Merge branch 'for-linus' into for-next
[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
37 #include <asm/uaccess.h>
38
39 /*
40  * for_each_console() allows you to iterate on each console
41  */
42 #define for_each_console(con) \
43         for (con = console_drivers; con != NULL; con = con->next)
44
45 /*
46  * Architectures can override it:
47  */
48 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
49 {
50 }
51
52 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
53
54 /* printk's without a loglevel use this.. */
55 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
56
57 /* We show everything that is MORE important than this.. */
58 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
59 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
60
61 DECLARE_WAIT_QUEUE_HEAD(log_wait);
62
63 int console_printk[4] = {
64         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
65         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
66         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
67         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
68 };
69
70 static int saved_console_loglevel = -1;
71
72 /*
73  * Low level drivers may need that to know if they can schedule in
74  * their unblank() callback or not. So let's export it.
75  */
76 int oops_in_progress;
77 EXPORT_SYMBOL(oops_in_progress);
78
79 /*
80  * console_sem protects the console_drivers list, and also
81  * provides serialisation for access to the entire console
82  * driver system.
83  */
84 static DECLARE_MUTEX(console_sem);
85 struct console *console_drivers;
86 EXPORT_SYMBOL_GPL(console_drivers);
87
88 /*
89  * This is used for debugging the mess that is the VT code by
90  * keeping track if we have the console semaphore held. It's
91  * definitely not the perfect debug tool (we don't know if _WE_
92  * hold it are racing, but it helps tracking those weird code
93  * path in the console code where we end up in places I want
94  * locked without the console sempahore held
95  */
96 static int console_locked, console_suspended;
97
98 /*
99  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
100  * It is also used in interesting ways to provide interlocking in
101  * release_console_sem().
102  */
103 static DEFINE_SPINLOCK(logbuf_lock);
104
105 #define LOG_BUF_MASK (log_buf_len-1)
106 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
107
108 /*
109  * The indices into log_buf are not constrained to log_buf_len - they
110  * must be masked before subscripting
111  */
112 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
113 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
114 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
115
116 /*
117  *      Array of consoles built from command line options (console=)
118  */
119 struct console_cmdline
120 {
121         char    name[8];                        /* Name of the driver       */
122         int     index;                          /* Minor dev. to use        */
123         char    *options;                       /* Options for the driver   */
124 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
125         char    *brl_options;                   /* Options for braille driver */
126 #endif
127 };
128
129 #define MAX_CMDLINECONSOLES 8
130
131 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
132 static int selected_console = -1;
133 static int preferred_console = -1;
134 int console_set_on_cmdline;
135 EXPORT_SYMBOL(console_set_on_cmdline);
136
137 /* Flag: console code may call schedule() */
138 static int console_may_schedule;
139
140 #ifdef CONFIG_PRINTK
141
142 static char __log_buf[__LOG_BUF_LEN];
143 static char *log_buf = __log_buf;
144 static int log_buf_len = __LOG_BUF_LEN;
145 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
146
147 #ifdef CONFIG_KEXEC
148 /*
149  * This appends the listed symbols to /proc/vmcoreinfo
150  *
151  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
152  * obtain access to symbols that are otherwise very difficult to locate.  These
153  * symbols are specifically used so that utilities can access and extract the
154  * dmesg log from a vmcore file after a crash.
155  */
156 void log_buf_kexec_setup(void)
157 {
158         VMCOREINFO_SYMBOL(log_buf);
159         VMCOREINFO_SYMBOL(log_end);
160         VMCOREINFO_SYMBOL(log_buf_len);
161         VMCOREINFO_SYMBOL(logged_chars);
162 }
163 #endif
164
165 static int __init log_buf_len_setup(char *str)
166 {
167         unsigned size = memparse(str, &str);
168         unsigned long flags;
169
170         if (size)
171                 size = roundup_pow_of_two(size);
172         if (size > log_buf_len) {
173                 unsigned start, dest_idx, offset;
174                 char *new_log_buf;
175
176                 new_log_buf = alloc_bootmem(size);
177                 if (!new_log_buf) {
178                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
179                         goto out;
180                 }
181
182                 spin_lock_irqsave(&logbuf_lock, flags);
183                 log_buf_len = size;
184                 log_buf = new_log_buf;
185
186                 offset = start = min(con_start, log_start);
187                 dest_idx = 0;
188                 while (start != log_end) {
189                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
190                         start++;
191                         dest_idx++;
192                 }
193                 log_start -= offset;
194                 con_start -= offset;
195                 log_end -= offset;
196                 spin_unlock_irqrestore(&logbuf_lock, flags);
197
198                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
199         }
200 out:
201         return 1;
202 }
203
204 __setup("log_buf_len=", log_buf_len_setup);
205
206 #ifdef CONFIG_BOOT_PRINTK_DELAY
207
208 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
209 static unsigned long long loops_per_msec;       /* based on boot_delay */
210
211 static int __init boot_delay_setup(char *str)
212 {
213         unsigned long lpj;
214
215         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
216         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
217
218         get_option(&str, &boot_delay);
219         if (boot_delay > 10 * 1000)
220                 boot_delay = 0;
221
222         pr_debug("boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
223                 "HZ: %d, loops_per_msec: %llu\n",
224                 boot_delay, preset_lpj, lpj, HZ, loops_per_msec);
225         return 1;
226 }
227 __setup("boot_delay=", boot_delay_setup);
228
229 static void boot_delay_msec(void)
230 {
231         unsigned long long k;
232         unsigned long timeout;
233
234         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
235                 return;
236
237         k = (unsigned long long)loops_per_msec * boot_delay;
238
239         timeout = jiffies + msecs_to_jiffies(boot_delay);
240         while (k) {
241                 k--;
242                 cpu_relax();
243                 /*
244                  * use (volatile) jiffies to prevent
245                  * compiler reduction; loop termination via jiffies
246                  * is secondary and may or may not happen.
247                  */
248                 if (time_after(jiffies, timeout))
249                         break;
250                 touch_nmi_watchdog();
251         }
252 }
253 #else
254 static inline void boot_delay_msec(void)
255 {
256 }
257 #endif
258
259 /*
260  * Commands to do_syslog:
261  *
262  *      0 -- Close the log.  Currently a NOP.
263  *      1 -- Open the log. Currently a NOP.
264  *      2 -- Read from the log.
265  *      3 -- Read all messages remaining in the ring buffer.
266  *      4 -- Read and clear all messages remaining in the ring buffer
267  *      5 -- Clear ring buffer.
268  *      6 -- Disable printk's to console
269  *      7 -- Enable printk's to console
270  *      8 -- Set level of messages printed to console
271  *      9 -- Return number of unread characters in the log buffer
272  *     10 -- Return size of the log buffer
273  */
274 int do_syslog(int type, char __user *buf, int len)
275 {
276         unsigned i, j, limit, count;
277         int do_clear = 0;
278         char c;
279         int error = 0;
280
281         error = security_syslog(type);
282         if (error)
283                 return error;
284
285         switch (type) {
286         case 0:         /* Close log */
287                 break;
288         case 1:         /* Open log */
289                 break;
290         case 2:         /* Read from log */
291                 error = -EINVAL;
292                 if (!buf || len < 0)
293                         goto out;
294                 error = 0;
295                 if (!len)
296                         goto out;
297                 if (!access_ok(VERIFY_WRITE, buf, len)) {
298                         error = -EFAULT;
299                         goto out;
300                 }
301                 error = wait_event_interruptible(log_wait,
302                                                         (log_start - log_end));
303                 if (error)
304                         goto out;
305                 i = 0;
306                 spin_lock_irq(&logbuf_lock);
307                 while (!error && (log_start != log_end) && i < len) {
308                         c = LOG_BUF(log_start);
309                         log_start++;
310                         spin_unlock_irq(&logbuf_lock);
311                         error = __put_user(c,buf);
312                         buf++;
313                         i++;
314                         cond_resched();
315                         spin_lock_irq(&logbuf_lock);
316                 }
317                 spin_unlock_irq(&logbuf_lock);
318                 if (!error)
319                         error = i;
320                 break;
321         case 4:         /* Read/clear last kernel messages */
322                 do_clear = 1;
323                 /* FALL THRU */
324         case 3:         /* Read last kernel messages */
325                 error = -EINVAL;
326                 if (!buf || len < 0)
327                         goto out;
328                 error = 0;
329                 if (!len)
330                         goto out;
331                 if (!access_ok(VERIFY_WRITE, buf, len)) {
332                         error = -EFAULT;
333                         goto out;
334                 }
335                 count = len;
336                 if (count > log_buf_len)
337                         count = log_buf_len;
338                 spin_lock_irq(&logbuf_lock);
339                 if (count > logged_chars)
340                         count = logged_chars;
341                 if (do_clear)
342                         logged_chars = 0;
343                 limit = log_end;
344                 /*
345                  * __put_user() could sleep, and while we sleep
346                  * printk() could overwrite the messages
347                  * we try to copy to user space. Therefore
348                  * the messages are copied in reverse. <manfreds>
349                  */
350                 for (i = 0; i < count && !error; i++) {
351                         j = limit-1-i;
352                         if (j + log_buf_len < log_end)
353                                 break;
354                         c = LOG_BUF(j);
355                         spin_unlock_irq(&logbuf_lock);
356                         error = __put_user(c,&buf[count-1-i]);
357                         cond_resched();
358                         spin_lock_irq(&logbuf_lock);
359                 }
360                 spin_unlock_irq(&logbuf_lock);
361                 if (error)
362                         break;
363                 error = i;
364                 if (i != count) {
365                         int offset = count-error;
366                         /* buffer overflow during copy, correct user buffer. */
367                         for (i = 0; i < error; i++) {
368                                 if (__get_user(c,&buf[i+offset]) ||
369                                     __put_user(c,&buf[i])) {
370                                         error = -EFAULT;
371                                         break;
372                                 }
373                                 cond_resched();
374                         }
375                 }
376                 break;
377         case 5:         /* Clear ring buffer */
378                 logged_chars = 0;
379                 break;
380         case 6:         /* Disable logging to console */
381                 if (saved_console_loglevel == -1)
382                         saved_console_loglevel = console_loglevel;
383                 console_loglevel = minimum_console_loglevel;
384                 break;
385         case 7:         /* Enable logging to console */
386                 if (saved_console_loglevel != -1) {
387                         console_loglevel = saved_console_loglevel;
388                         saved_console_loglevel = -1;
389                 }
390                 break;
391         case 8:         /* Set level of messages printed to console */
392                 error = -EINVAL;
393                 if (len < 1 || len > 8)
394                         goto out;
395                 if (len < minimum_console_loglevel)
396                         len = minimum_console_loglevel;
397                 console_loglevel = len;
398                 /* Implicitly re-enable logging to console */
399                 saved_console_loglevel = -1;
400                 error = 0;
401                 break;
402         case 9:         /* Number of chars in the log buffer */
403                 error = log_end - log_start;
404                 break;
405         case 10:        /* Size of the log buffer */
406                 error = log_buf_len;
407                 break;
408         default:
409                 error = -EINVAL;
410                 break;
411         }
412 out:
413         return error;
414 }
415
416 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
417 {
418         return do_syslog(type, buf, len);
419 }
420
421 /*
422  * Call the console drivers on a range of log_buf
423  */
424 static void __call_console_drivers(unsigned start, unsigned end)
425 {
426         struct console *con;
427
428         for_each_console(con) {
429                 if ((con->flags & CON_ENABLED) && con->write &&
430                                 (cpu_online(smp_processor_id()) ||
431                                 (con->flags & CON_ANYTIME)))
432                         con->write(con, &LOG_BUF(start), end - start);
433         }
434 }
435
436 static int __read_mostly ignore_loglevel;
437
438 static int __init ignore_loglevel_setup(char *str)
439 {
440         ignore_loglevel = 1;
441         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
442
443         return 0;
444 }
445
446 early_param("ignore_loglevel", ignore_loglevel_setup);
447
448 /*
449  * Write out chars from start to end - 1 inclusive
450  */
451 static void _call_console_drivers(unsigned start,
452                                 unsigned end, int msg_log_level)
453 {
454         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
455                         console_drivers && start != end) {
456                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
457                         /* wrapped write */
458                         __call_console_drivers(start & LOG_BUF_MASK,
459                                                 log_buf_len);
460                         __call_console_drivers(0, end & LOG_BUF_MASK);
461                 } else {
462                         __call_console_drivers(start, end);
463                 }
464         }
465 }
466
467 /*
468  * Call the console drivers, asking them to write out
469  * log_buf[start] to log_buf[end - 1].
470  * The console_sem must be held.
471  */
472 static void call_console_drivers(unsigned start, unsigned end)
473 {
474         unsigned cur_index, start_print;
475         static int msg_level = -1;
476
477         BUG_ON(((int)(start - end)) > 0);
478
479         cur_index = start;
480         start_print = start;
481         while (cur_index != end) {
482                 if (msg_level < 0 && ((end - cur_index) > 2) &&
483                                 LOG_BUF(cur_index + 0) == '<' &&
484                                 LOG_BUF(cur_index + 1) >= '0' &&
485                                 LOG_BUF(cur_index + 1) <= '7' &&
486                                 LOG_BUF(cur_index + 2) == '>') {
487                         msg_level = LOG_BUF(cur_index + 1) - '0';
488                         cur_index += 3;
489                         start_print = cur_index;
490                 }
491                 while (cur_index != end) {
492                         char c = LOG_BUF(cur_index);
493
494                         cur_index++;
495                         if (c == '\n') {
496                                 if (msg_level < 0) {
497                                         /*
498                                          * printk() has already given us loglevel tags in
499                                          * the buffer.  This code is here in case the
500                                          * log buffer has wrapped right round and scribbled
501                                          * on those tags
502                                          */
503                                         msg_level = default_message_loglevel;
504                                 }
505                                 _call_console_drivers(start_print, cur_index, msg_level);
506                                 msg_level = -1;
507                                 start_print = cur_index;
508                                 break;
509                         }
510                 }
511         }
512         _call_console_drivers(start_print, end, msg_level);
513 }
514
515 static void emit_log_char(char c)
516 {
517         LOG_BUF(log_end) = c;
518         log_end++;
519         if (log_end - log_start > log_buf_len)
520                 log_start = log_end - log_buf_len;
521         if (log_end - con_start > log_buf_len)
522                 con_start = log_end - log_buf_len;
523         if (logged_chars < log_buf_len)
524                 logged_chars++;
525 }
526
527 /*
528  * Zap console related locks when oopsing. Only zap at most once
529  * every 10 seconds, to leave time for slow consoles to print a
530  * full oops.
531  */
532 static void zap_locks(void)
533 {
534         static unsigned long oops_timestamp;
535
536         if (time_after_eq(jiffies, oops_timestamp) &&
537                         !time_after(jiffies, oops_timestamp + 30 * HZ))
538                 return;
539
540         oops_timestamp = jiffies;
541
542         /* If a crash is occurring, make sure we can't deadlock */
543         spin_lock_init(&logbuf_lock);
544         /* And make sure that we print immediately */
545         init_MUTEX(&console_sem);
546 }
547
548 #if defined(CONFIG_PRINTK_TIME)
549 static int printk_time = 1;
550 #else
551 static int printk_time = 0;
552 #endif
553 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
554
555 /* Check if we have any console registered that can be called early in boot. */
556 static int have_callable_console(void)
557 {
558         struct console *con;
559
560         for_each_console(con)
561                 if (con->flags & CON_ANYTIME)
562                         return 1;
563
564         return 0;
565 }
566
567 /**
568  * printk - print a kernel message
569  * @fmt: format string
570  *
571  * This is printk().  It can be called from any context.  We want it to work.
572  *
573  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
574  * call the console drivers.  If we fail to get the semaphore we place the output
575  * into the log buffer and return.  The current holder of the console_sem will
576  * notice the new output in release_console_sem() and will send it to the
577  * consoles before releasing the semaphore.
578  *
579  * One effect of this deferred printing is that code which calls printk() and
580  * then changes console_loglevel may break. This is because console_loglevel
581  * is inspected when the actual printing occurs.
582  *
583  * See also:
584  * printf(3)
585  *
586  * See the vsnprintf() documentation for format string extensions over C99.
587  */
588
589 asmlinkage int printk(const char *fmt, ...)
590 {
591         va_list args;
592         int r;
593
594         va_start(args, fmt);
595         r = vprintk(fmt, args);
596         va_end(args);
597
598         return r;
599 }
600
601 /* cpu currently holding logbuf_lock */
602 static volatile unsigned int printk_cpu = UINT_MAX;
603
604 /*
605  * Can we actually use the console at this time on this cpu?
606  *
607  * Console drivers may assume that per-cpu resources have
608  * been allocated. So unless they're explicitly marked as
609  * being able to cope (CON_ANYTIME) don't call them until
610  * this CPU is officially up.
611  */
612 static inline int can_use_console(unsigned int cpu)
613 {
614         return cpu_online(cpu) || have_callable_console();
615 }
616
617 /*
618  * Try to get console ownership to actually show the kernel
619  * messages from a 'printk'. Return true (and with the
620  * console_semaphore held, and 'console_locked' set) if it
621  * is successful, false otherwise.
622  *
623  * This gets called with the 'logbuf_lock' spinlock held and
624  * interrupts disabled. It should return with 'lockbuf_lock'
625  * released but interrupts still disabled.
626  */
627 static int acquire_console_semaphore_for_printk(unsigned int cpu)
628 {
629         int retval = 0;
630
631         if (!try_acquire_console_sem()) {
632                 retval = 1;
633
634                 /*
635                  * If we can't use the console, we need to release
636                  * the console semaphore by hand to avoid flushing
637                  * the buffer. We need to hold the console semaphore
638                  * in order to do this test safely.
639                  */
640                 if (!can_use_console(cpu)) {
641                         console_locked = 0;
642                         up(&console_sem);
643                         retval = 0;
644                 }
645         }
646         printk_cpu = UINT_MAX;
647         spin_unlock(&logbuf_lock);
648         return retval;
649 }
650 static const char recursion_bug_msg [] =
651                 KERN_CRIT "BUG: recent printk recursion!\n";
652 static int recursion_bug;
653 static int new_text_line = 1;
654 static char printk_buf[1024];
655
656 int printk_delay_msec __read_mostly;
657
658 static inline void printk_delay(void)
659 {
660         if (unlikely(printk_delay_msec)) {
661                 int m = printk_delay_msec;
662
663                 while (m--) {
664                         mdelay(1);
665                         touch_nmi_watchdog();
666                 }
667         }
668 }
669
670 asmlinkage int vprintk(const char *fmt, va_list args)
671 {
672         int printed_len = 0;
673         int current_log_level = default_message_loglevel;
674         unsigned long flags;
675         int this_cpu;
676         char *p;
677
678         boot_delay_msec();
679         printk_delay();
680
681         preempt_disable();
682         /* This stops the holder of console_sem just where we want him */
683         raw_local_irq_save(flags);
684         this_cpu = smp_processor_id();
685
686         /*
687          * Ouch, printk recursed into itself!
688          */
689         if (unlikely(printk_cpu == this_cpu)) {
690                 /*
691                  * If a crash is occurring during printk() on this CPU,
692                  * then try to get the crash message out but make sure
693                  * we can't deadlock. Otherwise just return to avoid the
694                  * recursion and return - but flag the recursion so that
695                  * it can be printed at the next appropriate moment:
696                  */
697                 if (!oops_in_progress) {
698                         recursion_bug = 1;
699                         goto out_restore_irqs;
700                 }
701                 zap_locks();
702         }
703
704         lockdep_off();
705         spin_lock(&logbuf_lock);
706         printk_cpu = this_cpu;
707
708         if (recursion_bug) {
709                 recursion_bug = 0;
710                 strcpy(printk_buf, recursion_bug_msg);
711                 printed_len = strlen(recursion_bug_msg);
712         }
713         /* Emit the output into the temporary buffer */
714         printed_len += vscnprintf(printk_buf + printed_len,
715                                   sizeof(printk_buf) - printed_len, fmt, args);
716
717
718         p = printk_buf;
719
720         /* Do we have a loglevel in the string? */
721         if (p[0] == '<') {
722                 unsigned char c = p[1];
723                 if (c && p[2] == '>') {
724                         switch (c) {
725                         case '0' ... '7': /* loglevel */
726                                 current_log_level = c - '0';
727                         /* Fallthrough - make sure we're on a new line */
728                         case 'd': /* KERN_DEFAULT */
729                                 if (!new_text_line) {
730                                         emit_log_char('\n');
731                                         new_text_line = 1;
732                                 }
733                         /* Fallthrough - skip the loglevel */
734                         case 'c': /* KERN_CONT */
735                                 p += 3;
736                                 break;
737                         }
738                 }
739         }
740
741         /*
742          * Copy the output into log_buf.  If the caller didn't provide
743          * appropriate log level tags, we insert them here
744          */
745         for ( ; *p; p++) {
746                 if (new_text_line) {
747                         /* Always output the token */
748                         emit_log_char('<');
749                         emit_log_char(current_log_level + '0');
750                         emit_log_char('>');
751                         printed_len += 3;
752                         new_text_line = 0;
753
754                         if (printk_time) {
755                                 /* Follow the token with the time */
756                                 char tbuf[50], *tp;
757                                 unsigned tlen;
758                                 unsigned long long t;
759                                 unsigned long nanosec_rem;
760
761                                 t = cpu_clock(printk_cpu);
762                                 nanosec_rem = do_div(t, 1000000000);
763                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
764                                                 (unsigned long) t,
765                                                 nanosec_rem / 1000);
766
767                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
768                                         emit_log_char(*tp);
769                                 printed_len += tlen;
770                         }
771
772                         if (!*p)
773                                 break;
774                 }
775
776                 emit_log_char(*p);
777                 if (*p == '\n')
778                         new_text_line = 1;
779         }
780
781         /*
782          * Try to acquire and then immediately release the
783          * console semaphore. The release will do all the
784          * actual magic (print out buffers, wake up klogd,
785          * etc). 
786          *
787          * The acquire_console_semaphore_for_printk() function
788          * will release 'logbuf_lock' regardless of whether it
789          * actually gets the semaphore or not.
790          */
791         if (acquire_console_semaphore_for_printk(this_cpu))
792                 release_console_sem();
793
794         lockdep_on();
795 out_restore_irqs:
796         raw_local_irq_restore(flags);
797
798         preempt_enable();
799         return printed_len;
800 }
801 EXPORT_SYMBOL(printk);
802 EXPORT_SYMBOL(vprintk);
803
804 #else
805
806 static void call_console_drivers(unsigned start, unsigned end)
807 {
808 }
809
810 #endif
811
812 static int __add_preferred_console(char *name, int idx, char *options,
813                                    char *brl_options)
814 {
815         struct console_cmdline *c;
816         int i;
817
818         /*
819          *      See if this tty is not yet registered, and
820          *      if we have a slot free.
821          */
822         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
823                 if (strcmp(console_cmdline[i].name, name) == 0 &&
824                           console_cmdline[i].index == idx) {
825                                 if (!brl_options)
826                                         selected_console = i;
827                                 return 0;
828                 }
829         if (i == MAX_CMDLINECONSOLES)
830                 return -E2BIG;
831         if (!brl_options)
832                 selected_console = i;
833         c = &console_cmdline[i];
834         strlcpy(c->name, name, sizeof(c->name));
835         c->options = options;
836 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
837         c->brl_options = brl_options;
838 #endif
839         c->index = idx;
840         return 0;
841 }
842 /*
843  * Set up a list of consoles.  Called from init/main.c
844  */
845 static int __init console_setup(char *str)
846 {
847         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
848         char *s, *options, *brl_options = NULL;
849         int idx;
850
851 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
852         if (!memcmp(str, "brl,", 4)) {
853                 brl_options = "";
854                 str += 4;
855         } else if (!memcmp(str, "brl=", 4)) {
856                 brl_options = str + 4;
857                 str = strchr(brl_options, ',');
858                 if (!str) {
859                         printk(KERN_ERR "need port name after brl=\n");
860                         return 1;
861                 }
862                 *(str++) = 0;
863         }
864 #endif
865
866         /*
867          * Decode str into name, index, options.
868          */
869         if (str[0] >= '0' && str[0] <= '9') {
870                 strcpy(buf, "ttyS");
871                 strncpy(buf + 4, str, sizeof(buf) - 5);
872         } else {
873                 strncpy(buf, str, sizeof(buf) - 1);
874         }
875         buf[sizeof(buf) - 1] = 0;
876         if ((options = strchr(str, ',')) != NULL)
877                 *(options++) = 0;
878 #ifdef __sparc__
879         if (!strcmp(str, "ttya"))
880                 strcpy(buf, "ttyS0");
881         if (!strcmp(str, "ttyb"))
882                 strcpy(buf, "ttyS1");
883 #endif
884         for (s = buf; *s; s++)
885                 if ((*s >= '0' && *s <= '9') || *s == ',')
886                         break;
887         idx = simple_strtoul(s, NULL, 10);
888         *s = 0;
889
890         __add_preferred_console(buf, idx, options, brl_options);
891         console_set_on_cmdline = 1;
892         return 1;
893 }
894 __setup("console=", console_setup);
895
896 /**
897  * add_preferred_console - add a device to the list of preferred consoles.
898  * @name: device name
899  * @idx: device index
900  * @options: options for this console
901  *
902  * The last preferred console added will be used for kernel messages
903  * and stdin/out/err for init.  Normally this is used by console_setup
904  * above to handle user-supplied console arguments; however it can also
905  * be used by arch-specific code either to override the user or more
906  * commonly to provide a default console (ie from PROM variables) when
907  * the user has not supplied one.
908  */
909 int add_preferred_console(char *name, int idx, char *options)
910 {
911         return __add_preferred_console(name, idx, options, NULL);
912 }
913
914 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
915 {
916         struct console_cmdline *c;
917         int i;
918
919         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
920                 if (strcmp(console_cmdline[i].name, name) == 0 &&
921                           console_cmdline[i].index == idx) {
922                                 c = &console_cmdline[i];
923                                 strlcpy(c->name, name_new, sizeof(c->name));
924                                 c->name[sizeof(c->name) - 1] = 0;
925                                 c->options = options;
926                                 c->index = idx_new;
927                                 return i;
928                 }
929         /* not found */
930         return -1;
931 }
932
933 int console_suspend_enabled = 1;
934 EXPORT_SYMBOL(console_suspend_enabled);
935
936 static int __init console_suspend_disable(char *str)
937 {
938         console_suspend_enabled = 0;
939         return 1;
940 }
941 __setup("no_console_suspend", console_suspend_disable);
942
943 /**
944  * suspend_console - suspend the console subsystem
945  *
946  * This disables printk() while we go into suspend states
947  */
948 void suspend_console(void)
949 {
950         if (!console_suspend_enabled)
951                 return;
952         printk("Suspending console(s) (use no_console_suspend to debug)\n");
953         acquire_console_sem();
954         console_suspended = 1;
955         up(&console_sem);
956 }
957
958 void resume_console(void)
959 {
960         if (!console_suspend_enabled)
961                 return;
962         down(&console_sem);
963         console_suspended = 0;
964         release_console_sem();
965 }
966
967 /**
968  * acquire_console_sem - lock the console system for exclusive use.
969  *
970  * Acquires a semaphore which guarantees that the caller has
971  * exclusive access to the console system and the console_drivers list.
972  *
973  * Can sleep, returns nothing.
974  */
975 void acquire_console_sem(void)
976 {
977         BUG_ON(in_interrupt());
978         down(&console_sem);
979         if (console_suspended)
980                 return;
981         console_locked = 1;
982         console_may_schedule = 1;
983 }
984 EXPORT_SYMBOL(acquire_console_sem);
985
986 int try_acquire_console_sem(void)
987 {
988         if (down_trylock(&console_sem))
989                 return -1;
990         if (console_suspended) {
991                 up(&console_sem);
992                 return -1;
993         }
994         console_locked = 1;
995         console_may_schedule = 0;
996         return 0;
997 }
998 EXPORT_SYMBOL(try_acquire_console_sem);
999
1000 int is_console_locked(void)
1001 {
1002         return console_locked;
1003 }
1004
1005 static DEFINE_PER_CPU(int, printk_pending);
1006
1007 void printk_tick(void)
1008 {
1009         if (__get_cpu_var(printk_pending)) {
1010                 __get_cpu_var(printk_pending) = 0;
1011                 wake_up_interruptible(&log_wait);
1012         }
1013 }
1014
1015 int printk_needs_cpu(int cpu)
1016 {
1017         return per_cpu(printk_pending, cpu);
1018 }
1019
1020 void wake_up_klogd(void)
1021 {
1022         if (waitqueue_active(&log_wait))
1023                 __raw_get_cpu_var(printk_pending) = 1;
1024 }
1025
1026 /**
1027  * release_console_sem - unlock the console system
1028  *
1029  * Releases the semaphore which the caller holds on the console system
1030  * and the console driver list.
1031  *
1032  * While the semaphore was held, console output may have been buffered
1033  * by printk().  If this is the case, release_console_sem() emits
1034  * the output prior to releasing the semaphore.
1035  *
1036  * If there is output waiting for klogd, we wake it up.
1037  *
1038  * release_console_sem() may be called from any context.
1039  */
1040 void release_console_sem(void)
1041 {
1042         unsigned long flags;
1043         unsigned _con_start, _log_end;
1044         unsigned wake_klogd = 0;
1045
1046         if (console_suspended) {
1047                 up(&console_sem);
1048                 return;
1049         }
1050
1051         console_may_schedule = 0;
1052
1053         for ( ; ; ) {
1054                 spin_lock_irqsave(&logbuf_lock, flags);
1055                 wake_klogd |= log_start - log_end;
1056                 if (con_start == log_end)
1057                         break;                  /* Nothing to print */
1058                 _con_start = con_start;
1059                 _log_end = log_end;
1060                 con_start = log_end;            /* Flush */
1061                 spin_unlock(&logbuf_lock);
1062                 stop_critical_timings();        /* don't trace print latency */
1063                 call_console_drivers(_con_start, _log_end);
1064                 start_critical_timings();
1065                 local_irq_restore(flags);
1066         }
1067         console_locked = 0;
1068         up(&console_sem);
1069         spin_unlock_irqrestore(&logbuf_lock, flags);
1070         if (wake_klogd)
1071                 wake_up_klogd();
1072 }
1073 EXPORT_SYMBOL(release_console_sem);
1074
1075 /**
1076  * console_conditional_schedule - yield the CPU if required
1077  *
1078  * If the console code is currently allowed to sleep, and
1079  * if this CPU should yield the CPU to another task, do
1080  * so here.
1081  *
1082  * Must be called within acquire_console_sem().
1083  */
1084 void __sched console_conditional_schedule(void)
1085 {
1086         if (console_may_schedule)
1087                 cond_resched();
1088 }
1089 EXPORT_SYMBOL(console_conditional_schedule);
1090
1091 void console_unblank(void)
1092 {
1093         struct console *c;
1094
1095         /*
1096          * console_unblank can no longer be called in interrupt context unless
1097          * oops_in_progress is set to 1..
1098          */
1099         if (oops_in_progress) {
1100                 if (down_trylock(&console_sem) != 0)
1101                         return;
1102         } else
1103                 acquire_console_sem();
1104
1105         console_locked = 1;
1106         console_may_schedule = 0;
1107         for_each_console(c)
1108                 if ((c->flags & CON_ENABLED) && c->unblank)
1109                         c->unblank();
1110         release_console_sem();
1111 }
1112
1113 /*
1114  * Return the console tty driver structure and its associated index
1115  */
1116 struct tty_driver *console_device(int *index)
1117 {
1118         struct console *c;
1119         struct tty_driver *driver = NULL;
1120
1121         acquire_console_sem();
1122         for_each_console(c) {
1123                 if (!c->device)
1124                         continue;
1125                 driver = c->device(c, index);
1126                 if (driver)
1127                         break;
1128         }
1129         release_console_sem();
1130         return driver;
1131 }
1132
1133 /*
1134  * Prevent further output on the passed console device so that (for example)
1135  * serial drivers can disable console output before suspending a port, and can
1136  * re-enable output afterwards.
1137  */
1138 void console_stop(struct console *console)
1139 {
1140         acquire_console_sem();
1141         console->flags &= ~CON_ENABLED;
1142         release_console_sem();
1143 }
1144 EXPORT_SYMBOL(console_stop);
1145
1146 void console_start(struct console *console)
1147 {
1148         acquire_console_sem();
1149         console->flags |= CON_ENABLED;
1150         release_console_sem();
1151 }
1152 EXPORT_SYMBOL(console_start);
1153
1154 /*
1155  * The console driver calls this routine during kernel initialization
1156  * to register the console printing procedure with printk() and to
1157  * print any messages that were printed by the kernel before the
1158  * console driver was initialized.
1159  *
1160  * This can happen pretty early during the boot process (because of
1161  * early_printk) - sometimes before setup_arch() completes - be careful
1162  * of what kernel features are used - they may not be initialised yet.
1163  *
1164  * There are two types of consoles - bootconsoles (early_printk) and
1165  * "real" consoles (everything which is not a bootconsole) which are
1166  * handled differently.
1167  *  - Any number of bootconsoles can be registered at any time.
1168  *  - As soon as a "real" console is registered, all bootconsoles
1169  *    will be unregistered automatically.
1170  *  - Once a "real" console is registered, any attempt to register a
1171  *    bootconsoles will be rejected
1172  */
1173 void register_console(struct console *newcon)
1174 {
1175         int i;
1176         unsigned long flags;
1177         struct console *bcon = NULL;
1178
1179         /*
1180          * before we register a new CON_BOOT console, make sure we don't
1181          * already have a valid console
1182          */
1183         if (console_drivers && newcon->flags & CON_BOOT) {
1184                 /* find the last or real console */
1185                 for_each_console(bcon) {
1186                         if (!(bcon->flags & CON_BOOT)) {
1187                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1188                                         newcon->name, newcon->index);
1189                                 return;
1190                         }
1191                 }
1192         }
1193
1194         if (console_drivers && console_drivers->flags & CON_BOOT)
1195                 bcon = console_drivers;
1196
1197         if (preferred_console < 0 || bcon || !console_drivers)
1198                 preferred_console = selected_console;
1199
1200         if (newcon->early_setup)
1201                 newcon->early_setup();
1202
1203         /*
1204          *      See if we want to use this console driver. If we
1205          *      didn't select a console we take the first one
1206          *      that registers here.
1207          */
1208         if (preferred_console < 0) {
1209                 if (newcon->index < 0)
1210                         newcon->index = 0;
1211                 if (newcon->setup == NULL ||
1212                     newcon->setup(newcon, NULL) == 0) {
1213                         newcon->flags |= CON_ENABLED;
1214                         if (newcon->device) {
1215                                 newcon->flags |= CON_CONSDEV;
1216                                 preferred_console = 0;
1217                         }
1218                 }
1219         }
1220
1221         /*
1222          *      See if this console matches one we selected on
1223          *      the command line.
1224          */
1225         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1226                         i++) {
1227                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1228                         continue;
1229                 if (newcon->index >= 0 &&
1230                     newcon->index != console_cmdline[i].index)
1231                         continue;
1232                 if (newcon->index < 0)
1233                         newcon->index = console_cmdline[i].index;
1234 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1235                 if (console_cmdline[i].brl_options) {
1236                         newcon->flags |= CON_BRL;
1237                         braille_register_console(newcon,
1238                                         console_cmdline[i].index,
1239                                         console_cmdline[i].options,
1240                                         console_cmdline[i].brl_options);
1241                         return;
1242                 }
1243 #endif
1244                 if (newcon->setup &&
1245                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1246                         break;
1247                 newcon->flags |= CON_ENABLED;
1248                 newcon->index = console_cmdline[i].index;
1249                 if (i == selected_console) {
1250                         newcon->flags |= CON_CONSDEV;
1251                         preferred_console = selected_console;
1252                 }
1253                 break;
1254         }
1255
1256         if (!(newcon->flags & CON_ENABLED))
1257                 return;
1258
1259         /*
1260          * If we have a bootconsole, and are switching to a real console,
1261          * don't print everything out again, since when the boot console, and
1262          * the real console are the same physical device, it's annoying to
1263          * see the beginning boot messages twice
1264          */
1265         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1266                 newcon->flags &= ~CON_PRINTBUFFER;
1267
1268         /*
1269          *      Put this console in the list - keep the
1270          *      preferred driver at the head of the list.
1271          */
1272         acquire_console_sem();
1273         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1274                 newcon->next = console_drivers;
1275                 console_drivers = newcon;
1276                 if (newcon->next)
1277                         newcon->next->flags &= ~CON_CONSDEV;
1278         } else {
1279                 newcon->next = console_drivers->next;
1280                 console_drivers->next = newcon;
1281         }
1282         if (newcon->flags & CON_PRINTBUFFER) {
1283                 /*
1284                  * release_console_sem() will print out the buffered messages
1285                  * for us.
1286                  */
1287                 spin_lock_irqsave(&logbuf_lock, flags);
1288                 con_start = log_start;
1289                 spin_unlock_irqrestore(&logbuf_lock, flags);
1290         }
1291         release_console_sem();
1292
1293         /*
1294          * By unregistering the bootconsoles after we enable the real console
1295          * we get the "console xxx enabled" message on all the consoles -
1296          * boot consoles, real consoles, etc - this is to ensure that end
1297          * users know there might be something in the kernel's log buffer that
1298          * went to the bootconsole (that they do not see on the real console)
1299          */
1300         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1301                 /* we need to iterate through twice, to make sure we print
1302                  * everything out, before we unregister the console(s)
1303                  */
1304                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1305                         newcon->name, newcon->index);
1306                 for_each_console(bcon)
1307                         if (bcon->flags & CON_BOOT)
1308                                 unregister_console(bcon);
1309         } else {
1310                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1311                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1312                         newcon->name, newcon->index);
1313         }
1314 }
1315 EXPORT_SYMBOL(register_console);
1316
1317 int unregister_console(struct console *console)
1318 {
1319         struct console *a, *b;
1320         int res = 1;
1321
1322 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1323         if (console->flags & CON_BRL)
1324                 return braille_unregister_console(console);
1325 #endif
1326
1327         acquire_console_sem();
1328         if (console_drivers == console) {
1329                 console_drivers=console->next;
1330                 res = 0;
1331         } else if (console_drivers) {
1332                 for (a=console_drivers->next, b=console_drivers ;
1333                      a; b=a, a=b->next) {
1334                         if (a == console) {
1335                                 b->next = a->next;
1336                                 res = 0;
1337                                 break;
1338                         }
1339                 }
1340         }
1341
1342         /*
1343          * If this isn't the last console and it has CON_CONSDEV set, we
1344          * need to set it on the next preferred console.
1345          */
1346         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1347                 console_drivers->flags |= CON_CONSDEV;
1348
1349         release_console_sem();
1350         return res;
1351 }
1352 EXPORT_SYMBOL(unregister_console);
1353
1354 static int __init disable_boot_consoles(void)
1355 {
1356         struct console *con;
1357
1358         for_each_console(con) {
1359                 if (con->flags & CON_BOOT) {
1360                         printk(KERN_INFO "turn off boot console %s%d\n",
1361                                 con->name, con->index);
1362                         unregister_console(con);
1363                 }
1364         }
1365         return 0;
1366 }
1367 late_initcall(disable_boot_consoles);
1368
1369 #if defined CONFIG_PRINTK
1370
1371 /*
1372  * printk rate limiting, lifted from the networking subsystem.
1373  *
1374  * This enforces a rate limit: not more than 10 kernel messages
1375  * every 5s to make a denial-of-service attack impossible.
1376  */
1377 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1378
1379 int printk_ratelimit(void)
1380 {
1381         return __ratelimit(&printk_ratelimit_state);
1382 }
1383 EXPORT_SYMBOL(printk_ratelimit);
1384
1385 /**
1386  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1387  * @caller_jiffies: pointer to caller's state
1388  * @interval_msecs: minimum interval between prints
1389  *
1390  * printk_timed_ratelimit() returns true if more than @interval_msecs
1391  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1392  * returned true.
1393  */
1394 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1395                         unsigned int interval_msecs)
1396 {
1397         if (*caller_jiffies == 0
1398                         || !time_in_range(jiffies, *caller_jiffies,
1399                                         *caller_jiffies
1400                                         + msecs_to_jiffies(interval_msecs))) {
1401                 *caller_jiffies = jiffies;
1402                 return true;
1403         }
1404         return false;
1405 }
1406 EXPORT_SYMBOL(printk_timed_ratelimit);
1407 #endif