fix - ensure we don't use bootconsoles after init has been released
[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_named(time, printk_time, bool, 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         printk(KERN_NOTICE "The 'time' option is deprecated and "
460                 "is scheduled for removal in early 2008\n");
461         printk(KERN_NOTICE "Use 'printk.time=<value>' instead\n");
462         return 1;
463 }
464
465 __setup("time", printk_time_setup);
466
467 __attribute__((weak)) unsigned long long printk_clock(void)
468 {
469         return sched_clock();
470 }
471
472 /* Check if we have any console registered that can be called early in boot. */
473 static int have_callable_console(void)
474 {
475         struct console *con;
476
477         for (con = console_drivers; con; con = con->next)
478                 if (con->flags & CON_ANYTIME)
479                         return 1;
480
481         return 0;
482 }
483
484 /**
485  * printk - print a kernel message
486  * @fmt: format string
487  *
488  * This is printk().  It can be called from any context.  We want it to work.
489  * Be aware of the fact that if oops_in_progress is not set, we might try to
490  * wake klogd up which could deadlock on runqueue lock if printk() is called
491  * from scheduler code.
492  *
493  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
494  * call the console drivers.  If we fail to get the semaphore we place the output
495  * into the log buffer and return.  The current holder of the console_sem will
496  * notice the new output in release_console_sem() and will send it to the
497  * consoles before releasing the semaphore.
498  *
499  * One effect of this deferred printing is that code which calls printk() and
500  * then changes console_loglevel may break. This is because console_loglevel
501  * is inspected when the actual printing occurs.
502  *
503  * See also:
504  * printf(3)
505  */
506
507 asmlinkage int printk(const char *fmt, ...)
508 {
509         va_list args;
510         int r;
511
512         va_start(args, fmt);
513         r = vprintk(fmt, args);
514         va_end(args);
515
516         return r;
517 }
518
519 /* cpu currently holding logbuf_lock */
520 static volatile unsigned int printk_cpu = UINT_MAX;
521
522 asmlinkage int vprintk(const char *fmt, va_list args)
523 {
524         unsigned long flags;
525         int printed_len;
526         char *p;
527         static char printk_buf[1024];
528         static int log_level_unknown = 1;
529
530         preempt_disable();
531         if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
532                 /* If a crash is occurring during printk() on this CPU,
533                  * make sure we can't deadlock */
534                 zap_locks();
535
536         /* This stops the holder of console_sem just where we want him */
537         raw_local_irq_save(flags);
538         lockdep_off();
539         spin_lock(&logbuf_lock);
540         printk_cpu = smp_processor_id();
541
542         /* Emit the output into the temporary buffer */
543         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
544
545         /*
546          * Copy the output into log_buf.  If the caller didn't provide
547          * appropriate log level tags, we insert them here
548          */
549         for (p = printk_buf; *p; p++) {
550                 if (log_level_unknown) {
551                         /* log_level_unknown signals the start of a new line */
552                         if (printk_time) {
553                                 int loglev_char;
554                                 char tbuf[50], *tp;
555                                 unsigned tlen;
556                                 unsigned long long t;
557                                 unsigned long nanosec_rem;
558
559                                 /*
560                                  * force the log level token to be
561                                  * before the time output.
562                                  */
563                                 if (p[0] == '<' && p[1] >='0' &&
564                                    p[1] <= '7' && p[2] == '>') {
565                                         loglev_char = p[1];
566                                         p += 3;
567                                         printed_len -= 3;
568                                 } else {
569                                         loglev_char = default_message_loglevel
570                                                 + '0';
571                                 }
572                                 t = printk_clock();
573                                 nanosec_rem = do_div(t, 1000000000);
574                                 tlen = sprintf(tbuf,
575                                                 "<%c>[%5lu.%06lu] ",
576                                                 loglev_char,
577                                                 (unsigned long)t,
578                                                 nanosec_rem/1000);
579
580                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
581                                         emit_log_char(*tp);
582                                 printed_len += tlen;
583                         } else {
584                                 if (p[0] != '<' || p[1] < '0' ||
585                                    p[1] > '7' || p[2] != '>') {
586                                         emit_log_char('<');
587                                         emit_log_char(default_message_loglevel
588                                                 + '0');
589                                         emit_log_char('>');
590                                         printed_len += 3;
591                                 }
592                         }
593                         log_level_unknown = 0;
594                         if (!*p)
595                                 break;
596                 }
597                 emit_log_char(*p);
598                 if (*p == '\n')
599                         log_level_unknown = 1;
600         }
601
602         if (!down_trylock(&console_sem)) {
603                 /*
604                  * We own the drivers.  We can drop the spinlock and
605                  * let release_console_sem() print the text, maybe ...
606                  */
607                 console_locked = 1;
608                 printk_cpu = UINT_MAX;
609                 spin_unlock(&logbuf_lock);
610
611                 /*
612                  * Console drivers may assume that per-cpu resources have
613                  * been allocated. So unless they're explicitly marked as
614                  * being able to cope (CON_ANYTIME) don't call them until
615                  * this CPU is officially up.
616                  */
617                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
618                         console_may_schedule = 0;
619                         release_console_sem();
620                 } else {
621                         /* Release by hand to avoid flushing the buffer. */
622                         console_locked = 0;
623                         up(&console_sem);
624                 }
625                 lockdep_on();
626                 raw_local_irq_restore(flags);
627         } else {
628                 /*
629                  * Someone else owns the drivers.  We drop the spinlock, which
630                  * allows the semaphore holder to proceed and to call the
631                  * console drivers with the output which we just produced.
632                  */
633                 printk_cpu = UINT_MAX;
634                 spin_unlock(&logbuf_lock);
635                 lockdep_on();
636                 raw_local_irq_restore(flags);
637         }
638
639         preempt_enable();
640         return printed_len;
641 }
642 EXPORT_SYMBOL(printk);
643 EXPORT_SYMBOL(vprintk);
644
645 #else
646
647 asmlinkage long sys_syslog(int type, char __user *buf, int len)
648 {
649         return -ENOSYS;
650 }
651
652 static void call_console_drivers(unsigned long start, unsigned long end)
653 {
654 }
655
656 #endif
657
658 /*
659  * Set up a list of consoles.  Called from init/main.c
660  */
661 static int __init console_setup(char *str)
662 {
663         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
664         char *s, *options;
665         int idx;
666
667         /*
668          * Decode str into name, index, options.
669          */
670         if (str[0] >= '0' && str[0] <= '9') {
671                 strcpy(buf, "ttyS");
672                 strncpy(buf + 4, str, sizeof(buf) - 5);
673         } else {
674                 strncpy(buf, str, sizeof(buf) - 1);
675         }
676         buf[sizeof(buf) - 1] = 0;
677         if ((options = strchr(str, ',')) != NULL)
678                 *(options++) = 0;
679 #ifdef __sparc__
680         if (!strcmp(str, "ttya"))
681                 strcpy(buf, "ttyS0");
682         if (!strcmp(str, "ttyb"))
683                 strcpy(buf, "ttyS1");
684 #endif
685         for (s = buf; *s; s++)
686                 if ((*s >= '0' && *s <= '9') || *s == ',')
687                         break;
688         idx = simple_strtoul(s, NULL, 10);
689         *s = 0;
690
691         add_preferred_console(buf, idx, options);
692         return 1;
693 }
694 __setup("console=", console_setup);
695
696 /**
697  * add_preferred_console - add a device to the list of preferred consoles.
698  * @name: device name
699  * @idx: device index
700  * @options: options for this console
701  *
702  * The last preferred console added will be used for kernel messages
703  * and stdin/out/err for init.  Normally this is used by console_setup
704  * above to handle user-supplied console arguments; however it can also
705  * be used by arch-specific code either to override the user or more
706  * commonly to provide a default console (ie from PROM variables) when
707  * the user has not supplied one.
708  */
709 int __init add_preferred_console(char *name, int idx, char *options)
710 {
711         struct console_cmdline *c;
712         int i;
713
714         /*
715          *      See if this tty is not yet registered, and
716          *      if we have a slot free.
717          */
718         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
719                 if (strcmp(console_cmdline[i].name, name) == 0 &&
720                           console_cmdline[i].index == idx) {
721                                 selected_console = i;
722                                 return 0;
723                 }
724         if (i == MAX_CMDLINECONSOLES)
725                 return -E2BIG;
726         selected_console = i;
727         c = &console_cmdline[i];
728         memcpy(c->name, name, sizeof(c->name));
729         c->name[sizeof(c->name) - 1] = 0;
730         c->options = options;
731         c->index = idx;
732         return 0;
733 }
734
735 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
736 {
737         struct console_cmdline *c;
738         int i;
739
740         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
741                 if (strcmp(console_cmdline[i].name, name) == 0 &&
742                           console_cmdline[i].index == idx) {
743                                 c = &console_cmdline[i];
744                                 memcpy(c->name, name_new, sizeof(c->name));
745                                 c->name[sizeof(c->name) - 1] = 0;
746                                 c->options = options;
747                                 c->index = idx_new;
748                                 return i;
749                 }
750         /* not found */
751         return -1;
752 }
753
754 #ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
755 /**
756  * suspend_console - suspend the console subsystem
757  *
758  * This disables printk() while we go into suspend states
759  */
760 void suspend_console(void)
761 {
762         printk("Suspending console(s)\n");
763         acquire_console_sem();
764         console_suspended = 1;
765 }
766
767 void resume_console(void)
768 {
769         console_suspended = 0;
770         release_console_sem();
771 }
772 #endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
773
774 /**
775  * acquire_console_sem - lock the console system for exclusive use.
776  *
777  * Acquires a semaphore which guarantees that the caller has
778  * exclusive access to the console system and the console_drivers list.
779  *
780  * Can sleep, returns nothing.
781  */
782 void acquire_console_sem(void)
783 {
784         BUG_ON(in_interrupt());
785         if (console_suspended) {
786                 down(&secondary_console_sem);
787                 return;
788         }
789         down(&console_sem);
790         console_locked = 1;
791         console_may_schedule = 1;
792 }
793 EXPORT_SYMBOL(acquire_console_sem);
794
795 int try_acquire_console_sem(void)
796 {
797         if (down_trylock(&console_sem))
798                 return -1;
799         console_locked = 1;
800         console_may_schedule = 0;
801         return 0;
802 }
803 EXPORT_SYMBOL(try_acquire_console_sem);
804
805 int is_console_locked(void)
806 {
807         return console_locked;
808 }
809
810 void wake_up_klogd(void)
811 {
812         if (!oops_in_progress && waitqueue_active(&log_wait))
813                 wake_up_interruptible(&log_wait);
814 }
815
816 /**
817  * release_console_sem - unlock the console system
818  *
819  * Releases the semaphore which the caller holds on the console system
820  * and the console driver list.
821  *
822  * While the semaphore was held, console output may have been buffered
823  * by printk().  If this is the case, release_console_sem() emits
824  * the output prior to releasing the semaphore.
825  *
826  * If there is output waiting for klogd, we wake it up.
827  *
828  * release_console_sem() may be called from any context.
829  */
830 void release_console_sem(void)
831 {
832         unsigned long flags;
833         unsigned long _con_start, _log_end;
834         unsigned long wake_klogd = 0;
835
836         if (console_suspended) {
837                 up(&secondary_console_sem);
838                 return;
839         }
840
841         console_may_schedule = 0;
842
843         for ( ; ; ) {
844                 spin_lock_irqsave(&logbuf_lock, flags);
845                 wake_klogd |= log_start - log_end;
846                 if (con_start == log_end)
847                         break;                  /* Nothing to print */
848                 _con_start = con_start;
849                 _log_end = log_end;
850                 con_start = log_end;            /* Flush */
851                 spin_unlock(&logbuf_lock);
852                 call_console_drivers(_con_start, _log_end);
853                 local_irq_restore(flags);
854         }
855         console_locked = 0;
856         up(&console_sem);
857         spin_unlock_irqrestore(&logbuf_lock, flags);
858         if (wake_klogd)
859                 wake_up_klogd();
860 }
861 EXPORT_SYMBOL(release_console_sem);
862
863 /**
864  * console_conditional_schedule - yield the CPU if required
865  *
866  * If the console code is currently allowed to sleep, and
867  * if this CPU should yield the CPU to another task, do
868  * so here.
869  *
870  * Must be called within acquire_console_sem().
871  */
872 void __sched console_conditional_schedule(void)
873 {
874         if (console_may_schedule)
875                 cond_resched();
876 }
877 EXPORT_SYMBOL(console_conditional_schedule);
878
879 void console_print(const char *s)
880 {
881         printk(KERN_EMERG "%s", s);
882 }
883 EXPORT_SYMBOL(console_print);
884
885 void console_unblank(void)
886 {
887         struct console *c;
888
889         /*
890          * console_unblank can no longer be called in interrupt context unless
891          * oops_in_progress is set to 1..
892          */
893         if (oops_in_progress) {
894                 if (down_trylock(&console_sem) != 0)
895                         return;
896         } else
897                 acquire_console_sem();
898
899         console_locked = 1;
900         console_may_schedule = 0;
901         for (c = console_drivers; c != NULL; c = c->next)
902                 if ((c->flags & CON_ENABLED) && c->unblank)
903                         c->unblank();
904         release_console_sem();
905 }
906
907 /*
908  * Return the console tty driver structure and its associated index
909  */
910 struct tty_driver *console_device(int *index)
911 {
912         struct console *c;
913         struct tty_driver *driver = NULL;
914
915         acquire_console_sem();
916         for (c = console_drivers; c != NULL; c = c->next) {
917                 if (!c->device)
918                         continue;
919                 driver = c->device(c, index);
920                 if (driver)
921                         break;
922         }
923         release_console_sem();
924         return driver;
925 }
926
927 /*
928  * Prevent further output on the passed console device so that (for example)
929  * serial drivers can disable console output before suspending a port, and can
930  * re-enable output afterwards.
931  */
932 void console_stop(struct console *console)
933 {
934         acquire_console_sem();
935         console->flags &= ~CON_ENABLED;
936         release_console_sem();
937 }
938 EXPORT_SYMBOL(console_stop);
939
940 void console_start(struct console *console)
941 {
942         acquire_console_sem();
943         console->flags |= CON_ENABLED;
944         release_console_sem();
945 }
946 EXPORT_SYMBOL(console_start);
947
948 /*
949  * The console driver calls this routine during kernel initialization
950  * to register the console printing procedure with printk() and to
951  * print any messages that were printed by the kernel before the
952  * console driver was initialized.
953  */
954 void register_console(struct console *console)
955 {
956         int i;
957         unsigned long flags;
958         struct console *bootconsole = NULL;
959
960         if (console_drivers) {
961                 if (console->flags & CON_BOOT)
962                         return;
963                 if (console_drivers->flags & CON_BOOT)
964                         bootconsole = console_drivers;
965         }
966
967         if (preferred_console < 0 || bootconsole || !console_drivers)
968                 preferred_console = selected_console;
969
970         if (console->early_setup)
971                 console->early_setup();
972
973         /*
974          *      See if we want to use this console driver. If we
975          *      didn't select a console we take the first one
976          *      that registers here.
977          */
978         if (preferred_console < 0) {
979                 if (console->index < 0)
980                         console->index = 0;
981                 if (console->setup == NULL ||
982                     console->setup(console, NULL) == 0) {
983                         console->flags |= CON_ENABLED | CON_CONSDEV;
984                         preferred_console = 0;
985                 }
986         }
987
988         /*
989          *      See if this console matches one we selected on
990          *      the command line.
991          */
992         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
993                         i++) {
994                 if (strcmp(console_cmdline[i].name, console->name) != 0)
995                         continue;
996                 if (console->index >= 0 &&
997                     console->index != console_cmdline[i].index)
998                         continue;
999                 if (console->index < 0)
1000                         console->index = console_cmdline[i].index;
1001                 if (console->setup &&
1002                     console->setup(console, console_cmdline[i].options) != 0)
1003                         break;
1004                 console->flags |= CON_ENABLED;
1005                 console->index = console_cmdline[i].index;
1006                 if (i == selected_console) {
1007                         console->flags |= CON_CONSDEV;
1008                         preferred_console = selected_console;
1009                 }
1010                 break;
1011         }
1012
1013         if (!(console->flags & CON_ENABLED))
1014                 return;
1015
1016         if (bootconsole && (console->flags & CON_CONSDEV)) {
1017                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1018                        bootconsole->name, bootconsole->index,
1019                        console->name, console->index);
1020                 unregister_console(bootconsole);
1021                 console->flags &= ~CON_PRINTBUFFER;
1022         } else {
1023                 printk(KERN_INFO "console [%s%d] enabled\n",
1024                        console->name, console->index);
1025         }
1026
1027         /*
1028          *      Put this console in the list - keep the
1029          *      preferred driver at the head of the list.
1030          */
1031         acquire_console_sem();
1032         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1033                 console->next = console_drivers;
1034                 console_drivers = console;
1035                 if (console->next)
1036                         console->next->flags &= ~CON_CONSDEV;
1037         } else {
1038                 console->next = console_drivers->next;
1039                 console_drivers->next = console;
1040         }
1041         if (console->flags & CON_PRINTBUFFER) {
1042                 /*
1043                  * release_console_sem() will print out the buffered messages
1044                  * for us.
1045                  */
1046                 spin_lock_irqsave(&logbuf_lock, flags);
1047                 con_start = log_start;
1048                 spin_unlock_irqrestore(&logbuf_lock, flags);
1049         }
1050         release_console_sem();
1051 }
1052 EXPORT_SYMBOL(register_console);
1053
1054 int unregister_console(struct console *console)
1055 {
1056         struct console *a, *b;
1057         int res = 1;
1058
1059         acquire_console_sem();
1060         if (console_drivers == console) {
1061                 console_drivers=console->next;
1062                 res = 0;
1063         } else if (console_drivers) {
1064                 for (a=console_drivers->next, b=console_drivers ;
1065                      a; b=a, a=b->next) {
1066                         if (a == console) {
1067                                 b->next = a->next;
1068                                 res = 0;
1069                                 break;
1070                         }
1071                 }
1072         }
1073
1074         /*
1075          * If this isn't the last console and it has CON_CONSDEV set, we
1076          * need to set it on the next preferred console.
1077          */
1078         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1079                 console_drivers->flags |= CON_CONSDEV;
1080
1081         release_console_sem();
1082         return res;
1083 }
1084 EXPORT_SYMBOL(unregister_console);
1085
1086 static int __init disable_boot_consoles(void)
1087 {
1088         if (console_drivers != NULL) {
1089                 if (console_drivers->flags & CON_BOOT) {
1090                         printk(KERN_INFO "turn off boot console %s%d\n",
1091                                 console_drivers->name, console_drivers->index);
1092                         return unregister_console(console_drivers);
1093                 }
1094         }
1095         return 0;
1096 }
1097 late_initcall(disable_boot_consoles);
1098
1099 /**
1100  * tty_write_message - write a message to a certain tty, not just the console.
1101  * @tty: the destination tty_struct
1102  * @msg: the message to write
1103  *
1104  * This is used for messages that need to be redirected to a specific tty.
1105  * We don't put it into the syslog queue right now maybe in the future if
1106  * really needed.
1107  */
1108 void tty_write_message(struct tty_struct *tty, char *msg)
1109 {
1110         if (tty && tty->driver->write)
1111                 tty->driver->write(tty, msg, strlen(msg));
1112         return;
1113 }
1114
1115 /*
1116  * printk rate limiting, lifted from the networking subsystem.
1117  *
1118  * This enforces a rate limit: not more than one kernel message
1119  * every printk_ratelimit_jiffies to make a denial-of-service
1120  * attack impossible.
1121  */
1122 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1123 {
1124         static DEFINE_SPINLOCK(ratelimit_lock);
1125         static unsigned long toks = 10 * 5 * HZ;
1126         static unsigned long last_msg;
1127         static int missed;
1128         unsigned long flags;
1129         unsigned long now = jiffies;
1130
1131         spin_lock_irqsave(&ratelimit_lock, flags);
1132         toks += now - last_msg;
1133         last_msg = now;
1134         if (toks > (ratelimit_burst * ratelimit_jiffies))
1135                 toks = ratelimit_burst * ratelimit_jiffies;
1136         if (toks >= ratelimit_jiffies) {
1137                 int lost = missed;
1138
1139                 missed = 0;
1140                 toks -= ratelimit_jiffies;
1141                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1142                 if (lost)
1143                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1144                 return 1;
1145         }
1146         missed++;
1147         spin_unlock_irqrestore(&ratelimit_lock, flags);
1148         return 0;
1149 }
1150 EXPORT_SYMBOL(__printk_ratelimit);
1151
1152 /* minimum time in jiffies between messages */
1153 int printk_ratelimit_jiffies = 5 * HZ;
1154
1155 /* number of messages we send before ratelimiting */
1156 int printk_ratelimit_burst = 10;
1157
1158 int printk_ratelimit(void)
1159 {
1160         return __printk_ratelimit(printk_ratelimit_jiffies,
1161                                 printk_ratelimit_burst);
1162 }
1163 EXPORT_SYMBOL(printk_ratelimit);
1164
1165 /**
1166  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1167  * @caller_jiffies: pointer to caller's state
1168  * @interval_msecs: minimum interval between prints
1169  *
1170  * printk_timed_ratelimit() returns true if more than @interval_msecs
1171  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1172  * returned true.
1173  */
1174 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1175                         unsigned int interval_msecs)
1176 {
1177         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1178                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1179                 return true;
1180         }
1181         return false;
1182 }
1183 EXPORT_SYMBOL(printk_timed_ratelimit);