mlme.c: fixup some merge damage
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / printk.c
blobc46a20a19a153f06e938d469bf760ee893b63114
1 /*
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).
11 * Ted Ts'o, 2/11/93.
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>
20 #include <linux/mm.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.
67 int oops_in_progress;
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
73 * driver system.
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 */
116 #define MAX_CMDLINECONSOLES 8
118 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
119 static int selected_console = -1;
120 static int preferred_console = -1;
122 /* Flag: console code may call schedule() */
123 static int console_may_schedule;
125 #ifdef CONFIG_PRINTK
127 static char __log_buf[__LOG_BUF_LEN];
128 static char *log_buf = __log_buf;
129 static int log_buf_len = __LOG_BUF_LEN;
130 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
132 static int __init log_buf_len_setup(char *str)
134 unsigned size = memparse(str, &str);
135 unsigned long flags;
137 if (size)
138 size = roundup_pow_of_two(size);
139 if (size > log_buf_len) {
140 unsigned start, dest_idx, offset;
141 char *new_log_buf;
143 new_log_buf = alloc_bootmem(size);
144 if (!new_log_buf) {
145 printk(KERN_WARNING "log_buf_len: allocation failed\n");
146 goto out;
149 spin_lock_irqsave(&logbuf_lock, flags);
150 log_buf_len = size;
151 log_buf = new_log_buf;
153 offset = start = min(con_start, log_start);
154 dest_idx = 0;
155 while (start != log_end) {
156 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
157 start++;
158 dest_idx++;
160 log_start -= offset;
161 con_start -= offset;
162 log_end -= offset;
163 spin_unlock_irqrestore(&logbuf_lock, flags);
165 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
167 out:
168 return 1;
171 __setup("log_buf_len=", log_buf_len_setup);
173 #ifdef CONFIG_BOOT_PRINTK_DELAY
175 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
176 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
178 static int __init boot_delay_setup(char *str)
180 unsigned long lpj;
181 unsigned long long loops_per_msec;
183 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
184 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
186 get_option(&str, &boot_delay);
187 if (boot_delay > 10 * 1000)
188 boot_delay = 0;
190 printk_delay_msec = loops_per_msec;
191 printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
192 "HZ: %d, printk_delay_msec: %llu\n",
193 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
194 return 1;
196 __setup("boot_delay=", boot_delay_setup);
198 static void boot_delay_msec(void)
200 unsigned long long k;
201 unsigned long timeout;
203 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
204 return;
206 k = (unsigned long long)printk_delay_msec * boot_delay;
208 timeout = jiffies + msecs_to_jiffies(boot_delay);
209 while (k) {
210 k--;
211 cpu_relax();
213 * use (volatile) jiffies to prevent
214 * compiler reduction; loop termination via jiffies
215 * is secondary and may or may not happen.
217 if (time_after(jiffies, timeout))
218 break;
219 touch_nmi_watchdog();
222 #else
223 static inline void boot_delay_msec(void)
226 #endif
229 * Return the number of unread characters in the log buffer.
231 int log_buf_get_len(void)
233 return logged_chars;
237 * Copy a range of characters from the log buffer.
239 int log_buf_copy(char *dest, int idx, int len)
241 int ret, max;
242 bool took_lock = false;
244 if (!oops_in_progress) {
245 spin_lock_irq(&logbuf_lock);
246 took_lock = true;
249 max = log_buf_get_len();
250 if (idx < 0 || idx >= max) {
251 ret = -1;
252 } else {
253 if (len > max)
254 len = max;
255 ret = len;
256 idx += (log_end - max);
257 while (len-- > 0)
258 dest[len] = LOG_BUF(idx + len);
261 if (took_lock)
262 spin_unlock_irq(&logbuf_lock);
264 return ret;
268 * Extract a single character from the log buffer.
270 int log_buf_read(int idx)
272 char ret;
274 if (log_buf_copy(&ret, idx, 1) == 1)
275 return ret;
276 else
277 return -1;
281 * Commands to do_syslog:
283 * 0 -- Close the log. Currently a NOP.
284 * 1 -- Open the log. Currently a NOP.
285 * 2 -- Read from the log.
286 * 3 -- Read all messages remaining in the ring buffer.
287 * 4 -- Read and clear all messages remaining in the ring buffer
288 * 5 -- Clear ring buffer.
289 * 6 -- Disable printk's to console
290 * 7 -- Enable printk's to console
291 * 8 -- Set level of messages printed to console
292 * 9 -- Return number of unread characters in the log buffer
293 * 10 -- Return size of the log buffer
295 int do_syslog(int type, char __user *buf, int len)
297 unsigned i, j, limit, count;
298 int do_clear = 0;
299 char c;
300 int error = 0;
302 error = security_syslog(type);
303 if (error)
304 return error;
306 switch (type) {
307 case 0: /* Close log */
308 break;
309 case 1: /* Open log */
310 break;
311 case 2: /* Read from log */
312 error = -EINVAL;
313 if (!buf || len < 0)
314 goto out;
315 error = 0;
316 if (!len)
317 goto out;
318 if (!access_ok(VERIFY_WRITE, buf, len)) {
319 error = -EFAULT;
320 goto out;
322 error = wait_event_interruptible(log_wait,
323 (log_start - log_end));
324 if (error)
325 goto out;
326 i = 0;
327 spin_lock_irq(&logbuf_lock);
328 while (!error && (log_start != log_end) && i < len) {
329 c = LOG_BUF(log_start);
330 log_start++;
331 spin_unlock_irq(&logbuf_lock);
332 error = __put_user(c,buf);
333 buf++;
334 i++;
335 cond_resched();
336 spin_lock_irq(&logbuf_lock);
338 spin_unlock_irq(&logbuf_lock);
339 if (!error)
340 error = i;
341 break;
342 case 4: /* Read/clear last kernel messages */
343 do_clear = 1;
344 /* FALL THRU */
345 case 3: /* Read last kernel messages */
346 error = -EINVAL;
347 if (!buf || len < 0)
348 goto out;
349 error = 0;
350 if (!len)
351 goto out;
352 if (!access_ok(VERIFY_WRITE, buf, len)) {
353 error = -EFAULT;
354 goto out;
356 count = len;
357 if (count > log_buf_len)
358 count = log_buf_len;
359 spin_lock_irq(&logbuf_lock);
360 if (count > logged_chars)
361 count = logged_chars;
362 if (do_clear)
363 logged_chars = 0;
364 limit = log_end;
366 * __put_user() could sleep, and while we sleep
367 * printk() could overwrite the messages
368 * we try to copy to user space. Therefore
369 * the messages are copied in reverse. <manfreds>
371 for (i = 0; i < count && !error; i++) {
372 j = limit-1-i;
373 if (j + log_buf_len < log_end)
374 break;
375 c = LOG_BUF(j);
376 spin_unlock_irq(&logbuf_lock);
377 error = __put_user(c,&buf[count-1-i]);
378 cond_resched();
379 spin_lock_irq(&logbuf_lock);
381 spin_unlock_irq(&logbuf_lock);
382 if (error)
383 break;
384 error = i;
385 if (i != count) {
386 int offset = count-error;
387 /* buffer overflow during copy, correct user buffer. */
388 for (i = 0; i < error; i++) {
389 if (__get_user(c,&buf[i+offset]) ||
390 __put_user(c,&buf[i])) {
391 error = -EFAULT;
392 break;
394 cond_resched();
397 break;
398 case 5: /* Clear ring buffer */
399 logged_chars = 0;
400 break;
401 case 6: /* Disable logging to console */
402 console_loglevel = minimum_console_loglevel;
403 break;
404 case 7: /* Enable logging to console */
405 console_loglevel = default_console_loglevel;
406 break;
407 case 8: /* Set level of messages printed to console */
408 error = -EINVAL;
409 if (len < 1 || len > 8)
410 goto out;
411 if (len < minimum_console_loglevel)
412 len = minimum_console_loglevel;
413 console_loglevel = len;
414 error = 0;
415 break;
416 case 9: /* Number of chars in the log buffer */
417 error = log_end - log_start;
418 break;
419 case 10: /* Size of the log buffer */
420 error = log_buf_len;
421 break;
422 default:
423 error = -EINVAL;
424 break;
426 out:
427 return error;
430 asmlinkage long sys_syslog(int type, char __user *buf, int len)
432 return do_syslog(type, buf, len);
436 * Call the console drivers on a range of log_buf
438 static void __call_console_drivers(unsigned start, unsigned end)
440 struct console *con;
442 for (con = console_drivers; con; con = con->next) {
443 if ((con->flags & CON_ENABLED) && con->write &&
444 (cpu_online(smp_processor_id()) ||
445 (con->flags & CON_ANYTIME)))
446 con->write(con, &LOG_BUF(start), end - start);
450 static int __read_mostly ignore_loglevel;
452 static int __init ignore_loglevel_setup(char *str)
454 ignore_loglevel = 1;
455 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
457 return 0;
460 early_param("ignore_loglevel", ignore_loglevel_setup);
463 * Write out chars from start to end - 1 inclusive
465 static void _call_console_drivers(unsigned start,
466 unsigned end, int msg_log_level)
468 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
469 console_drivers && start != end) {
470 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
471 /* wrapped write */
472 __call_console_drivers(start & LOG_BUF_MASK,
473 log_buf_len);
474 __call_console_drivers(0, end & LOG_BUF_MASK);
475 } else {
476 __call_console_drivers(start, end);
482 * Call the console drivers, asking them to write out
483 * log_buf[start] to log_buf[end - 1].
484 * The console_sem must be held.
486 static void call_console_drivers(unsigned start, unsigned end)
488 unsigned cur_index, start_print;
489 static int msg_level = -1;
491 BUG_ON(((int)(start - end)) > 0);
493 cur_index = start;
494 start_print = start;
495 while (cur_index != end) {
496 if (msg_level < 0 && ((end - cur_index) > 2) &&
497 LOG_BUF(cur_index + 0) == '<' &&
498 LOG_BUF(cur_index + 1) >= '0' &&
499 LOG_BUF(cur_index + 1) <= '7' &&
500 LOG_BUF(cur_index + 2) == '>') {
501 msg_level = LOG_BUF(cur_index + 1) - '0';
502 cur_index += 3;
503 start_print = cur_index;
505 while (cur_index != end) {
506 char c = LOG_BUF(cur_index);
508 cur_index++;
509 if (c == '\n') {
510 if (msg_level < 0) {
512 * printk() has already given us loglevel tags in
513 * the buffer. This code is here in case the
514 * log buffer has wrapped right round and scribbled
515 * on those tags
517 msg_level = default_message_loglevel;
519 _call_console_drivers(start_print, cur_index, msg_level);
520 msg_level = -1;
521 start_print = cur_index;
522 break;
526 _call_console_drivers(start_print, end, msg_level);
529 static void emit_log_char(char c)
531 LOG_BUF(log_end) = c;
532 log_end++;
533 if (log_end - log_start > log_buf_len)
534 log_start = log_end - log_buf_len;
535 if (log_end - con_start > log_buf_len)
536 con_start = log_end - log_buf_len;
537 if (logged_chars < log_buf_len)
538 logged_chars++;
542 * Zap console related locks when oopsing. Only zap at most once
543 * every 10 seconds, to leave time for slow consoles to print a
544 * full oops.
546 static void zap_locks(void)
548 static unsigned long oops_timestamp;
550 if (time_after_eq(jiffies, oops_timestamp) &&
551 !time_after(jiffies, oops_timestamp + 30 * HZ))
552 return;
554 oops_timestamp = jiffies;
556 /* If a crash is occurring, make sure we can't deadlock */
557 spin_lock_init(&logbuf_lock);
558 /* And make sure that we print immediately */
559 init_MUTEX(&console_sem);
562 #if defined(CONFIG_PRINTK_TIME)
563 static int printk_time = 1;
564 #else
565 static int printk_time = 0;
566 #endif
567 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
569 /* Check if we have any console registered that can be called early in boot. */
570 static int have_callable_console(void)
572 struct console *con;
574 for (con = console_drivers; con; con = con->next)
575 if (con->flags & CON_ANYTIME)
576 return 1;
578 return 0;
582 * printk - print a kernel message
583 * @fmt: format string
585 * This is printk(). It can be called from any context. We want it to work.
586 * Be aware of the fact that if oops_in_progress is not set, we might try to
587 * wake klogd up which could deadlock on runqueue lock if printk() is called
588 * from scheduler code.
590 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
591 * call the console drivers. If we fail to get the semaphore we place the output
592 * into the log buffer and return. The current holder of the console_sem will
593 * notice the new output in release_console_sem() and will send it to the
594 * consoles before releasing the semaphore.
596 * One effect of this deferred printing is that code which calls printk() and
597 * then changes console_loglevel may break. This is because console_loglevel
598 * is inspected when the actual printing occurs.
600 * See also:
601 * printf(3)
604 asmlinkage int printk(const char *fmt, ...)
606 va_list args;
607 int r;
609 va_start(args, fmt);
610 r = vprintk(fmt, args);
611 va_end(args);
613 return r;
616 /* cpu currently holding logbuf_lock */
617 static volatile unsigned int printk_cpu = UINT_MAX;
620 * Can we actually use the console at this time on this cpu?
622 * Console drivers may assume that per-cpu resources have
623 * been allocated. So unless they're explicitly marked as
624 * being able to cope (CON_ANYTIME) don't call them until
625 * this CPU is officially up.
627 static inline int can_use_console(unsigned int cpu)
629 return cpu_online(cpu) || have_callable_console();
633 * Try to get console ownership to actually show the kernel
634 * messages from a 'printk'. Return true (and with the
635 * console_semaphore held, and 'console_locked' set) if it
636 * is successful, false otherwise.
638 * This gets called with the 'logbuf_lock' spinlock held and
639 * interrupts disabled. It should return with 'lockbuf_lock'
640 * released but interrupts still disabled.
642 static int acquire_console_semaphore_for_printk(unsigned int cpu)
644 int retval = 0;
646 if (can_use_console(cpu))
647 retval = !try_acquire_console_sem();
648 printk_cpu = UINT_MAX;
649 spin_unlock(&logbuf_lock);
650 return retval;
653 const char printk_recursion_bug_msg [] =
654 KERN_CRIT "BUG: recent printk recursion!\n";
655 static int printk_recursion_bug;
657 asmlinkage int vprintk(const char *fmt, va_list args)
659 static int log_level_unknown = 1;
660 static char printk_buf[1024];
662 unsigned long flags;
663 int printed_len = 0;
664 int this_cpu;
665 char *p;
667 boot_delay_msec();
669 preempt_disable();
670 /* This stops the holder of console_sem just where we want him */
671 raw_local_irq_save(flags);
672 this_cpu = smp_processor_id();
675 * Ouch, printk recursed into itself!
677 if (unlikely(printk_cpu == this_cpu)) {
679 * If a crash is occurring during printk() on this CPU,
680 * then try to get the crash message out but make sure
681 * we can't deadlock. Otherwise just return to avoid the
682 * recursion and return - but flag the recursion so that
683 * it can be printed at the next appropriate moment:
685 if (!oops_in_progress) {
686 printk_recursion_bug = 1;
687 goto out_restore_irqs;
689 zap_locks();
692 lockdep_off();
693 spin_lock(&logbuf_lock);
694 printk_cpu = this_cpu;
696 if (printk_recursion_bug) {
697 printk_recursion_bug = 0;
698 strcpy(printk_buf, printk_recursion_bug_msg);
699 printed_len = sizeof(printk_recursion_bug_msg);
701 /* Emit the output into the temporary buffer */
702 printed_len += vscnprintf(printk_buf + printed_len,
703 sizeof(printk_buf) - printed_len, fmt, args);
706 * Copy the output into log_buf. If the caller didn't provide
707 * appropriate log level tags, we insert them here
709 for (p = printk_buf; *p; p++) {
710 if (log_level_unknown) {
711 /* log_level_unknown signals the start of a new line */
712 if (printk_time) {
713 int loglev_char;
714 char tbuf[50], *tp;
715 unsigned tlen;
716 unsigned long long t;
717 unsigned long nanosec_rem;
720 * force the log level token to be
721 * before the time output.
723 if (p[0] == '<' && p[1] >='0' &&
724 p[1] <= '7' && p[2] == '>') {
725 loglev_char = p[1];
726 p += 3;
727 printed_len -= 3;
728 } else {
729 loglev_char = default_message_loglevel
730 + '0';
732 t = cpu_clock(printk_cpu);
733 nanosec_rem = do_div(t, 1000000000);
734 tlen = sprintf(tbuf,
735 "<%c>[%5lu.%06lu] ",
736 loglev_char,
737 (unsigned long)t,
738 nanosec_rem/1000);
740 for (tp = tbuf; tp < tbuf + tlen; tp++)
741 emit_log_char(*tp);
742 printed_len += tlen;
743 } else {
744 if (p[0] != '<' || p[1] < '0' ||
745 p[1] > '7' || p[2] != '>') {
746 emit_log_char('<');
747 emit_log_char(default_message_loglevel
748 + '0');
749 emit_log_char('>');
750 printed_len += 3;
753 log_level_unknown = 0;
754 if (!*p)
755 break;
757 emit_log_char(*p);
758 if (*p == '\n')
759 log_level_unknown = 1;
763 * Try to acquire and then immediately release the
764 * console semaphore. The release will do all the
765 * actual magic (print out buffers, wake up klogd,
766 * etc).
768 * The acquire_console_semaphore_for_printk() function
769 * will release 'logbuf_lock' regardless of whether it
770 * actually gets the semaphore or not.
772 if (acquire_console_semaphore_for_printk(this_cpu))
773 release_console_sem();
775 lockdep_on();
776 out_restore_irqs:
777 raw_local_irq_restore(flags);
779 preempt_enable();
780 return printed_len;
782 EXPORT_SYMBOL(printk);
783 EXPORT_SYMBOL(vprintk);
785 #else
787 asmlinkage long sys_syslog(int type, char __user *buf, int len)
789 return -ENOSYS;
792 static void call_console_drivers(unsigned start, unsigned end)
796 #endif
799 * Set up a list of consoles. Called from init/main.c
801 static int __init console_setup(char *str)
803 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
804 char *s, *options;
805 int idx;
808 * Decode str into name, index, options.
810 if (str[0] >= '0' && str[0] <= '9') {
811 strcpy(buf, "ttyS");
812 strncpy(buf + 4, str, sizeof(buf) - 5);
813 } else {
814 strncpy(buf, str, sizeof(buf) - 1);
816 buf[sizeof(buf) - 1] = 0;
817 if ((options = strchr(str, ',')) != NULL)
818 *(options++) = 0;
819 #ifdef __sparc__
820 if (!strcmp(str, "ttya"))
821 strcpy(buf, "ttyS0");
822 if (!strcmp(str, "ttyb"))
823 strcpy(buf, "ttyS1");
824 #endif
825 for (s = buf; *s; s++)
826 if ((*s >= '0' && *s <= '9') || *s == ',')
827 break;
828 idx = simple_strtoul(s, NULL, 10);
829 *s = 0;
831 add_preferred_console(buf, idx, options);
832 return 1;
834 __setup("console=", console_setup);
837 * add_preferred_console - add a device to the list of preferred consoles.
838 * @name: device name
839 * @idx: device index
840 * @options: options for this console
842 * The last preferred console added will be used for kernel messages
843 * and stdin/out/err for init. Normally this is used by console_setup
844 * above to handle user-supplied console arguments; however it can also
845 * be used by arch-specific code either to override the user or more
846 * commonly to provide a default console (ie from PROM variables) when
847 * the user has not supplied one.
849 int add_preferred_console(char *name, int idx, char *options)
851 struct console_cmdline *c;
852 int i;
855 * See if this tty is not yet registered, and
856 * if we have a slot free.
858 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
859 if (strcmp(console_cmdline[i].name, name) == 0 &&
860 console_cmdline[i].index == idx) {
861 selected_console = i;
862 return 0;
864 if (i == MAX_CMDLINECONSOLES)
865 return -E2BIG;
866 selected_console = i;
867 c = &console_cmdline[i];
868 memcpy(c->name, name, sizeof(c->name));
869 c->name[sizeof(c->name) - 1] = 0;
870 c->options = options;
871 c->index = idx;
872 return 0;
875 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
877 struct console_cmdline *c;
878 int i;
880 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
881 if (strcmp(console_cmdline[i].name, name) == 0 &&
882 console_cmdline[i].index == idx) {
883 c = &console_cmdline[i];
884 memcpy(c->name, name_new, sizeof(c->name));
885 c->name[sizeof(c->name) - 1] = 0;
886 c->options = options;
887 c->index = idx_new;
888 return i;
890 /* not found */
891 return -1;
894 int console_suspend_enabled = 1;
895 EXPORT_SYMBOL(console_suspend_enabled);
897 static int __init console_suspend_disable(char *str)
899 console_suspend_enabled = 0;
900 return 1;
902 __setup("no_console_suspend", console_suspend_disable);
905 * suspend_console - suspend the console subsystem
907 * This disables printk() while we go into suspend states
909 void suspend_console(void)
911 if (!console_suspend_enabled)
912 return;
913 printk("Suspending console(s)\n");
914 acquire_console_sem();
915 console_suspended = 1;
918 void resume_console(void)
920 if (!console_suspend_enabled)
921 return;
922 console_suspended = 0;
923 release_console_sem();
927 * acquire_console_sem - lock the console system for exclusive use.
929 * Acquires a semaphore which guarantees that the caller has
930 * exclusive access to the console system and the console_drivers list.
932 * Can sleep, returns nothing.
934 void acquire_console_sem(void)
936 BUG_ON(in_interrupt());
937 if (console_suspended) {
938 down(&secondary_console_sem);
939 return;
941 down(&console_sem);
942 console_locked = 1;
943 console_may_schedule = 1;
945 EXPORT_SYMBOL(acquire_console_sem);
947 int try_acquire_console_sem(void)
949 if (down_trylock(&console_sem))
950 return -1;
951 console_locked = 1;
952 console_may_schedule = 0;
953 return 0;
955 EXPORT_SYMBOL(try_acquire_console_sem);
957 int is_console_locked(void)
959 return console_locked;
962 void wake_up_klogd(void)
964 if (!oops_in_progress && waitqueue_active(&log_wait))
965 wake_up_interruptible(&log_wait);
969 * release_console_sem - unlock the console system
971 * Releases the semaphore which the caller holds on the console system
972 * and the console driver list.
974 * While the semaphore was held, console output may have been buffered
975 * by printk(). If this is the case, release_console_sem() emits
976 * the output prior to releasing the semaphore.
978 * If there is output waiting for klogd, we wake it up.
980 * release_console_sem() may be called from any context.
982 void release_console_sem(void)
984 unsigned long flags;
985 unsigned _con_start, _log_end;
986 unsigned wake_klogd = 0;
988 if (console_suspended) {
989 up(&secondary_console_sem);
990 return;
993 console_may_schedule = 0;
995 for ( ; ; ) {
996 spin_lock_irqsave(&logbuf_lock, flags);
997 wake_klogd |= log_start - log_end;
998 if (con_start == log_end)
999 break; /* Nothing to print */
1000 _con_start = con_start;
1001 _log_end = log_end;
1002 con_start = log_end; /* Flush */
1003 spin_unlock(&logbuf_lock);
1004 call_console_drivers(_con_start, _log_end);
1005 local_irq_restore(flags);
1007 console_locked = 0;
1008 up(&console_sem);
1009 spin_unlock_irqrestore(&logbuf_lock, flags);
1010 if (wake_klogd)
1011 wake_up_klogd();
1013 EXPORT_SYMBOL(release_console_sem);
1016 * console_conditional_schedule - yield the CPU if required
1018 * If the console code is currently allowed to sleep, and
1019 * if this CPU should yield the CPU to another task, do
1020 * so here.
1022 * Must be called within acquire_console_sem().
1024 void __sched console_conditional_schedule(void)
1026 if (console_may_schedule)
1027 cond_resched();
1029 EXPORT_SYMBOL(console_conditional_schedule);
1031 void console_print(const char *s)
1033 printk(KERN_EMERG "%s", s);
1035 EXPORT_SYMBOL(console_print);
1037 void console_unblank(void)
1039 struct console *c;
1042 * console_unblank can no longer be called in interrupt context unless
1043 * oops_in_progress is set to 1..
1045 if (oops_in_progress) {
1046 if (down_trylock(&console_sem) != 0)
1047 return;
1048 } else
1049 acquire_console_sem();
1051 console_locked = 1;
1052 console_may_schedule = 0;
1053 for (c = console_drivers; c != NULL; c = c->next)
1054 if ((c->flags & CON_ENABLED) && c->unblank)
1055 c->unblank();
1056 release_console_sem();
1060 * Return the console tty driver structure and its associated index
1062 struct tty_driver *console_device(int *index)
1064 struct console *c;
1065 struct tty_driver *driver = NULL;
1067 acquire_console_sem();
1068 for (c = console_drivers; c != NULL; c = c->next) {
1069 if (!c->device)
1070 continue;
1071 driver = c->device(c, index);
1072 if (driver)
1073 break;
1075 release_console_sem();
1076 return driver;
1080 * Prevent further output on the passed console device so that (for example)
1081 * serial drivers can disable console output before suspending a port, and can
1082 * re-enable output afterwards.
1084 void console_stop(struct console *console)
1086 acquire_console_sem();
1087 console->flags &= ~CON_ENABLED;
1088 release_console_sem();
1090 EXPORT_SYMBOL(console_stop);
1092 void console_start(struct console *console)
1094 acquire_console_sem();
1095 console->flags |= CON_ENABLED;
1096 release_console_sem();
1098 EXPORT_SYMBOL(console_start);
1101 * The console driver calls this routine during kernel initialization
1102 * to register the console printing procedure with printk() and to
1103 * print any messages that were printed by the kernel before the
1104 * console driver was initialized.
1106 void register_console(struct console *console)
1108 int i;
1109 unsigned long flags;
1110 struct console *bootconsole = NULL;
1112 if (console_drivers) {
1113 if (console->flags & CON_BOOT)
1114 return;
1115 if (console_drivers->flags & CON_BOOT)
1116 bootconsole = console_drivers;
1119 if (preferred_console < 0 || bootconsole || !console_drivers)
1120 preferred_console = selected_console;
1122 if (console->early_setup)
1123 console->early_setup();
1126 * See if we want to use this console driver. If we
1127 * didn't select a console we take the first one
1128 * that registers here.
1130 if (preferred_console < 0) {
1131 if (console->index < 0)
1132 console->index = 0;
1133 if (console->setup == NULL ||
1134 console->setup(console, NULL) == 0) {
1135 console->flags |= CON_ENABLED | CON_CONSDEV;
1136 preferred_console = 0;
1141 * See if this console matches one we selected on
1142 * the command line.
1144 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1145 i++) {
1146 if (strcmp(console_cmdline[i].name, console->name) != 0)
1147 continue;
1148 if (console->index >= 0 &&
1149 console->index != console_cmdline[i].index)
1150 continue;
1151 if (console->index < 0)
1152 console->index = console_cmdline[i].index;
1153 if (console->setup &&
1154 console->setup(console, console_cmdline[i].options) != 0)
1155 break;
1156 console->flags |= CON_ENABLED;
1157 console->index = console_cmdline[i].index;
1158 if (i == selected_console) {
1159 console->flags |= CON_CONSDEV;
1160 preferred_console = selected_console;
1162 break;
1165 if (!(console->flags & CON_ENABLED))
1166 return;
1168 if (bootconsole && (console->flags & CON_CONSDEV)) {
1169 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1170 bootconsole->name, bootconsole->index,
1171 console->name, console->index);
1172 unregister_console(bootconsole);
1173 console->flags &= ~CON_PRINTBUFFER;
1174 } else {
1175 printk(KERN_INFO "console [%s%d] enabled\n",
1176 console->name, console->index);
1180 * Put this console in the list - keep the
1181 * preferred driver at the head of the list.
1183 acquire_console_sem();
1184 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1185 console->next = console_drivers;
1186 console_drivers = console;
1187 if (console->next)
1188 console->next->flags &= ~CON_CONSDEV;
1189 } else {
1190 console->next = console_drivers->next;
1191 console_drivers->next = console;
1193 if (console->flags & CON_PRINTBUFFER) {
1195 * release_console_sem() will print out the buffered messages
1196 * for us.
1198 spin_lock_irqsave(&logbuf_lock, flags);
1199 con_start = log_start;
1200 spin_unlock_irqrestore(&logbuf_lock, flags);
1202 release_console_sem();
1204 EXPORT_SYMBOL(register_console);
1206 int unregister_console(struct console *console)
1208 struct console *a, *b;
1209 int res = 1;
1211 acquire_console_sem();
1212 if (console_drivers == console) {
1213 console_drivers=console->next;
1214 res = 0;
1215 } else if (console_drivers) {
1216 for (a=console_drivers->next, b=console_drivers ;
1217 a; b=a, a=b->next) {
1218 if (a == console) {
1219 b->next = a->next;
1220 res = 0;
1221 break;
1227 * If this isn't the last console and it has CON_CONSDEV set, we
1228 * need to set it on the next preferred console.
1230 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1231 console_drivers->flags |= CON_CONSDEV;
1233 release_console_sem();
1234 return res;
1236 EXPORT_SYMBOL(unregister_console);
1238 static int __init disable_boot_consoles(void)
1240 if (console_drivers != NULL) {
1241 if (console_drivers->flags & CON_BOOT) {
1242 printk(KERN_INFO "turn off boot console %s%d\n",
1243 console_drivers->name, console_drivers->index);
1244 return unregister_console(console_drivers);
1247 return 0;
1249 late_initcall(disable_boot_consoles);
1252 * tty_write_message - write a message to a certain tty, not just the console.
1253 * @tty: the destination tty_struct
1254 * @msg: the message to write
1256 * This is used for messages that need to be redirected to a specific tty.
1257 * We don't put it into the syslog queue right now maybe in the future if
1258 * really needed.
1260 void tty_write_message(struct tty_struct *tty, char *msg)
1262 if (tty && tty->driver->write)
1263 tty->driver->write(tty, msg, strlen(msg));
1264 return;
1267 #if defined CONFIG_PRINTK
1269 * printk rate limiting, lifted from the networking subsystem.
1271 * This enforces a rate limit: not more than one kernel message
1272 * every printk_ratelimit_jiffies to make a denial-of-service
1273 * attack impossible.
1275 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1277 static DEFINE_SPINLOCK(ratelimit_lock);
1278 static unsigned toks = 10 * 5 * HZ;
1279 static unsigned long last_msg;
1280 static int missed;
1281 unsigned long flags;
1282 unsigned long now = jiffies;
1284 spin_lock_irqsave(&ratelimit_lock, flags);
1285 toks += now - last_msg;
1286 last_msg = now;
1287 if (toks > (ratelimit_burst * ratelimit_jiffies))
1288 toks = ratelimit_burst * ratelimit_jiffies;
1289 if (toks >= ratelimit_jiffies) {
1290 int lost = missed;
1292 missed = 0;
1293 toks -= ratelimit_jiffies;
1294 spin_unlock_irqrestore(&ratelimit_lock, flags);
1295 if (lost)
1296 printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1297 return 1;
1299 missed++;
1300 spin_unlock_irqrestore(&ratelimit_lock, flags);
1301 return 0;
1303 EXPORT_SYMBOL(__printk_ratelimit);
1305 /* minimum time in jiffies between messages */
1306 int printk_ratelimit_jiffies = 5 * HZ;
1308 /* number of messages we send before ratelimiting */
1309 int printk_ratelimit_burst = 10;
1311 int printk_ratelimit(void)
1313 return __printk_ratelimit(printk_ratelimit_jiffies,
1314 printk_ratelimit_burst);
1316 EXPORT_SYMBOL(printk_ratelimit);
1319 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1320 * @caller_jiffies: pointer to caller's state
1321 * @interval_msecs: minimum interval between prints
1323 * printk_timed_ratelimit() returns true if more than @interval_msecs
1324 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1325 * returned true.
1327 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1328 unsigned int interval_msecs)
1330 if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1331 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1332 return true;
1334 return false;
1336 EXPORT_SYMBOL(printk_timed_ratelimit);
1337 #endif