slow down printk during boot
[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/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h>                    /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/syscalls.h>
35 #include <linux/jiffies.h>
36
37 #include <asm/uaccess.h>
38
39 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
40
41 /* printk's without a loglevel use this.. */
42 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
43
44 /* We show everything that is MORE important than this.. */
45 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
46 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
47
48 DECLARE_WAIT_QUEUE_HEAD(log_wait);
49
50 int console_printk[4] = {
51         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
52         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
53         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
54         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
55 };
56
57 /*
58  * Low level drivers may need that to know if they can schedule in
59  * their unblank() callback or not. So let's export it.
60  */
61 int oops_in_progress;
62 EXPORT_SYMBOL(oops_in_progress);
63
64 /*
65  * console_sem protects the console_drivers list, and also
66  * provides serialisation for access to the entire console
67  * driver system.
68  */
69 static DECLARE_MUTEX(console_sem);
70 static DECLARE_MUTEX(secondary_console_sem);
71 struct console *console_drivers;
72 /*
73  * This is used for debugging the mess that is the VT code by
74  * keeping track if we have the console semaphore held. It's
75  * definitely not the perfect debug tool (we don't know if _WE_
76  * hold it are racing, but it helps tracking those weird code
77  * path in the console code where we end up in places I want
78  * locked without the console sempahore held
79  */
80 static int console_locked, console_suspended;
81
82 /*
83  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
84  * It is also used in interesting ways to provide interlocking in
85  * release_console_sem().
86  */
87 static DEFINE_SPINLOCK(logbuf_lock);
88
89 #define LOG_BUF_MASK    (log_buf_len-1)
90 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
91
92 /*
93  * The indices into log_buf are not constrained to log_buf_len - they
94  * must be masked before subscripting
95  */
96 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
97 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
98 static unsigned long log_end;   /* Index into log_buf: most-recently-written-char + 1 */
99
100 /*
101  *      Array of consoles built from command line options (console=)
102  */
103 struct console_cmdline
104 {
105         char    name[8];                        /* Name of the driver       */
106         int     index;                          /* Minor dev. to use        */
107         char    *options;                       /* Options for the driver   */
108 };
109
110 #define MAX_CMDLINECONSOLES 8
111
112 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
113 static int selected_console = -1;
114 static int preferred_console = -1;
115
116 /* Flag: console code may call schedule() */
117 static int console_may_schedule;
118
119 #ifdef CONFIG_PRINTK
120
121 static char __log_buf[__LOG_BUF_LEN];
122 static char *log_buf = __log_buf;
123 static int log_buf_len = __LOG_BUF_LEN;
124 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
125
126 static int __init log_buf_len_setup(char *str)
127 {
128         unsigned long size = memparse(str, &str);
129         unsigned long flags;
130
131         if (size)
132                 size = roundup_pow_of_two(size);
133         if (size > log_buf_len) {
134                 unsigned long start, dest_idx, offset;
135                 char *new_log_buf;
136
137                 new_log_buf = alloc_bootmem(size);
138                 if (!new_log_buf) {
139                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
140                         goto out;
141                 }
142
143                 spin_lock_irqsave(&logbuf_lock, flags);
144                 log_buf_len = size;
145                 log_buf = new_log_buf;
146
147                 offset = start = min(con_start, log_start);
148                 dest_idx = 0;
149                 while (start != log_end) {
150                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
151                         start++;
152                         dest_idx++;
153                 }
154                 log_start -= offset;
155                 con_start -= offset;
156                 log_end -= offset;
157                 spin_unlock_irqrestore(&logbuf_lock, flags);
158
159                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
160         }
161 out:
162         return 1;
163 }
164
165 __setup("log_buf_len=", log_buf_len_setup);
166
167 #ifdef CONFIG_BOOT_PRINTK_DELAY
168
169 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
170 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
171
172 static int __init boot_delay_setup(char *str)
173 {
174         unsigned long lpj;
175         unsigned long long loops_per_msec;
176
177         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
178         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
179
180         get_option(&str, &boot_delay);
181         if (boot_delay > 10 * 1000)
182                 boot_delay = 0;
183
184         printk_delay_msec = loops_per_msec;
185         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
186                 "HZ: %d, printk_delay_msec: %llu\n",
187                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
188         return 1;
189 }
190 __setup("boot_delay=", boot_delay_setup);
191
192 static void boot_delay_msec(void)
193 {
194         unsigned long long k;
195         unsigned long timeout;
196
197         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
198                 return;
199
200         k = (unsigned long long)printk_delay_msec * boot_delay;
201
202         timeout = jiffies + msecs_to_jiffies(boot_delay);
203         while (k) {
204                 k--;
205                 cpu_relax();
206                 /*
207                  * use (volatile) jiffies to prevent
208                  * compiler reduction; loop termination via jiffies
209                  * is secondary and may or may not happen.
210                  */
211                 if (time_after(jiffies, timeout))
212                         break;
213                 touch_nmi_watchdog();
214         }
215 }
216 #else
217 static inline void boot_delay_msec(void)
218 {
219 }
220 #endif
221
222 /*
223  * Commands to do_syslog:
224  *
225  *      0 -- Close the log.  Currently a NOP.
226  *      1 -- Open the log. Currently a NOP.
227  *      2 -- Read from the log.
228  *      3 -- Read all messages remaining in the ring buffer.
229  *      4 -- Read and clear all messages remaining in the ring buffer
230  *      5 -- Clear ring buffer.
231  *      6 -- Disable printk's to console
232  *      7 -- Enable printk's to console
233  *      8 -- Set level of messages printed to console
234  *      9 -- Return number of unread characters in the log buffer
235  *     10 -- Return size of the log buffer
236  */
237 int do_syslog(int type, char __user *buf, int len)
238 {
239         unsigned long i, j, limit, count;
240         int do_clear = 0;
241         char c;
242         int error = 0;
243
244         error = security_syslog(type);
245         if (error)
246                 return error;
247
248         switch (type) {
249         case 0:         /* Close log */
250                 break;
251         case 1:         /* Open log */
252                 break;
253         case 2:         /* Read from log */
254                 error = -EINVAL;
255                 if (!buf || len < 0)
256                         goto out;
257                 error = 0;
258                 if (!len)
259                         goto out;
260                 if (!access_ok(VERIFY_WRITE, buf, len)) {
261                         error = -EFAULT;
262                         goto out;
263                 }
264                 error = wait_event_interruptible(log_wait,
265                                                         (log_start - log_end));
266                 if (error)
267                         goto out;
268                 i = 0;
269                 spin_lock_irq(&logbuf_lock);
270                 while (!error && (log_start != log_end) && i < len) {
271                         c = LOG_BUF(log_start);
272                         log_start++;
273                         spin_unlock_irq(&logbuf_lock);
274                         error = __put_user(c,buf);
275                         buf++;
276                         i++;
277                         cond_resched();
278                         spin_lock_irq(&logbuf_lock);
279                 }
280                 spin_unlock_irq(&logbuf_lock);
281                 if (!error)
282                         error = i;
283                 break;
284         case 4:         /* Read/clear last kernel messages */
285                 do_clear = 1;
286                 /* FALL THRU */
287         case 3:         /* Read last kernel messages */
288                 error = -EINVAL;
289                 if (!buf || len < 0)
290                         goto out;
291                 error = 0;
292                 if (!len)
293                         goto out;
294                 if (!access_ok(VERIFY_WRITE, buf, len)) {
295                         error = -EFAULT;
296                         goto out;
297                 }
298                 count = len;
299                 if (count > log_buf_len)
300                         count = log_buf_len;
301                 spin_lock_irq(&logbuf_lock);
302                 if (count > logged_chars)
303                         count = logged_chars;
304                 if (do_clear)
305                         logged_chars = 0;
306                 limit = log_end;
307                 /*
308                  * __put_user() could sleep, and while we sleep
309                  * printk() could overwrite the messages
310                  * we try to copy to user space. Therefore
311                  * the messages are copied in reverse. <manfreds>
312                  */
313                 for (i = 0; i < count && !error; i++) {
314                         j = limit-1-i;
315                         if (j + log_buf_len < log_end)
316                                 break;
317                         c = LOG_BUF(j);
318                         spin_unlock_irq(&logbuf_lock);
319                         error = __put_user(c,&buf[count-1-i]);
320                         cond_resched();
321                         spin_lock_irq(&logbuf_lock);
322                 }
323                 spin_unlock_irq(&logbuf_lock);
324                 if (error)
325                         break;
326                 error = i;
327                 if (i != count) {
328                         int offset = count-error;
329                         /* buffer overflow during copy, correct user buffer. */
330                         for (i = 0; i < error; i++) {
331                                 if (__get_user(c,&buf[i+offset]) ||
332                                     __put_user(c,&buf[i])) {
333                                         error = -EFAULT;
334                                         break;
335                                 }
336                                 cond_resched();
337                         }
338                 }
339                 break;
340         case 5:         /* Clear ring buffer */
341                 logged_chars = 0;
342                 break;
343         case 6:         /* Disable logging to console */
344                 console_loglevel = minimum_console_loglevel;
345                 break;
346         case 7:         /* Enable logging to console */
347                 console_loglevel = default_console_loglevel;
348                 break;
349         case 8:         /* Set level of messages printed to console */
350                 error = -EINVAL;
351                 if (len < 1 || len > 8)
352                         goto out;
353                 if (len < minimum_console_loglevel)
354                         len = minimum_console_loglevel;
355                 console_loglevel = len;
356                 error = 0;
357                 break;
358         case 9:         /* Number of chars in the log buffer */
359                 error = log_end - log_start;
360                 break;
361         case 10:        /* Size of the log buffer */
362                 error = log_buf_len;
363                 break;
364         default:
365                 error = -EINVAL;
366                 break;
367         }
368 out:
369         return error;
370 }
371
372 asmlinkage long sys_syslog(int type, char __user *buf, int len)
373 {
374         return do_syslog(type, buf, len);
375 }
376
377 /*
378  * Call the console drivers on a range of log_buf
379  */
380 static void __call_console_drivers(unsigned long start, unsigned long end)
381 {
382         struct console *con;
383
384         for (con = console_drivers; con; con = con->next) {
385                 if ((con->flags & CON_ENABLED) && con->write &&
386                                 (cpu_online(smp_processor_id()) ||
387                                 (con->flags & CON_ANYTIME)))
388                         con->write(con, &LOG_BUF(start), end - start);
389         }
390 }
391
392 static int __read_mostly ignore_loglevel;
393
394 static int __init ignore_loglevel_setup(char *str)
395 {
396         ignore_loglevel = 1;
397         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
398
399         return 1;
400 }
401
402 __setup("ignore_loglevel", ignore_loglevel_setup);
403
404 /*
405  * Write out chars from start to end - 1 inclusive
406  */
407 static void _call_console_drivers(unsigned long start,
408                                 unsigned long end, int msg_log_level)
409 {
410         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
411                         console_drivers && start != end) {
412                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
413                         /* wrapped write */
414                         __call_console_drivers(start & LOG_BUF_MASK,
415                                                 log_buf_len);
416                         __call_console_drivers(0, end & LOG_BUF_MASK);
417                 } else {
418                         __call_console_drivers(start, end);
419                 }
420         }
421 }
422
423 /*
424  * Call the console drivers, asking them to write out
425  * log_buf[start] to log_buf[end - 1].
426  * The console_sem must be held.
427  */
428 static void call_console_drivers(unsigned long start, unsigned long end)
429 {
430         unsigned long cur_index, start_print;
431         static int msg_level = -1;
432
433         BUG_ON(((long)(start - end)) > 0);
434
435         cur_index = start;
436         start_print = start;
437         while (cur_index != end) {
438                 if (msg_level < 0 && ((end - cur_index) > 2) &&
439                                 LOG_BUF(cur_index + 0) == '<' &&
440                                 LOG_BUF(cur_index + 1) >= '0' &&
441                                 LOG_BUF(cur_index + 1) <= '7' &&
442                                 LOG_BUF(cur_index + 2) == '>') {
443                         msg_level = LOG_BUF(cur_index + 1) - '0';
444                         cur_index += 3;
445                         start_print = cur_index;
446                 }
447                 while (cur_index != end) {
448                         char c = LOG_BUF(cur_index);
449
450                         cur_index++;
451                         if (c == '\n') {
452                                 if (msg_level < 0) {
453                                         /*
454                                          * printk() has already given us loglevel tags in
455                                          * the buffer.  This code is here in case the
456                                          * log buffer has wrapped right round and scribbled
457                                          * on those tags
458                                          */
459                                         msg_level = default_message_loglevel;
460                                 }
461                                 _call_console_drivers(start_print, cur_index, msg_level);
462                                 msg_level = -1;
463                                 start_print = cur_index;
464                                 break;
465                         }
466                 }
467         }
468         _call_console_drivers(start_print, end, msg_level);
469 }
470
471 static void emit_log_char(char c)
472 {
473         LOG_BUF(log_end) = c;
474         log_end++;
475         if (log_end - log_start > log_buf_len)
476                 log_start = log_end - log_buf_len;
477         if (log_end - con_start > log_buf_len)
478                 con_start = log_end - log_buf_len;
479         if (logged_chars < log_buf_len)
480                 logged_chars++;
481 }
482
483 /*
484  * Zap console related locks when oopsing. Only zap at most once
485  * every 10 seconds, to leave time for slow consoles to print a
486  * full oops.
487  */
488 static void zap_locks(void)
489 {
490         static unsigned long oops_timestamp;
491
492         if (time_after_eq(jiffies, oops_timestamp) &&
493                         !time_after(jiffies, oops_timestamp + 30 * HZ))
494                 return;
495
496         oops_timestamp = jiffies;
497
498         /* If a crash is occurring, make sure we can't deadlock */
499         spin_lock_init(&logbuf_lock);
500         /* And make sure that we print immediately */
501         init_MUTEX(&console_sem);
502 }
503
504 #if defined(CONFIG_PRINTK_TIME)
505 static int printk_time = 1;
506 #else
507 static int printk_time = 0;
508 #endif
509 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
510
511 static int __init printk_time_setup(char *str)
512 {
513         if (*str)
514                 return 0;
515         printk_time = 1;
516         printk(KERN_NOTICE "The 'time' option is deprecated and "
517                 "is scheduled for removal in early 2008\n");
518         printk(KERN_NOTICE "Use 'printk.time=<value>' instead\n");
519         return 1;
520 }
521
522 __setup("time", printk_time_setup);
523
524 __attribute__((weak)) unsigned long long printk_clock(void)
525 {
526         return sched_clock();
527 }
528
529 /* Check if we have any console registered that can be called early in boot. */
530 static int have_callable_console(void)
531 {
532         struct console *con;
533
534         for (con = console_drivers; con; con = con->next)
535                 if (con->flags & CON_ANYTIME)
536                         return 1;
537
538         return 0;
539 }
540
541 /**
542  * printk - print a kernel message
543  * @fmt: format string
544  *
545  * This is printk().  It can be called from any context.  We want it to work.
546  * Be aware of the fact that if oops_in_progress is not set, we might try to
547  * wake klogd up which could deadlock on runqueue lock if printk() is called
548  * from scheduler code.
549  *
550  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
551  * call the console drivers.  If we fail to get the semaphore we place the output
552  * into the log buffer and return.  The current holder of the console_sem will
553  * notice the new output in release_console_sem() and will send it to the
554  * consoles before releasing the semaphore.
555  *
556  * One effect of this deferred printing is that code which calls printk() and
557  * then changes console_loglevel may break. This is because console_loglevel
558  * is inspected when the actual printing occurs.
559  *
560  * See also:
561  * printf(3)
562  */
563
564 asmlinkage int printk(const char *fmt, ...)
565 {
566         va_list args;
567         int r;
568
569         va_start(args, fmt);
570         r = vprintk(fmt, args);
571         va_end(args);
572
573         return r;
574 }
575
576 /* cpu currently holding logbuf_lock */
577 static volatile unsigned int printk_cpu = UINT_MAX;
578
579 asmlinkage int vprintk(const char *fmt, va_list args)
580 {
581         unsigned long flags;
582         int printed_len;
583         char *p;
584         static char printk_buf[1024];
585         static int log_level_unknown = 1;
586
587         boot_delay_msec();
588
589         preempt_disable();
590         if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
591                 /* If a crash is occurring during printk() on this CPU,
592                  * make sure we can't deadlock */
593                 zap_locks();
594
595         /* This stops the holder of console_sem just where we want him */
596         raw_local_irq_save(flags);
597         lockdep_off();
598         spin_lock(&logbuf_lock);
599         printk_cpu = smp_processor_id();
600
601         /* Emit the output into the temporary buffer */
602         printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
603
604         /*
605          * Copy the output into log_buf.  If the caller didn't provide
606          * appropriate log level tags, we insert them here
607          */
608         for (p = printk_buf; *p; p++) {
609                 if (log_level_unknown) {
610                         /* log_level_unknown signals the start of a new line */
611                         if (printk_time) {
612                                 int loglev_char;
613                                 char tbuf[50], *tp;
614                                 unsigned tlen;
615                                 unsigned long long t;
616                                 unsigned long nanosec_rem;
617
618                                 /*
619                                  * force the log level token to be
620                                  * before the time output.
621                                  */
622                                 if (p[0] == '<' && p[1] >='0' &&
623                                    p[1] <= '7' && p[2] == '>') {
624                                         loglev_char = p[1];
625                                         p += 3;
626                                         printed_len -= 3;
627                                 } else {
628                                         loglev_char = default_message_loglevel
629                                                 + '0';
630                                 }
631                                 t = printk_clock();
632                                 nanosec_rem = do_div(t, 1000000000);
633                                 tlen = sprintf(tbuf,
634                                                 "<%c>[%5lu.%06lu] ",
635                                                 loglev_char,
636                                                 (unsigned long)t,
637                                                 nanosec_rem/1000);
638
639                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
640                                         emit_log_char(*tp);
641                                 printed_len += tlen;
642                         } else {
643                                 if (p[0] != '<' || p[1] < '0' ||
644                                    p[1] > '7' || p[2] != '>') {
645                                         emit_log_char('<');
646                                         emit_log_char(default_message_loglevel
647                                                 + '0');
648                                         emit_log_char('>');
649                                         printed_len += 3;
650                                 }
651                         }
652                         log_level_unknown = 0;
653                         if (!*p)
654                                 break;
655                 }
656                 emit_log_char(*p);
657                 if (*p == '\n')
658                         log_level_unknown = 1;
659         }
660
661         if (!down_trylock(&console_sem)) {
662                 /*
663                  * We own the drivers.  We can drop the spinlock and
664                  * let release_console_sem() print the text, maybe ...
665                  */
666                 console_locked = 1;
667                 printk_cpu = UINT_MAX;
668                 spin_unlock(&logbuf_lock);
669
670                 /*
671                  * Console drivers may assume that per-cpu resources have
672                  * been allocated. So unless they're explicitly marked as
673                  * being able to cope (CON_ANYTIME) don't call them until
674                  * this CPU is officially up.
675                  */
676                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
677                         console_may_schedule = 0;
678                         release_console_sem();
679                 } else {
680                         /* Release by hand to avoid flushing the buffer. */
681                         console_locked = 0;
682                         up(&console_sem);
683                 }
684                 lockdep_on();
685                 raw_local_irq_restore(flags);
686         } else {
687                 /*
688                  * Someone else owns the drivers.  We drop the spinlock, which
689                  * allows the semaphore holder to proceed and to call the
690                  * console drivers with the output which we just produced.
691                  */
692                 printk_cpu = UINT_MAX;
693                 spin_unlock(&logbuf_lock);
694                 lockdep_on();
695                 raw_local_irq_restore(flags);
696         }
697
698         preempt_enable();
699         return printed_len;
700 }
701 EXPORT_SYMBOL(printk);
702 EXPORT_SYMBOL(vprintk);
703
704 #else
705
706 asmlinkage long sys_syslog(int type, char __user *buf, int len)
707 {
708         return -ENOSYS;
709 }
710
711 static void call_console_drivers(unsigned long start, unsigned long end)
712 {
713 }
714
715 #endif
716
717 /*
718  * Set up a list of consoles.  Called from init/main.c
719  */
720 static int __init console_setup(char *str)
721 {
722         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
723         char *s, *options;
724         int idx;
725
726         /*
727          * Decode str into name, index, options.
728          */
729         if (str[0] >= '0' && str[0] <= '9') {
730                 strcpy(buf, "ttyS");
731                 strncpy(buf + 4, str, sizeof(buf) - 5);
732         } else {
733                 strncpy(buf, str, sizeof(buf) - 1);
734         }
735         buf[sizeof(buf) - 1] = 0;
736         if ((options = strchr(str, ',')) != NULL)
737                 *(options++) = 0;
738 #ifdef __sparc__
739         if (!strcmp(str, "ttya"))
740                 strcpy(buf, "ttyS0");
741         if (!strcmp(str, "ttyb"))
742                 strcpy(buf, "ttyS1");
743 #endif
744         for (s = buf; *s; s++)
745                 if ((*s >= '0' && *s <= '9') || *s == ',')
746                         break;
747         idx = simple_strtoul(s, NULL, 10);
748         *s = 0;
749
750         add_preferred_console(buf, idx, options);
751         return 1;
752 }
753 __setup("console=", console_setup);
754
755 /**
756  * add_preferred_console - add a device to the list of preferred consoles.
757  * @name: device name
758  * @idx: device index
759  * @options: options for this console
760  *
761  * The last preferred console added will be used for kernel messages
762  * and stdin/out/err for init.  Normally this is used by console_setup
763  * above to handle user-supplied console arguments; however it can also
764  * be used by arch-specific code either to override the user or more
765  * commonly to provide a default console (ie from PROM variables) when
766  * the user has not supplied one.
767  */
768 int __init add_preferred_console(char *name, int idx, char *options)
769 {
770         struct console_cmdline *c;
771         int i;
772
773         /*
774          *      See if this tty is not yet registered, and
775          *      if we have a slot free.
776          */
777         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
778                 if (strcmp(console_cmdline[i].name, name) == 0 &&
779                           console_cmdline[i].index == idx) {
780                                 selected_console = i;
781                                 return 0;
782                 }
783         if (i == MAX_CMDLINECONSOLES)
784                 return -E2BIG;
785         selected_console = i;
786         c = &console_cmdline[i];
787         memcpy(c->name, name, sizeof(c->name));
788         c->name[sizeof(c->name) - 1] = 0;
789         c->options = options;
790         c->index = idx;
791         return 0;
792 }
793
794 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
795 {
796         struct console_cmdline *c;
797         int i;
798
799         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
800                 if (strcmp(console_cmdline[i].name, name) == 0 &&
801                           console_cmdline[i].index == idx) {
802                                 c = &console_cmdline[i];
803                                 memcpy(c->name, name_new, sizeof(c->name));
804                                 c->name[sizeof(c->name) - 1] = 0;
805                                 c->options = options;
806                                 c->index = idx_new;
807                                 return i;
808                 }
809         /* not found */
810         return -1;
811 }
812
813 #ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
814 /**
815  * suspend_console - suspend the console subsystem
816  *
817  * This disables printk() while we go into suspend states
818  */
819 void suspend_console(void)
820 {
821         printk("Suspending console(s)\n");
822         acquire_console_sem();
823         console_suspended = 1;
824 }
825
826 void resume_console(void)
827 {
828         console_suspended = 0;
829         release_console_sem();
830 }
831 #endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */
832
833 /**
834  * acquire_console_sem - lock the console system for exclusive use.
835  *
836  * Acquires a semaphore which guarantees that the caller has
837  * exclusive access to the console system and the console_drivers list.
838  *
839  * Can sleep, returns nothing.
840  */
841 void acquire_console_sem(void)
842 {
843         BUG_ON(in_interrupt());
844         if (console_suspended) {
845                 down(&secondary_console_sem);
846                 return;
847         }
848         down(&console_sem);
849         console_locked = 1;
850         console_may_schedule = 1;
851 }
852 EXPORT_SYMBOL(acquire_console_sem);
853
854 int try_acquire_console_sem(void)
855 {
856         if (down_trylock(&console_sem))
857                 return -1;
858         console_locked = 1;
859         console_may_schedule = 0;
860         return 0;
861 }
862 EXPORT_SYMBOL(try_acquire_console_sem);
863
864 int is_console_locked(void)
865 {
866         return console_locked;
867 }
868
869 void wake_up_klogd(void)
870 {
871         if (!oops_in_progress && waitqueue_active(&log_wait))
872                 wake_up_interruptible(&log_wait);
873 }
874
875 /**
876  * release_console_sem - unlock the console system
877  *
878  * Releases the semaphore which the caller holds on the console system
879  * and the console driver list.
880  *
881  * While the semaphore was held, console output may have been buffered
882  * by printk().  If this is the case, release_console_sem() emits
883  * the output prior to releasing the semaphore.
884  *
885  * If there is output waiting for klogd, we wake it up.
886  *
887  * release_console_sem() may be called from any context.
888  */
889 void release_console_sem(void)
890 {
891         unsigned long flags;
892         unsigned long _con_start, _log_end;
893         unsigned long wake_klogd = 0;
894
895         if (console_suspended) {
896                 up(&secondary_console_sem);
897                 return;
898         }
899
900         console_may_schedule = 0;
901
902         for ( ; ; ) {
903                 spin_lock_irqsave(&logbuf_lock, flags);
904                 wake_klogd |= log_start - log_end;
905                 if (con_start == log_end)
906                         break;                  /* Nothing to print */
907                 _con_start = con_start;
908                 _log_end = log_end;
909                 con_start = log_end;            /* Flush */
910                 spin_unlock(&logbuf_lock);
911                 call_console_drivers(_con_start, _log_end);
912                 local_irq_restore(flags);
913         }
914         console_locked = 0;
915         up(&console_sem);
916         spin_unlock_irqrestore(&logbuf_lock, flags);
917         if (wake_klogd)
918                 wake_up_klogd();
919 }
920 EXPORT_SYMBOL(release_console_sem);
921
922 /**
923  * console_conditional_schedule - yield the CPU if required
924  *
925  * If the console code is currently allowed to sleep, and
926  * if this CPU should yield the CPU to another task, do
927  * so here.
928  *
929  * Must be called within acquire_console_sem().
930  */
931 void __sched console_conditional_schedule(void)
932 {
933         if (console_may_schedule)
934                 cond_resched();
935 }
936 EXPORT_SYMBOL(console_conditional_schedule);
937
938 void console_print(const char *s)
939 {
940         printk(KERN_EMERG "%s", s);
941 }
942 EXPORT_SYMBOL(console_print);
943
944 void console_unblank(void)
945 {
946         struct console *c;
947
948         /*
949          * console_unblank can no longer be called in interrupt context unless
950          * oops_in_progress is set to 1..
951          */
952         if (oops_in_progress) {
953                 if (down_trylock(&console_sem) != 0)
954                         return;
955         } else
956                 acquire_console_sem();
957
958         console_locked = 1;
959         console_may_schedule = 0;
960         for (c = console_drivers; c != NULL; c = c->next)
961                 if ((c->flags & CON_ENABLED) && c->unblank)
962                         c->unblank();
963         release_console_sem();
964 }
965
966 /*
967  * Return the console tty driver structure and its associated index
968  */
969 struct tty_driver *console_device(int *index)
970 {
971         struct console *c;
972         struct tty_driver *driver = NULL;
973
974         acquire_console_sem();
975         for (c = console_drivers; c != NULL; c = c->next) {
976                 if (!c->device)
977                         continue;
978                 driver = c->device(c, index);
979                 if (driver)
980                         break;
981         }
982         release_console_sem();
983         return driver;
984 }
985
986 /*
987  * Prevent further output on the passed console device so that (for example)
988  * serial drivers can disable console output before suspending a port, and can
989  * re-enable output afterwards.
990  */
991 void console_stop(struct console *console)
992 {
993         acquire_console_sem();
994         console->flags &= ~CON_ENABLED;
995         release_console_sem();
996 }
997 EXPORT_SYMBOL(console_stop);
998
999 void console_start(struct console *console)
1000 {
1001         acquire_console_sem();
1002         console->flags |= CON_ENABLED;
1003         release_console_sem();
1004 }
1005 EXPORT_SYMBOL(console_start);
1006
1007 /*
1008  * The console driver calls this routine during kernel initialization
1009  * to register the console printing procedure with printk() and to
1010  * print any messages that were printed by the kernel before the
1011  * console driver was initialized.
1012  */
1013 void register_console(struct console *console)
1014 {
1015         int i;
1016         unsigned long flags;
1017         struct console *bootconsole = NULL;
1018
1019         if (console_drivers) {
1020                 if (console->flags & CON_BOOT)
1021                         return;
1022                 if (console_drivers->flags & CON_BOOT)
1023                         bootconsole = console_drivers;
1024         }
1025
1026         if (preferred_console < 0 || bootconsole || !console_drivers)
1027                 preferred_console = selected_console;
1028
1029         if (console->early_setup)
1030                 console->early_setup();
1031
1032         /*
1033          *      See if we want to use this console driver. If we
1034          *      didn't select a console we take the first one
1035          *      that registers here.
1036          */
1037         if (preferred_console < 0) {
1038                 if (console->index < 0)
1039                         console->index = 0;
1040                 if (console->setup == NULL ||
1041                     console->setup(console, NULL) == 0) {
1042                         console->flags |= CON_ENABLED | CON_CONSDEV;
1043                         preferred_console = 0;
1044                 }
1045         }
1046
1047         /*
1048          *      See if this console matches one we selected on
1049          *      the command line.
1050          */
1051         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1052                         i++) {
1053                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1054                         continue;
1055                 if (console->index >= 0 &&
1056                     console->index != console_cmdline[i].index)
1057                         continue;
1058                 if (console->index < 0)
1059                         console->index = console_cmdline[i].index;
1060                 if (console->setup &&
1061                     console->setup(console, console_cmdline[i].options) != 0)
1062                         break;
1063                 console->flags |= CON_ENABLED;
1064                 console->index = console_cmdline[i].index;
1065                 if (i == selected_console) {
1066                         console->flags |= CON_CONSDEV;
1067                         preferred_console = selected_console;
1068                 }
1069                 break;
1070         }
1071
1072         if (!(console->flags & CON_ENABLED))
1073                 return;
1074
1075         if (bootconsole && (console->flags & CON_CONSDEV)) {
1076                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1077                        bootconsole->name, bootconsole->index,
1078                        console->name, console->index);
1079                 unregister_console(bootconsole);
1080                 console->flags &= ~CON_PRINTBUFFER;
1081         } else {
1082                 printk(KERN_INFO "console [%s%d] enabled\n",
1083                        console->name, console->index);
1084         }
1085
1086         /*
1087          *      Put this console in the list - keep the
1088          *      preferred driver at the head of the list.
1089          */
1090         acquire_console_sem();
1091         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1092                 console->next = console_drivers;
1093                 console_drivers = console;
1094                 if (console->next)
1095                         console->next->flags &= ~CON_CONSDEV;
1096         } else {
1097                 console->next = console_drivers->next;
1098                 console_drivers->next = console;
1099         }
1100         if (console->flags & CON_PRINTBUFFER) {
1101                 /*
1102                  * release_console_sem() will print out the buffered messages
1103                  * for us.
1104                  */
1105                 spin_lock_irqsave(&logbuf_lock, flags);
1106                 con_start = log_start;
1107                 spin_unlock_irqrestore(&logbuf_lock, flags);
1108         }
1109         release_console_sem();
1110 }
1111 EXPORT_SYMBOL(register_console);
1112
1113 int unregister_console(struct console *console)
1114 {
1115         struct console *a, *b;
1116         int res = 1;
1117
1118         acquire_console_sem();
1119         if (console_drivers == console) {
1120                 console_drivers=console->next;
1121                 res = 0;
1122         } else if (console_drivers) {
1123                 for (a=console_drivers->next, b=console_drivers ;
1124                      a; b=a, a=b->next) {
1125                         if (a == console) {
1126                                 b->next = a->next;
1127                                 res = 0;
1128                                 break;
1129                         }
1130                 }
1131         }
1132
1133         /*
1134          * If this isn't the last console and it has CON_CONSDEV set, we
1135          * need to set it on the next preferred console.
1136          */
1137         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1138                 console_drivers->flags |= CON_CONSDEV;
1139
1140         release_console_sem();
1141         return res;
1142 }
1143 EXPORT_SYMBOL(unregister_console);
1144
1145 static int __init disable_boot_consoles(void)
1146 {
1147         if (console_drivers != NULL) {
1148                 if (console_drivers->flags & CON_BOOT) {
1149                         printk(KERN_INFO "turn off boot console %s%d\n",
1150                                 console_drivers->name, console_drivers->index);
1151                         return unregister_console(console_drivers);
1152                 }
1153         }
1154         return 0;
1155 }
1156 late_initcall(disable_boot_consoles);
1157
1158 /**
1159  * tty_write_message - write a message to a certain tty, not just the console.
1160  * @tty: the destination tty_struct
1161  * @msg: the message to write
1162  *
1163  * This is used for messages that need to be redirected to a specific tty.
1164  * We don't put it into the syslog queue right now maybe in the future if
1165  * really needed.
1166  */
1167 void tty_write_message(struct tty_struct *tty, char *msg)
1168 {
1169         if (tty && tty->driver->write)
1170                 tty->driver->write(tty, msg, strlen(msg));
1171         return;
1172 }
1173
1174 /*
1175  * printk rate limiting, lifted from the networking subsystem.
1176  *
1177  * This enforces a rate limit: not more than one kernel message
1178  * every printk_ratelimit_jiffies to make a denial-of-service
1179  * attack impossible.
1180  */
1181 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1182 {
1183         static DEFINE_SPINLOCK(ratelimit_lock);
1184         static unsigned long toks = 10 * 5 * HZ;
1185         static unsigned long last_msg;
1186         static int missed;
1187         unsigned long flags;
1188         unsigned long now = jiffies;
1189
1190         spin_lock_irqsave(&ratelimit_lock, flags);
1191         toks += now - last_msg;
1192         last_msg = now;
1193         if (toks > (ratelimit_burst * ratelimit_jiffies))
1194                 toks = ratelimit_burst * ratelimit_jiffies;
1195         if (toks >= ratelimit_jiffies) {
1196                 int lost = missed;
1197
1198                 missed = 0;
1199                 toks -= ratelimit_jiffies;
1200                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1201                 if (lost)
1202                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1203                 return 1;
1204         }
1205         missed++;
1206         spin_unlock_irqrestore(&ratelimit_lock, flags);
1207         return 0;
1208 }
1209 EXPORT_SYMBOL(__printk_ratelimit);
1210
1211 /* minimum time in jiffies between messages */
1212 int printk_ratelimit_jiffies = 5 * HZ;
1213
1214 /* number of messages we send before ratelimiting */
1215 int printk_ratelimit_burst = 10;
1216
1217 int printk_ratelimit(void)
1218 {
1219         return __printk_ratelimit(printk_ratelimit_jiffies,
1220                                 printk_ratelimit_burst);
1221 }
1222 EXPORT_SYMBOL(printk_ratelimit);
1223
1224 /**
1225  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1226  * @caller_jiffies: pointer to caller's state
1227  * @interval_msecs: minimum interval between prints
1228  *
1229  * printk_timed_ratelimit() returns true if more than @interval_msecs
1230  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1231  * returned true.
1232  */
1233 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1234                         unsigned int interval_msecs)
1235 {
1236         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1237                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1238                 return true;
1239         }
1240         return false;
1241 }
1242 EXPORT_SYMBOL(printk_timed_ratelimit);