Merge branch 'printk-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 #include <linux/kexec.h>
36
37 #include <asm/uaccess.h>
38
39 /*
40  * Architectures can override it:
41  */
42 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
43 {
44 }
45
46 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
47
48 /* printk's without a loglevel use this.. */
49 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
50
51 /* We show everything that is MORE important than this.. */
52 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
53 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
54
55 DECLARE_WAIT_QUEUE_HEAD(log_wait);
56
57 int console_printk[4] = {
58         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
59         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
60         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
61         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
62 };
63
64 /*
65  * Low level drivers may need that to know if they can schedule in
66  * their unblank() callback or not. So let's export it.
67  */
68 int oops_in_progress;
69 EXPORT_SYMBOL(oops_in_progress);
70
71 /*
72  * console_sem protects the console_drivers list, and also
73  * provides serialisation for access to the entire console
74  * driver system.
75  */
76 static DECLARE_MUTEX(console_sem);
77 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 #ifdef CONFIG_KEXEC
140 /*
141  * This appends the listed symbols to /proc/vmcoreinfo
142  *
143  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
144  * obtain access to symbols that are otherwise very difficult to locate.  These
145  * symbols are specifically used so that utilities can access and extract the
146  * dmesg log from a vmcore file after a crash.
147  */
148 void log_buf_kexec_setup(void)
149 {
150         VMCOREINFO_SYMBOL(log_buf);
151         VMCOREINFO_SYMBOL(log_end);
152         VMCOREINFO_SYMBOL(log_buf_len);
153         VMCOREINFO_SYMBOL(logged_chars);
154 }
155 #endif
156
157 static int __init log_buf_len_setup(char *str)
158 {
159         unsigned size = memparse(str, &str);
160         unsigned long flags;
161
162         if (size)
163                 size = roundup_pow_of_two(size);
164         if (size > log_buf_len) {
165                 unsigned start, dest_idx, offset;
166                 char *new_log_buf;
167
168                 new_log_buf = alloc_bootmem(size);
169                 if (!new_log_buf) {
170                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
171                         goto out;
172                 }
173
174                 spin_lock_irqsave(&logbuf_lock, flags);
175                 log_buf_len = size;
176                 log_buf = new_log_buf;
177
178                 offset = start = min(con_start, log_start);
179                 dest_idx = 0;
180                 while (start != log_end) {
181                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
182                         start++;
183                         dest_idx++;
184                 }
185                 log_start -= offset;
186                 con_start -= offset;
187                 log_end -= offset;
188                 spin_unlock_irqrestore(&logbuf_lock, flags);
189
190                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
191         }
192 out:
193         return 1;
194 }
195
196 __setup("log_buf_len=", log_buf_len_setup);
197
198 #ifdef CONFIG_BOOT_PRINTK_DELAY
199
200 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
201 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
202
203 static int __init boot_delay_setup(char *str)
204 {
205         unsigned long lpj;
206         unsigned long long loops_per_msec;
207
208         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
209         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
210
211         get_option(&str, &boot_delay);
212         if (boot_delay > 10 * 1000)
213                 boot_delay = 0;
214
215         printk_delay_msec = loops_per_msec;
216         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
217                 "HZ: %d, printk_delay_msec: %llu\n",
218                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
219         return 1;
220 }
221 __setup("boot_delay=", boot_delay_setup);
222
223 static void boot_delay_msec(void)
224 {
225         unsigned long long k;
226         unsigned long timeout;
227
228         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
229                 return;
230
231         k = (unsigned long long)printk_delay_msec * boot_delay;
232
233         timeout = jiffies + msecs_to_jiffies(boot_delay);
234         while (k) {
235                 k--;
236                 cpu_relax();
237                 /*
238                  * use (volatile) jiffies to prevent
239                  * compiler reduction; loop termination via jiffies
240                  * is secondary and may or may not happen.
241                  */
242                 if (time_after(jiffies, timeout))
243                         break;
244                 touch_nmi_watchdog();
245         }
246 }
247 #else
248 static inline void boot_delay_msec(void)
249 {
250 }
251 #endif
252
253 /*
254  * Commands to do_syslog:
255  *
256  *      0 -- Close the log.  Currently a NOP.
257  *      1 -- Open the log. Currently a NOP.
258  *      2 -- Read from the log.
259  *      3 -- Read all messages remaining in the ring buffer.
260  *      4 -- Read and clear all messages remaining in the ring buffer
261  *      5 -- Clear ring buffer.
262  *      6 -- Disable printk's to console
263  *      7 -- Enable printk's to console
264  *      8 -- Set level of messages printed to console
265  *      9 -- Return number of unread characters in the log buffer
266  *     10 -- Return size of the log buffer
267  */
268 int do_syslog(int type, char __user *buf, int len)
269 {
270         unsigned i, j, limit, count;
271         int do_clear = 0;
272         char c;
273         int error = 0;
274
275         error = security_syslog(type);
276         if (error)
277                 return error;
278
279         switch (type) {
280         case 0:         /* Close log */
281                 break;
282         case 1:         /* Open log */
283                 break;
284         case 2:         /* Read from log */
285                 error = -EINVAL;
286                 if (!buf || len < 0)
287                         goto out;
288                 error = 0;
289                 if (!len)
290                         goto out;
291                 if (!access_ok(VERIFY_WRITE, buf, len)) {
292                         error = -EFAULT;
293                         goto out;
294                 }
295                 error = wait_event_interruptible(log_wait,
296                                                         (log_start - log_end));
297                 if (error)
298                         goto out;
299                 i = 0;
300                 spin_lock_irq(&logbuf_lock);
301                 while (!error && (log_start != log_end) && i < len) {
302                         c = LOG_BUF(log_start);
303                         log_start++;
304                         spin_unlock_irq(&logbuf_lock);
305                         error = __put_user(c,buf);
306                         buf++;
307                         i++;
308                         cond_resched();
309                         spin_lock_irq(&logbuf_lock);
310                 }
311                 spin_unlock_irq(&logbuf_lock);
312                 if (!error)
313                         error = i;
314                 break;
315         case 4:         /* Read/clear last kernel messages */
316                 do_clear = 1;
317                 /* FALL THRU */
318         case 3:         /* Read last kernel messages */
319                 error = -EINVAL;
320                 if (!buf || len < 0)
321                         goto out;
322                 error = 0;
323                 if (!len)
324                         goto out;
325                 if (!access_ok(VERIFY_WRITE, buf, len)) {
326                         error = -EFAULT;
327                         goto out;
328                 }
329                 count = len;
330                 if (count > log_buf_len)
331                         count = log_buf_len;
332                 spin_lock_irq(&logbuf_lock);
333                 if (count > logged_chars)
334                         count = logged_chars;
335                 if (do_clear)
336                         logged_chars = 0;
337                 limit = log_end;
338                 /*
339                  * __put_user() could sleep, and while we sleep
340                  * printk() could overwrite the messages
341                  * we try to copy to user space. Therefore
342                  * the messages are copied in reverse. <manfreds>
343                  */
344                 for (i = 0; i < count && !error; i++) {
345                         j = limit-1-i;
346                         if (j + log_buf_len < log_end)
347                                 break;
348                         c = LOG_BUF(j);
349                         spin_unlock_irq(&logbuf_lock);
350                         error = __put_user(c,&buf[count-1-i]);
351                         cond_resched();
352                         spin_lock_irq(&logbuf_lock);
353                 }
354                 spin_unlock_irq(&logbuf_lock);
355                 if (error)
356                         break;
357                 error = i;
358                 if (i != count) {
359                         int offset = count-error;
360                         /* buffer overflow during copy, correct user buffer. */
361                         for (i = 0; i < error; i++) {
362                                 if (__get_user(c,&buf[i+offset]) ||
363                                     __put_user(c,&buf[i])) {
364                                         error = -EFAULT;
365                                         break;
366                                 }
367                                 cond_resched();
368                         }
369                 }
370                 break;
371         case 5:         /* Clear ring buffer */
372                 logged_chars = 0;
373                 break;
374         case 6:         /* Disable logging to console */
375                 console_loglevel = minimum_console_loglevel;
376                 break;
377         case 7:         /* Enable logging to console */
378                 console_loglevel = default_console_loglevel;
379                 break;
380         case 8:         /* Set level of messages printed to console */
381                 error = -EINVAL;
382                 if (len < 1 || len > 8)
383                         goto out;
384                 if (len < minimum_console_loglevel)
385                         len = minimum_console_loglevel;
386                 console_loglevel = len;
387                 error = 0;
388                 break;
389         case 9:         /* Number of chars in the log buffer */
390                 error = log_end - log_start;
391                 break;
392         case 10:        /* Size of the log buffer */
393                 error = log_buf_len;
394                 break;
395         default:
396                 error = -EINVAL;
397                 break;
398         }
399 out:
400         return error;
401 }
402
403 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
404 {
405         return do_syslog(type, buf, len);
406 }
407
408 /*
409  * Call the console drivers on a range of log_buf
410  */
411 static void __call_console_drivers(unsigned start, unsigned end)
412 {
413         struct console *con;
414
415         for (con = console_drivers; con; con = con->next) {
416                 if ((con->flags & CON_ENABLED) && con->write &&
417                                 (cpu_online(smp_processor_id()) ||
418                                 (con->flags & CON_ANYTIME)))
419                         con->write(con, &LOG_BUF(start), end - start);
420         }
421 }
422
423 static int __read_mostly ignore_loglevel;
424
425 static int __init ignore_loglevel_setup(char *str)
426 {
427         ignore_loglevel = 1;
428         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
429
430         return 0;
431 }
432
433 early_param("ignore_loglevel", ignore_loglevel_setup);
434
435 /*
436  * Write out chars from start to end - 1 inclusive
437  */
438 static void _call_console_drivers(unsigned start,
439                                 unsigned end, int msg_log_level)
440 {
441         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
442                         console_drivers && start != end) {
443                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
444                         /* wrapped write */
445                         __call_console_drivers(start & LOG_BUF_MASK,
446                                                 log_buf_len);
447                         __call_console_drivers(0, end & LOG_BUF_MASK);
448                 } else {
449                         __call_console_drivers(start, end);
450                 }
451         }
452 }
453
454 /*
455  * Call the console drivers, asking them to write out
456  * log_buf[start] to log_buf[end - 1].
457  * The console_sem must be held.
458  */
459 static void call_console_drivers(unsigned start, unsigned end)
460 {
461         unsigned cur_index, start_print;
462         static int msg_level = -1;
463
464         BUG_ON(((int)(start - end)) > 0);
465
466         cur_index = start;
467         start_print = start;
468         while (cur_index != end) {
469                 if (msg_level < 0 && ((end - cur_index) > 2) &&
470                                 LOG_BUF(cur_index + 0) == '<' &&
471                                 LOG_BUF(cur_index + 1) >= '0' &&
472                                 LOG_BUF(cur_index + 1) <= '7' &&
473                                 LOG_BUF(cur_index + 2) == '>') {
474                         msg_level = LOG_BUF(cur_index + 1) - '0';
475                         cur_index += 3;
476                         start_print = cur_index;
477                 }
478                 while (cur_index != end) {
479                         char c = LOG_BUF(cur_index);
480
481                         cur_index++;
482                         if (c == '\n') {
483                                 if (msg_level < 0) {
484                                         /*
485                                          * printk() has already given us loglevel tags in
486                                          * the buffer.  This code is here in case the
487                                          * log buffer has wrapped right round and scribbled
488                                          * on those tags
489                                          */
490                                         msg_level = default_message_loglevel;
491                                 }
492                                 _call_console_drivers(start_print, cur_index, msg_level);
493                                 msg_level = -1;
494                                 start_print = cur_index;
495                                 break;
496                         }
497                 }
498         }
499         _call_console_drivers(start_print, end, msg_level);
500 }
501
502 static void emit_log_char(char c)
503 {
504         LOG_BUF(log_end) = c;
505         log_end++;
506         if (log_end - log_start > log_buf_len)
507                 log_start = log_end - log_buf_len;
508         if (log_end - con_start > log_buf_len)
509                 con_start = log_end - log_buf_len;
510         if (logged_chars < log_buf_len)
511                 logged_chars++;
512 }
513
514 /*
515  * Zap console related locks when oopsing. Only zap at most once
516  * every 10 seconds, to leave time for slow consoles to print a
517  * full oops.
518  */
519 static void zap_locks(void)
520 {
521         static unsigned long oops_timestamp;
522
523         if (time_after_eq(jiffies, oops_timestamp) &&
524                         !time_after(jiffies, oops_timestamp + 30 * HZ))
525                 return;
526
527         oops_timestamp = jiffies;
528
529         /* If a crash is occurring, make sure we can't deadlock */
530         spin_lock_init(&logbuf_lock);
531         /* And make sure that we print immediately */
532         init_MUTEX(&console_sem);
533 }
534
535 #if defined(CONFIG_PRINTK_TIME)
536 static int printk_time = 1;
537 #else
538 static int printk_time = 0;
539 #endif
540 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
541
542 /* Check if we have any console registered that can be called early in boot. */
543 static int have_callable_console(void)
544 {
545         struct console *con;
546
547         for (con = console_drivers; con; con = con->next)
548                 if (con->flags & CON_ANYTIME)
549                         return 1;
550
551         return 0;
552 }
553
554 /**
555  * printk - print a kernel message
556  * @fmt: format string
557  *
558  * This is printk().  It can be called from any context.  We want it to work.
559  *
560  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
561  * call the console drivers.  If we fail to get the semaphore we place the output
562  * into the log buffer and return.  The current holder of the console_sem will
563  * notice the new output in release_console_sem() and will send it to the
564  * consoles before releasing the semaphore.
565  *
566  * One effect of this deferred printing is that code which calls printk() and
567  * then changes console_loglevel may break. This is because console_loglevel
568  * is inspected when the actual printing occurs.
569  *
570  * See also:
571  * printf(3)
572  *
573  * See the vsnprintf() documentation for format string extensions over C99.
574  */
575
576 asmlinkage int printk(const char *fmt, ...)
577 {
578         va_list args;
579         int r;
580
581         va_start(args, fmt);
582         r = vprintk(fmt, args);
583         va_end(args);
584
585         return r;
586 }
587
588 /* cpu currently holding logbuf_lock */
589 static volatile unsigned int printk_cpu = UINT_MAX;
590
591 /*
592  * Can we actually use the console at this time on this cpu?
593  *
594  * Console drivers may assume that per-cpu resources have
595  * been allocated. So unless they're explicitly marked as
596  * being able to cope (CON_ANYTIME) don't call them until
597  * this CPU is officially up.
598  */
599 static inline int can_use_console(unsigned int cpu)
600 {
601         return cpu_online(cpu) || have_callable_console();
602 }
603
604 /*
605  * Try to get console ownership to actually show the kernel
606  * messages from a 'printk'. Return true (and with the
607  * console_semaphore held, and 'console_locked' set) if it
608  * is successful, false otherwise.
609  *
610  * This gets called with the 'logbuf_lock' spinlock held and
611  * interrupts disabled. It should return with 'lockbuf_lock'
612  * released but interrupts still disabled.
613  */
614 static int acquire_console_semaphore_for_printk(unsigned int cpu)
615 {
616         int retval = 0;
617
618         if (!try_acquire_console_sem()) {
619                 retval = 1;
620
621                 /*
622                  * If we can't use the console, we need to release
623                  * the console semaphore by hand to avoid flushing
624                  * the buffer. We need to hold the console semaphore
625                  * in order to do this test safely.
626                  */
627                 if (!can_use_console(cpu)) {
628                         console_locked = 0;
629                         up(&console_sem);
630                         retval = 0;
631                 }
632         }
633         printk_cpu = UINT_MAX;
634         spin_unlock(&logbuf_lock);
635         return retval;
636 }
637 static const char recursion_bug_msg [] =
638                 KERN_CRIT "BUG: recent printk recursion!\n";
639 static int recursion_bug;
640 static int new_text_line = 1;
641 static char printk_buf[1024];
642
643 asmlinkage int vprintk(const char *fmt, va_list args)
644 {
645         int printed_len = 0;
646         int current_log_level = default_message_loglevel;
647         unsigned long flags;
648         int this_cpu;
649         char *p;
650
651         boot_delay_msec();
652
653         preempt_disable();
654         /* This stops the holder of console_sem just where we want him */
655         raw_local_irq_save(flags);
656         this_cpu = smp_processor_id();
657
658         /*
659          * Ouch, printk recursed into itself!
660          */
661         if (unlikely(printk_cpu == this_cpu)) {
662                 /*
663                  * If a crash is occurring during printk() on this CPU,
664                  * then try to get the crash message out but make sure
665                  * we can't deadlock. Otherwise just return to avoid the
666                  * recursion and return - but flag the recursion so that
667                  * it can be printed at the next appropriate moment:
668                  */
669                 if (!oops_in_progress) {
670                         recursion_bug = 1;
671                         goto out_restore_irqs;
672                 }
673                 zap_locks();
674         }
675
676         lockdep_off();
677         spin_lock(&logbuf_lock);
678         printk_cpu = this_cpu;
679
680         if (recursion_bug) {
681                 recursion_bug = 0;
682                 strcpy(printk_buf, recursion_bug_msg);
683                 printed_len = strlen(recursion_bug_msg);
684         }
685         /* Emit the output into the temporary buffer */
686         printed_len += vscnprintf(printk_buf + printed_len,
687                                   sizeof(printk_buf) - printed_len, fmt, args);
688
689
690         /*
691          * Copy the output into log_buf.  If the caller didn't provide
692          * appropriate log level tags, we insert them here
693          */
694         for (p = printk_buf; *p; p++) {
695                 if (new_text_line) {
696                         /* If a token, set current_log_level and skip over */
697                         if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
698                             p[2] == '>') {
699                                 current_log_level = p[1] - '0';
700                                 p += 3;
701                                 printed_len -= 3;
702                         }
703
704                         /* Always output the token */
705                         emit_log_char('<');
706                         emit_log_char(current_log_level + '0');
707                         emit_log_char('>');
708                         printed_len += 3;
709                         new_text_line = 0;
710
711                         if (printk_time) {
712                                 /* Follow the token with the time */
713                                 char tbuf[50], *tp;
714                                 unsigned tlen;
715                                 unsigned long long t;
716                                 unsigned long nanosec_rem;
717
718                                 t = cpu_clock(printk_cpu);
719                                 nanosec_rem = do_div(t, 1000000000);
720                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
721                                                 (unsigned long) t,
722                                                 nanosec_rem / 1000);
723
724                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
725                                         emit_log_char(*tp);
726                                 printed_len += tlen;
727                         }
728
729                         if (!*p)
730                                 break;
731                 }
732
733                 emit_log_char(*p);
734                 if (*p == '\n')
735                         new_text_line = 1;
736         }
737
738         /*
739          * Try to acquire and then immediately release the
740          * console semaphore. The release will do all the
741          * actual magic (print out buffers, wake up klogd,
742          * etc). 
743          *
744          * The acquire_console_semaphore_for_printk() function
745          * will release 'logbuf_lock' regardless of whether it
746          * actually gets the semaphore or not.
747          */
748         if (acquire_console_semaphore_for_printk(this_cpu))
749                 release_console_sem();
750
751         lockdep_on();
752 out_restore_irqs:
753         raw_local_irq_restore(flags);
754
755         preempt_enable();
756         return printed_len;
757 }
758 EXPORT_SYMBOL(printk);
759 EXPORT_SYMBOL(vprintk);
760
761 #else
762
763 static void call_console_drivers(unsigned start, unsigned end)
764 {
765 }
766
767 #endif
768
769 static int __add_preferred_console(char *name, int idx, char *options,
770                                    char *brl_options)
771 {
772         struct console_cmdline *c;
773         int i;
774
775         /*
776          *      See if this tty is not yet registered, and
777          *      if we have a slot free.
778          */
779         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
780                 if (strcmp(console_cmdline[i].name, name) == 0 &&
781                           console_cmdline[i].index == idx) {
782                                 if (!brl_options)
783                                         selected_console = i;
784                                 return 0;
785                 }
786         if (i == MAX_CMDLINECONSOLES)
787                 return -E2BIG;
788         if (!brl_options)
789                 selected_console = i;
790         c = &console_cmdline[i];
791         strlcpy(c->name, name, sizeof(c->name));
792         c->options = options;
793 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
794         c->brl_options = brl_options;
795 #endif
796         c->index = idx;
797         return 0;
798 }
799 /*
800  * Set up a list of consoles.  Called from init/main.c
801  */
802 static int __init console_setup(char *str)
803 {
804         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
805         char *s, *options, *brl_options = NULL;
806         int idx;
807
808 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
809         if (!memcmp(str, "brl,", 4)) {
810                 brl_options = "";
811                 str += 4;
812         } else if (!memcmp(str, "brl=", 4)) {
813                 brl_options = str + 4;
814                 str = strchr(brl_options, ',');
815                 if (!str) {
816                         printk(KERN_ERR "need port name after brl=\n");
817                         return 1;
818                 }
819                 *(str++) = 0;
820         }
821 #endif
822
823         /*
824          * Decode str into name, index, options.
825          */
826         if (str[0] >= '0' && str[0] <= '9') {
827                 strcpy(buf, "ttyS");
828                 strncpy(buf + 4, str, sizeof(buf) - 5);
829         } else {
830                 strncpy(buf, str, sizeof(buf) - 1);
831         }
832         buf[sizeof(buf) - 1] = 0;
833         if ((options = strchr(str, ',')) != NULL)
834                 *(options++) = 0;
835 #ifdef __sparc__
836         if (!strcmp(str, "ttya"))
837                 strcpy(buf, "ttyS0");
838         if (!strcmp(str, "ttyb"))
839                 strcpy(buf, "ttyS1");
840 #endif
841         for (s = buf; *s; s++)
842                 if ((*s >= '0' && *s <= '9') || *s == ',')
843                         break;
844         idx = simple_strtoul(s, NULL, 10);
845         *s = 0;
846
847         __add_preferred_console(buf, idx, options, brl_options);
848         console_set_on_cmdline = 1;
849         return 1;
850 }
851 __setup("console=", console_setup);
852
853 /**
854  * add_preferred_console - add a device to the list of preferred consoles.
855  * @name: device name
856  * @idx: device index
857  * @options: options for this console
858  *
859  * The last preferred console added will be used for kernel messages
860  * and stdin/out/err for init.  Normally this is used by console_setup
861  * above to handle user-supplied console arguments; however it can also
862  * be used by arch-specific code either to override the user or more
863  * commonly to provide a default console (ie from PROM variables) when
864  * the user has not supplied one.
865  */
866 int add_preferred_console(char *name, int idx, char *options)
867 {
868         return __add_preferred_console(name, idx, options, NULL);
869 }
870
871 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
872 {
873         struct console_cmdline *c;
874         int i;
875
876         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
877                 if (strcmp(console_cmdline[i].name, name) == 0 &&
878                           console_cmdline[i].index == idx) {
879                                 c = &console_cmdline[i];
880                                 strlcpy(c->name, name_new, sizeof(c->name));
881                                 c->name[sizeof(c->name) - 1] = 0;
882                                 c->options = options;
883                                 c->index = idx_new;
884                                 return i;
885                 }
886         /* not found */
887         return -1;
888 }
889
890 int console_suspend_enabled = 1;
891 EXPORT_SYMBOL(console_suspend_enabled);
892
893 static int __init console_suspend_disable(char *str)
894 {
895         console_suspend_enabled = 0;
896         return 1;
897 }
898 __setup("no_console_suspend", console_suspend_disable);
899
900 /**
901  * suspend_console - suspend the console subsystem
902  *
903  * This disables printk() while we go into suspend states
904  */
905 void suspend_console(void)
906 {
907         if (!console_suspend_enabled)
908                 return;
909         printk("Suspending console(s) (use no_console_suspend to debug)\n");
910         acquire_console_sem();
911         console_suspended = 1;
912         up(&console_sem);
913 }
914
915 void resume_console(void)
916 {
917         if (!console_suspend_enabled)
918                 return;
919         down(&console_sem);
920         console_suspended = 0;
921         release_console_sem();
922 }
923
924 /**
925  * acquire_console_sem - lock the console system for exclusive use.
926  *
927  * Acquires a semaphore which guarantees that the caller has
928  * exclusive access to the console system and the console_drivers list.
929  *
930  * Can sleep, returns nothing.
931  */
932 void acquire_console_sem(void)
933 {
934         BUG_ON(in_interrupt());
935         down(&console_sem);
936         if (console_suspended)
937                 return;
938         console_locked = 1;
939         console_may_schedule = 1;
940 }
941 EXPORT_SYMBOL(acquire_console_sem);
942
943 int try_acquire_console_sem(void)
944 {
945         if (down_trylock(&console_sem))
946                 return -1;
947         if (console_suspended) {
948                 up(&console_sem);
949                 return -1;
950         }
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 static DEFINE_PER_CPU(int, printk_pending);
963
964 void printk_tick(void)
965 {
966         if (__get_cpu_var(printk_pending)) {
967                 __get_cpu_var(printk_pending) = 0;
968                 wake_up_interruptible(&log_wait);
969         }
970 }
971
972 int printk_needs_cpu(int cpu)
973 {
974         return per_cpu(printk_pending, cpu);
975 }
976
977 void wake_up_klogd(void)
978 {
979         if (waitqueue_active(&log_wait))
980                 __raw_get_cpu_var(printk_pending) = 1;
981 }
982
983 /**
984  * release_console_sem - unlock the console system
985  *
986  * Releases the semaphore which the caller holds on the console system
987  * and the console driver list.
988  *
989  * While the semaphore was held, console output may have been buffered
990  * by printk().  If this is the case, release_console_sem() emits
991  * the output prior to releasing the semaphore.
992  *
993  * If there is output waiting for klogd, we wake it up.
994  *
995  * release_console_sem() may be called from any context.
996  */
997 void release_console_sem(void)
998 {
999         unsigned long flags;
1000         unsigned _con_start, _log_end;
1001         unsigned wake_klogd = 0;
1002
1003         if (console_suspended) {
1004                 up(&console_sem);
1005                 return;
1006         }
1007
1008         console_may_schedule = 0;
1009
1010         for ( ; ; ) {
1011                 spin_lock_irqsave(&logbuf_lock, flags);
1012                 wake_klogd |= log_start - log_end;
1013                 if (con_start == log_end)
1014                         break;                  /* Nothing to print */
1015                 _con_start = con_start;
1016                 _log_end = log_end;
1017                 con_start = log_end;            /* Flush */
1018                 spin_unlock(&logbuf_lock);
1019                 stop_critical_timings();        /* don't trace print latency */
1020                 call_console_drivers(_con_start, _log_end);
1021                 start_critical_timings();
1022                 local_irq_restore(flags);
1023         }
1024         console_locked = 0;
1025         up(&console_sem);
1026         spin_unlock_irqrestore(&logbuf_lock, flags);
1027         if (wake_klogd)
1028                 wake_up_klogd();
1029 }
1030 EXPORT_SYMBOL(release_console_sem);
1031
1032 /**
1033  * console_conditional_schedule - yield the CPU if required
1034  *
1035  * If the console code is currently allowed to sleep, and
1036  * if this CPU should yield the CPU to another task, do
1037  * so here.
1038  *
1039  * Must be called within acquire_console_sem().
1040  */
1041 void __sched console_conditional_schedule(void)
1042 {
1043         if (console_may_schedule)
1044                 cond_resched();
1045 }
1046 EXPORT_SYMBOL(console_conditional_schedule);
1047
1048 void console_print(const char *s)
1049 {
1050         printk(KERN_EMERG "%s", s);
1051 }
1052 EXPORT_SYMBOL(console_print);
1053
1054 void console_unblank(void)
1055 {
1056         struct console *c;
1057
1058         /*
1059          * console_unblank can no longer be called in interrupt context unless
1060          * oops_in_progress is set to 1..
1061          */
1062         if (oops_in_progress) {
1063                 if (down_trylock(&console_sem) != 0)
1064                         return;
1065         } else
1066                 acquire_console_sem();
1067
1068         console_locked = 1;
1069         console_may_schedule = 0;
1070         for (c = console_drivers; c != NULL; c = c->next)
1071                 if ((c->flags & CON_ENABLED) && c->unblank)
1072                         c->unblank();
1073         release_console_sem();
1074 }
1075
1076 /*
1077  * Return the console tty driver structure and its associated index
1078  */
1079 struct tty_driver *console_device(int *index)
1080 {
1081         struct console *c;
1082         struct tty_driver *driver = NULL;
1083
1084         acquire_console_sem();
1085         for (c = console_drivers; c != NULL; c = c->next) {
1086                 if (!c->device)
1087                         continue;
1088                 driver = c->device(c, index);
1089                 if (driver)
1090                         break;
1091         }
1092         release_console_sem();
1093         return driver;
1094 }
1095
1096 /*
1097  * Prevent further output on the passed console device so that (for example)
1098  * serial drivers can disable console output before suspending a port, and can
1099  * re-enable output afterwards.
1100  */
1101 void console_stop(struct console *console)
1102 {
1103         acquire_console_sem();
1104         console->flags &= ~CON_ENABLED;
1105         release_console_sem();
1106 }
1107 EXPORT_SYMBOL(console_stop);
1108
1109 void console_start(struct console *console)
1110 {
1111         acquire_console_sem();
1112         console->flags |= CON_ENABLED;
1113         release_console_sem();
1114 }
1115 EXPORT_SYMBOL(console_start);
1116
1117 /*
1118  * The console driver calls this routine during kernel initialization
1119  * to register the console printing procedure with printk() and to
1120  * print any messages that were printed by the kernel before the
1121  * console driver was initialized.
1122  */
1123 void register_console(struct console *console)
1124 {
1125         int i;
1126         unsigned long flags;
1127         struct console *bootconsole = NULL;
1128
1129         if (console_drivers) {
1130                 if (console->flags & CON_BOOT)
1131                         return;
1132                 if (console_drivers->flags & CON_BOOT)
1133                         bootconsole = console_drivers;
1134         }
1135
1136         if (preferred_console < 0 || bootconsole || !console_drivers)
1137                 preferred_console = selected_console;
1138
1139         if (console->early_setup)
1140                 console->early_setup();
1141
1142         /*
1143          *      See if we want to use this console driver. If we
1144          *      didn't select a console we take the first one
1145          *      that registers here.
1146          */
1147         if (preferred_console < 0) {
1148                 if (console->index < 0)
1149                         console->index = 0;
1150                 if (console->setup == NULL ||
1151                     console->setup(console, NULL) == 0) {
1152                         console->flags |= CON_ENABLED;
1153                         if (console->device) {
1154                                 console->flags |= CON_CONSDEV;
1155                                 preferred_console = 0;
1156                         }
1157                 }
1158         }
1159
1160         /*
1161          *      See if this console matches one we selected on
1162          *      the command line.
1163          */
1164         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1165                         i++) {
1166                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1167                         continue;
1168                 if (console->index >= 0 &&
1169                     console->index != console_cmdline[i].index)
1170                         continue;
1171                 if (console->index < 0)
1172                         console->index = console_cmdline[i].index;
1173 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1174                 if (console_cmdline[i].brl_options) {
1175                         console->flags |= CON_BRL;
1176                         braille_register_console(console,
1177                                         console_cmdline[i].index,
1178                                         console_cmdline[i].options,
1179                                         console_cmdline[i].brl_options);
1180                         return;
1181                 }
1182 #endif
1183                 if (console->setup &&
1184                     console->setup(console, console_cmdline[i].options) != 0)
1185                         break;
1186                 console->flags |= CON_ENABLED;
1187                 console->index = console_cmdline[i].index;
1188                 if (i == selected_console) {
1189                         console->flags |= CON_CONSDEV;
1190                         preferred_console = selected_console;
1191                 }
1192                 break;
1193         }
1194
1195         if (!(console->flags & CON_ENABLED))
1196                 return;
1197
1198         if (bootconsole && (console->flags & CON_CONSDEV)) {
1199                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1200                        bootconsole->name, bootconsole->index,
1201                        console->name, console->index);
1202                 unregister_console(bootconsole);
1203                 console->flags &= ~CON_PRINTBUFFER;
1204         } else {
1205                 printk(KERN_INFO "console [%s%d] enabled\n",
1206                        console->name, console->index);
1207         }
1208
1209         /*
1210          *      Put this console in the list - keep the
1211          *      preferred driver at the head of the list.
1212          */
1213         acquire_console_sem();
1214         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1215                 console->next = console_drivers;
1216                 console_drivers = console;
1217                 if (console->next)
1218                         console->next->flags &= ~CON_CONSDEV;
1219         } else {
1220                 console->next = console_drivers->next;
1221                 console_drivers->next = console;
1222         }
1223         if (console->flags & CON_PRINTBUFFER) {
1224                 /*
1225                  * release_console_sem() will print out the buffered messages
1226                  * for us.
1227                  */
1228                 spin_lock_irqsave(&logbuf_lock, flags);
1229                 con_start = log_start;
1230                 spin_unlock_irqrestore(&logbuf_lock, flags);
1231         }
1232         release_console_sem();
1233 }
1234 EXPORT_SYMBOL(register_console);
1235
1236 int unregister_console(struct console *console)
1237 {
1238         struct console *a, *b;
1239         int res = 1;
1240
1241 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1242         if (console->flags & CON_BRL)
1243                 return braille_unregister_console(console);
1244 #endif
1245
1246         acquire_console_sem();
1247         if (console_drivers == console) {
1248                 console_drivers=console->next;
1249                 res = 0;
1250         } else if (console_drivers) {
1251                 for (a=console_drivers->next, b=console_drivers ;
1252                      a; b=a, a=b->next) {
1253                         if (a == console) {
1254                                 b->next = a->next;
1255                                 res = 0;
1256                                 break;
1257                         }
1258                 }
1259         }
1260
1261         /*
1262          * If this isn't the last console and it has CON_CONSDEV set, we
1263          * need to set it on the next preferred console.
1264          */
1265         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1266                 console_drivers->flags |= CON_CONSDEV;
1267
1268         release_console_sem();
1269         return res;
1270 }
1271 EXPORT_SYMBOL(unregister_console);
1272
1273 static int __init disable_boot_consoles(void)
1274 {
1275         if (console_drivers != NULL) {
1276                 if (console_drivers->flags & CON_BOOT) {
1277                         printk(KERN_INFO "turn off boot console %s%d\n",
1278                                 console_drivers->name, console_drivers->index);
1279                         return unregister_console(console_drivers);
1280                 }
1281         }
1282         return 0;
1283 }
1284 late_initcall(disable_boot_consoles);
1285
1286 #if defined CONFIG_PRINTK
1287
1288 /*
1289  * printk rate limiting, lifted from the networking subsystem.
1290  *
1291  * This enforces a rate limit: not more than 10 kernel messages
1292  * every 5s to make a denial-of-service attack impossible.
1293  */
1294 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1295
1296 int printk_ratelimit(void)
1297 {
1298         return __ratelimit(&printk_ratelimit_state);
1299 }
1300 EXPORT_SYMBOL(printk_ratelimit);
1301
1302 /**
1303  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1304  * @caller_jiffies: pointer to caller's state
1305  * @interval_msecs: minimum interval between prints
1306  *
1307  * printk_timed_ratelimit() returns true if more than @interval_msecs
1308  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1309  * returned true.
1310  */
1311 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1312                         unsigned int interval_msecs)
1313 {
1314         if (*caller_jiffies == 0
1315                         || !time_in_range(jiffies, *caller_jiffies,
1316                                         *caller_jiffies
1317                                         + msecs_to_jiffies(interval_msecs))) {
1318                 *caller_jiffies = jiffies;
1319                 return true;
1320         }
1321         return false;
1322 }
1323 EXPORT_SYMBOL(printk_timed_ratelimit);
1324 #endif