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/syscalls.h>
35 #include <linux/kexec.h>
36 #include <linux/ratelimit.h>
37 #include <linux/kmsg_dump.h>
38 #include <linux/syslog.h>
40 #include <asm/uaccess.h>
43 * for_each_console() allows you to iterate on each console
45 #define for_each_console(con) \
46 for (con = console_drivers; con != NULL; con = con->next)
49 * Architectures can override it:
51 void asmlinkage
__attribute__((weak
)) early_printk(const char *fmt
, ...)
55 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
57 /* printk's without a loglevel use this.. */
58 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
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 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
66 int console_printk
[4] = {
67 DEFAULT_CONSOLE_LOGLEVEL
, /* console_loglevel */
68 DEFAULT_MESSAGE_LOGLEVEL
, /* default_message_loglevel */
69 MINIMUM_CONSOLE_LOGLEVEL
, /* minimum_console_loglevel */
70 DEFAULT_CONSOLE_LOGLEVEL
, /* default_console_loglevel */
74 * Low level drivers may need that to know if they can schedule in
75 * their unblank() callback or not. So let's export it.
78 EXPORT_SYMBOL(oops_in_progress
);
81 * console_sem protects the console_drivers list, and also
82 * provides serialisation for access to the entire console
85 static DECLARE_MUTEX(console_sem
);
86 struct console
*console_drivers
;
87 EXPORT_SYMBOL_GPL(console_drivers
);
90 * This is used for debugging the mess that is the VT code by
91 * keeping track if we have the console semaphore held. It's
92 * definitely not the perfect debug tool (we don't know if _WE_
93 * hold it are racing, but it helps tracking those weird code
94 * path in the console code where we end up in places I want
95 * locked without the console sempahore held
97 static int console_locked
, console_suspended
;
100 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
101 * It is also used in interesting ways to provide interlocking in
102 * release_console_sem().
104 static DEFINE_SPINLOCK(logbuf_lock
);
106 #define LOG_BUF_MASK (log_buf_len-1)
107 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
110 * The indices into log_buf are not constrained to log_buf_len - they
111 * must be masked before subscripting
113 static unsigned log_start
; /* Index into log_buf: next char to be read by syslog() */
114 static unsigned con_start
; /* Index into log_buf: next char to be sent to consoles */
115 static unsigned log_end
; /* Index into log_buf: most-recently-written-char + 1 */
118 * Array of consoles built from command line options (console=)
120 struct console_cmdline
122 char name
[8]; /* Name of the driver */
123 int index
; /* Minor dev. to use */
124 char *options
; /* Options for the driver */
125 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
126 char *brl_options
; /* Options for braille driver */
130 #define MAX_CMDLINECONSOLES 8
132 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
;
143 static char __log_buf
[__LOG_BUF_LEN
];
144 static char *log_buf
= __log_buf
;
145 static int log_buf_len
= __LOG_BUF_LEN
;
146 static unsigned logged_chars
; /* Number of chars produced since last read+clear operation */
147 static int saved_console_loglevel
= -1;
151 * This appends the listed symbols to /proc/vmcoreinfo
153 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
154 * obtain access to symbols that are otherwise very difficult to locate. These
155 * symbols are specifically used so that utilities can access and extract the
156 * dmesg log from a vmcore file after a crash.
158 void log_buf_kexec_setup(void)
160 VMCOREINFO_SYMBOL(log_buf
);
161 VMCOREINFO_SYMBOL(log_end
);
162 VMCOREINFO_SYMBOL(log_buf_len
);
163 VMCOREINFO_SYMBOL(logged_chars
);
167 static int __init
log_buf_len_setup(char *str
)
169 unsigned size
= memparse(str
, &str
);
173 size
= roundup_pow_of_two(size
);
174 if (size
> log_buf_len
) {
175 unsigned start
, dest_idx
, offset
;
178 new_log_buf
= alloc_bootmem(size
);
180 printk(KERN_WARNING
"log_buf_len: allocation failed\n");
184 spin_lock_irqsave(&logbuf_lock
, flags
);
186 log_buf
= new_log_buf
;
188 offset
= start
= min(con_start
, log_start
);
190 while (start
!= log_end
) {
191 log_buf
[dest_idx
] = __log_buf
[start
& (__LOG_BUF_LEN
- 1)];
198 spin_unlock_irqrestore(&logbuf_lock
, flags
);
200 printk(KERN_NOTICE
"log_buf_len: %d\n", log_buf_len
);
206 __setup("log_buf_len=", log_buf_len_setup
);
208 #ifdef CONFIG_BOOT_PRINTK_DELAY
210 static unsigned int boot_delay
; /* msecs delay after each printk during bootup */
211 static unsigned long long loops_per_msec
; /* based on boot_delay */
213 static int __init
boot_delay_setup(char *str
)
217 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
218 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
220 get_option(&str
, &boot_delay
);
221 if (boot_delay
> 10 * 1000)
224 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
225 "HZ: %d, loops_per_msec: %llu\n",
226 boot_delay
, preset_lpj
, lpj
, HZ
, loops_per_msec
);
229 __setup("boot_delay=", boot_delay_setup
);
231 static void boot_delay_msec(void)
233 unsigned long long k
;
234 unsigned long timeout
;
236 if (boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
239 k
= (unsigned long long)loops_per_msec
* boot_delay
;
241 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
246 * use (volatile) jiffies to prevent
247 * compiler reduction; loop termination via jiffies
248 * is secondary and may or may not happen.
250 if (time_after(jiffies
, timeout
))
252 touch_nmi_watchdog();
256 static inline void boot_delay_msec(void)
261 int do_syslog(int type
, char __user
*buf
, int len
, bool from_file
)
263 unsigned i
, j
, limit
, count
;
268 error
= security_syslog(type
, from_file
);
273 case SYSLOG_ACTION_CLOSE
: /* Close log */
275 case SYSLOG_ACTION_OPEN
: /* Open log */
277 case SYSLOG_ACTION_READ
: /* Read from log */
284 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
288 error
= wait_event_interruptible(log_wait
,
289 (log_start
- log_end
));
293 spin_lock_irq(&logbuf_lock
);
294 while (!error
&& (log_start
!= log_end
) && i
< len
) {
295 c
= LOG_BUF(log_start
);
297 spin_unlock_irq(&logbuf_lock
);
298 error
= __put_user(c
,buf
);
302 spin_lock_irq(&logbuf_lock
);
304 spin_unlock_irq(&logbuf_lock
);
308 /* Read/clear last kernel messages */
309 case SYSLOG_ACTION_READ_CLEAR
:
312 /* Read last kernel messages */
313 case SYSLOG_ACTION_READ_ALL
:
320 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
325 if (count
> log_buf_len
)
327 spin_lock_irq(&logbuf_lock
);
328 if (count
> logged_chars
)
329 count
= logged_chars
;
334 * __put_user() could sleep, and while we sleep
335 * printk() could overwrite the messages
336 * we try to copy to user space. Therefore
337 * the messages are copied in reverse. <manfreds>
339 for (i
= 0; i
< count
&& !error
; i
++) {
341 if (j
+ log_buf_len
< log_end
)
344 spin_unlock_irq(&logbuf_lock
);
345 error
= __put_user(c
,&buf
[count
-1-i
]);
347 spin_lock_irq(&logbuf_lock
);
349 spin_unlock_irq(&logbuf_lock
);
354 int offset
= count
-error
;
355 /* buffer overflow during copy, correct user buffer. */
356 for (i
= 0; i
< error
; i
++) {
357 if (__get_user(c
,&buf
[i
+offset
]) ||
358 __put_user(c
,&buf
[i
])) {
366 /* Clear ring buffer */
367 case SYSLOG_ACTION_CLEAR
:
370 /* Disable logging to console */
371 case SYSLOG_ACTION_CONSOLE_OFF
:
372 if (saved_console_loglevel
== -1)
373 saved_console_loglevel
= console_loglevel
;
374 console_loglevel
= minimum_console_loglevel
;
376 /* Enable logging to console */
377 case SYSLOG_ACTION_CONSOLE_ON
:
378 if (saved_console_loglevel
!= -1) {
379 console_loglevel
= saved_console_loglevel
;
380 saved_console_loglevel
= -1;
383 /* Set level of messages printed to console */
384 case SYSLOG_ACTION_CONSOLE_LEVEL
:
386 if (len
< 1 || len
> 8)
388 if (len
< minimum_console_loglevel
)
389 len
= minimum_console_loglevel
;
390 console_loglevel
= len
;
391 /* Implicitly re-enable logging to console */
392 saved_console_loglevel
= -1;
395 /* Number of chars in the log buffer */
396 case SYSLOG_ACTION_SIZE_UNREAD
:
397 error
= log_end
- log_start
;
399 /* Size of the log buffer */
400 case SYSLOG_ACTION_SIZE_BUFFER
:
411 SYSCALL_DEFINE3(syslog
, int, type
, char __user
*, buf
, int, len
)
413 return do_syslog(type
, buf
, len
, SYSLOG_FROM_CALL
);
416 #ifdef CONFIG_KGDB_KDB
417 /* kdb dmesg command needs access to the syslog buffer. do_syslog()
418 * uses locks so it cannot be used during debugging. Just tell kdb
419 * where the start and end of the physical and logical logs are. This
420 * is equivalent to do_syslog(3).
422 void kdb_syslog_data(char *syslog_data
[4])
424 syslog_data
[0] = log_buf
;
425 syslog_data
[1] = log_buf
+ log_buf_len
;
426 syslog_data
[2] = log_buf
+ log_end
-
427 (logged_chars
< log_buf_len
? logged_chars
: log_buf_len
);
428 syslog_data
[3] = log_buf
+ log_end
;
430 #endif /* CONFIG_KGDB_KDB */
433 * Call the console drivers on a range of log_buf
435 static void __call_console_drivers(unsigned start
, unsigned end
)
439 for_each_console(con
) {
440 if ((con
->flags
& CON_ENABLED
) && con
->write
&&
441 (cpu_online(smp_processor_id()) ||
442 (con
->flags
& CON_ANYTIME
)))
443 con
->write(con
, &LOG_BUF(start
), end
- start
);
447 static int __read_mostly ignore_loglevel
;
449 static int __init
ignore_loglevel_setup(char *str
)
452 printk(KERN_INFO
"debug: ignoring loglevel setting.\n");
457 early_param("ignore_loglevel", ignore_loglevel_setup
);
460 * Write out chars from start to end - 1 inclusive
462 static void _call_console_drivers(unsigned start
,
463 unsigned end
, int msg_log_level
)
465 if ((msg_log_level
< console_loglevel
|| ignore_loglevel
) &&
466 console_drivers
&& start
!= end
) {
467 if ((start
& LOG_BUF_MASK
) > (end
& LOG_BUF_MASK
)) {
469 __call_console_drivers(start
& LOG_BUF_MASK
,
471 __call_console_drivers(0, end
& LOG_BUF_MASK
);
473 __call_console_drivers(start
, end
);
479 * Call the console drivers, asking them to write out
480 * log_buf[start] to log_buf[end - 1].
481 * The console_sem must be held.
483 static void call_console_drivers(unsigned start
, unsigned end
)
485 unsigned cur_index
, start_print
;
486 static int msg_level
= -1;
488 BUG_ON(((int)(start
- end
)) > 0);
492 while (cur_index
!= end
) {
493 if (msg_level
< 0 && ((end
- cur_index
) > 2) &&
494 LOG_BUF(cur_index
+ 0) == '<' &&
495 LOG_BUF(cur_index
+ 1) >= '0' &&
496 LOG_BUF(cur_index
+ 1) <= '7' &&
497 LOG_BUF(cur_index
+ 2) == '>') {
498 msg_level
= LOG_BUF(cur_index
+ 1) - '0';
500 start_print
= cur_index
;
502 while (cur_index
!= end
) {
503 char c
= LOG_BUF(cur_index
);
509 * printk() has already given us loglevel tags in
510 * the buffer. This code is here in case the
511 * log buffer has wrapped right round and scribbled
514 msg_level
= default_message_loglevel
;
516 _call_console_drivers(start_print
, cur_index
, msg_level
);
518 start_print
= cur_index
;
523 _call_console_drivers(start_print
, end
, msg_level
);
526 static void emit_log_char(char c
)
528 LOG_BUF(log_end
) = c
;
530 if (log_end
- log_start
> log_buf_len
)
531 log_start
= log_end
- log_buf_len
;
532 if (log_end
- con_start
> log_buf_len
)
533 con_start
= log_end
- log_buf_len
;
534 if (logged_chars
< log_buf_len
)
539 * Zap console related locks when oopsing. Only zap at most once
540 * every 10 seconds, to leave time for slow consoles to print a
543 static void zap_locks(void)
545 static unsigned long oops_timestamp
;
547 if (time_after_eq(jiffies
, oops_timestamp
) &&
548 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
551 oops_timestamp
= jiffies
;
553 /* If a crash is occurring, make sure we can't deadlock */
554 spin_lock_init(&logbuf_lock
);
555 /* And make sure that we print immediately */
556 init_MUTEX(&console_sem
);
559 #if defined(CONFIG_PRINTK_TIME)
560 static int printk_time
= 1;
562 static int printk_time
= 0;
564 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
566 /* Check if we have any console registered that can be called early in boot. */
567 static int have_callable_console(void)
571 for_each_console(con
)
572 if (con
->flags
& CON_ANYTIME
)
579 * printk - print a kernel message
580 * @fmt: format string
582 * This is printk(). It can be called from any context. We want it to work.
584 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
585 * call the console drivers. If we fail to get the semaphore we place the output
586 * into the log buffer and return. The current holder of the console_sem will
587 * notice the new output in release_console_sem() and will send it to the
588 * consoles before releasing the semaphore.
590 * One effect of this deferred printing is that code which calls printk() and
591 * then changes console_loglevel may break. This is because console_loglevel
592 * is inspected when the actual printing occurs.
597 * See the vsnprintf() documentation for format string extensions over C99.
600 asmlinkage
int printk(const char *fmt
, ...)
606 r
= vprintk(fmt
, args
);
612 /* cpu currently holding logbuf_lock */
613 static volatile unsigned int printk_cpu
= UINT_MAX
;
616 * Can we actually use the console at this time on this cpu?
618 * Console drivers may assume that per-cpu resources have
619 * been allocated. So unless they're explicitly marked as
620 * being able to cope (CON_ANYTIME) don't call them until
621 * this CPU is officially up.
623 static inline int can_use_console(unsigned int cpu
)
625 return cpu_online(cpu
) || have_callable_console();
629 * Try to get console ownership to actually show the kernel
630 * messages from a 'printk'. Return true (and with the
631 * console_semaphore held, and 'console_locked' set) if it
632 * is successful, false otherwise.
634 * This gets called with the 'logbuf_lock' spinlock held and
635 * interrupts disabled. It should return with 'lockbuf_lock'
636 * released but interrupts still disabled.
638 static int acquire_console_semaphore_for_printk(unsigned int cpu
)
642 if (!try_acquire_console_sem()) {
646 * If we can't use the console, we need to release
647 * the console semaphore by hand to avoid flushing
648 * the buffer. We need to hold the console semaphore
649 * in order to do this test safely.
651 if (!can_use_console(cpu
)) {
657 printk_cpu
= UINT_MAX
;
658 spin_unlock(&logbuf_lock
);
661 static const char recursion_bug_msg
[] =
662 KERN_CRIT
"BUG: recent printk recursion!\n";
663 static int recursion_bug
;
664 static int new_text_line
= 1;
665 static char printk_buf
[1024];
667 int printk_delay_msec __read_mostly
;
669 static inline void printk_delay(void)
671 if (unlikely(printk_delay_msec
)) {
672 int m
= printk_delay_msec
;
676 touch_nmi_watchdog();
681 asmlinkage
int vprintk(const char *fmt
, va_list args
)
684 int current_log_level
= default_message_loglevel
;
693 /* This stops the holder of console_sem just where we want him */
694 raw_local_irq_save(flags
);
695 this_cpu
= smp_processor_id();
698 * Ouch, printk recursed into itself!
700 if (unlikely(printk_cpu
== this_cpu
)) {
702 * If a crash is occurring during printk() on this CPU,
703 * then try to get the crash message out but make sure
704 * we can't deadlock. Otherwise just return to avoid the
705 * recursion and return - but flag the recursion so that
706 * it can be printed at the next appropriate moment:
708 if (!oops_in_progress
) {
710 goto out_restore_irqs
;
716 spin_lock(&logbuf_lock
);
717 printk_cpu
= this_cpu
;
721 strcpy(printk_buf
, recursion_bug_msg
);
722 printed_len
= strlen(recursion_bug_msg
);
724 /* Emit the output into the temporary buffer */
725 printed_len
+= vscnprintf(printk_buf
+ printed_len
,
726 sizeof(printk_buf
) - printed_len
, fmt
, args
);
731 /* Do we have a loglevel in the string? */
733 unsigned char c
= p
[1];
734 if (c
&& p
[2] == '>') {
736 case '0' ... '7': /* loglevel */
737 current_log_level
= c
- '0';
738 /* Fallthrough - make sure we're on a new line */
739 case 'd': /* KERN_DEFAULT */
740 if (!new_text_line
) {
744 /* Fallthrough - skip the loglevel */
745 case 'c': /* KERN_CONT */
753 * Copy the output into log_buf. If the caller didn't provide
754 * appropriate log level tags, we insert them here
758 /* Always output the token */
760 emit_log_char(current_log_level
+ '0');
766 /* Follow the token with the time */
769 unsigned long long t
;
770 unsigned long nanosec_rem
;
772 t
= cpu_clock(printk_cpu
);
773 nanosec_rem
= do_div(t
, 1000000000);
774 tlen
= sprintf(tbuf
, "[%5lu.%06lu] ",
778 for (tp
= tbuf
; tp
< tbuf
+ tlen
; tp
++)
793 * Try to acquire and then immediately release the
794 * console semaphore. The release will do all the
795 * actual magic (print out buffers, wake up klogd,
798 * The acquire_console_semaphore_for_printk() function
799 * will release 'logbuf_lock' regardless of whether it
800 * actually gets the semaphore or not.
802 if (acquire_console_semaphore_for_printk(this_cpu
))
803 release_console_sem();
807 raw_local_irq_restore(flags
);
812 EXPORT_SYMBOL(printk
);
813 EXPORT_SYMBOL(vprintk
);
817 static void call_console_drivers(unsigned start
, unsigned end
)
823 static int __add_preferred_console(char *name
, int idx
, char *options
,
826 struct console_cmdline
*c
;
830 * See if this tty is not yet registered, and
831 * if we have a slot free.
833 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
834 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
835 console_cmdline
[i
].index
== idx
) {
837 selected_console
= i
;
840 if (i
== MAX_CMDLINECONSOLES
)
843 selected_console
= i
;
844 c
= &console_cmdline
[i
];
845 strlcpy(c
->name
, name
, sizeof(c
->name
));
846 c
->options
= options
;
847 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
848 c
->brl_options
= brl_options
;
854 * Set up a list of consoles. Called from init/main.c
856 static int __init
console_setup(char *str
)
858 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
859 char *s
, *options
, *brl_options
= NULL
;
862 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
863 if (!memcmp(str
, "brl,", 4)) {
866 } else if (!memcmp(str
, "brl=", 4)) {
867 brl_options
= str
+ 4;
868 str
= strchr(brl_options
, ',');
870 printk(KERN_ERR
"need port name after brl=\n");
878 * Decode str into name, index, options.
880 if (str
[0] >= '0' && str
[0] <= '9') {
882 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
884 strncpy(buf
, str
, sizeof(buf
) - 1);
886 buf
[sizeof(buf
) - 1] = 0;
887 if ((options
= strchr(str
, ',')) != NULL
)
890 if (!strcmp(str
, "ttya"))
891 strcpy(buf
, "ttyS0");
892 if (!strcmp(str
, "ttyb"))
893 strcpy(buf
, "ttyS1");
895 for (s
= buf
; *s
; s
++)
896 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
898 idx
= simple_strtoul(s
, NULL
, 10);
901 __add_preferred_console(buf
, idx
, options
, brl_options
);
902 console_set_on_cmdline
= 1;
905 __setup("console=", console_setup
);
908 * add_preferred_console - add a device to the list of preferred consoles.
911 * @options: options for this console
913 * The last preferred console added will be used for kernel messages
914 * and stdin/out/err for init. Normally this is used by console_setup
915 * above to handle user-supplied console arguments; however it can also
916 * be used by arch-specific code either to override the user or more
917 * commonly to provide a default console (ie from PROM variables) when
918 * the user has not supplied one.
920 int add_preferred_console(char *name
, int idx
, char *options
)
922 return __add_preferred_console(name
, idx
, options
, NULL
);
925 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
927 struct console_cmdline
*c
;
930 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
931 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
932 console_cmdline
[i
].index
== idx
) {
933 c
= &console_cmdline
[i
];
934 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
935 c
->name
[sizeof(c
->name
) - 1] = 0;
936 c
->options
= options
;
944 int console_suspend_enabled
= 1;
945 EXPORT_SYMBOL(console_suspend_enabled
);
947 static int __init
console_suspend_disable(char *str
)
949 console_suspend_enabled
= 0;
952 __setup("no_console_suspend", console_suspend_disable
);
955 * suspend_console - suspend the console subsystem
957 * This disables printk() while we go into suspend states
959 void suspend_console(void)
961 if (!console_suspend_enabled
)
963 printk("Suspending console(s) (use no_console_suspend to debug)\n");
964 acquire_console_sem();
965 console_suspended
= 1;
969 void resume_console(void)
971 if (!console_suspend_enabled
)
974 console_suspended
= 0;
975 release_console_sem();
979 * acquire_console_sem - lock the console system for exclusive use.
981 * Acquires a semaphore which guarantees that the caller has
982 * exclusive access to the console system and the console_drivers list.
984 * Can sleep, returns nothing.
986 void acquire_console_sem(void)
988 BUG_ON(in_interrupt());
990 if (console_suspended
)
993 console_may_schedule
= 1;
995 EXPORT_SYMBOL(acquire_console_sem
);
997 int try_acquire_console_sem(void)
999 if (down_trylock(&console_sem
))
1001 if (console_suspended
) {
1006 console_may_schedule
= 0;
1009 EXPORT_SYMBOL(try_acquire_console_sem
);
1011 int is_console_locked(void)
1013 return console_locked
;
1016 static DEFINE_PER_CPU(int, printk_pending
);
1018 void printk_tick(void)
1020 if (__get_cpu_var(printk_pending
)) {
1021 __get_cpu_var(printk_pending
) = 0;
1022 wake_up_interruptible(&log_wait
);
1026 int printk_needs_cpu(int cpu
)
1028 return per_cpu(printk_pending
, cpu
);
1031 void wake_up_klogd(void)
1033 if (waitqueue_active(&log_wait
))
1034 __raw_get_cpu_var(printk_pending
) = 1;
1038 * release_console_sem - unlock the console system
1040 * Releases the semaphore which the caller holds on the console system
1041 * and the console driver list.
1043 * While the semaphore was held, console output may have been buffered
1044 * by printk(). If this is the case, release_console_sem() emits
1045 * the output prior to releasing the semaphore.
1047 * If there is output waiting for klogd, we wake it up.
1049 * release_console_sem() may be called from any context.
1051 void release_console_sem(void)
1053 unsigned long flags
;
1054 unsigned _con_start
, _log_end
;
1055 unsigned wake_klogd
= 0;
1057 if (console_suspended
) {
1062 console_may_schedule
= 0;
1065 spin_lock_irqsave(&logbuf_lock
, flags
);
1066 wake_klogd
|= log_start
- log_end
;
1067 if (con_start
== log_end
)
1068 break; /* Nothing to print */
1069 _con_start
= con_start
;
1071 con_start
= log_end
; /* Flush */
1072 spin_unlock(&logbuf_lock
);
1073 stop_critical_timings(); /* don't trace print latency */
1074 call_console_drivers(_con_start
, _log_end
);
1075 start_critical_timings();
1076 local_irq_restore(flags
);
1080 spin_unlock_irqrestore(&logbuf_lock
, flags
);
1084 EXPORT_SYMBOL(release_console_sem
);
1087 * console_conditional_schedule - yield the CPU if required
1089 * If the console code is currently allowed to sleep, and
1090 * if this CPU should yield the CPU to another task, do
1093 * Must be called within acquire_console_sem().
1095 void __sched
console_conditional_schedule(void)
1097 if (console_may_schedule
)
1100 EXPORT_SYMBOL(console_conditional_schedule
);
1102 void console_unblank(void)
1107 * console_unblank can no longer be called in interrupt context unless
1108 * oops_in_progress is set to 1..
1110 if (oops_in_progress
) {
1111 if (down_trylock(&console_sem
) != 0)
1114 acquire_console_sem();
1117 console_may_schedule
= 0;
1119 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
1121 release_console_sem();
1125 * Return the console tty driver structure and its associated index
1127 struct tty_driver
*console_device(int *index
)
1130 struct tty_driver
*driver
= NULL
;
1132 acquire_console_sem();
1133 for_each_console(c
) {
1136 driver
= c
->device(c
, index
);
1140 release_console_sem();
1145 * Prevent further output on the passed console device so that (for example)
1146 * serial drivers can disable console output before suspending a port, and can
1147 * re-enable output afterwards.
1149 void console_stop(struct console
*console
)
1151 acquire_console_sem();
1152 console
->flags
&= ~CON_ENABLED
;
1153 release_console_sem();
1155 EXPORT_SYMBOL(console_stop
);
1157 void console_start(struct console
*console
)
1159 acquire_console_sem();
1160 console
->flags
|= CON_ENABLED
;
1161 release_console_sem();
1163 EXPORT_SYMBOL(console_start
);
1166 * The console driver calls this routine during kernel initialization
1167 * to register the console printing procedure with printk() and to
1168 * print any messages that were printed by the kernel before the
1169 * console driver was initialized.
1171 * This can happen pretty early during the boot process (because of
1172 * early_printk) - sometimes before setup_arch() completes - be careful
1173 * of what kernel features are used - they may not be initialised yet.
1175 * There are two types of consoles - bootconsoles (early_printk) and
1176 * "real" consoles (everything which is not a bootconsole) which are
1177 * handled differently.
1178 * - Any number of bootconsoles can be registered at any time.
1179 * - As soon as a "real" console is registered, all bootconsoles
1180 * will be unregistered automatically.
1181 * - Once a "real" console is registered, any attempt to register a
1182 * bootconsoles will be rejected
1184 void register_console(struct console
*newcon
)
1187 unsigned long flags
;
1188 struct console
*bcon
= NULL
;
1191 * before we register a new CON_BOOT console, make sure we don't
1192 * already have a valid console
1194 if (console_drivers
&& newcon
->flags
& CON_BOOT
) {
1195 /* find the last or real console */
1196 for_each_console(bcon
) {
1197 if (!(bcon
->flags
& CON_BOOT
)) {
1198 printk(KERN_INFO
"Too late to register bootconsole %s%d\n",
1199 newcon
->name
, newcon
->index
);
1205 if (console_drivers
&& console_drivers
->flags
& CON_BOOT
)
1206 bcon
= console_drivers
;
1208 if (preferred_console
< 0 || bcon
|| !console_drivers
)
1209 preferred_console
= selected_console
;
1211 if (newcon
->early_setup
)
1212 newcon
->early_setup();
1215 * See if we want to use this console driver. If we
1216 * didn't select a console we take the first one
1217 * that registers here.
1219 if (preferred_console
< 0) {
1220 if (newcon
->index
< 0)
1222 if (newcon
->setup
== NULL
||
1223 newcon
->setup(newcon
, NULL
) == 0) {
1224 newcon
->flags
|= CON_ENABLED
;
1225 if (newcon
->device
) {
1226 newcon
->flags
|= CON_CONSDEV
;
1227 preferred_console
= 0;
1233 * See if this console matches one we selected on
1236 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
1238 if (strcmp(console_cmdline
[i
].name
, newcon
->name
) != 0)
1240 if (newcon
->index
>= 0 &&
1241 newcon
->index
!= console_cmdline
[i
].index
)
1243 if (newcon
->index
< 0)
1244 newcon
->index
= console_cmdline
[i
].index
;
1245 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1246 if (console_cmdline
[i
].brl_options
) {
1247 newcon
->flags
|= CON_BRL
;
1248 braille_register_console(newcon
,
1249 console_cmdline
[i
].index
,
1250 console_cmdline
[i
].options
,
1251 console_cmdline
[i
].brl_options
);
1255 if (newcon
->setup
&&
1256 newcon
->setup(newcon
, console_cmdline
[i
].options
) != 0)
1258 newcon
->flags
|= CON_ENABLED
;
1259 newcon
->index
= console_cmdline
[i
].index
;
1260 if (i
== selected_console
) {
1261 newcon
->flags
|= CON_CONSDEV
;
1262 preferred_console
= selected_console
;
1267 if (!(newcon
->flags
& CON_ENABLED
))
1271 * If we have a bootconsole, and are switching to a real console,
1272 * don't print everything out again, since when the boot console, and
1273 * the real console are the same physical device, it's annoying to
1274 * see the beginning boot messages twice
1276 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
))
1277 newcon
->flags
&= ~CON_PRINTBUFFER
;
1280 * Put this console in the list - keep the
1281 * preferred driver at the head of the list.
1283 acquire_console_sem();
1284 if ((newcon
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
1285 newcon
->next
= console_drivers
;
1286 console_drivers
= newcon
;
1288 newcon
->next
->flags
&= ~CON_CONSDEV
;
1290 newcon
->next
= console_drivers
->next
;
1291 console_drivers
->next
= newcon
;
1293 if (newcon
->flags
& CON_PRINTBUFFER
) {
1295 * release_console_sem() will print out the buffered messages
1298 spin_lock_irqsave(&logbuf_lock
, flags
);
1299 con_start
= log_start
;
1300 spin_unlock_irqrestore(&logbuf_lock
, flags
);
1302 release_console_sem();
1305 * By unregistering the bootconsoles after we enable the real console
1306 * we get the "console xxx enabled" message on all the consoles -
1307 * boot consoles, real consoles, etc - this is to ensure that end
1308 * users know there might be something in the kernel's log buffer that
1309 * went to the bootconsole (that they do not see on the real console)
1311 if (bcon
&& ((newcon
->flags
& (CON_CONSDEV
| CON_BOOT
)) == CON_CONSDEV
)) {
1312 /* we need to iterate through twice, to make sure we print
1313 * everything out, before we unregister the console(s)
1315 printk(KERN_INFO
"console [%s%d] enabled, bootconsole disabled\n",
1316 newcon
->name
, newcon
->index
);
1317 for_each_console(bcon
)
1318 if (bcon
->flags
& CON_BOOT
)
1319 unregister_console(bcon
);
1321 printk(KERN_INFO
"%sconsole [%s%d] enabled\n",
1322 (newcon
->flags
& CON_BOOT
) ? "boot" : "" ,
1323 newcon
->name
, newcon
->index
);
1326 EXPORT_SYMBOL(register_console
);
1328 int unregister_console(struct console
*console
)
1330 struct console
*a
, *b
;
1333 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1334 if (console
->flags
& CON_BRL
)
1335 return braille_unregister_console(console
);
1338 acquire_console_sem();
1339 if (console_drivers
== console
) {
1340 console_drivers
=console
->next
;
1342 } else if (console_drivers
) {
1343 for (a
=console_drivers
->next
, b
=console_drivers
;
1344 a
; b
=a
, a
=b
->next
) {
1354 * If this isn't the last console and it has CON_CONSDEV set, we
1355 * need to set it on the next preferred console.
1357 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
1358 console_drivers
->flags
|= CON_CONSDEV
;
1360 release_console_sem();
1363 EXPORT_SYMBOL(unregister_console
);
1365 static int __init
disable_boot_consoles(void)
1367 struct console
*con
;
1369 for_each_console(con
) {
1370 if (con
->flags
& CON_BOOT
) {
1371 printk(KERN_INFO
"turn off boot console %s%d\n",
1372 con
->name
, con
->index
);
1373 unregister_console(con
);
1378 late_initcall(disable_boot_consoles
);
1380 #if defined CONFIG_PRINTK
1383 * printk rate limiting, lifted from the networking subsystem.
1385 * This enforces a rate limit: not more than 10 kernel messages
1386 * every 5s to make a denial-of-service attack impossible.
1388 DEFINE_RATELIMIT_STATE(printk_ratelimit_state
, 5 * HZ
, 10);
1390 int __printk_ratelimit(const char *func
)
1392 return ___ratelimit(&printk_ratelimit_state
, func
);
1394 EXPORT_SYMBOL(__printk_ratelimit
);
1397 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1398 * @caller_jiffies: pointer to caller's state
1399 * @interval_msecs: minimum interval between prints
1401 * printk_timed_ratelimit() returns true if more than @interval_msecs
1402 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1405 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
1406 unsigned int interval_msecs
)
1408 if (*caller_jiffies
== 0
1409 || !time_in_range(jiffies
, *caller_jiffies
,
1411 + msecs_to_jiffies(interval_msecs
))) {
1412 *caller_jiffies
= jiffies
;
1417 EXPORT_SYMBOL(printk_timed_ratelimit
);
1419 static DEFINE_SPINLOCK(dump_list_lock
);
1420 static LIST_HEAD(dump_list
);
1423 * kmsg_dump_register - register a kernel log dumper.
1424 * @dumper: pointer to the kmsg_dumper structure
1426 * Adds a kernel log dumper to the system. The dump callback in the
1427 * structure will be called when the kernel oopses or panics and must be
1428 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1430 int kmsg_dump_register(struct kmsg_dumper
*dumper
)
1432 unsigned long flags
;
1435 /* The dump callback needs to be set */
1439 spin_lock_irqsave(&dump_list_lock
, flags
);
1440 /* Don't allow registering multiple times */
1441 if (!dumper
->registered
) {
1442 dumper
->registered
= 1;
1443 list_add_tail(&dumper
->list
, &dump_list
);
1446 spin_unlock_irqrestore(&dump_list_lock
, flags
);
1450 EXPORT_SYMBOL_GPL(kmsg_dump_register
);
1453 * kmsg_dump_unregister - unregister a kmsg dumper.
1454 * @dumper: pointer to the kmsg_dumper structure
1456 * Removes a dump device from the system. Returns zero on success and
1457 * %-EINVAL otherwise.
1459 int kmsg_dump_unregister(struct kmsg_dumper
*dumper
)
1461 unsigned long flags
;
1464 spin_lock_irqsave(&dump_list_lock
, flags
);
1465 if (dumper
->registered
) {
1466 dumper
->registered
= 0;
1467 list_del(&dumper
->list
);
1470 spin_unlock_irqrestore(&dump_list_lock
, flags
);
1474 EXPORT_SYMBOL_GPL(kmsg_dump_unregister
);
1476 static const char const *kmsg_reasons
[] = {
1477 [KMSG_DUMP_OOPS
] = "oops",
1478 [KMSG_DUMP_PANIC
] = "panic",
1479 [KMSG_DUMP_KEXEC
] = "kexec",
1482 static const char *kmsg_to_str(enum kmsg_dump_reason reason
)
1484 if (reason
>= ARRAY_SIZE(kmsg_reasons
) || reason
< 0)
1487 return kmsg_reasons
[reason
];
1491 * kmsg_dump - dump kernel log to kernel message dumpers.
1492 * @reason: the reason (oops, panic etc) for dumping
1494 * Iterate through each of the dump devices and call the oops/panic
1495 * callbacks with the log buffer.
1497 void kmsg_dump(enum kmsg_dump_reason reason
)
1501 struct kmsg_dumper
*dumper
;
1502 const char *s1
, *s2
;
1503 unsigned long l1
, l2
;
1504 unsigned long flags
;
1506 /* Theoretically, the log could move on after we do this, but
1507 there's not a lot we can do about that. The new messages
1508 will overwrite the start of what we dump. */
1509 spin_lock_irqsave(&logbuf_lock
, flags
);
1510 end
= log_end
& LOG_BUF_MASK
;
1511 chars
= logged_chars
;
1512 spin_unlock_irqrestore(&logbuf_lock
, flags
);
1514 if (logged_chars
> end
) {
1515 s1
= log_buf
+ log_buf_len
- logged_chars
+ end
;
1516 l1
= logged_chars
- end
;
1524 s2
= log_buf
+ end
- logged_chars
;
1528 if (!spin_trylock_irqsave(&dump_list_lock
, flags
)) {
1529 printk(KERN_ERR
"dump_kmsg: dump list lock is held during %s, skipping dump\n",
1530 kmsg_to_str(reason
));
1533 list_for_each_entry(dumper
, &dump_list
, list
)
1534 dumper
->dump(dumper
, reason
, s1
, l1
, s2
, l2
);
1535 spin_unlock_irqrestore(&dump_list_lock
, flags
);