[PATCH] remove EXPORT_UNUSED_SYMBOL'ed symbols
[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/smp_lock.h>
24 #include <linux/console.h>
25 #include <linux/init.h>
26 #include <linux/module.h>
27 #include <linux/moduleparam.h>
28 #include <linux/interrupt.h>                    /* For in_interrupt() */
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 #include <linux/jiffies.h>
35
36 #include <asm/uaccess.h>
37
38 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
39
40 /* printk's without a loglevel use this.. */
41 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
42
43 /* We show everything that is MORE important than this.. */
44 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
45 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
46
47 DECLARE_WAIT_QUEUE_HEAD(log_wait);
48
49 int console_printk[4] = {
50         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
51         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
52         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
53         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
54 };
55
56 /*
57  * Low lever drivers may need that to know if they can schedule in
58  * their unblank() callback or not. So let's export it.
59  */
60 int oops_in_progress;
61 EXPORT_SYMBOL(oops_in_progress);
62
63 /*
64  * console_sem protects the console_drivers list, and also
65  * provides serialisation for access to the entire console
66  * driver system.
67  */
68 static DECLARE_MUTEX(console_sem);
69 static DECLARE_MUTEX(secondary_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, console_suspended;
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 static int __init log_buf_len_setup(char *str)
126 {
127         unsigned long size = memparse(str, &str);
128         unsigned long flags;
129
130         if (size)
131                 size = roundup_pow_of_two(size);
132         if (size > log_buf_len) {
133                 unsigned long start, dest_idx, offset;
134                 char *new_log_buf;
135
136                 new_log_buf = alloc_bootmem(size);
137                 if (!new_log_buf) {
138                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
139                         goto out;
140                 }
141
142                 spin_lock_irqsave(&logbuf_lock, flags);
143                 log_buf_len = size;
144                 log_buf = new_log_buf;
145
146                 offset = start = min(con_start, log_start);
147                 dest_idx = 0;
148                 while (start != log_end) {
149                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
150                         start++;
151                         dest_idx++;
152                 }
153                 log_start -= offset;
154                 con_start -= offset;
155                 log_end -= offset;
156                 spin_unlock_irqrestore(&logbuf_lock, flags);
157
158                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
159         }
160 out:
161         return 1;
162 }
163
164 __setup("log_buf_len=", log_buf_len_setup);
165
166 /*
167  * Commands to do_syslog:
168  *
169  *      0 -- Close the log.  Currently a NOP.
170  *      1 -- Open the log. Currently a NOP.
171  *      2 -- Read from the log.
172  *      3 -- Read all messages remaining in the ring buffer.
173  *      4 -- Read and clear all messages remaining in the ring buffer
174  *      5 -- Clear ring buffer.
175  *      6 -- Disable printk's to console
176  *      7 -- Enable printk's to console
177  *      8 -- Set level of messages printed to console
178  *      9 -- Return number of unread characters in the log buffer
179  *     10 -- Return size of the log buffer
180  */
181 int do_syslog(int type, char __user *buf, int len)
182 {
183         unsigned long i, j, limit, count;
184         int do_clear = 0;
185         char c;
186         int error = 0;
187
188         error = security_syslog(type);
189         if (error)
190                 return error;
191
192         switch (type) {
193         case 0:         /* Close log */
194                 break;
195         case 1:         /* Open log */
196                 break;
197         case 2:         /* Read from log */
198                 error = -EINVAL;
199                 if (!buf || len < 0)
200                         goto out;
201                 error = 0;
202                 if (!len)
203                         goto out;
204                 if (!access_ok(VERIFY_WRITE, buf, len)) {
205                         error = -EFAULT;
206                         goto out;
207                 }
208                 error = wait_event_interruptible(log_wait,
209                                                         (log_start - log_end));
210                 if (error)
211                         goto out;
212                 i = 0;
213                 spin_lock_irq(&logbuf_lock);
214                 while (!error && (log_start != log_end) && i < len) {
215                         c = LOG_BUF(log_start);
216                         log_start++;
217                         spin_unlock_irq(&logbuf_lock);
218                         error = __put_user(c,buf);
219                         buf++;
220                         i++;
221                         cond_resched();
222                         spin_lock_irq(&logbuf_lock);
223                 }
224                 spin_unlock_irq(&logbuf_lock);
225                 if (!error)
226                         error = i;
227                 break;
228         case 4:         /* Read/clear last kernel messages */
229                 do_clear = 1;
230                 /* FALL THRU */
231         case 3:         /* Read last kernel messages */
232                 error = -EINVAL;
233                 if (!buf || len < 0)
234                         goto out;
235                 error = 0;
236                 if (!len)
237                         goto out;
238                 if (!access_ok(VERIFY_WRITE, buf, len)) {
239                         error = -EFAULT;
240                         goto out;
241                 }
242                 count = len;
243                 if (count > log_buf_len)
244                         count = log_buf_len;
245                 spin_lock_irq(&logbuf_lock);
246                 if (count > logged_chars)
247                         count = logged_chars;
248                 if (do_clear)
249                         logged_chars = 0;
250                 limit = log_end;
251                 /*
252                  * __put_user() could sleep, and while we sleep
253                  * printk() could overwrite the messages
254                  * we try to copy to user space. Therefore
255                  * the messages are copied in reverse. <manfreds>
256                  */
257                 for (i = 0; i < count && !error; i++) {
258                         j = limit-1-i;
259                         if (j + log_buf_len < log_end)
260                                 break;
261                         c = LOG_BUF(j);
262                         spin_unlock_irq(&logbuf_lock);
263                         error = __put_user(c,&buf[count-1-i]);
264                         cond_resched();
265                         spin_lock_irq(&logbuf_lock);
266                 }
267                 spin_unlock_irq(&logbuf_lock);
268                 if (error)
269                         break;
270                 error = i;
271                 if (i != count) {
272                         int offset = count-error;
273                         /* buffer overflow during copy, correct user buffer. */
274                         for (i = 0; i < error; i++) {
275                                 if (__get_user(c,&buf[i+offset]) ||
276                                     __put_user(c,&buf[i])) {
277                                         error = -EFAULT;
278                                         break;
279                                 }
280                                 cond_resched();
281                         }
282                 }
283                 break;
284         case 5:         /* Clear ring buffer */
285                 logged_chars = 0;
286                 break;
287         case 6:         /* Disable logging to console */
288                 console_loglevel = minimum_console_loglevel;
289                 break;
290         case 7:         /* Enable logging to console */
291                 console_loglevel = default_console_loglevel;
292                 break;
293         case 8:         /* Set level of messages printed to console */
294                 error = -EINVAL;
295                 if (len < 1 || len > 8)
296                         goto out;
297                 if (len < minimum_console_loglevel)
298                         len = minimum_console_loglevel;
299                 console_loglevel = len;
300                 error = 0;
301                 break;
302         case 9:         /* Number of chars in the log buffer */
303                 error = log_end - log_start;
304                 break;
305         case 10:        /* Size of the log buffer */
306                 error = log_buf_len;
307                 break;
308         default:
309                 error = -EINVAL;
310                 break;
311         }
312 out:
313         return error;
314 }
315
316 asmlinkage long sys_syslog(int type, char __user *buf, int len)
317 {
318         return do_syslog(type, buf, len);
319 }
320
321 /*
322  * Call the console drivers on a range of log_buf
323  */
324 static void __call_console_drivers(unsigned long start, unsigned long end)
325 {
326         struct console *con;
327
328         for (con = console_drivers; con; con = con->next) {
329                 if ((con->flags & CON_ENABLED) && con->write &&
330                                 (cpu_online(smp_processor_id()) ||
331                                 (con->flags & CON_ANYTIME)))
332                         con->write(con, &LOG_BUF(start), end - start);
333         }
334 }
335
336 /*
337  * Write out chars from start to end - 1 inclusive
338  */
339 static void _call_console_drivers(unsigned long start,
340                                 unsigned long end, int msg_log_level)
341 {
342         if (msg_log_level < console_loglevel &&
343                         console_drivers && start != end) {
344                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
345                         /* wrapped write */
346                         __call_console_drivers(start & LOG_BUF_MASK,
347                                                 log_buf_len);
348                         __call_console_drivers(0, end & LOG_BUF_MASK);
349                 } else {
350                         __call_console_drivers(start, end);
351                 }
352         }
353 }
354
355 /*
356  * Call the console drivers, asking them to write out
357  * log_buf[start] to log_buf[end - 1].
358  * The console_sem must be held.
359  */
360 static void call_console_drivers(unsigned long start, unsigned long end)
361 {
362         unsigned long cur_index, start_print;
363         static int msg_level = -1;
364
365         BUG_ON(((long)(start - end)) > 0);
366
367         cur_index = start;
368         start_print = start;
369         while (cur_index != end) {
370                 if (msg_level < 0 && ((end - cur_index) > 2) &&
371                                 LOG_BUF(cur_index + 0) == '<' &&
372                                 LOG_BUF(cur_index + 1) >= '0' &&
373                                 LOG_BUF(cur_index + 1) <= '7' &&
374                                 LOG_BUF(cur_index + 2) == '>') {
375                         msg_level = LOG_BUF(cur_index + 1) - '0';
376                         cur_index += 3;
377                         start_print = cur_index;
378                 }
379                 while (cur_index != end) {
380                         char c = LOG_BUF(cur_index);
381
382                         cur_index++;
383                         if (c == '\n') {
384                                 if (msg_level < 0) {
385                                         /*
386                                          * printk() has already given us loglevel tags in
387                                          * the buffer.  This code is here in case the
388                                          * log buffer has wrapped right round and scribbled
389                                          * on those tags
390                                          */
391                                         msg_level = default_message_loglevel;
392                                 }
393                                 _call_console_drivers(start_print, cur_index, msg_level);
394                                 msg_level = -1;
395                                 start_print = cur_index;
396                                 break;
397                         }
398                 }
399         }
400         _call_console_drivers(start_print, end, msg_level);
401 }
402
403 static void emit_log_char(char c)
404 {
405         LOG_BUF(log_end) = c;
406         log_end++;
407         if (log_end - log_start > log_buf_len)
408                 log_start = log_end - log_buf_len;
409         if (log_end - con_start > log_buf_len)
410                 con_start = log_end - log_buf_len;
411         if (logged_chars < log_buf_len)
412                 logged_chars++;
413 }
414
415 /*
416  * Zap console related locks when oopsing. Only zap at most once
417  * every 10 seconds, to leave time for slow consoles to print a
418  * full oops.
419  */
420 static void zap_locks(void)
421 {
422         static unsigned long oops_timestamp;
423
424         if (time_after_eq(jiffies, oops_timestamp) &&
425                         !time_after(jiffies, oops_timestamp + 30 * HZ))
426                 return;
427
428         oops_timestamp = jiffies;
429
430         /* If a crash is occurring, make sure we can't deadlock */
431         spin_lock_init(&logbuf_lock);
432         /* And make sure that we print immediately */
433         init_MUTEX(&console_sem);
434 }
435
436 #if defined(CONFIG_PRINTK_TIME)
437 static int printk_time = 1;
438 #else
439 static int printk_time = 0;
440 #endif
441 module_param(printk_time, int, S_IRUGO | S_IWUSR);
442
443 static int __init printk_time_setup(char *str)
444 {
445         if (*str)
446                 return 0;
447         printk_time = 1;
448         return 1;
449 }
450
451 __setup("time", printk_time_setup);
452
453 __attribute__((weak)) unsigned long long printk_clock(void)
454 {
455         return sched_clock();
456 }
457
458 /* Check if we have any console registered that can be called early in boot. */
459 static int have_callable_console(void)
460 {
461         struct console *con;
462
463         for (con = console_drivers; con; con = con->next)
464                 if (con->flags & CON_ANYTIME)
465                         return 1;
466
467         return 0;
468 }
469
470 /**
471  * printk - print a kernel message
472  * @fmt: format string
473  *
474  * This is printk.  It can be called from any context.  We want it to work.
475  *
476  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
477  * call the console drivers.  If we fail to get the semaphore we place the output
478  * into the log buffer and return.  The current holder of the console_sem will
479  * notice the new output in release_console_sem() and will send it to the
480  * consoles before releasing the semaphore.
481  *
482  * One effect of this deferred printing is that code which calls printk() and
483  * then changes console_loglevel may break. This is because console_loglevel
484  * is inspected when the actual printing occurs.
485  *
486  * See also:
487  * printf(3)
488  */
489
490 asmlinkage int printk(const char *fmt, ...)
491 {
492         va_list args;
493         int r;
494
495         va_start(args, fmt);
496         r = vprintk(fmt, args);
497         va_end(args);
498
499         return r;
500 }
501
502 /* cpu currently holding logbuf_lock */
503 static volatile unsigned int printk_cpu = UINT_MAX;
504
505 asmlinkage int vprintk(const char *fmt, va_list args)
506 {
507         unsigned long flags;
508         int printed_len;
509         char *p;
510         static char printk_buf[1024];
511         static int log_level_unknown = 1;
512
513         preempt_disable();
514         if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
515                 /* If a crash is occurring during printk() on this CPU,
516                  * make sure we can't deadlock */
517                 zap_locks();
518
519         /* This stops the holder of console_sem just where we want him */
520         local_irq_save(flags);
521         lockdep_off();
522         spin_lock(&logbuf_lock);
523         printk_cpu = smp_processor_id();
524
525         /* Emit the output into the temporary buffer */
526         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
527
528         /*
529          * Copy the output into log_buf.  If the caller didn't provide
530          * appropriate log level tags, we insert them here
531          */
532         for (p = printk_buf; *p; p++) {
533                 if (log_level_unknown) {
534                         /* log_level_unknown signals the start of a new line */
535                         if (printk_time) {
536                                 int loglev_char;
537                                 char tbuf[50], *tp;
538                                 unsigned tlen;
539                                 unsigned long long t;
540                                 unsigned long nanosec_rem;
541
542                                 /*
543                                  * force the log level token to be
544                                  * before the time output.
545                                  */
546                                 if (p[0] == '<' && p[1] >='0' &&
547                                    p[1] <= '7' && p[2] == '>') {
548                                         loglev_char = p[1];
549                                         p += 3;
550                                         printed_len -= 3;
551                                 } else {
552                                         loglev_char = default_message_loglevel
553                                                 + '0';
554                                 }
555                                 t = printk_clock();
556                                 nanosec_rem = do_div(t, 1000000000);
557                                 tlen = sprintf(tbuf,
558                                                 "<%c>[%5lu.%06lu] ",
559                                                 loglev_char,
560                                                 (unsigned long)t,
561                                                 nanosec_rem/1000);
562
563                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
564                                         emit_log_char(*tp);
565                                 printed_len += tlen;
566                         } else {
567                                 if (p[0] != '<' || p[1] < '0' ||
568                                    p[1] > '7' || p[2] != '>') {
569                                         emit_log_char('<');
570                                         emit_log_char(default_message_loglevel
571                                                 + '0');
572                                         emit_log_char('>');
573                                         printed_len += 3;
574                                 }
575                         }
576                         log_level_unknown = 0;
577                         if (!*p)
578                                 break;
579                 }
580                 emit_log_char(*p);
581                 if (*p == '\n')
582                         log_level_unknown = 1;
583         }
584
585         if (!down_trylock(&console_sem)) {
586                 /*
587                  * We own the drivers.  We can drop the spinlock and
588                  * let release_console_sem() print the text, maybe ...
589                  */
590                 console_locked = 1;
591                 printk_cpu = UINT_MAX;
592                 spin_unlock(&logbuf_lock);
593
594                 /*
595                  * Console drivers may assume that per-cpu resources have
596                  * been allocated. So unless they're explicitly marked as
597                  * being able to cope (CON_ANYTIME) don't call them until
598                  * this CPU is officially up.
599                  */
600                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
601                         console_may_schedule = 0;
602                         release_console_sem();
603                 } else {
604                         /* Release by hand to avoid flushing the buffer. */
605                         console_locked = 0;
606                         up(&console_sem);
607                 }
608                 lockdep_on();
609                 local_irq_restore(flags);
610         } else {
611                 /*
612                  * Someone else owns the drivers.  We drop the spinlock, which
613                  * allows the semaphore holder to proceed and to call the
614                  * console drivers with the output which we just produced.
615                  */
616                 printk_cpu = UINT_MAX;
617                 spin_unlock(&logbuf_lock);
618                 lockdep_on();
619                 local_irq_restore(flags);
620         }
621
622         preempt_enable();
623         return printed_len;
624 }
625 EXPORT_SYMBOL(printk);
626 EXPORT_SYMBOL(vprintk);
627
628 #else
629
630 asmlinkage long sys_syslog(int type, char __user *buf, int len)
631 {
632         return -ENOSYS;
633 }
634
635 static void call_console_drivers(unsigned long start, unsigned long end)
636 {
637 }
638
639 #endif
640
641 /*
642  * Set up a list of consoles.  Called from init/main.c
643  */
644 static int __init console_setup(char *str)
645 {
646         char name[sizeof(console_cmdline[0].name)];
647         char *s, *options;
648         int idx;
649
650         /*
651          * Decode str into name, index, options.
652          */
653         if (str[0] >= '0' && str[0] <= '9') {
654                 strcpy(name, "ttyS");
655                 strncpy(name + 4, str, sizeof(name) - 5);
656         } else {
657                 strncpy(name, str, sizeof(name) - 1);
658         }
659         name[sizeof(name) - 1] = 0;
660         if ((options = strchr(str, ',')) != NULL)
661                 *(options++) = 0;
662 #ifdef __sparc__
663         if (!strcmp(str, "ttya"))
664                 strcpy(name, "ttyS0");
665         if (!strcmp(str, "ttyb"))
666                 strcpy(name, "ttyS1");
667 #endif
668         for (s = name; *s; s++)
669                 if ((*s >= '0' && *s <= '9') || *s == ',')
670                         break;
671         idx = simple_strtoul(s, NULL, 10);
672         *s = 0;
673
674         add_preferred_console(name, idx, options);
675         return 1;
676 }
677 __setup("console=", console_setup);
678
679 /**
680  * add_preferred_console - add a device to the list of preferred consoles.
681  * @name: device name
682  * @idx: device index
683  * @options: options for this console
684  *
685  * The last preferred console added will be used for kernel messages
686  * and stdin/out/err for init.  Normally this is used by console_setup
687  * above to handle user-supplied console arguments; however it can also
688  * be used by arch-specific code either to override the user or more
689  * commonly to provide a default console (ie from PROM variables) when
690  * the user has not supplied one.
691  */
692 int __init add_preferred_console(char *name, int idx, char *options)
693 {
694         struct console_cmdline *c;
695         int i;
696
697         /*
698          *      See if this tty is not yet registered, and
699          *      if we have a slot free.
700          */
701         for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
702                 if (strcmp(console_cmdline[i].name, name) == 0 &&
703                           console_cmdline[i].index == idx) {
704                                 selected_console = i;
705                                 return 0;
706                 }
707         if (i == MAX_CMDLINECONSOLES)
708                 return -E2BIG;
709         selected_console = i;
710         c = &console_cmdline[i];
711         memcpy(c->name, name, sizeof(c->name));
712         c->name[sizeof(c->name) - 1] = 0;
713         c->options = options;
714         c->index = idx;
715         return 0;
716 }
717
718 #ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
719 /**
720  * suspend_console - suspend the console subsystem
721  *
722  * This disables printk() while we go into suspend states
723  */
724 void suspend_console(void)
725 {
726         printk("Suspending console(s)\n");
727         acquire_console_sem();
728         console_suspended = 1;
729 }
730
731 void resume_console(void)
732 {
733         console_suspended = 0;
734         release_console_sem();
735 }
736 #endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
737
738 /**
739  * acquire_console_sem - lock the console system for exclusive use.
740  *
741  * Acquires a semaphore which guarantees that the caller has
742  * exclusive access to the console system and the console_drivers list.
743  *
744  * Can sleep, returns nothing.
745  */
746 void acquire_console_sem(void)
747 {
748         BUG_ON(in_interrupt());
749         if (console_suspended) {
750                 down(&secondary_console_sem);
751                 return;
752         }
753         down(&console_sem);
754         console_locked = 1;
755         console_may_schedule = 1;
756 }
757 EXPORT_SYMBOL(acquire_console_sem);
758
759 int try_acquire_console_sem(void)
760 {
761         if (down_trylock(&console_sem))
762                 return -1;
763         console_locked = 1;
764         console_may_schedule = 0;
765         return 0;
766 }
767 EXPORT_SYMBOL(try_acquire_console_sem);
768
769 int is_console_locked(void)
770 {
771         return console_locked;
772 }
773
774 /**
775  * release_console_sem - unlock the console system
776  *
777  * Releases the semaphore which the caller holds on the console system
778  * and the console driver list.
779  *
780  * While the semaphore was held, console output may have been buffered
781  * by printk().  If this is the case, release_console_sem() emits
782  * the output prior to releasing the semaphore.
783  *
784  * If there is output waiting for klogd, we wake it up.
785  *
786  * release_console_sem() may be called from any context.
787  */
788 void release_console_sem(void)
789 {
790         unsigned long flags;
791         unsigned long _con_start, _log_end;
792         unsigned long wake_klogd = 0;
793
794         if (console_suspended) {
795                 up(&secondary_console_sem);
796                 return;
797         }
798
799         console_may_schedule = 0;
800
801         for ( ; ; ) {
802                 spin_lock_irqsave(&logbuf_lock, flags);
803                 wake_klogd |= log_start - log_end;
804                 if (con_start == log_end)
805                         break;                  /* Nothing to print */
806                 _con_start = con_start;
807                 _log_end = log_end;
808                 con_start = log_end;            /* Flush */
809                 spin_unlock(&logbuf_lock);
810                 call_console_drivers(_con_start, _log_end);
811                 local_irq_restore(flags);
812         }
813         console_locked = 0;
814         up(&console_sem);
815         spin_unlock_irqrestore(&logbuf_lock, flags);
816         if (wake_klogd && !oops_in_progress && waitqueue_active(&log_wait))
817                 wake_up_interruptible(&log_wait);
818 }
819 EXPORT_SYMBOL(release_console_sem);
820
821 /**
822  * console_conditional_schedule - yield the CPU if required
823  *
824  * If the console code is currently allowed to sleep, and
825  * if this CPU should yield the CPU to another task, do
826  * so here.
827  *
828  * Must be called within acquire_console_sem().
829  */
830 void __sched console_conditional_schedule(void)
831 {
832         if (console_may_schedule)
833                 cond_resched();
834 }
835 EXPORT_SYMBOL(console_conditional_schedule);
836
837 void console_print(const char *s)
838 {
839         printk(KERN_EMERG "%s", s);
840 }
841 EXPORT_SYMBOL(console_print);
842
843 void console_unblank(void)
844 {
845         struct console *c;
846
847         /*
848          * console_unblank can no longer be called in interrupt context unless
849          * oops_in_progress is set to 1..
850          */
851         if (oops_in_progress) {
852                 if (down_trylock(&console_sem) != 0)
853                         return;
854         } else
855                 acquire_console_sem();
856
857         console_locked = 1;
858         console_may_schedule = 0;
859         for (c = console_drivers; c != NULL; c = c->next)
860                 if ((c->flags & CON_ENABLED) && c->unblank)
861                         c->unblank();
862         release_console_sem();
863 }
864
865 /*
866  * Return the console tty driver structure and its associated index
867  */
868 struct tty_driver *console_device(int *index)
869 {
870         struct console *c;
871         struct tty_driver *driver = NULL;
872
873         acquire_console_sem();
874         for (c = console_drivers; c != NULL; c = c->next) {
875                 if (!c->device)
876                         continue;
877                 driver = c->device(c, index);
878                 if (driver)
879                         break;
880         }
881         release_console_sem();
882         return driver;
883 }
884
885 /*
886  * Prevent further output on the passed console device so that (for example)
887  * serial drivers can disable console output before suspending a port, and can
888  * re-enable output afterwards.
889  */
890 void console_stop(struct console *console)
891 {
892         acquire_console_sem();
893         console->flags &= ~CON_ENABLED;
894         release_console_sem();
895 }
896 EXPORT_SYMBOL(console_stop);
897
898 void console_start(struct console *console)
899 {
900         acquire_console_sem();
901         console->flags |= CON_ENABLED;
902         release_console_sem();
903 }
904 EXPORT_SYMBOL(console_start);
905
906 /*
907  * The console driver calls this routine during kernel initialization
908  * to register the console printing procedure with printk() and to
909  * print any messages that were printed by the kernel before the
910  * console driver was initialized.
911  */
912 void register_console(struct console *console)
913 {
914         int i;
915         unsigned long flags;
916
917         if (preferred_console < 0)
918                 preferred_console = selected_console;
919
920         /*
921          *      See if we want to use this console driver. If we
922          *      didn't select a console we take the first one
923          *      that registers here.
924          */
925         if (preferred_console < 0) {
926                 if (console->index < 0)
927                         console->index = 0;
928                 if (console->setup == NULL ||
929                     console->setup(console, NULL) == 0) {
930                         console->flags |= CON_ENABLED | CON_CONSDEV;
931                         preferred_console = 0;
932                 }
933         }
934
935         /*
936          *      See if this console matches one we selected on
937          *      the command line.
938          */
939         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
940                         i++) {
941                 if (strcmp(console_cmdline[i].name, console->name) != 0)
942                         continue;
943                 if (console->index >= 0 &&
944                     console->index != console_cmdline[i].index)
945                         continue;
946                 if (console->index < 0)
947                         console->index = console_cmdline[i].index;
948                 if (console->setup &&
949                     console->setup(console, console_cmdline[i].options) != 0)
950                         break;
951                 console->flags |= CON_ENABLED;
952                 console->index = console_cmdline[i].index;
953                 if (i == selected_console) {
954                         console->flags |= CON_CONSDEV;
955                         preferred_console = selected_console;
956                 }
957                 break;
958         }
959
960         if (!(console->flags & CON_ENABLED))
961                 return;
962
963         if (console_drivers && (console_drivers->flags & CON_BOOT)) {
964                 unregister_console(console_drivers);
965                 console->flags &= ~CON_PRINTBUFFER;
966         }
967
968         /*
969          *      Put this console in the list - keep the
970          *      preferred driver at the head of the list.
971          */
972         acquire_console_sem();
973         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
974                 console->next = console_drivers;
975                 console_drivers = console;
976                 if (console->next)
977                         console->next->flags &= ~CON_CONSDEV;
978         } else {
979                 console->next = console_drivers->next;
980                 console_drivers->next = console;
981         }
982         if (console->flags & CON_PRINTBUFFER) {
983                 /*
984                  * release_console_sem() will print out the buffered messages
985                  * for us.
986                  */
987                 spin_lock_irqsave(&logbuf_lock, flags);
988                 con_start = log_start;
989                 spin_unlock_irqrestore(&logbuf_lock, flags);
990         }
991         release_console_sem();
992 }
993 EXPORT_SYMBOL(register_console);
994
995 int unregister_console(struct console *console)
996 {
997         struct console *a, *b;
998         int res = 1;
999
1000         acquire_console_sem();
1001         if (console_drivers == console) {
1002                 console_drivers=console->next;
1003                 res = 0;
1004         } else if (console_drivers) {
1005                 for (a=console_drivers->next, b=console_drivers ;
1006                      a; b=a, a=b->next) {
1007                         if (a == console) {
1008                                 b->next = a->next;
1009                                 res = 0;
1010                                 break;
1011                         }
1012                 }
1013         }
1014
1015         /* If last console is removed, we re-enable picking the first
1016          * one that gets registered. Without that, pmac early boot console
1017          * would prevent fbcon from taking over.
1018          *
1019          * If this isn't the last console and it has CON_CONSDEV set, we
1020          * need to set it on the next preferred console.
1021          */
1022         if (console_drivers == NULL)
1023                 preferred_console = selected_console;
1024         else if (console->flags & CON_CONSDEV)
1025                 console_drivers->flags |= CON_CONSDEV;
1026
1027         release_console_sem();
1028         return res;
1029 }
1030 EXPORT_SYMBOL(unregister_console);
1031
1032 /**
1033  * tty_write_message - write a message to a certain tty, not just the console.
1034  * @tty: the destination tty_struct
1035  * @msg: the message to write
1036  *
1037  * This is used for messages that need to be redirected to a specific tty.
1038  * We don't put it into the syslog queue right now maybe in the future if
1039  * really needed.
1040  */
1041 void tty_write_message(struct tty_struct *tty, char *msg)
1042 {
1043         if (tty && tty->driver->write)
1044                 tty->driver->write(tty, msg, strlen(msg));
1045         return;
1046 }
1047
1048 /*
1049  * printk rate limiting, lifted from the networking subsystem.
1050  *
1051  * This enforces a rate limit: not more than one kernel message
1052  * every printk_ratelimit_jiffies to make a denial-of-service
1053  * attack impossible.
1054  */
1055 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1056 {
1057         static DEFINE_SPINLOCK(ratelimit_lock);
1058         static unsigned long toks = 10 * 5 * HZ;
1059         static unsigned long last_msg;
1060         static int missed;
1061         unsigned long flags;
1062         unsigned long now = jiffies;
1063
1064         spin_lock_irqsave(&ratelimit_lock, flags);
1065         toks += now - last_msg;
1066         last_msg = now;
1067         if (toks > (ratelimit_burst * ratelimit_jiffies))
1068                 toks = ratelimit_burst * ratelimit_jiffies;
1069         if (toks >= ratelimit_jiffies) {
1070                 int lost = missed;
1071
1072                 missed = 0;
1073                 toks -= ratelimit_jiffies;
1074                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1075                 if (lost)
1076                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1077                 return 1;
1078         }
1079         missed++;
1080         spin_unlock_irqrestore(&ratelimit_lock, flags);
1081         return 0;
1082 }
1083 EXPORT_SYMBOL(__printk_ratelimit);
1084
1085 /* minimum time in jiffies between messages */
1086 int printk_ratelimit_jiffies = 5 * HZ;
1087
1088 /* number of messages we send before ratelimiting */
1089 int printk_ratelimit_burst = 10;
1090
1091 int printk_ratelimit(void)
1092 {
1093         return __printk_ratelimit(printk_ratelimit_jiffies,
1094                                 printk_ratelimit_burst);
1095 }
1096 EXPORT_SYMBOL(printk_ratelimit);
1097
1098 /**
1099  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1100  * @caller_jiffies: pointer to caller's state
1101  * @interval_msecs: minimum interval between prints
1102  *
1103  * printk_timed_ratelimit() returns true if more than @interval_msecs
1104  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1105  * returned true.
1106  */
1107 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1108                         unsigned int interval_msecs)
1109 {
1110         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1111                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1112                 return true;
1113         }
1114         return false;
1115 }
1116 EXPORT_SYMBOL(printk_timed_ratelimit);