[CVE-2009-0029] System call wrappers part 27
[linux-2.6.git] / kernel / printk.c
1 /*
2  *  linux/kernel/printk.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  *
6  * Modified to make sys_syslog() more flexible: added commands to
7  * return the last 4k of kernel messages, regardless of whether
8  * they've been read or not.  Added option to suppress kernel printk's
9  * to the console.  Added hook for sending the console messages
10  * elsewhere, in preparation for a serial line console (someday).
11  * Ted Ts'o, 2/11/93.
12  * Modified for sysctl support, 1/8/97, Chris Horn.
13  * Fixed SMP synchronization, 08/08/99, Manfred Spraul
14  *     manfred@colorfullife.com
15  * Rewrote bits to get rid of console_lock
16  *      01Mar01 Andrew Morton
17  */
18
19 #include <linux/kernel.h>
20 #include <linux/mm.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h>                    /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/syscalls.h>
35
36 #include <asm/uaccess.h>
37
38 /*
39  * Architectures can override it:
40  */
41 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
42 {
43 }
44
45 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
46
47 /* printk's without a loglevel use this.. */
48 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
49
50 /* We show everything that is MORE important than this.. */
51 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
52 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
53
54 DECLARE_WAIT_QUEUE_HEAD(log_wait);
55
56 int console_printk[4] = {
57         DEFAULT_CONSOLE_LOGLEVEL,       /* console_loglevel */
58         DEFAULT_MESSAGE_LOGLEVEL,       /* default_message_loglevel */
59         MINIMUM_CONSOLE_LOGLEVEL,       /* minimum_console_loglevel */
60         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
61 };
62
63 /*
64  * Low level drivers may need that to know if they can schedule in
65  * their unblank() callback or not. So let's export it.
66  */
67 int oops_in_progress;
68 EXPORT_SYMBOL(oops_in_progress);
69
70 /*
71  * console_sem protects the console_drivers list, and also
72  * provides serialisation for access to the entire console
73  * driver system.
74  */
75 static DECLARE_MUTEX(console_sem);
76 static DECLARE_MUTEX(secondary_console_sem);
77 struct console *console_drivers;
78 EXPORT_SYMBOL_GPL(console_drivers);
79
80 /*
81  * This is used for debugging the mess that is the VT code by
82  * keeping track if we have the console semaphore held. It's
83  * definitely not the perfect debug tool (we don't know if _WE_
84  * hold it are racing, but it helps tracking those weird code
85  * path in the console code where we end up in places I want
86  * locked without the console sempahore held
87  */
88 static int console_locked, console_suspended;
89
90 /*
91  * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
92  * It is also used in interesting ways to provide interlocking in
93  * release_console_sem().
94  */
95 static DEFINE_SPINLOCK(logbuf_lock);
96
97 #define LOG_BUF_MASK (log_buf_len-1)
98 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
99
100 /*
101  * The indices into log_buf are not constrained to log_buf_len - they
102  * must be masked before subscripting
103  */
104 static unsigned log_start;      /* Index into log_buf: next char to be read by syslog() */
105 static unsigned con_start;      /* Index into log_buf: next char to be sent to consoles */
106 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
107
108 /*
109  *      Array of consoles built from command line options (console=)
110  */
111 struct console_cmdline
112 {
113         char    name[8];                        /* Name of the driver       */
114         int     index;                          /* Minor dev. to use        */
115         char    *options;                       /* Options for the driver   */
116 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
117         char    *brl_options;                   /* Options for braille driver */
118 #endif
119 };
120
121 #define MAX_CMDLINECONSOLES 8
122
123 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
124 static int selected_console = -1;
125 static int preferred_console = -1;
126 int console_set_on_cmdline;
127 EXPORT_SYMBOL(console_set_on_cmdline);
128
129 /* Flag: console code may call schedule() */
130 static int console_may_schedule;
131
132 #ifdef CONFIG_PRINTK
133
134 static char __log_buf[__LOG_BUF_LEN];
135 static char *log_buf = __log_buf;
136 static int log_buf_len = __LOG_BUF_LEN;
137 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
138
139 static int __init log_buf_len_setup(char *str)
140 {
141         unsigned size = memparse(str, &str);
142         unsigned long flags;
143
144         if (size)
145                 size = roundup_pow_of_two(size);
146         if (size > log_buf_len) {
147                 unsigned start, dest_idx, offset;
148                 char *new_log_buf;
149
150                 new_log_buf = alloc_bootmem(size);
151                 if (!new_log_buf) {
152                         printk(KERN_WARNING "log_buf_len: allocation failed\n");
153                         goto out;
154                 }
155
156                 spin_lock_irqsave(&logbuf_lock, flags);
157                 log_buf_len = size;
158                 log_buf = new_log_buf;
159
160                 offset = start = min(con_start, log_start);
161                 dest_idx = 0;
162                 while (start != log_end) {
163                         log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
164                         start++;
165                         dest_idx++;
166                 }
167                 log_start -= offset;
168                 con_start -= offset;
169                 log_end -= offset;
170                 spin_unlock_irqrestore(&logbuf_lock, flags);
171
172                 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
173         }
174 out:
175         return 1;
176 }
177
178 __setup("log_buf_len=", log_buf_len_setup);
179
180 #ifdef CONFIG_BOOT_PRINTK_DELAY
181
182 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
183 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
184
185 static int __init boot_delay_setup(char *str)
186 {
187         unsigned long lpj;
188         unsigned long long loops_per_msec;
189
190         lpj = preset_lpj ? preset_lpj : 1000000;        /* some guess */
191         loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
192
193         get_option(&str, &boot_delay);
194         if (boot_delay > 10 * 1000)
195                 boot_delay = 0;
196
197         printk_delay_msec = loops_per_msec;
198         printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
199                 "HZ: %d, printk_delay_msec: %llu\n",
200                 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
201         return 1;
202 }
203 __setup("boot_delay=", boot_delay_setup);
204
205 static void boot_delay_msec(void)
206 {
207         unsigned long long k;
208         unsigned long timeout;
209
210         if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
211                 return;
212
213         k = (unsigned long long)printk_delay_msec * boot_delay;
214
215         timeout = jiffies + msecs_to_jiffies(boot_delay);
216         while (k) {
217                 k--;
218                 cpu_relax();
219                 /*
220                  * use (volatile) jiffies to prevent
221                  * compiler reduction; loop termination via jiffies
222                  * is secondary and may or may not happen.
223                  */
224                 if (time_after(jiffies, timeout))
225                         break;
226                 touch_nmi_watchdog();
227         }
228 }
229 #else
230 static inline void boot_delay_msec(void)
231 {
232 }
233 #endif
234
235 /*
236  * Commands to do_syslog:
237  *
238  *      0 -- Close the log.  Currently a NOP.
239  *      1 -- Open the log. Currently a NOP.
240  *      2 -- Read from the log.
241  *      3 -- Read all messages remaining in the ring buffer.
242  *      4 -- Read and clear all messages remaining in the ring buffer
243  *      5 -- Clear ring buffer.
244  *      6 -- Disable printk's to console
245  *      7 -- Enable printk's to console
246  *      8 -- Set level of messages printed to console
247  *      9 -- Return number of unread characters in the log buffer
248  *     10 -- Return size of the log buffer
249  */
250 int do_syslog(int type, char __user *buf, int len)
251 {
252         unsigned i, j, limit, count;
253         int do_clear = 0;
254         char c;
255         int error = 0;
256
257         error = security_syslog(type);
258         if (error)
259                 return error;
260
261         switch (type) {
262         case 0:         /* Close log */
263                 break;
264         case 1:         /* Open log */
265                 break;
266         case 2:         /* Read from log */
267                 error = -EINVAL;
268                 if (!buf || len < 0)
269                         goto out;
270                 error = 0;
271                 if (!len)
272                         goto out;
273                 if (!access_ok(VERIFY_WRITE, buf, len)) {
274                         error = -EFAULT;
275                         goto out;
276                 }
277                 error = wait_event_interruptible(log_wait,
278                                                         (log_start - log_end));
279                 if (error)
280                         goto out;
281                 i = 0;
282                 spin_lock_irq(&logbuf_lock);
283                 while (!error && (log_start != log_end) && i < len) {
284                         c = LOG_BUF(log_start);
285                         log_start++;
286                         spin_unlock_irq(&logbuf_lock);
287                         error = __put_user(c,buf);
288                         buf++;
289                         i++;
290                         cond_resched();
291                         spin_lock_irq(&logbuf_lock);
292                 }
293                 spin_unlock_irq(&logbuf_lock);
294                 if (!error)
295                         error = i;
296                 break;
297         case 4:         /* Read/clear last kernel messages */
298                 do_clear = 1;
299                 /* FALL THRU */
300         case 3:         /* Read last kernel messages */
301                 error = -EINVAL;
302                 if (!buf || len < 0)
303                         goto out;
304                 error = 0;
305                 if (!len)
306                         goto out;
307                 if (!access_ok(VERIFY_WRITE, buf, len)) {
308                         error = -EFAULT;
309                         goto out;
310                 }
311                 count = len;
312                 if (count > log_buf_len)
313                         count = log_buf_len;
314                 spin_lock_irq(&logbuf_lock);
315                 if (count > logged_chars)
316                         count = logged_chars;
317                 if (do_clear)
318                         logged_chars = 0;
319                 limit = log_end;
320                 /*
321                  * __put_user() could sleep, and while we sleep
322                  * printk() could overwrite the messages
323                  * we try to copy to user space. Therefore
324                  * the messages are copied in reverse. <manfreds>
325                  */
326                 for (i = 0; i < count && !error; i++) {
327                         j = limit-1-i;
328                         if (j + log_buf_len < log_end)
329                                 break;
330                         c = LOG_BUF(j);
331                         spin_unlock_irq(&logbuf_lock);
332                         error = __put_user(c,&buf[count-1-i]);
333                         cond_resched();
334                         spin_lock_irq(&logbuf_lock);
335                 }
336                 spin_unlock_irq(&logbuf_lock);
337                 if (error)
338                         break;
339                 error = i;
340                 if (i != count) {
341                         int offset = count-error;
342                         /* buffer overflow during copy, correct user buffer. */
343                         for (i = 0; i < error; i++) {
344                                 if (__get_user(c,&buf[i+offset]) ||
345                                     __put_user(c,&buf[i])) {
346                                         error = -EFAULT;
347                                         break;
348                                 }
349                                 cond_resched();
350                         }
351                 }
352                 break;
353         case 5:         /* Clear ring buffer */
354                 logged_chars = 0;
355                 break;
356         case 6:         /* Disable logging to console */
357                 console_loglevel = minimum_console_loglevel;
358                 break;
359         case 7:         /* Enable logging to console */
360                 console_loglevel = default_console_loglevel;
361                 break;
362         case 8:         /* Set level of messages printed to console */
363                 error = -EINVAL;
364                 if (len < 1 || len > 8)
365                         goto out;
366                 if (len < minimum_console_loglevel)
367                         len = minimum_console_loglevel;
368                 console_loglevel = len;
369                 error = 0;
370                 break;
371         case 9:         /* Number of chars in the log buffer */
372                 error = log_end - log_start;
373                 break;
374         case 10:        /* Size of the log buffer */
375                 error = log_buf_len;
376                 break;
377         default:
378                 error = -EINVAL;
379                 break;
380         }
381 out:
382         return error;
383 }
384
385 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
386 {
387         return do_syslog(type, buf, len);
388 }
389
390 /*
391  * Call the console drivers on a range of log_buf
392  */
393 static void __call_console_drivers(unsigned start, unsigned end)
394 {
395         struct console *con;
396
397         for (con = console_drivers; con; con = con->next) {
398                 if ((con->flags & CON_ENABLED) && con->write &&
399                                 (cpu_online(smp_processor_id()) ||
400                                 (con->flags & CON_ANYTIME)))
401                         con->write(con, &LOG_BUF(start), end - start);
402         }
403 }
404
405 static int __read_mostly ignore_loglevel;
406
407 static int __init ignore_loglevel_setup(char *str)
408 {
409         ignore_loglevel = 1;
410         printk(KERN_INFO "debug: ignoring loglevel setting.\n");
411
412         return 0;
413 }
414
415 early_param("ignore_loglevel", ignore_loglevel_setup);
416
417 /*
418  * Write out chars from start to end - 1 inclusive
419  */
420 static void _call_console_drivers(unsigned start,
421                                 unsigned end, int msg_log_level)
422 {
423         if ((msg_log_level < console_loglevel || ignore_loglevel) &&
424                         console_drivers && start != end) {
425                 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
426                         /* wrapped write */
427                         __call_console_drivers(start & LOG_BUF_MASK,
428                                                 log_buf_len);
429                         __call_console_drivers(0, end & LOG_BUF_MASK);
430                 } else {
431                         __call_console_drivers(start, end);
432                 }
433         }
434 }
435
436 /*
437  * Call the console drivers, asking them to write out
438  * log_buf[start] to log_buf[end - 1].
439  * The console_sem must be held.
440  */
441 static void call_console_drivers(unsigned start, unsigned end)
442 {
443         unsigned cur_index, start_print;
444         static int msg_level = -1;
445
446         BUG_ON(((int)(start - end)) > 0);
447
448         cur_index = start;
449         start_print = start;
450         while (cur_index != end) {
451                 if (msg_level < 0 && ((end - cur_index) > 2) &&
452                                 LOG_BUF(cur_index + 0) == '<' &&
453                                 LOG_BUF(cur_index + 1) >= '0' &&
454                                 LOG_BUF(cur_index + 1) <= '7' &&
455                                 LOG_BUF(cur_index + 2) == '>') {
456                         msg_level = LOG_BUF(cur_index + 1) - '0';
457                         cur_index += 3;
458                         start_print = cur_index;
459                 }
460                 while (cur_index != end) {
461                         char c = LOG_BUF(cur_index);
462
463                         cur_index++;
464                         if (c == '\n') {
465                                 if (msg_level < 0) {
466                                         /*
467                                          * printk() has already given us loglevel tags in
468                                          * the buffer.  This code is here in case the
469                                          * log buffer has wrapped right round and scribbled
470                                          * on those tags
471                                          */
472                                         msg_level = default_message_loglevel;
473                                 }
474                                 _call_console_drivers(start_print, cur_index, msg_level);
475                                 msg_level = -1;
476                                 start_print = cur_index;
477                                 break;
478                         }
479                 }
480         }
481         _call_console_drivers(start_print, end, msg_level);
482 }
483
484 static void emit_log_char(char c)
485 {
486         LOG_BUF(log_end) = c;
487         log_end++;
488         if (log_end - log_start > log_buf_len)
489                 log_start = log_end - log_buf_len;
490         if (log_end - con_start > log_buf_len)
491                 con_start = log_end - log_buf_len;
492         if (logged_chars < log_buf_len)
493                 logged_chars++;
494 }
495
496 /*
497  * Zap console related locks when oopsing. Only zap at most once
498  * every 10 seconds, to leave time for slow consoles to print a
499  * full oops.
500  */
501 static void zap_locks(void)
502 {
503         static unsigned long oops_timestamp;
504
505         if (time_after_eq(jiffies, oops_timestamp) &&
506                         !time_after(jiffies, oops_timestamp + 30 * HZ))
507                 return;
508
509         oops_timestamp = jiffies;
510
511         /* If a crash is occurring, make sure we can't deadlock */
512         spin_lock_init(&logbuf_lock);
513         /* And make sure that we print immediately */
514         init_MUTEX(&console_sem);
515 }
516
517 #if defined(CONFIG_PRINTK_TIME)
518 static int printk_time = 1;
519 #else
520 static int printk_time = 0;
521 #endif
522 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
523
524 /* Check if we have any console registered that can be called early in boot. */
525 static int have_callable_console(void)
526 {
527         struct console *con;
528
529         for (con = console_drivers; con; con = con->next)
530                 if (con->flags & CON_ANYTIME)
531                         return 1;
532
533         return 0;
534 }
535
536 /**
537  * printk - print a kernel message
538  * @fmt: format string
539  *
540  * This is printk().  It can be called from any context.  We want it to work.
541  *
542  * We try to grab the console_sem.  If we succeed, it's easy - we log the output and
543  * call the console drivers.  If we fail to get the semaphore we place the output
544  * into the log buffer and return.  The current holder of the console_sem will
545  * notice the new output in release_console_sem() and will send it to the
546  * consoles before releasing the semaphore.
547  *
548  * One effect of this deferred printing is that code which calls printk() and
549  * then changes console_loglevel may break. This is because console_loglevel
550  * is inspected when the actual printing occurs.
551  *
552  * See also:
553  * printf(3)
554  *
555  * See the vsnprintf() documentation for format string extensions over C99.
556  */
557
558 asmlinkage int printk(const char *fmt, ...)
559 {
560         va_list args;
561         int r;
562
563         va_start(args, fmt);
564         r = vprintk(fmt, args);
565         va_end(args);
566
567         return r;
568 }
569
570 /* cpu currently holding logbuf_lock */
571 static volatile unsigned int printk_cpu = UINT_MAX;
572
573 /*
574  * Can we actually use the console at this time on this cpu?
575  *
576  * Console drivers may assume that per-cpu resources have
577  * been allocated. So unless they're explicitly marked as
578  * being able to cope (CON_ANYTIME) don't call them until
579  * this CPU is officially up.
580  */
581 static inline int can_use_console(unsigned int cpu)
582 {
583         return cpu_online(cpu) || have_callable_console();
584 }
585
586 /*
587  * Try to get console ownership to actually show the kernel
588  * messages from a 'printk'. Return true (and with the
589  * console_semaphore held, and 'console_locked' set) if it
590  * is successful, false otherwise.
591  *
592  * This gets called with the 'logbuf_lock' spinlock held and
593  * interrupts disabled. It should return with 'lockbuf_lock'
594  * released but interrupts still disabled.
595  */
596 static int acquire_console_semaphore_for_printk(unsigned int cpu)
597 {
598         int retval = 0;
599
600         if (!try_acquire_console_sem()) {
601                 retval = 1;
602
603                 /*
604                  * If we can't use the console, we need to release
605                  * the console semaphore by hand to avoid flushing
606                  * the buffer. We need to hold the console semaphore
607                  * in order to do this test safely.
608                  */
609                 if (!can_use_console(cpu)) {
610                         console_locked = 0;
611                         up(&console_sem);
612                         retval = 0;
613                 }
614         }
615         printk_cpu = UINT_MAX;
616         spin_unlock(&logbuf_lock);
617         return retval;
618 }
619 static const char recursion_bug_msg [] =
620                 KERN_CRIT "BUG: recent printk recursion!\n";
621 static int recursion_bug;
622 static int new_text_line = 1;
623 static char printk_buf[1024];
624
625 asmlinkage int vprintk(const char *fmt, va_list args)
626 {
627         int printed_len = 0;
628         int current_log_level = default_message_loglevel;
629         unsigned long flags;
630         int this_cpu;
631         char *p;
632
633         boot_delay_msec();
634
635         preempt_disable();
636         /* This stops the holder of console_sem just where we want him */
637         raw_local_irq_save(flags);
638         this_cpu = smp_processor_id();
639
640         /*
641          * Ouch, printk recursed into itself!
642          */
643         if (unlikely(printk_cpu == this_cpu)) {
644                 /*
645                  * If a crash is occurring during printk() on this CPU,
646                  * then try to get the crash message out but make sure
647                  * we can't deadlock. Otherwise just return to avoid the
648                  * recursion and return - but flag the recursion so that
649                  * it can be printed at the next appropriate moment:
650                  */
651                 if (!oops_in_progress) {
652                         recursion_bug = 1;
653                         goto out_restore_irqs;
654                 }
655                 zap_locks();
656         }
657
658         lockdep_off();
659         spin_lock(&logbuf_lock);
660         printk_cpu = this_cpu;
661
662         if (recursion_bug) {
663                 recursion_bug = 0;
664                 strcpy(printk_buf, recursion_bug_msg);
665                 printed_len = strlen(recursion_bug_msg);
666         }
667         /* Emit the output into the temporary buffer */
668         printed_len += vscnprintf(printk_buf + printed_len,
669                                   sizeof(printk_buf) - printed_len, fmt, args);
670
671
672         /*
673          * Copy the output into log_buf.  If the caller didn't provide
674          * appropriate log level tags, we insert them here
675          */
676         for (p = printk_buf; *p; p++) {
677                 if (new_text_line) {
678                         /* If a token, set current_log_level and skip over */
679                         if (p[0] == '<' && p[1] >= '0' && p[1] <= '7' &&
680                             p[2] == '>') {
681                                 current_log_level = p[1] - '0';
682                                 p += 3;
683                                 printed_len -= 3;
684                         }
685
686                         /* Always output the token */
687                         emit_log_char('<');
688                         emit_log_char(current_log_level + '0');
689                         emit_log_char('>');
690                         printed_len += 3;
691                         new_text_line = 0;
692
693                         if (printk_time) {
694                                 /* Follow the token with the time */
695                                 char tbuf[50], *tp;
696                                 unsigned tlen;
697                                 unsigned long long t;
698                                 unsigned long nanosec_rem;
699
700                                 t = cpu_clock(printk_cpu);
701                                 nanosec_rem = do_div(t, 1000000000);
702                                 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
703                                                 (unsigned long) t,
704                                                 nanosec_rem / 1000);
705
706                                 for (tp = tbuf; tp < tbuf + tlen; tp++)
707                                         emit_log_char(*tp);
708                                 printed_len += tlen;
709                         }
710
711                         if (!*p)
712                                 break;
713                 }
714
715                 emit_log_char(*p);
716                 if (*p == '\n')
717                         new_text_line = 1;
718         }
719
720         /*
721          * Try to acquire and then immediately release the
722          * console semaphore. The release will do all the
723          * actual magic (print out buffers, wake up klogd,
724          * etc). 
725          *
726          * The acquire_console_semaphore_for_printk() function
727          * will release 'logbuf_lock' regardless of whether it
728          * actually gets the semaphore or not.
729          */
730         if (acquire_console_semaphore_for_printk(this_cpu))
731                 release_console_sem();
732
733         lockdep_on();
734 out_restore_irqs:
735         raw_local_irq_restore(flags);
736
737         preempt_enable();
738         return printed_len;
739 }
740 EXPORT_SYMBOL(printk);
741 EXPORT_SYMBOL(vprintk);
742
743 #else
744
745 static void call_console_drivers(unsigned start, unsigned end)
746 {
747 }
748
749 #endif
750
751 static int __add_preferred_console(char *name, int idx, char *options,
752                                    char *brl_options)
753 {
754         struct console_cmdline *c;
755         int i;
756
757         /*
758          *      See if this tty is not yet registered, and
759          *      if we have a slot free.
760          */
761         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
762                 if (strcmp(console_cmdline[i].name, name) == 0 &&
763                           console_cmdline[i].index == idx) {
764                                 if (!brl_options)
765                                         selected_console = i;
766                                 return 0;
767                 }
768         if (i == MAX_CMDLINECONSOLES)
769                 return -E2BIG;
770         if (!brl_options)
771                 selected_console = i;
772         c = &console_cmdline[i];
773         strlcpy(c->name, name, sizeof(c->name));
774         c->options = options;
775 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
776         c->brl_options = brl_options;
777 #endif
778         c->index = idx;
779         return 0;
780 }
781 /*
782  * Set up a list of consoles.  Called from init/main.c
783  */
784 static int __init console_setup(char *str)
785 {
786         char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
787         char *s, *options, *brl_options = NULL;
788         int idx;
789
790 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
791         if (!memcmp(str, "brl,", 4)) {
792                 brl_options = "";
793                 str += 4;
794         } else if (!memcmp(str, "brl=", 4)) {
795                 brl_options = str + 4;
796                 str = strchr(brl_options, ',');
797                 if (!str) {
798                         printk(KERN_ERR "need port name after brl=\n");
799                         return 1;
800                 }
801                 *(str++) = 0;
802         }
803 #endif
804
805         /*
806          * Decode str into name, index, options.
807          */
808         if (str[0] >= '0' && str[0] <= '9') {
809                 strcpy(buf, "ttyS");
810                 strncpy(buf + 4, str, sizeof(buf) - 5);
811         } else {
812                 strncpy(buf, str, sizeof(buf) - 1);
813         }
814         buf[sizeof(buf) - 1] = 0;
815         if ((options = strchr(str, ',')) != NULL)
816                 *(options++) = 0;
817 #ifdef __sparc__
818         if (!strcmp(str, "ttya"))
819                 strcpy(buf, "ttyS0");
820         if (!strcmp(str, "ttyb"))
821                 strcpy(buf, "ttyS1");
822 #endif
823         for (s = buf; *s; s++)
824                 if ((*s >= '0' && *s <= '9') || *s == ',')
825                         break;
826         idx = simple_strtoul(s, NULL, 10);
827         *s = 0;
828
829         __add_preferred_console(buf, idx, options, brl_options);
830         console_set_on_cmdline = 1;
831         return 1;
832 }
833 __setup("console=", console_setup);
834
835 /**
836  * add_preferred_console - add a device to the list of preferred consoles.
837  * @name: device name
838  * @idx: device index
839  * @options: options for this console
840  *
841  * The last preferred console added will be used for kernel messages
842  * and stdin/out/err for init.  Normally this is used by console_setup
843  * above to handle user-supplied console arguments; however it can also
844  * be used by arch-specific code either to override the user or more
845  * commonly to provide a default console (ie from PROM variables) when
846  * the user has not supplied one.
847  */
848 int add_preferred_console(char *name, int idx, char *options)
849 {
850         return __add_preferred_console(name, idx, options, NULL);
851 }
852
853 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
854 {
855         struct console_cmdline *c;
856         int i;
857
858         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
859                 if (strcmp(console_cmdline[i].name, name) == 0 &&
860                           console_cmdline[i].index == idx) {
861                                 c = &console_cmdline[i];
862                                 strlcpy(c->name, name_new, sizeof(c->name));
863                                 c->name[sizeof(c->name) - 1] = 0;
864                                 c->options = options;
865                                 c->index = idx_new;
866                                 return i;
867                 }
868         /* not found */
869         return -1;
870 }
871
872 int console_suspend_enabled = 1;
873 EXPORT_SYMBOL(console_suspend_enabled);
874
875 static int __init console_suspend_disable(char *str)
876 {
877         console_suspend_enabled = 0;
878         return 1;
879 }
880 __setup("no_console_suspend", console_suspend_disable);
881
882 /**
883  * suspend_console - suspend the console subsystem
884  *
885  * This disables printk() while we go into suspend states
886  */
887 void suspend_console(void)
888 {
889         if (!console_suspend_enabled)
890                 return;
891         printk("Suspending console(s) (use no_console_suspend to debug)\n");
892         acquire_console_sem();
893         console_suspended = 1;
894 }
895
896 void resume_console(void)
897 {
898         if (!console_suspend_enabled)
899                 return;
900         console_suspended = 0;
901         release_console_sem();
902 }
903
904 /**
905  * acquire_console_sem - lock the console system for exclusive use.
906  *
907  * Acquires a semaphore which guarantees that the caller has
908  * exclusive access to the console system and the console_drivers list.
909  *
910  * Can sleep, returns nothing.
911  */
912 void acquire_console_sem(void)
913 {
914         BUG_ON(in_interrupt());
915         if (console_suspended) {
916                 down(&secondary_console_sem);
917                 return;
918         }
919         down(&console_sem);
920         console_locked = 1;
921         console_may_schedule = 1;
922 }
923 EXPORT_SYMBOL(acquire_console_sem);
924
925 int try_acquire_console_sem(void)
926 {
927         if (down_trylock(&console_sem))
928                 return -1;
929         console_locked = 1;
930         console_may_schedule = 0;
931         return 0;
932 }
933 EXPORT_SYMBOL(try_acquire_console_sem);
934
935 int is_console_locked(void)
936 {
937         return console_locked;
938 }
939
940 static DEFINE_PER_CPU(int, printk_pending);
941
942 void printk_tick(void)
943 {
944         if (__get_cpu_var(printk_pending)) {
945                 __get_cpu_var(printk_pending) = 0;
946                 wake_up_interruptible(&log_wait);
947         }
948 }
949
950 int printk_needs_cpu(int cpu)
951 {
952         return per_cpu(printk_pending, cpu);
953 }
954
955 void wake_up_klogd(void)
956 {
957         if (waitqueue_active(&log_wait))
958                 __raw_get_cpu_var(printk_pending) = 1;
959 }
960
961 /**
962  * release_console_sem - unlock the console system
963  *
964  * Releases the semaphore which the caller holds on the console system
965  * and the console driver list.
966  *
967  * While the semaphore was held, console output may have been buffered
968  * by printk().  If this is the case, release_console_sem() emits
969  * the output prior to releasing the semaphore.
970  *
971  * If there is output waiting for klogd, we wake it up.
972  *
973  * release_console_sem() may be called from any context.
974  */
975 void release_console_sem(void)
976 {
977         unsigned long flags;
978         unsigned _con_start, _log_end;
979         unsigned wake_klogd = 0;
980
981         if (console_suspended) {
982                 up(&secondary_console_sem);
983                 return;
984         }
985
986         console_may_schedule = 0;
987
988         for ( ; ; ) {
989                 spin_lock_irqsave(&logbuf_lock, flags);
990                 wake_klogd |= log_start - log_end;
991                 if (con_start == log_end)
992                         break;                  /* Nothing to print */
993                 _con_start = con_start;
994                 _log_end = log_end;
995                 con_start = log_end;            /* Flush */
996                 spin_unlock(&logbuf_lock);
997                 stop_critical_timings();        /* don't trace print latency */
998                 call_console_drivers(_con_start, _log_end);
999                 start_critical_timings();
1000                 local_irq_restore(flags);
1001         }
1002         console_locked = 0;
1003         up(&console_sem);
1004         spin_unlock_irqrestore(&logbuf_lock, flags);
1005         if (wake_klogd)
1006                 wake_up_klogd();
1007 }
1008 EXPORT_SYMBOL(release_console_sem);
1009
1010 /**
1011  * console_conditional_schedule - yield the CPU if required
1012  *
1013  * If the console code is currently allowed to sleep, and
1014  * if this CPU should yield the CPU to another task, do
1015  * so here.
1016  *
1017  * Must be called within acquire_console_sem().
1018  */
1019 void __sched console_conditional_schedule(void)
1020 {
1021         if (console_may_schedule)
1022                 cond_resched();
1023 }
1024 EXPORT_SYMBOL(console_conditional_schedule);
1025
1026 void console_print(const char *s)
1027 {
1028         printk(KERN_EMERG "%s", s);
1029 }
1030 EXPORT_SYMBOL(console_print);
1031
1032 void console_unblank(void)
1033 {
1034         struct console *c;
1035
1036         /*
1037          * console_unblank can no longer be called in interrupt context unless
1038          * oops_in_progress is set to 1..
1039          */
1040         if (oops_in_progress) {
1041                 if (down_trylock(&console_sem) != 0)
1042                         return;
1043         } else
1044                 acquire_console_sem();
1045
1046         console_locked = 1;
1047         console_may_schedule = 0;
1048         for (c = console_drivers; c != NULL; c = c->next)
1049                 if ((c->flags & CON_ENABLED) && c->unblank)
1050                         c->unblank();
1051         release_console_sem();
1052 }
1053
1054 /*
1055  * Return the console tty driver structure and its associated index
1056  */
1057 struct tty_driver *console_device(int *index)
1058 {
1059         struct console *c;
1060         struct tty_driver *driver = NULL;
1061
1062         acquire_console_sem();
1063         for (c = console_drivers; c != NULL; c = c->next) {
1064                 if (!c->device)
1065                         continue;
1066                 driver = c->device(c, index);
1067                 if (driver)
1068                         break;
1069         }
1070         release_console_sem();
1071         return driver;
1072 }
1073
1074 /*
1075  * Prevent further output on the passed console device so that (for example)
1076  * serial drivers can disable console output before suspending a port, and can
1077  * re-enable output afterwards.
1078  */
1079 void console_stop(struct console *console)
1080 {
1081         acquire_console_sem();
1082         console->flags &= ~CON_ENABLED;
1083         release_console_sem();
1084 }
1085 EXPORT_SYMBOL(console_stop);
1086
1087 void console_start(struct console *console)
1088 {
1089         acquire_console_sem();
1090         console->flags |= CON_ENABLED;
1091         release_console_sem();
1092 }
1093 EXPORT_SYMBOL(console_start);
1094
1095 /*
1096  * The console driver calls this routine during kernel initialization
1097  * to register the console printing procedure with printk() and to
1098  * print any messages that were printed by the kernel before the
1099  * console driver was initialized.
1100  */
1101 void register_console(struct console *console)
1102 {
1103         int i;
1104         unsigned long flags;
1105         struct console *bootconsole = NULL;
1106
1107         if (console_drivers) {
1108                 if (console->flags & CON_BOOT)
1109                         return;
1110                 if (console_drivers->flags & CON_BOOT)
1111                         bootconsole = console_drivers;
1112         }
1113
1114         if (preferred_console < 0 || bootconsole || !console_drivers)
1115                 preferred_console = selected_console;
1116
1117         if (console->early_setup)
1118                 console->early_setup();
1119
1120         /*
1121          *      See if we want to use this console driver. If we
1122          *      didn't select a console we take the first one
1123          *      that registers here.
1124          */
1125         if (preferred_console < 0) {
1126                 if (console->index < 0)
1127                         console->index = 0;
1128                 if (console->setup == NULL ||
1129                     console->setup(console, NULL) == 0) {
1130                         console->flags |= CON_ENABLED;
1131                         if (console->device) {
1132                                 console->flags |= CON_CONSDEV;
1133                                 preferred_console = 0;
1134                         }
1135                 }
1136         }
1137
1138         /*
1139          *      See if this console matches one we selected on
1140          *      the command line.
1141          */
1142         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1143                         i++) {
1144                 if (strcmp(console_cmdline[i].name, console->name) != 0)
1145                         continue;
1146                 if (console->index >= 0 &&
1147                     console->index != console_cmdline[i].index)
1148                         continue;
1149                 if (console->index < 0)
1150                         console->index = console_cmdline[i].index;
1151 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1152                 if (console_cmdline[i].brl_options) {
1153                         console->flags |= CON_BRL;
1154                         braille_register_console(console,
1155                                         console_cmdline[i].index,
1156                                         console_cmdline[i].options,
1157                                         console_cmdline[i].brl_options);
1158                         return;
1159                 }
1160 #endif
1161                 if (console->setup &&
1162                     console->setup(console, console_cmdline[i].options) != 0)
1163                         break;
1164                 console->flags |= CON_ENABLED;
1165                 console->index = console_cmdline[i].index;
1166                 if (i == selected_console) {
1167                         console->flags |= CON_CONSDEV;
1168                         preferred_console = selected_console;
1169                 }
1170                 break;
1171         }
1172
1173         if (!(console->flags & CON_ENABLED))
1174                 return;
1175
1176         if (bootconsole && (console->flags & CON_CONSDEV)) {
1177                 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1178                        bootconsole->name, bootconsole->index,
1179                        console->name, console->index);
1180                 unregister_console(bootconsole);
1181                 console->flags &= ~CON_PRINTBUFFER;
1182         } else {
1183                 printk(KERN_INFO "console [%s%d] enabled\n",
1184                        console->name, console->index);
1185         }
1186
1187         /*
1188          *      Put this console in the list - keep the
1189          *      preferred driver at the head of the list.
1190          */
1191         acquire_console_sem();
1192         if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1193                 console->next = console_drivers;
1194                 console_drivers = console;
1195                 if (console->next)
1196                         console->next->flags &= ~CON_CONSDEV;
1197         } else {
1198                 console->next = console_drivers->next;
1199                 console_drivers->next = console;
1200         }
1201         if (console->flags & CON_PRINTBUFFER) {
1202                 /*
1203                  * release_console_sem() will print out the buffered messages
1204                  * for us.
1205                  */
1206                 spin_lock_irqsave(&logbuf_lock, flags);
1207                 con_start = log_start;
1208                 spin_unlock_irqrestore(&logbuf_lock, flags);
1209         }
1210         release_console_sem();
1211 }
1212 EXPORT_SYMBOL(register_console);
1213
1214 int unregister_console(struct console *console)
1215 {
1216         struct console *a, *b;
1217         int res = 1;
1218
1219 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1220         if (console->flags & CON_BRL)
1221                 return braille_unregister_console(console);
1222 #endif
1223
1224         acquire_console_sem();
1225         if (console_drivers == console) {
1226                 console_drivers=console->next;
1227                 res = 0;
1228         } else if (console_drivers) {
1229                 for (a=console_drivers->next, b=console_drivers ;
1230                      a; b=a, a=b->next) {
1231                         if (a == console) {
1232                                 b->next = a->next;
1233                                 res = 0;
1234                                 break;
1235                         }
1236                 }
1237         }
1238
1239         /*
1240          * If this isn't the last console and it has CON_CONSDEV set, we
1241          * need to set it on the next preferred console.
1242          */
1243         if (console_drivers != NULL && console->flags & CON_CONSDEV)
1244                 console_drivers->flags |= CON_CONSDEV;
1245
1246         release_console_sem();
1247         return res;
1248 }
1249 EXPORT_SYMBOL(unregister_console);
1250
1251 static int __init disable_boot_consoles(void)
1252 {
1253         if (console_drivers != NULL) {
1254                 if (console_drivers->flags & CON_BOOT) {
1255                         printk(KERN_INFO "turn off boot console %s%d\n",
1256                                 console_drivers->name, console_drivers->index);
1257                         return unregister_console(console_drivers);
1258                 }
1259         }
1260         return 0;
1261 }
1262 late_initcall(disable_boot_consoles);
1263
1264 #if defined CONFIG_PRINTK
1265
1266 /*
1267  * printk rate limiting, lifted from the networking subsystem.
1268  *
1269  * This enforces a rate limit: not more than 10 kernel messages
1270  * every 5s to make a denial-of-service attack impossible.
1271  */
1272 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1273
1274 int printk_ratelimit(void)
1275 {
1276         return __ratelimit(&printk_ratelimit_state);
1277 }
1278 EXPORT_SYMBOL(printk_ratelimit);
1279
1280 /**
1281  * printk_timed_ratelimit - caller-controlled printk ratelimiting
1282  * @caller_jiffies: pointer to caller's state
1283  * @interval_msecs: minimum interval between prints
1284  *
1285  * printk_timed_ratelimit() returns true if more than @interval_msecs
1286  * milliseconds have elapsed since the last time printk_timed_ratelimit()
1287  * returned true.
1288  */
1289 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1290                         unsigned int interval_msecs)
1291 {
1292         if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1293                 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1294                 return true;
1295         }
1296         return false;
1297 }
1298 EXPORT_SYMBOL(printk_timed_ratelimit);
1299 #endif