serial: convert early_uart to earlycon for 8250
[linux-2.6.git] / kernel / printk.c
1 /*
2  *  linux/kernel/printk.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  *
6  * Modified to make sys_syslog() more flexible: added commands to
7  * return the last 4k of kernel messages, regardless of whether
8  * they've been read or not.  Added option to suppress kernel printk's
9  * to the console.  Added hook for sending the console messages
10  * elsewhere, in preparation for a serial line console (someday).
11  * Ted Ts'o, 2/11/93.
12  * Modified for sysctl support, 1/8/97, Chris Horn.
13  * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14  *     manfred@colorfullife.com
15  * Rewrote bits to get rid of console_lock
16  *      01Mar01 Andrew Morton <andrewm@uow.edu.au>
17  */
18
19 #include <linux/kernel.h>
20 #include <linux/mm.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/module.h>
26 #include <linux/moduleparam.h>
27 #include <linux/interrupt.h>                    /* For in_interrupt() */
28 #include <linux/delay.h>
29 #include <linux/smp.h>
30 #include <linux/security.h>
31 #include <linux/bootmem.h>
32 #include <linux/syscalls.h>
33 #include <linux/jiffies.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 /*
56  * Low level drivers may need that to know if they can schedule in
57  * their unblank() callback or not. So let's export it.
58  */
59 int oops_in_progress;
60 EXPORT_SYMBOL(oops_in_progress);
61
62 /*
63  * console_sem protects the console_drivers list, and also
64  * provides serialisation for access to the entire console
65  * driver system.
66  */
67 static DECLARE_MUTEX(console_sem);
68 static DECLARE_MUTEX(secondary_console_sem);
69 struct console *console_drivers;
70 /*
71  * This is used for debugging the mess that is the VT code by
72  * keeping track if we have the console semaphore held. It's
73  * definitely not the perfect debug tool (we don't know if _WE_
74  * hold it are racing, but it helps tracking those weird code
75  * path in the console code where we end up in places I want
76  * locked without the console sempahore held
77  */
78 static int console_locked, console_suspended;
79
80 /*
81  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
82  * It is also used in interesting ways to provide interlocking in
83  * release_console_sem().
84  */
85 static DEFINE_SPINLOCK(logbuf_lock);
86
87 #define LOG_BUF_MASK    (log_buf_len-1)
88 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
89
90 /*
91  * The indices into log_buf are not constrained to log_buf_len - they
92  * must be masked before subscripting
93  */
94 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
95 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
96 static unsigned long log_end;   /* Index into log_buf: most-recently-written-char + 1 */
97
98 /*
99  *      Array of consoles built from command line options (console=)
100  */
101 struct console_cmdline
102 {
103         char    name[8];                        /* Name of the driver       */
104         int     index;                          /* Minor dev. to use        */
105         char    *options;                       /* Options for the driver   */
106 };
107
108 #define MAX_CMDLINECONSOLES 8
109
110 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
111 static int selected_console = -1;
112 static int preferred_console = -1;
113
114 /* Flag: console code may call schedule() */
115 static int console_may_schedule;
116
117 #ifdef CONFIG_PRINTK
118
119 static char __log_buf[__LOG_BUF_LEN];
120 static char *log_buf = __log_buf;
121 static int log_buf_len = __LOG_BUF_LEN;
122 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
123
124 static int __init log_buf_len_setup(char *str)
125 {
126         unsigned long size = memparse(str, &str);
127         unsigned long flags;
128
129         if (size)
130                 size = roundup_pow_of_two(size);
131         if (size > log_buf_len) {
132                 unsigned long start, dest_idx, offset;
133                 char *new_log_buf;
134
135                 new_log_buf = alloc_bootmem(size);
136                 if (!new_log_buf) {
137                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
138                         goto out;
139                 }
140
141                 spin_lock_irqsave(&logbuf_lock, flags);
142                 log_buf_len = size;
143                 log_buf = new_log_buf;
144
145                 offset = start = min(con_start, log_start);
146                 dest_idx = 0;
147                 while (start != log_end) {
148                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
149                         start++;
150                         dest_idx++;
151                 }
152                 log_start -= offset;
153                 con_start -= offset;
154                 log_end -= offset;
155                 spin_unlock_irqrestore(&logbuf_lock, flags);
156
157                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
158         }
159 out:
160         return 1;
161 }
162
163 __setup("log_buf_len=", log_buf_len_setup);
164
165 /*
166  * Commands to do_syslog:
167  *
168  *      0 -- Close the log.  Currently a NOP.
169  *      1 -- Open the log. Currently a NOP.
170  *      2 -- Read from the log.
171  *      3 -- Read all messages remaining in the ring buffer.
172  *      4 -- Read and clear all messages remaining in the ring buffer
173  *      5 -- Clear ring buffer.
174  *      6 -- Disable printk's to console
175  *      7 -- Enable printk's to console
176  *      8 -- Set level of messages printed to console
177  *      9 -- Return number of unread characters in the log buffer
178  *     10 -- Return size of the log buffer
179  */
180 int do_syslog(int type, char __user *buf, int len)
181 {
182         unsigned long i, j, limit, count;
183         int do_clear = 0;
184         char c;
185         int error = 0;
186
187         error = security_syslog(type);
188         if (error)
189                 return error;
190
191         switch (type) {
192         case 0:         /* Close log */
193                 break;
194         case 1:         /* Open log */
195                 break;
196         case 2:         /* Read from log */
197                 error = -EINVAL;
198                 if (!buf || len < 0)
199                         goto out;
200                 error = 0;
201                 if (!len)
202                         goto out;
203                 if (!access_ok(VERIFY_WRITE, buf, len)) {
204                         error = -EFAULT;
205                         goto out;
206                 }
207                 error = wait_event_interruptible(log_wait,
208                                                         (log_start - log_end));
209                 if (error)
210                         goto out;
211                 i = 0;
212                 spin_lock_irq(&logbuf_lock);
213                 while (!error && (log_start != log_end) && i < len) {
214                         c = LOG_BUF(log_start);
215                         log_start++;
216                         spin_unlock_irq(&logbuf_lock);
217                         error = __put_user(c,buf);
218                         buf++;
219                         i++;
220                         cond_resched();
221                         spin_lock_irq(&logbuf_lock);
222                 }
223                 spin_unlock_irq(&logbuf_lock);
224                 if (!error)
225                         error = i;
226                 break;
227         case 4:         /* Read/clear last kernel messages */
228                 do_clear = 1;
229                 /* FALL THRU */
230         case 3:         /* Read last kernel messages */
231                 error = -EINVAL;
232                 if (!buf || len < 0)
233                         goto out;
234                 error = 0;
235                 if (!len)
236                         goto out;
237                 if (!access_ok(VERIFY_WRITE, buf, len)) {
238                         error = -EFAULT;
239                         goto out;
240                 }
241                 count = len;
242                 if (count > log_buf_len)
243                         count = log_buf_len;
244                 spin_lock_irq(&logbuf_lock);
245                 if (count > logged_chars)
246                         count = logged_chars;
247                 if (do_clear)
248                         logged_chars = 0;
249                 limit = log_end;
250                 /*
251                  * __put_user() could sleep, and while we sleep
252                  * printk() could overwrite the messages
253                  * we try to copy to user space. Therefore
254                  * the messages are copied in reverse. <manfreds>
255                  */
256                 for (i = 0; i < count && !error; i++) {
257                         j = limit-1-i;
258                         if (j + log_buf_len < log_end)
259                                 break;
260                         c = LOG_BUF(j);
261                         spin_unlock_irq(&logbuf_lock);
262                         error = __put_user(c,&buf[count-1-i]);
263                         cond_resched();
264                         spin_lock_irq(&logbuf_lock);
265                 }
266                 spin_unlock_irq(&logbuf_lock);
267                 if (error)
268                         break;
269                 error = i;
270                 if (i != count) {
271                         int offset = count-error;
272                         /* buffer overflow during copy, correct user buffer. */
273                         for (i = 0; i < error; i++) {
274                                 if (__get_user(c,&buf[i+offset]) ||
275                                     __put_user(c,&buf[i])) {
276                                         error = -EFAULT;
277                                         break;
278                                 }
279                                 cond_resched();
280                         }
281                 }
282                 break;
283         case 5:         /* Clear ring buffer */
284                 logged_chars = 0;
285                 break;
286         case 6:         /* Disable logging to console */
287                 console_loglevel = minimum_console_loglevel;
288                 break;
289         case 7:         /* Enable logging to console */
290                 console_loglevel = default_console_loglevel;
291                 break;
292         case 8:         /* Set level of messages printed to console */
293                 error = -EINVAL;
294                 if (len < 1 || len > 8)
295                         goto out;
296                 if (len < minimum_console_loglevel)
297                         len = minimum_console_loglevel;
298                 console_loglevel = len;
299                 error = 0;
300                 break;
301         case 9:         /* Number of chars in the log buffer */
302                 error = log_end - log_start;
303                 break;
304         case 10:        /* Size of the log buffer */
305                 error = log_buf_len;
306                 break;
307         default:
308                 error = -EINVAL;
309                 break;
310         }
311 out:
312         return error;
313 }
314
315 asmlinkage long sys_syslog(int type, char __user *buf, int len)
316 {
317         return do_syslog(type, buf, len);
318 }
319
320 /*
321  * Call the console drivers on a range of log_buf
322  */
323 static void __call_console_drivers(unsigned long start, unsigned long end)
324 {
325         struct console *con;
326
327         for (con = console_drivers; con; con = con->next) {
328                 if ((con->flags & CON_ENABLED) && con->write &&
329                                 (cpu_online(smp_processor_id()) ||
330                                 (con->flags & CON_ANYTIME)))
331                         con->write(con, &LOG_BUF(start), end - start);
332         }
333 }
334
335 static int __read_mostly ignore_loglevel;
336
337 static int __init ignore_loglevel_setup(char *str)
338 {
339         ignore_loglevel = 1;
340         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
341
342         return 1;
343 }
344
345 __setup("ignore_loglevel", ignore_loglevel_setup);
346
347 /*
348  * Write out chars from start to end - 1 inclusive
349  */
350 static void _call_console_drivers(unsigned long start,
351                                 unsigned long end, int msg_log_level)
352 {
353         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
354                         console_drivers && start != end) {
355                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
356                         /* wrapped write */
357                         __call_console_drivers(start & LOG_BUF_MASK,
358                                                 log_buf_len);
359                         __call_console_drivers(0, end & LOG_BUF_MASK);
360                 } else {
361                         __call_console_drivers(start, end);
362                 }
363         }
364 }
365
366 /*
367  * Call the console drivers, asking them to write out
368  * log_buf[start] to log_buf[end - 1].
369  * The console_sem must be held.
370  */
371 static void call_console_drivers(unsigned long start, unsigned long end)
372 {
373         unsigned long cur_index, start_print;
374         static int msg_level = -1;
375
376         BUG_ON(((long)(start - end)) > 0);
377
378         cur_index = start;
379         start_print = start;
380         while (cur_index != end) {
381                 if (msg_level < 0 && ((end - cur_index) > 2) &&
382                                 LOG_BUF(cur_index + 0) == '<' &&
383                                 LOG_BUF(cur_index + 1) >= '0' &&
384                                 LOG_BUF(cur_index + 1) <= '7' &&
385                                 LOG_BUF(cur_index + 2) == '>') {
386                         msg_level = LOG_BUF(cur_index + 1) - '0';
387                         cur_index += 3;
388                         start_print = cur_index;
389                 }
390                 while (cur_index != end) {
391                         char c = LOG_BUF(cur_index);
392
393                         cur_index++;
394                         if (c == '\n') {
395                                 if (msg_level < 0) {
396                                         /*
397                                          * printk() has already given us loglevel tags in
398                                          * the buffer.  This code is here in case the
399                                          * log buffer has wrapped right round and scribbled
400                                          * on those tags
401                                          */
402                                         msg_level = default_message_loglevel;
403                                 }
404                                 _call_console_drivers(start_print, cur_index, msg_level);
405                                 msg_level = -1;
406                                 start_print = cur_index;
407                                 break;
408                         }
409                 }
410         }
411         _call_console_drivers(start_print, end, msg_level);
412 }
413
414 static void emit_log_char(char c)
415 {
416         LOG_BUF(log_end) = c;
417         log_end++;
418         if (log_end - log_start > log_buf_len)
419                 log_start = log_end - log_buf_len;
420         if (log_end - con_start > log_buf_len)
421                 con_start = log_end - log_buf_len;
422         if (logged_chars < log_buf_len)
423                 logged_chars++;
424 }
425
426 /*
427  * Zap console related locks when oopsing. Only zap at most once
428  * every 10 seconds, to leave time for slow consoles to print a
429  * full oops.
430  */
431 static void zap_locks(void)
432 {
433         static unsigned long oops_timestamp;
434
435         if (time_after_eq(jiffies, oops_timestamp) &&
436                         !time_after(jiffies, oops_timestamp + 30 * HZ))
437                 return;
438
439         oops_timestamp = jiffies;
440
441         /* If a crash is occurring, make sure we can't deadlock */
442         spin_lock_init(&logbuf_lock);
443         /* And make sure that we print immediately */
444         init_MUTEX(&console_sem);
445 }
446
447 #if defined(CONFIG_PRINTK_TIME)
448 static int printk_time = 1;
449 #else
450 static int printk_time = 0;
451 #endif
452 module_param(printk_time, int, S_IRUGO | S_IWUSR);
453
454 static int __init printk_time_setup(char *str)
455 {
456         if (*str)
457                 return 0;
458         printk_time = 1;
459         return 1;
460 }
461
462 __setup("time", printk_time_setup);
463
464 __attribute__((weak)) unsigned long long printk_clock(void)
465 {
466         return sched_clock();
467 }
468
469 /* Check if we have any console registered that can be called early in boot. */
470 static int have_callable_console(void)
471 {
472         struct console *con;
473
474         for (con = console_drivers; con; con = con->next)
475                 if (con->flags & CON_ANYTIME)
476                         return 1;
477
478         return 0;
479 }
480
481 /**
482  * printk - print a kernel message
483  * @fmt: format string
484  *
485  * This is printk().  It can be called from any context.  We want it to work.
486  *
487  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
488  * call the console drivers.  If we fail to get the semaphore we place the output
489  * into the log buffer and return.  The current holder of the console_sem will
490  * notice the new output in release_console_sem() and will send it to the
491  * consoles before releasing the semaphore.
492  *
493  * One effect of this deferred printing is that code which calls printk() and
494  * then changes console_loglevel may break. This is because console_loglevel
495  * is inspected when the actual printing occurs.
496  *
497  * See also:
498  * printf(3)
499  */
500
501 asmlinkage int printk(const char *fmt, ...)
502 {
503         va_list args;
504         int r;
505
506         va_start(args, fmt);
507         r = vprintk(fmt, args);
508         va_end(args);
509
510         return r;
511 }
512
513 /* cpu currently holding logbuf_lock */
514 static volatile unsigned int printk_cpu = UINT_MAX;
515
516 asmlinkage int vprintk(const char *fmt, va_list args)
517 {
518         unsigned long flags;
519         int printed_len;
520         char *p;
521         static char printk_buf[1024];
522         static int log_level_unknown = 1;
523
524         preempt_disable();
525         if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
526                 /* If a crash is occurring during printk() on this CPU,
527                  * make sure we can't deadlock */
528                 zap_locks();
529
530         /* This stops the holder of console_sem just where we want him */
531         raw_local_irq_save(flags);
532         lockdep_off();
533         spin_lock(&logbuf_lock);
534         printk_cpu = smp_processor_id();
535
536         /* Emit the output into the temporary buffer */
537         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
538
539         /*
540          * Copy the output into log_buf.  If the caller didn't provide
541          * appropriate log level tags, we insert them here
542          */
543         for (p = printk_buf; *p; p++) {
544                 if (log_level_unknown) {
545                         /* log_level_unknown signals the start of a new line */
546                         if (printk_time) {
547                                 int loglev_char;
548                                 char tbuf[50], *tp;
549                                 unsigned tlen;
550                                 unsigned long long t;
551                                 unsigned long nanosec_rem;
552
553                                 /*
554                                  * force the log level token to be
555                                  * before the time output.
556                                  */
557                                 if (p[0] == '<' && p[1] >='0' &&
558                                    p[1] <= '7' && p[2] == '>') {
559                                         loglev_char = p[1];
560                                         p += 3;
561                                         printed_len -= 3;
562                                 } else {
563                                         loglev_char = default_message_loglevel
564                                                 + '0';
565                                 }
566                                 t = printk_clock();
567                                 nanosec_rem = do_div(t, 1000000000);
568                                 tlen = sprintf(tbuf,
569                                                 "<%c>[%5lu.%06lu] ",
570                                                 loglev_char,
571                                                 (unsigned long)t,
572                                                 nanosec_rem/1000);
573
574                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
575                                         emit_log_char(*tp);
576                                 printed_len += tlen;
577                         } else {
578                                 if (p[0] != '<' || p[1] < '0' ||
579                                    p[1] > '7' || p[2] != '>') {
580                                         emit_log_char('<');
581                                         emit_log_char(default_message_loglevel
582                                                 + '0');
583                                         emit_log_char('>');
584                                         printed_len += 3;
585                                 }
586                         }
587                         log_level_unknown = 0;
588                         if (!*p)
589                                 break;
590                 }
591                 emit_log_char(*p);
592                 if (*p == '\n')
593                         log_level_unknown = 1;
594         }
595
596         if (!down_trylock(&console_sem)) {
597                 /*
598                  * We own the drivers.  We can drop the spinlock and
599                  * let release_console_sem() print the text, maybe ...
600                  */
601                 console_locked = 1;
602                 printk_cpu = UINT_MAX;
603                 spin_unlock(&logbuf_lock);
604
605                 /*
606                  * Console drivers may assume that per-cpu resources have
607                  * been allocated. So unless they're explicitly marked as
608                  * being able to cope (CON_ANYTIME) don't call them until
609                  * this CPU is officially up.
610                  */
611                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
612                         console_may_schedule = 0;
613                         release_console_sem();
614                 } else {
615                         /* Release by hand to avoid flushing the buffer. */
616                         console_locked = 0;
617                         up(&console_sem);
618                 }
619                 lockdep_on();
620                 raw_local_irq_restore(flags);
621         } else {
622                 /*
623                  * Someone else owns the drivers.  We drop the spinlock, which
624                  * allows the semaphore holder to proceed and to call the
625                  * console drivers with the output which we just produced.
626                  */
627                 printk_cpu = UINT_MAX;
628                 spin_unlock(&logbuf_lock);
629                 lockdep_on();
630                 raw_local_irq_restore(flags);
631         }
632
633         preempt_enable();
634         return printed_len;
635 }
636 EXPORT_SYMBOL(printk);
637 EXPORT_SYMBOL(vprintk);
638
639 #else
640
641 asmlinkage long sys_syslog(int type, char __user *buf, int len)
642 {
643         return -ENOSYS;
644 }
645
646 static void call_console_drivers(unsigned long start, unsigned long end)
647 {
648 }
649
650 #endif
651
652 /*
653  * Set up a list of consoles.  Called from init/main.c
654  */
655 static int __init console_setup(char *str)
656 {
657         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
658         char *s, *options;
659         int idx;
660
661         /*
662          * Decode str into name, index, options.
663          */
664         if (str[0] >= '0' && str[0] <= '9') {
665                 strcpy(buf, "ttyS");
666                 strncpy(buf + 4, str, sizeof(buf) - 5);
667         } else {
668                 strncpy(buf, str, sizeof(buf) - 1);
669         }
670         buf[sizeof(buf) - 1] = 0;
671         if ((options = strchr(str, ',')) != NULL)
672                 *(options++) = 0;
673 #ifdef __sparc__
674         if (!strcmp(str, "ttya"))
675                 strcpy(buf, "ttyS0");
676         if (!strcmp(str, "ttyb"))
677                 strcpy(buf, "ttyS1");
678 #endif
679         for (s = buf; *s; s++)
680                 if ((*s >= '0' && *s <= '9') || *s == ',')
681                         break;
682         idx = simple_strtoul(s, NULL, 10);
683         *s = 0;
684
685         add_preferred_console(buf, idx, options);
686         return 1;
687 }
688 __setup("console=", console_setup);
689
690 /**
691  * add_preferred_console - add a device to the list of preferred consoles.
692  * @name: device name
693  * @idx: device index
694  * @options: options for this console
695  *
696  * The last preferred console added will be used for kernel messages
697  * and stdin/out/err for init.  Normally this is used by console_setup
698  * above to handle user-supplied console arguments; however it can also
699  * be used by arch-specific code either to override the user or more
700  * commonly to provide a default console (ie from PROM variables) when
701  * the user has not supplied one.
702  */
703 int __init add_preferred_console(char *name, int idx, char *options)
704 {
705         struct console_cmdline *c;
706         int i;
707
708         /*
709          *      See if this tty is not yet registered, and
710          *      if we have a slot free.
711          */
712         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
713                 if (strcmp(console_cmdline[i].name, name) == 0 &&
714                           console_cmdline[i].index == idx) {
715                                 selected_console = i;
716                                 return 0;
717                 }
718         if (i == MAX_CMDLINECONSOLES)
719                 return -E2BIG;
720         selected_console = i;
721         c = &console_cmdline[i];
722         memcpy(c->name, name, sizeof(c->name));
723         c->name[sizeof(c->name) - 1] = 0;
724         c->options = options;
725         c->index = idx;
726         return 0;
727 }
728
729 int __init update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
730 {
731         struct console_cmdline *c;
732         int i;
733
734         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
735                 if (strcmp(console_cmdline[i].name, name) == 0 &&
736                           console_cmdline[i].index == idx) {
737                                 c = &console_cmdline[i];
738                                 memcpy(c->name, name_new, sizeof(c->name));
739                                 c->name[sizeof(c->name) - 1] = 0;
740                                 c->options = options;
741                                 c->index = idx_new;
742                                 return i;
743                 }
744         /* not found */
745         return -1;
746 }
747
748 #ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
749 /**
750  * suspend_console - suspend the console subsystem
751  *
752  * This disables printk() while we go into suspend states
753  */
754 void suspend_console(void)
755 {
756         printk("Suspending console(s)\n");
757         acquire_console_sem();
758         console_suspended = 1;
759 }
760
761 void resume_console(void)
762 {
763         console_suspended = 0;
764         release_console_sem();
765 }
766 #endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
767
768 /**
769  * acquire_console_sem - lock the console system for exclusive use.
770  *
771  * Acquires a semaphore which guarantees that the caller has
772  * exclusive access to the console system and the console_drivers list.
773  *
774  * Can sleep, returns nothing.
775  */
776 void acquire_console_sem(void)
777 {
778         BUG_ON(in_interrupt());
779         if (console_suspended) {
780                 down(&secondary_console_sem);
781                 return;
782         }
783         down(&console_sem);
784         console_locked = 1;
785         console_may_schedule = 1;
786 }
787 EXPORT_SYMBOL(acquire_console_sem);
788
789 int try_acquire_console_sem(void)
790 {
791         if (down_trylock(&console_sem))
792                 return -1;
793         console_locked = 1;
794         console_may_schedule = 0;
795         return 0;
796 }
797 EXPORT_SYMBOL(try_acquire_console_sem);
798
799 int is_console_locked(void)
800 {
801         return console_locked;
802 }
803
804 void wake_up_klogd(void)
805 {
806         if (!oops_in_progress && waitqueue_active(&log_wait))
807                 wake_up_interruptible(&log_wait);
808 }
809
810 /**
811  * release_console_sem - unlock the console system
812  *
813  * Releases the semaphore which the caller holds on the console system
814  * and the console driver list.
815  *
816  * While the semaphore was held, console output may have been buffered
817  * by printk().  If this is the case, release_console_sem() emits
818  * the output prior to releasing the semaphore.
819  *
820  * If there is output waiting for klogd, we wake it up.
821  *
822  * release_console_sem() may be called from any context.
823  */
824 void release_console_sem(void)
825 {
826         unsigned long flags;
827         unsigned long _con_start, _log_end;
828         unsigned long wake_klogd = 0;
829
830         if (console_suspended) {
831                 up(&secondary_console_sem);
832                 return;
833         }
834
835         console_may_schedule = 0;
836
837         for ( ; ; ) {
838                 spin_lock_irqsave(&logbuf_lock, flags);
839                 wake_klogd |= log_start - log_end;
840                 if (con_start == log_end)
841                         break;                  /* Nothing to print */
842                 _con_start = con_start;
843                 _log_end = log_end;
844                 con_start = log_end;            /* Flush */
845                 spin_unlock(&logbuf_lock);
846                 call_console_drivers(_con_start, _log_end);
847                 local_irq_restore(flags);
848         }
849         console_locked = 0;
850         up(&console_sem);
851         spin_unlock_irqrestore(&logbuf_lock, flags);
852         if (wake_klogd)
853                 wake_up_klogd();
854 }
855 EXPORT_SYMBOL(release_console_sem);
856
857 /**
858  * console_conditional_schedule - yield the CPU if required
859  *
860  * If the console code is currently allowed to sleep, and
861  * if this CPU should yield the CPU to another task, do
862  * so here.
863  *
864  * Must be called within acquire_console_sem().
865  */
866 void __sched console_conditional_schedule(void)
867 {
868         if (console_may_schedule)
869                 cond_resched();
870 }
871 EXPORT_SYMBOL(console_conditional_schedule);
872
873 void console_print(const char *s)
874 {
875         printk(KERN_EMERG "%s", s);
876 }
877 EXPORT_SYMBOL(console_print);
878
879 void console_unblank(void)
880 {
881         struct console *c;
882
883         /*
884          * console_unblank can no longer be called in interrupt context unless
885          * oops_in_progress is set to 1..
886          */
887         if (oops_in_progress) {
888                 if (down_trylock(&console_sem) != 0)
889                         return;
890         } else
891                 acquire_console_sem();
892
893         console_locked = 1;
894         console_may_schedule = 0;
895         for (c = console_drivers; c != NULL; c = c->next)
896                 if ((c->flags & CON_ENABLED) && c->unblank)
897                         c->unblank();
898         release_console_sem();
899 }
900
901 /*
902  * Return the console tty driver structure and its associated index
903  */
904 struct tty_driver *console_device(int *index)
905 {
906         struct console *c;
907         struct tty_driver *driver = NULL;
908
909         acquire_console_sem();
910         for (c = console_drivers; c != NULL; c = c->next) {
911                 if (!c->device)
912                         continue;
913                 driver = c->device(c, index);
914                 if (driver)
915                         break;
916         }
917         release_console_sem();
918         return driver;
919 }
920
921 /*
922  * Prevent further output on the passed console device so that (for example)
923  * serial drivers can disable console output before suspending a port, and can
924  * re-enable output afterwards.
925  */
926 void console_stop(struct console *console)
927 {
928         acquire_console_sem();
929         console->flags &= ~CON_ENABLED;
930         release_console_sem();
931 }
932 EXPORT_SYMBOL(console_stop);
933
934 void console_start(struct console *console)
935 {
936         acquire_console_sem();
937         console->flags |= CON_ENABLED;
938         release_console_sem();
939 }
940 EXPORT_SYMBOL(console_start);
941
942 /*
943  * The console driver calls this routine during kernel initialization
944  * to register the console printing procedure with printk() and to
945  * print any messages that were printed by the kernel before the
946  * console driver was initialized.
947  */
948 void register_console(struct console *console)
949 {
950         int i;
951         unsigned long flags;
952         struct console *bootconsole = NULL;
953
954         if (console_drivers) {
955                 if (console->flags & CON_BOOT)
956                         return;
957                 if (console_drivers->flags & CON_BOOT)
958                         bootconsole = console_drivers;
959         }
960
961         if (preferred_console < 0 || bootconsole || !console_drivers)
962                 preferred_console = selected_console;
963
964         if (console->early_setup)
965                 console->early_setup();
966
967         /*
968          *      See if we want to use this console driver. If we
969          *      didn't select a console we take the first one
970          *      that registers here.
971          */
972         if (preferred_console < 0) {
973                 if (console->index < 0)
974                         console->index = 0;
975                 if (console->setup == NULL ||
976                     console->setup(console, NULL) == 0) {
977                         console->flags |= CON_ENABLED | CON_CONSDEV;
978                         preferred_console = 0;
979                 }
980         }
981
982         /*
983          *      See if this console matches one we selected on
984          *      the command line.
985          */
986         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
987                         i++) {
988                 if (strcmp(console_cmdline[i].name, console->name) != 0)
989                         continue;
990                 if (console->index >= 0 &&
991                     console->index != console_cmdline[i].index)
992                         continue;
993                 if (console->index < 0)
994                         console->index = console_cmdline[i].index;
995                 if (console->setup &&
996                     console->setup(console, console_cmdline[i].options) != 0)
997                         break;
998                 console->flags |= CON_ENABLED;
999                 console->index = console_cmdline[i].index;
1000                 if (i == selected_console) {
1001                         console->flags |= CON_CONSDEV;
1002                         preferred_console = selected_console;
1003                 }
1004                 break;
1005         }
1006
1007         if (!(console->flags & CON_ENABLED))
1008                 return;
1009
1010         if (bootconsole && (console->flags & CON_CONSDEV)) {
1011                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1012                        bootconsole->name, bootconsole->index,
1013                        console->name, console->index);
1014                 unregister_console(bootconsole);
1015                 console->flags &= ~CON_PRINTBUFFER;
1016         } else {
1017                 printk(KERN_INFO "console [%s%d] enabled\n",
1018                        console->name, console->index);
1019         }
1020
1021         /*
1022          *      Put this console in the list - keep the
1023          *      preferred driver at the head of the list.
1024          */
1025         acquire_console_sem();
1026         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1027                 console->next = console_drivers;
1028                 console_drivers = console;
1029                 if (console->next)
1030                         console->next->flags &= ~CON_CONSDEV;
1031         } else {
1032                 console->next = console_drivers->next;
1033                 console_drivers->next = console;
1034         }
1035         if (console->flags & CON_PRINTBUFFER) {
1036                 /*
1037                  * release_console_sem() will print out the buffered messages
1038                  * for us.
1039                  */
1040                 spin_lock_irqsave(&logbuf_lock, flags);
1041                 con_start = log_start;
1042                 spin_unlock_irqrestore(&logbuf_lock, flags);
1043         }
1044         release_console_sem();
1045 }
1046 EXPORT_SYMBOL(register_console);
1047
1048 int unregister_console(struct console *console)
1049 {
1050         struct console *a, *b;
1051         int res = 1;
1052
1053         acquire_console_sem();
1054         if (console_drivers == console) {
1055                 console_drivers=console->next;
1056                 res = 0;
1057         } else if (console_drivers) {
1058                 for (a=console_drivers->next, b=console_drivers ;
1059                      a; b=a, a=b->next) {
1060                         if (a == console) {
1061                                 b->next = a->next;
1062                                 res = 0;
1063                                 break;
1064                         }
1065                 }
1066         }
1067
1068         /*
1069          * If this isn't the last console and it has CON_CONSDEV set, we
1070          * need to set it on the next preferred console.
1071          */
1072         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1073                 console_drivers->flags |= CON_CONSDEV;
1074
1075         release_console_sem();
1076         return res;
1077 }
1078 EXPORT_SYMBOL(unregister_console);
1079
1080 /**
1081  * tty_write_message - write a message to a certain tty, not just the console.
1082  * @tty: the destination tty_struct
1083  * @msg: the message to write
1084  *
1085  * This is used for messages that need to be redirected to a specific tty.
1086  * We don't put it into the syslog queue right now maybe in the future if
1087  * really needed.
1088  */
1089 void tty_write_message(struct tty_struct *tty, char *msg)
1090 {
1091         if (tty && tty->driver->write)
1092                 tty->driver->write(tty, msg, strlen(msg));
1093         return;
1094 }
1095
1096 /*
1097  * printk rate limiting, lifted from the networking subsystem.
1098  *
1099  * This enforces a rate limit: not more than one kernel message
1100  * every printk_ratelimit_jiffies to make a denial-of-service
1101  * attack impossible.
1102  */
1103 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1104 {
1105         static DEFINE_SPINLOCK(ratelimit_lock);
1106         static unsigned long toks = 10 * 5 * HZ;
1107         static unsigned long last_msg;
1108         static int missed;
1109         unsigned long flags;
1110         unsigned long now = jiffies;
1111
1112         spin_lock_irqsave(&ratelimit_lock, flags);
1113         toks += now - last_msg;
1114         last_msg = now;
1115         if (toks > (ratelimit_burst * ratelimit_jiffies))
1116                 toks = ratelimit_burst * ratelimit_jiffies;
1117         if (toks >= ratelimit_jiffies) {
1118                 int lost = missed;
1119
1120                 missed = 0;
1121                 toks -= ratelimit_jiffies;
1122                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1123                 if (lost)
1124                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1125                 return 1;
1126         }
1127         missed++;
1128         spin_unlock_irqrestore(&ratelimit_lock, flags);
1129         return 0;
1130 }
1131 EXPORT_SYMBOL(__printk_ratelimit);
1132
1133 /* minimum time in jiffies between messages */
1134 int printk_ratelimit_jiffies = 5 * HZ;
1135
1136 /* number of messages we send before ratelimiting */
1137 int printk_ratelimit_burst = 10;
1138
1139 int printk_ratelimit(void)
1140 {
1141         return __printk_ratelimit(printk_ratelimit_jiffies,
1142                                 printk_ratelimit_burst);
1143 }
1144 EXPORT_SYMBOL(printk_ratelimit);
1145
1146 /**
1147  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1148  * @caller_jiffies: pointer to caller's state
1149  * @interval_msecs: minimum interval between prints
1150  *
1151  * printk_timed_ratelimit() returns true if more than @interval_msecs
1152  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1153  * returned true.
1154  */
1155 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1156                         unsigned int interval_msecs)
1157 {
1158         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1159                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1160                 return true;
1161         }
1162         return false;
1163 }
1164 EXPORT_SYMBOL(printk_timed_ratelimit);