ia64/linux-2.6.18-xen.hg

view kernel/printk.c @ 0:831230e53067

Import 2.6.18 from kernel.org tarball.
author Ian Campbell <ian.campbell@xensource.com>
date Wed Apr 11 14:15:44 2007 +0100 (2007-04-11)
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1 /*
2 * linux/kernel/printk.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
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>
17 */
19 #include <linux/kernel.h>
20 #include <linux/mm.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/smp_lock.h>
24 #include <linux/console.h>
25 #include <linux/init.h>
26 #include <linux/module.h>
27 #include <linux/moduleparam.h>
28 #include <linux/interrupt.h> /* For in_interrupt() */
29 #include <linux/delay.h>
30 #include <linux/smp.h>
31 #include <linux/security.h>
32 #include <linux/bootmem.h>
33 #include <linux/syscalls.h>
35 #include <asm/uaccess.h>
37 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
39 /* printk's without a loglevel use this.. */
40 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
42 /* We show everything that is MORE important than this.. */
43 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
44 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
46 DECLARE_WAIT_QUEUE_HEAD(log_wait);
48 int console_printk[4] = {
49 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
50 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
51 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
52 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
53 };
55 EXPORT_UNUSED_SYMBOL(console_printk); /* June 2006 */
57 /*
58 * Low lever drivers may need that to know if they can schedule in
59 * their unblank() callback or not. So let's export it.
60 */
61 int oops_in_progress;
62 EXPORT_SYMBOL(oops_in_progress);
64 /*
65 * console_sem protects the console_drivers list, and also
66 * provides serialisation for access to the entire console
67 * driver system.
68 */
69 static DECLARE_MUTEX(console_sem);
70 static DECLARE_MUTEX(secondary_console_sem);
71 struct console *console_drivers;
72 /*
73 * This is used for debugging the mess that is the VT code by
74 * keeping track if we have the console semaphore held. It's
75 * definitely not the perfect debug tool (we don't know if _WE_
76 * hold it are racing, but it helps tracking those weird code
77 * path in the console code where we end up in places I want
78 * locked without the console sempahore held
79 */
80 static int console_locked, console_suspended;
82 /*
83 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
84 * It is also used in interesting ways to provide interlocking in
85 * release_console_sem().
86 */
87 static DEFINE_SPINLOCK(logbuf_lock);
89 #define LOG_BUF_MASK (log_buf_len-1)
90 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
92 /*
93 * The indices into log_buf are not constrained to log_buf_len - they
94 * must be masked before subscripting
95 */
96 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
97 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
98 static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */
100 /*
101 * Array of consoles built from command line options (console=)
102 */
103 struct console_cmdline
104 {
105 char name[8]; /* Name of the driver */
106 int index; /* Minor dev. to use */
107 char *options; /* Options for the driver */
108 };
110 #define MAX_CMDLINECONSOLES 8
112 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
113 static int selected_console = -1;
114 static int preferred_console = -1;
116 /* Flag: console code may call schedule() */
117 static int console_may_schedule;
119 #ifdef CONFIG_PRINTK
121 static char __log_buf[__LOG_BUF_LEN];
122 static char *log_buf = __log_buf;
123 static int log_buf_len = __LOG_BUF_LEN;
124 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
126 static int __init log_buf_len_setup(char *str)
127 {
128 unsigned long size = memparse(str, &str);
129 unsigned long flags;
131 if (size)
132 size = roundup_pow_of_two(size);
133 if (size > log_buf_len) {
134 unsigned long start, dest_idx, offset;
135 char *new_log_buf;
137 new_log_buf = alloc_bootmem(size);
138 if (!new_log_buf) {
139 printk(KERN_WARNING "log_buf_len: allocation failed\n");
140 goto out;
141 }
143 spin_lock_irqsave(&logbuf_lock, flags);
144 log_buf_len = size;
145 log_buf = new_log_buf;
147 offset = start = min(con_start, log_start);
148 dest_idx = 0;
149 while (start != log_end) {
150 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
151 start++;
152 dest_idx++;
153 }
154 log_start -= offset;
155 con_start -= offset;
156 log_end -= offset;
157 spin_unlock_irqrestore(&logbuf_lock, flags);
159 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
160 }
161 out:
162 return 1;
163 }
165 __setup("log_buf_len=", log_buf_len_setup);
167 /*
168 * Commands to do_syslog:
169 *
170 * 0 -- Close the log. Currently a NOP.
171 * 1 -- Open the log. Currently a NOP.
172 * 2 -- Read from the log.
173 * 3 -- Read all messages remaining in the ring buffer.
174 * 4 -- Read and clear all messages remaining in the ring buffer
175 * 5 -- Clear ring buffer.
176 * 6 -- Disable printk's to console
177 * 7 -- Enable printk's to console
178 * 8 -- Set level of messages printed to console
179 * 9 -- Return number of unread characters in the log buffer
180 * 10 -- Return size of the log buffer
181 */
182 int do_syslog(int type, char __user *buf, int len)
183 {
184 unsigned long i, j, limit, count;
185 int do_clear = 0;
186 char c;
187 int error = 0;
189 error = security_syslog(type);
190 if (error)
191 return error;
193 switch (type) {
194 case 0: /* Close log */
195 break;
196 case 1: /* Open log */
197 break;
198 case 2: /* Read from log */
199 error = -EINVAL;
200 if (!buf || len < 0)
201 goto out;
202 error = 0;
203 if (!len)
204 goto out;
205 if (!access_ok(VERIFY_WRITE, buf, len)) {
206 error = -EFAULT;
207 goto out;
208 }
209 error = wait_event_interruptible(log_wait,
210 (log_start - log_end));
211 if (error)
212 goto out;
213 i = 0;
214 spin_lock_irq(&logbuf_lock);
215 while (!error && (log_start != log_end) && i < len) {
216 c = LOG_BUF(log_start);
217 log_start++;
218 spin_unlock_irq(&logbuf_lock);
219 error = __put_user(c,buf);
220 buf++;
221 i++;
222 cond_resched();
223 spin_lock_irq(&logbuf_lock);
224 }
225 spin_unlock_irq(&logbuf_lock);
226 if (!error)
227 error = i;
228 break;
229 case 4: /* Read/clear last kernel messages */
230 do_clear = 1;
231 /* FALL THRU */
232 case 3: /* Read last kernel messages */
233 error = -EINVAL;
234 if (!buf || len < 0)
235 goto out;
236 error = 0;
237 if (!len)
238 goto out;
239 if (!access_ok(VERIFY_WRITE, buf, len)) {
240 error = -EFAULT;
241 goto out;
242 }
243 count = len;
244 if (count > log_buf_len)
245 count = log_buf_len;
246 spin_lock_irq(&logbuf_lock);
247 if (count > logged_chars)
248 count = logged_chars;
249 if (do_clear)
250 logged_chars = 0;
251 limit = log_end;
252 /*
253 * __put_user() could sleep, and while we sleep
254 * printk() could overwrite the messages
255 * we try to copy to user space. Therefore
256 * the messages are copied in reverse. <manfreds>
257 */
258 for (i = 0; i < count && !error; i++) {
259 j = limit-1-i;
260 if (j + log_buf_len < log_end)
261 break;
262 c = LOG_BUF(j);
263 spin_unlock_irq(&logbuf_lock);
264 error = __put_user(c,&buf[count-1-i]);
265 cond_resched();
266 spin_lock_irq(&logbuf_lock);
267 }
268 spin_unlock_irq(&logbuf_lock);
269 if (error)
270 break;
271 error = i;
272 if (i != count) {
273 int offset = count-error;
274 /* buffer overflow during copy, correct user buffer. */
275 for (i = 0; i < error; i++) {
276 if (__get_user(c,&buf[i+offset]) ||
277 __put_user(c,&buf[i])) {
278 error = -EFAULT;
279 break;
280 }
281 cond_resched();
282 }
283 }
284 break;
285 case 5: /* Clear ring buffer */
286 logged_chars = 0;
287 break;
288 case 6: /* Disable logging to console */
289 console_loglevel = minimum_console_loglevel;
290 break;
291 case 7: /* Enable logging to console */
292 console_loglevel = default_console_loglevel;
293 break;
294 case 8: /* Set level of messages printed to console */
295 error = -EINVAL;
296 if (len < 1 || len > 8)
297 goto out;
298 if (len < minimum_console_loglevel)
299 len = minimum_console_loglevel;
300 console_loglevel = len;
301 error = 0;
302 break;
303 case 9: /* Number of chars in the log buffer */
304 error = log_end - log_start;
305 break;
306 case 10: /* Size of the log buffer */
307 error = log_buf_len;
308 break;
309 default:
310 error = -EINVAL;
311 break;
312 }
313 out:
314 return error;
315 }
317 asmlinkage long sys_syslog(int type, char __user *buf, int len)
318 {
319 return do_syslog(type, buf, len);
320 }
322 /*
323 * Call the console drivers on a range of log_buf
324 */
325 static void __call_console_drivers(unsigned long start, unsigned long end)
326 {
327 struct console *con;
329 for (con = console_drivers; con; con = con->next) {
330 if ((con->flags & CON_ENABLED) && con->write &&
331 (cpu_online(smp_processor_id()) ||
332 (con->flags & CON_ANYTIME)))
333 con->write(con, &LOG_BUF(start), end - start);
334 }
335 }
337 /*
338 * Write out chars from start to end - 1 inclusive
339 */
340 static void _call_console_drivers(unsigned long start,
341 unsigned long end, int msg_log_level)
342 {
343 if (msg_log_level < console_loglevel &&
344 console_drivers && start != end) {
345 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
346 /* wrapped write */
347 __call_console_drivers(start & LOG_BUF_MASK,
348 log_buf_len);
349 __call_console_drivers(0, end & LOG_BUF_MASK);
350 } else {
351 __call_console_drivers(start, end);
352 }
353 }
354 }
356 /*
357 * Call the console drivers, asking them to write out
358 * log_buf[start] to log_buf[end - 1].
359 * The console_sem must be held.
360 */
361 static void call_console_drivers(unsigned long start, unsigned long end)
362 {
363 unsigned long cur_index, start_print;
364 static int msg_level = -1;
366 BUG_ON(((long)(start - end)) > 0);
368 cur_index = start;
369 start_print = start;
370 while (cur_index != end) {
371 if (msg_level < 0 && ((end - cur_index) > 2) &&
372 LOG_BUF(cur_index + 0) == '<' &&
373 LOG_BUF(cur_index + 1) >= '0' &&
374 LOG_BUF(cur_index + 1) <= '7' &&
375 LOG_BUF(cur_index + 2) == '>') {
376 msg_level = LOG_BUF(cur_index + 1) - '0';
377 cur_index += 3;
378 start_print = cur_index;
379 }
380 while (cur_index != end) {
381 char c = LOG_BUF(cur_index);
383 cur_index++;
384 if (c == '\n') {
385 if (msg_level < 0) {
386 /*
387 * printk() has already given us loglevel tags in
388 * the buffer. This code is here in case the
389 * log buffer has wrapped right round and scribbled
390 * on those tags
391 */
392 msg_level = default_message_loglevel;
393 }
394 _call_console_drivers(start_print, cur_index, msg_level);
395 msg_level = -1;
396 start_print = cur_index;
397 break;
398 }
399 }
400 }
401 _call_console_drivers(start_print, end, msg_level);
402 }
404 static void emit_log_char(char c)
405 {
406 LOG_BUF(log_end) = c;
407 log_end++;
408 if (log_end - log_start > log_buf_len)
409 log_start = log_end - log_buf_len;
410 if (log_end - con_start > log_buf_len)
411 con_start = log_end - log_buf_len;
412 if (logged_chars < log_buf_len)
413 logged_chars++;
414 }
416 /*
417 * Zap console related locks when oopsing. Only zap at most once
418 * every 10 seconds, to leave time for slow consoles to print a
419 * full oops.
420 */
421 static void zap_locks(void)
422 {
423 static unsigned long oops_timestamp;
425 if (time_after_eq(jiffies, oops_timestamp) &&
426 !time_after(jiffies, oops_timestamp + 30 * HZ))
427 return;
429 oops_timestamp = jiffies;
431 /* If a crash is occurring, make sure we can't deadlock */
432 spin_lock_init(&logbuf_lock);
433 /* And make sure that we print immediately */
434 init_MUTEX(&console_sem);
435 }
437 #if defined(CONFIG_PRINTK_TIME)
438 static int printk_time = 1;
439 #else
440 static int printk_time = 0;
441 #endif
442 module_param(printk_time, int, S_IRUGO | S_IWUSR);
444 static int __init printk_time_setup(char *str)
445 {
446 if (*str)
447 return 0;
448 printk_time = 1;
449 return 1;
450 }
452 __setup("time", printk_time_setup);
454 __attribute__((weak)) unsigned long long printk_clock(void)
455 {
456 return sched_clock();
457 }
459 /* Check if we have any console registered that can be called early in boot. */
460 static int have_callable_console(void)
461 {
462 struct console *con;
464 for (con = console_drivers; con; con = con->next)
465 if (con->flags & CON_ANYTIME)
466 return 1;
468 return 0;
469 }
471 /**
472 * printk - print a kernel message
473 * @fmt: format string
474 *
475 * This is printk. It can be called from any context. We want it to work.
476 *
477 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
478 * call the console drivers. If we fail to get the semaphore we place the output
479 * into the log buffer and return. The current holder of the console_sem will
480 * notice the new output in release_console_sem() and will send it to the
481 * consoles before releasing the semaphore.
482 *
483 * One effect of this deferred printing is that code which calls printk() and
484 * then changes console_loglevel may break. This is because console_loglevel
485 * is inspected when the actual printing occurs.
486 *
487 * See also:
488 * printf(3)
489 */
491 asmlinkage int printk(const char *fmt, ...)
492 {
493 va_list args;
494 int r;
496 va_start(args, fmt);
497 r = vprintk(fmt, args);
498 va_end(args);
500 return r;
501 }
503 /* cpu currently holding logbuf_lock */
504 static volatile unsigned int printk_cpu = UINT_MAX;
506 asmlinkage int vprintk(const char *fmt, va_list args)
507 {
508 unsigned long flags;
509 int printed_len;
510 char *p;
511 static char printk_buf[1024];
512 static int log_level_unknown = 1;
514 preempt_disable();
515 if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
516 /* If a crash is occurring during printk() on this CPU,
517 * make sure we can't deadlock */
518 zap_locks();
520 /* This stops the holder of console_sem just where we want him */
521 local_irq_save(flags);
522 lockdep_off();
523 spin_lock(&logbuf_lock);
524 printk_cpu = smp_processor_id();
526 /* Emit the output into the temporary buffer */
527 printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
529 /*
530 * Copy the output into log_buf. If the caller didn't provide
531 * appropriate log level tags, we insert them here
532 */
533 for (p = printk_buf; *p; p++) {
534 if (log_level_unknown) {
535 /* log_level_unknown signals the start of a new line */
536 if (printk_time) {
537 int loglev_char;
538 char tbuf[50], *tp;
539 unsigned tlen;
540 unsigned long long t;
541 unsigned long nanosec_rem;
543 /*
544 * force the log level token to be
545 * before the time output.
546 */
547 if (p[0] == '<' && p[1] >='0' &&
548 p[1] <= '7' && p[2] == '>') {
549 loglev_char = p[1];
550 p += 3;
551 printed_len -= 3;
552 } else {
553 loglev_char = default_message_loglevel
554 + '0';
555 }
556 t = printk_clock();
557 nanosec_rem = do_div(t, 1000000000);
558 tlen = sprintf(tbuf,
559 "<%c>[%5lu.%06lu] ",
560 loglev_char,
561 (unsigned long)t,
562 nanosec_rem/1000);
564 for (tp = tbuf; tp < tbuf + tlen; tp++)
565 emit_log_char(*tp);
566 printed_len += tlen;
567 } else {
568 if (p[0] != '<' || p[1] < '0' ||
569 p[1] > '7' || p[2] != '>') {
570 emit_log_char('<');
571 emit_log_char(default_message_loglevel
572 + '0');
573 emit_log_char('>');
574 printed_len += 3;
575 }
576 }
577 log_level_unknown = 0;
578 if (!*p)
579 break;
580 }
581 emit_log_char(*p);
582 if (*p == '\n')
583 log_level_unknown = 1;
584 }
586 if (!down_trylock(&console_sem)) {
587 /*
588 * We own the drivers. We can drop the spinlock and
589 * let release_console_sem() print the text, maybe ...
590 */
591 console_locked = 1;
592 printk_cpu = UINT_MAX;
593 spin_unlock(&logbuf_lock);
595 /*
596 * Console drivers may assume that per-cpu resources have
597 * been allocated. So unless they're explicitly marked as
598 * being able to cope (CON_ANYTIME) don't call them until
599 * this CPU is officially up.
600 */
601 if (cpu_online(smp_processor_id()) || have_callable_console()) {
602 console_may_schedule = 0;
603 release_console_sem();
604 } else {
605 /* Release by hand to avoid flushing the buffer. */
606 console_locked = 0;
607 up(&console_sem);
608 }
609 lockdep_on();
610 local_irq_restore(flags);
611 } else {
612 /*
613 * Someone else owns the drivers. We drop the spinlock, which
614 * allows the semaphore holder to proceed and to call the
615 * console drivers with the output which we just produced.
616 */
617 printk_cpu = UINT_MAX;
618 spin_unlock(&logbuf_lock);
619 lockdep_on();
620 local_irq_restore(flags);
621 }
623 preempt_enable();
624 return printed_len;
625 }
626 EXPORT_SYMBOL(printk);
627 EXPORT_SYMBOL(vprintk);
629 #else
631 asmlinkage long sys_syslog(int type, char __user *buf, int len)
632 {
633 return 0;
634 }
636 int do_syslog(int type, char __user *buf, int len)
637 {
638 return 0;
639 }
641 static void call_console_drivers(unsigned long start, unsigned long end)
642 {
643 }
645 #endif
647 /*
648 * Set up a list of consoles. Called from init/main.c
649 */
650 static int __init console_setup(char *str)
651 {
652 char name[sizeof(console_cmdline[0].name)];
653 char *s, *options;
654 int idx;
656 /*
657 * Decode str into name, index, options.
658 */
659 if (str[0] >= '0' && str[0] <= '9') {
660 strcpy(name, "ttyS");
661 strncpy(name + 4, str, sizeof(name) - 5);
662 } else {
663 strncpy(name, str, sizeof(name) - 1);
664 }
665 name[sizeof(name) - 1] = 0;
666 if ((options = strchr(str, ',')) != NULL)
667 *(options++) = 0;
668 #ifdef __sparc__
669 if (!strcmp(str, "ttya"))
670 strcpy(name, "ttyS0");
671 if (!strcmp(str, "ttyb"))
672 strcpy(name, "ttyS1");
673 #endif
674 for (s = name; *s; s++)
675 if ((*s >= '0' && *s <= '9') || *s == ',')
676 break;
677 idx = simple_strtoul(s, NULL, 10);
678 *s = 0;
680 add_preferred_console(name, idx, options);
681 return 1;
682 }
683 __setup("console=", console_setup);
685 /**
686 * add_preferred_console - add a device to the list of preferred consoles.
687 * @name: device name
688 * @idx: device index
689 * @options: options for this console
690 *
691 * The last preferred console added will be used for kernel messages
692 * and stdin/out/err for init. Normally this is used by console_setup
693 * above to handle user-supplied console arguments; however it can also
694 * be used by arch-specific code either to override the user or more
695 * commonly to provide a default console (ie from PROM variables) when
696 * the user has not supplied one.
697 */
698 int __init add_preferred_console(char *name, int idx, char *options)
699 {
700 struct console_cmdline *c;
701 int i;
703 /*
704 * See if this tty is not yet registered, and
705 * if we have a slot free.
706 */
707 for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
708 if (strcmp(console_cmdline[i].name, name) == 0 &&
709 console_cmdline[i].index == idx) {
710 selected_console = i;
711 return 0;
712 }
713 if (i == MAX_CMDLINECONSOLES)
714 return -E2BIG;
715 selected_console = i;
716 c = &console_cmdline[i];
717 memcpy(c->name, name, sizeof(c->name));
718 c->name[sizeof(c->name) - 1] = 0;
719 c->options = options;
720 c->index = idx;
721 return 0;
722 }
724 /**
725 * suspend_console - suspend the console subsystem
726 *
727 * This disables printk() while we go into suspend states
728 */
729 void suspend_console(void)
730 {
731 acquire_console_sem();
732 console_suspended = 1;
733 }
735 void resume_console(void)
736 {
737 console_suspended = 0;
738 release_console_sem();
739 }
741 /**
742 * acquire_console_sem - lock the console system for exclusive use.
743 *
744 * Acquires a semaphore which guarantees that the caller has
745 * exclusive access to the console system and the console_drivers list.
746 *
747 * Can sleep, returns nothing.
748 */
749 void acquire_console_sem(void)
750 {
751 BUG_ON(in_interrupt());
752 if (console_suspended) {
753 down(&secondary_console_sem);
754 return;
755 }
756 down(&console_sem);
757 console_locked = 1;
758 console_may_schedule = 1;
759 }
760 EXPORT_SYMBOL(acquire_console_sem);
762 int try_acquire_console_sem(void)
763 {
764 if (down_trylock(&console_sem))
765 return -1;
766 console_locked = 1;
767 console_may_schedule = 0;
768 return 0;
769 }
770 EXPORT_SYMBOL(try_acquire_console_sem);
772 int is_console_locked(void)
773 {
774 return console_locked;
775 }
776 EXPORT_UNUSED_SYMBOL(is_console_locked); /* June 2006 */
778 /**
779 * release_console_sem - unlock the console system
780 *
781 * Releases the semaphore which the caller holds on the console system
782 * and the console driver list.
783 *
784 * While the semaphore was held, console output may have been buffered
785 * by printk(). If this is the case, release_console_sem() emits
786 * the output prior to releasing the semaphore.
787 *
788 * If there is output waiting for klogd, we wake it up.
789 *
790 * release_console_sem() may be called from any context.
791 */
792 void release_console_sem(void)
793 {
794 unsigned long flags;
795 unsigned long _con_start, _log_end;
796 unsigned long wake_klogd = 0;
798 if (console_suspended) {
799 up(&secondary_console_sem);
800 return;
801 }
803 console_may_schedule = 0;
805 for ( ; ; ) {
806 spin_lock_irqsave(&logbuf_lock, flags);
807 wake_klogd |= log_start - log_end;
808 if (con_start == log_end)
809 break; /* Nothing to print */
810 _con_start = con_start;
811 _log_end = log_end;
812 con_start = log_end; /* Flush */
813 spin_unlock(&logbuf_lock);
814 call_console_drivers(_con_start, _log_end);
815 local_irq_restore(flags);
816 }
817 console_locked = 0;
818 up(&console_sem);
819 spin_unlock_irqrestore(&logbuf_lock, flags);
820 if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait)) {
821 /*
822 * If we printk from within the lock dependency code,
823 * from within the scheduler code, then do not lock
824 * up due to self-recursion:
825 */
826 if (!lockdep_internal())
827 wake_up_interruptible(&log_wait);
828 }
829 }
830 EXPORT_SYMBOL(release_console_sem);
832 /**
833 * console_conditional_schedule - yield the CPU if required
834 *
835 * If the console code is currently allowed to sleep, and
836 * if this CPU should yield the CPU to another task, do
837 * so here.
838 *
839 * Must be called within acquire_console_sem().
840 */
841 void __sched console_conditional_schedule(void)
842 {
843 if (console_may_schedule)
844 cond_resched();
845 }
846 EXPORT_SYMBOL(console_conditional_schedule);
848 void console_print(const char *s)
849 {
850 printk(KERN_EMERG "%s", s);
851 }
852 EXPORT_SYMBOL(console_print);
854 void console_unblank(void)
855 {
856 struct console *c;
858 /*
859 * console_unblank can no longer be called in interrupt context unless
860 * oops_in_progress is set to 1..
861 */
862 if (oops_in_progress) {
863 if (down_trylock(&console_sem) != 0)
864 return;
865 } else
866 acquire_console_sem();
868 console_locked = 1;
869 console_may_schedule = 0;
870 for (c = console_drivers; c != NULL; c = c->next)
871 if ((c->flags & CON_ENABLED) && c->unblank)
872 c->unblank();
873 release_console_sem();
874 }
876 /*
877 * Return the console tty driver structure and its associated index
878 */
879 struct tty_driver *console_device(int *index)
880 {
881 struct console *c;
882 struct tty_driver *driver = NULL;
884 acquire_console_sem();
885 for (c = console_drivers; c != NULL; c = c->next) {
886 if (!c->device)
887 continue;
888 driver = c->device(c, index);
889 if (driver)
890 break;
891 }
892 release_console_sem();
893 return driver;
894 }
896 /*
897 * Prevent further output on the passed console device so that (for example)
898 * serial drivers can disable console output before suspending a port, and can
899 * re-enable output afterwards.
900 */
901 void console_stop(struct console *console)
902 {
903 acquire_console_sem();
904 console->flags &= ~CON_ENABLED;
905 release_console_sem();
906 }
907 EXPORT_SYMBOL(console_stop);
909 void console_start(struct console *console)
910 {
911 acquire_console_sem();
912 console->flags |= CON_ENABLED;
913 release_console_sem();
914 }
915 EXPORT_SYMBOL(console_start);
917 /*
918 * The console driver calls this routine during kernel initialization
919 * to register the console printing procedure with printk() and to
920 * print any messages that were printed by the kernel before the
921 * console driver was initialized.
922 */
923 void register_console(struct console *console)
924 {
925 int i;
926 unsigned long flags;
928 if (preferred_console < 0)
929 preferred_console = selected_console;
931 /*
932 * See if we want to use this console driver. If we
933 * didn't select a console we take the first one
934 * that registers here.
935 */
936 if (preferred_console < 0) {
937 if (console->index < 0)
938 console->index = 0;
939 if (console->setup == NULL ||
940 console->setup(console, NULL) == 0) {
941 console->flags |= CON_ENABLED | CON_CONSDEV;
942 preferred_console = 0;
943 }
944 }
946 /*
947 * See if this console matches one we selected on
948 * the command line.
949 */
950 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
951 i++) {
952 if (strcmp(console_cmdline[i].name, console->name) != 0)
953 continue;
954 if (console->index >= 0 &&
955 console->index != console_cmdline[i].index)
956 continue;
957 if (console->index < 0)
958 console->index = console_cmdline[i].index;
959 if (console->setup &&
960 console->setup(console, console_cmdline[i].options) != 0)
961 break;
962 console->flags |= CON_ENABLED;
963 console->index = console_cmdline[i].index;
964 if (i == selected_console) {
965 console->flags |= CON_CONSDEV;
966 preferred_console = selected_console;
967 }
968 break;
969 }
971 if (!(console->flags & CON_ENABLED))
972 return;
974 if (console_drivers && (console_drivers->flags & CON_BOOT)) {
975 unregister_console(console_drivers);
976 console->flags &= ~CON_PRINTBUFFER;
977 }
979 /*
980 * Put this console in the list - keep the
981 * preferred driver at the head of the list.
982 */
983 acquire_console_sem();
984 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
985 console->next = console_drivers;
986 console_drivers = console;
987 if (console->next)
988 console->next->flags &= ~CON_CONSDEV;
989 } else {
990 console->next = console_drivers->next;
991 console_drivers->next = console;
992 }
993 if (console->flags & CON_PRINTBUFFER) {
994 /*
995 * release_console_sem() will print out the buffered messages
996 * for us.
997 */
998 spin_lock_irqsave(&logbuf_lock, flags);
999 con_start = log_start;
1000 spin_unlock_irqrestore(&logbuf_lock, flags);
1002 release_console_sem();
1004 EXPORT_SYMBOL(register_console);
1006 int unregister_console(struct console *console)
1008 struct console *a, *b;
1009 int res = 1;
1011 acquire_console_sem();
1012 if (console_drivers == console) {
1013 console_drivers=console->next;
1014 res = 0;
1015 } else if (console_drivers) {
1016 for (a=console_drivers->next, b=console_drivers ;
1017 a; b=a, a=b->next) {
1018 if (a == console) {
1019 b->next = a->next;
1020 res = 0;
1021 break;
1026 /* If last console is removed, we re-enable picking the first
1027 * one that gets registered. Without that, pmac early boot console
1028 * would prevent fbcon from taking over.
1030 * If this isn't the last console and it has CON_CONSDEV set, we
1031 * need to set it on the next preferred console.
1032 */
1033 if (console_drivers == NULL)
1034 preferred_console = selected_console;
1035 else if (console->flags & CON_CONSDEV)
1036 console_drivers->flags |= CON_CONSDEV;
1038 release_console_sem();
1039 return res;
1041 EXPORT_SYMBOL(unregister_console);
1043 /**
1044 * tty_write_message - write a message to a certain tty, not just the console.
1045 * @tty: the destination tty_struct
1046 * @msg: the message to write
1048 * This is used for messages that need to be redirected to a specific tty.
1049 * We don't put it into the syslog queue right now maybe in the future if
1050 * really needed.
1051 */
1052 void tty_write_message(struct tty_struct *tty, char *msg)
1054 if (tty && tty->driver->write)
1055 tty->driver->write(tty, msg, strlen(msg));
1056 return;
1059 /*
1060 * printk rate limiting, lifted from the networking subsystem.
1062 * This enforces a rate limit: not more than one kernel message
1063 * every printk_ratelimit_jiffies to make a denial-of-service
1064 * attack impossible.
1065 */
1066 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1068 static DEFINE_SPINLOCK(ratelimit_lock);
1069 static unsigned long toks = 10 * 5 * HZ;
1070 static unsigned long last_msg;
1071 static int missed;
1072 unsigned long flags;
1073 unsigned long now = jiffies;
1075 spin_lock_irqsave(&ratelimit_lock, flags);
1076 toks += now - last_msg;
1077 last_msg = now;
1078 if (toks > (ratelimit_burst * ratelimit_jiffies))
1079 toks = ratelimit_burst * ratelimit_jiffies;
1080 if (toks >= ratelimit_jiffies) {
1081 int lost = missed;
1083 missed = 0;
1084 toks -= ratelimit_jiffies;
1085 spin_unlock_irqrestore(&ratelimit_lock, flags);
1086 if (lost)
1087 printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1088 return 1;
1090 missed++;
1091 spin_unlock_irqrestore(&ratelimit_lock, flags);
1092 return 0;
1094 EXPORT_SYMBOL(__printk_ratelimit);
1096 /* minimum time in jiffies between messages */
1097 int printk_ratelimit_jiffies = 5 * HZ;
1099 /* number of messages we send before ratelimiting */
1100 int printk_ratelimit_burst = 10;
1102 int printk_ratelimit(void)
1104 return __printk_ratelimit(printk_ratelimit_jiffies,
1105 printk_ratelimit_burst);
1107 EXPORT_SYMBOL(printk_ratelimit);