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;
78 EXPORT_SYMBOL_GPL(console_drivers);
81 * This is used for debugging the mess that is the VT code by
82 * keeping track if we have the console semaphore held. It's
83 * definitely not the perfect debug tool (we don't know if _WE_
84 * hold it are racing, but it helps tracking those weird code
85 * path in the console code where we end up in places I want
86 * locked without the console sempahore held
88 static int console_locked, console_suspended;
91 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
92 * It is also used in interesting ways to provide interlocking in
93 * release_console_sem().
95 static DEFINE_SPINLOCK(logbuf_lock);
97 #define LOG_BUF_MASK (log_buf_len-1)
98 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
101 * The indices into log_buf are not constrained to log_buf_len - they
102 * must be masked before subscripting
104 static unsigned log_start; /* Index into log_buf: next char to be read by syslog() */
105 static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */
106 static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */
109 * Array of consoles built from command line options (console=)
111 struct console_cmdline
113 char name[8]; /* Name of the driver */
114 int index; /* Minor dev. to use */
115 char *options; /* Options for the driver */
116 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
117 char *brl_options; /* Options for braille driver */
121 #define MAX_CMDLINECONSOLES 8
123 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
124 static int selected_console = -1;
125 static int preferred_console = -1;
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 static 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 * Commands to do_syslog:
275 * 0 -- Close the log. Currently a NOP.
276 * 1 -- Open the log. Currently a NOP.
277 * 2 -- Read from the log.
278 * 3 -- Read all messages remaining in the ring buffer.
279 * 4 -- Read and clear all messages remaining in the ring buffer
280 * 5 -- Clear ring buffer.
281 * 6 -- Disable printk's to console
282 * 7 -- Enable printk's to console
283 * 8 -- Set level of messages printed to console
284 * 9 -- Return number of unread characters in the log buffer
285 * 10 -- Return size of the log buffer
287 int do_syslog(int type, char __user *buf, int len)
289 unsigned i, j, limit, count;
294 error = security_syslog(type);
299 case 0: /* Close log */
301 case 1: /* Open log */
303 case 2: /* Read from log */
310 if (!access_ok(VERIFY_WRITE, buf, len)) {
314 error = wait_event_interruptible(log_wait,
315 (log_start - log_end));
319 spin_lock_irq(&logbuf_lock);
320 while (!error && (log_start != log_end) && i < len) {
321 c = LOG_BUF(log_start);
323 spin_unlock_irq(&logbuf_lock);
324 error = __put_user(c,buf);
328 spin_lock_irq(&logbuf_lock);
330 spin_unlock_irq(&logbuf_lock);
334 case 4: /* Read/clear last kernel messages */
337 case 3: /* Read last kernel messages */
344 if (!access_ok(VERIFY_WRITE, buf, len)) {
349 if (count > log_buf_len)
351 spin_lock_irq(&logbuf_lock);
352 if (count > logged_chars)
353 count = logged_chars;
358 * __put_user() could sleep, and while we sleep
359 * printk() could overwrite the messages
360 * we try to copy to user space. Therefore
361 * the messages are copied in reverse. <manfreds>
363 for (i = 0; i < count && !error; i++) {
365 if (j + log_buf_len < log_end)
368 spin_unlock_irq(&logbuf_lock);
369 error = __put_user(c,&buf[count-1-i]);
371 spin_lock_irq(&logbuf_lock);
373 spin_unlock_irq(&logbuf_lock);
378 int offset = count-error;
379 /* buffer overflow during copy, correct user buffer. */
380 for (i = 0; i < error; i++) {
381 if (__get_user(c,&buf[i+offset]) ||
382 __put_user(c,&buf[i])) {
390 case 5: /* Clear ring buffer */
393 case 6: /* Disable logging to console */
394 console_loglevel = minimum_console_loglevel;
396 case 7: /* Enable logging to console */
397 console_loglevel = default_console_loglevel;
399 case 8: /* Set level of messages printed to console */
401 if (len < 1 || len > 8)
403 if (len < minimum_console_loglevel)
404 len = minimum_console_loglevel;
405 console_loglevel = len;
408 case 9: /* Number of chars in the log buffer */
409 error = log_end - log_start;
411 case 10: /* Size of the log buffer */
422 asmlinkage long sys_syslog(int type, char __user *buf, int len)
424 return do_syslog(type, buf, len);
428 * Call the console drivers on a range of log_buf
430 static void __call_console_drivers(unsigned start, unsigned end)
434 for (con = console_drivers; con; con = con->next) {
435 if ((con->flags & CON_ENABLED) && con->write &&
436 (cpu_online(smp_processor_id()) ||
437 (con->flags & CON_ANYTIME)))
438 con->write(con, &LOG_BUF(start), end - start);
442 static int __read_mostly ignore_loglevel;
444 static int __init ignore_loglevel_setup(char *str)
447 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
452 early_param("ignore_loglevel", ignore_loglevel_setup);
455 * Write out chars from start to end - 1 inclusive
457 static void _call_console_drivers(unsigned start,
458 unsigned end, int msg_log_level)
460 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
461 console_drivers && start != end) {
462 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
464 __call_console_drivers(start & LOG_BUF_MASK,
466 __call_console_drivers(0, end & LOG_BUF_MASK);
468 __call_console_drivers(start, end);
474 * Call the console drivers, asking them to write out
475 * log_buf[start] to log_buf[end - 1].
476 * The console_sem must be held.
478 static void call_console_drivers(unsigned start, unsigned end)
480 unsigned cur_index, start_print;
481 static int msg_level = -1;
483 BUG_ON(((int)(start - end)) > 0);
487 while (cur_index != end) {
488 if (msg_level < 0 && ((end - cur_index) > 2) &&
489 LOG_BUF(cur_index + 0) == '<' &&
490 LOG_BUF(cur_index + 1) >= '0' &&
491 LOG_BUF(cur_index + 1) <= '7' &&
492 LOG_BUF(cur_index + 2) == '>') {
493 msg_level = LOG_BUF(cur_index + 1) - '0';
495 start_print = cur_index;
497 while (cur_index != end) {
498 char c = LOG_BUF(cur_index);
504 * printk() has already given us loglevel tags in
505 * the buffer. This code is here in case the
506 * log buffer has wrapped right round and scribbled
509 msg_level = default_message_loglevel;
511 _call_console_drivers(start_print, cur_index, msg_level);
513 start_print = cur_index;
518 _call_console_drivers(start_print, end, msg_level);
521 static void emit_log_char(char c)
523 LOG_BUF(log_end) = c;
525 if (log_end - log_start > log_buf_len)
526 log_start = log_end - log_buf_len;
527 if (log_end - con_start > log_buf_len)
528 con_start = log_end - log_buf_len;
529 if (logged_chars < log_buf_len)
534 * Zap console related locks when oopsing. Only zap at most once
535 * every 10 seconds, to leave time for slow consoles to print a
538 static void zap_locks(void)
540 static unsigned long oops_timestamp;
542 if (time_after_eq(jiffies, oops_timestamp) &&
543 !time_after(jiffies, oops_timestamp + 30 * HZ))
546 oops_timestamp = jiffies;
548 /* If a crash is occurring, make sure we can't deadlock */
549 spin_lock_init(&logbuf_lock);
550 /* And make sure that we print immediately */
551 init_MUTEX(&console_sem);
554 #if defined(CONFIG_PRINTK_TIME)
555 static int printk_time = 1;
557 static int printk_time = 0;
559 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
561 /* Check if we have any console registered that can be called early in boot. */
562 static int have_callable_console(void)
566 for (con = console_drivers; con; con = con->next)
567 if (con->flags & CON_ANYTIME)
574 * printk - print a kernel message
575 * @fmt: format string
577 * This is printk(). It can be called from any context. We want it to work.
578 * Be aware of the fact that if oops_in_progress is not set, we might try to
579 * wake klogd up which could deadlock on runqueue lock if printk() is called
580 * from scheduler code.
582 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
583 * call the console drivers. If we fail to get the semaphore we place the output
584 * into the log buffer and return. The current holder of the console_sem will
585 * notice the new output in release_console_sem() and will send it to the
586 * consoles before releasing the semaphore.
588 * One effect of this deferred printing is that code which calls printk() and
589 * then changes console_loglevel may break. This is because console_loglevel
590 * is inspected when the actual printing occurs.
596 asmlinkage int printk(const char *fmt, ...)
602 r = vprintk(fmt, args);
608 /* cpu currently holding logbuf_lock */
609 static volatile unsigned int printk_cpu = UINT_MAX;
612 * Can we actually use the console at this time on this cpu?
614 * Console drivers may assume that per-cpu resources have
615 * been allocated. So unless they're explicitly marked as
616 * being able to cope (CON_ANYTIME) don't call them until
617 * this CPU is officially up.
619 static inline int can_use_console(unsigned int cpu)
621 return cpu_online(cpu) || have_callable_console();
625 * Try to get console ownership to actually show the kernel
626 * messages from a 'printk'. Return true (and with the
627 * console_semaphore held, and 'console_locked' set) if it
628 * is successful, false otherwise.
630 * This gets called with the 'logbuf_lock' spinlock held and
631 * interrupts disabled. It should return with 'lockbuf_lock'
632 * released but interrupts still disabled.
634 static int acquire_console_semaphore_for_printk(unsigned int cpu)
638 if (!try_acquire_console_sem()) {
642 * If we can't use the console, we need to release
643 * the console semaphore by hand to avoid flushing
644 * the buffer. We need to hold the console semaphore
645 * in order to do this test safely.
647 if (!can_use_console(cpu)) {
653 printk_cpu = UINT_MAX;
654 spin_unlock(&logbuf_lock);
657 static const char recursion_bug_msg [] =
658 KERN_CRIT "BUG: recent printk recursion!\n";
659 static int recursion_bug;
660 static int new_text_line = 1;
661 static char printk_buf[1024];
663 asmlinkage int vprintk(const char *fmt, va_list args)
666 int current_log_level = default_message_loglevel;
674 /* This stops the holder of console_sem just where we want him */
675 raw_local_irq_save(flags);
676 this_cpu = smp_processor_id();
679 * Ouch, printk recursed into itself!
681 if (unlikely(printk_cpu == this_cpu)) {
683 * If a crash is occurring during printk() on this CPU,
684 * then try to get the crash message out but make sure
685 * we can't deadlock. Otherwise just return to avoid the
686 * recursion and return - but flag the recursion so that
687 * it can be printed at the next appropriate moment:
689 if (!oops_in_progress) {
691 goto out_restore_irqs;
697 spin_lock(&logbuf_lock);
698 printk_cpu = this_cpu;
702 strcpy(printk_buf, recursion_bug_msg);
703 printed_len = sizeof(recursion_bug_msg);
705 /* Emit the output into the temporary buffer */
706 printed_len += vscnprintf(printk_buf + printed_len,
707 sizeof(printk_buf) - printed_len, fmt, args);
711 * Copy the output into log_buf. If the caller didn't provide
712 * appropriate log level tags, we insert them here
714 for (p = printk_buf; *p; p++) {
716 /* If a token, set current_log_level and skip over */
717 if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
719 current_log_level = p[1] - '0';
724 /* Always output the token */
726 emit_log_char(current_log_level + '0');
732 /* Follow the token with the time */
735 unsigned long long t;
736 unsigned long nanosec_rem;
738 t = cpu_clock(printk_cpu);
739 nanosec_rem = do_div(t, 1000000000);
740 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
744 for (tp = tbuf; tp < tbuf + tlen; tp++)
759 * Try to acquire and then immediately release the
760 * console semaphore. The release will do all the
761 * actual magic (print out buffers, wake up klogd,
764 * The acquire_console_semaphore_for_printk() function
765 * will release 'logbuf_lock' regardless of whether it
766 * actually gets the semaphore or not.
768 if (acquire_console_semaphore_for_printk(this_cpu))
769 release_console_sem();
773 raw_local_irq_restore(flags);
778 EXPORT_SYMBOL(printk);
779 EXPORT_SYMBOL(vprintk);
783 asmlinkage long sys_syslog(int type, char __user *buf, int len)
788 static void call_console_drivers(unsigned start, unsigned end)
794 static int __add_preferred_console(char *name, int idx, char *options,
797 struct console_cmdline *c;
801 * See if this tty is not yet registered, and
802 * if we have a slot free.
804 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
805 if (strcmp(console_cmdline[i].name, name) == 0 &&
806 console_cmdline[i].index == idx) {
808 selected_console = i;
811 if (i == MAX_CMDLINECONSOLES)
814 selected_console = i;
815 c = &console_cmdline[i];
816 strlcpy(c->name, name, sizeof(c->name));
817 c->options = options;
818 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
819 c->brl_options = brl_options;
825 * Set up a list of consoles. Called from init/main.c
827 static int __init console_setup(char *str)
829 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
830 char *s, *options, *brl_options = NULL;
833 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
834 if (!memcmp(str, "brl,", 4)) {
837 } else if (!memcmp(str, "brl=", 4)) {
838 brl_options = str + 4;
839 str = strchr(brl_options, ',');
841 printk(KERN_ERR "need port name after brl=\n");
849 * Decode str into name, index, options.
851 if (str[0] >= '0' && str[0] <= '9') {
853 strncpy(buf + 4, str, sizeof(buf) - 5);
855 strncpy(buf, str, sizeof(buf) - 1);
857 buf[sizeof(buf) - 1] = 0;
858 if ((options = strchr(str, ',')) != NULL)
861 if (!strcmp(str, "ttya"))
862 strcpy(buf, "ttyS0");
863 if (!strcmp(str, "ttyb"))
864 strcpy(buf, "ttyS1");
866 for (s = buf; *s; s++)
867 if ((*s >= '0' && *s <= '9') || *s == ',')
869 idx = simple_strtoul(s, NULL, 10);
872 __add_preferred_console(buf, idx, options, brl_options);
875 __setup("console=", console_setup);
878 * add_preferred_console - add a device to the list of preferred consoles.
881 * @options: options for this console
883 * The last preferred console added will be used for kernel messages
884 * and stdin/out/err for init. Normally this is used by console_setup
885 * above to handle user-supplied console arguments; however it can also
886 * be used by arch-specific code either to override the user or more
887 * commonly to provide a default console (ie from PROM variables) when
888 * the user has not supplied one.
890 int add_preferred_console(char *name, int idx, char *options)
892 return __add_preferred_console(name, idx, options, NULL);
895 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
897 struct console_cmdline *c;
900 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
901 if (strcmp(console_cmdline[i].name, name) == 0 &&
902 console_cmdline[i].index == idx) {
903 c = &console_cmdline[i];
904 strlcpy(c->name, name_new, sizeof(c->name));
905 c->name[sizeof(c->name) - 1] = 0;
906 c->options = options;
914 int console_suspend_enabled = 1;
915 EXPORT_SYMBOL(console_suspend_enabled);
917 static int __init console_suspend_disable(char *str)
919 console_suspend_enabled = 0;
922 __setup("no_console_suspend", console_suspend_disable);
925 * suspend_console - suspend the console subsystem
927 * This disables printk() while we go into suspend states
929 void suspend_console(void)
931 if (!console_suspend_enabled)
933 printk("Suspending console(s)\n");
934 acquire_console_sem();
935 console_suspended = 1;
938 void resume_console(void)
940 if (!console_suspend_enabled)
942 console_suspended = 0;
943 release_console_sem();
947 * acquire_console_sem - lock the console system for exclusive use.
949 * Acquires a semaphore which guarantees that the caller has
950 * exclusive access to the console system and the console_drivers list.
952 * Can sleep, returns nothing.
954 void acquire_console_sem(void)
956 BUG_ON(in_interrupt());
957 if (console_suspended) {
958 down(&secondary_console_sem);
963 console_may_schedule = 1;
965 EXPORT_SYMBOL(acquire_console_sem);
967 int try_acquire_console_sem(void)
969 if (down_trylock(&console_sem))
972 console_may_schedule = 0;
975 EXPORT_SYMBOL(try_acquire_console_sem);
977 int is_console_locked(void)
979 return console_locked;
982 void wake_up_klogd(void)
984 if (!oops_in_progress && waitqueue_active(&log_wait))
985 wake_up_interruptible(&log_wait);
989 * release_console_sem - unlock the console system
991 * Releases the semaphore which the caller holds on the console system
992 * and the console driver list.
994 * While the semaphore was held, console output may have been buffered
995 * by printk(). If this is the case, release_console_sem() emits
996 * the output prior to releasing the semaphore.
998 * If there is output waiting for klogd, we wake it up.
1000 * release_console_sem() may be called from any context.
1002 void release_console_sem(void)
1004 unsigned long flags;
1005 unsigned _con_start, _log_end;
1006 unsigned wake_klogd = 0;
1008 if (console_suspended) {
1009 up(&secondary_console_sem);
1013 console_may_schedule = 0;
1016 spin_lock_irqsave(&logbuf_lock, flags);
1017 wake_klogd |= log_start - log_end;
1018 if (con_start == log_end)
1019 break; /* Nothing to print */
1020 _con_start = con_start;
1022 con_start = log_end; /* Flush */
1023 spin_unlock(&logbuf_lock);
1024 call_console_drivers(_con_start, _log_end);
1025 local_irq_restore(flags);
1029 spin_unlock_irqrestore(&logbuf_lock, flags);
1033 EXPORT_SYMBOL(release_console_sem);
1036 * console_conditional_schedule - yield the CPU if required
1038 * If the console code is currently allowed to sleep, and
1039 * if this CPU should yield the CPU to another task, do
1042 * Must be called within acquire_console_sem().
1044 void __sched console_conditional_schedule(void)
1046 if (console_may_schedule)
1049 EXPORT_SYMBOL(console_conditional_schedule);
1051 void console_print(const char *s)
1053 printk(KERN_EMERG "%s", s);
1055 EXPORT_SYMBOL(console_print);
1057 void console_unblank(void)
1062 * console_unblank can no longer be called in interrupt context unless
1063 * oops_in_progress is set to 1..
1065 if (oops_in_progress) {
1066 if (down_trylock(&console_sem) != 0)
1069 acquire_console_sem();
1072 console_may_schedule = 0;
1073 for (c = console_drivers; c != NULL; c = c->next)
1074 if ((c->flags & CON_ENABLED) && c->unblank)
1076 release_console_sem();
1080 * Return the console tty driver structure and its associated index
1082 struct tty_driver *console_device(int *index)
1085 struct tty_driver *driver = NULL;
1087 acquire_console_sem();
1088 for (c = console_drivers; c != NULL; c = c->next) {
1091 driver = c->device(c, index);
1095 release_console_sem();
1100 * Prevent further output on the passed console device so that (for example)
1101 * serial drivers can disable console output before suspending a port, and can
1102 * re-enable output afterwards.
1104 void console_stop(struct console *console)
1106 acquire_console_sem();
1107 console->flags &= ~CON_ENABLED;
1108 release_console_sem();
1110 EXPORT_SYMBOL(console_stop);
1112 void console_start(struct console *console)
1114 acquire_console_sem();
1115 console->flags |= CON_ENABLED;
1116 release_console_sem();
1118 EXPORT_SYMBOL(console_start);
1121 * The console driver calls this routine during kernel initialization
1122 * to register the console printing procedure with printk() and to
1123 * print any messages that were printed by the kernel before the
1124 * console driver was initialized.
1126 void register_console(struct console *console)
1129 unsigned long flags;
1130 struct console *bootconsole = NULL;
1132 if (console_drivers) {
1133 if (console->flags & CON_BOOT)
1135 if (console_drivers->flags & CON_BOOT)
1136 bootconsole = console_drivers;
1139 if (preferred_console < 0 || bootconsole || !console_drivers)
1140 preferred_console = selected_console;
1142 if (console->early_setup)
1143 console->early_setup();
1146 * See if we want to use this console driver. If we
1147 * didn't select a console we take the first one
1148 * that registers here.
1150 if (preferred_console < 0) {
1151 if (console->index < 0)
1153 if (console->setup == NULL ||
1154 console->setup(console, NULL) == 0) {
1155 console->flags |= CON_ENABLED;
1156 if (console->device) {
1157 console->flags |= CON_CONSDEV;
1158 preferred_console = 0;
1164 * See if this console matches one we selected on
1167 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1169 if (strcmp(console_cmdline[i].name, console->name) != 0)
1171 if (console->index >= 0 &&
1172 console->index != console_cmdline[i].index)
1174 if (console->index < 0)
1175 console->index = console_cmdline[i].index;
1176 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1177 if (console_cmdline[i].brl_options) {
1178 console->flags |= CON_BRL;
1179 braille_register_console(console,
1180 console_cmdline[i].index,
1181 console_cmdline[i].options,
1182 console_cmdline[i].brl_options);
1186 if (console->setup &&
1187 console->setup(console, console_cmdline[i].options) != 0)
1189 console->flags |= CON_ENABLED;
1190 console->index = console_cmdline[i].index;
1191 if (i == selected_console) {
1192 console->flags |= CON_CONSDEV;
1193 preferred_console = selected_console;
1198 if (!(console->flags & CON_ENABLED))
1201 if (bootconsole && (console->flags & CON_CONSDEV)) {
1202 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1203 bootconsole->name, bootconsole->index,
1204 console->name, console->index);
1205 unregister_console(bootconsole);
1206 console->flags &= ~CON_PRINTBUFFER;
1208 printk(KERN_INFO "console [%s%d] enabled\n",
1209 console->name, console->index);
1213 * Put this console in the list - keep the
1214 * preferred driver at the head of the list.
1216 acquire_console_sem();
1217 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1218 console->next = console_drivers;
1219 console_drivers = console;
1221 console->next->flags &= ~CON_CONSDEV;
1223 console->next = console_drivers->next;
1224 console_drivers->next = console;
1226 if (console->flags & CON_PRINTBUFFER) {
1228 * release_console_sem() will print out the buffered messages
1231 spin_lock_irqsave(&logbuf_lock, flags);
1232 con_start = log_start;
1233 spin_unlock_irqrestore(&logbuf_lock, flags);
1235 release_console_sem();
1237 EXPORT_SYMBOL(register_console);
1239 int unregister_console(struct console *console)
1241 struct console *a, *b;
1244 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1245 if (console->flags & CON_BRL)
1246 return braille_unregister_console(console);
1249 acquire_console_sem();
1250 if (console_drivers == console) {
1251 console_drivers=console->next;
1253 } else if (console_drivers) {
1254 for (a=console_drivers->next, b=console_drivers ;
1255 a; b=a, a=b->next) {
1265 * If this isn't the last console and it has CON_CONSDEV set, we
1266 * need to set it on the next preferred console.
1268 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1269 console_drivers->flags |= CON_CONSDEV;
1271 release_console_sem();
1274 EXPORT_SYMBOL(unregister_console);
1276 static int __init disable_boot_consoles(void)
1278 if (console_drivers != NULL) {
1279 if (console_drivers->flags & CON_BOOT) {
1280 printk(KERN_INFO "turn off boot console %s%d\n",
1281 console_drivers->name, console_drivers->index);
1282 return unregister_console(console_drivers);
1287 late_initcall(disable_boot_consoles);
1290 * tty_write_message - write a message to a certain tty, not just the console.
1291 * @tty: the destination tty_struct
1292 * @msg: the message to write
1294 * This is used for messages that need to be redirected to a specific tty.
1295 * We don't put it into the syslog queue right now maybe in the future if
1298 void tty_write_message(struct tty_struct *tty, char *msg)
1300 if (tty && tty->ops->write)
1301 tty->ops->write(tty, msg, strlen(msg));
1305 #if defined CONFIG_PRINTK
1307 * printk rate limiting, lifted from the networking subsystem.
1309 * This enforces a rate limit: not more than one kernel message
1310 * every printk_ratelimit_jiffies to make a denial-of-service
1311 * attack impossible.
1313 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1315 return __ratelimit(ratelimit_jiffies, ratelimit_burst);
1317 EXPORT_SYMBOL(__printk_ratelimit);
1319 /* minimum time in jiffies between messages */
1320 int printk_ratelimit_jiffies = 5 * HZ;
1322 /* number of messages we send before ratelimiting */
1323 int printk_ratelimit_burst = 10;
1325 int printk_ratelimit(void)
1327 return __printk_ratelimit(printk_ratelimit_jiffies,
1328 printk_ratelimit_burst);
1330 EXPORT_SYMBOL(printk_ratelimit);
1333 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1334 * @caller_jiffies: pointer to caller's state
1335 * @interval_msecs: minimum interval between prints
1337 * printk_timed_ratelimit() returns true if more than @interval_msecs
1338 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1341 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1342 unsigned int interval_msecs)
1344 if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1345 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1350 EXPORT_SYMBOL(printk_timed_ratelimit);