Linux-2.6.12-rc2
[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  *     manfreds@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/smp_lock.h>
24 #include <linux/console.h>
25 #include <linux/init.h>
26 #include <linux/module.h>
27 #include <linux/interrupt.h>                    /* For in_interrupt() */
28 #include <linux/config.h>
29 #include <linux/delay.h>
30 #include <linux/smp.h>
31 #include <linux/security.h>
32 #include <linux/bootmem.h>
33 #include <linux/syscalls.h>
34
35 #include <asm/uaccess.h>
36
37 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
38
39 /* printk's without a loglevel use this.. */
40 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
41
42 /* We show everything that is MORE important than this.. */
43 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
44 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
45
46 DECLARE_WAIT_QUEUE_HEAD(log_wait);
47
48 int console_printk[4] = {
49         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
50         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
51         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
52         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
53 };
54
55 EXPORT_SYMBOL(console_printk);
56
57 /*
58  * Low lever drivers may need that to know if they can schedule in
59  * their unblank() callback or not. So let's export it.
60  */
61 int oops_in_progress;
62 EXPORT_SYMBOL(oops_in_progress);
63
64 /*
65  * console_sem protects the console_drivers list, and also
66  * provides serialisation for access to the entire console
67  * driver system.
68  */
69 static DECLARE_MUTEX(console_sem);
70 struct console *console_drivers;
71 /*
72  * This is used for debugging the mess that is the VT code by
73  * keeping track if we have the console semaphore held. It's
74  * definitely not the perfect debug tool (we don't know if _WE_
75  * hold it are racing, but it helps tracking those weird code
76  * path in the console code where we end up in places I want
77  * locked without the console sempahore held
78  */
79 static int console_locked;
80
81 /*
82  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
83  * It is also used in interesting ways to provide interlocking in
84  * release_console_sem().
85  */
86 static DEFINE_SPINLOCK(logbuf_lock);
87
88 static char __log_buf[__LOG_BUF_LEN];
89 static char *log_buf = __log_buf;
90 static int log_buf_len = __LOG_BUF_LEN;
91
92 #define LOG_BUF_MASK    (log_buf_len-1)
93 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
94
95 /*
96  * The indices into log_buf are not constrained to log_buf_len - they
97  * must be masked before subscripting
98  */
99 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
100 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
101 static unsigned long log_end;   /* Index into log_buf: most-recently-written-char + 1 */
102 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
103
104 /*
105  *      Array of consoles built from command line options (console=)
106  */
107 struct console_cmdline
108 {
109         char    name[8];                        /* Name of the driver       */
110         int     index;                          /* Minor dev. to use        */
111         char    *options;                       /* Options for the driver   */
112 };
113
114 #define MAX_CMDLINECONSOLES 8
115
116 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
117 static int selected_console = -1;
118 static int preferred_console = -1;
119
120 /* Flag: console code may call schedule() */
121 static int console_may_schedule;
122
123 /*
124  *      Setup a list of consoles. Called from init/main.c
125  */
126 static int __init console_setup(char *str)
127 {
128         char name[sizeof(console_cmdline[0].name)];
129         char *s, *options;
130         int idx;
131
132         /*
133          *      Decode str into name, index, options.
134          */
135         if (str[0] >= '0' && str[0] <= '9') {
136                 strcpy(name, "ttyS");
137                 strncpy(name + 4, str, sizeof(name) - 5);
138         } else
139                 strncpy(name, str, sizeof(name) - 1);
140         name[sizeof(name) - 1] = 0;
141         if ((options = strchr(str, ',')) != NULL)
142                 *(options++) = 0;
143 #ifdef __sparc__
144         if (!strcmp(str, "ttya"))
145                 strcpy(name, "ttyS0");
146         if (!strcmp(str, "ttyb"))
147                 strcpy(name, "ttyS1");
148 #endif
149         for(s = name; *s; s++)
150                 if ((*s >= '0' && *s <= '9') || *s == ',')
151                         break;
152         idx = simple_strtoul(s, NULL, 10);
153         *s = 0;
154
155         add_preferred_console(name, idx, options);
156         return 1;
157 }
158
159 __setup("console=", console_setup);
160
161 /**
162  * add_preferred_console - add a device to the list of preferred consoles.
163  *
164  * The last preferred console added will be used for kernel messages
165  * and stdin/out/err for init.  Normally this is used by console_setup
166  * above to handle user-supplied console arguments; however it can also
167  * be used by arch-specific code either to override the user or more
168  * commonly to provide a default console (ie from PROM variables) when
169  * the user has not supplied one.
170  */
171 int __init add_preferred_console(char *name, int idx, char *options)
172 {
173         struct console_cmdline *c;
174         int i;
175
176         /*
177          *      See if this tty is not yet registered, and
178          *      if we have a slot free.
179          */
180         for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
181                 if (strcmp(console_cmdline[i].name, name) == 0 &&
182                           console_cmdline[i].index == idx) {
183                                 selected_console = i;
184                                 return 0;
185                 }
186         if (i == MAX_CMDLINECONSOLES)
187                 return -E2BIG;
188         selected_console = i;
189         c = &console_cmdline[i];
190         memcpy(c->name, name, sizeof(c->name));
191         c->name[sizeof(c->name) - 1] = 0;
192         c->options = options;
193         c->index = idx;
194         return 0;
195 }
196
197 static int __init log_buf_len_setup(char *str)
198 {
199         unsigned long size = memparse(str, &str);
200         unsigned long flags;
201
202         if (size)
203                 size = roundup_pow_of_two(size);
204         if (size > log_buf_len) {
205                 unsigned long start, dest_idx, offset;
206                 char * new_log_buf;
207
208                 new_log_buf = alloc_bootmem(size);
209                 if (!new_log_buf) {
210                         printk("log_buf_len: allocation failed\n");
211                         goto out;
212                 }
213
214                 spin_lock_irqsave(&logbuf_lock, flags);
215                 log_buf_len = size;
216                 log_buf = new_log_buf;
217
218                 offset = start = min(con_start, log_start);
219                 dest_idx = 0;
220                 while (start != log_end) {
221                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
222                         start++;
223                         dest_idx++;
224                 }
225                 log_start -= offset;
226                 con_start -= offset;
227                 log_end -= offset;
228                 spin_unlock_irqrestore(&logbuf_lock, flags);
229
230                 printk("log_buf_len: %d\n", log_buf_len);
231         }
232 out:
233
234         return 1;
235 }
236
237 __setup("log_buf_len=", log_buf_len_setup);
238
239 /*
240  * Commands to do_syslog:
241  *
242  *      0 -- Close the log.  Currently a NOP.
243  *      1 -- Open the log. Currently a NOP.
244  *      2 -- Read from the log.
245  *      3 -- Read all messages remaining in the ring buffer.
246  *      4 -- Read and clear all messages remaining in the ring buffer
247  *      5 -- Clear ring buffer.
248  *      6 -- Disable printk's to console
249  *      7 -- Enable printk's to console
250  *      8 -- Set level of messages printed to console
251  *      9 -- Return number of unread characters in the log buffer
252  *     10 -- Return size of the log buffer
253  */
254 int do_syslog(int type, char __user * buf, int len)
255 {
256         unsigned long i, j, limit, count;
257         int do_clear = 0;
258         char c;
259         int error = 0;
260
261         error = security_syslog(type);
262         if (error)
263                 return error;
264
265         switch (type) {
266         case 0:         /* Close log */
267                 break;
268         case 1:         /* Open log */
269                 break;
270         case 2:         /* Read from log */
271                 error = -EINVAL;
272                 if (!buf || len < 0)
273                         goto out;
274                 error = 0;
275                 if (!len)
276                         goto out;
277                 if (!access_ok(VERIFY_WRITE, buf, len)) {
278                         error = -EFAULT;
279                         goto out;
280                 }
281                 error = wait_event_interruptible(log_wait, (log_start - log_end));
282                 if (error)
283                         goto out;
284                 i = 0;
285                 spin_lock_irq(&logbuf_lock);
286                 while (!error && (log_start != log_end) && i < len) {
287                         c = LOG_BUF(log_start);
288                         log_start++;
289                         spin_unlock_irq(&logbuf_lock);
290                         error = __put_user(c,buf);
291                         buf++;
292                         i++;
293                         cond_resched();
294                         spin_lock_irq(&logbuf_lock);
295                 }
296                 spin_unlock_irq(&logbuf_lock);
297                 if (!error)
298                         error = i;
299                 break;
300         case 4:         /* Read/clear last kernel messages */
301                 do_clear = 1; 
302                 /* FALL THRU */
303         case 3:         /* Read last kernel messages */
304                 error = -EINVAL;
305                 if (!buf || len < 0)
306                         goto out;
307                 error = 0;
308                 if (!len)
309                         goto out;
310                 if (!access_ok(VERIFY_WRITE, buf, len)) {
311                         error = -EFAULT;
312                         goto out;
313                 }
314                 count = len;
315                 if (count > log_buf_len)
316                         count = log_buf_len;
317                 spin_lock_irq(&logbuf_lock);
318                 if (count > logged_chars)
319                         count = logged_chars;
320                 if (do_clear)
321                         logged_chars = 0;
322                 limit = log_end;
323                 /*
324                  * __put_user() could sleep, and while we sleep
325                  * printk() could overwrite the messages 
326                  * we try to copy to user space. Therefore
327                  * the messages are copied in reverse. <manfreds>
328                  */
329                 for(i = 0; i < count && !error; i++) {
330                         j = limit-1-i;
331                         if (j + log_buf_len < log_end)
332                                 break;
333                         c = LOG_BUF(j);
334                         spin_unlock_irq(&logbuf_lock);
335                         error = __put_user(c,&buf[count-1-i]);
336                         cond_resched();
337                         spin_lock_irq(&logbuf_lock);
338                 }
339                 spin_unlock_irq(&logbuf_lock);
340                 if (error)
341                         break;
342                 error = i;
343                 if(i != count) {
344                         int offset = count-error;
345                         /* buffer overflow during copy, correct user buffer. */
346                         for(i=0;i<error;i++) {
347                                 if (__get_user(c,&buf[i+offset]) ||
348                                     __put_user(c,&buf[i])) {
349                                         error = -EFAULT;
350                                         break;
351                                 }
352                                 cond_resched();
353                         }
354                 }
355                 break;
356         case 5:         /* Clear ring buffer */
357                 logged_chars = 0;
358                 break;
359         case 6:         /* Disable logging to console */
360                 console_loglevel = minimum_console_loglevel;
361                 break;
362         case 7:         /* Enable logging to console */
363                 console_loglevel = default_console_loglevel;
364                 break;
365         case 8:         /* Set level of messages printed to console */
366                 error = -EINVAL;
367                 if (len < 1 || len > 8)
368                         goto out;
369                 if (len < minimum_console_loglevel)
370                         len = minimum_console_loglevel;
371                 console_loglevel = len;
372                 error = 0;
373                 break;
374         case 9:         /* Number of chars in the log buffer */
375                 error = log_end - log_start;
376                 break;
377         case 10:        /* Size of the log buffer */
378                 error = log_buf_len;
379                 break;
380         default:
381                 error = -EINVAL;
382                 break;
383         }
384 out:
385         return error;
386 }
387
388 asmlinkage long sys_syslog(int type, char __user * buf, int len)
389 {
390         return do_syslog(type, buf, len);
391 }
392
393 /*
394  * Call the console drivers on a range of log_buf
395  */
396 static void __call_console_drivers(unsigned long start, unsigned long end)
397 {
398         struct console *con;
399
400         for (con = console_drivers; con; con = con->next) {
401                 if ((con->flags & CON_ENABLED) && con->write)
402                         con->write(con, &LOG_BUF(start), end - start);
403         }
404 }
405
406 /*
407  * Write out chars from start to end - 1 inclusive
408  */
409 static void _call_console_drivers(unsigned long start,
410                                 unsigned long end, int msg_log_level)
411 {
412         if (msg_log_level < console_loglevel &&
413                         console_drivers && start != end) {
414                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
415                         /* wrapped write */
416                         __call_console_drivers(start & LOG_BUF_MASK,
417                                                 log_buf_len);
418                         __call_console_drivers(0, end & LOG_BUF_MASK);
419                 } else {
420                         __call_console_drivers(start, end);
421                 }
422         }
423 }
424
425 /*
426  * Call the console drivers, asking them to write out
427  * log_buf[start] to log_buf[end - 1].
428  * The console_sem must be held.
429  */
430 static void call_console_drivers(unsigned long start, unsigned long end)
431 {
432         unsigned long cur_index, start_print;
433         static int msg_level = -1;
434
435         if (((long)(start - end)) > 0)
436                 BUG();
437
438         cur_index = start;
439         start_print = start;
440         while (cur_index != end) {
441                 if (    msg_level < 0 &&
442                         ((end - cur_index) > 2) &&
443                         LOG_BUF(cur_index + 0) == '<' &&
444                         LOG_BUF(cur_index + 1) >= '0' &&
445                         LOG_BUF(cur_index + 1) <= '7' &&
446                         LOG_BUF(cur_index + 2) == '>')
447                 {
448                         msg_level = LOG_BUF(cur_index + 1) - '0';
449                         cur_index += 3;
450                         start_print = cur_index;
451                 }
452                 while (cur_index != end) {
453                         char c = LOG_BUF(cur_index);
454                         cur_index++;
455
456                         if (c == '\n') {
457                                 if (msg_level < 0) {
458                                         /*
459                                          * printk() has already given us loglevel tags in
460                                          * the buffer.  This code is here in case the
461                                          * log buffer has wrapped right round and scribbled
462                                          * on those tags
463                                          */
464                                         msg_level = default_message_loglevel;
465                                 }
466                                 _call_console_drivers(start_print, cur_index, msg_level);
467                                 msg_level = -1;
468                                 start_print = cur_index;
469                                 break;
470                         }
471                 }
472         }
473         _call_console_drivers(start_print, end, msg_level);
474 }
475
476 static void emit_log_char(char c)
477 {
478         LOG_BUF(log_end) = c;
479         log_end++;
480         if (log_end - log_start > log_buf_len)
481                 log_start = log_end - log_buf_len;
482         if (log_end - con_start > log_buf_len)
483                 con_start = log_end - log_buf_len;
484         if (logged_chars < log_buf_len)
485                 logged_chars++;
486 }
487
488 /*
489  * Zap console related locks when oopsing. Only zap at most once
490  * every 10 seconds, to leave time for slow consoles to print a
491  * full oops.
492  */
493 static void zap_locks(void)
494 {
495         static unsigned long oops_timestamp;
496
497         if (time_after_eq(jiffies, oops_timestamp) &&
498                         !time_after(jiffies, oops_timestamp + 30*HZ))
499                 return;
500
501         oops_timestamp = jiffies;
502
503         /* If a crash is occurring, make sure we can't deadlock */
504         spin_lock_init(&logbuf_lock);
505         /* And make sure that we print immediately */
506         init_MUTEX(&console_sem);
507 }
508
509 #if defined(CONFIG_PRINTK_TIME)
510 static int printk_time = 1;
511 #else
512 static int printk_time = 0;
513 #endif
514
515 static int __init printk_time_setup(char *str)
516 {
517         if (*str)
518                 return 0;
519         printk_time = 1;
520         return 1;
521 }
522
523 __setup("time", printk_time_setup);
524
525 /*
526  * This is printk.  It can be called from any context.  We want it to work.
527  * 
528  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
529  * call the console drivers.  If we fail to get the semaphore we place the output
530  * into the log buffer and return.  The current holder of the console_sem will
531  * notice the new output in release_console_sem() and will send it to the
532  * consoles before releasing the semaphore.
533  *
534  * One effect of this deferred printing is that code which calls printk() and
535  * then changes console_loglevel may break. This is because console_loglevel
536  * is inspected when the actual printing occurs.
537  */
538 asmlinkage int printk(const char *fmt, ...)
539 {
540         va_list args;
541         int r;
542
543         va_start(args, fmt);
544         r = vprintk(fmt, args);
545         va_end(args);
546
547         return r;
548 }
549
550 asmlinkage int vprintk(const char *fmt, va_list args)
551 {
552         unsigned long flags;
553         int printed_len;
554         char *p;
555         static char printk_buf[1024];
556         static int log_level_unknown = 1;
557
558         if (unlikely(oops_in_progress))
559                 zap_locks();
560
561         /* This stops the holder of console_sem just where we want him */
562         spin_lock_irqsave(&logbuf_lock, flags);
563
564         /* Emit the output into the temporary buffer */
565         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
566
567         /*
568          * Copy the output into log_buf.  If the caller didn't provide
569          * appropriate log level tags, we insert them here
570          */
571         for (p = printk_buf; *p; p++) {
572                 if (log_level_unknown) {
573                         /* log_level_unknown signals the start of a new line */
574                         if (printk_time) {
575                                 int loglev_char;
576                                 char tbuf[50], *tp;
577                                 unsigned tlen;
578                                 unsigned long long t;
579                                 unsigned long nanosec_rem;
580
581                                 /*
582                                  * force the log level token to be
583                                  * before the time output.
584                                  */
585                                 if (p[0] == '<' && p[1] >='0' &&
586                                    p[1] <= '7' && p[2] == '>') {
587                                         loglev_char = p[1];
588                                         p += 3;
589                                         printed_len += 3;
590                                 } else {
591                                         loglev_char = default_message_loglevel
592                                                 + '0';
593                                 }
594                                 t = sched_clock();
595                                 nanosec_rem = do_div(t, 1000000000);
596                                 tlen = sprintf(tbuf,
597                                                 "<%c>[%5lu.%06lu] ",
598                                                 loglev_char,
599                                                 (unsigned long)t,
600                                                 nanosec_rem/1000);
601
602                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
603                                         emit_log_char(*tp);
604                                 printed_len += tlen - 3;
605                         } else {
606                                 if (p[0] != '<' || p[1] < '0' ||
607                                    p[1] > '7' || p[2] != '>') {
608                                         emit_log_char('<');
609                                         emit_log_char(default_message_loglevel
610                                                 + '0');
611                                         emit_log_char('>');
612                                 }
613                                 printed_len += 3;
614                         }
615                         log_level_unknown = 0;
616                         if (!*p)
617                                 break;
618                 }
619                 emit_log_char(*p);
620                 if (*p == '\n')
621                         log_level_unknown = 1;
622         }
623
624         if (!cpu_online(smp_processor_id()) &&
625             system_state != SYSTEM_RUNNING) {
626                 /*
627                  * Some console drivers may assume that per-cpu resources have
628                  * been allocated.  So don't allow them to be called by this
629                  * CPU until it is officially up.  We shouldn't be calling into
630                  * random console drivers on a CPU which doesn't exist yet..
631                  */
632                 spin_unlock_irqrestore(&logbuf_lock, flags);
633                 goto out;
634         }
635         if (!down_trylock(&console_sem)) {
636                 console_locked = 1;
637                 /*
638                  * We own the drivers.  We can drop the spinlock and let
639                  * release_console_sem() print the text
640                  */
641                 spin_unlock_irqrestore(&logbuf_lock, flags);
642                 console_may_schedule = 0;
643                 release_console_sem();
644         } else {
645                 /*
646                  * Someone else owns the drivers.  We drop the spinlock, which
647                  * allows the semaphore holder to proceed and to call the
648                  * console drivers with the output which we just produced.
649                  */
650                 spin_unlock_irqrestore(&logbuf_lock, flags);
651         }
652 out:
653         return printed_len;
654 }
655 EXPORT_SYMBOL(printk);
656 EXPORT_SYMBOL(vprintk);
657
658 /**
659  * acquire_console_sem - lock the console system for exclusive use.
660  *
661  * Acquires a semaphore which guarantees that the caller has
662  * exclusive access to the console system and the console_drivers list.
663  *
664  * Can sleep, returns nothing.
665  */
666 void acquire_console_sem(void)
667 {
668         if (in_interrupt())
669                 BUG();
670         down(&console_sem);
671         console_locked = 1;
672         console_may_schedule = 1;
673 }
674 EXPORT_SYMBOL(acquire_console_sem);
675
676 int try_acquire_console_sem(void)
677 {
678         if (down_trylock(&console_sem))
679                 return -1;
680         console_locked = 1;
681         console_may_schedule = 0;
682         return 0;
683 }
684 EXPORT_SYMBOL(try_acquire_console_sem);
685
686 int is_console_locked(void)
687 {
688         return console_locked;
689 }
690 EXPORT_SYMBOL(is_console_locked);
691
692 /**
693  * release_console_sem - unlock the console system
694  *
695  * Releases the semaphore which the caller holds on the console system
696  * and the console driver list.
697  *
698  * While the semaphore was held, console output may have been buffered
699  * by printk().  If this is the case, release_console_sem() emits
700  * the output prior to releasing the semaphore.
701  *
702  * If there is output waiting for klogd, we wake it up.
703  *
704  * release_console_sem() may be called from any context.
705  */
706 void release_console_sem(void)
707 {
708         unsigned long flags;
709         unsigned long _con_start, _log_end;
710         unsigned long wake_klogd = 0;
711
712         for ( ; ; ) {
713                 spin_lock_irqsave(&logbuf_lock, flags);
714                 wake_klogd |= log_start - log_end;
715                 if (con_start == log_end)
716                         break;                  /* Nothing to print */
717                 _con_start = con_start;
718                 _log_end = log_end;
719                 con_start = log_end;            /* Flush */
720                 spin_unlock(&logbuf_lock);
721                 call_console_drivers(_con_start, _log_end);
722                 local_irq_restore(flags);
723         }
724         console_locked = 0;
725         console_may_schedule = 0;
726         up(&console_sem);
727         spin_unlock_irqrestore(&logbuf_lock, flags);
728         if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
729                 wake_up_interruptible(&log_wait);
730 }
731 EXPORT_SYMBOL(release_console_sem);
732
733 /** console_conditional_schedule - yield the CPU if required
734  *
735  * If the console code is currently allowed to sleep, and
736  * if this CPU should yield the CPU to another task, do
737  * so here.
738  *
739  * Must be called within acquire_console_sem().
740  */
741 void __sched console_conditional_schedule(void)
742 {
743         if (console_may_schedule)
744                 cond_resched();
745 }
746 EXPORT_SYMBOL(console_conditional_schedule);
747
748 void console_print(const char *s)
749 {
750         printk(KERN_EMERG "%s", s);
751 }
752 EXPORT_SYMBOL(console_print);
753
754 void console_unblank(void)
755 {
756         struct console *c;
757
758         /*
759          * console_unblank can no longer be called in interrupt context unless
760          * oops_in_progress is set to 1..
761          */
762         if (oops_in_progress) {
763                 if (down_trylock(&console_sem) != 0)
764                         return;
765         } else
766                 acquire_console_sem();
767
768         console_locked = 1;
769         console_may_schedule = 0;
770         for (c = console_drivers; c != NULL; c = c->next)
771                 if ((c->flags & CON_ENABLED) && c->unblank)
772                         c->unblank();
773         release_console_sem();
774 }
775 EXPORT_SYMBOL(console_unblank);
776
777 /*
778  * Return the console tty driver structure and its associated index
779  */
780 struct tty_driver *console_device(int *index)
781 {
782         struct console *c;
783         struct tty_driver *driver = NULL;
784
785         acquire_console_sem();
786         for (c = console_drivers; c != NULL; c = c->next) {
787                 if (!c->device)
788                         continue;
789                 driver = c->device(c, index);
790                 if (driver)
791                         break;
792         }
793         release_console_sem();
794         return driver;
795 }
796
797 /*
798  * Prevent further output on the passed console device so that (for example)
799  * serial drivers can disable console output before suspending a port, and can
800  * re-enable output afterwards.
801  */
802 void console_stop(struct console *console)
803 {
804         acquire_console_sem();
805         console->flags &= ~CON_ENABLED;
806         release_console_sem();
807 }
808 EXPORT_SYMBOL(console_stop);
809
810 void console_start(struct console *console)
811 {
812         acquire_console_sem();
813         console->flags |= CON_ENABLED;
814         release_console_sem();
815 }
816 EXPORT_SYMBOL(console_start);
817
818 /*
819  * The console driver calls this routine during kernel initialization
820  * to register the console printing procedure with printk() and to
821  * print any messages that were printed by the kernel before the
822  * console driver was initialized.
823  */
824 void register_console(struct console * console)
825 {
826         int     i;
827         unsigned long flags;
828
829         if (preferred_console < 0)
830                 preferred_console = selected_console;
831
832         /*
833          *      See if we want to use this console driver. If we
834          *      didn't select a console we take the first one
835          *      that registers here.
836          */
837         if (preferred_console < 0) {
838                 if (console->index < 0)
839                         console->index = 0;
840                 if (console->setup == NULL ||
841                     console->setup(console, NULL) == 0) {
842                         console->flags |= CON_ENABLED | CON_CONSDEV;
843                         preferred_console = 0;
844                 }
845         }
846
847         /*
848          *      See if this console matches one we selected on
849          *      the command line.
850          */
851         for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) {
852                 if (strcmp(console_cmdline[i].name, console->name) != 0)
853                         continue;
854                 if (console->index >= 0 &&
855                     console->index != console_cmdline[i].index)
856                         continue;
857                 if (console->index < 0)
858                         console->index = console_cmdline[i].index;
859                 if (console->setup &&
860                     console->setup(console, console_cmdline[i].options) != 0)
861                         break;
862                 console->flags |= CON_ENABLED;
863                 console->index = console_cmdline[i].index;
864                 if (i == preferred_console)
865                         console->flags |= CON_CONSDEV;
866                 break;
867         }
868
869         if (!(console->flags & CON_ENABLED))
870                 return;
871
872         if (console_drivers && (console_drivers->flags & CON_BOOT)) {
873                 unregister_console(console_drivers);
874                 console->flags &= ~CON_PRINTBUFFER;
875         }
876
877         /*
878          *      Put this console in the list - keep the
879          *      preferred driver at the head of the list.
880          */
881         acquire_console_sem();
882         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
883                 console->next = console_drivers;
884                 console_drivers = console;
885         } else {
886                 console->next = console_drivers->next;
887                 console_drivers->next = console;
888         }
889         if (console->flags & CON_PRINTBUFFER) {
890                 /*
891                  * release_console_sem() will print out the buffered messages
892                  * for us.
893                  */
894                 spin_lock_irqsave(&logbuf_lock, flags);
895                 con_start = log_start;
896                 spin_unlock_irqrestore(&logbuf_lock, flags);
897         }
898         release_console_sem();
899 }
900 EXPORT_SYMBOL(register_console);
901
902 int unregister_console(struct console * console)
903 {
904         struct console *a,*b;
905         int res = 1;
906
907         acquire_console_sem();
908         if (console_drivers == console) {
909                 console_drivers=console->next;
910                 res = 0;
911         } else {
912                 for (a=console_drivers->next, b=console_drivers ;
913                      a; b=a, a=b->next) {
914                         if (a == console) {
915                                 b->next = a->next;
916                                 res = 0;
917                                 break;
918                         }  
919                 }
920         }
921         
922         /* If last console is removed, we re-enable picking the first
923          * one that gets registered. Without that, pmac early boot console
924          * would prevent fbcon from taking over.
925          */
926         if (console_drivers == NULL)
927                 preferred_console = selected_console;
928                 
929
930         release_console_sem();
931         return res;
932 }
933 EXPORT_SYMBOL(unregister_console);
934         
935 /**
936  * tty_write_message - write a message to a certain tty, not just the console.
937  *
938  * This is used for messages that need to be redirected to a specific tty.
939  * We don't put it into the syslog queue right now maybe in the future if
940  * really needed.
941  */
942 void tty_write_message(struct tty_struct *tty, char *msg)
943 {
944         if (tty && tty->driver->write)
945                 tty->driver->write(tty, msg, strlen(msg));
946         return;
947 }
948
949 /*
950  * printk rate limiting, lifted from the networking subsystem.
951  *
952  * This enforces a rate limit: not more than one kernel message
953  * every printk_ratelimit_jiffies to make a denial-of-service
954  * attack impossible.
955  */
956 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
957 {
958         static DEFINE_SPINLOCK(ratelimit_lock);
959         static unsigned long toks = 10*5*HZ;
960         static unsigned long last_msg;
961         static int missed;
962         unsigned long flags;
963         unsigned long now = jiffies;
964
965         spin_lock_irqsave(&ratelimit_lock, flags);
966         toks += now - last_msg;
967         last_msg = now;
968         if (toks > (ratelimit_burst * ratelimit_jiffies))
969                 toks = ratelimit_burst * ratelimit_jiffies;
970         if (toks >= ratelimit_jiffies) {
971                 int lost = missed;
972                 missed = 0;
973                 toks -= ratelimit_jiffies;
974                 spin_unlock_irqrestore(&ratelimit_lock, flags);
975                 if (lost)
976                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
977                 return 1;
978         }
979         missed++;
980         spin_unlock_irqrestore(&ratelimit_lock, flags);
981         return 0;
982 }
983 EXPORT_SYMBOL(__printk_ratelimit);
984
985 /* minimum time in jiffies between messages */
986 int printk_ratelimit_jiffies = 5*HZ;
987
988 /* number of messages we send before ratelimiting */
989 int printk_ratelimit_burst = 10;
990
991 int printk_ratelimit(void)
992 {
993         return __printk_ratelimit(printk_ratelimit_jiffies,
994                                 printk_ratelimit_burst);
995 }
996 EXPORT_SYMBOL(printk_ratelimit);