ratelimit: Make suppressed output messages more useful
[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
38 #include <asm/uaccess.h>
39
40 /*
41  * for_each_console() allows you to iterate on each console
42  */
43 #define for_each_console(con) \
44         for (con = console_drivers; con != NULL; con = con->next)
45
46 /*
47  * Architectures can override it:
48  */
49 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
50 {
51 }
52
53 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
54
55 /* printk's without a loglevel use this.. */
56 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
57
58 /* We show everything that is MORE important than this.. */
59 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
60 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
61
62 DECLARE_WAIT_QUEUE_HEAD(log_wait);
63
64 int console_printk[4] = {
65         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
66         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
67         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
68         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
69 };
70
71 static int saved_console_loglevel = -1;
72
73 /*
74  * Low level drivers may need that to know if they can schedule in
75  * their unblank() callback or not. So let's export it.
76  */
77 int oops_in_progress;
78 EXPORT_SYMBOL(oops_in_progress);
79
80 /*
81  * console_sem protects the console_drivers list, and also
82  * provides serialisation for access to the entire console
83  * driver system.
84  */
85 static DECLARE_MUTEX(console_sem);
86 struct console *console_drivers;
87 EXPORT_SYMBOL_GPL(console_drivers);
88
89 /*
90  * This is used for debugging the mess that is the VT code by
91  * keeping track if we have the console semaphore held. It's
92  * definitely not the perfect debug tool (we don't know if _WE_
93  * hold it are racing, but it helps tracking those weird code
94  * path in the console code where we end up in places I want
95  * locked without the console sempahore held
96  */
97 static int console_locked, console_suspended;
98
99 /*
100  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
101  * It is also used in interesting ways to provide interlocking in
102  * release_console_sem().
103  */
104 static DEFINE_SPINLOCK(logbuf_lock);
105
106 #define LOG_BUF_MASK (log_buf_len-1)
107 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
108
109 /*
110  * The indices into log_buf are not constrained to log_buf_len - they
111  * must be masked before subscripting
112  */
113 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
114 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
115 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
116
117 /*
118  *      Array of consoles built from command line options (console=)
119  */
120 struct console_cmdline
121 {
122         char    name[8];                        /* Name of the driver       */
123         int     index;                          /* Minor dev. to use        */
124         char    *options;                       /* Options for the driver   */
125 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
126         char    *brl_options;                   /* Options for braille driver */
127 #endif
128 };
129
130 #define MAX_CMDLINECONSOLES 8
131
132 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
133 static int selected_console = -1;
134 static int preferred_console = -1;
135 int console_set_on_cmdline;
136 EXPORT_SYMBOL(console_set_on_cmdline);
137
138 /* Flag: console code may call schedule() */
139 static int console_may_schedule;
140
141 #ifdef CONFIG_PRINTK
142
143 static char __log_buf[__LOG_BUF_LEN];
144 static char *log_buf = __log_buf;
145 static int log_buf_len = __LOG_BUF_LEN;
146 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
147
148 #ifdef CONFIG_KEXEC
149 /*
150  * This appends the listed symbols to /proc/vmcoreinfo
151  *
152  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
153  * obtain access to symbols that are otherwise very difficult to locate.  These
154  * symbols are specifically used so that utilities can access and extract the
155  * dmesg log from a vmcore file after a crash.
156  */
157 void log_buf_kexec_setup(void)
158 {
159         VMCOREINFO_SYMBOL(log_buf);
160         VMCOREINFO_SYMBOL(log_end);
161         VMCOREINFO_SYMBOL(log_buf_len);
162         VMCOREINFO_SYMBOL(logged_chars);
163 }
164 #endif
165
166 static int __init log_buf_len_setup(char *str)
167 {
168         unsigned size = memparse(str, &str);
169         unsigned long flags;
170
171         if (size)
172                 size = roundup_pow_of_two(size);
173         if (size > log_buf_len) {
174                 unsigned start, dest_idx, offset;
175                 char *new_log_buf;
176
177                 new_log_buf = alloc_bootmem(size);
178                 if (!new_log_buf) {
179                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
180                         goto out;
181                 }
182
183                 spin_lock_irqsave(&logbuf_lock, flags);
184                 log_buf_len = size;
185                 log_buf = new_log_buf;
186
187                 offset = start = min(con_start, log_start);
188                 dest_idx = 0;
189                 while (start != log_end) {
190                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
191                         start++;
192                         dest_idx++;
193                 }
194                 log_start -= offset;
195                 con_start -= offset;
196                 log_end -= offset;
197                 spin_unlock_irqrestore(&logbuf_lock, flags);
198
199                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
200         }
201 out:
202         return 1;
203 }
204
205 __setup("log_buf_len=", log_buf_len_setup);
206
207 #ifdef CONFIG_BOOT_PRINTK_DELAY
208
209 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
210 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
211
212 static int __init boot_delay_setup(char *str)
213 {
214         unsigned long lpj;
215         unsigned long long loops_per_msec;
216
217         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
218         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
219
220         get_option(&str, &boot_delay);
221         if (boot_delay > 10 * 1000)
222                 boot_delay = 0;
223
224         printk_delay_msec = loops_per_msec;
225         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
226                 "HZ: %d, printk_delay_msec: %llu\n",
227                 boot_delay, preset_lpj, lpj, HZ, printk_delay_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)printk_delay_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 /*
263  * Commands to do_syslog:
264  *
265  *      0 -- Close the log.  Currently a NOP.
266  *      1 -- Open the log. Currently a NOP.
267  *      2 -- Read from the log.
268  *      3 -- Read all messages remaining in the ring buffer.
269  *      4 -- Read and clear all messages remaining in the ring buffer
270  *      5 -- Clear ring buffer.
271  *      6 -- Disable printk's to console
272  *      7 -- Enable printk's to console
273  *      8 -- Set level of messages printed to console
274  *      9 -- Return number of unread characters in the log buffer
275  *     10 -- Return size of the log buffer
276  */
277 int do_syslog(int type, char __user *buf, int len)
278 {
279         unsigned i, j, limit, count;
280         int do_clear = 0;
281         char c;
282         int error = 0;
283
284         error = security_syslog(type);
285         if (error)
286                 return error;
287
288         switch (type) {
289         case 0:         /* Close log */
290                 break;
291         case 1:         /* Open log */
292                 break;
293         case 2:         /* Read from log */
294                 error = -EINVAL;
295                 if (!buf || len < 0)
296                         goto out;
297                 error = 0;
298                 if (!len)
299                         goto out;
300                 if (!access_ok(VERIFY_WRITE, buf, len)) {
301                         error = -EFAULT;
302                         goto out;
303                 }
304                 error = wait_event_interruptible(log_wait,
305                                                         (log_start - log_end));
306                 if (error)
307                         goto out;
308                 i = 0;
309                 spin_lock_irq(&logbuf_lock);
310                 while (!error && (log_start != log_end) && i < len) {
311                         c = LOG_BUF(log_start);
312                         log_start++;
313                         spin_unlock_irq(&logbuf_lock);
314                         error = __put_user(c,buf);
315                         buf++;
316                         i++;
317                         cond_resched();
318                         spin_lock_irq(&logbuf_lock);
319                 }
320                 spin_unlock_irq(&logbuf_lock);
321                 if (!error)
322                         error = i;
323                 break;
324         case 4:         /* Read/clear last kernel messages */
325                 do_clear = 1;
326                 /* FALL THRU */
327         case 3:         /* Read last kernel messages */
328                 error = -EINVAL;
329                 if (!buf || len < 0)
330                         goto out;
331                 error = 0;
332                 if (!len)
333                         goto out;
334                 if (!access_ok(VERIFY_WRITE, buf, len)) {
335                         error = -EFAULT;
336                         goto out;
337                 }
338                 count = len;
339                 if (count > log_buf_len)
340                         count = log_buf_len;
341                 spin_lock_irq(&logbuf_lock);
342                 if (count > logged_chars)
343                         count = logged_chars;
344                 if (do_clear)
345                         logged_chars = 0;
346                 limit = log_end;
347                 /*
348                  * __put_user() could sleep, and while we sleep
349                  * printk() could overwrite the messages
350                  * we try to copy to user space. Therefore
351                  * the messages are copied in reverse. <manfreds>
352                  */
353                 for (i = 0; i < count && !error; i++) {
354                         j = limit-1-i;
355                         if (j + log_buf_len < log_end)
356                                 break;
357                         c = LOG_BUF(j);
358                         spin_unlock_irq(&logbuf_lock);
359                         error = __put_user(c,&buf[count-1-i]);
360                         cond_resched();
361                         spin_lock_irq(&logbuf_lock);
362                 }
363                 spin_unlock_irq(&logbuf_lock);
364                 if (error)
365                         break;
366                 error = i;
367                 if (i != count) {
368                         int offset = count-error;
369                         /* buffer overflow during copy, correct user buffer. */
370                         for (i = 0; i < error; i++) {
371                                 if (__get_user(c,&buf[i+offset]) ||
372                                     __put_user(c,&buf[i])) {
373                                         error = -EFAULT;
374                                         break;
375                                 }
376                                 cond_resched();
377                         }
378                 }
379                 break;
380         case 5:         /* Clear ring buffer */
381                 logged_chars = 0;
382                 break;
383         case 6:         /* Disable logging to console */
384                 if (saved_console_loglevel == -1)
385                         saved_console_loglevel = console_loglevel;
386                 console_loglevel = minimum_console_loglevel;
387                 break;
388         case 7:         /* Enable logging to console */
389                 if (saved_console_loglevel != -1) {
390                         console_loglevel = saved_console_loglevel;
391                         saved_console_loglevel = -1;
392                 }
393                 break;
394         case 8:         /* Set level of messages printed to console */
395                 error = -EINVAL;
396                 if (len < 1 || len > 8)
397                         goto out;
398                 if (len < minimum_console_loglevel)
399                         len = minimum_console_loglevel;
400                 console_loglevel = len;
401                 /* Implicitly re-enable logging to console */
402                 saved_console_loglevel = -1;
403                 error = 0;
404                 break;
405         case 9:         /* Number of chars in the log buffer */
406                 error = log_end - log_start;
407                 break;
408         case 10:        /* Size of the log buffer */
409                 error = log_buf_len;
410                 break;
411         default:
412                 error = -EINVAL;
413                 break;
414         }
415 out:
416         return error;
417 }
418
419 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
420 {
421         return do_syslog(type, buf, len);
422 }
423
424 /*
425  * Call the console drivers on a range of log_buf
426  */
427 static void __call_console_drivers(unsigned start, unsigned end)
428 {
429         struct console *con;
430
431         for_each_console(con) {
432                 if ((con->flags & CON_ENABLED) && con->write &&
433                                 (cpu_online(smp_processor_id()) ||
434                                 (con->flags & CON_ANYTIME)))
435                         con->write(con, &LOG_BUF(start), end - start);
436         }
437 }
438
439 static int __read_mostly ignore_loglevel;
440
441 static int __init ignore_loglevel_setup(char *str)
442 {
443         ignore_loglevel = 1;
444         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
445
446         return 0;
447 }
448
449 early_param("ignore_loglevel", ignore_loglevel_setup);
450
451 /*
452  * Write out chars from start to end - 1 inclusive
453  */
454 static void _call_console_drivers(unsigned start,
455                                 unsigned end, int msg_log_level)
456 {
457         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
458                         console_drivers && start != end) {
459                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
460                         /* wrapped write */
461                         __call_console_drivers(start & LOG_BUF_MASK,
462                                                 log_buf_len);
463                         __call_console_drivers(0, end & LOG_BUF_MASK);
464                 } else {
465                         __call_console_drivers(start, end);
466                 }
467         }
468 }
469
470 /*
471  * Call the console drivers, asking them to write out
472  * log_buf[start] to log_buf[end - 1].
473  * The console_sem must be held.
474  */
475 static void call_console_drivers(unsigned start, unsigned end)
476 {
477         unsigned cur_index, start_print;
478         static int msg_level = -1;
479
480         BUG_ON(((int)(start - end)) > 0);
481
482         cur_index = start;
483         start_print = start;
484         while (cur_index != end) {
485                 if (msg_level < 0 && ((end - cur_index) > 2) &&
486                                 LOG_BUF(cur_index + 0) == '<' &&
487                                 LOG_BUF(cur_index + 1) >= '0' &&
488                                 LOG_BUF(cur_index + 1) <= '7' &&
489                                 LOG_BUF(cur_index + 2) == '>') {
490                         msg_level = LOG_BUF(cur_index + 1) - '0';
491                         cur_index += 3;
492                         start_print = cur_index;
493                 }
494                 while (cur_index != end) {
495                         char c = LOG_BUF(cur_index);
496
497                         cur_index++;
498                         if (c == '\n') {
499                                 if (msg_level < 0) {
500                                         /*
501                                          * printk() has already given us loglevel tags in
502                                          * the buffer.  This code is here in case the
503                                          * log buffer has wrapped right round and scribbled
504                                          * on those tags
505                                          */
506                                         msg_level = default_message_loglevel;
507                                 }
508                                 _call_console_drivers(start_print, cur_index, msg_level);
509                                 msg_level = -1;
510                                 start_print = cur_index;
511                                 break;
512                         }
513                 }
514         }
515         _call_console_drivers(start_print, end, msg_level);
516 }
517
518 static void emit_log_char(char c)
519 {
520         LOG_BUF(log_end) = c;
521         log_end++;
522         if (log_end - log_start > log_buf_len)
523                 log_start = log_end - log_buf_len;
524         if (log_end - con_start > log_buf_len)
525                 con_start = log_end - log_buf_len;
526         if (logged_chars < log_buf_len)
527                 logged_chars++;
528 }
529
530 /*
531  * Zap console related locks when oopsing. Only zap at most once
532  * every 10 seconds, to leave time for slow consoles to print a
533  * full oops.
534  */
535 static void zap_locks(void)
536 {
537         static unsigned long oops_timestamp;
538
539         if (time_after_eq(jiffies, oops_timestamp) &&
540                         !time_after(jiffies, oops_timestamp + 30 * HZ))
541                 return;
542
543         oops_timestamp = jiffies;
544
545         /* If a crash is occurring, make sure we can't deadlock */
546         spin_lock_init(&logbuf_lock);
547         /* And make sure that we print immediately */
548         init_MUTEX(&console_sem);
549 }
550
551 #if defined(CONFIG_PRINTK_TIME)
552 static int printk_time = 1;
553 #else
554 static int printk_time = 0;
555 #endif
556 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
557
558 /* Check if we have any console registered that can be called early in boot. */
559 static int have_callable_console(void)
560 {
561         struct console *con;
562
563         for_each_console(con)
564                 if (con->flags & CON_ANYTIME)
565                         return 1;
566
567         return 0;
568 }
569
570 /**
571  * printk - print a kernel message
572  * @fmt: format string
573  *
574  * This is printk().  It can be called from any context.  We want it to work.
575  *
576  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
577  * call the console drivers.  If we fail to get the semaphore we place the output
578  * into the log buffer and return.  The current holder of the console_sem will
579  * notice the new output in release_console_sem() and will send it to the
580  * consoles before releasing the semaphore.
581  *
582  * One effect of this deferred printing is that code which calls printk() and
583  * then changes console_loglevel may break. This is because console_loglevel
584  * is inspected when the actual printing occurs.
585  *
586  * See also:
587  * printf(3)
588  *
589  * See the vsnprintf() documentation for format string extensions over C99.
590  */
591
592 asmlinkage int printk(const char *fmt, ...)
593 {
594         va_list args;
595         int r;
596
597         va_start(args, fmt);
598         r = vprintk(fmt, args);
599         va_end(args);
600
601         return r;
602 }
603
604 /* cpu currently holding logbuf_lock */
605 static volatile unsigned int printk_cpu = UINT_MAX;
606
607 /*
608  * Can we actually use the console at this time on this cpu?
609  *
610  * Console drivers may assume that per-cpu resources have
611  * been allocated. So unless they're explicitly marked as
612  * being able to cope (CON_ANYTIME) don't call them until
613  * this CPU is officially up.
614  */
615 static inline int can_use_console(unsigned int cpu)
616 {
617         return cpu_online(cpu) || have_callable_console();
618 }
619
620 /*
621  * Try to get console ownership to actually show the kernel
622  * messages from a 'printk'. Return true (and with the
623  * console_semaphore held, and 'console_locked' set) if it
624  * is successful, false otherwise.
625  *
626  * This gets called with the 'logbuf_lock' spinlock held and
627  * interrupts disabled. It should return with 'lockbuf_lock'
628  * released but interrupts still disabled.
629  */
630 static int acquire_console_semaphore_for_printk(unsigned int cpu)
631 {
632         int retval = 0;
633
634         if (!try_acquire_console_sem()) {
635                 retval = 1;
636
637                 /*
638                  * If we can't use the console, we need to release
639                  * the console semaphore by hand to avoid flushing
640                  * the buffer. We need to hold the console semaphore
641                  * in order to do this test safely.
642                  */
643                 if (!can_use_console(cpu)) {
644                         console_locked = 0;
645                         up(&console_sem);
646                         retval = 0;
647                 }
648         }
649         printk_cpu = UINT_MAX;
650         spin_unlock(&logbuf_lock);
651         return retval;
652 }
653 static const char recursion_bug_msg [] =
654                 KERN_CRIT "BUG: recent printk recursion!\n";
655 static int recursion_bug;
656 static int new_text_line = 1;
657 static char printk_buf[1024];
658
659 asmlinkage int vprintk(const char *fmt, va_list args)
660 {
661         int printed_len = 0;
662         int current_log_level = default_message_loglevel;
663         unsigned long flags;
664         int this_cpu;
665         char *p;
666
667         boot_delay_msec();
668
669         preempt_disable();
670         /* This stops the holder of console_sem just where we want him */
671         raw_local_irq_save(flags);
672         this_cpu = smp_processor_id();
673
674         /*
675          * Ouch, printk recursed into itself!
676          */
677         if (unlikely(printk_cpu == this_cpu)) {
678                 /*
679                  * If a crash is occurring during printk() on this CPU,
680                  * then try to get the crash message out but make sure
681                  * we can't deadlock. Otherwise just return to avoid the
682                  * recursion and return - but flag the recursion so that
683                  * it can be printed at the next appropriate moment:
684                  */
685                 if (!oops_in_progress) {
686                         recursion_bug = 1;
687                         goto out_restore_irqs;
688                 }
689                 zap_locks();
690         }
691
692         lockdep_off();
693         spin_lock(&logbuf_lock);
694         printk_cpu = this_cpu;
695
696         if (recursion_bug) {
697                 recursion_bug = 0;
698                 strcpy(printk_buf, recursion_bug_msg);
699                 printed_len = strlen(recursion_bug_msg);
700         }
701         /* Emit the output into the temporary buffer */
702         printed_len += vscnprintf(printk_buf + printed_len,
703                                   sizeof(printk_buf) - printed_len, fmt, args);
704
705
706         p = printk_buf;
707
708         /* Do we have a loglevel in the string? */
709         if (p[0] == '<') {
710                 unsigned char c = p[1];
711                 if (c && p[2] == '>') {
712                         switch (c) {
713                         case '0' ... '7': /* loglevel */
714                                 current_log_level = c - '0';
715                         /* Fallthrough - make sure we're on a new line */
716                         case 'd': /* KERN_DEFAULT */
717                                 if (!new_text_line) {
718                                         emit_log_char('\n');
719                                         new_text_line = 1;
720                                 }
721                         /* Fallthrough - skip the loglevel */
722                         case 'c': /* KERN_CONT */
723                                 p += 3;
724                                 break;
725                         }
726                 }
727         }
728
729         /*
730          * Copy the output into log_buf.  If the caller didn't provide
731          * appropriate log level tags, we insert them here
732          */
733         for ( ; *p; p++) {
734                 if (new_text_line) {
735                         /* Always output the token */
736                         emit_log_char('<');
737                         emit_log_char(current_log_level + '0');
738                         emit_log_char('>');
739                         printed_len += 3;
740                         new_text_line = 0;
741
742                         if (printk_time) {
743                                 /* Follow the token with the time */
744                                 char tbuf[50], *tp;
745                                 unsigned tlen;
746                                 unsigned long long t;
747                                 unsigned long nanosec_rem;
748
749                                 t = cpu_clock(printk_cpu);
750                                 nanosec_rem = do_div(t, 1000000000);
751                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
752                                                 (unsigned long) t,
753                                                 nanosec_rem / 1000);
754
755                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
756                                         emit_log_char(*tp);
757                                 printed_len += tlen;
758                         }
759
760                         if (!*p)
761                                 break;
762                 }
763
764                 emit_log_char(*p);
765                 if (*p == '\n')
766                         new_text_line = 1;
767         }
768
769         /*
770          * Try to acquire and then immediately release the
771          * console semaphore. The release will do all the
772          * actual magic (print out buffers, wake up klogd,
773          * etc). 
774          *
775          * The acquire_console_semaphore_for_printk() function
776          * will release 'logbuf_lock' regardless of whether it
777          * actually gets the semaphore or not.
778          */
779         if (acquire_console_semaphore_for_printk(this_cpu))
780                 release_console_sem();
781
782         lockdep_on();
783 out_restore_irqs:
784         raw_local_irq_restore(flags);
785
786         preempt_enable();
787         return printed_len;
788 }
789 EXPORT_SYMBOL(printk);
790 EXPORT_SYMBOL(vprintk);
791
792 #else
793
794 static void call_console_drivers(unsigned start, unsigned end)
795 {
796 }
797
798 #endif
799
800 static int __add_preferred_console(char *name, int idx, char *options,
801                                    char *brl_options)
802 {
803         struct console_cmdline *c;
804         int i;
805
806         /*
807          *      See if this tty is not yet registered, and
808          *      if we have a slot free.
809          */
810         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
811                 if (strcmp(console_cmdline[i].name, name) == 0 &&
812                           console_cmdline[i].index == idx) {
813                                 if (!brl_options)
814                                         selected_console = i;
815                                 return 0;
816                 }
817         if (i == MAX_CMDLINECONSOLES)
818                 return -E2BIG;
819         if (!brl_options)
820                 selected_console = i;
821         c = &console_cmdline[i];
822         strlcpy(c->name, name, sizeof(c->name));
823         c->options = options;
824 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
825         c->brl_options = brl_options;
826 #endif
827         c->index = idx;
828         return 0;
829 }
830 /*
831  * Set up a list of consoles.  Called from init/main.c
832  */
833 static int __init console_setup(char *str)
834 {
835         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
836         char *s, *options, *brl_options = NULL;
837         int idx;
838
839 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
840         if (!memcmp(str, "brl,", 4)) {
841                 brl_options = "";
842                 str += 4;
843         } else if (!memcmp(str, "brl=", 4)) {
844                 brl_options = str + 4;
845                 str = strchr(brl_options, ',');
846                 if (!str) {
847                         printk(KERN_ERR "need port name after brl=\n");
848                         return 1;
849                 }
850                 *(str++) = 0;
851         }
852 #endif
853
854         /*
855          * Decode str into name, index, options.
856          */
857         if (str[0] >= '0' && str[0] <= '9') {
858                 strcpy(buf, "ttyS");
859                 strncpy(buf + 4, str, sizeof(buf) - 5);
860         } else {
861                 strncpy(buf, str, sizeof(buf) - 1);
862         }
863         buf[sizeof(buf) - 1] = 0;
864         if ((options = strchr(str, ',')) != NULL)
865                 *(options++) = 0;
866 #ifdef __sparc__
867         if (!strcmp(str, "ttya"))
868                 strcpy(buf, "ttyS0");
869         if (!strcmp(str, "ttyb"))
870                 strcpy(buf, "ttyS1");
871 #endif
872         for (s = buf; *s; s++)
873                 if ((*s >= '0' && *s <= '9') || *s == ',')
874                         break;
875         idx = simple_strtoul(s, NULL, 10);
876         *s = 0;
877
878         __add_preferred_console(buf, idx, options, brl_options);
879         console_set_on_cmdline = 1;
880         return 1;
881 }
882 __setup("console=", console_setup);
883
884 /**
885  * add_preferred_console - add a device to the list of preferred consoles.
886  * @name: device name
887  * @idx: device index
888  * @options: options for this console
889  *
890  * The last preferred console added will be used for kernel messages
891  * and stdin/out/err for init.  Normally this is used by console_setup
892  * above to handle user-supplied console arguments; however it can also
893  * be used by arch-specific code either to override the user or more
894  * commonly to provide a default console (ie from PROM variables) when
895  * the user has not supplied one.
896  */
897 int add_preferred_console(char *name, int idx, char *options)
898 {
899         return __add_preferred_console(name, idx, options, NULL);
900 }
901
902 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
903 {
904         struct console_cmdline *c;
905         int i;
906
907         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
908                 if (strcmp(console_cmdline[i].name, name) == 0 &&
909                           console_cmdline[i].index == idx) {
910                                 c = &console_cmdline[i];
911                                 strlcpy(c->name, name_new, sizeof(c->name));
912                                 c->name[sizeof(c->name) - 1] = 0;
913                                 c->options = options;
914                                 c->index = idx_new;
915                                 return i;
916                 }
917         /* not found */
918         return -1;
919 }
920
921 int console_suspend_enabled = 1;
922 EXPORT_SYMBOL(console_suspend_enabled);
923
924 static int __init console_suspend_disable(char *str)
925 {
926         console_suspend_enabled = 0;
927         return 1;
928 }
929 __setup("no_console_suspend", console_suspend_disable);
930
931 /**
932  * suspend_console - suspend the console subsystem
933  *
934  * This disables printk() while we go into suspend states
935  */
936 void suspend_console(void)
937 {
938         if (!console_suspend_enabled)
939                 return;
940         printk("Suspending console(s) (use no_console_suspend to debug)\n");
941         acquire_console_sem();
942         console_suspended = 1;
943         up(&console_sem);
944 }
945
946 void resume_console(void)
947 {
948         if (!console_suspend_enabled)
949                 return;
950         down(&console_sem);
951         console_suspended = 0;
952         release_console_sem();
953 }
954
955 /**
956  * acquire_console_sem - lock the console system for exclusive use.
957  *
958  * Acquires a semaphore which guarantees that the caller has
959  * exclusive access to the console system and the console_drivers list.
960  *
961  * Can sleep, returns nothing.
962  */
963 void acquire_console_sem(void)
964 {
965         BUG_ON(in_interrupt());
966         down(&console_sem);
967         if (console_suspended)
968                 return;
969         console_locked = 1;
970         console_may_schedule = 1;
971 }
972 EXPORT_SYMBOL(acquire_console_sem);
973
974 int try_acquire_console_sem(void)
975 {
976         if (down_trylock(&console_sem))
977                 return -1;
978         if (console_suspended) {
979                 up(&console_sem);
980                 return -1;
981         }
982         console_locked = 1;
983         console_may_schedule = 0;
984         return 0;
985 }
986 EXPORT_SYMBOL(try_acquire_console_sem);
987
988 int is_console_locked(void)
989 {
990         return console_locked;
991 }
992
993 static DEFINE_PER_CPU(int, printk_pending);
994
995 void printk_tick(void)
996 {
997         if (__get_cpu_var(printk_pending)) {
998                 __get_cpu_var(printk_pending) = 0;
999                 wake_up_interruptible(&log_wait);
1000         }
1001 }
1002
1003 int printk_needs_cpu(int cpu)
1004 {
1005         return per_cpu(printk_pending, cpu);
1006 }
1007
1008 void wake_up_klogd(void)
1009 {
1010         if (waitqueue_active(&log_wait))
1011                 __raw_get_cpu_var(printk_pending) = 1;
1012 }
1013
1014 /**
1015  * release_console_sem - unlock the console system
1016  *
1017  * Releases the semaphore which the caller holds on the console system
1018  * and the console driver list.
1019  *
1020  * While the semaphore was held, console output may have been buffered
1021  * by printk().  If this is the case, release_console_sem() emits
1022  * the output prior to releasing the semaphore.
1023  *
1024  * If there is output waiting for klogd, we wake it up.
1025  *
1026  * release_console_sem() may be called from any context.
1027  */
1028 void release_console_sem(void)
1029 {
1030         unsigned long flags;
1031         unsigned _con_start, _log_end;
1032         unsigned wake_klogd = 0;
1033
1034         if (console_suspended) {
1035                 up(&console_sem);
1036                 return;
1037         }
1038
1039         console_may_schedule = 0;
1040
1041         for ( ; ; ) {
1042                 spin_lock_irqsave(&logbuf_lock, flags);
1043                 wake_klogd |= log_start - log_end;
1044                 if (con_start == log_end)
1045                         break;                  /* Nothing to print */
1046                 _con_start = con_start;
1047                 _log_end = log_end;
1048                 con_start = log_end;            /* Flush */
1049                 spin_unlock(&logbuf_lock);
1050                 stop_critical_timings();        /* don't trace print latency */
1051                 call_console_drivers(_con_start, _log_end);
1052                 start_critical_timings();
1053                 local_irq_restore(flags);
1054         }
1055         console_locked = 0;
1056         up(&console_sem);
1057         spin_unlock_irqrestore(&logbuf_lock, flags);
1058         if (wake_klogd)
1059                 wake_up_klogd();
1060 }
1061 EXPORT_SYMBOL(release_console_sem);
1062
1063 /**
1064  * console_conditional_schedule - yield the CPU if required
1065  *
1066  * If the console code is currently allowed to sleep, and
1067  * if this CPU should yield the CPU to another task, do
1068  * so here.
1069  *
1070  * Must be called within acquire_console_sem().
1071  */
1072 void __sched console_conditional_schedule(void)
1073 {
1074         if (console_may_schedule)
1075                 cond_resched();
1076 }
1077 EXPORT_SYMBOL(console_conditional_schedule);
1078
1079 void console_unblank(void)
1080 {
1081         struct console *c;
1082
1083         /*
1084          * console_unblank can no longer be called in interrupt context unless
1085          * oops_in_progress is set to 1..
1086          */
1087         if (oops_in_progress) {
1088                 if (down_trylock(&console_sem) != 0)
1089                         return;
1090         } else
1091                 acquire_console_sem();
1092
1093         console_locked = 1;
1094         console_may_schedule = 0;
1095         for_each_console(c)
1096                 if ((c->flags & CON_ENABLED) && c->unblank)
1097                         c->unblank();
1098         release_console_sem();
1099 }
1100
1101 /*
1102  * Return the console tty driver structure and its associated index
1103  */
1104 struct tty_driver *console_device(int *index)
1105 {
1106         struct console *c;
1107         struct tty_driver *driver = NULL;
1108
1109         acquire_console_sem();
1110         for_each_console(c) {
1111                 if (!c->device)
1112                         continue;
1113                 driver = c->device(c, index);
1114                 if (driver)
1115                         break;
1116         }
1117         release_console_sem();
1118         return driver;
1119 }
1120
1121 /*
1122  * Prevent further output on the passed console device so that (for example)
1123  * serial drivers can disable console output before suspending a port, and can
1124  * re-enable output afterwards.
1125  */
1126 void console_stop(struct console *console)
1127 {
1128         acquire_console_sem();
1129         console->flags &= ~CON_ENABLED;
1130         release_console_sem();
1131 }
1132 EXPORT_SYMBOL(console_stop);
1133
1134 void console_start(struct console *console)
1135 {
1136         acquire_console_sem();
1137         console->flags |= CON_ENABLED;
1138         release_console_sem();
1139 }
1140 EXPORT_SYMBOL(console_start);
1141
1142 /*
1143  * The console driver calls this routine during kernel initialization
1144  * to register the console printing procedure with printk() and to
1145  * print any messages that were printed by the kernel before the
1146  * console driver was initialized.
1147  *
1148  * This can happen pretty early during the boot process (because of
1149  * early_printk) - sometimes before setup_arch() completes - be careful
1150  * of what kernel features are used - they may not be initialised yet.
1151  *
1152  * There are two types of consoles - bootconsoles (early_printk) and
1153  * "real" consoles (everything which is not a bootconsole) which are
1154  * handled differently.
1155  *  - Any number of bootconsoles can be registered at any time.
1156  *  - As soon as a "real" console is registered, all bootconsoles
1157  *    will be unregistered automatically.
1158  *  - Once a "real" console is registered, any attempt to register a
1159  *    bootconsoles will be rejected
1160  */
1161 void register_console(struct console *newcon)
1162 {
1163         int i;
1164         unsigned long flags;
1165         struct console *bcon = NULL;
1166
1167         /*
1168          * before we register a new CON_BOOT console, make sure we don't
1169          * already have a valid console
1170          */
1171         if (console_drivers && newcon->flags & CON_BOOT) {
1172                 /* find the last or real console */
1173                 for_each_console(bcon) {
1174                         if (!(bcon->flags & CON_BOOT)) {
1175                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1176                                         newcon->name, newcon->index);
1177                                 return;
1178                         }
1179                 }
1180         }
1181
1182         if (console_drivers && console_drivers->flags & CON_BOOT)
1183                 bcon = console_drivers;
1184
1185         if (preferred_console < 0 || bcon || !console_drivers)
1186                 preferred_console = selected_console;
1187
1188         if (newcon->early_setup)
1189                 newcon->early_setup();
1190
1191         /*
1192          *      See if we want to use this console driver. If we
1193          *      didn't select a console we take the first one
1194          *      that registers here.
1195          */
1196         if (preferred_console < 0) {
1197                 if (newcon->index < 0)
1198                         newcon->index = 0;
1199                 if (newcon->setup == NULL ||
1200                     newcon->setup(newcon, NULL) == 0) {
1201                         newcon->flags |= CON_ENABLED;
1202                         if (newcon->device) {
1203                                 newcon->flags |= CON_CONSDEV;
1204                                 preferred_console = 0;
1205                         }
1206                 }
1207         }
1208
1209         /*
1210          *      See if this console matches one we selected on
1211          *      the command line.
1212          */
1213         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1214                         i++) {
1215                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1216                         continue;
1217                 if (newcon->index >= 0 &&
1218                     newcon->index != console_cmdline[i].index)
1219                         continue;
1220                 if (newcon->index < 0)
1221                         newcon->index = console_cmdline[i].index;
1222 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1223                 if (console_cmdline[i].brl_options) {
1224                         newcon->flags |= CON_BRL;
1225                         braille_register_console(newcon,
1226                                         console_cmdline[i].index,
1227                                         console_cmdline[i].options,
1228                                         console_cmdline[i].brl_options);
1229                         return;
1230                 }
1231 #endif
1232                 if (newcon->setup &&
1233                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1234                         break;
1235                 newcon->flags |= CON_ENABLED;
1236                 newcon->index = console_cmdline[i].index;
1237                 if (i == selected_console) {
1238                         newcon->flags |= CON_CONSDEV;
1239                         preferred_console = selected_console;
1240                 }
1241                 break;
1242         }
1243
1244         if (!(newcon->flags & CON_ENABLED))
1245                 return;
1246
1247         /*
1248          * If we have a bootconsole, and are switching to a real console,
1249          * don't print everything out again, since when the boot console, and
1250          * the real console are the same physical device, it's annoying to
1251          * see the beginning boot messages twice
1252          */
1253         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1254                 newcon->flags &= ~CON_PRINTBUFFER;
1255
1256         /*
1257          *      Put this console in the list - keep the
1258          *      preferred driver at the head of the list.
1259          */
1260         acquire_console_sem();
1261         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1262                 newcon->next = console_drivers;
1263                 console_drivers = newcon;
1264                 if (newcon->next)
1265                         newcon->next->flags &= ~CON_CONSDEV;
1266         } else {
1267                 newcon->next = console_drivers->next;
1268                 console_drivers->next = newcon;
1269         }
1270         if (newcon->flags & CON_PRINTBUFFER) {
1271                 /*
1272                  * release_console_sem() will print out the buffered messages
1273                  * for us.
1274                  */
1275                 spin_lock_irqsave(&logbuf_lock, flags);
1276                 con_start = log_start;
1277                 spin_unlock_irqrestore(&logbuf_lock, flags);
1278         }
1279         release_console_sem();
1280
1281         /*
1282          * By unregistering the bootconsoles after we enable the real console
1283          * we get the "console xxx enabled" message on all the consoles -
1284          * boot consoles, real consoles, etc - this is to ensure that end
1285          * users know there might be something in the kernel's log buffer that
1286          * went to the bootconsole (that they do not see on the real console)
1287          */
1288         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1289                 /* we need to iterate through twice, to make sure we print
1290                  * everything out, before we unregister the console(s)
1291                  */
1292                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1293                         newcon->name, newcon->index);
1294                 for_each_console(bcon)
1295                         if (bcon->flags & CON_BOOT)
1296                                 unregister_console(bcon);
1297         } else {
1298                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1299                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1300                         newcon->name, newcon->index);
1301         }
1302 }
1303 EXPORT_SYMBOL(register_console);
1304
1305 int unregister_console(struct console *console)
1306 {
1307         struct console *a, *b;
1308         int res = 1;
1309
1310 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1311         if (console->flags & CON_BRL)
1312                 return braille_unregister_console(console);
1313 #endif
1314
1315         acquire_console_sem();
1316         if (console_drivers == console) {
1317                 console_drivers=console->next;
1318                 res = 0;
1319         } else if (console_drivers) {
1320                 for (a=console_drivers->next, b=console_drivers ;
1321                      a; b=a, a=b->next) {
1322                         if (a == console) {
1323                                 b->next = a->next;
1324                                 res = 0;
1325                                 break;
1326                         }
1327                 }
1328         }
1329
1330         /*
1331          * If this isn't the last console and it has CON_CONSDEV set, we
1332          * need to set it on the next preferred console.
1333          */
1334         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1335                 console_drivers->flags |= CON_CONSDEV;
1336
1337         release_console_sem();
1338         return res;
1339 }
1340 EXPORT_SYMBOL(unregister_console);
1341
1342 static int __init disable_boot_consoles(void)
1343 {
1344         struct console *con;
1345
1346         for_each_console(con) {
1347                 if (con->flags & CON_BOOT) {
1348                         printk(KERN_INFO "turn off boot console %s%d\n",
1349                                 con->name, con->index);
1350                         unregister_console(con);
1351                 }
1352         }
1353         return 0;
1354 }
1355 late_initcall(disable_boot_consoles);
1356
1357 #if defined CONFIG_PRINTK
1358
1359 /*
1360  * printk rate limiting, lifted from the networking subsystem.
1361  *
1362  * This enforces a rate limit: not more than 10 kernel messages
1363  * every 5s to make a denial-of-service attack impossible.
1364  */
1365 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1366
1367 int __printk_ratelimit(const char *func)
1368 {
1369         return ___ratelimit(&printk_ratelimit_state, func);
1370 }
1371 EXPORT_SYMBOL(__printk_ratelimit);
1372
1373 /**
1374  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1375  * @caller_jiffies: pointer to caller's state
1376  * @interval_msecs: minimum interval between prints
1377  *
1378  * printk_timed_ratelimit() returns true if more than @interval_msecs
1379  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1380  * returned true.
1381  */
1382 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1383                         unsigned int interval_msecs)
1384 {
1385         if (*caller_jiffies == 0
1386                         || !time_in_range(jiffies, *caller_jiffies,
1387                                         *caller_jiffies
1388                                         + msecs_to_jiffies(interval_msecs))) {
1389                 *caller_jiffies = jiffies;
1390                 return true;
1391         }
1392         return false;
1393 }
1394 EXPORT_SYMBOL(printk_timed_ratelimit);
1395 #endif