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/aio.h>
36 #include <linux/syscalls.h>
37 #include <linux/kexec.h>
38 #include <linux/kdb.h>
39 #include <linux/ratelimit.h>
40 #include <linux/kmsg_dump.h>
41 #include <linux/syslog.h>
42 #include <linux/cpu.h>
43 #include <linux/notifier.h>
44 #include <linux/rculist.h>
45 #include <linux/poll.h>
46 #include <linux/irq_work.h>
47 #include <linux/utsname.h>
49 #include <asm/uaccess.h>
51 #define CREATE_TRACE_POINTS
52 #include <trace/events/printk.h>
54 #include "console_cmdline.h"
57 /* printk's without a loglevel use this.. */
58 #define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
60 /* We show everything that is MORE important than this.. */
61 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
62 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
64 int console_printk
[4] = {
65 DEFAULT_CONSOLE_LOGLEVEL
, /* console_loglevel */
66 DEFAULT_MESSAGE_LOGLEVEL
, /* default_message_loglevel */
67 MINIMUM_CONSOLE_LOGLEVEL
, /* minimum_console_loglevel */
68 DEFAULT_CONSOLE_LOGLEVEL
, /* default_console_loglevel */
71 /* Deferred messaged from sched code are marked by this special level */
72 #define SCHED_MESSAGE_LOGLEVEL -2
75 * Low level drivers may need that to know if they can schedule in
76 * their unblank() callback or not. So let's export it.
79 EXPORT_SYMBOL(oops_in_progress
);
82 * console_sem protects the console_drivers list, and also
83 * provides serialisation for access to the entire console
86 static DEFINE_SEMAPHORE(console_sem
);
87 struct console
*console_drivers
;
88 EXPORT_SYMBOL_GPL(console_drivers
);
91 static struct lockdep_map console_lock_dep_map
= {
92 .name
= "console_lock"
97 * Helper macros to handle lockdep when locking/unlocking console_sem. We use
98 * macros instead of functions so that _RET_IP_ contains useful information.
100 #define down_console_sem() do { \
102 mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
105 static int __down_trylock_console_sem(unsigned long ip
)
107 if (down_trylock(&console_sem
))
109 mutex_acquire(&console_lock_dep_map
, 0, 1, ip
);
112 #define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
114 #define up_console_sem() do { \
115 mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
120 * This is used for debugging the mess that is the VT code by
121 * keeping track if we have the console semaphore held. It's
122 * definitely not the perfect debug tool (we don't know if _WE_
123 * hold it are racing, but it helps tracking those weird code
124 * path in the console code where we end up in places I want
125 * locked without the console sempahore held
127 static int console_locked
, console_suspended
;
130 * If exclusive_console is non-NULL then only this console is to be printed to.
132 static struct console
*exclusive_console
;
135 * Array of consoles built from command line options (console=)
138 #define MAX_CMDLINECONSOLES 8
140 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
142 static int selected_console
= -1;
143 static int preferred_console
= -1;
144 int console_set_on_cmdline
;
145 EXPORT_SYMBOL(console_set_on_cmdline
);
147 /* Flag: console code may call schedule() */
148 static int console_may_schedule
;
151 * The printk log buffer consists of a chain of concatenated variable
152 * length records. Every record starts with a record header, containing
153 * the overall length of the record.
155 * The heads to the first and last entry in the buffer, as well as the
156 * sequence numbers of these both entries are maintained when messages
159 * If the heads indicate available messages, the length in the header
160 * tells the start next message. A length == 0 for the next message
161 * indicates a wrap-around to the beginning of the buffer.
163 * Every record carries the monotonic timestamp in microseconds, as well as
164 * the standard userspace syslog level and syslog facility. The usual
165 * kernel messages use LOG_KERN; userspace-injected messages always carry
166 * a matching syslog facility, by default LOG_USER. The origin of every
167 * message can be reliably determined that way.
169 * The human readable log message directly follows the message header. The
170 * length of the message text is stored in the header, the stored message
173 * Optionally, a message can carry a dictionary of properties (key/value pairs),
174 * to provide userspace with a machine-readable message context.
176 * Examples for well-defined, commonly used property names are:
177 * DEVICE=b12:8 device identifier
181 * +sound:card0 subsystem:devname
182 * SUBSYSTEM=pci driver-core subsystem name
184 * Valid characters in property names are [a-zA-Z0-9.-_]. The plain text value
185 * follows directly after a '=' character. Every property is terminated by
186 * a '\0' character. The last property is not terminated.
188 * Example of a message structure:
189 * 0000 ff 8f 00 00 00 00 00 00 monotonic time in nsec
190 * 0008 34 00 record is 52 bytes long
191 * 000a 0b 00 text is 11 bytes long
192 * 000c 1f 00 dictionary is 23 bytes long
193 * 000e 03 00 LOG_KERN (facility) LOG_ERR (level)
194 * 0010 69 74 27 73 20 61 20 6c "it's a l"
196 * 001b 44 45 56 49 43 "DEVIC"
197 * 45 3d 62 38 3a 32 00 44 "E=b8:2\0D"
198 * 52 49 56 45 52 3d 62 75 "RIVER=bu"
200 * 0032 00 00 00 padding to next message header
202 * The 'struct printk_log' buffer header must never be directly exported to
203 * userspace, it is a kernel-private implementation detail that might
204 * need to be changed in the future, when the requirements change.
206 * /dev/kmsg exports the structured data in the following line format:
207 * "level,sequnum,timestamp;<message text>\n"
209 * The optional key/value pairs are attached as continuation lines starting
210 * with a space character and terminated by a newline. All possible
211 * non-prinatable characters are escaped in the "\xff" notation.
213 * Users of the export format should ignore possible additional values
214 * separated by ',', and find the message after the ';' character.
218 LOG_NOCONS
= 1, /* already flushed, do not print to console */
219 LOG_NEWLINE
= 2, /* text ended with a newline */
220 LOG_PREFIX
= 4, /* text started with a prefix */
221 LOG_CONT
= 8, /* text is a fragment of a continuation line */
225 u64 ts_nsec
; /* timestamp in nanoseconds */
226 u16 len
; /* length of entire record */
227 u16 text_len
; /* length of text buffer */
228 u16 dict_len
; /* length of dictionary buffer */
229 u8 facility
; /* syslog facility */
230 u8 flags
:5; /* internal record flags */
231 u8 level
:3; /* syslog level */
235 * The logbuf_lock protects kmsg buffer, indices, counters. This can be taken
236 * within the scheduler's rq lock. It must be released before calling
237 * console_unlock() or anything else that might wake up a process.
239 static DEFINE_RAW_SPINLOCK(logbuf_lock
);
242 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
243 /* the next printk record to read by syslog(READ) or /proc/kmsg */
244 static u64 syslog_seq
;
245 static u32 syslog_idx
;
246 static enum log_flags syslog_prev
;
247 static size_t syslog_partial
;
249 /* index and sequence number of the first record stored in the buffer */
250 static u64 log_first_seq
;
251 static u32 log_first_idx
;
253 /* index and sequence number of the next record to store in the buffer */
254 static u64 log_next_seq
;
255 static u32 log_next_idx
;
257 /* the next printk record to write to the console */
258 static u64 console_seq
;
259 static u32 console_idx
;
260 static enum log_flags console_prev
;
262 /* the next printk record to read after the last 'clear' command */
263 static u64 clear_seq
;
264 static u32 clear_idx
;
266 #define PREFIX_MAX 32
267 #define LOG_LINE_MAX 1024 - PREFIX_MAX
270 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
273 #define LOG_ALIGN __alignof__(struct printk_log)
275 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
276 static char __log_buf
[__LOG_BUF_LEN
] __aligned(LOG_ALIGN
);
277 static char *log_buf
= __log_buf
;
278 static u32 log_buf_len
= __LOG_BUF_LEN
;
280 /* human readable text of the record */
281 static char *log_text(const struct printk_log
*msg
)
283 return (char *)msg
+ sizeof(struct printk_log
);
286 /* optional key/value pair dictionary attached to the record */
287 static char *log_dict(const struct printk_log
*msg
)
289 return (char *)msg
+ sizeof(struct printk_log
) + msg
->text_len
;
292 /* get record by index; idx must point to valid msg */
293 static struct printk_log
*log_from_idx(u32 idx
)
295 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
298 * A length == 0 record is the end of buffer marker. Wrap around and
299 * read the message at the start of the buffer.
302 return (struct printk_log
*)log_buf
;
306 /* get next record; idx must point to valid msg */
307 static u32
log_next(u32 idx
)
309 struct printk_log
*msg
= (struct printk_log
*)(log_buf
+ idx
);
311 /* length == 0 indicates the end of the buffer; wrap */
313 * A length == 0 record is the end of buffer marker. Wrap around and
314 * read the message at the start of the buffer as *this* one, and
315 * return the one after that.
318 msg
= (struct printk_log
*)log_buf
;
321 return idx
+ msg
->len
;
325 * Check whether there is enough free space for the given message.
327 * The same values of first_idx and next_idx mean that the buffer
328 * is either empty or full.
330 * If the buffer is empty, we must respect the position of the indexes.
331 * They cannot be reset to the beginning of the buffer.
333 static int logbuf_has_space(u32 msg_size
, bool empty
)
337 if (log_next_idx
> log_first_idx
|| empty
)
338 free
= max(log_buf_len
- log_next_idx
, log_first_idx
);
340 free
= log_first_idx
- log_next_idx
;
343 * We need space also for an empty header that signalizes wrapping
346 return free
>= msg_size
+ sizeof(struct printk_log
);
349 static int log_make_free_space(u32 msg_size
)
351 while (log_first_seq
< log_next_seq
) {
352 if (logbuf_has_space(msg_size
, false))
354 /* drop old messages until we have enough continuous space */
355 log_first_idx
= log_next(log_first_idx
);
359 /* sequence numbers are equal, so the log buffer is empty */
360 if (logbuf_has_space(msg_size
, true))
366 /* compute the message size including the padding bytes */
367 static u32
msg_used_size(u16 text_len
, u16 dict_len
, u32
*pad_len
)
371 size
= sizeof(struct printk_log
) + text_len
+ dict_len
;
372 *pad_len
= (-size
) & (LOG_ALIGN
- 1);
379 * Define how much of the log buffer we could take at maximum. The value
380 * must be greater than two. Note that only half of the buffer is available
381 * when the index points to the middle.
383 #define MAX_LOG_TAKE_PART 4
384 static const char trunc_msg
[] = "<truncated>";
386 static u32
truncate_msg(u16
*text_len
, u16
*trunc_msg_len
,
387 u16
*dict_len
, u32
*pad_len
)
390 * The message should not take the whole buffer. Otherwise, it might
391 * get removed too soon.
393 u32 max_text_len
= log_buf_len
/ MAX_LOG_TAKE_PART
;
394 if (*text_len
> max_text_len
)
395 *text_len
= max_text_len
;
396 /* enable the warning message */
397 *trunc_msg_len
= strlen(trunc_msg
);
398 /* disable the "dict" completely */
400 /* compute the size again, count also the warning message */
401 return msg_used_size(*text_len
+ *trunc_msg_len
, 0, pad_len
);
404 /* insert record into the buffer, discard old ones, update heads */
405 static int log_store(int facility
, int level
,
406 enum log_flags flags
, u64 ts_nsec
,
407 const char *dict
, u16 dict_len
,
408 const char *text
, u16 text_len
)
410 struct printk_log
*msg
;
412 u16 trunc_msg_len
= 0;
414 /* number of '\0' padding bytes to next message */
415 size
= msg_used_size(text_len
, dict_len
, &pad_len
);
417 if (log_make_free_space(size
)) {
418 /* truncate the message if it is too long for empty buffer */
419 size
= truncate_msg(&text_len
, &trunc_msg_len
,
420 &dict_len
, &pad_len
);
421 /* survive when the log buffer is too small for trunc_msg */
422 if (log_make_free_space(size
))
426 if (log_next_idx
+ size
+ sizeof(struct printk_log
) > log_buf_len
) {
428 * This message + an additional empty header does not fit
429 * at the end of the buffer. Add an empty header with len == 0
430 * to signify a wrap around.
432 memset(log_buf
+ log_next_idx
, 0, sizeof(struct printk_log
));
437 msg
= (struct printk_log
*)(log_buf
+ log_next_idx
);
438 memcpy(log_text(msg
), text
, text_len
);
439 msg
->text_len
= text_len
;
441 memcpy(log_text(msg
) + text_len
, trunc_msg
, trunc_msg_len
);
442 msg
->text_len
+= trunc_msg_len
;
444 memcpy(log_dict(msg
), dict
, dict_len
);
445 msg
->dict_len
= dict_len
;
446 msg
->facility
= facility
;
447 msg
->level
= level
& 7;
448 msg
->flags
= flags
& 0x1f;
450 msg
->ts_nsec
= ts_nsec
;
452 msg
->ts_nsec
= local_clock();
453 memset(log_dict(msg
) + dict_len
, 0, pad_len
);
457 log_next_idx
+= msg
->len
;
460 return msg
->text_len
;
463 #ifdef CONFIG_SECURITY_DMESG_RESTRICT
464 int dmesg_restrict
= 1;
469 static int syslog_action_restricted(int type
)
474 * Unless restricted, we allow "read all" and "get buffer size"
477 return type
!= SYSLOG_ACTION_READ_ALL
&&
478 type
!= SYSLOG_ACTION_SIZE_BUFFER
;
481 static int check_syslog_permissions(int type
, bool from_file
)
484 * If this is from /proc/kmsg and we've already opened it, then we've
485 * already done the capabilities checks at open time.
487 if (from_file
&& type
!= SYSLOG_ACTION_OPEN
)
490 if (syslog_action_restricted(type
)) {
491 if (capable(CAP_SYSLOG
))
494 * For historical reasons, accept CAP_SYS_ADMIN too, with
497 if (capable(CAP_SYS_ADMIN
)) {
498 pr_warn_once("%s (%d): Attempt to access syslog with "
499 "CAP_SYS_ADMIN but no CAP_SYSLOG "
501 current
->comm
, task_pid_nr(current
));
506 return security_syslog(type
);
510 /* /dev/kmsg - userspace message inject/listen interface */
511 struct devkmsg_user
{
519 static ssize_t
devkmsg_writev(struct kiocb
*iocb
, const struct iovec
*iv
,
520 unsigned long count
, loff_t pos
)
524 int level
= default_message_loglevel
;
525 int facility
= 1; /* LOG_USER */
526 size_t len
= iov_length(iv
, count
);
529 if (len
> LOG_LINE_MAX
)
531 buf
= kmalloc(len
+1, GFP_KERNEL
);
536 for (i
= 0; i
< count
; i
++) {
537 if (copy_from_user(line
, iv
[i
].iov_base
, iv
[i
].iov_len
)) {
541 line
+= iv
[i
].iov_len
;
545 * Extract and skip the syslog prefix <[0-9]*>. Coming from userspace
546 * the decimal value represents 32bit, the lower 3 bit are the log
547 * level, the rest are the log facility.
549 * If no prefix or no userspace facility is specified, we
550 * enforce LOG_USER, to be able to reliably distinguish
551 * kernel-generated messages from userspace-injected ones.
554 if (line
[0] == '<') {
557 i
= simple_strtoul(line
+1, &endp
, 10);
558 if (endp
&& endp
[0] == '>') {
569 printk_emit(facility
, level
, NULL
, 0, "%s", line
);
575 static ssize_t
devkmsg_read(struct file
*file
, char __user
*buf
,
576 size_t count
, loff_t
*ppos
)
578 struct devkmsg_user
*user
= file
->private_data
;
579 struct printk_log
*msg
;
589 ret
= mutex_lock_interruptible(&user
->lock
);
592 raw_spin_lock_irq(&logbuf_lock
);
593 while (user
->seq
== log_next_seq
) {
594 if (file
->f_flags
& O_NONBLOCK
) {
596 raw_spin_unlock_irq(&logbuf_lock
);
600 raw_spin_unlock_irq(&logbuf_lock
);
601 ret
= wait_event_interruptible(log_wait
,
602 user
->seq
!= log_next_seq
);
605 raw_spin_lock_irq(&logbuf_lock
);
608 if (user
->seq
< log_first_seq
) {
609 /* our last seen message is gone, return error and reset */
610 user
->idx
= log_first_idx
;
611 user
->seq
= log_first_seq
;
613 raw_spin_unlock_irq(&logbuf_lock
);
617 msg
= log_from_idx(user
->idx
);
618 ts_usec
= msg
->ts_nsec
;
619 do_div(ts_usec
, 1000);
622 * If we couldn't merge continuation line fragments during the print,
623 * export the stored flags to allow an optional external merge of the
624 * records. Merging the records isn't always neccessarily correct, like
625 * when we hit a race during printing. In most cases though, it produces
626 * better readable output. 'c' in the record flags mark the first
627 * fragment of a line, '+' the following.
629 if (msg
->flags
& LOG_CONT
&& !(user
->prev
& LOG_CONT
))
631 else if ((msg
->flags
& LOG_CONT
) ||
632 ((user
->prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
)))
635 len
= sprintf(user
->buf
, "%u,%llu,%llu,%c;",
636 (msg
->facility
<< 3) | msg
->level
,
637 user
->seq
, ts_usec
, cont
);
638 user
->prev
= msg
->flags
;
640 /* escape non-printable characters */
641 for (i
= 0; i
< msg
->text_len
; i
++) {
642 unsigned char c
= log_text(msg
)[i
];
644 if (c
< ' ' || c
>= 127 || c
== '\\')
645 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
647 user
->buf
[len
++] = c
;
649 user
->buf
[len
++] = '\n';
654 for (i
= 0; i
< msg
->dict_len
; i
++) {
655 unsigned char c
= log_dict(msg
)[i
];
658 user
->buf
[len
++] = ' ';
663 user
->buf
[len
++] = '\n';
668 if (c
< ' ' || c
>= 127 || c
== '\\') {
669 len
+= sprintf(user
->buf
+ len
, "\\x%02x", c
);
673 user
->buf
[len
++] = c
;
675 user
->buf
[len
++] = '\n';
678 user
->idx
= log_next(user
->idx
);
680 raw_spin_unlock_irq(&logbuf_lock
);
687 if (copy_to_user(buf
, user
->buf
, len
)) {
693 mutex_unlock(&user
->lock
);
697 static loff_t
devkmsg_llseek(struct file
*file
, loff_t offset
, int whence
)
699 struct devkmsg_user
*user
= file
->private_data
;
707 raw_spin_lock_irq(&logbuf_lock
);
710 /* the first record */
711 user
->idx
= log_first_idx
;
712 user
->seq
= log_first_seq
;
716 * The first record after the last SYSLOG_ACTION_CLEAR,
717 * like issued by 'dmesg -c'. Reading /dev/kmsg itself
718 * changes no global state, and does not clear anything.
720 user
->idx
= clear_idx
;
721 user
->seq
= clear_seq
;
724 /* after the last record */
725 user
->idx
= log_next_idx
;
726 user
->seq
= log_next_seq
;
731 raw_spin_unlock_irq(&logbuf_lock
);
735 static unsigned int devkmsg_poll(struct file
*file
, poll_table
*wait
)
737 struct devkmsg_user
*user
= file
->private_data
;
741 return POLLERR
|POLLNVAL
;
743 poll_wait(file
, &log_wait
, wait
);
745 raw_spin_lock_irq(&logbuf_lock
);
746 if (user
->seq
< log_next_seq
) {
747 /* return error when data has vanished underneath us */
748 if (user
->seq
< log_first_seq
)
749 ret
= POLLIN
|POLLRDNORM
|POLLERR
|POLLPRI
;
751 ret
= POLLIN
|POLLRDNORM
;
753 raw_spin_unlock_irq(&logbuf_lock
);
758 static int devkmsg_open(struct inode
*inode
, struct file
*file
)
760 struct devkmsg_user
*user
;
763 /* write-only does not need any file context */
764 if ((file
->f_flags
& O_ACCMODE
) == O_WRONLY
)
767 err
= check_syslog_permissions(SYSLOG_ACTION_READ_ALL
,
772 user
= kmalloc(sizeof(struct devkmsg_user
), GFP_KERNEL
);
776 mutex_init(&user
->lock
);
778 raw_spin_lock_irq(&logbuf_lock
);
779 user
->idx
= log_first_idx
;
780 user
->seq
= log_first_seq
;
781 raw_spin_unlock_irq(&logbuf_lock
);
783 file
->private_data
= user
;
787 static int devkmsg_release(struct inode
*inode
, struct file
*file
)
789 struct devkmsg_user
*user
= file
->private_data
;
794 mutex_destroy(&user
->lock
);
799 const struct file_operations kmsg_fops
= {
800 .open
= devkmsg_open
,
801 .read
= devkmsg_read
,
802 .aio_write
= devkmsg_writev
,
803 .llseek
= devkmsg_llseek
,
804 .poll
= devkmsg_poll
,
805 .release
= devkmsg_release
,
810 * This appends the listed symbols to /proc/vmcore
812 * /proc/vmcore is used by various utilities, like crash and makedumpfile to
813 * obtain access to symbols that are otherwise very difficult to locate. These
814 * symbols are specifically used so that utilities can access and extract the
815 * dmesg log from a vmcore file after a crash.
817 void log_buf_kexec_setup(void)
819 VMCOREINFO_SYMBOL(log_buf
);
820 VMCOREINFO_SYMBOL(log_buf_len
);
821 VMCOREINFO_SYMBOL(log_first_idx
);
822 VMCOREINFO_SYMBOL(log_next_idx
);
824 * Export struct printk_log size and field offsets. User space tools can
825 * parse it and detect any changes to structure down the line.
827 VMCOREINFO_STRUCT_SIZE(printk_log
);
828 VMCOREINFO_OFFSET(printk_log
, ts_nsec
);
829 VMCOREINFO_OFFSET(printk_log
, len
);
830 VMCOREINFO_OFFSET(printk_log
, text_len
);
831 VMCOREINFO_OFFSET(printk_log
, dict_len
);
835 /* requested log_buf_len from kernel cmdline */
836 static unsigned long __initdata new_log_buf_len
;
838 /* save requested log_buf_len since it's too early to process it */
839 static int __init
log_buf_len_setup(char *str
)
841 unsigned size
= memparse(str
, &str
);
844 size
= roundup_pow_of_two(size
);
845 if (size
> log_buf_len
)
846 new_log_buf_len
= size
;
850 early_param("log_buf_len", log_buf_len_setup
);
852 void __init
setup_log_buf(int early
)
858 if (!new_log_buf_len
)
863 memblock_virt_alloc(new_log_buf_len
, PAGE_SIZE
);
865 new_log_buf
= memblock_virt_alloc_nopanic(new_log_buf_len
, 0);
868 if (unlikely(!new_log_buf
)) {
869 pr_err("log_buf_len: %ld bytes not available\n",
874 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
875 log_buf_len
= new_log_buf_len
;
876 log_buf
= new_log_buf
;
878 free
= __LOG_BUF_LEN
- log_next_idx
;
879 memcpy(log_buf
, __log_buf
, __LOG_BUF_LEN
);
880 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
882 pr_info("log_buf_len: %d\n", log_buf_len
);
883 pr_info("early log buf free: %d(%d%%)\n",
884 free
, (free
* 100) / __LOG_BUF_LEN
);
887 static bool __read_mostly ignore_loglevel
;
889 static int __init
ignore_loglevel_setup(char *str
)
892 pr_info("debug: ignoring loglevel setting.\n");
897 early_param("ignore_loglevel", ignore_loglevel_setup
);
898 module_param(ignore_loglevel
, bool, S_IRUGO
| S_IWUSR
);
899 MODULE_PARM_DESC(ignore_loglevel
, "ignore loglevel setting, to"
900 "print all kernel messages to the console.");
902 #ifdef CONFIG_BOOT_PRINTK_DELAY
904 static int boot_delay
; /* msecs delay after each printk during bootup */
905 static unsigned long long loops_per_msec
; /* based on boot_delay */
907 static int __init
boot_delay_setup(char *str
)
911 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
912 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
914 get_option(&str
, &boot_delay
);
915 if (boot_delay
> 10 * 1000)
918 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
919 "HZ: %d, loops_per_msec: %llu\n",
920 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
923 early_param("boot_delay", boot_delay_setup
);
925 static void boot_delay_msec(int level
)
927 unsigned long long k
;
928 unsigned long timeout
;
930 if ((boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
931 || (level
>= console_loglevel
&& !ignore_loglevel
)) {
935 k
= (unsigned long long)loops_per_msec
* boot_delay
;
937 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
942 * use (volatile) jiffies to prevent
943 * compiler reduction; loop termination via jiffies
944 * is secondary and may or may not happen.
946 if (time_after(jiffies
, timeout
))
948 touch_nmi_watchdog();
952 static inline void boot_delay_msec(int level
)
957 #if defined(CONFIG_PRINTK_TIME)
958 static bool printk_time
= 1;
960 static bool printk_time
;
962 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
964 static size_t print_time(u64 ts
, char *buf
)
966 unsigned long rem_nsec
;
971 rem_nsec
= do_div(ts
, 1000000000);
974 return snprintf(NULL
, 0, "[%5lu.000000] ", (unsigned long)ts
);
976 return sprintf(buf
, "[%5lu.%06lu] ",
977 (unsigned long)ts
, rem_nsec
/ 1000);
980 static size_t print_prefix(const struct printk_log
*msg
, bool syslog
, char *buf
)
983 unsigned int prefix
= (msg
->facility
<< 3) | msg
->level
;
987 len
+= sprintf(buf
, "<%u>", prefix
);
992 else if (prefix
> 99)
999 len
+= print_time(msg
->ts_nsec
, buf
? buf
+ len
: NULL
);
1003 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1004 bool syslog
, char *buf
, size_t size
)
1006 const char *text
= log_text(msg
);
1007 size_t text_size
= msg
->text_len
;
1009 bool newline
= true;
1012 if ((prev
& LOG_CONT
) && !(msg
->flags
& LOG_PREFIX
))
1015 if (msg
->flags
& LOG_CONT
) {
1016 if ((prev
& LOG_CONT
) && !(prev
& LOG_NEWLINE
))
1019 if (!(msg
->flags
& LOG_NEWLINE
))
1024 const char *next
= memchr(text
, '\n', text_size
);
1028 text_len
= next
- text
;
1030 text_size
-= next
- text
;
1032 text_len
= text_size
;
1036 if (print_prefix(msg
, syslog
, NULL
) +
1037 text_len
+ 1 >= size
- len
)
1041 len
+= print_prefix(msg
, syslog
, buf
+ len
);
1042 memcpy(buf
+ len
, text
, text_len
);
1044 if (next
|| newline
)
1047 /* SYSLOG_ACTION_* buffer size only calculation */
1049 len
+= print_prefix(msg
, syslog
, NULL
);
1051 if (next
|| newline
)
1062 static int syslog_print(char __user
*buf
, int size
)
1065 struct printk_log
*msg
;
1068 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1076 raw_spin_lock_irq(&logbuf_lock
);
1077 if (syslog_seq
< log_first_seq
) {
1078 /* messages are gone, move to first one */
1079 syslog_seq
= log_first_seq
;
1080 syslog_idx
= log_first_idx
;
1084 if (syslog_seq
== log_next_seq
) {
1085 raw_spin_unlock_irq(&logbuf_lock
);
1089 skip
= syslog_partial
;
1090 msg
= log_from_idx(syslog_idx
);
1091 n
= msg_print_text(msg
, syslog_prev
, true, text
,
1092 LOG_LINE_MAX
+ PREFIX_MAX
);
1093 if (n
- syslog_partial
<= size
) {
1094 /* message fits into buffer, move forward */
1095 syslog_idx
= log_next(syslog_idx
);
1097 syslog_prev
= msg
->flags
;
1098 n
-= syslog_partial
;
1101 /* partial read(), remember position */
1103 syslog_partial
+= n
;
1106 raw_spin_unlock_irq(&logbuf_lock
);
1111 if (copy_to_user(buf
, text
+ skip
, n
)) {
1126 static int syslog_print_all(char __user
*buf
, int size
, bool clear
)
1131 text
= kmalloc(LOG_LINE_MAX
+ PREFIX_MAX
, GFP_KERNEL
);
1135 raw_spin_lock_irq(&logbuf_lock
);
1140 enum log_flags prev
;
1142 if (clear_seq
< log_first_seq
) {
1143 /* messages are gone, move to first available one */
1144 clear_seq
= log_first_seq
;
1145 clear_idx
= log_first_idx
;
1149 * Find first record that fits, including all following records,
1150 * into the user-provided buffer for this dump.
1155 while (seq
< log_next_seq
) {
1156 struct printk_log
*msg
= log_from_idx(idx
);
1158 len
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1160 idx
= log_next(idx
);
1164 /* move first record forward until length fits into the buffer */
1168 while (len
> size
&& seq
< log_next_seq
) {
1169 struct printk_log
*msg
= log_from_idx(idx
);
1171 len
-= msg_print_text(msg
, prev
, true, NULL
, 0);
1173 idx
= log_next(idx
);
1177 /* last message fitting into this dump */
1178 next_seq
= log_next_seq
;
1181 while (len
>= 0 && seq
< next_seq
) {
1182 struct printk_log
*msg
= log_from_idx(idx
);
1185 textlen
= msg_print_text(msg
, prev
, true, text
,
1186 LOG_LINE_MAX
+ PREFIX_MAX
);
1191 idx
= log_next(idx
);
1195 raw_spin_unlock_irq(&logbuf_lock
);
1196 if (copy_to_user(buf
+ len
, text
, textlen
))
1200 raw_spin_lock_irq(&logbuf_lock
);
1202 if (seq
< log_first_seq
) {
1203 /* messages are gone, move to next one */
1204 seq
= log_first_seq
;
1205 idx
= log_first_idx
;
1212 clear_seq
= log_next_seq
;
1213 clear_idx
= log_next_idx
;
1215 raw_spin_unlock_irq(&logbuf_lock
);
1221 int do_syslog(int type
, char __user
*buf
, int len
, bool from_file
)
1224 static int saved_console_loglevel
= -1;
1227 error
= check_syslog_permissions(type
, from_file
);
1231 error
= security_syslog(type
);
1236 case SYSLOG_ACTION_CLOSE
: /* Close log */
1238 case SYSLOG_ACTION_OPEN
: /* Open log */
1240 case SYSLOG_ACTION_READ
: /* Read from log */
1242 if (!buf
|| len
< 0)
1247 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1251 error
= wait_event_interruptible(log_wait
,
1252 syslog_seq
!= log_next_seq
);
1255 error
= syslog_print(buf
, len
);
1257 /* Read/clear last kernel messages */
1258 case SYSLOG_ACTION_READ_CLEAR
:
1261 /* Read last kernel messages */
1262 case SYSLOG_ACTION_READ_ALL
:
1264 if (!buf
|| len
< 0)
1269 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
1273 error
= syslog_print_all(buf
, len
, clear
);
1275 /* Clear ring buffer */
1276 case SYSLOG_ACTION_CLEAR
:
1277 syslog_print_all(NULL
, 0, true);
1279 /* Disable logging to console */
1280 case SYSLOG_ACTION_CONSOLE_OFF
:
1281 if (saved_console_loglevel
== -1)
1282 saved_console_loglevel
= console_loglevel
;
1283 console_loglevel
= minimum_console_loglevel
;
1285 /* Enable logging to console */
1286 case SYSLOG_ACTION_CONSOLE_ON
:
1287 if (saved_console_loglevel
!= -1) {
1288 console_loglevel
= saved_console_loglevel
;
1289 saved_console_loglevel
= -1;
1292 /* Set level of messages printed to console */
1293 case SYSLOG_ACTION_CONSOLE_LEVEL
:
1295 if (len
< 1 || len
> 8)
1297 if (len
< minimum_console_loglevel
)
1298 len
= minimum_console_loglevel
;
1299 console_loglevel
= len
;
1300 /* Implicitly re-enable logging to console */
1301 saved_console_loglevel
= -1;
1304 /* Number of chars in the log buffer */
1305 case SYSLOG_ACTION_SIZE_UNREAD
:
1306 raw_spin_lock_irq(&logbuf_lock
);
1307 if (syslog_seq
< log_first_seq
) {
1308 /* messages are gone, move to first one */
1309 syslog_seq
= log_first_seq
;
1310 syslog_idx
= log_first_idx
;
1316 * Short-cut for poll(/"proc/kmsg") which simply checks
1317 * for pending data, not the size; return the count of
1318 * records, not the length.
1320 error
= log_next_idx
- syslog_idx
;
1322 u64 seq
= syslog_seq
;
1323 u32 idx
= syslog_idx
;
1324 enum log_flags prev
= syslog_prev
;
1327 while (seq
< log_next_seq
) {
1328 struct printk_log
*msg
= log_from_idx(idx
);
1330 error
+= msg_print_text(msg
, prev
, true, NULL
, 0);
1331 idx
= log_next(idx
);
1335 error
-= syslog_partial
;
1337 raw_spin_unlock_irq(&logbuf_lock
);
1339 /* Size of the log buffer */
1340 case SYSLOG_ACTION_SIZE_BUFFER
:
1341 error
= log_buf_len
;
1351 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
1353 return do_syslog(type
, buf
, len
, SYSLOG_FROM_READER
);
1357 * Call the console drivers, asking them to write out
1358 * log_buf[start] to log_buf[end - 1].
1359 * The console_lock must be held.
1361 static void call_console_drivers(int level
, const char *text
, size_t len
)
1363 struct console
*con
;
1365 trace_console(text
, len
);
1367 if (level
>= console_loglevel
&& !ignore_loglevel
)
1369 if (!console_drivers
)
1372 for_each_console(con
) {
1373 if (exclusive_console
&& con
!= exclusive_console
)
1375 if (!(con
->flags
& CON_ENABLED
))
1379 if (!cpu_online(smp_processor_id()) &&
1380 !(con
->flags
& CON_ANYTIME
))
1382 con
->write(con
, text
, len
);
1387 * Zap console related locks when oopsing. Only zap at most once
1388 * every 10 seconds, to leave time for slow consoles to print a
1391 static void zap_locks(void)
1393 static unsigned long oops_timestamp
;
1395 if (time_after_eq(jiffies
, oops_timestamp
) &&
1396 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
1399 oops_timestamp
= jiffies
;
1402 /* If a crash is occurring, make sure we can't deadlock */
1403 raw_spin_lock_init(&logbuf_lock
);
1404 /* And make sure that we print immediately */
1405 sema_init(&console_sem
, 1);
1409 * Check if we have any console that is capable of printing while cpu is
1410 * booting or shutting down. Requires console_sem.
1412 static int have_callable_console(void)
1414 struct console
*con
;
1416 for_each_console(con
)
1417 if (con
->flags
& CON_ANYTIME
)
1424 * Can we actually use the console at this time on this cpu?
1426 * Console drivers may assume that per-cpu resources have been allocated. So
1427 * unless they're explicitly marked as being able to cope (CON_ANYTIME) don't
1428 * call them until this CPU is officially up.
1430 static inline int can_use_console(unsigned int cpu
)
1432 return cpu_online(cpu
) || have_callable_console();
1436 * Try to get console ownership to actually show the kernel
1437 * messages from a 'printk'. Return true (and with the
1438 * console_lock held, and 'console_locked' set) if it
1439 * is successful, false otherwise.
1441 static int console_trylock_for_printk(void)
1443 unsigned int cpu
= smp_processor_id();
1445 if (!console_trylock())
1448 * If we can't use the console, we need to release the console
1449 * semaphore by hand to avoid flushing the buffer. We need to hold the
1450 * console semaphore in order to do this test safely.
1452 if (!can_use_console(cpu
)) {
1460 int printk_delay_msec __read_mostly
;
1462 static inline void printk_delay(void)
1464 if (unlikely(printk_delay_msec
)) {
1465 int m
= printk_delay_msec
;
1469 touch_nmi_watchdog();
1475 * Continuation lines are buffered, and not committed to the record buffer
1476 * until the line is complete, or a race forces it. The line fragments
1477 * though, are printed immediately to the consoles to ensure everything has
1478 * reached the console in case of a kernel crash.
1480 static struct cont
{
1481 char buf
[LOG_LINE_MAX
];
1482 size_t len
; /* length == 0 means unused buffer */
1483 size_t cons
; /* bytes written to console */
1484 struct task_struct
*owner
; /* task of first print*/
1485 u64 ts_nsec
; /* time of first print */
1486 u8 level
; /* log level of first message */
1487 u8 facility
; /* log level of first message */
1488 enum log_flags flags
; /* prefix, newline flags */
1489 bool flushed
:1; /* buffer sealed and committed */
1492 static void cont_flush(enum log_flags flags
)
1501 * If a fragment of this line was directly flushed to the
1502 * console; wait for the console to pick up the rest of the
1503 * line. LOG_NOCONS suppresses a duplicated output.
1505 log_store(cont
.facility
, cont
.level
, flags
| LOG_NOCONS
,
1506 cont
.ts_nsec
, NULL
, 0, cont
.buf
, cont
.len
);
1508 cont
.flushed
= true;
1511 * If no fragment of this line ever reached the console,
1512 * just submit it to the store and free the buffer.
1514 log_store(cont
.facility
, cont
.level
, flags
, 0,
1515 NULL
, 0, cont
.buf
, cont
.len
);
1520 static bool cont_add(int facility
, int level
, const char *text
, size_t len
)
1522 if (cont
.len
&& cont
.flushed
)
1525 if (cont
.len
+ len
> sizeof(cont
.buf
)) {
1526 /* the line gets too long, split it up in separate records */
1527 cont_flush(LOG_CONT
);
1532 cont
.facility
= facility
;
1534 cont
.owner
= current
;
1535 cont
.ts_nsec
= local_clock();
1538 cont
.flushed
= false;
1541 memcpy(cont
.buf
+ cont
.len
, text
, len
);
1544 if (cont
.len
> (sizeof(cont
.buf
) * 80) / 100)
1545 cont_flush(LOG_CONT
);
1550 static size_t cont_print_text(char *text
, size_t size
)
1555 if (cont
.cons
== 0 && (console_prev
& LOG_NEWLINE
)) {
1556 textlen
+= print_time(cont
.ts_nsec
, text
);
1560 len
= cont
.len
- cont
.cons
;
1564 memcpy(text
+ textlen
, cont
.buf
+ cont
.cons
, len
);
1566 cont
.cons
= cont
.len
;
1570 if (cont
.flags
& LOG_NEWLINE
)
1571 text
[textlen
++] = '\n';
1572 /* got everything, release buffer */
1578 asmlinkage
int vprintk_emit(int facility
, int level
,
1579 const char *dict
, size_t dictlen
,
1580 const char *fmt
, va_list args
)
1582 static int recursion_bug
;
1583 static char textbuf
[LOG_LINE_MAX
];
1584 char *text
= textbuf
;
1585 size_t text_len
= 0;
1586 enum log_flags lflags
= 0;
1587 unsigned long flags
;
1589 int printed_len
= 0;
1590 bool in_sched
= false;
1591 /* cpu currently holding logbuf_lock in this function */
1592 static volatile unsigned int logbuf_cpu
= UINT_MAX
;
1594 if (level
== SCHED_MESSAGE_LOGLEVEL
) {
1599 boot_delay_msec(level
);
1602 /* This stops the holder of console_sem just where we want him */
1603 local_irq_save(flags
);
1604 this_cpu
= smp_processor_id();
1607 * Ouch, printk recursed into itself!
1609 if (unlikely(logbuf_cpu
== this_cpu
)) {
1611 * If a crash is occurring during printk() on this CPU,
1612 * then try to get the crash message out but make sure
1613 * we can't deadlock. Otherwise just return to avoid the
1614 * recursion and return - but flag the recursion so that
1615 * it can be printed at the next appropriate moment:
1617 if (!oops_in_progress
&& !lockdep_recursing(current
)) {
1619 local_irq_restore(flags
);
1626 raw_spin_lock(&logbuf_lock
);
1627 logbuf_cpu
= this_cpu
;
1629 if (recursion_bug
) {
1630 static const char recursion_msg
[] =
1631 "BUG: recent printk recursion!";
1634 text_len
= strlen(recursion_msg
);
1635 /* emit KERN_CRIT message */
1636 printed_len
+= log_store(0, 2, LOG_PREFIX
|LOG_NEWLINE
, 0,
1637 NULL
, 0, recursion_msg
, text_len
);
1641 * The printf needs to come first; we need the syslog
1642 * prefix which might be passed-in as a parameter.
1645 text_len
= scnprintf(text
, sizeof(textbuf
),
1646 KERN_WARNING
"[sched_delayed] ");
1648 text_len
+= vscnprintf(text
+ text_len
,
1649 sizeof(textbuf
) - text_len
, fmt
, args
);
1651 /* mark and strip a trailing newline */
1652 if (text_len
&& text
[text_len
-1] == '\n') {
1654 lflags
|= LOG_NEWLINE
;
1657 /* strip kernel syslog prefix and extract log level or control flags */
1658 if (facility
== 0) {
1659 int kern_level
= printk_get_level(text
);
1662 const char *end_of_header
= printk_skip_level(text
);
1663 switch (kern_level
) {
1666 level
= kern_level
- '0';
1667 case 'd': /* KERN_DEFAULT */
1668 lflags
|= LOG_PREFIX
;
1671 * No need to check length here because vscnprintf
1672 * put '\0' at the end of the string. Only valid and
1673 * newly printed level is detected.
1675 text_len
-= end_of_header
- text
;
1676 text
= (char *)end_of_header
;
1681 level
= default_message_loglevel
;
1684 lflags
|= LOG_PREFIX
|LOG_NEWLINE
;
1686 if (!(lflags
& LOG_NEWLINE
)) {
1688 * Flush the conflicting buffer. An earlier newline was missing,
1689 * or another task also prints continuation lines.
1691 if (cont
.len
&& (lflags
& LOG_PREFIX
|| cont
.owner
!= current
))
1692 cont_flush(LOG_NEWLINE
);
1694 /* buffer line if possible, otherwise store it right away */
1695 if (cont_add(facility
, level
, text
, text_len
))
1696 printed_len
+= text_len
;
1698 printed_len
+= log_store(facility
, level
,
1699 lflags
| LOG_CONT
, 0,
1700 dict
, dictlen
, text
, text_len
);
1702 bool stored
= false;
1705 * If an earlier newline was missing and it was the same task,
1706 * either merge it with the current buffer and flush, or if
1707 * there was a race with interrupts (prefix == true) then just
1708 * flush it out and store this line separately.
1709 * If the preceding printk was from a different task and missed
1710 * a newline, flush and append the newline.
1713 if (cont
.owner
== current
&& !(lflags
& LOG_PREFIX
))
1714 stored
= cont_add(facility
, level
, text
,
1716 cont_flush(LOG_NEWLINE
);
1720 printed_len
+= text_len
;
1722 printed_len
+= log_store(facility
, level
, lflags
, 0,
1723 dict
, dictlen
, text
, text_len
);
1726 logbuf_cpu
= UINT_MAX
;
1727 raw_spin_unlock(&logbuf_lock
);
1729 local_irq_restore(flags
);
1731 /* If called from the scheduler, we can not call up(). */
1736 * Disable preemption to avoid being preempted while holding
1737 * console_sem which would prevent anyone from printing to console
1741 * Try to acquire and then immediately release the console semaphore.
1742 * The release will print out buffers and wake up /dev/kmsg and syslog()
1745 if (console_trylock_for_printk())
1751 EXPORT_SYMBOL(vprintk_emit
);
1753 asmlinkage
int vprintk(const char *fmt
, va_list args
)
1755 return vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1757 EXPORT_SYMBOL(vprintk
);
1759 asmlinkage
int printk_emit(int facility
, int level
,
1760 const char *dict
, size_t dictlen
,
1761 const char *fmt
, ...)
1766 va_start(args
, fmt
);
1767 r
= vprintk_emit(facility
, level
, dict
, dictlen
, fmt
, args
);
1772 EXPORT_SYMBOL(printk_emit
);
1775 * printk - print a kernel message
1776 * @fmt: format string
1778 * This is printk(). It can be called from any context. We want it to work.
1780 * We try to grab the console_lock. If we succeed, it's easy - we log the
1781 * output and call the console drivers. If we fail to get the semaphore, we
1782 * place the output into the log buffer and return. The current holder of
1783 * the console_sem will notice the new output in console_unlock(); and will
1784 * send it to the consoles before releasing the lock.
1786 * One effect of this deferred printing is that code which calls printk() and
1787 * then changes console_loglevel may break. This is because console_loglevel
1788 * is inspected when the actual printing occurs.
1793 * See the vsnprintf() documentation for format string extensions over C99.
1795 asmlinkage __visible
int printk(const char *fmt
, ...)
1800 #ifdef CONFIG_KGDB_KDB
1801 if (unlikely(kdb_trap_printk
)) {
1802 va_start(args
, fmt
);
1803 r
= vkdb_printf(fmt
, args
);
1808 va_start(args
, fmt
);
1809 r
= vprintk_emit(0, -1, NULL
, 0, fmt
, args
);
1814 EXPORT_SYMBOL(printk
);
1816 #else /* CONFIG_PRINTK */
1818 #define LOG_LINE_MAX 0
1819 #define PREFIX_MAX 0
1820 #define LOG_LINE_MAX 0
1821 static u64 syslog_seq
;
1822 static u32 syslog_idx
;
1823 static u64 console_seq
;
1824 static u32 console_idx
;
1825 static enum log_flags syslog_prev
;
1826 static u64 log_first_seq
;
1827 static u32 log_first_idx
;
1828 static u64 log_next_seq
;
1829 static enum log_flags console_prev
;
1830 static struct cont
{
1836 static struct printk_log
*log_from_idx(u32 idx
) { return NULL
; }
1837 static u32
log_next(u32 idx
) { return 0; }
1838 static void call_console_drivers(int level
, const char *text
, size_t len
) {}
1839 static size_t msg_print_text(const struct printk_log
*msg
, enum log_flags prev
,
1840 bool syslog
, char *buf
, size_t size
) { return 0; }
1841 static size_t cont_print_text(char *text
, size_t size
) { return 0; }
1843 #endif /* CONFIG_PRINTK */
1845 #ifdef CONFIG_EARLY_PRINTK
1846 struct console
*early_console
;
1848 void early_vprintk(const char *fmt
, va_list ap
)
1850 if (early_console
) {
1852 int n
= vscnprintf(buf
, sizeof(buf
), fmt
, ap
);
1854 early_console
->write(early_console
, buf
, n
);
1858 asmlinkage __visible
void early_printk(const char *fmt
, ...)
1863 early_vprintk(fmt
, ap
);
1868 static int __add_preferred_console(char *name
, int idx
, char *options
,
1871 struct console_cmdline
*c
;
1875 * See if this tty is not yet registered, and
1876 * if we have a slot free.
1878 for (i
= 0, c
= console_cmdline
;
1879 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1881 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
1883 selected_console
= i
;
1887 if (i
== MAX_CMDLINECONSOLES
)
1890 selected_console
= i
;
1891 strlcpy(c
->name
, name
, sizeof(c
->name
));
1892 c
->options
= options
;
1893 braille_set_options(c
, brl_options
);
1899 * Set up a list of consoles. Called from init/main.c
1901 static int __init
console_setup(char *str
)
1903 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
1904 char *s
, *options
, *brl_options
= NULL
;
1907 if (_braille_console_setup(&str
, &brl_options
))
1911 * Decode str into name, index, options.
1913 if (str
[0] >= '0' && str
[0] <= '9') {
1914 strcpy(buf
, "ttyS");
1915 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
1917 strncpy(buf
, str
, sizeof(buf
) - 1);
1919 buf
[sizeof(buf
) - 1] = 0;
1920 if ((options
= strchr(str
, ',')) != NULL
)
1923 if (!strcmp(str
, "ttya"))
1924 strcpy(buf
, "ttyS0");
1925 if (!strcmp(str
, "ttyb"))
1926 strcpy(buf
, "ttyS1");
1928 for (s
= buf
; *s
; s
++)
1929 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
1931 idx
= simple_strtoul(s
, NULL
, 10);
1934 __add_preferred_console(buf
, idx
, options
, brl_options
);
1935 console_set_on_cmdline
= 1;
1938 __setup("console=", console_setup
);
1941 * add_preferred_console - add a device to the list of preferred consoles.
1942 * @name: device name
1943 * @idx: device index
1944 * @options: options for this console
1946 * The last preferred console added will be used for kernel messages
1947 * and stdin/out/err for init. Normally this is used by console_setup
1948 * above to handle user-supplied console arguments; however it can also
1949 * be used by arch-specific code either to override the user or more
1950 * commonly to provide a default console (ie from PROM variables) when
1951 * the user has not supplied one.
1953 int add_preferred_console(char *name
, int idx
, char *options
)
1955 return __add_preferred_console(name
, idx
, options
, NULL
);
1958 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
1960 struct console_cmdline
*c
;
1963 for (i
= 0, c
= console_cmdline
;
1964 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
1966 if (strcmp(c
->name
, name
) == 0 && c
->index
== idx
) {
1967 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
1968 c
->name
[sizeof(c
->name
) - 1] = 0;
1969 c
->options
= options
;
1977 bool console_suspend_enabled
= 1;
1978 EXPORT_SYMBOL(console_suspend_enabled
);
1980 static int __init
console_suspend_disable(char *str
)
1982 console_suspend_enabled
= 0;
1985 __setup("no_console_suspend", console_suspend_disable
);
1986 module_param_named(console_suspend
, console_suspend_enabled
,
1987 bool, S_IRUGO
| S_IWUSR
);
1988 MODULE_PARM_DESC(console_suspend
, "suspend console during suspend"
1989 " and hibernate operations");
1992 * suspend_console - suspend the console subsystem
1994 * This disables printk() while we go into suspend states
1996 void suspend_console(void)
1998 if (!console_suspend_enabled
)
2000 printk("Suspending console(s) (use no_console_suspend to debug)\n");
2002 console_suspended
= 1;
2006 void resume_console(void)
2008 if (!console_suspend_enabled
)
2011 console_suspended
= 0;
2016 * console_cpu_notify - print deferred console messages after CPU hotplug
2017 * @self: notifier struct
2018 * @action: CPU hotplug event
2021 * If printk() is called from a CPU that is not online yet, the messages
2022 * will be spooled but will not show up on the console. This function is
2023 * called when a new CPU comes online (or fails to come up), and ensures
2024 * that any such output gets printed.
2026 static int console_cpu_notify(struct notifier_block
*self
,
2027 unsigned long action
, void *hcpu
)
2032 case CPU_DOWN_FAILED
:
2033 case CPU_UP_CANCELED
:
2041 * console_lock - lock the console system for exclusive use.
2043 * Acquires a lock which guarantees that the caller has
2044 * exclusive access to the console system and the console_drivers list.
2046 * Can sleep, returns nothing.
2048 void console_lock(void)
2053 if (console_suspended
)
2056 console_may_schedule
= 1;
2058 EXPORT_SYMBOL(console_lock
);
2061 * console_trylock - try to lock the console system for exclusive use.
2063 * Tried to acquire a lock which guarantees that the caller has
2064 * exclusive access to the console system and the console_drivers list.
2066 * returns 1 on success, and 0 on failure to acquire the lock.
2068 int console_trylock(void)
2070 if (down_trylock_console_sem())
2072 if (console_suspended
) {
2077 console_may_schedule
= 0;
2080 EXPORT_SYMBOL(console_trylock
);
2082 int is_console_locked(void)
2084 return console_locked
;
2087 static void console_cont_flush(char *text
, size_t size
)
2089 unsigned long flags
;
2092 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2098 * We still queue earlier records, likely because the console was
2099 * busy. The earlier ones need to be printed before this one, we
2100 * did not flush any fragment so far, so just let it queue up.
2102 if (console_seq
< log_next_seq
&& !cont
.cons
)
2105 len
= cont_print_text(text
, size
);
2106 raw_spin_unlock(&logbuf_lock
);
2107 stop_critical_timings();
2108 call_console_drivers(cont
.level
, text
, len
);
2109 start_critical_timings();
2110 local_irq_restore(flags
);
2113 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2117 * console_unlock - unlock the console system
2119 * Releases the console_lock which the caller holds on the console system
2120 * and the console driver list.
2122 * While the console_lock was held, console output may have been buffered
2123 * by printk(). If this is the case, console_unlock(); emits
2124 * the output prior to releasing the lock.
2126 * If there is output waiting, we wake /dev/kmsg and syslog() users.
2128 * console_unlock(); may be called from any context.
2130 void console_unlock(void)
2132 static char text
[LOG_LINE_MAX
+ PREFIX_MAX
];
2133 static u64 seen_seq
;
2134 unsigned long flags
;
2135 bool wake_klogd
= false;
2138 if (console_suspended
) {
2143 console_may_schedule
= 0;
2145 /* flush buffered message fragment immediately to console */
2146 console_cont_flush(text
, sizeof(text
));
2149 struct printk_log
*msg
;
2153 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2154 if (seen_seq
!= log_next_seq
) {
2156 seen_seq
= log_next_seq
;
2159 if (console_seq
< log_first_seq
) {
2160 len
= sprintf(text
, "** %u printk messages dropped ** ",
2161 (unsigned)(log_first_seq
- console_seq
));
2163 /* messages are gone, move to first one */
2164 console_seq
= log_first_seq
;
2165 console_idx
= log_first_idx
;
2171 if (console_seq
== log_next_seq
)
2174 msg
= log_from_idx(console_idx
);
2175 if (msg
->flags
& LOG_NOCONS
) {
2177 * Skip record we have buffered and already printed
2178 * directly to the console when we received it.
2180 console_idx
= log_next(console_idx
);
2183 * We will get here again when we register a new
2184 * CON_PRINTBUFFER console. Clear the flag so we
2185 * will properly dump everything later.
2187 msg
->flags
&= ~LOG_NOCONS
;
2188 console_prev
= msg
->flags
;
2193 len
+= msg_print_text(msg
, console_prev
, false,
2194 text
+ len
, sizeof(text
) - len
);
2195 console_idx
= log_next(console_idx
);
2197 console_prev
= msg
->flags
;
2198 raw_spin_unlock(&logbuf_lock
);
2200 stop_critical_timings(); /* don't trace print latency */
2201 call_console_drivers(level
, text
, len
);
2202 start_critical_timings();
2203 local_irq_restore(flags
);
2207 /* Release the exclusive_console once it is used */
2208 if (unlikely(exclusive_console
))
2209 exclusive_console
= NULL
;
2211 raw_spin_unlock(&logbuf_lock
);
2216 * Someone could have filled up the buffer again, so re-check if there's
2217 * something to flush. In case we cannot trylock the console_sem again,
2218 * there's a new owner and the console_unlock() from them will do the
2219 * flush, no worries.
2221 raw_spin_lock(&logbuf_lock
);
2222 retry
= console_seq
!= log_next_seq
;
2223 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2225 if (retry
&& console_trylock())
2231 EXPORT_SYMBOL(console_unlock
);
2234 * console_conditional_schedule - yield the CPU if required
2236 * If the console code is currently allowed to sleep, and
2237 * if this CPU should yield the CPU to another task, do
2240 * Must be called within console_lock();.
2242 void __sched
console_conditional_schedule(void)
2244 if (console_may_schedule
)
2247 EXPORT_SYMBOL(console_conditional_schedule
);
2249 void console_unblank(void)
2254 * console_unblank can no longer be called in interrupt context unless
2255 * oops_in_progress is set to 1..
2257 if (oops_in_progress
) {
2258 if (down_trylock_console_sem() != 0)
2264 console_may_schedule
= 0;
2266 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
2272 * Return the console tty driver structure and its associated index
2274 struct tty_driver
*console_device(int *index
)
2277 struct tty_driver
*driver
= NULL
;
2280 for_each_console(c
) {
2283 driver
= c
->device(c
, index
);
2292 * Prevent further output on the passed console device so that (for example)
2293 * serial drivers can disable console output before suspending a port, and can
2294 * re-enable output afterwards.
2296 void console_stop(struct console
*console
)
2299 console
->flags
&= ~CON_ENABLED
;
2302 EXPORT_SYMBOL(console_stop
);
2304 void console_start(struct console
*console
)
2307 console
->flags
|= CON_ENABLED
;
2310 EXPORT_SYMBOL(console_start
);
2312 static int __read_mostly keep_bootcon
;
2314 static int __init
keep_bootcon_setup(char *str
)
2317 pr_info("debug: skip boot console de-registration.\n");
2322 early_param("keep_bootcon", keep_bootcon_setup
);
2325 * The console driver calls this routine during kernel initialization
2326 * to register the console printing procedure with printk() and to
2327 * print any messages that were printed by the kernel before the
2328 * console driver was initialized.
2330 * This can happen pretty early during the boot process (because of
2331 * early_printk) - sometimes before setup_arch() completes - be careful
2332 * of what kernel features are used - they may not be initialised yet.
2334 * There are two types of consoles - bootconsoles (early_printk) and
2335 * "real" consoles (everything which is not a bootconsole) which are
2336 * handled differently.
2337 * - Any number of bootconsoles can be registered at any time.
2338 * - As soon as a "real" console is registered, all bootconsoles
2339 * will be unregistered automatically.
2340 * - Once a "real" console is registered, any attempt to register a
2341 * bootconsoles will be rejected
2343 void register_console(struct console
*newcon
)
2346 unsigned long flags
;
2347 struct console
*bcon
= NULL
;
2348 struct console_cmdline
*c
;
2350 if (console_drivers
)
2351 for_each_console(bcon
)
2352 if (WARN(bcon
== newcon
,
2353 "console '%s%d' already registered\n",
2354 bcon
->name
, bcon
->index
))
2358 * before we register a new CON_BOOT console, make sure we don't
2359 * already have a valid console
2361 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
2362 /* find the last or real console */
2363 for_each_console(bcon
) {
2364 if (!(bcon
->flags
& CON_BOOT
)) {
2365 pr_info("Too late to register bootconsole %s%d\n",
2366 newcon
->name
, newcon
->index
);
2372 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
2373 bcon
= console_drivers
;
2375 if (preferred_console
< 0 || bcon
|| !console_drivers
)
2376 preferred_console
= selected_console
;
2378 if (newcon
->early_setup
)
2379 newcon
->early_setup();
2382 * See if we want to use this console driver. If we
2383 * didn't select a console we take the first one
2384 * that registers here.
2386 if (preferred_console
< 0) {
2387 if (newcon
->index
< 0)
2389 if (newcon
->setup
== NULL
||
2390 newcon
->setup(newcon
, NULL
) == 0) {
2391 newcon
->flags
|= CON_ENABLED
;
2392 if (newcon
->device
) {
2393 newcon
->flags
|= CON_CONSDEV
;
2394 preferred_console
= 0;
2400 * See if this console matches one we selected on
2403 for (i
= 0, c
= console_cmdline
;
2404 i
< MAX_CMDLINECONSOLES
&& c
->name
[0];
2406 if (strcmp(c
->name
, newcon
->name
) != 0)
2408 if (newcon
->index
>= 0 &&
2409 newcon
->index
!= c
->index
)
2411 if (newcon
->index
< 0)
2412 newcon
->index
= c
->index
;
2414 if (_braille_register_console(newcon
, c
))
2417 if (newcon
->setup
&&
2418 newcon
->setup(newcon
, console_cmdline
[i
].options
) != 0)
2420 newcon
->flags
|= CON_ENABLED
;
2421 newcon
->index
= c
->index
;
2422 if (i
== selected_console
) {
2423 newcon
->flags
|= CON_CONSDEV
;
2424 preferred_console
= selected_console
;
2429 if (!(newcon
->flags
& CON_ENABLED
))
2433 * If we have a bootconsole, and are switching to a real console,
2434 * don't print everything out again, since when the boot console, and
2435 * the real console are the same physical device, it's annoying to
2436 * see the beginning boot messages twice
2438 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
2439 newcon
->flags
&= ~CON_PRINTBUFFER
;
2442 * Put this console in the list - keep the
2443 * preferred driver at the head of the list.
2446 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
2447 newcon
->next
= console_drivers
;
2448 console_drivers
= newcon
;
2450 newcon
->next
->flags
&= ~CON_CONSDEV
;
2452 newcon
->next
= console_drivers
->next
;
2453 console_drivers
->next
= newcon
;
2455 if (newcon
->flags
& CON_PRINTBUFFER
) {
2457 * console_unlock(); will print out the buffered messages
2460 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2461 console_seq
= syslog_seq
;
2462 console_idx
= syslog_idx
;
2463 console_prev
= syslog_prev
;
2464 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2466 * We're about to replay the log buffer. Only do this to the
2467 * just-registered console to avoid excessive message spam to
2468 * the already-registered consoles.
2470 exclusive_console
= newcon
;
2473 console_sysfs_notify();
2476 * By unregistering the bootconsoles after we enable the real console
2477 * we get the "console xxx enabled" message on all the consoles -
2478 * boot consoles, real consoles, etc - this is to ensure that end
2479 * users know there might be something in the kernel's log buffer that
2480 * went to the bootconsole (that they do not see on the real console)
2482 pr_info("%sconsole [%s%d] enabled\n",
2483 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
2484 newcon
->name
, newcon
->index
);
2486 ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
) &&
2488 /* We need to iterate through all boot consoles, to make
2489 * sure we print everything out, before we unregister them.
2491 for_each_console(bcon
)
2492 if (bcon
->flags
& CON_BOOT
)
2493 unregister_console(bcon
);
2496 EXPORT_SYMBOL(register_console
);
2498 int unregister_console(struct console
*console
)
2500 struct console
*a
, *b
;
2503 pr_info("%sconsole [%s%d] disabled\n",
2504 (console
->flags
& CON_BOOT
) ? "boot" : "" ,
2505 console
->name
, console
->index
);
2507 res
= _braille_unregister_console(console
);
2513 if (console_drivers
== console
) {
2514 console_drivers
=console
->next
;
2516 } else if (console_drivers
) {
2517 for (a
=console_drivers
->next
, b
=console_drivers
;
2518 a
; b
=a
, a
=b
->next
) {
2528 * If this isn't the last console and it has CON_CONSDEV set, we
2529 * need to set it on the next preferred console.
2531 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
2532 console_drivers
->flags
|= CON_CONSDEV
;
2534 console
->flags
&= ~CON_ENABLED
;
2536 console_sysfs_notify();
2539 EXPORT_SYMBOL(unregister_console
);
2541 static int __init
printk_late_init(void)
2543 struct console
*con
;
2545 for_each_console(con
) {
2546 if (!keep_bootcon
&& con
->flags
& CON_BOOT
) {
2547 unregister_console(con
);
2550 hotcpu_notifier(console_cpu_notify
, 0);
2553 late_initcall(printk_late_init
);
2555 #if defined CONFIG_PRINTK
2557 * Delayed printk version, for scheduler-internal messages:
2559 #define PRINTK_PENDING_WAKEUP 0x01
2560 #define PRINTK_PENDING_OUTPUT 0x02
2562 static DEFINE_PER_CPU(int, printk_pending
);
2564 static void wake_up_klogd_work_func(struct irq_work
*irq_work
)
2566 int pending
= __this_cpu_xchg(printk_pending
, 0);
2568 if (pending
& PRINTK_PENDING_OUTPUT
) {
2569 /* If trylock fails, someone else is doing the printing */
2570 if (console_trylock())
2574 if (pending
& PRINTK_PENDING_WAKEUP
)
2575 wake_up_interruptible(&log_wait
);
2578 static DEFINE_PER_CPU(struct irq_work
, wake_up_klogd_work
) = {
2579 .func
= wake_up_klogd_work_func
,
2580 .flags
= IRQ_WORK_LAZY
,
2583 void wake_up_klogd(void)
2586 if (waitqueue_active(&log_wait
)) {
2587 this_cpu_or(printk_pending
, PRINTK_PENDING_WAKEUP
);
2588 irq_work_queue(&__get_cpu_var(wake_up_klogd_work
));
2593 int printk_deferred(const char *fmt
, ...)
2599 va_start(args
, fmt
);
2600 r
= vprintk_emit(0, SCHED_MESSAGE_LOGLEVEL
, NULL
, 0, fmt
, args
);
2603 __this_cpu_or(printk_pending
, PRINTK_PENDING_OUTPUT
);
2604 irq_work_queue(&__get_cpu_var(wake_up_klogd_work
));
2611 * printk rate limiting, lifted from the networking subsystem.
2613 * This enforces a rate limit: not more than 10 kernel messages
2614 * every 5s to make a denial-of-service attack impossible.
2616 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
2618 int __printk_ratelimit(const char *func
)
2620 return ___ratelimit(&printk_ratelimit_state
, func
);
2622 EXPORT_SYMBOL(__printk_ratelimit
);
2625 * printk_timed_ratelimit - caller-controlled printk ratelimiting
2626 * @caller_jiffies: pointer to caller's state
2627 * @interval_msecs: minimum interval between prints
2629 * printk_timed_ratelimit() returns true if more than @interval_msecs
2630 * milliseconds have elapsed since the last time printk_timed_ratelimit()
2633 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
2634 unsigned int interval_msecs
)
2636 if (*caller_jiffies
== 0
2637 || !time_in_range(jiffies
, *caller_jiffies
,
2639 + msecs_to_jiffies(interval_msecs
))) {
2640 *caller_jiffies
= jiffies
;
2645 EXPORT_SYMBOL(printk_timed_ratelimit
);
2647 static DEFINE_SPINLOCK(dump_list_lock
);
2648 static LIST_HEAD(dump_list
);
2651 * kmsg_dump_register - register a kernel log dumper.
2652 * @dumper: pointer to the kmsg_dumper structure
2654 * Adds a kernel log dumper to the system. The dump callback in the
2655 * structure will be called when the kernel oopses or panics and must be
2656 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
2658 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
2660 unsigned long flags
;
2663 /* The dump callback needs to be set */
2667 spin_lock_irqsave(&dump_list_lock
, flags
);
2668 /* Don't allow registering multiple times */
2669 if (!dumper
->registered
) {
2670 dumper
->registered
= 1;
2671 list_add_tail_rcu(&dumper
->list
, &dump_list
);
2674 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2678 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
2681 * kmsg_dump_unregister - unregister a kmsg dumper.
2682 * @dumper: pointer to the kmsg_dumper structure
2684 * Removes a dump device from the system. Returns zero on success and
2685 * %-EINVAL otherwise.
2687 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
2689 unsigned long flags
;
2692 spin_lock_irqsave(&dump_list_lock
, flags
);
2693 if (dumper
->registered
) {
2694 dumper
->registered
= 0;
2695 list_del_rcu(&dumper
->list
);
2698 spin_unlock_irqrestore(&dump_list_lock
, flags
);
2703 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
2705 static bool always_kmsg_dump
;
2706 module_param_named(always_kmsg_dump
, always_kmsg_dump
, bool, S_IRUGO
| S_IWUSR
);
2709 * kmsg_dump - dump kernel log to kernel message dumpers.
2710 * @reason: the reason (oops, panic etc) for dumping
2712 * Call each of the registered dumper's dump() callback, which can
2713 * retrieve the kmsg records with kmsg_dump_get_line() or
2714 * kmsg_dump_get_buffer().
2716 void kmsg_dump(enum kmsg_dump_reason reason
)
2718 struct kmsg_dumper
*dumper
;
2719 unsigned long flags
;
2721 if ((reason
> KMSG_DUMP_OOPS
) && !always_kmsg_dump
)
2725 list_for_each_entry_rcu(dumper
, &dump_list
, list
) {
2726 if (dumper
->max_reason
&& reason
> dumper
->max_reason
)
2729 /* initialize iterator with data about the stored records */
2730 dumper
->active
= true;
2732 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2733 dumper
->cur_seq
= clear_seq
;
2734 dumper
->cur_idx
= clear_idx
;
2735 dumper
->next_seq
= log_next_seq
;
2736 dumper
->next_idx
= log_next_idx
;
2737 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2739 /* invoke dumper which will iterate over records */
2740 dumper
->dump(dumper
, reason
);
2742 /* reset iterator */
2743 dumper
->active
= false;
2749 * kmsg_dump_get_line_nolock - retrieve one kmsg log line (unlocked version)
2750 * @dumper: registered kmsg dumper
2751 * @syslog: include the "<4>" prefixes
2752 * @line: buffer to copy the line to
2753 * @size: maximum size of the buffer
2754 * @len: length of line placed into buffer
2756 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2757 * record, and copy one record into the provided buffer.
2759 * Consecutive calls will return the next available record moving
2760 * towards the end of the buffer with the youngest messages.
2762 * A return value of FALSE indicates that there are no more records to
2765 * The function is similar to kmsg_dump_get_line(), but grabs no locks.
2767 bool kmsg_dump_get_line_nolock(struct kmsg_dumper
*dumper
, bool syslog
,
2768 char *line
, size_t size
, size_t *len
)
2770 struct printk_log
*msg
;
2774 if (!dumper
->active
)
2777 if (dumper
->cur_seq
< log_first_seq
) {
2778 /* messages are gone, move to first available one */
2779 dumper
->cur_seq
= log_first_seq
;
2780 dumper
->cur_idx
= log_first_idx
;
2784 if (dumper
->cur_seq
>= log_next_seq
)
2787 msg
= log_from_idx(dumper
->cur_idx
);
2788 l
= msg_print_text(msg
, 0, syslog
, line
, size
);
2790 dumper
->cur_idx
= log_next(dumper
->cur_idx
);
2800 * kmsg_dump_get_line - retrieve one kmsg log line
2801 * @dumper: registered kmsg dumper
2802 * @syslog: include the "<4>" prefixes
2803 * @line: buffer to copy the line to
2804 * @size: maximum size of the buffer
2805 * @len: length of line placed into buffer
2807 * Start at the beginning of the kmsg buffer, with the oldest kmsg
2808 * record, and copy one record into the provided buffer.
2810 * Consecutive calls will return the next available record moving
2811 * towards the end of the buffer with the youngest messages.
2813 * A return value of FALSE indicates that there are no more records to
2816 bool kmsg_dump_get_line(struct kmsg_dumper
*dumper
, bool syslog
,
2817 char *line
, size_t size
, size_t *len
)
2819 unsigned long flags
;
2822 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2823 ret
= kmsg_dump_get_line_nolock(dumper
, syslog
, line
, size
, len
);
2824 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2828 EXPORT_SYMBOL_GPL(kmsg_dump_get_line
);
2831 * kmsg_dump_get_buffer - copy kmsg log lines
2832 * @dumper: registered kmsg dumper
2833 * @syslog: include the "<4>" prefixes
2834 * @buf: buffer to copy the line to
2835 * @size: maximum size of the buffer
2836 * @len: length of line placed into buffer
2838 * Start at the end of the kmsg buffer and fill the provided buffer
2839 * with as many of the the *youngest* kmsg records that fit into it.
2840 * If the buffer is large enough, all available kmsg records will be
2841 * copied with a single call.
2843 * Consecutive calls will fill the buffer with the next block of
2844 * available older records, not including the earlier retrieved ones.
2846 * A return value of FALSE indicates that there are no more records to
2849 bool kmsg_dump_get_buffer(struct kmsg_dumper
*dumper
, bool syslog
,
2850 char *buf
, size_t size
, size_t *len
)
2852 unsigned long flags
;
2857 enum log_flags prev
;
2861 if (!dumper
->active
)
2864 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2865 if (dumper
->cur_seq
< log_first_seq
) {
2866 /* messages are gone, move to first available one */
2867 dumper
->cur_seq
= log_first_seq
;
2868 dumper
->cur_idx
= log_first_idx
;
2872 if (dumper
->cur_seq
>= dumper
->next_seq
) {
2873 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2877 /* calculate length of entire buffer */
2878 seq
= dumper
->cur_seq
;
2879 idx
= dumper
->cur_idx
;
2881 while (seq
< dumper
->next_seq
) {
2882 struct printk_log
*msg
= log_from_idx(idx
);
2884 l
+= msg_print_text(msg
, prev
, true, NULL
, 0);
2885 idx
= log_next(idx
);
2890 /* move first record forward until length fits into the buffer */
2891 seq
= dumper
->cur_seq
;
2892 idx
= dumper
->cur_idx
;
2894 while (l
> size
&& seq
< dumper
->next_seq
) {
2895 struct printk_log
*msg
= log_from_idx(idx
);
2897 l
-= msg_print_text(msg
, prev
, true, NULL
, 0);
2898 idx
= log_next(idx
);
2903 /* last message in next interation */
2908 while (seq
< dumper
->next_seq
) {
2909 struct printk_log
*msg
= log_from_idx(idx
);
2911 l
+= msg_print_text(msg
, prev
, syslog
, buf
+ l
, size
- l
);
2912 idx
= log_next(idx
);
2917 dumper
->next_seq
= next_seq
;
2918 dumper
->next_idx
= next_idx
;
2920 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2926 EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer
);
2929 * kmsg_dump_rewind_nolock - reset the interator (unlocked version)
2930 * @dumper: registered kmsg dumper
2932 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2933 * kmsg_dump_get_buffer() can be called again and used multiple
2934 * times within the same dumper.dump() callback.
2936 * The function is similar to kmsg_dump_rewind(), but grabs no locks.
2938 void kmsg_dump_rewind_nolock(struct kmsg_dumper
*dumper
)
2940 dumper
->cur_seq
= clear_seq
;
2941 dumper
->cur_idx
= clear_idx
;
2942 dumper
->next_seq
= log_next_seq
;
2943 dumper
->next_idx
= log_next_idx
;
2947 * kmsg_dump_rewind - reset the interator
2948 * @dumper: registered kmsg dumper
2950 * Reset the dumper's iterator so that kmsg_dump_get_line() and
2951 * kmsg_dump_get_buffer() can be called again and used multiple
2952 * times within the same dumper.dump() callback.
2954 void kmsg_dump_rewind(struct kmsg_dumper
*dumper
)
2956 unsigned long flags
;
2958 raw_spin_lock_irqsave(&logbuf_lock
, flags
);
2959 kmsg_dump_rewind_nolock(dumper
);
2960 raw_spin_unlock_irqrestore(&logbuf_lock
, flags
);
2962 EXPORT_SYMBOL_GPL(kmsg_dump_rewind
);
2964 static char dump_stack_arch_desc_str
[128];
2967 * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
2968 * @fmt: printf-style format string
2969 * @...: arguments for the format string
2971 * The configured string will be printed right after utsname during task
2972 * dumps. Usually used to add arch-specific system identifiers. If an
2973 * arch wants to make use of such an ID string, it should initialize this
2974 * as soon as possible during boot.
2976 void __init
dump_stack_set_arch_desc(const char *fmt
, ...)
2980 va_start(args
, fmt
);
2981 vsnprintf(dump_stack_arch_desc_str
, sizeof(dump_stack_arch_desc_str
),
2987 * dump_stack_print_info - print generic debug info for dump_stack()
2988 * @log_lvl: log level
2990 * Arch-specific dump_stack() implementations can use this function to
2991 * print out the same debug information as the generic dump_stack().
2993 void dump_stack_print_info(const char *log_lvl
)
2995 printk("%sCPU: %d PID: %d Comm: %.20s %s %s %.*s\n",
2996 log_lvl
, raw_smp_processor_id(), current
->pid
, current
->comm
,
2997 print_tainted(), init_utsname()->release
,
2998 (int)strcspn(init_utsname()->version
, " "),
2999 init_utsname()->version
);
3001 if (dump_stack_arch_desc_str
[0] != '\0')
3002 printk("%sHardware name: %s\n",
3003 log_lvl
, dump_stack_arch_desc_str
);
3005 print_worker_info(log_lvl
, current
);
3009 * show_regs_print_info - print generic debug info for show_regs()
3010 * @log_lvl: log level
3012 * show_regs() implementations can use this function to print out generic
3013 * debug information.
3015 void show_regs_print_info(const char *log_lvl
)
3017 dump_stack_print_info(log_lvl
);
3019 printk("%stask: %p ti: %p task.ti: %p\n",
3020 log_lvl
, current
, current_thread_info(),
3021 task_thread_info(current
));