444b770c95959261a491b8a673ff42e29a181592
[linux-3.10.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/kdb.h>
37 #include <linux/ratelimit.h>
38 #include <linux/kmsg_dump.h>
39 #include <linux/syslog.h>
40
41 #include <asm/uaccess.h>
42
43 /*
44  * for_each_console() allows you to iterate on each console
45  */
46 #define for_each_console(con) \
47         for (con = console_drivers; con != NULL; con = con->next)
48
49 /*
50  * Architectures can override it:
51  */
52 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
53 {
54 }
55
56 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
57
58 /* printk's without a loglevel use this.. */
59 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
60
61 /* We show everything that is MORE important than this.. */
62 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
63 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
64
65 DECLARE_WAIT_QUEUE_HEAD(log_wait);
66
67 int console_printk[4] = {
68         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
69         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
70         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
71         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
72 };
73
74 /*
75  * Low level drivers may need that to know if they can schedule in
76  * their unblank() callback or not. So let's export it.
77  */
78 int oops_in_progress;
79 EXPORT_SYMBOL(oops_in_progress);
80
81 /*
82  * console_sem protects the console_drivers list, and also
83  * provides serialisation for access to the entire console
84  * driver system.
85  */
86 static DECLARE_MUTEX(console_sem);
87 struct console *console_drivers;
88 EXPORT_SYMBOL_GPL(console_drivers);
89
90 /*
91  * This is used for debugging the mess that is the VT code by
92  * keeping track if we have the console semaphore held. It's
93  * definitely not the perfect debug tool (we don't know if _WE_
94  * hold it are racing, but it helps tracking those weird code
95  * path in the console code where we end up in places I want
96  * locked without the console sempahore held
97  */
98 static int console_locked, console_suspended;
99
100 /*
101  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
102  * It is also used in interesting ways to provide interlocking in
103  * release_console_sem().
104  */
105 static DEFINE_SPINLOCK(logbuf_lock);
106
107 #define LOG_BUF_MASK (log_buf_len-1)
108 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
109
110 /*
111  * The indices into log_buf are not constrained to log_buf_len - they
112  * must be masked before subscripting
113  */
114 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
115 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
116 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
117
118 /*
119  *      Array of consoles built from command line options (console=)
120  */
121 struct console_cmdline
122 {
123         char    name[8];                        /* Name of the driver       */
124         int     index;                          /* Minor dev. to use        */
125         char    *options;                       /* Options for the driver   */
126 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
127         char    *brl_options;                   /* Options for braille driver */
128 #endif
129 };
130
131 #define MAX_CMDLINECONSOLES 8
132
133 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
134 static int selected_console = -1;
135 static int preferred_console = -1;
136 int console_set_on_cmdline;
137 EXPORT_SYMBOL(console_set_on_cmdline);
138
139 /* Flag: console code may call schedule() */
140 static int console_may_schedule;
141
142 #ifdef CONFIG_PRINTK
143
144 static char __log_buf[__LOG_BUF_LEN];
145 static char *log_buf = __log_buf;
146 static int log_buf_len = __LOG_BUF_LEN;
147 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
148 static int saved_console_loglevel = -1;
149
150 #ifdef CONFIG_KEXEC
151 /*
152  * This appends the listed symbols to /proc/vmcoreinfo
153  *
154  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
155  * obtain access to symbols that are otherwise very difficult to locate.  These
156  * symbols are specifically used so that utilities can access and extract the
157  * dmesg log from a vmcore file after a crash.
158  */
159 void log_buf_kexec_setup(void)
160 {
161         VMCOREINFO_SYMBOL(log_buf);
162         VMCOREINFO_SYMBOL(log_end);
163         VMCOREINFO_SYMBOL(log_buf_len);
164         VMCOREINFO_SYMBOL(logged_chars);
165 }
166 #endif
167
168 static int __init log_buf_len_setup(char *str)
169 {
170         unsigned size = memparse(str, &str);
171         unsigned long flags;
172
173         if (size)
174                 size = roundup_pow_of_two(size);
175         if (size > log_buf_len) {
176                 unsigned start, dest_idx, offset;
177                 char *new_log_buf;
178
179                 new_log_buf = alloc_bootmem(size);
180                 if (!new_log_buf) {
181                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
182                         goto out;
183                 }
184
185                 spin_lock_irqsave(&logbuf_lock, flags);
186                 log_buf_len = size;
187                 log_buf = new_log_buf;
188
189                 offset = start = min(con_start, log_start);
190                 dest_idx = 0;
191                 while (start != log_end) {
192                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
193                         start++;
194                         dest_idx++;
195                 }
196                 log_start -= offset;
197                 con_start -= offset;
198                 log_end -= offset;
199                 spin_unlock_irqrestore(&logbuf_lock, flags);
200
201                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
202         }
203 out:
204         return 1;
205 }
206
207 __setup("log_buf_len=", log_buf_len_setup);
208
209 #ifdef CONFIG_BOOT_PRINTK_DELAY
210
211 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
212 static unsigned long long loops_per_msec;       /* based on boot_delay */
213
214 static int __init boot_delay_setup(char *str)
215 {
216         unsigned long lpj;
217
218         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
219         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
220
221         get_option(&str, &boot_delay);
222         if (boot_delay > 10 * 1000)
223                 boot_delay = 0;
224
225         pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
226                 "HZ: %d, loops_per_msec: %llu\n",
227                 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
228         return 1;
229 }
230 __setup("boot_delay=", boot_delay_setup);
231
232 static void boot_delay_msec(void)
233 {
234         unsigned long long k;
235         unsigned long timeout;
236
237         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
238                 return;
239
240         k = (unsigned long long)loops_per_msec * boot_delay;
241
242         timeout = jiffies + msecs_to_jiffies(boot_delay);
243         while (k) {
244                 k--;
245                 cpu_relax();
246                 /*
247                  * use (volatile) jiffies to prevent
248                  * compiler reduction; loop termination via jiffies
249                  * is secondary and may or may not happen.
250                  */
251                 if (time_after(jiffies, timeout))
252                         break;
253                 touch_nmi_watchdog();
254         }
255 }
256 #else
257 static inline void boot_delay_msec(void)
258 {
259 }
260 #endif
261
262 int do_syslog(int type, char __user *buf, int len, bool from_file)
263 {
264         unsigned i, j, limit, count;
265         int do_clear = 0;
266         char c;
267         int error = 0;
268
269         error = security_syslog(type, from_file);
270         if (error)
271                 return error;
272
273         switch (type) {
274         case SYSLOG_ACTION_CLOSE:       /* Close log */
275                 break;
276         case SYSLOG_ACTION_OPEN:        /* Open log */
277                 break;
278         case SYSLOG_ACTION_READ:        /* Read from log */
279                 error = -EINVAL;
280                 if (!buf || len < 0)
281                         goto out;
282                 error = 0;
283                 if (!len)
284                         goto out;
285                 if (!access_ok(VERIFY_WRITE, buf, len)) {
286                         error = -EFAULT;
287                         goto out;
288                 }
289                 error = wait_event_interruptible(log_wait,
290                                                         (log_start - log_end));
291                 if (error)
292                         goto out;
293                 i = 0;
294                 spin_lock_irq(&logbuf_lock);
295                 while (!error && (log_start != log_end) && i < len) {
296                         c = LOG_BUF(log_start);
297                         log_start++;
298                         spin_unlock_irq(&logbuf_lock);
299                         error = __put_user(c,buf);
300                         buf++;
301                         i++;
302                         cond_resched();
303                         spin_lock_irq(&logbuf_lock);
304                 }
305                 spin_unlock_irq(&logbuf_lock);
306                 if (!error)
307                         error = i;
308                 break;
309         /* Read/clear last kernel messages */
310         case SYSLOG_ACTION_READ_CLEAR:
311                 do_clear = 1;
312                 /* FALL THRU */
313         /* Read last kernel messages */
314         case SYSLOG_ACTION_READ_ALL:
315                 error = -EINVAL;
316                 if (!buf || len < 0)
317                         goto out;
318                 error = 0;
319                 if (!len)
320                         goto out;
321                 if (!access_ok(VERIFY_WRITE, buf, len)) {
322                         error = -EFAULT;
323                         goto out;
324                 }
325                 count = len;
326                 if (count > log_buf_len)
327                         count = log_buf_len;
328                 spin_lock_irq(&logbuf_lock);
329                 if (count > logged_chars)
330                         count = logged_chars;
331                 if (do_clear)
332                         logged_chars = 0;
333                 limit = log_end;
334                 /*
335                  * __put_user() could sleep, and while we sleep
336                  * printk() could overwrite the messages
337                  * we try to copy to user space. Therefore
338                  * the messages are copied in reverse. <manfreds>
339                  */
340                 for (i = 0; i < count && !error; i++) {
341                         j = limit-1-i;
342                         if (j + log_buf_len < log_end)
343                                 break;
344                         c = LOG_BUF(j);
345                         spin_unlock_irq(&logbuf_lock);
346                         error = __put_user(c,&buf[count-1-i]);
347                         cond_resched();
348                         spin_lock_irq(&logbuf_lock);
349                 }
350                 spin_unlock_irq(&logbuf_lock);
351                 if (error)
352                         break;
353                 error = i;
354                 if (i != count) {
355                         int offset = count-error;
356                         /* buffer overflow during copy, correct user buffer. */
357                         for (i = 0; i < error; i++) {
358                                 if (__get_user(c,&buf[i+offset]) ||
359                                     __put_user(c,&buf[i])) {
360                                         error = -EFAULT;
361                                         break;
362                                 }
363                                 cond_resched();
364                         }
365                 }
366                 break;
367         /* Clear ring buffer */
368         case SYSLOG_ACTION_CLEAR:
369                 logged_chars = 0;
370                 break;
371         /* Disable logging to console */
372         case SYSLOG_ACTION_CONSOLE_OFF:
373                 if (saved_console_loglevel == -1)
374                         saved_console_loglevel = console_loglevel;
375                 console_loglevel = minimum_console_loglevel;
376                 break;
377         /* Enable logging to console */
378         case SYSLOG_ACTION_CONSOLE_ON:
379                 if (saved_console_loglevel != -1) {
380                         console_loglevel = saved_console_loglevel;
381                         saved_console_loglevel = -1;
382                 }
383                 break;
384         /* Set level of messages printed to console */
385         case SYSLOG_ACTION_CONSOLE_LEVEL:
386                 error = -EINVAL;
387                 if (len < 1 || len > 8)
388                         goto out;
389                 if (len < minimum_console_loglevel)
390                         len = minimum_console_loglevel;
391                 console_loglevel = len;
392                 /* Implicitly re-enable logging to console */
393                 saved_console_loglevel = -1;
394                 error = 0;
395                 break;
396         /* Number of chars in the log buffer */
397         case SYSLOG_ACTION_SIZE_UNREAD:
398                 error = log_end - log_start;
399                 break;
400         /* Size of the log buffer */
401         case SYSLOG_ACTION_SIZE_BUFFER:
402                 error = log_buf_len;
403                 break;
404         default:
405                 error = -EINVAL;
406                 break;
407         }
408 out:
409         return error;
410 }
411
412 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
413 {
414         return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
415 }
416
417 #ifdef  CONFIG_KGDB_KDB
418 /* kdb dmesg command needs access to the syslog buffer.  do_syslog()
419  * uses locks so it cannot be used during debugging.  Just tell kdb
420  * where the start and end of the physical and logical logs are.  This
421  * is equivalent to do_syslog(3).
422  */
423 void kdb_syslog_data(char *syslog_data[4])
424 {
425         syslog_data[0] = log_buf;
426         syslog_data[1] = log_buf + log_buf_len;
427         syslog_data[2] = log_buf + log_end -
428                 (logged_chars < log_buf_len ? logged_chars : log_buf_len);
429         syslog_data[3] = log_buf + log_end;
430 }
431 #endif  /* CONFIG_KGDB_KDB */
432
433 /*
434  * Call the console drivers on a range of log_buf
435  */
436 static void __call_console_drivers(unsigned start, unsigned end)
437 {
438         struct console *con;
439
440         for_each_console(con) {
441                 if ((con->flags & CON_ENABLED) && con->write &&
442                                 (cpu_online(smp_processor_id()) ||
443                                 (con->flags & CON_ANYTIME)))
444                         con->write(con, &LOG_BUF(start), end - start);
445         }
446 }
447
448 static int __read_mostly ignore_loglevel;
449
450 static int __init ignore_loglevel_setup(char *str)
451 {
452         ignore_loglevel = 1;
453         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
454
455         return 0;
456 }
457
458 early_param("ignore_loglevel", ignore_loglevel_setup);
459
460 /*
461  * Write out chars from start to end - 1 inclusive
462  */
463 static void _call_console_drivers(unsigned start,
464                                 unsigned end, int msg_log_level)
465 {
466         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
467                         console_drivers && start != end) {
468                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
469                         /* wrapped write */
470                         __call_console_drivers(start & LOG_BUF_MASK,
471                                                 log_buf_len);
472                         __call_console_drivers(0, end & LOG_BUF_MASK);
473                 } else {
474                         __call_console_drivers(start, end);
475                 }
476         }
477 }
478
479 /*
480  * Call the console drivers, asking them to write out
481  * log_buf[start] to log_buf[end - 1].
482  * The console_sem must be held.
483  */
484 static void call_console_drivers(unsigned start, unsigned end)
485 {
486         unsigned cur_index, start_print;
487         static int msg_level = -1;
488
489         BUG_ON(((int)(start - end)) > 0);
490
491         cur_index = start;
492         start_print = start;
493         while (cur_index != end) {
494                 if (msg_level < 0 && ((end - cur_index) > 2) &&
495                                 LOG_BUF(cur_index + 0) == '<' &&
496                                 LOG_BUF(cur_index + 1) >= '0' &&
497                                 LOG_BUF(cur_index + 1) <= '7' &&
498                                 LOG_BUF(cur_index + 2) == '>') {
499                         msg_level = LOG_BUF(cur_index + 1) - '0';
500                         cur_index += 3;
501                         start_print = cur_index;
502                 }
503                 while (cur_index != end) {
504                         char c = LOG_BUF(cur_index);
505
506                         cur_index++;
507                         if (c == '\n') {
508                                 if (msg_level < 0) {
509                                         /*
510                                          * printk() has already given us loglevel tags in
511                                          * the buffer.  This code is here in case the
512                                          * log buffer has wrapped right round and scribbled
513                                          * on those tags
514                                          */
515                                         msg_level = default_message_loglevel;
516                                 }
517                                 _call_console_drivers(start_print, cur_index, msg_level);
518                                 msg_level = -1;
519                                 start_print = cur_index;
520                                 break;
521                         }
522                 }
523         }
524         _call_console_drivers(start_print, end, msg_level);
525 }
526
527 static void emit_log_char(char c)
528 {
529         LOG_BUF(log_end) = c;
530         log_end++;
531         if (log_end - log_start > log_buf_len)
532                 log_start = log_end - log_buf_len;
533         if (log_end - con_start > log_buf_len)
534                 con_start = log_end - log_buf_len;
535         if (logged_chars < log_buf_len)
536                 logged_chars++;
537 }
538
539 /*
540  * Zap console related locks when oopsing. Only zap at most once
541  * every 10 seconds, to leave time for slow consoles to print a
542  * full oops.
543  */
544 static void zap_locks(void)
545 {
546         static unsigned long oops_timestamp;
547
548         if (time_after_eq(jiffies, oops_timestamp) &&
549                         !time_after(jiffies, oops_timestamp + 30 * HZ))
550                 return;
551
552         oops_timestamp = jiffies;
553
554         /* If a crash is occurring, make sure we can't deadlock */
555         spin_lock_init(&logbuf_lock);
556         /* And make sure that we print immediately */
557         init_MUTEX(&console_sem);
558 }
559
560 #if defined(CONFIG_PRINTK_TIME)
561 static int printk_time = 1;
562 #else
563 static int printk_time = 0;
564 #endif
565 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
566
567 /* Check if we have any console registered that can be called early in boot. */
568 static int have_callable_console(void)
569 {
570         struct console *con;
571
572         for_each_console(con)
573                 if (con->flags & CON_ANYTIME)
574                         return 1;
575
576         return 0;
577 }
578
579 /**
580  * printk - print a kernel message
581  * @fmt: format string
582  *
583  * This is printk().  It can be called from any context.  We want it to work.
584  *
585  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
586  * call the console drivers.  If we fail to get the semaphore we place the output
587  * into the log buffer and return.  The current holder of the console_sem will
588  * notice the new output in release_console_sem() and will send it to the
589  * consoles before releasing the semaphore.
590  *
591  * One effect of this deferred printing is that code which calls printk() and
592  * then changes console_loglevel may break. This is because console_loglevel
593  * is inspected when the actual printing occurs.
594  *
595  * See also:
596  * printf(3)
597  *
598  * See the vsnprintf() documentation for format string extensions over C99.
599  */
600
601 asmlinkage int printk(const char *fmt, ...)
602 {
603         va_list args;
604         int r;
605
606 #ifdef CONFIG_KGDB_KDB
607         if (unlikely(kdb_trap_printk)) {
608                 va_start(args, fmt);
609                 r = vkdb_printf(fmt, args);
610                 va_end(args);
611                 return r;
612         }
613 #endif
614         va_start(args, fmt);
615         r = vprintk(fmt, args);
616         va_end(args);
617
618         return r;
619 }
620
621 /* cpu currently holding logbuf_lock */
622 static volatile unsigned int printk_cpu = UINT_MAX;
623
624 /*
625  * Can we actually use the console at this time on this cpu?
626  *
627  * Console drivers may assume that per-cpu resources have
628  * been allocated. So unless they're explicitly marked as
629  * being able to cope (CON_ANYTIME) don't call them until
630  * this CPU is officially up.
631  */
632 static inline int can_use_console(unsigned int cpu)
633 {
634         return cpu_online(cpu) || have_callable_console();
635 }
636
637 /*
638  * Try to get console ownership to actually show the kernel
639  * messages from a 'printk'. Return true (and with the
640  * console_semaphore held, and 'console_locked' set) if it
641  * is successful, false otherwise.
642  *
643  * This gets called with the 'logbuf_lock' spinlock held and
644  * interrupts disabled. It should return with 'lockbuf_lock'
645  * released but interrupts still disabled.
646  */
647 static int acquire_console_semaphore_for_printk(unsigned int cpu)
648 {
649         int retval = 0;
650
651         if (!try_acquire_console_sem()) {
652                 retval = 1;
653
654                 /*
655                  * If we can't use the console, we need to release
656                  * the console semaphore by hand to avoid flushing
657                  * the buffer. We need to hold the console semaphore
658                  * in order to do this test safely.
659                  */
660                 if (!can_use_console(cpu)) {
661                         console_locked = 0;
662                         up(&console_sem);
663                         retval = 0;
664                 }
665         }
666         printk_cpu = UINT_MAX;
667         spin_unlock(&logbuf_lock);
668         return retval;
669 }
670 static const char recursion_bug_msg [] =
671                 KERN_CRIT "BUG: recent printk recursion!\n";
672 static int recursion_bug;
673 static int new_text_line = 1;
674 static char printk_buf[1024];
675
676 int printk_delay_msec __read_mostly;
677
678 static inline void printk_delay(void)
679 {
680         if (unlikely(printk_delay_msec)) {
681                 int m = printk_delay_msec;
682
683                 while (m--) {
684                         mdelay(1);
685                         touch_nmi_watchdog();
686                 }
687         }
688 }
689
690 asmlinkage int vprintk(const char *fmt, va_list args)
691 {
692         int printed_len = 0;
693         int current_log_level = default_message_loglevel;
694         unsigned long flags;
695         int this_cpu;
696         char *p;
697
698         boot_delay_msec();
699         printk_delay();
700
701         preempt_disable();
702         /* This stops the holder of console_sem just where we want him */
703         raw_local_irq_save(flags);
704         this_cpu = smp_processor_id();
705
706         /*
707          * Ouch, printk recursed into itself!
708          */
709         if (unlikely(printk_cpu == this_cpu)) {
710                 /*
711                  * If a crash is occurring during printk() on this CPU,
712                  * then try to get the crash message out but make sure
713                  * we can't deadlock. Otherwise just return to avoid the
714                  * recursion and return - but flag the recursion so that
715                  * it can be printed at the next appropriate moment:
716                  */
717                 if (!oops_in_progress) {
718                         recursion_bug = 1;
719                         goto out_restore_irqs;
720                 }
721                 zap_locks();
722         }
723
724         lockdep_off();
725         spin_lock(&logbuf_lock);
726         printk_cpu = this_cpu;
727
728         if (recursion_bug) {
729                 recursion_bug = 0;
730                 strcpy(printk_buf, recursion_bug_msg);
731                 printed_len = strlen(recursion_bug_msg);
732         }
733         /* Emit the output into the temporary buffer */
734         printed_len += vscnprintf(printk_buf + printed_len,
735                                   sizeof(printk_buf) - printed_len, fmt, args);
736
737
738         p = printk_buf;
739
740         /* Do we have a loglevel in the string? */
741         if (p[0] == '<') {
742                 unsigned char c = p[1];
743                 if (c && p[2] == '>') {
744                         switch (c) {
745                         case '0' ... '7': /* loglevel */
746                                 current_log_level = c - '0';
747                         /* Fallthrough - make sure we're on a new line */
748                         case 'd': /* KERN_DEFAULT */
749                                 if (!new_text_line) {
750                                         emit_log_char('\n');
751                                         new_text_line = 1;
752                                 }
753                         /* Fallthrough - skip the loglevel */
754                         case 'c': /* KERN_CONT */
755                                 p += 3;
756                                 break;
757                         }
758                 }
759         }
760
761         /*
762          * Copy the output into log_buf.  If the caller didn't provide
763          * appropriate log level tags, we insert them here
764          */
765         for ( ; *p; p++) {
766                 if (new_text_line) {
767                         /* Always output the token */
768                         emit_log_char('<');
769                         emit_log_char(current_log_level + '0');
770                         emit_log_char('>');
771                         printed_len += 3;
772                         new_text_line = 0;
773
774                         if (printk_time) {
775                                 /* Follow the token with the time */
776                                 char tbuf[50], *tp;
777                                 unsigned tlen;
778                                 unsigned long long t;
779                                 unsigned long nanosec_rem;
780
781                                 t = cpu_clock(printk_cpu);
782                                 nanosec_rem = do_div(t, 1000000000);
783                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
784                                                 (unsigned long) t,
785                                                 nanosec_rem / 1000);
786
787                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
788                                         emit_log_char(*tp);
789                                 printed_len += tlen;
790                         }
791
792                         if (!*p)
793                                 break;
794                 }
795
796                 emit_log_char(*p);
797                 if (*p == '\n')
798                         new_text_line = 1;
799         }
800
801         /*
802          * Try to acquire and then immediately release the
803          * console semaphore. The release will do all the
804          * actual magic (print out buffers, wake up klogd,
805          * etc). 
806          *
807          * The acquire_console_semaphore_for_printk() function
808          * will release 'logbuf_lock' regardless of whether it
809          * actually gets the semaphore or not.
810          */
811         if (acquire_console_semaphore_for_printk(this_cpu))
812                 release_console_sem();
813
814         lockdep_on();
815 out_restore_irqs:
816         raw_local_irq_restore(flags);
817
818         preempt_enable();
819         return printed_len;
820 }
821 EXPORT_SYMBOL(printk);
822 EXPORT_SYMBOL(vprintk);
823
824 #else
825
826 static void call_console_drivers(unsigned start, unsigned end)
827 {
828 }
829
830 #endif
831
832 static int __add_preferred_console(char *name, int idx, char *options,
833                                    char *brl_options)
834 {
835         struct console_cmdline *c;
836         int i;
837
838         /*
839          *      See if this tty is not yet registered, and
840          *      if we have a slot free.
841          */
842         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
843                 if (strcmp(console_cmdline[i].name, name) == 0 &&
844                           console_cmdline[i].index == idx) {
845                                 if (!brl_options)
846                                         selected_console = i;
847                                 return 0;
848                 }
849         if (i == MAX_CMDLINECONSOLES)
850                 return -E2BIG;
851         if (!brl_options)
852                 selected_console = i;
853         c = &console_cmdline[i];
854         strlcpy(c->name, name, sizeof(c->name));
855         c->options = options;
856 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
857         c->brl_options = brl_options;
858 #endif
859         c->index = idx;
860         return 0;
861 }
862 /*
863  * Set up a list of consoles.  Called from init/main.c
864  */
865 static int __init console_setup(char *str)
866 {
867         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
868         char *s, *options, *brl_options = NULL;
869         int idx;
870
871 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
872         if (!memcmp(str, "brl,", 4)) {
873                 brl_options = "";
874                 str += 4;
875         } else if (!memcmp(str, "brl=", 4)) {
876                 brl_options = str + 4;
877                 str = strchr(brl_options, ',');
878                 if (!str) {
879                         printk(KERN_ERR "need port name after brl=\n");
880                         return 1;
881                 }
882                 *(str++) = 0;
883         }
884 #endif
885
886         /*
887          * Decode str into name, index, options.
888          */
889         if (str[0] >= '0' && str[0] <= '9') {
890                 strcpy(buf, "ttyS");
891                 strncpy(buf + 4, str, sizeof(buf) - 5);
892         } else {
893                 strncpy(buf, str, sizeof(buf) - 1);
894         }
895         buf[sizeof(buf) - 1] = 0;
896         if ((options = strchr(str, ',')) != NULL)
897                 *(options++) = 0;
898 #ifdef __sparc__
899         if (!strcmp(str, "ttya"))
900                 strcpy(buf, "ttyS0");
901         if (!strcmp(str, "ttyb"))
902                 strcpy(buf, "ttyS1");
903 #endif
904         for (s = buf; *s; s++)
905                 if ((*s >= '0' && *s <= '9') || *s == ',')
906                         break;
907         idx = simple_strtoul(s, NULL, 10);
908         *s = 0;
909
910         __add_preferred_console(buf, idx, options, brl_options);
911         console_set_on_cmdline = 1;
912         return 1;
913 }
914 __setup("console=", console_setup);
915
916 /**
917  * add_preferred_console - add a device to the list of preferred consoles.
918  * @name: device name
919  * @idx: device index
920  * @options: options for this console
921  *
922  * The last preferred console added will be used for kernel messages
923  * and stdin/out/err for init.  Normally this is used by console_setup
924  * above to handle user-supplied console arguments; however it can also
925  * be used by arch-specific code either to override the user or more
926  * commonly to provide a default console (ie from PROM variables) when
927  * the user has not supplied one.
928  */
929 int add_preferred_console(char *name, int idx, char *options)
930 {
931         return __add_preferred_console(name, idx, options, NULL);
932 }
933
934 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
935 {
936         struct console_cmdline *c;
937         int i;
938
939         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
940                 if (strcmp(console_cmdline[i].name, name) == 0 &&
941                           console_cmdline[i].index == idx) {
942                                 c = &console_cmdline[i];
943                                 strlcpy(c->name, name_new, sizeof(c->name));
944                                 c->name[sizeof(c->name) - 1] = 0;
945                                 c->options = options;
946                                 c->index = idx_new;
947                                 return i;
948                 }
949         /* not found */
950         return -1;
951 }
952
953 int console_suspend_enabled = 1;
954 EXPORT_SYMBOL(console_suspend_enabled);
955
956 static int __init console_suspend_disable(char *str)
957 {
958         console_suspend_enabled = 0;
959         return 1;
960 }
961 __setup("no_console_suspend", console_suspend_disable);
962
963 /**
964  * suspend_console - suspend the console subsystem
965  *
966  * This disables printk() while we go into suspend states
967  */
968 void suspend_console(void)
969 {
970         if (!console_suspend_enabled)
971                 return;
972         printk("Suspending console(s) (use no_console_suspend to debug)\n");
973         acquire_console_sem();
974         console_suspended = 1;
975         up(&console_sem);
976 }
977
978 void resume_console(void)
979 {
980         if (!console_suspend_enabled)
981                 return;
982         down(&console_sem);
983         console_suspended = 0;
984         release_console_sem();
985 }
986
987 /**
988  * acquire_console_sem - lock the console system for exclusive use.
989  *
990  * Acquires a semaphore which guarantees that the caller has
991  * exclusive access to the console system and the console_drivers list.
992  *
993  * Can sleep, returns nothing.
994  */
995 void acquire_console_sem(void)
996 {
997         BUG_ON(in_interrupt());
998         down(&console_sem);
999         if (console_suspended)
1000                 return;
1001         console_locked = 1;
1002         console_may_schedule = 1;
1003 }
1004 EXPORT_SYMBOL(acquire_console_sem);
1005
1006 int try_acquire_console_sem(void)
1007 {
1008         if (down_trylock(&console_sem))
1009                 return -1;
1010         if (console_suspended) {
1011                 up(&console_sem);
1012                 return -1;
1013         }
1014         console_locked = 1;
1015         console_may_schedule = 0;
1016         return 0;
1017 }
1018 EXPORT_SYMBOL(try_acquire_console_sem);
1019
1020 int is_console_locked(void)
1021 {
1022         return console_locked;
1023 }
1024
1025 static DEFINE_PER_CPU(int, printk_pending);
1026
1027 void printk_tick(void)
1028 {
1029         if (__get_cpu_var(printk_pending)) {
1030                 __get_cpu_var(printk_pending) = 0;
1031                 wake_up_interruptible(&log_wait);
1032         }
1033 }
1034
1035 int printk_needs_cpu(int cpu)
1036 {
1037         return per_cpu(printk_pending, cpu);
1038 }
1039
1040 void wake_up_klogd(void)
1041 {
1042         if (waitqueue_active(&log_wait))
1043                 __raw_get_cpu_var(printk_pending) = 1;
1044 }
1045
1046 /**
1047  * release_console_sem - unlock the console system
1048  *
1049  * Releases the semaphore which the caller holds on the console system
1050  * and the console driver list.
1051  *
1052  * While the semaphore was held, console output may have been buffered
1053  * by printk().  If this is the case, release_console_sem() emits
1054  * the output prior to releasing the semaphore.
1055  *
1056  * If there is output waiting for klogd, we wake it up.
1057  *
1058  * release_console_sem() may be called from any context.
1059  */
1060 void release_console_sem(void)
1061 {
1062         unsigned long flags;
1063         unsigned _con_start, _log_end;
1064         unsigned wake_klogd = 0;
1065
1066         if (console_suspended) {
1067                 up(&console_sem);
1068                 return;
1069         }
1070
1071         console_may_schedule = 0;
1072
1073         for ( ; ; ) {
1074                 spin_lock_irqsave(&logbuf_lock, flags);
1075                 wake_klogd |= log_start - log_end;
1076                 if (con_start == log_end)
1077                         break;                  /* Nothing to print */
1078                 _con_start = con_start;
1079                 _log_end = log_end;
1080                 con_start = log_end;            /* Flush */
1081                 spin_unlock(&logbuf_lock);
1082                 stop_critical_timings();        /* don't trace print latency */
1083                 call_console_drivers(_con_start, _log_end);
1084                 start_critical_timings();
1085                 local_irq_restore(flags);
1086         }
1087         console_locked = 0;
1088         up(&console_sem);
1089         spin_unlock_irqrestore(&logbuf_lock, flags);
1090         if (wake_klogd)
1091                 wake_up_klogd();
1092 }
1093 EXPORT_SYMBOL(release_console_sem);
1094
1095 /**
1096  * console_conditional_schedule - yield the CPU if required
1097  *
1098  * If the console code is currently allowed to sleep, and
1099  * if this CPU should yield the CPU to another task, do
1100  * so here.
1101  *
1102  * Must be called within acquire_console_sem().
1103  */
1104 void __sched console_conditional_schedule(void)
1105 {
1106         if (console_may_schedule)
1107                 cond_resched();
1108 }
1109 EXPORT_SYMBOL(console_conditional_schedule);
1110
1111 void console_unblank(void)
1112 {
1113         struct console *c;
1114
1115         /*
1116          * console_unblank can no longer be called in interrupt context unless
1117          * oops_in_progress is set to 1..
1118          */
1119         if (oops_in_progress) {
1120                 if (down_trylock(&console_sem) != 0)
1121                         return;
1122         } else
1123                 acquire_console_sem();
1124
1125         console_locked = 1;
1126         console_may_schedule = 0;
1127         for_each_console(c)
1128                 if ((c->flags & CON_ENABLED) && c->unblank)
1129                         c->unblank();
1130         release_console_sem();
1131 }
1132
1133 /*
1134  * Return the console tty driver structure and its associated index
1135  */
1136 struct tty_driver *console_device(int *index)
1137 {
1138         struct console *c;
1139         struct tty_driver *driver = NULL;
1140
1141         acquire_console_sem();
1142         for_each_console(c) {
1143                 if (!c->device)
1144                         continue;
1145                 driver = c->device(c, index);
1146                 if (driver)
1147                         break;
1148         }
1149         release_console_sem();
1150         return driver;
1151 }
1152
1153 /*
1154  * Prevent further output on the passed console device so that (for example)
1155  * serial drivers can disable console output before suspending a port, and can
1156  * re-enable output afterwards.
1157  */
1158 void console_stop(struct console *console)
1159 {
1160         acquire_console_sem();
1161         console->flags &= ~CON_ENABLED;
1162         release_console_sem();
1163 }
1164 EXPORT_SYMBOL(console_stop);
1165
1166 void console_start(struct console *console)
1167 {
1168         acquire_console_sem();
1169         console->flags |= CON_ENABLED;
1170         release_console_sem();
1171 }
1172 EXPORT_SYMBOL(console_start);
1173
1174 /*
1175  * The console driver calls this routine during kernel initialization
1176  * to register the console printing procedure with printk() and to
1177  * print any messages that were printed by the kernel before the
1178  * console driver was initialized.
1179  *
1180  * This can happen pretty early during the boot process (because of
1181  * early_printk) - sometimes before setup_arch() completes - be careful
1182  * of what kernel features are used - they may not be initialised yet.
1183  *
1184  * There are two types of consoles - bootconsoles (early_printk) and
1185  * "real" consoles (everything which is not a bootconsole) which are
1186  * handled differently.
1187  *  - Any number of bootconsoles can be registered at any time.
1188  *  - As soon as a "real" console is registered, all bootconsoles
1189  *    will be unregistered automatically.
1190  *  - Once a "real" console is registered, any attempt to register a
1191  *    bootconsoles will be rejected
1192  */
1193 void register_console(struct console *newcon)
1194 {
1195         int i;
1196         unsigned long flags;
1197         struct console *bcon = NULL;
1198
1199         /*
1200          * before we register a new CON_BOOT console, make sure we don't
1201          * already have a valid console
1202          */
1203         if (console_drivers && newcon->flags & CON_BOOT) {
1204                 /* find the last or real console */
1205                 for_each_console(bcon) {
1206                         if (!(bcon->flags & CON_BOOT)) {
1207                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1208                                         newcon->name, newcon->index);
1209                                 return;
1210                         }
1211                 }
1212         }
1213
1214         if (console_drivers && console_drivers->flags & CON_BOOT)
1215                 bcon = console_drivers;
1216
1217         if (preferred_console < 0 || bcon || !console_drivers)
1218                 preferred_console = selected_console;
1219
1220         if (newcon->early_setup)
1221                 newcon->early_setup();
1222
1223         /*
1224          *      See if we want to use this console driver. If we
1225          *      didn't select a console we take the first one
1226          *      that registers here.
1227          */
1228         if (preferred_console < 0) {
1229                 if (newcon->index < 0)
1230                         newcon->index = 0;
1231                 if (newcon->setup == NULL ||
1232                     newcon->setup(newcon, NULL) == 0) {
1233                         newcon->flags |= CON_ENABLED;
1234                         if (newcon->device) {
1235                                 newcon->flags |= CON_CONSDEV;
1236                                 preferred_console = 0;
1237                         }
1238                 }
1239         }
1240
1241         /*
1242          *      See if this console matches one we selected on
1243          *      the command line.
1244          */
1245         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1246                         i++) {
1247                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1248                         continue;
1249                 if (newcon->index >= 0 &&
1250                     newcon->index != console_cmdline[i].index)
1251                         continue;
1252                 if (newcon->index < 0)
1253                         newcon->index = console_cmdline[i].index;
1254 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1255                 if (console_cmdline[i].brl_options) {
1256                         newcon->flags |= CON_BRL;
1257                         braille_register_console(newcon,
1258                                         console_cmdline[i].index,
1259                                         console_cmdline[i].options,
1260                                         console_cmdline[i].brl_options);
1261                         return;
1262                 }
1263 #endif
1264                 if (newcon->setup &&
1265                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1266                         break;
1267                 newcon->flags |= CON_ENABLED;
1268                 newcon->index = console_cmdline[i].index;
1269                 if (i == selected_console) {
1270                         newcon->flags |= CON_CONSDEV;
1271                         preferred_console = selected_console;
1272                 }
1273                 break;
1274         }
1275
1276         if (!(newcon->flags & CON_ENABLED))
1277                 return;
1278
1279         /*
1280          * If we have a bootconsole, and are switching to a real console,
1281          * don't print everything out again, since when the boot console, and
1282          * the real console are the same physical device, it's annoying to
1283          * see the beginning boot messages twice
1284          */
1285         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1286                 newcon->flags &= ~CON_PRINTBUFFER;
1287
1288         /*
1289          *      Put this console in the list - keep the
1290          *      preferred driver at the head of the list.
1291          */
1292         acquire_console_sem();
1293         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1294                 newcon->next = console_drivers;
1295                 console_drivers = newcon;
1296                 if (newcon->next)
1297                         newcon->next->flags &= ~CON_CONSDEV;
1298         } else {
1299                 newcon->next = console_drivers->next;
1300                 console_drivers->next = newcon;
1301         }
1302         if (newcon->flags & CON_PRINTBUFFER) {
1303                 /*
1304                  * release_console_sem() will print out the buffered messages
1305                  * for us.
1306                  */
1307                 spin_lock_irqsave(&logbuf_lock, flags);
1308                 con_start = log_start;
1309                 spin_unlock_irqrestore(&logbuf_lock, flags);
1310         }
1311         release_console_sem();
1312
1313         /*
1314          * By unregistering the bootconsoles after we enable the real console
1315          * we get the "console xxx enabled" message on all the consoles -
1316          * boot consoles, real consoles, etc - this is to ensure that end
1317          * users know there might be something in the kernel's log buffer that
1318          * went to the bootconsole (that they do not see on the real console)
1319          */
1320         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1321                 /* we need to iterate through twice, to make sure we print
1322                  * everything out, before we unregister the console(s)
1323                  */
1324                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1325                         newcon->name, newcon->index);
1326                 for_each_console(bcon)
1327                         if (bcon->flags & CON_BOOT)
1328                                 unregister_console(bcon);
1329         } else {
1330                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1331                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1332                         newcon->name, newcon->index);
1333         }
1334 }
1335 EXPORT_SYMBOL(register_console);
1336
1337 int unregister_console(struct console *console)
1338 {
1339         struct console *a, *b;
1340         int res = 1;
1341
1342 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1343         if (console->flags & CON_BRL)
1344                 return braille_unregister_console(console);
1345 #endif
1346
1347         acquire_console_sem();
1348         if (console_drivers == console) {
1349                 console_drivers=console->next;
1350                 res = 0;
1351         } else if (console_drivers) {
1352                 for (a=console_drivers->next, b=console_drivers ;
1353                      a; b=a, a=b->next) {
1354                         if (a == console) {
1355                                 b->next = a->next;
1356                                 res = 0;
1357                                 break;
1358                         }
1359                 }
1360         }
1361
1362         /*
1363          * If this isn't the last console and it has CON_CONSDEV set, we
1364          * need to set it on the next preferred console.
1365          */
1366         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1367                 console_drivers->flags |= CON_CONSDEV;
1368
1369         release_console_sem();
1370         return res;
1371 }
1372 EXPORT_SYMBOL(unregister_console);
1373
1374 static int __init disable_boot_consoles(void)
1375 {
1376         struct console *con;
1377
1378         for_each_console(con) {
1379                 if (con->flags & CON_BOOT) {
1380                         printk(KERN_INFO "turn off boot console %s%d\n",
1381                                 con->name, con->index);
1382                         unregister_console(con);
1383                 }
1384         }
1385         return 0;
1386 }
1387 late_initcall(disable_boot_consoles);
1388
1389 #if defined CONFIG_PRINTK
1390
1391 /*
1392  * printk rate limiting, lifted from the networking subsystem.
1393  *
1394  * This enforces a rate limit: not more than 10 kernel messages
1395  * every 5s to make a denial-of-service attack impossible.
1396  */
1397 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1398
1399 int __printk_ratelimit(const char *func)
1400 {
1401         return ___ratelimit(&printk_ratelimit_state, func);
1402 }
1403 EXPORT_SYMBOL(__printk_ratelimit);
1404
1405 /**
1406  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1407  * @caller_jiffies: pointer to caller's state
1408  * @interval_msecs: minimum interval between prints
1409  *
1410  * printk_timed_ratelimit() returns true if more than @interval_msecs
1411  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1412  * returned true.
1413  */
1414 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1415                         unsigned int interval_msecs)
1416 {
1417         if (*caller_jiffies == 0
1418                         || !time_in_range(jiffies, *caller_jiffies,
1419                                         *caller_jiffies
1420                                         + msecs_to_jiffies(interval_msecs))) {
1421                 *caller_jiffies = jiffies;
1422                 return true;
1423         }
1424         return false;
1425 }
1426 EXPORT_SYMBOL(printk_timed_ratelimit);
1427
1428 static DEFINE_SPINLOCK(dump_list_lock);
1429 static LIST_HEAD(dump_list);
1430
1431 /**
1432  * kmsg_dump_register - register a kernel log dumper.
1433  * @dumper: pointer to the kmsg_dumper structure
1434  *
1435  * Adds a kernel log dumper to the system. The dump callback in the
1436  * structure will be called when the kernel oopses or panics and must be
1437  * set. Returns zero on success and %-EINVAL or %-EBUSY otherwise.
1438  */
1439 int kmsg_dump_register(struct kmsg_dumper *dumper)
1440 {
1441         unsigned long flags;
1442         int err = -EBUSY;
1443
1444         /* The dump callback needs to be set */
1445         if (!dumper->dump)
1446                 return -EINVAL;
1447
1448         spin_lock_irqsave(&dump_list_lock, flags);
1449         /* Don't allow registering multiple times */
1450         if (!dumper->registered) {
1451                 dumper->registered = 1;
1452                 list_add_tail(&dumper->list, &dump_list);
1453                 err = 0;
1454         }
1455         spin_unlock_irqrestore(&dump_list_lock, flags);
1456
1457         return err;
1458 }
1459 EXPORT_SYMBOL_GPL(kmsg_dump_register);
1460
1461 /**
1462  * kmsg_dump_unregister - unregister a kmsg dumper.
1463  * @dumper: pointer to the kmsg_dumper structure
1464  *
1465  * Removes a dump device from the system. Returns zero on success and
1466  * %-EINVAL otherwise.
1467  */
1468 int kmsg_dump_unregister(struct kmsg_dumper *dumper)
1469 {
1470         unsigned long flags;
1471         int err = -EINVAL;
1472
1473         spin_lock_irqsave(&dump_list_lock, flags);
1474         if (dumper->registered) {
1475                 dumper->registered = 0;
1476                 list_del(&dumper->list);
1477                 err = 0;
1478         }
1479         spin_unlock_irqrestore(&dump_list_lock, flags);
1480
1481         return err;
1482 }
1483 EXPORT_SYMBOL_GPL(kmsg_dump_unregister);
1484
1485 static const char const *kmsg_reasons[] = {
1486         [KMSG_DUMP_OOPS]        = "oops",
1487         [KMSG_DUMP_PANIC]       = "panic",
1488         [KMSG_DUMP_KEXEC]       = "kexec",
1489 };
1490
1491 static const char *kmsg_to_str(enum kmsg_dump_reason reason)
1492 {
1493         if (reason >= ARRAY_SIZE(kmsg_reasons) || reason < 0)
1494                 return "unknown";
1495
1496         return kmsg_reasons[reason];
1497 }
1498
1499 /**
1500  * kmsg_dump - dump kernel log to kernel message dumpers.
1501  * @reason: the reason (oops, panic etc) for dumping
1502  *
1503  * Iterate through each of the dump devices and call the oops/panic
1504  * callbacks with the log buffer.
1505  */
1506 void kmsg_dump(enum kmsg_dump_reason reason)
1507 {
1508         unsigned long end;
1509         unsigned chars;
1510         struct kmsg_dumper *dumper;
1511         const char *s1, *s2;
1512         unsigned long l1, l2;
1513         unsigned long flags;
1514
1515         /* Theoretically, the log could move on after we do this, but
1516            there's not a lot we can do about that. The new messages
1517            will overwrite the start of what we dump. */
1518         spin_lock_irqsave(&logbuf_lock, flags);
1519         end = log_end & LOG_BUF_MASK;
1520         chars = logged_chars;
1521         spin_unlock_irqrestore(&logbuf_lock, flags);
1522
1523         if (logged_chars > end) {
1524                 s1 = log_buf + log_buf_len - logged_chars + end;
1525                 l1 = logged_chars - end;
1526
1527                 s2 = log_buf;
1528                 l2 = end;
1529         } else {
1530                 s1 = "";
1531                 l1 = 0;
1532
1533                 s2 = log_buf + end - logged_chars;
1534                 l2 = logged_chars;
1535         }
1536
1537         if (!spin_trylock_irqsave(&dump_list_lock, flags)) {
1538                 printk(KERN_ERR "dump_kmsg: dump list lock is held during %s, skipping dump\n",
1539                                 kmsg_to_str(reason));
1540                 return;
1541         }
1542         list_for_each_entry(dumper, &dump_list, list)
1543                 dumper->dump(dumper, reason, s1, l1, s2, l2);
1544         spin_unlock_irqrestore(&dump_list_lock, flags);
1545 }
1546 #endif