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;
124 int console_set_on_cmdline
;
125 EXPORT_SYMBOL(console_set_on_cmdline
);
127 /* Flag: console code may call schedule() */
128 static int console_may_schedule
;
132 static char __log_buf
[__LOG_BUF_LEN
];
133 static char *log_buf
= __log_buf
;
134 static int log_buf_len
= __LOG_BUF_LEN
;
135 static unsigned logged_chars
; /* Number of chars produced since last read+clear operation */
137 static int __init
log_buf_len_setup(char *str
)
139 unsigned size
= memparse(str
, &str
);
143 size
= roundup_pow_of_two(size
);
144 if (size
> log_buf_len
) {
145 unsigned start
, dest_idx
, offset
;
148 new_log_buf
= alloc_bootmem(size
);
150 printk(KERN_WARNING
"log_buf_len: allocation failed\n");
154 spin_lock_irqsave(&logbuf_lock
, flags
);
156 log_buf
= new_log_buf
;
158 offset
= start
= min(con_start
, log_start
);
160 while (start
!= log_end
) {
161 log_buf
[dest_idx
] = __log_buf
[start
& (__LOG_BUF_LEN
- 1)];
168 spin_unlock_irqrestore(&logbuf_lock
, flags
);
170 printk(KERN_NOTICE
"log_buf_len: %d\n", log_buf_len
);
176 __setup("log_buf_len=", log_buf_len_setup
);
178 #ifdef CONFIG_BOOT_PRINTK_DELAY
180 static unsigned int boot_delay
; /* msecs delay after each printk during bootup */
181 static unsigned long long printk_delay_msec
; /* per msec, based on boot_delay */
183 static int __init
boot_delay_setup(char *str
)
186 unsigned long long loops_per_msec
;
188 lpj
= preset_lpj
? preset_lpj
: 1000000; /* some guess */
189 loops_per_msec
= (unsigned long long)lpj
/ 1000 * HZ
;
191 get_option(&str
, &boot_delay
);
192 if (boot_delay
> 10 * 1000)
195 printk_delay_msec
= loops_per_msec
;
196 printk(KERN_DEBUG
"boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
197 "HZ: %d, printk_delay_msec: %llu\n",
198 boot_delay
, preset_lpj
, lpj
, HZ
, printk_delay_msec
);
201 __setup("boot_delay=", boot_delay_setup
);
203 static void boot_delay_msec(void)
205 unsigned long long k
;
206 unsigned long timeout
;
208 if (boot_delay
== 0 || system_state
!= SYSTEM_BOOTING
)
211 k
= (unsigned long long)printk_delay_msec
* boot_delay
;
213 timeout
= jiffies
+ msecs_to_jiffies(boot_delay
);
218 * use (volatile) jiffies to prevent
219 * compiler reduction; loop termination via jiffies
220 * is secondary and may or may not happen.
222 if (time_after(jiffies
, timeout
))
224 touch_nmi_watchdog();
228 static inline void boot_delay_msec(void)
234 * Return the number of unread characters in the log buffer.
236 int log_buf_get_len(void)
242 * Copy a range of characters from the log buffer.
244 int log_buf_copy(char *dest
, int idx
, int len
)
247 bool took_lock
= false;
249 if (!oops_in_progress
) {
250 spin_lock_irq(&logbuf_lock
);
254 max
= log_buf_get_len();
255 if (idx
< 0 || idx
>= max
) {
261 idx
+= (log_end
- max
);
263 dest
[len
] = LOG_BUF(idx
+ len
);
267 spin_unlock_irq(&logbuf_lock
);
273 * Extract a single character from the log buffer.
275 int log_buf_read(int idx
)
279 if (log_buf_copy(&ret
, idx
, 1) == 1)
286 * Commands to do_syslog:
288 * 0 -- Close the log. Currently a NOP.
289 * 1 -- Open the log. Currently a NOP.
290 * 2 -- Read from the log.
291 * 3 -- Read all messages remaining in the ring buffer.
292 * 4 -- Read and clear all messages remaining in the ring buffer
293 * 5 -- Clear ring buffer.
294 * 6 -- Disable printk's to console
295 * 7 -- Enable printk's to console
296 * 8 -- Set level of messages printed to console
297 * 9 -- Return number of unread characters in the log buffer
298 * 10 -- Return size of the log buffer
300 int do_syslog(int type
, char __user
*buf
, int len
)
302 unsigned i
, j
, limit
, count
;
307 error
= security_syslog(type
);
312 case 0: /* Close log */
314 case 1: /* Open log */
316 case 2: /* Read from log */
323 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
327 error
= wait_event_interruptible(log_wait
,
328 (log_start
- log_end
));
332 spin_lock_irq(&logbuf_lock
);
333 while (!error
&& (log_start
!= log_end
) && i
< len
) {
334 c
= LOG_BUF(log_start
);
336 spin_unlock_irq(&logbuf_lock
);
337 error
= __put_user(c
,buf
);
341 spin_lock_irq(&logbuf_lock
);
343 spin_unlock_irq(&logbuf_lock
);
347 case 4: /* Read/clear last kernel messages */
350 case 3: /* Read last kernel messages */
357 if (!access_ok(VERIFY_WRITE
, buf
, len
)) {
362 if (count
> log_buf_len
)
364 spin_lock_irq(&logbuf_lock
);
365 if (count
> logged_chars
)
366 count
= logged_chars
;
371 * __put_user() could sleep, and while we sleep
372 * printk() could overwrite the messages
373 * we try to copy to user space. Therefore
374 * the messages are copied in reverse. <manfreds>
376 for (i
= 0; i
< count
&& !error
; i
++) {
378 if (j
+ log_buf_len
< log_end
)
381 spin_unlock_irq(&logbuf_lock
);
382 error
= __put_user(c
,&buf
[count
-1-i
]);
384 spin_lock_irq(&logbuf_lock
);
386 spin_unlock_irq(&logbuf_lock
);
391 int offset
= count
-error
;
392 /* buffer overflow during copy, correct user buffer. */
393 for (i
= 0; i
< error
; i
++) {
394 if (__get_user(c
,&buf
[i
+offset
]) ||
395 __put_user(c
,&buf
[i
])) {
403 case 5: /* Clear ring buffer */
406 case 6: /* Disable logging to console */
407 console_loglevel
= minimum_console_loglevel
;
409 case 7: /* Enable logging to console */
410 console_loglevel
= default_console_loglevel
;
412 case 8: /* Set level of messages printed to console */
414 if (len
< 1 || len
> 8)
416 if (len
< minimum_console_loglevel
)
417 len
= minimum_console_loglevel
;
418 console_loglevel
= len
;
421 case 9: /* Number of chars in the log buffer */
422 error
= log_end
- log_start
;
424 case 10: /* Size of the log buffer */
435 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
437 return do_syslog(type
, buf
, len
);
441 * Call the console drivers on a range of log_buf
443 static void __call_console_drivers(unsigned start
, unsigned end
)
447 for (con
= console_drivers
; con
; con
= con
->next
) {
448 if ((con
->flags
& CON_ENABLED
) && con
->write
&&
449 (cpu_online(smp_processor_id()) ||
450 (con
->flags
& CON_ANYTIME
)))
451 con
->write(con
, &LOG_BUF(start
), end
- start
);
455 static int __read_mostly ignore_loglevel
;
457 static int __init
ignore_loglevel_setup(char *str
)
460 printk(KERN_INFO
"debug: ignoring loglevel setting.\n");
465 early_param("ignore_loglevel", ignore_loglevel_setup
);
468 * Write out chars from start to end - 1 inclusive
470 static void _call_console_drivers(unsigned start
,
471 unsigned end
, int msg_log_level
)
473 if ((msg_log_level
< console_loglevel
|| ignore_loglevel
) &&
474 console_drivers
&& start
!= end
) {
475 if ((start
& LOG_BUF_MASK
) > (end
& LOG_BUF_MASK
)) {
477 __call_console_drivers(start
& LOG_BUF_MASK
,
479 __call_console_drivers(0, end
& LOG_BUF_MASK
);
481 __call_console_drivers(start
, end
);
487 * Call the console drivers, asking them to write out
488 * log_buf[start] to log_buf[end - 1].
489 * The console_sem must be held.
491 static void call_console_drivers(unsigned start
, unsigned end
)
493 unsigned cur_index
, start_print
;
494 static int msg_level
= -1;
496 BUG_ON(((int)(start
- end
)) > 0);
500 while (cur_index
!= end
) {
501 if (msg_level
< 0 && ((end
- cur_index
) > 2) &&
502 LOG_BUF(cur_index
+ 0) == '<' &&
503 LOG_BUF(cur_index
+ 1) >= '0' &&
504 LOG_BUF(cur_index
+ 1) <= '7' &&
505 LOG_BUF(cur_index
+ 2) == '>') {
506 msg_level
= LOG_BUF(cur_index
+ 1) - '0';
508 start_print
= cur_index
;
510 while (cur_index
!= end
) {
511 char c
= LOG_BUF(cur_index
);
517 * printk() has already given us loglevel tags in
518 * the buffer. This code is here in case the
519 * log buffer has wrapped right round and scribbled
522 msg_level
= default_message_loglevel
;
524 _call_console_drivers(start_print
, cur_index
, msg_level
);
526 start_print
= cur_index
;
531 _call_console_drivers(start_print
, end
, msg_level
);
534 static void emit_log_char(char c
)
536 LOG_BUF(log_end
) = c
;
538 if (log_end
- log_start
> log_buf_len
)
539 log_start
= log_end
- log_buf_len
;
540 if (log_end
- con_start
> log_buf_len
)
541 con_start
= log_end
- log_buf_len
;
542 if (logged_chars
< log_buf_len
)
547 * Zap console related locks when oopsing. Only zap at most once
548 * every 10 seconds, to leave time for slow consoles to print a
551 static void zap_locks(void)
553 static unsigned long oops_timestamp
;
555 if (time_after_eq(jiffies
, oops_timestamp
) &&
556 !time_after(jiffies
, oops_timestamp
+ 30 * HZ
))
559 oops_timestamp
= jiffies
;
561 /* If a crash is occurring, make sure we can't deadlock */
562 spin_lock_init(&logbuf_lock
);
563 /* And make sure that we print immediately */
564 init_MUTEX(&console_sem
);
567 #if defined(CONFIG_PRINTK_TIME)
568 static int printk_time
= 1;
570 static int printk_time
= 0;
572 module_param_named(time
, printk_time
, bool, S_IRUGO
| S_IWUSR
);
574 /* Check if we have any console registered that can be called early in boot. */
575 static int have_callable_console(void)
579 for (con
= console_drivers
; con
; con
= con
->next
)
580 if (con
->flags
& CON_ANYTIME
)
587 * printk - print a kernel message
588 * @fmt: format string
590 * This is printk(). It can be called from any context. We want it to work.
591 * Be aware of the fact that if oops_in_progress is not set, we might try to
592 * wake klogd up which could deadlock on runqueue lock if printk() is called
593 * from scheduler code.
595 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
596 * call the console drivers. If we fail to get the semaphore we place the output
597 * into the log buffer and return. The current holder of the console_sem will
598 * notice the new output in release_console_sem() and will send it to the
599 * consoles before releasing the semaphore.
601 * One effect of this deferred printing is that code which calls printk() and
602 * then changes console_loglevel may break. This is because console_loglevel
603 * is inspected when the actual printing occurs.
609 asmlinkage
int printk(const char *fmt
, ...)
615 r
= vprintk(fmt
, args
);
621 /* cpu currently holding logbuf_lock */
622 static volatile unsigned int printk_cpu
= UINT_MAX
;
625 * Can we actually use the console at this time on this cpu?
627 * Console drivers may assume that per-cpu resources have
628 * been allocated. So unless they're explicitly marked as
629 * being able to cope (CON_ANYTIME) don't call them until
630 * this CPU is officially up.
632 static inline int can_use_console(unsigned int cpu
)
634 return cpu_online(cpu
) || have_callable_console();
638 * Try to get console ownership to actually show the kernel
639 * messages from a 'printk'. Return true (and with the
640 * console_semaphore held, and 'console_locked' set) if it
641 * is successful, false otherwise.
643 * This gets called with the 'logbuf_lock' spinlock held and
644 * interrupts disabled. It should return with 'lockbuf_lock'
645 * released but interrupts still disabled.
647 static int acquire_console_semaphore_for_printk(unsigned int cpu
)
651 if (!try_acquire_console_sem()) {
655 * If we can't use the console, we need to release
656 * the console semaphore by hand to avoid flushing
657 * the buffer. We need to hold the console semaphore
658 * in order to do this test safely.
660 if (!can_use_console(cpu
)) {
666 printk_cpu
= UINT_MAX
;
667 spin_unlock(&logbuf_lock
);
671 const char printk_recursion_bug_msg
[] =
672 KERN_CRIT
"BUG: recent printk recursion!\n";
673 static int printk_recursion_bug
;
675 asmlinkage
int vprintk(const char *fmt
, va_list args
)
677 static int log_level_unknown
= 1;
678 static char printk_buf
[1024];
688 /* This stops the holder of console_sem just where we want him */
689 raw_local_irq_save(flags
);
690 this_cpu
= smp_processor_id();
693 * Ouch, printk recursed into itself!
695 if (unlikely(printk_cpu
== this_cpu
)) {
697 * If a crash is occurring during printk() on this CPU,
698 * then try to get the crash message out but make sure
699 * we can't deadlock. Otherwise just return to avoid the
700 * recursion and return - but flag the recursion so that
701 * it can be printed at the next appropriate moment:
703 if (!oops_in_progress
) {
704 printk_recursion_bug
= 1;
705 goto out_restore_irqs
;
711 spin_lock(&logbuf_lock
);
712 printk_cpu
= this_cpu
;
714 if (printk_recursion_bug
) {
715 printk_recursion_bug
= 0;
716 strcpy(printk_buf
, printk_recursion_bug_msg
);
717 printed_len
= sizeof(printk_recursion_bug_msg
);
719 /* Emit the output into the temporary buffer */
720 printed_len
+= vscnprintf(printk_buf
+ printed_len
,
721 sizeof(printk_buf
) - printed_len
, fmt
, args
);
724 * Copy the output into log_buf. If the caller didn't provide
725 * appropriate log level tags, we insert them here
727 for (p
= printk_buf
; *p
; p
++) {
728 if (log_level_unknown
) {
729 /* log_level_unknown signals the start of a new line */
734 unsigned long long t
;
735 unsigned long nanosec_rem
;
738 * force the log level token to be
739 * before the time output.
741 if (p
[0] == '<' && p
[1] >='0' &&
742 p
[1] <= '7' && p
[2] == '>') {
747 loglev_char
= default_message_loglevel
750 t
= cpu_clock(printk_cpu
);
751 nanosec_rem
= do_div(t
, 1000000000);
758 for (tp
= tbuf
; tp
< tbuf
+ tlen
; tp
++)
762 if (p
[0] != '<' || p
[1] < '0' ||
763 p
[1] > '7' || p
[2] != '>') {
765 emit_log_char(default_message_loglevel
771 log_level_unknown
= 0;
777 log_level_unknown
= 1;
781 * Try to acquire and then immediately release the
782 * console semaphore. The release will do all the
783 * actual magic (print out buffers, wake up klogd,
786 * The acquire_console_semaphore_for_printk() function
787 * will release 'logbuf_lock' regardless of whether it
788 * actually gets the semaphore or not.
790 if (acquire_console_semaphore_for_printk(this_cpu
))
791 release_console_sem();
795 raw_local_irq_restore(flags
);
800 EXPORT_SYMBOL(printk
);
801 EXPORT_SYMBOL(vprintk
);
805 asmlinkage
long sys_syslog(int type
, char __user
*buf
, int len
)
810 static void call_console_drivers(unsigned start
, unsigned end
)
816 static int __add_preferred_console(char *name
, int idx
, char *options
,
819 struct console_cmdline
*c
;
823 * See if this tty is not yet registered, and
824 * if we have a slot free.
826 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
827 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
828 console_cmdline
[i
].index
== idx
) {
830 selected_console
= i
;
833 if (i
== MAX_CMDLINECONSOLES
)
836 selected_console
= i
;
837 c
= &console_cmdline
[i
];
838 strlcpy(c
->name
, name
, sizeof(c
->name
));
839 c
->options
= options
;
840 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
841 c
->brl_options
= brl_options
;
847 * Set up a list of consoles. Called from init/main.c
849 static int __init
console_setup(char *str
)
851 char buf
[sizeof(console_cmdline
[0].name
) + 4]; /* 4 for index */
852 char *s
, *options
, *brl_options
= NULL
;
855 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
856 if (!memcmp(str
, "brl,", 4)) {
859 } else if (!memcmp(str
, "brl=", 4)) {
860 brl_options
= str
+ 4;
861 str
= strchr(brl_options
, ',');
863 printk(KERN_ERR
"need port name after brl=\n");
871 * Decode str into name, index, options.
873 if (str
[0] >= '0' && str
[0] <= '9') {
875 strncpy(buf
+ 4, str
, sizeof(buf
) - 5);
877 strncpy(buf
, str
, sizeof(buf
) - 1);
879 buf
[sizeof(buf
) - 1] = 0;
880 if ((options
= strchr(str
, ',')) != NULL
)
883 if (!strcmp(str
, "ttya"))
884 strcpy(buf
, "ttyS0");
885 if (!strcmp(str
, "ttyb"))
886 strcpy(buf
, "ttyS1");
888 for (s
= buf
; *s
; s
++)
889 if ((*s
>= '0' && *s
<= '9') || *s
== ',')
891 idx
= simple_strtoul(s
, NULL
, 10);
894 __add_preferred_console(buf
, idx
, options
, brl_options
);
895 console_set_on_cmdline
= 1;
898 __setup("console=", console_setup
);
901 * add_preferred_console - add a device to the list of preferred consoles.
904 * @options: options for this console
906 * The last preferred console added will be used for kernel messages
907 * and stdin/out/err for init. Normally this is used by console_setup
908 * above to handle user-supplied console arguments; however it can also
909 * be used by arch-specific code either to override the user or more
910 * commonly to provide a default console (ie from PROM variables) when
911 * the user has not supplied one.
913 int add_preferred_console(char *name
, int idx
, char *options
)
915 return __add_preferred_console(name
, idx
, options
, NULL
);
918 int update_console_cmdline(char *name
, int idx
, char *name_new
, int idx_new
, char *options
)
920 struct console_cmdline
*c
;
923 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0]; i
++)
924 if (strcmp(console_cmdline
[i
].name
, name
) == 0 &&
925 console_cmdline
[i
].index
== idx
) {
926 c
= &console_cmdline
[i
];
927 strlcpy(c
->name
, name_new
, sizeof(c
->name
));
928 c
->name
[sizeof(c
->name
) - 1] = 0;
929 c
->options
= options
;
937 int console_suspend_enabled
= 1;
938 EXPORT_SYMBOL(console_suspend_enabled
);
940 static int __init
console_suspend_disable(char *str
)
942 console_suspend_enabled
= 0;
945 __setup("no_console_suspend", console_suspend_disable
);
948 * suspend_console - suspend the console subsystem
950 * This disables printk() while we go into suspend states
952 void suspend_console(void)
954 if (!console_suspend_enabled
)
956 printk("Suspending console(s)\n");
957 acquire_console_sem();
958 console_suspended
= 1;
961 void resume_console(void)
963 if (!console_suspend_enabled
)
965 console_suspended
= 0;
966 release_console_sem();
970 * acquire_console_sem - lock the console system for exclusive use.
972 * Acquires a semaphore which guarantees that the caller has
973 * exclusive access to the console system and the console_drivers list.
975 * Can sleep, returns nothing.
977 void acquire_console_sem(void)
979 BUG_ON(in_interrupt());
980 if (console_suspended
) {
981 down(&secondary_console_sem
);
986 console_may_schedule
= 1;
988 EXPORT_SYMBOL(acquire_console_sem
);
990 int try_acquire_console_sem(void)
992 if (down_trylock(&console_sem
))
995 console_may_schedule
= 0;
998 EXPORT_SYMBOL(try_acquire_console_sem
);
1000 int is_console_locked(void)
1002 return console_locked
;
1005 void wake_up_klogd(void)
1007 if (!oops_in_progress
&& waitqueue_active(&log_wait
))
1008 wake_up_interruptible(&log_wait
);
1012 * release_console_sem - unlock the console system
1014 * Releases the semaphore which the caller holds on the console system
1015 * and the console driver list.
1017 * While the semaphore was held, console output may have been buffered
1018 * by printk(). If this is the case, release_console_sem() emits
1019 * the output prior to releasing the semaphore.
1021 * If there is output waiting for klogd, we wake it up.
1023 * release_console_sem() may be called from any context.
1025 void release_console_sem(void)
1027 unsigned long flags
;
1028 unsigned _con_start
, _log_end
;
1029 unsigned wake_klogd
= 0;
1031 if (console_suspended
) {
1032 up(&secondary_console_sem
);
1036 console_may_schedule
= 0;
1039 spin_lock_irqsave(&logbuf_lock
, flags
);
1040 wake_klogd
|= log_start
- log_end
;
1041 if (con_start
== log_end
)
1042 break; /* Nothing to print */
1043 _con_start
= con_start
;
1045 con_start
= log_end
; /* Flush */
1046 spin_unlock(&logbuf_lock
);
1047 call_console_drivers(_con_start
, _log_end
);
1048 local_irq_restore(flags
);
1052 spin_unlock_irqrestore(&logbuf_lock
, flags
);
1056 EXPORT_SYMBOL(release_console_sem
);
1059 * console_conditional_schedule - yield the CPU if required
1061 * If the console code is currently allowed to sleep, and
1062 * if this CPU should yield the CPU to another task, do
1065 * Must be called within acquire_console_sem().
1067 void __sched
console_conditional_schedule(void)
1069 if (console_may_schedule
)
1072 EXPORT_SYMBOL(console_conditional_schedule
);
1074 void console_print(const char *s
)
1076 printk(KERN_EMERG
"%s", s
);
1078 EXPORT_SYMBOL(console_print
);
1080 void console_unblank(void)
1085 * console_unblank can no longer be called in interrupt context unless
1086 * oops_in_progress is set to 1..
1088 if (oops_in_progress
) {
1089 if (down_trylock(&console_sem
) != 0)
1092 acquire_console_sem();
1095 console_may_schedule
= 0;
1096 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
)
1097 if ((c
->flags
& CON_ENABLED
) && c
->unblank
)
1099 release_console_sem();
1103 * Return the console tty driver structure and its associated index
1105 struct tty_driver
*console_device(int *index
)
1108 struct tty_driver
*driver
= NULL
;
1110 acquire_console_sem();
1111 for (c
= console_drivers
; c
!= NULL
; c
= c
->next
) {
1114 driver
= c
->device(c
, index
);
1118 release_console_sem();
1123 * Prevent further output on the passed console device so that (for example)
1124 * serial drivers can disable console output before suspending a port, and can
1125 * re-enable output afterwards.
1127 void console_stop(struct console
*console
)
1129 acquire_console_sem();
1130 console
->flags
&= ~CON_ENABLED
;
1131 release_console_sem();
1133 EXPORT_SYMBOL(console_stop
);
1135 void console_start(struct console
*console
)
1137 acquire_console_sem();
1138 console
->flags
|= CON_ENABLED
;
1139 release_console_sem();
1141 EXPORT_SYMBOL(console_start
);
1144 * The console driver calls this routine during kernel initialization
1145 * to register the console printing procedure with printk() and to
1146 * print any messages that were printed by the kernel before the
1147 * console driver was initialized.
1149 void register_console(struct console
*console
)
1152 unsigned long flags
;
1153 struct console
*bootconsole
= NULL
;
1155 if (console_drivers
) {
1156 if (console
->flags
& CON_BOOT
)
1158 if (console_drivers
->flags
& CON_BOOT
)
1159 bootconsole
= console_drivers
;
1162 if (preferred_console
< 0 || bootconsole
|| !console_drivers
)
1163 preferred_console
= selected_console
;
1165 if (console
->early_setup
)
1166 console
->early_setup();
1169 * See if we want to use this console driver. If we
1170 * didn't select a console we take the first one
1171 * that registers here.
1173 if (preferred_console
< 0) {
1174 if (console
->index
< 0)
1176 if (console
->setup
== NULL
||
1177 console
->setup(console
, NULL
) == 0) {
1178 console
->flags
|= CON_ENABLED
| CON_CONSDEV
;
1179 preferred_console
= 0;
1184 * See if this console matches one we selected on
1187 for (i
= 0; i
< MAX_CMDLINECONSOLES
&& console_cmdline
[i
].name
[0];
1189 if (strcmp(console_cmdline
[i
].name
, console
->name
) != 0)
1191 if (console
->index
>= 0 &&
1192 console
->index
!= console_cmdline
[i
].index
)
1194 if (console
->index
< 0)
1195 console
->index
= console_cmdline
[i
].index
;
1196 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1197 if (console_cmdline
[i
].brl_options
) {
1198 console
->flags
|= CON_BRL
;
1199 braille_register_console(console
,
1200 console_cmdline
[i
].index
,
1201 console_cmdline
[i
].options
,
1202 console_cmdline
[i
].brl_options
);
1206 if (console
->setup
&&
1207 console
->setup(console
, console_cmdline
[i
].options
) != 0)
1209 console
->flags
|= CON_ENABLED
;
1210 console
->index
= console_cmdline
[i
].index
;
1211 if (i
== selected_console
) {
1212 console
->flags
|= CON_CONSDEV
;
1213 preferred_console
= selected_console
;
1218 if (!(console
->flags
& CON_ENABLED
))
1221 if (bootconsole
&& (console
->flags
& CON_CONSDEV
)) {
1222 printk(KERN_INFO
"console handover: boot [%s%d] -> real [%s%d]\n",
1223 bootconsole
->name
, bootconsole
->index
,
1224 console
->name
, console
->index
);
1225 unregister_console(bootconsole
);
1226 console
->flags
&= ~CON_PRINTBUFFER
;
1228 printk(KERN_INFO
"console [%s%d] enabled\n",
1229 console
->name
, console
->index
);
1233 * Put this console in the list - keep the
1234 * preferred driver at the head of the list.
1236 acquire_console_sem();
1237 if ((console
->flags
& CON_CONSDEV
) || console_drivers
== NULL
) {
1238 console
->next
= console_drivers
;
1239 console_drivers
= console
;
1241 console
->next
->flags
&= ~CON_CONSDEV
;
1243 console
->next
= console_drivers
->next
;
1244 console_drivers
->next
= console
;
1246 if (console
->flags
& CON_PRINTBUFFER
) {
1248 * release_console_sem() will print out the buffered messages
1251 spin_lock_irqsave(&logbuf_lock
, flags
);
1252 con_start
= log_start
;
1253 spin_unlock_irqrestore(&logbuf_lock
, flags
);
1255 release_console_sem();
1257 EXPORT_SYMBOL(register_console
);
1259 int unregister_console(struct console
*console
)
1261 struct console
*a
, *b
;
1264 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1265 if (console
->flags
& CON_BRL
)
1266 return braille_unregister_console(console
);
1269 acquire_console_sem();
1270 if (console_drivers
== console
) {
1271 console_drivers
=console
->next
;
1273 } else if (console_drivers
) {
1274 for (a
=console_drivers
->next
, b
=console_drivers
;
1275 a
; b
=a
, a
=b
->next
) {
1285 * If this isn't the last console and it has CON_CONSDEV set, we
1286 * need to set it on the next preferred console.
1288 if (console_drivers
!= NULL
&& console
->flags
& CON_CONSDEV
)
1289 console_drivers
->flags
|= CON_CONSDEV
;
1291 release_console_sem();
1294 EXPORT_SYMBOL(unregister_console
);
1296 static int __init
disable_boot_consoles(void)
1298 if (console_drivers
!= NULL
) {
1299 if (console_drivers
->flags
& CON_BOOT
) {
1300 printk(KERN_INFO
"turn off boot console %s%d\n",
1301 console_drivers
->name
, console_drivers
->index
);
1302 return unregister_console(console_drivers
);
1307 late_initcall(disable_boot_consoles
);
1310 * tty_write_message - write a message to a certain tty, not just the console.
1311 * @tty: the destination tty_struct
1312 * @msg: the message to write
1314 * This is used for messages that need to be redirected to a specific tty.
1315 * We don't put it into the syslog queue right now maybe in the future if
1318 void tty_write_message(struct tty_struct
*tty
, char *msg
)
1320 if (tty
&& tty
->ops
->write
)
1321 tty
->ops
->write(tty
, msg
, strlen(msg
));
1325 #if defined CONFIG_PRINTK
1327 * printk rate limiting, lifted from the networking subsystem.
1329 * This enforces a rate limit: not more than one kernel message
1330 * every printk_ratelimit_jiffies to make a denial-of-service
1331 * attack impossible.
1333 int __printk_ratelimit(int ratelimit_jiffies
, int ratelimit_burst
)
1335 return __ratelimit(ratelimit_jiffies
, ratelimit_burst
);
1337 EXPORT_SYMBOL(__printk_ratelimit
);
1339 /* minimum time in jiffies between messages */
1340 int printk_ratelimit_jiffies
= 5 * HZ
;
1342 /* number of messages we send before ratelimiting */
1343 int printk_ratelimit_burst
= 10;
1345 int printk_ratelimit(void)
1347 return __printk_ratelimit(printk_ratelimit_jiffies
,
1348 printk_ratelimit_burst
);
1350 EXPORT_SYMBOL(printk_ratelimit
);
1353 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1354 * @caller_jiffies: pointer to caller's state
1355 * @interval_msecs: minimum interval between prints
1357 * printk_timed_ratelimit() returns true if more than @interval_msecs
1358 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1361 bool printk_timed_ratelimit(unsigned long *caller_jiffies
,
1362 unsigned int interval_msecs
)
1364 if (*caller_jiffies
== 0 || time_after(jiffies
, *caller_jiffies
)) {
1365 *caller_jiffies
= jiffies
+ msecs_to_jiffies(interval_msecs
);
1370 EXPORT_SYMBOL(printk_timed_ratelimit
);