
->next_seq
) {
3003 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3007 /* calculate length of entire buffer */
3008 seq
= dumper
->cur_seq
;
3009 idx
= dumper
->cur_idx
;
3010 while (seq
< dumper
->next_seq
) {
3011 struct printk_log
*msg
= log_from_idx(idx
);
3013 l
+= msg_print_text(msg
, true, NULL
, 0);
3014 idx
= log_next(idx
);
3018 /* move first record forward until length fits into the buffer */
3019 seq
= dumper
->cur_seq
;
3020 idx
= dumper
->cur_idx
;
3021 while (l
> size
&& seq
< dumper
->next_seq
) {
3022 struct printk_log
*msg
= log_from_idx(idx
);
3024 l
-= msg_print_text(msg
, true, NULL
, 0);
3025 idx
= log_next(idx
);
3029 /* last message in next interation */
3034 while (seq
< dumper
->next_seq
) {
3035 struct printk_log
*msg
= log_from_idx(idx
);
3037 l
+= msg_print_text(msg
, syslog
, buf
+ l
, size
- l
);
3038 idx
= log_next(idx
);
3042 dumper
->next_seq
= next_seq
;
3043 dumper
->next_idx
= next_idx
;
3045 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3051 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3054 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3055 * @dumper: registered kmsg dumper
3057 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3058 * kmsg_dump_get_buffer() can be called again and used multiple
3059 * times within the same dumper.dump() callback.
3061 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3063 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3065 dumper
->cur_seq
= clear_seq
;
3066 dumper
->cur_idx
= clear_idx
;
3067 dumper
->next_seq
= log_next_seq
;
3068 dumper
->next_idx
= log_next_idx
;
3072 * kmsg_dump_rewind - reset the interator
3073 * @dumper: registered kmsg dumper
3075 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3076 * kmsg_dump_get_buffer() can be called again and used multiple
3077 * times within the same dumper.dump() callback.
3079 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3081 unsigned long flags
;
3083 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3084 kmsg_dump_rewind_nolock(dumper
);
3085 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3087 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3089 static char dump_stack_arch_desc_str
[128];
3092 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3093 * @fmt: printf-style format string
3094 * @...: arguments for the format string
3096 * The configured string will be printed right after utsname during task
3097 * dumps. Usually used to add arch-specific system identifiers. If an
3098 * arch wants to make use of such an ID string, it should initialize this
3099 * as soon as possible during boot.
3101 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3105 va_start(args
, fmt
);
3106 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3112 * dump_stack_print_info - print generic debug info for dump_stack()
3113 * @log_lvl: log level
3115 * Arch-specific dump_stack() implementations can use this function to
3116 * print out the same debug information as the generic dump_stack().
3118 void dump_stack_print_info(const char *log_lvl
)
3120 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3121 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3122 print_tainted(), init_utsname()->release
,
3123 (int)strcspn(init_utsname()->version
, " "),
3124 init_utsname()->version
);
3126 if (dump_stack_arch_desc_str
[0] != '\0')
3127 printk("%sHardware name: %s\n",
3128 log_lvl
, dump_stack_arch_desc_str
);
3130 print_worker_info(log_lvl
, current
);
3134 * show_regs_print_info - print generic debug info for show_regs()
3135 * @log_lvl: log level
3137 * show_regs() implementations can use this function to print out generic
3138 * debug information.
3140 void show_regs_print_info(const char *log_lvl
)
3142 dump_stack_print_info(log_lvl
);
3144 printk("%stask: %p task.stack: %p\n",
3145 log_lvl
, current
, task_stack_page(current
));