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