blk_end_request: changing ide normal caller (take 4)
[linux-2.6] / 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 = cpu_clock(printk_cpu);
706                                 nanosec_rem = do_div(t, 1000000000);
707                                 tlen = sprintf(tbuf,
708                                                 "<%c>[%5lu.%06lu] ",
709                                                 loglev_char,
710                                                 (unsigned long)t,
711                                                 nanosec_rem/1000);
712
713                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
714                                         emit_log_char(*tp);
715                                 printed_len += tlen;
716                         } else {
717                                 if (p[0] != '<' || p[1] < '0' ||
718                                    p[1] > '7' || p[2] != '>') {
719                                         emit_log_char('<');
720                                         emit_log_char(default_message_loglevel
721                                                 + '0');
722                                         emit_log_char('>');
723                                         printed_len += 3;
724                                 }
725                         }
726                         log_level_unknown = 0;
727                         if (!*p)
728                                 break;
729                 }
730                 emit_log_char(*p);
731                 if (*p == '\n')
732                         log_level_unknown = 1;
733         }
734
735         if (!down_trylock(&console_sem)) {
736                 /*
737                  * We own the drivers.  We can drop the spinlock and
738                  * let release_console_sem() print the text, maybe ...
739                  */
740                 console_locked = 1;
741                 printk_cpu = UINT_MAX;
742                 spin_unlock(&logbuf_lock);
743
744                 /*
745                  * Console drivers may assume that per-cpu resources have
746                  * been allocated. So unless they're explicitly marked as
747                  * being able to cope (CON_ANYTIME) don't call them until
748                  * this CPU is officially up.
749                  */
750                 if (cpu_online(smp_processor_id()) || have_callable_console()) {
751                         console_may_schedule = 0;
752                         release_console_sem();
753                 } else {
754                         /* Release by hand to avoid flushing the buffer. */
755                         console_locked = 0;
756                         up(&console_sem);
757                 }
758                 lockdep_on();
759                 raw_local_irq_restore(flags);
760         } else {
761                 /*
762                  * Someone else owns the drivers.  We drop the spinlock, which
763                  * allows the semaphore holder to proceed and to call the
764                  * console drivers with the output which we just produced.
765                  */
766                 printk_cpu = UINT_MAX;
767                 spin_unlock(&logbuf_lock);
768                 lockdep_on();
769 out_restore_irqs:
770                 raw_local_irq_restore(flags);
771         }
772
773         preempt_enable();
774         return printed_len;
775 }
776 EXPORT_SYMBOL(printk);
777 EXPORT_SYMBOL(vprintk);
778
779 #else
780
781 asmlinkage long sys_syslog(int type, char __user *buf, int len)
782 {
783         return -ENOSYS;
784 }
785
786 static void call_console_drivers(unsigned long start, unsigned long end)
787 {
788 }
789
790 #endif
791
792 /*
793  * Set up a list of consoles.  Called from init/main.c
794  */
795 static int __init console_setup(char *str)
796 {
797         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
798         char *s, *options;
799         int idx;
800
801         /*
802          * Decode str into name, index, options.
803          */
804         if (str[0] >= '0' && str[0] <= '9') {
805                 strcpy(buf, "ttyS");
806                 strncpy(buf + 4, str, sizeof(buf) - 5);
807         } else {
808                 strncpy(buf, str, sizeof(buf) - 1);
809         }
810         buf[sizeof(buf) - 1] = 0;
811         if ((options = strchr(str, ',')) != NULL)
812                 *(options++) = 0;
813 #ifdef __sparc__
814         if (!strcmp(str, "ttya"))
815                 strcpy(buf, "ttyS0");
816         if (!strcmp(str, "ttyb"))
817                 strcpy(buf, "ttyS1");
818 #endif
819         for (s = buf; *s; s++)
820                 if ((*s >= '0' && *s <= '9') || *s == ',')
821                         break;
822         idx = simple_strtoul(s, NULL, 10);
823         *s = 0;
824
825         add_preferred_console(buf, idx, options);
826         return 1;
827 }
828 __setup("console=", console_setup);
829
830 /**
831  * add_preferred_console - add a device to the list of preferred consoles.
832  * @name: device name
833  * @idx: device index
834  * @options: options for this console
835  *
836  * The last preferred console added will be used for kernel messages
837  * and stdin/out/err for init.  Normally this is used by console_setup
838  * above to handle user-supplied console arguments; however it can also
839  * be used by arch-specific code either to override the user or more
840  * commonly to provide a default console (ie from PROM variables) when
841  * the user has not supplied one.
842  */
843 int add_preferred_console(char *name, int idx, char *options)
844 {
845         struct console_cmdline *c;
846         int i;
847
848         /*
849          *      See if this tty is not yet registered, and
850          *      if we have a slot free.
851          */
852         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
853                 if (strcmp(console_cmdline[i].name, name) == 0 &&
854                           console_cmdline[i].index == idx) {
855                                 selected_console = i;
856                                 return 0;
857                 }
858         if (i == MAX_CMDLINECONSOLES)
859                 return -E2BIG;
860         selected_console = i;
861         c = &console_cmdline[i];
862         memcpy(c->name, name, sizeof(c->name));
863         c->name[sizeof(c->name) - 1] = 0;
864         c->options = options;
865         c->index = idx;
866         return 0;
867 }
868
869 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
870 {
871         struct console_cmdline *c;
872         int i;
873
874         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
875                 if (strcmp(console_cmdline[i].name, name) == 0 &&
876                           console_cmdline[i].index == idx) {
877                                 c = &console_cmdline[i];
878                                 memcpy(c->name, name_new, sizeof(c->name));
879                                 c->name[sizeof(c->name) - 1] = 0;
880                                 c->options = options;
881                                 c->index = idx_new;
882                                 return i;
883                 }
884         /* not found */
885         return -1;
886 }
887
888 int console_suspend_enabled = 1;
889 EXPORT_SYMBOL(console_suspend_enabled);
890
891 static int __init console_suspend_disable(char *str)
892 {
893         console_suspend_enabled = 0;
894         return 1;
895 }
896 __setup("no_console_suspend", console_suspend_disable);
897
898 /**
899  * suspend_console - suspend the console subsystem
900  *
901  * This disables printk() while we go into suspend states
902  */
903 void suspend_console(void)
904 {
905         if (!console_suspend_enabled)
906                 return;
907         printk("Suspending console(s)\n");
908         acquire_console_sem();
909         console_suspended = 1;
910 }
911
912 void resume_console(void)
913 {
914         if (!console_suspend_enabled)
915                 return;
916         console_suspended = 0;
917         release_console_sem();
918 }
919
920 /**
921  * acquire_console_sem - lock the console system for exclusive use.
922  *
923  * Acquires a semaphore which guarantees that the caller has
924  * exclusive access to the console system and the console_drivers list.
925  *
926  * Can sleep, returns nothing.
927  */
928 void acquire_console_sem(void)
929 {
930         BUG_ON(in_interrupt());
931         if (console_suspended) {
932                 down(&secondary_console_sem);
933                 return;
934         }
935         down(&console_sem);
936         console_locked = 1;
937         console_may_schedule = 1;
938 }
939 EXPORT_SYMBOL(acquire_console_sem);
940
941 int try_acquire_console_sem(void)
942 {
943         if (down_trylock(&console_sem))
944                 return -1;
945         console_locked = 1;
946         console_may_schedule = 0;
947         return 0;
948 }
949 EXPORT_SYMBOL(try_acquire_console_sem);
950
951 int is_console_locked(void)
952 {
953         return console_locked;
954 }
955
956 void wake_up_klogd(void)
957 {
958         if (!oops_in_progress && waitqueue_active(&log_wait))
959                 wake_up_interruptible(&log_wait);
960 }
961
962 /**
963  * release_console_sem - unlock the console system
964  *
965  * Releases the semaphore which the caller holds on the console system
966  * and the console driver list.
967  *
968  * While the semaphore was held, console output may have been buffered
969  * by printk().  If this is the case, release_console_sem() emits
970  * the output prior to releasing the semaphore.
971  *
972  * If there is output waiting for klogd, we wake it up.
973  *
974  * release_console_sem() may be called from any context.
975  */
976 void release_console_sem(void)
977 {
978         unsigned long flags;
979         unsigned long _con_start, _log_end;
980         unsigned long wake_klogd = 0;
981
982         if (console_suspended) {
983                 up(&secondary_console_sem);
984                 return;
985         }
986
987         console_may_schedule = 0;
988
989         for ( ; ; ) {
990                 spin_lock_irqsave(&logbuf_lock, flags);
991                 wake_klogd |= log_start - log_end;
992                 if (con_start == log_end)
993                         break;                  /* Nothing to print */
994                 _con_start = con_start;
995                 _log_end = log_end;
996                 con_start = log_end;            /* Flush */
997                 spin_unlock(&logbuf_lock);
998                 call_console_drivers(_con_start, _log_end);
999                 local_irq_restore(flags);
1000         }
1001         console_locked = 0;
1002         up(&console_sem);
1003         spin_unlock_irqrestore(&logbuf_lock, flags);
1004         if (wake_klogd)
1005                 wake_up_klogd();
1006 }
1007 EXPORT_SYMBOL(release_console_sem);
1008
1009 /**
1010  * console_conditional_schedule - yield the CPU if required
1011  *
1012  * If the console code is currently allowed to sleep, and
1013  * if this CPU should yield the CPU to another task, do
1014  * so here.
1015  *
1016  * Must be called within acquire_console_sem().
1017  */
1018 void __sched console_conditional_schedule(void)
1019 {
1020         if (console_may_schedule)
1021                 cond_resched();
1022 }
1023 EXPORT_SYMBOL(console_conditional_schedule);
1024
1025 void console_print(const char *s)
1026 {
1027         printk(KERN_EMERG "%s", s);
1028 }
1029 EXPORT_SYMBOL(console_print);
1030
1031 void console_unblank(void)
1032 {
1033         struct console *c;
1034
1035         /*
1036          * console_unblank can no longer be called in interrupt context unless
1037          * oops_in_progress is set to 1..
1038          */
1039         if (oops_in_progress) {
1040                 if (down_trylock(&console_sem) != 0)
1041                         return;
1042         } else
1043                 acquire_console_sem();
1044
1045         console_locked = 1;
1046         console_may_schedule = 0;
1047         for (c = console_drivers; c != NULL; c = c->next)
1048                 if ((c->flags & CON_ENABLED) && c->unblank)
1049                         c->unblank();
1050         release_console_sem();
1051 }
1052
1053 /*
1054  * Return the console tty driver structure and its associated index
1055  */
1056 struct tty_driver *console_device(int *index)
1057 {
1058         struct console *c;
1059         struct tty_driver *driver = NULL;
1060
1061         acquire_console_sem();
1062         for (c = console_drivers; c != NULL; c = c->next) {
1063                 if (!c->device)
1064                         continue;
1065                 driver = c->device(c, index);
1066                 if (driver)
1067                         break;
1068         }
1069         release_console_sem();
1070         return driver;
1071 }
1072
1073 /*
1074  * Prevent further output on the passed console device so that (for example)
1075  * serial drivers can disable console output before suspending a port, and can
1076  * re-enable output afterwards.
1077  */
1078 void console_stop(struct console *console)
1079 {
1080         acquire_console_sem();
1081         console->flags &= ~CON_ENABLED;
1082         release_console_sem();
1083 }
1084 EXPORT_SYMBOL(console_stop);
1085
1086 void console_start(struct console *console)
1087 {
1088         acquire_console_sem();
1089         console->flags |= CON_ENABLED;
1090         release_console_sem();
1091 }
1092 EXPORT_SYMBOL(console_start);
1093
1094 /*
1095  * The console driver calls this routine during kernel initialization
1096  * to register the console printing procedure with printk() and to
1097  * print any messages that were printed by the kernel before the
1098  * console driver was initialized.
1099  */
1100 void register_console(struct console *console)
1101 {
1102         int i;
1103         unsigned long flags;
1104         struct console *bootconsole = NULL;
1105
1106         if (console_drivers) {
1107                 if (console->flags & CON_BOOT)
1108                         return;
1109                 if (console_drivers->flags & CON_BOOT)
1110                         bootconsole = console_drivers;
1111         }
1112
1113         if (preferred_console < 0 || bootconsole || !console_drivers)
1114                 preferred_console = selected_console;
1115
1116         if (console->early_setup)
1117                 console->early_setup();
1118
1119         /*
1120          *      See if we want to use this console driver. If we
1121          *      didn't select a console we take the first one
1122          *      that registers here.
1123          */
1124         if (preferred_console < 0) {
1125                 if (console->index < 0)
1126                         console->index = 0;
1127                 if (console->setup == NULL ||
1128                     console->setup(console, NULL) == 0) {
1129                         console->flags |= CON_ENABLED | CON_CONSDEV;
1130                         preferred_console = 0;
1131                 }
1132         }
1133
1134         /*
1135          *      See if this console matches one we selected on
1136          *      the command line.
1137          */
1138         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1139                         i++) {
1140                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1141                         continue;
1142                 if (console->index >= 0 &&
1143                     console->index != console_cmdline[i].index)
1144                         continue;
1145                 if (console->index < 0)
1146                         console->index = console_cmdline[i].index;
1147                 if (console->setup &&
1148                     console->setup(console, console_cmdline[i].options) != 0)
1149                         break;
1150                 console->flags |= CON_ENABLED;
1151                 console->index = console_cmdline[i].index;
1152                 if (i == selected_console) {
1153                         console->flags |= CON_CONSDEV;
1154                         preferred_console = selected_console;
1155                 }
1156                 break;
1157         }
1158
1159         if (!(console->flags & CON_ENABLED))
1160                 return;
1161
1162         if (bootconsole && (console->flags & CON_CONSDEV)) {
1163                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1164                        bootconsole->name, bootconsole->index,
1165                        console->name, console->index);
1166                 unregister_console(bootconsole);
1167                 console->flags &= ~CON_PRINTBUFFER;
1168         } else {
1169                 printk(KERN_INFO "console [%s%d] enabled\n",
1170                        console->name, console->index);
1171         }
1172
1173         /*
1174          *      Put this console in the list - keep the
1175          *      preferred driver at the head of the list.
1176          */
1177         acquire_console_sem();
1178         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1179                 console->next = console_drivers;
1180                 console_drivers = console;
1181                 if (console->next)
1182                         console->next->flags &= ~CON_CONSDEV;
1183         } else {
1184                 console->next = console_drivers->next;
1185                 console_drivers->next = console;
1186         }
1187         if (console->flags & CON_PRINTBUFFER) {
1188                 /*
1189                  * release_console_sem() will print out the buffered messages
1190                  * for us.
1191                  */
1192                 spin_lock_irqsave(&logbuf_lock, flags);
1193                 con_start = log_start;
1194                 spin_unlock_irqrestore(&logbuf_lock, flags);
1195         }
1196         release_console_sem();
1197 }
1198 EXPORT_SYMBOL(register_console);
1199
1200 int unregister_console(struct console *console)
1201 {
1202         struct console *a, *b;
1203         int res = 1;
1204
1205         acquire_console_sem();
1206         if (console_drivers == console) {
1207                 console_drivers=console->next;
1208                 res = 0;
1209         } else if (console_drivers) {
1210                 for (a=console_drivers->next, b=console_drivers ;
1211                      a; b=a, a=b->next) {
1212                         if (a == console) {
1213                                 b->next = a->next;
1214                                 res = 0;
1215                                 break;
1216                         }
1217                 }
1218         }
1219
1220         /*
1221          * If this isn't the last console and it has CON_CONSDEV set, we
1222          * need to set it on the next preferred console.
1223          */
1224         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1225                 console_drivers->flags |= CON_CONSDEV;
1226
1227         release_console_sem();
1228         return res;
1229 }
1230 EXPORT_SYMBOL(unregister_console);
1231
1232 static int __init disable_boot_consoles(void)
1233 {
1234         if (console_drivers != NULL) {
1235                 if (console_drivers->flags & CON_BOOT) {
1236                         printk(KERN_INFO "turn off boot console %s%d\n",
1237                                 console_drivers->name, console_drivers->index);
1238                         return unregister_console(console_drivers);
1239                 }
1240         }
1241         return 0;
1242 }
1243 late_initcall(disable_boot_consoles);
1244
1245 /**
1246  * tty_write_message - write a message to a certain tty, not just the console.
1247  * @tty: the destination tty_struct
1248  * @msg: the message to write
1249  *
1250  * This is used for messages that need to be redirected to a specific tty.
1251  * We don't put it into the syslog queue right now maybe in the future if
1252  * really needed.
1253  */
1254 void tty_write_message(struct tty_struct *tty, char *msg)
1255 {
1256         if (tty && tty->driver->write)
1257                 tty->driver->write(tty, msg, strlen(msg));
1258         return;
1259 }
1260
1261 /*
1262  * printk rate limiting, lifted from the networking subsystem.
1263  *
1264  * This enforces a rate limit: not more than one kernel message
1265  * every printk_ratelimit_jiffies to make a denial-of-service
1266  * attack impossible.
1267  */
1268 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1269 {
1270         static DEFINE_SPINLOCK(ratelimit_lock);
1271         static unsigned long toks = 10 * 5 * HZ;
1272         static unsigned long last_msg;
1273         static int missed;
1274         unsigned long flags;
1275         unsigned long now = jiffies;
1276
1277         spin_lock_irqsave(&ratelimit_lock, flags);
1278         toks += now - last_msg;
1279         last_msg = now;
1280         if (toks > (ratelimit_burst * ratelimit_jiffies))
1281                 toks = ratelimit_burst * ratelimit_jiffies;
1282         if (toks >= ratelimit_jiffies) {
1283                 int lost = missed;
1284
1285                 missed = 0;
1286                 toks -= ratelimit_jiffies;
1287                 spin_unlock_irqrestore(&ratelimit_lock, flags);
1288                 if (lost)
1289                         printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1290                 return 1;
1291         }
1292         missed++;
1293         spin_unlock_irqrestore(&ratelimit_lock, flags);
1294         return 0;
1295 }
1296 EXPORT_SYMBOL(__printk_ratelimit);
1297
1298 /* minimum time in jiffies between messages */
1299 int printk_ratelimit_jiffies = 5 * HZ;
1300
1301 /* number of messages we send before ratelimiting */
1302 int printk_ratelimit_burst = 10;
1303
1304 int printk_ratelimit(void)
1305 {
1306         return __printk_ratelimit(printk_ratelimit_jiffies,
1307                                 printk_ratelimit_burst);
1308 }
1309 EXPORT_SYMBOL(printk_ratelimit);
1310
1311 /**
1312  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1313  * @caller_jiffies: pointer to caller's state
1314  * @interval_msecs: minimum interval between prints
1315  *
1316  * printk_timed_ratelimit() returns true if more than @interval_msecs
1317  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1318  * returned true.
1319  */
1320 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1321                         unsigned int interval_msecs)
1322 {
1323         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1324                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1325                 return true;
1326         }
1327         return false;
1328 }
1329 EXPORT_SYMBOL(printk_timed_ratelimit);