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
19 #include <linux/kernel.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/syscalls.h>
35 #include <linux/kexec.h>
37 #include <asm/uaccess.h>
40 * Architectures can override it:
42 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
46 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
48 #ifdef CONFIG_DEBUG_LL
49 extern void printascii(char *);
52 /* printk's without a loglevel use this.. */
53 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
55 /* We show everything that is MORE important than this.. */
56 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
57 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
59 DECLARE_WAIT_QUEUE_HEAD(log_wait);
61 int console_printk[4] = {
62 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
63 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
64 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
65 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
69 * Low level drivers may need that to know if they can schedule in
70 * their unblank() callback or not. So let's export it.
73 EXPORT_SYMBOL(oops_in_progress);
76 * console_sem protects the console_drivers list, and also
77 * provides serialisation for access to the entire console
80 static DECLARE_MUTEX(console_sem);
81 struct console *console_drivers;
82 EXPORT_SYMBOL_GPL(console_drivers);
85 * This is used for debugging the mess that is the VT code by
86 * keeping track if we have the console semaphore held. It's
87 * definitely not the perfect debug tool (we don't know if _WE_
88 * hold it are racing, but it helps tracking those weird code
89 * path in the console code where we end up in places I want
90 * locked without the console sempahore held
92 static int console_locked, console_suspended;
95 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
96 * It is also used in interesting ways to provide interlocking in
97 * release_console_sem().
99 static DEFINE_SPINLOCK(logbuf_lock);
101 #define LOG_BUF_MASK (log_buf_len-1)
102 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
105 * The indices into log_buf are not constrained to log_buf_len - they
106 * must be masked before subscripting
108 static unsigned log_start; /* Index into log_buf: next char to be read by syslog() */
109 static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */
110 static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */
113 * Array of consoles built from command line options (console=)
115 struct console_cmdline
117 char name[8]; /* Name of the driver */
118 int index; /* Minor dev. to use */
119 char *options; /* Options for the driver */
120 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
121 char *brl_options; /* Options for braille driver */
125 #define MAX_CMDLINECONSOLES 8
127 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
128 static int selected_console = -1;
129 static int preferred_console = -1;
130 int console_set_on_cmdline;
131 EXPORT_SYMBOL(console_set_on_cmdline);
133 /* Flag: console code may call schedule() */
134 static int console_may_schedule;
138 static char __log_buf[__LOG_BUF_LEN];
139 static char *log_buf = __log_buf;
140 static int log_buf_len = __LOG_BUF_LEN;
141 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
145 * This appends the listed symbols to /proc/vmcoreinfo
147 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
148 * obtain access to symbols that are otherwise very difficult to locate. These
149 * symbols are specifically used so that utilities can access and extract the
150 * dmesg log from a vmcore file after a crash.
152 void log_buf_kexec_setup(void)
154 VMCOREINFO_SYMBOL(log_buf);
155 VMCOREINFO_SYMBOL(log_end);
156 VMCOREINFO_SYMBOL(log_buf_len);
157 VMCOREINFO_SYMBOL(logged_chars);
161 static int __init log_buf_len_setup(char *str)
163 unsigned size = memparse(str, &str);
167 size = roundup_pow_of_two(size);
168 if (size > log_buf_len) {
169 unsigned start, dest_idx, offset;
172 new_log_buf = alloc_bootmem(size);
174 printk(KERN_WARNING "log_buf_len: allocation failed\n");
178 spin_lock_irqsave(&logbuf_lock, flags);
180 log_buf = new_log_buf;
182 offset = start = min(con_start, log_start);
184 while (start != log_end) {
185 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
192 spin_unlock_irqrestore(&logbuf_lock, flags);
194 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
200 __setup("log_buf_len=", log_buf_len_setup);
202 #ifdef CONFIG_BOOT_PRINTK_DELAY
204 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
205 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
207 static int __init boot_delay_setup(char *str)
210 unsigned long long loops_per_msec;
212 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
213 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
215 get_option(&str, &boot_delay);
216 if (boot_delay > 10 * 1000)
219 printk_delay_msec = loops_per_msec;
220 printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
221 "HZ: %d, printk_delay_msec: %llu\n",
222 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
225 __setup("boot_delay=", boot_delay_setup);
227 static void boot_delay_msec(void)
229 unsigned long long k;
230 unsigned long timeout;
232 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
235 k = (unsigned long long)printk_delay_msec * boot_delay;
237 timeout = jiffies + msecs_to_jiffies(boot_delay);
242 * use (volatile) jiffies to prevent
243 * compiler reduction; loop termination via jiffies
244 * is secondary and may or may not happen.
246 if (time_after(jiffies, timeout))
248 touch_nmi_watchdog();
252 static inline void boot_delay_msec(void)
258 * Commands to do_syslog:
260 * 0 -- Close the log. Currently a NOP.
261 * 1 -- Open the log. Currently a NOP.
262 * 2 -- Read from the log.
263 * 3 -- Read all messages remaining in the ring buffer.
264 * 4 -- Read and clear all messages remaining in the ring buffer
265 * 5 -- Clear ring buffer.
266 * 6 -- Disable printk's to console
267 * 7 -- Enable printk's to console
268 * 8 -- Set level of messages printed to console
269 * 9 -- Return number of unread characters in the log buffer
270 * 10 -- Return size of the log buffer
272 int do_syslog(int type, char __user *buf, int len)
274 unsigned i, j, limit, count;
279 error = security_syslog(type);
284 case 0: /* Close log */
286 case 1: /* Open log */
288 case 2: /* Read from log */
295 if (!access_ok(VERIFY_WRITE, buf, len)) {
299 error = wait_event_interruptible(log_wait,
300 (log_start - log_end));
304 spin_lock_irq(&logbuf_lock);
305 while (!error && (log_start != log_end) && i < len) {
306 c = LOG_BUF(log_start);
308 spin_unlock_irq(&logbuf_lock);
309 error = __put_user(c,buf);
313 spin_lock_irq(&logbuf_lock);
315 spin_unlock_irq(&logbuf_lock);
319 case 4: /* Read/clear last kernel messages */
322 case 3: /* Read last kernel messages */
329 if (!access_ok(VERIFY_WRITE, buf, len)) {
334 if (count > log_buf_len)
336 spin_lock_irq(&logbuf_lock);
337 if (count > logged_chars)
338 count = logged_chars;
343 * __put_user() could sleep, and while we sleep
344 * printk() could overwrite the messages
345 * we try to copy to user space. Therefore
346 * the messages are copied in reverse. <manfreds>
348 for (i = 0; i < count && !error; i++) {
350 if (j + log_buf_len < log_end)
353 spin_unlock_irq(&logbuf_lock);
354 error = __put_user(c,&buf[count-1-i]);
356 spin_lock_irq(&logbuf_lock);
358 spin_unlock_irq(&logbuf_lock);
363 int offset = count-error;
364 /* buffer overflow during copy, correct user buffer. */
365 for (i = 0; i < error; i++) {
366 if (__get_user(c,&buf[i+offset]) ||
367 __put_user(c,&buf[i])) {
375 case 5: /* Clear ring buffer */
378 case 6: /* Disable logging to console */
379 console_loglevel = minimum_console_loglevel;
381 case 7: /* Enable logging to console */
382 console_loglevel = default_console_loglevel;
384 case 8: /* Set level of messages printed to console */
386 if (len < 1 || len > 8)
388 if (len < minimum_console_loglevel)
389 len = minimum_console_loglevel;
390 console_loglevel = len;
393 case 9: /* Number of chars in the log buffer */
394 error = log_end - log_start;
396 case 10: /* Size of the log buffer */
407 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
409 return do_syslog(type, buf, len);
413 * Call the console drivers on a range of log_buf
415 static void __call_console_drivers(unsigned start, unsigned end)
419 for (con = console_drivers; con; con = con->next) {
420 if ((con->flags & CON_ENABLED) && con->write &&
421 (cpu_online(smp_processor_id()) ||
422 (con->flags & CON_ANYTIME)))
423 con->write(con, &LOG_BUF(start), end - start);
427 static int __read_mostly ignore_loglevel;
429 static int __init ignore_loglevel_setup(char *str)
432 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
437 early_param("ignore_loglevel", ignore_loglevel_setup);
440 * Write out chars from start to end - 1 inclusive
442 static void _call_console_drivers(unsigned start,
443 unsigned end, int msg_log_level)
445 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
446 console_drivers && start != end) {
447 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
449 __call_console_drivers(start & LOG_BUF_MASK,
451 __call_console_drivers(0, end & LOG_BUF_MASK);
453 __call_console_drivers(start, end);
459 * Call the console drivers, asking them to write out
460 * log_buf[start] to log_buf[end - 1].
461 * The console_sem must be held.
463 static void call_console_drivers(unsigned start, unsigned end)
465 unsigned cur_index, start_print;
466 static int msg_level = -1;
468 BUG_ON(((int)(start - end)) > 0);
472 while (cur_index != end) {
473 if (msg_level < 0 && ((end - cur_index) > 2) &&
474 LOG_BUF(cur_index + 0) == '<' &&
475 LOG_BUF(cur_index + 1) >= '0' &&
476 LOG_BUF(cur_index + 1) <= '7' &&
477 LOG_BUF(cur_index + 2) == '>') {
478 msg_level = LOG_BUF(cur_index + 1) - '0';
480 start_print = cur_index;
482 while (cur_index != end) {
483 char c = LOG_BUF(cur_index);
489 * printk() has already given us loglevel tags in
490 * the buffer. This code is here in case the
491 * log buffer has wrapped right round and scribbled
494 msg_level = default_message_loglevel;
496 _call_console_drivers(start_print, cur_index, msg_level);
498 start_print = cur_index;
503 _call_console_drivers(start_print, end, msg_level);
506 static void emit_log_char(char c)
508 LOG_BUF(log_end) = c;
510 if (log_end - log_start > log_buf_len)
511 log_start = log_end - log_buf_len;
512 if (log_end - con_start > log_buf_len)
513 con_start = log_end - log_buf_len;
514 if (logged_chars < log_buf_len)
519 * Zap console related locks when oopsing. Only zap at most once
520 * every 10 seconds, to leave time for slow consoles to print a
523 static void zap_locks(void)
525 static unsigned long oops_timestamp;
527 if (time_after_eq(jiffies, oops_timestamp) &&
528 !time_after(jiffies, oops_timestamp + 30 * HZ))
531 oops_timestamp = jiffies;
533 /* If a crash is occurring, make sure we can't deadlock */
534 spin_lock_init(&logbuf_lock);
535 /* And make sure that we print immediately */
536 init_MUTEX(&console_sem);
539 #if defined(CONFIG_PRINTK_TIME)
540 static int printk_time = 1;
542 static int printk_time = 0;
544 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
546 /* Check if we have any console registered that can be called early in boot. */
547 static int have_callable_console(void)
551 for (con = console_drivers; con; con = con->next)
552 if (con->flags & CON_ANYTIME)
559 * printk - print a kernel message
560 * @fmt: format string
562 * This is printk(). It can be called from any context. We want it to work.
564 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
565 * call the console drivers. If we fail to get the semaphore we place the output
566 * into the log buffer and return. The current holder of the console_sem will
567 * notice the new output in release_console_sem() and will send it to the
568 * consoles before releasing the semaphore.
570 * One effect of this deferred printing is that code which calls printk() and
571 * then changes console_loglevel may break. This is because console_loglevel
572 * is inspected when the actual printing occurs.
577 * See the vsnprintf() documentation for format string extensions over C99.
580 asmlinkage int printk(const char *fmt, ...)
586 r = vprintk(fmt, args);
592 /* cpu currently holding logbuf_lock */
593 static volatile unsigned int printk_cpu = UINT_MAX;
596 * Can we actually use the console at this time on this cpu?
598 * Console drivers may assume that per-cpu resources have
599 * been allocated. So unless they're explicitly marked as
600 * being able to cope (CON_ANYTIME) don't call them until
601 * this CPU is officially up.
603 static inline int can_use_console(unsigned int cpu)
605 return cpu_online(cpu) || have_callable_console();
609 * Try to get console ownership to actually show the kernel
610 * messages from a 'printk'. Return true (and with the
611 * console_semaphore held, and 'console_locked' set) if it
612 * is successful, false otherwise.
614 * This gets called with the 'logbuf_lock' spinlock held and
615 * interrupts disabled. It should return with 'lockbuf_lock'
616 * released but interrupts still disabled.
618 static int acquire_console_semaphore_for_printk(unsigned int cpu)
622 if (!try_acquire_console_sem()) {
626 * If we can't use the console, we need to release
627 * the console semaphore by hand to avoid flushing
628 * the buffer. We need to hold the console semaphore
629 * in order to do this test safely.
631 if (!can_use_console(cpu)) {
637 printk_cpu = UINT_MAX;
638 spin_unlock(&logbuf_lock);
641 static const char recursion_bug_msg [] =
642 KERN_CRIT "BUG: recent printk recursion!\n";
643 static int recursion_bug;
644 static int new_text_line = 1;
645 static char printk_buf[1024];
647 asmlinkage int vprintk(const char *fmt, va_list args)
650 int current_log_level = default_message_loglevel;
658 /* This stops the holder of console_sem just where we want him */
659 raw_local_irq_save(flags);
660 this_cpu = smp_processor_id();
663 * Ouch, printk recursed into itself!
665 if (unlikely(printk_cpu == this_cpu)) {
667 * If a crash is occurring during printk() on this CPU,
668 * then try to get the crash message out but make sure
669 * we can't deadlock. Otherwise just return to avoid the
670 * recursion and return - but flag the recursion so that
671 * it can be printed at the next appropriate moment:
673 if (!oops_in_progress) {
675 goto out_restore_irqs;
681 spin_lock(&logbuf_lock);
682 printk_cpu = this_cpu;
686 strcpy(printk_buf, recursion_bug_msg);
687 printed_len = strlen(recursion_bug_msg);
689 /* Emit the output into the temporary buffer */
690 printed_len += vscnprintf(printk_buf + printed_len,
691 sizeof(printk_buf) - printed_len, fmt, args);
693 #ifdef CONFIG_DEBUG_LL
694 printascii(printk_buf);
698 * Copy the output into log_buf. If the caller didn't provide
699 * appropriate log level tags, we insert them here
701 for (p = printk_buf; *p; p++) {
703 /* If a token, set current_log_level and skip over */
704 if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
706 current_log_level = p[1] - '0';
711 /* Always output the token */
713 emit_log_char(current_log_level + '0');
719 /* Follow the token with the time */
722 unsigned long long t;
723 unsigned long nanosec_rem;
725 t = cpu_clock(printk_cpu);
726 nanosec_rem = do_div(t, 1000000000);
727 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
731 for (tp = tbuf; tp < tbuf + tlen; tp++)
746 * Try to acquire and then immediately release the
747 * console semaphore. The release will do all the
748 * actual magic (print out buffers, wake up klogd,
751 * The acquire_console_semaphore_for_printk() function
752 * will release 'logbuf_lock' regardless of whether it
753 * actually gets the semaphore or not.
755 if (acquire_console_semaphore_for_printk(this_cpu))
756 release_console_sem();
760 raw_local_irq_restore(flags);
765 EXPORT_SYMBOL(printk);
766 EXPORT_SYMBOL(vprintk);
770 static void call_console_drivers(unsigned start, unsigned end)
776 static int __add_preferred_console(char *name, int idx, char *options,
779 struct console_cmdline *c;
783 * See if this tty is not yet registered, and
784 * if we have a slot free.
786 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
787 if (strcmp(console_cmdline[i].name, name) == 0 &&
788 console_cmdline[i].index == idx) {
790 selected_console = i;
793 if (i == MAX_CMDLINECONSOLES)
796 selected_console = i;
797 c = &console_cmdline[i];
798 strlcpy(c->name, name, sizeof(c->name));
799 c->options = options;
800 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
801 c->brl_options = brl_options;
807 * Set up a list of consoles. Called from init/main.c
809 static int __init console_setup(char *str)
811 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
812 char *s, *options, *brl_options = NULL;
815 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
816 if (!memcmp(str, "brl,", 4)) {
819 } else if (!memcmp(str, "brl=", 4)) {
820 brl_options = str + 4;
821 str = strchr(brl_options, ',');
823 printk(KERN_ERR "need port name after brl=\n");
831 * Decode str into name, index, options.
833 if (str[0] >= '0' && str[0] <= '9') {
835 strncpy(buf + 4, str, sizeof(buf) - 5);
837 strncpy(buf, str, sizeof(buf) - 1);
839 buf[sizeof(buf) - 1] = 0;
840 if ((options = strchr(str, ',')) != NULL)
843 if (!strcmp(str, "ttya"))
844 strcpy(buf, "ttyS0");
845 if (!strcmp(str, "ttyb"))
846 strcpy(buf, "ttyS1");
848 for (s = buf; *s; s++)
849 if ((*s >= '0' && *s <= '9') || *s == ',')
851 idx = simple_strtoul(s, NULL, 10);
854 __add_preferred_console(buf, idx, options, brl_options);
855 console_set_on_cmdline = 1;
858 __setup("console=", console_setup);
861 * add_preferred_console - add a device to the list of preferred consoles.
864 * @options: options for this console
866 * The last preferred console added will be used for kernel messages
867 * and stdin/out/err for init. Normally this is used by console_setup
868 * above to handle user-supplied console arguments; however it can also
869 * be used by arch-specific code either to override the user or more
870 * commonly to provide a default console (ie from PROM variables) when
871 * the user has not supplied one.
873 int add_preferred_console(char *name, int idx, char *options)
875 return __add_preferred_console(name, idx, options, NULL);
878 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
880 struct console_cmdline *c;
883 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
884 if (strcmp(console_cmdline[i].name, name) == 0 &&
885 console_cmdline[i].index == idx) {
886 c = &console_cmdline[i];
887 strlcpy(c->name, name_new, sizeof(c->name));
888 c->name[sizeof(c->name) - 1] = 0;
889 c->options = options;
897 int console_suspend_enabled = 1;
898 EXPORT_SYMBOL(console_suspend_enabled);
900 static int __init console_suspend_disable(char *str)
902 console_suspend_enabled = 0;
905 __setup("no_console_suspend", console_suspend_disable);
908 * suspend_console - suspend the console subsystem
910 * This disables printk() while we go into suspend states
912 void suspend_console(void)
914 if (!console_suspend_enabled)
916 printk("Suspending console(s) (use no_console_suspend to debug)\n");
917 acquire_console_sem();
918 console_suspended = 1;
922 void resume_console(void)
924 if (!console_suspend_enabled)
927 console_suspended = 0;
928 release_console_sem();
932 * acquire_console_sem - lock the console system for exclusive use.
934 * Acquires a semaphore which guarantees that the caller has
935 * exclusive access to the console system and the console_drivers list.
937 * Can sleep, returns nothing.
939 void acquire_console_sem(void)
941 BUG_ON(in_interrupt());
943 if (console_suspended)
946 console_may_schedule = 1;
948 EXPORT_SYMBOL(acquire_console_sem);
950 int try_acquire_console_sem(void)
952 if (down_trylock(&console_sem))
954 if (console_suspended) {
959 console_may_schedule = 0;
962 EXPORT_SYMBOL(try_acquire_console_sem);
964 int is_console_locked(void)
966 return console_locked;
969 static DEFINE_PER_CPU(int, printk_pending);
971 void printk_tick(void)
973 if (__get_cpu_var(printk_pending)) {
974 __get_cpu_var(printk_pending) = 0;
975 wake_up_interruptible(&log_wait);
979 int printk_needs_cpu(int cpu)
981 return per_cpu(printk_pending, cpu);
984 void wake_up_klogd(void)
986 if (waitqueue_active(&log_wait))
987 __raw_get_cpu_var(printk_pending) = 1;
991 * release_console_sem - unlock the console system
993 * Releases the semaphore which the caller holds on the console system
994 * and the console driver list.
996 * While the semaphore was held, console output may have been buffered
997 * by printk(). If this is the case, release_console_sem() emits
998 * the output prior to releasing the semaphore.
1000 * If there is output waiting for klogd, we wake it up.
1002 * release_console_sem() may be called from any context.
1004 void release_console_sem(void)
1006 unsigned long flags;
1007 unsigned _con_start, _log_end;
1008 unsigned wake_klogd = 0;
1010 if (console_suspended) {
1015 console_may_schedule = 0;
1018 spin_lock_irqsave(&logbuf_lock, flags);
1019 wake_klogd |= log_start - log_end;
1020 if (con_start == log_end)
1021 break; /* Nothing to print */
1022 _con_start = con_start;
1024 con_start = log_end; /* Flush */
1025 spin_unlock(&logbuf_lock);
1026 stop_critical_timings(); /* don't trace print latency */
1027 call_console_drivers(_con_start, _log_end);
1028 start_critical_timings();
1029 local_irq_restore(flags);
1033 spin_unlock_irqrestore(&logbuf_lock, flags);
1037 EXPORT_SYMBOL(release_console_sem);
1040 * console_conditional_schedule - yield the CPU if required
1042 * If the console code is currently allowed to sleep, and
1043 * if this CPU should yield the CPU to another task, do
1046 * Must be called within acquire_console_sem().
1048 void __sched console_conditional_schedule(void)
1050 if (console_may_schedule)
1053 EXPORT_SYMBOL(console_conditional_schedule);
1055 void console_print(const char *s)
1057 printk(KERN_EMERG "%s", s);
1059 EXPORT_SYMBOL(console_print);
1061 void console_unblank(void)
1066 * console_unblank can no longer be called in interrupt context unless
1067 * oops_in_progress is set to 1..
1069 if (oops_in_progress) {
1070 if (down_trylock(&console_sem) != 0)
1073 acquire_console_sem();
1076 console_may_schedule = 0;
1077 for (c = console_drivers; c != NULL; c = c->next)
1078 if ((c->flags & CON_ENABLED) && c->unblank)
1080 release_console_sem();
1084 * Return the console tty driver structure and its associated index
1086 struct tty_driver *console_device(int *index)
1089 struct tty_driver *driver = NULL;
1091 acquire_console_sem();
1092 for (c = console_drivers; c != NULL; c = c->next) {
1095 driver = c->device(c, index);
1099 release_console_sem();
1104 * Prevent further output on the passed console device so that (for example)
1105 * serial drivers can disable console output before suspending a port, and can
1106 * re-enable output afterwards.
1108 void console_stop(struct console *console)
1110 acquire_console_sem();
1111 console->flags &= ~CON_ENABLED;
1112 release_console_sem();
1114 EXPORT_SYMBOL(console_stop);
1116 void console_start(struct console *console)
1118 acquire_console_sem();
1119 console->flags |= CON_ENABLED;
1120 release_console_sem();
1122 EXPORT_SYMBOL(console_start);
1125 * The console driver calls this routine during kernel initialization
1126 * to register the console printing procedure with printk() and to
1127 * print any messages that were printed by the kernel before the
1128 * console driver was initialized.
1130 void register_console(struct console *console)
1133 unsigned long flags;
1134 struct console *bootconsole = NULL;
1136 if (console_drivers) {
1137 if (console->flags & CON_BOOT)
1139 if (console_drivers->flags & CON_BOOT)
1140 bootconsole = console_drivers;
1143 if (preferred_console < 0 || bootconsole || !console_drivers)
1144 preferred_console = selected_console;
1146 if (console->early_setup)
1147 console->early_setup();
1150 * See if we want to use this console driver. If we
1151 * didn't select a console we take the first one
1152 * that registers here.
1154 if (preferred_console < 0) {
1155 if (console->index < 0)
1157 if (console->setup == NULL ||
1158 console->setup(console, NULL) == 0) {
1159 console->flags |= CON_ENABLED;
1160 if (console->device) {
1161 console->flags |= CON_CONSDEV;
1162 preferred_console = 0;
1168 * See if this console matches one we selected on
1171 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1173 if (strcmp(console_cmdline[i].name, console->name) != 0)
1175 if (console->index >= 0 &&
1176 console->index != console_cmdline[i].index)
1178 if (console->index < 0)
1179 console->index = console_cmdline[i].index;
1180 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1181 if (console_cmdline[i].brl_options) {
1182 console->flags |= CON_BRL;
1183 braille_register_console(console,
1184 console_cmdline[i].index,
1185 console_cmdline[i].options,
1186 console_cmdline[i].brl_options);
1190 if (console->setup &&
1191 console->setup(console, console_cmdline[i].options) != 0)
1193 console->flags |= CON_ENABLED;
1194 console->index = console_cmdline[i].index;
1195 if (i == selected_console) {
1196 console->flags |= CON_CONSDEV;
1197 preferred_console = selected_console;
1202 if (!(console->flags & CON_ENABLED))
1205 if (bootconsole && (console->flags & CON_CONSDEV)) {
1206 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1207 bootconsole->name, bootconsole->index,
1208 console->name, console->index);
1209 unregister_console(bootconsole);
1210 console->flags &= ~CON_PRINTBUFFER;
1212 printk(KERN_INFO "console [%s%d] enabled\n",
1213 console->name, console->index);
1217 * Put this console in the list - keep the
1218 * preferred driver at the head of the list.
1220 acquire_console_sem();
1221 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1222 console->next = console_drivers;
1223 console_drivers = console;
1225 console->next->flags &= ~CON_CONSDEV;
1227 console->next = console_drivers->next;
1228 console_drivers->next = console;
1230 if (console->flags & CON_PRINTBUFFER) {
1232 * release_console_sem() will print out the buffered messages
1235 spin_lock_irqsave(&logbuf_lock, flags);
1236 con_start = log_start;
1237 spin_unlock_irqrestore(&logbuf_lock, flags);
1239 release_console_sem();
1241 EXPORT_SYMBOL(register_console);
1243 int unregister_console(struct console *console)
1245 struct console *a, *b;
1248 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1249 if (console->flags & CON_BRL)
1250 return braille_unregister_console(console);
1253 acquire_console_sem();
1254 if (console_drivers == console) {
1255 console_drivers=console->next;
1257 } else if (console_drivers) {
1258 for (a=console_drivers->next, b=console_drivers ;
1259 a; b=a, a=b->next) {
1269 * If this isn't the last console and it has CON_CONSDEV set, we
1270 * need to set it on the next preferred console.
1272 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1273 console_drivers->flags |= CON_CONSDEV;
1275 release_console_sem();
1278 EXPORT_SYMBOL(unregister_console);
1280 static int __init disable_boot_consoles(void)
1282 if (console_drivers != NULL) {
1283 if (console_drivers->flags & CON_BOOT) {
1284 printk(KERN_INFO "turn off boot console %s%d\n",
1285 console_drivers->name, console_drivers->index);
1286 return unregister_console(console_drivers);
1291 late_initcall(disable_boot_consoles);
1293 #if defined CONFIG_PRINTK
1296 * printk rate limiting, lifted from the networking subsystem.
1298 * This enforces a rate limit: not more than 10 kernel messages
1299 * every 5s to make a denial-of-service attack impossible.
1301 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1303 int printk_ratelimit(void)
1305 return __ratelimit(&printk_ratelimit_state);
1307 EXPORT_SYMBOL(printk_ratelimit);
1310 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1311 * @caller_jiffies: pointer to caller's state
1312 * @interval_msecs: minimum interval between prints
1314 * printk_timed_ratelimit() returns true if more than @interval_msecs
1315 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1318 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1319 unsigned int interval_msecs)
1321 if (*caller_jiffies == 0
1322 || !time_in_range(jiffies, *caller_jiffies,
1324 + msecs_to_jiffies(interval_msecs))) {
1325 *caller_jiffies = jiffies;
1330 EXPORT_SYMBOL(printk_timed_ratelimit);