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 * for_each_console() allows you to iterate on each console
42 #define for_each_console(con) \
43 for (con = console_drivers; con != NULL; con = con->next)
46 * Architectures can override it:
48 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
52 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
54 /* printk's without a loglevel use this.. */
55 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
57 /* We show everything that is MORE important than this.. */
58 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
59 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
61 DECLARE_WAIT_QUEUE_HEAD(log_wait);
63 int console_printk[4] = {
64 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
65 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
66 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
67 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
71 * Low level drivers may need that to know if they can schedule in
72 * their unblank() callback or not. So let's export it.
75 EXPORT_SYMBOL(oops_in_progress);
78 * console_sem protects the console_drivers list, and also
79 * provides serialisation for access to the entire console
82 static DECLARE_MUTEX(console_sem);
83 struct console *console_drivers;
84 EXPORT_SYMBOL_GPL(console_drivers);
87 * This is used for debugging the mess that is the VT code by
88 * keeping track if we have the console semaphore held. It's
89 * definitely not the perfect debug tool (we don't know if _WE_
90 * hold it are racing, but it helps tracking those weird code
91 * path in the console code where we end up in places I want
92 * locked without the console sempahore held
94 static int console_locked, console_suspended;
97 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
98 * It is also used in interesting ways to provide interlocking in
99 * release_console_sem().
101 static DEFINE_SPINLOCK(logbuf_lock);
103 #define LOG_BUF_MASK (log_buf_len-1)
104 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
107 * The indices into log_buf are not constrained to log_buf_len - they
108 * must be masked before subscripting
110 static unsigned log_start; /* Index into log_buf: next char to be read by syslog() */
111 static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */
112 static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */
115 * Array of consoles built from command line options (console=)
117 struct console_cmdline
119 char name[8]; /* Name of the driver */
120 int index; /* Minor dev. to use */
121 char *options; /* Options for the driver */
122 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
123 char *brl_options; /* Options for braille driver */
127 #define MAX_CMDLINECONSOLES 8
129 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
130 static int selected_console = -1;
131 static int preferred_console = -1;
132 int console_set_on_cmdline;
133 EXPORT_SYMBOL(console_set_on_cmdline);
135 /* Flag: console code may call schedule() */
136 static int console_may_schedule;
140 static char __log_buf[__LOG_BUF_LEN];
141 static char *log_buf = __log_buf;
142 static int log_buf_len = __LOG_BUF_LEN;
143 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
147 * This appends the listed symbols to /proc/vmcoreinfo
149 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
150 * obtain access to symbols that are otherwise very difficult to locate. These
151 * symbols are specifically used so that utilities can access and extract the
152 * dmesg log from a vmcore file after a crash.
154 void log_buf_kexec_setup(void)
156 VMCOREINFO_SYMBOL(log_buf);
157 VMCOREINFO_SYMBOL(log_end);
158 VMCOREINFO_SYMBOL(log_buf_len);
159 VMCOREINFO_SYMBOL(logged_chars);
163 static int __init log_buf_len_setup(char *str)
165 unsigned size = memparse(str, &str);
169 size = roundup_pow_of_two(size);
170 if (size > log_buf_len) {
171 unsigned start, dest_idx, offset;
174 new_log_buf = alloc_bootmem(size);
176 printk(KERN_WARNING "log_buf_len: allocation failed\n");
180 spin_lock_irqsave(&logbuf_lock, flags);
182 log_buf = new_log_buf;
184 offset = start = min(con_start, log_start);
186 while (start != log_end) {
187 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
194 spin_unlock_irqrestore(&logbuf_lock, flags);
196 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
202 __setup("log_buf_len=", log_buf_len_setup);
204 #ifdef CONFIG_BOOT_PRINTK_DELAY
206 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
207 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
209 static int __init boot_delay_setup(char *str)
212 unsigned long long loops_per_msec;
214 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
215 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
217 get_option(&str, &boot_delay);
218 if (boot_delay > 10 * 1000)
221 printk_delay_msec = loops_per_msec;
222 printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
223 "HZ: %d, printk_delay_msec: %llu\n",
224 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
227 __setup("boot_delay=", boot_delay_setup);
229 static void boot_delay_msec(void)
231 unsigned long long k;
232 unsigned long timeout;
234 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
237 k = (unsigned long long)printk_delay_msec * boot_delay;
239 timeout = jiffies + msecs_to_jiffies(boot_delay);
244 * use (volatile) jiffies to prevent
245 * compiler reduction; loop termination via jiffies
246 * is secondary and may or may not happen.
248 if (time_after(jiffies, timeout))
250 touch_nmi_watchdog();
254 static inline void boot_delay_msec(void)
260 * Commands to do_syslog:
262 * 0 -- Close the log. Currently a NOP.
263 * 1 -- Open the log. Currently a NOP.
264 * 2 -- Read from the log.
265 * 3 -- Read all messages remaining in the ring buffer.
266 * 4 -- Read and clear all messages remaining in the ring buffer
267 * 5 -- Clear ring buffer.
268 * 6 -- Disable printk's to console
269 * 7 -- Enable printk's to console
270 * 8 -- Set level of messages printed to console
271 * 9 -- Return number of unread characters in the log buffer
272 * 10 -- Return size of the log buffer
274 int do_syslog(int type, char __user *buf, int len)
276 unsigned i, j, limit, count;
281 error = security_syslog(type);
286 case 0: /* Close log */
288 case 1: /* Open log */
290 case 2: /* Read from log */
297 if (!access_ok(VERIFY_WRITE, buf, len)) {
301 error = wait_event_interruptible(log_wait,
302 (log_start - log_end));
306 spin_lock_irq(&logbuf_lock);
307 while (!error && (log_start != log_end) && i < len) {
308 c = LOG_BUF(log_start);
310 spin_unlock_irq(&logbuf_lock);
311 error = __put_user(c,buf);
315 spin_lock_irq(&logbuf_lock);
317 spin_unlock_irq(&logbuf_lock);
321 case 4: /* Read/clear last kernel messages */
324 case 3: /* Read last kernel messages */
331 if (!access_ok(VERIFY_WRITE, buf, len)) {
336 if (count > log_buf_len)
338 spin_lock_irq(&logbuf_lock);
339 if (count > logged_chars)
340 count = logged_chars;
345 * __put_user() could sleep, and while we sleep
346 * printk() could overwrite the messages
347 * we try to copy to user space. Therefore
348 * the messages are copied in reverse. <manfreds>
350 for (i = 0; i < count && !error; i++) {
352 if (j + log_buf_len < log_end)
355 spin_unlock_irq(&logbuf_lock);
356 error = __put_user(c,&buf[count-1-i]);
358 spin_lock_irq(&logbuf_lock);
360 spin_unlock_irq(&logbuf_lock);
365 int offset = count-error;
366 /* buffer overflow during copy, correct user buffer. */
367 for (i = 0; i < error; i++) {
368 if (__get_user(c,&buf[i+offset]) ||
369 __put_user(c,&buf[i])) {
377 case 5: /* Clear ring buffer */
380 case 6: /* Disable logging to console */
381 console_loglevel = minimum_console_loglevel;
383 case 7: /* Enable logging to console */
384 console_loglevel = default_console_loglevel;
386 case 8: /* Set level of messages printed to console */
388 if (len < 1 || len > 8)
390 if (len < minimum_console_loglevel)
391 len = minimum_console_loglevel;
392 console_loglevel = len;
395 case 9: /* Number of chars in the log buffer */
396 error = log_end - log_start;
398 case 10: /* Size of the log buffer */
409 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
411 return do_syslog(type, buf, len);
415 * Call the console drivers on a range of log_buf
417 static void __call_console_drivers(unsigned start, unsigned end)
421 for_each_console(con) {
422 if ((con->flags & CON_ENABLED) && con->write &&
423 (cpu_online(smp_processor_id()) ||
424 (con->flags & CON_ANYTIME)))
425 con->write(con, &LOG_BUF(start), end - start);
429 static int __read_mostly ignore_loglevel;
431 static int __init ignore_loglevel_setup(char *str)
434 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
439 early_param("ignore_loglevel", ignore_loglevel_setup);
442 * Write out chars from start to end - 1 inclusive
444 static void _call_console_drivers(unsigned start,
445 unsigned end, int msg_log_level)
447 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
448 console_drivers && start != end) {
449 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
451 __call_console_drivers(start & LOG_BUF_MASK,
453 __call_console_drivers(0, end & LOG_BUF_MASK);
455 __call_console_drivers(start, end);
461 * Call the console drivers, asking them to write out
462 * log_buf[start] to log_buf[end - 1].
463 * The console_sem must be held.
465 static void call_console_drivers(unsigned start, unsigned end)
467 unsigned cur_index, start_print;
468 static int msg_level = -1;
470 BUG_ON(((int)(start - end)) > 0);
474 while (cur_index != end) {
475 if (msg_level < 0 && ((end - cur_index) > 2) &&
476 LOG_BUF(cur_index + 0) == '<' &&
477 LOG_BUF(cur_index + 1) >= '0' &&
478 LOG_BUF(cur_index + 1) <= '7' &&
479 LOG_BUF(cur_index + 2) == '>') {
480 msg_level = LOG_BUF(cur_index + 1) - '0';
482 start_print = cur_index;
484 while (cur_index != end) {
485 char c = LOG_BUF(cur_index);
491 * printk() has already given us loglevel tags in
492 * the buffer. This code is here in case the
493 * log buffer has wrapped right round and scribbled
496 msg_level = default_message_loglevel;
498 _call_console_drivers(start_print, cur_index, msg_level);
500 start_print = cur_index;
505 _call_console_drivers(start_print, end, msg_level);
508 static void emit_log_char(char c)
510 LOG_BUF(log_end) = c;
512 if (log_end - log_start > log_buf_len)
513 log_start = log_end - log_buf_len;
514 if (log_end - con_start > log_buf_len)
515 con_start = log_end - log_buf_len;
516 if (logged_chars < log_buf_len)
521 * Zap console related locks when oopsing. Only zap at most once
522 * every 10 seconds, to leave time for slow consoles to print a
525 static void zap_locks(void)
527 static unsigned long oops_timestamp;
529 if (time_after_eq(jiffies, oops_timestamp) &&
530 !time_after(jiffies, oops_timestamp + 30 * HZ))
533 oops_timestamp = jiffies;
535 /* If a crash is occurring, make sure we can't deadlock */
536 spin_lock_init(&logbuf_lock);
537 /* And make sure that we print immediately */
538 init_MUTEX(&console_sem);
541 #if defined(CONFIG_PRINTK_TIME)
542 static int printk_time = 1;
544 static int printk_time = 0;
546 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
548 /* Check if we have any console registered that can be called early in boot. */
549 static int have_callable_console(void)
553 for_each_console(con)
554 if (con->flags & CON_ANYTIME)
561 * printk - print a kernel message
562 * @fmt: format string
564 * This is printk(). It can be called from any context. We want it to work.
566 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
567 * call the console drivers. If we fail to get the semaphore we place the output
568 * into the log buffer and return. The current holder of the console_sem will
569 * notice the new output in release_console_sem() and will send it to the
570 * consoles before releasing the semaphore.
572 * One effect of this deferred printing is that code which calls printk() and
573 * then changes console_loglevel may break. This is because console_loglevel
574 * is inspected when the actual printing occurs.
579 * See the vsnprintf() documentation for format string extensions over C99.
582 asmlinkage int printk(const char *fmt, ...)
588 r = vprintk(fmt, args);
594 /* cpu currently holding logbuf_lock */
595 static volatile unsigned int printk_cpu = UINT_MAX;
598 * Can we actually use the console at this time on this cpu?
600 * Console drivers may assume that per-cpu resources have
601 * been allocated. So unless they're explicitly marked as
602 * being able to cope (CON_ANYTIME) don't call them until
603 * this CPU is officially up.
605 static inline int can_use_console(unsigned int cpu)
607 return cpu_online(cpu) || have_callable_console();
611 * Try to get console ownership to actually show the kernel
612 * messages from a 'printk'. Return true (and with the
613 * console_semaphore held, and 'console_locked' set) if it
614 * is successful, false otherwise.
616 * This gets called with the 'logbuf_lock' spinlock held and
617 * interrupts disabled. It should return with 'lockbuf_lock'
618 * released but interrupts still disabled.
620 static int acquire_console_semaphore_for_printk(unsigned int cpu)
624 if (!try_acquire_console_sem()) {
628 * If we can't use the console, we need to release
629 * the console semaphore by hand to avoid flushing
630 * the buffer. We need to hold the console semaphore
631 * in order to do this test safely.
633 if (!can_use_console(cpu)) {
639 printk_cpu = UINT_MAX;
640 spin_unlock(&logbuf_lock);
643 static const char recursion_bug_msg [] =
644 KERN_CRIT "BUG: recent printk recursion!\n";
645 static int recursion_bug;
646 static int new_text_line = 1;
647 static char printk_buf[1024];
649 asmlinkage int vprintk(const char *fmt, va_list args)
652 int current_log_level = default_message_loglevel;
660 /* This stops the holder of console_sem just where we want him */
661 raw_local_irq_save(flags);
662 this_cpu = smp_processor_id();
665 * Ouch, printk recursed into itself!
667 if (unlikely(printk_cpu == this_cpu)) {
669 * If a crash is occurring during printk() on this CPU,
670 * then try to get the crash message out but make sure
671 * we can't deadlock. Otherwise just return to avoid the
672 * recursion and return - but flag the recursion so that
673 * it can be printed at the next appropriate moment:
675 if (!oops_in_progress) {
677 goto out_restore_irqs;
683 spin_lock(&logbuf_lock);
684 printk_cpu = this_cpu;
688 strcpy(printk_buf, recursion_bug_msg);
689 printed_len = strlen(recursion_bug_msg);
691 /* Emit the output into the temporary buffer */
692 printed_len += vscnprintf(printk_buf + printed_len,
693 sizeof(printk_buf) - printed_len, fmt, args);
698 /* Do we have a loglevel in the string? */
700 unsigned char c = p[1];
701 if (c && p[2] == '>') {
703 case '0' ... '7': /* loglevel */
704 current_log_level = c - '0';
705 /* Fallthrough - make sure we're on a new line */
706 case 'd': /* KERN_DEFAULT */
707 if (!new_text_line) {
711 /* Fallthrough - skip the loglevel */
712 case 'c': /* KERN_CONT */
720 * Copy the output into log_buf. If the caller didn't provide
721 * appropriate log level tags, we insert them here
725 /* Always output the token */
727 emit_log_char(current_log_level + '0');
733 /* Follow the token with the time */
736 unsigned long long t;
737 unsigned long nanosec_rem;
739 t = cpu_clock(printk_cpu);
740 nanosec_rem = do_div(t, 1000000000);
741 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
745 for (tp = tbuf; tp < tbuf + tlen; tp++)
760 * Try to acquire and then immediately release the
761 * console semaphore. The release will do all the
762 * actual magic (print out buffers, wake up klogd,
765 * The acquire_console_semaphore_for_printk() function
766 * will release 'logbuf_lock' regardless of whether it
767 * actually gets the semaphore or not.
769 if (acquire_console_semaphore_for_printk(this_cpu))
770 release_console_sem();
774 raw_local_irq_restore(flags);
779 EXPORT_SYMBOL(printk);
780 EXPORT_SYMBOL(vprintk);
784 static void call_console_drivers(unsigned start, unsigned end)
790 static int __add_preferred_console(char *name, int idx, char *options,
793 struct console_cmdline *c;
797 * See if this tty is not yet registered, and
798 * if we have a slot free.
800 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
801 if (strcmp(console_cmdline[i].name, name) == 0 &&
802 console_cmdline[i].index == idx) {
804 selected_console = i;
807 if (i == MAX_CMDLINECONSOLES)
810 selected_console = i;
811 c = &console_cmdline[i];
812 strlcpy(c->name, name, sizeof(c->name));
813 c->options = options;
814 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
815 c->brl_options = brl_options;
821 * Set up a list of consoles. Called from init/main.c
823 static int __init console_setup(char *str)
825 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
826 char *s, *options, *brl_options = NULL;
829 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
830 if (!memcmp(str, "brl,", 4)) {
833 } else if (!memcmp(str, "brl=", 4)) {
834 brl_options = str + 4;
835 str = strchr(brl_options, ',');
837 printk(KERN_ERR "need port name after brl=\n");
845 * Decode str into name, index, options.
847 if (str[0] >= '0' && str[0] <= '9') {
849 strncpy(buf + 4, str, sizeof(buf) - 5);
851 strncpy(buf, str, sizeof(buf) - 1);
853 buf[sizeof(buf) - 1] = 0;
854 if ((options = strchr(str, ',')) != NULL)
857 if (!strcmp(str, "ttya"))
858 strcpy(buf, "ttyS0");
859 if (!strcmp(str, "ttyb"))
860 strcpy(buf, "ttyS1");
862 for (s = buf; *s; s++)
863 if ((*s >= '0' && *s <= '9') || *s == ',')
865 idx = simple_strtoul(s, NULL, 10);
868 __add_preferred_console(buf, idx, options, brl_options);
869 console_set_on_cmdline = 1;
872 __setup("console=", console_setup);
875 * add_preferred_console - add a device to the list of preferred consoles.
878 * @options: options for this console
880 * The last preferred console added will be used for kernel messages
881 * and stdin/out/err for init. Normally this is used by console_setup
882 * above to handle user-supplied console arguments; however it can also
883 * be used by arch-specific code either to override the user or more
884 * commonly to provide a default console (ie from PROM variables) when
885 * the user has not supplied one.
887 int add_preferred_console(char *name, int idx, char *options)
889 return __add_preferred_console(name, idx, options, NULL);
892 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
894 struct console_cmdline *c;
897 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
898 if (strcmp(console_cmdline[i].name, name) == 0 &&
899 console_cmdline[i].index == idx) {
900 c = &console_cmdline[i];
901 strlcpy(c->name, name_new, sizeof(c->name));
902 c->name[sizeof(c->name) - 1] = 0;
903 c->options = options;
911 int console_suspend_enabled = 1;
912 EXPORT_SYMBOL(console_suspend_enabled);
914 static int __init console_suspend_disable(char *str)
916 console_suspend_enabled = 0;
919 __setup("no_console_suspend", console_suspend_disable);
922 * suspend_console - suspend the console subsystem
924 * This disables printk() while we go into suspend states
926 void suspend_console(void)
928 if (!console_suspend_enabled)
930 printk("Suspending console(s) (use no_console_suspend to debug)\n");
931 acquire_console_sem();
932 console_suspended = 1;
936 void resume_console(void)
938 if (!console_suspend_enabled)
941 console_suspended = 0;
942 release_console_sem();
946 * acquire_console_sem - lock the console system for exclusive use.
948 * Acquires a semaphore which guarantees that the caller has
949 * exclusive access to the console system and the console_drivers list.
951 * Can sleep, returns nothing.
953 void acquire_console_sem(void)
955 BUG_ON(in_interrupt());
957 if (console_suspended)
960 console_may_schedule = 1;
962 EXPORT_SYMBOL(acquire_console_sem);
964 int try_acquire_console_sem(void)
966 if (down_trylock(&console_sem))
968 if (console_suspended) {
973 console_may_schedule = 0;
976 EXPORT_SYMBOL(try_acquire_console_sem);
978 int is_console_locked(void)
980 return console_locked;
983 static DEFINE_PER_CPU(int, printk_pending);
985 void printk_tick(void)
987 if (__get_cpu_var(printk_pending)) {
988 __get_cpu_var(printk_pending) = 0;
989 wake_up_interruptible(&log_wait);
993 int printk_needs_cpu(int cpu)
995 return per_cpu(printk_pending, cpu);
998 void wake_up_klogd(void)
1000 if (waitqueue_active(&log_wait))
1001 __raw_get_cpu_var(printk_pending) = 1;
1005 * release_console_sem - unlock the console system
1007 * Releases the semaphore which the caller holds on the console system
1008 * and the console driver list.
1010 * While the semaphore was held, console output may have been buffered
1011 * by printk(). If this is the case, release_console_sem() emits
1012 * the output prior to releasing the semaphore.
1014 * If there is output waiting for klogd, we wake it up.
1016 * release_console_sem() may be called from any context.
1018 void release_console_sem(void)
1020 unsigned long flags;
1021 unsigned _con_start, _log_end;
1022 unsigned wake_klogd = 0;
1024 if (console_suspended) {
1029 console_may_schedule = 0;
1032 spin_lock_irqsave(&logbuf_lock, flags);
1033 wake_klogd |= log_start - log_end;
1034 if (con_start == log_end)
1035 break; /* Nothing to print */
1036 _con_start = con_start;
1038 con_start = log_end; /* Flush */
1039 spin_unlock(&logbuf_lock);
1040 stop_critical_timings(); /* don't trace print latency */
1041 call_console_drivers(_con_start, _log_end);
1042 start_critical_timings();
1043 local_irq_restore(flags);
1047 spin_unlock_irqrestore(&logbuf_lock, flags);
1051 EXPORT_SYMBOL(release_console_sem);
1054 * console_conditional_schedule - yield the CPU if required
1056 * If the console code is currently allowed to sleep, and
1057 * if this CPU should yield the CPU to another task, do
1060 * Must be called within acquire_console_sem().
1062 void __sched console_conditional_schedule(void)
1064 if (console_may_schedule)
1067 EXPORT_SYMBOL(console_conditional_schedule);
1069 void console_print(const char *s)
1071 printk(KERN_EMERG "%s", s);
1073 EXPORT_SYMBOL(console_print);
1075 void console_unblank(void)
1080 * console_unblank can no longer be called in interrupt context unless
1081 * oops_in_progress is set to 1..
1083 if (oops_in_progress) {
1084 if (down_trylock(&console_sem) != 0)
1087 acquire_console_sem();
1090 console_may_schedule = 0;
1092 if ((c->flags & CON_ENABLED) && c->unblank)
1094 release_console_sem();
1098 * Return the console tty driver structure and its associated index
1100 struct tty_driver *console_device(int *index)
1103 struct tty_driver *driver = NULL;
1105 acquire_console_sem();
1106 for_each_console(c) {
1109 driver = c->device(c, index);
1113 release_console_sem();
1118 * Prevent further output on the passed console device so that (for example)
1119 * serial drivers can disable console output before suspending a port, and can
1120 * re-enable output afterwards.
1122 void console_stop(struct console *console)
1124 acquire_console_sem();
1125 console->flags &= ~CON_ENABLED;
1126 release_console_sem();
1128 EXPORT_SYMBOL(console_stop);
1130 void console_start(struct console *console)
1132 acquire_console_sem();
1133 console->flags |= CON_ENABLED;
1134 release_console_sem();
1136 EXPORT_SYMBOL(console_start);
1139 * The console driver calls this routine during kernel initialization
1140 * to register the console printing procedure with printk() and to
1141 * print any messages that were printed by the kernel before the
1142 * console driver was initialized.
1144 * This can happen pretty early during the boot process (because of
1145 * early_printk) - sometimes before setup_arch() completes - be careful
1146 * of what kernel features are used - they may not be initialised yet.
1148 * There are two types of consoles - bootconsoles (early_printk) and
1149 * "real" consoles (everything which is not a bootconsole) which are
1150 * handled differently.
1151 * - Any number of bootconsoles can be registered at any time.
1152 * - As soon as a "real" console is registered, all bootconsoles
1153 * will be unregistered automatically.
1154 * - Once a "real" console is registered, any attempt to register a
1155 * bootconsoles will be rejected
1157 void register_console(struct console *newcon)
1160 unsigned long flags;
1161 struct console *bcon = NULL;
1164 * before we register a new CON_BOOT console, make sure we don't
1165 * already have a valid console
1167 if (console_drivers && newcon->flags & CON_BOOT) {
1168 /* find the last or real console */
1169 for_each_console(bcon) {
1170 if (!(bcon->flags & CON_BOOT)) {
1171 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1172 newcon->name, newcon->index);
1178 if (console_drivers && console_drivers->flags & CON_BOOT)
1179 bcon = console_drivers;
1181 if (preferred_console < 0 || bcon || !console_drivers)
1182 preferred_console = selected_console;
1184 if (newcon->early_setup)
1185 newcon->early_setup();
1188 * See if we want to use this console driver. If we
1189 * didn't select a console we take the first one
1190 * that registers here.
1192 if (preferred_console < 0) {
1193 if (newcon->index < 0)
1195 if (newcon->setup == NULL ||
1196 newcon->setup(newcon, NULL) == 0) {
1197 newcon->flags |= CON_ENABLED;
1198 if (newcon->device) {
1199 newcon->flags |= CON_CONSDEV;
1200 preferred_console = 0;
1206 * See if this console matches one we selected on
1209 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1211 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1213 if (newcon->index >= 0 &&
1214 newcon->index != console_cmdline[i].index)
1216 if (newcon->index < 0)
1217 newcon->index = console_cmdline[i].index;
1218 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1219 if (console_cmdline[i].brl_options) {
1220 newcon->flags |= CON_BRL;
1221 braille_register_console(newcon,
1222 console_cmdline[i].index,
1223 console_cmdline[i].options,
1224 console_cmdline[i].brl_options);
1228 if (newcon->setup &&
1229 newcon->setup(newcon, console_cmdline[i].options) != 0)
1231 newcon->flags |= CON_ENABLED;
1232 newcon->index = console_cmdline[i].index;
1233 if (i == selected_console) {
1234 newcon->flags |= CON_CONSDEV;
1235 preferred_console = selected_console;
1240 if (!(newcon->flags & CON_ENABLED))
1244 * If we have a bootconsole, and are switching to a real console,
1245 * don't print everything out again, since when the boot console, and
1246 * the real console are the same physical device, it's annoying to
1247 * see the beginning boot messages twice
1249 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1250 newcon->flags &= ~CON_PRINTBUFFER;
1253 * Put this console in the list - keep the
1254 * preferred driver at the head of the list.
1256 acquire_console_sem();
1257 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1258 newcon->next = console_drivers;
1259 console_drivers = newcon;
1261 newcon->next->flags &= ~CON_CONSDEV;
1263 newcon->next = console_drivers->next;
1264 console_drivers->next = newcon;
1266 if (newcon->flags & CON_PRINTBUFFER) {
1268 * release_console_sem() will print out the buffered messages
1271 spin_lock_irqsave(&logbuf_lock, flags);
1272 con_start = log_start;
1273 spin_unlock_irqrestore(&logbuf_lock, flags);
1275 release_console_sem();
1278 * By unregistering the bootconsoles after we enable the real console
1279 * we get the "console xxx enabled" message on all the consoles -
1280 * boot consoles, real consoles, etc - this is to ensure that end
1281 * users know there might be something in the kernel's log buffer that
1282 * went to the bootconsole (that they do not see on the real console)
1284 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1285 /* we need to iterate through twice, to make sure we print
1286 * everything out, before we unregister the console(s)
1288 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1289 newcon->name, newcon->index);
1290 for_each_console(bcon)
1291 if (bcon->flags & CON_BOOT)
1292 unregister_console(bcon);
1294 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1295 (newcon->flags & CON_BOOT) ? "boot" : "" ,
1296 newcon->name, newcon->index);
1299 EXPORT_SYMBOL(register_console);
1301 int unregister_console(struct console *console)
1303 struct console *a, *b;
1306 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1307 if (console->flags & CON_BRL)
1308 return braille_unregister_console(console);
1311 acquire_console_sem();
1312 if (console_drivers == console) {
1313 console_drivers=console->next;
1315 } else if (console_drivers) {
1316 for (a=console_drivers->next, b=console_drivers ;
1317 a; b=a, a=b->next) {
1327 * If this isn't the last console and it has CON_CONSDEV set, we
1328 * need to set it on the next preferred console.
1330 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1331 console_drivers->flags |= CON_CONSDEV;
1333 release_console_sem();
1336 EXPORT_SYMBOL(unregister_console);
1338 static int __init disable_boot_consoles(void)
1340 struct console *con;
1342 for_each_console(con) {
1343 if (con->flags & CON_BOOT) {
1344 printk(KERN_INFO "turn off boot console %s%d\n",
1345 con->name, con->index);
1346 return unregister_console(con);
1351 late_initcall(disable_boot_consoles);
1353 #if defined CONFIG_PRINTK
1356 * printk rate limiting, lifted from the networking subsystem.
1358 * This enforces a rate limit: not more than 10 kernel messages
1359 * every 5s to make a denial-of-service attack impossible.
1361 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1363 int printk_ratelimit(void)
1365 return __ratelimit(&printk_ratelimit_state);
1367 EXPORT_SYMBOL(printk_ratelimit);
1370 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1371 * @caller_jiffies: pointer to caller's state
1372 * @interval_msecs: minimum interval between prints
1374 * printk_timed_ratelimit() returns true if more than @interval_msecs
1375 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1378 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1379 unsigned int interval_msecs)
1381 if (*caller_jiffies == 0
1382 || !time_in_range(jiffies, *caller_jiffies,
1384 + msecs_to_jiffies(interval_msecs))) {
1385 *caller_jiffies = jiffies;
1390 EXPORT_SYMBOL(printk_timed_ratelimit);