x86: make early printk selectable on 64-bit as well
[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 /*
40  * Architectures can override it:
41  */
42 void __attribute__((weak)) early_printk(const char *fmt, ...)
43 {
44 }
45
46 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
47
48 /* printk's without a loglevel use this.. */
49 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
50
51 /* We show everything that is MORE important than this.. */
52 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
53 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
54
55 DECLARE_WAIT_QUEUE_HEAD(log_wait);
56
57 int console_printk[4] = {
58         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
59         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
60         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
61         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
62 };
63
64 /*
65  * Low level drivers may need that to know if they can schedule in
66  * their unblank() callback or not. So let's export it.
67  */
68 int oops_in_progress;
69 EXPORT_SYMBOL(oops_in_progress);
70
71 /*
72  * console_sem protects the console_drivers list, and also
73  * provides serialisation for access to the entire console
74  * driver system.
75  */
76 static DECLARE_MUTEX(console_sem);
77 static DECLARE_MUTEX(secondary_console_sem);
78 struct console *console_drivers;
79 /*
80  * This is used for debugging the mess that is the VT code by
81  * keeping track if we have the console semaphore held. It's
82  * definitely not the perfect debug tool (we don't know if _WE_
83  * hold it are racing, but it helps tracking those weird code
84  * path in the console code where we end up in places I want
85  * locked without the console sempahore held
86  */
87 static int console_locked, console_suspended;
88
89 /*
90  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
91  * It is also used in interesting ways to provide interlocking in
92  * release_console_sem().
93  */
94 static DEFINE_SPINLOCK(logbuf_lock);
95
96 #define LOG_BUF_MASK    (log_buf_len-1)
97 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
98
99 /*
100  * The indices into log_buf are not constrained to log_buf_len - they
101  * must be masked before subscripting
102  */
103 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
104 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
105 static unsigned long log_end;   /* Index into log_buf: most-recently-written-char + 1 */
106
107 /*
108  *      Array of consoles built from command line options (console=)
109  */
110 struct console_cmdline
111 {
112         char    name[8];                        /* Name of the driver       */
113         int     index;                          /* Minor dev. to use        */
114         char    *options;                       /* Options for the driver   */
115 };
116
117 #define MAX_CMDLINECONSOLES 8
118
119 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
120 static int selected_console = -1;
121 static int preferred_console = -1;
122
123 /* Flag: console code may call schedule() */
124 static int console_may_schedule;
125
126 #ifdef CONFIG_PRINTK
127
128 static char __log_buf[__LOG_BUF_LEN];
129 static char *log_buf = __log_buf;
130 static int log_buf_len = __LOG_BUF_LEN;
131 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
132
133 static int __init log_buf_len_setup(char *str)
134 {
135         unsigned long size = memparse(str, &str);
136         unsigned long flags;
137
138         if (size)
139                 size = roundup_pow_of_two(size);
140         if (size > log_buf_len) {
141                 unsigned long start, dest_idx, offset;
142                 char *new_log_buf;
143
144                 new_log_buf = alloc_bootmem(size);
145                 if (!new_log_buf) {
146                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
147                         goto out;
148                 }
149
150                 spin_lock_irqsave(&logbuf_lock, flags);
151                 log_buf_len = size;
152                 log_buf = new_log_buf;
153
154                 offset = start = min(con_start, log_start);
155                 dest_idx = 0;
156                 while (start != log_end) {
157                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
158                         start++;
159                         dest_idx++;
160                 }
161                 log_start -= offset;
162                 con_start -= offset;
163                 log_end -= offset;
164                 spin_unlock_irqrestore(&logbuf_lock, flags);
165
166                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
167         }
168 out:
169         return 1;
170 }
171
172 __setup("log_buf_len=", log_buf_len_setup);
173
174 #ifdef CONFIG_BOOT_PRINTK_DELAY
175
176 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
177 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
178
179 static int __init boot_delay_setup(char *str)
180 {
181         unsigned long lpj;
182         unsigned long long loops_per_msec;
183
184         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
185         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
186
187         get_option(&str, &boot_delay);
188         if (boot_delay > 10 * 1000)
189                 boot_delay = 0;
190
191         printk_delay_msec = loops_per_msec;
192         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
193                 "HZ: %d, printk_delay_msec: %llu\n",
194                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
195         return 1;
196 }
197 __setup("boot_delay=", boot_delay_setup);
198
199 static void boot_delay_msec(void)
200 {
201         unsigned long long k;
202         unsigned long timeout;
203
204         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
205                 return;
206
207         k = (unsigned long long)printk_delay_msec * boot_delay;
208
209         timeout = jiffies + msecs_to_jiffies(boot_delay);
210         while (k) {
211                 k--;
212                 cpu_relax();
213                 /*
214                  * use (volatile) jiffies to prevent
215                  * compiler reduction; loop termination via jiffies
216                  * is secondary and may or may not happen.
217                  */
218                 if (time_after(jiffies, timeout))
219                         break;
220                 touch_nmi_watchdog();
221         }
222 }
223 #else
224 static inline void boot_delay_msec(void)
225 {
226 }
227 #endif
228
229 /*
230  * Return the number of unread characters in the log buffer.
231  */
232 int log_buf_get_len(void)
233 {
234         return logged_chars;
235 }
236
237 /*
238  * Copy a range of characters from the log buffer.
239  */
240 int log_buf_copy(char *dest, int idx, int len)
241 {
242         int ret, max;
243         bool took_lock = false;
244
245         if (!oops_in_progress) {
246                 spin_lock_irq(&logbuf_lock);
247                 took_lock = true;
248         }
249
250         max = log_buf_get_len();
251         if (idx < 0 || idx >= max) {
252                 ret = -1;
253         } else {
254                 if (len > max)
255                         len = max;
256                 ret = len;
257                 idx += (log_end - max);
258                 while (len-- > 0)
259                         dest[len] = LOG_BUF(idx + len);
260         }
261
262         if (took_lock)
263                 spin_unlock_irq(&logbuf_lock);
264
265         return ret;
266 }
267
268 /*
269  * Extract a single character from the log buffer.
270  */
271 int log_buf_read(int idx)
272 {
273         char ret;
274
275         if (log_buf_copy(&ret, idx, 1) == 1)
276                 return ret;
277         else
278                 return -1;
279 }
280
281 /*
282  * Commands to do_syslog:
283  *
284  *      0 -- Close the log.  Currently a NOP.
285  *      1 -- Open the log. Currently a NOP.
286  *      2 -- Read from the log.
287  *      3 -- Read all messages remaining in the ring buffer.
288  *      4 -- Read and clear all messages remaining in the ring buffer
289  *      5 -- Clear ring buffer.
290  *      6 -- Disable printk's to console
291  *      7 -- Enable printk's to console
292  *      8 -- Set level of messages printed to console
293  *      9 -- Return number of unread characters in the log buffer
294  *     10 -- Return size of the log buffer
295  */
296 int do_syslog(int type, char __user *buf, int len)
297 {
298         unsigned long i, j, limit, count;
299         int do_clear = 0;
300         char c;
301         int error = 0;
302
303         error = security_syslog(type);
304         if (error)
305                 return error;
306
307         switch (type) {
308         case 0:         /* Close log */
309                 break;
310         case 1:         /* Open log */
311                 break;
312         case 2:         /* Read from log */
313                 error = -EINVAL;
314                 if (!buf || len < 0)
315                         goto out;
316                 error = 0;
317                 if (!len)
318                         goto out;
319                 if (!access_ok(VERIFY_WRITE, buf, len)) {
320                         error = -EFAULT;
321                         goto out;
322                 }
323                 error = wait_event_interruptible(log_wait,
324                                                         (log_start - log_end));
325                 if (error)
326                         goto out;
327                 i = 0;
328                 spin_lock_irq(&logbuf_lock);
329                 while (!error && (log_start != log_end) && i < len) {
330                         c = LOG_BUF(log_start);
331                         log_start++;
332                         spin_unlock_irq(&logbuf_lock);
333                         error = __put_user(c,buf);
334                         buf++;
335                         i++;
336                         cond_resched();
337                         spin_lock_irq(&logbuf_lock);
338                 }
339                 spin_unlock_irq(&logbuf_lock);
340                 if (!error)
341                         error = i;
342                 break;
343         case 4:         /* Read/clear last kernel messages */
344                 do_clear = 1;
345                 /* FALL THRU */
346         case 3:         /* Read last kernel messages */
347                 error = -EINVAL;
348                 if (!buf || len < 0)
349                         goto out;
350                 error = 0;
351                 if (!len)
352                         goto out;
353                 if (!access_ok(VERIFY_WRITE, buf, len)) {
354                         error = -EFAULT;
355                         goto out;
356                 }
357                 count = len;
358                 if (count > log_buf_len)
359                         count = log_buf_len;
360                 spin_lock_irq(&logbuf_lock);
361                 if (count > logged_chars)
362                         count = logged_chars;
363                 if (do_clear)
364                         logged_chars = 0;
365                 limit = log_end;
366                 /*
367                  * __put_user() could sleep, and while we sleep
368                  * printk() could overwrite the messages
369                  * we try to copy to user space. Therefore
370                  * the messages are copied in reverse. <manfreds>
371                  */
372                 for (i = 0; i < count && !error; i++) {
373                         j = limit-1-i;
374                         if (j + log_buf_len < log_end)
375                                 break;
376                         c = LOG_BUF(j);
377                         spin_unlock_irq(&logbuf_lock);
378                         error = __put_user(c,&buf[count-1-i]);
379                         cond_resched();
380                         spin_lock_irq(&logbuf_lock);
381                 }
382                 spin_unlock_irq(&logbuf_lock);
383                 if (error)
384                         break;
385                 error = i;
386                 if (i != count) {
387                         int offset = count-error;
388                         /* buffer overflow during copy, correct user buffer. */
389                         for (i = 0; i < error; i++) {
390                                 if (__get_user(c,&buf[i+offset]) ||
391                                     __put_user(c,&buf[i])) {
392                                         error = -EFAULT;
393                                         break;
394                                 }
395                                 cond_resched();
396                         }
397                 }
398                 break;
399         case 5:         /* Clear ring buffer */
400                 logged_chars = 0;
401                 break;
402         case 6:         /* Disable logging to console */
403                 console_loglevel = minimum_console_loglevel;
404                 break;
405         case 7:         /* Enable logging to console */
406                 console_loglevel = default_console_loglevel;
407                 break;
408         case 8:         /* Set level of messages printed to console */
409                 error = -EINVAL;
410                 if (len < 1 || len > 8)
411                         goto out;
412                 if (len < minimum_console_loglevel)
413                         len = minimum_console_loglevel;
414                 console_loglevel = len;
415                 error = 0;
416                 break;
417         case 9:         /* Number of chars in the log buffer */
418                 error = log_end - log_start;
419                 break;
420         case 10:        /* Size of the log buffer */
421                 error = log_buf_len;
422                 break;
423         default:
424                 error = -EINVAL;
425                 break;
426         }
427 out:
428         return error;
429 }
430
431 asmlinkage long sys_syslog(int type, char __user *buf, int len)
432 {
433         return do_syslog(type, buf, len);
434 }
435
436 /*
437  * Call the console drivers on a range of log_buf
438  */
439 static void __call_console_drivers(unsigned long start, unsigned long end)
440 {
441         struct console *con;
442
443         for (con = console_drivers; con; con = con->next) {
444                 if ((con->flags & CON_ENABLED) && con->write &&
445                                 (cpu_online(smp_processor_id()) ||
446                                 (con->flags & CON_ANYTIME)))
447                         con->write(con, &LOG_BUF(start), end - start);
448         }
449 }
450
451 static int __read_mostly ignore_loglevel;
452
453 static int __init ignore_loglevel_setup(char *str)
454 {
455         ignore_loglevel = 1;
456         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
457
458         return 1;
459 }
460
461 __setup("ignore_loglevel", ignore_loglevel_setup);
462
463 /*
464  * Write out chars from start to end - 1 inclusive
465  */
466 static void _call_console_drivers(unsigned long start,
467                                 unsigned long end, int msg_log_level)
468 {
469         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
470                         console_drivers && start != end) {
471                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
472                         /* wrapped write */
473                         __call_console_drivers(start & LOG_BUF_MASK,
474                                                 log_buf_len);
475                         __call_console_drivers(0, end & LOG_BUF_MASK);
476                 } else {
477                         __call_console_drivers(start, end);
478                 }
479         }
480 }
481
482 /*
483  * Call the console drivers, asking them to write out
484  * log_buf[start] to log_buf[end - 1].
485  * The console_sem must be held.
486  */
487 static void call_console_drivers(unsigned long start, unsigned long end)
488 {
489         unsigned long cur_index, start_print;
490         static int msg_level = -1;
491
492         BUG_ON(((long)(start - end)) > 0);
493
494         cur_index = start;
495         start_print = start;
496         while (cur_index != end) {
497                 if (msg_level < 0 && ((end - cur_index) > 2) &&
498                                 LOG_BUF(cur_index + 0) == '<' &&
499                                 LOG_BUF(cur_index + 1) >= '0' &&
500                                 LOG_BUF(cur_index + 1) <= '7' &&
501                                 LOG_BUF(cur_index + 2) == '>') {
502                         msg_level = LOG_BUF(cur_index + 1) - '0';
503                         cur_index += 3;
504                         start_print = cur_index;
505                 }
506                 while (cur_index != end) {
507                         char c = LOG_BUF(cur_index);
508
509                         cur_index++;
510                         if (c == '\n') {
511                                 if (msg_level < 0) {
512                                         /*
513                                          * printk() has already given us loglevel tags in
514                                          * the buffer.  This code is here in case the
515                                          * log buffer has wrapped right round and scribbled
516                                          * on those tags
517                                          */
518                                         msg_level = default_message_loglevel;
519                                 }
520                                 _call_console_drivers(start_print, cur_index, msg_level);
521                                 msg_level = -1;
522                                 start_print = cur_index;
523                                 break;
524                         }
525                 }
526         }
527         _call_console_drivers(start_print, end, msg_level);
528 }
529
530 static void emit_log_char(char c)
531 {
532         LOG_BUF(log_end) = c;
533         log_end++;
534         if (log_end - log_start > log_buf_len)
535                 log_start = log_end - log_buf_len;
536         if (log_end - con_start > log_buf_len)
537                 con_start = log_end - log_buf_len;
538         if (logged_chars < log_buf_len)
539                 logged_chars++;
540 }
541
542 /*
543  * Zap console related locks when oopsing. Only zap at most once
544  * every 10 seconds, to leave time for slow consoles to print a
545  * full oops.
546  */
547 static void zap_locks(void)
548 {
549         static unsigned long oops_timestamp;
550
551         if (time_after_eq(jiffies, oops_timestamp) &&
552                         !time_after(jiffies, oops_timestamp + 30 * HZ))
553                 return;
554
555         oops_timestamp = jiffies;
556
557         /* If a crash is occurring, make sure we can't deadlock */
558         spin_lock_init(&logbuf_lock);
559         /* And make sure that we print immediately */
560         init_MUTEX(&console_sem);
561 }
562
563 #if defined(CONFIG_PRINTK_TIME)
564 static int printk_time = 1;
565 #else
566 static int printk_time = 0;
567 #endif
568 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
569
570 static int __init printk_time_setup(char *str)
571 {
572         if (*str)
573                 return 0;
574         printk_time = 1;
575         printk(KERN_NOTICE "The 'time' option is deprecated and "
576                 "is scheduled for removal in early 2008\n");
577         printk(KERN_NOTICE "Use 'printk.time=<value>' instead\n");
578         return 1;
579 }
580
581 __setup("time", printk_time_setup);
582
583 /* Check if we have any console registered that can be called early in boot. */
584 static int have_callable_console(void)
585 {
586         struct console *con;
587
588         for (con = console_drivers; con; con = con->next)
589                 if (con->flags & CON_ANYTIME)
590                         return 1;
591
592         return 0;
593 }
594
595 /**
596  * printk - print a kernel message
597  * @fmt: format string
598  *
599  * This is printk().  It can be called from any context.  We want it to work.
600  * Be aware of the fact that if oops_in_progress is not set, we might try to
601  * wake klogd up which could deadlock on runqueue lock if printk() is called
602  * from scheduler code.
603  *
604  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
605  * call the console drivers.  If we fail to get the semaphore we place the output
606  * into the log buffer and return.  The current holder of the console_sem will
607  * notice the new output in release_console_sem() and will send it to the
608  * consoles before releasing the semaphore.
609  *
610  * One effect of this deferred printing is that code which calls printk() and
611  * then changes console_loglevel may break. This is because console_loglevel
612  * is inspected when the actual printing occurs.
613  *
614  * See also:
615  * printf(3)
616  */
617
618 asmlinkage int printk(const char *fmt, ...)
619 {
620         va_list args;
621         int r;
622
623         va_start(args, fmt);
624         r = vprintk(fmt, args);
625         va_end(args);
626
627         return r;
628 }
629
630 /* cpu currently holding logbuf_lock */
631 static volatile unsigned int printk_cpu = UINT_MAX;
632
633 const char printk_recursion_bug_msg [] =
634                         KERN_CRIT "BUG: recent printk recursion!\n";
635 static int printk_recursion_bug;
636
637 asmlinkage int vprintk(const char *fmt, va_list args)
638 {
639         static int log_level_unknown = 1;
640         static char printk_buf[1024];
641
642         unsigned long flags;
643         int printed_len = 0;
644         int this_cpu;
645         char *p;
646
647         boot_delay_msec();
648
649         preempt_disable();
650         /* This stops the holder of console_sem just where we want him */
651         raw_local_irq_save(flags);
652         this_cpu = smp_processor_id();
653
654         /*
655          * Ouch, printk recursed into itself!
656          */
657         if (unlikely(printk_cpu == this_cpu)) {
658                 /*
659                  * If a crash is occurring during printk() on this CPU,
660                  * then try to get the crash message out but make sure
661                  * we can't deadlock. Otherwise just return to avoid the
662                  * recursion and return - but flag the recursion so that
663                  * it can be printed at the next appropriate moment:
664                  */
665                 if (!oops_in_progress) {
666                         printk_recursion_bug = 1;
667                         goto out_restore_irqs;
668                 }
669                 zap_locks();
670         }
671
672         lockdep_off();
673         spin_lock(&logbuf_lock);
674         printk_cpu = this_cpu;
675
676         if (printk_recursion_bug) {
677                 printk_recursion_bug = 0;
678                 strcpy(printk_buf, printk_recursion_bug_msg);
679                 printed_len = sizeof(printk_recursion_bug_msg);
680         }
681         /* Emit the output into the temporary buffer */
682         printed_len += vscnprintf(printk_buf + printed_len,
683                                   sizeof(printk_buf), fmt, args);
684
685         /*
686          * Copy the output into log_buf.  If the caller didn't provide
687          * appropriate log level tags, we insert them here
688          */
689         for (p = printk_buf; *p; p++) {
690                 if (log_level_unknown) {
691                         /* log_level_unknown signals the start of a new line */
692                         if (printk_time) {
693                                 int loglev_char;
694                                 char tbuf[50], *tp;
695                                 unsigned tlen;
696                                 unsigned long long t;
697                                 unsigned long nanosec_rem;
698
699                                 /*
700                                  * force the log level token to be
701                                  * before the time output.
702                                  */
703                                 if (p[0] == '<' && p[1] >='0' &&
704                                    p[1] <= '7' && p[2] == '>') {
705                                         loglev_char = p[1];
706                                         p += 3;
707                                         printed_len -= 3;
708                                 } else {
709                                         loglev_char = default_message_loglevel
710                                                 + '0';
711                                 }
712                                 t = cpu_clock(printk_cpu);
713                                 nanosec_rem = do_div(t, 1000000000);
714                                 tlen = sprintf(tbuf,
715                                                 "<%c>[%5lu.%06lu] ",
716                                                 loglev_char,
717                                                 (unsigned long)t,
718                                                 nanosec_rem/1000);
719
720                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
721                                         emit_log_char(*tp);
722                                 printed_len += tlen;
723                         } else {
724                                 if (p[0] != '<' || p[1] < '0' ||
725                                    p[1] > '7' || p[2] != '>') {
726                                         emit_log_char('<');
727                                         emit_log_char(default_message_loglevel
728                                                 + '0');
729                                         emit_log_char('>');
730                                         printed_len += 3;
731                                 }
732                         }
733                         log_level_unknown = 0;
734                         if (!*p)
735                                 break;
736                 }
737                 emit_log_char(*p);
738                 if (*p == '\n')
739                         log_level_unknown = 1;
740         }
741
742         if (!down_trylock(&console_sem)) {
743                 /*
744                  * We own the drivers.  We can drop the spinlock and
745                  * let release_console_sem() print the text, maybe ...
746                  */
747                 console_locked = 1;
748                 printk_cpu = UINT_MAX;
749                 spin_unlock(&logbuf_lock);
750
751                 /*
752                  * Console drivers may assume that per-cpu resources have
753                  * been allocated. So unless they're explicitly marked as
754                  * being able to cope (CON_ANYTIME) don't call them until
755                  * this CPU is officially up.
756                  */
757                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
758                         console_may_schedule = 0;
759                         release_console_sem();
760                 } else {
761                         /* Release by hand to avoid flushing the buffer. */
762                         console_locked = 0;
763                         up(&console_sem);
764                 }
765                 lockdep_on();
766                 raw_local_irq_restore(flags);
767         } else {
768                 /*
769                  * Someone else owns the drivers.  We drop the spinlock, which
770                  * allows the semaphore holder to proceed and to call the
771                  * console drivers with the output which we just produced.
772                  */
773                 printk_cpu = UINT_MAX;
774                 spin_unlock(&logbuf_lock);
775                 lockdep_on();
776 out_restore_irqs:
777                 raw_local_irq_restore(flags);
778         }
779
780         preempt_enable();
781         return printed_len;
782 }
783 EXPORT_SYMBOL(printk);
784 EXPORT_SYMBOL(vprintk);
785
786 #else
787
788 asmlinkage long sys_syslog(int type, char __user *buf, int len)
789 {
790         return -ENOSYS;
791 }
792
793 static void call_console_drivers(unsigned long start, unsigned long end)
794 {
795 }
796
797 #endif
798
799 /*
800  * Set up a list of consoles.  Called from init/main.c
801  */
802 static int __init console_setup(char *str)
803 {
804         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
805         char *s, *options;
806         int idx;
807
808         /*
809          * Decode str into name, index, options.
810          */
811         if (str[0] >= '0' && str[0] <= '9') {
812                 strcpy(buf, "ttyS");
813                 strncpy(buf + 4, str, sizeof(buf) - 5);
814         } else {
815                 strncpy(buf, str, sizeof(buf) - 1);
816         }
817         buf[sizeof(buf) - 1] = 0;
818         if ((options = strchr(str, ',')) != NULL)
819                 *(options++) = 0;
820 #ifdef __sparc__
821         if (!strcmp(str, "ttya"))
822                 strcpy(buf, "ttyS0");
823         if (!strcmp(str, "ttyb"))
824                 strcpy(buf, "ttyS1");
825 #endif
826         for (s = buf; *s; s++)
827                 if ((*s >= '0' && *s <= '9') || *s == ',')
828                         break;
829         idx = simple_strtoul(s, NULL, 10);
830         *s = 0;
831
832         add_preferred_console(buf, idx, options);
833         return 1;
834 }
835 __setup("console=", console_setup);
836
837 /**
838  * add_preferred_console - add a device to the list of preferred consoles.
839  * @name: device name
840  * @idx: device index
841  * @options: options for this console
842  *
843  * The last preferred console added will be used for kernel messages
844  * and stdin/out/err for init.  Normally this is used by console_setup
845  * above to handle user-supplied console arguments; however it can also
846  * be used by arch-specific code either to override the user or more
847  * commonly to provide a default console (ie from PROM variables) when
848  * the user has not supplied one.
849  */
850 int add_preferred_console(char *name, int idx, char *options)
851 {
852         struct console_cmdline *c;
853         int i;
854
855         /*
856          *      See if this tty is not yet registered, and
857          *      if we have a slot free.
858          */
859         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
860                 if (strcmp(console_cmdline[i].name, name) == 0 &&
861                           console_cmdline[i].index == idx) {
862                                 selected_console = i;
863                                 return 0;
864                 }
865         if (i == MAX_CMDLINECONSOLES)
866                 return -E2BIG;
867         selected_console = i;
868         c = &console_cmdline[i];
869         memcpy(c->name, name, sizeof(c->name));
870         c->name[sizeof(c->name) - 1] = 0;
871         c->options = options;
872         c->index = idx;
873         return 0;
874 }
875
876 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
877 {
878         struct console_cmdline *c;
879         int i;
880
881         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
882                 if (strcmp(console_cmdline[i].name, name) == 0 &&
883                           console_cmdline[i].index == idx) {
884                                 c = &console_cmdline[i];
885                                 memcpy(c->name, name_new, sizeof(c->name));
886                                 c->name[sizeof(c->name) - 1] = 0;
887                                 c->options = options;
888                                 c->index = idx_new;
889                                 return i;
890                 }
891         /* not found */
892         return -1;
893 }
894
895 int console_suspend_enabled = 1;
896 EXPORT_SYMBOL(console_suspend_enabled);
897
898 static int __init console_suspend_disable(char *str)
899 {
900         console_suspend_enabled = 0;
901         return 1;
902 }
903 __setup("no_console_suspend", console_suspend_disable);
904
905 /**
906  * suspend_console - suspend the console subsystem
907  *
908  * This disables printk() while we go into suspend states
909  */
910 void suspend_console(void)
911 {
912         if (!console_suspend_enabled)
913                 return;
914         printk("Suspending console(s)\n");
915         acquire_console_sem();
916         console_suspended = 1;
917 }
918
919 void resume_console(void)
920 {
921         if (!console_suspend_enabled)
922                 return;
923         console_suspended = 0;
924         release_console_sem();
925 }
926
927 /**
928  * acquire_console_sem - lock the console system for exclusive use.
929  *
930  * Acquires a semaphore which guarantees that the caller has
931  * exclusive access to the console system and the console_drivers list.
932  *
933  * Can sleep, returns nothing.
934  */
935 void acquire_console_sem(void)
936 {
937         BUG_ON(in_interrupt());
938         if (console_suspended) {
939                 down(&secondary_console_sem);
940                 return;
941         }
942         down(&console_sem);
943         console_locked = 1;
944         console_may_schedule = 1;
945 }
946 EXPORT_SYMBOL(acquire_console_sem);
947
948 int try_acquire_console_sem(void)
949 {
950         if (down_trylock(&console_sem))
951                 return -1;
952         console_locked = 1;
953         console_may_schedule = 0;
954         return 0;
955 }
956 EXPORT_SYMBOL(try_acquire_console_sem);
957
958 int is_console_locked(void)
959 {
960         return console_locked;
961 }
962
963 void wake_up_klogd(void)
964 {
965         if (!oops_in_progress && waitqueue_active(&log_wait))
966                 wake_up_interruptible(&log_wait);
967 }
968
969 /**
970  * release_console_sem - unlock the console system
971  *
972  * Releases the semaphore which the caller holds on the console system
973  * and the console driver list.
974  *
975  * While the semaphore was held, console output may have been buffered
976  * by printk().  If this is the case, release_console_sem() emits
977  * the output prior to releasing the semaphore.
978  *
979  * If there is output waiting for klogd, we wake it up.
980  *
981  * release_console_sem() may be called from any context.
982  */
983 void release_console_sem(void)
984 {
985         unsigned long flags;
986         unsigned long _con_start, _log_end;
987         unsigned long wake_klogd = 0;
988
989         if (console_suspended) {
990                 up(&secondary_console_sem);
991                 return;
992         }
993
994         console_may_schedule = 0;
995
996         for ( ; ; ) {
997                 spin_lock_irqsave(&logbuf_lock, flags);
998                 wake_klogd |= log_start - log_end;
999                 if (con_start == log_end)
1000                         break;                  /* Nothing to print */
1001                 _con_start = con_start;
1002                 _log_end = log_end;
1003                 con_start = log_end;            /* Flush */
1004                 spin_unlock(&logbuf_lock);
1005                 call_console_drivers(_con_start, _log_end);
1006                 local_irq_restore(flags);
1007         }
1008         console_locked = 0;
1009         up(&console_sem);
1010         spin_unlock_irqrestore(&logbuf_lock, flags);
1011         if (wake_klogd)
1012                 wake_up_klogd();
1013 }
1014 EXPORT_SYMBOL(release_console_sem);
1015
1016 /**
1017  * console_conditional_schedule - yield the CPU if required
1018  *
1019  * If the console code is currently allowed to sleep, and
1020  * if this CPU should yield the CPU to another task, do
1021  * so here.
1022  *
1023  * Must be called within acquire_console_sem().
1024  */
1025 void __sched console_conditional_schedule(void)
1026 {
1027         if (console_may_schedule)
1028                 cond_resched();
1029 }
1030 EXPORT_SYMBOL(console_conditional_schedule);
1031
1032 void console_print(const char *s)
1033 {
1034         printk(KERN_EMERG "%s", s);
1035 }
1036 EXPORT_SYMBOL(console_print);
1037
1038 void console_unblank(void)
1039 {
1040         struct console *c;
1041
1042         /*
1043          * console_unblank can no longer be called in interrupt context unless
1044          * oops_in_progress is set to 1..
1045          */
1046         if (oops_in_progress) {
1047                 if (down_trylock(&console_sem) != 0)
1048                         return;
1049         } else
1050                 acquire_console_sem();
1051
1052         console_locked = 1;
1053         console_may_schedule = 0;
1054         for (c = console_drivers; c != NULL; c = c->next)
1055                 if ((c->flags & CON_ENABLED) && c->unblank)
1056                         c->unblank();
1057         release_console_sem();
1058 }
1059
1060 /*
1061  * Return the console tty driver structure and its associated index
1062  */
1063 struct tty_driver *console_device(int *index)
1064 {
1065         struct console *c;
1066         struct tty_driver *driver = NULL;
1067
1068         acquire_console_sem();
1069         for (c = console_drivers; c != NULL; c = c->next) {
1070                 if (!c->device)
1071                         continue;
1072                 driver = c->device(c, index);
1073                 if (driver)
1074                         break;
1075         }
1076         release_console_sem();
1077         return driver;
1078 }
1079
1080 /*
1081  * Prevent further output on the passed console device so that (for example)
1082  * serial drivers can disable console output before suspending a port, and can
1083  * re-enable output afterwards.
1084  */
1085 void console_stop(struct console *console)
1086 {
1087         acquire_console_sem();
1088         console->flags &= ~CON_ENABLED;
1089         release_console_sem();
1090 }
1091 EXPORT_SYMBOL(console_stop);
1092
1093 void console_start(struct console *console)
1094 {
1095         acquire_console_sem();
1096         console->flags |= CON_ENABLED;
1097         release_console_sem();
1098 }
1099 EXPORT_SYMBOL(console_start);
1100
1101 /*
1102  * The console driver calls this routine during kernel initialization
1103  * to register the console printing procedure with printk() and to
1104  * print any messages that were printed by the kernel before the
1105  * console driver was initialized.
1106  */
1107 void register_console(struct console *console)
1108 {
1109         int i;
1110         unsigned long flags;
1111         struct console *bootconsole = NULL;
1112
1113         if (console_drivers) {
1114                 if (console->flags & CON_BOOT)
1115                         return;
1116                 if (console_drivers->flags & CON_BOOT)
1117                         bootconsole = console_drivers;
1118         }
1119
1120         if (preferred_console < 0 || bootconsole || !console_drivers)
1121                 preferred_console = selected_console;
1122
1123         if (console->early_setup)
1124                 console->early_setup();
1125
1126         /*
1127          *      See if we want to use this console driver. If we
1128          *      didn't select a console we take the first one
1129          *      that registers here.
1130          */
1131         if (preferred_console < 0) {
1132                 if (console->index < 0)
1133                         console->index = 0;
1134                 if (console->setup == NULL ||
1135                     console->setup(console, NULL) == 0) {
1136                         console->flags |= CON_ENABLED | CON_CONSDEV;
1137                         preferred_console = 0;
1138                 }
1139         }
1140
1141         /*
1142          *      See if this console matches one we selected on
1143          *      the command line.
1144          */
1145         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1146                         i++) {
1147                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1148                         continue;
1149                 if (console->index >= 0 &&
1150                     console->index != console_cmdline[i].index)
1151                         continue;
1152                 if (console->index < 0)
1153                         console->index = console_cmdline[i].index;
1154                 if (console->setup &&
1155                     console->setup(console, console_cmdline[i].options) != 0)
1156                         break;
1157                 console->flags |= CON_ENABLED;
1158                 console->index = console_cmdline[i].index;
1159                 if (i == selected_console) {
1160                         console->flags |= CON_CONSDEV;
1161                         preferred_console = selected_console;
1162                 }
1163                 break;
1164         }
1165
1166         if (!(console->flags & CON_ENABLED))
1167                 return;
1168
1169         if (bootconsole && (console->flags & CON_CONSDEV)) {
1170                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1171                        bootconsole->name, bootconsole->index,
1172                        console->name, console->index);
1173                 unregister_console(bootconsole);
1174                 console->flags &= ~CON_PRINTBUFFER;
1175         } else {
1176                 printk(KERN_INFO "console [%s%d] enabled\n",
1177                        console->name, console->index);
1178         }
1179
1180         /*
1181          *      Put this console in the list - keep the
1182          *      preferred driver at the head of the list.
1183          */
1184         acquire_console_sem();
1185         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1186                 console->next = console_drivers;
1187                 console_drivers = console;
1188                 if (console->next)
1189                         console->next->flags &= ~CON_CONSDEV;
1190         } else {
1191                 console->next = console_drivers->next;
1192                 console_drivers->next = console;
1193         }
1194         if (console->flags & CON_PRINTBUFFER) {
1195                 /*
1196                  * release_console_sem() will print out the buffered messages
1197                  * for us.
1198                  */
1199                 spin_lock_irqsave(&logbuf_lock, flags);
1200                 con_start = log_start;
1201                 spin_unlock_irqrestore(&logbuf_lock, flags);
1202         }
1203         release_console_sem();
1204 }
1205 EXPORT_SYMBOL(register_console);
1206
1207 int unregister_console(struct console *console)
1208 {
1209         struct console *a, *b;
1210         int res = 1;
1211
1212         acquire_console_sem();
1213         if (console_drivers == console) {
1214                 console_drivers=console->next;
1215                 res = 0;
1216         } else if (console_drivers) {
1217                 for (a=console_drivers->next, b=console_drivers ;
1218                      a; b=a, a=b->next) {
1219                         if (a == console) {
1220                                 b->next = a->next;
1221                                 res = 0;
1222                                 break;
1223                         }
1224                 }
1225         }
1226
1227         /*
1228          * If this isn't the last console and it has CON_CONSDEV set, we
1229          * need to set it on the next preferred console.
1230          */
1231         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1232                 console_drivers->flags |= CON_CONSDEV;
1233
1234         release_console_sem();
1235         return res;
1236 }
1237 EXPORT_SYMBOL(unregister_console);
1238
1239 static int __init disable_boot_consoles(void)
1240 {
1241         if (console_drivers != NULL) {
1242                 if (console_drivers->flags & CON_BOOT) {
1243                         printk(KERN_INFO "turn off boot console %s%d\n",
1244                                 console_drivers->name, console_drivers->index);
1245                         return unregister_console(console_drivers);
1246                 }
1247         }
1248         return 0;
1249 }
1250 late_initcall(disable_boot_consoles);
1251
1252 /**
1253  * tty_write_message - write a message to a certain tty, not just the console.
1254  * @tty: the destination tty_struct
1255  * @msg: the message to write
1256  *
1257  * This is used for messages that need to be redirected to a specific tty.
1258  * We don't put it into the syslog queue right now maybe in the future if
1259  * really needed.
1260  */
1261 void tty_write_message(struct tty_struct *tty, char *msg)
1262 {
1263         if (tty && tty->driver->write)
1264                 tty->driver->write(tty, msg, strlen(msg));
1265         return;
1266 }
1267
1268 /*
1269  * printk rate limiting, lifted from the networking subsystem.
1270  *
1271  * This enforces a rate limit: not more than one kernel message
1272  * every printk_ratelimit_jiffies to make a denial-of-service
1273  * attack impossible.
1274  */
1275 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1276 {
1277         static DEFINE_SPINLOCK(ratelimit_lock);
1278         static unsigned long toks = 10 * 5 * HZ;
1279         static unsigned long last_msg;
1280         static int missed;
1281         unsigned long flags;
1282         unsigned long now = jiffies;
1283
1284         spin_lock_irqsave(&ratelimit_lock, flags);
1285         toks += now - last_msg;
1286         last_msg = now;
1287         if (toks > (ratelimit_burst * ratelimit_jiffies))
1288                 toks = ratelimit_burst * ratelimit_jiffies;
1289         if (toks >= ratelimit_jiffies) {
1290                 int lost = missed;
1291
1292                 missed = 0;
1293                 toks -= ratelimit_jiffies;
1294                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1295                 if (lost)
1296                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1297                 return 1;
1298         }
1299         missed++;
1300         spin_unlock_irqrestore(&ratelimit_lock, flags);
1301         return 0;
1302 }
1303 EXPORT_SYMBOL(__printk_ratelimit);
1304
1305 /* minimum time in jiffies between messages */
1306 int printk_ratelimit_jiffies = 5 * HZ;
1307
1308 /* number of messages we send before ratelimiting */
1309 int printk_ratelimit_burst = 10;
1310
1311 int printk_ratelimit(void)
1312 {
1313         return __printk_ratelimit(printk_ratelimit_jiffies,
1314                                 printk_ratelimit_burst);
1315 }
1316 EXPORT_SYMBOL(printk_ratelimit);
1317
1318 /**
1319  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1320  * @caller_jiffies: pointer to caller's state
1321  * @interval_msecs: minimum interval between prints
1322  *
1323  * printk_timed_ratelimit() returns true if more than @interval_msecs
1324  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1325  * returned true.
1326  */
1327 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1328                         unsigned int interval_msecs)
1329 {
1330         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1331                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1332                 return true;
1333         }
1334         return false;
1335 }
1336 EXPORT_SYMBOL(printk_timed_ratelimit);