Merge master.kernel.org:/home/rmk/linux-2.6-arm
[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 #define LOG_BUF_MASK    (log_buf_len-1)
89 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
90
91 /*
92  * The indices into log_buf are not constrained to log_buf_len - they
93  * must be masked before subscripting
94  */
95 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
96 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
97 static unsigned long log_end;   /* Index into log_buf: most-recently-written-char + 1 */
98
99 /*
100  *      Array of consoles built from command line options (console=)
101  */
102 struct console_cmdline
103 {
104         char    name[8];                        /* Name of the driver       */
105         int     index;                          /* Minor dev. to use        */
106         char    *options;                       /* Options for the driver   */
107 };
108
109 #define MAX_CMDLINECONSOLES 8
110
111 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
112 static int selected_console = -1;
113 static int preferred_console = -1;
114
115 /* Flag: console code may call schedule() */
116 static int console_may_schedule;
117
118 #ifdef CONFIG_PRINTK
119
120 static char __log_buf[__LOG_BUF_LEN];
121 static char *log_buf = __log_buf;
122 static int log_buf_len = __LOG_BUF_LEN;
123 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
124
125 /*
126  *      Setup a list of consoles. Called from init/main.c
127  */
128 static int __init console_setup(char *str)
129 {
130         char name[sizeof(console_cmdline[0].name)];
131         char *s, *options;
132         int idx;
133
134         /*
135          *      Decode str into name, index, options.
136          */
137         if (str[0] >= '0' && str[0] <= '9') {
138                 strcpy(name, "ttyS");
139                 strncpy(name + 4, str, sizeof(name) - 5);
140         } else
141                 strncpy(name, str, sizeof(name) - 1);
142         name[sizeof(name) - 1] = 0;
143         if ((options = strchr(str, ',')) != NULL)
144                 *(options++) = 0;
145 #ifdef __sparc__
146         if (!strcmp(str, "ttya"))
147                 strcpy(name, "ttyS0");
148         if (!strcmp(str, "ttyb"))
149                 strcpy(name, "ttyS1");
150 #endif
151         for (s = name; *s; s++)
152                 if ((*s >= '0' && *s <= '9') || *s == ',')
153                         break;
154         idx = simple_strtoul(s, NULL, 10);
155         *s = 0;
156
157         add_preferred_console(name, idx, options);
158         return 1;
159 }
160
161 __setup("console=", console_setup);
162
163 static int __init log_buf_len_setup(char *str)
164 {
165         unsigned long size = memparse(str, &str);
166         unsigned long flags;
167
168         if (size)
169                 size = roundup_pow_of_two(size);
170         if (size > log_buf_len) {
171                 unsigned long start, dest_idx, offset;
172                 char *new_log_buf;
173
174                 new_log_buf = alloc_bootmem(size);
175                 if (!new_log_buf) {
176                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
177                         goto out;
178                 }
179
180                 spin_lock_irqsave(&logbuf_lock, flags);
181                 log_buf_len = size;
182                 log_buf = new_log_buf;
183
184                 offset = start = min(con_start, log_start);
185                 dest_idx = 0;
186                 while (start != log_end) {
187                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
188                         start++;
189                         dest_idx++;
190                 }
191                 log_start -= offset;
192                 con_start -= offset;
193                 log_end -= offset;
194                 spin_unlock_irqrestore(&logbuf_lock, flags);
195
196                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
197         }
198 out:
199         return 1;
200 }
201
202 __setup("log_buf_len=", log_buf_len_setup);
203
204 /*
205  * Commands to do_syslog:
206  *
207  *      0 -- Close the log.  Currently a NOP.
208  *      1 -- Open the log. Currently a NOP.
209  *      2 -- Read from the log.
210  *      3 -- Read all messages remaining in the ring buffer.
211  *      4 -- Read and clear all messages remaining in the ring buffer
212  *      5 -- Clear ring buffer.
213  *      6 -- Disable printk's to console
214  *      7 -- Enable printk's to console
215  *      8 -- Set level of messages printed to console
216  *      9 -- Return number of unread characters in the log buffer
217  *     10 -- Return size of the log buffer
218  */
219 int do_syslog(int type, char __user *buf, int len)
220 {
221         unsigned long i, j, limit, count;
222         int do_clear = 0;
223         char c;
224         int error = 0;
225
226         error = security_syslog(type);
227         if (error)
228                 return error;
229
230         switch (type) {
231         case 0:         /* Close log */
232                 break;
233         case 1:         /* Open log */
234                 break;
235         case 2:         /* Read from log */
236                 error = -EINVAL;
237                 if (!buf || len < 0)
238                         goto out;
239                 error = 0;
240                 if (!len)
241                         goto out;
242                 if (!access_ok(VERIFY_WRITE, buf, len)) {
243                         error = -EFAULT;
244                         goto out;
245                 }
246                 error = wait_event_interruptible(log_wait,
247                                                         (log_start - log_end));
248                 if (error)
249                         goto out;
250                 i = 0;
251                 spin_lock_irq(&logbuf_lock);
252                 while (!error && (log_start != log_end) && i < len) {
253                         c = LOG_BUF(log_start);
254                         log_start++;
255                         spin_unlock_irq(&logbuf_lock);
256                         error = __put_user(c,buf);
257                         buf++;
258                         i++;
259                         cond_resched();
260                         spin_lock_irq(&logbuf_lock);
261                 }
262                 spin_unlock_irq(&logbuf_lock);
263                 if (!error)
264                         error = i;
265                 break;
266         case 4:         /* Read/clear last kernel messages */
267                 do_clear = 1;
268                 /* FALL THRU */
269         case 3:         /* Read last kernel messages */
270                 error = -EINVAL;
271                 if (!buf || len < 0)
272                         goto out;
273                 error = 0;
274                 if (!len)
275                         goto out;
276                 if (!access_ok(VERIFY_WRITE, buf, len)) {
277                         error = -EFAULT;
278                         goto out;
279                 }
280                 count = len;
281                 if (count > log_buf_len)
282                         count = log_buf_len;
283                 spin_lock_irq(&logbuf_lock);
284                 if (count > logged_chars)
285                         count = logged_chars;
286                 if (do_clear)
287                         logged_chars = 0;
288                 limit = log_end;
289                 /*
290                  * __put_user() could sleep, and while we sleep
291                  * printk() could overwrite the messages
292                  * we try to copy to user space. Therefore
293                  * the messages are copied in reverse. <manfreds>
294                  */
295                 for (i = 0; i < count && !error; i++) {
296                         j = limit-1-i;
297                         if (j + log_buf_len < log_end)
298                                 break;
299                         c = LOG_BUF(j);
300                         spin_unlock_irq(&logbuf_lock);
301                         error = __put_user(c,&buf[count-1-i]);
302                         cond_resched();
303                         spin_lock_irq(&logbuf_lock);
304                 }
305                 spin_unlock_irq(&logbuf_lock);
306                 if (error)
307                         break;
308                 error = i;
309                 if (i != count) {
310                         int offset = count-error;
311                         /* buffer overflow during copy, correct user buffer. */
312                         for (i = 0; i < error; i++) {
313                                 if (__get_user(c,&buf[i+offset]) ||
314                                     __put_user(c,&buf[i])) {
315                                         error = -EFAULT;
316                                         break;
317                                 }
318                                 cond_resched();
319                         }
320                 }
321                 break;
322         case 5:         /* Clear ring buffer */
323                 logged_chars = 0;
324                 break;
325         case 6:         /* Disable logging to console */
326                 console_loglevel = minimum_console_loglevel;
327                 break;
328         case 7:         /* Enable logging to console */
329                 console_loglevel = default_console_loglevel;
330                 break;
331         case 8:         /* Set level of messages printed to console */
332                 error = -EINVAL;
333                 if (len < 1 || len > 8)
334                         goto out;
335                 if (len < minimum_console_loglevel)
336                         len = minimum_console_loglevel;
337                 console_loglevel = len;
338                 error = 0;
339                 break;
340         case 9:         /* Number of chars in the log buffer */
341                 error = log_end - log_start;
342                 break;
343         case 10:        /* Size of the log buffer */
344                 error = log_buf_len;
345                 break;
346         default:
347                 error = -EINVAL;
348                 break;
349         }
350 out:
351         return error;
352 }
353
354 asmlinkage long sys_syslog(int type, char __user *buf, int len)
355 {
356         return do_syslog(type, buf, len);
357 }
358
359 /*
360  * Call the console drivers on a range of log_buf
361  */
362 static void __call_console_drivers(unsigned long start, unsigned long end)
363 {
364         struct console *con;
365
366         for (con = console_drivers; con; con = con->next) {
367                 if ((con->flags & CON_ENABLED) && con->write)
368                         con->write(con, &LOG_BUF(start), end - start);
369         }
370 }
371
372 /*
373  * Write out chars from start to end - 1 inclusive
374  */
375 static void _call_console_drivers(unsigned long start,
376                                 unsigned long end, int msg_log_level)
377 {
378         if (msg_log_level < console_loglevel &&
379                         console_drivers && start != end) {
380                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
381                         /* wrapped write */
382                         __call_console_drivers(start & LOG_BUF_MASK,
383                                                 log_buf_len);
384                         __call_console_drivers(0, end & LOG_BUF_MASK);
385                 } else {
386                         __call_console_drivers(start, end);
387                 }
388         }
389 }
390
391 /*
392  * Call the console drivers, asking them to write out
393  * log_buf[start] to log_buf[end - 1].
394  * The console_sem must be held.
395  */
396 static void call_console_drivers(unsigned long start, unsigned long end)
397 {
398         unsigned long cur_index, start_print;
399         static int msg_level = -1;
400
401         if (((long)(start - end)) > 0)
402                 BUG();
403
404         cur_index = start;
405         start_print = start;
406         while (cur_index != end) {
407                 if (msg_level < 0 && ((end - cur_index) > 2) &&
408                                 LOG_BUF(cur_index + 0) == '<' &&
409                                 LOG_BUF(cur_index + 1) >= '0' &&
410                                 LOG_BUF(cur_index + 1) <= '7' &&
411                                 LOG_BUF(cur_index + 2) == '>') {
412                         msg_level = LOG_BUF(cur_index + 1) - '0';
413                         cur_index += 3;
414                         start_print = cur_index;
415                 }
416                 while (cur_index != end) {
417                         char c = LOG_BUF(cur_index);
418
419                         cur_index++;
420                         if (c == '\n') {
421                                 if (msg_level < 0) {
422                                         /*
423                                          * printk() has already given us loglevel tags in
424                                          * the buffer.  This code is here in case the
425                                          * log buffer has wrapped right round and scribbled
426                                          * on those tags
427                                          */
428                                         msg_level = default_message_loglevel;
429                                 }
430                                 _call_console_drivers(start_print, cur_index, msg_level);
431                                 msg_level = -1;
432                                 start_print = cur_index;
433                                 break;
434                         }
435                 }
436         }
437         _call_console_drivers(start_print, end, msg_level);
438 }
439
440 static void emit_log_char(char c)
441 {
442         LOG_BUF(log_end) = c;
443         log_end++;
444         if (log_end - log_start > log_buf_len)
445                 log_start = log_end - log_buf_len;
446         if (log_end - con_start > log_buf_len)
447                 con_start = log_end - log_buf_len;
448         if (logged_chars < log_buf_len)
449                 logged_chars++;
450 }
451
452 /*
453  * Zap console related locks when oopsing. Only zap at most once
454  * every 10 seconds, to leave time for slow consoles to print a
455  * full oops.
456  */
457 static void zap_locks(void)
458 {
459         static unsigned long oops_timestamp;
460
461         if (time_after_eq(jiffies, oops_timestamp) &&
462                         !time_after(jiffies, oops_timestamp + 30 * HZ))
463                 return;
464
465         oops_timestamp = jiffies;
466
467         /* If a crash is occurring, make sure we can't deadlock */
468         spin_lock_init(&logbuf_lock);
469         /* And make sure that we print immediately */
470         init_MUTEX(&console_sem);
471 }
472
473 #if defined(CONFIG_PRINTK_TIME)
474 static int printk_time = 1;
475 #else
476 static int printk_time = 0;
477 #endif
478
479 static int __init printk_time_setup(char *str)
480 {
481         if (*str)
482                 return 0;
483         printk_time = 1;
484         return 1;
485 }
486
487 __setup("time", printk_time_setup);
488
489 __attribute__((weak)) unsigned long long printk_clock(void)
490 {
491         return sched_clock();
492 }
493
494 /**
495  * printk - print a kernel message
496  * @fmt: format string
497  *
498  * This is printk.  It can be called from any context.  We want it to work.
499  *
500  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
501  * call the console drivers.  If we fail to get the semaphore we place the output
502  * into the log buffer and return.  The current holder of the console_sem will
503  * notice the new output in release_console_sem() and will send it to the
504  * consoles before releasing the semaphore.
505  *
506  * One effect of this deferred printing is that code which calls printk() and
507  * then changes console_loglevel may break. This is because console_loglevel
508  * is inspected when the actual printing occurs.
509  *
510  * See also:
511  * printf(3)
512  */
513
514 asmlinkage int printk(const char *fmt, ...)
515 {
516         va_list args;
517         int r;
518
519         va_start(args, fmt);
520         r = vprintk(fmt, args);
521         va_end(args);
522
523         return r;
524 }
525
526 /* cpu currently holding logbuf_lock */
527 static volatile unsigned int printk_cpu = UINT_MAX;
528
529 asmlinkage int vprintk(const char *fmt, va_list args)
530 {
531         unsigned long flags;
532         int printed_len;
533         char *p;
534         static char printk_buf[1024];
535         static int log_level_unknown = 1;
536
537         preempt_disable();
538         if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
539                 /* If a crash is occurring during printk() on this CPU,
540                  * make sure we can't deadlock */
541                 zap_locks();
542
543         /* This stops the holder of console_sem just where we want him */
544         spin_lock_irqsave(&logbuf_lock, flags);
545         printk_cpu = smp_processor_id();
546
547         /* Emit the output into the temporary buffer */
548         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
549
550         /*
551          * Copy the output into log_buf.  If the caller didn't provide
552          * appropriate log level tags, we insert them here
553          */
554         for (p = printk_buf; *p; p++) {
555                 if (log_level_unknown) {
556                         /* log_level_unknown signals the start of a new line */
557                         if (printk_time) {
558                                 int loglev_char;
559                                 char tbuf[50], *tp;
560                                 unsigned tlen;
561                                 unsigned long long t;
562                                 unsigned long nanosec_rem;
563
564                                 /*
565                                  * force the log level token to be
566                                  * before the time output.
567                                  */
568                                 if (p[0] == '<' && p[1] >='0' &&
569                                    p[1] <= '7' && p[2] == '>') {
570                                         loglev_char = p[1];
571                                         p += 3;
572                                         printed_len -= 3;
573                                 } else {
574                                         loglev_char = default_message_loglevel
575                                                 + '0';
576                                 }
577                                 t = printk_clock();
578                                 nanosec_rem = do_div(t, 1000000000);
579                                 tlen = sprintf(tbuf,
580                                                 "<%c>[%5lu.%06lu] ",
581                                                 loglev_char,
582                                                 (unsigned long)t,
583                                                 nanosec_rem/1000);
584
585                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
586                                         emit_log_char(*tp);
587                                 printed_len += tlen;
588                         } else {
589                                 if (p[0] != '<' || p[1] < '0' ||
590                                    p[1] > '7' || p[2] != '>') {
591                                         emit_log_char('<');
592                                         emit_log_char(default_message_loglevel
593                                                 + '0');
594                                         emit_log_char('>');
595                                         printed_len += 3;
596                                 }
597                         }
598                         log_level_unknown = 0;
599                         if (!*p)
600                                 break;
601                 }
602                 emit_log_char(*p);
603                 if (*p == '\n')
604                         log_level_unknown = 1;
605         }
606
607         if (!cpu_online(smp_processor_id())) {
608                 /*
609                  * Some console drivers may assume that per-cpu resources have
610                  * been allocated.  So don't allow them to be called by this
611                  * CPU until it is officially up.  We shouldn't be calling into
612                  * random console drivers on a CPU which doesn't exist yet..
613                  */
614                 printk_cpu = UINT_MAX;
615                 spin_unlock_irqrestore(&logbuf_lock, flags);
616                 goto out;
617         }
618         if (!down_trylock(&console_sem)) {
619                 console_locked = 1;
620                 /*
621                  * We own the drivers.  We can drop the spinlock and let
622                  * release_console_sem() print the text
623                  */
624                 printk_cpu = UINT_MAX;
625                 spin_unlock_irqrestore(&logbuf_lock, flags);
626                 console_may_schedule = 0;
627                 release_console_sem();
628         } else {
629                 /*
630                  * Someone else owns the drivers.  We drop the spinlock, which
631                  * allows the semaphore holder to proceed and to call the
632                  * console drivers with the output which we just produced.
633                  */
634                 printk_cpu = UINT_MAX;
635                 spin_unlock_irqrestore(&logbuf_lock, flags);
636         }
637 out:
638         preempt_enable();
639         return printed_len;
640 }
641 EXPORT_SYMBOL(printk);
642 EXPORT_SYMBOL(vprintk);
643
644 #else
645
646 asmlinkage long sys_syslog(int type, char __user *buf, int len)
647 {
648         return 0;
649 }
650
651 int do_syslog(int type, char __user *buf, int len)
652 {
653         return 0;
654 }
655
656 static void call_console_drivers(unsigned long start, unsigned long end)
657 {
658 }
659
660 #endif
661
662 /**
663  * add_preferred_console - add a device to the list of preferred consoles.
664  * @name: device name
665  * @idx: device index
666  * @options: options for this console
667  *
668  * The last preferred console added will be used for kernel messages
669  * and stdin/out/err for init.  Normally this is used by console_setup
670  * above to handle user-supplied console arguments; however it can also
671  * be used by arch-specific code either to override the user or more
672  * commonly to provide a default console (ie from PROM variables) when
673  * the user has not supplied one.
674  */
675 int __init add_preferred_console(char *name, int idx, char *options)
676 {
677         struct console_cmdline *c;
678         int i;
679
680         /*
681          *      See if this tty is not yet registered, and
682          *      if we have a slot free.
683          */
684         for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
685                 if (strcmp(console_cmdline[i].name, name) == 0 &&
686                           console_cmdline[i].index == idx) {
687                                 selected_console = i;
688                                 return 0;
689                 }
690         if (i == MAX_CMDLINECONSOLES)
691                 return -E2BIG;
692         selected_console = i;
693         c = &console_cmdline[i];
694         memcpy(c->name, name, sizeof(c->name));
695         c->name[sizeof(c->name) - 1] = 0;
696         c->options = options;
697         c->index = idx;
698         return 0;
699 }
700
701 /**
702  * acquire_console_sem - lock the console system for exclusive use.
703  *
704  * Acquires a semaphore which guarantees that the caller has
705  * exclusive access to the console system and the console_drivers list.
706  *
707  * Can sleep, returns nothing.
708  */
709 void acquire_console_sem(void)
710 {
711         if (in_interrupt())
712                 BUG();
713         down(&console_sem);
714         console_locked = 1;
715         console_may_schedule = 1;
716 }
717 EXPORT_SYMBOL(acquire_console_sem);
718
719 int try_acquire_console_sem(void)
720 {
721         if (down_trylock(&console_sem))
722                 return -1;
723         console_locked = 1;
724         console_may_schedule = 0;
725         return 0;
726 }
727 EXPORT_SYMBOL(try_acquire_console_sem);
728
729 int is_console_locked(void)
730 {
731         return console_locked;
732 }
733 EXPORT_SYMBOL(is_console_locked);
734
735 /**
736  * release_console_sem - unlock the console system
737  *
738  * Releases the semaphore which the caller holds on the console system
739  * and the console driver list.
740  *
741  * While the semaphore was held, console output may have been buffered
742  * by printk().  If this is the case, release_console_sem() emits
743  * the output prior to releasing the semaphore.
744  *
745  * If there is output waiting for klogd, we wake it up.
746  *
747  * release_console_sem() may be called from any context.
748  */
749 void release_console_sem(void)
750 {
751         unsigned long flags;
752         unsigned long _con_start, _log_end;
753         unsigned long wake_klogd = 0;
754
755         for ( ; ; ) {
756                 spin_lock_irqsave(&logbuf_lock, flags);
757                 wake_klogd |= log_start - log_end;
758                 if (con_start == log_end)
759                         break;                  /* Nothing to print */
760                 _con_start = con_start;
761                 _log_end = log_end;
762                 con_start = log_end;            /* Flush */
763                 spin_unlock(&logbuf_lock);
764                 call_console_drivers(_con_start, _log_end);
765                 local_irq_restore(flags);
766         }
767         console_locked = 0;
768         console_may_schedule = 0;
769         up(&console_sem);
770         spin_unlock_irqrestore(&logbuf_lock, flags);
771         if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
772                 wake_up_interruptible(&log_wait);
773 }
774 EXPORT_SYMBOL(release_console_sem);
775
776 /**
777  * console_conditional_schedule - yield the CPU if required
778  *
779  * If the console code is currently allowed to sleep, and
780  * if this CPU should yield the CPU to another task, do
781  * so here.
782  *
783  * Must be called within acquire_console_sem().
784  */
785 void __sched console_conditional_schedule(void)
786 {
787         if (console_may_schedule)
788                 cond_resched();
789 }
790 EXPORT_SYMBOL(console_conditional_schedule);
791
792 void console_print(const char *s)
793 {
794         printk(KERN_EMERG "%s", s);
795 }
796 EXPORT_SYMBOL(console_print);
797
798 void console_unblank(void)
799 {
800         struct console *c;
801
802         /*
803          * console_unblank can no longer be called in interrupt context unless
804          * oops_in_progress is set to 1..
805          */
806         if (oops_in_progress) {
807                 if (down_trylock(&console_sem) != 0)
808                         return;
809         } else
810                 acquire_console_sem();
811
812         console_locked = 1;
813         console_may_schedule = 0;
814         for (c = console_drivers; c != NULL; c = c->next)
815                 if ((c->flags & CON_ENABLED) && c->unblank)
816                         c->unblank();
817         release_console_sem();
818 }
819
820 /*
821  * Return the console tty driver structure and its associated index
822  */
823 struct tty_driver *console_device(int *index)
824 {
825         struct console *c;
826         struct tty_driver *driver = NULL;
827
828         acquire_console_sem();
829         for (c = console_drivers; c != NULL; c = c->next) {
830                 if (!c->device)
831                         continue;
832                 driver = c->device(c, index);
833                 if (driver)
834                         break;
835         }
836         release_console_sem();
837         return driver;
838 }
839
840 /*
841  * Prevent further output on the passed console device so that (for example)
842  * serial drivers can disable console output before suspending a port, and can
843  * re-enable output afterwards.
844  */
845 void console_stop(struct console *console)
846 {
847         acquire_console_sem();
848         console->flags &= ~CON_ENABLED;
849         release_console_sem();
850 }
851 EXPORT_SYMBOL(console_stop);
852
853 void console_start(struct console *console)
854 {
855         acquire_console_sem();
856         console->flags |= CON_ENABLED;
857         release_console_sem();
858 }
859 EXPORT_SYMBOL(console_start);
860
861 /*
862  * The console driver calls this routine during kernel initialization
863  * to register the console printing procedure with printk() and to
864  * print any messages that were printed by the kernel before the
865  * console driver was initialized.
866  */
867 void register_console(struct console *console)
868 {
869         int i;
870         unsigned long flags;
871
872         if (preferred_console < 0)
873                 preferred_console = selected_console;
874
875         /*
876          *      See if we want to use this console driver. If we
877          *      didn't select a console we take the first one
878          *      that registers here.
879          */
880         if (preferred_console < 0) {
881                 if (console->index < 0)
882                         console->index = 0;
883                 if (console->setup == NULL ||
884                     console->setup(console, NULL) == 0) {
885                         console->flags |= CON_ENABLED | CON_CONSDEV;
886                         preferred_console = 0;
887                 }
888         }
889
890         /*
891          *      See if this console matches one we selected on
892          *      the command line.
893          */
894         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
895                         i++) {
896                 if (strcmp(console_cmdline[i].name, console->name) != 0)
897                         continue;
898                 if (console->index >= 0 &&
899                     console->index != console_cmdline[i].index)
900                         continue;
901                 if (console->index < 0)
902                         console->index = console_cmdline[i].index;
903                 if (console->setup &&
904                     console->setup(console, console_cmdline[i].options) != 0)
905                         break;
906                 console->flags |= CON_ENABLED;
907                 console->index = console_cmdline[i].index;
908                 if (i == selected_console) {
909                         console->flags |= CON_CONSDEV;
910                         preferred_console = selected_console;
911                 }
912                 break;
913         }
914
915         if (!(console->flags & CON_ENABLED))
916                 return;
917
918         if (console_drivers && (console_drivers->flags & CON_BOOT)) {
919                 unregister_console(console_drivers);
920                 console->flags &= ~CON_PRINTBUFFER;
921         }
922
923         /*
924          *      Put this console in the list - keep the
925          *      preferred driver at the head of the list.
926          */
927         acquire_console_sem();
928         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
929                 console->next = console_drivers;
930                 console_drivers = console;
931                 if (console->next)
932                         console->next->flags &= ~CON_CONSDEV;
933         } else {
934                 console->next = console_drivers->next;
935                 console_drivers->next = console;
936         }
937         if (console->flags & CON_PRINTBUFFER) {
938                 /*
939                  * release_console_sem() will print out the buffered messages
940                  * for us.
941                  */
942                 spin_lock_irqsave(&logbuf_lock, flags);
943                 con_start = log_start;
944                 spin_unlock_irqrestore(&logbuf_lock, flags);
945         }
946         release_console_sem();
947 }
948 EXPORT_SYMBOL(register_console);
949
950 int unregister_console(struct console *console)
951 {
952         struct console *a, *b;
953         int res = 1;
954
955         acquire_console_sem();
956         if (console_drivers == console) {
957                 console_drivers=console->next;
958                 res = 0;
959         } else if (console_drivers) {
960                 for (a=console_drivers->next, b=console_drivers ;
961                      a; b=a, a=b->next) {
962                         if (a == console) {
963                                 b->next = a->next;
964                                 res = 0;
965                                 break;
966                         }
967                 }
968         }
969
970         /* If last console is removed, we re-enable picking the first
971          * one that gets registered. Without that, pmac early boot console
972          * would prevent fbcon from taking over.
973          *
974          * If this isn't the last console and it has CON_CONSDEV set, we
975          * need to set it on the next preferred console.
976          */
977         if (console_drivers == NULL)
978                 preferred_console = selected_console;
979         else if (console->flags & CON_CONSDEV)
980                 console_drivers->flags |= CON_CONSDEV;
981
982         release_console_sem();
983         return res;
984 }
985 EXPORT_SYMBOL(unregister_console);
986
987 /**
988  * tty_write_message - write a message to a certain tty, not just the console.
989  * @tty: the destination tty_struct
990  * @msg: the message to write
991  *
992  * This is used for messages that need to be redirected to a specific tty.
993  * We don't put it into the syslog queue right now maybe in the future if
994  * really needed.
995  */
996 void tty_write_message(struct tty_struct *tty, char *msg)
997 {
998         if (tty && tty->driver->write)
999                 tty->driver->write(tty, msg, strlen(msg));
1000         return;
1001 }
1002
1003 /*
1004  * printk rate limiting, lifted from the networking subsystem.
1005  *
1006  * This enforces a rate limit: not more than one kernel message
1007  * every printk_ratelimit_jiffies to make a denial-of-service
1008  * attack impossible.
1009  */
1010 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1011 {
1012         static DEFINE_SPINLOCK(ratelimit_lock);
1013         static unsigned long toks = 10 * 5 * HZ;
1014         static unsigned long last_msg;
1015         static int missed;
1016         unsigned long flags;
1017         unsigned long now = jiffies;
1018
1019         spin_lock_irqsave(&ratelimit_lock, flags);
1020         toks += now - last_msg;
1021         last_msg = now;
1022         if (toks > (ratelimit_burst * ratelimit_jiffies))
1023                 toks = ratelimit_burst * ratelimit_jiffies;
1024         if (toks >= ratelimit_jiffies) {
1025                 int lost = missed;
1026
1027                 missed = 0;
1028                 toks -= ratelimit_jiffies;
1029                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1030                 if (lost)
1031                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1032                 return 1;
1033         }
1034         missed++;
1035         spin_unlock_irqrestore(&ratelimit_lock, flags);
1036         return 0;
1037 }
1038 EXPORT_SYMBOL(__printk_ratelimit);
1039
1040 /* minimum time in jiffies between messages */
1041 int printk_ratelimit_jiffies = 5 * HZ;
1042
1043 /* number of messages we send before ratelimiting */
1044 int printk_ratelimit_burst = 10;
1045
1046 int printk_ratelimit(void)
1047 {
1048         return __printk_ratelimit(printk_ratelimit_jiffies,
1049                                 printk_ratelimit_burst);
1050 }
1051 EXPORT_SYMBOL(printk_ratelimit);