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1 /*
2 * linux/kernel/panic.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
6
7 /*
8 * This function is used through-out the kernel (including mm and fs)
9 * to indicate a major problem.
10 */
11 #include <linux/debug_locks.h>
12 #include <linux/interrupt.h>
13 #include <linux/kmsg_dump.h>
14 #include <linux/kallsyms.h>
15 #include <linux/notifier.h>
16 #include <linux/module.h>
17 #include <linux/random.h>
18 #include <linux/reboot.h>
19 #include <linux/delay.h>
20 #include <linux/kexec.h>
21 #include <linux/sched.h>
22 #include <linux/sysrq.h>
23 #include <linux/init.h>
24 #include <linux/nmi.h>
25
26 #define PANIC_TIMER_STEP 100
27 #define PANIC_BLINK_SPD 18
28
29 int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
30 static unsigned long tainted_mask;
31 static int pause_on_oops;
32 static int pause_on_oops_flag;
33 static DEFINE_SPINLOCK(pause_on_oops_lock);
34
35 int panic_timeout;
36 EXPORT_SYMBOL_GPL(panic_timeout);
37
38 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
39
40 EXPORT_SYMBOL(panic_notifier_list);
41
42 static long no_blink(int state)
43 {
44 return 0;
45 }
46
47 /* Returns how long it waited in ms */
48 long (*panic_blink)(int state);
49 EXPORT_SYMBOL(panic_blink);
50
51 /*
52 * Stop ourself in panic -- architecture code may override this
53 */
54 void __weak panic_smp_self_stop(void)
55 {
56 while (1)
57 cpu_relax();
58 }
59
60 /**
61 * panic - halt the system
62 * @fmt: The text string to print
63 *
64 * Display a message, then perform cleanups.
65 *
66 * This function never returns.
67 */
68 void panic(const char *fmt, ...)
69 {
70 static DEFINE_SPINLOCK(panic_lock);
71 static char buf[1024];
72 va_list args;
73 long i, i_next = 0;
74 int state = 0;
75
76 /*
77 * Disable local interrupts. This will prevent panic_smp_self_stop
78 * from deadlocking the first cpu that invokes the panic, since
79 * there is nothing to prevent an interrupt handler (that runs
80 * after the panic_lock is acquired) from invoking panic again.
81 */
82 local_irq_disable();
83
84 /*
85 * It's possible to come here directly from a panic-assertion and
86 * not have preempt disabled. Some functions called from here want
87 * preempt to be disabled. No point enabling it later though...
88 *
89 * Only one CPU is allowed to execute the panic code from here. For
90 * multiple parallel invocations of panic, all other CPUs either
91 * stop themself or will wait until they are stopped by the 1st CPU
92 * with smp_send_stop().
93 */
94 if (!spin_trylock(&panic_lock))
95 panic_smp_self_stop();
96
97 console_verbose();
98 bust_spinlocks(1);
99 va_start(args, fmt);
100 vsnprintf(buf, sizeof(buf), fmt, args);
101 va_end(args);
102 printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
103 #ifdef CONFIG_DEBUG_BUGVERBOSE
104 /*
105 * Avoid nested stack-dumping if a panic occurs during oops processing
106 */
107 if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
108 dump_stack();
109 #endif
110
111 /*
112 * If we have crashed and we have a crash kernel loaded let it handle
113 * everything else.
114 * Do we want to call this before we try to display a message?
115 */
116 crash_kexec(NULL);
117
118 /*
119 * Note smp_send_stop is the usual smp shutdown function, which
120 * unfortunately means it may not be hardened to work in a panic
121 * situation.
122 */
123 smp_send_stop();
124
125 kmsg_dump(KMSG_DUMP_PANIC);
126
127 atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
128
129 bust_spinlocks(0);
130
131 if (!panic_blink)
132 panic_blink = no_blink;
133
134 if (panic_timeout > 0) {
135 /*
136 * Delay timeout seconds before rebooting the machine.
137 * We can't use the "normal" timers since we just panicked.
138 */
139 printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
140
141 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
142 touch_nmi_watchdog();
143 if (i >= i_next) {
144 i += panic_blink(state ^= 1);
145 i_next = i + 3600 / PANIC_BLINK_SPD;
146 }
147 mdelay(PANIC_TIMER_STEP);
148 }
149 }
150 if (panic_timeout != 0) {
151 /*
152 * This will not be a clean reboot, with everything
153 * shutting down. But if there is a chance of
154 * rebooting the system it will be rebooted.
155 */
156 emergency_restart();
157 }
158 #ifdef __sparc__
159 {
160 extern int stop_a_enabled;
161 /* Make sure the user can actually press Stop-A (L1-A) */
162 stop_a_enabled = 1;
163 printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
164 }
165 #endif
166 #if defined(CONFIG_S390)
167 {
168 unsigned long caller;
169
170 caller = (unsigned long)__builtin_return_address(0);
171 disabled_wait(caller);
172 }
173 #endif
174 local_irq_enable();
175 for (i = 0; ; i += PANIC_TIMER_STEP) {
176 touch_softlockup_watchdog();
177 if (i >= i_next) {
178 i += panic_blink(state ^= 1);
179 i_next = i + 3600 / PANIC_BLINK_SPD;
180 }
181 mdelay(PANIC_TIMER_STEP);
182 }
183 }
184
185 EXPORT_SYMBOL(panic);
186
187
188 struct tnt {
189 u8 bit;
190 char true;
191 char false;
192 };
193
194 static const struct tnt tnts[] = {
195 { TAINT_PROPRIETARY_MODULE, 'P', 'G' },
196 { TAINT_FORCED_MODULE, 'F', ' ' },
197 { TAINT_UNSAFE_SMP, 'S', ' ' },
198 { TAINT_FORCED_RMMOD, 'R', ' ' },
199 { TAINT_MACHINE_CHECK, 'M', ' ' },
200 { TAINT_BAD_PAGE, 'B', ' ' },
201 { TAINT_USER, 'U', ' ' },
202 { TAINT_DIE, 'D', ' ' },
203 { TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },
204 { TAINT_WARN, 'W', ' ' },
205 { TAINT_CRAP, 'C', ' ' },
206 { TAINT_FIRMWARE_WORKAROUND, 'I', ' ' },
207 { TAINT_OOT_MODULE, 'O', ' ' },
208 };
209
210 /**
211 * print_tainted - return a string to represent the kernel taint state.
212 *
213 * 'P' - Proprietary module has been loaded.
214 * 'F' - Module has been forcibly loaded.
215 * 'S' - SMP with CPUs not designed for SMP.
216 * 'R' - User forced a module unload.
217 * 'M' - System experienced a machine check exception.
218 * 'B' - System has hit bad_page.
219 * 'U' - Userspace-defined naughtiness.
220 * 'D' - Kernel has oopsed before
221 * 'A' - ACPI table overridden.
222 * 'W' - Taint on warning.
223 * 'C' - modules from drivers/staging are loaded.
224 * 'I' - Working around severe firmware bug.
225 * 'O' - Out-of-tree module has been loaded.
226 *
227 * The string is overwritten by the next call to print_tainted().
228 */
229 const char *print_tainted(void)
230 {
231 static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
232
233 if (tainted_mask) {
234 char *s;
235 int i;
236
237 s = buf + sprintf(buf, "Tainted: ");
238 for (i = 0; i < ARRAY_SIZE(tnts); i++) {
239 const struct tnt *t = &tnts[i];
240 *s++ = test_bit(t->bit, &tainted_mask) ?
241 t->true : t->false;
242 }
243 *s = 0;
244 } else
245 snprintf(buf, sizeof(buf), "Not tainted");
246
247 return buf;
248 }
249
250 int test_taint(unsigned flag)
251 {
252 return test_bit(flag, &tainted_mask);
253 }
254 EXPORT_SYMBOL(test_taint);
255
256 unsigned long get_taint(void)
257 {
258 return tainted_mask;
259 }
260
261 /**
262 * add_taint: add a taint flag if not already set.
263 * @flag: one of the TAINT_* constants.
264 * @lockdep_ok: whether lock debugging is still OK.
265 *
266 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
267 * some notewortht-but-not-corrupting cases, it can be set to true.
268 */
269 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
270 {
271 if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
272 printk(KERN_WARNING
273 "Disabling lock debugging due to kernel taint\n");
274
275 set_bit(flag, &tainted_mask);
276 }
277 EXPORT_SYMBOL(add_taint);
278
279 static void spin_msec(int msecs)
280 {
281 int i;
282
283 for (i = 0; i < msecs; i++) {
284 touch_nmi_watchdog();
285 mdelay(1);
286 }
287 }
288
289 /*
290 * It just happens that oops_enter() and oops_exit() are identically
291 * implemented...
292 */
293 static void do_oops_enter_exit(void)
294 {
295 unsigned long flags;
296 static int spin_counter;
297
298 if (!pause_on_oops)
299 return;
300
301 spin_lock_irqsave(&pause_on_oops_lock, flags);
302 if (pause_on_oops_flag == 0) {
303 /* This CPU may now print the oops message */
304 pause_on_oops_flag = 1;
305 } else {
306 /* We need to stall this CPU */
307 if (!spin_counter) {
308 /* This CPU gets to do the counting */
309 spin_counter = pause_on_oops;
310 do {
311 spin_unlock(&pause_on_oops_lock);
312 spin_msec(MSEC_PER_SEC);
313 spin_lock(&pause_on_oops_lock);
314 } while (--spin_counter);
315 pause_on_oops_flag = 0;
316 } else {
317 /* This CPU waits for a different one */
318 while (spin_counter) {
319 spin_unlock(&pause_on_oops_lock);
320 spin_msec(1);
321 spin_lock(&pause_on_oops_lock);
322 }
323 }
324 }
325 spin_unlock_irqrestore(&pause_on_oops_lock, flags);
326 }
327
328 /*
329 * Return true if the calling CPU is allowed to print oops-related info.
330 * This is a bit racy..
331 */
332 int oops_may_print(void)
333 {
334 return pause_on_oops_flag == 0;
335 }
336
337 /*
338 * Called when the architecture enters its oops handler, before it prints
339 * anything. If this is the first CPU to oops, and it's oopsing the first
340 * time then let it proceed.
341 *
342 * This is all enabled by the pause_on_oops kernel boot option. We do all
343 * this to ensure that oopses don't scroll off the screen. It has the
344 * side-effect of preventing later-oopsing CPUs from mucking up the display,
345 * too.
346 *
347 * It turns out that the CPU which is allowed to print ends up pausing for
348 * the right duration, whereas all the other CPUs pause for twice as long:
349 * once in oops_enter(), once in oops_exit().
350 */
351 void oops_enter(void)
352 {
353 tracing_off();
354 /* can't trust the integrity of the kernel anymore: */
355 debug_locks_off();
356 do_oops_enter_exit();
357 }
358
359 /*
360 * 64-bit random ID for oopses:
361 */
362 static u64 oops_id;
363
364 static int init_oops_id(void)
365 {
366 if (!oops_id)
367 get_random_bytes(&oops_id, sizeof(oops_id));
368 else
369 oops_id++;
370
371 return 0;
372 }
373 late_initcall(init_oops_id);
374
375 void print_oops_end_marker(void)
376 {
377 init_oops_id();
378 printk(KERN_WARNING "---[ end trace %016llx ]---\n",
379 (unsigned long long)oops_id);
380 }
381
382 /*
383 * Called when the architecture exits its oops handler, after printing
384 * everything.
385 */
386 void oops_exit(void)
387 {
388 do_oops_enter_exit();
389 print_oops_end_marker();
390 kmsg_dump(KMSG_DUMP_OOPS);
391 }
392
393 #ifdef WANT_WARN_ON_SLOWPATH
394 struct slowpath_args {
395 const char *fmt;
396 va_list args;
397 };
398
399 static void warn_slowpath_common(const char *file, int line, void *caller,
400 unsigned taint, struct slowpath_args *args)
401 {
402 printk(KERN_WARNING "------------[ cut here ]------------\n");
403 printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
404
405 if (args)
406 vprintk(args->fmt, args->args);
407
408 print_modules();
409 dump_stack();
410 print_oops_end_marker();
411 /* Just a warning, don't kill lockdep. */
412 add_taint(taint, LOCKDEP_STILL_OK);
413 }
414
415 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
416 {
417 struct slowpath_args args;
418
419 args.fmt = fmt;
420 va_start(args.args, fmt);
421 warn_slowpath_common(file, line, __builtin_return_address(0),
422 TAINT_WARN, &args);
423 va_end(args.args);
424 }
425 EXPORT_SYMBOL(warn_slowpath_fmt);
426
427 void warn_slowpath_fmt_taint(const char *file, int line,
428 unsigned taint, const char *fmt, ...)
429 {
430 struct slowpath_args args;
431
432 args.fmt = fmt;
433 va_start(args.args, fmt);
434 warn_slowpath_common(file, line, __builtin_return_address(0),
435 taint, &args);
436 va_end(args.args);
437 }
438 EXPORT_SYMBOL(warn_slowpath_fmt_taint);
439
440 void warn_slowpath_null(const char *file, int line)
441 {
442 warn_slowpath_common(file, line, __builtin_return_address(0),
443 TAINT_WARN, NULL);
444 }
445 EXPORT_SYMBOL(warn_slowpath_null);
446 #endif
447
448 #ifdef CONFIG_CC_STACKPROTECTOR
449
450 /*
451 * Called when gcc's -fstack-protector feature is used, and
452 * gcc detects corruption of the on-stack canary value
453 */
454 void __stack_chk_fail(void)
455 {
456 panic("stack-protector: Kernel stack is corrupted in: %p\n",
457 __builtin_return_address(0));
458 }
459 EXPORT_SYMBOL(__stack_chk_fail);
460
461 #endif
462
463 core_param(panic, panic_timeout, int, 0644);
464 core_param(pause_on_oops, pause_on_oops, int, 0644);
465
466 static int __init oops_setup(char *s)
467 {
468 if (!s)
469 return -EINVAL;
470 if (!strcmp(s, "panic"))
471 panic_on_oops = 1;
472 return 0;
473 }
474 early_param("oops", oops_setup);