printk: Ensure that "console enabled" messages are printed on the console
[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  * for_each_console() allows you to iterate on each console
41  */
42 #define for_each_console(con) \
43         for (con = console_drivers; con != NULL; con = con->next)
44
45 /*
46  * Architectures can override it:
47  */
48 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
49 {
50 }
51
52 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
53
54 /* printk's without a loglevel use this.. */
55 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
56
57 /* We show everything that is MORE important than this.. */
58 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
59 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
60
61 DECLARE_WAIT_QUEUE_HEAD(log_wait);
62
63 int console_printk[4] = {
64         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
65         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
66         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
67         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
68 };
69
70 /*
71  * Low level drivers may need that to know if they can schedule in
72  * their unblank() callback or not. So let's export it.
73  */
74 int oops_in_progress;
75 EXPORT_SYMBOL(oops_in_progress);
76
77 /*
78  * console_sem protects the console_drivers list, and also
79  * provides serialisation for access to the entire console
80  * driver system.
81  */
82 static DECLARE_MUTEX(console_sem);
83 struct console *console_drivers;
84 EXPORT_SYMBOL_GPL(console_drivers);
85
86 /*
87  * This is used for debugging the mess that is the VT code by
88  * keeping track if we have the console semaphore held. It's
89  * definitely not the perfect debug tool (we don't know if _WE_
90  * hold it are racing, but it helps tracking those weird code
91  * path in the console code where we end up in places I want
92  * locked without the console sempahore held
93  */
94 static int console_locked, console_suspended;
95
96 /*
97  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
98  * It is also used in interesting ways to provide interlocking in
99  * release_console_sem().
100  */
101 static DEFINE_SPINLOCK(logbuf_lock);
102
103 #define LOG_BUF_MASK (log_buf_len-1)
104 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
105
106 /*
107  * The indices into log_buf are not constrained to log_buf_len - they
108  * must be masked before subscripting
109  */
110 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
111 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
112 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
113
114 /*
115  *      Array of consoles built from command line options (console=)
116  */
117 struct console_cmdline
118 {
119         char    name[8];                        /* Name of the driver       */
120         int     index;                          /* Minor dev. to use        */
121         char    *options;                       /* Options for the driver   */
122 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
123         char    *brl_options;                   /* Options for braille driver */
124 #endif
125 };
126
127 #define MAX_CMDLINECONSOLES 8
128
129 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
130 static int selected_console = -1;
131 static int preferred_console = -1;
132 int console_set_on_cmdline;
133 EXPORT_SYMBOL(console_set_on_cmdline);
134
135 /* Flag: console code may call schedule() */
136 static int console_may_schedule;
137
138 #ifdef CONFIG_PRINTK
139
140 static char __log_buf[__LOG_BUF_LEN];
141 static char *log_buf = __log_buf;
142 static int log_buf_len = __LOG_BUF_LEN;
143 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
144
145 #ifdef CONFIG_KEXEC
146 /*
147  * This appends the listed symbols to /proc/vmcoreinfo
148  *
149  * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
150  * obtain access to symbols that are otherwise very difficult to locate.  These
151  * symbols are specifically used so that utilities can access and extract the
152  * dmesg log from a vmcore file after a crash.
153  */
154 void log_buf_kexec_setup(void)
155 {
156         VMCOREINFO_SYMBOL(log_buf);
157         VMCOREINFO_SYMBOL(log_end);
158         VMCOREINFO_SYMBOL(log_buf_len);
159         VMCOREINFO_SYMBOL(logged_chars);
160 }
161 #endif
162
163 static int __init log_buf_len_setup(char *str)
164 {
165         unsigned size = memparse(str, &str);
166         unsigned long flags;
167
168         if (size)
169                 size = roundup_pow_of_two(size);
170         if (size > log_buf_len) {
171                 unsigned start, dest_idx, offset;
172                 char *new_log_buf;
173
174                 new_log_buf = alloc_bootmem(size);
175                 if (!new_log_buf) {
176                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
177                         goto out;
178                 }
179
180                 spin_lock_irqsave(&logbuf_lock, flags);
181                 log_buf_len = size;
182                 log_buf = new_log_buf;
183
184                 offset = start = min(con_start, log_start);
185                 dest_idx = 0;
186                 while (start != log_end) {
187                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
188                         start++;
189                         dest_idx++;
190                 }
191                 log_start -= offset;
192                 con_start -= offset;
193                 log_end -= offset;
194                 spin_unlock_irqrestore(&logbuf_lock, flags);
195
196                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
197         }
198 out:
199         return 1;
200 }
201
202 __setup("log_buf_len=", log_buf_len_setup);
203
204 #ifdef CONFIG_BOOT_PRINTK_DELAY
205
206 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
207 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
208
209 static int __init boot_delay_setup(char *str)
210 {
211         unsigned long lpj;
212         unsigned long long loops_per_msec;
213
214         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
215         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
216
217         get_option(&str, &boot_delay);
218         if (boot_delay > 10 * 1000)
219                 boot_delay = 0;
220
221         printk_delay_msec = loops_per_msec;
222         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
223                 "HZ: %d, printk_delay_msec: %llu\n",
224                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
225         return 1;
226 }
227 __setup("boot_delay=", boot_delay_setup);
228
229 static void boot_delay_msec(void)
230 {
231         unsigned long long k;
232         unsigned long timeout;
233
234         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
235                 return;
236
237         k = (unsigned long long)printk_delay_msec * boot_delay;
238
239         timeout = jiffies + msecs_to_jiffies(boot_delay);
240         while (k) {
241                 k--;
242                 cpu_relax();
243                 /*
244                  * use (volatile) jiffies to prevent
245                  * compiler reduction; loop termination via jiffies
246                  * is secondary and may or may not happen.
247                  */
248                 if (time_after(jiffies, timeout))
249                         break;
250                 touch_nmi_watchdog();
251         }
252 }
253 #else
254 static inline void boot_delay_msec(void)
255 {
256 }
257 #endif
258
259 /*
260  * Commands to do_syslog:
261  *
262  *      0 -- Close the log.  Currently a NOP.
263  *      1 -- Open the log. Currently a NOP.
264  *      2 -- Read from the log.
265  *      3 -- Read all messages remaining in the ring buffer.
266  *      4 -- Read and clear all messages remaining in the ring buffer
267  *      5 -- Clear ring buffer.
268  *      6 -- Disable printk's to console
269  *      7 -- Enable printk's to console
270  *      8 -- Set level of messages printed to console
271  *      9 -- Return number of unread characters in the log buffer
272  *     10 -- Return size of the log buffer
273  */
274 int do_syslog(int type, char __user *buf, int len)
275 {
276         unsigned i, j, limit, count;
277         int do_clear = 0;
278         char c;
279         int error = 0;
280
281         error = security_syslog(type);
282         if (error)
283                 return error;
284
285         switch (type) {
286         case 0:         /* Close log */
287                 break;
288         case 1:         /* Open log */
289                 break;
290         case 2:         /* Read from log */
291                 error = -EINVAL;
292                 if (!buf || len < 0)
293                         goto out;
294                 error = 0;
295                 if (!len)
296                         goto out;
297                 if (!access_ok(VERIFY_WRITE, buf, len)) {
298                         error = -EFAULT;
299                         goto out;
300                 }
301                 error = wait_event_interruptible(log_wait,
302                                                         (log_start - log_end));
303                 if (error)
304                         goto out;
305                 i = 0;
306                 spin_lock_irq(&logbuf_lock);
307                 while (!error && (log_start != log_end) && i < len) {
308                         c = LOG_BUF(log_start);
309                         log_start++;
310                         spin_unlock_irq(&logbuf_lock);
311                         error = __put_user(c,buf);
312                         buf++;
313                         i++;
314                         cond_resched();
315                         spin_lock_irq(&logbuf_lock);
316                 }
317                 spin_unlock_irq(&logbuf_lock);
318                 if (!error)
319                         error = i;
320                 break;
321         case 4:         /* Read/clear last kernel messages */
322                 do_clear = 1;
323                 /* FALL THRU */
324         case 3:         /* Read last kernel messages */
325                 error = -EINVAL;
326                 if (!buf || len < 0)
327                         goto out;
328                 error = 0;
329                 if (!len)
330                         goto out;
331                 if (!access_ok(VERIFY_WRITE, buf, len)) {
332                         error = -EFAULT;
333                         goto out;
334                 }
335                 count = len;
336                 if (count > log_buf_len)
337                         count = log_buf_len;
338                 spin_lock_irq(&logbuf_lock);
339                 if (count > logged_chars)
340                         count = logged_chars;
341                 if (do_clear)
342                         logged_chars = 0;
343                 limit = log_end;
344                 /*
345                  * __put_user() could sleep, and while we sleep
346                  * printk() could overwrite the messages
347                  * we try to copy to user space. Therefore
348                  * the messages are copied in reverse. <manfreds>
349                  */
350                 for (i = 0; i < count && !error; i++) {
351                         j = limit-1-i;
352                         if (j + log_buf_len < log_end)
353                                 break;
354                         c = LOG_BUF(j);
355                         spin_unlock_irq(&logbuf_lock);
356                         error = __put_user(c,&buf[count-1-i]);
357                         cond_resched();
358                         spin_lock_irq(&logbuf_lock);
359                 }
360                 spin_unlock_irq(&logbuf_lock);
361                 if (error)
362                         break;
363                 error = i;
364                 if (i != count) {
365                         int offset = count-error;
366                         /* buffer overflow during copy, correct user buffer. */
367                         for (i = 0; i < error; i++) {
368                                 if (__get_user(c,&buf[i+offset]) ||
369                                     __put_user(c,&buf[i])) {
370                                         error = -EFAULT;
371                                         break;
372                                 }
373                                 cond_resched();
374                         }
375                 }
376                 break;
377         case 5:         /* Clear ring buffer */
378                 logged_chars = 0;
379                 break;
380         case 6:         /* Disable logging to console */
381                 console_loglevel = minimum_console_loglevel;
382                 break;
383         case 7:         /* Enable logging to console */
384                 console_loglevel = default_console_loglevel;
385                 break;
386         case 8:         /* Set level of messages printed to console */
387                 error = -EINVAL;
388                 if (len < 1 || len > 8)
389                         goto out;
390                 if (len < minimum_console_loglevel)
391                         len = minimum_console_loglevel;
392                 console_loglevel = len;
393                 error = 0;
394                 break;
395         case 9:         /* Number of chars in the log buffer */
396                 error = log_end - log_start;
397                 break;
398         case 10:        /* Size of the log buffer */
399                 error = log_buf_len;
400                 break;
401         default:
402                 error = -EINVAL;
403                 break;
404         }
405 out:
406         return error;
407 }
408
409 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
410 {
411         return do_syslog(type, buf, len);
412 }
413
414 /*
415  * Call the console drivers on a range of log_buf
416  */
417 static void __call_console_drivers(unsigned start, unsigned end)
418 {
419         struct console *con;
420
421         for_each_console(con) {
422                 if ((con->flags & CON_ENABLED) && con->write &&
423                                 (cpu_online(smp_processor_id()) ||
424                                 (con->flags & CON_ANYTIME)))
425                         con->write(con, &LOG_BUF(start), end - start);
426         }
427 }
428
429 static int __read_mostly ignore_loglevel;
430
431 static int __init ignore_loglevel_setup(char *str)
432 {
433         ignore_loglevel = 1;
434         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
435
436         return 0;
437 }
438
439 early_param("ignore_loglevel", ignore_loglevel_setup);
440
441 /*
442  * Write out chars from start to end - 1 inclusive
443  */
444 static void _call_console_drivers(unsigned start,
445                                 unsigned end, int msg_log_level)
446 {
447         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
448                         console_drivers && start != end) {
449                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
450                         /* wrapped write */
451                         __call_console_drivers(start & LOG_BUF_MASK,
452                                                 log_buf_len);
453                         __call_console_drivers(0, end & LOG_BUF_MASK);
454                 } else {
455                         __call_console_drivers(start, end);
456                 }
457         }
458 }
459
460 /*
461  * Call the console drivers, asking them to write out
462  * log_buf[start] to log_buf[end - 1].
463  * The console_sem must be held.
464  */
465 static void call_console_drivers(unsigned start, unsigned end)
466 {
467         unsigned cur_index, start_print;
468         static int msg_level = -1;
469
470         BUG_ON(((int)(start - end)) > 0);
471
472         cur_index = start;
473         start_print = start;
474         while (cur_index != end) {
475                 if (msg_level < 0 && ((end - cur_index) > 2) &&
476                                 LOG_BUF(cur_index + 0) == '<' &&
477                                 LOG_BUF(cur_index + 1) >= '0' &&
478                                 LOG_BUF(cur_index + 1) <= '7' &&
479                                 LOG_BUF(cur_index + 2) == '>') {
480                         msg_level = LOG_BUF(cur_index + 1) - '0';
481                         cur_index += 3;
482                         start_print = cur_index;
483                 }
484                 while (cur_index != end) {
485                         char c = LOG_BUF(cur_index);
486
487                         cur_index++;
488                         if (c == '\n') {
489                                 if (msg_level < 0) {
490                                         /*
491                                          * printk() has already given us loglevel tags in
492                                          * the buffer.  This code is here in case the
493                                          * log buffer has wrapped right round and scribbled
494                                          * on those tags
495                                          */
496                                         msg_level = default_message_loglevel;
497                                 }
498                                 _call_console_drivers(start_print, cur_index, msg_level);
499                                 msg_level = -1;
500                                 start_print = cur_index;
501                                 break;
502                         }
503                 }
504         }
505         _call_console_drivers(start_print, end, msg_level);
506 }
507
508 static void emit_log_char(char c)
509 {
510         LOG_BUF(log_end) = c;
511         log_end++;
512         if (log_end - log_start > log_buf_len)
513                 log_start = log_end - log_buf_len;
514         if (log_end - con_start > log_buf_len)
515                 con_start = log_end - log_buf_len;
516         if (logged_chars < log_buf_len)
517                 logged_chars++;
518 }
519
520 /*
521  * Zap console related locks when oopsing. Only zap at most once
522  * every 10 seconds, to leave time for slow consoles to print a
523  * full oops.
524  */
525 static void zap_locks(void)
526 {
527         static unsigned long oops_timestamp;
528
529         if (time_after_eq(jiffies, oops_timestamp) &&
530                         !time_after(jiffies, oops_timestamp + 30 * HZ))
531                 return;
532
533         oops_timestamp = jiffies;
534
535         /* If a crash is occurring, make sure we can't deadlock */
536         spin_lock_init(&logbuf_lock);
537         /* And make sure that we print immediately */
538         init_MUTEX(&console_sem);
539 }
540
541 #if defined(CONFIG_PRINTK_TIME)
542 static int printk_time = 1;
543 #else
544 static int printk_time = 0;
545 #endif
546 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
547
548 /* Check if we have any console registered that can be called early in boot. */
549 static int have_callable_console(void)
550 {
551         struct console *con;
552
553         for_each_console(con)
554                 if (con->flags & CON_ANYTIME)
555                         return 1;
556
557         return 0;
558 }
559
560 /**
561  * printk - print a kernel message
562  * @fmt: format string
563  *
564  * This is printk().  It can be called from any context.  We want it to work.
565  *
566  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
567  * call the console drivers.  If we fail to get the semaphore we place the output
568  * into the log buffer and return.  The current holder of the console_sem will
569  * notice the new output in release_console_sem() and will send it to the
570  * consoles before releasing the semaphore.
571  *
572  * One effect of this deferred printing is that code which calls printk() and
573  * then changes console_loglevel may break. This is because console_loglevel
574  * is inspected when the actual printing occurs.
575  *
576  * See also:
577  * printf(3)
578  *
579  * See the vsnprintf() documentation for format string extensions over C99.
580  */
581
582 asmlinkage int printk(const char *fmt, ...)
583 {
584         va_list args;
585         int r;
586
587         va_start(args, fmt);
588         r = vprintk(fmt, args);
589         va_end(args);
590
591         return r;
592 }
593
594 /* cpu currently holding logbuf_lock */
595 static volatile unsigned int printk_cpu = UINT_MAX;
596
597 /*
598  * Can we actually use the console at this time on this cpu?
599  *
600  * Console drivers may assume that per-cpu resources have
601  * been allocated. So unless they're explicitly marked as
602  * being able to cope (CON_ANYTIME) don't call them until
603  * this CPU is officially up.
604  */
605 static inline int can_use_console(unsigned int cpu)
606 {
607         return cpu_online(cpu) || have_callable_console();
608 }
609
610 /*
611  * Try to get console ownership to actually show the kernel
612  * messages from a 'printk'. Return true (and with the
613  * console_semaphore held, and 'console_locked' set) if it
614  * is successful, false otherwise.
615  *
616  * This gets called with the 'logbuf_lock' spinlock held and
617  * interrupts disabled. It should return with 'lockbuf_lock'
618  * released but interrupts still disabled.
619  */
620 static int acquire_console_semaphore_for_printk(unsigned int cpu)
621 {
622         int retval = 0;
623
624         if (!try_acquire_console_sem()) {
625                 retval = 1;
626
627                 /*
628                  * If we can't use the console, we need to release
629                  * the console semaphore by hand to avoid flushing
630                  * the buffer. We need to hold the console semaphore
631                  * in order to do this test safely.
632                  */
633                 if (!can_use_console(cpu)) {
634                         console_locked = 0;
635                         up(&console_sem);
636                         retval = 0;
637                 }
638         }
639         printk_cpu = UINT_MAX;
640         spin_unlock(&logbuf_lock);
641         return retval;
642 }
643 static const char recursion_bug_msg [] =
644                 KERN_CRIT "BUG: recent printk recursion!\n";
645 static int recursion_bug;
646 static int new_text_line = 1;
647 static char printk_buf[1024];
648
649 asmlinkage int vprintk(const char *fmt, va_list args)
650 {
651         int printed_len = 0;
652         int current_log_level = default_message_loglevel;
653         unsigned long flags;
654         int this_cpu;
655         char *p;
656
657         boot_delay_msec();
658
659         preempt_disable();
660         /* This stops the holder of console_sem just where we want him */
661         raw_local_irq_save(flags);
662         this_cpu = smp_processor_id();
663
664         /*
665          * Ouch, printk recursed into itself!
666          */
667         if (unlikely(printk_cpu == this_cpu)) {
668                 /*
669                  * If a crash is occurring during printk() on this CPU,
670                  * then try to get the crash message out but make sure
671                  * we can't deadlock. Otherwise just return to avoid the
672                  * recursion and return - but flag the recursion so that
673                  * it can be printed at the next appropriate moment:
674                  */
675                 if (!oops_in_progress) {
676                         recursion_bug = 1;
677                         goto out_restore_irqs;
678                 }
679                 zap_locks();
680         }
681
682         lockdep_off();
683         spin_lock(&logbuf_lock);
684         printk_cpu = this_cpu;
685
686         if (recursion_bug) {
687                 recursion_bug = 0;
688                 strcpy(printk_buf, recursion_bug_msg);
689                 printed_len = strlen(recursion_bug_msg);
690         }
691         /* Emit the output into the temporary buffer */
692         printed_len += vscnprintf(printk_buf + printed_len,
693                                   sizeof(printk_buf) - printed_len, fmt, args);
694
695
696         p = printk_buf;
697
698         /* Do we have a loglevel in the string? */
699         if (p[0] == '<') {
700                 unsigned char c = p[1];
701                 if (c && p[2] == '>') {
702                         switch (c) {
703                         case '0' ... '7': /* loglevel */
704                                 current_log_level = c - '0';
705                         /* Fallthrough - make sure we're on a new line */
706                         case 'd': /* KERN_DEFAULT */
707                                 if (!new_text_line) {
708                                         emit_log_char('\n');
709                                         new_text_line = 1;
710                                 }
711                         /* Fallthrough - skip the loglevel */
712                         case 'c': /* KERN_CONT */
713                                 p += 3;
714                                 break;
715                         }
716                 }
717         }
718
719         /*
720          * Copy the output into log_buf.  If the caller didn't provide
721          * appropriate log level tags, we insert them here
722          */
723         for ( ; *p; p++) {
724                 if (new_text_line) {
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 static void call_console_drivers(unsigned start, unsigned end)
785 {
786 }
787
788 #endif
789
790 static int __add_preferred_console(char *name, int idx, char *options,
791                                    char *brl_options)
792 {
793         struct console_cmdline *c;
794         int i;
795
796         /*
797          *      See if this tty is not yet registered, and
798          *      if we have a slot free.
799          */
800         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
801                 if (strcmp(console_cmdline[i].name, name) == 0 &&
802                           console_cmdline[i].index == idx) {
803                                 if (!brl_options)
804                                         selected_console = i;
805                                 return 0;
806                 }
807         if (i == MAX_CMDLINECONSOLES)
808                 return -E2BIG;
809         if (!brl_options)
810                 selected_console = i;
811         c = &console_cmdline[i];
812         strlcpy(c->name, name, sizeof(c->name));
813         c->options = options;
814 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
815         c->brl_options = brl_options;
816 #endif
817         c->index = idx;
818         return 0;
819 }
820 /*
821  * Set up a list of consoles.  Called from init/main.c
822  */
823 static int __init console_setup(char *str)
824 {
825         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
826         char *s, *options, *brl_options = NULL;
827         int idx;
828
829 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
830         if (!memcmp(str, "brl,", 4)) {
831                 brl_options = "";
832                 str += 4;
833         } else if (!memcmp(str, "brl=", 4)) {
834                 brl_options = str + 4;
835                 str = strchr(brl_options, ',');
836                 if (!str) {
837                         printk(KERN_ERR "need port name after brl=\n");
838                         return 1;
839                 }
840                 *(str++) = 0;
841         }
842 #endif
843
844         /*
845          * Decode str into name, index, options.
846          */
847         if (str[0] >= '0' && str[0] <= '9') {
848                 strcpy(buf, "ttyS");
849                 strncpy(buf + 4, str, sizeof(buf) - 5);
850         } else {
851                 strncpy(buf, str, sizeof(buf) - 1);
852         }
853         buf[sizeof(buf) - 1] = 0;
854         if ((options = strchr(str, ',')) != NULL)
855                 *(options++) = 0;
856 #ifdef __sparc__
857         if (!strcmp(str, "ttya"))
858                 strcpy(buf, "ttyS0");
859         if (!strcmp(str, "ttyb"))
860                 strcpy(buf, "ttyS1");
861 #endif
862         for (s = buf; *s; s++)
863                 if ((*s >= '0' && *s <= '9') || *s == ',')
864                         break;
865         idx = simple_strtoul(s, NULL, 10);
866         *s = 0;
867
868         __add_preferred_console(buf, idx, options, brl_options);
869         console_set_on_cmdline = 1;
870         return 1;
871 }
872 __setup("console=", console_setup);
873
874 /**
875  * add_preferred_console - add a device to the list of preferred consoles.
876  * @name: device name
877  * @idx: device index
878  * @options: options for this console
879  *
880  * The last preferred console added will be used for kernel messages
881  * and stdin/out/err for init.  Normally this is used by console_setup
882  * above to handle user-supplied console arguments; however it can also
883  * be used by arch-specific code either to override the user or more
884  * commonly to provide a default console (ie from PROM variables) when
885  * the user has not supplied one.
886  */
887 int add_preferred_console(char *name, int idx, char *options)
888 {
889         return __add_preferred_console(name, idx, options, NULL);
890 }
891
892 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
893 {
894         struct console_cmdline *c;
895         int i;
896
897         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
898                 if (strcmp(console_cmdline[i].name, name) == 0 &&
899                           console_cmdline[i].index == idx) {
900                                 c = &console_cmdline[i];
901                                 strlcpy(c->name, name_new, sizeof(c->name));
902                                 c->name[sizeof(c->name) - 1] = 0;
903                                 c->options = options;
904                                 c->index = idx_new;
905                                 return i;
906                 }
907         /* not found */
908         return -1;
909 }
910
911 int console_suspend_enabled = 1;
912 EXPORT_SYMBOL(console_suspend_enabled);
913
914 static int __init console_suspend_disable(char *str)
915 {
916         console_suspend_enabled = 0;
917         return 1;
918 }
919 __setup("no_console_suspend", console_suspend_disable);
920
921 /**
922  * suspend_console - suspend the console subsystem
923  *
924  * This disables printk() while we go into suspend states
925  */
926 void suspend_console(void)
927 {
928         if (!console_suspend_enabled)
929                 return;
930         printk("Suspending console(s) (use no_console_suspend to debug)\n");
931         acquire_console_sem();
932         console_suspended = 1;
933         up(&console_sem);
934 }
935
936 void resume_console(void)
937 {
938         if (!console_suspend_enabled)
939                 return;
940         down(&console_sem);
941         console_suspended = 0;
942         release_console_sem();
943 }
944
945 /**
946  * acquire_console_sem - lock the console system for exclusive use.
947  *
948  * Acquires a semaphore which guarantees that the caller has
949  * exclusive access to the console system and the console_drivers list.
950  *
951  * Can sleep, returns nothing.
952  */
953 void acquire_console_sem(void)
954 {
955         BUG_ON(in_interrupt());
956         down(&console_sem);
957         if (console_suspended)
958                 return;
959         console_locked = 1;
960         console_may_schedule = 1;
961 }
962 EXPORT_SYMBOL(acquire_console_sem);
963
964 int try_acquire_console_sem(void)
965 {
966         if (down_trylock(&console_sem))
967                 return -1;
968         if (console_suspended) {
969                 up(&console_sem);
970                 return -1;
971         }
972         console_locked = 1;
973         console_may_schedule = 0;
974         return 0;
975 }
976 EXPORT_SYMBOL(try_acquire_console_sem);
977
978 int is_console_locked(void)
979 {
980         return console_locked;
981 }
982
983 static DEFINE_PER_CPU(int, printk_pending);
984
985 void printk_tick(void)
986 {
987         if (__get_cpu_var(printk_pending)) {
988                 __get_cpu_var(printk_pending) = 0;
989                 wake_up_interruptible(&log_wait);
990         }
991 }
992
993 int printk_needs_cpu(int cpu)
994 {
995         return per_cpu(printk_pending, cpu);
996 }
997
998 void wake_up_klogd(void)
999 {
1000         if (waitqueue_active(&log_wait))
1001                 __raw_get_cpu_var(printk_pending) = 1;
1002 }
1003
1004 /**
1005  * release_console_sem - unlock the console system
1006  *
1007  * Releases the semaphore which the caller holds on the console system
1008  * and the console driver list.
1009  *
1010  * While the semaphore was held, console output may have been buffered
1011  * by printk().  If this is the case, release_console_sem() emits
1012  * the output prior to releasing the semaphore.
1013  *
1014  * If there is output waiting for klogd, we wake it up.
1015  *
1016  * release_console_sem() may be called from any context.
1017  */
1018 void release_console_sem(void)
1019 {
1020         unsigned long flags;
1021         unsigned _con_start, _log_end;
1022         unsigned wake_klogd = 0;
1023
1024         if (console_suspended) {
1025                 up(&console_sem);
1026                 return;
1027         }
1028
1029         console_may_schedule = 0;
1030
1031         for ( ; ; ) {
1032                 spin_lock_irqsave(&logbuf_lock, flags);
1033                 wake_klogd |= log_start - log_end;
1034                 if (con_start == log_end)
1035                         break;                  /* Nothing to print */
1036                 _con_start = con_start;
1037                 _log_end = log_end;
1038                 con_start = log_end;            /* Flush */
1039                 spin_unlock(&logbuf_lock);
1040                 stop_critical_timings();        /* don't trace print latency */
1041                 call_console_drivers(_con_start, _log_end);
1042                 start_critical_timings();
1043                 local_irq_restore(flags);
1044         }
1045         console_locked = 0;
1046         up(&console_sem);
1047         spin_unlock_irqrestore(&logbuf_lock, flags);
1048         if (wake_klogd)
1049                 wake_up_klogd();
1050 }
1051 EXPORT_SYMBOL(release_console_sem);
1052
1053 /**
1054  * console_conditional_schedule - yield the CPU if required
1055  *
1056  * If the console code is currently allowed to sleep, and
1057  * if this CPU should yield the CPU to another task, do
1058  * so here.
1059  *
1060  * Must be called within acquire_console_sem().
1061  */
1062 void __sched console_conditional_schedule(void)
1063 {
1064         if (console_may_schedule)
1065                 cond_resched();
1066 }
1067 EXPORT_SYMBOL(console_conditional_schedule);
1068
1069 void console_print(const char *s)
1070 {
1071         printk(KERN_EMERG "%s", s);
1072 }
1073 EXPORT_SYMBOL(console_print);
1074
1075 void console_unblank(void)
1076 {
1077         struct console *c;
1078
1079         /*
1080          * console_unblank can no longer be called in interrupt context unless
1081          * oops_in_progress is set to 1..
1082          */
1083         if (oops_in_progress) {
1084                 if (down_trylock(&console_sem) != 0)
1085                         return;
1086         } else
1087                 acquire_console_sem();
1088
1089         console_locked = 1;
1090         console_may_schedule = 0;
1091         for_each_console(c)
1092                 if ((c->flags & CON_ENABLED) && c->unblank)
1093                         c->unblank();
1094         release_console_sem();
1095 }
1096
1097 /*
1098  * Return the console tty driver structure and its associated index
1099  */
1100 struct tty_driver *console_device(int *index)
1101 {
1102         struct console *c;
1103         struct tty_driver *driver = NULL;
1104
1105         acquire_console_sem();
1106         for_each_console(c) {
1107                 if (!c->device)
1108                         continue;
1109                 driver = c->device(c, index);
1110                 if (driver)
1111                         break;
1112         }
1113         release_console_sem();
1114         return driver;
1115 }
1116
1117 /*
1118  * Prevent further output on the passed console device so that (for example)
1119  * serial drivers can disable console output before suspending a port, and can
1120  * re-enable output afterwards.
1121  */
1122 void console_stop(struct console *console)
1123 {
1124         acquire_console_sem();
1125         console->flags &= ~CON_ENABLED;
1126         release_console_sem();
1127 }
1128 EXPORT_SYMBOL(console_stop);
1129
1130 void console_start(struct console *console)
1131 {
1132         acquire_console_sem();
1133         console->flags |= CON_ENABLED;
1134         release_console_sem();
1135 }
1136 EXPORT_SYMBOL(console_start);
1137
1138 /*
1139  * The console driver calls this routine during kernel initialization
1140  * to register the console printing procedure with printk() and to
1141  * print any messages that were printed by the kernel before the
1142  * console driver was initialized.
1143  *
1144  * This can happen pretty early during the boot process (because of
1145  * early_printk) - sometimes before setup_arch() completes - be careful
1146  * of what kernel features are used - they may not be initialised yet.
1147  *
1148  * There are two types of consoles - bootconsoles (early_printk) and
1149  * "real" consoles (everything which is not a bootconsole) which are
1150  * handled differently.
1151  *  - Any number of bootconsoles can be registered at any time.
1152  *  - As soon as a "real" console is registered, all bootconsoles
1153  *    will be unregistered automatically.
1154  *  - Once a "real" console is registered, any attempt to register a
1155  *    bootconsoles will be rejected
1156  */
1157 void register_console(struct console *newcon)
1158 {
1159         int i;
1160         unsigned long flags;
1161         struct console *bcon = NULL;
1162
1163         /*
1164          * before we register a new CON_BOOT console, make sure we don't
1165          * already have a valid console
1166          */
1167         if (console_drivers && newcon->flags & CON_BOOT) {
1168                 /* find the last or real console */
1169                 for_each_console(bcon) {
1170                         if (!(bcon->flags & CON_BOOT)) {
1171                                 printk(KERN_INFO "Too late to register bootconsole %s%d\n",
1172                                         newcon->name, newcon->index);
1173                                 return;
1174                         }
1175                 }
1176         }
1177
1178         if (console_drivers && console_drivers->flags & CON_BOOT)
1179                 bcon = console_drivers;
1180
1181         if (preferred_console < 0 || bcon || !console_drivers)
1182                 preferred_console = selected_console;
1183
1184         if (newcon->early_setup)
1185                 newcon->early_setup();
1186
1187         /*
1188          *      See if we want to use this console driver. If we
1189          *      didn't select a console we take the first one
1190          *      that registers here.
1191          */
1192         if (preferred_console < 0) {
1193                 if (newcon->index < 0)
1194                         newcon->index = 0;
1195                 if (newcon->setup == NULL ||
1196                     newcon->setup(newcon, NULL) == 0) {
1197                         newcon->flags |= CON_ENABLED;
1198                         if (newcon->device) {
1199                                 newcon->flags |= CON_CONSDEV;
1200                                 preferred_console = 0;
1201                         }
1202                 }
1203         }
1204
1205         /*
1206          *      See if this console matches one we selected on
1207          *      the command line.
1208          */
1209         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1210                         i++) {
1211                 if (strcmp(console_cmdline[i].name, newcon->name) != 0)
1212                         continue;
1213                 if (newcon->index >= 0 &&
1214                     newcon->index != console_cmdline[i].index)
1215                         continue;
1216                 if (newcon->index < 0)
1217                         newcon->index = console_cmdline[i].index;
1218 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1219                 if (console_cmdline[i].brl_options) {
1220                         newcon->flags |= CON_BRL;
1221                         braille_register_console(newcon,
1222                                         console_cmdline[i].index,
1223                                         console_cmdline[i].options,
1224                                         console_cmdline[i].brl_options);
1225                         return;
1226                 }
1227 #endif
1228                 if (newcon->setup &&
1229                     newcon->setup(newcon, console_cmdline[i].options) != 0)
1230                         break;
1231                 newcon->flags |= CON_ENABLED;
1232                 newcon->index = console_cmdline[i].index;
1233                 if (i == selected_console) {
1234                         newcon->flags |= CON_CONSDEV;
1235                         preferred_console = selected_console;
1236                 }
1237                 break;
1238         }
1239
1240         if (!(newcon->flags & CON_ENABLED))
1241                 return;
1242
1243         /*
1244          * If we have a bootconsole, and are switching to a real console,
1245          * don't print everything out again, since when the boot console, and
1246          * the real console are the same physical device, it's annoying to
1247          * see the beginning boot messages twice
1248          */
1249         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
1250                 newcon->flags &= ~CON_PRINTBUFFER;
1251
1252         /*
1253          *      Put this console in the list - keep the
1254          *      preferred driver at the head of the list.
1255          */
1256         acquire_console_sem();
1257         if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
1258                 newcon->next = console_drivers;
1259                 console_drivers = newcon;
1260                 if (newcon->next)
1261                         newcon->next->flags &= ~CON_CONSDEV;
1262         } else {
1263                 newcon->next = console_drivers->next;
1264                 console_drivers->next = newcon;
1265         }
1266         if (newcon->flags & CON_PRINTBUFFER) {
1267                 /*
1268                  * release_console_sem() will print out the buffered messages
1269                  * for us.
1270                  */
1271                 spin_lock_irqsave(&logbuf_lock, flags);
1272                 con_start = log_start;
1273                 spin_unlock_irqrestore(&logbuf_lock, flags);
1274         }
1275         release_console_sem();
1276
1277         /*
1278          * By unregistering the bootconsoles after we enable the real console
1279          * we get the "console xxx enabled" message on all the consoles -
1280          * boot consoles, real consoles, etc - this is to ensure that end
1281          * users know there might be something in the kernel's log buffer that
1282          * went to the bootconsole (that they do not see on the real console)
1283          */
1284         if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
1285                 /* we need to iterate through twice, to make sure we print
1286                  * everything out, before we unregister the console(s)
1287                  */
1288                 printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
1289                         newcon->name, newcon->index);
1290                 for_each_console(bcon)
1291                         if (bcon->flags & CON_BOOT)
1292                                 unregister_console(bcon);
1293         } else {
1294                 printk(KERN_INFO "%sconsole [%s%d] enabled\n",
1295                         (newcon->flags & CON_BOOT) ? "boot" : "" ,
1296                         newcon->name, newcon->index);
1297         }
1298 }
1299 EXPORT_SYMBOL(register_console);
1300
1301 int unregister_console(struct console *console)
1302 {
1303         struct console *a, *b;
1304         int res = 1;
1305
1306 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1307         if (console->flags & CON_BRL)
1308                 return braille_unregister_console(console);
1309 #endif
1310
1311         acquire_console_sem();
1312         if (console_drivers == console) {
1313                 console_drivers=console->next;
1314                 res = 0;
1315         } else if (console_drivers) {
1316                 for (a=console_drivers->next, b=console_drivers ;
1317                      a; b=a, a=b->next) {
1318                         if (a == console) {
1319                                 b->next = a->next;
1320                                 res = 0;
1321                                 break;
1322                         }
1323                 }
1324         }
1325
1326         /*
1327          * If this isn't the last console and it has CON_CONSDEV set, we
1328          * need to set it on the next preferred console.
1329          */
1330         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1331                 console_drivers->flags |= CON_CONSDEV;
1332
1333         release_console_sem();
1334         return res;
1335 }
1336 EXPORT_SYMBOL(unregister_console);
1337
1338 static int __init disable_boot_consoles(void)
1339 {
1340         struct console *con;
1341
1342         for_each_console(con) {
1343                 if (con->flags & CON_BOOT) {
1344                         printk(KERN_INFO "turn off boot console %s%d\n",
1345                                 con->name, con->index);
1346                         return unregister_console(con);
1347                 }
1348         }
1349         return 0;
1350 }
1351 late_initcall(disable_boot_consoles);
1352
1353 #if defined CONFIG_PRINTK
1354
1355 /*
1356  * printk rate limiting, lifted from the networking subsystem.
1357  *
1358  * This enforces a rate limit: not more than 10 kernel messages
1359  * every 5s to make a denial-of-service attack impossible.
1360  */
1361 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1362
1363 int printk_ratelimit(void)
1364 {
1365         return __ratelimit(&printk_ratelimit_state);
1366 }
1367 EXPORT_SYMBOL(printk_ratelimit);
1368
1369 /**
1370  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1371  * @caller_jiffies: pointer to caller's state
1372  * @interval_msecs: minimum interval between prints
1373  *
1374  * printk_timed_ratelimit() returns true if more than @interval_msecs
1375  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1376  * returned true.
1377  */
1378 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1379                         unsigned int interval_msecs)
1380 {
1381         if (*caller_jiffies == 0
1382                         || !time_in_range(jiffies, *caller_jiffies,
1383                                         *caller_jiffies
1384                                         + msecs_to_jiffies(interval_msecs))) {
1385                 *caller_jiffies = jiffies;
1386                 return true;
1387         }
1388         return false;
1389 }
1390 EXPORT_SYMBOL(printk_timed_ratelimit);
1391 #endif