projects/linux·blob v2.6.21 · refs

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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 * [email protected]
15 * Rewrote bits to get rid of console_lock
16 * 01Mar01 Andrew Morton <[email protected]>
17 */
18
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>
34#include <linux/jiffies.h>
35
36#include <asm/uaccess.h>
37
38#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
39
40/* printk's without a loglevel use this.. */
41#define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
42
43/* We show everything that is MORE important than this.. */
44#define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
45#define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
46
47DECLARE_WAIT_QUEUE_HEAD(log_wait);
48
49int console_printk[4] = {
50 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
51 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
52 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
53 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
54};
55
56/*
57 * Low level drivers may need that to know if they can schedule in
58 * their unblank() callback or not. So let's export it.
59 */
60int oops_in_progress;
61EXPORT_SYMBOL(oops_in_progress);
62
63/*
64 * console_sem protects the console_drivers list, and also
65 * provides serialisation for access to the entire console
66 * driver system.
67 */
68static DECLARE_MUTEX(console_sem);
69static DECLARE_MUTEX(secondary_console_sem);
70struct console *console_drivers;
71/*
72 * This is used for debugging the mess that is the VT code by
73 * keeping track if we have the console semaphore held. It's
74 * definitely not the perfect debug tool (we don't know if _WE_
75 * hold it are racing, but it helps tracking those weird code
76 * path in the console code where we end up in places I want
77 * locked without the console sempahore held
78 */
79static int console_locked, console_suspended;
80
81/*
82 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
83 * It is also used in interesting ways to provide interlocking in
84 * release_console_sem().
85 */
86static DEFINE_SPINLOCK(logbuf_lock);
87
88#define LOG_BUF_MASK (log_buf_len-1)
89#define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
90
91/*
92 * The indices into log_buf are not constrained to log_buf_len - they
93 * must be masked before subscripting
94 */
95static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
96static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
97static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */
98
99/*
100 * Array of consoles built from command line options (console=)
101 */
102struct console_cmdline
103{
104 char name[8]; /* Name of the driver */
105 int index; /* Minor dev. to use */
106 char *options; /* Options for the driver */
107};
108
109#define MAX_CMDLINECONSOLES 8
110
111static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
112static int selected_console = -1;
113static int preferred_console = -1;
114
115/* Flag: console code may call schedule() */
116static int console_may_schedule;
117
118#ifdef CONFIG_PRINTK
119
120static char __log_buf[__LOG_BUF_LEN];
121static char *log_buf = __log_buf;
122static int log_buf_len = __LOG_BUF_LEN;
123static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
124
125static int __init log_buf_len_setup(char *str)
126{
127 unsigned long size = memparse(str, &str);
128 unsigned long flags;
129
130 if (size)
131 size = roundup_pow_of_two(size);
132 if (size > log_buf_len) {
133 unsigned long start, dest_idx, offset;
134 char *new_log_buf;
135
136 new_log_buf = alloc_bootmem(size);
137 if (!new_log_buf) {
138 printk(KERN_WARNING "log_buf_len: allocation failed\n");
139 goto out;
140 }
141
142 spin_lock_irqsave(&logbuf_lock, flags);
143 log_buf_len = size;
144 log_buf = new_log_buf;
145
146 offset = start = min(con_start, log_start);
147 dest_idx = 0;
148 while (start != log_end) {
149 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
150 start++;
151 dest_idx++;
152 }
153 log_start -= offset;
154 con_start -= offset;
155 log_end -= offset;
156 spin_unlock_irqrestore(&logbuf_lock, flags);
157
158 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
159 }
160out:
161 return 1;
162}
163
164__setup("log_buf_len=", log_buf_len_setup);
165
166/*
167 * Commands to do_syslog:
168 *
169 * 0 -- Close the log. Currently a NOP.
170 * 1 -- Open the log. Currently a NOP.
171 * 2 -- Read from the log.
172 * 3 -- Read all messages remaining in the ring buffer.
173 * 4 -- Read and clear all messages remaining in the ring buffer
174 * 5 -- Clear ring buffer.
175 * 6 -- Disable printk's to console
176 * 7 -- Enable printk's to console
177 * 8 -- Set level of messages printed to console
178 * 9 -- Return number of unread characters in the log buffer
179 * 10 -- Return size of the log buffer
180 */
181int do_syslog(int type, char __user *buf, int len)
182{
183 unsigned long i, j, limit, count;
184 int do_clear = 0;
185 char c;
186 int error = 0;
187
188 error = security_syslog(type);
189 if (error)
190 return error;
191
192 switch (type) {
193 case 0: /* Close log */
194 break;
195 case 1: /* Open log */
196 break;
197 case 2: /* Read from log */
198 error = -EINVAL;
199 if (!buf || len < 0)
200 goto out;
201 error = 0;
202 if (!len)
203 goto out;
204 if (!access_ok(VERIFY_WRITE, buf, len)) {
205 error = -EFAULT;
206 goto out;
207 }
208 error = wait_event_interruptible(log_wait,
209 (log_start - log_end));
210 if (error)
211 goto out;
212 i = 0;
213 spin_lock_irq(&logbuf_lock);
214 while (!error && (log_start != log_end) && i < len) {
215 c = LOG_BUF(log_start);
216 log_start++;
217 spin_unlock_irq(&logbuf_lock);
218 error = __put_user(c,buf);
219 buf++;
220 i++;
221 cond_resched();
222 spin_lock_irq(&logbuf_lock);
223 }
224 spin_unlock_irq(&logbuf_lock);
225 if (!error)
226 error = i;
227 break;
228 case 4: /* Read/clear last kernel messages */
229 do_clear = 1;
230 /* FALL THRU */
231 case 3: /* Read last kernel messages */
232 error = -EINVAL;
233 if (!buf || len < 0)
234 goto out;
235 error = 0;
236 if (!len)
237 goto out;
238 if (!access_ok(VERIFY_WRITE, buf, len)) {
239 error = -EFAULT;
240 goto out;
241 }
242 count = len;
243 if (count > log_buf_len)
244 count = log_buf_len;
245 spin_lock_irq(&logbuf_lock);
246 if (count > logged_chars)
247 count = logged_chars;
248 if (do_clear)
249 logged_chars = 0;
250 limit = log_end;
251 /*
252 * __put_user() could sleep, and while we sleep
253 * printk() could overwrite the messages
254 * we try to copy to user space. Therefore
255 * the messages are copied in reverse. <manfreds>
256 */
257 for (i = 0; i < count && !error; i++) {
258 j = limit-1-i;
259 if (j + log_buf_len < log_end)
260 break;
261 c = LOG_BUF(j);
262 spin_unlock_irq(&logbuf_lock);
263 error = __put_user(c,&buf[count-1-i]);
264 cond_resched();
265 spin_lock_irq(&logbuf_lock);
266 }
267 spin_unlock_irq(&logbuf_lock);
268 if (error)
269 break;
270 error = i;
271 if (i != count) {
272 int offset = count-error;
273 /* buffer overflow during copy, correct user buffer. */
274 for (i = 0; i < error; i++) {
275 if (__get_user(c,&buf[i+offset]) ||
276 __put_user(c,&buf[i])) {
277 error = -EFAULT;
278 break;
279 }
280 cond_resched();
281 }
282 }
283 break;
284 case 5: /* Clear ring buffer */
285 logged_chars = 0;
286 break;
287 case 6: /* Disable logging to console */
288 console_loglevel = minimum_console_loglevel;
289 break;
290 case 7: /* Enable logging to console */
291 console_loglevel = default_console_loglevel;
292 break;
293 case 8: /* Set level of messages printed to console */
294 error = -EINVAL;
295 if (len < 1 || len > 8)
296 goto out;
297 if (len < minimum_console_loglevel)
298 len = minimum_console_loglevel;
299 console_loglevel = len;
300 error = 0;
301 break;
302 case 9: /* Number of chars in the log buffer */
303 error = log_end - log_start;
304 break;
305 case 10: /* Size of the log buffer */
306 error = log_buf_len;
307 break;
308 default:
309 error = -EINVAL;
310 break;
311 }
312out:
313 return error;
314}
315
316asmlinkage long sys_syslog(int type, char __user *buf, int len)
317{
318 return do_syslog(type, buf, len);
319}
320
321/*
322 * Call the console drivers on a range of log_buf
323 */
324static void __call_console_drivers(unsigned long start, unsigned long end)
325{
326 struct console *con;
327
328 for (con = console_drivers; con; con = con->next) {
329 if ((con->flags & CON_ENABLED) && con->write &&
330 (cpu_online(smp_processor_id()) ||
331 (con->flags & CON_ANYTIME)))
332 con->write(con, &LOG_BUF(start), end - start);
333 }
334}
335
336static int __read_mostly ignore_loglevel;
337
338static int __init ignore_loglevel_setup(char *str)
339{
340 ignore_loglevel = 1;
341 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
342
343 return 1;
344}
345
346__setup("ignore_loglevel", ignore_loglevel_setup);
347
348/*
349 * Write out chars from start to end - 1 inclusive
350 */
351static void _call_console_drivers(unsigned long start,
352 unsigned long end, int msg_log_level)
353{
354 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
355 console_drivers && start != end) {
356 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
357 /* wrapped write */
358 __call_console_drivers(start & LOG_BUF_MASK,
359 log_buf_len);
360 __call_console_drivers(0, end & LOG_BUF_MASK);
361 } else {
362 __call_console_drivers(start, end);
363 }
364 }
365}
366
367/*
368 * Call the console drivers, asking them to write out
369 * log_buf[start] to log_buf[end - 1].
370 * The console_sem must be held.
371 */
372static void call_console_drivers(unsigned long start, unsigned long end)
373{
374 unsigned long cur_index, start_print;
375 static int msg_level = -1;
376
377 BUG_ON(((long)(start - end)) > 0);
378
379 cur_index = start;
380 start_print = start;
381 while (cur_index != end) {
382 if (msg_level < 0 && ((end - cur_index) > 2) &&
383 LOG_BUF(cur_index + 0) == '<' &&
384 LOG_BUF(cur_index + 1) >= '0' &&
385 LOG_BUF(cur_index + 1) <= '7' &&
386 LOG_BUF(cur_index + 2) == '>') {
387 msg_level = LOG_BUF(cur_index + 1) - '0';
388 cur_index += 3;
389 start_print = cur_index;
390 }
391 while (cur_index != end) {
392 char c = LOG_BUF(cur_index);
393
394 cur_index++;
395 if (c == '\n') {
396 if (msg_level < 0) {
397 /*
398 * printk() has already given us loglevel tags in
399 * the buffer. This code is here in case the
400 * log buffer has wrapped right round and scribbled
401 * on those tags
402 */
403 msg_level = default_message_loglevel;
404 }
405 _call_console_drivers(start_print, cur_index, msg_level);
406 msg_level = -1;
407 start_print = cur_index;
408 break;
409 }
410 }
411 }
412 _call_console_drivers(start_print, end, msg_level);
413}
414
415static void emit_log_char(char c)
416{
417 LOG_BUF(log_end) = c;
418 log_end++;
419 if (log_end - log_start > log_buf_len)
420 log_start = log_end - log_buf_len;
421 if (log_end - con_start > log_buf_len)
422 con_start = log_end - log_buf_len;
423 if (logged_chars < log_buf_len)
424 logged_chars++;
425}
426
427/*
428 * Zap console related locks when oopsing. Only zap at most once
429 * every 10 seconds, to leave time for slow consoles to print a
430 * full oops.
431 */
432static void zap_locks(void)
433{
434 static unsigned long oops_timestamp;
435
436 if (time_after_eq(jiffies, oops_timestamp) &&
437 !time_after(jiffies, oops_timestamp + 30 * HZ))
438 return;
439
440 oops_timestamp = jiffies;
441
442 /* If a crash is occurring, make sure we can't deadlock */
443 spin_lock_init(&logbuf_lock);
444 /* And make sure that we print immediately */
445 init_MUTEX(&console_sem);
446}
447
448#if defined(CONFIG_PRINTK_TIME)
449static int printk_time = 1;
450#else
451static int printk_time = 0;
452#endif
453module_param(printk_time, int, S_IRUGO | S_IWUSR);
454
455static int __init printk_time_setup(char *str)
456{
457 if (*str)
458 return 0;
459 printk_time = 1;
460 return 1;
461}
462
463__setup("time", printk_time_setup);
464
465__attribute__((weak)) unsigned long long printk_clock(void)
466{
467 return sched_clock();
468}
469
470/* Check if we have any console registered that can be called early in boot. */
471static int have_callable_console(void)
472{
473 struct console *con;
474
475 for (con = console_drivers; con; con = con->next)
476 if (con->flags & CON_ANYTIME)
477 return 1;
478
479 return 0;
480}
481
482/**
483 * printk - print a kernel message
484 * @fmt: format string
485 *
486 * This is printk(). It can be called from any context. We want it to work.
487 *
488 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
489 * call the console drivers. If we fail to get the semaphore we place the output
490 * into the log buffer and return. The current holder of the console_sem will
491 * notice the new output in release_console_sem() and will send it to the
492 * consoles before releasing the semaphore.
493 *
494 * One effect of this deferred printing is that code which calls printk() and
495 * then changes console_loglevel may break. This is because console_loglevel
496 * is inspected when the actual printing occurs.
497 *
498 * See also:
499 * printf(3)
500 */
501
502asmlinkage int printk(const char *fmt, ...)
503{
504 va_list args;
505 int r;
506
507 va_start(args, fmt);
508 r = vprintk(fmt, args);
509 va_end(args);
510
511 return r;
512}
513
514/* cpu currently holding logbuf_lock */
515static volatile unsigned int printk_cpu = UINT_MAX;
516
517asmlinkage int vprintk(const char *fmt, va_list args)
518{
519 unsigned long flags;
520 int printed_len;
521 char *p;
522 static char printk_buf[1024];
523 static int log_level_unknown = 1;
524
525 preempt_disable();
526 if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
527 /* If a crash is occurring during printk() on this CPU,
528 * make sure we can't deadlock */
529 zap_locks();
530
531 /* This stops the holder of console_sem just where we want him */
532 raw_local_irq_save(flags);
533 lockdep_off();
534 spin_lock(&logbuf_lock);
535 printk_cpu = smp_processor_id();
536
537 /* Emit the output into the temporary buffer */
538 printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
539
540 /*
541 * Copy the output into log_buf. If the caller didn't provide
542 * appropriate log level tags, we insert them here
543 */
544 for (p = printk_buf; *p; p++) {
545 if (log_level_unknown) {
546 /* log_level_unknown signals the start of a new line */
547 if (printk_time) {
548 int loglev_char;
549 char tbuf[50], *tp;
550 unsigned tlen;
551 unsigned long long t;
552 unsigned long nanosec_rem;
553
554 /*
555 * force the log level token to be
556 * before the time output.
557 */
558 if (p[0] == '<' && p[1] >='0' &&
559 p[1] <= '7' && p[2] == '>') {
560 loglev_char = p[1];
561 p += 3;
562 printed_len -= 3;
563 } else {
564 loglev_char = default_message_loglevel
565 + '0';
566 }
567 t = printk_clock();
568 nanosec_rem = do_div(t, 1000000000);
569 tlen = sprintf(tbuf,
570 "<%c>[%5lu.%06lu] ",
571 loglev_char,
572 (unsigned long)t,
573 nanosec_rem/1000);
574
575 for (tp = tbuf; tp < tbuf + tlen; tp++)
576 emit_log_char(*tp);
577 printed_len += tlen;
578 } else {
579 if (p[0] != '<' || p[1] < '0' ||
580 p[1] > '7' || p[2] != '>') {
581 emit_log_char('<');
582 emit_log_char(default_message_loglevel
583 + '0');
584 emit_log_char('>');
585 printed_len += 3;
586 }
587 }
588 log_level_unknown = 0;
589 if (!*p)
590 break;
591 }
592 emit_log_char(*p);
593 if (*p == '\n')
594 log_level_unknown = 1;
595 }
596
597 if (!down_trylock(&console_sem)) {
598 /*
599 * We own the drivers. We can drop the spinlock and
600 * let release_console_sem() print the text, maybe ...
601 */
602 console_locked = 1;
603 printk_cpu = UINT_MAX;
604 spin_unlock(&logbuf_lock);
605
606 /*
607 * Console drivers may assume that per-cpu resources have
608 * been allocated. So unless they're explicitly marked as
609 * being able to cope (CON_ANYTIME) don't call them until
610 * this CPU is officially up.
611 */
612 if (cpu_online(smp_processor_id()) || have_callable_console()) {
613 console_may_schedule = 0;
614 release_console_sem();
615 } else {
616 /* Release by hand to avoid flushing the buffer. */
617 console_locked = 0;
618 up(&console_sem);
619 }
620 lockdep_on();
621 raw_local_irq_restore(flags);
622 } else {
623 /*
624 * Someone else owns the drivers. We drop the spinlock, which
625 * allows the semaphore holder to proceed and to call the
626 * console drivers with the output which we just produced.
627 */
628 printk_cpu = UINT_MAX;
629 spin_unlock(&logbuf_lock);
630 lockdep_on();
631 raw_local_irq_restore(flags);
632 }
633
634 preempt_enable();
635 return printed_len;
636}
637EXPORT_SYMBOL(printk);
638EXPORT_SYMBOL(vprintk);
639
640#else
641
642asmlinkage long sys_syslog(int type, char __user *buf, int len)
643{
644 return -ENOSYS;
645}
646
647static void call_console_drivers(unsigned long start, unsigned long end)
648{
649}
650
651#endif
652
653/*
654 * Set up a list of consoles. Called from init/main.c
655 */
656static int __init console_setup(char *str)
657{
658 char name[sizeof(console_cmdline[0].name)];
659 char *s, *options;
660 int idx;
661
662 /*
663 * Decode str into name, index, options.
664 */
665 if (str[0] >= '0' && str[0] <= '9') {
666 strcpy(name, "ttyS");
667 strncpy(name + 4, str, sizeof(name) - 5);
668 } else {
669 strncpy(name, str, sizeof(name) - 1);
670 }
671 name[sizeof(name) - 1] = 0;
672 if ((options = strchr(str, ',')) != NULL)
673 *(options++) = 0;
674#ifdef __sparc__
675 if (!strcmp(str, "ttya"))
676 strcpy(name, "ttyS0");
677 if (!strcmp(str, "ttyb"))
678 strcpy(name, "ttyS1");
679#endif
680 for (s = name; *s; s++)
681 if ((*s >= '0' && *s <= '9') || *s == ',')
682 break;
683 idx = simple_strtoul(s, NULL, 10);
684 *s = 0;
685
686 add_preferred_console(name, idx, options);
687 return 1;
688}
689__setup("console=", console_setup);
690
691/**
692 * add_preferred_console - add a device to the list of preferred consoles.
693 * @name: device name
694 * @idx: device index
695 * @options: options for this console
696 *
697 * The last preferred console added will be used for kernel messages
698 * and stdin/out/err for init. Normally this is used by console_setup
699 * above to handle user-supplied console arguments; however it can also
700 * be used by arch-specific code either to override the user or more
701 * commonly to provide a default console (ie from PROM variables) when
702 * the user has not supplied one.
703 */
704int __init add_preferred_console(char *name, int idx, char *options)
705{
706 struct console_cmdline *c;
707 int i;
708
709 /*
710 * See if this tty is not yet registered, and
711 * if we have a slot free.
712 */
713 for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
714 if (strcmp(console_cmdline[i].name, name) == 0 &&
715 console_cmdline[i].index == idx) {
716 selected_console = i;
717 return 0;
718 }
719 if (i == MAX_CMDLINECONSOLES)
720 return -E2BIG;
721 selected_console = i;
722 c = &console_cmdline[i];
723 memcpy(c->name, name, sizeof(c->name));
724 c->name[sizeof(c->name) - 1] = 0;
725 c->options = options;
726 c->index = idx;
727 return 0;
728}
729
730#ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
731/**
732 * suspend_console - suspend the console subsystem
733 *
734 * This disables printk() while we go into suspend states
735 */
736void suspend_console(void)
737{
738 printk("Suspending console(s)\n");
739 acquire_console_sem();
740 console_suspended = 1;
741}
742
743void resume_console(void)
744{
745 console_suspended = 0;
746 release_console_sem();
747}
748#endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
749
750/**
751 * acquire_console_sem - lock the console system for exclusive use.
752 *
753 * Acquires a semaphore which guarantees that the caller has
754 * exclusive access to the console system and the console_drivers list.
755 *
756 * Can sleep, returns nothing.
757 */
758void acquire_console_sem(void)
759{
760 BUG_ON(in_interrupt());
761 if (console_suspended) {
762 down(&secondary_console_sem);
763 return;
764 }
765 down(&console_sem);
766 console_locked = 1;
767 console_may_schedule = 1;
768}
769EXPORT_SYMBOL(acquire_console_sem);
770
771int try_acquire_console_sem(void)
772{
773 if (down_trylock(&console_sem))
774 return -1;
775 console_locked = 1;
776 console_may_schedule = 0;
777 return 0;
778}
779EXPORT_SYMBOL(try_acquire_console_sem);
780
781int is_console_locked(void)
782{
783 return console_locked;
784}
785
786void wake_up_klogd(void)
787{
788 if (!oops_in_progress && waitqueue_active(&log_wait))
789 wake_up_interruptible(&log_wait);
790}
791
792/**
793 * release_console_sem - unlock the console system
794 *
795 * Releases the semaphore which the caller holds on the console system
796 * and the console driver list.
797 *
798 * While the semaphore was held, console output may have been buffered
799 * by printk(). If this is the case, release_console_sem() emits
800 * the output prior to releasing the semaphore.
801 *
802 * If there is output waiting for klogd, we wake it up.
803 *
804 * release_console_sem() may be called from any context.
805 */
806void release_console_sem(void)
807{
808 unsigned long flags;
809 unsigned long _con_start, _log_end;
810 unsigned long wake_klogd = 0;
811
812 if (console_suspended) {
813 up(&secondary_console_sem);
814 return;
815 }
816
817 console_may_schedule = 0;
818
819 for ( ; ; ) {
820 spin_lock_irqsave(&logbuf_lock, flags);
821 wake_klogd |= log_start - log_end;
822 if (con_start == log_end)
823 break; /* Nothing to print */
824 _con_start = con_start;
825 _log_end = log_end;
826 con_start = log_end; /* Flush */
827 spin_unlock(&logbuf_lock);
828 call_console_drivers(_con_start, _log_end);
829 local_irq_restore(flags);
830 }
831 console_locked = 0;
832 up(&console_sem);
833 spin_unlock_irqrestore(&logbuf_lock, flags);
834 if (wake_klogd)
835 wake_up_klogd();
836}
837EXPORT_SYMBOL(release_console_sem);
838
839/**
840 * console_conditional_schedule - yield the CPU if required
841 *
842 * If the console code is currently allowed to sleep, and
843 * if this CPU should yield the CPU to another task, do
844 * so here.
845 *
846 * Must be called within acquire_console_sem().
847 */
848void __sched console_conditional_schedule(void)
849{
850 if (console_may_schedule)
851 cond_resched();
852}
853EXPORT_SYMBOL(console_conditional_schedule);
854
855void console_print(const char *s)
856{
857 printk(KERN_EMERG "%s", s);
858}
859EXPORT_SYMBOL(console_print);
860
861void console_unblank(void)
862{
863 struct console *c;
864
865 /*
866 * console_unblank can no longer be called in interrupt context unless
867 * oops_in_progress is set to 1..
868 */
869 if (oops_in_progress) {
870 if (down_trylock(&console_sem) != 0)
871 return;
872 } else
873 acquire_console_sem();
874
875 console_locked = 1;
876 console_may_schedule = 0;
877 for (c = console_drivers; c != NULL; c = c->next)
878 if ((c->flags & CON_ENABLED) && c->unblank)
879 c->unblank();
880 release_console_sem();
881}
882
883/*
884 * Return the console tty driver structure and its associated index
885 */
886struct tty_driver *console_device(int *index)
887{
888 struct console *c;
889 struct tty_driver *driver = NULL;
890
891 acquire_console_sem();
892 for (c = console_drivers; c != NULL; c = c->next) {
893 if (!c->device)
894 continue;
895 driver = c->device(c, index);
896 if (driver)
897 break;
898 }
899 release_console_sem();
900 return driver;
901}
902
903/*
904 * Prevent further output on the passed console device so that (for example)
905 * serial drivers can disable console output before suspending a port, and can
906 * re-enable output afterwards.
907 */
908void console_stop(struct console *console)
909{
910 acquire_console_sem();
911 console->flags &= ~CON_ENABLED;
912 release_console_sem();
913}
914EXPORT_SYMBOL(console_stop);
915
916void console_start(struct console *console)
917{
918 acquire_console_sem();
919 console->flags |= CON_ENABLED;
920 release_console_sem();
921}
922EXPORT_SYMBOL(console_start);
923
924/*
925 * The console driver calls this routine during kernel initialization
926 * to register the console printing procedure with printk() and to
927 * print any messages that were printed by the kernel before the
928 * console driver was initialized.
929 */
930void register_console(struct console *console)
931{
932 int i;
933 unsigned long flags;
934
935 if (preferred_console < 0)
936 preferred_console = selected_console;
937
938 /*
939 * See if we want to use this console driver. If we
940 * didn't select a console we take the first one
941 * that registers here.
942 */
943 if (preferred_console < 0) {
944 if (console->index < 0)
945 console->index = 0;
946 if (console->setup == NULL ||
947 console->setup(console, NULL) == 0) {
948 console->flags |= CON_ENABLED | CON_CONSDEV;
949 preferred_console = 0;
950 }
951 }
952
953 /*
954 * See if this console matches one we selected on
955 * the command line.
956 */
957 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
958 i++) {
959 if (strcmp(console_cmdline[i].name, console->name) != 0)
960 continue;
961 if (console->index >= 0 &&
962 console->index != console_cmdline[i].index)
963 continue;
964 if (console->index < 0)
965 console->index = console_cmdline[i].index;
966 if (console->setup &&
967 console->setup(console, console_cmdline[i].options) != 0)
968 break;
969 console->flags |= CON_ENABLED;
970 console->index = console_cmdline[i].index;
971 if (i == selected_console) {
972 console->flags |= CON_CONSDEV;
973 preferred_console = selected_console;
974 }
975 break;
976 }
977
978 if (!(console->flags & CON_ENABLED))
979 return;
980
981 if (console_drivers && (console_drivers->flags & CON_BOOT)) {
982 unregister_console(console_drivers);
983 console->flags &= ~CON_PRINTBUFFER;
984 }
985
986 /*
987 * Put this console in the list - keep the
988 * preferred driver at the head of the list.
989 */
990 acquire_console_sem();
991 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
992 console->next = console_drivers;
993 console_drivers = console;
994 if (console->next)
995 console->next->flags &= ~CON_CONSDEV;
996 } else {
997 console->next = console_drivers->next;
998 console_drivers->next = console;
999 }
1000 if (console->flags & CON_PRINTBUFFER) {
1001 /*
1002 * release_console_sem() will print out the buffered messages
1003 * for us.
1004 */
1005 spin_lock_irqsave(&logbuf_lock, flags);
1006 con_start = log_start;
1007 spin_unlock_irqrestore(&logbuf_lock, flags);
1008 }
1009 release_console_sem();
1010}
1011EXPORT_SYMBOL(register_console);
1012
1013int unregister_console(struct console *console)
1014{
1015 struct console *a, *b;
1016 int res = 1;
1017
1018 acquire_console_sem();
1019 if (console_drivers == console) {
1020 console_drivers=console->next;
1021 res = 0;
1022 } else if (console_drivers) {
1023 for (a=console_drivers->next, b=console_drivers ;
1024 a; b=a, a=b->next) {
1025 if (a == console) {
1026 b->next = a->next;
1027 res = 0;
1028 break;
1029 }
1030 }
1031 }
1032
1033 /* If last console is removed, we re-enable picking the first
1034 * one that gets registered. Without that, pmac early boot console
1035 * would prevent fbcon from taking over.
1036 *
1037 * If this isn't the last console and it has CON_CONSDEV set, we
1038 * need to set it on the next preferred console.
1039 */
1040 if (console_drivers == NULL)
1041 preferred_console = selected_console;
1042 else if (console->flags & CON_CONSDEV)
1043 console_drivers->flags |= CON_CONSDEV;
1044
1045 release_console_sem();
1046 return res;
1047}
1048EXPORT_SYMBOL(unregister_console);
1049
1050/**
1051 * tty_write_message - write a message to a certain tty, not just the console.
1052 * @tty: the destination tty_struct
1053 * @msg: the message to write
1054 *
1055 * This is used for messages that need to be redirected to a specific tty.
1056 * We don't put it into the syslog queue right now maybe in the future if
1057 * really needed.
1058 */
1059void tty_write_message(struct tty_struct *tty, char *msg)
1060{
1061 if (tty && tty->driver->write)
1062 tty->driver->write(tty, msg, strlen(msg));
1063 return;
1064}
1065
1066/*
1067 * printk rate limiting, lifted from the networking subsystem.
1068 *
1069 * This enforces a rate limit: not more than one kernel message
1070 * every printk_ratelimit_jiffies to make a denial-of-service
1071 * attack impossible.
1072 */
1073int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1074{
1075 static DEFINE_SPINLOCK(ratelimit_lock);
1076 static unsigned long toks = 10 * 5 * HZ;
1077 static unsigned long last_msg;
1078 static int missed;
1079 unsigned long flags;
1080 unsigned long now = jiffies;
1081
1082 spin_lock_irqsave(&ratelimit_lock, flags);
1083 toks += now - last_msg;
1084 last_msg = now;
1085 if (toks > (ratelimit_burst * ratelimit_jiffies))
1086 toks = ratelimit_burst * ratelimit_jiffies;
1087 if (toks >= ratelimit_jiffies) {
1088 int lost = missed;
1089
1090 missed = 0;
1091 toks -= ratelimit_jiffies;
1092 spin_unlock_irqrestore(&ratelimit_lock, flags);
1093 if (lost)
1094 printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1095 return 1;
1096 }
1097 missed++;
1098 spin_unlock_irqrestore(&ratelimit_lock, flags);
1099 return 0;
1100}
1101EXPORT_SYMBOL(__printk_ratelimit);
1102
1103/* minimum time in jiffies between messages */
1104int printk_ratelimit_jiffies = 5 * HZ;
1105
1106/* number of messages we send before ratelimiting */
1107int printk_ratelimit_burst = 10;
1108
1109int printk_ratelimit(void)
1110{
1111 return __printk_ratelimit(printk_ratelimit_jiffies,
1112 printk_ratelimit_burst);
1113}
1114EXPORT_SYMBOL(printk_ratelimit);
1115
1116/**
1117 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1118 * @caller_jiffies: pointer to caller's state
1119 * @interval_msecs: minimum interval between prints
1120 *
1121 * printk_timed_ratelimit() returns true if more than @interval_msecs
1122 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1123 * returned true.
1124 */
1125bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1126 unsigned int interval_msecs)
1127{
1128 if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1129 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1130 return true;
1131 }
1132 return false;
1133}
1134EXPORT_SYMBOL(printk_timed_ratelimit);