9213b8b5bb4fe4affb913b40d48b0e2c2af0d0e2
[linux-2.6.git] / kernel / printk.c
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/syscalls.h>
35 #include <linux/kexec.h>
36 #include <linux/ratelimit.h>
37 #include <linux/kmsg_dump.h>
38 #include <linux/syslog.h>
39
40 #include <asm/uaccess.h>
41
42 /*
43  * for_each_console() allows you to iterate on each console
44  */
45 #define for_each_console(con) \
46         for (con = console_drivers; con != NULL; con = con->next)
47
48 /*
49  * Architectures can override it:
50  */
51 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
52 {
53 }
54
55 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
56
57 /* printk's without a loglevel use this.. */
58 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
59
60 /* We show everything that is MORE important than this.. */
61 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
62 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
63
64 DECLARE_WAIT_QUEUE_HEAD(log_wait);
65
66 int console_printk[4] = {
67         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
68         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
69         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
70         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
71 };
72
73 /*
74  * Low level drivers may need that to know if they can schedule in
75  * their unblank() callback or not. So let's export it.
76  */
77 int oops_in_progress;
78 EXPORT_SYMBOL(oops_in_progress);
79
80 /*
81  * console_sem protects the console_drivers list, and also
82  * provides serialisation for access to the entire console
83  * driver system.
84  */
85 static DECLARE_MUTEX(console_sem);
86 struct console *console_drivers;
87 EXPORT_SYMBOL_GPL(console_drivers);
88
89 /*
90  * This is used for debugging the mess that is the VT code by
91  * keeping track if we have the console semaphore held. It's
92  * definitely not the perfect debug tool (we don't know if _WE_
93  * hold it are racing, but it helps tracking those weird code
94  * path in the console code where we end up in places I want
95  * locked without the console sempahore held
96  */
97 static int console_locked, console_suspended;
98
99 /*
100  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
101  * It is also used in interesting ways to provide interlocking in
102  * release_console_sem().
103  */
104 static DEFINE_SPINLOCK(logbuf_lock);
105
106 #define LOG_BUF_MASK (log_buf_len-1)
107 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
108
109 /*
110  * The indices into log_buf are not constrained to log_buf_len - they
111  * must be masked before subscripting
112  */
113 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
114 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
115 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
116
117 /*
118  *      Array of consoles built from command line options (console=)
119  */
120 struct console_cmdline
121 {
122         char    name[8];                        /* Name of the driver       */
123         int     index;                          /* Minor dev. to use        */
124         char    *options;                       /* Options for the driver   */
125 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
126         char    *brl_options;                   /* Options for braille driver */
127 #endif
128 };
129
130 #define MAX_CMDLINECONSOLES 8
131
132 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
133 static int selected_console = -1;
134 static int preferred_console = -1;
135 int console_set_on_cmdline;
136 EXPORT_SYMBOL(console_set_on_cmdline);
137
138 /* Flag: console code may call schedule() */
139 static int console_may_schedule;
140
141 #ifdef CONFIG_PRINTK
142
143 static char __log_buf[__LOG_BUF_LEN];
144 static char *log_buf = __log_buf;
145 static int log_buf_len = __LOG_BUF_LEN;
146 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
147 static int saved_console_loglevel = -1;
148
149 #ifdef CONFIG_KEXEC
150 /*
151  * This appends the listed symbols to /proc/vmcoreinfo
152  *
153  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
154  * obtain access to symbols that are otherwise very difficult to locate.  These
155  * symbols are specifically used so that utilities can access and extract the
156  * dmesg log from a vmcore file after a crash.
157  */
158 void log_buf_kexec_setup(void)
159 {
160         VMCOREINFO_SYMBOL(log_buf);
161         VMCOREINFO_SYMBOL(log_end);
162         VMCOREINFO_SYMBOL(log_buf_len);
163         VMCOREINFO_SYMBOL(logged_chars);
164 }
165 #endif
166
167 static int __init log_buf_len_setup(char *str)
168 {
169         unsigned size = memparse(str, &str);
170         unsigned long flags;
171
172         if (size)
173                 size = roundup_pow_of_two(size);
174         if (size > log_buf_len) {
175                 unsigned start, dest_idx, offset;
176                 char *new_log_buf;
177
178                 new_log_buf = alloc_bootmem(size);
179                 if (!new_log_buf) {
180                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
181                         goto out;
182                 }
183
184                 spin_lock_irqsave(&logbuf_lock, flags);
185                 log_buf_len = size;
186                 log_buf = new_log_buf;
187
188                 offset = start = min(con_start, log_start);
189                 dest_idx = 0;
190                 while (start != log_end) {
191                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
192                         start++;
193                         dest_idx++;
194                 }
195                 log_start -= offset;
196                 con_start -= offset;
197                 log_end -= offset;
198                 spin_unlock_irqrestore(&logbuf_lock, flags);
199
200                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
201         }
202 out:
203         return 1;
204 }
205
206 __setup("log_buf_len=", log_buf_len_setup);
207
208 #ifdef CONFIG_BOOT_PRINTK_DELAY
209
210 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
211 static unsigned long long loops_per_msec;       /* based on boot_delay */
212
213 static int __init boot_delay_setup(char *str)
214 {
215         unsigned long lpj;
216
217         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
218         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
219
220         get_option(&str, &boot_delay);
221         if (boot_delay > 10 * 1000)
222                 boot_delay = 0;
223
224         pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
225                 "HZ: %d, loops_per_msec: %llu\n",
226                 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
227         return 1;
228 }
229 __setup("boot_delay=", boot_delay_setup);
230
231 static void boot_delay_msec(void)
232 {
233         unsigned long long k;
234         unsigned long timeout;
235
236         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
237                 return;
238
239         k = (unsigned long long)loops_per_msec * boot_delay;
240
241         timeout = jiffies + msecs_to_jiffies(boot_delay);
242         while (k) {
243                 k--;
244                 cpu_relax();
245                 /*
246                  * use (volatile) jiffies to prevent
247                  * compiler reduction; loop termination via jiffies
248                  * is secondary and may or may not happen.
249                  */
250                 if (time_after(jiffies, timeout))
251                         break;
252                 touch_nmi_watchdog();
253         }
254 }
255 #else
256 static inline void boot_delay_msec(void)
257 {
258 }
259 #endif
260
261 int do_syslog(int type, char __user *buf, int len, bool from_file)
262 {
263         unsigned i, j, limit, count;
264         int do_clear = 0;
265         char c;
266         int error = 0;
267
268         error = security_syslog(type, from_file);
269         if (error)
270                 return error;
271
272         switch (type) {
273         case SYSLOG_ACTION_CLOSE:       /* Close log */
274                 break;
275         case SYSLOG_ACTION_OPEN:        /* Open log */
276                 break;
277         case SYSLOG_ACTION_READ:        /* Read from log */
278                 error = -EINVAL;
279                 if (!buf || len < 0)
280                         goto out;
281                 error = 0;
282                 if (!len)
283                         goto out;
284                 if (!access_ok(VERIFY_WRITE, buf, len)) {
285                         error = -EFAULT;
286                         goto out;
287                 }
288                 error = wait_event_interruptible(log_wait,
289                                                         (log_start - log_end));
290                 if (error)
291                         goto out;
292                 i = 0;
293                 spin_lock_irq(&logbuf_lock);
294                 while (!error && (log_start != log_end) && i < len) {
295                         c = LOG_BUF(log_start);
296                         log_start++;
297                         spin_unlock_irq(&logbuf_lock);
298                         error = __put_user(c,buf);
299                         buf++;
300                         i++;
301                         cond_resched();
302                         spin_lock_irq(&logbuf_lock);
303                 }
304                 spin_unlock_irq(&logbuf_lock);
305                 if (!error)
306                         error = i;
307                 break;
308         /* Read/clear last kernel messages */
309         case SYSLOG_ACTION_READ_CLEAR:
310                 do_clear = 1;
311                 /* FALL THRU */
312         /* Read last kernel messages */
313         case SYSLOG_ACTION_READ_ALL:
314                 error = -EINVAL;
315                 if (!buf || len < 0)
316                         goto out;
317                 error = 0;
318                 if (!len)
319                         goto out;
320                 if (!access_ok(VERIFY_WRITE, buf, len)) {
321                         error = -EFAULT;
322                         goto out;
323                 }
324                 count = len;
325                 if (count > log_buf_len)
326                         count = log_buf_len;
327                 spin_lock_irq(&logbuf_lock);
328                 if (count > logged_chars)
329                         count = logged_chars;
330                 if (do_clear)
331                         logged_chars = 0;
332                 limit = log_end;
333                 /*
334                  * __put_user() could sleep, and while we sleep
335                  * printk() could overwrite the messages
336                  * we try to copy to user space. Therefore
337                  * the messages are copied in reverse. <manfreds>
338                  */
339                 for (i = 0; i < count && !error; i++) {
340                         j = limit-1-i;
341                         if (j + log_buf_len < log_end)
342                                 break;
343                         c = LOG_BUF(j);
344                         spin_unlock_irq(&logbuf_lock);
345                         error = __put_user(c,&buf[count-1-i]);
346                         cond_resched();
347                         spin_lock_irq(&logbuf_lock);
348                 }
349                 spin_unlock_irq(&logbuf_lock);
350                 if (error)
351                         break;
352                 error = i;
353                 if (i != count) {
354                         int offset = count-error;
355                         /* buffer overflow during copy, correct user buffer. */
356                         for (i = 0; i < error; i++) {
357                                 if (__get_user(c,&buf[i+offset]) ||
358                                     __put_user(c,&buf[i])) {
359                                         error = -EFAULT;
360                                         break;
361                                 }
362                                 cond_resched();
363                         }
364                 }
365                 break;
366         /* Clear ring buffer */
367         case SYSLOG_ACTION_CLEAR:
368                 logged_chars = 0;
369                 break;
370         /* Disable logging to console */
371         case SYSLOG_ACTION_CONSOLE_OFF:
372                 if (saved_console_loglevel == -1)
373                         saved_console_loglevel = console_loglevel;
374                 console_loglevel = minimum_console_loglevel;
375                 break;
376         /* Enable logging to console */
377         case SYSLOG_ACTION_CONSOLE_ON:
378                 if (saved_console_loglevel != -1) {
379                         console_loglevel = saved_console_loglevel;
380                         saved_console_loglevel = -1;
381                 }
382                 break;
383         /* Set level of messages printed to console */
384         case SYSLOG_ACTION_CONSOLE_LEVEL:
385                 error = -EINVAL;
386                 if (len < 1 || len > 8)
387                         goto out;
388                 if (len < minimum_console_loglevel)
389                         len = minimum_console_loglevel;
390                 console_loglevel = len;
391                 /* Implicitly re-enable logging to console */
392                 saved_console_loglevel = -1;
393                 error = 0;
394                 break;
395         /* Number of chars in the log buffer */
396         case SYSLOG_ACTION_SIZE_UNREAD:
397                 error = log_end - log_start;
398                 break;
399         /* Size of the log buffer */
400         case SYSLOG_ACTION_SIZE_BUFFER:
401                 error = log_buf_len;
402                 break;
403         default:
404                 error = -EINVAL;
405                 break;
406         }
407 out:
408         return error;
409 }
410
411 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
412 {
413         return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
414 }
415
416 #ifdef  CONFIG_KGDB_KDB
417 /* kdb dmesg command needs access to the syslog buffer.  do_syslog()
418  * uses locks so it cannot be used during debugging.  Just tell kdb
419  * where the start and end of the physical and logical logs are.  This
420  * is equivalent to do_syslog(3).
421  */
422 void kdb_syslog_data(char *syslog_data[4])
423 {
424         syslog_data[0] = log_buf;
425         syslog_data[1] = log_buf + log_buf_len;
426         syslog_data[2] = log_buf + log_end -
427                 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
428         syslog_data[3] = log_buf + log_end;
429 }
430 #endif  /* CONFIG_KGDB_KDB */
431
432 /*
433  * Call the console drivers on a range of log_buf
434  */
435 static void __call_console_drivers(unsigned start, unsigned end)
436 {
437         struct console *con;
438
439         for_each_console(con) {
440                 if ((con->flags & CON_ENABLED) && con->write &&
441                                 (cpu_online(smp_processor_id()) ||
442                                 (con->flags & CON_ANYTIME)))
443                         con->write(con, &LOG_BUF(start), end - start);
444         }
445 }
446
447 static int __read_mostly ignore_loglevel;
448
449 static int __init ignore_loglevel_setup(char *str)
450 {
451         ignore_loglevel = 1;
452         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
453
454         return 0;
455 }
456
457 early_param("ignore_loglevel", ignore_loglevel_setup);
458
459 /*
460  * Write out chars from start to end - 1 inclusive
461  */
462 static void _call_console_drivers(unsigned start,
463                                 unsigned end, int msg_log_level)
464 {
465         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
466                         console_drivers && start != end) {
467                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
468                         /* wrapped write */
469                         __call_console_drivers(start & LOG_BUF_MASK,
470                                                 log_buf_len);
471                         __call_console_drivers(0, end & LOG_BUF_MASK);
472                 } else {
473                         __call_console_drivers(start, end);
474                 }
475         }
476 }
477
478 /*
479  * Call the console drivers, asking them to write out
480  * log_buf[start] to log_buf[end - 1].
481  * The console_sem must be held.
482  */
483 static void call_console_drivers(unsigned start, unsigned end)
484 {
485         unsigned cur_index, start_print;
486         static int msg_level = -1;
487
488         BUG_ON(((int)(start - end)) > 0);
489
490         cur_index = start;
491         start_print = start;
492         while (cur_index != end) {
493                 if (msg_level < 0 && ((end - cur_index) > 2) &&
494                                 LOG_BUF(cur_index + 0) == '<' &&
495                                 LOG_BUF(cur_index + 1) >= '0' &&
496                                 LOG_BUF(cur_index + 1) <= '7' &&
497                                 LOG_BUF(cur_index + 2) == '>') {
498                         msg_level = LOG_BUF(cur_index + 1) - '0';
499                         cur_index += 3;
500                         start_print = cur_index;
501                 }
502                 while (cur_index != end) {
503                         char c = LOG_BUF(cur_index);
504
505                         cur_index++;
506                         if (c == '\n') {
507                                 if (msg_level < 0) {
508                                         /*
509                                          * printk() has already given us loglevel tags in
510                                          * the buffer.  This code is here in case the
511                                          * log buffer has wrapped right round and scribbled
512                                          * on those tags
513                                          */
514                                         msg_level = default_message_loglevel;
515                                 }
516                                 _call_console_drivers(start_print, cur_index, msg_level);
517                                 msg_level = -1;
518                                 start_print = cur_index;
519                                 break;
520                         }
521                 }
522         }
523         _call_console_drivers(start_print, end, msg_level);
524 }
525
526 static void emit_log_char(char c)
527 {
528         LOG_BUF(log_end) = c;
529         log_end++;
530         if (log_end - log_start > log_buf_len)
531                 log_start = log_end - log_buf_len;
532         if (log_end - con_start > log_buf_len)
533                 con_start = log_end - log_buf_len;
534         if (logged_chars < log_buf_len)
535                 logged_chars++;
536 }
537
538 /*
539  * Zap console related locks when oopsing. Only zap at most once
540  * every 10 seconds, to leave time for slow consoles to print a
541  * full oops.
542  */
543 static void zap_locks(void)
544 {
545         static unsigned long oops_timestamp;
546
547         if (time_after_eq(jiffies, oops_timestamp) &&
548                         !time_after(jiffies, oops_timestamp + 30 * HZ))
549                 return;
550
551         oops_timestamp = jiffies;
552
553         /* If a crash is occurring, make sure we can't deadlock */
554         spin_lock_init(&logbuf_lock);
555         /* And make sure that we print immediately */
556         init_MUTEX(&console_sem);
557 }
558
559 #if defined(CONFIG_PRINTK_TIME)
560 static int printk_time = 1;
561 #else
562 static int printk_time = 0;
563 #endif
564 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
565
566 /* Check if we have any console registered that can be called early in boot. */
567 static int have_callable_console(void)
568 {
569         struct console *con;
570
571         for_each_console(con)
572                 if (con->flags & CON_ANYTIME)
573                         return 1;
574
575         return 0;
576 }
577
578 /**
579  * printk - print a kernel message
580  * @fmt: format string
581  *
582  * This is printk().  It can be called from any context.  We want it to work.
583  *
584  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
585  * call the console drivers.  If we fail to get the semaphore we place the output
586  * into the log buffer and return.  The current holder of the console_sem will
587  * notice the new output in release_console_sem() and will send it to the
588  * consoles before releasing the semaphore.
589  *
590  * One effect of this deferred printing is that code which calls printk() and
591  * then changes console_loglevel may break. This is because console_loglevel
592  * is inspected when the actual printing occurs.
593  *
594  * See also:
595  * printf(3)
596  *
597  * See the vsnprintf() documentation for format string extensions over C99.
598  */
599
600 asmlinkage int printk(const char *fmt, ...)
601 {
602         va_list args;
603         int r;
604
605         va_start(args, fmt);
606         r = vprintk(fmt, args);
607         va_end(args);
608
609         return r;
610 }
611
612 /* cpu currently holding logbuf_lock */
613 static volatile unsigned int printk_cpu = UINT_MAX;
614
615 /*
616  * Can we actually use the console at this time on this cpu?
617  *
618  * Console drivers may assume that per-cpu resources have
619  * been allocated. So unless they're explicitly marked as
620  * being able to cope (CON_ANYTIME) don't call them until
621  * this CPU is officially up.
622  */
623 static inline int can_use_console(unsigned int cpu)
624 {
625         return cpu_online(cpu) || have_callable_console();
626 }
627
628 /*
629  * Try to get console ownership to actually show the kernel
630  * messages from a 'printk'. Return true (and with the
631  * console_semaphore held, and 'console_locked' set) if it
632  * is successful, false otherwise.
633  *
634  * This gets called with the 'logbuf_lock' spinlock held and
635  * interrupts disabled. It should return with 'lockbuf_lock'
636  * released but interrupts still disabled.
637  */
638 static int acquire_console_semaphore_for_printk(unsigned int cpu)
639 {
640         int retval = 0;
641
642         if (!try_acquire_console_sem()) {
643                 retval = 1;
644
645                 /*
646                  * If we can't use the console, we need to release
647                  * the console semaphore by hand to avoid flushing
648                  * the buffer. We need to hold the console semaphore
649                  * in order to do this test safely.
650                  */
651                 if (!can_use_console(cpu)) {
652                         console_locked = 0;
653                         up(&console_sem);
654                         retval = 0;
655                 }
656         }
657         printk_cpu = UINT_MAX;
658         spin_unlock(&logbuf_lock);
659         return retval;
660 }
661 static const char recursion_bug_msg [] =
662                 KERN_CRIT "BUG: recent printk recursion!\n";
663 static int recursion_bug;
664 static int new_text_line = 1;
665 static char printk_buf[1024];
666
667 int printk_delay_msec __read_mostly;
668
669 static inline void printk_delay(void)
670 {
671         if (unlikely(printk_delay_msec)) {
672                 int m = printk_delay_msec;
673
674                 while (m--) {
675                         mdelay(1);
676                         touch_nmi_watchdog();
677                 }
678         }
679 }
680
681 asmlinkage int vprintk(const char *fmt, va_list args)
682 {
683         int printed_len = 0;
684         int current_log_level = default_message_loglevel;
685         unsigned long flags;
686         int this_cpu;
687         char *p;
688
689         boot_delay_msec();
690         printk_delay();
691
692         preempt_disable();
693         /* This stops the holder of console_sem just where we want him */
694         raw_local_irq_save(flags);
695         this_cpu = smp_processor_id();
696
697         /*
698          * Ouch, printk recursed into itself!
699          */
700         if (unlikely(printk_cpu == this_cpu)) {
701                 /*
702                  * If a crash is occurring during printk() on this CPU,
703                  * then try to get the crash message out but make sure
704                  * we can't deadlock. Otherwise just return to avoid the
705                  * recursion and return - but flag the recursion so that
706                  * it can be printed at the next appropriate moment:
707                  */
708                 if (!oops_in_progress) {
709                         recursion_bug = 1;
710                         goto out_restore_irqs;
711                 }
712                 zap_locks();
713         }
714
715         lockdep_off();
716         spin_lock(&logbuf_lock);
717         printk_cpu = this_cpu;
718
719         if (recursion_bug) {
720                 recursion_bug = 0;
721                 strcpy(printk_buf, recursion_bug_msg);
722                 printed_len = strlen(recursion_bug_msg);
723         }
724         /* Emit the output into the temporary buffer */
725         printed_len += vscnprintf(printk_buf + printed_len,
726                                   sizeof(printk_buf) - printed_len, fmt, args);
727
728
729         p = printk_buf;
730
731         /* Do we have a loglevel in the string? */
732         if (p[0] == '<') {
733                 unsigned char c = p[1];
734                 if (c && p[2] == '>') {
735                         switch (c) {
736                         case '0' ... '7': /* loglevel */
737                                 current_log_level = c - '0';
738                         /* Fallthrough - make sure we're on a new line */
739                         case 'd': /* KERN_DEFAULT */
740                                 if (!new_text_line) {
741                                         emit_log_char('\n');
742                                         new_text_line = 1;
743                                 }
744                         /* Fallthrough - skip the loglevel */
745                         case 'c': /* KERN_CONT */
746                                 p += 3;
747                                 break;
748                         }
749                 }
750         }
751
752         /*
753          * Copy the output into log_buf.  If the caller didn't provide
754          * appropriate log level tags, we insert them here
755          */
756         for ( ; *p; p++) {
757                 if (new_text_line) {
758                         /* Always output the token */
759                         emit_log_char('<');
760                         emit_log_char(current_log_level + '0');
761                         emit_log_char('>');
762                         printed_len += 3;
763                         new_text_line = 0;
764
765                         if (printk_time) {
766                                 /* Follow the token with the time */
767                                 char tbuf[50], *tp;
768                                 unsigned tlen;
769                                 unsigned long long t;
770                                 unsigned long nanosec_rem;
771
772                                 t = cpu_clock(printk_cpu);
773                                 nanosec_rem = do_div(t, 1000000000);
774                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
775                                                 (unsigned long) t,
776                                                 nanosec_rem / 1000);
777
778                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
779                                         emit_log_char(*tp);
780                                 printed_len += tlen;
781                         }
782
783                         if (!*p)
784                                 break;
785                 }
786
787                 emit_log_char(*p);
788                 if (*p == '\n')
789                         new_text_line = 1;
790         }
791
792         /*
793          * Try to acquire and then immediately release the
794          * console semaphore. The release will do all the
795          * actual magic (print out buffers, wake up klogd,
796          * etc). 
797          *
798          * The acquire_console_semaphore_for_printk() function
799          * will release 'logbuf_lock' regardless of whether it
800          * actually gets the semaphore or not.
801          */
802         if (acquire_console_semaphore_for_printk(this_cpu))
803                 release_console_sem();
804
805         lockdep_on();
806 out_restore_irqs:
807         raw_local_irq_restore(flags);
808
809         preempt_enable();
810         return printed_len;
811 }
812 EXPORT_SYMBOL(printk);
813 EXPORT_SYMBOL(vprintk);
814
815 #else
816
817 static void call_console_drivers(unsigned start, unsigned end)
818 {
819 }
820
821 #endif
822
823 static int __add_preferred_console(char *name, int idx, char *options,
824                                    char *brl_options)
825 {
826         struct console_cmdline *c;
827         int i;
828
829         /*
830          *      See if this tty is not yet registered, and
831          *      if we have a slot free.
832          */
833         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
834                 if (strcmp(console_cmdline[i].name, name) == 0 &&
835                           console_cmdline[i].index == idx) {
836                                 if (!brl_options)
837                                         selected_console = i;
838                                 return 0;
839                 }
840         if (i == MAX_CMDLINECONSOLES)
841                 return -E2BIG;
842         if (!brl_options)
843                 selected_console = i;
844         c = &console_cmdline[i];
845         strlcpy(c->name, name, sizeof(c->name));
846         c->options = options;
847 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
848         c->brl_options = brl_options;
849 #endif
850         c->index = idx;
851         return 0;
852 }
853 /*
854  * Set up a list of consoles.  Called from init/main.c
855  */
856 static int __init console_setup(char *str)
857 {
858         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
859         char *s, *options, *brl_options = NULL;
860         int idx;
861
862 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
863         if (!memcmp(str, "brl,", 4)) {
864                 brl_options = "";
865                 str += 4;
866         } else if (!memcmp(str, "brl=", 4)) {
867                 brl_options = str + 4;
868                 str = strchr(brl_options, ',');
869                 if (!str) {
870                         printk(KERN_ERR "need port name after brl=\n");
871                         return 1;
872                 }
873                 *(str++) = 0;
874         }
875 #endif
876
877         /*
878          * Decode str into name, index, options.
879          */
880         if (str[0] >= '0' && str[0] <= '9') {
881                 strcpy(buf, "ttyS");
882                 strncpy(buf + 4, str, sizeof(buf) - 5);
883         } else {
884                 strncpy(buf, str, sizeof(buf) - 1);
885         }
886         buf[sizeof(buf) - 1] = 0;
887         if ((options = strchr(str, ',')) != NULL)
888                 *(options++) = 0;
889 #ifdef __sparc__
890         if (!strcmp(str, "ttya"))
891                 strcpy(buf, "ttyS0");
892         if (!strcmp(str, "ttyb"))
893                 strcpy(buf, "ttyS1");
894 #endif
895         for (s = buf; *s; s++)
896                 if ((*s >= '0' && *s <= '9') || *s == ',')
897                         break;
898         idx = simple_strtoul(s, NULL, 10);
899         *s = 0;
900
901         __add_preferred_console(buf, idx, options, brl_options);
902         console_set_on_cmdline = 1;
903         return 1;
904 }
905 __setup("console=", console_setup);
906
907 /**
908  * add_preferred_console - add a device to the list of preferred consoles.
909  * @name: device name
910  * @idx: device index
911  * @options: options for this console
912  *
913  * The last preferred console added will be used for kernel messages
914  * and stdin/out/err for init.  Normally this is used by console_setup
915  * above to handle user-supplied console arguments; however it can also
916  * be used by arch-specific code either to override the user or more
917  * commonly to provide a default console (ie from PROM variables) when
918  * the user has not supplied one.
919  */
920 int add_preferred_console(char *name, int idx, char *options)
921 {
922         return __add_preferred_console(name, idx, options, NULL);
923 }
924
925 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
926 {
927         struct console_cmdline *c;
928         int i;
929
930         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
931                 if (strcmp(console_cmdline[i].name, name) == 0 &&
932                           console_cmdline[i].index == idx) {
933                                 c = &console_cmdline[i];
934                                 strlcpy(c->name, name_new, sizeof(c->name));
935                                 c->name[sizeof(c->name) - 1] = 0;
936                                 c->options = options;
937                                 c->index = idx_new;
938                                 return i;
939                 }
940         /* not found */
941         return -1;
942 }
943
944 int console_suspend_enabled = 1;
945 EXPORT_SYMBOL(console_suspend_enabled);
946
947 static int __init console_suspend_disable(char *str)
948 {
949         console_suspend_enabled = 0;
950         return 1;
951 }
952 __setup("no_console_suspend", console_suspend_disable);
953
954 /**
955  * suspend_console - suspend the console subsystem
956  *
957  * This disables printk() while we go into suspend states
958  */
959 void suspend_console(void)
960 {
961         if (!console_suspend_enabled)
962                 return;
963         printk("Suspending console(s) (use no_console_suspend to debug)\n");
964         acquire_console_sem();
965         console_suspended = 1;
966         up(&console_sem);
967 }
968
969 void resume_console(void)
970 {
971         if (!console_suspend_enabled)
972                 return;
973         down(&console_sem);
974         console_suspended = 0;
975         release_console_sem();
976 }
977
978 /**
979  * acquire_console_sem - lock the console system for exclusive use.
980  *
981  * Acquires a semaphore which guarantees that the caller has
982  * exclusive access to the console system and the console_drivers list.
983  *
984  * Can sleep, returns nothing.
985  */
986 void acquire_console_sem(void)
987 {
988         BUG_ON(in_interrupt());
989         down(&console_sem);
990         if (console_suspended)
991                 return;
992         console_locked = 1;
993         console_may_schedule = 1;
994 }
995 EXPORT_SYMBOL(acquire_console_sem);
996
997 int try_acquire_console_sem(void)
998 {
999         if (down_trylock(&console_sem))
1000                 return -1;
1001         if (console_suspended) {
1002                 up(&console_sem);
1003                 return -1;
1004         }
1005         console_locked = 1;
1006         console_may_schedule = 0;
1007         return 0;
1008 }
1009 EXPORT_SYMBOL(try_acquire_console_sem);
1010
1011 int is_console_locked(void)
1012 {
1013         return console_locked;
1014 }
1015
1016 static DEFINE_PER_CPU(int, printk_pending);
1017
1018 void printk_tick(void)
1019 {
1020         if (__get_cpu_var(printk_pending)) {
1021                 __get_cpu_var(printk_pending) = 0;
1022                 wake_up_interruptible(&log_wait);
1023         }
1024 }
1025
1026 int printk_needs_cpu(int cpu)
1027 {
1028         return per_cpu(printk_pending, cpu);
1029 }
1030
1031 void wake_up_klogd(void)
1032 {
1033         if (waitqueue_active(&log_wait))
1034                 __raw_get_cpu_var(printk_pending) = 1;
1035 }
1036
1037 /**
1038  * release_console_sem - unlock the console system
1039  *
1040  * Releases the semaphore which the caller holds on the console system
1041  * and the console driver list.
1042  *
1043  * While the semaphore was held, console output may have been buffered
1044  * by printk().  If this is the case, release_console_sem() emits
1045  * the output prior to releasing the semaphore.
1046  *
1047  * If there is output waiting for klogd, we wake it up.
1048  *
1049  * release_console_sem() may be called from any context.
1050  */
1051 void release_console_sem(void)
1052 {
1053         unsigned long flags;
1054         unsigned _con_start, _log_end;
1055         unsigned wake_klogd = 0;
1056
1057         if (console_suspended) {
1058                 up(&console_sem);
1059                 return;
1060         }
1061
1062         console_may_schedule = 0;
1063
1064         for ( ; ; ) {
1065                 spin_lock_irqsave(&logbuf_lock, flags);
1066                 wake_klogd |= log_start - log_end;
1067                 if (con_start == log_end)
1068                         break;                  /* Nothing to print */
1069                 _con_start = con_start;
1070                 _log_end = log_end;
1071                 con_start = log_end;            /* Flush */
1072                 spin_unlock(&logbuf_lock);
1073                 stop_critical_timings();        /* don't trace print latency */
1074                 call_console_drivers(_con_start, _log_end);
1075                 start_critical_timings();
1076                 local_irq_restore(flags);
1077         }
1078         console_locked = 0;
1079         up(&console_sem);
1080         spin_unlock_irqrestore(&logbuf_lock, flags);
1081         if (wake_klogd)
1082                 wake_up_klogd();
1083 }
1084 EXPORT_SYMBOL(release_console_sem);
1085
1086 /**
1087  * console_conditional_schedule - yield the CPU if required
1088  *
1089  * If the console code is currently allowed to sleep, and
1090  * if this CPU should yield the CPU to another task, do
1091  * so here.
1092  *
1093  * Must be called within acquire_console_sem().
1094  */
1095 void __sched console_conditional_schedule(void)
1096 {
1097         if (console_may_schedule)
1098                 cond_resched();
1099 }
1100 EXPORT_SYMBOL(console_conditional_schedule);
1101
1102 void console_unblank(void)
1103 {
1104         struct console *c;
1105
1106         /*
1107          * console_unblank can no longer be called in interrupt context unless
1108          * oops_in_progress is set to 1..
1109          */
1110         if (oops_in_progress) {
1111                 if (down_trylock(&console_sem) != 0)
1112                         return;
1113         } else
1114                 acquire_console_sem();
1115
1116         console_locked = 1;
1117         console_may_schedule = 0;
1118         for_each_console(c)
1119                 if ((c->flags & CON_ENABLED) && c->unblank)
1120                         c->unblank();
1121         release_console_sem();
1122 }
1123
1124 /*
1125  * Return the console tty driver structure and its associated index
1126  */
1127 struct tty_driver *console_device(int *index)
1128 {
1129         struct console *c;
1130         struct tty_driver *driver = NULL;
1131
1132         acquire_console_sem();
1133         for_each_console(c) {
1134                 if (!c->device)
1135                         continue;
1136                 driver = c->device(c, index);
1137                 if (driver)
1138                         break;
1139         }
1140         release_console_sem();
1141         return driver;
1142 }
1143
1144 /*
1145  * Prevent further output on the passed console device so that (for example)
1146  * serial drivers can disable console output before suspending a port, and can
1147  * re-enable output afterwards.
1148  */
1149 void console_stop(struct console *console)
1150 {
1151         acquire_console_sem();
1152         console->flags &= ~CON_ENABLED;
1153         release_console_sem();
1154 }
1155 EXPORT_SYMBOL(console_stop);
1156
1157 void console_start(struct console *console)
1158 {
1159         acquire_console_sem();
1160         console->flags |= CON_ENABLED;
1161         release_console_sem();
1162 }
1163 EXPORT_SYMBOL(console_start);
1164
1165 /*
1166  * The console driver calls this routine during kernel initialization
1167  * to register the console printing procedure with printk() and to
1168  * print any messages that were printed by the kernel before the
1169  * console driver was initialized.
1170  *
1171  * This can happen pretty early during the boot process (because of
1172  * early_printk) - sometimes before setup_arch() completes - be careful
1173  * of what kernel features are used - they may not be initialised yet.
1174  *
1175  * There are two types of consoles - bootconsoles (early_printk) and
1176  * "real" consoles (everything which is not a bootconsole) which are
1177  * handled differently.
1178  *  - Any number of bootconsoles can be registered at any time.
1179  *  - As soon as a "real" console is registered, all bootconsoles
1180  *    will be unregistered automatically.
1181  *  - Once a "real" console is registered, any attempt to register a
1182  *    bootconsoles will be rejected
1183  */
1184 void register_console(struct console *newcon)
1185 {
1186         int i;
1187         unsigned long flags;
1188         struct console *bcon = NULL;
1189
1190         /*
1191          * before we register a new CON_BOOT console, make sure we don't
1192          * already have a valid console
1193          */
1194         if (console_drivers && newcon->flags & CON_BOOT) {
1195                 /* find the last or real console */
1196                 for_each_console(bcon) {
1197                         if (!(bcon->flags & CON_BOOT)) {
1198                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1199                                         newcon->name, newcon->index);
1200                                 return;
1201                         }
1202                 }
1203         }
1204
1205         if (console_drivers && console_drivers->flags & CON_BOOT)
1206                 bcon = console_drivers;
1207
1208         if (preferred_console < 0 || bcon || !console_drivers)
1209                 preferred_console = selected_console;
1210
1211         if (newcon->early_setup)
1212                 newcon->early_setup();
1213
1214         /*
1215          *      See if we want to use this console driver. If we
1216          *      didn't select a console we take the first one
1217          *      that registers here.
1218          */
1219         if (preferred_console < 0) {
1220                 if (newcon->index < 0)
1221                         newcon->index = 0;
1222                 if (newcon->setup == NULL ||
1223                     newcon->setup(newcon, NULL) == 0) {
1224                         newcon->flags |= CON_ENABLED;
1225                         if (newcon->device) {
1226                                 newcon->flags |= CON_CONSDEV;
1227                                 preferred_console = 0;
1228                         }
1229                 }
1230         }
1231
1232         /*
1233          *      See if this console matches one we selected on
1234          *      the command line.
1235          */
1236         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1237                         i++) {
1238                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1239                         continue;
1240                 if (newcon->index >= 0 &&
1241                     newcon->index != console_cmdline[i].index)
1242                         continue;
1243                 if (newcon->index < 0)
1244                         newcon->index = console_cmdline[i].index;
1245 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1246                 if (console_cmdline[i].brl_options) {
1247                         newcon->flags |= CON_BRL;
1248                         braille_register_console(newcon,
1249                                         console_cmdline[i].index,
1250                                         console_cmdline[i].options,
1251                                         console_cmdline[i].brl_options);
1252                         return;
1253                 }
1254 #endif
1255                 if (newcon->setup &&
1256                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1257                         break;
1258                 newcon->flags |= CON_ENABLED;
1259                 newcon->index = console_cmdline[i].index;
1260                 if (i == selected_console) {
1261                         newcon->flags |= CON_CONSDEV;
1262                         preferred_console = selected_console;
1263                 }
1264                 break;
1265         }
1266
1267         if (!(newcon->flags & CON_ENABLED))
1268                 return;
1269
1270         /*
1271          * If we have a bootconsole, and are switching to a real console,
1272          * don't print everything out again, since when the boot console, and
1273          * the real console are the same physical device, it's annoying to
1274          * see the beginning boot messages twice
1275          */
1276         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1277                 newcon->flags &= ~CON_PRINTBUFFER;
1278
1279         /*
1280          *      Put this console in the list - keep the
1281          *      preferred driver at the head of the list.
1282          */
1283         acquire_console_sem();
1284         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1285                 newcon->next = console_drivers;
1286                 console_drivers = newcon;
1287                 if (newcon->next)
1288                         newcon->next->flags &= ~CON_CONSDEV;
1289         } else {
1290                 newcon->next = console_drivers->next;
1291                 console_drivers->next = newcon;
1292         }
1293         if (newcon->flags & CON_PRINTBUFFER) {
1294                 /*
1295                  * release_console_sem() will print out the buffered messages
1296                  * for us.
1297                  */
1298                 spin_lock_irqsave(&logbuf_lock, flags);
1299                 con_start = log_start;
1300                 spin_unlock_irqrestore(&logbuf_lock, flags);
1301         }
1302         release_console_sem();
1303
1304         /*
1305          * By unregistering the bootconsoles after we enable the real console
1306          * we get the "console xxx enabled" message on all the consoles -
1307          * boot consoles, real consoles, etc - this is to ensure that end
1308          * users know there might be something in the kernel's log buffer that
1309          * went to the bootconsole (that they do not see on the real console)
1310          */
1311         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1312                 /* we need to iterate through twice, to make sure we print
1313                  * everything out, before we unregister the console(s)
1314                  */
1315                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1316                         newcon->name, newcon->index);
1317                 for_each_console(bcon)
1318                         if (bcon->flags & CON_BOOT)
1319                                 unregister_console(bcon);
1320         } else {
1321                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1322                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1323                         newcon->name, newcon->index);
1324         }
1325 }
1326 EXPORT_SYMBOL(register_console);
1327
1328 int unregister_console(struct console *console)
1329 {
1330         struct console *a, *b;
1331         int res = 1;
1332
1333 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1334         if (console->flags & CON_BRL)
1335                 return braille_unregister_console(console);
1336 #endif
1337
1338         acquire_console_sem();
1339         if (console_drivers == console) {
1340                 console_drivers=console->next;
1341                 res = 0;
1342         } else if (console_drivers) {
1343                 for (a=console_drivers->next, b=console_drivers ;
1344                      a; b=a, a=b->next) {
1345                         if (a == console) {
1346                                 b->next = a->next;
1347                                 res = 0;
1348                                 break;
1349                         }
1350                 }
1351         }
1352
1353         /*
1354          * If this isn't the last console and it has CON_CONSDEV set, we
1355          * need to set it on the next preferred console.
1356          */
1357         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1358                 console_drivers->flags |= CON_CONSDEV;
1359
1360         release_console_sem();
1361         return res;
1362 }
1363 EXPORT_SYMBOL(unregister_console);
1364
1365 static int __init disable_boot_consoles(void)
1366 {
1367         struct console *con;
1368
1369         for_each_console(con) {
1370                 if (con->flags & CON_BOOT) {
1371                         printk(KERN_INFO "turn off boot console %s%d\n",
1372                                 con->name, con->index);
1373                         unregister_console(con);
1374                 }
1375         }
1376         return 0;
1377 }
1378 late_initcall(disable_boot_consoles);
1379
1380 #if defined CONFIG_PRINTK
1381
1382 /*
1383  * printk rate limiting, lifted from the networking subsystem.
1384  *
1385  * This enforces a rate limit: not more than 10 kernel messages
1386  * every 5s to make a denial-of-service attack impossible.
1387  */
1388 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1389
1390 int __printk_ratelimit(const char *func)
1391 {
1392         return ___ratelimit(&printk_ratelimit_state, func);
1393 }
1394 EXPORT_SYMBOL(__printk_ratelimit);
1395
1396 /**
1397  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1398  * @caller_jiffies: pointer to caller's state
1399  * @interval_msecs: minimum interval between prints
1400  *
1401  * printk_timed_ratelimit() returns true if more than @interval_msecs
1402  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1403  * returned true.
1404  */
1405 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1406                         unsigned int interval_msecs)
1407 {
1408         if (*caller_jiffies == 0
1409                         || !time_in_range(jiffies, *caller_jiffies,
1410                                         *caller_jiffies
1411                                         + msecs_to_jiffies(interval_msecs))) {
1412                 *caller_jiffies = jiffies;
1413                 return true;
1414         }
1415         return false;
1416 }
1417 EXPORT_SYMBOL(printk_timed_ratelimit);
1418
1419 static DEFINE_SPINLOCK(dump_list_lock);
1420 static LIST_HEAD(dump_list);
1421
1422 /**
1423  * kmsg_dump_register - register a kernel log dumper.
1424  * @dumper: pointer to the kmsg_dumper structure
1425  *
1426  * Adds a kernel log dumper to the system. The dump callback in the
1427  * structure will be called when the kernel oopses or panics and must be
1428  * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1429  */
1430 int kmsg_dump_register(struct kmsg_dumper *dumper)
1431 {
1432         unsigned long flags;
1433         int err = -EBUSY;
1434
1435         /* The dump callback needs to be set */
1436         if (!dumper->dump)
1437                 return -EINVAL;
1438
1439         spin_lock_irqsave(&dump_list_lock, flags);
1440         /* Don't allow registering multiple times */
1441         if (!dumper->registered) {
1442                 dumper->registered = 1;
1443                 list_add_tail(&dumper->list, &dump_list);
1444                 err = 0;
1445         }
1446         spin_unlock_irqrestore(&dump_list_lock, flags);
1447
1448         return err;
1449 }
1450 EXPORT_SYMBOL_GPL(kmsg_dump_register);
1451
1452 /**
1453  * kmsg_dump_unregister - unregister a kmsg dumper.
1454  * @dumper: pointer to the kmsg_dumper structure
1455  *
1456  * Removes a dump device from the system. Returns zero on success and
1457  * %-EINVAL otherwise.
1458  */
1459 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1460 {
1461         unsigned long flags;
1462         int err = -EINVAL;
1463
1464         spin_lock_irqsave(&dump_list_lock, flags);
1465         if (dumper->registered) {
1466                 dumper->registered = 0;
1467                 list_del(&dumper->list);
1468                 err = 0;
1469         }
1470         spin_unlock_irqrestore(&dump_list_lock, flags);
1471
1472         return err;
1473 }
1474 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1475
1476 static const char const *kmsg_reasons[] = {
1477         [KMSG_DUMP_OOPS]        = "oops",
1478         [KMSG_DUMP_PANIC]       = "panic",
1479         [KMSG_DUMP_KEXEC]       = "kexec",
1480 };
1481
1482 static const char *kmsg_to_str(enum kmsg_dump_reason reason)
1483 {
1484         if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0)
1485                 return "unknown";
1486
1487         return kmsg_reasons[reason];
1488 }
1489
1490 /**
1491  * kmsg_dump - dump kernel log to kernel message dumpers.
1492  * @reason: the reason (oops, panic etc) for dumping
1493  *
1494  * Iterate through each of the dump devices and call the oops/panic
1495  * callbacks with the log buffer.
1496  */
1497 void kmsg_dump(enum kmsg_dump_reason reason)
1498 {
1499         unsigned long end;
1500         unsigned chars;
1501         struct kmsg_dumper *dumper;
1502         const char *s1, *s2;
1503         unsigned long l1, l2;
1504         unsigned long flags;
1505
1506         /* Theoretically, the log could move on after we do this, but
1507            there's not a lot we can do about that. The new messages
1508            will overwrite the start of what we dump. */
1509         spin_lock_irqsave(&logbuf_lock, flags);
1510         end = log_end & LOG_BUF_MASK;
1511         chars = logged_chars;
1512         spin_unlock_irqrestore(&logbuf_lock, flags);
1513
1514         if (logged_chars > end) {
1515                 s1 = log_buf + log_buf_len - logged_chars + end;
1516                 l1 = logged_chars - end;
1517
1518                 s2 = log_buf;
1519                 l2 = end;
1520         } else {
1521                 s1 = "";
1522                 l1 = 0;
1523
1524                 s2 = log_buf + end - logged_chars;
1525                 l2 = logged_chars;
1526         }
1527
1528         if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
1529                 printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
1530                                 kmsg_to_str(reason));
1531                 return;
1532         }
1533         list_for_each_entry(dumper, &dump_list, list)
1534                 dumper->dump(dumper, reason, s1, l1, s2, l2);
1535         spin_unlock_irqrestore(&dump_list_lock, flags);
1536 }
1537 #endif