2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
6 * Modified to make sys_syslog() more flexible: added commands to
7 * return the last 4k of kernel messages, regardless of whether
8 * they've been read or not. Added option to suppress kernel printk's
9 * to the console. Added hook for sending the console messages
10 * elsewhere, in preparation for a serial line console (someday).
12 * Modified for sysctl support, 1/8/97, Chris Horn.
13 * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14 * manfred@colorfullife.com
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/memblock.h>
35 #include <linux/syscalls.h>
36 #include <linux/kexec.h>
37 #include <linux/kdb.h>
38 #include <linux/ratelimit.h>
39 #include <linux/kmsg_dump.h>
40 #include <linux/syslog.h>
41 #include <linux/cpu.h>
42 #include <linux/notifier.h>
43 #include <linux/rculist.h>
44 #include <linux/poll.h>
45 #include <linux/irq_work.h>
46 #include <linux/utsname.h>
47 #include <linux/ctype.h>
48 #include <linux/uio.h>
50 #include <asm/uaccess.h>
52 #define CREATE_TRACE_POINTS
53 #include <trace/events/printk.h>
55 #include "console_cmdline.h"
58 int console_printk
[4] = {
59 CONSOLE_LOGLEVEL_DEFAULT
, /* console_loglevel */
60 MESSAGE_LOGLEVEL_DEFAULT
, /* default_message_loglevel */
61 CONSOLE_LOGLEVEL_MIN
, /* minimum_console_loglevel */
62 CONSOLE_LOGLEVEL_DEFAULT
, /* default_console_loglevel */
66 * Low level drivers may need that to know if they can schedule in
67 * their unblank() callback or not. So let's export it.
70 EXPORT_SYMBOL(oops_in_progress
);
73 * console_sem protects the console_drivers list, and also
74 * provides serialisation for access to the entire console
77 static DEFINE_SEMAPHORE(console_sem
);
78 struct console
*console_drivers
;
79 EXPORT_SYMBOL_GPL(console_drivers
);
82 static struct lockdep_map console_lock_dep_map
= {
83 .name
= "console_lock"
88 * Number of registered extended console drivers.
90 * If extended consoles are present, in-kernel cont reassembly is disabled
91 * and each fragment is stored as a separate log entry with proper
92 * continuation flag so that every emitted message has full metadata. This
93 * doesn't change the result for regular consoles or /proc/kmsg. For
94 * /dev/kmsg, as long as the reader concatenates messages according to
95 * consecutive continuation flags, the end result should be the same too.
97 static int nr_ext_console_drivers
;
100 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
101 * macros instead of functions so that _RET_IP_ contains useful information.
103 #define down_console_sem() do { \
105 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
108 static int __down_trylock_console_sem(unsigned long ip
)
110 if (down_trylock(&console_sem
))
112 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
115 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
117 #define up_console_sem() do { \
118 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
123 * This is used for debugging the mess that is the VT code by
124 * keeping track if we have the console semaphore held. It's
125 * definitely not the perfect debug tool (we don't know if _WE_
126 * hold it and are racing, but it helps tracking those weird code
127 * paths in the console code where we end up in places I want
128 * locked without the console sempahore held).
130 static int console_locked
, console_suspended
;
133 * If exclusive_console is non-NULL then only this console is to be printed to.
135 static struct console
*exclusive_console
;
138 * Array of consoles built from command line options (console=)
141 #define MAX_CMDLINECONSOLES 8
143 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
145 static int selected_console
= -1;
146 static int preferred_console
= -1;
147 int console_set_on_cmdline
;
148 EXPORT_SYMBOL(console_set_on_cmdline
);
150 /* Flag: console code may call schedule() */
151 static int console_may_schedule
;
154 * The printk log buffer consists of a chain of concatenated variable
155 * length records. Every record starts with a record header, containing
156 * the overall length of the record.
158 * The heads to the first and last entry in the buffer, as well as the
159 * sequence numbers of these entries are maintained when messages are
162 * If the heads indicate available messages, the length in the header
163 * tells the start next message. A length == 0 for the next message
164 * indicates a wrap-around to the beginning of the buffer.
166 * Every record carries the monotonic timestamp in microseconds, as well as
167 * the standard userspace syslog level and syslog facility. The usual
168 * kernel messages use LOG_KERN; userspace-injected messages always carry
169 * a matching syslog facility, by default LOG_USER. The origin of every
170 * message can be reliably determined that way.
172 * The human readable log message directly follows the message header. The
173 * length of the message text is stored in the header, the stored message
176 * Optionally, a message can carry a dictionary of properties (key/value pairs),
177 * to provide userspace with a machine-readable message context.
179 * Examples for well-defined, commonly used property names are:
180 * DEVICE=b12:8 device identifier
184 * +sound:card0 subsystem:devname
185 * SUBSYSTEM=pci driver-core subsystem name
187 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
188 * follows directly after a '=' character. Every property is terminated by
189 * a '\0' character. The last property is not terminated.
191 * Example of a message structure:
192 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
193 * 0008 34 00 record is 52 bytes long
194 * 000a 0b 00 text is 11 bytes long
195 * 000c 1f 00 dictionary is 23 bytes long
196 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
197 * 0010 69 74 27 73 20 61 20 6c "it's a l"
199 * 001b 44 45 56 49 43 "DEVIC"
200 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
201 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
203 * 0032 00 00 00 padding to next message header
205 * The 'struct printk_log' buffer header must never be directly exported to
206 * userspace, it is a kernel-private implementation detail that might
207 * need to be changed in the future, when the requirements change.
209 * /dev/kmsg exports the structured data in the following line format:
210 * "<level>,<sequnum>,<timestamp>,<contflag>[,additional_values, ... ];<message text>\n"
212 * Users of the export format should ignore possible additional values
213 * separated by ',', and find the message after the ';' character.
215 * The optional key/value pairs are attached as continuation lines starting
216 * with a space character and terminated by a newline. All possible
217 * non-prinatable characters are escaped in the "\xff" notation.
221 LOG_NOCONS
= 1, /* already flushed, do not print to console */
222 LOG_NEWLINE
= 2, /* text ended with a newline */
223 LOG_PREFIX
= 4, /* text started with a prefix */
224 LOG_CONT
= 8, /* text is a fragment of a continuation line */
228 u64 ts_nsec
; /* timestamp in nanoseconds */
229 u16 len
; /* length of entire record */
230 u16 text_len
; /* length of text buffer */
231 u16 dict_len
; /* length of dictionary buffer */
232 u8 facility
; /* syslog facility */
233 u8 flags
:5; /* internal record flags */
234 u8 level
:3; /* syslog level */
238 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
239 * within the scheduler's rq lock. It must be released before calling
240 * console_unlock() or anything else that might wake up a process.
242 static DEFINE_RAW_SPINLOCK(logbuf_lock
);
245 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
246 /* the next printk record to read by syslog(READ) or /proc/kmsg */
247 static u64 syslog_seq
;
248 static u32 syslog_idx
;
249 static enum log_flags syslog_prev
;
250 static size_t syslog_partial
;
252 /* index and sequence number of the first record stored in the buffer */
253 static u64 log_first_seq
;
254 static u32 log_first_idx
;
256 /* index and sequence number of the next record to store in the buffer */
257 static u64 log_next_seq
;
258 static u32 log_next_idx
;
260 /* the next printk record to write to the console */
261 static u64 console_seq
;
262 static u32 console_idx
;
263 static enum log_flags console_prev
;
265 /* the next printk record to read after the last 'clear' command */
266 static u64 clear_seq
;
267 static u32 clear_idx
;
269 #define PREFIX_MAX 32
270 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
273 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
276 #define LOG_ALIGN __alignof__(struct printk_log)
278 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
279 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
280 static char *log_buf
= __log_buf
;
281 static u32 log_buf_len
= __LOG_BUF_LEN
;
283 /* Return log buffer address */
284 char *log_buf_addr_get(void)
289 /* Return log buffer size */
290 u32
log_buf_len_get(void)
295 /* human readable text of the record */
296 static char *log_text(const struct printk_log
*msg
)
298 return (char *)msg
+ sizeof(struct printk_log
);
301 /* optional key/value pair dictionary attached to the record */
302 static char *log_dict(const struct printk_log
*msg
)
304 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
307 /* get record by index; idx must point to valid msg */
308 static struct printk_log
*log_from_idx(u32 idx
)
310 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
313 * A length == 0 record is the end of buffer marker. Wrap around and
314 * read the message at the start of the buffer.
317 return (struct printk_log
*)log_buf
;
321 /* get next record; idx must point to valid msg */
322 static u32
log_next(u32 idx
)
324 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
326 /* length == 0 indicates the end of the buffer; wrap */
328 * A length == 0 record is the end of buffer marker. Wrap around and
329 * read the message at the start of the buffer as *this* one, and
330 * return the one after that.
333 msg
= (struct printk_log
*)log_buf
;
336 return idx
+ msg
->len
;
340 * Check whether there is enough free space for the given message.
342 * The same values of first_idx and next_idx mean that the buffer
343 * is either empty or full.
345 * If the buffer is empty, we must respect the position of the indexes.
346 * They cannot be reset to the beginning of the buffer.
348 static int logbuf_has_space(u32 msg_size
, bool empty
)
352 if (log_next_idx
> log_first_idx
|| empty
)
353 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
355 free
= log_first_idx
- log_next_idx
;
358 * We need space also for an empty header that signalizes wrapping
361 return free
>= msg_size
+ sizeof(struct printk_log
);
364 static int log_make_free_space(u32 msg_size
)
366 while (log_first_seq
< log_next_seq
) {
367 if (logbuf_has_space(msg_size
, false))
369 /* drop old messages until we have enough contiguous space */
370 log_first_idx
= log_next(log_first_idx
);
374 /* sequence numbers are equal, so the log buffer is empty */
375 if (logbuf_has_space(msg_size
, true))
381 /* compute the message size including the padding bytes */
382 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
386 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
387 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
394 * Define how much of the log buffer we could take at maximum. The value
395 * must be greater than two. Note that only half of the buffer is available
396 * when the index points to the middle.
398 #define MAX_LOG_TAKE_PART 4
399 static const char trunc_msg
[] = "<truncated>";
401 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
402 u16
*dict_len
, u32
*pad_len
)
405 * The message should not take the whole buffer. Otherwise, it might
406 * get removed too soon.
408 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
409 if (*text_len
> max_text_len
)
410 *text_len
= max_text_len
;
411 /* enable the warning message */
412 *trunc_msg_len
= strlen(trunc_msg
);
413 /* disable the "dict" completely */
415 /* compute the size again, count also the warning message */
416 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
419 /* insert record into the buffer, discard old ones, update heads */
420 static int log_store(int facility
, int level
,
421 enum log_flags flags
, u64 ts_nsec
,
422 const char *dict
, u16 dict_len
,
423 const char *text
, u16 text_len
)
425 struct printk_log
*msg
;
427 u16 trunc_msg_len
= 0;
429 /* number of '\0' padding bytes to next message */
430 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
432 if (log_make_free_space(size
)) {
433 /* truncate the message if it is too long for empty buffer */
434 size
= truncate_msg(&text_len
, &trunc_msg_len
,
435 &dict_len
, &pad_len
);
436 /* survive when the log buffer is too small for trunc_msg */
437 if (log_make_free_space(size
))
441 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
443 * This message + an additional empty header does not fit
444 * at the end of the buffer. Add an empty header with len == 0
445 * to signify a wrap around.
447 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
452 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
453 memcpy(log_text(msg
), text
, text_len
);
454 msg
->text_len
= text_len
;
456 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
457 msg
->text_len
+= trunc_msg_len
;
459 memcpy(log_dict(msg
), dict
, dict_len
);
460 msg
->dict_len
= dict_len
;
461 msg
->facility
= facility
;
462 msg
->level
= level
& 7;
463 msg
->flags
= flags
& 0x1f;
465 msg
->ts_nsec
= ts_nsec
;
467 msg
->ts_nsec
= local_clock();
468 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
472 log_next_idx
+= msg
->len
;
475 return msg
->text_len
;
478 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
480 static int syslog_action_restricted(int type
)
485 * Unless restricted, we allow "read all" and "get buffer size"
488 return type
!= SYSLOG_ACTION_READ_ALL
&&
489 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
492 int check_syslog_permissions(int type
, int source
)
495 * If this is from /proc/kmsg and we've already opened it, then we've
496 * already done the capabilities checks at open time.
498 if (source
== SYSLOG_FROM_PROC
&& type
!= SYSLOG_ACTION_OPEN
)
501 if (syslog_action_restricted(type
)) {
502 if (capable(CAP_SYSLOG
))
505 * For historical reasons, accept CAP_SYS_ADMIN too, with
508 if (capable(CAP_SYS_ADMIN
)) {
509 pr_warn_once("%s (%d): Attempt to access syslog with "
510 "CAP_SYS_ADMIN but no CAP_SYSLOG "
512 current
->comm
, task_pid_nr(current
));
518 return security_syslog(type
);
520 EXPORT_SYMBOL_GPL(check_syslog_permissions
);
522 static void append_char(char **pp
, char *e
, char c
)
528 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
529 struct printk_log
*msg
, u64 seq
,
530 enum log_flags prev_flags
)
532 u64 ts_usec
= msg
->ts_nsec
;
535 do_div(ts_usec
, 1000);
538 * If we couldn't merge continuation line fragments during the print,
539 * export the stored flags to allow an optional external merge of the
540 * records. Merging the records isn't always neccessarily correct, like
541 * when we hit a race during printing. In most cases though, it produces
542 * better readable output. 'c' in the record flags mark the first
543 * fragment of a line, '+' the following.
545 if (msg
->flags
& LOG_CONT
&& !(prev_flags
& LOG_CONT
))
547 else if ((msg
->flags
& LOG_CONT
) ||
548 ((prev_flags
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
)))
551 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
552 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
, cont
);
555 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
556 char *dict
, size_t dict_len
,
557 char *text
, size_t text_len
)
559 char *p
= buf
, *e
= buf
+ size
;
562 /* escape non-printable characters */
563 for (i
= 0; i
< text_len
; i
++) {
564 unsigned char c
= text
[i
];
566 if (c
< ' ' || c
>= 127 || c
== '\\')
567 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
569 append_char(&p
, e
, c
);
571 append_char(&p
, e
, '\n');
576 for (i
= 0; i
< dict_len
; i
++) {
577 unsigned char c
= dict
[i
];
580 append_char(&p
, e
, ' ');
585 append_char(&p
, e
, '\n');
590 if (c
< ' ' || c
>= 127 || c
== '\\') {
591 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
595 append_char(&p
, e
, c
);
597 append_char(&p
, e
, '\n');
603 /* /dev/kmsg - userspace message inject/listen interface */
604 struct devkmsg_user
{
609 char buf
[CONSOLE_EXT_LOG_MAX
];
612 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
616 int level
= default_message_loglevel
;
617 int facility
= 1; /* LOG_USER */
618 size_t len
= iov_iter_count(from
);
621 if (len
> LOG_LINE_MAX
)
623 buf
= kmalloc(len
+1, GFP_KERNEL
);
628 if (copy_from_iter(buf
, len
, from
) != len
) {
634 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
635 * the decimal value represents 32bit, the lower 3 bit are the log
636 * level, the rest are the log facility.
638 * If no prefix or no userspace facility is specified, we
639 * enforce LOG_USER, to be able to reliably distinguish
640 * kernel-generated messages from userspace-injected ones.
643 if (line
[0] == '<') {
646 i
= simple_strtoul(line
+1, &endp
, 10);
647 if (endp
&& endp
[0] == '>') {
657 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
662 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
663 size_t count
, loff_t
*ppos
)
665 struct devkmsg_user
*user
= file
->private_data
;
666 struct printk_log
*msg
;
673 ret
= mutex_lock_interruptible(&user
->lock
);
676 raw_spin_lock_irq(&logbuf_lock
);
677 while (user
->seq
== log_next_seq
) {
678 if (file
->f_flags
& O_NONBLOCK
) {
680 raw_spin_unlock_irq(&logbuf_lock
);
684 raw_spin_unlock_irq(&logbuf_lock
);
685 ret
= wait_event_interruptible(log_wait
,
686 user
->seq
!= log_next_seq
);
689 raw_spin_lock_irq(&logbuf_lock
);
692 if (user
->seq
< log_first_seq
) {
693 /* our last seen message is gone, return error and reset */
694 user
->idx
= log_first_idx
;
695 user
->seq
= log_first_seq
;
697 raw_spin_unlock_irq(&logbuf_lock
);
701 msg
= log_from_idx(user
->idx
);
702 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
703 msg
, user
->seq
, user
->prev
);
704 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
705 log_dict(msg
), msg
->dict_len
,
706 log_text(msg
), msg
->text_len
);
708 user
->prev
= msg
->flags
;
709 user
->idx
= log_next(user
->idx
);
711 raw_spin_unlock_irq(&logbuf_lock
);
718 if (copy_to_user(buf
, user
->buf
, len
)) {
724 mutex_unlock(&user
->lock
);
728 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
730 struct devkmsg_user
*user
= file
->private_data
;
738 raw_spin_lock_irq(&logbuf_lock
);
741 /* the first record */
742 user
->idx
= log_first_idx
;
743 user
->seq
= log_first_seq
;
747 * The first record after the last SYSLOG_ACTION_CLEAR,
748 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
749 * changes no global state, and does not clear anything.
751 user
->idx
= clear_idx
;
752 user
->seq
= clear_seq
;
755 /* after the last record */
756 user
->idx
= log_next_idx
;
757 user
->seq
= log_next_seq
;
762 raw_spin_unlock_irq(&logbuf_lock
);
766 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
768 struct devkmsg_user
*user
= file
->private_data
;
772 return POLLERR
|POLLNVAL
;
774 poll_wait(file
, &log_wait
, wait
);
776 raw_spin_lock_irq(&logbuf_lock
);
777 if (user
->seq
< log_next_seq
) {
778 /* return error when data has vanished underneath us */
779 if (user
->seq
< log_first_seq
)
780 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
782 ret
= POLLIN
|POLLRDNORM
;
784 raw_spin_unlock_irq(&logbuf_lock
);
789 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
791 struct devkmsg_user
*user
;
794 /* write-only does not need any file context */
795 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
798 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
803 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
807 mutex_init(&user
->lock
);
809 raw_spin_lock_irq(&logbuf_lock
);
810 user
->idx
= log_first_idx
;
811 user
->seq
= log_first_seq
;
812 raw_spin_unlock_irq(&logbuf_lock
);
814 file
->private_data
= user
;
818 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
820 struct devkmsg_user
*user
= file
->private_data
;
825 mutex_destroy(&user
->lock
);
830 const struct file_operations kmsg_fops
= {
831 .open
= devkmsg_open
,
832 .read
= devkmsg_read
,
833 .write_iter
= devkmsg_write
,
834 .llseek
= devkmsg_llseek
,
835 .poll
= devkmsg_poll
,
836 .release
= devkmsg_release
,
839 #ifdef CONFIG_KEXEC_CORE
841 * This appends the listed symbols to /proc/vmcore
843 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
844 * obtain access to symbols that are otherwise very difficult to locate. These
845 * symbols are specifically used so that utilities can access and extract the
846 * dmesg log from a vmcore file after a crash.
848 void log_buf_kexec_setup(void)
850 VMCOREINFO_SYMBOL(log_buf
);
851 VMCOREINFO_SYMBOL(log_buf_len
);
852 VMCOREINFO_SYMBOL(log_first_idx
);
853 VMCOREINFO_SYMBOL(log_next_idx
);
855 * Export struct printk_log size and field offsets. User space tools can
856 * parse it and detect any changes to structure down the line.
858 VMCOREINFO_STRUCT_SIZE(printk_log
);
859 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
860 VMCOREINFO_OFFSET(printk_log
, len
);
861 VMCOREINFO_OFFSET(printk_log
, text_len
);
862 VMCOREINFO_OFFSET(printk_log
, dict_len
);
866 /* requested log_buf_len from kernel cmdline */
867 static unsigned long __initdata new_log_buf_len
;
869 /* we practice scaling the ring buffer by powers of 2 */
870 static void __init
log_buf_len_update(unsigned size
)
873 size
= roundup_pow_of_two(size
);
874 if (size
> log_buf_len
)
875 new_log_buf_len
= size
;
878 /* save requested log_buf_len since it's too early to process it */
879 static int __init
log_buf_len_setup(char *str
)
881 unsigned size
= memparse(str
, &str
);
883 log_buf_len_update(size
);
887 early_param("log_buf_len", log_buf_len_setup
);
890 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
892 static void __init
log_buf_add_cpu(void)
894 unsigned int cpu_extra
;
897 * archs should set up cpu_possible_bits properly with
898 * set_cpu_possible() after setup_arch() but just in
899 * case lets ensure this is valid.
901 if (num_possible_cpus() == 1)
904 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
906 /* by default this will only continue through for large > 64 CPUs */
907 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
910 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
911 __LOG_CPU_MAX_BUF_LEN
);
912 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
914 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
916 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
918 #else /* !CONFIG_SMP */
919 static inline void log_buf_add_cpu(void) {}
920 #endif /* CONFIG_SMP */
922 void __init
setup_log_buf(int early
)
928 if (log_buf
!= __log_buf
)
931 if (!early
&& !new_log_buf_len
)
934 if (!new_log_buf_len
)
939 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
941 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
945 if (unlikely(!new_log_buf
)) {
946 pr_err("log_buf_len: %ld bytes not available\n",
951 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
952 log_buf_len
= new_log_buf_len
;
953 log_buf
= new_log_buf
;
955 free
= __LOG_BUF_LEN
- log_next_idx
;
956 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
957 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
959 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
960 pr_info("early log buf free: %d(%d%%)\n",
961 free
, (free
* 100) / __LOG_BUF_LEN
);
964 static bool __read_mostly ignore_loglevel
;
966 static int __init
ignore_loglevel_setup(char *str
)
968 ignore_loglevel
= true;
969 pr_info("debug: ignoring loglevel setting.\n");
974 early_param("ignore_loglevel", ignore_loglevel_setup
);
975 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
976 MODULE_PARM_DESC(ignore_loglevel
,
977 "ignore loglevel setting (prints all kernel messages to the console)");
979 #ifdef CONFIG_BOOT_PRINTK_DELAY
981 static int boot_delay
; /* msecs delay after each printk during bootup */
982 static unsigned long long loops_per_msec
; /* based on boot_delay */
984 static int __init
boot_delay_setup(char *str
)
988 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
989 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
991 get_option(&str
, &boot_delay
);
992 if (boot_delay
> 10 * 1000)
995 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
996 "HZ: %d, loops_per_msec: %llu\n",
997 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
1000 early_param("boot_delay", boot_delay_setup
);
1002 static void boot_delay_msec(int level
)
1004 unsigned long long k
;
1005 unsigned long timeout
;
1007 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
1008 || (level
>= console_loglevel
&& !ignore_loglevel
)) {
1012 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1014 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1019 * use (volatile) jiffies to prevent
1020 * compiler reduction; loop termination via jiffies
1021 * is secondary and may or may not happen.
1023 if (time_after(jiffies
, timeout
))
1025 touch_nmi_watchdog();
1029 static inline void boot_delay_msec(int level
)
1034 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1035 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1037 static size_t print_time(u64 ts
, char *buf
)
1039 unsigned long rem_nsec
;
1044 rem_nsec
= do_div(ts
, 1000000000);
1047 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1049 return sprintf(buf
, "[%5lu.%06lu] ",
1050 (unsigned long)ts
, rem_nsec
/ 1000);
1053 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1056 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1060 len
+= sprintf(buf
, "<%u>", prefix
);
1065 else if (prefix
> 99)
1067 else if (prefix
> 9)
1072 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1076 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1077 bool syslog
, char *buf
, size_t size
)
1079 const char *text
= log_text(msg
);
1080 size_t text_size
= msg
->text_len
;
1082 bool newline
= true;
1085 if ((prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
))
1088 if (msg
->flags
& LOG_CONT
) {
1089 if ((prev
& LOG_CONT
) && !(prev
& LOG_NEWLINE
))
1092 if (!(msg
->flags
& LOG_NEWLINE
))
1097 const char *next
= memchr(text
, '\n', text_size
);
1101 text_len
= next
- text
;
1103 text_size
-= next
- text
;
1105 text_len
= text_size
;
1109 if (print_prefix(msg
, syslog
, NULL
) +
1110 text_len
+ 1 >= size
- len
)
1114 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1115 memcpy(buf
+ len
, text
, text_len
);
1117 if (next
|| newline
)
1120 /* SYSLOG_ACTION_* buffer size only calculation */
1122 len
+= print_prefix(msg
, syslog
, NULL
);
1124 if (next
|| newline
)
1135 static int syslog_print(char __user
*buf
, int size
)
1138 struct printk_log
*msg
;
1141 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1149 raw_spin_lock_irq(&logbuf_lock
);
1150 if (syslog_seq
< log_first_seq
) {
1151 /* messages are gone, move to first one */
1152 syslog_seq
= log_first_seq
;
1153 syslog_idx
= log_first_idx
;
1157 if (syslog_seq
== log_next_seq
) {
1158 raw_spin_unlock_irq(&logbuf_lock
);
1162 skip
= syslog_partial
;
1163 msg
= log_from_idx(syslog_idx
);
1164 n
= msg_print_text(msg
, syslog_prev
, true, text
,
1165 LOG_LINE_MAX
+ PREFIX_MAX
);
1166 if (n
- syslog_partial
<= size
) {
1167 /* message fits into buffer, move forward */
1168 syslog_idx
= log_next(syslog_idx
);
1170 syslog_prev
= msg
->flags
;
1171 n
-= syslog_partial
;
1174 /* partial read(), remember position */
1176 syslog_partial
+= n
;
1179 raw_spin_unlock_irq(&logbuf_lock
);
1184 if (copy_to_user(buf
, text
+ skip
, n
)) {
1199 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1204 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1208 raw_spin_lock_irq(&logbuf_lock
);
1213 enum log_flags prev
;
1215 if (clear_seq
< log_first_seq
) {
1216 /* messages are gone, move to first available one */
1217 clear_seq
= log_first_seq
;
1218 clear_idx
= log_first_idx
;
1222 * Find first record that fits, including all following records,
1223 * into the user-provided buffer for this dump.
1228 while (seq
< log_next_seq
) {
1229 struct printk_log
*msg
= log_from_idx(idx
);
1231 len
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1233 idx
= log_next(idx
);
1237 /* move first record forward until length fits into the buffer */
1241 while (len
> size
&& seq
< log_next_seq
) {
1242 struct printk_log
*msg
= log_from_idx(idx
);
1244 len
-= msg_print_text(msg
, prev
, true, NULL
, 0);
1246 idx
= log_next(idx
);
1250 /* last message fitting into this dump */
1251 next_seq
= log_next_seq
;
1254 while (len
>= 0 && seq
< next_seq
) {
1255 struct printk_log
*msg
= log_from_idx(idx
);
1258 textlen
= msg_print_text(msg
, prev
, true, text
,
1259 LOG_LINE_MAX
+ PREFIX_MAX
);
1264 idx
= log_next(idx
);
1268 raw_spin_unlock_irq(&logbuf_lock
);
1269 if (copy_to_user(buf
+ len
, text
, textlen
))
1273 raw_spin_lock_irq(&logbuf_lock
);
1275 if (seq
< log_first_seq
) {
1276 /* messages are gone, move to next one */
1277 seq
= log_first_seq
;
1278 idx
= log_first_idx
;
1285 clear_seq
= log_next_seq
;
1286 clear_idx
= log_next_idx
;
1288 raw_spin_unlock_irq(&logbuf_lock
);
1294 int do_syslog(int type
, char __user
*buf
, int len
, int source
)
1297 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1300 error
= check_syslog_permissions(type
, source
);
1305 case SYSLOG_ACTION_CLOSE
: /* Close log */
1307 case SYSLOG_ACTION_OPEN
: /* Open log */
1309 case SYSLOG_ACTION_READ
: /* Read from log */
1311 if (!buf
|| len
< 0)
1316 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1320 error
= wait_event_interruptible(log_wait
,
1321 syslog_seq
!= log_next_seq
);
1324 error
= syslog_print(buf
, len
);
1326 /* Read/clear last kernel messages */
1327 case SYSLOG_ACTION_READ_CLEAR
:
1330 /* Read last kernel messages */
1331 case SYSLOG_ACTION_READ_ALL
:
1333 if (!buf
|| len
< 0)
1338 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1342 error
= syslog_print_all(buf
, len
, clear
);
1344 /* Clear ring buffer */
1345 case SYSLOG_ACTION_CLEAR
:
1346 syslog_print_all(NULL
, 0, true);
1348 /* Disable logging to console */
1349 case SYSLOG_ACTION_CONSOLE_OFF
:
1350 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1351 saved_console_loglevel
= console_loglevel
;
1352 console_loglevel
= minimum_console_loglevel
;
1354 /* Enable logging to console */
1355 case SYSLOG_ACTION_CONSOLE_ON
:
1356 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1357 console_loglevel
= saved_console_loglevel
;
1358 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1361 /* Set level of messages printed to console */
1362 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1364 if (len
< 1 || len
> 8)
1366 if (len
< minimum_console_loglevel
)
1367 len
= minimum_console_loglevel
;
1368 console_loglevel
= len
;
1369 /* Implicitly re-enable logging to console */
1370 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1373 /* Number of chars in the log buffer */
1374 case SYSLOG_ACTION_SIZE_UNREAD
:
1375 raw_spin_lock_irq(&logbuf_lock
);
1376 if (syslog_seq
< log_first_seq
) {
1377 /* messages are gone, move to first one */
1378 syslog_seq
= log_first_seq
;
1379 syslog_idx
= log_first_idx
;
1383 if (source
== SYSLOG_FROM_PROC
) {
1385 * Short-cut for poll(/"proc/kmsg") which simply checks
1386 * for pending data, not the size; return the count of
1387 * records, not the length.
1389 error
= log_next_seq
- syslog_seq
;
1391 u64 seq
= syslog_seq
;
1392 u32 idx
= syslog_idx
;
1393 enum log_flags prev
= syslog_prev
;
1396 while (seq
< log_next_seq
) {
1397 struct printk_log
*msg
= log_from_idx(idx
);
1399 error
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1400 idx
= log_next(idx
);
1404 error
-= syslog_partial
;
1406 raw_spin_unlock_irq(&logbuf_lock
);
1408 /* Size of the log buffer */
1409 case SYSLOG_ACTION_SIZE_BUFFER
:
1410 error
= log_buf_len
;
1420 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1422 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1426 * Call the console drivers, asking them to write out
1427 * log_buf[start] to log_buf[end - 1].
1428 * The console_lock must be held.
1430 static void call_console_drivers(int level
,
1431 const char *ext_text
, size_t ext_len
,
1432 const char *text
, size_t len
)
1434 struct console
*con
;
1436 trace_console(text
, len
);
1438 if (level
>= console_loglevel
&& !ignore_loglevel
)
1440 if (!console_drivers
)
1443 for_each_console(con
) {
1444 if (exclusive_console
&& con
!= exclusive_console
)
1446 if (!(con
->flags
& CON_ENABLED
))
1450 if (!cpu_online(smp_processor_id()) &&
1451 !(con
->flags
& CON_ANYTIME
))
1453 if (con
->flags
& CON_EXTENDED
)
1454 con
->write(con
, ext_text
, ext_len
);
1456 con
->write(con
, text
, len
);
1461 * Zap console related locks when oopsing.
1462 * To leave time for slow consoles to print a full oops,
1463 * only zap at most once every 30 seconds.
1465 static void zap_locks(void)
1467 static unsigned long oops_timestamp
;
1469 if (time_after_eq(jiffies
, oops_timestamp
) &&
1470 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1473 oops_timestamp
= jiffies
;
1476 /* If a crash is occurring, make sure we can't deadlock */
1477 raw_spin_lock_init(&logbuf_lock
);
1478 /* And make sure that we print immediately */
1479 sema_init(&console_sem
, 1);
1483 * Check if we have any console that is capable of printing while cpu is
1484 * booting or shutting down. Requires console_sem.
1486 static int have_callable_console(void)
1488 struct console
*con
;
1490 for_each_console(con
)
1491 if (con
->flags
& CON_ANYTIME
)
1498 * Can we actually use the console at this time on this cpu?
1500 * Console drivers may assume that per-cpu resources have been allocated. So
1501 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1502 * call them until this CPU is officially up.
1504 static inline int can_use_console(unsigned int cpu
)
1506 return cpu_online(cpu
) || have_callable_console();
1510 * Try to get console ownership to actually show the kernel
1511 * messages from a 'printk'. Return true (and with the
1512 * console_lock held, and 'console_locked' set) if it
1513 * is successful, false otherwise.
1515 static int console_trylock_for_printk(void)
1517 unsigned int cpu
= smp_processor_id();
1519 if (!console_trylock())
1522 * If we can't use the console, we need to release the console
1523 * semaphore by hand to avoid flushing the buffer. We need to hold the
1524 * console semaphore in order to do this test safely.
1526 if (!can_use_console(cpu
)) {
1534 int printk_delay_msec __read_mostly
;
1536 static inline void printk_delay(void)
1538 if (unlikely(printk_delay_msec
)) {
1539 int m
= printk_delay_msec
;
1543 touch_nmi_watchdog();
1549 * Continuation lines are buffered, and not committed to the record buffer
1550 * until the line is complete, or a race forces it. The line fragments
1551 * though, are printed immediately to the consoles to ensure everything has
1552 * reached the console in case of a kernel crash.
1554 static struct cont
{
1555 char buf
[LOG_LINE_MAX
];
1556 size_t len
; /* length == 0 means unused buffer */
1557 size_t cons
; /* bytes written to console */
1558 struct task_struct
*owner
; /* task of first print*/
1559 u64 ts_nsec
; /* time of first print */
1560 u8 level
; /* log level of first message */
1561 u8 facility
; /* log facility of first message */
1562 enum log_flags flags
; /* prefix, newline flags */
1563 bool flushed
:1; /* buffer sealed and committed */
1566 static void cont_flush(enum log_flags flags
)
1575 * If a fragment of this line was directly flushed to the
1576 * console; wait for the console to pick up the rest of the
1577 * line. LOG_NOCONS suppresses a duplicated output.
1579 log_store(cont
.facility
, cont
.level
, flags
| LOG_NOCONS
,
1580 cont
.ts_nsec
, NULL
, 0, cont
.buf
, cont
.len
);
1582 cont
.flushed
= true;
1585 * If no fragment of this line ever reached the console,
1586 * just submit it to the store and free the buffer.
1588 log_store(cont
.facility
, cont
.level
, flags
, 0,
1589 NULL
, 0, cont
.buf
, cont
.len
);
1594 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1596 if (cont
.len
&& cont
.flushed
)
1600 * If ext consoles are present, flush and skip in-kernel
1601 * continuation. See nr_ext_console_drivers definition. Also, if
1602 * the line gets too long, split it up in separate records.
1604 if (nr_ext_console_drivers
|| cont
.len
+ len
> sizeof(cont
.buf
)) {
1605 cont_flush(LOG_CONT
);
1610 cont
.facility
= facility
;
1612 cont
.owner
= current
;
1613 cont
.ts_nsec
= local_clock();
1616 cont
.flushed
= false;
1619 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1622 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1623 cont_flush(LOG_CONT
);
1628 static size_t cont_print_text(char *text
, size_t size
)
1633 if (cont
.cons
== 0 && (console_prev
& LOG_NEWLINE
)) {
1634 textlen
+= print_time(cont
.ts_nsec
, text
);
1638 len
= cont
.len
- cont
.cons
;
1642 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1644 cont
.cons
= cont
.len
;
1648 if (cont
.flags
& LOG_NEWLINE
)
1649 text
[textlen
++] = '\n';
1650 /* got everything, release buffer */
1656 asmlinkage
int vprintk_emit(int facility
, int level
,
1657 const char *dict
, size_t dictlen
,
1658 const char *fmt
, va_list args
)
1660 static int recursion_bug
;
1661 static char textbuf
[LOG_LINE_MAX
];
1662 char *text
= textbuf
;
1663 size_t text_len
= 0;
1664 enum log_flags lflags
= 0;
1665 unsigned long flags
;
1667 int printed_len
= 0;
1668 bool in_sched
= false;
1669 /* cpu currently holding logbuf_lock in this function */
1670 static unsigned int logbuf_cpu
= UINT_MAX
;
1672 if (level
== LOGLEVEL_SCHED
) {
1673 level
= LOGLEVEL_DEFAULT
;
1677 boot_delay_msec(level
);
1680 /* This stops the holder of console_sem just where we want him */
1681 local_irq_save(flags
);
1682 this_cpu
= smp_processor_id();
1685 * Ouch, printk recursed into itself!
1687 if (unlikely(logbuf_cpu
== this_cpu
)) {
1689 * If a crash is occurring during printk() on this CPU,
1690 * then try to get the crash message out but make sure
1691 * we can't deadlock. Otherwise just return to avoid the
1692 * recursion and return - but flag the recursion so that
1693 * it can be printed at the next appropriate moment:
1695 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1697 local_irq_restore(flags
);
1704 raw_spin_lock(&logbuf_lock
);
1705 logbuf_cpu
= this_cpu
;
1707 if (unlikely(recursion_bug
)) {
1708 static const char recursion_msg
[] =
1709 "BUG: recent printk recursion!";
1712 /* emit KERN_CRIT message */
1713 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1714 NULL
, 0, recursion_msg
,
1715 strlen(recursion_msg
));
1719 * The printf needs to come first; we need the syslog
1720 * prefix which might be passed-in as a parameter.
1722 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1724 /* mark and strip a trailing newline */
1725 if (text_len
&& text
[text_len
-1] == '\n') {
1727 lflags
|= LOG_NEWLINE
;
1730 /* strip kernel syslog prefix and extract log level or control flags */
1731 if (facility
== 0) {
1732 int kern_level
= printk_get_level(text
);
1735 const char *end_of_header
= printk_skip_level(text
);
1736 switch (kern_level
) {
1738 if (level
== LOGLEVEL_DEFAULT
)
1739 level
= kern_level
- '0';
1741 case 'd': /* KERN_DEFAULT */
1742 lflags
|= LOG_PREFIX
;
1745 * No need to check length here because vscnprintf
1746 * put '\0' at the end of the string. Only valid and
1747 * newly printed level is detected.
1749 text_len
-= end_of_header
- text
;
1750 text
= (char *)end_of_header
;
1754 if (level
== LOGLEVEL_DEFAULT
)
1755 level
= default_message_loglevel
;
1758 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1760 if (!(lflags
& LOG_NEWLINE
)) {
1762 * Flush the conflicting buffer. An earlier newline was missing,
1763 * or another task also prints continuation lines.
1765 if (cont
.len
&& (lflags
& LOG_PREFIX
|| cont
.owner
!= current
))
1766 cont_flush(LOG_NEWLINE
);
1768 /* buffer line if possible, otherwise store it right away */
1769 if (cont_add(facility
, level
, text
, text_len
))
1770 printed_len
+= text_len
;
1772 printed_len
+= log_store(facility
, level
,
1773 lflags
| LOG_CONT
, 0,
1774 dict
, dictlen
, text
, text_len
);
1776 bool stored
= false;
1779 * If an earlier newline was missing and it was the same task,
1780 * either merge it with the current buffer and flush, or if
1781 * there was a race with interrupts (prefix == true) then just
1782 * flush it out and store this line separately.
1783 * If the preceding printk was from a different task and missed
1784 * a newline, flush and append the newline.
1787 if (cont
.owner
== current
&& !(lflags
& LOG_PREFIX
))
1788 stored
= cont_add(facility
, level
, text
,
1790 cont_flush(LOG_NEWLINE
);
1794 printed_len
+= text_len
;
1796 printed_len
+= log_store(facility
, level
, lflags
, 0,
1797 dict
, dictlen
, text
, text_len
);
1800 logbuf_cpu
= UINT_MAX
;
1801 raw_spin_unlock(&logbuf_lock
);
1803 local_irq_restore(flags
);
1805 /* If called from the scheduler, we can not call up(). */
1809 * Disable preemption to avoid being preempted while holding
1810 * console_sem which would prevent anyone from printing to
1816 * Try to acquire and then immediately release the console
1817 * semaphore. The release will print out buffers and wake up
1818 * /dev/kmsg and syslog() users.
1820 if (console_trylock_for_printk())
1828 EXPORT_SYMBOL(vprintk_emit
);
1830 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1832 return vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1834 EXPORT_SYMBOL(vprintk
);
1836 asmlinkage
int printk_emit(int facility
, int level
,
1837 const char *dict
, size_t dictlen
,
1838 const char *fmt
, ...)
1843 va_start(args
, fmt
);
1844 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1849 EXPORT_SYMBOL(printk_emit
);
1851 int vprintk_default(const char *fmt
, va_list args
)
1855 #ifdef CONFIG_KGDB_KDB
1856 if (unlikely(kdb_trap_printk
)) {
1857 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1861 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1865 EXPORT_SYMBOL_GPL(vprintk_default
);
1868 * This allows printk to be diverted to another function per cpu.
1869 * This is useful for calling printk functions from within NMI
1870 * without worrying about race conditions that can lock up the
1873 DEFINE_PER_CPU(printk_func_t
, printk_func
) = vprintk_default
;
1876 * printk - print a kernel message
1877 * @fmt: format string
1879 * This is printk(). It can be called from any context. We want it to work.
1881 * We try to grab the console_lock. If we succeed, it's easy - we log the
1882 * output and call the console drivers. If we fail to get the semaphore, we
1883 * place the output into the log buffer and return. The current holder of
1884 * the console_sem will notice the new output in console_unlock(); and will
1885 * send it to the consoles before releasing the lock.
1887 * One effect of this deferred printing is that code which calls printk() and
1888 * then changes console_loglevel may break. This is because console_loglevel
1889 * is inspected when the actual printing occurs.
1894 * See the vsnprintf() documentation for format string extensions over C99.
1896 asmlinkage __visible
int printk(const char *fmt
, ...)
1898 printk_func_t vprintk_func
;
1902 va_start(args
, fmt
);
1905 * If a caller overrides the per_cpu printk_func, then it needs
1906 * to disable preemption when calling printk(). Otherwise
1907 * the printk_func should be set to the default. No need to
1908 * disable preemption here.
1910 vprintk_func
= this_cpu_read(printk_func
);
1911 r
= vprintk_func(fmt
, args
);
1917 EXPORT_SYMBOL(printk
);
1919 #else /* CONFIG_PRINTK */
1921 #define LOG_LINE_MAX 0
1922 #define PREFIX_MAX 0
1924 static u64 syslog_seq
;
1925 static u32 syslog_idx
;
1926 static u64 console_seq
;
1927 static u32 console_idx
;
1928 static enum log_flags syslog_prev
;
1929 static u64 log_first_seq
;
1930 static u32 log_first_idx
;
1931 static u64 log_next_seq
;
1932 static enum log_flags console_prev
;
1933 static struct cont
{
1939 static char *log_text(const struct printk_log
*msg
) { return NULL
; }
1940 static char *log_dict(const struct printk_log
*msg
) { return NULL
; }
1941 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
1942 static u32
log_next(u32 idx
) { return 0; }
1943 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
1944 struct printk_log
*msg
, u64 seq
,
1945 enum log_flags prev_flags
) { return 0; }
1946 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
1947 char *dict
, size_t dict_len
,
1948 char *text
, size_t text_len
) { return 0; }
1949 static void call_console_drivers(int level
,
1950 const char *ext_text
, size_t ext_len
,
1951 const char *text
, size_t len
) {}
1952 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1953 bool syslog
, char *buf
, size_t size
) { return 0; }
1954 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
1956 /* Still needs to be defined for users */
1957 DEFINE_PER_CPU(printk_func_t
, printk_func
);
1959 #endif /* CONFIG_PRINTK */
1961 #ifdef CONFIG_EARLY_PRINTK
1962 struct console
*early_console
;
1964 asmlinkage __visible
void early_printk(const char *fmt
, ...)
1974 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
1977 early_console
->write(early_console
, buf
, n
);
1981 static int __add_preferred_console(char *name
, int idx
, char *options
,
1984 struct console_cmdline
*c
;
1988 * See if this tty is not yet registered, and
1989 * if we have a slot free.
1991 for (i
= 0, c
= console_cmdline
;
1992 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1994 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
1996 selected_console
= i
;
2000 if (i
== MAX_CMDLINECONSOLES
)
2003 selected_console
= i
;
2004 strlcpy(c
->name
, name
, sizeof(c
->name
));
2005 c
->options
= options
;
2006 braille_set_options(c
, brl_options
);
2012 * Set up a console. Called via do_early_param() in init/main.c
2013 * for each "console=" parameter in the boot command line.
2015 static int __init
console_setup(char *str
)
2017 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
2018 char *s
, *options
, *brl_options
= NULL
;
2021 if (_braille_console_setup(&str
, &brl_options
))
2025 * Decode str into name, index, options.
2027 if (str
[0] >= '0' && str
[0] <= '9') {
2028 strcpy(buf
, "ttyS");
2029 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
2031 strncpy(buf
, str
, sizeof(buf
) - 1);
2033 buf
[sizeof(buf
) - 1] = 0;
2034 options
= strchr(str
, ',');
2038 if (!strcmp(str
, "ttya"))
2039 strcpy(buf
, "ttyS0");
2040 if (!strcmp(str
, "ttyb"))
2041 strcpy(buf
, "ttyS1");
2043 for (s
= buf
; *s
; s
++)
2044 if (isdigit(*s
) || *s
== ',')
2046 idx
= simple_strtoul(s
, NULL
, 10);
2049 __add_preferred_console(buf
, idx
, options
, brl_options
);
2050 console_set_on_cmdline
= 1;
2053 __setup("console=", console_setup
);
2056 * add_preferred_console - add a device to the list of preferred consoles.
2057 * @name: device name
2058 * @idx: device index
2059 * @options: options for this console
2061 * The last preferred console added will be used for kernel messages
2062 * and stdin/out/err for init. Normally this is used by console_setup
2063 * above to handle user-supplied console arguments; however it can also
2064 * be used by arch-specific code either to override the user or more
2065 * commonly to provide a default console (ie from PROM variables) when
2066 * the user has not supplied one.
2068 int add_preferred_console(char *name
, int idx
, char *options
)
2070 return __add_preferred_console(name
, idx
, options
, NULL
);
2073 bool console_suspend_enabled
= true;
2074 EXPORT_SYMBOL(console_suspend_enabled
);
2076 static int __init
console_suspend_disable(char *str
)
2078 console_suspend_enabled
= false;
2081 __setup("no_console_suspend", console_suspend_disable
);
2082 module_param_named(console_suspend
, console_suspend_enabled
,
2083 bool, S_IRUGO
| S_IWUSR
);
2084 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2085 " and hibernate operations");
2088 * suspend_console - suspend the console subsystem
2090 * This disables printk() while we go into suspend states
2092 void suspend_console(void)
2094 if (!console_suspend_enabled
)
2096 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2098 console_suspended
= 1;
2102 void resume_console(void)
2104 if (!console_suspend_enabled
)
2107 console_suspended
= 0;
2112 * console_cpu_notify - print deferred console messages after CPU hotplug
2113 * @self: notifier struct
2114 * @action: CPU hotplug event
2117 * If printk() is called from a CPU that is not online yet, the messages
2118 * will be spooled but will not show up on the console. This function is
2119 * called when a new CPU comes online (or fails to come up), and ensures
2120 * that any such output gets printed.
2122 static int console_cpu_notify(struct notifier_block
*self
,
2123 unsigned long action
, void *hcpu
)
2128 case CPU_DOWN_FAILED
:
2129 case CPU_UP_CANCELED
:
2137 * console_lock - lock the console system for exclusive use.
2139 * Acquires a lock which guarantees that the caller has
2140 * exclusive access to the console system and the console_drivers list.
2142 * Can sleep, returns nothing.
2144 void console_lock(void)
2149 if (console_suspended
)
2152 console_may_schedule
= 1;
2154 EXPORT_SYMBOL(console_lock
);
2157 * console_trylock - try to lock the console system for exclusive use.
2159 * Try to acquire a lock which guarantees that the caller has exclusive
2160 * access to the console system and the console_drivers list.
2162 * returns 1 on success, and 0 on failure to acquire the lock.
2164 int console_trylock(void)
2166 if (down_trylock_console_sem())
2168 if (console_suspended
) {
2173 console_may_schedule
= 0;
2176 EXPORT_SYMBOL(console_trylock
);
2178 int is_console_locked(void)
2180 return console_locked
;
2183 static void console_cont_flush(char *text
, size_t size
)
2185 unsigned long flags
;
2188 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2194 * We still queue earlier records, likely because the console was
2195 * busy. The earlier ones need to be printed before this one, we
2196 * did not flush any fragment so far, so just let it queue up.
2198 if (console_seq
< log_next_seq
&& !cont
.cons
)
2201 len
= cont_print_text(text
, size
);
2202 raw_spin_unlock(&logbuf_lock
);
2203 stop_critical_timings();
2204 call_console_drivers(cont
.level
, NULL
, 0, text
, len
);
2205 start_critical_timings();
2206 local_irq_restore(flags
);
2209 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2213 * console_unlock - unlock the console system
2215 * Releases the console_lock which the caller holds on the console system
2216 * and the console driver list.
2218 * While the console_lock was held, console output may have been buffered
2219 * by printk(). If this is the case, console_unlock(); emits
2220 * the output prior to releasing the lock.
2222 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2224 * console_unlock(); may be called from any context.
2226 void console_unlock(void)
2228 static char ext_text
[CONSOLE_EXT_LOG_MAX
];
2229 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2230 static u64 seen_seq
;
2231 unsigned long flags
;
2232 bool wake_klogd
= false;
2235 if (console_suspended
) {
2240 console_may_schedule
= 0;
2242 /* flush buffered message fragment immediately to console */
2243 console_cont_flush(text
, sizeof(text
));
2246 struct printk_log
*msg
;
2251 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2252 if (seen_seq
!= log_next_seq
) {
2254 seen_seq
= log_next_seq
;
2257 if (console_seq
< log_first_seq
) {
2258 len
= sprintf(text
, "** %u printk messages dropped ** ",
2259 (unsigned)(log_first_seq
- console_seq
));
2261 /* messages are gone, move to first one */
2262 console_seq
= log_first_seq
;
2263 console_idx
= log_first_idx
;
2269 if (console_seq
== log_next_seq
)
2272 msg
= log_from_idx(console_idx
);
2273 if (msg
->flags
& LOG_NOCONS
) {
2275 * Skip record we have buffered and already printed
2276 * directly to the console when we received it.
2278 console_idx
= log_next(console_idx
);
2281 * We will get here again when we register a new
2282 * CON_PRINTBUFFER console. Clear the flag so we
2283 * will properly dump everything later.
2285 msg
->flags
&= ~LOG_NOCONS
;
2286 console_prev
= msg
->flags
;
2291 len
+= msg_print_text(msg
, console_prev
, false,
2292 text
+ len
, sizeof(text
) - len
);
2293 if (nr_ext_console_drivers
) {
2294 ext_len
= msg_print_ext_header(ext_text
,
2296 msg
, console_seq
, console_prev
);
2297 ext_len
+= msg_print_ext_body(ext_text
+ ext_len
,
2298 sizeof(ext_text
) - ext_len
,
2299 log_dict(msg
), msg
->dict_len
,
2300 log_text(msg
), msg
->text_len
);
2302 console_idx
= log_next(console_idx
);
2304 console_prev
= msg
->flags
;
2305 raw_spin_unlock(&logbuf_lock
);
2307 stop_critical_timings(); /* don't trace print latency */
2308 call_console_drivers(level
, ext_text
, ext_len
, text
, len
);
2309 start_critical_timings();
2310 local_irq_restore(flags
);
2314 /* Release the exclusive_console once it is used */
2315 if (unlikely(exclusive_console
))
2316 exclusive_console
= NULL
;
2318 raw_spin_unlock(&logbuf_lock
);
2323 * Someone could have filled up the buffer again, so re-check if there's
2324 * something to flush. In case we cannot trylock the console_sem again,
2325 * there's a new owner and the console_unlock() from them will do the
2326 * flush, no worries.
2328 raw_spin_lock(&logbuf_lock
);
2329 retry
= console_seq
!= log_next_seq
;
2330 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2332 if (retry
&& console_trylock())
2338 EXPORT_SYMBOL(console_unlock
);
2341 * console_conditional_schedule - yield the CPU if required
2343 * If the console code is currently allowed to sleep, and
2344 * if this CPU should yield the CPU to another task, do
2347 * Must be called within console_lock();.
2349 void __sched
console_conditional_schedule(void)
2351 if (console_may_schedule
)
2354 EXPORT_SYMBOL(console_conditional_schedule
);
2356 void console_unblank(void)
2361 * console_unblank can no longer be called in interrupt context unless
2362 * oops_in_progress is set to 1..
2364 if (oops_in_progress
) {
2365 if (down_trylock_console_sem() != 0)
2371 console_may_schedule
= 0;
2373 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2379 * Return the console tty driver structure and its associated index
2381 struct tty_driver
*console_device(int *index
)
2384 struct tty_driver
*driver
= NULL
;
2387 for_each_console(c
) {
2390 driver
= c
->device(c
, index
);
2399 * Prevent further output on the passed console device so that (for example)
2400 * serial drivers can disable console output before suspending a port, and can
2401 * re-enable output afterwards.
2403 void console_stop(struct console
*console
)
2406 console
->flags
&= ~CON_ENABLED
;
2409 EXPORT_SYMBOL(console_stop
);
2411 void console_start(struct console
*console
)
2414 console
->flags
|= CON_ENABLED
;
2417 EXPORT_SYMBOL(console_start
);
2419 static int __read_mostly keep_bootcon
;
2421 static int __init
keep_bootcon_setup(char *str
)
2424 pr_info("debug: skip boot console de-registration.\n");
2429 early_param("keep_bootcon", keep_bootcon_setup
);
2432 * The console driver calls this routine during kernel initialization
2433 * to register the console printing procedure with printk() and to
2434 * print any messages that were printed by the kernel before the
2435 * console driver was initialized.
2437 * This can happen pretty early during the boot process (because of
2438 * early_printk) - sometimes before setup_arch() completes - be careful
2439 * of what kernel features are used - they may not be initialised yet.
2441 * There are two types of consoles - bootconsoles (early_printk) and
2442 * "real" consoles (everything which is not a bootconsole) which are
2443 * handled differently.
2444 * - Any number of bootconsoles can be registered at any time.
2445 * - As soon as a "real" console is registered, all bootconsoles
2446 * will be unregistered automatically.
2447 * - Once a "real" console is registered, any attempt to register a
2448 * bootconsoles will be rejected
2450 void register_console(struct console
*newcon
)
2453 unsigned long flags
;
2454 struct console
*bcon
= NULL
;
2455 struct console_cmdline
*c
;
2457 if (console_drivers
)
2458 for_each_console(bcon
)
2459 if (WARN(bcon
== newcon
,
2460 "console '%s%d' already registered\n",
2461 bcon
->name
, bcon
->index
))
2465 * before we register a new CON_BOOT console, make sure we don't
2466 * already have a valid console
2468 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2469 /* find the last or real console */
2470 for_each_console(bcon
) {
2471 if (!(bcon
->flags
& CON_BOOT
)) {
2472 pr_info("Too late to register bootconsole %s%d\n",
2473 newcon
->name
, newcon
->index
);
2479 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2480 bcon
= console_drivers
;
2482 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2483 preferred_console
= selected_console
;
2486 * See if we want to use this console driver. If we
2487 * didn't select a console we take the first one
2488 * that registers here.
2490 if (preferred_console
< 0) {
2491 if (newcon
->index
< 0)
2493 if (newcon
->setup
== NULL
||
2494 newcon
->setup(newcon
, NULL
) == 0) {
2495 newcon
->flags
|= CON_ENABLED
;
2496 if (newcon
->device
) {
2497 newcon
->flags
|= CON_CONSDEV
;
2498 preferred_console
= 0;
2504 * See if this console matches one we selected on
2507 for (i
= 0, c
= console_cmdline
;
2508 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2510 if (!newcon
->match
||
2511 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2512 /* default matching */
2513 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2514 if (strcmp(c
->name
, newcon
->name
) != 0)
2516 if (newcon
->index
>= 0 &&
2517 newcon
->index
!= c
->index
)
2519 if (newcon
->index
< 0)
2520 newcon
->index
= c
->index
;
2522 if (_braille_register_console(newcon
, c
))
2525 if (newcon
->setup
&&
2526 newcon
->setup(newcon
, c
->options
) != 0)
2530 newcon
->flags
|= CON_ENABLED
;
2531 if (i
== selected_console
) {
2532 newcon
->flags
|= CON_CONSDEV
;
2533 preferred_console
= selected_console
;
2538 if (!(newcon
->flags
& CON_ENABLED
))
2542 * If we have a bootconsole, and are switching to a real console,
2543 * don't print everything out again, since when the boot console, and
2544 * the real console are the same physical device, it's annoying to
2545 * see the beginning boot messages twice
2547 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2548 newcon
->flags
&= ~CON_PRINTBUFFER
;
2551 * Put this console in the list - keep the
2552 * preferred driver at the head of the list.
2555 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2556 newcon
->next
= console_drivers
;
2557 console_drivers
= newcon
;
2559 newcon
->next
->flags
&= ~CON_CONSDEV
;
2561 newcon
->next
= console_drivers
->next
;
2562 console_drivers
->next
= newcon
;
2565 if (newcon
->flags
& CON_EXTENDED
)
2566 if (!nr_ext_console_drivers
++)
2567 pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
2569 if (newcon
->flags
& CON_PRINTBUFFER
) {
2571 * console_unlock(); will print out the buffered messages
2574 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2575 console_seq
= syslog_seq
;
2576 console_idx
= syslog_idx
;
2577 console_prev
= syslog_prev
;
2578 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2580 * We're about to replay the log buffer. Only do this to the
2581 * just-registered console to avoid excessive message spam to
2582 * the already-registered consoles.
2584 exclusive_console
= newcon
;
2587 console_sysfs_notify();
2590 * By unregistering the bootconsoles after we enable the real console
2591 * we get the "console xxx enabled" message on all the consoles -
2592 * boot consoles, real consoles, etc - this is to ensure that end
2593 * users know there might be something in the kernel's log buffer that
2594 * went to the bootconsole (that they do not see on the real console)
2596 pr_info("%sconsole [%s%d] enabled\n",
2597 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2598 newcon
->name
, newcon
->index
);
2600 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2602 /* We need to iterate through all boot consoles, to make
2603 * sure we print everything out, before we unregister them.
2605 for_each_console(bcon
)
2606 if (bcon
->flags
& CON_BOOT
)
2607 unregister_console(bcon
);
2610 EXPORT_SYMBOL(register_console
);
2612 int unregister_console(struct console
*console
)
2614 struct console
*a
, *b
;
2617 pr_info("%sconsole [%s%d] disabled\n",
2618 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2619 console
->name
, console
->index
);
2621 res
= _braille_unregister_console(console
);
2627 if (console_drivers
== console
) {
2628 console_drivers
=console
->next
;
2630 } else if (console_drivers
) {
2631 for (a
=console_drivers
->next
, b
=console_drivers
;
2632 a
; b
=a
, a
=b
->next
) {
2641 if (!res
&& (console
->flags
& CON_EXTENDED
))
2642 nr_ext_console_drivers
--;
2645 * If this isn't the last console and it has CON_CONSDEV set, we
2646 * need to set it on the next preferred console.
2648 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2649 console_drivers
->flags
|= CON_CONSDEV
;
2651 console
->flags
&= ~CON_ENABLED
;
2653 console_sysfs_notify();
2656 EXPORT_SYMBOL(unregister_console
);
2658 static int __init
printk_late_init(void)
2660 struct console
*con
;
2662 for_each_console(con
) {
2663 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2664 unregister_console(con
);
2667 hotcpu_notifier(console_cpu_notify
, 0);
2670 late_initcall(printk_late_init
);
2672 #if defined CONFIG_PRINTK
2674 * Delayed printk version, for scheduler-internal messages:
2676 #define PRINTK_PENDING_WAKEUP 0x01
2677 #define PRINTK_PENDING_OUTPUT 0x02
2679 static DEFINE_PER_CPU(int, printk_pending
);
2681 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2683 int pending
= __this_cpu_xchg(printk_pending
, 0);
2685 if (pending
& PRINTK_PENDING_OUTPUT
) {
2686 /* If trylock fails, someone else is doing the printing */
2687 if (console_trylock())
2691 if (pending
& PRINTK_PENDING_WAKEUP
)
2692 wake_up_interruptible(&log_wait
);
2695 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2696 .func
= wake_up_klogd_work_func
,
2697 .flags
= IRQ_WORK_LAZY
,
2700 void wake_up_klogd(void)
2703 if (waitqueue_active(&log_wait
)) {
2704 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2705 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2710 int printk_deferred(const char *fmt
, ...)
2716 va_start(args
, fmt
);
2717 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2720 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2721 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2728 * printk rate limiting, lifted from the networking subsystem.
2730 * This enforces a rate limit: not more than 10 kernel messages
2731 * every 5s to make a denial-of-service attack impossible.
2733 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2735 int __printk_ratelimit(const char *func
)
2737 return ___ratelimit(&printk_ratelimit_state
, func
);
2739 EXPORT_SYMBOL(__printk_ratelimit
);
2742 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2743 * @caller_jiffies: pointer to caller's state
2744 * @interval_msecs: minimum interval between prints
2746 * printk_timed_ratelimit() returns true if more than @interval_msecs
2747 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2750 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2751 unsigned int interval_msecs
)
2753 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2755 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2758 *caller_jiffies
= jiffies
;
2761 EXPORT_SYMBOL(printk_timed_ratelimit
);
2763 static DEFINE_SPINLOCK(dump_list_lock
);
2764 static LIST_HEAD(dump_list
);
2767 * kmsg_dump_register - register a kernel log dumper.
2768 * @dumper: pointer to the kmsg_dumper structure
2770 * Adds a kernel log dumper to the system. The dump callback in the
2771 * structure will be called when the kernel oopses or panics and must be
2772 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2774 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2776 unsigned long flags
;
2779 /* The dump callback needs to be set */
2783 spin_lock_irqsave(&dump_list_lock
, flags
);
2784 /* Don't allow registering multiple times */
2785 if (!dumper
->registered
) {
2786 dumper
->registered
= 1;
2787 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2790 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2794 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2797 * kmsg_dump_unregister - unregister a kmsg dumper.
2798 * @dumper: pointer to the kmsg_dumper structure
2800 * Removes a dump device from the system. Returns zero on success and
2801 * %-EINVAL otherwise.
2803 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2805 unsigned long flags
;
2808 spin_lock_irqsave(&dump_list_lock
, flags
);
2809 if (dumper
->registered
) {
2810 dumper
->registered
= 0;
2811 list_del_rcu(&dumper
->list
);
2814 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2819 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2821 static bool always_kmsg_dump
;
2822 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2825 * kmsg_dump - dump kernel log to kernel message dumpers.
2826 * @reason: the reason (oops, panic etc) for dumping
2828 * Call each of the registered dumper's dump() callback, which can
2829 * retrieve the kmsg records with kmsg_dump_get_line() or
2830 * kmsg_dump_get_buffer().
2832 void kmsg_dump(enum kmsg_dump_reason reason
)
2834 struct kmsg_dumper
*dumper
;
2835 unsigned long flags
;
2837 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2841 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2842 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2845 /* initialize iterator with data about the stored records */
2846 dumper
->active
= true;
2848 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2849 dumper
->cur_seq
= clear_seq
;
2850 dumper
->cur_idx
= clear_idx
;
2851 dumper
->next_seq
= log_next_seq
;
2852 dumper
->next_idx
= log_next_idx
;
2853 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2855 /* invoke dumper which will iterate over records */
2856 dumper
->dump(dumper
, reason
);
2858 /* reset iterator */
2859 dumper
->active
= false;
2865 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2866 * @dumper: registered kmsg dumper
2867 * @syslog: include the "<4>" prefixes
2868 * @line: buffer to copy the line to
2869 * @size: maximum size of the buffer
2870 * @len: length of line placed into buffer
2872 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2873 * record, and copy one record into the provided buffer.
2875 * Consecutive calls will return the next available record moving
2876 * towards the end of the buffer with the youngest messages.
2878 * A return value of FALSE indicates that there are no more records to
2881 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2883 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
2884 char *line
, size_t size
, size_t *len
)
2886 struct printk_log
*msg
;
2890 if (!dumper
->active
)
2893 if (dumper
->cur_seq
< log_first_seq
) {
2894 /* messages are gone, move to first available one */
2895 dumper
->cur_seq
= log_first_seq
;
2896 dumper
->cur_idx
= log_first_idx
;
2900 if (dumper
->cur_seq
>= log_next_seq
)
2903 msg
= log_from_idx(dumper
->cur_idx
);
2904 l
= msg_print_text(msg
, 0, syslog
, line
, size
);
2906 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2916 * kmsg_dump_get_line - retrieve one kmsg log line
2917 * @dumper: registered kmsg dumper
2918 * @syslog: include the "<4>" prefixes
2919 * @line: buffer to copy the line to
2920 * @size: maximum size of the buffer
2921 * @len: length of line placed into buffer
2923 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2924 * record, and copy one record into the provided buffer.
2926 * Consecutive calls will return the next available record moving
2927 * towards the end of the buffer with the youngest messages.
2929 * A return value of FALSE indicates that there are no more records to
2932 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2933 char *line
, size_t size
, size_t *len
)
2935 unsigned long flags
;
2938 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2939 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
2940 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2944 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2947 * kmsg_dump_get_buffer - copy kmsg log lines
2948 * @dumper: registered kmsg dumper
2949 * @syslog: include the "<4>" prefixes
2950 * @buf: buffer to copy the line to
2951 * @size: maximum size of the buffer
2952 * @len: length of line placed into buffer
2954 * Start at the end of the kmsg buffer and fill the provided buffer
2955 * with as many of the the *youngest* kmsg records that fit into it.
2956 * If the buffer is large enough, all available kmsg records will be
2957 * copied with a single call.
2959 * Consecutive calls will fill the buffer with the next block of
2960 * available older records, not including the earlier retrieved ones.
2962 * A return value of FALSE indicates that there are no more records to
2965 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
2966 char *buf
, size_t size
, size_t *len
)
2968 unsigned long flags
;
2973 enum log_flags prev
;
2977 if (!dumper
->active
)
2980 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2981 if (dumper
->cur_seq
< log_first_seq
) {
2982 /* messages are gone, move to first available one */
2983 dumper
->cur_seq
= log_first_seq
;
2984 dumper
->cur_idx
= log_first_idx
;
2988 if (dumper
->cur_seq
>= dumper
->next_seq
) {
2989 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2993 /* calculate length of entire buffer */
2994 seq
= dumper
->cur_seq
;
2995 idx
= dumper
->cur_idx
;
2997 while (seq
< dumper
->next_seq
) {
2998 struct printk_log
*msg
= log_from_idx(idx
);
3000 l
+= msg_print_text(msg
, prev
, true, NULL
, 0);
3001 idx
= log_next(idx
);
3006 /* move first record forward until length fits into the buffer */
3007 seq
= dumper
->cur_seq
;
3008 idx
= dumper
->cur_idx
;
3010 while (l
> size
&& seq
< dumper
->next_seq
) {
3011 struct printk_log
*msg
= log_from_idx(idx
);
3013 l
-= msg_print_text(msg
, prev
, true, NULL
, 0);
3014 idx
= log_next(idx
);
3019 /* last message in next interation */
3024 while (seq
< dumper
->next_seq
) {
3025 struct printk_log
*msg
= log_from_idx(idx
);
3027 l
+= msg_print_text(msg
, prev
, syslog
, buf
+ l
, size
- l
);
3028 idx
= log_next(idx
);
3033 dumper
->next_seq
= next_seq
;
3034 dumper
->next_idx
= next_idx
;
3036 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3042 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
3045 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
3046 * @dumper: registered kmsg dumper
3048 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3049 * kmsg_dump_get_buffer() can be called again and used multiple
3050 * times within the same dumper.dump() callback.
3052 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3054 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3056 dumper
->cur_seq
= clear_seq
;
3057 dumper
->cur_idx
= clear_idx
;
3058 dumper
->next_seq
= log_next_seq
;
3059 dumper
->next_idx
= log_next_idx
;
3063 * kmsg_dump_rewind - reset the interator
3064 * @dumper: registered kmsg dumper
3066 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3067 * kmsg_dump_get_buffer() can be called again and used multiple
3068 * times within the same dumper.dump() callback.
3070 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3072 unsigned long flags
;
3074 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3075 kmsg_dump_rewind_nolock(dumper
);
3076 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3078 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3080 static char dump_stack_arch_desc_str
[128];
3083 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3084 * @fmt: printf-style format string
3085 * @...: arguments for the format string
3087 * The configured string will be printed right after utsname during task
3088 * dumps. Usually used to add arch-specific system identifiers. If an
3089 * arch wants to make use of such an ID string, it should initialize this
3090 * as soon as possible during boot.
3092 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3096 va_start(args
, fmt
);
3097 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3103 * dump_stack_print_info - print generic debug info for dump_stack()
3104 * @log_lvl: log level
3106 * Arch-specific dump_stack() implementations can use this function to
3107 * print out the same debug information as the generic dump_stack().
3109 void dump_stack_print_info(const char *log_lvl
)
3111 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3112 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3113 print_tainted(), init_utsname()->release
,
3114 (int)strcspn(init_utsname()->version
, " "),
3115 init_utsname()->version
);
3117 if (dump_stack_arch_desc_str
[0] != '\0')
3118 printk("%sHardware name: %s\n",
3119 log_lvl
, dump_stack_arch_desc_str
);
3121 print_worker_info(log_lvl
, current
);
3125 * show_regs_print_info - print generic debug info for show_regs()
3126 * @log_lvl: log level
3128 * show_regs() implementations can use this function to print out generic
3129 * debug information.
3131 void show_regs_print_info(const char *log_lvl
)
3133 dump_stack_print_info(log_lvl
);
3135 printk("%stask: %p ti: %p task.ti: %p\n",
3136 log_lvl
, current
, current_thread_info(),
3137 task_thread_info(current
));