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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
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/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/memblock.h>
35#include <linux/syscalls.h>
36#include <linux/kexec.h>
37#include <linux/kdb.h>
38#include <linux/ratelimit.h>
39#include <linux/kmsg_dump.h>
40#include <linux/syslog.h>
41#include <linux/cpu.h>
42#include <linux/notifier.h>
43#include <linux/rculist.h>
44
45#include <asm/uaccess.h>
46
47/*
48 * Architectures can override it:
49 */
50void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
51{
52}
53
54#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
55
56/* printk's without a loglevel use this.. */
57#define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
58
59/* We show everything that is MORE important than this.. */
60#define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
61#define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
62
63DECLARE_WAIT_QUEUE_HEAD(log_wait);
64
65int console_printk[4] = {
66 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
67 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
68 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
69 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
70};
71
72/*
73 * Low level drivers may need that to know if they can schedule in
74 * their unblank() callback or not. So let's export it.
75 */
76int oops_in_progress;
77EXPORT_SYMBOL(oops_in_progress);
78
79/*
80 * console_sem protects the console_drivers list, and also
81 * provides serialisation for access to the entire console
82 * driver system.
83 */
84static DEFINE_SEMAPHORE(console_sem);
85struct console *console_drivers;
86EXPORT_SYMBOL_GPL(console_drivers);
87
88/*
89 * This is used for debugging the mess that is the VT code by
90 * keeping track if we have the console semaphore held. It's
91 * definitely not the perfect debug tool (we don't know if _WE_
92 * hold it are racing, but it helps tracking those weird code
93 * path in the console code where we end up in places I want
94 * locked without the console sempahore held
95 */
96static int console_locked, console_suspended;
97
98/*
99 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
100 * It is also used in interesting ways to provide interlocking in
101 * console_unlock();.
102 */
103static DEFINE_SPINLOCK(logbuf_lock);
104
105#define LOG_BUF_MASK (log_buf_len-1)
106#define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
107
108/*
109 * The indices into log_buf are not constrained to log_buf_len - they
110 * must be masked before subscripting
111 */
112static unsigned log_start; /* Index into log_buf: next char to be read by syslog() */
113static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */
114static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */
115
116/*
117 * If exclusive_console is non-NULL then only this console is to be printed to.
118 */
119static struct console *exclusive_console;
120
121/*
122 * Array of consoles built from command line options (console=)
123 */
124struct console_cmdline
125{
126 char name[8]; /* Name of the driver */
127 int index; /* Minor dev. to use */
128 char *options; /* Options for the driver */
129#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
130 char *brl_options; /* Options for braille driver */
131#endif
132};
133
134#define MAX_CMDLINECONSOLES 8
135
136static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
137static int selected_console = -1;
138static int preferred_console = -1;
139int console_set_on_cmdline;
140EXPORT_SYMBOL(console_set_on_cmdline);
141
142/* Flag: console code may call schedule() */
143static int console_may_schedule;
144
145#ifdef CONFIG_PRINTK
146
147static char __log_buf[__LOG_BUF_LEN];
148static char *log_buf = __log_buf;
149static int log_buf_len = __LOG_BUF_LEN;
150static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
151static int saved_console_loglevel = -1;
152
153#ifdef CONFIG_KEXEC
154/*
155 * This appends the listed symbols to /proc/vmcoreinfo
156 *
157 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
158 * obtain access to symbols that are otherwise very difficult to locate. These
159 * symbols are specifically used so that utilities can access and extract the
160 * dmesg log from a vmcore file after a crash.
161 */
162void log_buf_kexec_setup(void)
163{
164 VMCOREINFO_SYMBOL(log_buf);
165 VMCOREINFO_SYMBOL(log_end);
166 VMCOREINFO_SYMBOL(log_buf_len);
167 VMCOREINFO_SYMBOL(logged_chars);
168}
169#endif
170
171/* requested log_buf_len from kernel cmdline */
172static unsigned long __initdata new_log_buf_len;
173
174/* save requested log_buf_len since it's too early to process it */
175static int __init log_buf_len_setup(char *str)
176{
177 unsigned size = memparse(str, &str);
178
179 if (size)
180 size = roundup_pow_of_two(size);
181 if (size > log_buf_len)
182 new_log_buf_len = size;
183
184 return 0;
185}
186early_param("log_buf_len", log_buf_len_setup);
187
188void __init setup_log_buf(int early)
189{
190 unsigned long flags;
191 unsigned start, dest_idx, offset;
192 char *new_log_buf;
193 int free;
194
195 if (!new_log_buf_len)
196 return;
197
198 if (early) {
199 unsigned long mem;
200
201 mem = memblock_alloc(new_log_buf_len, PAGE_SIZE);
202 if (mem == MEMBLOCK_ERROR)
203 return;
204 new_log_buf = __va(mem);
205 } else {
206 new_log_buf = alloc_bootmem_nopanic(new_log_buf_len);
207 }
208
209 if (unlikely(!new_log_buf)) {
210 pr_err("log_buf_len: %ld bytes not available\n",
211 new_log_buf_len);
212 return;
213 }
214
215 spin_lock_irqsave(&logbuf_lock, flags);
216 log_buf_len = new_log_buf_len;
217 log_buf = new_log_buf;
218 new_log_buf_len = 0;
219 free = __LOG_BUF_LEN - log_end;
220
221 offset = start = min(con_start, log_start);
222 dest_idx = 0;
223 while (start != log_end) {
224 unsigned log_idx_mask = start & (__LOG_BUF_LEN - 1);
225
226 log_buf[dest_idx] = __log_buf[log_idx_mask];
227 start++;
228 dest_idx++;
229 }
230 log_start -= offset;
231 con_start -= offset;
232 log_end -= offset;
233 spin_unlock_irqrestore(&logbuf_lock, flags);
234
235 pr_info("log_buf_len: %d\n", log_buf_len);
236 pr_info("early log buf free: %d(%d%%)\n",
237 free, (free * 100) / __LOG_BUF_LEN);
238}
239
240#ifdef CONFIG_BOOT_PRINTK_DELAY
241
242static int boot_delay; /* msecs delay after each printk during bootup */
243static unsigned long long loops_per_msec; /* based on boot_delay */
244
245static int __init boot_delay_setup(char *str)
246{
247 unsigned long lpj;
248
249 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
250 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
251
252 get_option(&str, &boot_delay);
253 if (boot_delay > 10 * 1000)
254 boot_delay = 0;
255
256 pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
257 "HZ: %d, loops_per_msec: %llu\n",
258 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
259 return 1;
260}
261__setup("boot_delay=", boot_delay_setup);
262
263static void boot_delay_msec(void)
264{
265 unsigned long long k;
266 unsigned long timeout;
267
268 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
269 return;
270
271 k = (unsigned long long)loops_per_msec * boot_delay;
272
273 timeout = jiffies + msecs_to_jiffies(boot_delay);
274 while (k) {
275 k--;
276 cpu_relax();
277 /*
278 * use (volatile) jiffies to prevent
279 * compiler reduction; loop termination via jiffies
280 * is secondary and may or may not happen.
281 */
282 if (time_after(jiffies, timeout))
283 break;
284 touch_nmi_watchdog();
285 }
286}
287#else
288static inline void boot_delay_msec(void)
289{
290}
291#endif
292
293#ifdef CONFIG_SECURITY_DMESG_RESTRICT
294int dmesg_restrict = 1;
295#else
296int dmesg_restrict;
297#endif
298
299static int syslog_action_restricted(int type)
300{
301 if (dmesg_restrict)
302 return 1;
303 /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
304 return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
305}
306
307static int check_syslog_permissions(int type, bool from_file)
308{
309 /*
310 * If this is from /proc/kmsg and we've already opened it, then we've
311 * already done the capabilities checks at open time.
312 */
313 if (from_file && type != SYSLOG_ACTION_OPEN)
314 return 0;
315
316 if (syslog_action_restricted(type)) {
317 if (capable(CAP_SYSLOG))
318 return 0;
319 /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
320 if (capable(CAP_SYS_ADMIN)) {
321 printk_once(KERN_WARNING "%s (%d): "
322 "Attempt to access syslog with CAP_SYS_ADMIN "
323 "but no CAP_SYSLOG (deprecated).\n",
324 current->comm, task_pid_nr(current));
325 return 0;
326 }
327 return -EPERM;
328 }
329 return 0;
330}
331
332int do_syslog(int type, char __user *buf, int len, bool from_file)
333{
334 unsigned i, j, limit, count;
335 int do_clear = 0;
336 char c;
337 int error;
338
339 error = check_syslog_permissions(type, from_file);
340 if (error)
341 goto out;
342
343 error = security_syslog(type);
344 if (error)
345 return error;
346
347 switch (type) {
348 case SYSLOG_ACTION_CLOSE: /* Close log */
349 break;
350 case SYSLOG_ACTION_OPEN: /* Open log */
351 break;
352 case SYSLOG_ACTION_READ: /* Read from log */
353 error = -EINVAL;
354 if (!buf || len < 0)
355 goto out;
356 error = 0;
357 if (!len)
358 goto out;
359 if (!access_ok(VERIFY_WRITE, buf, len)) {
360 error = -EFAULT;
361 goto out;
362 }
363 error = wait_event_interruptible(log_wait,
364 (log_start - log_end));
365 if (error)
366 goto out;
367 i = 0;
368 spin_lock_irq(&logbuf_lock);
369 while (!error && (log_start != log_end) && i < len) {
370 c = LOG_BUF(log_start);
371 log_start++;
372 spin_unlock_irq(&logbuf_lock);
373 error = __put_user(c,buf);
374 buf++;
375 i++;
376 cond_resched();
377 spin_lock_irq(&logbuf_lock);
378 }
379 spin_unlock_irq(&logbuf_lock);
380 if (!error)
381 error = i;
382 break;
383 /* Read/clear last kernel messages */
384 case SYSLOG_ACTION_READ_CLEAR:
385 do_clear = 1;
386 /* FALL THRU */
387 /* Read last kernel messages */
388 case SYSLOG_ACTION_READ_ALL:
389 error = -EINVAL;
390 if (!buf || len < 0)
391 goto out;
392 error = 0;
393 if (!len)
394 goto out;
395 if (!access_ok(VERIFY_WRITE, buf, len)) {
396 error = -EFAULT;
397 goto out;
398 }
399 count = len;
400 if (count > log_buf_len)
401 count = log_buf_len;
402 spin_lock_irq(&logbuf_lock);
403 if (count > logged_chars)
404 count = logged_chars;
405 if (do_clear)
406 logged_chars = 0;
407 limit = log_end;
408 /*
409 * __put_user() could sleep, and while we sleep
410 * printk() could overwrite the messages
411 * we try to copy to user space. Therefore
412 * the messages are copied in reverse. <manfreds>
413 */
414 for (i = 0; i < count && !error; i++) {
415 j = limit-1-i;
416 if (j + log_buf_len < log_end)
417 break;
418 c = LOG_BUF(j);
419 spin_unlock_irq(&logbuf_lock);
420 error = __put_user(c,&buf[count-1-i]);
421 cond_resched();
422 spin_lock_irq(&logbuf_lock);
423 }
424 spin_unlock_irq(&logbuf_lock);
425 if (error)
426 break;
427 error = i;
428 if (i != count) {
429 int offset = count-error;
430 /* buffer overflow during copy, correct user buffer. */
431 for (i = 0; i < error; i++) {
432 if (__get_user(c,&buf[i+offset]) ||
433 __put_user(c,&buf[i])) {
434 error = -EFAULT;
435 break;
436 }
437 cond_resched();
438 }
439 }
440 break;
441 /* Clear ring buffer */
442 case SYSLOG_ACTION_CLEAR:
443 logged_chars = 0;
444 break;
445 /* Disable logging to console */
446 case SYSLOG_ACTION_CONSOLE_OFF:
447 if (saved_console_loglevel == -1)
448 saved_console_loglevel = console_loglevel;
449 console_loglevel = minimum_console_loglevel;
450 break;
451 /* Enable logging to console */
452 case SYSLOG_ACTION_CONSOLE_ON:
453 if (saved_console_loglevel != -1) {
454 console_loglevel = saved_console_loglevel;
455 saved_console_loglevel = -1;
456 }
457 break;
458 /* Set level of messages printed to console */
459 case SYSLOG_ACTION_CONSOLE_LEVEL:
460 error = -EINVAL;
461 if (len < 1 || len > 8)
462 goto out;
463 if (len < minimum_console_loglevel)
464 len = minimum_console_loglevel;
465 console_loglevel = len;
466 /* Implicitly re-enable logging to console */
467 saved_console_loglevel = -1;
468 error = 0;
469 break;
470 /* Number of chars in the log buffer */
471 case SYSLOG_ACTION_SIZE_UNREAD:
472 error = log_end - log_start;
473 break;
474 /* Size of the log buffer */
475 case SYSLOG_ACTION_SIZE_BUFFER:
476 error = log_buf_len;
477 break;
478 default:
479 error = -EINVAL;
480 break;
481 }
482out:
483 return error;
484}
485
486SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
487{
488 return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
489}
490
491#ifdef CONFIG_KGDB_KDB
492/* kdb dmesg command needs access to the syslog buffer. do_syslog()
493 * uses locks so it cannot be used during debugging. Just tell kdb
494 * where the start and end of the physical and logical logs are. This
495 * is equivalent to do_syslog(3).
496 */
497void kdb_syslog_data(char *syslog_data[4])
498{
499 syslog_data[0] = log_buf;
500 syslog_data[1] = log_buf + log_buf_len;
501 syslog_data[2] = log_buf + log_end -
502 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
503 syslog_data[3] = log_buf + log_end;
504}
505#endif /* CONFIG_KGDB_KDB */
506
507/*
508 * Call the console drivers on a range of log_buf
509 */
510static void __call_console_drivers(unsigned start, unsigned end)
511{
512 struct console *con;
513
514 for_each_console(con) {
515 if (exclusive_console && con != exclusive_console)
516 continue;
517 if ((con->flags & CON_ENABLED) && con->write &&
518 (cpu_online(smp_processor_id()) ||
519 (con->flags & CON_ANYTIME)))
520 con->write(con, &LOG_BUF(start), end - start);
521 }
522}
523
524static int __read_mostly ignore_loglevel;
525
526static int __init ignore_loglevel_setup(char *str)
527{
528 ignore_loglevel = 1;
529 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
530
531 return 0;
532}
533
534early_param("ignore_loglevel", ignore_loglevel_setup);
535
536/*
537 * Write out chars from start to end - 1 inclusive
538 */
539static void _call_console_drivers(unsigned start,
540 unsigned end, int msg_log_level)
541{
542 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
543 console_drivers && start != end) {
544 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
545 /* wrapped write */
546 __call_console_drivers(start & LOG_BUF_MASK,
547 log_buf_len);
548 __call_console_drivers(0, end & LOG_BUF_MASK);
549 } else {
550 __call_console_drivers(start, end);
551 }
552 }
553}
554
555/*
556 * Parse the syslog header <[0-9]*>. The decimal value represents 32bit, the
557 * lower 3 bit are the log level, the rest are the log facility. In case
558 * userspace passes usual userspace syslog messages to /dev/kmsg or
559 * /dev/ttyprintk, the log prefix might contain the facility. Printk needs
560 * to extract the correct log level for in-kernel processing, and not mangle
561 * the original value.
562 *
563 * If a prefix is found, the length of the prefix is returned. If 'level' is
564 * passed, it will be filled in with the log level without a possible facility
565 * value. If 'special' is passed, the special printk prefix chars are accepted
566 * and returned. If no valid header is found, 0 is returned and the passed
567 * variables are not touched.
568 */
569static size_t log_prefix(const char *p, unsigned int *level, char *special)
570{
571 unsigned int lev = 0;
572 char sp = '\0';
573 size_t len;
574
575 if (p[0] != '<' || !p[1])
576 return 0;
577 if (p[2] == '>') {
578 /* usual single digit level number or special char */
579 switch (p[1]) {
580 case '0' ... '7':
581 lev = p[1] - '0';
582 break;
583 case 'c': /* KERN_CONT */
584 case 'd': /* KERN_DEFAULT */
585 sp = p[1];
586 break;
587 default:
588 return 0;
589 }
590 len = 3;
591 } else {
592 /* multi digit including the level and facility number */
593 char *endp = NULL;
594
595 if (p[1] < '0' && p[1] > '9')
596 return 0;
597
598 lev = (simple_strtoul(&p[1], &endp, 10) & 7);
599 if (endp == NULL || endp[0] != '>')
600 return 0;
601 len = (endp + 1) - p;
602 }
603
604 /* do not accept special char if not asked for */
605 if (sp && !special)
606 return 0;
607
608 if (special) {
609 *special = sp;
610 /* return special char, do not touch level */
611 if (sp)
612 return len;
613 }
614
615 if (level)
616 *level = lev;
617 return len;
618}
619
620/*
621 * Call the console drivers, asking them to write out
622 * log_buf[start] to log_buf[end - 1].
623 * The console_lock must be held.
624 */
625static void call_console_drivers(unsigned start, unsigned end)
626{
627 unsigned cur_index, start_print;
628 static int msg_level = -1;
629
630 BUG_ON(((int)(start - end)) > 0);
631
632 cur_index = start;
633 start_print = start;
634 while (cur_index != end) {
635 if (msg_level < 0 && ((end - cur_index) > 2)) {
636 /* strip log prefix */
637 cur_index += log_prefix(&LOG_BUF(cur_index), &msg_level, NULL);
638 start_print = cur_index;
639 }
640 while (cur_index != end) {
641 char c = LOG_BUF(cur_index);
642
643 cur_index++;
644 if (c == '\n') {
645 if (msg_level < 0) {
646 /*
647 * printk() has already given us loglevel tags in
648 * the buffer. This code is here in case the
649 * log buffer has wrapped right round and scribbled
650 * on those tags
651 */
652 msg_level = default_message_loglevel;
653 }
654 _call_console_drivers(start_print, cur_index, msg_level);
655 msg_level = -1;
656 start_print = cur_index;
657 break;
658 }
659 }
660 }
661 _call_console_drivers(start_print, end, msg_level);
662}
663
664static void emit_log_char(char c)
665{
666 LOG_BUF(log_end) = c;
667 log_end++;
668 if (log_end - log_start > log_buf_len)
669 log_start = log_end - log_buf_len;
670 if (log_end - con_start > log_buf_len)
671 con_start = log_end - log_buf_len;
672 if (logged_chars < log_buf_len)
673 logged_chars++;
674}
675
676/*
677 * Zap console related locks when oopsing. Only zap at most once
678 * every 10 seconds, to leave time for slow consoles to print a
679 * full oops.
680 */
681static void zap_locks(void)
682{
683 static unsigned long oops_timestamp;
684
685 if (time_after_eq(jiffies, oops_timestamp) &&
686 !time_after(jiffies, oops_timestamp + 30 * HZ))
687 return;
688
689 oops_timestamp = jiffies;
690
691 /* If a crash is occurring, make sure we can't deadlock */
692 spin_lock_init(&logbuf_lock);
693 /* And make sure that we print immediately */
694 sema_init(&console_sem, 1);
695}
696
697#if defined(CONFIG_PRINTK_TIME)
698static int printk_time = 1;
699#else
700static int printk_time = 0;
701#endif
702module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
703
704/* Check if we have any console registered that can be called early in boot. */
705static int have_callable_console(void)
706{
707 struct console *con;
708
709 for_each_console(con)
710 if (con->flags & CON_ANYTIME)
711 return 1;
712
713 return 0;
714}
715
716/**
717 * printk - print a kernel message
718 * @fmt: format string
719 *
720 * This is printk(). It can be called from any context. We want it to work.
721 *
722 * We try to grab the console_lock. If we succeed, it's easy - we log the output and
723 * call the console drivers. If we fail to get the semaphore we place the output
724 * into the log buffer and return. The current holder of the console_sem will
725 * notice the new output in console_unlock(); and will send it to the
726 * consoles before releasing the lock.
727 *
728 * One effect of this deferred printing is that code which calls printk() and
729 * then changes console_loglevel may break. This is because console_loglevel
730 * is inspected when the actual printing occurs.
731 *
732 * See also:
733 * printf(3)
734 *
735 * See the vsnprintf() documentation for format string extensions over C99.
736 */
737
738asmlinkage int printk(const char *fmt, ...)
739{
740 va_list args;
741 int r;
742
743#ifdef CONFIG_KGDB_KDB
744 if (unlikely(kdb_trap_printk)) {
745 va_start(args, fmt);
746 r = vkdb_printf(fmt, args);
747 va_end(args);
748 return r;
749 }
750#endif
751 va_start(args, fmt);
752 r = vprintk(fmt, args);
753 va_end(args);
754
755 return r;
756}
757
758/* cpu currently holding logbuf_lock */
759static volatile unsigned int printk_cpu = UINT_MAX;
760
761/*
762 * Can we actually use the console at this time on this cpu?
763 *
764 * Console drivers may assume that per-cpu resources have
765 * been allocated. So unless they're explicitly marked as
766 * being able to cope (CON_ANYTIME) don't call them until
767 * this CPU is officially up.
768 */
769static inline int can_use_console(unsigned int cpu)
770{
771 return cpu_online(cpu) || have_callable_console();
772}
773
774/*
775 * Try to get console ownership to actually show the kernel
776 * messages from a 'printk'. Return true (and with the
777 * console_lock held, and 'console_locked' set) if it
778 * is successful, false otherwise.
779 *
780 * This gets called with the 'logbuf_lock' spinlock held and
781 * interrupts disabled. It should return with 'lockbuf_lock'
782 * released but interrupts still disabled.
783 */
784static int console_trylock_for_printk(unsigned int cpu)
785 __releases(&logbuf_lock)
786{
787 int retval = 0, wake = 0;
788
789 if (console_trylock()) {
790 retval = 1;
791
792 /*
793 * If we can't use the console, we need to release
794 * the console semaphore by hand to avoid flushing
795 * the buffer. We need to hold the console semaphore
796 * in order to do this test safely.
797 */
798 if (!can_use_console(cpu)) {
799 console_locked = 0;
800 wake = 1;
801 retval = 0;
802 }
803 }
804 printk_cpu = UINT_MAX;
805 spin_unlock(&logbuf_lock);
806 if (wake)
807 up(&console_sem);
808 return retval;
809}
810static const char recursion_bug_msg [] =
811 KERN_CRIT "BUG: recent printk recursion!\n";
812static int recursion_bug;
813static int new_text_line = 1;
814static char printk_buf[1024];
815
816int printk_delay_msec __read_mostly;
817
818static inline void printk_delay(void)
819{
820 if (unlikely(printk_delay_msec)) {
821 int m = printk_delay_msec;
822
823 while (m--) {
824 mdelay(1);
825 touch_nmi_watchdog();
826 }
827 }
828}
829
830asmlinkage int vprintk(const char *fmt, va_list args)
831{
832 int printed_len = 0;
833 int current_log_level = default_message_loglevel;
834 unsigned long flags;
835 int this_cpu;
836 char *p;
837 size_t plen;
838 char special;
839
840 boot_delay_msec();
841 printk_delay();
842
843 preempt_disable();
844 /* This stops the holder of console_sem just where we want him */
845 raw_local_irq_save(flags);
846 this_cpu = smp_processor_id();
847
848 /*
849 * Ouch, printk recursed into itself!
850 */
851 if (unlikely(printk_cpu == this_cpu)) {
852 /*
853 * If a crash is occurring during printk() on this CPU,
854 * then try to get the crash message out but make sure
855 * we can't deadlock. Otherwise just return to avoid the
856 * recursion and return - but flag the recursion so that
857 * it can be printed at the next appropriate moment:
858 */
859 if (!oops_in_progress) {
860 recursion_bug = 1;
861 goto out_restore_irqs;
862 }
863 zap_locks();
864 }
865
866 lockdep_off();
867 spin_lock(&logbuf_lock);
868 printk_cpu = this_cpu;
869
870 if (recursion_bug) {
871 recursion_bug = 0;
872 strcpy(printk_buf, recursion_bug_msg);
873 printed_len = strlen(recursion_bug_msg);
874 }
875 /* Emit the output into the temporary buffer */
876 printed_len += vscnprintf(printk_buf + printed_len,
877 sizeof(printk_buf) - printed_len, fmt, args);
878
879 p = printk_buf;
880
881 /* Read log level and handle special printk prefix */
882 plen = log_prefix(p, ¤t_log_level, &special);
883 if (plen) {
884 p += plen;
885
886 switch (special) {
887 case 'c': /* Strip <c> KERN_CONT, continue line */
888 plen = 0;
889 break;
890 case 'd': /* Strip <d> KERN_DEFAULT, start new line */
891 plen = 0;
892 default:
893 if (!new_text_line) {
894 emit_log_char('\n');
895 new_text_line = 1;
896 }
897 }
898 }
899
900 /*
901 * Copy the output into log_buf. If the caller didn't provide
902 * the appropriate log prefix, we insert them here
903 */
904 for (; *p; p++) {
905 if (new_text_line) {
906 new_text_line = 0;
907
908 if (plen) {
909 /* Copy original log prefix */
910 int i;
911
912 for (i = 0; i < plen; i++)
913 emit_log_char(printk_buf[i]);
914 printed_len += plen;
915 } else {
916 /* Add log prefix */
917 emit_log_char('<');
918 emit_log_char(current_log_level + '0');
919 emit_log_char('>');
920 printed_len += 3;
921 }
922
923 if (printk_time) {
924 /* Add the current time stamp */
925 char tbuf[50], *tp;
926 unsigned tlen;
927 unsigned long long t;
928 unsigned long nanosec_rem;
929
930 t = cpu_clock(printk_cpu);
931 nanosec_rem = do_div(t, 1000000000);
932 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
933 (unsigned long) t,
934 nanosec_rem / 1000);
935
936 for (tp = tbuf; tp < tbuf + tlen; tp++)
937 emit_log_char(*tp);
938 printed_len += tlen;
939 }
940
941 if (!*p)
942 break;
943 }
944
945 emit_log_char(*p);
946 if (*p == '\n')
947 new_text_line = 1;
948 }
949
950 /*
951 * Try to acquire and then immediately release the
952 * console semaphore. The release will do all the
953 * actual magic (print out buffers, wake up klogd,
954 * etc).
955 *
956 * The console_trylock_for_printk() function
957 * will release 'logbuf_lock' regardless of whether it
958 * actually gets the semaphore or not.
959 */
960 if (console_trylock_for_printk(this_cpu))
961 console_unlock();
962
963 lockdep_on();
964out_restore_irqs:
965 raw_local_irq_restore(flags);
966
967 preempt_enable();
968 return printed_len;
969}
970EXPORT_SYMBOL(printk);
971EXPORT_SYMBOL(vprintk);
972
973#else
974
975static void call_console_drivers(unsigned start, unsigned end)
976{
977}
978
979#endif
980
981static int __add_preferred_console(char *name, int idx, char *options,
982 char *brl_options)
983{
984 struct console_cmdline *c;
985 int i;
986
987 /*
988 * See if this tty is not yet registered, and
989 * if we have a slot free.
990 */
991 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
992 if (strcmp(console_cmdline[i].name, name) == 0 &&
993 console_cmdline[i].index == idx) {
994 if (!brl_options)
995 selected_console = i;
996 return 0;
997 }
998 if (i == MAX_CMDLINECONSOLES)
999 return -E2BIG;
1000 if (!brl_options)
1001 selected_console = i;
1002 c = &console_cmdline[i];
1003 strlcpy(c->name, name, sizeof(c->name));
1004 c->options = options;
1005#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1006 c->brl_options = brl_options;
1007#endif
1008 c->index = idx;
1009 return 0;
1010}
1011/*
1012 * Set up a list of consoles. Called from init/main.c
1013 */
1014static int __init console_setup(char *str)
1015{
1016 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
1017 char *s, *options, *brl_options = NULL;
1018 int idx;
1019
1020#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1021 if (!memcmp(str, "brl,", 4)) {
1022 brl_options = "";
1023 str += 4;
1024 } else if (!memcmp(str, "brl=", 4)) {
1025 brl_options = str + 4;
1026 str = strchr(brl_options, ',');
1027 if (!str) {
1028 printk(KERN_ERR "need port name after brl=\n");
1029 return 1;
1030 }
1031 *(str++) = 0;
1032 }
1033#endif
1034
1035 /*
1036 * Decode str into name, index, options.
1037 */
1038 if (str[0] >= '0' && str[0] <= '9') {
1039 strcpy(buf, "ttyS");
1040 strncpy(buf + 4, str, sizeof(buf) - 5);
1041 } else {
1042 strncpy(buf, str, sizeof(buf) - 1);
1043 }
1044 buf[sizeof(buf) - 1] = 0;
1045 if ((options = strchr(str, ',')) != NULL)
1046 *(options++) = 0;
1047#ifdef __sparc__
1048 if (!strcmp(str, "ttya"))
1049 strcpy(buf, "ttyS0");
1050 if (!strcmp(str, "ttyb"))
1051 strcpy(buf, "ttyS1");
1052#endif
1053 for (s = buf; *s; s++)
1054 if ((*s >= '0' && *s <= '9') || *s == ',')
1055 break;
1056 idx = simple_strtoul(s, NULL, 10);
1057 *s = 0;
1058
1059 __add_preferred_console(buf, idx, options, brl_options);
1060 console_set_on_cmdline = 1;
1061 return 1;
1062}
1063__setup("console=", console_setup);
1064
1065/**
1066 * add_preferred_console - add a device to the list of preferred consoles.
1067 * @name: device name
1068 * @idx: device index
1069 * @options: options for this console
1070 *
1071 * The last preferred console added will be used for kernel messages
1072 * and stdin/out/err for init. Normally this is used by console_setup
1073 * above to handle user-supplied console arguments; however it can also
1074 * be used by arch-specific code either to override the user or more
1075 * commonly to provide a default console (ie from PROM variables) when
1076 * the user has not supplied one.
1077 */
1078int add_preferred_console(char *name, int idx, char *options)
1079{
1080 return __add_preferred_console(name, idx, options, NULL);
1081}
1082
1083int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
1084{
1085 struct console_cmdline *c;
1086 int i;
1087
1088 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
1089 if (strcmp(console_cmdline[i].name, name) == 0 &&
1090 console_cmdline[i].index == idx) {
1091 c = &console_cmdline[i];
1092 strlcpy(c->name, name_new, sizeof(c->name));
1093 c->name[sizeof(c->name) - 1] = 0;
1094 c->options = options;
1095 c->index = idx_new;
1096 return i;
1097 }
1098 /* not found */
1099 return -1;
1100}
1101
1102int console_suspend_enabled = 1;
1103EXPORT_SYMBOL(console_suspend_enabled);
1104
1105static int __init console_suspend_disable(char *str)
1106{
1107 console_suspend_enabled = 0;
1108 return 1;
1109}
1110__setup("no_console_suspend", console_suspend_disable);
1111
1112/**
1113 * suspend_console - suspend the console subsystem
1114 *
1115 * This disables printk() while we go into suspend states
1116 */
1117void suspend_console(void)
1118{
1119 if (!console_suspend_enabled)
1120 return;
1121 printk("Suspending console(s) (use no_console_suspend to debug)\n");
1122 console_lock();
1123 console_suspended = 1;
1124 up(&console_sem);
1125}
1126
1127void resume_console(void)
1128{
1129 if (!console_suspend_enabled)
1130 return;
1131 down(&console_sem);
1132 console_suspended = 0;
1133 console_unlock();
1134}
1135
1136/**
1137 * console_cpu_notify - print deferred console messages after CPU hotplug
1138 * @self: notifier struct
1139 * @action: CPU hotplug event
1140 * @hcpu: unused
1141 *
1142 * If printk() is called from a CPU that is not online yet, the messages
1143 * will be spooled but will not show up on the console. This function is
1144 * called when a new CPU comes online (or fails to come up), and ensures
1145 * that any such output gets printed.
1146 */
1147static int __cpuinit console_cpu_notify(struct notifier_block *self,
1148 unsigned long action, void *hcpu)
1149{
1150 switch (action) {
1151 case CPU_ONLINE:
1152 case CPU_DEAD:
1153 case CPU_DYING:
1154 case CPU_DOWN_FAILED:
1155 case CPU_UP_CANCELED:
1156 console_lock();
1157 console_unlock();
1158 }
1159 return NOTIFY_OK;
1160}
1161
1162/**
1163 * console_lock - lock the console system for exclusive use.
1164 *
1165 * Acquires a lock which guarantees that the caller has
1166 * exclusive access to the console system and the console_drivers list.
1167 *
1168 * Can sleep, returns nothing.
1169 */
1170void console_lock(void)
1171{
1172 BUG_ON(in_interrupt());
1173 down(&console_sem);
1174 if (console_suspended)
1175 return;
1176 console_locked = 1;
1177 console_may_schedule = 1;
1178}
1179EXPORT_SYMBOL(console_lock);
1180
1181/**
1182 * console_trylock - try to lock the console system for exclusive use.
1183 *
1184 * Tried to acquire a lock which guarantees that the caller has
1185 * exclusive access to the console system and the console_drivers list.
1186 *
1187 * returns 1 on success, and 0 on failure to acquire the lock.
1188 */
1189int console_trylock(void)
1190{
1191 if (down_trylock(&console_sem))
1192 return 0;
1193 if (console_suspended) {
1194 up(&console_sem);
1195 return 0;
1196 }
1197 console_locked = 1;
1198 console_may_schedule = 0;
1199 return 1;
1200}
1201EXPORT_SYMBOL(console_trylock);
1202
1203int is_console_locked(void)
1204{
1205 return console_locked;
1206}
1207
1208static DEFINE_PER_CPU(int, printk_pending);
1209
1210void printk_tick(void)
1211{
1212 if (__this_cpu_read(printk_pending)) {
1213 __this_cpu_write(printk_pending, 0);
1214 wake_up_interruptible(&log_wait);
1215 }
1216}
1217
1218int printk_needs_cpu(int cpu)
1219{
1220 if (cpu_is_offline(cpu))
1221 printk_tick();
1222 return __this_cpu_read(printk_pending);
1223}
1224
1225void wake_up_klogd(void)
1226{
1227 if (waitqueue_active(&log_wait))
1228 this_cpu_write(printk_pending, 1);
1229}
1230
1231/**
1232 * console_unlock - unlock the console system
1233 *
1234 * Releases the console_lock which the caller holds on the console system
1235 * and the console driver list.
1236 *
1237 * While the console_lock was held, console output may have been buffered
1238 * by printk(). If this is the case, console_unlock(); emits
1239 * the output prior to releasing the lock.
1240 *
1241 * If there is output waiting for klogd, we wake it up.
1242 *
1243 * console_unlock(); may be called from any context.
1244 */
1245void console_unlock(void)
1246{
1247 unsigned long flags;
1248 unsigned _con_start, _log_end;
1249 unsigned wake_klogd = 0, retry = 0;
1250
1251 if (console_suspended) {
1252 up(&console_sem);
1253 return;
1254 }
1255
1256 console_may_schedule = 0;
1257
1258again:
1259 for ( ; ; ) {
1260 spin_lock_irqsave(&logbuf_lock, flags);
1261 wake_klogd |= log_start - log_end;
1262 if (con_start == log_end)
1263 break; /* Nothing to print */
1264 _con_start = con_start;
1265 _log_end = log_end;
1266 con_start = log_end; /* Flush */
1267 spin_unlock(&logbuf_lock);
1268 stop_critical_timings(); /* don't trace print latency */
1269 call_console_drivers(_con_start, _log_end);
1270 start_critical_timings();
1271 local_irq_restore(flags);
1272 }
1273 console_locked = 0;
1274
1275 /* Release the exclusive_console once it is used */
1276 if (unlikely(exclusive_console))
1277 exclusive_console = NULL;
1278
1279 spin_unlock(&logbuf_lock);
1280
1281 up(&console_sem);
1282
1283 /*
1284 * Someone could have filled up the buffer again, so re-check if there's
1285 * something to flush. In case we cannot trylock the console_sem again,
1286 * there's a new owner and the console_unlock() from them will do the
1287 * flush, no worries.
1288 */
1289 spin_lock(&logbuf_lock);
1290 if (con_start != log_end)
1291 retry = 1;
1292 spin_unlock_irqrestore(&logbuf_lock, flags);
1293 if (retry && console_trylock())
1294 goto again;
1295
1296 if (wake_klogd)
1297 wake_up_klogd();
1298}
1299EXPORT_SYMBOL(console_unlock);
1300
1301/**
1302 * console_conditional_schedule - yield the CPU if required
1303 *
1304 * If the console code is currently allowed to sleep, and
1305 * if this CPU should yield the CPU to another task, do
1306 * so here.
1307 *
1308 * Must be called within console_lock();.
1309 */
1310void __sched console_conditional_schedule(void)
1311{
1312 if (console_may_schedule)
1313 cond_resched();
1314}
1315EXPORT_SYMBOL(console_conditional_schedule);
1316
1317void console_unblank(void)
1318{
1319 struct console *c;
1320
1321 /*
1322 * console_unblank can no longer be called in interrupt context unless
1323 * oops_in_progress is set to 1..
1324 */
1325 if (oops_in_progress) {
1326 if (down_trylock(&console_sem) != 0)
1327 return;
1328 } else
1329 console_lock();
1330
1331 console_locked = 1;
1332 console_may_schedule = 0;
1333 for_each_console(c)
1334 if ((c->flags & CON_ENABLED) && c->unblank)
1335 c->unblank();
1336 console_unlock();
1337}
1338
1339/*
1340 * Return the console tty driver structure and its associated index
1341 */
1342struct tty_driver *console_device(int *index)
1343{
1344 struct console *c;
1345 struct tty_driver *driver = NULL;
1346
1347 console_lock();
1348 for_each_console(c) {
1349 if (!c->device)
1350 continue;
1351 driver = c->device(c, index);
1352 if (driver)
1353 break;
1354 }
1355 console_unlock();
1356 return driver;
1357}
1358
1359/*
1360 * Prevent further output on the passed console device so that (for example)
1361 * serial drivers can disable console output before suspending a port, and can
1362 * re-enable output afterwards.
1363 */
1364void console_stop(struct console *console)
1365{
1366 console_lock();
1367 console->flags &= ~CON_ENABLED;
1368 console_unlock();
1369}
1370EXPORT_SYMBOL(console_stop);
1371
1372void console_start(struct console *console)
1373{
1374 console_lock();
1375 console->flags |= CON_ENABLED;
1376 console_unlock();
1377}
1378EXPORT_SYMBOL(console_start);
1379
1380static int __read_mostly keep_bootcon;
1381
1382static int __init keep_bootcon_setup(char *str)
1383{
1384 keep_bootcon = 1;
1385 printk(KERN_INFO "debug: skip boot console de-registration.\n");
1386
1387 return 0;
1388}
1389
1390early_param("keep_bootcon", keep_bootcon_setup);
1391
1392/*
1393 * The console driver calls this routine during kernel initialization
1394 * to register the console printing procedure with printk() and to
1395 * print any messages that were printed by the kernel before the
1396 * console driver was initialized.
1397 *
1398 * This can happen pretty early during the boot process (because of
1399 * early_printk) - sometimes before setup_arch() completes - be careful
1400 * of what kernel features are used - they may not be initialised yet.
1401 *
1402 * There are two types of consoles - bootconsoles (early_printk) and
1403 * "real" consoles (everything which is not a bootconsole) which are
1404 * handled differently.
1405 * - Any number of bootconsoles can be registered at any time.
1406 * - As soon as a "real" console is registered, all bootconsoles
1407 * will be unregistered automatically.
1408 * - Once a "real" console is registered, any attempt to register a
1409 * bootconsoles will be rejected
1410 */
1411void register_console(struct console *newcon)
1412{
1413 int i;
1414 unsigned long flags;
1415 struct console *bcon = NULL;
1416
1417 /*
1418 * before we register a new CON_BOOT console, make sure we don't
1419 * already have a valid console
1420 */
1421 if (console_drivers && newcon->flags & CON_BOOT) {
1422 /* find the last or real console */
1423 for_each_console(bcon) {
1424 if (!(bcon->flags & CON_BOOT)) {
1425 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1426 newcon->name, newcon->index);
1427 return;
1428 }
1429 }
1430 }
1431
1432 if (console_drivers && console_drivers->flags & CON_BOOT)
1433 bcon = console_drivers;
1434
1435 if (preferred_console < 0 || bcon || !console_drivers)
1436 preferred_console = selected_console;
1437
1438 if (newcon->early_setup)
1439 newcon->early_setup();
1440
1441 /*
1442 * See if we want to use this console driver. If we
1443 * didn't select a console we take the first one
1444 * that registers here.
1445 */
1446 if (preferred_console < 0) {
1447 if (newcon->index < 0)
1448 newcon->index = 0;
1449 if (newcon->setup == NULL ||
1450 newcon->setup(newcon, NULL) == 0) {
1451 newcon->flags |= CON_ENABLED;
1452 if (newcon->device) {
1453 newcon->flags |= CON_CONSDEV;
1454 preferred_console = 0;
1455 }
1456 }
1457 }
1458
1459 /*
1460 * See if this console matches one we selected on
1461 * the command line.
1462 */
1463 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1464 i++) {
1465 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1466 continue;
1467 if (newcon->index >= 0 &&
1468 newcon->index != console_cmdline[i].index)
1469 continue;
1470 if (newcon->index < 0)
1471 newcon->index = console_cmdline[i].index;
1472#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1473 if (console_cmdline[i].brl_options) {
1474 newcon->flags |= CON_BRL;
1475 braille_register_console(newcon,
1476 console_cmdline[i].index,
1477 console_cmdline[i].options,
1478 console_cmdline[i].brl_options);
1479 return;
1480 }
1481#endif
1482 if (newcon->setup &&
1483 newcon->setup(newcon, console_cmdline[i].options) != 0)
1484 break;
1485 newcon->flags |= CON_ENABLED;
1486 newcon->index = console_cmdline[i].index;
1487 if (i == selected_console) {
1488 newcon->flags |= CON_CONSDEV;
1489 preferred_console = selected_console;
1490 }
1491 break;
1492 }
1493
1494 if (!(newcon->flags & CON_ENABLED))
1495 return;
1496
1497 /*
1498 * If we have a bootconsole, and are switching to a real console,
1499 * don't print everything out again, since when the boot console, and
1500 * the real console are the same physical device, it's annoying to
1501 * see the beginning boot messages twice
1502 */
1503 if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1504 newcon->flags &= ~CON_PRINTBUFFER;
1505
1506 /*
1507 * Put this console in the list - keep the
1508 * preferred driver at the head of the list.
1509 */
1510 console_lock();
1511 if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1512 newcon->next = console_drivers;
1513 console_drivers = newcon;
1514 if (newcon->next)
1515 newcon->next->flags &= ~CON_CONSDEV;
1516 } else {
1517 newcon->next = console_drivers->next;
1518 console_drivers->next = newcon;
1519 }
1520 if (newcon->flags & CON_PRINTBUFFER) {
1521 /*
1522 * console_unlock(); will print out the buffered messages
1523 * for us.
1524 */
1525 spin_lock_irqsave(&logbuf_lock, flags);
1526 con_start = log_start;
1527 spin_unlock_irqrestore(&logbuf_lock, flags);
1528 /*
1529 * We're about to replay the log buffer. Only do this to the
1530 * just-registered console to avoid excessive message spam to
1531 * the already-registered consoles.
1532 */
1533 exclusive_console = newcon;
1534 }
1535 console_unlock();
1536 console_sysfs_notify();
1537
1538 /*
1539 * By unregistering the bootconsoles after we enable the real console
1540 * we get the "console xxx enabled" message on all the consoles -
1541 * boot consoles, real consoles, etc - this is to ensure that end
1542 * users know there might be something in the kernel's log buffer that
1543 * went to the bootconsole (that they do not see on the real console)
1544 */
1545 if (bcon &&
1546 ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
1547 !keep_bootcon) {
1548 /* we need to iterate through twice, to make sure we print
1549 * everything out, before we unregister the console(s)
1550 */
1551 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1552 newcon->name, newcon->index);
1553 for_each_console(bcon)
1554 if (bcon->flags & CON_BOOT)
1555 unregister_console(bcon);
1556 } else {
1557 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1558 (newcon->flags & CON_BOOT) ? "boot" : "" ,
1559 newcon->name, newcon->index);
1560 }
1561}
1562EXPORT_SYMBOL(register_console);
1563
1564int unregister_console(struct console *console)
1565{
1566 struct console *a, *b;
1567 int res = 1;
1568
1569#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1570 if (console->flags & CON_BRL)
1571 return braille_unregister_console(console);
1572#endif
1573
1574 console_lock();
1575 if (console_drivers == console) {
1576 console_drivers=console->next;
1577 res = 0;
1578 } else if (console_drivers) {
1579 for (a=console_drivers->next, b=console_drivers ;
1580 a; b=a, a=b->next) {
1581 if (a == console) {
1582 b->next = a->next;
1583 res = 0;
1584 break;
1585 }
1586 }
1587 }
1588
1589 /*
1590 * If this isn't the last console and it has CON_CONSDEV set, we
1591 * need to set it on the next preferred console.
1592 */
1593 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1594 console_drivers->flags |= CON_CONSDEV;
1595
1596 console_unlock();
1597 console_sysfs_notify();
1598 return res;
1599}
1600EXPORT_SYMBOL(unregister_console);
1601
1602static int __init printk_late_init(void)
1603{
1604 struct console *con;
1605
1606 for_each_console(con) {
1607 if (!keep_bootcon && con->flags & CON_BOOT) {
1608 printk(KERN_INFO "turn off boot console %s%d\n",
1609 con->name, con->index);
1610 unregister_console(con);
1611 }
1612 }
1613 hotcpu_notifier(console_cpu_notify, 0);
1614 return 0;
1615}
1616late_initcall(printk_late_init);
1617
1618#if defined CONFIG_PRINTK
1619
1620/*
1621 * printk rate limiting, lifted from the networking subsystem.
1622 *
1623 * This enforces a rate limit: not more than 10 kernel messages
1624 * every 5s to make a denial-of-service attack impossible.
1625 */
1626DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1627
1628int __printk_ratelimit(const char *func)
1629{
1630 return ___ratelimit(&printk_ratelimit_state, func);
1631}
1632EXPORT_SYMBOL(__printk_ratelimit);
1633
1634/**
1635 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1636 * @caller_jiffies: pointer to caller's state
1637 * @interval_msecs: minimum interval between prints
1638 *
1639 * printk_timed_ratelimit() returns true if more than @interval_msecs
1640 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1641 * returned true.
1642 */
1643bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1644 unsigned int interval_msecs)
1645{
1646 if (*caller_jiffies == 0
1647 || !time_in_range(jiffies, *caller_jiffies,
1648 *caller_jiffies
1649 + msecs_to_jiffies(interval_msecs))) {
1650 *caller_jiffies = jiffies;
1651 return true;
1652 }
1653 return false;
1654}
1655EXPORT_SYMBOL(printk_timed_ratelimit);
1656
1657static DEFINE_SPINLOCK(dump_list_lock);
1658static LIST_HEAD(dump_list);
1659
1660/**
1661 * kmsg_dump_register - register a kernel log dumper.
1662 * @dumper: pointer to the kmsg_dumper structure
1663 *
1664 * Adds a kernel log dumper to the system. The dump callback in the
1665 * structure will be called when the kernel oopses or panics and must be
1666 * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1667 */
1668int kmsg_dump_register(struct kmsg_dumper *dumper)
1669{
1670 unsigned long flags;
1671 int err = -EBUSY;
1672
1673 /* The dump callback needs to be set */
1674 if (!dumper->dump)
1675 return -EINVAL;
1676
1677 spin_lock_irqsave(&dump_list_lock, flags);
1678 /* Don't allow registering multiple times */
1679 if (!dumper->registered) {
1680 dumper->registered = 1;
1681 list_add_tail_rcu(&dumper->list, &dump_list);
1682 err = 0;
1683 }
1684 spin_unlock_irqrestore(&dump_list_lock, flags);
1685
1686 return err;
1687}
1688EXPORT_SYMBOL_GPL(kmsg_dump_register);
1689
1690/**
1691 * kmsg_dump_unregister - unregister a kmsg dumper.
1692 * @dumper: pointer to the kmsg_dumper structure
1693 *
1694 * Removes a dump device from the system. Returns zero on success and
1695 * %-EINVAL otherwise.
1696 */
1697int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1698{
1699 unsigned long flags;
1700 int err = -EINVAL;
1701
1702 spin_lock_irqsave(&dump_list_lock, flags);
1703 if (dumper->registered) {
1704 dumper->registered = 0;
1705 list_del_rcu(&dumper->list);
1706 err = 0;
1707 }
1708 spin_unlock_irqrestore(&dump_list_lock, flags);
1709 synchronize_rcu();
1710
1711 return err;
1712}
1713EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1714
1715/**
1716 * kmsg_dump - dump kernel log to kernel message dumpers.
1717 * @reason: the reason (oops, panic etc) for dumping
1718 *
1719 * Iterate through each of the dump devices and call the oops/panic
1720 * callbacks with the log buffer.
1721 */
1722void kmsg_dump(enum kmsg_dump_reason reason)
1723{
1724 unsigned long end;
1725 unsigned chars;
1726 struct kmsg_dumper *dumper;
1727 const char *s1, *s2;
1728 unsigned long l1, l2;
1729 unsigned long flags;
1730
1731 /* Theoretically, the log could move on after we do this, but
1732 there's not a lot we can do about that. The new messages
1733 will overwrite the start of what we dump. */
1734 spin_lock_irqsave(&logbuf_lock, flags);
1735 end = log_end & LOG_BUF_MASK;
1736 chars = logged_chars;
1737 spin_unlock_irqrestore(&logbuf_lock, flags);
1738
1739 if (chars > end) {
1740 s1 = log_buf + log_buf_len - chars + end;
1741 l1 = chars - end;
1742
1743 s2 = log_buf;
1744 l2 = end;
1745 } else {
1746 s1 = "";
1747 l1 = 0;
1748
1749 s2 = log_buf + end - chars;
1750 l2 = chars;
1751 }
1752
1753 rcu_read_lock();
1754 list_for_each_entry_rcu(dumper, &dump_list, list)
1755 dumper->dump(dumper, reason, s1, l1, s2, l2);
1756 rcu_read_unlock();
1757}
1758#endif