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>
36 #include <asm/uaccess.h>
39 * Architectures can override it:
41 void __attribute__((weak
)) early_printk(const char *fmt
, ...)
45 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
47 /* printk's without a loglevel use this.. */
48 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
50 /* We show everything that is MORE important than this.. */
51 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
52 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
54 DECLARE_WAIT_QUEUE_HEAD(log_wait
);
56 int console_printk
[4] = {
57 DEFAULT_CONSOLE_LOGLEVEL
, /* console_loglevel */
58 DEFAULT_MESSAGE_LOGLEVEL
, /* default_message_loglevel */
59 MINIMUM_CONSOLE_LOGLEVEL
, /* minimum_console_loglevel */
60 DEFAULT_CONSOLE_LOGLEVEL
, /* default_console_loglevel */
64 * Low level drivers may need that to know if they can schedule in
65 * their unblank() callback or not. So let's export it.
68 EXPORT_SYMBOL(oops_in_progress
);
71 * console_sem protects the console_drivers list, and also
72 * provides serialisation for access to the entire console
75 static DECLARE_MUTEX(console_sem
);
76 static DECLARE_MUTEX(secondary_console_sem
);
77 struct console
*console_drivers
;
79 * This is used for debugging the mess that is the VT code by
80 * keeping track if we have the console semaphore held. It's
81 * definitely not the perfect debug tool (we don't know if _WE_
82 * hold it are racing, but it helps tracking those weird code
83 * path in the console code where we end up in places I want
84 * locked without the console sempahore held
86 static int console_locked
, console_suspended
;
89 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
90 * It is also used in interesting ways to provide interlocking in
91 * release_console_sem().
93 static DEFINE_SPINLOCK(logbuf_lock
);
95 #define LOG_BUF_MASK (log_buf_len-1)
96 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
99 * The indices into log_buf are not constrained to log_buf_len - they
100 * must be masked before subscripting
102 static unsigned log_start
; /* Index into log_buf: next char to be read by syslog() */
103 static unsigned con_start
; /* Index into log_buf: next char to be sent to consoles */
104 static unsigned log_end
; /* Index into log_buf: most-recently-written-char + 1 */
107 * Array of consoles built from command line options (console=)
109 struct console_cmdline
111 char name
[8]; /* Name of the driver */
112 int index
; /* Minor dev. to use */
113 char *options
; /* Options for the driver */
114 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
115 char *brl_options
; /* Options for braille driver */
119 #define MAX_CMDLINECONSOLES 8
121 static struct console_cmdline console_cmdline
[MAX_CMDLINECONSOLES
];
122 static int selected_console
= -1;
123 static int preferred_console
= -1;
125 /* Flag: console code may call schedule() */
126 static int console_may_schedule
;
130 static char __log_buf
[__LOG_BUF_LEN
];
131 static char *log_buf
= __log_buf
;
132 static int log_buf_len
= __LOG_BUF_LEN
;
133 static unsigned logged_chars
; /* Number of chars produced since last read+clear operation */
135 static int __init
log_buf_len_setup(char *str
)
137 unsigned size
= memparse(str
, &str
);
141 size
= roundup_pow_of_two(size
);
142 if (size
> log_buf_len
) {
143 unsigned start
, dest_idx
, offset
;
146 new_log_buf
= alloc_bootmem(size
);
148 printk(KERN_WARNING
"log_buf_len: allocation failed\n");
152 spin_lock_irqsave(&logbuf_lock
, flags
);
154 log_buf
= new_log_buf
;
156 offset
= start
= min(con_start
, log_start
);
158 while (start
!= log_end
) {
159 log_buf
[dest_idx
] = __log_buf
[start
& (__LOG_BUF_LEN
- 1)];
166 spin_unlock_irqrestore(&logbuf_lock
, flags
);
168 printk(KERN_NOTICE
"log_buf_len: %d\n", log_buf_len
);
174 __setup("log_buf_len=", log_buf_len_setup
);
176 #ifdef CONFIG_BOOT_PRINTK_DELAY
178 static unsigned int boot_delay
; /* msecs delay after each printk during bootup */
179 static unsigned long long printk_delay_msec
; /* per msec, based on boot_delay */
181 static int __init
boot_delay_setup(char *str
)
184 unsigned long long loops_per_msec
;
186 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
187 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
189 get_option(&str
, &boot_delay
);
190 if (boot_delay
> 10 * 1000)
193 printk_delay_msec
= loops_per_msec
;
194 printk(KERN_DEBUG
"boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
195 "HZ: %d, printk_delay_msec: %llu\n",
196 boot_delay
, preset_lpj
, lpj
, HZ
, printk_delay_msec
);
199 __setup("boot_delay=", boot_delay_setup
);
201 static void boot_delay_msec(void)
203 unsigned long long k
;
204 unsigned long timeout
;
206 if (boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
209 k
= (unsigned long long)printk_delay_msec
* boot_delay
;
211 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
216 * use (volatile) jiffies to prevent
217 * compiler reduction; loop termination via jiffies
218 * is secondary and may or may not happen.
220 if (time_after(jiffies
, timeout
))
222 touch_nmi_watchdog();
226 static inline void boot_delay_msec(void)
232 * Return the number of unread characters in the log buffer.
234 static int log_buf_get_len(void)
240 * Copy a range of characters from the log buffer.
242 int log_buf_copy(char *dest
, int idx
, int len
)
245 bool took_lock
= false;
247 if (!oops_in_progress
) {
248 spin_lock_irq(&logbuf_lock
);
252 max
= log_buf_get_len();
253 if (idx
< 0 || idx
>= max
) {
259 idx
+= (log_end
- max
);
261 dest
[len
] = LOG_BUF(idx
+ len
);
265 spin_unlock_irq(&logbuf_lock
);
271 * Commands to do_syslog:
273 * 0 -- Close the log. Currently a NOP.
274 * 1 -- Open the log. Currently a NOP.
275 * 2 -- Read from the log.
276 * 3 -- Read all messages remaining in the ring buffer.
277 * 4 -- Read and clear all messages remaining in the ring buffer
278 * 5 -- Clear ring buffer.
279 * 6 -- Disable printk's to console
280 * 7 -- Enable printk's to console
281 * 8 -- Set level of messages printed to console
282 * 9 -- Return number of unread characters in the log buffer
283 * 10 -- Return size of the log buffer
285 int do_syslog(int type
, char __user
*buf
, int len
)
287 unsigned i
, j
, limit
, count
;
292 error
= security_syslog(type
);
297 case 0: /* Close log */
299 case 1: /* Open log */
301 case 2: /* Read from log */
308 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
312 error
= wait_event_interruptible(log_wait
,
313 (log_start
- log_end
));
317 spin_lock_irq(&logbuf_lock
);
318 while (!error
&& (log_start
!= log_end
) && i
< len
) {
319 c
= LOG_BUF(log_start
);
321 spin_unlock_irq(&logbuf_lock
);
322 error
= __put_user(c
,buf
);
326 spin_lock_irq(&logbuf_lock
);
328 spin_unlock_irq(&logbuf_lock
);
332 case 4: /* Read/clear last kernel messages */
335 case 3: /* Read last kernel messages */
342 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
347 if (count
> log_buf_len
)
349 spin_lock_irq(&logbuf_lock
);
350 if (count
> logged_chars
)
351 count
= logged_chars
;
356 * __put_user() could sleep, and while we sleep
357 * printk() could overwrite the messages
358 * we try to copy to user space. Therefore
359 * the messages are copied in reverse. <manfreds>
361 for (i
= 0; i
< count
&& !error
; i
++) {
363 if (j
+ log_buf_len
< log_end
)
366 spin_unlock_irq(&logbuf_lock
);
367 error
= __put_user(c
,&buf
[count
-1-i
]);
369 spin_lock_irq(&logbuf_lock
);
371 spin_unlock_irq(&logbuf_lock
);
376 int offset
= count
-error
;
377 /* buffer overflow during copy, correct user buffer. */
378 for (i
= 0; i
< error
; i
++) {
379 if (__get_user(c
,&buf
[i
+offset
]) ||
380 __put_user(c
,&buf
[i
])) {
388 case 5: /* Clear ring buffer */
391 case 6: /* Disable logging to console */
392 console_loglevel
= minimum_console_loglevel
;
394 case 7: /* Enable logging to console */
395 console_loglevel
= default_console_loglevel
;
397 case 8: /* Set level of messages printed to console */
399 if (len
< 1 || len
> 8)
401 if (len
< minimum_console_loglevel
)
402 len
= minimum_console_loglevel
;
403 console_loglevel
= len
;
406 case 9: /* Number of chars in the log buffer */
407 error
= log_end
- log_start
;
409 case 10: /* Size of the log buffer */
420 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
422 return do_syslog(type
, buf
, len
);
426 * Call the console drivers on a range of log_buf
428 static void __call_console_drivers(unsigned start
, unsigned end
)
432 for (con
= console_drivers
; con
; con
= con
->next
) {
433 if ((con
->flags
& CON_ENABLED
) && con
->write
&&
434 (cpu_online(smp_processor_id()) ||
435 (con
->flags
& CON_ANYTIME
)))
436 con
->write(con
, &LOG_BUF(start
), end
- start
);
440 static int __read_mostly ignore_loglevel
;
442 static int __init
ignore_loglevel_setup(char *str
)
445 printk(KERN_INFO
"debug: ignoring loglevel setting.\n");
450 early_param("ignore_loglevel", ignore_loglevel_setup
);
453 * Write out chars from start to end - 1 inclusive
455 static void _call_console_drivers(unsigned start
,
456 unsigned end
, int msg_log_level
)
458 if ((msg_log_level
< console_loglevel
|| ignore_loglevel
) &&
459 console_drivers
&& start
!= end
) {
460 if ((start
& LOG_BUF_MASK
) > (end
& LOG_BUF_MASK
)) {
462 __call_console_drivers(start
& LOG_BUF_MASK
,
464 __call_console_drivers(0, end
& LOG_BUF_MASK
);
466 __call_console_drivers(start
, end
);
472 * Call the console drivers, asking them to write out
473 * log_buf[start] to log_buf[end - 1].
474 * The console_sem must be held.
476 static void call_console_drivers(unsigned start
, unsigned end
)
478 unsigned cur_index
, start_print
;
479 static int msg_level
= -1;
481 BUG_ON(((int)(start
- end
)) > 0);
485 while (cur_index
!= end
) {
486 if (msg_level
< 0 && ((end
- cur_index
) > 2) &&
487 LOG_BUF(cur_index
+ 0) == '<' &&
488 LOG_BUF(cur_index
+ 1) >= '0' &&
489 LOG_BUF(cur_index
+ 1) <= '7' &&
490 LOG_BUF(cur_index
+ 2) == '>') {
491 msg_level
= LOG_BUF(cur_index
+ 1) - '0';
493 start_print
= cur_index
;
495 while (cur_index
!= end
) {
496 char c
= LOG_BUF(cur_index
);
502 * printk() has already given us loglevel tags in
503 * the buffer. This code is here in case the
504 * log buffer has wrapped right round and scribbled
507 msg_level
= default_message_loglevel
;
509 _call_console_drivers(start_print
, cur_index
, msg_level
);
511 start_print
= cur_index
;
516 _call_console_drivers(start_print
, end
, msg_level
);
519 static void emit_log_char(char c
)
521 LOG_BUF(log_end
) = c
;
523 if (log_end
- log_start
> log_buf_len
)
524 log_start
= log_end
- log_buf_len
;
525 if (log_end
- con_start
> log_buf_len
)
526 con_start
= log_end
- log_buf_len
;
527 if (logged_chars
< log_buf_len
)
532 * Zap console related locks when oopsing. Only zap at most once
533 * every 10 seconds, to leave time for slow consoles to print a
536 static void zap_locks(void)
538 static unsigned long oops_timestamp
;
540 if (time_after_eq(jiffies
, oops_timestamp
) &&
541 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
544 oops_timestamp
= jiffies
;
546 /* If a crash is occurring, make sure we can't deadlock */
547 spin_lock_init(&logbuf_lock
);
548 /* And make sure that we print immediately */
549 init_MUTEX(&console_sem
);
552 #if defined(CONFIG_PRINTK_TIME)
553 static int printk_time
= 1;
555 static int printk_time
= 0;
557 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
559 /* Check if we have any console registered that can be called early in boot. */
560 static int have_callable_console(void)
564 for (con
= console_drivers
; con
; con
= con
->next
)
565 if (con
->flags
& CON_ANYTIME
)
572 * printk - print a kernel message
573 * @fmt: format string
575 * This is printk(). It can be called from any context. We want it to work.
576 * Be aware of the fact that if oops_in_progress is not set, we might try to
577 * wake klogd up which could deadlock on runqueue lock if printk() is called
578 * from scheduler code.
580 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
581 * call the console drivers. If we fail to get the semaphore we place the output
582 * into the log buffer and return. The current holder of the console_sem will
583 * notice the new output in release_console_sem() and will send it to the
584 * consoles before releasing the semaphore.
586 * One effect of this deferred printing is that code which calls printk() and
587 * then changes console_loglevel may break. This is because console_loglevel
588 * is inspected when the actual printing occurs.
594 asmlinkage
int printk(const char *fmt
, ...)
600 r
= vprintk(fmt
, args
);
606 /* cpu currently holding logbuf_lock */
607 static volatile unsigned int printk_cpu
= UINT_MAX
;
610 * Can we actually use the console at this time on this cpu?
612 * Console drivers may assume that per-cpu resources have
613 * been allocated. So unless they're explicitly marked as
614 * being able to cope (CON_ANYTIME) don't call them until
615 * this CPU is officially up.
617 static inline int can_use_console(unsigned int cpu
)
619 return cpu_online(cpu
) || have_callable_console();
623 * Try to get console ownership to actually show the kernel
624 * messages from a 'printk'. Return true (and with the
625 * console_semaphore held, and 'console_locked' set) if it
626 * is successful, false otherwise.
628 * This gets called with the 'logbuf_lock' spinlock held and
629 * interrupts disabled. It should return with 'lockbuf_lock'
630 * released but interrupts still disabled.
632 static int acquire_console_semaphore_for_printk(unsigned int cpu
)
636 if (!try_acquire_console_sem()) {
640 * If we can't use the console, we need to release
641 * the console semaphore by hand to avoid flushing
642 * the buffer. We need to hold the console semaphore
643 * in order to do this test safely.
645 if (!can_use_console(cpu
)) {
651 printk_cpu
= UINT_MAX
;
652 spin_unlock(&logbuf_lock
);
655 static const char recursion_bug_msg
[] =
656 KERN_CRIT
"BUG: recent printk recursion!\n";
657 static int recursion_bug
;
658 static int new_text_line
= 1;
659 static char printk_buf
[1024];
661 asmlinkage
int vprintk(const char *fmt
, va_list args
)
671 /* This stops the holder of console_sem just where we want him */
672 raw_local_irq_save(flags
);
673 this_cpu
= smp_processor_id();
676 * Ouch, printk recursed into itself!
678 if (unlikely(printk_cpu
== this_cpu
)) {
680 * If a crash is occurring during printk() on this CPU,
681 * then try to get the crash message out but make sure
682 * we can't deadlock. Otherwise just return to avoid the
683 * recursion and return - but flag the recursion so that
684 * it can be printed at the next appropriate moment:
686 if (!oops_in_progress
) {
688 goto out_restore_irqs
;
694 spin_lock(&logbuf_lock
);
695 printk_cpu
= this_cpu
;
699 strcpy(printk_buf
, recursion_bug_msg
);
700 printed_len
= sizeof(recursion_bug_msg
);
702 /* Emit the output into the temporary buffer */
703 printed_len
+= vscnprintf(printk_buf
+ printed_len
,
704 sizeof(printk_buf
) - printed_len
, fmt
, args
);
708 * Copy the output into log_buf. If the caller didn't provide
709 * appropriate log level tags, we insert them here
711 for (p
= printk_buf
; *p
; p
++) {
713 int current_log_level
= default_message_loglevel
;
714 /* If a token, set current_log_level and skip over */
715 if (p
[0] == '<' && p
[1] >= '0' && p
[1] <= '7' &&
717 current_log_level
= p
[1] - '0';
722 /* Always output the token */
724 emit_log_char(current_log_level
+ '0');
730 /* Follow the token with the time */
733 unsigned long long t
;
734 unsigned long nanosec_rem
;
736 t
= cpu_clock(printk_cpu
);
737 nanosec_rem
= do_div(t
, 1000000000);
738 tlen
= sprintf(tbuf
, "[%5lu.%06lu] ",
742 for (tp
= tbuf
; tp
< tbuf
+ tlen
; tp
++)
757 * Try to acquire and then immediately release the
758 * console semaphore. The release will do all the
759 * actual magic (print out buffers, wake up klogd,
762 * The acquire_console_semaphore_for_printk() function
763 * will release 'logbuf_lock' regardless of whether it
764 * actually gets the semaphore or not.
766 if (acquire_console_semaphore_for_printk(this_cpu
))
767 release_console_sem();
771 raw_local_irq_restore(flags
);
776 EXPORT_SYMBOL(printk
);
777 EXPORT_SYMBOL(vprintk
);
781 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
786 static void call_console_drivers(unsigned start
, unsigned end
)
792 static int __add_preferred_console(char *name
, int idx
, char *options
,
795 struct console_cmdline
*c
;
799 * See if this tty is not yet registered, and
800 * if we have a slot free.
802 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
803 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
804 console_cmdline
[i
].index
== idx
) {
806 selected_console
= i
;
809 if (i
== MAX_CMDLINECONSOLES
)
812 selected_console
= i
;
813 c
= &console_cmdline
[i
];
814 strlcpy(c
->name
, name
, sizeof(c
->name
));
815 c
->options
= options
;
816 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
817 c
->brl_options
= brl_options
;
823 * Set up a list of consoles. Called from init/main.c
825 static int __init
console_setup(char *str
)
827 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
828 char *s
, *options
, *brl_options
= NULL
;
831 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
832 if (!memcmp(str
, "brl,", 4)) {
835 } else if (!memcmp(str
, "brl=", 4)) {
836 brl_options
= str
+ 4;
837 str
= strchr(brl_options
, ',');
839 printk(KERN_ERR
"need port name after brl=\n");
847 * Decode str into name, index, options.
849 if (str
[0] >= '0' && str
[0] <= '9') {
851 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
853 strncpy(buf
, str
, sizeof(buf
) - 1);
855 buf
[sizeof(buf
) - 1] = 0;
856 if ((options
= strchr(str
, ',')) != NULL
)
859 if (!strcmp(str
, "ttya"))
860 strcpy(buf
, "ttyS0");
861 if (!strcmp(str
, "ttyb"))
862 strcpy(buf
, "ttyS1");
864 for (s
= buf
; *s
; s
++)
865 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
867 idx
= simple_strtoul(s
, NULL
, 10);
870 __add_preferred_console(buf
, idx
, options
, brl_options
);
873 __setup("console=", console_setup
);
876 * add_preferred_console - add a device to the list of preferred consoles.
879 * @options: options for this console
881 * The last preferred console added will be used for kernel messages
882 * and stdin/out/err for init. Normally this is used by console_setup
883 * above to handle user-supplied console arguments; however it can also
884 * be used by arch-specific code either to override the user or more
885 * commonly to provide a default console (ie from PROM variables) when
886 * the user has not supplied one.
888 int add_preferred_console(char *name
, int idx
, char *options
)
890 return __add_preferred_console(name
, idx
, options
, NULL
);
893 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
895 struct console_cmdline
*c
;
898 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
899 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
900 console_cmdline
[i
].index
== idx
) {
901 c
= &console_cmdline
[i
];
902 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
903 c
->name
[sizeof(c
->name
) - 1] = 0;
904 c
->options
= options
;
912 int console_suspend_enabled
= 1;
913 EXPORT_SYMBOL(console_suspend_enabled
);
915 static int __init
console_suspend_disable(char *str
)
917 console_suspend_enabled
= 0;
920 __setup("no_console_suspend", console_suspend_disable
);
923 * suspend_console - suspend the console subsystem
925 * This disables printk() while we go into suspend states
927 void suspend_console(void)
929 if (!console_suspend_enabled
)
931 printk("Suspending console(s)\n");
932 acquire_console_sem();
933 console_suspended
= 1;
936 void resume_console(void)
938 if (!console_suspend_enabled
)
940 console_suspended
= 0;
941 release_console_sem();
945 * acquire_console_sem - lock the console system for exclusive use.
947 * Acquires a semaphore which guarantees that the caller has
948 * exclusive access to the console system and the console_drivers list.
950 * Can sleep, returns nothing.
952 void acquire_console_sem(void)
954 BUG_ON(in_interrupt());
955 if (console_suspended
) {
956 down(&secondary_console_sem
);
961 console_may_schedule
= 1;
963 EXPORT_SYMBOL(acquire_console_sem
);
965 int try_acquire_console_sem(void)
967 if (down_trylock(&console_sem
))
970 console_may_schedule
= 0;
973 EXPORT_SYMBOL(try_acquire_console_sem
);
975 int is_console_locked(void)
977 return console_locked
;
980 void wake_up_klogd(void)
982 if (!oops_in_progress
&& waitqueue_active(&log_wait
))
983 wake_up_interruptible(&log_wait
);
987 * release_console_sem - unlock the console system
989 * Releases the semaphore which the caller holds on the console system
990 * and the console driver list.
992 * While the semaphore was held, console output may have been buffered
993 * by printk(). If this is the case, release_console_sem() emits
994 * the output prior to releasing the semaphore.
996 * If there is output waiting for klogd, we wake it up.
998 * release_console_sem() may be called from any context.
1000 void release_console_sem(void)
1002 unsigned long flags
;
1003 unsigned _con_start
, _log_end
;
1004 unsigned wake_klogd
= 0;
1006 if (console_suspended
) {
1007 up(&secondary_console_sem
);
1011 console_may_schedule
= 0;
1014 spin_lock_irqsave(&logbuf_lock
, flags
);
1015 wake_klogd
|= log_start
- log_end
;
1016 if (con_start
== log_end
)
1017 break; /* Nothing to print */
1018 _con_start
= con_start
;
1020 con_start
= log_end
; /* Flush */
1021 spin_unlock(&logbuf_lock
);
1022 call_console_drivers(_con_start
, _log_end
);
1023 local_irq_restore(flags
);
1027 spin_unlock_irqrestore(&logbuf_lock
, flags
);
1031 EXPORT_SYMBOL(release_console_sem
);
1034 * console_conditional_schedule - yield the CPU if required
1036 * If the console code is currently allowed to sleep, and
1037 * if this CPU should yield the CPU to another task, do
1040 * Must be called within acquire_console_sem().
1042 void __sched
console_conditional_schedule(void)
1044 if (console_may_schedule
)
1047 EXPORT_SYMBOL(console_conditional_schedule
);
1049 void console_print(const char *s
)
1051 printk(KERN_EMERG
"%s", s
);
1053 EXPORT_SYMBOL(console_print
);
1055 void console_unblank(void)
1060 * console_unblank can no longer be called in interrupt context unless
1061 * oops_in_progress is set to 1..
1063 if (oops_in_progress
) {
1064 if (down_trylock(&console_sem
) != 0)
1067 acquire_console_sem();
1070 console_may_schedule
= 0;
1071 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
)
1072 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
1074 release_console_sem();
1078 * Return the console tty driver structure and its associated index
1080 struct tty_driver
*console_device(int *index
)
1083 struct tty_driver
*driver
= NULL
;
1085 acquire_console_sem();
1086 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
) {
1089 driver
= c
->device(c
, index
);
1093 release_console_sem();
1098 * Prevent further output on the passed console device so that (for example)
1099 * serial drivers can disable console output before suspending a port, and can
1100 * re-enable output afterwards.
1102 void console_stop(struct console
*console
)
1104 acquire_console_sem();
1105 console
->flags
&= ~CON_ENABLED
;
1106 release_console_sem();
1108 EXPORT_SYMBOL(console_stop
);
1110 void console_start(struct console
*console
)
1112 acquire_console_sem();
1113 console
->flags
|= CON_ENABLED
;
1114 release_console_sem();
1116 EXPORT_SYMBOL(console_start
);
1119 * The console driver calls this routine during kernel initialization
1120 * to register the console printing procedure with printk() and to
1121 * print any messages that were printed by the kernel before the
1122 * console driver was initialized.
1124 void register_console(struct console
*console
)
1127 unsigned long flags
;
1128 struct console
*bootconsole
= NULL
;
1130 if (console_drivers
) {
1131 if (console
->flags
& CON_BOOT
)
1133 if (console_drivers
->flags
& CON_BOOT
)
1134 bootconsole
= console_drivers
;
1137 if (preferred_console
< 0 || bootconsole
|| !console_drivers
)
1138 preferred_console
= selected_console
;
1140 if (console
->early_setup
)
1141 console
->early_setup();
1144 * See if we want to use this console driver. If we
1145 * didn't select a console we take the first one
1146 * that registers here.
1148 if (preferred_console
< 0) {
1149 if (console
->index
< 0)
1151 if (console
->setup
== NULL
||
1152 console
->setup(console
, NULL
) == 0) {
1153 console
->flags
|= CON_ENABLED
;
1154 if (console
->device
) {
1155 console
->flags
|= CON_CONSDEV
;
1156 preferred_console
= 0;
1162 * See if this console matches one we selected on
1165 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
1167 if (strcmp(console_cmdline
[i
].name
, console
->name
) != 0)
1169 if (console
->index
>= 0 &&
1170 console
->index
!= console_cmdline
[i
].index
)
1172 if (console
->index
< 0)
1173 console
->index
= console_cmdline
[i
].index
;
1174 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1175 if (console_cmdline
[i
].brl_options
) {
1176 console
->flags
|= CON_BRL
;
1177 braille_register_console(console
,
1178 console_cmdline
[i
].index
,
1179 console_cmdline
[i
].options
,
1180 console_cmdline
[i
].brl_options
);
1184 if (console
->setup
&&
1185 console
->setup(console
, console_cmdline
[i
].options
) != 0)
1187 console
->flags
|= CON_ENABLED
;
1188 console
->index
= console_cmdline
[i
].index
;
1189 if (i
== selected_console
) {
1190 console
->flags
|= CON_CONSDEV
;
1191 preferred_console
= selected_console
;
1196 if (!(console
->flags
& CON_ENABLED
))
1199 if (bootconsole
&& (console
->flags
& CON_CONSDEV
)) {
1200 printk(KERN_INFO
"console handover: boot [%s%d] -> real [%s%d]\n",
1201 bootconsole
->name
, bootconsole
->index
,
1202 console
->name
, console
->index
);
1203 unregister_console(bootconsole
);
1204 console
->flags
&= ~CON_PRINTBUFFER
;
1206 printk(KERN_INFO
"console [%s%d] enabled\n",
1207 console
->name
, console
->index
);
1211 * Put this console in the list - keep the
1212 * preferred driver at the head of the list.
1214 acquire_console_sem();
1215 if ((console
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
1216 console
->next
= console_drivers
;
1217 console_drivers
= console
;
1219 console
->next
->flags
&= ~CON_CONSDEV
;
1221 console
->next
= console_drivers
->next
;
1222 console_drivers
->next
= console
;
1224 if (console
->flags
& CON_PRINTBUFFER
) {
1226 * release_console_sem() will print out the buffered messages
1229 spin_lock_irqsave(&logbuf_lock
, flags
);
1230 con_start
= log_start
;
1231 spin_unlock_irqrestore(&logbuf_lock
, flags
);
1233 release_console_sem();
1235 EXPORT_SYMBOL(register_console
);
1237 int unregister_console(struct console
*console
)
1239 struct console
*a
, *b
;
1242 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1243 if (console
->flags
& CON_BRL
)
1244 return braille_unregister_console(console
);
1247 acquire_console_sem();
1248 if (console_drivers
== console
) {
1249 console_drivers
=console
->next
;
1251 } else if (console_drivers
) {
1252 for (a
=console_drivers
->next
, b
=console_drivers
;
1253 a
; b
=a
, a
=b
->next
) {
1263 * If this isn't the last console and it has CON_CONSDEV set, we
1264 * need to set it on the next preferred console.
1266 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
1267 console_drivers
->flags
|= CON_CONSDEV
;
1269 release_console_sem();
1272 EXPORT_SYMBOL(unregister_console
);
1274 static int __init
disable_boot_consoles(void)
1276 if (console_drivers
!= NULL
) {
1277 if (console_drivers
->flags
& CON_BOOT
) {
1278 printk(KERN_INFO
"turn off boot console %s%d\n",
1279 console_drivers
->name
, console_drivers
->index
);
1280 return unregister_console(console_drivers
);
1285 late_initcall(disable_boot_consoles
);
1288 * tty_write_message - write a message to a certain tty, not just the console.
1289 * @tty: the destination tty_struct
1290 * @msg: the message to write
1292 * This is used for messages that need to be redirected to a specific tty.
1293 * We don't put it into the syslog queue right now maybe in the future if
1296 void tty_write_message(struct tty_struct
*tty
, char *msg
)
1298 if (tty
&& tty
->ops
->write
)
1299 tty
->ops
->write(tty
, msg
, strlen(msg
));
1303 #if defined CONFIG_PRINTK
1305 * printk rate limiting, lifted from the networking subsystem.
1307 * This enforces a rate limit: not more than one kernel message
1308 * every printk_ratelimit_jiffies to make a denial-of-service
1309 * attack impossible.
1311 int __printk_ratelimit(int ratelimit_jiffies
, int ratelimit_burst
)
1313 return __ratelimit(ratelimit_jiffies
, ratelimit_burst
);
1315 EXPORT_SYMBOL(__printk_ratelimit
);
1317 /* minimum time in jiffies between messages */
1318 int printk_ratelimit_jiffies
= 5 * HZ
;
1320 /* number of messages we send before ratelimiting */
1321 int printk_ratelimit_burst
= 10;
1323 int printk_ratelimit(void)
1325 return __printk_ratelimit(printk_ratelimit_jiffies
,
1326 printk_ratelimit_burst
);
1328 EXPORT_SYMBOL(printk_ratelimit
);
1331 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1332 * @caller_jiffies: pointer to caller's state
1333 * @interval_msecs: minimum interval between prints
1335 * printk_timed_ratelimit() returns true if more than @interval_msecs
1336 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1339 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
1340 unsigned int interval_msecs
)
1342 if (*caller_jiffies
== 0 || time_after(jiffies
, *caller_jiffies
)) {
1343 *caller_jiffies
= jiffies
+ msecs_to_jiffies(interval_msecs
);
1348 EXPORT_SYMBOL(printk_timed_ratelimit
);