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 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
89 * macros instead of functions so that _RET_IP_ contains useful information.
91 #define down_console_sem() do { \
93 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
96 static int __down_trylock_console_sem(unsigned long ip
)
98 if (down_trylock(&console_sem
))
100 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
103 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
105 #define up_console_sem() do { \
106 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
111 * This is used for debugging the mess that is the VT code by
112 * keeping track if we have the console semaphore held. It's
113 * definitely not the perfect debug tool (we don't know if _WE_
114 * hold it and are racing, but it helps tracking those weird code
115 * paths in the console code where we end up in places I want
116 * locked without the console sempahore held).
118 static int console_locked
, console_suspended
;
121 * If exclusive_console is non-NULL then only this console is to be printed to.
123 static struct console
*exclusive_console
;
126 * Array of consoles built from command line options (console=)
129 #define MAX_CMDLINECONSOLES 8
131 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
133 static int selected_console
= -1;
134 static int preferred_console
= -1;
135 int console_set_on_cmdline
;
136 EXPORT_SYMBOL(console_set_on_cmdline
);
138 /* Flag: console code may call schedule() */
139 static int console_may_schedule
;
142 * The printk log buffer consists of a chain of concatenated variable
143 * length records. Every record starts with a record header, containing
144 * the overall length of the record.
146 * The heads to the first and last entry in the buffer, as well as the
147 * sequence numbers of these entries are maintained when messages are
150 * If the heads indicate available messages, the length in the header
151 * tells the start next message. A length == 0 for the next message
152 * indicates a wrap-around to the beginning of the buffer.
154 * Every record carries the monotonic timestamp in microseconds, as well as
155 * the standard userspace syslog level and syslog facility. The usual
156 * kernel messages use LOG_KERN; userspace-injected messages always carry
157 * a matching syslog facility, by default LOG_USER. The origin of every
158 * message can be reliably determined that way.
160 * The human readable log message directly follows the message header. The
161 * length of the message text is stored in the header, the stored message
164 * Optionally, a message can carry a dictionary of properties (key/value pairs),
165 * to provide userspace with a machine-readable message context.
167 * Examples for well-defined, commonly used property names are:
168 * DEVICE=b12:8 device identifier
172 * +sound:card0 subsystem:devname
173 * SUBSYSTEM=pci driver-core subsystem name
175 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
176 * follows directly after a '=' character. Every property is terminated by
177 * a '\0' character. The last property is not terminated.
179 * Example of a message structure:
180 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
181 * 0008 34 00 record is 52 bytes long
182 * 000a 0b 00 text is 11 bytes long
183 * 000c 1f 00 dictionary is 23 bytes long
184 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
185 * 0010 69 74 27 73 20 61 20 6c "it's a l"
187 * 001b 44 45 56 49 43 "DEVIC"
188 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
189 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
191 * 0032 00 00 00 padding to next message header
193 * The 'struct printk_log' buffer header must never be directly exported to
194 * userspace, it is a kernel-private implementation detail that might
195 * need to be changed in the future, when the requirements change.
197 * /dev/kmsg exports the structured data in the following line format:
198 * "level,sequnum,timestamp;<message text>\n"
200 * The optional key/value pairs are attached as continuation lines starting
201 * with a space character and terminated by a newline. All possible
202 * non-prinatable characters are escaped in the "\xff" notation.
204 * Users of the export format should ignore possible additional values
205 * separated by ',', and find the message after the ';' character.
209 LOG_NOCONS
= 1, /* already flushed, do not print to console */
210 LOG_NEWLINE
= 2, /* text ended with a newline */
211 LOG_PREFIX
= 4, /* text started with a prefix */
212 LOG_CONT
= 8, /* text is a fragment of a continuation line */
216 u64 ts_nsec
; /* timestamp in nanoseconds */
217 u16 len
; /* length of entire record */
218 u16 text_len
; /* length of text buffer */
219 u16 dict_len
; /* length of dictionary buffer */
220 u8 facility
; /* syslog facility */
221 u8 flags
:5; /* internal record flags */
222 u8 level
:3; /* syslog level */
226 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
227 * within the scheduler's rq lock. It must be released before calling
228 * console_unlock() or anything else that might wake up a process.
230 static DEFINE_RAW_SPINLOCK(logbuf_lock
);
233 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
234 /* the next printk record to read by syslog(READ) or /proc/kmsg */
235 static u64 syslog_seq
;
236 static u32 syslog_idx
;
237 static enum log_flags syslog_prev
;
238 static size_t syslog_partial
;
240 /* index and sequence number of the first record stored in the buffer */
241 static u64 log_first_seq
;
242 static u32 log_first_idx
;
244 /* index and sequence number of the next record to store in the buffer */
245 static u64 log_next_seq
;
246 static u32 log_next_idx
;
248 /* the next printk record to write to the console */
249 static u64 console_seq
;
250 static u32 console_idx
;
251 static enum log_flags console_prev
;
253 /* the next printk record to read after the last 'clear' command */
254 static u64 clear_seq
;
255 static u32 clear_idx
;
257 #define PREFIX_MAX 32
258 #define LOG_LINE_MAX (1024 - PREFIX_MAX)
261 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
264 #define LOG_ALIGN __alignof__(struct printk_log)
266 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
267 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
268 static char *log_buf
= __log_buf
;
269 static u32 log_buf_len
= __LOG_BUF_LEN
;
271 /* Return log buffer address */
272 char *log_buf_addr_get(void)
277 /* Return log buffer size */
278 u32
log_buf_len_get(void)
283 /* human readable text of the record */
284 static char *log_text(const struct printk_log
*msg
)
286 return (char *)msg
+ sizeof(struct printk_log
);
289 /* optional key/value pair dictionary attached to the record */
290 static char *log_dict(const struct printk_log
*msg
)
292 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
295 /* get record by index; idx must point to valid msg */
296 static struct printk_log
*log_from_idx(u32 idx
)
298 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
301 * A length == 0 record is the end of buffer marker. Wrap around and
302 * read the message at the start of the buffer.
305 return (struct printk_log
*)log_buf
;
309 /* get next record; idx must point to valid msg */
310 static u32
log_next(u32 idx
)
312 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
314 /* length == 0 indicates the end of the buffer; wrap */
316 * A length == 0 record is the end of buffer marker. Wrap around and
317 * read the message at the start of the buffer as *this* one, and
318 * return the one after that.
321 msg
= (struct printk_log
*)log_buf
;
324 return idx
+ msg
->len
;
328 * Check whether there is enough free space for the given message.
330 * The same values of first_idx and next_idx mean that the buffer
331 * is either empty or full.
333 * If the buffer is empty, we must respect the position of the indexes.
334 * They cannot be reset to the beginning of the buffer.
336 static int logbuf_has_space(u32 msg_size
, bool empty
)
340 if (log_next_idx
> log_first_idx
|| empty
)
341 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
343 free
= log_first_idx
- log_next_idx
;
346 * We need space also for an empty header that signalizes wrapping
349 return free
>= msg_size
+ sizeof(struct printk_log
);
352 static int log_make_free_space(u32 msg_size
)
354 while (log_first_seq
< log_next_seq
) {
355 if (logbuf_has_space(msg_size
, false))
357 /* drop old messages until we have enough contiguous space */
358 log_first_idx
= log_next(log_first_idx
);
362 /* sequence numbers are equal, so the log buffer is empty */
363 if (logbuf_has_space(msg_size
, true))
369 /* compute the message size including the padding bytes */
370 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
374 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
375 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
382 * Define how much of the log buffer we could take at maximum. The value
383 * must be greater than two. Note that only half of the buffer is available
384 * when the index points to the middle.
386 #define MAX_LOG_TAKE_PART 4
387 static const char trunc_msg
[] = "<truncated>";
389 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
390 u16
*dict_len
, u32
*pad_len
)
393 * The message should not take the whole buffer. Otherwise, it might
394 * get removed too soon.
396 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
397 if (*text_len
> max_text_len
)
398 *text_len
= max_text_len
;
399 /* enable the warning message */
400 *trunc_msg_len
= strlen(trunc_msg
);
401 /* disable the "dict" completely */
403 /* compute the size again, count also the warning message */
404 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
407 /* insert record into the buffer, discard old ones, update heads */
408 static int log_store(int facility
, int level
,
409 enum log_flags flags
, u64 ts_nsec
,
410 const char *dict
, u16 dict_len
,
411 const char *text
, u16 text_len
)
413 struct printk_log
*msg
;
415 u16 trunc_msg_len
= 0;
417 /* number of '\0' padding bytes to next message */
418 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
420 if (log_make_free_space(size
)) {
421 /* truncate the message if it is too long for empty buffer */
422 size
= truncate_msg(&text_len
, &trunc_msg_len
,
423 &dict_len
, &pad_len
);
424 /* survive when the log buffer is too small for trunc_msg */
425 if (log_make_free_space(size
))
429 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
431 * This message + an additional empty header does not fit
432 * at the end of the buffer. Add an empty header with len == 0
433 * to signify a wrap around.
435 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
440 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
441 memcpy(log_text(msg
), text
, text_len
);
442 msg
->text_len
= text_len
;
444 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
445 msg
->text_len
+= trunc_msg_len
;
447 memcpy(log_dict(msg
), dict
, dict_len
);
448 msg
->dict_len
= dict_len
;
449 msg
->facility
= facility
;
450 msg
->level
= level
& 7;
451 msg
->flags
= flags
& 0x1f;
453 msg
->ts_nsec
= ts_nsec
;
455 msg
->ts_nsec
= local_clock();
456 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
460 log_next_idx
+= msg
->len
;
463 return msg
->text_len
;
466 int dmesg_restrict
= IS_ENABLED(CONFIG_SECURITY_DMESG_RESTRICT
);
468 static int syslog_action_restricted(int type
)
473 * Unless restricted, we allow "read all" and "get buffer size"
476 return type
!= SYSLOG_ACTION_READ_ALL
&&
477 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
480 int check_syslog_permissions(int type
, bool from_file
)
483 * If this is from /proc/kmsg and we've already opened it, then we've
484 * already done the capabilities checks at open time.
486 if (from_file
&& type
!= SYSLOG_ACTION_OPEN
)
489 if (syslog_action_restricted(type
)) {
490 if (capable(CAP_SYSLOG
))
493 * For historical reasons, accept CAP_SYS_ADMIN too, with
496 if (capable(CAP_SYS_ADMIN
)) {
497 pr_warn_once("%s (%d): Attempt to access syslog with "
498 "CAP_SYS_ADMIN but no CAP_SYSLOG "
500 current
->comm
, task_pid_nr(current
));
505 return security_syslog(type
);
508 static void append_char(char **pp
, char *e
, char c
)
514 static ssize_t
msg_print_ext_header(char *buf
, size_t size
,
515 struct printk_log
*msg
, u64 seq
,
516 enum log_flags prev_flags
)
518 u64 ts_usec
= msg
->ts_nsec
;
521 do_div(ts_usec
, 1000);
524 * If we couldn't merge continuation line fragments during the print,
525 * export the stored flags to allow an optional external merge of the
526 * records. Merging the records isn't always neccessarily correct, like
527 * when we hit a race during printing. In most cases though, it produces
528 * better readable output. 'c' in the record flags mark the first
529 * fragment of a line, '+' the following.
531 if (msg
->flags
& LOG_CONT
&& !(prev_flags
& LOG_CONT
))
533 else if ((msg
->flags
& LOG_CONT
) ||
534 ((prev_flags
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
)))
537 return scnprintf(buf
, size
, "%u,%llu,%llu,%c;",
538 (msg
->facility
<< 3) | msg
->level
, seq
, ts_usec
, cont
);
541 static ssize_t
msg_print_ext_body(char *buf
, size_t size
,
542 char *dict
, size_t dict_len
,
543 char *text
, size_t text_len
)
545 char *p
= buf
, *e
= buf
+ size
;
548 /* escape non-printable characters */
549 for (i
= 0; i
< text_len
; i
++) {
550 unsigned char c
= text
[i
];
552 if (c
< ' ' || c
>= 127 || c
== '\\')
553 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
555 append_char(&p
, e
, c
);
557 append_char(&p
, e
, '\n');
562 for (i
= 0; i
< dict_len
; i
++) {
563 unsigned char c
= dict
[i
];
566 append_char(&p
, e
, ' ');
571 append_char(&p
, e
, '\n');
576 if (c
< ' ' || c
>= 127 || c
== '\\') {
577 p
+= scnprintf(p
, e
- p
, "\\x%02x", c
);
581 append_char(&p
, e
, c
);
583 append_char(&p
, e
, '\n');
589 /* /dev/kmsg - userspace message inject/listen interface */
590 struct devkmsg_user
{
595 char buf
[CONSOLE_EXT_LOG_MAX
];
598 static ssize_t
devkmsg_write(struct kiocb
*iocb
, struct iov_iter
*from
)
602 int level
= default_message_loglevel
;
603 int facility
= 1; /* LOG_USER */
604 size_t len
= iov_iter_count(from
);
607 if (len
> LOG_LINE_MAX
)
609 buf
= kmalloc(len
+1, GFP_KERNEL
);
614 if (copy_from_iter(buf
, len
, from
) != len
) {
620 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
621 * the decimal value represents 32bit, the lower 3 bit are the log
622 * level, the rest are the log facility.
624 * If no prefix or no userspace facility is specified, we
625 * enforce LOG_USER, to be able to reliably distinguish
626 * kernel-generated messages from userspace-injected ones.
629 if (line
[0] == '<') {
632 i
= simple_strtoul(line
+1, &endp
, 10);
633 if (endp
&& endp
[0] == '>') {
643 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
648 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
649 size_t count
, loff_t
*ppos
)
651 struct devkmsg_user
*user
= file
->private_data
;
652 struct printk_log
*msg
;
659 ret
= mutex_lock_interruptible(&user
->lock
);
662 raw_spin_lock_irq(&logbuf_lock
);
663 while (user
->seq
== log_next_seq
) {
664 if (file
->f_flags
& O_NONBLOCK
) {
666 raw_spin_unlock_irq(&logbuf_lock
);
670 raw_spin_unlock_irq(&logbuf_lock
);
671 ret
= wait_event_interruptible(log_wait
,
672 user
->seq
!= log_next_seq
);
675 raw_spin_lock_irq(&logbuf_lock
);
678 if (user
->seq
< log_first_seq
) {
679 /* our last seen message is gone, return error and reset */
680 user
->idx
= log_first_idx
;
681 user
->seq
= log_first_seq
;
683 raw_spin_unlock_irq(&logbuf_lock
);
687 msg
= log_from_idx(user
->idx
);
688 len
= msg_print_ext_header(user
->buf
, sizeof(user
->buf
),
689 msg
, user
->seq
, user
->prev
);
690 len
+= msg_print_ext_body(user
->buf
+ len
, sizeof(user
->buf
) - len
,
691 log_dict(msg
), msg
->dict_len
,
692 log_text(msg
), msg
->text_len
);
694 user
->prev
= msg
->flags
;
695 user
->idx
= log_next(user
->idx
);
697 raw_spin_unlock_irq(&logbuf_lock
);
704 if (copy_to_user(buf
, user
->buf
, len
)) {
710 mutex_unlock(&user
->lock
);
714 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
716 struct devkmsg_user
*user
= file
->private_data
;
724 raw_spin_lock_irq(&logbuf_lock
);
727 /* the first record */
728 user
->idx
= log_first_idx
;
729 user
->seq
= log_first_seq
;
733 * The first record after the last SYSLOG_ACTION_CLEAR,
734 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
735 * changes no global state, and does not clear anything.
737 user
->idx
= clear_idx
;
738 user
->seq
= clear_seq
;
741 /* after the last record */
742 user
->idx
= log_next_idx
;
743 user
->seq
= log_next_seq
;
748 raw_spin_unlock_irq(&logbuf_lock
);
752 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
754 struct devkmsg_user
*user
= file
->private_data
;
758 return POLLERR
|POLLNVAL
;
760 poll_wait(file
, &log_wait
, wait
);
762 raw_spin_lock_irq(&logbuf_lock
);
763 if (user
->seq
< log_next_seq
) {
764 /* return error when data has vanished underneath us */
765 if (user
->seq
< log_first_seq
)
766 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
768 ret
= POLLIN
|POLLRDNORM
;
770 raw_spin_unlock_irq(&logbuf_lock
);
775 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
777 struct devkmsg_user
*user
;
780 /* write-only does not need any file context */
781 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
784 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
789 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
793 mutex_init(&user
->lock
);
795 raw_spin_lock_irq(&logbuf_lock
);
796 user
->idx
= log_first_idx
;
797 user
->seq
= log_first_seq
;
798 raw_spin_unlock_irq(&logbuf_lock
);
800 file
->private_data
= user
;
804 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
806 struct devkmsg_user
*user
= file
->private_data
;
811 mutex_destroy(&user
->lock
);
816 const struct file_operations kmsg_fops
= {
817 .open
= devkmsg_open
,
818 .read
= devkmsg_read
,
819 .write_iter
= devkmsg_write
,
820 .llseek
= devkmsg_llseek
,
821 .poll
= devkmsg_poll
,
822 .release
= devkmsg_release
,
827 * This appends the listed symbols to /proc/vmcore
829 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
830 * obtain access to symbols that are otherwise very difficult to locate. These
831 * symbols are specifically used so that utilities can access and extract the
832 * dmesg log from a vmcore file after a crash.
834 void log_buf_kexec_setup(void)
836 VMCOREINFO_SYMBOL(log_buf
);
837 VMCOREINFO_SYMBOL(log_buf_len
);
838 VMCOREINFO_SYMBOL(log_first_idx
);
839 VMCOREINFO_SYMBOL(log_next_idx
);
841 * Export struct printk_log size and field offsets. User space tools can
842 * parse it and detect any changes to structure down the line.
844 VMCOREINFO_STRUCT_SIZE(printk_log
);
845 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
846 VMCOREINFO_OFFSET(printk_log
, len
);
847 VMCOREINFO_OFFSET(printk_log
, text_len
);
848 VMCOREINFO_OFFSET(printk_log
, dict_len
);
852 /* requested log_buf_len from kernel cmdline */
853 static unsigned long __initdata new_log_buf_len
;
855 /* we practice scaling the ring buffer by powers of 2 */
856 static void __init
log_buf_len_update(unsigned size
)
859 size
= roundup_pow_of_two(size
);
860 if (size
> log_buf_len
)
861 new_log_buf_len
= size
;
864 /* save requested log_buf_len since it's too early to process it */
865 static int __init
log_buf_len_setup(char *str
)
867 unsigned size
= memparse(str
, &str
);
869 log_buf_len_update(size
);
873 early_param("log_buf_len", log_buf_len_setup
);
876 #define __LOG_CPU_MAX_BUF_LEN (1 << CONFIG_LOG_CPU_MAX_BUF_SHIFT)
878 static void __init
log_buf_add_cpu(void)
880 unsigned int cpu_extra
;
883 * archs should set up cpu_possible_bits properly with
884 * set_cpu_possible() after setup_arch() but just in
885 * case lets ensure this is valid.
887 if (num_possible_cpus() == 1)
890 cpu_extra
= (num_possible_cpus() - 1) * __LOG_CPU_MAX_BUF_LEN
;
892 /* by default this will only continue through for large > 64 CPUs */
893 if (cpu_extra
<= __LOG_BUF_LEN
/ 2)
896 pr_info("log_buf_len individual max cpu contribution: %d bytes\n",
897 __LOG_CPU_MAX_BUF_LEN
);
898 pr_info("log_buf_len total cpu_extra contributions: %d bytes\n",
900 pr_info("log_buf_len min size: %d bytes\n", __LOG_BUF_LEN
);
902 log_buf_len_update(cpu_extra
+ __LOG_BUF_LEN
);
904 #else /* !CONFIG_SMP */
905 static inline void log_buf_add_cpu(void) {}
906 #endif /* CONFIG_SMP */
908 void __init
setup_log_buf(int early
)
914 if (log_buf
!= __log_buf
)
917 if (!early
&& !new_log_buf_len
)
920 if (!new_log_buf_len
)
925 memblock_virt_alloc(new_log_buf_len
, LOG_ALIGN
);
927 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
,
931 if (unlikely(!new_log_buf
)) {
932 pr_err("log_buf_len: %ld bytes not available\n",
937 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
938 log_buf_len
= new_log_buf_len
;
939 log_buf
= new_log_buf
;
941 free
= __LOG_BUF_LEN
- log_next_idx
;
942 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
943 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
945 pr_info("log_buf_len: %d bytes\n", log_buf_len
);
946 pr_info("early log buf free: %d(%d%%)\n",
947 free
, (free
* 100) / __LOG_BUF_LEN
);
950 static bool __read_mostly ignore_loglevel
;
952 static int __init
ignore_loglevel_setup(char *str
)
954 ignore_loglevel
= true;
955 pr_info("debug: ignoring loglevel setting.\n");
960 early_param("ignore_loglevel", ignore_loglevel_setup
);
961 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
962 MODULE_PARM_DESC(ignore_loglevel
,
963 "ignore loglevel setting (prints all kernel messages to the console)");
965 #ifdef CONFIG_BOOT_PRINTK_DELAY
967 static int boot_delay
; /* msecs delay after each printk during bootup */
968 static unsigned long long loops_per_msec
; /* based on boot_delay */
970 static int __init
boot_delay_setup(char *str
)
974 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
975 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
977 get_option(&str
, &boot_delay
);
978 if (boot_delay
> 10 * 1000)
981 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
982 "HZ: %d, loops_per_msec: %llu\n",
983 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
986 early_param("boot_delay", boot_delay_setup
);
988 static void boot_delay_msec(int level
)
990 unsigned long long k
;
991 unsigned long timeout
;
993 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
994 || (level
>= console_loglevel
&& !ignore_loglevel
)) {
998 k
= (unsigned long long)loops_per_msec
* boot_delay
;
1000 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
1005 * use (volatile) jiffies to prevent
1006 * compiler reduction; loop termination via jiffies
1007 * is secondary and may or may not happen.
1009 if (time_after(jiffies
, timeout
))
1011 touch_nmi_watchdog();
1015 static inline void boot_delay_msec(int level
)
1020 static bool printk_time
= IS_ENABLED(CONFIG_PRINTK_TIME
);
1021 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
1023 static size_t print_time(u64 ts
, char *buf
)
1025 unsigned long rem_nsec
;
1030 rem_nsec
= do_div(ts
, 1000000000);
1033 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
1035 return sprintf(buf
, "[%5lu.%06lu] ",
1036 (unsigned long)ts
, rem_nsec
/ 1000);
1039 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
1042 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
1046 len
+= sprintf(buf
, "<%u>", prefix
);
1051 else if (prefix
> 99)
1053 else if (prefix
> 9)
1058 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1062 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1063 bool syslog
, char *buf
, size_t size
)
1065 const char *text
= log_text(msg
);
1066 size_t text_size
= msg
->text_len
;
1068 bool newline
= true;
1071 if ((prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
))
1074 if (msg
->flags
& LOG_CONT
) {
1075 if ((prev
& LOG_CONT
) && !(prev
& LOG_NEWLINE
))
1078 if (!(msg
->flags
& LOG_NEWLINE
))
1083 const char *next
= memchr(text
, '\n', text_size
);
1087 text_len
= next
- text
;
1089 text_size
-= next
- text
;
1091 text_len
= text_size
;
1095 if (print_prefix(msg
, syslog
, NULL
) +
1096 text_len
+ 1 >= size
- len
)
1100 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1101 memcpy(buf
+ len
, text
, text_len
);
1103 if (next
|| newline
)
1106 /* SYSLOG_ACTION_* buffer size only calculation */
1108 len
+= print_prefix(msg
, syslog
, NULL
);
1110 if (next
|| newline
)
1121 static int syslog_print(char __user
*buf
, int size
)
1124 struct printk_log
*msg
;
1127 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1135 raw_spin_lock_irq(&logbuf_lock
);
1136 if (syslog_seq
< log_first_seq
) {
1137 /* messages are gone, move to first one */
1138 syslog_seq
= log_first_seq
;
1139 syslog_idx
= log_first_idx
;
1143 if (syslog_seq
== log_next_seq
) {
1144 raw_spin_unlock_irq(&logbuf_lock
);
1148 skip
= syslog_partial
;
1149 msg
= log_from_idx(syslog_idx
);
1150 n
= msg_print_text(msg
, syslog_prev
, true, text
,
1151 LOG_LINE_MAX
+ PREFIX_MAX
);
1152 if (n
- syslog_partial
<= size
) {
1153 /* message fits into buffer, move forward */
1154 syslog_idx
= log_next(syslog_idx
);
1156 syslog_prev
= msg
->flags
;
1157 n
-= syslog_partial
;
1160 /* partial read(), remember position */
1162 syslog_partial
+= n
;
1165 raw_spin_unlock_irq(&logbuf_lock
);
1170 if (copy_to_user(buf
, text
+ skip
, n
)) {
1185 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1190 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1194 raw_spin_lock_irq(&logbuf_lock
);
1199 enum log_flags prev
;
1201 if (clear_seq
< log_first_seq
) {
1202 /* messages are gone, move to first available one */
1203 clear_seq
= log_first_seq
;
1204 clear_idx
= log_first_idx
;
1208 * Find first record that fits, including all following records,
1209 * into the user-provided buffer for this dump.
1214 while (seq
< log_next_seq
) {
1215 struct printk_log
*msg
= log_from_idx(idx
);
1217 len
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1219 idx
= log_next(idx
);
1223 /* move first record forward until length fits into the buffer */
1227 while (len
> size
&& seq
< log_next_seq
) {
1228 struct printk_log
*msg
= log_from_idx(idx
);
1230 len
-= msg_print_text(msg
, prev
, true, NULL
, 0);
1232 idx
= log_next(idx
);
1236 /* last message fitting into this dump */
1237 next_seq
= log_next_seq
;
1240 while (len
>= 0 && seq
< next_seq
) {
1241 struct printk_log
*msg
= log_from_idx(idx
);
1244 textlen
= msg_print_text(msg
, prev
, true, text
,
1245 LOG_LINE_MAX
+ PREFIX_MAX
);
1250 idx
= log_next(idx
);
1254 raw_spin_unlock_irq(&logbuf_lock
);
1255 if (copy_to_user(buf
+ len
, text
, textlen
))
1259 raw_spin_lock_irq(&logbuf_lock
);
1261 if (seq
< log_first_seq
) {
1262 /* messages are gone, move to next one */
1263 seq
= log_first_seq
;
1264 idx
= log_first_idx
;
1271 clear_seq
= log_next_seq
;
1272 clear_idx
= log_next_idx
;
1274 raw_spin_unlock_irq(&logbuf_lock
);
1280 int do_syslog(int type
, char __user
*buf
, int len
, bool from_file
)
1283 static int saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1286 error
= check_syslog_permissions(type
, from_file
);
1290 error
= security_syslog(type
);
1295 case SYSLOG_ACTION_CLOSE
: /* Close log */
1297 case SYSLOG_ACTION_OPEN
: /* Open log */
1299 case SYSLOG_ACTION_READ
: /* Read from log */
1301 if (!buf
|| len
< 0)
1306 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1310 error
= wait_event_interruptible(log_wait
,
1311 syslog_seq
!= log_next_seq
);
1314 error
= syslog_print(buf
, len
);
1316 /* Read/clear last kernel messages */
1317 case SYSLOG_ACTION_READ_CLEAR
:
1320 /* Read last kernel messages */
1321 case SYSLOG_ACTION_READ_ALL
:
1323 if (!buf
|| len
< 0)
1328 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1332 error
= syslog_print_all(buf
, len
, clear
);
1334 /* Clear ring buffer */
1335 case SYSLOG_ACTION_CLEAR
:
1336 syslog_print_all(NULL
, 0, true);
1338 /* Disable logging to console */
1339 case SYSLOG_ACTION_CONSOLE_OFF
:
1340 if (saved_console_loglevel
== LOGLEVEL_DEFAULT
)
1341 saved_console_loglevel
= console_loglevel
;
1342 console_loglevel
= minimum_console_loglevel
;
1344 /* Enable logging to console */
1345 case SYSLOG_ACTION_CONSOLE_ON
:
1346 if (saved_console_loglevel
!= LOGLEVEL_DEFAULT
) {
1347 console_loglevel
= saved_console_loglevel
;
1348 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1351 /* Set level of messages printed to console */
1352 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1354 if (len
< 1 || len
> 8)
1356 if (len
< minimum_console_loglevel
)
1357 len
= minimum_console_loglevel
;
1358 console_loglevel
= len
;
1359 /* Implicitly re-enable logging to console */
1360 saved_console_loglevel
= LOGLEVEL_DEFAULT
;
1363 /* Number of chars in the log buffer */
1364 case SYSLOG_ACTION_SIZE_UNREAD
:
1365 raw_spin_lock_irq(&logbuf_lock
);
1366 if (syslog_seq
< log_first_seq
) {
1367 /* messages are gone, move to first one */
1368 syslog_seq
= log_first_seq
;
1369 syslog_idx
= log_first_idx
;
1375 * Short-cut for poll(/"proc/kmsg") which simply checks
1376 * for pending data, not the size; return the count of
1377 * records, not the length.
1379 error
= log_next_seq
- syslog_seq
;
1381 u64 seq
= syslog_seq
;
1382 u32 idx
= syslog_idx
;
1383 enum log_flags prev
= syslog_prev
;
1386 while (seq
< log_next_seq
) {
1387 struct printk_log
*msg
= log_from_idx(idx
);
1389 error
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1390 idx
= log_next(idx
);
1394 error
-= syslog_partial
;
1396 raw_spin_unlock_irq(&logbuf_lock
);
1398 /* Size of the log buffer */
1399 case SYSLOG_ACTION_SIZE_BUFFER
:
1400 error
= log_buf_len
;
1410 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1412 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1416 * Call the console drivers, asking them to write out
1417 * log_buf[start] to log_buf[end - 1].
1418 * The console_lock must be held.
1420 static void call_console_drivers(int level
, const char *text
, size_t len
)
1422 struct console
*con
;
1424 trace_console(text
, len
);
1426 if (level
>= console_loglevel
&& !ignore_loglevel
)
1428 if (!console_drivers
)
1431 for_each_console(con
) {
1432 if (exclusive_console
&& con
!= exclusive_console
)
1434 if (!(con
->flags
& CON_ENABLED
))
1438 if (!cpu_online(smp_processor_id()) &&
1439 !(con
->flags
& CON_ANYTIME
))
1441 con
->write(con
, text
, len
);
1446 * Zap console related locks when oopsing.
1447 * To leave time for slow consoles to print a full oops,
1448 * only zap at most once every 30 seconds.
1450 static void zap_locks(void)
1452 static unsigned long oops_timestamp
;
1454 if (time_after_eq(jiffies
, oops_timestamp
) &&
1455 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1458 oops_timestamp
= jiffies
;
1461 /* If a crash is occurring, make sure we can't deadlock */
1462 raw_spin_lock_init(&logbuf_lock
);
1463 /* And make sure that we print immediately */
1464 sema_init(&console_sem
, 1);
1468 * Check if we have any console that is capable of printing while cpu is
1469 * booting or shutting down. Requires console_sem.
1471 static int have_callable_console(void)
1473 struct console
*con
;
1475 for_each_console(con
)
1476 if (con
->flags
& CON_ANYTIME
)
1483 * Can we actually use the console at this time on this cpu?
1485 * Console drivers may assume that per-cpu resources have been allocated. So
1486 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1487 * call them until this CPU is officially up.
1489 static inline int can_use_console(unsigned int cpu
)
1491 return cpu_online(cpu
) || have_callable_console();
1495 * Try to get console ownership to actually show the kernel
1496 * messages from a 'printk'. Return true (and with the
1497 * console_lock held, and 'console_locked' set) if it
1498 * is successful, false otherwise.
1500 static int console_trylock_for_printk(void)
1502 unsigned int cpu
= smp_processor_id();
1504 if (!console_trylock())
1507 * If we can't use the console, we need to release the console
1508 * semaphore by hand to avoid flushing the buffer. We need to hold the
1509 * console semaphore in order to do this test safely.
1511 if (!can_use_console(cpu
)) {
1519 int printk_delay_msec __read_mostly
;
1521 static inline void printk_delay(void)
1523 if (unlikely(printk_delay_msec
)) {
1524 int m
= printk_delay_msec
;
1528 touch_nmi_watchdog();
1534 * Continuation lines are buffered, and not committed to the record buffer
1535 * until the line is complete, or a race forces it. The line fragments
1536 * though, are printed immediately to the consoles to ensure everything has
1537 * reached the console in case of a kernel crash.
1539 static struct cont
{
1540 char buf
[LOG_LINE_MAX
];
1541 size_t len
; /* length == 0 means unused buffer */
1542 size_t cons
; /* bytes written to console */
1543 struct task_struct
*owner
; /* task of first print*/
1544 u64 ts_nsec
; /* time of first print */
1545 u8 level
; /* log level of first message */
1546 u8 facility
; /* log facility of first message */
1547 enum log_flags flags
; /* prefix, newline flags */
1548 bool flushed
:1; /* buffer sealed and committed */
1551 static void cont_flush(enum log_flags flags
)
1560 * If a fragment of this line was directly flushed to the
1561 * console; wait for the console to pick up the rest of the
1562 * line. LOG_NOCONS suppresses a duplicated output.
1564 log_store(cont
.facility
, cont
.level
, flags
| LOG_NOCONS
,
1565 cont
.ts_nsec
, NULL
, 0, cont
.buf
, cont
.len
);
1567 cont
.flushed
= true;
1570 * If no fragment of this line ever reached the console,
1571 * just submit it to the store and free the buffer.
1573 log_store(cont
.facility
, cont
.level
, flags
, 0,
1574 NULL
, 0, cont
.buf
, cont
.len
);
1579 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1581 if (cont
.len
&& cont
.flushed
)
1584 if (cont
.len
+ len
> sizeof(cont
.buf
)) {
1585 /* the line gets too long, split it up in separate records */
1586 cont_flush(LOG_CONT
);
1591 cont
.facility
= facility
;
1593 cont
.owner
= current
;
1594 cont
.ts_nsec
= local_clock();
1597 cont
.flushed
= false;
1600 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1603 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1604 cont_flush(LOG_CONT
);
1609 static size_t cont_print_text(char *text
, size_t size
)
1614 if (cont
.cons
== 0 && (console_prev
& LOG_NEWLINE
)) {
1615 textlen
+= print_time(cont
.ts_nsec
, text
);
1619 len
= cont
.len
- cont
.cons
;
1623 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1625 cont
.cons
= cont
.len
;
1629 if (cont
.flags
& LOG_NEWLINE
)
1630 text
[textlen
++] = '\n';
1631 /* got everything, release buffer */
1637 asmlinkage
int vprintk_emit(int facility
, int level
,
1638 const char *dict
, size_t dictlen
,
1639 const char *fmt
, va_list args
)
1641 static int recursion_bug
;
1642 static char textbuf
[LOG_LINE_MAX
];
1643 char *text
= textbuf
;
1644 size_t text_len
= 0;
1645 enum log_flags lflags
= 0;
1646 unsigned long flags
;
1648 int printed_len
= 0;
1649 bool in_sched
= false;
1650 /* cpu currently holding logbuf_lock in this function */
1651 static unsigned int logbuf_cpu
= UINT_MAX
;
1653 if (level
== LOGLEVEL_SCHED
) {
1654 level
= LOGLEVEL_DEFAULT
;
1658 boot_delay_msec(level
);
1661 /* This stops the holder of console_sem just where we want him */
1662 local_irq_save(flags
);
1663 this_cpu
= smp_processor_id();
1666 * Ouch, printk recursed into itself!
1668 if (unlikely(logbuf_cpu
== this_cpu
)) {
1670 * If a crash is occurring during printk() on this CPU,
1671 * then try to get the crash message out but make sure
1672 * we can't deadlock. Otherwise just return to avoid the
1673 * recursion and return - but flag the recursion so that
1674 * it can be printed at the next appropriate moment:
1676 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1678 local_irq_restore(flags
);
1685 raw_spin_lock(&logbuf_lock
);
1686 logbuf_cpu
= this_cpu
;
1688 if (unlikely(recursion_bug
)) {
1689 static const char recursion_msg
[] =
1690 "BUG: recent printk recursion!";
1693 /* emit KERN_CRIT message */
1694 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1695 NULL
, 0, recursion_msg
,
1696 strlen(recursion_msg
));
1700 * The printf needs to come first; we need the syslog
1701 * prefix which might be passed-in as a parameter.
1703 text_len
= vscnprintf(text
, sizeof(textbuf
), fmt
, args
);
1705 /* mark and strip a trailing newline */
1706 if (text_len
&& text
[text_len
-1] == '\n') {
1708 lflags
|= LOG_NEWLINE
;
1711 /* strip kernel syslog prefix and extract log level or control flags */
1712 if (facility
== 0) {
1713 int kern_level
= printk_get_level(text
);
1716 const char *end_of_header
= printk_skip_level(text
);
1717 switch (kern_level
) {
1719 if (level
== LOGLEVEL_DEFAULT
)
1720 level
= kern_level
- '0';
1722 case 'd': /* KERN_DEFAULT */
1723 lflags
|= LOG_PREFIX
;
1726 * No need to check length here because vscnprintf
1727 * put '\0' at the end of the string. Only valid and
1728 * newly printed level is detected.
1730 text_len
-= end_of_header
- text
;
1731 text
= (char *)end_of_header
;
1735 if (level
== LOGLEVEL_DEFAULT
)
1736 level
= default_message_loglevel
;
1739 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1741 if (!(lflags
& LOG_NEWLINE
)) {
1743 * Flush the conflicting buffer. An earlier newline was missing,
1744 * or another task also prints continuation lines.
1746 if (cont
.len
&& (lflags
& LOG_PREFIX
|| cont
.owner
!= current
))
1747 cont_flush(LOG_NEWLINE
);
1749 /* buffer line if possible, otherwise store it right away */
1750 if (cont_add(facility
, level
, text
, text_len
))
1751 printed_len
+= text_len
;
1753 printed_len
+= log_store(facility
, level
,
1754 lflags
| LOG_CONT
, 0,
1755 dict
, dictlen
, text
, text_len
);
1757 bool stored
= false;
1760 * If an earlier newline was missing and it was the same task,
1761 * either merge it with the current buffer and flush, or if
1762 * there was a race with interrupts (prefix == true) then just
1763 * flush it out and store this line separately.
1764 * If the preceding printk was from a different task and missed
1765 * a newline, flush and append the newline.
1768 if (cont
.owner
== current
&& !(lflags
& LOG_PREFIX
))
1769 stored
= cont_add(facility
, level
, text
,
1771 cont_flush(LOG_NEWLINE
);
1775 printed_len
+= text_len
;
1777 printed_len
+= log_store(facility
, level
, lflags
, 0,
1778 dict
, dictlen
, text
, text_len
);
1781 logbuf_cpu
= UINT_MAX
;
1782 raw_spin_unlock(&logbuf_lock
);
1784 local_irq_restore(flags
);
1786 /* If called from the scheduler, we can not call up(). */
1790 * Disable preemption to avoid being preempted while holding
1791 * console_sem which would prevent anyone from printing to
1797 * Try to acquire and then immediately release the console
1798 * semaphore. The release will print out buffers and wake up
1799 * /dev/kmsg and syslog() users.
1801 if (console_trylock_for_printk())
1809 EXPORT_SYMBOL(vprintk_emit
);
1811 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1813 return vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1815 EXPORT_SYMBOL(vprintk
);
1817 asmlinkage
int printk_emit(int facility
, int level
,
1818 const char *dict
, size_t dictlen
,
1819 const char *fmt
, ...)
1824 va_start(args
, fmt
);
1825 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1830 EXPORT_SYMBOL(printk_emit
);
1832 int vprintk_default(const char *fmt
, va_list args
)
1836 #ifdef CONFIG_KGDB_KDB
1837 if (unlikely(kdb_trap_printk
)) {
1838 r
= vkdb_printf(KDB_MSGSRC_PRINTK
, fmt
, args
);
1842 r
= vprintk_emit(0, LOGLEVEL_DEFAULT
, NULL
, 0, fmt
, args
);
1846 EXPORT_SYMBOL_GPL(vprintk_default
);
1849 * This allows printk to be diverted to another function per cpu.
1850 * This is useful for calling printk functions from within NMI
1851 * without worrying about race conditions that can lock up the
1854 DEFINE_PER_CPU(printk_func_t
, printk_func
) = vprintk_default
;
1857 * printk - print a kernel message
1858 * @fmt: format string
1860 * This is printk(). It can be called from any context. We want it to work.
1862 * We try to grab the console_lock. If we succeed, it's easy - we log the
1863 * output and call the console drivers. If we fail to get the semaphore, we
1864 * place the output into the log buffer and return. The current holder of
1865 * the console_sem will notice the new output in console_unlock(); and will
1866 * send it to the consoles before releasing the lock.
1868 * One effect of this deferred printing is that code which calls printk() and
1869 * then changes console_loglevel may break. This is because console_loglevel
1870 * is inspected when the actual printing occurs.
1875 * See the vsnprintf() documentation for format string extensions over C99.
1877 asmlinkage __visible
int printk(const char *fmt
, ...)
1879 printk_func_t vprintk_func
;
1883 va_start(args
, fmt
);
1886 * If a caller overrides the per_cpu printk_func, then it needs
1887 * to disable preemption when calling printk(). Otherwise
1888 * the printk_func should be set to the default. No need to
1889 * disable preemption here.
1891 vprintk_func
= this_cpu_read(printk_func
);
1892 r
= vprintk_func(fmt
, args
);
1898 EXPORT_SYMBOL(printk
);
1900 #else /* CONFIG_PRINTK */
1902 #define LOG_LINE_MAX 0
1903 #define PREFIX_MAX 0
1905 static u64 syslog_seq
;
1906 static u32 syslog_idx
;
1907 static u64 console_seq
;
1908 static u32 console_idx
;
1909 static enum log_flags syslog_prev
;
1910 static u64 log_first_seq
;
1911 static u32 log_first_idx
;
1912 static u64 log_next_seq
;
1913 static enum log_flags console_prev
;
1914 static struct cont
{
1920 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
1921 static u32
log_next(u32 idx
) { return 0; }
1922 static void call_console_drivers(int level
, const char *text
, size_t len
) {}
1923 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1924 bool syslog
, char *buf
, size_t size
) { return 0; }
1925 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
1927 /* Still needs to be defined for users */
1928 DEFINE_PER_CPU(printk_func_t
, printk_func
);
1930 #endif /* CONFIG_PRINTK */
1932 #ifdef CONFIG_EARLY_PRINTK
1933 struct console
*early_console
;
1935 asmlinkage __visible
void early_printk(const char *fmt
, ...)
1945 n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
1948 early_console
->write(early_console
, buf
, n
);
1952 static int __add_preferred_console(char *name
, int idx
, char *options
,
1955 struct console_cmdline
*c
;
1959 * See if this tty is not yet registered, and
1960 * if we have a slot free.
1962 for (i
= 0, c
= console_cmdline
;
1963 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1965 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
1967 selected_console
= i
;
1971 if (i
== MAX_CMDLINECONSOLES
)
1974 selected_console
= i
;
1975 strlcpy(c
->name
, name
, sizeof(c
->name
));
1976 c
->options
= options
;
1977 braille_set_options(c
, brl_options
);
1983 * Set up a console. Called via do_early_param() in init/main.c
1984 * for each "console=" parameter in the boot command line.
1986 static int __init
console_setup(char *str
)
1988 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for "ttyS" */
1989 char *s
, *options
, *brl_options
= NULL
;
1992 if (_braille_console_setup(&str
, &brl_options
))
1996 * Decode str into name, index, options.
1998 if (str
[0] >= '0' && str
[0] <= '9') {
1999 strcpy(buf
, "ttyS");
2000 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
2002 strncpy(buf
, str
, sizeof(buf
) - 1);
2004 buf
[sizeof(buf
) - 1] = 0;
2005 options
= strchr(str
, ',');
2009 if (!strcmp(str
, "ttya"))
2010 strcpy(buf
, "ttyS0");
2011 if (!strcmp(str
, "ttyb"))
2012 strcpy(buf
, "ttyS1");
2014 for (s
= buf
; *s
; s
++)
2015 if (isdigit(*s
) || *s
== ',')
2017 idx
= simple_strtoul(s
, NULL
, 10);
2020 __add_preferred_console(buf
, idx
, options
, brl_options
);
2021 console_set_on_cmdline
= 1;
2024 __setup("console=", console_setup
);
2027 * add_preferred_console - add a device to the list of preferred consoles.
2028 * @name: device name
2029 * @idx: device index
2030 * @options: options for this console
2032 * The last preferred console added will be used for kernel messages
2033 * and stdin/out/err for init. Normally this is used by console_setup
2034 * above to handle user-supplied console arguments; however it can also
2035 * be used by arch-specific code either to override the user or more
2036 * commonly to provide a default console (ie from PROM variables) when
2037 * the user has not supplied one.
2039 int add_preferred_console(char *name
, int idx
, char *options
)
2041 return __add_preferred_console(name
, idx
, options
, NULL
);
2044 bool console_suspend_enabled
= true;
2045 EXPORT_SYMBOL(console_suspend_enabled
);
2047 static int __init
console_suspend_disable(char *str
)
2049 console_suspend_enabled
= false;
2052 __setup("no_console_suspend", console_suspend_disable
);
2053 module_param_named(console_suspend
, console_suspend_enabled
,
2054 bool, S_IRUGO
| S_IWUSR
);
2055 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
2056 " and hibernate operations");
2059 * suspend_console - suspend the console subsystem
2061 * This disables printk() while we go into suspend states
2063 void suspend_console(void)
2065 if (!console_suspend_enabled
)
2067 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2069 console_suspended
= 1;
2073 void resume_console(void)
2075 if (!console_suspend_enabled
)
2078 console_suspended
= 0;
2083 * console_cpu_notify - print deferred console messages after CPU hotplug
2084 * @self: notifier struct
2085 * @action: CPU hotplug event
2088 * If printk() is called from a CPU that is not online yet, the messages
2089 * will be spooled but will not show up on the console. This function is
2090 * called when a new CPU comes online (or fails to come up), and ensures
2091 * that any such output gets printed.
2093 static int console_cpu_notify(struct notifier_block
*self
,
2094 unsigned long action
, void *hcpu
)
2099 case CPU_DOWN_FAILED
:
2100 case CPU_UP_CANCELED
:
2108 * console_lock - lock the console system for exclusive use.
2110 * Acquires a lock which guarantees that the caller has
2111 * exclusive access to the console system and the console_drivers list.
2113 * Can sleep, returns nothing.
2115 void console_lock(void)
2120 if (console_suspended
)
2123 console_may_schedule
= 1;
2125 EXPORT_SYMBOL(console_lock
);
2128 * console_trylock - try to lock the console system for exclusive use.
2130 * Try to acquire a lock which guarantees that the caller has exclusive
2131 * access to the console system and the console_drivers list.
2133 * returns 1 on success, and 0 on failure to acquire the lock.
2135 int console_trylock(void)
2137 if (down_trylock_console_sem())
2139 if (console_suspended
) {
2144 console_may_schedule
= 0;
2147 EXPORT_SYMBOL(console_trylock
);
2149 int is_console_locked(void)
2151 return console_locked
;
2154 static void console_cont_flush(char *text
, size_t size
)
2156 unsigned long flags
;
2159 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2165 * We still queue earlier records, likely because the console was
2166 * busy. The earlier ones need to be printed before this one, we
2167 * did not flush any fragment so far, so just let it queue up.
2169 if (console_seq
< log_next_seq
&& !cont
.cons
)
2172 len
= cont_print_text(text
, size
);
2173 raw_spin_unlock(&logbuf_lock
);
2174 stop_critical_timings();
2175 call_console_drivers(cont
.level
, text
, len
);
2176 start_critical_timings();
2177 local_irq_restore(flags
);
2180 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2184 * console_unlock - unlock the console system
2186 * Releases the console_lock which the caller holds on the console system
2187 * and the console driver list.
2189 * While the console_lock was held, console output may have been buffered
2190 * by printk(). If this is the case, console_unlock(); emits
2191 * the output prior to releasing the lock.
2193 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2195 * console_unlock(); may be called from any context.
2197 void console_unlock(void)
2199 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2200 static u64 seen_seq
;
2201 unsigned long flags
;
2202 bool wake_klogd
= false;
2205 if (console_suspended
) {
2210 console_may_schedule
= 0;
2212 /* flush buffered message fragment immediately to console */
2213 console_cont_flush(text
, sizeof(text
));
2216 struct printk_log
*msg
;
2220 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2221 if (seen_seq
!= log_next_seq
) {
2223 seen_seq
= log_next_seq
;
2226 if (console_seq
< log_first_seq
) {
2227 len
= sprintf(text
, "** %u printk messages dropped ** ",
2228 (unsigned)(log_first_seq
- console_seq
));
2230 /* messages are gone, move to first one */
2231 console_seq
= log_first_seq
;
2232 console_idx
= log_first_idx
;
2238 if (console_seq
== log_next_seq
)
2241 msg
= log_from_idx(console_idx
);
2242 if (msg
->flags
& LOG_NOCONS
) {
2244 * Skip record we have buffered and already printed
2245 * directly to the console when we received it.
2247 console_idx
= log_next(console_idx
);
2250 * We will get here again when we register a new
2251 * CON_PRINTBUFFER console. Clear the flag so we
2252 * will properly dump everything later.
2254 msg
->flags
&= ~LOG_NOCONS
;
2255 console_prev
= msg
->flags
;
2260 len
+= msg_print_text(msg
, console_prev
, false,
2261 text
+ len
, sizeof(text
) - len
);
2262 console_idx
= log_next(console_idx
);
2264 console_prev
= msg
->flags
;
2265 raw_spin_unlock(&logbuf_lock
);
2267 stop_critical_timings(); /* don't trace print latency */
2268 call_console_drivers(level
, text
, len
);
2269 start_critical_timings();
2270 local_irq_restore(flags
);
2274 /* Release the exclusive_console once it is used */
2275 if (unlikely(exclusive_console
))
2276 exclusive_console
= NULL
;
2278 raw_spin_unlock(&logbuf_lock
);
2283 * Someone could have filled up the buffer again, so re-check if there's
2284 * something to flush. In case we cannot trylock the console_sem again,
2285 * there's a new owner and the console_unlock() from them will do the
2286 * flush, no worries.
2288 raw_spin_lock(&logbuf_lock
);
2289 retry
= console_seq
!= log_next_seq
;
2290 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2292 if (retry
&& console_trylock())
2298 EXPORT_SYMBOL(console_unlock
);
2301 * console_conditional_schedule - yield the CPU if required
2303 * If the console code is currently allowed to sleep, and
2304 * if this CPU should yield the CPU to another task, do
2307 * Must be called within console_lock();.
2309 void __sched
console_conditional_schedule(void)
2311 if (console_may_schedule
)
2314 EXPORT_SYMBOL(console_conditional_schedule
);
2316 void console_unblank(void)
2321 * console_unblank can no longer be called in interrupt context unless
2322 * oops_in_progress is set to 1..
2324 if (oops_in_progress
) {
2325 if (down_trylock_console_sem() != 0)
2331 console_may_schedule
= 0;
2333 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2339 * Return the console tty driver structure and its associated index
2341 struct tty_driver
*console_device(int *index
)
2344 struct tty_driver
*driver
= NULL
;
2347 for_each_console(c
) {
2350 driver
= c
->device(c
, index
);
2359 * Prevent further output on the passed console device so that (for example)
2360 * serial drivers can disable console output before suspending a port, and can
2361 * re-enable output afterwards.
2363 void console_stop(struct console
*console
)
2366 console
->flags
&= ~CON_ENABLED
;
2369 EXPORT_SYMBOL(console_stop
);
2371 void console_start(struct console
*console
)
2374 console
->flags
|= CON_ENABLED
;
2377 EXPORT_SYMBOL(console_start
);
2379 static int __read_mostly keep_bootcon
;
2381 static int __init
keep_bootcon_setup(char *str
)
2384 pr_info("debug: skip boot console de-registration.\n");
2389 early_param("keep_bootcon", keep_bootcon_setup
);
2392 * The console driver calls this routine during kernel initialization
2393 * to register the console printing procedure with printk() and to
2394 * print any messages that were printed by the kernel before the
2395 * console driver was initialized.
2397 * This can happen pretty early during the boot process (because of
2398 * early_printk) - sometimes before setup_arch() completes - be careful
2399 * of what kernel features are used - they may not be initialised yet.
2401 * There are two types of consoles - bootconsoles (early_printk) and
2402 * "real" consoles (everything which is not a bootconsole) which are
2403 * handled differently.
2404 * - Any number of bootconsoles can be registered at any time.
2405 * - As soon as a "real" console is registered, all bootconsoles
2406 * will be unregistered automatically.
2407 * - Once a "real" console is registered, any attempt to register a
2408 * bootconsoles will be rejected
2410 void register_console(struct console
*newcon
)
2413 unsigned long flags
;
2414 struct console
*bcon
= NULL
;
2415 struct console_cmdline
*c
;
2417 if (console_drivers
)
2418 for_each_console(bcon
)
2419 if (WARN(bcon
== newcon
,
2420 "console '%s%d' already registered\n",
2421 bcon
->name
, bcon
->index
))
2425 * before we register a new CON_BOOT console, make sure we don't
2426 * already have a valid console
2428 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2429 /* find the last or real console */
2430 for_each_console(bcon
) {
2431 if (!(bcon
->flags
& CON_BOOT
)) {
2432 pr_info("Too late to register bootconsole %s%d\n",
2433 newcon
->name
, newcon
->index
);
2439 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2440 bcon
= console_drivers
;
2442 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2443 preferred_console
= selected_console
;
2446 * See if we want to use this console driver. If we
2447 * didn't select a console we take the first one
2448 * that registers here.
2450 if (preferred_console
< 0) {
2451 if (newcon
->index
< 0)
2453 if (newcon
->setup
== NULL
||
2454 newcon
->setup(newcon
, NULL
) == 0) {
2455 newcon
->flags
|= CON_ENABLED
;
2456 if (newcon
->device
) {
2457 newcon
->flags
|= CON_CONSDEV
;
2458 preferred_console
= 0;
2464 * See if this console matches one we selected on
2467 for (i
= 0, c
= console_cmdline
;
2468 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2470 if (!newcon
->match
||
2471 newcon
->match(newcon
, c
->name
, c
->index
, c
->options
) != 0) {
2472 /* default matching */
2473 BUILD_BUG_ON(sizeof(c
->name
) != sizeof(newcon
->name
));
2474 if (strcmp(c
->name
, newcon
->name
) != 0)
2476 if (newcon
->index
>= 0 &&
2477 newcon
->index
!= c
->index
)
2479 if (newcon
->index
< 0)
2480 newcon
->index
= c
->index
;
2482 if (_braille_register_console(newcon
, c
))
2485 if (newcon
->setup
&&
2486 newcon
->setup(newcon
, c
->options
) != 0)
2490 newcon
->flags
|= CON_ENABLED
;
2491 if (i
== selected_console
) {
2492 newcon
->flags
|= CON_CONSDEV
;
2493 preferred_console
= selected_console
;
2498 if (!(newcon
->flags
& CON_ENABLED
))
2502 * If we have a bootconsole, and are switching to a real console,
2503 * don't print everything out again, since when the boot console, and
2504 * the real console are the same physical device, it's annoying to
2505 * see the beginning boot messages twice
2507 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2508 newcon
->flags
&= ~CON_PRINTBUFFER
;
2511 * Put this console in the list - keep the
2512 * preferred driver at the head of the list.
2515 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2516 newcon
->next
= console_drivers
;
2517 console_drivers
= newcon
;
2519 newcon
->next
->flags
&= ~CON_CONSDEV
;
2521 newcon
->next
= console_drivers
->next
;
2522 console_drivers
->next
= newcon
;
2524 if (newcon
->flags
& CON_PRINTBUFFER
) {
2526 * console_unlock(); will print out the buffered messages
2529 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2530 console_seq
= syslog_seq
;
2531 console_idx
= syslog_idx
;
2532 console_prev
= syslog_prev
;
2533 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2535 * We're about to replay the log buffer. Only do this to the
2536 * just-registered console to avoid excessive message spam to
2537 * the already-registered consoles.
2539 exclusive_console
= newcon
;
2542 console_sysfs_notify();
2545 * By unregistering the bootconsoles after we enable the real console
2546 * we get the "console xxx enabled" message on all the consoles -
2547 * boot consoles, real consoles, etc - this is to ensure that end
2548 * users know there might be something in the kernel's log buffer that
2549 * went to the bootconsole (that they do not see on the real console)
2551 pr_info("%sconsole [%s%d] enabled\n",
2552 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2553 newcon
->name
, newcon
->index
);
2555 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2557 /* We need to iterate through all boot consoles, to make
2558 * sure we print everything out, before we unregister them.
2560 for_each_console(bcon
)
2561 if (bcon
->flags
& CON_BOOT
)
2562 unregister_console(bcon
);
2565 EXPORT_SYMBOL(register_console
);
2567 int unregister_console(struct console
*console
)
2569 struct console
*a
, *b
;
2572 pr_info("%sconsole [%s%d] disabled\n",
2573 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2574 console
->name
, console
->index
);
2576 res
= _braille_unregister_console(console
);
2582 if (console_drivers
== console
) {
2583 console_drivers
=console
->next
;
2585 } else if (console_drivers
) {
2586 for (a
=console_drivers
->next
, b
=console_drivers
;
2587 a
; b
=a
, a
=b
->next
) {
2597 * If this isn't the last console and it has CON_CONSDEV set, we
2598 * need to set it on the next preferred console.
2600 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2601 console_drivers
->flags
|= CON_CONSDEV
;
2603 console
->flags
&= ~CON_ENABLED
;
2605 console_sysfs_notify();
2608 EXPORT_SYMBOL(unregister_console
);
2610 static int __init
printk_late_init(void)
2612 struct console
*con
;
2614 for_each_console(con
) {
2615 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2616 unregister_console(con
);
2619 hotcpu_notifier(console_cpu_notify
, 0);
2622 late_initcall(printk_late_init
);
2624 #if defined CONFIG_PRINTK
2626 * Delayed printk version, for scheduler-internal messages:
2628 #define PRINTK_PENDING_WAKEUP 0x01
2629 #define PRINTK_PENDING_OUTPUT 0x02
2631 static DEFINE_PER_CPU(int, printk_pending
);
2633 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2635 int pending
= __this_cpu_xchg(printk_pending
, 0);
2637 if (pending
& PRINTK_PENDING_OUTPUT
) {
2638 /* If trylock fails, someone else is doing the printing */
2639 if (console_trylock())
2643 if (pending
& PRINTK_PENDING_WAKEUP
)
2644 wake_up_interruptible(&log_wait
);
2647 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2648 .func
= wake_up_klogd_work_func
,
2649 .flags
= IRQ_WORK_LAZY
,
2652 void wake_up_klogd(void)
2655 if (waitqueue_active(&log_wait
)) {
2656 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2657 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2662 int printk_deferred(const char *fmt
, ...)
2668 va_start(args
, fmt
);
2669 r
= vprintk_emit(0, LOGLEVEL_SCHED
, NULL
, 0, fmt
, args
);
2672 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2673 irq_work_queue(this_cpu_ptr(&wake_up_klogd_work
));
2680 * printk rate limiting, lifted from the networking subsystem.
2682 * This enforces a rate limit: not more than 10 kernel messages
2683 * every 5s to make a denial-of-service attack impossible.
2685 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2687 int __printk_ratelimit(const char *func
)
2689 return ___ratelimit(&printk_ratelimit_state
, func
);
2691 EXPORT_SYMBOL(__printk_ratelimit
);
2694 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2695 * @caller_jiffies: pointer to caller's state
2696 * @interval_msecs: minimum interval between prints
2698 * printk_timed_ratelimit() returns true if more than @interval_msecs
2699 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2702 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2703 unsigned int interval_msecs
)
2705 unsigned long elapsed
= jiffies
- *caller_jiffies
;
2707 if (*caller_jiffies
&& elapsed
<= msecs_to_jiffies(interval_msecs
))
2710 *caller_jiffies
= jiffies
;
2713 EXPORT_SYMBOL(printk_timed_ratelimit
);
2715 static DEFINE_SPINLOCK(dump_list_lock
);
2716 static LIST_HEAD(dump_list
);
2719 * kmsg_dump_register - register a kernel log dumper.
2720 * @dumper: pointer to the kmsg_dumper structure
2722 * Adds a kernel log dumper to the system. The dump callback in the
2723 * structure will be called when the kernel oopses or panics and must be
2724 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2726 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2728 unsigned long flags
;
2731 /* The dump callback needs to be set */
2735 spin_lock_irqsave(&dump_list_lock
, flags
);
2736 /* Don't allow registering multiple times */
2737 if (!dumper
->registered
) {
2738 dumper
->registered
= 1;
2739 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2742 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2746 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2749 * kmsg_dump_unregister - unregister a kmsg dumper.
2750 * @dumper: pointer to the kmsg_dumper structure
2752 * Removes a dump device from the system. Returns zero on success and
2753 * %-EINVAL otherwise.
2755 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2757 unsigned long flags
;
2760 spin_lock_irqsave(&dump_list_lock
, flags
);
2761 if (dumper
->registered
) {
2762 dumper
->registered
= 0;
2763 list_del_rcu(&dumper
->list
);
2766 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2771 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2773 static bool always_kmsg_dump
;
2774 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2777 * kmsg_dump - dump kernel log to kernel message dumpers.
2778 * @reason: the reason (oops, panic etc) for dumping
2780 * Call each of the registered dumper's dump() callback, which can
2781 * retrieve the kmsg records with kmsg_dump_get_line() or
2782 * kmsg_dump_get_buffer().
2784 void kmsg_dump(enum kmsg_dump_reason reason
)
2786 struct kmsg_dumper
*dumper
;
2787 unsigned long flags
;
2789 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2793 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2794 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2797 /* initialize iterator with data about the stored records */
2798 dumper
->active
= true;
2800 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2801 dumper
->cur_seq
= clear_seq
;
2802 dumper
->cur_idx
= clear_idx
;
2803 dumper
->next_seq
= log_next_seq
;
2804 dumper
->next_idx
= log_next_idx
;
2805 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2807 /* invoke dumper which will iterate over records */
2808 dumper
->dump(dumper
, reason
);
2810 /* reset iterator */
2811 dumper
->active
= false;
2817 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2818 * @dumper: registered kmsg dumper
2819 * @syslog: include the "<4>" prefixes
2820 * @line: buffer to copy the line to
2821 * @size: maximum size of the buffer
2822 * @len: length of line placed into buffer
2824 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2825 * record, and copy one record into the provided buffer.
2827 * Consecutive calls will return the next available record moving
2828 * towards the end of the buffer with the youngest messages.
2830 * A return value of FALSE indicates that there are no more records to
2833 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2835 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
2836 char *line
, size_t size
, size_t *len
)
2838 struct printk_log
*msg
;
2842 if (!dumper
->active
)
2845 if (dumper
->cur_seq
< log_first_seq
) {
2846 /* messages are gone, move to first available one */
2847 dumper
->cur_seq
= log_first_seq
;
2848 dumper
->cur_idx
= log_first_idx
;
2852 if (dumper
->cur_seq
>= log_next_seq
)
2855 msg
= log_from_idx(dumper
->cur_idx
);
2856 l
= msg_print_text(msg
, 0, syslog
, line
, size
);
2858 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2868 * kmsg_dump_get_line - retrieve one kmsg log line
2869 * @dumper: registered kmsg dumper
2870 * @syslog: include the "<4>" prefixes
2871 * @line: buffer to copy the line to
2872 * @size: maximum size of the buffer
2873 * @len: length of line placed into buffer
2875 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2876 * record, and copy one record into the provided buffer.
2878 * Consecutive calls will return the next available record moving
2879 * towards the end of the buffer with the youngest messages.
2881 * A return value of FALSE indicates that there are no more records to
2884 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2885 char *line
, size_t size
, size_t *len
)
2887 unsigned long flags
;
2890 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2891 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
2892 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2896 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2899 * kmsg_dump_get_buffer - copy kmsg log lines
2900 * @dumper: registered kmsg dumper
2901 * @syslog: include the "<4>" prefixes
2902 * @buf: buffer to copy the line to
2903 * @size: maximum size of the buffer
2904 * @len: length of line placed into buffer
2906 * Start at the end of the kmsg buffer and fill the provided buffer
2907 * with as many of the the *youngest* kmsg records that fit into it.
2908 * If the buffer is large enough, all available kmsg records will be
2909 * copied with a single call.
2911 * Consecutive calls will fill the buffer with the next block of
2912 * available older records, not including the earlier retrieved ones.
2914 * A return value of FALSE indicates that there are no more records to
2917 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
2918 char *buf
, size_t size
, size_t *len
)
2920 unsigned long flags
;
2925 enum log_flags prev
;
2929 if (!dumper
->active
)
2932 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2933 if (dumper
->cur_seq
< log_first_seq
) {
2934 /* messages are gone, move to first available one */
2935 dumper
->cur_seq
= log_first_seq
;
2936 dumper
->cur_idx
= log_first_idx
;
2940 if (dumper
->cur_seq
>= dumper
->next_seq
) {
2941 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2945 /* calculate length of entire buffer */
2946 seq
= dumper
->cur_seq
;
2947 idx
= dumper
->cur_idx
;
2949 while (seq
< dumper
->next_seq
) {
2950 struct printk_log
*msg
= log_from_idx(idx
);
2952 l
+= msg_print_text(msg
, prev
, true, NULL
, 0);
2953 idx
= log_next(idx
);
2958 /* move first record forward until length fits into the buffer */
2959 seq
= dumper
->cur_seq
;
2960 idx
= dumper
->cur_idx
;
2962 while (l
> size
&& seq
< dumper
->next_seq
) {
2963 struct printk_log
*msg
= log_from_idx(idx
);
2965 l
-= msg_print_text(msg
, prev
, true, NULL
, 0);
2966 idx
= log_next(idx
);
2971 /* last message in next interation */
2976 while (seq
< dumper
->next_seq
) {
2977 struct printk_log
*msg
= log_from_idx(idx
);
2979 l
+= msg_print_text(msg
, prev
, syslog
, buf
+ l
, size
- l
);
2980 idx
= log_next(idx
);
2985 dumper
->next_seq
= next_seq
;
2986 dumper
->next_idx
= next_idx
;
2988 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2994 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
2997 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2998 * @dumper: registered kmsg dumper
3000 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3001 * kmsg_dump_get_buffer() can be called again and used multiple
3002 * times within the same dumper.dump() callback.
3004 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
3006 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
3008 dumper
->cur_seq
= clear_seq
;
3009 dumper
->cur_idx
= clear_idx
;
3010 dumper
->next_seq
= log_next_seq
;
3011 dumper
->next_idx
= log_next_idx
;
3015 * kmsg_dump_rewind - reset the interator
3016 * @dumper: registered kmsg dumper
3018 * Reset the dumper's iterator so that kmsg_dump_get_line() and
3019 * kmsg_dump_get_buffer() can be called again and used multiple
3020 * times within the same dumper.dump() callback.
3022 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
3024 unsigned long flags
;
3026 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
3027 kmsg_dump_rewind_nolock(dumper
);
3028 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
3030 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
3032 static char dump_stack_arch_desc_str
[128];
3035 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
3036 * @fmt: printf-style format string
3037 * @...: arguments for the format string
3039 * The configured string will be printed right after utsname during task
3040 * dumps. Usually used to add arch-specific system identifiers. If an
3041 * arch wants to make use of such an ID string, it should initialize this
3042 * as soon as possible during boot.
3044 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
3048 va_start(args
, fmt
);
3049 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
3055 * dump_stack_print_info - print generic debug info for dump_stack()
3056 * @log_lvl: log level
3058 * Arch-specific dump_stack() implementations can use this function to
3059 * print out the same debug information as the generic dump_stack().
3061 void dump_stack_print_info(const char *log_lvl
)
3063 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
3064 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
3065 print_tainted(), init_utsname()->release
,
3066 (int)strcspn(init_utsname()->version
, " "),
3067 init_utsname()->version
);
3069 if (dump_stack_arch_desc_str
[0] != '\0')
3070 printk("%sHardware name: %s\n",
3071 log_lvl
, dump_stack_arch_desc_str
);
3073 print_worker_info(log_lvl
, current
);
3077 * show_regs_print_info - print generic debug info for show_regs()
3078 * @log_lvl: log level
3080 * show_regs() implementations can use this function to print out generic
3081 * debug information.
3083 void show_regs_print_info(const char *log_lvl
)
3085 dump_stack_print_info(log_lvl
);
3087 printk("%stask: %p ti: %p task.ti: %p\n",
3088 log_lvl
, current
, current_thread_info(),
3089 task_thread_info(current
));