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>
48 #include <linux/sched/clock.h>
50 #include <linux/uaccess.h>
51 #include <asm/sections.h>
53 #define CREATE_TRACE_POINTS
54 #include <trace/events/printk.h>
56 #include "console_cmdline.h"
60 int console_printk
[4] = {
61 CONSOLE_LOGLEVEL_DEFAULT
, /* console_loglevel */
62 MESSAGE_LOGLEVEL_DEFAULT
, /* default_message_loglevel */
63 CONSOLE_LOGLEVEL_MIN
, /* minimum_console_loglevel */
64 CONSOLE_LOGLEVEL_DEFAULT
, /* default_console_loglevel */
68 * Low level drivers may need that to know if they can schedule in
69 * their unblank() callback or not. So let's export it.
72 EXPORT_SYMBOL(oops_in_progress
);
75 * console_sem protects the console_drivers list, and also
76 * provides serialisation for access to the entire console
79 static DEFINE_SEMAPHORE(console_sem
);
80 struct console
*console_drivers
;
81 EXPORT_SYMBOL_GPL(console_drivers
);
84 static struct lockdep_map console_lock_dep_map
= {
85 .name
= "console_lock"
89 enum devkmsg_log_bits
{
90 __DEVKMSG_LOG_BIT_ON
= 0,
91 __DEVKMSG_LOG_BIT_OFF
,
92 __DEVKMSG_LOG_BIT_LOCK
,
95 enum devkmsg_log_masks
{
96 DEVKMSG_LOG_MASK_ON
= BIT(__DEVKMSG_LOG_BIT_ON
),
97 DEVKMSG_LOG_MASK_OFF
= BIT(__DEVKMSG_LOG_BIT_OFF
),
98 DEVKMSG_LOG_MASK_LOCK
= BIT(__DEVKMSG_LOG_BIT_LOCK
),
101 /* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
102 #define DEVKMSG_LOG_MASK_DEFAULT 0
104 static unsigned int __read_mostly devkmsg_log
= DEVKMSG_LOG_MASK_DEFAULT
;
106 static int __control_devkmsg(char *str
)
111 if (!strncmp(str
, "on", 2)) {
112 devkmsg_log
= DEVKMSG_LOG_MASK_ON
;
114 } else if (!strncmp(str
, "off", 3)) {
115 devkmsg_log
= DEVKMSG_LOG_MASK_OFF
;
117 } else if (!strncmp(str
, "ratelimit", 9)) {
118 devkmsg_log
= DEVKMSG_LOG_MASK_DEFAULT
;
124 static int __init
control_devkmsg(char *str
)
126 if (__control_devkmsg(str
) < 0)
130 * Set sysctl string accordingly:
132 if (devkmsg_log
== DEVKMSG_LOG_MASK_ON
) {
133 memset(devkmsg_log_str
, 0, DEVKMSG_STR_MAX_SIZE
);
134 strncpy(devkmsg_log_str
, "on", 2);
135 } else if (devkmsg_log
== DEVKMSG_LOG_MASK_OFF
) {
136 memset(devkmsg_log_str
, 0, DEVKMSG_STR_MAX_SIZE
);
137 strncpy(devkmsg_log_str
, "off", 3);
139 /* else "ratelimit" which is set by default. */
142 * Sysctl cannot change it anymore. The kernel command line setting of
143 * this parameter is to force the setting to be permanent throughout the
144 * runtime of the system. This is a precation measure against userspace
145 * trying to be a smarta** and attempting to change it up on us.
147 devkmsg_log
|= DEVKMSG_LOG_MASK_LOCK
;
151 __setup("printk.devkmsg=", control_devkmsg
);
153 char devkmsg_log_str
[DEVKMSG_STR_MAX_SIZE
] = "ratelimit";
155 int devkmsg_sysctl_set_loglvl(struct ctl_table
*table
, int write
,
156 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
158 char old_str
[DEVKMSG_STR_MAX_SIZE
];
163 if (devkmsg_log
& DEVKMSG_LOG_MASK_LOCK
)
167 strncpy(old_str
, devkmsg_log_str
, DEVKMSG_STR_MAX_SIZE
);
170 err
= proc_dostring(table
, write
, buffer
, lenp
, ppos
);
175 err
= __control_devkmsg(devkmsg_log_str
);
178 * Do not accept an unknown string OR a known string with
181 if (err
< 0 || (err
+ 1 != *lenp
)) {
183 /* ... and restore old setting. */
185 strncpy(devkmsg_log_str
, old_str
, DEVKMSG_STR_MAX_SIZE
);
195 * Number of registered extended console drivers.
197 * If extended consoles are present, in-kernel cont reassembly is disabled
198 * and each fragment is stored as a separate log entry with proper
199 * continuation flag so that every emitted message has full metadata. This
200 * doesn't change the result for regular consoles or /proc/kmsg. For
201 * /dev/kmsg, as long as the reader concatenates messages according to
202 * consecutive continuation flags, the end result should be the same too.
204 static int nr_ext_console_drivers
;
207 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
208 * macros instead of functions so that _RET_IP_ contains useful information.
210 #define down_console_sem() do { \
212 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
215 static int __down_trylock_console_sem(unsigned long ip
)
221 * Here and in __up_console_sem() we need to be in safe mode,
222 * because spindump/WARN/etc from under console ->lock will
223 * deadlock in printk()->down_trylock_console_sem() otherwise.
225 printk_safe_enter_irqsave(flags
);
226 lock_failed
= down_trylock(&console_sem
);
227 printk_safe_exit_irqrestore(flags
);
231 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
234 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
236 static void __up_console_sem(unsigned long ip
)
240 mutex_release(&console_lock_dep_map
, 1, ip
);
242 printk_safe_enter_irqsave(flags
);
244 printk_safe_exit_irqrestore(flags
);
246 #define up_console_sem() __up_console_sem(_RET_IP_)
249 * This is used for debugging the mess that is the VT code by
250 * keeping track if we have the console semaphore held. It's
251 * definitely not the perfect debug tool (we don't know if _WE_
252 * hold it and are racing, but it helps tracking those weird code
253 * paths in the console code where we end up in places I want
254 * locked without the console sempahore held).
256 static int console_locked
, console_suspended
;
259 * If exclusive_console is non-NULL then only this console is to be printed to.
261 static struct console
*exclusive_console
;
264 * Array of consoles built from command line options (console=)
267 #define MAX_CMDLINECONSOLES 8
269 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
271 static int selected_console
= -1;
272 static int preferred_console
= -1;
273 int console_set_on_cmdline
;
274 EXPORT_SYMBOL(console_set_on_cmdline
);
276 /* Flag: console code may call schedule() */
277 static int console_may_schedule
;
280 * The printk log buffer consists of a chain of concatenated variable
281 * length records. Every record starts with a record header, containing
282 * the overall length of the record.
284 * The heads to the first and last entry in the buffer, as well as the
285 * sequence numbers of these entries are maintained when messages are
288 * If the heads indicate available messages, the length in the header
289 * tells the start next message. A length == 0 for the next message
290 * indicates a wrap-around to the beginning of the buffer.
292 * Every record carries the monotonic timestamp in microseconds, as well as
293 * the standard userspace syslog level and syslog facility. The usual
294 * kernel messages use LOG_KERN; userspace-injected messages always carry
295 * a matching syslog facility, by default LOG_USER. The origin of every
296 * message can be reliably determined that way.
298 * The human readable log message directly follows the message header. The
299 * length of the message text is stored in the header, the stored message
302 * Optionally, a message can carry a dictionary of properties (key/value pairs),
303 * to provide userspace with a machine-readable message context.
305 * Examples for well-defined, commonly used property names are:
306 * DEVICE=b12:8 device identifier
310 * +sound:card0 subsystem:devname
311 * SUBSYSTEM=pci driver-core subsystem name
313 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
314 * follows directly after a '=' character. Every property is terminated by
315 * a '\0' character. The last property is not terminated.
317 * Example of a message structure:
318 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
319 * 0008 34 00 record is 52 bytes long
320 * 000a 0b 00 text is 11 bytes long
321 * 000c 1f 00 dictionary is 23 bytes long
322 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
323 * 0010 69 74 27 73 20 61 20 6c "it's a l"
325 * 001b 44 45 56 49 43 "DEVIC"
326 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
327 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
329 * 0032 00 00 00 padding to next message header
331 * The 'struct printk_log' buffer header must never be directly exported to
332 * userspace, it is a kernel-private implementation detail that might
333 * need to be changed in the future, when the requirements change.
335 * /dev/kmsg exports the structured data in the following line format:
336 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
338 * Users of the export format should ignore possible additional values
339 * separated by ',', and find the message after the ';' character.
341 * The optional key/value pairs are attached as continuation lines starting
342 * with a space character and terminated by a newline. All possible
343 * non-prinatable characters are escaped in the "\xff" notation.
347 LOG_NOCONS
= 1, /* already flushed, do not print to console */
348 LOG_NEWLINE
= 2, /* text ended with a newline */
349 LOG_PREFIX
= 4, /* text started with a prefix */
350 LOG_CONT
= 8, /* text is a fragment of a continuation line */
354 u64 ts_nsec
; /* timestamp in nanoseconds */
355 u16 len
; /* length of entire record */
356 u16 text_len
; /* length of text buffer */
357 u16 dict_len
; /* length of dictionary buffer */
358 u8 facility
; /* syslog facility */
359 u8 flags
:5; /* internal record flags */
360 u8 level
:3; /* syslog level */
362 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
363 __packed
__aligned(4)
368 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
369 * within the scheduler's rq lock. It must be released before calling
370 * console_unlock() or anything else that might wake up a process.
372 DEFINE_RAW_SPINLOCK(logbuf_lock
);
375 * Helper macros to lock/unlock logbuf_lock and switch between
376 * printk-safe/unsafe modes.
378 #define logbuf_lock_irq() \
380 printk_safe_enter_irq(); \
381 raw_spin_lock(&logbuf_lock); \
384 #define logbuf_unlock_irq() \
386 raw_spin_unlock(&logbuf_lock); \
387 printk_safe_exit_irq(); \
390 #define logbuf_lock_irqsave(flags) \
392 printk_safe_enter_irqsave(flags); \
393 raw_spin_lock(&logbuf_lock); \
396 #define logbuf_unlock_irqrestore(flags) \
398 raw_spin_unlock(&logbuf_lock); \
399 printk_safe_exit_irqrestore(flags); \
403 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
404 /* the next printk record to read by syslog(READ) or /proc/kmsg */
405 static u64 syslog_seq
;
406 static u32 syslog_idx
;
407 static size_t syslog_partial
;
409 /* index and sequence number of the first record stored in the buffer */
410 static u64 log_first_seq
;
411 static u32 log_first_idx
;
413 /* index and sequence number of the next record to store in the buffer */
414 static u64 log_next_seq
;
415 static u32 log_next_idx
;
417 /* the next printk record to write to the console */
418 static u64 console_seq
;
419 static u32 console_idx
;
421 /* the next printk record to read after the last 'clear' command */
422 static u64 clear_seq
;
423 static u32 clear_idx
;
425 #define PREFIX_MAX 32
426 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
428 #define LOG_LEVEL(v) ((v) & 0x07)
429 #define LOG_FACILITY(v) ((v) >> 3 & 0xff)
432 #define LOG_ALIGN __alignof__(struct printk_log)
433 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
434 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
435 static char *log_buf
= __log_buf
;
436 static u32 log_buf_len
= __LOG_BUF_LEN
;
438 /* Return log buffer address */
439 char *log_buf_addr_get(void)
444 /* Return log buffer size */
445 u32
log_buf_len_get(void)
450 /* human readable text of the record */
451 static char *log_text(const struct printk_log
*msg
)
453 return (char *)msg
+ sizeof(struct printk_log
);
456 /* optional key/value pair dictionary attached to the record */
457 static char *log_dict(const struct printk_log
*msg
)
459 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
462 /* get record by index; idx must point to valid msg */
463 static struct printk_log
*log_from_idx(u32 idx
)
465 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
468 * A length == 0 record is the end of buffer marker. Wrap around and
469 * read the message at the start of the buffer.
472 return (struct printk_log
*)log_buf
;
476 /* get next record; idx must point to valid msg */
477 static u32
log_next(u32 idx
)
479 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
481 /* length == 0 indicates the end of the buffer; wrap */
483 * A length == 0 record is the end of buffer marker. Wrap around and
484 * read the message at the start of the buffer as *this* one, and
485 * return the one after that.
488 msg
= (struct printk_log
*)log_buf
;
491 return idx
+ msg
->len
;
495 * Check whether there is enough free space for the given message.
497 * The same values of first_idx and next_idx mean that the buffer
498 * is either empty or full.
500 * If the buffer is empty, we must respect the position of the indexes.
501 * They cannot be reset to the beginning of the buffer.
503 static int logbuf_has_space(u32 msg_size
, bool empty
)
507 if (log_next_idx
> log_first_idx
|| empty
)
508 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
510 free
= log_first_idx
- log_next_idx
;
513 * We need space also for an empty header that signalizes wrapping
516 return free
>= msg_size
+ sizeof(struct printk_log
);
519 static int log_make_free_space(u32 msg_size
)
521 while (log_first_seq
< log_next_seq
&&
522 !logbuf_has_space(msg_size
, false)) {
523 /* drop old messages until we have enough contiguous space */
524 log_first_idx
= log_next(log_first_idx
);
528 if (clear_seq
< log_first_seq
) {
529 clear_seq
= log_first_seq
;
530 clear_idx
= log_first_idx
;
533 /* sequence numbers are equal, so the log buffer is empty */
534 if (logbuf_has_space(msg_size
, log_first_seq
== log_next_seq
))
540 /* compute the message size including the padding bytes */
541 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
545 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
546 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
553 * Define how much of the log buffer we could take at maximum. The value
554 * must be greater than two. Note that only half of the buffer is available
555 * when the index points to the middle.
557 #define MAX_LOG_TAKE_PART 4
558 static const char trunc_msg
[] = "<truncated>";
560 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
561 u16
*dict_len
, u32
*pad_len
)
564 * The message should not take the whole buffer. Otherwise, it might
565 * get removed too soon.
567 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
568 if (*text_len
> max_text_len
)
569 *text_len
= max_text_len
;
570 /* enable the warning message */
571 *trunc_msg_len
= strlen(trunc_msg
);
572 /* disable the "dict" completely */
574 /* compute the size again, count also the warning message */
575 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
578 /* insert record into the buffer, discard old ones, update heads */
579 static int log_store(int facility
, int level
,
580 enum log_flags flags
, u64 ts_nsec
,
581 const char *dict
, u16 dict_len
,
582 const char *text
, u16 text_len
)
584 struct printk_log
*msg
;
586 u16 trunc_msg_len
= 0;
588 /* number of '\0' padding bytes to next message */
589 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
591 if (log_make_free_space(size
)) {
592 /* truncate the message if it is too long for empty buffer */
593 size
= truncate_msg(&text_len
, &trunc_msg_len
,
594 &dict_len
, &pad_len
);
595 /* survive when the log buffer is too small for trunc_msg */
596 if (log_make_free_space(size
))
600 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
602 * This message + an additional empty header does not fit
603 * at the end of the buffer. Add an empty header with len == 0
604 * to signify a wrap around.
606 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
611 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
612 memcpy(log_text(msg
), text
, text_len
);
613 msg
->text_len
= text_len
;
615 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
616 msg
->text_len
+= trunc_msg_len
;
618 memcpy(log_dict(msg
), dict
, dict_len
);
619 msg
->dict_len
= dict_len
;
620 msg
->facility
= facility
;
621 msg
->level
= level
& 7;
622 msg
->flags
= flags
& 0x1f;
624 msg
->ts_nsec
= ts_nsec
;
626 msg
->ts_nsec
= local_clock();
627 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
631 log_next_idx
+= msg
->len
;
634 return msg
->text_len
;
637 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
639 static int syslog_action_restricted(int type
)
644 * Unless restricted, we allow "read all" and "get buffer size"
647 return type
!= SYSLOG_ACTION_READ_ALL
&&
648 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
651 int check_syslog_permissions(int type
, int source
)
654 * If this is from /proc/kmsg and we've already opened it, then we've
655 * already done the capabilities checks at open time.
657 if (source
== SYSLOG_FROM_PROC
&& type
!= SYSLOG_ACTION_OPEN
)
660 if (syslog_action_restricted(type
)) {
661 if (capable(CAP_SYSLOG
))
664 * For historical reasons, accept CAP_SYS_ADMIN too, with
667 if (capable(CAP_SYS_ADMIN
)) {
668 pr_warn_once("%s (%d): Attempt to access syslog with "
669 "CAP_SYS_ADMIN but no CAP_SYSLOG "
671 current
->comm
, task_pid_nr(current
));
677 return security_syslog(type
);
679 EXPORT_SYMBOL_GPL(check_syslog_permissions
);
681 static void append_char(char **pp
, char *e
, char c
)
687 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
688 struct printk_log
*msg
, u64 seq
)
690 u64 ts_usec
= msg
->ts_nsec
;
692 do_div(ts_usec
, 1000);
694 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
695 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
,
696 msg
->flags
& LOG_CONT
? 'c' : '-');
699 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
700 char *dict
, size_t dict_len
,
701 char *text
, size_t text_len
)
703 char *p
= buf
, *e
= buf
+ size
;
706 /* escape non-printable characters */
707 for (i
= 0; i
< text_len
; i
++) {
708 unsigned char c
= text
[i
];
710 if (c
< ' ' || c
>= 127 || c
== '\\')
711 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
713 append_char(&p
, e
, c
);
715 append_char(&p
, e
, '\n');
720 for (i
= 0; i
< dict_len
; i
++) {
721 unsigned char c
= dict
[i
];
724 append_char(&p
, e
, ' ');
729 append_char(&p
, e
, '\n');
734 if (c
< ' ' || c
>= 127 || c
== '\\') {
735 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
739 append_char(&p
, e
, c
);
741 append_char(&p
, e
, '\n');
747 /* /dev/kmsg - userspace message inject/listen interface */
748 struct devkmsg_user
{
751 struct ratelimit_state rs
;
753 char buf
[CONSOLE_EXT_LOG_MAX
];
756 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
759 int level
= default_message_loglevel
;
760 int facility
= 1; /* LOG_USER */
761 struct file
*file
= iocb
->ki_filp
;
762 struct devkmsg_user
*user
= file
->private_data
;
763 size_t len
= iov_iter_count(from
);
766 if (!user
|| len
> LOG_LINE_MAX
)
769 /* Ignore when user logging is disabled. */
770 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
773 /* Ratelimit when not explicitly enabled. */
774 if (!(devkmsg_log
& DEVKMSG_LOG_MASK_ON
)) {
775 if (!___ratelimit(&user
->rs
, current
->comm
))
779 buf
= kmalloc(len
+1, GFP_KERNEL
);
784 if (!copy_from_iter_full(buf
, len
, from
)) {
790 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
791 * the decimal value represents 32bit, the lower 3 bit are the log
792 * level, the rest are the log facility.
794 * If no prefix or no userspace facility is specified, we
795 * enforce LOG_USER, to be able to reliably distinguish
796 * kernel-generated messages from userspace-injected ones.
799 if (line
[0] == '<') {
803 u
= simple_strtoul(line
+ 1, &endp
, 10);
804 if (endp
&& endp
[0] == '>') {
805 level
= LOG_LEVEL(u
);
806 if (LOG_FACILITY(u
) != 0)
807 facility
= LOG_FACILITY(u
);
814 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
819 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
820 size_t count
, loff_t
*ppos
)
822 struct devkmsg_user
*user
= file
->private_data
;
823 struct printk_log
*msg
;
830 ret
= mutex_lock_interruptible(&user
->lock
);
835 while (user
->seq
== log_next_seq
) {
836 if (file
->f_flags
& O_NONBLOCK
) {
843 ret
= wait_event_interruptible(log_wait
,
844 user
->seq
!= log_next_seq
);
850 if (user
->seq
< log_first_seq
) {
851 /* our last seen message is gone, return error and reset */
852 user
->idx
= log_first_idx
;
853 user
->seq
= log_first_seq
;
859 msg
= log_from_idx(user
->idx
);
860 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
862 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
863 log_dict(msg
), msg
->dict_len
,
864 log_text(msg
), msg
->text_len
);
866 user
->idx
= log_next(user
->idx
);
875 if (copy_to_user(buf
, user
->buf
, len
)) {
881 mutex_unlock(&user
->lock
);
885 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
887 struct devkmsg_user
*user
= file
->private_data
;
898 /* the first record */
899 user
->idx
= log_first_idx
;
900 user
->seq
= log_first_seq
;
904 * The first record after the last SYSLOG_ACTION_CLEAR,
905 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
906 * changes no global state, and does not clear anything.
908 user
->idx
= clear_idx
;
909 user
->seq
= clear_seq
;
912 /* after the last record */
913 user
->idx
= log_next_idx
;
914 user
->seq
= log_next_seq
;
923 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
925 struct devkmsg_user
*user
= file
->private_data
;
929 return POLLERR
|POLLNVAL
;
931 poll_wait(file
, &log_wait
, wait
);
934 if (user
->seq
< log_next_seq
) {
935 /* return error when data has vanished underneath us */
936 if (user
->seq
< log_first_seq
)
937 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
939 ret
= POLLIN
|POLLRDNORM
;
946 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
948 struct devkmsg_user
*user
;
951 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
954 /* write-only does not need any file context */
955 if ((file
->f_flags
& O_ACCMODE
) != O_WRONLY
) {
956 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
962 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
966 ratelimit_default_init(&user
->rs
);
967 ratelimit_set_flags(&user
->rs
, RATELIMIT_MSG_ON_RELEASE
);
969 mutex_init(&user
->lock
);
972 user
->idx
= log_first_idx
;
973 user
->seq
= log_first_seq
;
976 file
->private_data
= user
;
980 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
982 struct devkmsg_user
*user
= file
->private_data
;
987 ratelimit_state_exit(&user
->rs
);
989 mutex_destroy(&user
->lock
);
994 const struct file_operations kmsg_fops
= {
995 .open
= devkmsg_open
,
996 .read
= devkmsg_read
,
997 .write_iter
= devkmsg_write
,
998 .llseek
= devkmsg_llseek
,
999 .poll
= devkmsg_poll
,
1000 .release
= devkmsg_release
,
1003 #ifdef CONFIG_KEXEC_CORE
1005 * This appends the listed symbols to /proc/vmcore
1007 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
1008 * obtain access to symbols that are otherwise very difficult to locate. These
1009 * symbols are specifically used so that utilities can access and extract the
1010 * dmesg log from a vmcore file after a crash.
1012 void log_buf_kexec_setup(void)
1014 VMCOREINFO_SYMBOL(log_buf
);
1015 VMCOREINFO_SYMBOL(log_buf_len
);
1016 VMCOREINFO_SYMBOL(log_first_idx
);
1017 VMCOREINFO_SYMBOL(clear_idx
);
1018 VMCOREINFO_SYMBOL(log_next_idx
);
1020 * Export struct printk_log size and field offsets. User space tools can
1021 * parse it and detect any changes to structure down the line.
1023 VMCOREINFO_STRUCT_SIZE(printk_log
);
1024 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
1025 VMCOREINFO_OFFSET(printk_log
, len
);
1026 VMCOREINFO_OFFSET(printk_log
, text_len
);
1027 VMCOREINFO_OFFSET(printk_log
, dict_len
);
1031 /* requested log_buf_len from kernel cmdline */
1032 static unsigned long __initdata new_log_buf_len
;
1034 /* we practice scaling the ring buffer by powers of 2 */
1035 static void __init
log_buf_len_update(unsigned size
)
1038 size
= roundup_pow_of_two(size
);
1039 if (size
> log_buf_len
)
1040 new_log_buf_len
= size
;
1043 /* save requested log_buf_len since it's too early to process it */
1044 static int __init
log_buf_len_setup(char *str
)
1046 unsigned size
= memparse(str
, &str
);
1048 log_buf_len_update(size
);
1052 early_param("log_buf_len", log_buf_len_setup
);
1055 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1057 static void __init
log_buf_add_cpu(void)
1059 unsigned int cpu_extra
;
1062 * archs should set up cpu_possible_bits properly with
1063 * set_cpu_possible() after setup_arch() but just in
1064 * case lets ensure this is valid.
1066 if (num_possible_cpus() == 1)
1069 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
1071 /* by default this will only continue through for large > 64 CPUs */
1072 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
1075 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1076 __LOG_CPU_MAX_BUF_LEN
);
1077 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1079 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
1081 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
1083 #else /* !CONFIG_SMP */
1084 static inline void log_buf_add_cpu(void) {}
1085 #endif /* CONFIG_SMP */
1087 void __init
setup_log_buf(int early
)
1089 unsigned long flags
;
1093 if (log_buf
!= __log_buf
)
1096 if (!early
&& !new_log_buf_len
)
1099 if (!new_log_buf_len
)
1104 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
1106 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
1110 if (unlikely(!new_log_buf
)) {
1111 pr_err("log_buf_len: %ld bytes not available\n",
1116 logbuf_lock_irqsave(flags
);
1117 log_buf_len
= new_log_buf_len
;
1118 log_buf
= new_log_buf
;
1119 new_log_buf_len
= 0;
1120 free
= __LOG_BUF_LEN
- log_next_idx
;
1121 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
1122 logbuf_unlock_irqrestore(flags
);
1124 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
1125 pr_info("early log buf free: %d(%d%%)\n",
1126 free
, (free
* 100) / __LOG_BUF_LEN
);
1129 static bool __read_mostly ignore_loglevel
;
1131 static int __init
ignore_loglevel_setup(char *str
)
1133 ignore_loglevel
= true;
1134 pr_info("debug: ignoring loglevel setting.\n");
1139 early_param("ignore_loglevel", ignore_loglevel_setup
);
1140 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1141 MODULE_PARM_DESC(ignore_loglevel
,
1142 "ignore loglevel setting (prints all kernel messages to the console)");
1144 static bool suppress_message_printing(int level
)
1146 return (level
>= console_loglevel
&& !ignore_loglevel
);
1149 #ifdef CONFIG_BOOT_PRINTK_DELAY
1151 static int boot_delay
; /* msecs delay after each printk during bootup */
1152 static unsigned long long loops_per_msec
; /* based on boot_delay */
1154 static int __init
boot_delay_setup(char *str
)
1158 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
1159 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
1161 get_option(&str
, &boot_delay
);
1162 if (boot_delay
> 10 * 1000)
1165 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1166 "HZ: %d, loops_per_msec: %llu\n",
1167 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1170 early_param("boot_delay", boot_delay_setup
);
1172 static void boot_delay_msec(int level
)
1174 unsigned long long k
;
1175 unsigned long timeout
;
1177 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
1178 || suppress_message_printing(level
)) {
1182 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1184 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1189 * use (volatile) jiffies to prevent
1190 * compiler reduction; loop termination via jiffies
1191 * is secondary and may or may not happen.
1193 if (time_after(jiffies
, timeout
))
1195 touch_nmi_watchdog();
1199 static inline void boot_delay_msec(int level
)
1204 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1205 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1207 static size_t print_time(u64 ts
, char *buf
)
1209 unsigned long rem_nsec
;
1214 rem_nsec
= do_div(ts
, 1000000000);
1217 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1219 return sprintf(buf
, "[%5lu.%06lu] ",
1220 (unsigned long)ts
, rem_nsec
/ 1000);
1223 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1226 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1230 len
+= sprintf(buf
, "<%u>", prefix
);
1235 else if (prefix
> 99)
1237 else if (prefix
> 9)
1242 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1246 static size_t msg_print_text(const struct printk_log
*msg
, bool syslog
, char *buf
, size_t size
)
1248 const char *text
= log_text(msg
);
1249 size_t text_size
= msg
->text_len
;
1253 const char *next
= memchr(text
, '\n', text_size
);
1257 text_len
= next
- text
;
1259 text_size
-= next
- text
;
1261 text_len
= text_size
;
1265 if (print_prefix(msg
, syslog
, NULL
) +
1266 text_len
+ 1 >= size
- len
)
1269 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1270 memcpy(buf
+ len
, text
, text_len
);
1274 /* SYSLOG_ACTION_* buffer size only calculation */
1275 len
+= print_prefix(msg
, syslog
, NULL
);
1286 static int syslog_print(char __user
*buf
, int size
)
1289 struct printk_log
*msg
;
1292 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1301 if (syslog_seq
< log_first_seq
) {
1302 /* messages are gone, move to first one */
1303 syslog_seq
= log_first_seq
;
1304 syslog_idx
= log_first_idx
;
1307 if (syslog_seq
== log_next_seq
) {
1308 logbuf_unlock_irq();
1312 skip
= syslog_partial
;
1313 msg
= log_from_idx(syslog_idx
);
1314 n
= msg_print_text(msg
, true, text
, LOG_LINE_MAX
+ PREFIX_MAX
);
1315 if (n
- syslog_partial
<= size
) {
1316 /* message fits into buffer, move forward */
1317 syslog_idx
= log_next(syslog_idx
);
1319 n
-= syslog_partial
;
1322 /* partial read(), remember position */
1324 syslog_partial
+= n
;
1327 logbuf_unlock_irq();
1332 if (copy_to_user(buf
, text
+ skip
, n
)) {
1347 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1352 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1363 * Find first record that fits, including all following records,
1364 * into the user-provided buffer for this dump.
1368 while (seq
< log_next_seq
) {
1369 struct printk_log
*msg
= log_from_idx(idx
);
1371 len
+= msg_print_text(msg
, true, NULL
, 0);
1372 idx
= log_next(idx
);
1376 /* move first record forward until length fits into the buffer */
1379 while (len
> size
&& seq
< log_next_seq
) {
1380 struct printk_log
*msg
= log_from_idx(idx
);
1382 len
-= msg_print_text(msg
, true, NULL
, 0);
1383 idx
= log_next(idx
);
1387 /* last message fitting into this dump */
1388 next_seq
= log_next_seq
;
1391 while (len
>= 0 && seq
< next_seq
) {
1392 struct printk_log
*msg
= log_from_idx(idx
);
1395 textlen
= msg_print_text(msg
, true, text
,
1396 LOG_LINE_MAX
+ PREFIX_MAX
);
1401 idx
= log_next(idx
);
1404 logbuf_unlock_irq();
1405 if (copy_to_user(buf
+ len
, text
, textlen
))
1411 if (seq
< log_first_seq
) {
1412 /* messages are gone, move to next one */
1413 seq
= log_first_seq
;
1414 idx
= log_first_idx
;
1420 clear_seq
= log_next_seq
;
1421 clear_idx
= log_next_idx
;
1423 logbuf_unlock_irq();
1429 int do_syslog(int type
, char __user
*buf
, int len
, int source
)
1432 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1435 error
= check_syslog_permissions(type
, source
);
1440 case SYSLOG_ACTION_CLOSE
: /* Close log */
1442 case SYSLOG_ACTION_OPEN
: /* Open log */
1444 case SYSLOG_ACTION_READ
: /* Read from log */
1446 if (!buf
|| len
< 0)
1451 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1455 error
= wait_event_interruptible(log_wait
,
1456 syslog_seq
!= log_next_seq
);
1459 error
= syslog_print(buf
, len
);
1461 /* Read/clear last kernel messages */
1462 case SYSLOG_ACTION_READ_CLEAR
:
1465 /* Read last kernel messages */
1466 case SYSLOG_ACTION_READ_ALL
:
1468 if (!buf
|| len
< 0)
1473 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1477 error
= syslog_print_all(buf
, len
, clear
);
1479 /* Clear ring buffer */
1480 case SYSLOG_ACTION_CLEAR
:
1481 syslog_print_all(NULL
, 0, true);
1483 /* Disable logging to console */
1484 case SYSLOG_ACTION_CONSOLE_OFF
:
1485 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1486 saved_console_loglevel
= console_loglevel
;
1487 console_loglevel
= minimum_console_loglevel
;
1489 /* Enable logging to console */
1490 case SYSLOG_ACTION_CONSOLE_ON
:
1491 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1492 console_loglevel
= saved_console_loglevel
;
1493 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1496 /* Set level of messages printed to console */
1497 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1499 if (len
< 1 || len
> 8)
1501 if (len
< minimum_console_loglevel
)
1502 len
= minimum_console_loglevel
;
1503 console_loglevel
= len
;
1504 /* Implicitly re-enable logging to console */
1505 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1508 /* Number of chars in the log buffer */
1509 case SYSLOG_ACTION_SIZE_UNREAD
:
1511 if (syslog_seq
< log_first_seq
) {
1512 /* messages are gone, move to first one */
1513 syslog_seq
= log_first_seq
;
1514 syslog_idx
= log_first_idx
;
1517 if (source
== SYSLOG_FROM_PROC
) {
1519 * Short-cut for poll(/"proc/kmsg") which simply checks
1520 * for pending data, not the size; return the count of
1521 * records, not the length.
1523 error
= log_next_seq
- syslog_seq
;
1525 u64 seq
= syslog_seq
;
1526 u32 idx
= syslog_idx
;
1529 while (seq
< log_next_seq
) {
1530 struct printk_log
*msg
= log_from_idx(idx
);
1532 error
+= msg_print_text(msg
, true, NULL
, 0);
1533 idx
= log_next(idx
);
1536 error
-= syslog_partial
;
1538 logbuf_unlock_irq();
1540 /* Size of the log buffer */
1541 case SYSLOG_ACTION_SIZE_BUFFER
:
1542 error
= log_buf_len
;
1552 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1554 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1558 * Call the console drivers, asking them to write out
1559 * log_buf[start] to log_buf[end - 1].
1560 * The console_lock must be held.
1562 static void call_console_drivers(const char *ext_text
, size_t ext_len
,
1563 const char *text
, size_t len
)
1565 struct console
*con
;
1567 trace_console_rcuidle(text
, len
);
1569 if (!console_drivers
)
1572 for_each_console(con
) {
1573 if (exclusive_console
&& con
!= exclusive_console
)
1575 if (!(con
->flags
& CON_ENABLED
))
1579 if (!cpu_online(smp_processor_id()) &&
1580 !(con
->flags
& CON_ANYTIME
))
1582 if (con
->flags
& CON_EXTENDED
)
1583 con
->write(con
, ext_text
, ext_len
);
1585 con
->write(con
, text
, len
);
1589 int printk_delay_msec __read_mostly
;
1591 static inline void printk_delay(void)
1593 if (unlikely(printk_delay_msec
)) {
1594 int m
= printk_delay_msec
;
1598 touch_nmi_watchdog();
1604 * Continuation lines are buffered, and not committed to the record buffer
1605 * until the line is complete, or a race forces it. The line fragments
1606 * though, are printed immediately to the consoles to ensure everything has
1607 * reached the console in case of a kernel crash.
1609 static struct cont
{
1610 char buf
[LOG_LINE_MAX
];
1611 size_t len
; /* length == 0 means unused buffer */
1612 struct task_struct
*owner
; /* task of first print*/
1613 u64 ts_nsec
; /* time of first print */
1614 u8 level
; /* log level of first message */
1615 u8 facility
; /* log facility of first message */
1616 enum log_flags flags
; /* prefix, newline flags */
1619 static void cont_flush(void)
1624 log_store(cont
.facility
, cont
.level
, cont
.flags
, cont
.ts_nsec
,
1625 NULL
, 0, cont
.buf
, cont
.len
);
1629 static bool cont_add(int facility
, int level
, enum log_flags flags
, const char *text
, size_t len
)
1632 * If ext consoles are present, flush and skip in-kernel
1633 * continuation. See nr_ext_console_drivers definition. Also, if
1634 * the line gets too long, split it up in separate records.
1636 if (nr_ext_console_drivers
|| cont
.len
+ len
> sizeof(cont
.buf
)) {
1642 cont
.facility
= facility
;
1644 cont
.owner
= current
;
1645 cont
.ts_nsec
= local_clock();
1649 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1652 // The original flags come from the first line,
1653 // but later continuations can add a newline.
1654 if (flags
& LOG_NEWLINE
) {
1655 cont
.flags
|= LOG_NEWLINE
;
1659 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1665 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
)
1668 * If an earlier line was buffered, and we're a continuation
1669 * write from the same process, try to add it to the buffer.
1672 if (cont
.owner
== current
&& (lflags
& LOG_CONT
)) {
1673 if (cont_add(facility
, level
, lflags
, text
, text_len
))
1676 /* Otherwise, make sure it's flushed */
1680 /* Skip empty continuation lines that couldn't be added - they just flush */
1681 if (!text_len
&& (lflags
& LOG_CONT
))
1684 /* If it doesn't end in a newline, try to buffer the current line */
1685 if (!(lflags
& LOG_NEWLINE
)) {
1686 if (cont_add(facility
, level
, lflags
, text
, text_len
))
1690 /* Store it in the record log */
1691 return log_store(facility
, level
, lflags
, 0, dict
, dictlen
, text
, text_len
);
1694 asmlinkage
int vprintk_emit(int facility
, int level
,
1695 const char *dict
, size_t dictlen
,
1696 const char *fmt
, va_list args
)
1698 static char textbuf
[LOG_LINE_MAX
];
1699 char *text
= textbuf
;
1700 size_t text_len
= 0;
1701 enum log_flags lflags
= 0;
1702 unsigned long flags
;
1703 int printed_len
= 0;
1704 bool in_sched
= false;
1706 if (level
== LOGLEVEL_SCHED
) {
1707 level
= LOGLEVEL_DEFAULT
;
1711 boot_delay_msec(level
);
1714 /* This stops the holder of console_sem just where we want him */
1715 logbuf_lock_irqsave(flags
);
1717 * The printf needs to come first; we need the syslog
1718 * prefix which might be passed-in as a parameter.
1720 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1722 /* mark and strip a trailing newline */
1723 if (text_len
&& text
[text_len
-1] == '\n') {
1725 lflags
|= LOG_NEWLINE
;
1728 /* strip kernel syslog prefix and extract log level or control flags */
1729 if (facility
== 0) {
1732 while ((kern_level
= printk_get_level(text
)) != 0) {
1733 switch (kern_level
) {
1735 if (level
== LOGLEVEL_DEFAULT
)
1736 level
= kern_level
- '0';
1738 case 'd': /* KERN_DEFAULT */
1739 lflags
|= LOG_PREFIX
;
1741 case 'c': /* KERN_CONT */
1750 if (level
== LOGLEVEL_DEFAULT
)
1751 level
= default_message_loglevel
;
1754 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1756 printed_len
+= log_output(facility
, level
, lflags
, dict
, dictlen
, text
, text_len
);
1758 logbuf_unlock_irqrestore(flags
);
1760 /* If called from the scheduler, we can not call up(). */
1763 * Try to acquire and then immediately release the console
1764 * semaphore. The release will print out buffers and wake up
1765 * /dev/kmsg and syslog() users.
1767 if (console_trylock())
1773 EXPORT_SYMBOL(vprintk_emit
);
1775 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1777 return vprintk_func(fmt
, args
);
1779 EXPORT_SYMBOL(vprintk
);
1781 asmlinkage
int printk_emit(int facility
, int level
,
1782 const char *dict
, size_t dictlen
,
1783 const char *fmt
, ...)
1788 va_start(args
, fmt
);
1789 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1794 EXPORT_SYMBOL(printk_emit
);
1796 int vprintk_default(const char *fmt
, va_list args
)
1800 #ifdef CONFIG_KGDB_KDB
1801 /* Allow to pass printk() to kdb but avoid a recursion. */
1802 if (unlikely(kdb_trap_printk
&& kdb_printf_cpu
< 0)) {
1803 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1807 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1811 EXPORT_SYMBOL_GPL(vprintk_default
);
1814 * printk - print a kernel message
1815 * @fmt: format string
1817 * This is printk(). It can be called from any context. We want it to work.
1819 * We try to grab the console_lock. If we succeed, it's easy - we log the
1820 * output and call the console drivers. If we fail to get the semaphore, we
1821 * place the output into the log buffer and return. The current holder of
1822 * the console_sem will notice the new output in console_unlock(); and will
1823 * send it to the consoles before releasing the lock.
1825 * One effect of this deferred printing is that code which calls printk() and
1826 * then changes console_loglevel may break. This is because console_loglevel
1827 * is inspected when the actual printing occurs.
1832 * See the vsnprintf() documentation for format string extensions over C99.
1834 asmlinkage __visible
int printk(const char *fmt
, ...)
1839 va_start(args
, fmt
);
1840 r
= vprintk_func(fmt
, args
);
1845 EXPORT_SYMBOL(printk
);
1847 #else /* CONFIG_PRINTK */
1849 #define LOG_LINE_MAX 0
1850 #define PREFIX_MAX 0
1852 static u64 syslog_seq
;
1853 static u32 syslog_idx
;
1854 static u64 console_seq
;
1855 static u32 console_idx
;
1856 static u64 log_first_seq
;
1857 static u32 log_first_idx
;
1858 static u64 log_next_seq
;
1859 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
1860 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
1861 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
1862 static u32
log_next(u32 idx
) { return 0; }
1863 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
1864 struct printk_log
*msg
,
1865 u64 seq
) { return 0; }
1866 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
1867 char *dict
, size_t dict_len
,
1868 char *text
, size_t text_len
) { return 0; }
1869 static void call_console_drivers(const char *ext_text
, size_t ext_len
,
1870 const char *text
, size_t len
) {}
1871 static size_t msg_print_text(const struct printk_log
*msg
,
1872 bool syslog
, char *buf
, size_t size
) { return 0; }
1873 static bool suppress_message_printing(int level
) { return false; }
1875 #endif /* CONFIG_PRINTK */
1877 #ifdef CONFIG_EARLY_PRINTK
1878 struct console
*early_console
;
1880 asmlinkage __visible
void early_printk(const char *fmt
, ...)
1890 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
1893 early_console
->write(early_console
, buf
, n
);
1897 static int __add_preferred_console(char *name
, int idx
, char *options
,
1900 struct console_cmdline
*c
;
1904 * See if this tty is not yet registered, and
1905 * if we have a slot free.
1907 for (i
= 0, c
= console_cmdline
;
1908 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1910 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
1912 selected_console
= i
;
1916 if (i
== MAX_CMDLINECONSOLES
)
1919 selected_console
= i
;
1920 strlcpy(c
->name
, name
, sizeof(c
->name
));
1921 c
->options
= options
;
1922 braille_set_options(c
, brl_options
);
1928 * Set up a console. Called via do_early_param() in init/main.c
1929 * for each "console=" parameter in the boot command line.
1931 static int __init
console_setup(char *str
)
1933 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
1934 char *s
, *options
, *brl_options
= NULL
;
1937 if (_braille_console_setup(&str
, &brl_options
))
1941 * Decode str into name, index, options.
1943 if (str
[0] >= '0' && str
[0] <= '9') {
1944 strcpy(buf
, "ttyS");
1945 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1947 strncpy(buf
, str
, sizeof(buf
) - 1);
1949 buf
[sizeof(buf
) - 1] = 0;
1950 options
= strchr(str
, ',');
1954 if (!strcmp(str
, "ttya"))
1955 strcpy(buf
, "ttyS0");
1956 if (!strcmp(str
, "ttyb"))
1957 strcpy(buf
, "ttyS1");
1959 for (s
= buf
; *s
; s
++)
1960 if (isdigit(*s
) || *s
== ',')
1962 idx
= simple_strtoul(s
, NULL
, 10);
1965 __add_preferred_console(buf
, idx
, options
, brl_options
);
1966 console_set_on_cmdline
= 1;
1969 __setup("console=", console_setup
);
1972 * add_preferred_console - add a device to the list of preferred consoles.
1973 * @name: device name
1974 * @idx: device index
1975 * @options: options for this console
1977 * The last preferred console added will be used for kernel messages
1978 * and stdin/out/err for init. Normally this is used by console_setup
1979 * above to handle user-supplied console arguments; however it can also
1980 * be used by arch-specific code either to override the user or more
1981 * commonly to provide a default console (ie from PROM variables) when
1982 * the user has not supplied one.
1984 int add_preferred_console(char *name
, int idx
, char *options
)
1986 return __add_preferred_console(name
, idx
, options
, NULL
);
1989 bool console_suspend_enabled
= true;
1990 EXPORT_SYMBOL(console_suspend_enabled
);
1992 static int __init
console_suspend_disable(char *str
)
1994 console_suspend_enabled
= false;
1997 __setup("no_console_suspend", console_suspend_disable
);
1998 module_param_named(console_suspend
, console_suspend_enabled
,
1999 bool, S_IRUGO
| S_IWUSR
);
2000 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2001 " and hibernate operations");
2004 * suspend_console - suspend the console subsystem
2006 * This disables printk() while we go into suspend states
2008 void suspend_console(void)
2010 if (!console_suspend_enabled
)
2012 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2014 console_suspended
= 1;
2018 void resume_console(void)
2020 if (!console_suspend_enabled
)
2023 console_suspended
= 0;
2028 * console_cpu_notify - print deferred console messages after CPU hotplug
2031 * If printk() is called from a CPU that is not online yet, the messages
2032 * will be spooled but will not show up on the console. This function is
2033 * called when a new CPU comes online (or fails to come up), and ensures
2034 * that any such output gets printed.
2036 static int console_cpu_notify(unsigned int cpu
)
2038 if (!cpuhp_tasks_frozen
) {
2046 * console_lock - lock the console system for exclusive use.
2048 * Acquires a lock which guarantees that the caller has
2049 * exclusive access to the console system and the console_drivers list.
2051 * Can sleep, returns nothing.
2053 void console_lock(void)
2058 if (console_suspended
)
2061 console_may_schedule
= 1;
2063 EXPORT_SYMBOL(console_lock
);
2066 * console_trylock - try to lock the console system for exclusive use.
2068 * Try to acquire a lock which guarantees that the caller has exclusive
2069 * access to the console system and the console_drivers list.
2071 * returns 1 on success, and 0 on failure to acquire the lock.
2073 int console_trylock(void)
2075 if (down_trylock_console_sem())
2077 if (console_suspended
) {
2083 * When PREEMPT_COUNT disabled we can't reliably detect if it's
2084 * safe to schedule (e.g. calling printk while holding a spin_lock),
2085 * because preempt_disable()/preempt_enable() are just barriers there
2086 * and preempt_count() is always 0.
2088 * RCU read sections have a separate preemption counter when
2089 * PREEMPT_RCU enabled thus we must take extra care and check
2090 * rcu_preempt_depth(), otherwise RCU read sections modify
2093 console_may_schedule
= !oops_in_progress
&&
2095 !rcu_preempt_depth();
2098 EXPORT_SYMBOL(console_trylock
);
2100 int is_console_locked(void)
2102 return console_locked
;
2106 * Check if we have any console that is capable of printing while cpu is
2107 * booting or shutting down. Requires console_sem.
2109 static int have_callable_console(void)
2111 struct console
*con
;
2113 for_each_console(con
)
2114 if ((con
->flags
& CON_ENABLED
) &&
2115 (con
->flags
& CON_ANYTIME
))
2122 * Can we actually use the console at this time on this cpu?
2124 * Console drivers may assume that per-cpu resources have been allocated. So
2125 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2126 * call them until this CPU is officially up.
2128 static inline int can_use_console(void)
2130 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2134 * console_unlock - unlock the console system
2136 * Releases the console_lock which the caller holds on the console system
2137 * and the console driver list.
2139 * While the console_lock was held, console output may have been buffered
2140 * by printk(). If this is the case, console_unlock(); emits
2141 * the output prior to releasing the lock.
2143 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2145 * console_unlock(); may be called from any context.
2147 void console_unlock(void)
2149 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2150 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2151 static u64 seen_seq
;
2152 unsigned long flags
;
2153 bool wake_klogd
= false;
2154 bool do_cond_resched
, retry
;
2156 if (console_suspended
) {
2162 * Console drivers are called under logbuf_lock, so
2163 * @console_may_schedule should be cleared before; however, we may
2164 * end up dumping a lot of lines, for example, if called from
2165 * console registration path, and should invoke cond_resched()
2166 * between lines if allowable. Not doing so can cause a very long
2167 * scheduling stall on a slow console leading to RCU stall and
2168 * softlockup warnings which exacerbate the issue with more
2169 * messages practically incapacitating the system.
2171 do_cond_resched
= console_may_schedule
;
2172 console_may_schedule
= 0;
2176 * We released the console_sem lock, so we need to recheck if
2177 * cpu is online and (if not) is there at least one CON_ANYTIME
2180 if (!can_use_console()) {
2187 struct printk_log
*msg
;
2191 printk_safe_enter_irqsave(flags
);
2192 raw_spin_lock(&logbuf_lock
);
2193 if (seen_seq
!= log_next_seq
) {
2195 seen_seq
= log_next_seq
;
2198 if (console_seq
< log_first_seq
) {
2199 len
= sprintf(text
, "** %u printk messages dropped ** ",
2200 (unsigned)(log_first_seq
- console_seq
));
2202 /* messages are gone, move to first one */
2203 console_seq
= log_first_seq
;
2204 console_idx
= log_first_idx
;
2209 if (console_seq
== log_next_seq
)
2212 msg
= log_from_idx(console_idx
);
2213 if (suppress_message_printing(msg
->level
)) {
2215 * Skip record we have buffered and already printed
2216 * directly to the console when we received it, and
2217 * record that has level above the console loglevel.
2219 console_idx
= log_next(console_idx
);
2224 len
+= msg_print_text(msg
, false, text
+ len
, sizeof(text
) - len
);
2225 if (nr_ext_console_drivers
) {
2226 ext_len
= msg_print_ext_header(ext_text
,
2229 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2230 sizeof(ext_text
) - ext_len
,
2231 log_dict(msg
), msg
->dict_len
,
2232 log_text(msg
), msg
->text_len
);
2234 console_idx
= log_next(console_idx
);
2236 raw_spin_unlock(&logbuf_lock
);
2238 stop_critical_timings(); /* don't trace print latency */
2239 call_console_drivers(ext_text
, ext_len
, text
, len
);
2240 start_critical_timings();
2241 printk_safe_exit_irqrestore(flags
);
2243 if (do_cond_resched
)
2248 /* Release the exclusive_console once it is used */
2249 if (unlikely(exclusive_console
))
2250 exclusive_console
= NULL
;
2252 raw_spin_unlock(&logbuf_lock
);
2257 * Someone could have filled up the buffer again, so re-check if there's
2258 * something to flush. In case we cannot trylock the console_sem again,
2259 * there's a new owner and the console_unlock() from them will do the
2260 * flush, no worries.
2262 raw_spin_lock(&logbuf_lock
);
2263 retry
= console_seq
!= log_next_seq
;
2264 raw_spin_unlock(&logbuf_lock
);
2265 printk_safe_exit_irqrestore(flags
);
2267 if (retry
&& console_trylock())
2273 EXPORT_SYMBOL(console_unlock
);
2276 * console_conditional_schedule - yield the CPU if required
2278 * If the console code is currently allowed to sleep, and
2279 * if this CPU should yield the CPU to another task, do
2282 * Must be called within console_lock();.
2284 void __sched
console_conditional_schedule(void)
2286 if (console_may_schedule
)
2289 EXPORT_SYMBOL(console_conditional_schedule
);
2291 void console_unblank(void)
2296 * console_unblank can no longer be called in interrupt context unless
2297 * oops_in_progress is set to 1..
2299 if (oops_in_progress
) {
2300 if (down_trylock_console_sem() != 0)
2306 console_may_schedule
= 0;
2308 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2314 * console_flush_on_panic - flush console content on panic
2316 * Immediately output all pending messages no matter what.
2318 void console_flush_on_panic(void)
2321 * If someone else is holding the console lock, trylock will fail
2322 * and may_schedule may be set. Ignore and proceed to unlock so
2323 * that messages are flushed out. As this can be called from any
2324 * context and we don't want to get preempted while flushing,
2325 * ensure may_schedule is cleared.
2328 console_may_schedule
= 0;
2333 * Return the console tty driver structure and its associated index
2335 struct tty_driver
*console_device(int *index
)
2338 struct tty_driver
*driver
= NULL
;
2341 for_each_console(c
) {
2344 driver
= c
->device(c
, index
);
2353 * Prevent further output on the passed console device so that (for example)
2354 * serial drivers can disable console output before suspending a port, and can
2355 * re-enable output afterwards.
2357 void console_stop(struct console
*console
)
2360 console
->flags
&= ~CON_ENABLED
;
2363 EXPORT_SYMBOL(console_stop
);
2365 void console_start(struct console
*console
)
2368 console
->flags
|= CON_ENABLED
;
2371 EXPORT_SYMBOL(console_start
);
2373 static int __read_mostly keep_bootcon
;
2375 static int __init
keep_bootcon_setup(char *str
)
2378 pr_info("debug: skip boot console de-registration.\n");
2383 early_param("keep_bootcon", keep_bootcon_setup
);
2386 * The console driver calls this routine during kernel initialization
2387 * to register the console printing procedure with printk() and to
2388 * print any messages that were printed by the kernel before the
2389 * console driver was initialized.
2391 * This can happen pretty early during the boot process (because of
2392 * early_printk) - sometimes before setup_arch() completes - be careful
2393 * of what kernel features are used - they may not be initialised yet.
2395 * There are two types of consoles - bootconsoles (early_printk) and
2396 * "real" consoles (everything which is not a bootconsole) which are
2397 * handled differently.
2398 * - Any number of bootconsoles can be registered at any time.
2399 * - As soon as a "real" console is registered, all bootconsoles
2400 * will be unregistered automatically.
2401 * - Once a "real" console is registered, any attempt to register a
2402 * bootconsoles will be rejected
2404 void register_console(struct console
*newcon
)
2407 unsigned long flags
;
2408 struct console
*bcon
= NULL
;
2409 struct console_cmdline
*c
;
2411 if (console_drivers
)
2412 for_each_console(bcon
)
2413 if (WARN(bcon
== newcon
,
2414 "console '%s%d' already registered\n",
2415 bcon
->name
, bcon
->index
))
2419 * before we register a new CON_BOOT console, make sure we don't
2420 * already have a valid console
2422 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2423 /* find the last or real console */
2424 for_each_console(bcon
) {
2425 if (!(bcon
->flags
& CON_BOOT
)) {
2426 pr_info("Too late to register bootconsole %s%d\n",
2427 newcon
->name
, newcon
->index
);
2433 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2434 bcon
= console_drivers
;
2436 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2437 preferred_console
= selected_console
;
2440 * See if we want to use this console driver. If we
2441 * didn't select a console we take the first one
2442 * that registers here.
2444 if (preferred_console
< 0) {
2445 if (newcon
->index
< 0)
2447 if (newcon
->setup
== NULL
||
2448 newcon
->setup(newcon
, NULL
) == 0) {
2449 newcon
->flags
|= CON_ENABLED
;
2450 if (newcon
->device
) {
2451 newcon
->flags
|= CON_CONSDEV
;
2452 preferred_console
= 0;
2458 * See if this console matches one we selected on
2461 for (i
= 0, c
= console_cmdline
;
2462 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2464 if (!newcon
->match
||
2465 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2466 /* default matching */
2467 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2468 if (strcmp(c
->name
, newcon
->name
) != 0)
2470 if (newcon
->index
>= 0 &&
2471 newcon
->index
!= c
->index
)
2473 if (newcon
->index
< 0)
2474 newcon
->index
= c
->index
;
2476 if (_braille_register_console(newcon
, c
))
2479 if (newcon
->setup
&&
2480 newcon
->setup(newcon
, c
->options
) != 0)
2484 newcon
->flags
|= CON_ENABLED
;
2485 if (i
== selected_console
) {
2486 newcon
->flags
|= CON_CONSDEV
;
2487 preferred_console
= selected_console
;
2492 if (!(newcon
->flags
& CON_ENABLED
))
2496 * If we have a bootconsole, and are switching to a real console,
2497 * don't print everything out again, since when the boot console, and
2498 * the real console are the same physical device, it's annoying to
2499 * see the beginning boot messages twice
2501 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2502 newcon
->flags
&= ~CON_PRINTBUFFER
;
2505 * Put this console in the list - keep the
2506 * preferred driver at the head of the list.
2509 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2510 newcon
->next
= console_drivers
;
2511 console_drivers
= newcon
;
2513 newcon
->next
->flags
&= ~CON_CONSDEV
;
2515 newcon
->next
= console_drivers
->next
;
2516 console_drivers
->next
= newcon
;
2519 if (newcon
->flags
& CON_EXTENDED
)
2520 if (!nr_ext_console_drivers
++)
2521 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2523 if (newcon
->flags
& CON_PRINTBUFFER
) {
2525 * console_unlock(); will print out the buffered messages
2528 logbuf_lock_irqsave(flags
);
2529 console_seq
= syslog_seq
;
2530 console_idx
= syslog_idx
;
2531 logbuf_unlock_irqrestore(flags
);
2533 * We're about to replay the log buffer. Only do this to the
2534 * just-registered console to avoid excessive message spam to
2535 * the already-registered consoles.
2537 exclusive_console
= newcon
;
2540 console_sysfs_notify();
2543 * By unregistering the bootconsoles after we enable the real console
2544 * we get the "console xxx enabled" message on all the consoles -
2545 * boot consoles, real consoles, etc - this is to ensure that end
2546 * users know there might be something in the kernel's log buffer that
2547 * went to the bootconsole (that they do not see on the real console)
2549 pr_info("%sconsole [%s%d] enabled\n",
2550 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2551 newcon
->name
, newcon
->index
);
2553 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2555 /* We need to iterate through all boot consoles, to make
2556 * sure we print everything out, before we unregister them.
2558 for_each_console(bcon
)
2559 if (bcon
->flags
& CON_BOOT
)
2560 unregister_console(bcon
);
2563 EXPORT_SYMBOL(register_console
);
2565 int unregister_console(struct console
*console
)
2567 struct console
*a
, *b
;
2570 pr_info("%sconsole [%s%d] disabled\n",
2571 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2572 console
->name
, console
->index
);
2574 res
= _braille_unregister_console(console
);
2580 if (console_drivers
== console
) {
2581 console_drivers
=console
->next
;
2583 } else if (console_drivers
) {
2584 for (a
=console_drivers
->next
, b
=console_drivers
;
2585 a
; b
=a
, a
=b
->next
) {
2594 if (!res
&& (console
->flags
& CON_EXTENDED
))
2595 nr_ext_console_drivers
--;
2598 * If this isn't the last console and it has CON_CONSDEV set, we
2599 * need to set it on the next preferred console.
2601 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2602 console_drivers
->flags
|= CON_CONSDEV
;
2604 console
->flags
&= ~CON_ENABLED
;
2606 console_sysfs_notify();
2609 EXPORT_SYMBOL(unregister_console
);
2612 * Some boot consoles access data that is in the init section and which will
2613 * be discarded after the initcalls have been run. To make sure that no code
2614 * will access this data, unregister the boot consoles in a late initcall.
2616 * If for some reason, such as deferred probe or the driver being a loadable
2617 * module, the real console hasn't registered yet at this point, there will
2618 * be a brief interval in which no messages are logged to the console, which
2619 * makes it difficult to diagnose problems that occur during this time.
2621 * To mitigate this problem somewhat, only unregister consoles whose memory
2622 * intersects with the init section. Note that code exists elsewhere to get
2623 * rid of the boot console as soon as the proper console shows up, so there
2624 * won't be side-effects from postponing the removal.
2626 static int __init
printk_late_init(void)
2628 struct console
*con
;
2631 for_each_console(con
) {
2632 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2634 * Make sure to unregister boot consoles whose data
2635 * resides in the init section before the init section
2636 * is discarded. Boot consoles whose data will stick
2637 * around will automatically be unregistered when the
2638 * proper console replaces them.
2640 if (init_section_intersects(con
, sizeof(*con
)))
2641 unregister_console(con
);
2644 ret
= cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD
, "printk:dead", NULL
,
2645 console_cpu_notify
);
2647 ret
= cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN
, "printk:online",
2648 console_cpu_notify
, NULL
);
2652 late_initcall(printk_late_init
);
2654 #if defined CONFIG_PRINTK
2656 * Delayed printk version, for scheduler-internal messages:
2658 #define PRINTK_PENDING_WAKEUP 0x01
2659 #define PRINTK_PENDING_OUTPUT 0x02
2661 static DEFINE_PER_CPU(int, printk_pending
);
2663 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2665 int pending
= __this_cpu_xchg(printk_pending
, 0);
2667 if (pending
& PRINTK_PENDING_OUTPUT
) {
2668 /* If trylock fails, someone else is doing the printing */
2669 if (console_trylock())
2673 if (pending
& PRINTK_PENDING_WAKEUP
)
2674 wake_up_interruptible(&log_wait
);
2677 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2678 .func
= wake_up_klogd_work_func
,
2679 .flags
= IRQ_WORK_LAZY
,
2682 void wake_up_klogd(void)
2685 if (waitqueue_active(&log_wait
)) {
2686 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2687 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2692 int printk_deferred(const char *fmt
, ...)
2698 va_start(args
, fmt
);
2699 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2702 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2703 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2710 * printk rate limiting, lifted from the networking subsystem.
2712 * This enforces a rate limit: not more than 10 kernel messages
2713 * every 5s to make a denial-of-service attack impossible.
2715 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2717 int __printk_ratelimit(const char *func
)
2719 return ___ratelimit(&printk_ratelimit_state
, func
);
2721 EXPORT_SYMBOL(__printk_ratelimit
);
2724 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2725 * @caller_jiffies: pointer to caller's state
2726 * @interval_msecs: minimum interval between prints
2728 * printk_timed_ratelimit() returns true if more than @interval_msecs
2729 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2732 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2733 unsigned int interval_msecs
)
2735 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2737 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2740 *caller_jiffies
= jiffies
;
2743 EXPORT_SYMBOL(printk_timed_ratelimit
);
2745 static DEFINE_SPINLOCK(dump_list_lock
);
2746 static LIST_HEAD(dump_list
);
2749 * kmsg_dump_register - register a kernel log dumper.
2750 * @dumper: pointer to the kmsg_dumper structure
2752 * Adds a kernel log dumper to the system. The dump callback in the
2753 * structure will be called when the kernel oopses or panics and must be
2754 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2756 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2758 unsigned long flags
;
2761 /* The dump callback needs to be set */
2765 spin_lock_irqsave(&dump_list_lock
, flags
);
2766 /* Don't allow registering multiple times */
2767 if (!dumper
->registered
) {
2768 dumper
->registered
= 1;
2769 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2772 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2776 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2779 * kmsg_dump_unregister - unregister a kmsg dumper.
2780 * @dumper: pointer to the kmsg_dumper structure
2782 * Removes a dump device from the system. Returns zero on success and
2783 * %-EINVAL otherwise.
2785 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2787 unsigned long flags
;
2790 spin_lock_irqsave(&dump_list_lock
, flags
);
2791 if (dumper
->registered
) {
2792 dumper
->registered
= 0;
2793 list_del_rcu(&dumper
->list
);
2796 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2801 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2803 static bool always_kmsg_dump
;
2804 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2807 * kmsg_dump - dump kernel log to kernel message dumpers.
2808 * @reason: the reason (oops, panic etc) for dumping
2810 * Call each of the registered dumper's dump() callback, which can
2811 * retrieve the kmsg records with kmsg_dump_get_line() or
2812 * kmsg_dump_get_buffer().
2814 void kmsg_dump(enum kmsg_dump_reason reason
)
2816 struct kmsg_dumper
*dumper
;
2817 unsigned long flags
;
2819 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2823 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2824 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2827 /* initialize iterator with data about the stored records */
2828 dumper
->active
= true;
2830 logbuf_lock_irqsave(flags
);
2831 dumper
->cur_seq
= clear_seq
;
2832 dumper
->cur_idx
= clear_idx
;
2833 dumper
->next_seq
= log_next_seq
;
2834 dumper
->next_idx
= log_next_idx
;
2835 logbuf_unlock_irqrestore(flags
);
2837 /* invoke dumper which will iterate over records */
2838 dumper
->dump(dumper
, reason
);
2840 /* reset iterator */
2841 dumper
->active
= false;
2847 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2848 * @dumper: registered kmsg dumper
2849 * @syslog: include the "<4>" prefixes
2850 * @line: buffer to copy the line to
2851 * @size: maximum size of the buffer
2852 * @len: length of line placed into buffer
2854 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2855 * record, and copy one record into the provided buffer.
2857 * Consecutive calls will return the next available record moving
2858 * towards the end of the buffer with the youngest messages.
2860 * A return value of FALSE indicates that there are no more records to
2863 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2865 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
2866 char *line
, size_t size
, size_t *len
)
2868 struct printk_log
*msg
;
2872 if (!dumper
->active
)
2875 if (dumper
->cur_seq
< log_first_seq
) {
2876 /* messages are gone, move to first available one */
2877 dumper
->cur_seq
= log_first_seq
;
2878 dumper
->cur_idx
= log_first_idx
;
2882 if (dumper
->cur_seq
>= log_next_seq
)
2885 msg
= log_from_idx(dumper
->cur_idx
);
2886 l
= msg_print_text(msg
, syslog
, line
, size
);
2888 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2898 * kmsg_dump_get_line - retrieve one kmsg log line
2899 * @dumper: registered kmsg dumper
2900 * @syslog: include the "<4>" prefixes
2901 * @line: buffer to copy the line to
2902 * @size: maximum size of the buffer
2903 * @len: length of line placed into buffer
2905 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2906 * record, and copy one record into the provided buffer.
2908 * Consecutive calls will return the next available record moving
2909 * towards the end of the buffer with the youngest messages.
2911 * A return value of FALSE indicates that there are no more records to
2914 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2915 char *line
, size_t size
, size_t *len
)
2917 unsigned long flags
;
2920 logbuf_lock_irqsave(flags
);
2921 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
2922 logbuf_unlock_irqrestore(flags
);
2926 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2929 * kmsg_dump_get_buffer - copy kmsg log lines
2930 * @dumper: registered kmsg dumper
2931 * @syslog: include the "<4>" prefixes
2932 * @buf: buffer to copy the line to
2933 * @size: maximum size of the buffer
2934 * @len: length of line placed into buffer
2936 * Start at the end of the kmsg buffer and fill the provided buffer
2937 * with as many of the the *youngest* kmsg records that fit into it.
2938 * If the buffer is large enough, all available kmsg records will be
2939 * copied with a single call.
2941 * Consecutive calls will fill the buffer with the next block of
2942 * available older records, not including the earlier retrieved ones.
2944 * A return value of FALSE indicates that there are no more records to
2947 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
2948 char *buf
, size_t size
, size_t *len
)
2950 unsigned long flags
;
2958 if (!dumper
->active
)
2961 logbuf_lock_irqsave(flags
);
2962 if (dumper
->cur_seq
< log_first_seq
) {
2963 /* messages are gone, move to first available one */
2964 dumper
->cur_seq
= log_first_seq
;
2965 dumper
->cur_idx
= log_first_idx
;
2969 if (dumper
->cur_seq
>= dumper
->next_seq
) {
2970 logbuf_unlock_irqrestore(flags
);
2974 /* calculate length of entire buffer */
2975 seq
= dumper
->cur_seq
;
2976 idx
= dumper
->cur_idx
;
2977 while (seq
< dumper
->next_seq
) {
2978 struct printk_log
*msg
= log_from_idx(idx
);
2980 l
+= msg_print_text(msg
, true, NULL
, 0);
2981 idx
= log_next(idx
);
2985 /* move first record forward until length fits into the buffer */
2986 seq
= dumper
->cur_seq
;
2987 idx
= dumper
->cur_idx
;
2988 while (l
> size
&& seq
< dumper
->next_seq
) {
2989 struct printk_log
*msg
= log_from_idx(idx
);
2991 l
-= msg_print_text(msg
, true, NULL
, 0);
2992 idx
= log_next(idx
);
2996 /* last message in next interation */
3001 while (seq
< dumper
->next_seq
) {
3002 struct printk_log
*msg
= log_from_idx(idx
);
3004 l
+= msg_print_text(msg
, syslog
, buf
+ l
, size
- l
);
3005 idx
= log_next(idx
);
3009 dumper
->next_seq
= next_seq
;
3010 dumper
->next_idx
= next_idx
;
3012 logbuf_unlock_irqrestore(flags
);
3018 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3021 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3022 * @dumper: registered kmsg dumper
3024 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3025 * kmsg_dump_get_buffer() can be called again and used multiple
3026 * times within the same dumper.dump() callback.
3028 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3030 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3032 dumper
->cur_seq
= clear_seq
;
3033 dumper
->cur_idx
= clear_idx
;
3034 dumper
->next_seq
= log_next_seq
;
3035 dumper
->next_idx
= log_next_idx
;
3039 * kmsg_dump_rewind - reset the interator
3040 * @dumper: registered kmsg dumper
3042 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3043 * kmsg_dump_get_buffer() can be called again and used multiple
3044 * times within the same dumper.dump() callback.
3046 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3048 unsigned long flags
;
3050 logbuf_lock_irqsave(flags
);
3051 kmsg_dump_rewind_nolock(dumper
);
3052 logbuf_unlock_irqrestore(flags
);
3054 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3056 static char dump_stack_arch_desc_str
[128];
3059 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3060 * @fmt: printf-style format string
3061 * @...: arguments for the format string
3063 * The configured string will be printed right after utsname during task
3064 * dumps. Usually used to add arch-specific system identifiers. If an
3065 * arch wants to make use of such an ID string, it should initialize this
3066 * as soon as possible during boot.
3068 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3072 va_start(args
, fmt
);
3073 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3079 * dump_stack_print_info - print generic debug info for dump_stack()
3080 * @log_lvl: log level
3082 * Arch-specific dump_stack() implementations can use this function to
3083 * print out the same debug information as the generic dump_stack().
3085 void dump_stack_print_info(const char *log_lvl
)
3087 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3088 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3089 print_tainted(), init_utsname()->release
,
3090 (int)strcspn(init_utsname()->version
, " "),
3091 init_utsname()->version
);
3093 if (dump_stack_arch_desc_str
[0] != '\0')
3094 printk("%sHardware name: %s\n",
3095 log_lvl
, dump_stack_arch_desc_str
);
3097 print_worker_info(log_lvl
, current
);
3101 * show_regs_print_info - print generic debug info for show_regs()
3102 * @log_lvl: log level
3104 * show_regs() implementations can use this function to print out generic
3105 * debug information.
3107 void show_regs_print_info(const char *log_lvl
)
3109 dump_stack_print_info(log_lvl
);
3111 printk("%stask: %p task.stack: %p\n",
3112 log_lvl
, current
, task_stack_page(current
));