projects/linux·blob v4.9 · refs

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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/ftrace.h>
19#include <linux/reboot.h>
20#include <linux/delay.h>
21#include <linux/kexec.h>
22#include <linux/sched.h>
23#include <linux/sysrq.h>
24#include <linux/init.h>
25#include <linux/nmi.h>
26#include <linux/console.h>
27#include <linux/bug.h>
28
29#define PANIC_TIMER_STEP 100
30#define PANIC_BLINK_SPD 18
31
32int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
33static unsigned long tainted_mask;
34static int pause_on_oops;
35static int pause_on_oops_flag;
36static DEFINE_SPINLOCK(pause_on_oops_lock);
37bool crash_kexec_post_notifiers;
38int panic_on_warn __read_mostly;
39
40int panic_timeout = CONFIG_PANIC_TIMEOUT;
41EXPORT_SYMBOL_GPL(panic_timeout);
42
43ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
44
45EXPORT_SYMBOL(panic_notifier_list);
46
47static long no_blink(int state)
48{
49 return 0;
50}
51
52/* Returns how long it waited in ms */
53long (*panic_blink)(int state);
54EXPORT_SYMBOL(panic_blink);
55
56/*
57 * Stop ourself in panic -- architecture code may override this
58 */
59void __weak panic_smp_self_stop(void)
60{
61 while (1)
62 cpu_relax();
63}
64
65/*
66 * Stop ourselves in NMI context if another CPU has already panicked. Arch code
67 * may override this to prepare for crash dumping, e.g. save regs info.
68 */
69void __weak nmi_panic_self_stop(struct pt_regs *regs)
70{
71 panic_smp_self_stop();
72}
73
74/*
75 * Stop other CPUs in panic. Architecture dependent code may override this
76 * with more suitable version. For example, if the architecture supports
77 * crash dump, it should save registers of each stopped CPU and disable
78 * per-CPU features such as virtualization extensions.
79 */
80void __weak crash_smp_send_stop(void)
81{
82 static int cpus_stopped;
83
84 /*
85 * This function can be called twice in panic path, but obviously
86 * we execute this only once.
87 */
88 if (cpus_stopped)
89 return;
90
91 /*
92 * Note smp_send_stop is the usual smp shutdown function, which
93 * unfortunately means it may not be hardened to work in a panic
94 * situation.
95 */
96 smp_send_stop();
97 cpus_stopped = 1;
98}
99
100atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
101
102/*
103 * A variant of panic() called from NMI context. We return if we've already
104 * panicked on this CPU. If another CPU already panicked, loop in
105 * nmi_panic_self_stop() which can provide architecture dependent code such
106 * as saving register state for crash dump.
107 */
108void nmi_panic(struct pt_regs *regs, const char *msg)
109{
110 int old_cpu, cpu;
111
112 cpu = raw_smp_processor_id();
113 old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu);
114
115 if (old_cpu == PANIC_CPU_INVALID)
116 panic("%s", msg);
117 else if (old_cpu != cpu)
118 nmi_panic_self_stop(regs);
119}
120EXPORT_SYMBOL(nmi_panic);
121
122/**
123 * panic - halt the system
124 * @fmt: The text string to print
125 *
126 * Display a message, then perform cleanups.
127 *
128 * This function never returns.
129 */
130void panic(const char *fmt, ...)
131{
132 static char buf[1024];
133 va_list args;
134 long i, i_next = 0;
135 int state = 0;
136 int old_cpu, this_cpu;
137 bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
138
139 /*
140 * Disable local interrupts. This will prevent panic_smp_self_stop
141 * from deadlocking the first cpu that invokes the panic, since
142 * there is nothing to prevent an interrupt handler (that runs
143 * after setting panic_cpu) from invoking panic() again.
144 */
145 local_irq_disable();
146
147 /*
148 * It's possible to come here directly from a panic-assertion and
149 * not have preempt disabled. Some functions called from here want
150 * preempt to be disabled. No point enabling it later though...
151 *
152 * Only one CPU is allowed to execute the panic code from here. For
153 * multiple parallel invocations of panic, all other CPUs either
154 * stop themself or will wait until they are stopped by the 1st CPU
155 * with smp_send_stop().
156 *
157 * `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which
158 * comes here, so go ahead.
159 * `old_cpu == this_cpu' means we came from nmi_panic() which sets
160 * panic_cpu to this CPU. In this case, this is also the 1st CPU.
161 */
162 this_cpu = raw_smp_processor_id();
163 old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
164
165 if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)
166 panic_smp_self_stop();
167
168 console_verbose();
169 bust_spinlocks(1);
170 va_start(args, fmt);
171 vsnprintf(buf, sizeof(buf), fmt, args);
172 va_end(args);
173 pr_emerg("Kernel panic - not syncing: %s\n", buf);
174#ifdef CONFIG_DEBUG_BUGVERBOSE
175 /*
176 * Avoid nested stack-dumping if a panic occurs during oops processing
177 */
178 if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
179 dump_stack();
180#endif
181
182 /*
183 * If we have crashed and we have a crash kernel loaded let it handle
184 * everything else.
185 * If we want to run this after calling panic_notifiers, pass
186 * the "crash_kexec_post_notifiers" option to the kernel.
187 *
188 * Bypass the panic_cpu check and call __crash_kexec directly.
189 */
190 if (!_crash_kexec_post_notifiers) {
191 printk_nmi_flush_on_panic();
192 __crash_kexec(NULL);
193
194 /*
195 * Note smp_send_stop is the usual smp shutdown function, which
196 * unfortunately means it may not be hardened to work in a
197 * panic situation.
198 */
199 smp_send_stop();
200 } else {
201 /*
202 * If we want to do crash dump after notifier calls and
203 * kmsg_dump, we will need architecture dependent extra
204 * works in addition to stopping other CPUs.
205 */
206 crash_smp_send_stop();
207 }
208
209 /*
210 * Run any panic handlers, including those that might need to
211 * add information to the kmsg dump output.
212 */
213 atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
214
215 /* Call flush even twice. It tries harder with a single online CPU */
216 printk_nmi_flush_on_panic();
217 kmsg_dump(KMSG_DUMP_PANIC);
218
219 /*
220 * If you doubt kdump always works fine in any situation,
221 * "crash_kexec_post_notifiers" offers you a chance to run
222 * panic_notifiers and dumping kmsg before kdump.
223 * Note: since some panic_notifiers can make crashed kernel
224 * more unstable, it can increase risks of the kdump failure too.
225 *
226 * Bypass the panic_cpu check and call __crash_kexec directly.
227 */
228 if (_crash_kexec_post_notifiers)
229 __crash_kexec(NULL);
230
231 bust_spinlocks(0);
232
233 /*
234 * We may have ended up stopping the CPU holding the lock (in
235 * smp_send_stop()) while still having some valuable data in the console
236 * buffer. Try to acquire the lock then release it regardless of the
237 * result. The release will also print the buffers out. Locks debug
238 * should be disabled to avoid reporting bad unlock balance when
239 * panic() is not being callled from OOPS.
240 */
241 debug_locks_off();
242 console_flush_on_panic();
243
244 if (!panic_blink)
245 panic_blink = no_blink;
246
247 if (panic_timeout > 0) {
248 /*
249 * Delay timeout seconds before rebooting the machine.
250 * We can't use the "normal" timers since we just panicked.
251 */
252 pr_emerg("Rebooting in %d seconds..", panic_timeout);
253
254 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
255 touch_nmi_watchdog();
256 if (i >= i_next) {
257 i += panic_blink(state ^= 1);
258 i_next = i + 3600 / PANIC_BLINK_SPD;
259 }
260 mdelay(PANIC_TIMER_STEP);
261 }
262 }
263 if (panic_timeout != 0) {
264 /*
265 * This will not be a clean reboot, with everything
266 * shutting down. But if there is a chance of
267 * rebooting the system it will be rebooted.
268 */
269 emergency_restart();
270 }
271#ifdef __sparc__
272 {
273 extern int stop_a_enabled;
274 /* Make sure the user can actually press Stop-A (L1-A) */
275 stop_a_enabled = 1;
276 pr_emerg("Press Stop-A (L1-A) to return to the boot prom\n");
277 }
278#endif
279#if defined(CONFIG_S390)
280 {
281 unsigned long caller;
282
283 caller = (unsigned long)__builtin_return_address(0);
284 disabled_wait(caller);
285 }
286#endif
287 pr_emerg("---[ end Kernel panic - not syncing: %s\n", buf);
288 local_irq_enable();
289 for (i = 0; ; i += PANIC_TIMER_STEP) {
290 touch_softlockup_watchdog();
291 if (i >= i_next) {
292 i += panic_blink(state ^= 1);
293 i_next = i + 3600 / PANIC_BLINK_SPD;
294 }
295 mdelay(PANIC_TIMER_STEP);
296 }
297}
298
299EXPORT_SYMBOL(panic);
300
301
302struct tnt {
303 u8 bit;
304 char true;
305 char false;
306};
307
308static const struct tnt tnts[] = {
309 { TAINT_PROPRIETARY_MODULE, 'P', 'G' },
310 { TAINT_FORCED_MODULE, 'F', ' ' },
311 { TAINT_CPU_OUT_OF_SPEC, 'S', ' ' },
312 { TAINT_FORCED_RMMOD, 'R', ' ' },
313 { TAINT_MACHINE_CHECK, 'M', ' ' },
314 { TAINT_BAD_PAGE, 'B', ' ' },
315 { TAINT_USER, 'U', ' ' },
316 { TAINT_DIE, 'D', ' ' },
317 { TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },
318 { TAINT_WARN, 'W', ' ' },
319 { TAINT_CRAP, 'C', ' ' },
320 { TAINT_FIRMWARE_WORKAROUND, 'I', ' ' },
321 { TAINT_OOT_MODULE, 'O', ' ' },
322 { TAINT_UNSIGNED_MODULE, 'E', ' ' },
323 { TAINT_SOFTLOCKUP, 'L', ' ' },
324 { TAINT_LIVEPATCH, 'K', ' ' },
325};
326
327/**
328 * print_tainted - return a string to represent the kernel taint state.
329 *
330 * 'P' - Proprietary module has been loaded.
331 * 'F' - Module has been forcibly loaded.
332 * 'S' - SMP with CPUs not designed for SMP.
333 * 'R' - User forced a module unload.
334 * 'M' - System experienced a machine check exception.
335 * 'B' - System has hit bad_page.
336 * 'U' - Userspace-defined naughtiness.
337 * 'D' - Kernel has oopsed before
338 * 'A' - ACPI table overridden.
339 * 'W' - Taint on warning.
340 * 'C' - modules from drivers/staging are loaded.
341 * 'I' - Working around severe firmware bug.
342 * 'O' - Out-of-tree module has been loaded.
343 * 'E' - Unsigned module has been loaded.
344 * 'L' - A soft lockup has previously occurred.
345 * 'K' - Kernel has been live patched.
346 *
347 * The string is overwritten by the next call to print_tainted().
348 */
349const char *print_tainted(void)
350{
351 static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ")];
352
353 if (tainted_mask) {
354 char *s;
355 int i;
356
357 s = buf + sprintf(buf, "Tainted: ");
358 for (i = 0; i < ARRAY_SIZE(tnts); i++) {
359 const struct tnt *t = &tnts[i];
360 *s++ = test_bit(t->bit, &tainted_mask) ?
361 t->true : t->false;
362 }
363 *s = 0;
364 } else
365 snprintf(buf, sizeof(buf), "Not tainted");
366
367 return buf;
368}
369
370int test_taint(unsigned flag)
371{
372 return test_bit(flag, &tainted_mask);
373}
374EXPORT_SYMBOL(test_taint);
375
376unsigned long get_taint(void)
377{
378 return tainted_mask;
379}
380
381/**
382 * add_taint: add a taint flag if not already set.
383 * @flag: one of the TAINT_* constants.
384 * @lockdep_ok: whether lock debugging is still OK.
385 *
386 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
387 * some notewortht-but-not-corrupting cases, it can be set to true.
388 */
389void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
390{
391 if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
392 pr_warn("Disabling lock debugging due to kernel taint\n");
393
394 set_bit(flag, &tainted_mask);
395}
396EXPORT_SYMBOL(add_taint);
397
398static void spin_msec(int msecs)
399{
400 int i;
401
402 for (i = 0; i < msecs; i++) {
403 touch_nmi_watchdog();
404 mdelay(1);
405 }
406}
407
408/*
409 * It just happens that oops_enter() and oops_exit() are identically
410 * implemented...
411 */
412static void do_oops_enter_exit(void)
413{
414 unsigned long flags;
415 static int spin_counter;
416
417 if (!pause_on_oops)
418 return;
419
420 spin_lock_irqsave(&pause_on_oops_lock, flags);
421 if (pause_on_oops_flag == 0) {
422 /* This CPU may now print the oops message */
423 pause_on_oops_flag = 1;
424 } else {
425 /* We need to stall this CPU */
426 if (!spin_counter) {
427 /* This CPU gets to do the counting */
428 spin_counter = pause_on_oops;
429 do {
430 spin_unlock(&pause_on_oops_lock);
431 spin_msec(MSEC_PER_SEC);
432 spin_lock(&pause_on_oops_lock);
433 } while (--spin_counter);
434 pause_on_oops_flag = 0;
435 } else {
436 /* This CPU waits for a different one */
437 while (spin_counter) {
438 spin_unlock(&pause_on_oops_lock);
439 spin_msec(1);
440 spin_lock(&pause_on_oops_lock);
441 }
442 }
443 }
444 spin_unlock_irqrestore(&pause_on_oops_lock, flags);
445}
446
447/*
448 * Return true if the calling CPU is allowed to print oops-related info.
449 * This is a bit racy..
450 */
451int oops_may_print(void)
452{
453 return pause_on_oops_flag == 0;
454}
455
456/*
457 * Called when the architecture enters its oops handler, before it prints
458 * anything. If this is the first CPU to oops, and it's oopsing the first
459 * time then let it proceed.
460 *
461 * This is all enabled by the pause_on_oops kernel boot option. We do all
462 * this to ensure that oopses don't scroll off the screen. It has the
463 * side-effect of preventing later-oopsing CPUs from mucking up the display,
464 * too.
465 *
466 * It turns out that the CPU which is allowed to print ends up pausing for
467 * the right duration, whereas all the other CPUs pause for twice as long:
468 * once in oops_enter(), once in oops_exit().
469 */
470void oops_enter(void)
471{
472 tracing_off();
473 /* can't trust the integrity of the kernel anymore: */
474 debug_locks_off();
475 do_oops_enter_exit();
476}
477
478/*
479 * 64-bit random ID for oopses:
480 */
481static u64 oops_id;
482
483static int init_oops_id(void)
484{
485 if (!oops_id)
486 get_random_bytes(&oops_id, sizeof(oops_id));
487 else
488 oops_id++;
489
490 return 0;
491}
492late_initcall(init_oops_id);
493
494void print_oops_end_marker(void)
495{
496 init_oops_id();
497 pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id);
498}
499
500/*
501 * Called when the architecture exits its oops handler, after printing
502 * everything.
503 */
504void oops_exit(void)
505{
506 do_oops_enter_exit();
507 print_oops_end_marker();
508 kmsg_dump(KMSG_DUMP_OOPS);
509}
510
511struct warn_args {
512 const char *fmt;
513 va_list args;
514};
515
516void __warn(const char *file, int line, void *caller, unsigned taint,
517 struct pt_regs *regs, struct warn_args *args)
518{
519 disable_trace_on_warning();
520
521 pr_warn("------------[ cut here ]------------\n");
522
523 if (file)
524 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
525 raw_smp_processor_id(), current->pid, file, line,
526 caller);
527 else
528 pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
529 raw_smp_processor_id(), current->pid, caller);
530
531 if (args)
532 vprintk(args->fmt, args->args);
533
534 if (panic_on_warn) {
535 /*
536 * This thread may hit another WARN() in the panic path.
537 * Resetting this prevents additional WARN() from panicking the
538 * system on this thread. Other threads are blocked by the
539 * panic_mutex in panic().
540 */
541 panic_on_warn = 0;
542 panic("panic_on_warn set ...\n");
543 }
544
545 print_modules();
546
547 if (regs)
548 show_regs(regs);
549 else
550 dump_stack();
551
552 print_oops_end_marker();
553
554 /* Just a warning, don't kill lockdep. */
555 add_taint(taint, LOCKDEP_STILL_OK);
556}
557
558#ifdef WANT_WARN_ON_SLOWPATH
559void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
560{
561 struct warn_args args;
562
563 args.fmt = fmt;
564 va_start(args.args, fmt);
565 __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL,
566 &args);
567 va_end(args.args);
568}
569EXPORT_SYMBOL(warn_slowpath_fmt);
570
571void warn_slowpath_fmt_taint(const char *file, int line,
572 unsigned taint, const char *fmt, ...)
573{
574 struct warn_args args;
575
576 args.fmt = fmt;
577 va_start(args.args, fmt);
578 __warn(file, line, __builtin_return_address(0), taint, NULL, &args);
579 va_end(args.args);
580}
581EXPORT_SYMBOL(warn_slowpath_fmt_taint);
582
583void warn_slowpath_null(const char *file, int line)
584{
585 __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, NULL);
586}
587EXPORT_SYMBOL(warn_slowpath_null);
588#endif
589
590#ifdef CONFIG_CC_STACKPROTECTOR
591
592/*
593 * Called when gcc's -fstack-protector feature is used, and
594 * gcc detects corruption of the on-stack canary value
595 */
596__visible void __stack_chk_fail(void)
597{
598 panic("stack-protector: Kernel stack is corrupted in: %p\n",
599 __builtin_return_address(0));
600}
601EXPORT_SYMBOL(__stack_chk_fail);
602
603#endif
604
605core_param(panic, panic_timeout, int, 0644);
606core_param(pause_on_oops, pause_on_oops, int, 0644);
607core_param(panic_on_warn, panic_on_warn, int, 0644);
608core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
609
610static int __init oops_setup(char *s)
611{
612 if (!s)
613 return -EINVAL;
614 if (!strcmp(s, "panic"))
615 panic_on_oops = 1;
616 return 0;
617}
618early_param("oops", oops_setup);