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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
21 #include <linux/kernel.h>
23 #include <linux/tty.h>
24 #include <linux/tty_driver.h>
25 #include <linux/console.h>
26 #include <linux/init.h>
27 #include <linux/jiffies.h>
28 #include <linux/nmi.h>
29 #include <linux/module.h>
30 #include <linux/moduleparam.h>
31 #include <linux/delay.h>
32 #include <linux/smp.h>
33 #include <linux/security.h>
34 #include <linux/bootmem.h>
35 #include <linux/memblock.h>
36 #include <linux/syscalls.h>
37 #include <linux/crash_core.h>
38 #include <linux/kdb.h>
39 #include <linux/ratelimit.h>
40 #include <linux/kmsg_dump.h>
41 #include <linux/syslog.h>
42 #include <linux/cpu.h>
43 #include <linux/rculist.h>
44 #include <linux/poll.h>
45 #include <linux/irq_work.h>
46 #include <linux/ctype.h>
47 #include <linux/uio.h>
48 #include <linux/sched/clock.h>
49 #include <linux/sched/debug.h>
50 #include <linux/sched/task_stack.h>
52 #include <linux/uaccess.h>
53 #include <asm/sections.h>
55 #include <trace/events/initcall.h>
56 #define CREATE_TRACE_POINTS
57 #include <trace/events/printk.h>
59 #include "console_cmdline.h"
63 int console_printk
[4] = {
64 CONSOLE_LOGLEVEL_DEFAULT
, /* console_loglevel */
65 MESSAGE_LOGLEVEL_DEFAULT
, /* default_message_loglevel */
66 CONSOLE_LOGLEVEL_MIN
, /* minimum_console_loglevel */
67 CONSOLE_LOGLEVEL_DEFAULT
, /* default_console_loglevel */
70 atomic_t ignore_console_lock_warning __read_mostly
= ATOMIC_INIT(0);
71 EXPORT_SYMBOL(ignore_console_lock_warning
);
74 * Low level drivers may need that to know if they can schedule in
75 * their unblank() callback or not. So let's export it.
78 EXPORT_SYMBOL(oops_in_progress
);
81 * console_sem protects the console_drivers list, and also
82 * provides serialisation for access to the entire console
85 static DEFINE_SEMAPHORE(console_sem
);
86 struct console
*console_drivers
;
87 EXPORT_SYMBOL_GPL(console_drivers
);
90 static struct lockdep_map console_lock_dep_map
= {
91 .name
= "console_lock"
95 enum devkmsg_log_bits
{
96 __DEVKMSG_LOG_BIT_ON
= 0,
97 __DEVKMSG_LOG_BIT_OFF
,
98 __DEVKMSG_LOG_BIT_LOCK
,
101 enum devkmsg_log_masks
{
102 DEVKMSG_LOG_MASK_ON
= BIT(__DEVKMSG_LOG_BIT_ON
),
103 DEVKMSG_LOG_MASK_OFF
= BIT(__DEVKMSG_LOG_BIT_OFF
),
104 DEVKMSG_LOG_MASK_LOCK
= BIT(__DEVKMSG_LOG_BIT_LOCK
),
107 /* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
108 #define DEVKMSG_LOG_MASK_DEFAULT 0
110 static unsigned int __read_mostly devkmsg_log
= DEVKMSG_LOG_MASK_DEFAULT
;
112 static int __control_devkmsg(char *str
)
117 if (!strncmp(str
, "on", 2)) {
118 devkmsg_log
= DEVKMSG_LOG_MASK_ON
;
120 } else if (!strncmp(str
, "off", 3)) {
121 devkmsg_log
= DEVKMSG_LOG_MASK_OFF
;
123 } else if (!strncmp(str
, "ratelimit", 9)) {
124 devkmsg_log
= DEVKMSG_LOG_MASK_DEFAULT
;
130 static int __init
control_devkmsg(char *str
)
132 if (__control_devkmsg(str
) < 0)
136 * Set sysctl string accordingly:
138 if (devkmsg_log
== DEVKMSG_LOG_MASK_ON
)
139 strcpy(devkmsg_log_str
, "on");
140 else if (devkmsg_log
== DEVKMSG_LOG_MASK_OFF
)
141 strcpy(devkmsg_log_str
, "off");
142 /* else "ratelimit" which is set by default. */
145 * Sysctl cannot change it anymore. The kernel command line setting of
146 * this parameter is to force the setting to be permanent throughout the
147 * runtime of the system. This is a precation measure against userspace
148 * trying to be a smarta** and attempting to change it up on us.
150 devkmsg_log
|= DEVKMSG_LOG_MASK_LOCK
;
154 __setup("printk.devkmsg=", control_devkmsg
);
156 char devkmsg_log_str
[DEVKMSG_STR_MAX_SIZE
] = "ratelimit";
158 int devkmsg_sysctl_set_loglvl(struct ctl_table
*table
, int write
,
159 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
161 char old_str
[DEVKMSG_STR_MAX_SIZE
];
166 if (devkmsg_log
& DEVKMSG_LOG_MASK_LOCK
)
170 strncpy(old_str
, devkmsg_log_str
, DEVKMSG_STR_MAX_SIZE
);
173 err
= proc_dostring(table
, write
, buffer
, lenp
, ppos
);
178 err
= __control_devkmsg(devkmsg_log_str
);
181 * Do not accept an unknown string OR a known string with
184 if (err
< 0 || (err
+ 1 != *lenp
)) {
186 /* ... and restore old setting. */
188 strncpy(devkmsg_log_str
, old_str
, DEVKMSG_STR_MAX_SIZE
);
197 /* Number of registered extended console drivers. */
198 static int nr_ext_console_drivers
;
201 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
202 * macros instead of functions so that _RET_IP_ contains useful information.
204 #define down_console_sem() do { \
206 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
209 static int __down_trylock_console_sem(unsigned long ip
)
215 * Here and in __up_console_sem() we need to be in safe mode,
216 * because spindump/WARN/etc from under console ->lock will
217 * deadlock in printk()->down_trylock_console_sem() otherwise.
219 printk_safe_enter_irqsave(flags
);
220 lock_failed
= down_trylock(&console_sem
);
221 printk_safe_exit_irqrestore(flags
);
225 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
228 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
230 static void __up_console_sem(unsigned long ip
)
234 mutex_release(&console_lock_dep_map
, 1, ip
);
236 printk_safe_enter_irqsave(flags
);
238 printk_safe_exit_irqrestore(flags
);
240 #define up_console_sem() __up_console_sem(_RET_IP_)
243 * This is used for debugging the mess that is the VT code by
244 * keeping track if we have the console semaphore held. It's
245 * definitely not the perfect debug tool (we don't know if _WE_
246 * hold it and are racing, but it helps tracking those weird code
247 * paths in the console code where we end up in places I want
248 * locked without the console sempahore held).
250 static int console_locked
, console_suspended
;
253 * If exclusive_console is non-NULL then only this console is to be printed to.
255 static struct console
*exclusive_console
;
258 * Array of consoles built from command line options (console=)
261 #define MAX_CMDLINECONSOLES 8
263 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
265 static int preferred_console
= -1;
266 int console_set_on_cmdline
;
267 EXPORT_SYMBOL(console_set_on_cmdline
);
269 /* Flag: console code may call schedule() */
270 static int console_may_schedule
;
272 enum con_msg_format_flags
{
273 MSG_FORMAT_DEFAULT
= 0,
274 MSG_FORMAT_SYSLOG
= (1 << 0),
277 static int console_msg_format
= MSG_FORMAT_DEFAULT
;
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_NEWLINE
= 2, /* text ended with a newline */
348 LOG_PREFIX
= 4, /* text started with a prefix */
349 LOG_CONT
= 8, /* text is a fragment of a continuation line */
353 u64 ts_nsec
; /* timestamp in nanoseconds */
354 u16 len
; /* length of entire record */
355 u16 text_len
; /* length of text buffer */
356 u16 dict_len
; /* length of dictionary buffer */
357 u8 facility
; /* syslog facility */
358 u8 flags
:5; /* internal record flags */
359 u8 level
:3; /* syslog level */
361 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
362 __packed
__aligned(4)
367 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
368 * within the scheduler's rq lock. It must be released before calling
369 * console_unlock() or anything else that might wake up a process.
371 DEFINE_RAW_SPINLOCK(logbuf_lock
);
374 * Helper macros to lock/unlock logbuf_lock and switch between
375 * printk-safe/unsafe modes.
377 #define logbuf_lock_irq() \
379 printk_safe_enter_irq(); \
380 raw_spin_lock(&logbuf_lock); \
383 #define logbuf_unlock_irq() \
385 raw_spin_unlock(&logbuf_lock); \
386 printk_safe_exit_irq(); \
389 #define logbuf_lock_irqsave(flags) \
391 printk_safe_enter_irqsave(flags); \
392 raw_spin_lock(&logbuf_lock); \
395 #define logbuf_unlock_irqrestore(flags) \
397 raw_spin_unlock(&logbuf_lock); \
398 printk_safe_exit_irqrestore(flags); \
402 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
403 /* the next printk record to read by syslog(READ) or /proc/kmsg */
404 static u64 syslog_seq
;
405 static u32 syslog_idx
;
406 static size_t syslog_partial
;
408 /* index and sequence number of the first record stored in the buffer */
409 static u64 log_first_seq
;
410 static u32 log_first_idx
;
412 /* index and sequence number of the next record to store in the buffer */
413 static u64 log_next_seq
;
414 static u32 log_next_idx
;
416 /* the next printk record to write to the console */
417 static u64 console_seq
;
418 static u32 console_idx
;
419 static u64 exclusive_console_stop_seq
;
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 #define LOG_BUF_LEN_MAX (u32)(1 << 31)
435 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
436 static char *log_buf
= __log_buf
;
437 static u32 log_buf_len
= __LOG_BUF_LEN
;
439 /* Return log buffer address */
440 char *log_buf_addr_get(void)
445 /* Return log buffer size */
446 u32
log_buf_len_get(void)
451 /* human readable text of the record */
452 static char *log_text(const struct printk_log
*msg
)
454 return (char *)msg
+ sizeof(struct printk_log
);
457 /* optional key/value pair dictionary attached to the record */
458 static char *log_dict(const struct printk_log
*msg
)
460 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
463 /* get record by index; idx must point to valid msg */
464 static struct printk_log
*log_from_idx(u32 idx
)
466 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
469 * A length == 0 record is the end of buffer marker. Wrap around and
470 * read the message at the start of the buffer.
473 return (struct printk_log
*)log_buf
;
477 /* get next record; idx must point to valid msg */
478 static u32
log_next(u32 idx
)
480 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
482 /* length == 0 indicates the end of the buffer; wrap */
484 * A length == 0 record is the end of buffer marker. Wrap around and
485 * read the message at the start of the buffer as *this* one, and
486 * return the one after that.
489 msg
= (struct printk_log
*)log_buf
;
492 return idx
+ msg
->len
;
496 * Check whether there is enough free space for the given message.
498 * The same values of first_idx and next_idx mean that the buffer
499 * is either empty or full.
501 * If the buffer is empty, we must respect the position of the indexes.
502 * They cannot be reset to the beginning of the buffer.
504 static int logbuf_has_space(u32 msg_size
, bool empty
)
508 if (log_next_idx
> log_first_idx
|| empty
)
509 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
511 free
= log_first_idx
- log_next_idx
;
514 * We need space also for an empty header that signalizes wrapping
517 return free
>= msg_size
+ sizeof(struct printk_log
);
520 static int log_make_free_space(u32 msg_size
)
522 while (log_first_seq
< log_next_seq
&&
523 !logbuf_has_space(msg_size
, false)) {
524 /* drop old messages until we have enough contiguous space */
525 log_first_idx
= log_next(log_first_idx
);
529 if (clear_seq
< log_first_seq
) {
530 clear_seq
= log_first_seq
;
531 clear_idx
= log_first_idx
;
534 /* sequence numbers are equal, so the log buffer is empty */
535 if (logbuf_has_space(msg_size
, log_first_seq
== log_next_seq
))
541 /* compute the message size including the padding bytes */
542 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
546 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
547 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
554 * Define how much of the log buffer we could take at maximum. The value
555 * must be greater than two. Note that only half of the buffer is available
556 * when the index points to the middle.
558 #define MAX_LOG_TAKE_PART 4
559 static const char trunc_msg
[] = "<truncated>";
561 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
562 u16
*dict_len
, u32
*pad_len
)
565 * The message should not take the whole buffer. Otherwise, it might
566 * get removed too soon.
568 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
569 if (*text_len
> max_text_len
)
570 *text_len
= max_text_len
;
571 /* enable the warning message */
572 *trunc_msg_len
= strlen(trunc_msg
);
573 /* disable the "dict" completely */
575 /* compute the size again, count also the warning message */
576 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
579 /* insert record into the buffer, discard old ones, update heads */
580 static int log_store(int facility
, int level
,
581 enum log_flags flags
, u64 ts_nsec
,
582 const char *dict
, u16 dict_len
,
583 const char *text
, u16 text_len
)
585 struct printk_log
*msg
;
587 u16 trunc_msg_len
= 0;
589 /* number of '\0' padding bytes to next message */
590 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
592 if (log_make_free_space(size
)) {
593 /* truncate the message if it is too long for empty buffer */
594 size
= truncate_msg(&text_len
, &trunc_msg_len
,
595 &dict_len
, &pad_len
);
596 /* survive when the log buffer is too small for trunc_msg */
597 if (log_make_free_space(size
))
601 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
603 * This message + an additional empty header does not fit
604 * at the end of the buffer. Add an empty header with len == 0
605 * to signify a wrap around.
607 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
612 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
613 memcpy(log_text(msg
), text
, text_len
);
614 msg
->text_len
= text_len
;
616 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
617 msg
->text_len
+= trunc_msg_len
;
619 memcpy(log_dict(msg
), dict
, dict_len
);
620 msg
->dict_len
= dict_len
;
621 msg
->facility
= facility
;
622 msg
->level
= level
& 7;
623 msg
->flags
= flags
& 0x1f;
625 msg
->ts_nsec
= ts_nsec
;
627 msg
->ts_nsec
= local_clock();
628 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
632 log_next_idx
+= msg
->len
;
635 return msg
->text_len
;
638 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
640 static int syslog_action_restricted(int type
)
645 * Unless restricted, we allow "read all" and "get buffer size"
648 return type
!= SYSLOG_ACTION_READ_ALL
&&
649 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
652 static int check_syslog_permissions(int type
, int source
)
655 * If this is from /proc/kmsg and we've already opened it, then we've
656 * already done the capabilities checks at open time.
658 if (source
== SYSLOG_FROM_PROC
&& type
!= SYSLOG_ACTION_OPEN
)
661 if (syslog_action_restricted(type
)) {
662 if (capable(CAP_SYSLOG
))
665 * For historical reasons, accept CAP_SYS_ADMIN too, with
668 if (capable(CAP_SYS_ADMIN
)) {
669 pr_warn_once("%s (%d): Attempt to access syslog with "
670 "CAP_SYS_ADMIN but no CAP_SYSLOG "
672 current
->comm
, task_pid_nr(current
));
678 return security_syslog(type
);
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 __printf(3, 4) __cold
757 int devkmsg_emit(int facility
, int level
, const char *fmt
, ...)
763 r
= vprintk_emit(facility
, level
, NULL
, 0, fmt
, args
);
769 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
772 int level
= default_message_loglevel
;
773 int facility
= 1; /* LOG_USER */
774 struct file
*file
= iocb
->ki_filp
;
775 struct devkmsg_user
*user
= file
->private_data
;
776 size_t len
= iov_iter_count(from
);
779 if (!user
|| len
> LOG_LINE_MAX
)
782 /* Ignore when user logging is disabled. */
783 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
786 /* Ratelimit when not explicitly enabled. */
787 if (!(devkmsg_log
& DEVKMSG_LOG_MASK_ON
)) {
788 if (!___ratelimit(&user
->rs
, current
->comm
))
792 buf
= kmalloc(len
+1, GFP_KERNEL
);
797 if (!copy_from_iter_full(buf
, len
, from
)) {
803 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
804 * the decimal value represents 32bit, the lower 3 bit are the log
805 * level, the rest are the log facility.
807 * If no prefix or no userspace facility is specified, we
808 * enforce LOG_USER, to be able to reliably distinguish
809 * kernel-generated messages from userspace-injected ones.
812 if (line
[0] == '<') {
816 u
= simple_strtoul(line
+ 1, &endp
, 10);
817 if (endp
&& endp
[0] == '>') {
818 level
= LOG_LEVEL(u
);
819 if (LOG_FACILITY(u
) != 0)
820 facility
= LOG_FACILITY(u
);
827 devkmsg_emit(facility
, level
, "%s", line
);
832 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
833 size_t count
, loff_t
*ppos
)
835 struct devkmsg_user
*user
= file
->private_data
;
836 struct printk_log
*msg
;
843 ret
= mutex_lock_interruptible(&user
->lock
);
848 while (user
->seq
== log_next_seq
) {
849 if (file
->f_flags
& O_NONBLOCK
) {
856 ret
= wait_event_interruptible(log_wait
,
857 user
->seq
!= log_next_seq
);
863 if (user
->seq
< log_first_seq
) {
864 /* our last seen message is gone, return error and reset */
865 user
->idx
= log_first_idx
;
866 user
->seq
= log_first_seq
;
872 msg
= log_from_idx(user
->idx
);
873 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
875 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
876 log_dict(msg
), msg
->dict_len
,
877 log_text(msg
), msg
->text_len
);
879 user
->idx
= log_next(user
->idx
);
888 if (copy_to_user(buf
, user
->buf
, len
)) {
894 mutex_unlock(&user
->lock
);
898 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
900 struct devkmsg_user
*user
= file
->private_data
;
911 /* the first record */
912 user
->idx
= log_first_idx
;
913 user
->seq
= log_first_seq
;
917 * The first record after the last SYSLOG_ACTION_CLEAR,
918 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
919 * changes no global state, and does not clear anything.
921 user
->idx
= clear_idx
;
922 user
->seq
= clear_seq
;
925 /* after the last record */
926 user
->idx
= log_next_idx
;
927 user
->seq
= log_next_seq
;
936 static __poll_t
devkmsg_poll(struct file
*file
, poll_table
*wait
)
938 struct devkmsg_user
*user
= file
->private_data
;
942 return EPOLLERR
|EPOLLNVAL
;
944 poll_wait(file
, &log_wait
, wait
);
947 if (user
->seq
< log_next_seq
) {
948 /* return error when data has vanished underneath us */
949 if (user
->seq
< log_first_seq
)
950 ret
= EPOLLIN
|EPOLLRDNORM
|EPOLLERR
|EPOLLPRI
;
952 ret
= EPOLLIN
|EPOLLRDNORM
;
959 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
961 struct devkmsg_user
*user
;
964 if (devkmsg_log
& DEVKMSG_LOG_MASK_OFF
)
967 /* write-only does not need any file context */
968 if ((file
->f_flags
& O_ACCMODE
) != O_WRONLY
) {
969 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
975 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
979 ratelimit_default_init(&user
->rs
);
980 ratelimit_set_flags(&user
->rs
, RATELIMIT_MSG_ON_RELEASE
);
982 mutex_init(&user
->lock
);
985 user
->idx
= log_first_idx
;
986 user
->seq
= log_first_seq
;
989 file
->private_data
= user
;
993 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
995 struct devkmsg_user
*user
= file
->private_data
;
1000 ratelimit_state_exit(&user
->rs
);
1002 mutex_destroy(&user
->lock
);
1007 const struct file_operations kmsg_fops
= {
1008 .open
= devkmsg_open
,
1009 .read
= devkmsg_read
,
1010 .write_iter
= devkmsg_write
,
1011 .llseek
= devkmsg_llseek
,
1012 .poll
= devkmsg_poll
,
1013 .release
= devkmsg_release
,
1016 #ifdef CONFIG_CRASH_CORE
1018 * This appends the listed symbols to /proc/vmcore
1020 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
1021 * obtain access to symbols that are otherwise very difficult to locate. These
1022 * symbols are specifically used so that utilities can access and extract the
1023 * dmesg log from a vmcore file after a crash.
1025 void log_buf_vmcoreinfo_setup(void)
1027 VMCOREINFO_SYMBOL(log_buf
);
1028 VMCOREINFO_SYMBOL(log_buf_len
);
1029 VMCOREINFO_SYMBOL(log_first_idx
);
1030 VMCOREINFO_SYMBOL(clear_idx
);
1031 VMCOREINFO_SYMBOL(log_next_idx
);
1033 * Export struct printk_log size and field offsets. User space tools can
1034 * parse it and detect any changes to structure down the line.
1036 VMCOREINFO_STRUCT_SIZE(printk_log
);
1037 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
1038 VMCOREINFO_OFFSET(printk_log
, len
);
1039 VMCOREINFO_OFFSET(printk_log
, text_len
);
1040 VMCOREINFO_OFFSET(printk_log
, dict_len
);
1044 /* requested log_buf_len from kernel cmdline */
1045 static unsigned long __initdata new_log_buf_len
;
1047 /* we practice scaling the ring buffer by powers of 2 */
1048 static void __init
log_buf_len_update(u64 size
)
1050 if (size
> (u64
)LOG_BUF_LEN_MAX
) {
1051 size
= (u64
)LOG_BUF_LEN_MAX
;
1052 pr_err("log_buf over 2G is not supported.\n");
1056 size
= roundup_pow_of_two(size
);
1057 if (size
> log_buf_len
)
1058 new_log_buf_len
= (unsigned long)size
;
1061 /* save requested log_buf_len since it's too early to process it */
1062 static int __init
log_buf_len_setup(char *str
)
1069 size
= memparse(str
, &str
);
1071 log_buf_len_update(size
);
1075 early_param("log_buf_len", log_buf_len_setup
);
1078 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
1080 static void __init
log_buf_add_cpu(void)
1082 unsigned int cpu_extra
;
1085 * archs should set up cpu_possible_bits properly with
1086 * set_cpu_possible() after setup_arch() but just in
1087 * case lets ensure this is valid.
1089 if (num_possible_cpus() == 1)
1092 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
1094 /* by default this will only continue through for large > 64 CPUs */
1095 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
1098 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
1099 __LOG_CPU_MAX_BUF_LEN
);
1100 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
1102 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
1104 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
1106 #else /* !CONFIG_SMP */
1107 static inline void log_buf_add_cpu(void) {}
1108 #endif /* CONFIG_SMP */
1110 void __init
setup_log_buf(int early
)
1112 unsigned long flags
;
1116 if (log_buf
!= __log_buf
)
1119 if (!early
&& !new_log_buf_len
)
1122 if (!new_log_buf_len
)
1127 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
1129 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
1133 if (unlikely(!new_log_buf
)) {
1134 pr_err("log_buf_len: %lu bytes not available\n",
1139 logbuf_lock_irqsave(flags
);
1140 log_buf_len
= new_log_buf_len
;
1141 log_buf
= new_log_buf
;
1142 new_log_buf_len
= 0;
1143 free
= __LOG_BUF_LEN
- log_next_idx
;
1144 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
1145 logbuf_unlock_irqrestore(flags
);
1147 pr_info("log_buf_len: %u bytes\n", log_buf_len
);
1148 pr_info("early log buf free: %u(%u%%)\n",
1149 free
, (free
* 100) / __LOG_BUF_LEN
);
1152 static bool __read_mostly ignore_loglevel
;
1154 static int __init
ignore_loglevel_setup(char *str
)
1156 ignore_loglevel
= true;
1157 pr_info("debug: ignoring loglevel setting.\n");
1162 early_param("ignore_loglevel", ignore_loglevel_setup
);
1163 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
1164 MODULE_PARM_DESC(ignore_loglevel
,
1165 "ignore loglevel setting (prints all kernel messages to the console)");
1167 static bool suppress_message_printing(int level
)
1169 return (level
>= console_loglevel
&& !ignore_loglevel
);
1172 #ifdef CONFIG_BOOT_PRINTK_DELAY
1174 static int boot_delay
; /* msecs delay after each printk during bootup */
1175 static unsigned long long loops_per_msec
; /* based on boot_delay */
1177 static int __init
boot_delay_setup(char *str
)
1181 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
1182 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
1184 get_option(&str
, &boot_delay
);
1185 if (boot_delay
> 10 * 1000)
1188 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
1189 "HZ: %d, loops_per_msec: %llu\n",
1190 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1193 early_param("boot_delay", boot_delay_setup
);
1195 static void boot_delay_msec(int level
)
1197 unsigned long long k
;
1198 unsigned long timeout
;
1200 if ((boot_delay
== 0 || system_state
>= SYSTEM_RUNNING
)
1201 || suppress_message_printing(level
)) {
1205 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1207 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1212 * use (volatile) jiffies to prevent
1213 * compiler reduction; loop termination via jiffies
1214 * is secondary and may or may not happen.
1216 if (time_after(jiffies
, timeout
))
1218 touch_nmi_watchdog();
1222 static inline void boot_delay_msec(int level
)
1227 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1228 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1230 static size_t print_time(u64 ts
, char *buf
)
1232 unsigned long rem_nsec
;
1237 rem_nsec
= do_div(ts
, 1000000000);
1240 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1242 return sprintf(buf
, "[%5lu.%06lu] ",
1243 (unsigned long)ts
, rem_nsec
/ 1000);
1246 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1249 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1253 len
+= sprintf(buf
, "<%u>", prefix
);
1258 else if (prefix
> 99)
1260 else if (prefix
> 9)
1265 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1269 static size_t msg_print_text(const struct printk_log
*msg
, bool syslog
, char *buf
, size_t size
)
1271 const char *text
= log_text(msg
);
1272 size_t text_size
= msg
->text_len
;
1276 const char *next
= memchr(text
, '\n', text_size
);
1280 text_len
= next
- text
;
1282 text_size
-= next
- text
;
1284 text_len
= text_size
;
1288 if (print_prefix(msg
, syslog
, NULL
) +
1289 text_len
+ 1 >= size
- len
)
1292 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1293 memcpy(buf
+ len
, text
, text_len
);
1297 /* SYSLOG_ACTION_* buffer size only calculation */
1298 len
+= print_prefix(msg
, syslog
, NULL
);
1309 static int syslog_print(char __user
*buf
, int size
)
1312 struct printk_log
*msg
;
1315 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1324 if (syslog_seq
< log_first_seq
) {
1325 /* messages are gone, move to first one */
1326 syslog_seq
= log_first_seq
;
1327 syslog_idx
= log_first_idx
;
1330 if (syslog_seq
== log_next_seq
) {
1331 logbuf_unlock_irq();
1335 skip
= syslog_partial
;
1336 msg
= log_from_idx(syslog_idx
);
1337 n
= msg_print_text(msg
, true, text
, LOG_LINE_MAX
+ PREFIX_MAX
);
1338 if (n
- syslog_partial
<= size
) {
1339 /* message fits into buffer, move forward */
1340 syslog_idx
= log_next(syslog_idx
);
1342 n
-= syslog_partial
;
1345 /* partial read(), remember position */
1347 syslog_partial
+= n
;
1350 logbuf_unlock_irq();
1355 if (copy_to_user(buf
, text
+ skip
, n
)) {
1370 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1378 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1384 * Find first record that fits, including all following records,
1385 * into the user-provided buffer for this dump.
1389 while (seq
< log_next_seq
) {
1390 struct printk_log
*msg
= log_from_idx(idx
);
1392 len
+= msg_print_text(msg
, true, NULL
, 0);
1393 idx
= log_next(idx
);
1397 /* move first record forward until length fits into the buffer */
1400 while (len
> size
&& seq
< log_next_seq
) {
1401 struct printk_log
*msg
= log_from_idx(idx
);
1403 len
-= msg_print_text(msg
, true, NULL
, 0);
1404 idx
= log_next(idx
);
1408 /* last message fitting into this dump */
1409 next_seq
= log_next_seq
;
1412 while (len
>= 0 && seq
< next_seq
) {
1413 struct printk_log
*msg
= log_from_idx(idx
);
1416 textlen
= msg_print_text(msg
, true, text
,
1417 LOG_LINE_MAX
+ PREFIX_MAX
);
1422 idx
= log_next(idx
);
1425 logbuf_unlock_irq();
1426 if (copy_to_user(buf
+ len
, text
, textlen
))
1432 if (seq
< log_first_seq
) {
1433 /* messages are gone, move to next one */
1434 seq
= log_first_seq
;
1435 idx
= log_first_idx
;
1440 clear_seq
= log_next_seq
;
1441 clear_idx
= log_next_idx
;
1443 logbuf_unlock_irq();
1449 static void syslog_clear(void)
1452 clear_seq
= log_next_seq
;
1453 clear_idx
= log_next_idx
;
1454 logbuf_unlock_irq();
1457 int do_syslog(int type
, char __user
*buf
, int len
, int source
)
1460 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1463 error
= check_syslog_permissions(type
, source
);
1468 case SYSLOG_ACTION_CLOSE
: /* Close log */
1470 case SYSLOG_ACTION_OPEN
: /* Open log */
1472 case SYSLOG_ACTION_READ
: /* Read from log */
1473 if (!buf
|| len
< 0)
1477 if (!access_ok(VERIFY_WRITE
, buf
, len
))
1479 error
= wait_event_interruptible(log_wait
,
1480 syslog_seq
!= log_next_seq
);
1483 error
= syslog_print(buf
, len
);
1485 /* Read/clear last kernel messages */
1486 case SYSLOG_ACTION_READ_CLEAR
:
1489 /* Read last kernel messages */
1490 case SYSLOG_ACTION_READ_ALL
:
1491 if (!buf
|| len
< 0)
1495 if (!access_ok(VERIFY_WRITE
, buf
, len
))
1497 error
= syslog_print_all(buf
, len
, clear
);
1499 /* Clear ring buffer */
1500 case SYSLOG_ACTION_CLEAR
:
1503 /* Disable logging to console */
1504 case SYSLOG_ACTION_CONSOLE_OFF
:
1505 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1506 saved_console_loglevel
= console_loglevel
;
1507 console_loglevel
= minimum_console_loglevel
;
1509 /* Enable logging to console */
1510 case SYSLOG_ACTION_CONSOLE_ON
:
1511 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1512 console_loglevel
= saved_console_loglevel
;
1513 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1516 /* Set level of messages printed to console */
1517 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1518 if (len
< 1 || len
> 8)
1520 if (len
< minimum_console_loglevel
)
1521 len
= minimum_console_loglevel
;
1522 console_loglevel
= len
;
1523 /* Implicitly re-enable logging to console */
1524 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1526 /* Number of chars in the log buffer */
1527 case SYSLOG_ACTION_SIZE_UNREAD
:
1529 if (syslog_seq
< log_first_seq
) {
1530 /* messages are gone, move to first one */
1531 syslog_seq
= log_first_seq
;
1532 syslog_idx
= log_first_idx
;
1535 if (source
== SYSLOG_FROM_PROC
) {
1537 * Short-cut for poll(/"proc/kmsg") which simply checks
1538 * for pending data, not the size; return the count of
1539 * records, not the length.
1541 error
= log_next_seq
- syslog_seq
;
1543 u64 seq
= syslog_seq
;
1544 u32 idx
= syslog_idx
;
1546 while (seq
< log_next_seq
) {
1547 struct printk_log
*msg
= log_from_idx(idx
);
1549 error
+= msg_print_text(msg
, true, NULL
, 0);
1550 idx
= log_next(idx
);
1553 error
-= syslog_partial
;
1555 logbuf_unlock_irq();
1557 /* Size of the log buffer */
1558 case SYSLOG_ACTION_SIZE_BUFFER
:
1559 error
= log_buf_len
;
1569 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1571 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1575 * Special console_lock variants that help to reduce the risk of soft-lockups.
1576 * They allow to pass console_lock to another printk() call using a busy wait.
1579 #ifdef CONFIG_LOCKDEP
1580 static struct lockdep_map console_owner_dep_map
= {
1581 .name
= "console_owner"
1585 static DEFINE_RAW_SPINLOCK(console_owner_lock
);
1586 static struct task_struct
*console_owner
;
1587 static bool console_waiter
;
1590 * console_lock_spinning_enable - mark beginning of code where another
1591 * thread might safely busy wait
1593 * This basically converts console_lock into a spinlock. This marks
1594 * the section where the console_lock owner can not sleep, because
1595 * there may be a waiter spinning (like a spinlock). Also it must be
1596 * ready to hand over the lock at the end of the section.
1598 static void console_lock_spinning_enable(void)
1600 raw_spin_lock(&console_owner_lock
);
1601 console_owner
= current
;
1602 raw_spin_unlock(&console_owner_lock
);
1604 /* The waiter may spin on us after setting console_owner */
1605 spin_acquire(&console_owner_dep_map
, 0, 0, _THIS_IP_
);
1609 * console_lock_spinning_disable_and_check - mark end of code where another
1610 * thread was able to busy wait and check if there is a waiter
1612 * This is called at the end of the section where spinning is allowed.
1613 * It has two functions. First, it is a signal that it is no longer
1614 * safe to start busy waiting for the lock. Second, it checks if
1615 * there is a busy waiter and passes the lock rights to her.
1617 * Important: Callers lose the lock if there was a busy waiter.
1618 * They must not touch items synchronized by console_lock
1621 * Return: 1 if the lock rights were passed, 0 otherwise.
1623 static int console_lock_spinning_disable_and_check(void)
1627 raw_spin_lock(&console_owner_lock
);
1628 waiter
= READ_ONCE(console_waiter
);
1629 console_owner
= NULL
;
1630 raw_spin_unlock(&console_owner_lock
);
1633 spin_release(&console_owner_dep_map
, 1, _THIS_IP_
);
1637 /* The waiter is now free to continue */
1638 WRITE_ONCE(console_waiter
, false);
1640 spin_release(&console_owner_dep_map
, 1, _THIS_IP_
);
1643 * Hand off console_lock to waiter. The waiter will perform
1644 * the up(). After this, the waiter is the console_lock owner.
1646 mutex_release(&console_lock_dep_map
, 1, _THIS_IP_
);
1651 * console_trylock_spinning - try to get console_lock by busy waiting
1653 * This allows to busy wait for the console_lock when the current
1654 * owner is running in specially marked sections. It means that
1655 * the current owner is running and cannot reschedule until it
1656 * is ready to lose the lock.
1658 * Return: 1 if we got the lock, 0 othrewise
1660 static int console_trylock_spinning(void)
1662 struct task_struct
*owner
= NULL
;
1665 unsigned long flags
;
1667 if (console_trylock())
1670 printk_safe_enter_irqsave(flags
);
1672 raw_spin_lock(&console_owner_lock
);
1673 owner
= READ_ONCE(console_owner
);
1674 waiter
= READ_ONCE(console_waiter
);
1675 if (!waiter
&& owner
&& owner
!= current
) {
1676 WRITE_ONCE(console_waiter
, true);
1679 raw_spin_unlock(&console_owner_lock
);
1682 * If there is an active printk() writing to the
1683 * consoles, instead of having it write our data too,
1684 * see if we can offload that load from the active
1685 * printer, and do some printing ourselves.
1686 * Go into a spin only if there isn't already a waiter
1687 * spinning, and there is an active printer, and
1688 * that active printer isn't us (recursive printk?).
1691 printk_safe_exit_irqrestore(flags
);
1695 /* We spin waiting for the owner to release us */
1696 spin_acquire(&console_owner_dep_map
, 0, 0, _THIS_IP_
);
1697 /* Owner will clear console_waiter on hand off */
1698 while (READ_ONCE(console_waiter
))
1700 spin_release(&console_owner_dep_map
, 1, _THIS_IP_
);
1702 printk_safe_exit_irqrestore(flags
);
1704 * The owner passed the console lock to us.
1705 * Since we did not spin on console lock, annotate
1706 * this as a trylock. Otherwise lockdep will
1709 mutex_acquire(&console_lock_dep_map
, 0, 1, _THIS_IP_
);
1715 * Call the console drivers, asking them to write out
1716 * log_buf[start] to log_buf[end - 1].
1717 * The console_lock must be held.
1719 static void call_console_drivers(const char *ext_text
, size_t ext_len
,
1720 const char *text
, size_t len
)
1722 struct console
*con
;
1724 trace_console_rcuidle(text
, len
);
1726 if (!console_drivers
)
1729 for_each_console(con
) {
1730 if (exclusive_console
&& con
!= exclusive_console
)
1732 if (!(con
->flags
& CON_ENABLED
))
1736 if (!cpu_online(smp_processor_id()) &&
1737 !(con
->flags
& CON_ANYTIME
))
1739 if (con
->flags
& CON_EXTENDED
)
1740 con
->write(con
, ext_text
, ext_len
);
1742 con
->write(con
, text
, len
);
1746 int printk_delay_msec __read_mostly
;
1748 static inline void printk_delay(void)
1750 if (unlikely(printk_delay_msec
)) {
1751 int m
= printk_delay_msec
;
1755 touch_nmi_watchdog();
1761 * Continuation lines are buffered, and not committed to the record buffer
1762 * until the line is complete, or a race forces it. The line fragments
1763 * though, are printed immediately to the consoles to ensure everything has
1764 * reached the console in case of a kernel crash.
1766 static struct cont
{
1767 char buf
[LOG_LINE_MAX
];
1768 size_t len
; /* length == 0 means unused buffer */
1769 struct task_struct
*owner
; /* task of first print*/
1770 u64 ts_nsec
; /* time of first print */
1771 u8 level
; /* log level of first message */
1772 u8 facility
; /* log facility of first message */
1773 enum log_flags flags
; /* prefix, newline flags */
1776 static void cont_flush(void)
1781 log_store(cont
.facility
, cont
.level
, cont
.flags
, cont
.ts_nsec
,
1782 NULL
, 0, cont
.buf
, cont
.len
);
1786 static bool cont_add(int facility
, int level
, enum log_flags flags
, const char *text
, size_t len
)
1788 /* If the line gets too long, split it up in separate records. */
1789 if (cont
.len
+ len
> sizeof(cont
.buf
)) {
1795 cont
.facility
= facility
;
1797 cont
.owner
= current
;
1798 cont
.ts_nsec
= local_clock();
1802 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1805 // The original flags come from the first line,
1806 // but later continuations can add a newline.
1807 if (flags
& LOG_NEWLINE
) {
1808 cont
.flags
|= LOG_NEWLINE
;
1815 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
)
1818 * If an earlier line was buffered, and we're a continuation
1819 * write from the same process, try to add it to the buffer.
1822 if (cont
.owner
== current
&& (lflags
& LOG_CONT
)) {
1823 if (cont_add(facility
, level
, lflags
, text
, text_len
))
1826 /* Otherwise, make sure it's flushed */
1830 /* Skip empty continuation lines that couldn't be added - they just flush */
1831 if (!text_len
&& (lflags
& LOG_CONT
))
1834 /* If it doesn't end in a newline, try to buffer the current line */
1835 if (!(lflags
& LOG_NEWLINE
)) {
1836 if (cont_add(facility
, level
, lflags
, text
, text_len
))
1840 /* Store it in the record log */
1841 return log_store(facility
, level
, lflags
, 0, dict
, dictlen
, text
, text_len
);
1844 /* Must be called under logbuf_lock. */
1845 int vprintk_store(int facility
, int level
,
1846 const char *dict
, size_t dictlen
,
1847 const char *fmt
, va_list args
)
1849 static char textbuf
[LOG_LINE_MAX
];
1850 char *text
= textbuf
;
1852 enum log_flags lflags
= 0;
1855 * The printf needs to come first; we need the syslog
1856 * prefix which might be passed-in as a parameter.
1858 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1860 /* mark and strip a trailing newline */
1861 if (text_len
&& text
[text_len
-1] == '\n') {
1863 lflags
|= LOG_NEWLINE
;
1866 /* strip kernel syslog prefix and extract log level or control flags */
1867 if (facility
== 0) {
1870 while ((kern_level
= printk_get_level(text
)) != 0) {
1871 switch (kern_level
) {
1873 if (level
== LOGLEVEL_DEFAULT
)
1874 level
= kern_level
- '0';
1876 case 'd': /* KERN_DEFAULT */
1877 lflags
|= LOG_PREFIX
;
1879 case 'c': /* KERN_CONT */
1888 if (level
== LOGLEVEL_DEFAULT
)
1889 level
= default_message_loglevel
;
1892 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1894 return log_output(facility
, level
, lflags
,
1895 dict
, dictlen
, text
, text_len
);
1898 asmlinkage
int vprintk_emit(int facility
, int level
,
1899 const char *dict
, size_t dictlen
,
1900 const char *fmt
, va_list args
)
1903 bool in_sched
= false, pending_output
;
1904 unsigned long flags
;
1907 if (level
== LOGLEVEL_SCHED
) {
1908 level
= LOGLEVEL_DEFAULT
;
1912 boot_delay_msec(level
);
1915 /* This stops the holder of console_sem just where we want him */
1916 logbuf_lock_irqsave(flags
);
1917 curr_log_seq
= log_next_seq
;
1918 printed_len
= vprintk_store(facility
, level
, dict
, dictlen
, fmt
, args
);
1919 pending_output
= (curr_log_seq
!= log_next_seq
);
1920 logbuf_unlock_irqrestore(flags
);
1922 /* If called from the scheduler, we can not call up(). */
1923 if (!in_sched
&& pending_output
) {
1925 * Disable preemption to avoid being preempted while holding
1926 * console_sem which would prevent anyone from printing to
1931 * Try to acquire and then immediately release the console
1932 * semaphore. The release will print out buffers and wake up
1933 * /dev/kmsg and syslog() users.
1935 if (console_trylock_spinning())
1944 EXPORT_SYMBOL(vprintk_emit
);
1946 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1948 return vprintk_func(fmt
, args
);
1950 EXPORT_SYMBOL(vprintk
);
1952 int vprintk_default(const char *fmt
, va_list args
)
1956 #ifdef CONFIG_KGDB_KDB
1957 /* Allow to pass printk() to kdb but avoid a recursion. */
1958 if (unlikely(kdb_trap_printk
&& kdb_printf_cpu
< 0)) {
1959 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1963 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1967 EXPORT_SYMBOL_GPL(vprintk_default
);
1970 * printk - print a kernel message
1971 * @fmt: format string
1973 * This is printk(). It can be called from any context. We want it to work.
1975 * We try to grab the console_lock. If we succeed, it's easy - we log the
1976 * output and call the console drivers. If we fail to get the semaphore, we
1977 * place the output into the log buffer and return. The current holder of
1978 * the console_sem will notice the new output in console_unlock(); and will
1979 * send it to the consoles before releasing the lock.
1981 * One effect of this deferred printing is that code which calls printk() and
1982 * then changes console_loglevel may break. This is because console_loglevel
1983 * is inspected when the actual printing occurs.
1988 * See the vsnprintf() documentation for format string extensions over C99.
1990 asmlinkage __visible
int printk(const char *fmt
, ...)
1995 va_start(args
, fmt
);
1996 r
= vprintk_func(fmt
, args
);
2001 EXPORT_SYMBOL(printk
);
2003 #else /* CONFIG_PRINTK */
2005 #define LOG_LINE_MAX 0
2006 #define PREFIX_MAX 0
2008 static u64 syslog_seq
;
2009 static u32 syslog_idx
;
2010 static u64 console_seq
;
2011 static u32 console_idx
;
2012 static u64 exclusive_console_stop_seq
;
2013 static u64 log_first_seq
;
2014 static u32 log_first_idx
;
2015 static u64 log_next_seq
;
2016 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
2017 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
2018 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
2019 static u32
log_next(u32 idx
) { return 0; }
2020 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
2021 struct printk_log
*msg
,
2022 u64 seq
) { return 0; }
2023 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
2024 char *dict
, size_t dict_len
,
2025 char *text
, size_t text_len
) { return 0; }
2026 static void console_lock_spinning_enable(void) { }
2027 static int console_lock_spinning_disable_and_check(void) { return 0; }
2028 static void call_console_drivers(const char *ext_text
, size_t ext_len
,
2029 const char *text
, size_t len
) {}
2030 static size_t msg_print_text(const struct printk_log
*msg
,
2031 bool syslog
, char *buf
, size_t size
) { return 0; }
2032 static bool suppress_message_printing(int level
) { return false; }
2034 #endif /* CONFIG_PRINTK */
2036 #ifdef CONFIG_EARLY_PRINTK
2037 struct console
*early_console
;
2039 asmlinkage __visible
void early_printk(const char *fmt
, ...)
2049 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
2052 early_console
->write(early_console
, buf
, n
);
2056 static int __add_preferred_console(char *name
, int idx
, char *options
,
2059 struct console_cmdline
*c
;
2063 * See if this tty is not yet registered, and
2064 * if we have a slot free.
2066 for (i
= 0, c
= console_cmdline
;
2067 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2069 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
2071 preferred_console
= i
;
2075 if (i
== MAX_CMDLINECONSOLES
)
2078 preferred_console
= i
;
2079 strlcpy(c
->name
, name
, sizeof(c
->name
));
2080 c
->options
= options
;
2081 braille_set_options(c
, brl_options
);
2087 static int __init
console_msg_format_setup(char *str
)
2089 if (!strcmp(str
, "syslog"))
2090 console_msg_format
= MSG_FORMAT_SYSLOG
;
2091 if (!strcmp(str
, "default"))
2092 console_msg_format
= MSG_FORMAT_DEFAULT
;
2095 __setup("console_msg_format=", console_msg_format_setup
);
2098 * Set up a console. Called via do_early_param() in init/main.c
2099 * for each "console=" parameter in the boot command line.
2101 static int __init
console_setup(char *str
)
2103 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
2104 char *s
, *options
, *brl_options
= NULL
;
2107 if (_braille_console_setup(&str
, &brl_options
))
2111 * Decode str into name, index, options.
2113 if (str
[0] >= '0' && str
[0] <= '9') {
2114 strcpy(buf
, "ttyS");
2115 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
2117 strncpy(buf
, str
, sizeof(buf
) - 1);
2119 buf
[sizeof(buf
) - 1] = 0;
2120 options
= strchr(str
, ',');
2124 if (!strcmp(str
, "ttya"))
2125 strcpy(buf
, "ttyS0");
2126 if (!strcmp(str
, "ttyb"))
2127 strcpy(buf
, "ttyS1");
2129 for (s
= buf
; *s
; s
++)
2130 if (isdigit(*s
) || *s
== ',')
2132 idx
= simple_strtoul(s
, NULL
, 10);
2135 __add_preferred_console(buf
, idx
, options
, brl_options
);
2136 console_set_on_cmdline
= 1;
2139 __setup("console=", console_setup
);
2142 * add_preferred_console - add a device to the list of preferred consoles.
2143 * @name: device name
2144 * @idx: device index
2145 * @options: options for this console
2147 * The last preferred console added will be used for kernel messages
2148 * and stdin/out/err for init. Normally this is used by console_setup
2149 * above to handle user-supplied console arguments; however it can also
2150 * be used by arch-specific code either to override the user or more
2151 * commonly to provide a default console (ie from PROM variables) when
2152 * the user has not supplied one.
2154 int add_preferred_console(char *name
, int idx
, char *options
)
2156 return __add_preferred_console(name
, idx
, options
, NULL
);
2159 bool console_suspend_enabled
= true;
2160 EXPORT_SYMBOL(console_suspend_enabled
);
2162 static int __init
console_suspend_disable(char *str
)
2164 console_suspend_enabled
= false;
2167 __setup("no_console_suspend", console_suspend_disable
);
2168 module_param_named(console_suspend
, console_suspend_enabled
,
2169 bool, S_IRUGO
| S_IWUSR
);
2170 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2171 " and hibernate operations");
2174 * suspend_console - suspend the console subsystem
2176 * This disables printk() while we go into suspend states
2178 void suspend_console(void)
2180 if (!console_suspend_enabled
)
2182 pr_info("Suspending console(s) (use no_console_suspend to debug)\n");
2184 console_suspended
= 1;
2188 void resume_console(void)
2190 if (!console_suspend_enabled
)
2193 console_suspended
= 0;
2198 * console_cpu_notify - print deferred console messages after CPU hotplug
2201 * If printk() is called from a CPU that is not online yet, the messages
2202 * will be printed on the console only if there are CON_ANYTIME consoles.
2203 * This function is called when a new CPU comes online (or fails to come
2204 * up) or goes offline.
2206 static int console_cpu_notify(unsigned int cpu
)
2208 if (!cpuhp_tasks_frozen
) {
2209 /* If trylock fails, someone else is doing the printing */
2210 if (console_trylock())
2217 * console_lock - lock the console system for exclusive use.
2219 * Acquires a lock which guarantees that the caller has
2220 * exclusive access to the console system and the console_drivers list.
2222 * Can sleep, returns nothing.
2224 void console_lock(void)
2229 if (console_suspended
)
2232 console_may_schedule
= 1;
2234 EXPORT_SYMBOL(console_lock
);
2237 * console_trylock - try to lock the console system for exclusive use.
2239 * Try to acquire a lock which guarantees that the caller has exclusive
2240 * access to the console system and the console_drivers list.
2242 * returns 1 on success, and 0 on failure to acquire the lock.
2244 int console_trylock(void)
2246 if (down_trylock_console_sem())
2248 if (console_suspended
) {
2253 console_may_schedule
= 0;
2256 EXPORT_SYMBOL(console_trylock
);
2258 int is_console_locked(void)
2260 return console_locked
;
2262 EXPORT_SYMBOL(is_console_locked
);
2265 * Check if we have any console that is capable of printing while cpu is
2266 * booting or shutting down. Requires console_sem.
2268 static int have_callable_console(void)
2270 struct console
*con
;
2272 for_each_console(con
)
2273 if ((con
->flags
& CON_ENABLED
) &&
2274 (con
->flags
& CON_ANYTIME
))
2281 * Can we actually use the console at this time on this cpu?
2283 * Console drivers may assume that per-cpu resources have been allocated. So
2284 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
2285 * call them until this CPU is officially up.
2287 static inline int can_use_console(void)
2289 return cpu_online(raw_smp_processor_id()) || have_callable_console();
2293 * console_unlock - unlock the console system
2295 * Releases the console_lock which the caller holds on the console system
2296 * and the console driver list.
2298 * While the console_lock was held, console output may have been buffered
2299 * by printk(). If this is the case, console_unlock(); emits
2300 * the output prior to releasing the lock.
2302 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2304 * console_unlock(); may be called from any context.
2306 void console_unlock(void)
2308 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2309 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2310 unsigned long flags
;
2311 bool do_cond_resched
, retry
;
2313 if (console_suspended
) {
2319 * Console drivers are called with interrupts disabled, so
2320 * @console_may_schedule should be cleared before; however, we may
2321 * end up dumping a lot of lines, for example, if called from
2322 * console registration path, and should invoke cond_resched()
2323 * between lines if allowable. Not doing so can cause a very long
2324 * scheduling stall on a slow console leading to RCU stall and
2325 * softlockup warnings which exacerbate the issue with more
2326 * messages practically incapacitating the system.
2328 * console_trylock() is not able to detect the preemptive
2329 * context reliably. Therefore the value must be stored before
2330 * and cleared after the the "again" goto label.
2332 do_cond_resched
= console_may_schedule
;
2334 console_may_schedule
= 0;
2337 * We released the console_sem lock, so we need to recheck if
2338 * cpu is online and (if not) is there at least one CON_ANYTIME
2341 if (!can_use_console()) {
2348 struct printk_log
*msg
;
2352 printk_safe_enter_irqsave(flags
);
2353 raw_spin_lock(&logbuf_lock
);
2354 if (console_seq
< log_first_seq
) {
2356 "** %llu printk messages dropped **\n",
2357 log_first_seq
- console_seq
);
2359 /* messages are gone, move to first one */
2360 console_seq
= log_first_seq
;
2361 console_idx
= log_first_idx
;
2366 if (console_seq
== log_next_seq
)
2369 msg
= log_from_idx(console_idx
);
2370 if (suppress_message_printing(msg
->level
)) {
2372 * Skip record we have buffered and already printed
2373 * directly to the console when we received it, and
2374 * record that has level above the console loglevel.
2376 console_idx
= log_next(console_idx
);
2381 /* Output to all consoles once old messages replayed. */
2382 if (unlikely(exclusive_console
&&
2383 console_seq
>= exclusive_console_stop_seq
)) {
2384 exclusive_console
= NULL
;
2387 len
+= msg_print_text(msg
,
2388 console_msg_format
& MSG_FORMAT_SYSLOG
,
2390 sizeof(text
) - len
);
2391 if (nr_ext_console_drivers
) {
2392 ext_len
= msg_print_ext_header(ext_text
,
2395 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2396 sizeof(ext_text
) - ext_len
,
2397 log_dict(msg
), msg
->dict_len
,
2398 log_text(msg
), msg
->text_len
);
2400 console_idx
= log_next(console_idx
);
2402 raw_spin_unlock(&logbuf_lock
);
2405 * While actively printing out messages, if another printk()
2406 * were to occur on another CPU, it may wait for this one to
2407 * finish. This task can not be preempted if there is a
2408 * waiter waiting to take over.
2410 console_lock_spinning_enable();
2412 stop_critical_timings(); /* don't trace print latency */
2413 call_console_drivers(ext_text
, ext_len
, text
, len
);
2414 start_critical_timings();
2416 if (console_lock_spinning_disable_and_check()) {
2417 printk_safe_exit_irqrestore(flags
);
2421 printk_safe_exit_irqrestore(flags
);
2423 if (do_cond_resched
)
2429 raw_spin_unlock(&logbuf_lock
);
2434 * Someone could have filled up the buffer again, so re-check if there's
2435 * something to flush. In case we cannot trylock the console_sem again,
2436 * there's a new owner and the console_unlock() from them will do the
2437 * flush, no worries.
2439 raw_spin_lock(&logbuf_lock
);
2440 retry
= console_seq
!= log_next_seq
;
2441 raw_spin_unlock(&logbuf_lock
);
2442 printk_safe_exit_irqrestore(flags
);
2444 if (retry
&& console_trylock())
2447 EXPORT_SYMBOL(console_unlock
);
2450 * console_conditional_schedule - yield the CPU if required
2452 * If the console code is currently allowed to sleep, and
2453 * if this CPU should yield the CPU to another task, do
2456 * Must be called within console_lock();.
2458 void __sched
console_conditional_schedule(void)
2460 if (console_may_schedule
)
2463 EXPORT_SYMBOL(console_conditional_schedule
);
2465 void console_unblank(void)
2470 * console_unblank can no longer be called in interrupt context unless
2471 * oops_in_progress is set to 1..
2473 if (oops_in_progress
) {
2474 if (down_trylock_console_sem() != 0)
2480 console_may_schedule
= 0;
2482 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2488 * console_flush_on_panic - flush console content on panic
2490 * Immediately output all pending messages no matter what.
2492 void console_flush_on_panic(void)
2495 * If someone else is holding the console lock, trylock will fail
2496 * and may_schedule may be set. Ignore and proceed to unlock so
2497 * that messages are flushed out. As this can be called from any
2498 * context and we don't want to get preempted while flushing,
2499 * ensure may_schedule is cleared.
2502 console_may_schedule
= 0;
2507 * Return the console tty driver structure and its associated index
2509 struct tty_driver
*console_device(int *index
)
2512 struct tty_driver
*driver
= NULL
;
2515 for_each_console(c
) {
2518 driver
= c
->device(c
, index
);
2527 * Prevent further output on the passed console device so that (for example)
2528 * serial drivers can disable console output before suspending a port, and can
2529 * re-enable output afterwards.
2531 void console_stop(struct console
*console
)
2534 console
->flags
&= ~CON_ENABLED
;
2537 EXPORT_SYMBOL(console_stop
);
2539 void console_start(struct console
*console
)
2542 console
->flags
|= CON_ENABLED
;
2545 EXPORT_SYMBOL(console_start
);
2547 static int __read_mostly keep_bootcon
;
2549 static int __init
keep_bootcon_setup(char *str
)
2552 pr_info("debug: skip boot console de-registration.\n");
2557 early_param("keep_bootcon", keep_bootcon_setup
);
2560 * The console driver calls this routine during kernel initialization
2561 * to register the console printing procedure with printk() and to
2562 * print any messages that were printed by the kernel before the
2563 * console driver was initialized.
2565 * This can happen pretty early during the boot process (because of
2566 * early_printk) - sometimes before setup_arch() completes - be careful
2567 * of what kernel features are used - they may not be initialised yet.
2569 * There are two types of consoles - bootconsoles (early_printk) and
2570 * "real" consoles (everything which is not a bootconsole) which are
2571 * handled differently.
2572 * - Any number of bootconsoles can be registered at any time.
2573 * - As soon as a "real" console is registered, all bootconsoles
2574 * will be unregistered automatically.
2575 * - Once a "real" console is registered, any attempt to register a
2576 * bootconsoles will be rejected
2578 void register_console(struct console
*newcon
)
2581 unsigned long flags
;
2582 struct console
*bcon
= NULL
;
2583 struct console_cmdline
*c
;
2584 static bool has_preferred
;
2586 if (console_drivers
)
2587 for_each_console(bcon
)
2588 if (WARN(bcon
== newcon
,
2589 "console '%s%d' already registered\n",
2590 bcon
->name
, bcon
->index
))
2594 * before we register a new CON_BOOT console, make sure we don't
2595 * already have a valid console
2597 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2598 /* find the last or real console */
2599 for_each_console(bcon
) {
2600 if (!(bcon
->flags
& CON_BOOT
)) {
2601 pr_info("Too late to register bootconsole %s%d\n",
2602 newcon
->name
, newcon
->index
);
2608 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2609 bcon
= console_drivers
;
2611 if (!has_preferred
|| bcon
|| !console_drivers
)
2612 has_preferred
= preferred_console
>= 0;
2615 * See if we want to use this console driver. If we
2616 * didn't select a console we take the first one
2617 * that registers here.
2619 if (!has_preferred
) {
2620 if (newcon
->index
< 0)
2622 if (newcon
->setup
== NULL
||
2623 newcon
->setup(newcon
, NULL
) == 0) {
2624 newcon
->flags
|= CON_ENABLED
;
2625 if (newcon
->device
) {
2626 newcon
->flags
|= CON_CONSDEV
;
2627 has_preferred
= true;
2633 * See if this console matches one we selected on
2636 for (i
= 0, c
= console_cmdline
;
2637 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2639 if (!newcon
->match
||
2640 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2641 /* default matching */
2642 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2643 if (strcmp(c
->name
, newcon
->name
) != 0)
2645 if (newcon
->index
>= 0 &&
2646 newcon
->index
!= c
->index
)
2648 if (newcon
->index
< 0)
2649 newcon
->index
= c
->index
;
2651 if (_braille_register_console(newcon
, c
))
2654 if (newcon
->setup
&&
2655 newcon
->setup(newcon
, c
->options
) != 0)
2659 newcon
->flags
|= CON_ENABLED
;
2660 if (i
== preferred_console
) {
2661 newcon
->flags
|= CON_CONSDEV
;
2662 has_preferred
= true;
2667 if (!(newcon
->flags
& CON_ENABLED
))
2671 * If we have a bootconsole, and are switching to a real console,
2672 * don't print everything out again, since when the boot console, and
2673 * the real console are the same physical device, it's annoying to
2674 * see the beginning boot messages twice
2676 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2677 newcon
->flags
&= ~CON_PRINTBUFFER
;
2680 * Put this console in the list - keep the
2681 * preferred driver at the head of the list.
2684 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2685 newcon
->next
= console_drivers
;
2686 console_drivers
= newcon
;
2688 newcon
->next
->flags
&= ~CON_CONSDEV
;
2690 newcon
->next
= console_drivers
->next
;
2691 console_drivers
->next
= newcon
;
2694 if (newcon
->flags
& CON_EXTENDED
)
2695 nr_ext_console_drivers
++;
2697 if (newcon
->flags
& CON_PRINTBUFFER
) {
2699 * console_unlock(); will print out the buffered messages
2702 logbuf_lock_irqsave(flags
);
2703 console_seq
= syslog_seq
;
2704 console_idx
= syslog_idx
;
2706 * We're about to replay the log buffer. Only do this to the
2707 * just-registered console to avoid excessive message spam to
2708 * the already-registered consoles.
2710 * Set exclusive_console with disabled interrupts to reduce
2711 * race window with eventual console_flush_on_panic() that
2712 * ignores console_lock.
2714 exclusive_console
= newcon
;
2715 exclusive_console_stop_seq
= console_seq
;
2716 logbuf_unlock_irqrestore(flags
);
2719 console_sysfs_notify();
2722 * By unregistering the bootconsoles after we enable the real console
2723 * we get the "console xxx enabled" message on all the consoles -
2724 * boot consoles, real consoles, etc - this is to ensure that end
2725 * users know there might be something in the kernel's log buffer that
2726 * went to the bootconsole (that they do not see on the real console)
2728 pr_info("%sconsole [%s%d] enabled\n",
2729 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2730 newcon
->name
, newcon
->index
);
2732 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2734 /* We need to iterate through all boot consoles, to make
2735 * sure we print everything out, before we unregister them.
2737 for_each_console(bcon
)
2738 if (bcon
->flags
& CON_BOOT
)
2739 unregister_console(bcon
);
2742 EXPORT_SYMBOL(register_console
);
2744 int unregister_console(struct console
*console
)
2746 struct console
*a
, *b
;
2749 pr_info("%sconsole [%s%d] disabled\n",
2750 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2751 console
->name
, console
->index
);
2753 res
= _braille_unregister_console(console
);
2759 if (console_drivers
== console
) {
2760 console_drivers
=console
->next
;
2762 } else if (console_drivers
) {
2763 for (a
=console_drivers
->next
, b
=console_drivers
;
2764 a
; b
=a
, a
=b
->next
) {
2773 if (!res
&& (console
->flags
& CON_EXTENDED
))
2774 nr_ext_console_drivers
--;
2777 * If this isn't the last console and it has CON_CONSDEV set, we
2778 * need to set it on the next preferred console.
2780 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2781 console_drivers
->flags
|= CON_CONSDEV
;
2783 console
->flags
&= ~CON_ENABLED
;
2785 console_sysfs_notify();
2788 EXPORT_SYMBOL(unregister_console
);
2791 * Initialize the console device. This is called *early*, so
2792 * we can't necessarily depend on lots of kernel help here.
2793 * Just do some early initializations, and do the complex setup
2796 void __init
console_init(void)
2800 initcall_entry_t
*ce
;
2802 /* Setup the default TTY line discipline. */
2806 * set up the console device so that later boot sequences can
2807 * inform about problems etc..
2809 ce
= __con_initcall_start
;
2810 trace_initcall_level("console");
2811 while (ce
< __con_initcall_end
) {
2812 call
= initcall_from_entry(ce
);
2813 trace_initcall_start(call
);
2815 trace_initcall_finish(call
, ret
);
2821 * Some boot consoles access data that is in the init section and which will
2822 * be discarded after the initcalls have been run. To make sure that no code
2823 * will access this data, unregister the boot consoles in a late initcall.
2825 * If for some reason, such as deferred probe or the driver being a loadable
2826 * module, the real console hasn't registered yet at this point, there will
2827 * be a brief interval in which no messages are logged to the console, which
2828 * makes it difficult to diagnose problems that occur during this time.
2830 * To mitigate this problem somewhat, only unregister consoles whose memory
2831 * intersects with the init section. Note that all other boot consoles will
2832 * get unregistred when the real preferred console is registered.
2834 static int __init
printk_late_init(void)
2836 struct console
*con
;
2839 for_each_console(con
) {
2840 if (!(con
->flags
& CON_BOOT
))
2843 /* Check addresses that might be used for enabled consoles. */
2844 if (init_section_intersects(con
, sizeof(*con
)) ||
2845 init_section_contains(con
->write
, 0) ||
2846 init_section_contains(con
->read
, 0) ||
2847 init_section_contains(con
->device
, 0) ||
2848 init_section_contains(con
->unblank
, 0) ||
2849 init_section_contains(con
->data
, 0)) {
2851 * Please, consider moving the reported consoles out
2852 * of the init section.
2854 pr_warn("bootconsole [%s%d] uses init memory and must be disabled even before the real one is ready\n",
2855 con
->name
, con
->index
);
2856 unregister_console(con
);
2859 ret
= cpuhp_setup_state_nocalls(CPUHP_PRINTK_DEAD
, "printk:dead", NULL
,
2860 console_cpu_notify
);
2862 ret
= cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN
, "printk:online",
2863 console_cpu_notify
, NULL
);
2867 late_initcall(printk_late_init
);
2869 #if defined CONFIG_PRINTK
2871 * Delayed printk version, for scheduler-internal messages:
2873 #define PRINTK_PENDING_WAKEUP 0x01
2874 #define PRINTK_PENDING_OUTPUT 0x02
2876 static DEFINE_PER_CPU(int, printk_pending
);
2878 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2880 int pending
= __this_cpu_xchg(printk_pending
, 0);
2882 if (pending
& PRINTK_PENDING_OUTPUT
) {
2883 /* If trylock fails, someone else is doing the printing */
2884 if (console_trylock())
2888 if (pending
& PRINTK_PENDING_WAKEUP
)
2889 wake_up_interruptible(&log_wait
);
2892 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2893 .func
= wake_up_klogd_work_func
,
2894 .flags
= IRQ_WORK_LAZY
,
2897 void wake_up_klogd(void)
2900 if (waitqueue_active(&log_wait
)) {
2901 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2902 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2907 void defer_console_output(void)
2910 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2911 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2915 int vprintk_deferred(const char *fmt
, va_list args
)
2919 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2920 defer_console_output();
2925 int printk_deferred(const char *fmt
, ...)
2930 va_start(args
, fmt
);
2931 r
= vprintk_deferred(fmt
, args
);
2938 * printk rate limiting, lifted from the networking subsystem.
2940 * This enforces a rate limit: not more than 10 kernel messages
2941 * every 5s to make a denial-of-service attack impossible.
2943 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2945 int __printk_ratelimit(const char *func
)
2947 return ___ratelimit(&printk_ratelimit_state
, func
);
2949 EXPORT_SYMBOL(__printk_ratelimit
);
2952 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2953 * @caller_jiffies: pointer to caller's state
2954 * @interval_msecs: minimum interval between prints
2956 * printk_timed_ratelimit() returns true if more than @interval_msecs
2957 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2960 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2961 unsigned int interval_msecs
)
2963 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2965 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2968 *caller_jiffies
= jiffies
;
2971 EXPORT_SYMBOL(printk_timed_ratelimit
);
2973 static DEFINE_SPINLOCK(dump_list_lock
);
2974 static LIST_HEAD(dump_list
);
2977 * kmsg_dump_register - register a kernel log dumper.
2978 * @dumper: pointer to the kmsg_dumper structure
2980 * Adds a kernel log dumper to the system. The dump callback in the
2981 * structure will be called when the kernel oopses or panics and must be
2982 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2984 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2986 unsigned long flags
;
2989 /* The dump callback needs to be set */
2993 spin_lock_irqsave(&dump_list_lock
, flags
);
2994 /* Don't allow registering multiple times */
2995 if (!dumper
->registered
) {
2996 dumper
->registered
= 1;
2997 list_add_tail_rcu(&dumper
->list
, &dump_list
);
3000 spin_unlock_irqrestore(&dump_list_lock
, flags
);
3004 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
3007 * kmsg_dump_unregister - unregister a kmsg dumper.
3008 * @dumper: pointer to the kmsg_dumper structure
3010 * Removes a dump device from the system. Returns zero on success and
3011 * %-EINVAL otherwise.
3013 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
3015 unsigned long flags
;
3018 spin_lock_irqsave(&dump_list_lock
, flags
);
3019 if (dumper
->registered
) {
3020 dumper
->registered
= 0;
3021 list_del_rcu(&dumper
->list
);
3024 spin_unlock_irqrestore(&dump_list_lock
, flags
);
3029 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
3031 static bool always_kmsg_dump
;
3032 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
3035 * kmsg_dump - dump kernel log to kernel message dumpers.
3036 * @reason: the reason (oops, panic etc) for dumping
3038 * Call each of the registered dumper's dump() callback, which can
3039 * retrieve the kmsg records with kmsg_dump_get_line() or
3040 * kmsg_dump_get_buffer().
3042 void kmsg_dump(enum kmsg_dump_reason reason
)
3044 struct kmsg_dumper
*dumper
;
3045 unsigned long flags
;
3047 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
3051 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
3052 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
3055 /* initialize iterator with data about the stored records */
3056 dumper
->active
= true;
3058 logbuf_lock_irqsave(flags
);
3059 dumper
->cur_seq
= clear_seq
;
3060 dumper
->cur_idx
= clear_idx
;
3061 dumper
->next_seq
= log_next_seq
;
3062 dumper
->next_idx
= log_next_idx
;
3063 logbuf_unlock_irqrestore(flags
);
3065 /* invoke dumper which will iterate over records */
3066 dumper
->dump(dumper
, reason
);
3068 /* reset iterator */
3069 dumper
->active
= false;
3075 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
3076 * @dumper: registered kmsg dumper
3077 * @syslog: include the "<4>" prefixes
3078 * @line: buffer to copy the line to
3079 * @size: maximum size of the buffer
3080 * @len: length of line placed into buffer
3082 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3083 * record, and copy one record into the provided buffer.
3085 * Consecutive calls will return the next available record moving
3086 * towards the end of the buffer with the youngest messages.
3088 * A return value of FALSE indicates that there are no more records to
3091 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
3093 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
3094 char *line
, size_t size
, size_t *len
)
3096 struct printk_log
*msg
;
3100 if (!dumper
->active
)
3103 if (dumper
->cur_seq
< log_first_seq
) {
3104 /* messages are gone, move to first available one */
3105 dumper
->cur_seq
= log_first_seq
;
3106 dumper
->cur_idx
= log_first_idx
;
3110 if (dumper
->cur_seq
>= log_next_seq
)
3113 msg
= log_from_idx(dumper
->cur_idx
);
3114 l
= msg_print_text(msg
, syslog
, line
, size
);
3116 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
3126 * kmsg_dump_get_line - retrieve one kmsg log line
3127 * @dumper: registered kmsg dumper
3128 * @syslog: include the "<4>" prefixes
3129 * @line: buffer to copy the line to
3130 * @size: maximum size of the buffer
3131 * @len: length of line placed into buffer
3133 * Start at the beginning of the kmsg buffer, with the oldest kmsg
3134 * record, and copy one record into the provided buffer.
3136 * Consecutive calls will return the next available record moving
3137 * towards the end of the buffer with the youngest messages.
3139 * A return value of FALSE indicates that there are no more records to
3142 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
3143 char *line
, size_t size
, size_t *len
)
3145 unsigned long flags
;
3148 logbuf_lock_irqsave(flags
);
3149 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
3150 logbuf_unlock_irqrestore(flags
);
3154 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
3157 * kmsg_dump_get_buffer - copy kmsg log lines
3158 * @dumper: registered kmsg dumper
3159 * @syslog: include the "<4>" prefixes
3160 * @buf: buffer to copy the line to
3161 * @size: maximum size of the buffer
3162 * @len: length of line placed into buffer
3164 * Start at the end of the kmsg buffer and fill the provided buffer
3165 * with as many of the the *youngest* kmsg records that fit into it.
3166 * If the buffer is large enough, all available kmsg records will be
3167 * copied with a single call.
3169 * Consecutive calls will fill the buffer with the next block of
3170 * available older records, not including the earlier retrieved ones.
3172 * A return value of FALSE indicates that there are no more records to
3175 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
3176 char *buf
, size_t size
, size_t *len
)
3178 unsigned long flags
;
3186 if (!dumper
->active
)
3189 logbuf_lock_irqsave(flags
);
3190 if (dumper
->cur_seq
< log_first_seq
) {
3191 /* messages are gone, move to first available one */
3192 dumper
->cur_seq
= log_first_seq
;
3193 dumper
->cur_idx
= log_first_idx
;
3197 if (dumper
->cur_seq
>= dumper
->next_seq
) {
3198 logbuf_unlock_irqrestore(flags
);
3202 /* calculate length of entire buffer */
3203 seq
= dumper
->cur_seq
;
3204 idx
= dumper
->cur_idx
;
3205 while (seq
< dumper
->next_seq
) {
3206 struct printk_log
*msg
= log_from_idx(idx
);
3208 l
+= msg_print_text(msg
, true, NULL
, 0);
3209 idx
= log_next(idx
);
3213 /* move first record forward until length fits into the buffer */
3214 seq
= dumper
->cur_seq
;
3215 idx
= dumper
->cur_idx
;
3216 while (l
> size
&& seq
< dumper
->next_seq
) {
3217 struct printk_log
*msg
= log_from_idx(idx
);
3219 l
-= msg_print_text(msg
, true, NULL
, 0);
3220 idx
= log_next(idx
);
3224 /* last message in next interation */
3229 while (seq
< dumper
->next_seq
) {
3230 struct printk_log
*msg
= log_from_idx(idx
);
3232 l
+= msg_print_text(msg
, syslog
, buf
+ l
, size
- l
);
3233 idx
= log_next(idx
);
3237 dumper
->next_seq
= next_seq
;
3238 dumper
->next_idx
= next_idx
;
3240 logbuf_unlock_irqrestore(flags
);
3246 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3249 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3250 * @dumper: registered kmsg dumper
3252 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3253 * kmsg_dump_get_buffer() can be called again and used multiple
3254 * times within the same dumper.dump() callback.
3256 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3258 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3260 dumper
->cur_seq
= clear_seq
;
3261 dumper
->cur_idx
= clear_idx
;
3262 dumper
->next_seq
= log_next_seq
;
3263 dumper
->next_idx
= log_next_idx
;
3267 * kmsg_dump_rewind - reset the interator
3268 * @dumper: registered kmsg dumper
3270 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3271 * kmsg_dump_get_buffer() can be called again and used multiple
3272 * times within the same dumper.dump() callback.
3274 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3276 unsigned long flags
;
3278 logbuf_lock_irqsave(flags
);
3279 kmsg_dump_rewind_nolock(dumper
);
3280 logbuf_unlock_irqrestore(flags
);
3282 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);