printk: use ktime_get()
[linux-2.6.git] / kernel / printk.c
1 /*
2  *  linux/kernel/printk.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  *
6  * Modified to make sys_syslog() more flexible: added commands to
7  * return the last 4k of kernel messages, regardless of whether
8  * they've been read or not.  Added option to suppress kernel printk's
9  * to the console.  Added hook for sending the console messages
10  * elsewhere, in preparation for a serial line console (someday).
11  * Ted Ts'o, 2/11/93.
12  * Modified for sysctl support, 1/8/97, Chris Horn.
13  * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14  *     manfred@colorfullife.com
15  * Rewrote bits to get rid of console_lock
16  *      01Mar01 Andrew Morton <andrewm@uow.edu.au>
17  */
18
19 #include <linux/kernel.h>
20 #include <linux/mm.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h>                    /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/syscalls.h>
35 #include <linux/jiffies.h>
36
37 #include <asm/uaccess.h>
38
39 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
40
41 /* printk's without a loglevel use this.. */
42 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
43
44 /* We show everything that is MORE important than this.. */
45 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
46 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
47
48 DECLARE_WAIT_QUEUE_HEAD(log_wait);
49
50 int console_printk[4] = {
51         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
52         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
53         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
54         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
55 };
56
57 /*
58  * Low level drivers may need that to know if they can schedule in
59  * their unblank() callback or not. So let's export it.
60  */
61 int oops_in_progress;
62 EXPORT_SYMBOL(oops_in_progress);
63
64 /*
65  * console_sem protects the console_drivers list, and also
66  * provides serialisation for access to the entire console
67  * driver system.
68  */
69 static DECLARE_MUTEX(console_sem);
70 static DECLARE_MUTEX(secondary_console_sem);
71 struct console *console_drivers;
72 /*
73  * This is used for debugging the mess that is the VT code by
74  * keeping track if we have the console semaphore held. It's
75  * definitely not the perfect debug tool (we don't know if _WE_
76  * hold it are racing, but it helps tracking those weird code
77  * path in the console code where we end up in places I want
78  * locked without the console sempahore held
79  */
80 static int console_locked, console_suspended;
81
82 /*
83  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
84  * It is also used in interesting ways to provide interlocking in
85  * release_console_sem().
86  */
87 static DEFINE_SPINLOCK(logbuf_lock);
88
89 #define LOG_BUF_MASK    (log_buf_len-1)
90 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
91
92 /*
93  * The indices into log_buf are not constrained to log_buf_len - they
94  * must be masked before subscripting
95  */
96 static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */
97 static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */
98 static unsigned long log_end;   /* Index into log_buf: most-recently-written-char + 1 */
99
100 /*
101  *      Array of consoles built from command line options (console=)
102  */
103 struct console_cmdline
104 {
105         char    name[8];                        /* Name of the driver       */
106         int     index;                          /* Minor dev. to use        */
107         char    *options;                       /* Options for the driver   */
108 };
109
110 #define MAX_CMDLINECONSOLES 8
111
112 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
113 static int selected_console = -1;
114 static int preferred_console = -1;
115
116 /* Flag: console code may call schedule() */
117 static int console_may_schedule;
118
119 #ifdef CONFIG_PRINTK
120
121 static char __log_buf[__LOG_BUF_LEN];
122 static char *log_buf = __log_buf;
123 static int log_buf_len = __LOG_BUF_LEN;
124 static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */
125
126 static int __init log_buf_len_setup(char *str)
127 {
128         unsigned long size = memparse(str, &str);
129         unsigned long flags;
130
131         if (size)
132                 size = roundup_pow_of_two(size);
133         if (size > log_buf_len) {
134                 unsigned long start, dest_idx, offset;
135                 char *new_log_buf;
136
137                 new_log_buf = alloc_bootmem(size);
138                 if (!new_log_buf) {
139                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
140                         goto out;
141                 }
142
143                 spin_lock_irqsave(&logbuf_lock, flags);
144                 log_buf_len = size;
145                 log_buf = new_log_buf;
146
147                 offset = start = min(con_start, log_start);
148                 dest_idx = 0;
149                 while (start != log_end) {
150                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
151                         start++;
152                         dest_idx++;
153                 }
154                 log_start -= offset;
155                 con_start -= offset;
156                 log_end -= offset;
157                 spin_unlock_irqrestore(&logbuf_lock, flags);
158
159                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
160         }
161 out:
162         return 1;
163 }
164
165 __setup("log_buf_len=", log_buf_len_setup);
166
167 #ifdef CONFIG_BOOT_PRINTK_DELAY
168
169 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
170 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
171
172 static int __init boot_delay_setup(char *str)
173 {
174         unsigned long lpj;
175         unsigned long long loops_per_msec;
176
177         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
178         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
179
180         get_option(&str, &boot_delay);
181         if (boot_delay > 10 * 1000)
182                 boot_delay = 0;
183
184         printk_delay_msec = loops_per_msec;
185         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
186                 "HZ: %d, printk_delay_msec: %llu\n",
187                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
188         return 1;
189 }
190 __setup("boot_delay=", boot_delay_setup);
191
192 static void boot_delay_msec(void)
193 {
194         unsigned long long k;
195         unsigned long timeout;
196
197         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
198                 return;
199
200         k = (unsigned long long)printk_delay_msec * boot_delay;
201
202         timeout = jiffies + msecs_to_jiffies(boot_delay);
203         while (k) {
204                 k--;
205                 cpu_relax();
206                 /*
207                  * use (volatile) jiffies to prevent
208                  * compiler reduction; loop termination via jiffies
209                  * is secondary and may or may not happen.
210                  */
211                 if (time_after(jiffies, timeout))
212                         break;
213                 touch_nmi_watchdog();
214         }
215 }
216 #else
217 static inline void boot_delay_msec(void)
218 {
219 }
220 #endif
221
222 /*
223  * Return the number of unread characters in the log buffer.
224  */
225 int log_buf_get_len(void)
226 {
227         return logged_chars;
228 }
229
230 /*
231  * Copy a range of characters from the log buffer.
232  */
233 int log_buf_copy(char *dest, int idx, int len)
234 {
235         int ret, max;
236         bool took_lock = false;
237
238         if (!oops_in_progress) {
239                 spin_lock_irq(&logbuf_lock);
240                 took_lock = true;
241         }
242
243         max = log_buf_get_len();
244         if (idx < 0 || idx >= max) {
245                 ret = -1;
246         } else {
247                 if (len > max)
248                         len = max;
249                 ret = len;
250                 idx += (log_end - max);
251                 while (len-- > 0)
252                         dest[len] = LOG_BUF(idx + len);
253         }
254
255         if (took_lock)
256                 spin_unlock_irq(&logbuf_lock);
257
258         return ret;
259 }
260
261 /*
262  * Extract a single character from the log buffer.
263  */
264 int log_buf_read(int idx)
265 {
266         char ret;
267
268         if (log_buf_copy(&ret, idx, 1) == 1)
269                 return ret;
270         else
271                 return -1;
272 }
273
274 /*
275  * Commands to do_syslog:
276  *
277  *      0 -- Close the log.  Currently a NOP.
278  *      1 -- Open the log. Currently a NOP.
279  *      2 -- Read from the log.
280  *      3 -- Read all messages remaining in the ring buffer.
281  *      4 -- Read and clear all messages remaining in the ring buffer
282  *      5 -- Clear ring buffer.
283  *      6 -- Disable printk's to console
284  *      7 -- Enable printk's to console
285  *      8 -- Set level of messages printed to console
286  *      9 -- Return number of unread characters in the log buffer
287  *     10 -- Return size of the log buffer
288  */
289 int do_syslog(int type, char __user *buf, int len)
290 {
291         unsigned long i, j, limit, count;
292         int do_clear = 0;
293         char c;
294         int error = 0;
295
296         error = security_syslog(type);
297         if (error)
298                 return error;
299
300         switch (type) {
301         case 0:         /* Close log */
302                 break;
303         case 1:         /* Open log */
304                 break;
305         case 2:         /* Read from log */
306                 error = -EINVAL;
307                 if (!buf || len < 0)
308                         goto out;
309                 error = 0;
310                 if (!len)
311                         goto out;
312                 if (!access_ok(VERIFY_WRITE, buf, len)) {
313                         error = -EFAULT;
314                         goto out;
315                 }
316                 error = wait_event_interruptible(log_wait,
317                                                         (log_start - log_end));
318                 if (error)
319                         goto out;
320                 i = 0;
321                 spin_lock_irq(&logbuf_lock);
322                 while (!error && (log_start != log_end) && i < len) {
323                         c = LOG_BUF(log_start);
324                         log_start++;
325                         spin_unlock_irq(&logbuf_lock);
326                         error = __put_user(c,buf);
327                         buf++;
328                         i++;
329                         cond_resched();
330                         spin_lock_irq(&logbuf_lock);
331                 }
332                 spin_unlock_irq(&logbuf_lock);
333                 if (!error)
334                         error = i;
335                 break;
336         case 4:         /* Read/clear last kernel messages */
337                 do_clear = 1;
338                 /* FALL THRU */
339         case 3:         /* Read last kernel messages */
340                 error = -EINVAL;
341                 if (!buf || len < 0)
342                         goto out;
343                 error = 0;
344                 if (!len)
345                         goto out;
346                 if (!access_ok(VERIFY_WRITE, buf, len)) {
347                         error = -EFAULT;
348                         goto out;
349                 }
350                 count = len;
351                 if (count > log_buf_len)
352                         count = log_buf_len;
353                 spin_lock_irq(&logbuf_lock);
354                 if (count > logged_chars)
355                         count = logged_chars;
356                 if (do_clear)
357                         logged_chars = 0;
358                 limit = log_end;
359                 /*
360                  * __put_user() could sleep, and while we sleep
361                  * printk() could overwrite the messages
362                  * we try to copy to user space. Therefore
363                  * the messages are copied in reverse. <manfreds>
364                  */
365                 for (i = 0; i < count && !error; i++) {
366                         j = limit-1-i;
367                         if (j + log_buf_len < log_end)
368                                 break;
369                         c = LOG_BUF(j);
370                         spin_unlock_irq(&logbuf_lock);
371                         error = __put_user(c,&buf[count-1-i]);
372                         cond_resched();
373                         spin_lock_irq(&logbuf_lock);
374                 }
375                 spin_unlock_irq(&logbuf_lock);
376                 if (error)
377                         break;
378                 error = i;
379                 if (i != count) {
380                         int offset = count-error;
381                         /* buffer overflow during copy, correct user buffer. */
382                         for (i = 0; i < error; i++) {
383                                 if (__get_user(c,&buf[i+offset]) ||
384                                     __put_user(c,&buf[i])) {
385                                         error = -EFAULT;
386                                         break;
387                                 }
388                                 cond_resched();
389                         }
390                 }
391                 break;
392         case 5:         /* Clear ring buffer */
393                 logged_chars = 0;
394                 break;
395         case 6:         /* Disable logging to console */
396                 console_loglevel = minimum_console_loglevel;
397                 break;
398         case 7:         /* Enable logging to console */
399                 console_loglevel = default_console_loglevel;
400                 break;
401         case 8:         /* Set level of messages printed to console */
402                 error = -EINVAL;
403                 if (len < 1 || len > 8)
404                         goto out;
405                 if (len < minimum_console_loglevel)
406                         len = minimum_console_loglevel;
407                 console_loglevel = len;
408                 error = 0;
409                 break;
410         case 9:         /* Number of chars in the log buffer */
411                 error = log_end - log_start;
412                 break;
413         case 10:        /* Size of the log buffer */
414                 error = log_buf_len;
415                 break;
416         default:
417                 error = -EINVAL;
418                 break;
419         }
420 out:
421         return error;
422 }
423
424 asmlinkage long sys_syslog(int type, char __user *buf, int len)
425 {
426         return do_syslog(type, buf, len);
427 }
428
429 /*
430  * Call the console drivers on a range of log_buf
431  */
432 static void __call_console_drivers(unsigned long start, unsigned long end)
433 {
434         struct console *con;
435
436         for (con = console_drivers; con; con = con->next) {
437                 if ((con->flags & CON_ENABLED) && con->write &&
438                                 (cpu_online(smp_processor_id()) ||
439                                 (con->flags & CON_ANYTIME)))
440                         con->write(con, &LOG_BUF(start), end - start);
441         }
442 }
443
444 static int __read_mostly ignore_loglevel;
445
446 static int __init ignore_loglevel_setup(char *str)
447 {
448         ignore_loglevel = 1;
449         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
450
451         return 1;
452 }
453
454 __setup("ignore_loglevel", ignore_loglevel_setup);
455
456 /*
457  * Write out chars from start to end - 1 inclusive
458  */
459 static void _call_console_drivers(unsigned long start,
460                                 unsigned long end, int msg_log_level)
461 {
462         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
463                         console_drivers && start != end) {
464                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
465                         /* wrapped write */
466                         __call_console_drivers(start & LOG_BUF_MASK,
467                                                 log_buf_len);
468                         __call_console_drivers(0, end & LOG_BUF_MASK);
469                 } else {
470                         __call_console_drivers(start, end);
471                 }
472         }
473 }
474
475 /*
476  * Call the console drivers, asking them to write out
477  * log_buf[start] to log_buf[end - 1].
478  * The console_sem must be held.
479  */
480 static void call_console_drivers(unsigned long start, unsigned long end)
481 {
482         unsigned long cur_index, start_print;
483         static int msg_level = -1;
484
485         BUG_ON(((long)(start - end)) > 0);
486
487         cur_index = start;
488         start_print = start;
489         while (cur_index != end) {
490                 if (msg_level < 0 && ((end - cur_index) > 2) &&
491                                 LOG_BUF(cur_index + 0) == '<' &&
492                                 LOG_BUF(cur_index + 1) >= '0' &&
493                                 LOG_BUF(cur_index + 1) <= '7' &&
494                                 LOG_BUF(cur_index + 2) == '>') {
495                         msg_level = LOG_BUF(cur_index + 1) - '0';
496                         cur_index += 3;
497                         start_print = cur_index;
498                 }
499                 while (cur_index != end) {
500                         char c = LOG_BUF(cur_index);
501
502                         cur_index++;
503                         if (c == '\n') {
504                                 if (msg_level < 0) {
505                                         /*
506                                          * printk() has already given us loglevel tags in
507                                          * the buffer.  This code is here in case the
508                                          * log buffer has wrapped right round and scribbled
509                                          * on those tags
510                                          */
511                                         msg_level = default_message_loglevel;
512                                 }
513                                 _call_console_drivers(start_print, cur_index, msg_level);
514                                 msg_level = -1;
515                                 start_print = cur_index;
516                                 break;
517                         }
518                 }
519         }
520         _call_console_drivers(start_print, end, msg_level);
521 }
522
523 static void emit_log_char(char c)
524 {
525         LOG_BUF(log_end) = c;
526         log_end++;
527         if (log_end - log_start > log_buf_len)
528                 log_start = log_end - log_buf_len;
529         if (log_end - con_start > log_buf_len)
530                 con_start = log_end - log_buf_len;
531         if (logged_chars < log_buf_len)
532                 logged_chars++;
533 }
534
535 /*
536  * Zap console related locks when oopsing. Only zap at most once
537  * every 10 seconds, to leave time for slow consoles to print a
538  * full oops.
539  */
540 static void zap_locks(void)
541 {
542         static unsigned long oops_timestamp;
543
544         if (time_after_eq(jiffies, oops_timestamp) &&
545                         !time_after(jiffies, oops_timestamp + 30 * HZ))
546                 return;
547
548         oops_timestamp = jiffies;
549
550         /* If a crash is occurring, make sure we can't deadlock */
551         spin_lock_init(&logbuf_lock);
552         /* And make sure that we print immediately */
553         init_MUTEX(&console_sem);
554 }
555
556 #if defined(CONFIG_PRINTK_TIME)
557 static int printk_time = 1;
558 #else
559 static int printk_time = 0;
560 #endif
561 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
562
563 static int __init printk_time_setup(char *str)
564 {
565         if (*str)
566                 return 0;
567         printk_time = 1;
568         printk(KERN_NOTICE "The 'time' option is deprecated and "
569                 "is scheduled for removal in early 2008\n");
570         printk(KERN_NOTICE "Use 'printk.time=<value>' instead\n");
571         return 1;
572 }
573
574 __setup("time", printk_time_setup);
575
576 /* Check if we have any console registered that can be called early in boot. */
577 static int have_callable_console(void)
578 {
579         struct console *con;
580
581         for (con = console_drivers; con; con = con->next)
582                 if (con->flags & CON_ANYTIME)
583                         return 1;
584
585         return 0;
586 }
587
588 /**
589  * printk - print a kernel message
590  * @fmt: format string
591  *
592  * This is printk().  It can be called from any context.  We want it to work.
593  * Be aware of the fact that if oops_in_progress is not set, we might try to
594  * wake klogd up which could deadlock on runqueue lock if printk() is called
595  * from scheduler code.
596  *
597  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
598  * call the console drivers.  If we fail to get the semaphore we place the output
599  * into the log buffer and return.  The current holder of the console_sem will
600  * notice the new output in release_console_sem() and will send it to the
601  * consoles before releasing the semaphore.
602  *
603  * One effect of this deferred printing is that code which calls printk() and
604  * then changes console_loglevel may break. This is because console_loglevel
605  * is inspected when the actual printing occurs.
606  *
607  * See also:
608  * printf(3)
609  */
610
611 asmlinkage int printk(const char *fmt, ...)
612 {
613         va_list args;
614         int r;
615
616         va_start(args, fmt);
617         r = vprintk(fmt, args);
618         va_end(args);
619
620         return r;
621 }
622
623 /* cpu currently holding logbuf_lock */
624 static volatile unsigned int printk_cpu = UINT_MAX;
625
626 const char printk_recursion_bug_msg [] =
627                         KERN_CRIT "BUG: recent printk recursion!\n";
628 static int printk_recursion_bug;
629
630 asmlinkage int vprintk(const char *fmt, va_list args)
631 {
632         static int log_level_unknown = 1;
633         static char printk_buf[1024];
634
635         unsigned long flags;
636         int printed_len = 0;
637         int this_cpu;
638         char *p;
639
640         boot_delay_msec();
641
642         preempt_disable();
643         /* This stops the holder of console_sem just where we want him */
644         raw_local_irq_save(flags);
645         this_cpu = smp_processor_id();
646
647         /*
648          * Ouch, printk recursed into itself!
649          */
650         if (unlikely(printk_cpu == this_cpu)) {
651                 /*
652                  * If a crash is occurring during printk() on this CPU,
653                  * then try to get the crash message out but make sure
654                  * we can't deadlock. Otherwise just return to avoid the
655                  * recursion and return - but flag the recursion so that
656                  * it can be printed at the next appropriate moment:
657                  */
658                 if (!oops_in_progress) {
659                         printk_recursion_bug = 1;
660                         goto out_restore_irqs;
661                 }
662                 zap_locks();
663         }
664
665         lockdep_off();
666         spin_lock(&logbuf_lock);
667         printk_cpu = this_cpu;
668
669         if (printk_recursion_bug) {
670                 printk_recursion_bug = 0;
671                 strcpy(printk_buf, printk_recursion_bug_msg);
672                 printed_len = sizeof(printk_recursion_bug_msg);
673         }
674         /* Emit the output into the temporary buffer */
675         printed_len += vscnprintf(printk_buf + printed_len,
676                                   sizeof(printk_buf), fmt, args);
677
678         /*
679          * Copy the output into log_buf.  If the caller didn't provide
680          * appropriate log level tags, we insert them here
681          */
682         for (p = printk_buf; *p; p++) {
683                 if (log_level_unknown) {
684                         /* log_level_unknown signals the start of a new line */
685                         if (printk_time) {
686                                 int loglev_char;
687                                 char tbuf[50], *tp;
688                                 unsigned tlen;
689                                 unsigned long long t;
690                                 unsigned long nanosec_rem;
691
692                                 /*
693                                  * force the log level token to be
694                                  * before the time output.
695                                  */
696                                 if (p[0] == '<' && p[1] >='0' &&
697                                    p[1] <= '7' && p[2] == '>') {
698                                         loglev_char = p[1];
699                                         p += 3;
700                                         printed_len -= 3;
701                                 } else {
702                                         loglev_char = default_message_loglevel
703                                                 + '0';
704                                 }
705                                 t = 0;
706                                 if (system_state != SYSTEM_BOOTING)
707                                         t = ktime_to_ns(ktime_get());
708                                 nanosec_rem = do_div(t, 1000000000);
709                                 tlen = sprintf(tbuf,
710                                                 "<%c>[%5lu.%06lu] ",
711                                                 loglev_char,
712                                                 (unsigned long)t,
713                                                 nanosec_rem/1000);
714
715                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
716                                         emit_log_char(*tp);
717                                 printed_len += tlen;
718                         } else {
719                                 if (p[0] != '<' || p[1] < '0' ||
720                                    p[1] > '7' || p[2] != '>') {
721                                         emit_log_char('<');
722                                         emit_log_char(default_message_loglevel
723                                                 + '0');
724                                         emit_log_char('>');
725                                         printed_len += 3;
726                                 }
727                         }
728                         log_level_unknown = 0;
729                         if (!*p)
730                                 break;
731                 }
732                 emit_log_char(*p);
733                 if (*p == '\n')
734                         log_level_unknown = 1;
735         }
736
737         if (!down_trylock(&console_sem)) {
738                 /*
739                  * We own the drivers.  We can drop the spinlock and
740                  * let release_console_sem() print the text, maybe ...
741                  */
742                 console_locked = 1;
743                 printk_cpu = UINT_MAX;
744                 spin_unlock(&logbuf_lock);
745
746                 /*
747                  * Console drivers may assume that per-cpu resources have
748                  * been allocated. So unless they're explicitly marked as
749                  * being able to cope (CON_ANYTIME) don't call them until
750                  * this CPU is officially up.
751                  */
752                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
753                         console_may_schedule = 0;
754                         release_console_sem();
755                 } else {
756                         /* Release by hand to avoid flushing the buffer. */
757                         console_locked = 0;
758                         up(&console_sem);
759                 }
760                 lockdep_on();
761                 raw_local_irq_restore(flags);
762         } else {
763                 /*
764                  * Someone else owns the drivers.  We drop the spinlock, which
765                  * allows the semaphore holder to proceed and to call the
766                  * console drivers with the output which we just produced.
767                  */
768                 printk_cpu = UINT_MAX;
769                 spin_unlock(&logbuf_lock);
770                 lockdep_on();
771 out_restore_irqs:
772                 raw_local_irq_restore(flags);
773         }
774
775         preempt_enable();
776         return printed_len;
777 }
778 EXPORT_SYMBOL(printk);
779 EXPORT_SYMBOL(vprintk);
780
781 #else
782
783 asmlinkage long sys_syslog(int type, char __user *buf, int len)
784 {
785         return -ENOSYS;
786 }
787
788 static void call_console_drivers(unsigned long start, unsigned long end)
789 {
790 }
791
792 #endif
793
794 /*
795  * Set up a list of consoles.  Called from init/main.c
796  */
797 static int __init console_setup(char *str)
798 {
799         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
800         char *s, *options;
801         int idx;
802
803         /*
804          * Decode str into name, index, options.
805          */
806         if (str[0] >= '0' && str[0] <= '9') {
807                 strcpy(buf, "ttyS");
808                 strncpy(buf + 4, str, sizeof(buf) - 5);
809         } else {
810                 strncpy(buf, str, sizeof(buf) - 1);
811         }
812         buf[sizeof(buf) - 1] = 0;
813         if ((options = strchr(str, ',')) != NULL)
814                 *(options++) = 0;
815 #ifdef __sparc__
816         if (!strcmp(str, "ttya"))
817                 strcpy(buf, "ttyS0");
818         if (!strcmp(str, "ttyb"))
819                 strcpy(buf, "ttyS1");
820 #endif
821         for (s = buf; *s; s++)
822                 if ((*s >= '0' && *s <= '9') || *s == ',')
823                         break;
824         idx = simple_strtoul(s, NULL, 10);
825         *s = 0;
826
827         add_preferred_console(buf, idx, options);
828         return 1;
829 }
830 __setup("console=", console_setup);
831
832 /**
833  * add_preferred_console - add a device to the list of preferred consoles.
834  * @name: device name
835  * @idx: device index
836  * @options: options for this console
837  *
838  * The last preferred console added will be used for kernel messages
839  * and stdin/out/err for init.  Normally this is used by console_setup
840  * above to handle user-supplied console arguments; however it can also
841  * be used by arch-specific code either to override the user or more
842  * commonly to provide a default console (ie from PROM variables) when
843  * the user has not supplied one.
844  */
845 int add_preferred_console(char *name, int idx, char *options)
846 {
847         struct console_cmdline *c;
848         int i;
849
850         /*
851          *      See if this tty is not yet registered, and
852          *      if we have a slot free.
853          */
854         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
855                 if (strcmp(console_cmdline[i].name, name) == 0 &&
856                           console_cmdline[i].index == idx) {
857                                 selected_console = i;
858                                 return 0;
859                 }
860         if (i == MAX_CMDLINECONSOLES)
861                 return -E2BIG;
862         selected_console = i;
863         c = &console_cmdline[i];
864         memcpy(c->name, name, sizeof(c->name));
865         c->name[sizeof(c->name) - 1] = 0;
866         c->options = options;
867         c->index = idx;
868         return 0;
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                                 memcpy(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)\n");
910         acquire_console_sem();
911         console_suspended = 1;
912 }
913
914 void resume_console(void)
915 {
916         if (!console_suspend_enabled)
917                 return;
918         console_suspended = 0;
919         release_console_sem();
920 }
921
922 /**
923  * acquire_console_sem - lock the console system for exclusive use.
924  *
925  * Acquires a semaphore which guarantees that the caller has
926  * exclusive access to the console system and the console_drivers list.
927  *
928  * Can sleep, returns nothing.
929  */
930 void acquire_console_sem(void)
931 {
932         BUG_ON(in_interrupt());
933         if (console_suspended) {
934                 down(&secondary_console_sem);
935                 return;
936         }
937         down(&console_sem);
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         console_locked = 1;
948         console_may_schedule = 0;
949         return 0;
950 }
951 EXPORT_SYMBOL(try_acquire_console_sem);
952
953 int is_console_locked(void)
954 {
955         return console_locked;
956 }
957
958 void wake_up_klogd(void)
959 {
960         if (!oops_in_progress && waitqueue_active(&log_wait))
961                 wake_up_interruptible(&log_wait);
962 }
963
964 /**
965  * release_console_sem - unlock the console system
966  *
967  * Releases the semaphore which the caller holds on the console system
968  * and the console driver list.
969  *
970  * While the semaphore was held, console output may have been buffered
971  * by printk().  If this is the case, release_console_sem() emits
972  * the output prior to releasing the semaphore.
973  *
974  * If there is output waiting for klogd, we wake it up.
975  *
976  * release_console_sem() may be called from any context.
977  */
978 void release_console_sem(void)
979 {
980         unsigned long flags;
981         unsigned long _con_start, _log_end;
982         unsigned long wake_klogd = 0;
983
984         if (console_suspended) {
985                 up(&secondary_console_sem);
986                 return;
987         }
988
989         console_may_schedule = 0;
990
991         for ( ; ; ) {
992                 spin_lock_irqsave(&logbuf_lock, flags);
993                 wake_klogd |= log_start - log_end;
994                 if (con_start == log_end)
995                         break;                  /* Nothing to print */
996                 _con_start = con_start;
997                 _log_end = log_end;
998                 con_start = log_end;            /* Flush */
999                 spin_unlock(&logbuf_lock);
1000                 call_console_drivers(_con_start, _log_end);
1001                 local_irq_restore(flags);
1002         }
1003         console_locked = 0;
1004         up(&console_sem);
1005         spin_unlock_irqrestore(&logbuf_lock, flags);
1006         if (wake_klogd)
1007                 wake_up_klogd();
1008 }
1009 EXPORT_SYMBOL(release_console_sem);
1010
1011 /**
1012  * console_conditional_schedule - yield the CPU if required
1013  *
1014  * If the console code is currently allowed to sleep, and
1015  * if this CPU should yield the CPU to another task, do
1016  * so here.
1017  *
1018  * Must be called within acquire_console_sem().
1019  */
1020 void __sched console_conditional_schedule(void)
1021 {
1022         if (console_may_schedule)
1023                 cond_resched();
1024 }
1025 EXPORT_SYMBOL(console_conditional_schedule);
1026
1027 void console_print(const char *s)
1028 {
1029         printk(KERN_EMERG "%s", s);
1030 }
1031 EXPORT_SYMBOL(console_print);
1032
1033 void console_unblank(void)
1034 {
1035         struct console *c;
1036
1037         /*
1038          * console_unblank can no longer be called in interrupt context unless
1039          * oops_in_progress is set to 1..
1040          */
1041         if (oops_in_progress) {
1042                 if (down_trylock(&console_sem) != 0)
1043                         return;
1044         } else
1045                 acquire_console_sem();
1046
1047         console_locked = 1;
1048         console_may_schedule = 0;
1049         for (c = console_drivers; c != NULL; c = c->next)
1050                 if ((c->flags & CON_ENABLED) && c->unblank)
1051                         c->unblank();
1052         release_console_sem();
1053 }
1054
1055 /*
1056  * Return the console tty driver structure and its associated index
1057  */
1058 struct tty_driver *console_device(int *index)
1059 {
1060         struct console *c;
1061         struct tty_driver *driver = NULL;
1062
1063         acquire_console_sem();
1064         for (c = console_drivers; c != NULL; c = c->next) {
1065                 if (!c->device)
1066                         continue;
1067                 driver = c->device(c, index);
1068                 if (driver)
1069                         break;
1070         }
1071         release_console_sem();
1072         return driver;
1073 }
1074
1075 /*
1076  * Prevent further output on the passed console device so that (for example)
1077  * serial drivers can disable console output before suspending a port, and can
1078  * re-enable output afterwards.
1079  */
1080 void console_stop(struct console *console)
1081 {
1082         acquire_console_sem();
1083         console->flags &= ~CON_ENABLED;
1084         release_console_sem();
1085 }
1086 EXPORT_SYMBOL(console_stop);
1087
1088 void console_start(struct console *console)
1089 {
1090         acquire_console_sem();
1091         console->flags |= CON_ENABLED;
1092         release_console_sem();
1093 }
1094 EXPORT_SYMBOL(console_start);
1095
1096 /*
1097  * The console driver calls this routine during kernel initialization
1098  * to register the console printing procedure with printk() and to
1099  * print any messages that were printed by the kernel before the
1100  * console driver was initialized.
1101  */
1102 void register_console(struct console *console)
1103 {
1104         int i;
1105         unsigned long flags;
1106         struct console *bootconsole = NULL;
1107
1108         if (console_drivers) {
1109                 if (console->flags & CON_BOOT)
1110                         return;
1111                 if (console_drivers->flags & CON_BOOT)
1112                         bootconsole = console_drivers;
1113         }
1114
1115         if (preferred_console < 0 || bootconsole || !console_drivers)
1116                 preferred_console = selected_console;
1117
1118         if (console->early_setup)
1119                 console->early_setup();
1120
1121         /*
1122          *      See if we want to use this console driver. If we
1123          *      didn't select a console we take the first one
1124          *      that registers here.
1125          */
1126         if (preferred_console < 0) {
1127                 if (console->index < 0)
1128                         console->index = 0;
1129                 if (console->setup == NULL ||
1130                     console->setup(console, NULL) == 0) {
1131                         console->flags |= CON_ENABLED | CON_CONSDEV;
1132                         preferred_console = 0;
1133                 }
1134         }
1135
1136         /*
1137          *      See if this console matches one we selected on
1138          *      the command line.
1139          */
1140         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1141                         i++) {
1142                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1143                         continue;
1144                 if (console->index >= 0 &&
1145                     console->index != console_cmdline[i].index)
1146                         continue;
1147                 if (console->index < 0)
1148                         console->index = console_cmdline[i].index;
1149                 if (console->setup &&
1150                     console->setup(console, console_cmdline[i].options) != 0)
1151                         break;
1152                 console->flags |= CON_ENABLED;
1153                 console->index = console_cmdline[i].index;
1154                 if (i == selected_console) {
1155                         console->flags |= CON_CONSDEV;
1156                         preferred_console = selected_console;
1157                 }
1158                 break;
1159         }
1160
1161         if (!(console->flags & CON_ENABLED))
1162                 return;
1163
1164         if (bootconsole && (console->flags & CON_CONSDEV)) {
1165                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1166                        bootconsole->name, bootconsole->index,
1167                        console->name, console->index);
1168                 unregister_console(bootconsole);
1169                 console->flags &= ~CON_PRINTBUFFER;
1170         } else {
1171                 printk(KERN_INFO "console [%s%d] enabled\n",
1172                        console->name, console->index);
1173         }
1174
1175         /*
1176          *      Put this console in the list - keep the
1177          *      preferred driver at the head of the list.
1178          */
1179         acquire_console_sem();
1180         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1181                 console->next = console_drivers;
1182                 console_drivers = console;
1183                 if (console->next)
1184                         console->next->flags &= ~CON_CONSDEV;
1185         } else {
1186                 console->next = console_drivers->next;
1187                 console_drivers->next = console;
1188         }
1189         if (console->flags & CON_PRINTBUFFER) {
1190                 /*
1191                  * release_console_sem() will print out the buffered messages
1192                  * for us.
1193                  */
1194                 spin_lock_irqsave(&logbuf_lock, flags);
1195                 con_start = log_start;
1196                 spin_unlock_irqrestore(&logbuf_lock, flags);
1197         }
1198         release_console_sem();
1199 }
1200 EXPORT_SYMBOL(register_console);
1201
1202 int unregister_console(struct console *console)
1203 {
1204         struct console *a, *b;
1205         int res = 1;
1206
1207         acquire_console_sem();
1208         if (console_drivers == console) {
1209                 console_drivers=console->next;
1210                 res = 0;
1211         } else if (console_drivers) {
1212                 for (a=console_drivers->next, b=console_drivers ;
1213                      a; b=a, a=b->next) {
1214                         if (a == console) {
1215                                 b->next = a->next;
1216                                 res = 0;
1217                                 break;
1218                         }
1219                 }
1220         }
1221
1222         /*
1223          * If this isn't the last console and it has CON_CONSDEV set, we
1224          * need to set it on the next preferred console.
1225          */
1226         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1227                 console_drivers->flags |= CON_CONSDEV;
1228
1229         release_console_sem();
1230         return res;
1231 }
1232 EXPORT_SYMBOL(unregister_console);
1233
1234 static int __init disable_boot_consoles(void)
1235 {
1236         if (console_drivers != NULL) {
1237                 if (console_drivers->flags & CON_BOOT) {
1238                         printk(KERN_INFO "turn off boot console %s%d\n",
1239                                 console_drivers->name, console_drivers->index);
1240                         return unregister_console(console_drivers);
1241                 }
1242         }
1243         return 0;
1244 }
1245 late_initcall(disable_boot_consoles);
1246
1247 /**
1248  * tty_write_message - write a message to a certain tty, not just the console.
1249  * @tty: the destination tty_struct
1250  * @msg: the message to write
1251  *
1252  * This is used for messages that need to be redirected to a specific tty.
1253  * We don't put it into the syslog queue right now maybe in the future if
1254  * really needed.
1255  */
1256 void tty_write_message(struct tty_struct *tty, char *msg)
1257 {
1258         if (tty && tty->driver->write)
1259                 tty->driver->write(tty, msg, strlen(msg));
1260         return;
1261 }
1262
1263 /*
1264  * printk rate limiting, lifted from the networking subsystem.
1265  *
1266  * This enforces a rate limit: not more than one kernel message
1267  * every printk_ratelimit_jiffies to make a denial-of-service
1268  * attack impossible.
1269  */
1270 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1271 {
1272         static DEFINE_SPINLOCK(ratelimit_lock);
1273         static unsigned long toks = 10 * 5 * HZ;
1274         static unsigned long last_msg;
1275         static int missed;
1276         unsigned long flags;
1277         unsigned long now = jiffies;
1278
1279         spin_lock_irqsave(&ratelimit_lock, flags);
1280         toks += now - last_msg;
1281         last_msg = now;
1282         if (toks > (ratelimit_burst * ratelimit_jiffies))
1283                 toks = ratelimit_burst * ratelimit_jiffies;
1284         if (toks >= ratelimit_jiffies) {
1285                 int lost = missed;
1286
1287                 missed = 0;
1288                 toks -= ratelimit_jiffies;
1289                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1290                 if (lost)
1291                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1292                 return 1;
1293         }
1294         missed++;
1295         spin_unlock_irqrestore(&ratelimit_lock, flags);
1296         return 0;
1297 }
1298 EXPORT_SYMBOL(__printk_ratelimit);
1299
1300 /* minimum time in jiffies between messages */
1301 int printk_ratelimit_jiffies = 5 * HZ;
1302
1303 /* number of messages we send before ratelimiting */
1304 int printk_ratelimit_burst = 10;
1305
1306 int printk_ratelimit(void)
1307 {
1308         return __printk_ratelimit(printk_ratelimit_jiffies,
1309                                 printk_ratelimit_burst);
1310 }
1311 EXPORT_SYMBOL(printk_ratelimit);
1312
1313 /**
1314  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1315  * @caller_jiffies: pointer to caller's state
1316  * @interval_msecs: minimum interval between prints
1317  *
1318  * printk_timed_ratelimit() returns true if more than @interval_msecs
1319  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1320  * returned true.
1321  */
1322 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1323                         unsigned int interval_msecs)
1324 {
1325         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1326                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1327                 return true;
1328         }
1329         return false;
1330 }
1331 EXPORT_SYMBOL(printk_timed_ratelimit);