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)
664 int current_log_level = default_message_loglevel;
672 /* This stops the holder of console_sem just where we want him */
673 raw_local_irq_save(flags);
674 this_cpu = smp_processor_id();
677 * Ouch, printk recursed into itself!
679 if (unlikely(printk_cpu == this_cpu)) {
681 * If a crash is occurring during printk() on this CPU,
682 * then try to get the crash message out but make sure
683 * we can't deadlock. Otherwise just return to avoid the
684 * recursion and return - but flag the recursion so that
685 * it can be printed at the next appropriate moment:
687 if (!oops_in_progress) {
689 goto out_restore_irqs;
695 spin_lock(&logbuf_lock);
696 printk_cpu = this_cpu;
700 strcpy(printk_buf, recursion_bug_msg);
701 printed_len = sizeof(recursion_bug_msg);
703 /* Emit the output into the temporary buffer */
704 printed_len += vscnprintf(printk_buf + printed_len,
705 sizeof(printk_buf) - printed_len, fmt, args);
709 * Copy the output into log_buf. If the caller didn't provide
710 * appropriate log level tags, we insert them here
712 for (p = printk_buf; *p; p++) {
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);