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Commit | Line | Data |
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1da177e4 LT |
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. | |
40dc5651 | 13 | * Fixed SMP synchronization, 08/08/99, Manfred Spraul |
624dffcb | 14 | * manfred@colorfullife.com |
1da177e4 LT |
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> | |
1da177e4 LT |
23 | #include <linux/console.h> |
24 | #include <linux/init.h> | |
bfe8df3d RD |
25 | #include <linux/jiffies.h> |
26 | #include <linux/nmi.h> | |
1da177e4 | 27 | #include <linux/module.h> |
3b9c0410 | 28 | #include <linux/moduleparam.h> |
1da177e4 | 29 | #include <linux/interrupt.h> /* For in_interrupt() */ |
1da177e4 LT |
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> | |
f46c4833 | 35 | #include <linux/jiffies.h> |
1da177e4 LT |
36 | |
37 | #include <asm/uaccess.h> | |
38 | ||
39 | #define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT) | |
40 | ||
41 | /* printk's without a loglevel use this.. */ | |
42 | #define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */ | |
43 | ||
44 | /* We show everything that is MORE important than this.. */ | |
45 | #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */ | |
46 | #define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */ | |
47 | ||
48 | DECLARE_WAIT_QUEUE_HEAD(log_wait); | |
49 | ||
50 | int console_printk[4] = { | |
51 | DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */ | |
52 | DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */ | |
53 | MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */ | |
54 | DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */ | |
55 | }; | |
56 | ||
1da177e4 | 57 | /* |
0bbfb7c2 | 58 | * Low level drivers may need that to know if they can schedule in |
1da177e4 LT |
59 | * their unblank() callback or not. So let's export it. |
60 | */ | |
61 | int oops_in_progress; | |
62 | EXPORT_SYMBOL(oops_in_progress); | |
63 | ||
64 | /* | |
65 | * console_sem protects the console_drivers list, and also | |
66 | * provides serialisation for access to the entire console | |
67 | * driver system. | |
68 | */ | |
69 | static DECLARE_MUTEX(console_sem); | |
557240b4 | 70 | static DECLARE_MUTEX(secondary_console_sem); |
1da177e4 LT |
71 | struct console *console_drivers; |
72 | /* | |
73 | * This is used for debugging the mess that is the VT code by | |
74 | * keeping track if we have the console semaphore held. It's | |
75 | * definitely not the perfect debug tool (we don't know if _WE_ | |
76 | * hold it are racing, but it helps tracking those weird code | |
77 | * path in the console code where we end up in places I want | |
78 | * locked without the console sempahore held | |
79 | */ | |
557240b4 | 80 | static int console_locked, console_suspended; |
1da177e4 LT |
81 | |
82 | /* | |
83 | * logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars | |
84 | * It is also used in interesting ways to provide interlocking in | |
85 | * release_console_sem(). | |
86 | */ | |
87 | static DEFINE_SPINLOCK(logbuf_lock); | |
88 | ||
1da177e4 LT |
89 | #define LOG_BUF_MASK (log_buf_len-1) |
90 | #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK]) | |
91 | ||
92 | /* | |
93 | * The indices into log_buf are not constrained to log_buf_len - they | |
94 | * must be masked before subscripting | |
95 | */ | |
96 | static unsigned long log_start; /* Index into log_buf: next char to be read by syslog() */ | |
97 | static unsigned long con_start; /* Index into log_buf: next char to be sent to consoles */ | |
98 | static unsigned long log_end; /* Index into log_buf: most-recently-written-char + 1 */ | |
1da177e4 LT |
99 | |
100 | /* | |
101 | * Array of consoles built from command line options (console=) | |
102 | */ | |
103 | struct console_cmdline | |
104 | { | |
105 | char name[8]; /* Name of the driver */ | |
106 | int index; /* Minor dev. to use */ | |
107 | char *options; /* Options for the driver */ | |
108 | }; | |
109 | ||
110 | #define MAX_CMDLINECONSOLES 8 | |
111 | ||
112 | static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES]; | |
113 | static int selected_console = -1; | |
114 | static int preferred_console = -1; | |
115 | ||
116 | /* Flag: console code may call schedule() */ | |
117 | static int console_may_schedule; | |
118 | ||
d59745ce MM |
119 | #ifdef CONFIG_PRINTK |
120 | ||
121 | static char __log_buf[__LOG_BUF_LEN]; | |
122 | static char *log_buf = __log_buf; | |
123 | static int log_buf_len = __LOG_BUF_LEN; | |
124 | static unsigned long logged_chars; /* Number of chars produced since last read+clear operation */ | |
125 | ||
1da177e4 LT |
126 | static int __init log_buf_len_setup(char *str) |
127 | { | |
128 | unsigned long size = memparse(str, &str); | |
129 | unsigned long flags; | |
130 | ||
131 | if (size) | |
132 | size = roundup_pow_of_two(size); | |
133 | if (size > log_buf_len) { | |
134 | unsigned long start, dest_idx, offset; | |
40dc5651 | 135 | char *new_log_buf; |
1da177e4 LT |
136 | |
137 | new_log_buf = alloc_bootmem(size); | |
138 | if (!new_log_buf) { | |
40dc5651 | 139 | printk(KERN_WARNING "log_buf_len: allocation failed\n"); |
1da177e4 LT |
140 | goto out; |
141 | } | |
142 | ||
143 | spin_lock_irqsave(&logbuf_lock, flags); | |
144 | log_buf_len = size; | |
145 | log_buf = new_log_buf; | |
146 | ||
147 | offset = start = min(con_start, log_start); | |
148 | dest_idx = 0; | |
149 | while (start != log_end) { | |
150 | log_buf[dest_idx] = __log_buf[start & (__LOG_BUF_LEN - 1)]; | |
151 | start++; | |
152 | dest_idx++; | |
153 | } | |
154 | log_start -= offset; | |
155 | con_start -= offset; | |
156 | log_end -= offset; | |
157 | spin_unlock_irqrestore(&logbuf_lock, flags); | |
158 | ||
40dc5651 | 159 | printk(KERN_NOTICE "log_buf_len: %d\n", log_buf_len); |
1da177e4 LT |
160 | } |
161 | out: | |
1da177e4 LT |
162 | return 1; |
163 | } | |
164 | ||
165 | __setup("log_buf_len=", log_buf_len_setup); | |
166 | ||
bfe8df3d RD |
167 | #ifdef CONFIG_BOOT_PRINTK_DELAY |
168 | ||
169 | static unsigned int boot_delay; /* msecs delay after each printk during bootup */ | |
170 | static unsigned long long printk_delay_msec; /* per msec, based on boot_delay */ | |
171 | ||
172 | static int __init boot_delay_setup(char *str) | |
173 | { | |
174 | unsigned long lpj; | |
175 | unsigned long long loops_per_msec; | |
176 | ||
177 | lpj = preset_lpj ? preset_lpj : 1000000; /* some guess */ | |
178 | loops_per_msec = (unsigned long long)lpj / 1000 * HZ; | |
179 | ||
180 | get_option(&str, &boot_delay); | |
181 | if (boot_delay > 10 * 1000) | |
182 | boot_delay = 0; | |
183 | ||
184 | printk_delay_msec = loops_per_msec; | |
185 | printk(KERN_DEBUG "boot_delay: %u, preset_lpj: %ld, lpj: %lu, " | |
186 | "HZ: %d, printk_delay_msec: %llu\n", | |
187 | boot_delay, preset_lpj, lpj, HZ, printk_delay_msec); | |
188 | return 1; | |
189 | } | |
190 | __setup("boot_delay=", boot_delay_setup); | |
191 | ||
192 | static void boot_delay_msec(void) | |
193 | { | |
194 | unsigned long long k; | |
195 | unsigned long timeout; | |
196 | ||
197 | if (boot_delay == 0 || system_state != SYSTEM_BOOTING) | |
198 | return; | |
199 | ||
200 | k = (unsigned long long)printk_delay_msec * boot_delay; | |
201 | ||
202 | timeout = jiffies + msecs_to_jiffies(boot_delay); | |
203 | while (k) { | |
204 | k--; | |
205 | cpu_relax(); | |
206 | /* | |
207 | * use (volatile) jiffies to prevent | |
208 | * compiler reduction; loop termination via jiffies | |
209 | * is secondary and may or may not happen. | |
210 | */ | |
211 | if (time_after(jiffies, timeout)) | |
212 | break; | |
213 | touch_nmi_watchdog(); | |
214 | } | |
215 | } | |
216 | #else | |
217 | static inline void boot_delay_msec(void) | |
218 | { | |
219 | } | |
220 | #endif | |
221 | ||
0b15d04a MF |
222 | /* |
223 | * Return the number of unread characters in the log buffer. | |
224 | */ | |
225 | int log_buf_get_len(void) | |
226 | { | |
227 | return logged_chars; | |
228 | } | |
229 | ||
230 | /* | |
231 | * Copy a range of characters from the log buffer. | |
232 | */ | |
233 | int log_buf_copy(char *dest, int idx, int len) | |
234 | { | |
235 | int ret, max; | |
236 | bool took_lock = false; | |
237 | ||
238 | if (!oops_in_progress) { | |
239 | spin_lock_irq(&logbuf_lock); | |
240 | took_lock = true; | |
241 | } | |
242 | ||
243 | max = log_buf_get_len(); | |
244 | if (idx < 0 || idx >= max) { | |
245 | ret = -1; | |
246 | } else { | |
247 | if (len > max) | |
248 | len = max; | |
249 | ret = len; | |
250 | idx += (log_end - max); | |
251 | while (len-- > 0) | |
252 | dest[len] = LOG_BUF(idx + len); | |
253 | } | |
254 | ||
255 | if (took_lock) | |
256 | spin_unlock_irq(&logbuf_lock); | |
257 | ||
258 | return ret; | |
259 | } | |
260 | ||
261 | /* | |
262 | * Extract a single character from the log buffer. | |
263 | */ | |
264 | int log_buf_read(int idx) | |
265 | { | |
266 | char ret; | |
267 | ||
268 | if (log_buf_copy(&ret, idx, 1) == 1) | |
269 | return ret; | |
270 | else | |
271 | return -1; | |
272 | } | |
273 | ||
1da177e4 LT |
274 | /* |
275 | * Commands to do_syslog: | |
276 | * | |
277 | * 0 -- Close the log. Currently a NOP. | |
278 | * 1 -- Open the log. Currently a NOP. | |
279 | * 2 -- Read from the log. | |
280 | * 3 -- Read all messages remaining in the ring buffer. | |
281 | * 4 -- Read and clear all messages remaining in the ring buffer | |
282 | * 5 -- Clear ring buffer. | |
283 | * 6 -- Disable printk's to console | |
284 | * 7 -- Enable printk's to console | |
285 | * 8 -- Set level of messages printed to console | |
286 | * 9 -- Return number of unread characters in the log buffer | |
287 | * 10 -- Return size of the log buffer | |
288 | */ | |
40dc5651 | 289 | int do_syslog(int type, char __user *buf, int len) |
1da177e4 LT |
290 | { |
291 | unsigned long i, j, limit, count; | |
292 | int do_clear = 0; | |
293 | char c; | |
294 | int error = 0; | |
295 | ||
296 | error = security_syslog(type); | |
297 | if (error) | |
298 | return error; | |
299 | ||
300 | switch (type) { | |
301 | case 0: /* Close log */ | |
302 | break; | |
303 | case 1: /* Open log */ | |
304 | break; | |
305 | case 2: /* Read from log */ | |
306 | error = -EINVAL; | |
307 | if (!buf || len < 0) | |
308 | goto out; | |
309 | error = 0; | |
310 | if (!len) | |
311 | goto out; | |
312 | if (!access_ok(VERIFY_WRITE, buf, len)) { | |
313 | error = -EFAULT; | |
314 | goto out; | |
315 | } | |
40dc5651 JJ |
316 | error = wait_event_interruptible(log_wait, |
317 | (log_start - log_end)); | |
1da177e4 LT |
318 | if (error) |
319 | goto out; | |
320 | i = 0; | |
321 | spin_lock_irq(&logbuf_lock); | |
322 | while (!error && (log_start != log_end) && i < len) { | |
323 | c = LOG_BUF(log_start); | |
324 | log_start++; | |
325 | spin_unlock_irq(&logbuf_lock); | |
326 | error = __put_user(c,buf); | |
327 | buf++; | |
328 | i++; | |
329 | cond_resched(); | |
330 | spin_lock_irq(&logbuf_lock); | |
331 | } | |
332 | spin_unlock_irq(&logbuf_lock); | |
333 | if (!error) | |
334 | error = i; | |
335 | break; | |
336 | case 4: /* Read/clear last kernel messages */ | |
40dc5651 | 337 | do_clear = 1; |
1da177e4 LT |
338 | /* FALL THRU */ |
339 | case 3: /* Read last kernel messages */ | |
340 | error = -EINVAL; | |
341 | if (!buf || len < 0) | |
342 | goto out; | |
343 | error = 0; | |
344 | if (!len) | |
345 | goto out; | |
346 | if (!access_ok(VERIFY_WRITE, buf, len)) { | |
347 | error = -EFAULT; | |
348 | goto out; | |
349 | } | |
350 | count = len; | |
351 | if (count > log_buf_len) | |
352 | count = log_buf_len; | |
353 | spin_lock_irq(&logbuf_lock); | |
354 | if (count > logged_chars) | |
355 | count = logged_chars; | |
356 | if (do_clear) | |
357 | logged_chars = 0; | |
358 | limit = log_end; | |
359 | /* | |
360 | * __put_user() could sleep, and while we sleep | |
40dc5651 | 361 | * printk() could overwrite the messages |
1da177e4 LT |
362 | * we try to copy to user space. Therefore |
363 | * the messages are copied in reverse. <manfreds> | |
364 | */ | |
40dc5651 | 365 | for (i = 0; i < count && !error; i++) { |
1da177e4 LT |
366 | j = limit-1-i; |
367 | if (j + log_buf_len < log_end) | |
368 | break; | |
369 | c = LOG_BUF(j); | |
370 | spin_unlock_irq(&logbuf_lock); | |
371 | error = __put_user(c,&buf[count-1-i]); | |
372 | cond_resched(); | |
373 | spin_lock_irq(&logbuf_lock); | |
374 | } | |
375 | spin_unlock_irq(&logbuf_lock); | |
376 | if (error) | |
377 | break; | |
378 | error = i; | |
40dc5651 | 379 | if (i != count) { |
1da177e4 LT |
380 | int offset = count-error; |
381 | /* buffer overflow during copy, correct user buffer. */ | |
40dc5651 | 382 | for (i = 0; i < error; i++) { |
1da177e4 LT |
383 | if (__get_user(c,&buf[i+offset]) || |
384 | __put_user(c,&buf[i])) { | |
385 | error = -EFAULT; | |
386 | break; | |
387 | } | |
388 | cond_resched(); | |
389 | } | |
390 | } | |
391 | break; | |
392 | case 5: /* Clear ring buffer */ | |
393 | logged_chars = 0; | |
394 | break; | |
395 | case 6: /* Disable logging to console */ | |
396 | console_loglevel = minimum_console_loglevel; | |
397 | break; | |
398 | case 7: /* Enable logging to console */ | |
399 | console_loglevel = default_console_loglevel; | |
400 | break; | |
401 | case 8: /* Set level of messages printed to console */ | |
402 | error = -EINVAL; | |
403 | if (len < 1 || len > 8) | |
404 | goto out; | |
405 | if (len < minimum_console_loglevel) | |
406 | len = minimum_console_loglevel; | |
407 | console_loglevel = len; | |
408 | error = 0; | |
409 | break; | |
410 | case 9: /* Number of chars in the log buffer */ | |
411 | error = log_end - log_start; | |
412 | break; | |
413 | case 10: /* Size of the log buffer */ | |
414 | error = log_buf_len; | |
415 | break; | |
416 | default: | |
417 | error = -EINVAL; | |
418 | break; | |
419 | } | |
420 | out: | |
421 | return error; | |
422 | } | |
423 | ||
40dc5651 | 424 | asmlinkage long sys_syslog(int type, char __user *buf, int len) |
1da177e4 LT |
425 | { |
426 | return do_syslog(type, buf, len); | |
427 | } | |
428 | ||
429 | /* | |
430 | * Call the console drivers on a range of log_buf | |
431 | */ | |
432 | static void __call_console_drivers(unsigned long start, unsigned long end) | |
433 | { | |
434 | struct console *con; | |
435 | ||
436 | for (con = console_drivers; con; con = con->next) { | |
76a8ad29 ME |
437 | if ((con->flags & CON_ENABLED) && con->write && |
438 | (cpu_online(smp_processor_id()) || | |
439 | (con->flags & CON_ANYTIME))) | |
1da177e4 LT |
440 | con->write(con, &LOG_BUF(start), end - start); |
441 | } | |
442 | } | |
443 | ||
79290822 IM |
444 | static int __read_mostly ignore_loglevel; |
445 | ||
99eea6a1 | 446 | static int __init ignore_loglevel_setup(char *str) |
79290822 IM |
447 | { |
448 | ignore_loglevel = 1; | |
449 | printk(KERN_INFO "debug: ignoring loglevel setting.\n"); | |
450 | ||
451 | return 1; | |
452 | } | |
453 | ||
454 | __setup("ignore_loglevel", ignore_loglevel_setup); | |
455 | ||
1da177e4 LT |
456 | /* |
457 | * Write out chars from start to end - 1 inclusive | |
458 | */ | |
459 | static void _call_console_drivers(unsigned long start, | |
460 | unsigned long end, int msg_log_level) | |
461 | { | |
79290822 | 462 | if ((msg_log_level < console_loglevel || ignore_loglevel) && |
1da177e4 LT |
463 | console_drivers && start != end) { |
464 | if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) { | |
465 | /* wrapped write */ | |
466 | __call_console_drivers(start & LOG_BUF_MASK, | |
467 | log_buf_len); | |
468 | __call_console_drivers(0, end & LOG_BUF_MASK); | |
469 | } else { | |
470 | __call_console_drivers(start, end); | |
471 | } | |
472 | } | |
473 | } | |
474 | ||
475 | /* | |
476 | * Call the console drivers, asking them to write out | |
477 | * log_buf[start] to log_buf[end - 1]. | |
478 | * The console_sem must be held. | |
479 | */ | |
480 | static void call_console_drivers(unsigned long start, unsigned long end) | |
481 | { | |
482 | unsigned long cur_index, start_print; | |
483 | static int msg_level = -1; | |
484 | ||
8abd8e29 | 485 | BUG_ON(((long)(start - end)) > 0); |
1da177e4 LT |
486 | |
487 | cur_index = start; | |
488 | start_print = start; | |
489 | while (cur_index != end) { | |
40dc5651 JJ |
490 | if (msg_level < 0 && ((end - cur_index) > 2) && |
491 | LOG_BUF(cur_index + 0) == '<' && | |
492 | LOG_BUF(cur_index + 1) >= '0' && | |
493 | LOG_BUF(cur_index + 1) <= '7' && | |
494 | LOG_BUF(cur_index + 2) == '>') { | |
1da177e4 LT |
495 | msg_level = LOG_BUF(cur_index + 1) - '0'; |
496 | cur_index += 3; | |
497 | start_print = cur_index; | |
498 | } | |
499 | while (cur_index != end) { | |
500 | char c = LOG_BUF(cur_index); | |
1da177e4 | 501 | |
40dc5651 | 502 | cur_index++; |
1da177e4 LT |
503 | if (c == '\n') { |
504 | if (msg_level < 0) { | |
505 | /* | |
506 | * printk() has already given us loglevel tags in | |
507 | * the buffer. This code is here in case the | |
508 | * log buffer has wrapped right round and scribbled | |
509 | * on those tags | |
510 | */ | |
511 | msg_level = default_message_loglevel; | |
512 | } | |
513 | _call_console_drivers(start_print, cur_index, msg_level); | |
514 | msg_level = -1; | |
515 | start_print = cur_index; | |
516 | break; | |
517 | } | |
518 | } | |
519 | } | |
520 | _call_console_drivers(start_print, end, msg_level); | |
521 | } | |
522 | ||
523 | static void emit_log_char(char c) | |
524 | { | |
525 | LOG_BUF(log_end) = c; | |
526 | log_end++; | |
527 | if (log_end - log_start > log_buf_len) | |
528 | log_start = log_end - log_buf_len; | |
529 | if (log_end - con_start > log_buf_len) | |
530 | con_start = log_end - log_buf_len; | |
531 | if (logged_chars < log_buf_len) | |
532 | logged_chars++; | |
533 | } | |
534 | ||
535 | /* | |
536 | * Zap console related locks when oopsing. Only zap at most once | |
537 | * every 10 seconds, to leave time for slow consoles to print a | |
538 | * full oops. | |
539 | */ | |
540 | static void zap_locks(void) | |
541 | { | |
542 | static unsigned long oops_timestamp; | |
543 | ||
544 | if (time_after_eq(jiffies, oops_timestamp) && | |
40dc5651 | 545 | !time_after(jiffies, oops_timestamp + 30 * HZ)) |
1da177e4 LT |
546 | return; |
547 | ||
548 | oops_timestamp = jiffies; | |
549 | ||
550 | /* If a crash is occurring, make sure we can't deadlock */ | |
551 | spin_lock_init(&logbuf_lock); | |
552 | /* And make sure that we print immediately */ | |
553 | init_MUTEX(&console_sem); | |
554 | } | |
555 | ||
556 | #if defined(CONFIG_PRINTK_TIME) | |
557 | static int printk_time = 1; | |
558 | #else | |
559 | static int printk_time = 0; | |
560 | #endif | |
e84845c4 | 561 | module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR); |
1da177e4 LT |
562 | |
563 | static int __init printk_time_setup(char *str) | |
564 | { | |
565 | if (*str) | |
566 | return 0; | |
567 | printk_time = 1; | |
e84845c4 RD |
568 | printk(KERN_NOTICE "The 'time' option is deprecated and " |
569 | "is scheduled for removal in early 2008\n"); | |
570 | printk(KERN_NOTICE "Use 'printk.time=<value>' instead\n"); | |
1da177e4 LT |
571 | return 1; |
572 | } | |
573 | ||
574 | __setup("time", printk_time_setup); | |
575 | ||
76a8ad29 ME |
576 | /* Check if we have any console registered that can be called early in boot. */ |
577 | static int have_callable_console(void) | |
578 | { | |
579 | struct console *con; | |
580 | ||
581 | for (con = console_drivers; con; con = con->next) | |
582 | if (con->flags & CON_ANYTIME) | |
583 | return 1; | |
584 | ||
585 | return 0; | |
586 | } | |
587 | ||
ddad86c2 MW |
588 | /** |
589 | * printk - print a kernel message | |
590 | * @fmt: format string | |
591 | * | |
72fd4a35 | 592 | * This is printk(). It can be called from any context. We want it to work. |
1492192b JK |
593 | * Be aware of the fact that if oops_in_progress is not set, we might try to |
594 | * wake klogd up which could deadlock on runqueue lock if printk() is called | |
595 | * from scheduler code. | |
40dc5651 | 596 | * |
1da177e4 LT |
597 | * We try to grab the console_sem. If we succeed, it's easy - we log the output and |
598 | * call the console drivers. If we fail to get the semaphore we place the output | |
599 | * into the log buffer and return. The current holder of the console_sem will | |
600 | * notice the new output in release_console_sem() and will send it to the | |
601 | * consoles before releasing the semaphore. | |
602 | * | |
603 | * One effect of this deferred printing is that code which calls printk() and | |
604 | * then changes console_loglevel may break. This is because console_loglevel | |
605 | * is inspected when the actual printing occurs. | |
ddad86c2 MW |
606 | * |
607 | * See also: | |
608 | * printf(3) | |
1da177e4 | 609 | */ |
d59745ce | 610 | |
1da177e4 LT |
611 | asmlinkage int printk(const char *fmt, ...) |
612 | { | |
613 | va_list args; | |
614 | int r; | |
615 | ||
616 | va_start(args, fmt); | |
617 | r = vprintk(fmt, args); | |
618 | va_end(args); | |
619 | ||
620 | return r; | |
621 | } | |
622 | ||
fe21773d DH |
623 | /* cpu currently holding logbuf_lock */ |
624 | static volatile unsigned int printk_cpu = UINT_MAX; | |
625 | ||
32a76006 IM |
626 | const char printk_recursion_bug_msg [] = |
627 | KERN_CRIT "BUG: recent printk recursion!\n"; | |
628 | static int printk_recursion_bug; | |
629 | ||
1da177e4 LT |
630 | asmlinkage int vprintk(const char *fmt, va_list args) |
631 | { | |
32a76006 IM |
632 | static int log_level_unknown = 1; |
633 | static char printk_buf[1024]; | |
634 | ||
1da177e4 | 635 | unsigned long flags; |
32a76006 IM |
636 | int printed_len = 0; |
637 | int this_cpu; | |
1da177e4 | 638 | char *p; |
1da177e4 | 639 | |
bfe8df3d RD |
640 | boot_delay_msec(); |
641 | ||
fe21773d | 642 | preempt_disable(); |
1da177e4 | 643 | /* This stops the holder of console_sem just where we want him */ |
1efc5da3 | 644 | raw_local_irq_save(flags); |
32a76006 IM |
645 | this_cpu = smp_processor_id(); |
646 | ||
647 | /* | |
648 | * Ouch, printk recursed into itself! | |
649 | */ | |
650 | if (unlikely(printk_cpu == this_cpu)) { | |
651 | /* | |
652 | * If a crash is occurring during printk() on this CPU, | |
653 | * then try to get the crash message out but make sure | |
654 | * we can't deadlock. Otherwise just return to avoid the | |
655 | * recursion and return - but flag the recursion so that | |
656 | * it can be printed at the next appropriate moment: | |
657 | */ | |
658 | if (!oops_in_progress) { | |
659 | printk_recursion_bug = 1; | |
660 | goto out_restore_irqs; | |
661 | } | |
662 | zap_locks(); | |
663 | } | |
664 | ||
a0f1ccfd IM |
665 | lockdep_off(); |
666 | spin_lock(&logbuf_lock); | |
32a76006 | 667 | printk_cpu = this_cpu; |
1da177e4 | 668 | |
32a76006 IM |
669 | if (printk_recursion_bug) { |
670 | printk_recursion_bug = 0; | |
671 | strcpy(printk_buf, printk_recursion_bug_msg); | |
672 | printed_len = sizeof(printk_recursion_bug_msg); | |
673 | } | |
1da177e4 | 674 | /* Emit the output into the temporary buffer */ |
32a76006 IM |
675 | printed_len += vscnprintf(printk_buf + printed_len, |
676 | sizeof(printk_buf), fmt, args); | |
1da177e4 LT |
677 | |
678 | /* | |
679 | * Copy the output into log_buf. If the caller didn't provide | |
680 | * appropriate log level tags, we insert them here | |
681 | */ | |
682 | for (p = printk_buf; *p; p++) { | |
683 | if (log_level_unknown) { | |
684 | /* log_level_unknown signals the start of a new line */ | |
685 | if (printk_time) { | |
686 | int loglev_char; | |
687 | char tbuf[50], *tp; | |
688 | unsigned tlen; | |
689 | unsigned long long t; | |
690 | unsigned long nanosec_rem; | |
691 | ||
692 | /* | |
693 | * force the log level token to be | |
694 | * before the time output. | |
695 | */ | |
696 | if (p[0] == '<' && p[1] >='0' && | |
697 | p[1] <= '7' && p[2] == '>') { | |
698 | loglev_char = p[1]; | |
699 | p += 3; | |
025510cd | 700 | printed_len -= 3; |
1da177e4 LT |
701 | } else { |
702 | loglev_char = default_message_loglevel | |
703 | + '0'; | |
704 | } | |
d713f519 | 705 | t = cpu_clock(printk_cpu); |
1da177e4 LT |
706 | nanosec_rem = do_div(t, 1000000000); |
707 | tlen = sprintf(tbuf, | |
708 | "<%c>[%5lu.%06lu] ", | |
709 | loglev_char, | |
710 | (unsigned long)t, | |
711 | nanosec_rem/1000); | |
712 | ||
713 | for (tp = tbuf; tp < tbuf + tlen; tp++) | |
714 | emit_log_char(*tp); | |
025510cd | 715 | printed_len += tlen; |
1da177e4 LT |
716 | } else { |
717 | if (p[0] != '<' || p[1] < '0' || | |
718 | p[1] > '7' || p[2] != '>') { | |
719 | emit_log_char('<'); | |
720 | emit_log_char(default_message_loglevel | |
721 | + '0'); | |
722 | emit_log_char('>'); | |
025510cd | 723 | printed_len += 3; |
1da177e4 | 724 | } |
1da177e4 LT |
725 | } |
726 | log_level_unknown = 0; | |
727 | if (!*p) | |
728 | break; | |
729 | } | |
730 | emit_log_char(*p); | |
731 | if (*p == '\n') | |
732 | log_level_unknown = 1; | |
733 | } | |
734 | ||
76a8ad29 | 735 | if (!down_trylock(&console_sem)) { |
1da177e4 | 736 | /* |
76a8ad29 ME |
737 | * We own the drivers. We can drop the spinlock and |
738 | * let release_console_sem() print the text, maybe ... | |
1da177e4 | 739 | */ |
76a8ad29 | 740 | console_locked = 1; |
fe21773d | 741 | printk_cpu = UINT_MAX; |
a0f1ccfd | 742 | spin_unlock(&logbuf_lock); |
76a8ad29 | 743 | |
1da177e4 | 744 | /* |
76a8ad29 ME |
745 | * Console drivers may assume that per-cpu resources have |
746 | * been allocated. So unless they're explicitly marked as | |
747 | * being able to cope (CON_ANYTIME) don't call them until | |
748 | * this CPU is officially up. | |
1da177e4 | 749 | */ |
76a8ad29 ME |
750 | if (cpu_online(smp_processor_id()) || have_callable_console()) { |
751 | console_may_schedule = 0; | |
752 | release_console_sem(); | |
753 | } else { | |
754 | /* Release by hand to avoid flushing the buffer. */ | |
755 | console_locked = 0; | |
756 | up(&console_sem); | |
757 | } | |
a0f1ccfd | 758 | lockdep_on(); |
1efc5da3 | 759 | raw_local_irq_restore(flags); |
1da177e4 LT |
760 | } else { |
761 | /* | |
762 | * Someone else owns the drivers. We drop the spinlock, which | |
763 | * allows the semaphore holder to proceed and to call the | |
764 | * console drivers with the output which we just produced. | |
765 | */ | |
fe21773d | 766 | printk_cpu = UINT_MAX; |
a0f1ccfd IM |
767 | spin_unlock(&logbuf_lock); |
768 | lockdep_on(); | |
32a76006 | 769 | out_restore_irqs: |
1efc5da3 | 770 | raw_local_irq_restore(flags); |
1da177e4 | 771 | } |
76a8ad29 | 772 | |
fe21773d | 773 | preempt_enable(); |
1da177e4 LT |
774 | return printed_len; |
775 | } | |
776 | EXPORT_SYMBOL(printk); | |
777 | EXPORT_SYMBOL(vprintk); | |
778 | ||
d59745ce MM |
779 | #else |
780 | ||
40dc5651 | 781 | asmlinkage long sys_syslog(int type, char __user *buf, int len) |
d59745ce | 782 | { |
c36264df | 783 | return -ENOSYS; |
40dc5651 JJ |
784 | } |
785 | ||
786 | static void call_console_drivers(unsigned long start, unsigned long end) | |
787 | { | |
788 | } | |
d59745ce MM |
789 | |
790 | #endif | |
791 | ||
2ea1c539 JB |
792 | /* |
793 | * Set up a list of consoles. Called from init/main.c | |
794 | */ | |
795 | static int __init console_setup(char *str) | |
796 | { | |
eaa944af | 797 | char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for index */ |
2ea1c539 JB |
798 | char *s, *options; |
799 | int idx; | |
800 | ||
801 | /* | |
802 | * Decode str into name, index, options. | |
803 | */ | |
804 | if (str[0] >= '0' && str[0] <= '9') { | |
eaa944af YL |
805 | strcpy(buf, "ttyS"); |
806 | strncpy(buf + 4, str, sizeof(buf) - 5); | |
2ea1c539 | 807 | } else { |
eaa944af | 808 | strncpy(buf, str, sizeof(buf) - 1); |
2ea1c539 | 809 | } |
eaa944af | 810 | buf[sizeof(buf) - 1] = 0; |
2ea1c539 JB |
811 | if ((options = strchr(str, ',')) != NULL) |
812 | *(options++) = 0; | |
813 | #ifdef __sparc__ | |
814 | if (!strcmp(str, "ttya")) | |
eaa944af | 815 | strcpy(buf, "ttyS0"); |
2ea1c539 | 816 | if (!strcmp(str, "ttyb")) |
eaa944af | 817 | strcpy(buf, "ttyS1"); |
2ea1c539 | 818 | #endif |
eaa944af | 819 | for (s = buf; *s; s++) |
2ea1c539 JB |
820 | if ((*s >= '0' && *s <= '9') || *s == ',') |
821 | break; | |
822 | idx = simple_strtoul(s, NULL, 10); | |
823 | *s = 0; | |
824 | ||
eaa944af | 825 | add_preferred_console(buf, idx, options); |
2ea1c539 JB |
826 | return 1; |
827 | } | |
828 | __setup("console=", console_setup); | |
829 | ||
3c0547ba MM |
830 | /** |
831 | * add_preferred_console - add a device to the list of preferred consoles. | |
ddad86c2 MW |
832 | * @name: device name |
833 | * @idx: device index | |
834 | * @options: options for this console | |
3c0547ba MM |
835 | * |
836 | * The last preferred console added will be used for kernel messages | |
837 | * and stdin/out/err for init. Normally this is used by console_setup | |
838 | * above to handle user-supplied console arguments; however it can also | |
839 | * be used by arch-specific code either to override the user or more | |
840 | * commonly to provide a default console (ie from PROM variables) when | |
841 | * the user has not supplied one. | |
842 | */ | |
fb445ee5 | 843 | int add_preferred_console(char *name, int idx, char *options) |
3c0547ba MM |
844 | { |
845 | struct console_cmdline *c; | |
846 | int i; | |
847 | ||
848 | /* | |
849 | * See if this tty is not yet registered, and | |
850 | * if we have a slot free. | |
851 | */ | |
eaa944af | 852 | for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) |
3c0547ba MM |
853 | if (strcmp(console_cmdline[i].name, name) == 0 && |
854 | console_cmdline[i].index == idx) { | |
855 | selected_console = i; | |
856 | return 0; | |
857 | } | |
858 | if (i == MAX_CMDLINECONSOLES) | |
859 | return -E2BIG; | |
860 | selected_console = i; | |
861 | c = &console_cmdline[i]; | |
862 | memcpy(c->name, name, sizeof(c->name)); | |
863 | c->name[sizeof(c->name) - 1] = 0; | |
864 | c->options = options; | |
865 | c->index = idx; | |
866 | return 0; | |
867 | } | |
868 | ||
b6b1d877 | 869 | int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options) |
18a8bd94 YL |
870 | { |
871 | struct console_cmdline *c; | |
872 | int i; | |
873 | ||
874 | for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) | |
875 | if (strcmp(console_cmdline[i].name, name) == 0 && | |
876 | console_cmdline[i].index == idx) { | |
877 | c = &console_cmdline[i]; | |
878 | memcpy(c->name, name_new, sizeof(c->name)); | |
879 | c->name[sizeof(c->name) - 1] = 0; | |
880 | c->options = options; | |
881 | c->index = idx_new; | |
882 | return i; | |
883 | } | |
884 | /* not found */ | |
885 | return -1; | |
886 | } | |
887 | ||
8f4ce8c3 AS |
888 | int console_suspend_enabled = 1; |
889 | EXPORT_SYMBOL(console_suspend_enabled); | |
890 | ||
891 | static int __init console_suspend_disable(char *str) | |
892 | { | |
893 | console_suspend_enabled = 0; | |
894 | return 1; | |
895 | } | |
896 | __setup("no_console_suspend", console_suspend_disable); | |
897 | ||
557240b4 LT |
898 | /** |
899 | * suspend_console - suspend the console subsystem | |
900 | * | |
901 | * This disables printk() while we go into suspend states | |
902 | */ | |
903 | void suspend_console(void) | |
904 | { | |
8f4ce8c3 AS |
905 | if (!console_suspend_enabled) |
906 | return; | |
c8eb8b40 | 907 | printk("Suspending console(s)\n"); |
557240b4 LT |
908 | acquire_console_sem(); |
909 | console_suspended = 1; | |
910 | } | |
911 | ||
912 | void resume_console(void) | |
913 | { | |
8f4ce8c3 AS |
914 | if (!console_suspend_enabled) |
915 | return; | |
557240b4 LT |
916 | console_suspended = 0; |
917 | release_console_sem(); | |
918 | } | |
919 | ||
1da177e4 LT |
920 | /** |
921 | * acquire_console_sem - lock the console system for exclusive use. | |
922 | * | |
923 | * Acquires a semaphore which guarantees that the caller has | |
924 | * exclusive access to the console system and the console_drivers list. | |
925 | * | |
926 | * Can sleep, returns nothing. | |
927 | */ | |
928 | void acquire_console_sem(void) | |
929 | { | |
8abd8e29 | 930 | BUG_ON(in_interrupt()); |
557240b4 LT |
931 | if (console_suspended) { |
932 | down(&secondary_console_sem); | |
933 | return; | |
934 | } | |
1da177e4 LT |
935 | down(&console_sem); |
936 | console_locked = 1; | |
937 | console_may_schedule = 1; | |
938 | } | |
939 | EXPORT_SYMBOL(acquire_console_sem); | |
940 | ||
941 | int try_acquire_console_sem(void) | |
942 | { | |
943 | if (down_trylock(&console_sem)) | |
944 | return -1; | |
945 | console_locked = 1; | |
946 | console_may_schedule = 0; | |
947 | return 0; | |
948 | } | |
949 | EXPORT_SYMBOL(try_acquire_console_sem); | |
950 | ||
951 | int is_console_locked(void) | |
952 | { | |
953 | return console_locked; | |
954 | } | |
1da177e4 | 955 | |
e3e8a75d KK |
956 | void wake_up_klogd(void) |
957 | { | |
958 | if (!oops_in_progress && waitqueue_active(&log_wait)) | |
959 | wake_up_interruptible(&log_wait); | |
960 | } | |
961 | ||
1da177e4 LT |
962 | /** |
963 | * release_console_sem - unlock the console system | |
964 | * | |
965 | * Releases the semaphore which the caller holds on the console system | |
966 | * and the console driver list. | |
967 | * | |
968 | * While the semaphore was held, console output may have been buffered | |
969 | * by printk(). If this is the case, release_console_sem() emits | |
970 | * the output prior to releasing the semaphore. | |
971 | * | |
972 | * If there is output waiting for klogd, we wake it up. | |
973 | * | |
974 | * release_console_sem() may be called from any context. | |
975 | */ | |
976 | void release_console_sem(void) | |
977 | { | |
978 | unsigned long flags; | |
979 | unsigned long _con_start, _log_end; | |
980 | unsigned long wake_klogd = 0; | |
981 | ||
557240b4 LT |
982 | if (console_suspended) { |
983 | up(&secondary_console_sem); | |
984 | return; | |
985 | } | |
78944e54 AD |
986 | |
987 | console_may_schedule = 0; | |
988 | ||
1da177e4 LT |
989 | for ( ; ; ) { |
990 | spin_lock_irqsave(&logbuf_lock, flags); | |
991 | wake_klogd |= log_start - log_end; | |
992 | if (con_start == log_end) | |
993 | break; /* Nothing to print */ | |
994 | _con_start = con_start; | |
995 | _log_end = log_end; | |
996 | con_start = log_end; /* Flush */ | |
997 | spin_unlock(&logbuf_lock); | |
998 | call_console_drivers(_con_start, _log_end); | |
999 | local_irq_restore(flags); | |
1000 | } | |
1001 | console_locked = 0; | |
1da177e4 LT |
1002 | up(&console_sem); |
1003 | spin_unlock_irqrestore(&logbuf_lock, flags); | |
e3e8a75d KK |
1004 | if (wake_klogd) |
1005 | wake_up_klogd(); | |
1da177e4 LT |
1006 | } |
1007 | EXPORT_SYMBOL(release_console_sem); | |
1008 | ||
ddad86c2 MW |
1009 | /** |
1010 | * console_conditional_schedule - yield the CPU if required | |
1da177e4 LT |
1011 | * |
1012 | * If the console code is currently allowed to sleep, and | |
1013 | * if this CPU should yield the CPU to another task, do | |
1014 | * so here. | |
1015 | * | |
1016 | * Must be called within acquire_console_sem(). | |
1017 | */ | |
1018 | void __sched console_conditional_schedule(void) | |
1019 | { | |
1020 | if (console_may_schedule) | |
1021 | cond_resched(); | |
1022 | } | |
1023 | EXPORT_SYMBOL(console_conditional_schedule); | |
1024 | ||
1025 | void console_print(const char *s) | |
1026 | { | |
1027 | printk(KERN_EMERG "%s", s); | |
1028 | } | |
1029 | EXPORT_SYMBOL(console_print); | |
1030 | ||
1031 | void console_unblank(void) | |
1032 | { | |
1033 | struct console *c; | |
1034 | ||
1035 | /* | |
1036 | * console_unblank can no longer be called in interrupt context unless | |
1037 | * oops_in_progress is set to 1.. | |
1038 | */ | |
1039 | if (oops_in_progress) { | |
1040 | if (down_trylock(&console_sem) != 0) | |
1041 | return; | |
1042 | } else | |
1043 | acquire_console_sem(); | |
1044 | ||
1045 | console_locked = 1; | |
1046 | console_may_schedule = 0; | |
1047 | for (c = console_drivers; c != NULL; c = c->next) | |
1048 | if ((c->flags & CON_ENABLED) && c->unblank) | |
1049 | c->unblank(); | |
1050 | release_console_sem(); | |
1051 | } | |
1da177e4 LT |
1052 | |
1053 | /* | |
1054 | * Return the console tty driver structure and its associated index | |
1055 | */ | |
1056 | struct tty_driver *console_device(int *index) | |
1057 | { | |
1058 | struct console *c; | |
1059 | struct tty_driver *driver = NULL; | |
1060 | ||
1061 | acquire_console_sem(); | |
1062 | for (c = console_drivers; c != NULL; c = c->next) { | |
1063 | if (!c->device) | |
1064 | continue; | |
1065 | driver = c->device(c, index); | |
1066 | if (driver) | |
1067 | break; | |
1068 | } | |
1069 | release_console_sem(); | |
1070 | return driver; | |
1071 | } | |
1072 | ||
1073 | /* | |
1074 | * Prevent further output on the passed console device so that (for example) | |
1075 | * serial drivers can disable console output before suspending a port, and can | |
1076 | * re-enable output afterwards. | |
1077 | */ | |
1078 | void console_stop(struct console *console) | |
1079 | { | |
1080 | acquire_console_sem(); | |
1081 | console->flags &= ~CON_ENABLED; | |
1082 | release_console_sem(); | |
1083 | } | |
1084 | EXPORT_SYMBOL(console_stop); | |
1085 | ||
1086 | void console_start(struct console *console) | |
1087 | { | |
1088 | acquire_console_sem(); | |
1089 | console->flags |= CON_ENABLED; | |
1090 | release_console_sem(); | |
1091 | } | |
1092 | EXPORT_SYMBOL(console_start); | |
1093 | ||
1094 | /* | |
1095 | * The console driver calls this routine during kernel initialization | |
1096 | * to register the console printing procedure with printk() and to | |
1097 | * print any messages that were printed by the kernel before the | |
1098 | * console driver was initialized. | |
1099 | */ | |
40dc5651 | 1100 | void register_console(struct console *console) |
1da177e4 | 1101 | { |
40dc5651 | 1102 | int i; |
1da177e4 | 1103 | unsigned long flags; |
69331af7 | 1104 | struct console *bootconsole = NULL; |
1da177e4 | 1105 | |
69331af7 GH |
1106 | if (console_drivers) { |
1107 | if (console->flags & CON_BOOT) | |
1108 | return; | |
1109 | if (console_drivers->flags & CON_BOOT) | |
1110 | bootconsole = console_drivers; | |
1111 | } | |
1112 | ||
1113 | if (preferred_console < 0 || bootconsole || !console_drivers) | |
1da177e4 LT |
1114 | preferred_console = selected_console; |
1115 | ||
18a8bd94 YL |
1116 | if (console->early_setup) |
1117 | console->early_setup(); | |
1118 | ||
1da177e4 LT |
1119 | /* |
1120 | * See if we want to use this console driver. If we | |
1121 | * didn't select a console we take the first one | |
1122 | * that registers here. | |
1123 | */ | |
1124 | if (preferred_console < 0) { | |
1125 | if (console->index < 0) | |
1126 | console->index = 0; | |
1127 | if (console->setup == NULL || | |
1128 | console->setup(console, NULL) == 0) { | |
1129 | console->flags |= CON_ENABLED | CON_CONSDEV; | |
1130 | preferred_console = 0; | |
1131 | } | |
1132 | } | |
1133 | ||
1134 | /* | |
1135 | * See if this console matches one we selected on | |
1136 | * the command line. | |
1137 | */ | |
40dc5651 JJ |
1138 | for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; |
1139 | i++) { | |
1da177e4 LT |
1140 | if (strcmp(console_cmdline[i].name, console->name) != 0) |
1141 | continue; | |
1142 | if (console->index >= 0 && | |
1143 | console->index != console_cmdline[i].index) | |
1144 | continue; | |
1145 | if (console->index < 0) | |
1146 | console->index = console_cmdline[i].index; | |
1147 | if (console->setup && | |
1148 | console->setup(console, console_cmdline[i].options) != 0) | |
1149 | break; | |
1150 | console->flags |= CON_ENABLED; | |
1151 | console->index = console_cmdline[i].index; | |
ab4af03a | 1152 | if (i == selected_console) { |
1da177e4 | 1153 | console->flags |= CON_CONSDEV; |
ab4af03a GE |
1154 | preferred_console = selected_console; |
1155 | } | |
1da177e4 LT |
1156 | break; |
1157 | } | |
1158 | ||
1159 | if (!(console->flags & CON_ENABLED)) | |
1160 | return; | |
1161 | ||
d37bf60d | 1162 | if (bootconsole && (console->flags & CON_CONSDEV)) { |
69331af7 GH |
1163 | printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n", |
1164 | bootconsole->name, bootconsole->index, | |
1165 | console->name, console->index); | |
1166 | unregister_console(bootconsole); | |
1da177e4 | 1167 | console->flags &= ~CON_PRINTBUFFER; |
d37bf60d YL |
1168 | } else { |
1169 | printk(KERN_INFO "console [%s%d] enabled\n", | |
1170 | console->name, console->index); | |
1da177e4 LT |
1171 | } |
1172 | ||
1173 | /* | |
1174 | * Put this console in the list - keep the | |
1175 | * preferred driver at the head of the list. | |
1176 | */ | |
1177 | acquire_console_sem(); | |
1178 | if ((console->flags & CON_CONSDEV) || console_drivers == NULL) { | |
1179 | console->next = console_drivers; | |
1180 | console_drivers = console; | |
ab4af03a GE |
1181 | if (console->next) |
1182 | console->next->flags &= ~CON_CONSDEV; | |
1da177e4 LT |
1183 | } else { |
1184 | console->next = console_drivers->next; | |
1185 | console_drivers->next = console; | |
1186 | } | |
1187 | if (console->flags & CON_PRINTBUFFER) { | |
1188 | /* | |
1189 | * release_console_sem() will print out the buffered messages | |
1190 | * for us. | |
1191 | */ | |
1192 | spin_lock_irqsave(&logbuf_lock, flags); | |
1193 | con_start = log_start; | |
1194 | spin_unlock_irqrestore(&logbuf_lock, flags); | |
1195 | } | |
1196 | release_console_sem(); | |
1197 | } | |
1198 | EXPORT_SYMBOL(register_console); | |
1199 | ||
40dc5651 | 1200 | int unregister_console(struct console *console) |
1da177e4 | 1201 | { |
40dc5651 | 1202 | struct console *a, *b; |
1da177e4 LT |
1203 | int res = 1; |
1204 | ||
1205 | acquire_console_sem(); | |
1206 | if (console_drivers == console) { | |
1207 | console_drivers=console->next; | |
1208 | res = 0; | |
e9b15b54 | 1209 | } else if (console_drivers) { |
1da177e4 LT |
1210 | for (a=console_drivers->next, b=console_drivers ; |
1211 | a; b=a, a=b->next) { | |
1212 | if (a == console) { | |
1213 | b->next = a->next; | |
1214 | res = 0; | |
1215 | break; | |
40dc5651 | 1216 | } |
1da177e4 LT |
1217 | } |
1218 | } | |
40dc5651 | 1219 | |
69331af7 | 1220 | /* |
ab4af03a GE |
1221 | * If this isn't the last console and it has CON_CONSDEV set, we |
1222 | * need to set it on the next preferred console. | |
1da177e4 | 1223 | */ |
69331af7 | 1224 | if (console_drivers != NULL && console->flags & CON_CONSDEV) |
ab4af03a | 1225 | console_drivers->flags |= CON_CONSDEV; |
1da177e4 LT |
1226 | |
1227 | release_console_sem(); | |
1228 | return res; | |
1229 | } | |
1230 | EXPORT_SYMBOL(unregister_console); | |
d59745ce | 1231 | |
0c5564bd RG |
1232 | static int __init disable_boot_consoles(void) |
1233 | { | |
cb00e99c RG |
1234 | if (console_drivers != NULL) { |
1235 | if (console_drivers->flags & CON_BOOT) { | |
1236 | printk(KERN_INFO "turn off boot console %s%d\n", | |
1237 | console_drivers->name, console_drivers->index); | |
1238 | return unregister_console(console_drivers); | |
1239 | } | |
0c5564bd RG |
1240 | } |
1241 | return 0; | |
1242 | } | |
1243 | late_initcall(disable_boot_consoles); | |
1244 | ||
1da177e4 LT |
1245 | /** |
1246 | * tty_write_message - write a message to a certain tty, not just the console. | |
ddad86c2 MW |
1247 | * @tty: the destination tty_struct |
1248 | * @msg: the message to write | |
1da177e4 LT |
1249 | * |
1250 | * This is used for messages that need to be redirected to a specific tty. | |
1251 | * We don't put it into the syslog queue right now maybe in the future if | |
1252 | * really needed. | |
1253 | */ | |
1254 | void tty_write_message(struct tty_struct *tty, char *msg) | |
1255 | { | |
1256 | if (tty && tty->driver->write) | |
1257 | tty->driver->write(tty, msg, strlen(msg)); | |
1258 | return; | |
1259 | } | |
1260 | ||
1261 | /* | |
1262 | * printk rate limiting, lifted from the networking subsystem. | |
1263 | * | |
1264 | * This enforces a rate limit: not more than one kernel message | |
1265 | * every printk_ratelimit_jiffies to make a denial-of-service | |
1266 | * attack impossible. | |
1267 | */ | |
1268 | int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst) | |
1269 | { | |
1270 | static DEFINE_SPINLOCK(ratelimit_lock); | |
40dc5651 | 1271 | static unsigned long toks = 10 * 5 * HZ; |
1da177e4 LT |
1272 | static unsigned long last_msg; |
1273 | static int missed; | |
1274 | unsigned long flags; | |
1275 | unsigned long now = jiffies; | |
1276 | ||
1277 | spin_lock_irqsave(&ratelimit_lock, flags); | |
1278 | toks += now - last_msg; | |
1279 | last_msg = now; | |
1280 | if (toks > (ratelimit_burst * ratelimit_jiffies)) | |
1281 | toks = ratelimit_burst * ratelimit_jiffies; | |
1282 | if (toks >= ratelimit_jiffies) { | |
1283 | int lost = missed; | |
40dc5651 | 1284 | |
1da177e4 LT |
1285 | missed = 0; |
1286 | toks -= ratelimit_jiffies; | |
1287 | spin_unlock_irqrestore(&ratelimit_lock, flags); | |
1288 | if (lost) | |
1289 | printk(KERN_WARNING "printk: %d messages suppressed.\n", lost); | |
1290 | return 1; | |
1291 | } | |
1292 | missed++; | |
1293 | spin_unlock_irqrestore(&ratelimit_lock, flags); | |
1294 | return 0; | |
1295 | } | |
1296 | EXPORT_SYMBOL(__printk_ratelimit); | |
1297 | ||
1298 | /* minimum time in jiffies between messages */ | |
40dc5651 | 1299 | int printk_ratelimit_jiffies = 5 * HZ; |
1da177e4 LT |
1300 | |
1301 | /* number of messages we send before ratelimiting */ | |
1302 | int printk_ratelimit_burst = 10; | |
1303 | ||
1304 | int printk_ratelimit(void) | |
1305 | { | |
1306 | return __printk_ratelimit(printk_ratelimit_jiffies, | |
1307 | printk_ratelimit_burst); | |
1308 | } | |
1309 | EXPORT_SYMBOL(printk_ratelimit); | |
f46c4833 AM |
1310 | |
1311 | /** | |
1312 | * printk_timed_ratelimit - caller-controlled printk ratelimiting | |
1313 | * @caller_jiffies: pointer to caller's state | |
1314 | * @interval_msecs: minimum interval between prints | |
1315 | * | |
1316 | * printk_timed_ratelimit() returns true if more than @interval_msecs | |
1317 | * milliseconds have elapsed since the last time printk_timed_ratelimit() | |
1318 | * returned true. | |
1319 | */ | |
1320 | bool printk_timed_ratelimit(unsigned long *caller_jiffies, | |
1321 | unsigned int interval_msecs) | |
1322 | { | |
1323 | if (*caller_jiffies == 0 || time_after(jiffies, *caller_jiffies)) { | |
1324 | *caller_jiffies = jiffies + msecs_to_jiffies(interval_msecs); | |
1325 | return true; | |
1326 | } | |
1327 | return false; | |
1328 | } | |
1329 | EXPORT_SYMBOL(printk_timed_ratelimit); |