Merge branch 'core-v28-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...
[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
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 asmlinkage __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 EXPORT_SYMBOL_GPL(console_drivers);
79
80 /*
81  * This is used for debugging the mess that is the VT code by
82  * keeping track if we have the console semaphore held. It's
83  * definitely not the perfect debug tool (we don't know if _WE_
84  * hold it are racing, but it helps tracking those weird code
85  * path in the console code where we end up in places I want
86  * locked without the console sempahore held
87  */
88 static int console_locked, console_suspended;
89
90 /*
91  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
92  * It is also used in interesting ways to provide interlocking in
93  * release_console_sem().
94  */
95 static DEFINE_SPINLOCK(logbuf_lock);
96
97 #define LOG_BUF_MASK (log_buf_len-1)
98 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
99
100 /*
101  * The indices into log_buf are not constrained to log_buf_len - they
102  * must be masked before subscripting
103  */
104 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
105 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
106 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
107
108 /*
109  *      Array of consoles built from command line options (console=)
110  */
111 struct console_cmdline
112 {
113         char    name[8];                        /* Name of the driver       */
114         int     index;                          /* Minor dev. to use        */
115         char    *options;                       /* Options for the driver   */
116 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
117         char    *brl_options;                   /* Options for braille driver */
118 #endif
119 };
120
121 #define MAX_CMDLINECONSOLES 8
122
123 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
124 static int selected_console = -1;
125 static int preferred_console = -1;
126 int console_set_on_cmdline;
127 EXPORT_SYMBOL(console_set_on_cmdline);
128
129 /* Flag: console code may call schedule() */
130 static int console_may_schedule;
131
132 #ifdef CONFIG_PRINTK
133
134 static char __log_buf[__LOG_BUF_LEN];
135 static char *log_buf = __log_buf;
136 static int log_buf_len = __LOG_BUF_LEN;
137 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
138
139 static int __init log_buf_len_setup(char *str)
140 {
141         unsigned size = memparse(str, &str);
142         unsigned long flags;
143
144         if (size)
145                 size = roundup_pow_of_two(size);
146         if (size > log_buf_len) {
147                 unsigned start, dest_idx, offset;
148                 char *new_log_buf;
149
150                 new_log_buf = alloc_bootmem(size);
151                 if (!new_log_buf) {
152                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
153                         goto out;
154                 }
155
156                 spin_lock_irqsave(&logbuf_lock, flags);
157                 log_buf_len = size;
158                 log_buf = new_log_buf;
159
160                 offset = start = min(con_start, log_start);
161                 dest_idx = 0;
162                 while (start != log_end) {
163                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
164                         start++;
165                         dest_idx++;
166                 }
167                 log_start -= offset;
168                 con_start -= offset;
169                 log_end -= offset;
170                 spin_unlock_irqrestore(&logbuf_lock, flags);
171
172                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
173         }
174 out:
175         return 1;
176 }
177
178 __setup("log_buf_len=", log_buf_len_setup);
179
180 #ifdef CONFIG_BOOT_PRINTK_DELAY
181
182 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
183 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
184
185 static int __init boot_delay_setup(char *str)
186 {
187         unsigned long lpj;
188         unsigned long long loops_per_msec;
189
190         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
191         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
192
193         get_option(&str, &boot_delay);
194         if (boot_delay > 10 * 1000)
195                 boot_delay = 0;
196
197         printk_delay_msec = loops_per_msec;
198         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
199                 "HZ: %d, printk_delay_msec: %llu\n",
200                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
201         return 1;
202 }
203 __setup("boot_delay=", boot_delay_setup);
204
205 static void boot_delay_msec(void)
206 {
207         unsigned long long k;
208         unsigned long timeout;
209
210         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
211                 return;
212
213         k = (unsigned long long)printk_delay_msec * boot_delay;
214
215         timeout = jiffies + msecs_to_jiffies(boot_delay);
216         while (k) {
217                 k--;
218                 cpu_relax();
219                 /*
220                  * use (volatile) jiffies to prevent
221                  * compiler reduction; loop termination via jiffies
222                  * is secondary and may or may not happen.
223                  */
224                 if (time_after(jiffies, timeout))
225                         break;
226                 touch_nmi_watchdog();
227         }
228 }
229 #else
230 static inline void boot_delay_msec(void)
231 {
232 }
233 #endif
234
235 /*
236  * Return the number of unread characters in the log buffer.
237  */
238 static int log_buf_get_len(void)
239 {
240         return logged_chars;
241 }
242
243 /*
244  * Copy a range of characters from the log buffer.
245  */
246 int log_buf_copy(char *dest, int idx, int len)
247 {
248         int ret, max;
249         bool took_lock = false;
250
251         if (!oops_in_progress) {
252                 spin_lock_irq(&logbuf_lock);
253                 took_lock = true;
254         }
255
256         max = log_buf_get_len();
257         if (idx < 0 || idx >= max) {
258                 ret = -1;
259         } else {
260                 if (len > max)
261                         len = max;
262                 ret = len;
263                 idx += (log_end - max);
264                 while (len-- > 0)
265                         dest[len] = LOG_BUF(idx + len);
266         }
267
268         if (took_lock)
269                 spin_unlock_irq(&logbuf_lock);
270
271         return ret;
272 }
273
274 /*
275  * Commands to do_syslog:
276  *
277  *      0 -- Close the log.  Currently a NOP.
278  *      1 -- Open the log. Currently a NOP.
279  *      2 -- Read from the log.
280  *      3 -- Read all messages remaining in the ring buffer.
281  *      4 -- Read and clear all messages remaining in the ring buffer
282  *      5 -- Clear ring buffer.
283  *      6 -- Disable printk's to console
284  *      7 -- Enable printk's to console
285  *      8 -- Set level of messages printed to console
286  *      9 -- Return number of unread characters in the log buffer
287  *     10 -- Return size of the log buffer
288  */
289 int do_syslog(int type, char __user *buf, int len)
290 {
291         unsigned i, j, limit, count;
292         int do_clear = 0;
293         char c;
294         int error = 0;
295
296         error = security_syslog(type);
297         if (error)
298                 return error;
299
300         switch (type) {
301         case 0:         /* Close log */
302                 break;
303         case 1:         /* Open log */
304                 break;
305         case 2:         /* Read from log */
306                 error = -EINVAL;
307                 if (!buf || len < 0)
308                         goto out;
309                 error = 0;
310                 if (!len)
311                         goto out;
312                 if (!access_ok(VERIFY_WRITE, buf, len)) {
313                         error = -EFAULT;
314                         goto out;
315                 }
316                 error = wait_event_interruptible(log_wait,
317                                                         (log_start - log_end));
318                 if (error)
319                         goto out;
320                 i = 0;
321                 spin_lock_irq(&logbuf_lock);
322                 while (!error && (log_start != log_end) && i < len) {
323                         c = LOG_BUF(log_start);
324                         log_start++;
325                         spin_unlock_irq(&logbuf_lock);
326                         error = __put_user(c,buf);
327                         buf++;
328                         i++;
329                         cond_resched();
330                         spin_lock_irq(&logbuf_lock);
331                 }
332                 spin_unlock_irq(&logbuf_lock);
333                 if (!error)
334                         error = i;
335                 break;
336         case 4:         /* Read/clear last kernel messages */
337                 do_clear = 1;
338                 /* FALL THRU */
339         case 3:         /* Read last kernel messages */
340                 error = -EINVAL;
341                 if (!buf || len < 0)
342                         goto out;
343                 error = 0;
344                 if (!len)
345                         goto out;
346                 if (!access_ok(VERIFY_WRITE, buf, len)) {
347                         error = -EFAULT;
348                         goto out;
349                 }
350                 count = len;
351                 if (count > log_buf_len)
352                         count = log_buf_len;
353                 spin_lock_irq(&logbuf_lock);
354                 if (count > logged_chars)
355                         count = logged_chars;
356                 if (do_clear)
357                         logged_chars = 0;
358                 limit = log_end;
359                 /*
360                  * __put_user() could sleep, and while we sleep
361                  * printk() could overwrite the messages
362                  * we try to copy to user space. Therefore
363                  * the messages are copied in reverse. <manfreds>
364                  */
365                 for (i = 0; i < count && !error; i++) {
366                         j = limit-1-i;
367                         if (j + log_buf_len < log_end)
368                                 break;
369                         c = LOG_BUF(j);
370                         spin_unlock_irq(&logbuf_lock);
371                         error = __put_user(c,&buf[count-1-i]);
372                         cond_resched();
373                         spin_lock_irq(&logbuf_lock);
374                 }
375                 spin_unlock_irq(&logbuf_lock);
376                 if (error)
377                         break;
378                 error = i;
379                 if (i != count) {
380                         int offset = count-error;
381                         /* buffer overflow during copy, correct user buffer. */
382                         for (i = 0; i < error; i++) {
383                                 if (__get_user(c,&buf[i+offset]) ||
384                                     __put_user(c,&buf[i])) {
385                                         error = -EFAULT;
386                                         break;
387                                 }
388                                 cond_resched();
389                         }
390                 }
391                 break;
392         case 5:         /* Clear ring buffer */
393                 logged_chars = 0;
394                 break;
395         case 6:         /* Disable logging to console */
396                 console_loglevel = minimum_console_loglevel;
397                 break;
398         case 7:         /* Enable logging to console */
399                 console_loglevel = default_console_loglevel;
400                 break;
401         case 8:         /* Set level of messages printed to console */
402                 error = -EINVAL;
403                 if (len < 1 || len > 8)
404                         goto out;
405                 if (len < minimum_console_loglevel)
406                         len = minimum_console_loglevel;
407                 console_loglevel = len;
408                 error = 0;
409                 break;
410         case 9:         /* Number of chars in the log buffer */
411                 error = log_end - log_start;
412                 break;
413         case 10:        /* Size of the log buffer */
414                 error = log_buf_len;
415                 break;
416         default:
417                 error = -EINVAL;
418                 break;
419         }
420 out:
421         return error;
422 }
423
424 asmlinkage long sys_syslog(int type, char __user *buf, int len)
425 {
426         return do_syslog(type, buf, len);
427 }
428
429 /*
430  * Call the console drivers on a range of log_buf
431  */
432 static void __call_console_drivers(unsigned start, unsigned end)
433 {
434         struct console *con;
435
436         for (con = console_drivers; con; con = con->next) {
437                 if ((con->flags & CON_ENABLED) && con->write &&
438                                 (cpu_online(smp_processor_id()) ||
439                                 (con->flags & CON_ANYTIME)))
440                         con->write(con, &LOG_BUF(start), end - start);
441         }
442 }
443
444 static int __read_mostly ignore_loglevel;
445
446 static int __init ignore_loglevel_setup(char *str)
447 {
448         ignore_loglevel = 1;
449         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
450
451         return 0;
452 }
453
454 early_param("ignore_loglevel", ignore_loglevel_setup);
455
456 /*
457  * Write out chars from start to end - 1 inclusive
458  */
459 static void _call_console_drivers(unsigned start,
460                                 unsigned end, int msg_log_level)
461 {
462         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
463                         console_drivers && start != end) {
464                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
465                         /* wrapped write */
466                         __call_console_drivers(start & LOG_BUF_MASK,
467                                                 log_buf_len);
468                         __call_console_drivers(0, end & LOG_BUF_MASK);
469                 } else {
470                         __call_console_drivers(start, end);
471                 }
472         }
473 }
474
475 /*
476  * Call the console drivers, asking them to write out
477  * log_buf[start] to log_buf[end - 1].
478  * The console_sem must be held.
479  */
480 static void call_console_drivers(unsigned start, unsigned end)
481 {
482         unsigned cur_index, start_print;
483         static int msg_level = -1;
484
485         BUG_ON(((int)(start - end)) > 0);
486
487         cur_index = start;
488         start_print = start;
489         while (cur_index != end) {
490                 if (msg_level < 0 && ((end - cur_index) > 2) &&
491                                 LOG_BUF(cur_index + 0) == '<' &&
492                                 LOG_BUF(cur_index + 1) >= '0' &&
493                                 LOG_BUF(cur_index + 1) <= '7' &&
494                                 LOG_BUF(cur_index + 2) == '>') {
495                         msg_level = LOG_BUF(cur_index + 1) - '0';
496                         cur_index += 3;
497                         start_print = cur_index;
498                 }
499                 while (cur_index != end) {
500                         char c = LOG_BUF(cur_index);
501
502                         cur_index++;
503                         if (c == '\n') {
504                                 if (msg_level < 0) {
505                                         /*
506                                          * printk() has already given us loglevel tags in
507                                          * the buffer.  This code is here in case the
508                                          * log buffer has wrapped right round and scribbled
509                                          * on those tags
510                                          */
511                                         msg_level = default_message_loglevel;
512                                 }
513                                 _call_console_drivers(start_print, cur_index, msg_level);
514                                 msg_level = -1;
515                                 start_print = cur_index;
516                                 break;
517                         }
518                 }
519         }
520         _call_console_drivers(start_print, end, msg_level);
521 }
522
523 static void emit_log_char(char c)
524 {
525         LOG_BUF(log_end) = c;
526         log_end++;
527         if (log_end - log_start > log_buf_len)
528                 log_start = log_end - log_buf_len;
529         if (log_end - con_start > log_buf_len)
530                 con_start = log_end - log_buf_len;
531         if (logged_chars < log_buf_len)
532                 logged_chars++;
533 }
534
535 /*
536  * Zap console related locks when oopsing. Only zap at most once
537  * every 10 seconds, to leave time for slow consoles to print a
538  * full oops.
539  */
540 static void zap_locks(void)
541 {
542         static unsigned long oops_timestamp;
543
544         if (time_after_eq(jiffies, oops_timestamp) &&
545                         !time_after(jiffies, oops_timestamp + 30 * HZ))
546                 return;
547
548         oops_timestamp = jiffies;
549
550         /* If a crash is occurring, make sure we can't deadlock */
551         spin_lock_init(&logbuf_lock);
552         /* And make sure that we print immediately */
553         init_MUTEX(&console_sem);
554 }
555
556 #if defined(CONFIG_PRINTK_TIME)
557 static int printk_time = 1;
558 #else
559 static int printk_time = 0;
560 #endif
561 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
562
563 /* Check if we have any console registered that can be called early in boot. */
564 static int have_callable_console(void)
565 {
566         struct console *con;
567
568         for (con = console_drivers; con; con = con->next)
569                 if (con->flags & CON_ANYTIME)
570                         return 1;
571
572         return 0;
573 }
574
575 /**
576  * printk - print a kernel message
577  * @fmt: format string
578  *
579  * This is printk().  It can be called from any context.  We want it to work.
580  *
581  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
582  * call the console drivers.  If we fail to get the semaphore we place the output
583  * into the log buffer and return.  The current holder of the console_sem will
584  * notice the new output in release_console_sem() and will send it to the
585  * consoles before releasing the semaphore.
586  *
587  * One effect of this deferred printing is that code which calls printk() and
588  * then changes console_loglevel may break. This is because console_loglevel
589  * is inspected when the actual printing occurs.
590  *
591  * See also:
592  * printf(3)
593  *
594  * See the vsnprintf() documentation for format string extensions over C99.
595  */
596
597 asmlinkage int printk(const char *fmt, ...)
598 {
599         va_list args;
600         int r;
601
602         va_start(args, fmt);
603         r = vprintk(fmt, args);
604         va_end(args);
605
606         return r;
607 }
608
609 /* cpu currently holding logbuf_lock */
610 static volatile unsigned int printk_cpu = UINT_MAX;
611
612 /*
613  * Can we actually use the console at this time on this cpu?
614  *
615  * Console drivers may assume that per-cpu resources have
616  * been allocated. So unless they're explicitly marked as
617  * being able to cope (CON_ANYTIME) don't call them until
618  * this CPU is officially up.
619  */
620 static inline int can_use_console(unsigned int cpu)
621 {
622         return cpu_online(cpu) || have_callable_console();
623 }
624
625 /*
626  * Try to get console ownership to actually show the kernel
627  * messages from a 'printk'. Return true (and with the
628  * console_semaphore held, and 'console_locked' set) if it
629  * is successful, false otherwise.
630  *
631  * This gets called with the 'logbuf_lock' spinlock held and
632  * interrupts disabled. It should return with 'lockbuf_lock'
633  * released but interrupts still disabled.
634  */
635 static int acquire_console_semaphore_for_printk(unsigned int cpu)
636 {
637         int retval = 0;
638
639         if (!try_acquire_console_sem()) {
640                 retval = 1;
641
642                 /*
643                  * If we can't use the console, we need to release
644                  * the console semaphore by hand to avoid flushing
645                  * the buffer. We need to hold the console semaphore
646                  * in order to do this test safely.
647                  */
648                 if (!can_use_console(cpu)) {
649                         console_locked = 0;
650                         up(&console_sem);
651                         retval = 0;
652                 }
653         }
654         printk_cpu = UINT_MAX;
655         spin_unlock(&logbuf_lock);
656         return retval;
657 }
658 static const char recursion_bug_msg [] =
659                 KERN_CRIT "BUG: recent printk recursion!\n";
660 static int recursion_bug;
661         static int new_text_line = 1;
662 static char printk_buf[1024];
663
664 asmlinkage int vprintk(const char *fmt, va_list args)
665 {
666         int printed_len = 0;
667         int current_log_level = default_message_loglevel;
668         unsigned long flags;
669         int this_cpu;
670         char *p;
671
672         boot_delay_msec();
673
674         preempt_disable();
675         /* This stops the holder of console_sem just where we want him */
676         raw_local_irq_save(flags);
677         this_cpu = smp_processor_id();
678
679         /*
680          * Ouch, printk recursed into itself!
681          */
682         if (unlikely(printk_cpu == this_cpu)) {
683                 /*
684                  * If a crash is occurring during printk() on this CPU,
685                  * then try to get the crash message out but make sure
686                  * we can't deadlock. Otherwise just return to avoid the
687                  * recursion and return - but flag the recursion so that
688                  * it can be printed at the next appropriate moment:
689                  */
690                 if (!oops_in_progress) {
691                         recursion_bug = 1;
692                         goto out_restore_irqs;
693                 }
694                 zap_locks();
695         }
696
697         lockdep_off();
698         spin_lock(&logbuf_lock);
699         printk_cpu = this_cpu;
700
701         if (recursion_bug) {
702                 recursion_bug = 0;
703                 strcpy(printk_buf, recursion_bug_msg);
704                 printed_len = sizeof(recursion_bug_msg);
705         }
706         /* Emit the output into the temporary buffer */
707         printed_len += vscnprintf(printk_buf + printed_len,
708                                   sizeof(printk_buf) - printed_len, fmt, args);
709
710
711         /*
712          * Copy the output into log_buf.  If the caller didn't provide
713          * appropriate log level tags, we insert them here
714          */
715         for (p = printk_buf; *p; p++) {
716                 if (new_text_line) {
717                         /* If a token, set current_log_level and skip over */
718                         if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
719                             p[2] == '>') {
720                                 current_log_level = p[1] - '0';
721                                 p += 3;
722                                 printed_len -= 3;
723                         }
724
725                         /* Always output the token */
726                         emit_log_char('<');
727                         emit_log_char(current_log_level + '0');
728                         emit_log_char('>');
729                         printed_len += 3;
730                         new_text_line = 0;
731
732                         if (printk_time) {
733                                 /* Follow the token with the time */
734                                 char tbuf[50], *tp;
735                                 unsigned tlen;
736                                 unsigned long long t;
737                                 unsigned long nanosec_rem;
738
739                                 t = cpu_clock(printk_cpu);
740                                 nanosec_rem = do_div(t, 1000000000);
741                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
742                                                 (unsigned long) t,
743                                                 nanosec_rem / 1000);
744
745                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
746                                         emit_log_char(*tp);
747                                 printed_len += tlen;
748                         }
749
750                         if (!*p)
751                                 break;
752                 }
753
754                 emit_log_char(*p);
755                 if (*p == '\n')
756                         new_text_line = 1;
757         }
758
759         /*
760          * Try to acquire and then immediately release the
761          * console semaphore. The release will do all the
762          * actual magic (print out buffers, wake up klogd,
763          * etc). 
764          *
765          * The acquire_console_semaphore_for_printk() function
766          * will release 'logbuf_lock' regardless of whether it
767          * actually gets the semaphore or not.
768          */
769         if (acquire_console_semaphore_for_printk(this_cpu))
770                 release_console_sem();
771
772         lockdep_on();
773 out_restore_irqs:
774         raw_local_irq_restore(flags);
775
776         preempt_enable();
777         return printed_len;
778 }
779 EXPORT_SYMBOL(printk);
780 EXPORT_SYMBOL(vprintk);
781
782 #else
783
784 asmlinkage long sys_syslog(int type, char __user *buf, int len)
785 {
786         return -ENOSYS;
787 }
788
789 static void call_console_drivers(unsigned start, unsigned end)
790 {
791 }
792
793 #endif
794
795 static int __add_preferred_console(char *name, int idx, char *options,
796                                    char *brl_options)
797 {
798         struct console_cmdline *c;
799         int i;
800
801         /*
802          *      See if this tty is not yet registered, and
803          *      if we have a slot free.
804          */
805         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
806                 if (strcmp(console_cmdline[i].name, name) == 0 &&
807                           console_cmdline[i].index == idx) {
808                                 if (!brl_options)
809                                         selected_console = i;
810                                 return 0;
811                 }
812         if (i == MAX_CMDLINECONSOLES)
813                 return -E2BIG;
814         if (!brl_options)
815                 selected_console = i;
816         c = &console_cmdline[i];
817         strlcpy(c->name, name, sizeof(c->name));
818         c->options = options;
819 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
820         c->brl_options = brl_options;
821 #endif
822         c->index = idx;
823         return 0;
824 }
825 /*
826  * Set up a list of consoles.  Called from init/main.c
827  */
828 static int __init console_setup(char *str)
829 {
830         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
831         char *s, *options, *brl_options = NULL;
832         int idx;
833
834 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
835         if (!memcmp(str, "brl,", 4)) {
836                 brl_options = "";
837                 str += 4;
838         } else if (!memcmp(str, "brl=", 4)) {
839                 brl_options = str + 4;
840                 str = strchr(brl_options, ',');
841                 if (!str) {
842                         printk(KERN_ERR "need port name after brl=\n");
843                         return 1;
844                 }
845                 *(str++) = 0;
846         }
847 #endif
848
849         /*
850          * Decode str into name, index, options.
851          */
852         if (str[0] >= '0' && str[0] <= '9') {
853                 strcpy(buf, "ttyS");
854                 strncpy(buf + 4, str, sizeof(buf) - 5);
855         } else {
856                 strncpy(buf, str, sizeof(buf) - 1);
857         }
858         buf[sizeof(buf) - 1] = 0;
859         if ((options = strchr(str, ',')) != NULL)
860                 *(options++) = 0;
861 #ifdef __sparc__
862         if (!strcmp(str, "ttya"))
863                 strcpy(buf, "ttyS0");
864         if (!strcmp(str, "ttyb"))
865                 strcpy(buf, "ttyS1");
866 #endif
867         for (s = buf; *s; s++)
868                 if ((*s >= '0' && *s <= '9') || *s == ',')
869                         break;
870         idx = simple_strtoul(s, NULL, 10);
871         *s = 0;
872
873         __add_preferred_console(buf, idx, options, brl_options);
874         console_set_on_cmdline = 1;
875         return 1;
876 }
877 __setup("console=", console_setup);
878
879 /**
880  * add_preferred_console - add a device to the list of preferred consoles.
881  * @name: device name
882  * @idx: device index
883  * @options: options for this console
884  *
885  * The last preferred console added will be used for kernel messages
886  * and stdin/out/err for init.  Normally this is used by console_setup
887  * above to handle user-supplied console arguments; however it can also
888  * be used by arch-specific code either to override the user or more
889  * commonly to provide a default console (ie from PROM variables) when
890  * the user has not supplied one.
891  */
892 int add_preferred_console(char *name, int idx, char *options)
893 {
894         return __add_preferred_console(name, idx, options, NULL);
895 }
896
897 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
898 {
899         struct console_cmdline *c;
900         int i;
901
902         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
903                 if (strcmp(console_cmdline[i].name, name) == 0 &&
904                           console_cmdline[i].index == idx) {
905                                 c = &console_cmdline[i];
906                                 strlcpy(c->name, name_new, sizeof(c->name));
907                                 c->name[sizeof(c->name) - 1] = 0;
908                                 c->options = options;
909                                 c->index = idx_new;
910                                 return i;
911                 }
912         /* not found */
913         return -1;
914 }
915
916 int console_suspend_enabled = 1;
917 EXPORT_SYMBOL(console_suspend_enabled);
918
919 static int __init console_suspend_disable(char *str)
920 {
921         console_suspend_enabled = 0;
922         return 1;
923 }
924 __setup("no_console_suspend", console_suspend_disable);
925
926 /**
927  * suspend_console - suspend the console subsystem
928  *
929  * This disables printk() while we go into suspend states
930  */
931 void suspend_console(void)
932 {
933         if (!console_suspend_enabled)
934                 return;
935         printk("Suspending console(s) (use no_console_suspend to debug)\n");
936         acquire_console_sem();
937         console_suspended = 1;
938 }
939
940 void resume_console(void)
941 {
942         if (!console_suspend_enabled)
943                 return;
944         console_suspended = 0;
945         release_console_sem();
946 }
947
948 /**
949  * acquire_console_sem - lock the console system for exclusive use.
950  *
951  * Acquires a semaphore which guarantees that the caller has
952  * exclusive access to the console system and the console_drivers list.
953  *
954  * Can sleep, returns nothing.
955  */
956 void acquire_console_sem(void)
957 {
958         BUG_ON(in_interrupt());
959         if (console_suspended) {
960                 down(&secondary_console_sem);
961                 return;
962         }
963         down(&console_sem);
964         console_locked = 1;
965         console_may_schedule = 1;
966 }
967 EXPORT_SYMBOL(acquire_console_sem);
968
969 int try_acquire_console_sem(void)
970 {
971         if (down_trylock(&console_sem))
972                 return -1;
973         console_locked = 1;
974         console_may_schedule = 0;
975         return 0;
976 }
977 EXPORT_SYMBOL(try_acquire_console_sem);
978
979 int is_console_locked(void)
980 {
981         return console_locked;
982 }
983
984 static DEFINE_PER_CPU(int, printk_pending);
985
986 void printk_tick(void)
987 {
988         if (__get_cpu_var(printk_pending)) {
989                 __get_cpu_var(printk_pending) = 0;
990                 wake_up_interruptible(&log_wait);
991         }
992 }
993
994 int printk_needs_cpu(int cpu)
995 {
996         return per_cpu(printk_pending, cpu);
997 }
998
999 void wake_up_klogd(void)
1000 {
1001         if (waitqueue_active(&log_wait))
1002                 __raw_get_cpu_var(printk_pending) = 1;
1003 }
1004
1005 /**
1006  * release_console_sem - unlock the console system
1007  *
1008  * Releases the semaphore which the caller holds on the console system
1009  * and the console driver list.
1010  *
1011  * While the semaphore was held, console output may have been buffered
1012  * by printk().  If this is the case, release_console_sem() emits
1013  * the output prior to releasing the semaphore.
1014  *
1015  * If there is output waiting for klogd, we wake it up.
1016  *
1017  * release_console_sem() may be called from any context.
1018  */
1019 void release_console_sem(void)
1020 {
1021         unsigned long flags;
1022         unsigned _con_start, _log_end;
1023         unsigned wake_klogd = 0;
1024
1025         if (console_suspended) {
1026                 up(&secondary_console_sem);
1027                 return;
1028         }
1029
1030         console_may_schedule = 0;
1031
1032         for ( ; ; ) {
1033                 spin_lock_irqsave(&logbuf_lock, flags);
1034                 wake_klogd |= log_start - log_end;
1035                 if (con_start == log_end)
1036                         break;                  /* Nothing to print */
1037                 _con_start = con_start;
1038                 _log_end = log_end;
1039                 con_start = log_end;            /* Flush */
1040                 spin_unlock(&logbuf_lock);
1041                 stop_critical_timings();        /* don't trace print latency */
1042                 call_console_drivers(_con_start, _log_end);
1043                 start_critical_timings();
1044                 local_irq_restore(flags);
1045         }
1046         console_locked = 0;
1047         up(&console_sem);
1048         spin_unlock_irqrestore(&logbuf_lock, flags);
1049         if (wake_klogd)
1050                 wake_up_klogd();
1051 }
1052 EXPORT_SYMBOL(release_console_sem);
1053
1054 /**
1055  * console_conditional_schedule - yield the CPU if required
1056  *
1057  * If the console code is currently allowed to sleep, and
1058  * if this CPU should yield the CPU to another task, do
1059  * so here.
1060  *
1061  * Must be called within acquire_console_sem().
1062  */
1063 void __sched console_conditional_schedule(void)
1064 {
1065         if (console_may_schedule)
1066                 cond_resched();
1067 }
1068 EXPORT_SYMBOL(console_conditional_schedule);
1069
1070 void console_print(const char *s)
1071 {
1072         printk(KERN_EMERG "%s", s);
1073 }
1074 EXPORT_SYMBOL(console_print);
1075
1076 void console_unblank(void)
1077 {
1078         struct console *c;
1079
1080         /*
1081          * console_unblank can no longer be called in interrupt context unless
1082          * oops_in_progress is set to 1..
1083          */
1084         if (oops_in_progress) {
1085                 if (down_trylock(&console_sem) != 0)
1086                         return;
1087         } else
1088                 acquire_console_sem();
1089
1090         console_locked = 1;
1091         console_may_schedule = 0;
1092         for (c = console_drivers; c != NULL; c = c->next)
1093                 if ((c->flags & CON_ENABLED) && c->unblank)
1094                         c->unblank();
1095         release_console_sem();
1096 }
1097
1098 /*
1099  * Return the console tty driver structure and its associated index
1100  */
1101 struct tty_driver *console_device(int *index)
1102 {
1103         struct console *c;
1104         struct tty_driver *driver = NULL;
1105
1106         acquire_console_sem();
1107         for (c = console_drivers; c != NULL; c = c->next) {
1108                 if (!c->device)
1109                         continue;
1110                 driver = c->device(c, index);
1111                 if (driver)
1112                         break;
1113         }
1114         release_console_sem();
1115         return driver;
1116 }
1117
1118 /*
1119  * Prevent further output on the passed console device so that (for example)
1120  * serial drivers can disable console output before suspending a port, and can
1121  * re-enable output afterwards.
1122  */
1123 void console_stop(struct console *console)
1124 {
1125         acquire_console_sem();
1126         console->flags &= ~CON_ENABLED;
1127         release_console_sem();
1128 }
1129 EXPORT_SYMBOL(console_stop);
1130
1131 void console_start(struct console *console)
1132 {
1133         acquire_console_sem();
1134         console->flags |= CON_ENABLED;
1135         release_console_sem();
1136 }
1137 EXPORT_SYMBOL(console_start);
1138
1139 /*
1140  * The console driver calls this routine during kernel initialization
1141  * to register the console printing procedure with printk() and to
1142  * print any messages that were printed by the kernel before the
1143  * console driver was initialized.
1144  */
1145 void register_console(struct console *console)
1146 {
1147         int i;
1148         unsigned long flags;
1149         struct console *bootconsole = NULL;
1150
1151         if (console_drivers) {
1152                 if (console->flags & CON_BOOT)
1153                         return;
1154                 if (console_drivers->flags & CON_BOOT)
1155                         bootconsole = console_drivers;
1156         }
1157
1158         if (preferred_console < 0 || bootconsole || !console_drivers)
1159                 preferred_console = selected_console;
1160
1161         if (console->early_setup)
1162                 console->early_setup();
1163
1164         /*
1165          *      See if we want to use this console driver. If we
1166          *      didn't select a console we take the first one
1167          *      that registers here.
1168          */
1169         if (preferred_console < 0) {
1170                 if (console->index < 0)
1171                         console->index = 0;
1172                 if (console->setup == NULL ||
1173                     console->setup(console, NULL) == 0) {
1174                         console->flags |= CON_ENABLED;
1175                         if (console->device) {
1176                                 console->flags |= CON_CONSDEV;
1177                                 preferred_console = 0;
1178                         }
1179                 }
1180         }
1181
1182         /*
1183          *      See if this console matches one we selected on
1184          *      the command line.
1185          */
1186         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1187                         i++) {
1188                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1189                         continue;
1190                 if (console->index >= 0 &&
1191                     console->index != console_cmdline[i].index)
1192                         continue;
1193                 if (console->index < 0)
1194                         console->index = console_cmdline[i].index;
1195 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1196                 if (console_cmdline[i].brl_options) {
1197                         console->flags |= CON_BRL;
1198                         braille_register_console(console,
1199                                         console_cmdline[i].index,
1200                                         console_cmdline[i].options,
1201                                         console_cmdline[i].brl_options);
1202                         return;
1203                 }
1204 #endif
1205                 if (console->setup &&
1206                     console->setup(console, console_cmdline[i].options) != 0)
1207                         break;
1208                 console->flags |= CON_ENABLED;
1209                 console->index = console_cmdline[i].index;
1210                 if (i == selected_console) {
1211                         console->flags |= CON_CONSDEV;
1212                         preferred_console = selected_console;
1213                 }
1214                 break;
1215         }
1216
1217         if (!(console->flags & CON_ENABLED))
1218                 return;
1219
1220         if (bootconsole && (console->flags & CON_CONSDEV)) {
1221                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1222                        bootconsole->name, bootconsole->index,
1223                        console->name, console->index);
1224                 unregister_console(bootconsole);
1225                 console->flags &= ~CON_PRINTBUFFER;
1226         } else {
1227                 printk(KERN_INFO "console [%s%d] enabled\n",
1228                        console->name, console->index);
1229         }
1230
1231         /*
1232          *      Put this console in the list - keep the
1233          *      preferred driver at the head of the list.
1234          */
1235         acquire_console_sem();
1236         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1237                 console->next = console_drivers;
1238                 console_drivers = console;
1239                 if (console->next)
1240                         console->next->flags &= ~CON_CONSDEV;
1241         } else {
1242                 console->next = console_drivers->next;
1243                 console_drivers->next = console;
1244         }
1245         if (console->flags & CON_PRINTBUFFER) {
1246                 /*
1247                  * release_console_sem() will print out the buffered messages
1248                  * for us.
1249                  */
1250                 spin_lock_irqsave(&logbuf_lock, flags);
1251                 con_start = log_start;
1252                 spin_unlock_irqrestore(&logbuf_lock, flags);
1253         }
1254         release_console_sem();
1255 }
1256 EXPORT_SYMBOL(register_console);
1257
1258 int unregister_console(struct console *console)
1259 {
1260         struct console *a, *b;
1261         int res = 1;
1262
1263 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1264         if (console->flags & CON_BRL)
1265                 return braille_unregister_console(console);
1266 #endif
1267
1268         acquire_console_sem();
1269         if (console_drivers == console) {
1270                 console_drivers=console->next;
1271                 res = 0;
1272         } else if (console_drivers) {
1273                 for (a=console_drivers->next, b=console_drivers ;
1274                      a; b=a, a=b->next) {
1275                         if (a == console) {
1276                                 b->next = a->next;
1277                                 res = 0;
1278                                 break;
1279                         }
1280                 }
1281         }
1282
1283         /*
1284          * If this isn't the last console and it has CON_CONSDEV set, we
1285          * need to set it on the next preferred console.
1286          */
1287         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1288                 console_drivers->flags |= CON_CONSDEV;
1289
1290         release_console_sem();
1291         return res;
1292 }
1293 EXPORT_SYMBOL(unregister_console);
1294
1295 static int __init disable_boot_consoles(void)
1296 {
1297         if (console_drivers != NULL) {
1298                 if (console_drivers->flags & CON_BOOT) {
1299                         printk(KERN_INFO "turn off boot console %s%d\n",
1300                                 console_drivers->name, console_drivers->index);
1301                         return unregister_console(console_drivers);
1302                 }
1303         }
1304         return 0;
1305 }
1306 late_initcall(disable_boot_consoles);
1307
1308 #if defined CONFIG_PRINTK
1309
1310 /*
1311  * printk rate limiting, lifted from the networking subsystem.
1312  *
1313  * This enforces a rate limit: not more than 10 kernel messages
1314  * every 5s to make a denial-of-service attack impossible.
1315  */
1316 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1317
1318 int printk_ratelimit(void)
1319 {
1320         return __ratelimit(&printk_ratelimit_state);
1321 }
1322 EXPORT_SYMBOL(printk_ratelimit);
1323
1324 /**
1325  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1326  * @caller_jiffies: pointer to caller's state
1327  * @interval_msecs: minimum interval between prints
1328  *
1329  * printk_timed_ratelimit() returns true if more than @interval_msecs
1330  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1331  * returned true.
1332  */
1333 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1334                         unsigned int interval_msecs)
1335 {
1336         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1337                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1338                 return true;
1339         }
1340         return false;
1341 }
1342 EXPORT_SYMBOL(printk_timed_ratelimit);
1343 #endif