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
36 #include <asm/uaccess.h>
37
38 /*
39 * Architectures can override it:
40 */
41 void __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 /*
79 * This is used for debugging the mess that is the VT code by
80 * keeping track if we have the console semaphore held. It's
81 * definitely not the perfect debug tool (we don't know if _WE_
82 * hold it are racing, but it helps tracking those weird code
83 * path in the console code where we end up in places I want
84 * locked without the console sempahore held
85 */
86 static int console_locked, console_suspended;
87
88 /*
89 * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
90 * It is also used in interesting ways to provide interlocking in
91 * release_console_sem().
92 */
93 static DEFINE_RAW_SPINLOCK(logbuf_lock);
94
95 #define LOG_BUF_MASK (log_buf_len-1)
96 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
97
98 /*
99 * The indices into log_buf are not constrained to log_buf_len - they
100 * must be masked before subscripting
101 */
102 static unsigned log_start; /* Index into log_buf: next char to be read by syslog() */
103 static unsigned con_start; /* Index into log_buf: next char to be sent to consoles */
104 static unsigned log_end; /* Index into log_buf: most-recently-written-char + 1 */
105
106 /*
107 * Array of consoles built from command line options (console=)
108 */
109 struct console_cmdline
110 {
111 char name[8]; /* Name of the driver */
112 int index; /* Minor dev. to use */
113 char *options; /* Options for the driver */
114 };
115
116 #define MAX_CMDLINECONSOLES 8
117
118 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
119 static int selected_console = -1;
120 static int preferred_console = -1;
121
122 /* Flag: console code may call schedule() */
123 static int console_may_schedule;
124
125 #ifdef CONFIG_PRINTK
126
127 static char __log_buf[__LOG_BUF_LEN];
128 static char *log_buf = __log_buf;
129 static int log_buf_len = __LOG_BUF_LEN;
130 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
131
132 static int __init log_buf_len_setup(char *str)
133 {
134 unsigned size = memparse(str, &str);
135 unsigned long flags;
136
137 if (size)
138 size = roundup_pow_of_two(size);
139 if (size > log_buf_len) {
140 unsigned start, dest_idx, offset;
141 char *new_log_buf;
142
143 new_log_buf = alloc_bootmem(size);
144 if (!new_log_buf) {
145 printk(KERN_WARNING "log_buf_len: allocation failed\n");
146 goto out;
147 }
148
149 spin_lock_irqsave(&logbuf_lock, flags);
150 log_buf_len = size;
151 log_buf = new_log_buf;
152
153 offset = start = min(con_start, log_start);
154 dest_idx = 0;
155 while (start != log_end) {
156 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
157 start++;
158 dest_idx++;
159 }
160 log_start -= offset;
161 con_start -= offset;
162 log_end -= offset;
163 spin_unlock_irqrestore(&logbuf_lock, flags);
164
165 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
166 }
167 out:
168 return 1;
169 }
170
171 __setup("log_buf_len=", log_buf_len_setup);
172
173 #ifdef CONFIG_BOOT_PRINTK_DELAY
174
175 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
176 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
177
178 static int __init boot_delay_setup(char *str)
179 {
180 unsigned long lpj;
181 unsigned long long loops_per_msec;
182
183 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
184 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
185
186 get_option(&str, &boot_delay);
187 if (boot_delay > 10 * 1000)
188 boot_delay = 0;
189
190 printk_delay_msec = loops_per_msec;
191 printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
192 "HZ: %d, printk_delay_msec: %llu\n",
193 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
194 return 1;
195 }
196 __setup("boot_delay=", boot_delay_setup);
197
198 static void boot_delay_msec(void)
199 {
200 unsigned long long k;
201 unsigned long timeout;
202
203 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
204 return;
205
206 k = (unsigned long long)printk_delay_msec * boot_delay;
207
208 timeout = jiffies + msecs_to_jiffies(boot_delay);
209 while (k) {
210 k--;
211 cpu_relax();
212 /*
213 * use (volatile) jiffies to prevent
214 * compiler reduction; loop termination via jiffies
215 * is secondary and may or may not happen.
216 */
217 if (time_after(jiffies, timeout))
218 break;
219 touch_nmi_watchdog();
220 }
221 }
222 #else
223 static inline void boot_delay_msec(void)
224 {
225 }
226 #endif
227
228 /*
229 * Return the number of unread characters in the log buffer.
230 */
231 int log_buf_get_len(void)
232 {
233 return logged_chars;
234 }
235
236 /*
237 * Copy a range of characters from the log buffer.
238 */
239 int log_buf_copy(char *dest, int idx, int len)
240 {
241 int ret, max;
242 bool took_lock = false;
243
244 if (!oops_in_progress) {
245 spin_lock_irq(&logbuf_lock);
246 took_lock = true;
247 }
248
249 max = log_buf_get_len();
250 if (idx < 0 || idx >= max) {
251 ret = -1;
252 } else {
253 if (len > max)
254 len = max;
255 ret = len;
256 idx += (log_end - max);
257 while (len-- > 0)
258 dest[len] = LOG_BUF(idx + len);
259 }
260
261 if (took_lock)
262 spin_unlock_irq(&logbuf_lock);
263
264 return ret;
265 }
266
267 /*
268 * Extract a single character from the log buffer.
269 */
270 int log_buf_read(int idx)
271 {
272 char ret;
273
274 if (log_buf_copy(&ret, idx, 1) == 1)
275 return ret;
276 else
277 return -1;
278 }
279
280 /*
281 * Commands to do_syslog:
282 *
283 * 0 -- Close the log. Currently a NOP.
284 * 1 -- Open the log. Currently a NOP.
285 * 2 -- Read from the log.
286 * 3 -- Read all messages remaining in the ring buffer.
287 * 4 -- Read and clear all messages remaining in the ring buffer
288 * 5 -- Clear ring buffer.
289 * 6 -- Disable printk's to console
290 * 7 -- Enable printk's to console
291 * 8 -- Set level of messages printed to console
292 * 9 -- Return number of unread characters in the log buffer
293 * 10 -- Return size of the log buffer
294 */
295 int do_syslog(int type, char __user *buf, int len)
296 {
297 unsigned i, j, limit, count;
298 int do_clear = 0;
299 char c;
300 int error = 0;
301
302 error = security_syslog(type);
303 if (error)
304 return error;
305
306 switch (type) {
307 case 0: /* Close log */
308 break;
309 case 1: /* Open log */
310 break;
311 case 2: /* Read from log */
312 error = -EINVAL;
313 if (!buf || len < 0)
314 goto out;
315 error = 0;
316 if (!len)
317 goto out;
318 if (!access_ok(VERIFY_WRITE, buf, len)) {
319 error = -EFAULT;
320 goto out;
321 }
322 error = wait_event_interruptible(log_wait,
323 (log_start - log_end));
324 if (error)
325 goto out;
326 i = 0;
327 spin_lock_irq(&logbuf_lock);
328 while (!error && (log_start != log_end) && i < len) {
329 c = LOG_BUF(log_start);
330 log_start++;
331 spin_unlock_irq(&logbuf_lock);
332 error = __put_user(c,buf);
333 buf++;
334 i++;
335 cond_resched();
336 spin_lock_irq(&logbuf_lock);
337 }
338 spin_unlock_irq(&logbuf_lock);
339 if (!error)
340 error = i;
341 break;
342 case 4: /* Read/clear last kernel messages */
343 do_clear = 1;
344 /* FALL THRU */
345 case 3: /* Read last kernel messages */
346 error = -EINVAL;
347 if (!buf || len < 0)
348 goto out;
349 error = 0;
350 if (!len)
351 goto out;
352 if (!access_ok(VERIFY_WRITE, buf, len)) {
353 error = -EFAULT;
354 goto out;
355 }
356 count = len;
357 if (count > log_buf_len)
358 count = log_buf_len;
359 spin_lock_irq(&logbuf_lock);
360 if (count > logged_chars)
361 count = logged_chars;
362 if (do_clear)
363 logged_chars = 0;
364 limit = log_end;
365 /*
366 * __put_user() could sleep, and while we sleep
367 * printk() could overwrite the messages
368 * we try to copy to user space. Therefore
369 * the messages are copied in reverse. <manfreds>
370 */
371 for (i = 0; i < count && !error; i++) {
372 j = limit-1-i;
373 if (j + log_buf_len < log_end)
374 break;
375 c = LOG_BUF(j);
376 spin_unlock_irq(&logbuf_lock);
377 error = __put_user(c,&buf[count-1-i]);
378 cond_resched();
379 spin_lock_irq(&logbuf_lock);
380 }
381 spin_unlock_irq(&logbuf_lock);
382 if (error)
383 break;
384 error = i;
385 if (i != count) {
386 int offset = count-error;
387 /* buffer overflow during copy, correct user buffer. */
388 for (i = 0; i < error; i++) {
389 if (__get_user(c,&buf[i+offset]) ||
390 __put_user(c,&buf[i])) {
391 error = -EFAULT;
392 break;
393 }
394 cond_resched();
395 }
396 }
397 break;
398 case 5: /* Clear ring buffer */
399 logged_chars = 0;
400 break;
401 case 6: /* Disable logging to console */
402 console_loglevel = minimum_console_loglevel;
403 break;
404 case 7: /* Enable logging to console */
405 console_loglevel = default_console_loglevel;
406 break;
407 case 8: /* Set level of messages printed to console */
408 error = -EINVAL;
409 if (len < 1 || len > 8)
410 goto out;
411 if (len < minimum_console_loglevel)
412 len = minimum_console_loglevel;
413 console_loglevel = len;
414 error = 0;
415 break;
416 case 9: /* Number of chars in the log buffer */
417 error = log_end - log_start;
418 break;
419 case 10: /* Size of the log buffer */
420 error = log_buf_len;
421 break;
422 default:
423 error = -EINVAL;
424 break;
425 }
426 out:
427 return error;
428 }
429
430 asmlinkage long sys_syslog(int type, char __user *buf, int len)
431 {
432 return do_syslog(type, buf, len);
433 }
434
435 /*
436 * Call the console drivers on a range of log_buf
437 */
438 static void __call_console_drivers(unsigned start, unsigned end)
439 {
440 struct console *con;
441
442 for (con = console_drivers; con; con = con->next) {
443 if ((con->flags & CON_ENABLED) && con->write &&
444 console_atomic_safe(con) &&
445 (cpu_online(raw_smp_processor_id()) ||
446 (con->flags & CON_ANYTIME))) {
447 set_printk_might_sleep(1);
448 con->write(con, &LOG_BUF(start), end - start);
449 set_printk_might_sleep(0);
450 }
451 }
452 }
453
454 static int __read_mostly ignore_loglevel;
455
456 static int __init ignore_loglevel_setup(char *str)
457 {
458 ignore_loglevel = 1;
459 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
460
461 return 0;
462 }
463
464 early_param("ignore_loglevel", ignore_loglevel_setup);
465
466 /*
467 * Write out chars from start to end - 1 inclusive
468 */
469 static void _call_console_drivers(unsigned start,
470 unsigned end, int msg_log_level)
471 {
472 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
473 console_drivers && start != end) {
474 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
475 /* wrapped write */
476 __call_console_drivers(start & LOG_BUF_MASK,
477 log_buf_len);
478 __call_console_drivers(0, end & LOG_BUF_MASK);
479 } else {
480 __call_console_drivers(start, end);
481 }
482 }
483 }
484
485 /*
486 * Call the console drivers, asking them to write out
487 * log_buf[start] to log_buf[end - 1].
488 * The console_sem must be held.
489 */
490 static void call_console_drivers(unsigned start, unsigned end)
491 {
492 unsigned cur_index, start_print;
493 static int msg_level = -1;
494
495 BUG_ON(((int)(start - end)) > 0);
496
497 cur_index = start;
498 start_print = start;
499 while (cur_index != end) {
500 if (msg_level < 0 && ((end - cur_index) > 2) &&
501 LOG_BUF(cur_index + 0) == '<' &&
502 LOG_BUF(cur_index + 1) >= '' &&
503 LOG_BUF(cur_index + 1) <= '7' &&
504 LOG_BUF(cur_index + 2) == '>') {
505 msg_level = LOG_BUF(cur_index + 1) - '';
506 cur_index += 3;
507 start_print = cur_index;
508 }
509 while (cur_index != end) {
510 char c = LOG_BUF(cur_index);
511
512 cur_index++;
513 if (c == '\n') {
514 if (msg_level < 0) {
515 /*
516 * printk() has already given us loglevel tags in
517 * the buffer. This code is here in case the
518 * log buffer has wrapped right round and scribbled
519 * on those tags
520 */
521 msg_level = default_message_loglevel;
522 }
523 _call_console_drivers(start_print, cur_index, msg_level);
524 msg_level = -1;
525 start_print = cur_index;
526 break;
527 }
528 }
529 }
530 _call_console_drivers(start_print, end, msg_level);
531 }
532
533 static void emit_log_char(char c)
534 {
535 LOG_BUF(log_end) = c;
536 log_end++;
537 if (log_end - log_start > log_buf_len)
538 log_start = log_end - log_buf_len;
539 if (log_end - con_start > log_buf_len)
540 con_start = log_end - log_buf_len;
541 if (logged_chars < log_buf_len)
542 logged_chars++;
543 }
544
545 /*
546 * Zap console related locks when oopsing. Only zap at most once
547 * every 10 seconds, to leave time for slow consoles to print a
548 * full oops.
549 */
550 static void zap_locks(void)
551 {
552 static unsigned long oops_timestamp;
553
554 if (time_after_eq(jiffies, oops_timestamp) &&
555 !time_after(jiffies, oops_timestamp + 30 * HZ))
556 return;
557
558 oops_timestamp = jiffies;
559
560 /* If a crash is occurring, make sure we can't deadlock */
561 spin_lock_init(&logbuf_lock);
562 /* And make sure that we print immediately */
563 init_MUTEX(&console_sem);
564 zap_rt_locks();
565 }
566
567 #if defined(CONFIG_PRINTK_TIME)
568 static int printk_time = 1;
569 #else
570 static int printk_time = 0;
571 #endif
572 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
573
574 /* Check if we have any console registered that can be called early in boot. */
575 static int have_callable_console(void)
576 {
577 struct console *con;
578
579 for (con = console_drivers; con; con = con->next)
580 if (con->flags & CON_ANYTIME)
581 return 1;
582
583 return 0;
584 }
585
586 /**
587 * printk - print a kernel message
588 * @fmt: format string
589 *
590 * This is printk(). It can be called from any context. We want it to work.
591 * Be aware of the fact that if oops_in_progress is not set, we might try to
592 * wake klogd up which could deadlock on runqueue lock if printk() is called
593 * from scheduler code.
594 *
595 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
596 * call the console drivers. If we fail to get the semaphore we place the output
597 * into the log buffer and return. The current holder of the console_sem will
598 * notice the new output in release_console_sem() and will send it to the
599 * consoles before releasing the semaphore.
600 *
601 * One effect of this deferred printing is that code which calls printk() and
602 * then changes console_loglevel may break. This is because console_loglevel
603 * is inspected when the actual printing occurs.
604 *
605 * See also:
606 * printf(3)
607 */
608
609 asmlinkage int printk(const char *fmt, ...)
610 {
611 va_list args;
612 int r;
613
614 va_start(args, fmt);
615 r = vprintk(fmt, args);
616 va_end(args);
617
618 return r;
619 }
620
621 /* cpu currently holding logbuf_lock */
622 static volatile unsigned int printk_cpu = UINT_MAX;
623
624 /*
625 * Can we actually use the console at this time on this cpu?
626 *
627 * Console drivers may assume that per-cpu resources have
628 * been allocated. So unless they're explicitly marked as
629 * being able to cope (CON_ANYTIME) don't call them until
630 * this CPU is officially up.
631 */
632 static inline int can_use_console(unsigned int cpu)
633 {
634 return cpu_online(cpu) || have_callable_console();
635 }
636
637 /*
638 * Try to get console ownership to actually show the kernel
639 * messages from a 'printk'. Return true (and with the
640 * console_semaphore held, and 'console_locked' set) if it
641 * is successful, false otherwise.
642 *
643 * This gets called with the 'logbuf_lock' spinlock held and
644 * interrupts disabled. It should return with 'lockbuf_lock'
645 * released but interrupts still disabled.
646 */
647 static int acquire_console_semaphore_for_printk(unsigned int cpu,
648 unsigned long flags)
649 {
650 int retval = 0;
651
652 if (!try_acquire_console_sem()) {
653 retval = 1;
654
655 /*
656 * If we can't use the console, we need to release
657 * the console semaphore by hand to avoid flushing
658 * the buffer. We need to hold the console semaphore
659 * in order to do this test safely.
660 */
661 if (!can_use_console(cpu)) {
662 console_locked = 0;
663 up(&console_sem);
664 retval = 0;
665 }
666 }
667 printk_cpu = UINT_MAX;
668 spin_unlock(&logbuf_lock);
669 lockdep_on();
670 local_irq_restore(flags);
671 return retval;
672 }
673
674 const char printk_recursion_bug_msg [] =
675 KERN_CRIT "BUG: recent printk recursion!\n";
676 static int printk_recursion_bug;
677
678 asmlinkage int vprintk(const char *fmt, va_list args)
679 {
680 static int log_level_unknown = 1;
681 static char printk_buf[1024];
682
683 unsigned long flags;
684 int printed_len = 0;
685 int this_cpu;
686 char *p;
687
688 boot_delay_msec();
689
690 preempt_disable();
691 /* This stops the holder of console_sem just where we want him */
692 raw_local_irq_save(flags);
693 this_cpu = raw_smp_processor_id();
694
695 /*
696 * Ouch, printk recursed into itself!
697 */
698 if (unlikely(printk_cpu == this_cpu)) {
699 /*
700 * If a crash is occurring during printk() on this CPU,
701 * then try to get the crash message out but make sure
702 * we can't deadlock. Otherwise just return to avoid the
703 * recursion and return - but flag the recursion so that
704 * it can be printed at the next appropriate moment:
705 */
706 if (!oops_in_progress) {
707 printk_recursion_bug = 1;
708 raw_local_irq_restore(flags);
709 goto out;
710 }
711 zap_locks();
712 }
713
714 lockdep_off();
715 spin_lock(&logbuf_lock);
716 printk_cpu = this_cpu;
717 preempt_enable();
718
719 if (printk_recursion_bug) {
720 printk_recursion_bug = 0;
721 strcpy(printk_buf, printk_recursion_bug_msg);
722 printed_len = sizeof(printk_recursion_bug_msg);
723 }
724 /* Emit the output into the temporary buffer */
725 printed_len += vscnprintf(printk_buf + printed_len,
726 sizeof(printk_buf) - printed_len, fmt, args);
727
728 /*
729 * Copy the output into log_buf. If the caller didn't provide
730 * appropriate log level tags, we insert them here
731 */
732 for (p = printk_buf; *p; p++) {
733 if (log_level_unknown) {
734 /* log_level_unknown signals the start of a new line */
735 if (printk_time) {
736 int loglev_char;
737 char tbuf[50], *tp;
738 unsigned tlen;
739 unsigned long long t;
740 unsigned long nanosec_rem;
741
742 /*
743 * force the log level token to be
744 * before the time output.
745 */
746 if (p[0] == '<' && p[1] >='' &&
747 p[1] <= '7' && p[2] == '>') {
748 loglev_char = p[1];
749 p += 3;
750 printed_len -= 3;
751 } else {
752 loglev_char = default_message_loglevel
753 + '';
754 }
755 t = cpu_clock(printk_cpu);
756 nanosec_rem = do_div(t, 1000000000);
757 tlen = sprintf(tbuf,
758 "<%c>[%5lu.%06lu] ",
759 loglev_char,
760 (unsigned long)t,
761 nanosec_rem/1000);
762
763 for (tp = tbuf; tp < tbuf + tlen; tp++)
764 emit_log_char(*tp);
765 printed_len += tlen;
766 } else {
767 if (p[0] != '<' || p[1] < '' ||
768 p[1] > '7' || p[2] != '>') {
769 emit_log_char('<');
770 emit_log_char(default_message_loglevel
771 + '');
772 emit_log_char('>');
773 printed_len += 3;
774 }
775 }
776 log_level_unknown = 0;
777 if (!*p)
778 break;
779 }
780 emit_log_char(*p);
781 if (*p == '\n')
782 log_level_unknown = 1;
783 }
784
785 /*
786 * Try to acquire and then immediately release the
787 * console semaphore. The release will do all the
788 * actual magic (print out buffers, wake up klogd,
789 * etc).
790 *
791 * The acquire_console_semaphore_for_printk() function
792 * will release 'logbuf_lock' regardless of whether it
793 * actually gets the semaphore or not.
794 */
795 if (acquire_console_semaphore_for_printk(this_cpu, flags))
796 release_console_sem();
797
798 out:
799 return printed_len;
800 }
801 EXPORT_SYMBOL(printk);
802 EXPORT_SYMBOL(vprintk);
803
804 #else
805
806 asmlinkage long sys_syslog(int type, char __user *buf, int len)
807 {
808 return -ENOSYS;
809 }
810
811 static void call_console_drivers(unsigned start, unsigned end)
812 {
813 }
814
815 #endif
816
817 /*
818 * Set up a list of consoles. Called from init/main.c
819 */
820 static int __init console_setup(char *str)
821 {
822 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
823 char *s, *options;
824 int idx;
825
826 /*
827 * Decode str into name, index, options.
828 */
829 if (str[0] >= '' && str[0] <= '9') {
830 strcpy(buf, "ttyS");
831 strncpy(buf + 4, str, sizeof(buf) - 5);
832 } else {
833 strncpy(buf, str, sizeof(buf) - 1);
834 }
835 buf[sizeof(buf) - 1] = 0;
836 if ((options = strchr(str, ',')) != NULL)
837 *(options++) = 0;
838 #ifdef __sparc__
839 if (!strcmp(str, "ttya"))
840 strcpy(buf, "ttyS0");
841 if (!strcmp(str, "ttyb"))
842 strcpy(buf, "ttyS1");
843 #endif
844 for (s = buf; *s; s++)
845 if ((*s >= '' && *s <= '9') || *s == ',')
846 break;
847 idx = simple_strtoul(s, NULL, 10);
848 *s = 0;
849
850 add_preferred_console(buf, idx, options);
851 return 1;
852 }
853 __setup("console=", console_setup);
854
855 /**
856 * add_preferred_console - add a device to the list of preferred consoles.
857 * @name: device name
858 * @idx: device index
859 * @options: options for this console
860 *
861 * The last preferred console added will be used for kernel messages
862 * and stdin/out/err for init. Normally this is used by console_setup
863 * above to handle user-supplied console arguments; however it can also
864 * be used by arch-specific code either to override the user or more
865 * commonly to provide a default console (ie from PROM variables) when
866 * the user has not supplied one.
867 */
868 int add_preferred_console(char *name, int idx, char *options)
869 {
870 struct console_cmdline *c;
871 int i;
872
873 /*
874 * See if this tty is not yet registered, and
875 * if we have a slot free.
876 */
877 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
878 if (strcmp(console_cmdline[i].name, name) == 0 &&
879 console_cmdline[i].index == idx) {
880 selected_console = i;
881 return 0;
882 }
883 if (i == MAX_CMDLINECONSOLES)
884 return -E2BIG;
885 selected_console = i;
886 c = &console_cmdline[i];
887 memcpy(c->name, name, sizeof(c->name));
888 c->name[sizeof(c->name) - 1] = 0;
889 c->options = options;
890 c->index = idx;
891 return 0;
892 }
893
894 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
895 {
896 struct console_cmdline *c;
897 int i;
898
899 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
900 if (strcmp(console_cmdline[i].name, name) == 0 &&
901 console_cmdline[i].index == idx) {
902 c = &console_cmdline[i];
903 memcpy(c->name, name_new, sizeof(c->name));
904 c->name[sizeof(c->name) - 1] = 0;
905 c->options = options;
906 c->index = idx_new;
907 return i;
908 }
909 /* not found */
910 return -1;
911 }
912
913 int console_suspend_enabled = 1;
914 EXPORT_SYMBOL(console_suspend_enabled);
915
916 static int __init console_suspend_disable(char *str)
917 {
918 console_suspend_enabled = 0;
919 return 1;
920 }
921 __setup("no_console_suspend", console_suspend_disable);
922
923 /**
924 * suspend_console - suspend the console subsystem
925 *
926 * This disables printk() while we go into suspend states
927 */
928 void suspend_console(void)
929 {
930 if (!console_suspend_enabled)
931 return;
932 printk("Suspending console(s)\n");
933 acquire_console_sem();
934 console_suspended = 1;
935 }
936
937 void resume_console(void)
938 {
939 if (!console_suspend_enabled)
940 return;
941 console_suspended = 0;
942 release_console_sem();
943 }
944
945 /**
946 * acquire_console_sem - lock the console system for exclusive use.
947 *
948 * Acquires a semaphore which guarantees that the caller has
949 * exclusive access to the console system and the console_drivers list.
950 *
951 * Can sleep, returns nothing.
952 */
953 void acquire_console_sem(void)
954 {
955 BUG_ON(in_interrupt());
956 if (console_suspended) {
957 down(&secondary_console_sem);
958 return;
959 }
960 down(&console_sem);
961 console_locked = 1;
962 console_may_schedule = 1;
963 }
964 EXPORT_SYMBOL(acquire_console_sem);
965
966 int try_acquire_console_sem(void)
967 {
968 if (down_trylock(&console_sem))
969 return -1;
970 console_locked = 1;
971 console_may_schedule = 0;
972 return 0;
973 }
974 EXPORT_SYMBOL(try_acquire_console_sem);
975
976 int is_console_locked(void)
977 {
978 return console_locked;
979 }
980
981 void wake_up_klogd(void)
982 {
983 if (!oops_in_progress && waitqueue_active(&log_wait))
984 wake_up_interruptible(&log_wait);
985 }
986
987 /**
988 * release_console_sem - unlock the console system
989 *
990 * Releases the semaphore which the caller holds on the console system
991 * and the console driver list.
992 *
993 * While the semaphore was held, console output may have been buffered
994 * by printk(). If this is the case, release_console_sem() emits
995 * the output prior to releasing the semaphore.
996 *
997 * If there is output waiting for klogd, we wake it up.
998 *
999 * release_console_sem() may be called from any context.
1000 */
1001 void release_console_sem(void)
1002 {
1003 unsigned long flags;
1004 unsigned _con_start, _log_end;
1005 unsigned wake_klogd = 0;
1006
1007 if (console_suspended) {
1008 up(&secondary_console_sem);
1009 return;
1010 }
1011
1012 console_may_schedule = 0;
1013
1014 for ( ; ; ) {
1015 spin_lock_irqsave(&logbuf_lock, flags);
1016 wake_klogd |= log_start - log_end;
1017 if (con_start == log_end)
1018 break; /* Nothing to print */
1019 _con_start = con_start;
1020 _log_end = log_end;
1021 con_start = log_end; /* Flush */
1022 /*
1023 * on PREEMPT_RT, call console drivers with
1024 * interrupts enabled (if printk was called
1025 * with interrupts disabled):
1026 */
1027 #ifdef CONFIG_PREEMPT_RT
1028 spin_unlock_irqrestore(&logbuf_lock, flags);
1029 #else
1030 spin_unlock(&logbuf_lock);
1031 #endif
1032 call_console_drivers(_con_start, _log_end);
1033 #ifndef CONFIG_PREEMPT_RT
1034 local_irq_restore(flags);
1035 #endif
1036 }
1037 console_locked = 0;
1038 spin_unlock_irqrestore(&logbuf_lock, flags);
1039 up(&console_sem);
1040 /*
1041 * On PREEMPT_RT kernels __wake_up may sleep, so wake syslogd
1042 * up only if we are in a preemptible section. We normally dont
1043 * printk from non-preemptible sections so this is for the emergency
1044 * case only.
1045 */
1046 #ifdef CONFIG_PREEMPT_RT
1047 if (!in_atomic() && !irqs_disabled())
1048 #endif
1049 if (wake_klogd)
1050 wake_up_klogd();
1051 }
1052 EXPORT_SYMBOL(release_console_sem);
1053
1054 /**
1055 * console_conditional_schedule - yield the CPU if required
1056 *
1057 * If the console code is currently allowed to sleep, and
1058 * if this CPU should yield the CPU to another task, do
1059 * so here.
1060 *
1061 * Must be called within acquire_console_sem().
1062 */
1063 void __sched console_conditional_schedule(void)
1064 {
1065 if (console_may_schedule)
1066 cond_resched();
1067 }
1068 EXPORT_SYMBOL(console_conditional_schedule);
1069
1070 void console_print(const char *s)
1071 {
1072 printk(KERN_EMERG "%s", s);
1073 }
1074 EXPORT_SYMBOL(console_print);
1075
1076 void console_unblank(void)
1077 {
1078 struct console *c;
1079
1080 /*
1081 * console_unblank can no longer be called in interrupt context unless
1082 * oops_in_progress is set to 1..
1083 */
1084 if (oops_in_progress) {
1085 if (down_trylock(&console_sem) != 0)
1086 return;
1087 } else
1088 acquire_console_sem();
1089
1090 console_locked = 1;
1091 console_may_schedule = 0;
1092 for (c = console_drivers; c != NULL; c = c->next)
1093 if ((c->flags & CON_ENABLED) && c->unblank)
1094 c->unblank();
1095 release_console_sem();
1096 }
1097
1098 /*
1099 * Return the console tty driver structure and its associated index
1100 */
1101 struct tty_driver *console_device(int *index)
1102 {
1103 struct console *c;
1104 struct tty_driver *driver = NULL;
1105
1106 acquire_console_sem();
1107 for (c = console_drivers; c != NULL; c = c->next) {
1108 if (!c->device)
1109 continue;
1110 driver = c->device(c, index);
1111 if (driver)
1112 break;
1113 }
1114 release_console_sem();
1115 return driver;
1116 }
1117
1118 /*
1119 * Prevent further output on the passed console device so that (for example)
1120 * serial drivers can disable console output before suspending a port, and can
1121 * re-enable output afterwards.
1122 */
1123 void console_stop(struct console *console)
1124 {
1125 acquire_console_sem();
1126 console->flags &= ~CON_ENABLED;
1127 release_console_sem();
1128 }
1129 EXPORT_SYMBOL(console_stop);
1130
1131 void console_start(struct console *console)
1132 {
1133 acquire_console_sem();
1134 console->flags |= CON_ENABLED;
1135 release_console_sem();
1136 }
1137 EXPORT_SYMBOL(console_start);
1138
1139 /*
1140 * The console driver calls this routine during kernel initialization
1141 * to register the console printing procedure with printk() and to
1142 * print any messages that were printed by the kernel before the
1143 * console driver was initialized.
1144 */
1145 void register_console(struct console *console)
1146 {
1147 int i;
1148 unsigned long flags;
1149 struct console *bootconsole = NULL;
1150
1151 if (console_drivers) {
1152 if (console->flags & CON_BOOT)
1153 return;
1154 if (console_drivers->flags & CON_BOOT)
1155 bootconsole = console_drivers;
1156 }
1157
1158 if (preferred_console < 0 || bootconsole || !console_drivers)
1159 preferred_console = selected_console;
1160
1161 if (console->early_setup)
1162 console->early_setup();
1163
1164 /*
1165 * See if we want to use this console driver. If we
1166 * didn't select a console we take the first one
1167 * that registers here.
1168 */
1169 if (preferred_console < 0) {
1170 if (console->index < 0)
1171 console->index = 0;
1172 if (console->setup == NULL ||
1173 console->setup(console, NULL) == 0) {
1174 console->flags |= CON_ENABLED | CON_CONSDEV;
1175 preferred_console = 0;
1176 }
1177 }
1178
1179 /*
1180 * See if this console matches one we selected on
1181 * the command line.
1182 */
1183 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1184 i++) {
1185 if (strcmp(console_cmdline[i].name, console->name) != 0)
1186 continue;
1187 if (console->index >= 0 &&
1188 console->index != console_cmdline[i].index)
1189 continue;
1190 if (console->index < 0)
1191 console->index = console_cmdline[i].index;
1192 if (console->setup &&
1193 console->setup(console, console_cmdline[i].options) != 0)
1194 break;
1195 console->flags |= CON_ENABLED;
1196 console->index = console_cmdline[i].index;
1197 if (i == selected_console) {
1198 console->flags |= CON_CONSDEV;
1199 preferred_console = selected_console;
1200 }
1201 break;
1202 }
1203
1204 if (!(console->flags & CON_ENABLED))
1205 return;
1206
1207 if (bootconsole && (console->flags & CON_CONSDEV)) {
1208 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1209 bootconsole->name, bootconsole->index,
1210 console->name, console->index);
1211 unregister_console(bootconsole);
1212 console->flags &= ~CON_PRINTBUFFER;
1213 } else {
1214 printk(KERN_INFO "console [%s%d] enabled\n",
1215 console->name, console->index);
1216 }
1217
1218 /*
1219 * Put this console in the list - keep the
1220 * preferred driver at the head of the list.
1221 */
1222 acquire_console_sem();
1223 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1224 console->next = console_drivers;
1225 console_drivers = console;
1226 if (console->next)
1227 console->next->flags &= ~CON_CONSDEV;
1228 } else {
1229 console->next = console_drivers->next;
1230 console_drivers->next = console;
1231 }
1232 if (console->flags & CON_PRINTBUFFER) {
1233 /*
1234 * release_console_sem() will print out the buffered messages
1235 * for us.
1236 */
1237 spin_lock_irqsave(&logbuf_lock, flags);
1238 con_start = log_start;
1239 spin_unlock_irqrestore(&logbuf_lock, flags);
1240 }
1241 release_console_sem();
1242 }
1243 EXPORT_SYMBOL(register_console);
1244
1245 int unregister_console(struct console *console)
1246 {
1247 struct console *a, *b;
1248 int res = 1;
1249
1250 acquire_console_sem();
1251 if (console_drivers == console) {
1252 console_drivers=console->next;
1253 res = 0;
1254 } else if (console_drivers) {
1255 for (a=console_drivers->next, b=console_drivers ;
1256 a; b=a, a=b->next) {
1257 if (a == console) {
1258 b->next = a->next;
1259 res = 0;
1260 break;
1261 }
1262 }
1263 }
1264
1265 /*
1266 * If this isn't the last console and it has CON_CONSDEV set, we
1267 * need to set it on the next preferred console.
1268 */
1269 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1270 console_drivers->flags |= CON_CONSDEV;
1271
1272 release_console_sem();
1273 return res;
1274 }
1275 EXPORT_SYMBOL(unregister_console);
1276
1277 static int __init disable_boot_consoles(void)
1278 {
1279 if (console_drivers != NULL) {
1280 if (console_drivers->flags & CON_BOOT) {
1281 printk(KERN_INFO "turn off boot console %s%d\n",
1282 console_drivers->name, console_drivers->index);
1283 return unregister_console(console_drivers);
1284 }
1285 }
1286 return 0;
1287 }
1288 late_initcall(disable_boot_consoles);
1289
1290 /**
1291 * tty_write_message - write a message to a certain tty, not just the console.
1292 * @tty: the destination tty_struct
1293 * @msg: the message to write
1294 *
1295 * This is used for messages that need to be redirected to a specific tty.
1296 * We don't put it into the syslog queue right now maybe in the future if
1297 * really needed.
1298 */
1299 void tty_write_message(struct tty_struct *tty, char *msg)
1300 {
1301 if (tty && tty->driver->write)
1302 tty->driver->write(tty, msg, strlen(msg));
1303 return;
1304 }
1305
1306 #if defined CONFIG_PRINTK
1307 /*
1308 * printk rate limiting, lifted from the networking subsystem.
1309 *
1310 * This enforces a rate limit: not more than one kernel message
1311 * every printk_ratelimit_jiffies to make a denial-of-service
1312 * attack impossible.
1313 */
1314 int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
1315 {
1316 static DEFINE_RAW_SPINLOCK(ratelimit_lock);
1317 static unsigned toks = 10 * 5 * HZ;
1318 static unsigned long last_msg;
1319 static int missed;
1320 unsigned long flags;
1321 unsigned long now = jiffies;
1322
1323 spin_lock_irqsave(&ratelimit_lock, flags);
1324 toks += now - last_msg;
1325 last_msg = now;
1326 if (toks > (ratelimit_burst * ratelimit_jiffies))
1327 toks = ratelimit_burst * ratelimit_jiffies;
1328 if (toks >= ratelimit_jiffies) {
1329 int lost = missed;
1330
1331 missed = 0;
1332 toks -= ratelimit_jiffies;
1333 spin_unlock_irqrestore(&ratelimit_lock, flags);
1334 if (lost)
1335 printk(KERN_WARNING "printk: %d messages suppressed.\n", lost);
1336 return 1;
1337 }
1338 missed++;
1339 spin_unlock_irqrestore(&ratelimit_lock, flags);
1340 return 0;
1341 }
1342 EXPORT_SYMBOL(__printk_ratelimit);
1343
1344 /* minimum time in jiffies between messages */
1345 int printk_ratelimit_jiffies = 5 * HZ;
1346
1347 /* number of messages we send before ratelimiting */
1348 int printk_ratelimit_burst = 10;
1349
1350 int printk_ratelimit(void)
1351 {
1352 return __printk_ratelimit(printk_ratelimit_jiffies,
1353 printk_ratelimit_burst);
1354 }
1355 EXPORT_SYMBOL(printk_ratelimit);
1356
1357 static DEFINE_RAW_SPINLOCK(warn_lock);
1358
1359 void __WARN_ON(const char *func, const char *file, const int line)
1360 {
1361 unsigned long flags;
1362
1363 spin_lock_irqsave(&warn_lock, flags);
1364 printk("%s/%d[CPU#%d]: BUG in %s at %s:%d\n",
1365 current->comm, current->pid, raw_smp_processor_id(),
1366 func, file, line);
1367 dump_stack();
1368 spin_unlock_irqrestore(&warn_lock, flags);
1369 }
1370
1371 EXPORT_SYMBOL(__WARN_ON);
1372
1373
1374 /**
1375 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1376 * @caller_jiffies: pointer to caller's state
1377 * @interval_msecs: minimum interval between prints
1378 *
1379 * printk_timed_ratelimit() returns true if more than @interval_msecs
1380 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1381 * returned true.
1382 */
1383 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1384 unsigned int interval_msecs)
1385 {
1386 if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) {
1387 *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs);
1388 return true;
1389 }
1390 return false;
1391 }
1392 EXPORT_SYMBOL(printk_timed_ratelimit);
1393 #endif
1394
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