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