c46a20a19a153f06e938d469bf760ee893b63114
[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
36 #include <asm/uaccess.h>
37
38 /*
39  * Architectures can override it:
40  */
41 void __attribute__((weak)) early_printk(const char *fmt, ...)
42 {
43 }
44
45 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
46
47 /* printk's without a loglevel use this.. */
48 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
49
50 /* We show everything that is MORE important than this.. */
51 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
52 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
53
54 DECLARE_WAIT_QUEUE_HEAD(log_wait);
55
56 int console_printk[4] = {
57         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
58         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
59         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
60         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
61 };
62
63 /*
64  * Low level drivers may need that to know if they can schedule in
65  * their unblank() callback or not. So let's export it.
66  */
67 int oops_in_progress;
68 EXPORT_SYMBOL(oops_in_progress);
69
70 /*
71  * console_sem protects the console_drivers list, and also
72  * provides serialisation for access to the entire console
73  * driver system.
74  */
75 static DECLARE_MUTEX(console_sem);
76 static DECLARE_MUTEX(secondary_console_sem);
77 struct console *console_drivers;
78 /*
79  * This is used for debugging the mess that is the VT code by
80  * keeping track if we have the console semaphore held. It's
81  * definitely not the perfect debug tool (we don't know if _WE_
82  * hold it are racing, but it helps tracking those weird code
83  * path in the console code where we end up in places I want
84  * locked without the console sempahore held
85  */
86 static int console_locked, console_suspended;
87
88 /*
89  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
90  * It is also used in interesting ways to provide interlocking in
91  * release_console_sem().
92  */
93 static DEFINE_SPINLOCK(logbuf_lock);
94
95 #define LOG_BUF_MASK (log_buf_len-1)
96 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
97
98 /*
99  * The indices into log_buf are not constrained to log_buf_len - they
100  * must be masked before subscripting
101  */
102 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
103 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
104 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
105
106 /*
107  *      Array of consoles built from command line options (console=)
108  */
109 struct console_cmdline
110 {
111         char    name[8];                        /* Name of the driver       */
112         int     index;                          /* Minor dev. to use        */
113         char    *options;                       /* Options for the driver   */
114 };
115
116 #define MAX_CMDLINECONSOLES 8
117
118 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
119 static int selected_console = -1;
120 static int preferred_console = -1;
121
122 /* Flag: console code may call schedule() */
123 static int console_may_schedule;
124
125 #ifdef CONFIG_PRINTK
126
127 static char __log_buf[__LOG_BUF_LEN];
128 static char *log_buf = __log_buf;
129 static int log_buf_len = __LOG_BUF_LEN;
130 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
131
132 static int __init log_buf_len_setup(char *str)
133 {
134         unsigned size = memparse(str, &str);
135         unsigned long flags;
136
137         if (size)
138                 size = roundup_pow_of_two(size);
139         if (size > log_buf_len) {
140                 unsigned start, dest_idx, offset;
141                 char *new_log_buf;
142
143                 new_log_buf = alloc_bootmem(size);
144                 if (!new_log_buf) {
145                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
146                         goto out;
147                 }
148
149                 spin_lock_irqsave(&logbuf_lock, flags);
150                 log_buf_len = size;
151                 log_buf = new_log_buf;
152
153                 offset = start = min(con_start, log_start);
154                 dest_idx = 0;
155                 while (start != log_end) {
156                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
157                         start++;
158                         dest_idx++;
159                 }
160                 log_start -= offset;
161                 con_start -= offset;
162                 log_end -= offset;
163                 spin_unlock_irqrestore(&logbuf_lock, flags);
164
165                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
166         }
167 out:
168         return 1;
169 }
170
171 __setup("log_buf_len=", log_buf_len_setup);
172
173 #ifdef CONFIG_BOOT_PRINTK_DELAY
174
175 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
176 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
177
178 static int __init boot_delay_setup(char *str)
179 {
180         unsigned long lpj;
181         unsigned long long loops_per_msec;
182
183         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
184         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
185
186         get_option(&str, &boot_delay);
187         if (boot_delay > 10 * 1000)
188                 boot_delay = 0;
189
190         printk_delay_msec = loops_per_msec;
191         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
192                 "HZ: %d, printk_delay_msec: %llu\n",
193                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
194         return 1;
195 }
196 __setup("boot_delay=", boot_delay_setup);
197
198 static void boot_delay_msec(void)
199 {
200         unsigned long long k;
201         unsigned long timeout;
202
203         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
204                 return;
205
206         k = (unsigned long long)printk_delay_msec * boot_delay;
207
208         timeout = jiffies + msecs_to_jiffies(boot_delay);
209         while (k) {
210                 k--;
211                 cpu_relax();
212                 /*
213                  * use (volatile) jiffies to prevent
214                  * compiler reduction; loop termination via jiffies
215                  * is secondary and may or may not happen.
216                  */
217                 if (time_after(jiffies, timeout))
218                         break;
219                 touch_nmi_watchdog();
220         }
221 }
222 #else
223 static inline void boot_delay_msec(void)
224 {
225 }
226 #endif
227
228 /*
229  * Return the number of unread characters in the log buffer.
230  */
231 int log_buf_get_len(void)
232 {
233         return logged_chars;
234 }
235
236 /*
237  * Copy a range of characters from the log buffer.
238  */
239 int log_buf_copy(char *dest, int idx, int len)
240 {
241         int ret, max;
242         bool took_lock = false;
243
244         if (!oops_in_progress) {
245                 spin_lock_irq(&logbuf_lock);
246                 took_lock = true;
247         }
248
249         max = log_buf_get_len();
250         if (idx < 0 || idx >= max) {
251                 ret = -1;
252         } else {
253                 if (len > max)
254                         len = max;
255                 ret = len;
256                 idx += (log_end - max);
257                 while (len-- > 0)
258                         dest[len] = LOG_BUF(idx + len);
259         }
260
261         if (took_lock)
262                 spin_unlock_irq(&logbuf_lock);
263
264         return ret;
265 }
266
267 /*
268  * Extract a single character from the log buffer.
269  */
270 int log_buf_read(int idx)
271 {
272         char ret;
273
274         if (log_buf_copy(&ret, idx, 1) == 1)
275                 return ret;
276         else
277                 return -1;
278 }
279
280 /*
281  * Commands to do_syslog:
282  *
283  *      0 -- Close the log.  Currently a NOP.
284  *      1 -- Open the log. Currently a NOP.
285  *      2 -- Read from the log.
286  *      3 -- Read all messages remaining in the ring buffer.
287  *      4 -- Read and clear all messages remaining in the ring buffer
288  *      5 -- Clear ring buffer.
289  *      6 -- Disable printk's to console
290  *      7 -- Enable printk's to console
291  *      8 -- Set level of messages printed to console
292  *      9 -- Return number of unread characters in the log buffer
293  *     10 -- Return size of the log buffer
294  */
295 int do_syslog(int type, char __user *buf, int len)
296 {
297         unsigned i, j, limit, count;
298         int do_clear = 0;
299         char c;
300         int error = 0;
301
302         error = security_syslog(type);
303         if (error)
304                 return error;
305
306         switch (type) {
307         case 0:         /* Close log */
308                 break;
309         case 1:         /* Open log */
310                 break;
311         case 2:         /* Read from log */
312                 error = -EINVAL;
313                 if (!buf || len < 0)
314                         goto out;
315                 error = 0;
316                 if (!len)
317                         goto out;
318                 if (!access_ok(VERIFY_WRITE, buf, len)) {
319                         error = -EFAULT;
320                         goto out;
321                 }
322                 error = wait_event_interruptible(log_wait,
323                                                         (log_start - log_end));
324                 if (error)
325                         goto out;
326                 i = 0;
327                 spin_lock_irq(&logbuf_lock);
328                 while (!error && (log_start != log_end) && i < len) {
329                         c = LOG_BUF(log_start);
330                         log_start++;
331                         spin_unlock_irq(&logbuf_lock);
332                         error = __put_user(c,buf);
333                         buf++;
334                         i++;
335                         cond_resched();
336                         spin_lock_irq(&logbuf_lock);
337                 }
338                 spin_unlock_irq(&logbuf_lock);
339                 if (!error)
340                         error = i;
341                 break;
342         case 4:         /* Read/clear last kernel messages */
343                 do_clear = 1;
344                 /* FALL THRU */
345         case 3:         /* Read last kernel messages */
346                 error = -EINVAL;
347                 if (!buf || len < 0)
348                         goto out;
349                 error = 0;
350                 if (!len)
351                         goto out;
352                 if (!access_ok(VERIFY_WRITE, buf, len)) {
353                         error = -EFAULT;
354                         goto out;
355                 }
356                 count = len;
357                 if (count > log_buf_len)
358                         count = log_buf_len;
359                 spin_lock_irq(&logbuf_lock);
360                 if (count > logged_chars)
361                         count = logged_chars;
362                 if (do_clear)
363                         logged_chars = 0;
364                 limit = log_end;
365                 /*
366                  * __put_user() could sleep, and while we sleep
367                  * printk() could overwrite the messages
368                  * we try to copy to user space. Therefore
369                  * the messages are copied in reverse. <manfreds>
370                  */
371                 for (i = 0; i < count && !error; i++) {
372                         j = limit-1-i;
373                         if (j + log_buf_len < log_end)
374                                 break;
375                         c = LOG_BUF(j);
376                         spin_unlock_irq(&logbuf_lock);
377                         error = __put_user(c,&buf[count-1-i]);
378                         cond_resched();
379                         spin_lock_irq(&logbuf_lock);
380                 }
381                 spin_unlock_irq(&logbuf_lock);
382                 if (error)
383                         break;
384                 error = i;
385                 if (i != count) {
386                         int offset = count-error;
387                         /* buffer overflow during copy, correct user buffer. */
388                         for (i = 0; i < error; i++) {
389                                 if (__get_user(c,&buf[i+offset]) ||
390                                     __put_user(c,&buf[i])) {
391                                         error = -EFAULT;
392                                         break;
393                                 }
394                                 cond_resched();
395                         }
396                 }
397                 break;
398         case 5:         /* Clear ring buffer */
399                 logged_chars = 0;
400                 break;
401         case 6:         /* Disable logging to console */
402                 console_loglevel = minimum_console_loglevel;
403                 break;
404         case 7:         /* Enable logging to console */
405                 console_loglevel = default_console_loglevel;
406                 break;
407         case 8:         /* Set level of messages printed to console */
408                 error = -EINVAL;
409                 if (len < 1 || len > 8)
410                         goto out;
411                 if (len < minimum_console_loglevel)
412                         len = minimum_console_loglevel;
413                 console_loglevel = len;
414                 error = 0;
415                 break;
416         case 9:         /* Number of chars in the log buffer */
417                 error = log_end - log_start;
418                 break;
419         case 10:        /* Size of the log buffer */
420                 error = log_buf_len;
421                 break;
422         default:
423                 error = -EINVAL;
424                 break;
425         }
426 out:
427         return error;
428 }
429
430 asmlinkage long sys_syslog(int type, char __user *buf, int len)
431 {
432         return do_syslog(type, buf, len);
433 }
434
435 /*
436  * Call the console drivers on a range of log_buf
437  */
438 static void __call_console_drivers(unsigned start, unsigned end)
439 {
440         struct console *con;
441
442         for (con = console_drivers; con; con = con->next) {
443                 if ((con->flags & CON_ENABLED) && con->write &&
444                                 (cpu_online(smp_processor_id()) ||
445                                 (con->flags & CON_ANYTIME)))
446                         con->write(con, &LOG_BUF(start), end - start);
447         }
448 }
449
450 static int __read_mostly ignore_loglevel;
451
452 static int __init ignore_loglevel_setup(char *str)
453 {
454         ignore_loglevel = 1;
455         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
456
457         return 0;
458 }
459
460 early_param("ignore_loglevel", ignore_loglevel_setup);
461
462 /*
463  * Write out chars from start to end - 1 inclusive
464  */
465 static void _call_console_drivers(unsigned start,
466                                 unsigned end, int msg_log_level)
467 {
468         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
469                         console_drivers && start != end) {
470                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
471                         /* wrapped write */
472                         __call_console_drivers(start & LOG_BUF_MASK,
473                                                 log_buf_len);
474                         __call_console_drivers(0, end & LOG_BUF_MASK);
475                 } else {
476                         __call_console_drivers(start, end);
477                 }
478         }
479 }
480
481 /*
482  * Call the console drivers, asking them to write out
483  * log_buf[start] to log_buf[end - 1].
484  * The console_sem must be held.
485  */
486 static void call_console_drivers(unsigned start, unsigned end)
487 {
488         unsigned cur_index, start_print;
489         static int msg_level = -1;
490
491         BUG_ON(((int)(start - end)) > 0);
492
493         cur_index = start;
494         start_print = start;
495         while (cur_index != end) {
496                 if (msg_level < 0 && ((end - cur_index) > 2) &&
497                                 LOG_BUF(cur_index + 0) == '<' &&
498                                 LOG_BUF(cur_index + 1) >= '0' &&
499                                 LOG_BUF(cur_index + 1) <= '7' &&
500                                 LOG_BUF(cur_index + 2) == '>') {
501                         msg_level = LOG_BUF(cur_index + 1) - '0';
502                         cur_index += 3;
503                         start_print = cur_index;
504                 }
505                 while (cur_index != end) {
506                         char c = LOG_BUF(cur_index);
507
508                         cur_index++;
509                         if (c == '\n') {
510                                 if (msg_level < 0) {
511                                         /*
512                                          * printk() has already given us loglevel tags in
513                                          * the buffer.  This code is here in case the
514                                          * log buffer has wrapped right round and scribbled
515                                          * on those tags
516                                          */
517                                         msg_level = default_message_loglevel;
518                                 }
519                                 _call_console_drivers(start_print, cur_index, msg_level);
520                                 msg_level = -1;
521                                 start_print = cur_index;
522                                 break;
523                         }
524                 }
525         }
526         _call_console_drivers(start_print, end, msg_level);
527 }
528
529 static void emit_log_char(char c)
530 {
531         LOG_BUF(log_end) = c;
532         log_end++;
533         if (log_end - log_start > log_buf_len)
534                 log_start = log_end - log_buf_len;
535         if (log_end - con_start > log_buf_len)
536                 con_start = log_end - log_buf_len;
537         if (logged_chars < log_buf_len)
538                 logged_chars++;
539 }
540
541 /*
542  * Zap console related locks when oopsing. Only zap at most once
543  * every 10 seconds, to leave time for slow consoles to print a
544  * full oops.
545  */
546 static void zap_locks(void)
547 {
548         static unsigned long oops_timestamp;
549
550         if (time_after_eq(jiffies, oops_timestamp) &&
551                         !time_after(jiffies, oops_timestamp + 30 * HZ))
552                 return;
553
554         oops_timestamp = jiffies;
555
556         /* If a crash is occurring, make sure we can't deadlock */
557         spin_lock_init(&logbuf_lock);
558         /* And make sure that we print immediately */
559         init_MUTEX(&console_sem);
560 }
561
562 #if defined(CONFIG_PRINTK_TIME)
563 static int printk_time = 1;
564 #else
565 static int printk_time = 0;
566 #endif
567 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
568
569 /* Check if we have any console registered that can be called early in boot. */
570 static int have_callable_console(void)
571 {
572         struct console *con;
573
574         for (con = console_drivers; con; con = con->next)
575                 if (con->flags & CON_ANYTIME)
576                         return 1;
577
578         return 0;
579 }
580
581 /**
582  * printk - print a kernel message
583  * @fmt: format string
584  *
585  * This is printk().  It can be called from any context.  We want it to work.
586  * Be aware of the fact that if oops_in_progress is not set, we might try to
587  * wake klogd up which could deadlock on runqueue lock if printk() is called
588  * from scheduler code.
589  *
590  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
591  * call the console drivers.  If we fail to get the semaphore we place the output
592  * into the log buffer and return.  The current holder of the console_sem will
593  * notice the new output in release_console_sem() and will send it to the
594  * consoles before releasing the semaphore.
595  *
596  * One effect of this deferred printing is that code which calls printk() and
597  * then changes console_loglevel may break. This is because console_loglevel
598  * is inspected when the actual printing occurs.
599  *
600  * See also:
601  * printf(3)
602  */
603
604 asmlinkage int printk(const char *fmt, ...)
605 {
606         va_list args;
607         int r;
608
609         va_start(args, fmt);
610         r = vprintk(fmt, args);
611         va_end(args);
612
613         return r;
614 }
615
616 /* cpu currently holding logbuf_lock */
617 static volatile unsigned int printk_cpu = UINT_MAX;
618
619 /*
620  * Can we actually use the console at this time on this cpu?
621  *
622  * Console drivers may assume that per-cpu resources have
623  * been allocated. So unless they're explicitly marked as
624  * being able to cope (CON_ANYTIME) don't call them until
625  * this CPU is officially up.
626  */
627 static inline int can_use_console(unsigned int cpu)
628 {
629         return cpu_online(cpu) || have_callable_console();
630 }
631
632 /*
633  * Try to get console ownership to actually show the kernel
634  * messages from a 'printk'. Return true (and with the
635  * console_semaphore held, and 'console_locked' set) if it
636  * is successful, false otherwise.
637  *
638  * This gets called with the 'logbuf_lock' spinlock held and
639  * interrupts disabled. It should return with 'lockbuf_lock'
640  * released but interrupts still disabled.
641  */
642 static int acquire_console_semaphore_for_printk(unsigned int cpu)
643 {
644         int retval = 0;
645
646         if (can_use_console(cpu))
647                 retval = !try_acquire_console_sem();
648         printk_cpu = UINT_MAX;
649         spin_unlock(&logbuf_lock);
650         return retval;
651 }
652
653 const char printk_recursion_bug_msg [] =
654                         KERN_CRIT "BUG: recent printk recursion!\n";
655 static int printk_recursion_bug;
656
657 asmlinkage int vprintk(const char *fmt, va_list args)
658 {
659         static int log_level_unknown = 1;
660         static char printk_buf[1024];
661
662         unsigned long flags;
663         int printed_len = 0;
664         int this_cpu;
665         char *p;
666
667         boot_delay_msec();
668
669         preempt_disable();
670         /* This stops the holder of console_sem just where we want him */
671         raw_local_irq_save(flags);
672         this_cpu = smp_processor_id();
673
674         /*
675          * Ouch, printk recursed into itself!
676          */
677         if (unlikely(printk_cpu == this_cpu)) {
678                 /*
679                  * If a crash is occurring during printk() on this CPU,
680                  * then try to get the crash message out but make sure
681                  * we can't deadlock. Otherwise just return to avoid the
682                  * recursion and return - but flag the recursion so that
683                  * it can be printed at the next appropriate moment:
684                  */
685                 if (!oops_in_progress) {
686                         printk_recursion_bug = 1;
687                         goto out_restore_irqs;
688                 }
689                 zap_locks();
690         }
691
692         lockdep_off();
693         spin_lock(&logbuf_lock);
694         printk_cpu = this_cpu;
695
696         if (printk_recursion_bug) {
697                 printk_recursion_bug = 0;
698                 strcpy(printk_buf, printk_recursion_bug_msg);
699                 printed_len = sizeof(printk_recursion_bug_msg);
700         }
701         /* Emit the output into the temporary buffer */
702         printed_len += vscnprintf(printk_buf + printed_len,
703                                   sizeof(printk_buf) - printed_len, fmt, args);
704
705         /*
706          * Copy the output into log_buf.  If the caller didn't provide
707          * appropriate log level tags, we insert them here
708          */
709         for (p = printk_buf; *p; p++) {
710                 if (log_level_unknown) {
711                         /* log_level_unknown signals the start of a new line */
712                         if (printk_time) {
713                                 int loglev_char;
714                                 char tbuf[50], *tp;
715                                 unsigned tlen;
716                                 unsigned long long t;
717                                 unsigned long nanosec_rem;
718
719                                 /*
720                                  * force the log level token to be
721                                  * before the time output.
722                                  */
723                                 if (p[0] == '<' && p[1] >='0' &&
724                                    p[1] <= '7' && p[2] == '>') {
725                                         loglev_char = p[1];
726                                         p += 3;
727                                         printed_len -= 3;
728                                 } else {
729                                         loglev_char = default_message_loglevel
730                                                 + '0';
731                                 }
732                                 t = cpu_clock(printk_cpu);
733                                 nanosec_rem = do_div(t, 1000000000);
734                                 tlen = sprintf(tbuf,
735                                                 "<%c>[%5lu.%06lu] ",
736                                                 loglev_char,
737                                                 (unsigned long)t,
738                                                 nanosec_rem/1000);
739
740                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
741                                         emit_log_char(*tp);
742                                 printed_len += tlen;
743                         } else {
744                                 if (p[0] != '<' || p[1] < '0' ||
745                                    p[1] > '7' || p[2] != '>') {
746                                         emit_log_char('<');
747                                         emit_log_char(default_message_loglevel
748                                                 + '0');
749                                         emit_log_char('>');
750                                         printed_len += 3;
751                                 }
752                         }
753                         log_level_unknown = 0;
754                         if (!*p)
755                                 break;
756                 }
757                 emit_log_char(*p);
758                 if (*p == '\n')
759                         log_level_unknown = 1;
760         }
761
762         /*
763          * Try to acquire and then immediately release the
764          * console semaphore. The release will do all the
765          * actual magic (print out buffers, wake up klogd,
766          * etc). 
767          *
768          * The acquire_console_semaphore_for_printk() function
769          * will release 'logbuf_lock' regardless of whether it
770          * actually gets the semaphore or not.
771          */
772         if (acquire_console_semaphore_for_printk(this_cpu))
773                 release_console_sem();
774
775         lockdep_on();
776 out_restore_irqs:
777         raw_local_irq_restore(flags);
778
779         preempt_enable();
780         return printed_len;
781 }
782 EXPORT_SYMBOL(printk);
783 EXPORT_SYMBOL(vprintk);
784
785 #else
786
787 asmlinkage long sys_syslog(int type, char __user *buf, int len)
788 {
789         return -ENOSYS;
790 }
791
792 static void call_console_drivers(unsigned start, unsigned end)
793 {
794 }
795
796 #endif
797
798 /*
799  * Set up a list of consoles.  Called from init/main.c
800  */
801 static int __init console_setup(char *str)
802 {
803         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
804         char *s, *options;
805         int idx;
806
807         /*
808          * Decode str into name, index, options.
809          */
810         if (str[0] >= '0' && str[0] <= '9') {
811                 strcpy(buf, "ttyS");
812                 strncpy(buf + 4, str, sizeof(buf) - 5);
813         } else {
814                 strncpy(buf, str, sizeof(buf) - 1);
815         }
816         buf[sizeof(buf) - 1] = 0;
817         if ((options = strchr(str, ',')) != NULL)
818                 *(options++) = 0;
819 #ifdef __sparc__
820         if (!strcmp(str, "ttya"))
821                 strcpy(buf, "ttyS0");
822         if (!strcmp(str, "ttyb"))
823                 strcpy(buf, "ttyS1");
824 #endif
825         for (s = buf; *s; s++)
826                 if ((*s >= '0' && *s <= '9') || *s == ',')
827                         break;
828         idx = simple_strtoul(s, NULL, 10);
829         *s = 0;
830
831         add_preferred_console(buf, idx, options);
832         return 1;
833 }
834 __setup("console=", console_setup);
835
836 /**
837  * add_preferred_console - add a device to the list of preferred consoles.
838  * @name: device name
839  * @idx: device index
840  * @options: options for this console
841  *
842  * The last preferred console added will be used for kernel messages
843  * and stdin/out/err for init.  Normally this is used by console_setup
844  * above to handle user-supplied console arguments; however it can also
845  * be used by arch-specific code either to override the user or more
846  * commonly to provide a default console (ie from PROM variables) when
847  * the user has not supplied one.
848  */
849 int add_preferred_console(char *name, int idx, char *options)
850 {
851         struct console_cmdline *c;
852         int i;
853
854         /*
855          *      See if this tty is not yet registered, and
856          *      if we have a slot free.
857          */
858         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
859                 if (strcmp(console_cmdline[i].name, name) == 0 &&
860                           console_cmdline[i].index == idx) {
861                                 selected_console = i;
862                                 return 0;
863                 }
864         if (i == MAX_CMDLINECONSOLES)
865                 return -E2BIG;
866         selected_console = i;
867         c = &console_cmdline[i];
868         memcpy(c->name, name, sizeof(c->name));
869         c->name[sizeof(c->name) - 1] = 0;
870         c->options = options;
871         c->index = idx;
872         return 0;
873 }
874
875 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
876 {
877         struct console_cmdline *c;
878         int i;
879
880         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
881                 if (strcmp(console_cmdline[i].name, name) == 0 &&
882                           console_cmdline[i].index == idx) {
883                                 c = &console_cmdline[i];
884                                 memcpy(c->name, name_new, sizeof(c->name));
885                                 c->name[sizeof(c->name) - 1] = 0;
886                                 c->options = options;
887                                 c->index = idx_new;
888                                 return i;
889                 }
890         /* not found */
891         return -1;
892 }
893
894 int console_suspend_enabled = 1;
895 EXPORT_SYMBOL(console_suspend_enabled);
896
897 static int __init console_suspend_disable(char *str)
898 {
899         console_suspend_enabled = 0;
900         return 1;
901 }
902 __setup("no_console_suspend", console_suspend_disable);
903
904 /**
905  * suspend_console - suspend the console subsystem
906  *
907  * This disables printk() while we go into suspend states
908  */
909 void suspend_console(void)
910 {
911         if (!console_suspend_enabled)
912                 return;
913         printk("Suspending console(s)\n");
914         acquire_console_sem();
915         console_suspended = 1;
916 }
917
918 void resume_console(void)
919 {
920         if (!console_suspend_enabled)
921                 return;
922         console_suspended = 0;
923         release_console_sem();
924 }
925
926 /**
927  * acquire_console_sem - lock the console system for exclusive use.
928  *
929  * Acquires a semaphore which guarantees that the caller has
930  * exclusive access to the console system and the console_drivers list.
931  *
932  * Can sleep, returns nothing.
933  */
934 void acquire_console_sem(void)
935 {
936         BUG_ON(in_interrupt());
937         if (console_suspended) {
938                 down(&secondary_console_sem);
939                 return;
940         }
941         down(&console_sem);
942         console_locked = 1;
943         console_may_schedule = 1;
944 }
945 EXPORT_SYMBOL(acquire_console_sem);
946
947 int try_acquire_console_sem(void)
948 {
949         if (down_trylock(&console_sem))
950                 return -1;
951         console_locked = 1;
952         console_may_schedule = 0;
953         return 0;
954 }
955 EXPORT_SYMBOL(try_acquire_console_sem);
956
957 int is_console_locked(void)
958 {
959         return console_locked;
960 }
961
962 void wake_up_klogd(void)
963 {
964         if (!oops_in_progress && waitqueue_active(&log_wait))
965                 wake_up_interruptible(&log_wait);
966 }
967
968 /**
969  * release_console_sem - unlock the console system
970  *
971  * Releases the semaphore which the caller holds on the console system
972  * and the console driver list.
973  *
974  * While the semaphore was held, console output may have been buffered
975  * by printk().  If this is the case, release_console_sem() emits
976  * the output prior to releasing the semaphore.
977  *
978  * If there is output waiting for klogd, we wake it up.
979  *
980  * release_console_sem() may be called from any context.
981  */
982 void release_console_sem(void)
983 {
984         unsigned long flags;
985         unsigned _con_start, _log_end;
986         unsigned wake_klogd = 0;
987
988         if (console_suspended) {
989                 up(&secondary_console_sem);
990                 return;
991         }
992
993         console_may_schedule = 0;
994
995         for ( ; ; ) {
996                 spin_lock_irqsave(&logbuf_lock, flags);
997                 wake_klogd |= log_start - log_end;
998                 if (con_start == log_end)
999                         break;                  /* Nothing to print */
1000                 _con_start = con_start;
1001                 _log_end = log_end;
1002                 con_start = log_end;            /* Flush */
1003                 spin_unlock(&logbuf_lock);
1004                 call_console_drivers(_con_start, _log_end);
1005                 local_irq_restore(flags);
1006         }
1007         console_locked = 0;
1008         up(&console_sem);
1009         spin_unlock_irqrestore(&logbuf_lock, flags);
1010         if (wake_klogd)
1011                 wake_up_klogd();
1012 }
1013 EXPORT_SYMBOL(release_console_sem);
1014
1015 /**
1016  * console_conditional_schedule - yield the CPU if required
1017  *
1018  * If the console code is currently allowed to sleep, and
1019  * if this CPU should yield the CPU to another task, do
1020  * so here.
1021  *
1022  * Must be called within acquire_console_sem().
1023  */
1024 void __sched console_conditional_schedule(void)
1025 {
1026         if (console_may_schedule)
1027                 cond_resched();
1028 }
1029 EXPORT_SYMBOL(console_conditional_schedule);
1030
1031 void console_print(const char *s)
1032 {
1033         printk(KERN_EMERG "%s", s);
1034 }
1035 EXPORT_SYMBOL(console_print);
1036
1037 void console_unblank(void)
1038 {
1039         struct console *c;
1040
1041         /*
1042          * console_unblank can no longer be called in interrupt context unless
1043          * oops_in_progress is set to 1..
1044          */
1045         if (oops_in_progress) {
1046                 if (down_trylock(&console_sem) != 0)
1047                         return;
1048         } else
1049                 acquire_console_sem();
1050
1051         console_locked = 1;
1052         console_may_schedule = 0;
1053         for (c = console_drivers; c != NULL; c = c->next)
1054                 if ((c->flags & CON_ENABLED) && c->unblank)
1055                         c->unblank();
1056         release_console_sem();
1057 }
1058
1059 /*
1060  * Return the console tty driver structure and its associated index
1061  */
1062 struct tty_driver *console_device(int *index)
1063 {
1064         struct console *c;
1065         struct tty_driver *driver = NULL;
1066
1067         acquire_console_sem();
1068         for (c = console_drivers; c != NULL; c = c->next) {
1069                 if (!c->device)
1070                         continue;
1071                 driver = c->device(c, index);
1072                 if (driver)
1073                         break;
1074         }
1075         release_console_sem();
1076         return driver;
1077 }
1078
1079 /*
1080  * Prevent further output on the passed console device so that (for example)
1081  * serial drivers can disable console output before suspending a port, and can
1082  * re-enable output afterwards.
1083  */
1084 void console_stop(struct console *console)
1085 {
1086         acquire_console_sem();
1087         console->flags &= ~CON_ENABLED;
1088         release_console_sem();
1089 }
1090 EXPORT_SYMBOL(console_stop);
1091
1092 void console_start(struct console *console)
1093 {
1094         acquire_console_sem();
1095         console->flags |= CON_ENABLED;
1096         release_console_sem();
1097 }
1098 EXPORT_SYMBOL(console_start);
1099
1100 /*
1101  * The console driver calls this routine during kernel initialization
1102  * to register the console printing procedure with printk() and to
1103  * print any messages that were printed by the kernel before the
1104  * console driver was initialized.
1105  */
1106 void register_console(struct console *console)
1107 {
1108         int i;
1109         unsigned long flags;
1110         struct console *bootconsole = NULL;
1111
1112         if (console_drivers) {
1113                 if (console->flags & CON_BOOT)
1114                         return;
1115                 if (console_drivers->flags & CON_BOOT)
1116                         bootconsole = console_drivers;
1117         }
1118
1119         if (preferred_console < 0 || bootconsole || !console_drivers)
1120                 preferred_console = selected_console;
1121
1122         if (console->early_setup)
1123                 console->early_setup();
1124
1125         /*
1126          *      See if we want to use this console driver. If we
1127          *      didn't select a console we take the first one
1128          *      that registers here.
1129          */
1130         if (preferred_console < 0) {
1131                 if (console->index < 0)
1132                         console->index = 0;
1133                 if (console->setup == NULL ||
1134                     console->setup(console, NULL) == 0) {
1135                         console->flags |= CON_ENABLED | CON_CONSDEV;
1136                         preferred_console = 0;
1137                 }
1138         }
1139
1140         /*
1141          *      See if this console matches one we selected on
1142          *      the command line.
1143          */
1144         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1145                         i++) {
1146                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1147                         continue;
1148                 if (console->index >= 0 &&
1149                     console->index != console_cmdline[i].index)
1150                         continue;
1151                 if (console->index < 0)
1152                         console->index = console_cmdline[i].index;
1153                 if (console->setup &&
1154                     console->setup(console, console_cmdline[i].options) != 0)
1155                         break;
1156                 console->flags |= CON_ENABLED;
1157                 console->index = console_cmdline[i].index;
1158                 if (i == selected_console) {
1159                         console->flags |= CON_CONSDEV;
1160                         preferred_console = selected_console;
1161                 }
1162                 break;
1163         }
1164
1165         if (!(console->flags & CON_ENABLED))
1166                 return;
1167
1168         if (bootconsole && (console->flags & CON_CONSDEV)) {
1169                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1170                        bootconsole->name, bootconsole->index,
1171                        console->name, console->index);
1172                 unregister_console(bootconsole);
1173                 console->flags &= ~CON_PRINTBUFFER;
1174         } else {
1175                 printk(KERN_INFO "console [%s%d] enabled\n",
1176                        console->name, console->index);
1177         }
1178
1179         /*
1180          *      Put this console in the list - keep the
1181          *      preferred driver at the head of the list.
1182          */
1183         acquire_console_sem();
1184         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1185                 console->next = console_drivers;
1186                 console_drivers = console;
1187                 if (console->next)
1188                         console->next->flags &= ~CON_CONSDEV;
1189         } else {
1190                 console->next = console_drivers->next;
1191                 console_drivers->next = console;
1192         }
1193         if (console->flags & CON_PRINTBUFFER) {
1194                 /*
1195                  * release_console_sem() will print out the buffered messages
1196                  * for us.
1197                  */
1198                 spin_lock_irqsave(&logbuf_lock, flags);
1199                 con_start = log_start;
1200                 spin_unlock_irqrestore(&logbuf_lock, flags);
1201         }
1202         release_console_sem();
1203 }
1204 EXPORT_SYMBOL(register_console);
1205
1206 int unregister_console(struct console *console)
1207 {
1208         struct console *a, *b;
1209         int res = 1;
1210
1211         acquire_console_sem();
1212         if (console_drivers == console) {
1213                 console_drivers=console->next;
1214                 res = 0;
1215         } else if (console_drivers) {
1216                 for (a=console_drivers->next, b=console_drivers ;
1217                      a; b=a, a=b->next) {
1218                         if (a == console) {
1219                                 b->next = a->next;
1220                                 res = 0;
1221                                 break;
1222                         }
1223                 }
1224         }
1225
1226         /*
1227          * If this isn't the last console and it has CON_CONSDEV set, we
1228          * need to set it on the next preferred console.
1229          */
1230         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1231                 console_drivers->flags |= CON_CONSDEV;
1232
1233         release_console_sem();
1234         return res;
1235 }
1236 EXPORT_SYMBOL(unregister_console);
1237
1238 static int __init disable_boot_consoles(void)
1239 {
1240         if (console_drivers != NULL) {
1241                 if (console_drivers->flags & CON_BOOT) {
1242                         printk(KERN_INFO "turn off boot console %s%d\n",
1243                                 console_drivers->name, console_drivers->index);
1244                         return unregister_console(console_drivers);
1245                 }
1246         }
1247         return 0;
1248 }
1249 late_initcall(disable_boot_consoles);
1250
1251 /**
1252  * tty_write_message - write a message to a certain tty, not just the console.
1253  * @tty: the destination tty_struct
1254  * @msg: the message to write
1255  *
1256  * This is used for messages that need to be redirected to a specific tty.
1257  * We don't put it into the syslog queue right now maybe in the future if
1258  * really needed.
1259  */
1260 void tty_write_message(struct tty_struct *tty, char *msg)
1261 {
1262         if (tty && tty->driver->write)
1263                 tty->driver->write(tty, msg, strlen(msg));
1264         return;
1265 }
1266
1267 #if defined CONFIG_PRINTK
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 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);
1337 #endif