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 <andrewm@uow.edu.au>
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/jiffies.h>
37 #include <asm/uaccess.h>
39 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
41 /* printk's without a loglevel use this.. */
42 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
44 /* We show everything that is MORE important than this.. */
45 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
46 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
48 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
50 int console_printk
[4] = {
51 DEFAULT_CONSOLE_LOGLEVEL
, /* console_loglevel */
52 DEFAULT_MESSAGE_LOGLEVEL
, /* default_message_loglevel */
53 MINIMUM_CONSOLE_LOGLEVEL
, /* minimum_console_loglevel */
54 DEFAULT_CONSOLE_LOGLEVEL
, /* default_console_loglevel */
58 * Low level drivers may need that to know if they can schedule in
59 * their unblank() callback or not. So let's export it.
62 EXPORT_SYMBOL(oops_in_progress
);
65 * console_sem protects the console_drivers list, and also
66 * provides serialisation for access to the entire console
69 static DECLARE_MUTEX(console_sem
);
70 static DECLARE_MUTEX(secondary_console_sem
);
71 struct console
*console_drivers
;
73 * This is used for debugging the mess that is the VT code by
74 * keeping track if we have the console semaphore held. It's
75 * definitely not the perfect debug tool (we don't know if _WE_
76 * hold it are racing, but it helps tracking those weird code
77 * path in the console code where we end up in places I want
78 * locked without the console sempahore held
80 static int console_locked
, console_suspended
;
83 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
84 * It is also used in interesting ways to provide interlocking in
85 * release_console_sem().
87 static DEFINE_SPINLOCK(logbuf_lock
);
89 #define LOG_BUF_MASK (log_buf_len-1)
90 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
93 * The indices into log_buf are not constrained to log_buf_len - they
94 * must be masked before subscripting
96 static unsigned long log_start
; /* Index into log_buf: next char to be read by syslog() */
97 static unsigned long con_start
; /* Index into log_buf: next char to be sent to consoles */
98 static unsigned long log_end
; /* Index into log_buf: most-recently-written-char + 1 */
101 * Array of consoles built from command line options (console=)
103 struct console_cmdline
105 char name
[8]; /* Name of the driver */
106 int index
; /* Minor dev. to use */
107 char *options
; /* Options for the driver */
110 #define MAX_CMDLINECONSOLES 8
112 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
113 static int selected_console
= -1;
114 static int preferred_console
= -1;
116 /* Flag: console code may call schedule() */
117 static int console_may_schedule
;
121 static char __log_buf
[__LOG_BUF_LEN
];
122 static char *log_buf
= __log_buf
;
123 static int log_buf_len
= __LOG_BUF_LEN
;
124 static unsigned long logged_chars
; /* Number of chars produced since last read+clear operation */
126 static int __init
log_buf_len_setup(char *str
)
128 unsigned long size
= memparse(str
, &str
);
132 size
= roundup_pow_of_two(size
);
133 if (size
> log_buf_len
) {
134 unsigned long start
, dest_idx
, offset
;
137 new_log_buf
= alloc_bootmem(size
);
139 printk(KERN_WARNING
"log_buf_len: allocation failed\n");
143 spin_lock_irqsave(&logbuf_lock
, flags
);
145 log_buf
= new_log_buf
;
147 offset
= start
= min(con_start
, log_start
);
149 while (start
!= log_end
) {
150 log_buf
[dest_idx
] = __log_buf
[start
& (__LOG_BUF_LEN
- 1)];
157 spin_unlock_irqrestore(&logbuf_lock
, flags
);
159 printk(KERN_NOTICE
"log_buf_len: %d\n", log_buf_len
);
165 __setup("log_buf_len=", log_buf_len_setup
);
167 #ifdef CONFIG_BOOT_PRINTK_DELAY
169 static unsigned int boot_delay
; /* msecs delay after each printk during bootup */
170 static unsigned long long printk_delay_msec
; /* per msec, based on boot_delay */
172 static int __init
boot_delay_setup(char *str
)
175 unsigned long long loops_per_msec
;
177 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
178 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
180 get_option(&str
, &boot_delay
);
181 if (boot_delay
> 10 * 1000)
184 printk_delay_msec
= loops_per_msec
;
185 printk(KERN_DEBUG
"boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
186 "HZ: %d, printk_delay_msec: %llu\n",
187 boot_delay
, preset_lpj
, lpj
, HZ
, printk_delay_msec
);
190 __setup("boot_delay=", boot_delay_setup
);
192 static void boot_delay_msec(void)
194 unsigned long long k
;
195 unsigned long timeout
;
197 if (boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
200 k
= (unsigned long long)printk_delay_msec
* boot_delay
;
202 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
207 * use (volatile) jiffies to prevent
208 * compiler reduction; loop termination via jiffies
209 * is secondary and may or may not happen.
211 if (time_after(jiffies
, timeout
))
213 touch_nmi_watchdog();
217 static inline void boot_delay_msec(void)
223 * Commands to do_syslog:
225 * 0 -- Close the log. Currently a NOP.
226 * 1 -- Open the log. Currently a NOP.
227 * 2 -- Read from the log.
228 * 3 -- Read all messages remaining in the ring buffer.
229 * 4 -- Read and clear all messages remaining in the ring buffer
230 * 5 -- Clear ring buffer.
231 * 6 -- Disable printk's to console
232 * 7 -- Enable printk's to console
233 * 8 -- Set level of messages printed to console
234 * 9 -- Return number of unread characters in the log buffer
235 * 10 -- Return size of the log buffer
237 int do_syslog(int type
, char __user
*buf
, int len
)
239 unsigned long i
, j
, limit
, count
;
244 error
= security_syslog(type
);
249 case 0: /* Close log */
251 case 1: /* Open log */
253 case 2: /* Read from log */
260 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
264 error
= wait_event_interruptible(log_wait
,
265 (log_start
- log_end
));
269 spin_lock_irq(&logbuf_lock
);
270 while (!error
&& (log_start
!= log_end
) && i
< len
) {
271 c
= LOG_BUF(log_start
);
273 spin_unlock_irq(&logbuf_lock
);
274 error
= __put_user(c
,buf
);
278 spin_lock_irq(&logbuf_lock
);
280 spin_unlock_irq(&logbuf_lock
);
284 case 4: /* Read/clear last kernel messages */
287 case 3: /* Read last kernel messages */
294 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
299 if (count
> log_buf_len
)
301 spin_lock_irq(&logbuf_lock
);
302 if (count
> logged_chars
)
303 count
= logged_chars
;
308 * __put_user() could sleep, and while we sleep
309 * printk() could overwrite the messages
310 * we try to copy to user space. Therefore
311 * the messages are copied in reverse. <manfreds>
313 for (i
= 0; i
< count
&& !error
; i
++) {
315 if (j
+ log_buf_len
< log_end
)
318 spin_unlock_irq(&logbuf_lock
);
319 error
= __put_user(c
,&buf
[count
-1-i
]);
321 spin_lock_irq(&logbuf_lock
);
323 spin_unlock_irq(&logbuf_lock
);
328 int offset
= count
-error
;
329 /* buffer overflow during copy, correct user buffer. */
330 for (i
= 0; i
< error
; i
++) {
331 if (__get_user(c
,&buf
[i
+offset
]) ||
332 __put_user(c
,&buf
[i
])) {
340 case 5: /* Clear ring buffer */
343 case 6: /* Disable logging to console */
344 console_loglevel
= minimum_console_loglevel
;
346 case 7: /* Enable logging to console */
347 console_loglevel
= default_console_loglevel
;
349 case 8: /* Set level of messages printed to console */
351 if (len
< 1 || len
> 8)
353 if (len
< minimum_console_loglevel
)
354 len
= minimum_console_loglevel
;
355 console_loglevel
= len
;
358 case 9: /* Number of chars in the log buffer */
359 error
= log_end
- log_start
;
361 case 10: /* Size of the log buffer */
372 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
374 return do_syslog(type
, buf
, len
);
378 * Call the console drivers on a range of log_buf
380 static void __call_console_drivers(unsigned long start
, unsigned long end
)
384 for (con
= console_drivers
; con
; con
= con
->next
) {
385 if ((con
->flags
& CON_ENABLED
) && con
->write
&&
386 (cpu_online(smp_processor_id()) ||
387 (con
->flags
& CON_ANYTIME
)))
388 con
->write(con
, &LOG_BUF(start
), end
- start
);
392 static int __read_mostly ignore_loglevel
;
394 static int __init
ignore_loglevel_setup(char *str
)
397 printk(KERN_INFO
"debug: ignoring loglevel setting.\n");
402 __setup("ignore_loglevel", ignore_loglevel_setup
);
405 * Write out chars from start to end - 1 inclusive
407 static void _call_console_drivers(unsigned long start
,
408 unsigned long end
, int msg_log_level
)
410 if ((msg_log_level
< console_loglevel
|| ignore_loglevel
) &&
411 console_drivers
&& start
!= end
) {
412 if ((start
& LOG_BUF_MASK
) > (end
& LOG_BUF_MASK
)) {
414 __call_console_drivers(start
& LOG_BUF_MASK
,
416 __call_console_drivers(0, end
& LOG_BUF_MASK
);
418 __call_console_drivers(start
, end
);
424 * Call the console drivers, asking them to write out
425 * log_buf[start] to log_buf[end - 1].
426 * The console_sem must be held.
428 static void call_console_drivers(unsigned long start
, unsigned long end
)
430 unsigned long cur_index
, start_print
;
431 static int msg_level
= -1;
433 BUG_ON(((long)(start
- end
)) > 0);
437 while (cur_index
!= end
) {
438 if (msg_level
< 0 && ((end
- cur_index
) > 2) &&
439 LOG_BUF(cur_index
+ 0) == '<' &&
440 LOG_BUF(cur_index
+ 1) >= '0' &&
441 LOG_BUF(cur_index
+ 1) <= '7' &&
442 LOG_BUF(cur_index
+ 2) == '>') {
443 msg_level
= LOG_BUF(cur_index
+ 1) - '0';
445 start_print
= cur_index
;
447 while (cur_index
!= end
) {
448 char c
= LOG_BUF(cur_index
);
454 * printk() has already given us loglevel tags in
455 * the buffer. This code is here in case the
456 * log buffer has wrapped right round and scribbled
459 msg_level
= default_message_loglevel
;
461 _call_console_drivers(start_print
, cur_index
, msg_level
);
463 start_print
= cur_index
;
468 _call_console_drivers(start_print
, end
, msg_level
);
471 static void emit_log_char(char c
)
473 LOG_BUF(log_end
) = c
;
475 if (log_end
- log_start
> log_buf_len
)
476 log_start
= log_end
- log_buf_len
;
477 if (log_end
- con_start
> log_buf_len
)
478 con_start
= log_end
- log_buf_len
;
479 if (logged_chars
< log_buf_len
)
484 * Zap console related locks when oopsing. Only zap at most once
485 * every 10 seconds, to leave time for slow consoles to print a
488 static void zap_locks(void)
490 static unsigned long oops_timestamp
;
492 if (time_after_eq(jiffies
, oops_timestamp
) &&
493 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
496 oops_timestamp
= jiffies
;
498 /* If a crash is occurring, make sure we can't deadlock */
499 spin_lock_init(&logbuf_lock
);
500 /* And make sure that we print immediately */
501 init_MUTEX(&console_sem
);
504 #if defined(CONFIG_PRINTK_TIME)
505 static int printk_time
= 1;
507 static int printk_time
= 0;
509 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
511 static int __init
printk_time_setup(char *str
)
516 printk(KERN_NOTICE
"The 'time' option is deprecated and "
517 "is scheduled for removal in early 2008\n");
518 printk(KERN_NOTICE
"Use 'printk.time=<value>' instead\n");
522 __setup("time", printk_time_setup
);
524 __attribute__((weak
)) unsigned long long printk_clock(void)
526 return sched_clock();
529 /* Check if we have any console registered that can be called early in boot. */
530 static int have_callable_console(void)
534 for (con
= console_drivers
; con
; con
= con
->next
)
535 if (con
->flags
& CON_ANYTIME
)
542 * printk - print a kernel message
543 * @fmt: format string
545 * This is printk(). It can be called from any context. We want it to work.
546 * Be aware of the fact that if oops_in_progress is not set, we might try to
547 * wake klogd up which could deadlock on runqueue lock if printk() is called
548 * from scheduler code.
550 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
551 * call the console drivers. If we fail to get the semaphore we place the output
552 * into the log buffer and return. The current holder of the console_sem will
553 * notice the new output in release_console_sem() and will send it to the
554 * consoles before releasing the semaphore.
556 * One effect of this deferred printing is that code which calls printk() and
557 * then changes console_loglevel may break. This is because console_loglevel
558 * is inspected when the actual printing occurs.
564 asmlinkage
int printk(const char *fmt
, ...)
570 r
= vprintk(fmt
, args
);
576 /* cpu currently holding logbuf_lock */
577 static volatile unsigned int printk_cpu
= UINT_MAX
;
579 asmlinkage
int vprintk(const char *fmt
, va_list args
)
584 static char printk_buf
[1024];
585 static int log_level_unknown
= 1;
590 if (unlikely(oops_in_progress
) && printk_cpu
== smp_processor_id())
591 /* If a crash is occurring during printk() on this CPU,
592 * make sure we can't deadlock */
595 /* This stops the holder of console_sem just where we want him */
596 raw_local_irq_save(flags
);
598 spin_lock(&logbuf_lock
);
599 printk_cpu
= smp_processor_id();
601 /* Emit the output into the temporary buffer */
602 printed_len
= vscnprintf(printk_buf
, sizeof(printk_buf
), fmt
, args
);
605 * Copy the output into log_buf. If the caller didn't provide
606 * appropriate log level tags, we insert them here
608 for (p
= printk_buf
; *p
; p
++) {
609 if (log_level_unknown
) {
610 /* log_level_unknown signals the start of a new line */
615 unsigned long long t
;
616 unsigned long nanosec_rem
;
619 * force the log level token to be
620 * before the time output.
622 if (p
[0] == '<' && p
[1] >='0' &&
623 p
[1] <= '7' && p
[2] == '>') {
628 loglev_char
= default_message_loglevel
632 nanosec_rem
= do_div(t
, 1000000000);
639 for (tp
= tbuf
; tp
< tbuf
+ tlen
; tp
++)
643 if (p
[0] != '<' || p
[1] < '0' ||
644 p
[1] > '7' || p
[2] != '>') {
646 emit_log_char(default_message_loglevel
652 log_level_unknown
= 0;
658 log_level_unknown
= 1;
661 if (!down_trylock(&console_sem
)) {
663 * We own the drivers. We can drop the spinlock and
664 * let release_console_sem() print the text, maybe ...
667 printk_cpu
= UINT_MAX
;
668 spin_unlock(&logbuf_lock
);
671 * Console drivers may assume that per-cpu resources have
672 * been allocated. So unless they're explicitly marked as
673 * being able to cope (CON_ANYTIME) don't call them until
674 * this CPU is officially up.
676 if (cpu_online(smp_processor_id()) || have_callable_console()) {
677 console_may_schedule
= 0;
678 release_console_sem();
680 /* Release by hand to avoid flushing the buffer. */
685 raw_local_irq_restore(flags
);
688 * Someone else owns the drivers. We drop the spinlock, which
689 * allows the semaphore holder to proceed and to call the
690 * console drivers with the output which we just produced.
692 printk_cpu
= UINT_MAX
;
693 spin_unlock(&logbuf_lock
);
695 raw_local_irq_restore(flags
);
701 EXPORT_SYMBOL(printk
);
702 EXPORT_SYMBOL(vprintk
);
706 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
711 static void call_console_drivers(unsigned long start
, unsigned long end
)
718 * Set up a list of consoles. Called from init/main.c
720 static int __init
console_setup(char *str
)
722 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
727 * Decode str into name, index, options.
729 if (str
[0] >= '0' && str
[0] <= '9') {
731 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
733 strncpy(buf
, str
, sizeof(buf
) - 1);
735 buf
[sizeof(buf
) - 1] = 0;
736 if ((options
= strchr(str
, ',')) != NULL
)
739 if (!strcmp(str
, "ttya"))
740 strcpy(buf
, "ttyS0");
741 if (!strcmp(str
, "ttyb"))
742 strcpy(buf
, "ttyS1");
744 for (s
= buf
; *s
; s
++)
745 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
747 idx
= simple_strtoul(s
, NULL
, 10);
750 add_preferred_console(buf
, idx
, options
);
753 __setup("console=", console_setup
);
756 * add_preferred_console - add a device to the list of preferred consoles.
759 * @options: options for this console
761 * The last preferred console added will be used for kernel messages
762 * and stdin/out/err for init. Normally this is used by console_setup
763 * above to handle user-supplied console arguments; however it can also
764 * be used by arch-specific code either to override the user or more
765 * commonly to provide a default console (ie from PROM variables) when
766 * the user has not supplied one.
768 int __init
add_preferred_console(char *name
, int idx
, char *options
)
770 struct console_cmdline
*c
;
774 * See if this tty is not yet registered, and
775 * if we have a slot free.
777 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
778 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
779 console_cmdline
[i
].index
== idx
) {
780 selected_console
= i
;
783 if (i
== MAX_CMDLINECONSOLES
)
785 selected_console
= i
;
786 c
= &console_cmdline
[i
];
787 memcpy(c
->name
, name
, sizeof(c
->name
));
788 c
->name
[sizeof(c
->name
) - 1] = 0;
789 c
->options
= options
;
794 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
796 struct console_cmdline
*c
;
799 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
800 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
801 console_cmdline
[i
].index
== idx
) {
802 c
= &console_cmdline
[i
];
803 memcpy(c
->name
, name_new
, sizeof(c
->name
));
804 c
->name
[sizeof(c
->name
) - 1] = 0;
805 c
->options
= options
;
813 #ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
815 * suspend_console - suspend the console subsystem
817 * This disables printk() while we go into suspend states
819 void suspend_console(void)
821 printk("Suspending console(s)\n");
822 acquire_console_sem();
823 console_suspended
= 1;
826 void resume_console(void)
828 console_suspended
= 0;
829 release_console_sem();
831 #endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
834 * acquire_console_sem - lock the console system for exclusive use.
836 * Acquires a semaphore which guarantees that the caller has
837 * exclusive access to the console system and the console_drivers list.
839 * Can sleep, returns nothing.
841 void acquire_console_sem(void)
843 BUG_ON(in_interrupt());
844 if (console_suspended
) {
845 down(&secondary_console_sem
);
850 console_may_schedule
= 1;
852 EXPORT_SYMBOL(acquire_console_sem
);
854 int try_acquire_console_sem(void)
856 if (down_trylock(&console_sem
))
859 console_may_schedule
= 0;
862 EXPORT_SYMBOL(try_acquire_console_sem
);
864 int is_console_locked(void)
866 return console_locked
;
869 void wake_up_klogd(void)
871 if (!oops_in_progress
&& waitqueue_active(&log_wait
))
872 wake_up_interruptible(&log_wait
);
876 * release_console_sem - unlock the console system
878 * Releases the semaphore which the caller holds on the console system
879 * and the console driver list.
881 * While the semaphore was held, console output may have been buffered
882 * by printk(). If this is the case, release_console_sem() emits
883 * the output prior to releasing the semaphore.
885 * If there is output waiting for klogd, we wake it up.
887 * release_console_sem() may be called from any context.
889 void release_console_sem(void)
892 unsigned long _con_start
, _log_end
;
893 unsigned long wake_klogd
= 0;
895 if (console_suspended
) {
896 up(&secondary_console_sem
);
900 console_may_schedule
= 0;
903 spin_lock_irqsave(&logbuf_lock
, flags
);
904 wake_klogd
|= log_start
- log_end
;
905 if (con_start
== log_end
)
906 break; /* Nothing to print */
907 _con_start
= con_start
;
909 con_start
= log_end
; /* Flush */
910 spin_unlock(&logbuf_lock
);
911 call_console_drivers(_con_start
, _log_end
);
912 local_irq_restore(flags
);
916 spin_unlock_irqrestore(&logbuf_lock
, flags
);
920 EXPORT_SYMBOL(release_console_sem
);
923 * console_conditional_schedule - yield the CPU if required
925 * If the console code is currently allowed to sleep, and
926 * if this CPU should yield the CPU to another task, do
929 * Must be called within acquire_console_sem().
931 void __sched
console_conditional_schedule(void)
933 if (console_may_schedule
)
936 EXPORT_SYMBOL(console_conditional_schedule
);
938 void console_print(const char *s
)
940 printk(KERN_EMERG
"%s", s
);
942 EXPORT_SYMBOL(console_print
);
944 void console_unblank(void)
949 * console_unblank can no longer be called in interrupt context unless
950 * oops_in_progress is set to 1..
952 if (oops_in_progress
) {
953 if (down_trylock(&console_sem
) != 0)
956 acquire_console_sem();
959 console_may_schedule
= 0;
960 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
)
961 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
963 release_console_sem();
967 * Return the console tty driver structure and its associated index
969 struct tty_driver
*console_device(int *index
)
972 struct tty_driver
*driver
= NULL
;
974 acquire_console_sem();
975 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
) {
978 driver
= c
->device(c
, index
);
982 release_console_sem();
987 * Prevent further output on the passed console device so that (for example)
988 * serial drivers can disable console output before suspending a port, and can
989 * re-enable output afterwards.
991 void console_stop(struct console
*console
)
993 acquire_console_sem();
994 console
->flags
&= ~CON_ENABLED
;
995 release_console_sem();
997 EXPORT_SYMBOL(console_stop
);
999 void console_start(struct console
*console
)
1001 acquire_console_sem();
1002 console
->flags
|= CON_ENABLED
;
1003 release_console_sem();
1005 EXPORT_SYMBOL(console_start
);
1008 * The console driver calls this routine during kernel initialization
1009 * to register the console printing procedure with printk() and to
1010 * print any messages that were printed by the kernel before the
1011 * console driver was initialized.
1013 void register_console(struct console
*console
)
1016 unsigned long flags
;
1017 struct console
*bootconsole
= NULL
;
1019 if (console_drivers
) {
1020 if (console
->flags
& CON_BOOT
)
1022 if (console_drivers
->flags
& CON_BOOT
)
1023 bootconsole
= console_drivers
;
1026 if (preferred_console
< 0 || bootconsole
|| !console_drivers
)
1027 preferred_console
= selected_console
;
1029 if (console
->early_setup
)
1030 console
->early_setup();
1033 * See if we want to use this console driver. If we
1034 * didn't select a console we take the first one
1035 * that registers here.
1037 if (preferred_console
< 0) {
1038 if (console
->index
< 0)
1040 if (console
->setup
== NULL
||
1041 console
->setup(console
, NULL
) == 0) {
1042 console
->flags
|= CON_ENABLED
| CON_CONSDEV
;
1043 preferred_console
= 0;
1048 * See if this console matches one we selected on
1051 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
1053 if (strcmp(console_cmdline
[i
].name
, console
->name
) != 0)
1055 if (console
->index
>= 0 &&
1056 console
->index
!= console_cmdline
[i
].index
)
1058 if (console
->index
< 0)
1059 console
->index
= console_cmdline
[i
].index
;
1060 if (console
->setup
&&
1061 console
->setup(console
, console_cmdline
[i
].options
) != 0)
1063 console
->flags
|= CON_ENABLED
;
1064 console
->index
= console_cmdline
[i
].index
;
1065 if (i
== selected_console
) {
1066 console
->flags
|= CON_CONSDEV
;
1067 preferred_console
= selected_console
;
1072 if (!(console
->flags
& CON_ENABLED
))
1075 if (bootconsole
&& (console
->flags
& CON_CONSDEV
)) {
1076 printk(KERN_INFO
"console handover: boot [%s%d] -> real [%s%d]\n",
1077 bootconsole
->name
, bootconsole
->index
,
1078 console
->name
, console
->index
);
1079 unregister_console(bootconsole
);
1080 console
->flags
&= ~CON_PRINTBUFFER
;
1082 printk(KERN_INFO
"console [%s%d] enabled\n",
1083 console
->name
, console
->index
);
1087 * Put this console in the list - keep the
1088 * preferred driver at the head of the list.
1090 acquire_console_sem();
1091 if ((console
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
1092 console
->next
= console_drivers
;
1093 console_drivers
= console
;
1095 console
->next
->flags
&= ~CON_CONSDEV
;
1097 console
->next
= console_drivers
->next
;
1098 console_drivers
->next
= console
;
1100 if (console
->flags
& CON_PRINTBUFFER
) {
1102 * release_console_sem() will print out the buffered messages
1105 spin_lock_irqsave(&logbuf_lock
, flags
);
1106 con_start
= log_start
;
1107 spin_unlock_irqrestore(&logbuf_lock
, flags
);
1109 release_console_sem();
1111 EXPORT_SYMBOL(register_console
);
1113 int unregister_console(struct console
*console
)
1115 struct console
*a
, *b
;
1118 acquire_console_sem();
1119 if (console_drivers
== console
) {
1120 console_drivers
=console
->next
;
1122 } else if (console_drivers
) {
1123 for (a
=console_drivers
->next
, b
=console_drivers
;
1124 a
; b
=a
, a
=b
->next
) {
1134 * If this isn't the last console and it has CON_CONSDEV set, we
1135 * need to set it on the next preferred console.
1137 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
1138 console_drivers
->flags
|= CON_CONSDEV
;
1140 release_console_sem();
1143 EXPORT_SYMBOL(unregister_console
);
1145 static int __init
disable_boot_consoles(void)
1147 if (console_drivers
!= NULL
) {
1148 if (console_drivers
->flags
& CON_BOOT
) {
1149 printk(KERN_INFO
"turn off boot console %s%d\n",
1150 console_drivers
->name
, console_drivers
->index
);
1151 return unregister_console(console_drivers
);
1156 late_initcall(disable_boot_consoles
);
1159 * tty_write_message - write a message to a certain tty, not just the console.
1160 * @tty: the destination tty_struct
1161 * @msg: the message to write
1163 * This is used for messages that need to be redirected to a specific tty.
1164 * We don't put it into the syslog queue right now maybe in the future if
1167 void tty_write_message(struct tty_struct
*tty
, char *msg
)
1169 if (tty
&& tty
->driver
->write
)
1170 tty
->driver
->write(tty
, msg
, strlen(msg
));
1175 * printk rate limiting, lifted from the networking subsystem.
1177 * This enforces a rate limit: not more than one kernel message
1178 * every printk_ratelimit_jiffies to make a denial-of-service
1179 * attack impossible.
1181 int __printk_ratelimit(int ratelimit_jiffies
, int ratelimit_burst
)
1183 static DEFINE_SPINLOCK(ratelimit_lock
);
1184 static unsigned long toks
= 10 * 5 * HZ
;
1185 static unsigned long last_msg
;
1187 unsigned long flags
;
1188 unsigned long now
= jiffies
;
1190 spin_lock_irqsave(&ratelimit_lock
, flags
);
1191 toks
+= now
- last_msg
;
1193 if (toks
> (ratelimit_burst
* ratelimit_jiffies
))
1194 toks
= ratelimit_burst
* ratelimit_jiffies
;
1195 if (toks
>= ratelimit_jiffies
) {
1199 toks
-= ratelimit_jiffies
;
1200 spin_unlock_irqrestore(&ratelimit_lock
, flags
);
1202 printk(KERN_WARNING
"printk: %d messages suppressed.\n", lost
);
1206 spin_unlock_irqrestore(&ratelimit_lock
, flags
);
1209 EXPORT_SYMBOL(__printk_ratelimit
);
1211 /* minimum time in jiffies between messages */
1212 int printk_ratelimit_jiffies
= 5 * HZ
;
1214 /* number of messages we send before ratelimiting */
1215 int printk_ratelimit_burst
= 10;
1217 int printk_ratelimit(void)
1219 return __printk_ratelimit(printk_ratelimit_jiffies
,
1220 printk_ratelimit_burst
);
1222 EXPORT_SYMBOL(printk_ratelimit
);
1225 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1226 * @caller_jiffies: pointer to caller's state
1227 * @interval_msecs: minimum interval between prints
1229 * printk_timed_ratelimit() returns true if more than @interval_msecs
1230 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1233 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
1234 unsigned int interval_msecs
)
1236 if (*caller_jiffies
== 0 || time_after(jiffies
, *caller_jiffies
)) {
1237 *caller_jiffies
= jiffies
+ msecs_to_jiffies(interval_msecs
);
1242 EXPORT_SYMBOL(printk_timed_ratelimit
);