sparc64: Fix stack debugging IRQ stack regression.
[linux-2.6/mini2440.git] / kernel / printk.c
blobb4d97b54c1ecfa729eaa4b07dc2f721c25bca3ca
1 /*
2 * linux/kernel/printk.c
4 * Copyright (C) 1991, 1992 Linus Torvalds
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
19 #include <linux/kernel.h>
20 #include <linux/mm.h>
21 #include <linux/tty.h>
22 #include <linux/tty_driver.h>
23 #include <linux/console.h>
24 #include <linux/init.h>
25 #include <linux/jiffies.h>
26 #include <linux/nmi.h>
27 #include <linux/module.h>
28 #include <linux/moduleparam.h>
29 #include <linux/interrupt.h> /* For in_interrupt() */
30 #include <linux/delay.h>
31 #include <linux/smp.h>
32 #include <linux/security.h>
33 #include <linux/bootmem.h>
34 #include <linux/syscalls.h>
35 #include <linux/kexec.h>
37 #include <asm/uaccess.h>
40 * Architectures can override it:
42 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
46 #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
48 /* printk's without a loglevel use this.. */
49 #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
51 /* We show everything that is MORE important than this.. */
52 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
53 #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */
55 DECLARE_WAIT_QUEUE_HEAD(log_wait);
57 int console_printk[4] = {
58 DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */
59 DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */
60 MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */
61 DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
65 * Low level drivers may need that to know if they can schedule in
66 * their unblank() callback or not. So let's export it.
68 int oops_in_progress;
69 EXPORT_SYMBOL(oops_in_progress);
72 * console_sem protects the console_drivers list, and also
73 * provides serialisation for access to the entire console
74 * driver system.
76 static DECLARE_MUTEX(console_sem);
77 struct console *console_drivers;
78 EXPORT_SYMBOL_GPL(console_drivers);
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
88 static int console_locked, console_suspended;
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().
95 static DEFINE_SPINLOCK(logbuf_lock);
97 #define LOG_BUF_MASK (log_buf_len-1)
98 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
101 * The indices into log_buf are not constrained to log_buf_len - they
102 * must be masked before subscripting
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 */
109 * Array of consoles built from command line options (console=)
111 struct console_cmdline
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
121 #define MAX_CMDLINECONSOLES 8
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);
129 /* Flag: console code may call schedule() */
130 static int console_may_schedule;
132 #ifdef CONFIG_PRINTK
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 */
139 #ifdef CONFIG_KEXEC
141 * This appends the listed symbols to /proc/vmcoreinfo
143 * /proc/vmcoreinfo is used by various utiilties, like crash and makedumpfile to
144 * obtain access to symbols that are otherwise very difficult to locate. These
145 * symbols are specifically used so that utilities can access and extract the
146 * dmesg log from a vmcore file after a crash.
148 void log_buf_kexec_setup(void)
150 VMCOREINFO_SYMBOL(log_buf);
151 VMCOREINFO_SYMBOL(log_end);
152 VMCOREINFO_SYMBOL(log_buf_len);
153 VMCOREINFO_SYMBOL(logged_chars);
155 #endif
157 static int __init log_buf_len_setup(char *str)
159 unsigned size = memparse(str, &str);
160 unsigned long flags;
162 if (size)
163 size = roundup_pow_of_two(size);
164 if (size > log_buf_len) {
165 unsigned start, dest_idx, offset;
166 char *new_log_buf;
168 new_log_buf = alloc_bootmem(size);
169 if (!new_log_buf) {
170 printk(KERN_WARNING "log_buf_len: allocation failed\n");
171 goto out;
174 spin_lock_irqsave(&logbuf_lock, flags);
175 log_buf_len = size;
176 log_buf = new_log_buf;
178 offset = start = min(con_start, log_start);
179 dest_idx = 0;
180 while (start != log_end) {
181 log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)];
182 start++;
183 dest_idx++;
185 log_start -= offset;
186 con_start -= offset;
187 log_end -= offset;
188 spin_unlock_irqrestore(&logbuf_lock, flags);
190 printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len);
192 out:
193 return 1;
196 __setup("log_buf_len=", log_buf_len_setup);
198 #ifdef CONFIG_BOOT_PRINTK_DELAY
200 static unsigned int boot_delay; /* msecs delay after each printk during bootup */
201 static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */
203 static int __init boot_delay_setup(char *str)
205 unsigned long lpj;
206 unsigned long long loops_per_msec;
208 lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */
209 loops_per_msec = (unsigned long long)lpj / 1000 * HZ;
211 get_option(&str, &boot_delay);
212 if (boot_delay > 10 * 1000)
213 boot_delay = 0;
215 printk_delay_msec = loops_per_msec;
216 printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, "
217 "HZ: %d, printk_delay_msec: %llu\n",
218 boot_delay, preset_lpj, lpj, HZ, printk_delay_msec);
219 return 1;
221 __setup("boot_delay=", boot_delay_setup);
223 static void boot_delay_msec(void)
225 unsigned long long k;
226 unsigned long timeout;
228 if (boot_delay == 0 || system_state != SYSTEM_BOOTING)
229 return;
231 k = (unsigned long long)printk_delay_msec * boot_delay;
233 timeout = jiffies + msecs_to_jiffies(boot_delay);
234 while (k) {
235 k--;
236 cpu_relax();
238 * use (volatile) jiffies to prevent
239 * compiler reduction; loop termination via jiffies
240 * is secondary and may or may not happen.
242 if (time_after(jiffies, timeout))
243 break;
244 touch_nmi_watchdog();
247 #else
248 static inline void boot_delay_msec(void)
251 #endif
254 * Commands to do_syslog:
256 * 0 -- Close the log. Currently a NOP.
257 * 1 -- Open the log. Currently a NOP.
258 * 2 -- Read from the log.
259 * 3 -- Read all messages remaining in the ring buffer.
260 * 4 -- Read and clear all messages remaining in the ring buffer
261 * 5 -- Clear ring buffer.
262 * 6 -- Disable printk's to console
263 * 7 -- Enable printk's to console
264 * 8 -- Set level of messages printed to console
265 * 9 -- Return number of unread characters in the log buffer
266 * 10 -- Return size of the log buffer
268 int do_syslog(int type, char __user *buf, int len)
270 unsigned i, j, limit, count;
271 int do_clear = 0;
272 char c;
273 int error = 0;
275 error = security_syslog(type);
276 if (error)
277 return error;
279 switch (type) {
280 case 0: /* Close log */
281 break;
282 case 1: /* Open log */
283 break;
284 case 2: /* Read from log */
285 error = -EINVAL;
286 if (!buf || len < 0)
287 goto out;
288 error = 0;
289 if (!len)
290 goto out;
291 if (!access_ok(VERIFY_WRITE, buf, len)) {
292 error = -EFAULT;
293 goto out;
295 error = wait_event_interruptible(log_wait,
296 (log_start - log_end));
297 if (error)
298 goto out;
299 i = 0;
300 spin_lock_irq(&logbuf_lock);
301 while (!error && (log_start != log_end) && i < len) {
302 c = LOG_BUF(log_start);
303 log_start++;
304 spin_unlock_irq(&logbuf_lock);
305 error = __put_user(c,buf);
306 buf++;
307 i++;
308 cond_resched();
309 spin_lock_irq(&logbuf_lock);
311 spin_unlock_irq(&logbuf_lock);
312 if (!error)
313 error = i;
314 break;
315 case 4: /* Read/clear last kernel messages */
316 do_clear = 1;
317 /* FALL THRU */
318 case 3: /* Read last kernel messages */
319 error = -EINVAL;
320 if (!buf || len < 0)
321 goto out;
322 error = 0;
323 if (!len)
324 goto out;
325 if (!access_ok(VERIFY_WRITE, buf, len)) {
326 error = -EFAULT;
327 goto out;
329 count = len;
330 if (count > log_buf_len)
331 count = log_buf_len;
332 spin_lock_irq(&logbuf_lock);
333 if (count > logged_chars)
334 count = logged_chars;
335 if (do_clear)
336 logged_chars = 0;
337 limit = log_end;
339 * __put_user() could sleep, and while we sleep
340 * printk() could overwrite the messages
341 * we try to copy to user space. Therefore
342 * the messages are copied in reverse. <manfreds>
344 for (i = 0; i < count && !error; i++) {
345 j = limit-1-i;
346 if (j + log_buf_len < log_end)
347 break;
348 c = LOG_BUF(j);
349 spin_unlock_irq(&logbuf_lock);
350 error = __put_user(c,&buf[count-1-i]);
351 cond_resched();
352 spin_lock_irq(&logbuf_lock);
354 spin_unlock_irq(&logbuf_lock);
355 if (error)
356 break;
357 error = i;
358 if (i != count) {
359 int offset = count-error;
360 /* buffer overflow during copy, correct user buffer. */
361 for (i = 0; i < error; i++) {
362 if (__get_user(c,&buf[i+offset]) ||
363 __put_user(c,&buf[i])) {
364 error = -EFAULT;
365 break;
367 cond_resched();
370 break;
371 case 5: /* Clear ring buffer */
372 logged_chars = 0;
373 break;
374 case 6: /* Disable logging to console */
375 console_loglevel = minimum_console_loglevel;
376 break;
377 case 7: /* Enable logging to console */
378 console_loglevel = default_console_loglevel;
379 break;
380 case 8: /* Set level of messages printed to console */
381 error = -EINVAL;
382 if (len < 1 || len > 8)
383 goto out;
384 if (len < minimum_console_loglevel)
385 len = minimum_console_loglevel;
386 console_loglevel = len;
387 error = 0;
388 break;
389 case 9: /* Number of chars in the log buffer */
390 error = log_end - log_start;
391 break;
392 case 10: /* Size of the log buffer */
393 error = log_buf_len;
394 break;
395 default:
396 error = -EINVAL;
397 break;
399 out:
400 return error;
403 SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
405 return do_syslog(type, buf, len);
409 * Call the console drivers on a range of log_buf
411 static void __call_console_drivers(unsigned start, unsigned end)
413 struct console *con;
415 for (con = console_drivers; con; con = con->next) {
416 if ((con->flags & CON_ENABLED) && con->write &&
417 (cpu_online(smp_processor_id()) ||
418 (con->flags & CON_ANYTIME)))
419 con->write(con, &LOG_BUF(start), end - start);
423 static int __read_mostly ignore_loglevel;
425 static int __init ignore_loglevel_setup(char *str)
427 ignore_loglevel = 1;
428 printk(KERN_INFO "debug: ignoring loglevel setting.\n");
430 return 0;
433 early_param("ignore_loglevel", ignore_loglevel_setup);
436 * Write out chars from start to end - 1 inclusive
438 static void _call_console_drivers(unsigned start,
439 unsigned end, int msg_log_level)
441 if ((msg_log_level < console_loglevel || ignore_loglevel) &&
442 console_drivers && start != end) {
443 if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
444 /* wrapped write */
445 __call_console_drivers(start & LOG_BUF_MASK,
446 log_buf_len);
447 __call_console_drivers(0, end & LOG_BUF_MASK);
448 } else {
449 __call_console_drivers(start, end);
455 * Call the console drivers, asking them to write out
456 * log_buf[start] to log_buf[end - 1].
457 * The console_sem must be held.
459 static void call_console_drivers(unsigned start, unsigned end)
461 unsigned cur_index, start_print;
462 static int msg_level = -1;
464 BUG_ON(((int)(start - end)) > 0);
466 cur_index = start;
467 start_print = start;
468 while (cur_index != end) {
469 if (msg_level < 0 && ((end - cur_index) > 2) &&
470 LOG_BUF(cur_index + 0) == '<' &&
471 LOG_BUF(cur_index + 1) >= '0' &&
472 LOG_BUF(cur_index + 1) <= '7' &&
473 LOG_BUF(cur_index + 2) == '>') {
474 msg_level = LOG_BUF(cur_index + 1) - '0';
475 cur_index += 3;
476 start_print = cur_index;
478 while (cur_index != end) {
479 char c = LOG_BUF(cur_index);
481 cur_index++;
482 if (c == '\n') {
483 if (msg_level < 0) {
485 * printk() has already given us loglevel tags in
486 * the buffer. This code is here in case the
487 * log buffer has wrapped right round and scribbled
488 * on those tags
490 msg_level = default_message_loglevel;
492 _call_console_drivers(start_print, cur_index, msg_level);
493 msg_level = -1;
494 start_print = cur_index;
495 break;
499 _call_console_drivers(start_print, end, msg_level);
502 static void emit_log_char(char c)
504 LOG_BUF(log_end) = c;
505 log_end++;
506 if (log_end - log_start > log_buf_len)
507 log_start = log_end - log_buf_len;
508 if (log_end - con_start > log_buf_len)
509 con_start = log_end - log_buf_len;
510 if (logged_chars < log_buf_len)
511 logged_chars++;
515 * Zap console related locks when oopsing. Only zap at most once
516 * every 10 seconds, to leave time for slow consoles to print a
517 * full oops.
519 static void zap_locks(void)
521 static unsigned long oops_timestamp;
523 if (time_after_eq(jiffies, oops_timestamp) &&
524 !time_after(jiffies, oops_timestamp + 30 * HZ))
525 return;
527 oops_timestamp = jiffies;
529 /* If a crash is occurring, make sure we can't deadlock */
530 spin_lock_init(&logbuf_lock);
531 /* And make sure that we print immediately */
532 init_MUTEX(&console_sem);
535 #if defined(CONFIG_PRINTK_TIME)
536 static int printk_time = 1;
537 #else
538 static int printk_time = 0;
539 #endif
540 module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
542 /* Check if we have any console registered that can be called early in boot. */
543 static int have_callable_console(void)
545 struct console *con;
547 for (con = console_drivers; con; con = con->next)
548 if (con->flags & CON_ANYTIME)
549 return 1;
551 return 0;
555 * printk - print a kernel message
556 * @fmt: format string
558 * This is printk(). It can be called from any context. We want it to work.
560 * We try to grab the console_sem. If we succeed, it's easy - we log the output and
561 * call the console drivers. If we fail to get the semaphore we place the output
562 * into the log buffer and return. The current holder of the console_sem will
563 * notice the new output in release_console_sem() and will send it to the
564 * consoles before releasing the semaphore.
566 * One effect of this deferred printing is that code which calls printk() and
567 * then changes console_loglevel may break. This is because console_loglevel
568 * is inspected when the actual printing occurs.
570 * See also:
571 * printf(3)
573 * See the vsnprintf() documentation for format string extensions over C99.
576 asmlinkage int printk(const char *fmt, ...)
578 va_list args;
579 int r;
581 va_start(args, fmt);
582 r = vprintk(fmt, args);
583 va_end(args);
585 return r;
588 /* cpu currently holding logbuf_lock */
589 static volatile unsigned int printk_cpu = UINT_MAX;
592 * Can we actually use the console at this time on this cpu?
594 * Console drivers may assume that per-cpu resources have
595 * been allocated. So unless they're explicitly marked as
596 * being able to cope (CON_ANYTIME) don't call them until
597 * this CPU is officially up.
599 static inline int can_use_console(unsigned int cpu)
601 return cpu_online(cpu) || have_callable_console();
605 * Try to get console ownership to actually show the kernel
606 * messages from a 'printk'. Return true (and with the
607 * console_semaphore held, and 'console_locked' set) if it
608 * is successful, false otherwise.
610 * This gets called with the 'logbuf_lock' spinlock held and
611 * interrupts disabled. It should return with 'lockbuf_lock'
612 * released but interrupts still disabled.
614 static int acquire_console_semaphore_for_printk(unsigned int cpu)
616 int retval = 0;
618 if (!try_acquire_console_sem()) {
619 retval = 1;
622 * If we can't use the console, we need to release
623 * the console semaphore by hand to avoid flushing
624 * the buffer. We need to hold the console semaphore
625 * in order to do this test safely.
627 if (!can_use_console(cpu)) {
628 console_locked = 0;
629 up(&console_sem);
630 retval = 0;
633 printk_cpu = UINT_MAX;
634 spin_unlock(&logbuf_lock);
635 return retval;
637 static const char recursion_bug_msg [] =
638 KERN_CRIT "BUG: recent printk recursion!\n";
639 static int recursion_bug;
640 static int new_text_line = 1;
641 static char printk_buf[1024];
643 asmlinkage int vprintk(const char *fmt, va_list args)
645 int printed_len = 0;
646 int current_log_level = default_message_loglevel;
647 unsigned long flags;
648 int this_cpu;
649 char *p;
651 boot_delay_msec();
653 preempt_disable();
654 /* This stops the holder of console_sem just where we want him */
655 raw_local_irq_save(flags);
656 this_cpu = smp_processor_id();
659 * Ouch, printk recursed into itself!
661 if (unlikely(printk_cpu == this_cpu)) {
663 * If a crash is occurring during printk() on this CPU,
664 * then try to get the crash message out but make sure
665 * we can't deadlock. Otherwise just return to avoid the
666 * recursion and return - but flag the recursion so that
667 * it can be printed at the next appropriate moment:
669 if (!oops_in_progress) {
670 recursion_bug = 1;
671 goto out_restore_irqs;
673 zap_locks();
676 lockdep_off();
677 spin_lock(&logbuf_lock);
678 printk_cpu = this_cpu;
680 if (recursion_bug) {
681 recursion_bug = 0;
682 strcpy(printk_buf, recursion_bug_msg);
683 printed_len = strlen(recursion_bug_msg);
685 /* Emit the output into the temporary buffer */
686 printed_len += vscnprintf(printk_buf + printed_len,
687 sizeof(printk_buf) - printed_len, fmt, args);
690 p = printk_buf;
692 /* Do we have a loglevel in the string? */
693 if (p[0] == '<') {
694 unsigned char c = p[1];
695 if (c && p[2] == '>') {
696 switch (c) {
697 case '0' ... '7': /* loglevel */
698 current_log_level = c - '0';
699 /* Fallthrough - make sure we're on a new line */
700 case 'd': /* KERN_DEFAULT */
701 if (!new_text_line) {
702 emit_log_char('\n');
703 new_text_line = 1;
705 /* Fallthrough - skip the loglevel */
706 case 'c': /* KERN_CONT */
707 p += 3;
708 break;
714 * Copy the output into log_buf. If the caller didn't provide
715 * appropriate log level tags, we insert them here
717 for ( ; *p; p++) {
718 if (new_text_line) {
719 /* Always output the token */
720 emit_log_char('<');
721 emit_log_char(current_log_level + '0');
722 emit_log_char('>');
723 printed_len += 3;
724 new_text_line = 0;
726 if (printk_time) {
727 /* Follow the token with the time */
728 char tbuf[50], *tp;
729 unsigned tlen;
730 unsigned long long t;
731 unsigned long nanosec_rem;
733 t = cpu_clock(printk_cpu);
734 nanosec_rem = do_div(t, 1000000000);
735 tlen = sprintf(tbuf, "[%5lu.%06lu] ",
736 (unsigned long) t,
737 nanosec_rem / 1000);
739 for (tp = tbuf; tp < tbuf + tlen; tp++)
740 emit_log_char(*tp);
741 printed_len += tlen;
744 if (!*p)
745 break;
748 emit_log_char(*p);
749 if (*p == '\n')
750 new_text_line = 1;
754 * Try to acquire and then immediately release the
755 * console semaphore. The release will do all the
756 * actual magic (print out buffers, wake up klogd,
757 * etc).
759 * The acquire_console_semaphore_for_printk() function
760 * will release 'logbuf_lock' regardless of whether it
761 * actually gets the semaphore or not.
763 if (acquire_console_semaphore_for_printk(this_cpu))
764 release_console_sem();
766 lockdep_on();
767 out_restore_irqs:
768 raw_local_irq_restore(flags);
770 preempt_enable();
771 return printed_len;
773 EXPORT_SYMBOL(printk);
774 EXPORT_SYMBOL(vprintk);
776 #else
778 static void call_console_drivers(unsigned start, unsigned end)
782 #endif
784 static int __add_preferred_console(char *name, int idx, char *options,
785 char *brl_options)
787 struct console_cmdline *c;
788 int i;
791 * See if this tty is not yet registered, and
792 * if we have a slot free.
794 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
795 if (strcmp(console_cmdline[i].name, name) == 0 &&
796 console_cmdline[i].index == idx) {
797 if (!brl_options)
798 selected_console = i;
799 return 0;
801 if (i == MAX_CMDLINECONSOLES)
802 return -E2BIG;
803 if (!brl_options)
804 selected_console = i;
805 c = &console_cmdline[i];
806 strlcpy(c->name, name, sizeof(c->name));
807 c->options = options;
808 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
809 c->brl_options = brl_options;
810 #endif
811 c->index = idx;
812 return 0;
815 * Set up a list of consoles. Called from init/main.c
817 static int __init console_setup(char *str)
819 char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */
820 char *s, *options, *brl_options = NULL;
821 int idx;
823 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
824 if (!memcmp(str, "brl,", 4)) {
825 brl_options = "";
826 str += 4;
827 } else if (!memcmp(str, "brl=", 4)) {
828 brl_options = str + 4;
829 str = strchr(brl_options, ',');
830 if (!str) {
831 printk(KERN_ERR "need port name after brl=\n");
832 return 1;
834 *(str++) = 0;
836 #endif
839 * Decode str into name, index, options.
841 if (str[0] >= '0' && str[0] <= '9') {
842 strcpy(buf, "ttyS");
843 strncpy(buf + 4, str, sizeof(buf) - 5);
844 } else {
845 strncpy(buf, str, sizeof(buf) - 1);
847 buf[sizeof(buf) - 1] = 0;
848 if ((options = strchr(str, ',')) != NULL)
849 *(options++) = 0;
850 #ifdef __sparc__
851 if (!strcmp(str, "ttya"))
852 strcpy(buf, "ttyS0");
853 if (!strcmp(str, "ttyb"))
854 strcpy(buf, "ttyS1");
855 #endif
856 for (s = buf; *s; s++)
857 if ((*s >= '0' && *s <= '9') || *s == ',')
858 break;
859 idx = simple_strtoul(s, NULL, 10);
860 *s = 0;
862 __add_preferred_console(buf, idx, options, brl_options);
863 console_set_on_cmdline = 1;
864 return 1;
866 __setup("console=", console_setup);
869 * add_preferred_console - add a device to the list of preferred consoles.
870 * @name: device name
871 * @idx: device index
872 * @options: options for this console
874 * The last preferred console added will be used for kernel messages
875 * and stdin/out/err for init. Normally this is used by console_setup
876 * above to handle user-supplied console arguments; however it can also
877 * be used by arch-specific code either to override the user or more
878 * commonly to provide a default console (ie from PROM variables) when
879 * the user has not supplied one.
881 int add_preferred_console(char *name, int idx, char *options)
883 return __add_preferred_console(name, idx, options, NULL);
886 int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options)
888 struct console_cmdline *c;
889 int i;
891 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)
892 if (strcmp(console_cmdline[i].name, name) == 0 &&
893 console_cmdline[i].index == idx) {
894 c = &console_cmdline[i];
895 strlcpy(c->name, name_new, sizeof(c->name));
896 c->name[sizeof(c->name) - 1] = 0;
897 c->options = options;
898 c->index = idx_new;
899 return i;
901 /* not found */
902 return -1;
905 int console_suspend_enabled = 1;
906 EXPORT_SYMBOL(console_suspend_enabled);
908 static int __init console_suspend_disable(char *str)
910 console_suspend_enabled = 0;
911 return 1;
913 __setup("no_console_suspend", console_suspend_disable);
916 * suspend_console - suspend the console subsystem
918 * This disables printk() while we go into suspend states
920 void suspend_console(void)
922 if (!console_suspend_enabled)
923 return;
924 printk("Suspending console(s) (use no_console_suspend to debug)\n");
925 acquire_console_sem();
926 console_suspended = 1;
927 up(&console_sem);
930 void resume_console(void)
932 if (!console_suspend_enabled)
933 return;
934 down(&console_sem);
935 console_suspended = 0;
936 release_console_sem();
940 * acquire_console_sem - lock the console system for exclusive use.
942 * Acquires a semaphore which guarantees that the caller has
943 * exclusive access to the console system and the console_drivers list.
945 * Can sleep, returns nothing.
947 void acquire_console_sem(void)
949 BUG_ON(in_interrupt());
950 down(&console_sem);
951 if (console_suspended)
952 return;
953 console_locked = 1;
954 console_may_schedule = 1;
956 EXPORT_SYMBOL(acquire_console_sem);
958 int try_acquire_console_sem(void)
960 if (down_trylock(&console_sem))
961 return -1;
962 if (console_suspended) {
963 up(&console_sem);
964 return -1;
966 console_locked = 1;
967 console_may_schedule = 0;
968 return 0;
970 EXPORT_SYMBOL(try_acquire_console_sem);
972 int is_console_locked(void)
974 return console_locked;
977 static DEFINE_PER_CPU(int, printk_pending);
979 void printk_tick(void)
981 if (__get_cpu_var(printk_pending)) {
982 __get_cpu_var(printk_pending) = 0;
983 wake_up_interruptible(&log_wait);
987 int printk_needs_cpu(int cpu)
989 return per_cpu(printk_pending, cpu);
992 void wake_up_klogd(void)
994 if (waitqueue_active(&log_wait))
995 __raw_get_cpu_var(printk_pending) = 1;
999 * release_console_sem - unlock the console system
1001 * Releases the semaphore which the caller holds on the console system
1002 * and the console driver list.
1004 * While the semaphore was held, console output may have been buffered
1005 * by printk(). If this is the case, release_console_sem() emits
1006 * the output prior to releasing the semaphore.
1008 * If there is output waiting for klogd, we wake it up.
1010 * release_console_sem() may be called from any context.
1012 void release_console_sem(void)
1014 unsigned long flags;
1015 unsigned _con_start, _log_end;
1016 unsigned wake_klogd = 0;
1018 if (console_suspended) {
1019 up(&console_sem);
1020 return;
1023 console_may_schedule = 0;
1025 for ( ; ; ) {
1026 spin_lock_irqsave(&logbuf_lock, flags);
1027 wake_klogd |= log_start - log_end;
1028 if (con_start == log_end)
1029 break; /* Nothing to print */
1030 _con_start = con_start;
1031 _log_end = log_end;
1032 con_start = log_end; /* Flush */
1033 spin_unlock(&logbuf_lock);
1034 stop_critical_timings(); /* don't trace print latency */
1035 call_console_drivers(_con_start, _log_end);
1036 start_critical_timings();
1037 local_irq_restore(flags);
1039 console_locked = 0;
1040 up(&console_sem);
1041 spin_unlock_irqrestore(&logbuf_lock, flags);
1042 if (wake_klogd)
1043 wake_up_klogd();
1045 EXPORT_SYMBOL(release_console_sem);
1048 * console_conditional_schedule - yield the CPU if required
1050 * If the console code is currently allowed to sleep, and
1051 * if this CPU should yield the CPU to another task, do
1052 * so here.
1054 * Must be called within acquire_console_sem().
1056 void __sched console_conditional_schedule(void)
1058 if (console_may_schedule)
1059 cond_resched();
1061 EXPORT_SYMBOL(console_conditional_schedule);
1063 void console_print(const char *s)
1065 printk(KERN_EMERG "%s", s);
1067 EXPORT_SYMBOL(console_print);
1069 void console_unblank(void)
1071 struct console *c;
1074 * console_unblank can no longer be called in interrupt context unless
1075 * oops_in_progress is set to 1..
1077 if (oops_in_progress) {
1078 if (down_trylock(&console_sem) != 0)
1079 return;
1080 } else
1081 acquire_console_sem();
1083 console_locked = 1;
1084 console_may_schedule = 0;
1085 for (c = console_drivers; c != NULL; c = c->next)
1086 if ((c->flags & CON_ENABLED) && c->unblank)
1087 c->unblank();
1088 release_console_sem();
1092 * Return the console tty driver structure and its associated index
1094 struct tty_driver *console_device(int *index)
1096 struct console *c;
1097 struct tty_driver *driver = NULL;
1099 acquire_console_sem();
1100 for (c = console_drivers; c != NULL; c = c->next) {
1101 if (!c->device)
1102 continue;
1103 driver = c->device(c, index);
1104 if (driver)
1105 break;
1107 release_console_sem();
1108 return driver;
1112 * Prevent further output on the passed console device so that (for example)
1113 * serial drivers can disable console output before suspending a port, and can
1114 * re-enable output afterwards.
1116 void console_stop(struct console *console)
1118 acquire_console_sem();
1119 console->flags &= ~CON_ENABLED;
1120 release_console_sem();
1122 EXPORT_SYMBOL(console_stop);
1124 void console_start(struct console *console)
1126 acquire_console_sem();
1127 console->flags |= CON_ENABLED;
1128 release_console_sem();
1130 EXPORT_SYMBOL(console_start);
1133 * The console driver calls this routine during kernel initialization
1134 * to register the console printing procedure with printk() and to
1135 * print any messages that were printed by the kernel before the
1136 * console driver was initialized.
1138 void register_console(struct console *console)
1140 int i;
1141 unsigned long flags;
1142 struct console *bootconsole = NULL;
1144 if (console_drivers) {
1145 if (console->flags & CON_BOOT)
1146 return;
1147 if (console_drivers->flags & CON_BOOT)
1148 bootconsole = console_drivers;
1151 if (preferred_console < 0 || bootconsole || !console_drivers)
1152 preferred_console = selected_console;
1154 if (console->early_setup)
1155 console->early_setup();
1158 * See if we want to use this console driver. If we
1159 * didn't select a console we take the first one
1160 * that registers here.
1162 if (preferred_console < 0) {
1163 if (console->index < 0)
1164 console->index = 0;
1165 if (console->setup == NULL ||
1166 console->setup(console, NULL) == 0) {
1167 console->flags |= CON_ENABLED;
1168 if (console->device) {
1169 console->flags |= CON_CONSDEV;
1170 preferred_console = 0;
1176 * See if this console matches one we selected on
1177 * the command line.
1179 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
1180 i++) {
1181 if (strcmp(console_cmdline[i].name, console->name) != 0)
1182 continue;
1183 if (console->index >= 0 &&
1184 console->index != console_cmdline[i].index)
1185 continue;
1186 if (console->index < 0)
1187 console->index = console_cmdline[i].index;
1188 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1189 if (console_cmdline[i].brl_options) {
1190 console->flags |= CON_BRL;
1191 braille_register_console(console,
1192 console_cmdline[i].index,
1193 console_cmdline[i].options,
1194 console_cmdline[i].brl_options);
1195 return;
1197 #endif
1198 if (console->setup &&
1199 console->setup(console, console_cmdline[i].options) != 0)
1200 break;
1201 console->flags |= CON_ENABLED;
1202 console->index = console_cmdline[i].index;
1203 if (i == selected_console) {
1204 console->flags |= CON_CONSDEV;
1205 preferred_console = selected_console;
1207 break;
1210 if (!(console->flags & CON_ENABLED))
1211 return;
1213 if (bootconsole && (console->flags & CON_CONSDEV)) {
1214 printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
1215 bootconsole->name, bootconsole->index,
1216 console->name, console->index);
1217 unregister_console(bootconsole);
1218 console->flags &= ~CON_PRINTBUFFER;
1219 } else {
1220 printk(KERN_INFO "console [%s%d] enabled\n",
1221 console->name, console->index);
1225 * Put this console in the list - keep the
1226 * preferred driver at the head of the list.
1228 acquire_console_sem();
1229 if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
1230 console->next = console_drivers;
1231 console_drivers = console;
1232 if (console->next)
1233 console->next->flags &= ~CON_CONSDEV;
1234 } else {
1235 console->next = console_drivers->next;
1236 console_drivers->next = console;
1238 if (console->flags & CON_PRINTBUFFER) {
1240 * release_console_sem() will print out the buffered messages
1241 * for us.
1243 spin_lock_irqsave(&logbuf_lock, flags);
1244 con_start = log_start;
1245 spin_unlock_irqrestore(&logbuf_lock, flags);
1247 release_console_sem();
1249 EXPORT_SYMBOL(register_console);
1251 int unregister_console(struct console *console)
1253 struct console *a, *b;
1254 int res = 1;
1256 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
1257 if (console->flags & CON_BRL)
1258 return braille_unregister_console(console);
1259 #endif
1261 acquire_console_sem();
1262 if (console_drivers == console) {
1263 console_drivers=console->next;
1264 res = 0;
1265 } else if (console_drivers) {
1266 for (a=console_drivers->next, b=console_drivers ;
1267 a; b=a, a=b->next) {
1268 if (a == console) {
1269 b->next = a->next;
1270 res = 0;
1271 break;
1277 * If this isn't the last console and it has CON_CONSDEV set, we
1278 * need to set it on the next preferred console.
1280 if (console_drivers != NULL && console->flags & CON_CONSDEV)
1281 console_drivers->flags |= CON_CONSDEV;
1283 release_console_sem();
1284 return res;
1286 EXPORT_SYMBOL(unregister_console);
1288 static int __init disable_boot_consoles(void)
1290 if (console_drivers != NULL) {
1291 if (console_drivers->flags & CON_BOOT) {
1292 printk(KERN_INFO "turn off boot console %s%d\n",
1293 console_drivers->name, console_drivers->index);
1294 return unregister_console(console_drivers);
1297 return 0;
1299 late_initcall(disable_boot_consoles);
1301 #if defined CONFIG_PRINTK
1304 * printk rate limiting, lifted from the networking subsystem.
1306 * This enforces a rate limit: not more than 10 kernel messages
1307 * every 5s to make a denial-of-service attack impossible.
1309 DEFINE_RATELIMIT_STATE(printk_ratelimit_state, 5 * HZ, 10);
1311 int printk_ratelimit(void)
1313 return __ratelimit(&printk_ratelimit_state);
1315 EXPORT_SYMBOL(printk_ratelimit);
1318 * printk_timed_ratelimit - caller-controlled printk ratelimiting
1319 * @caller_jiffies: pointer to caller's state
1320 * @interval_msecs: minimum interval between prints
1322 * printk_timed_ratelimit() returns true if more than @interval_msecs
1323 * milliseconds have elapsed since the last time printk_timed_ratelimit()
1324 * returned true.
1326 bool printk_timed_ratelimit(unsigned long *caller_jiffies,
1327 unsigned int interval_msecs)
1329 if (*caller_jiffies == 0
1330 || !time_in_range(jiffies, *caller_jiffies,
1331 *caller_jiffies
1332 + msecs_to_jiffies(interval_msecs))) {
1333 *caller_jiffies = jiffies;
1334 return true;
1336 return false;
1338 EXPORT_SYMBOL(printk_timed_ratelimit);
1339 #endif