projects/linux·blob v4.12 · 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/sched/debug.h>
13#include <linux/interrupt.h>
14#include <linux/kmsg_dump.h>
15#include <linux/kallsyms.h>
16#include <linux/notifier.h>
17#include <linux/module.h>
18#include <linux/random.h>
19#include <linux/ftrace.h>
20#include <linux/reboot.h>
21#include <linux/delay.h>
22#include <linux/kexec.h>
23#include <linux/sched.h>
24#include <linux/sysrq.h>
25#include <linux/init.h>
26#include <linux/nmi.h>
27#include <linux/console.h>
28#include <linux/bug.h>
29
30#define PANIC_TIMER_STEP 100
31#define PANIC_BLINK_SPD 18
32
33int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
34static unsigned long tainted_mask;
35static int pause_on_oops;
36static int pause_on_oops_flag;
37static DEFINE_SPINLOCK(pause_on_oops_lock);
38bool crash_kexec_post_notifiers;
39int panic_on_warn __read_mostly;
40
41int panic_timeout = CONFIG_PANIC_TIMEOUT;
42EXPORT_SYMBOL_GPL(panic_timeout);
43
44ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
45
46EXPORT_SYMBOL(panic_notifier_list);
47
48static long no_blink(int state)
49{
50 return 0;
51}
52
53/* Returns how long it waited in ms */
54long (*panic_blink)(int state);
55EXPORT_SYMBOL(panic_blink);
56
57/*
58 * Stop ourself in panic -- architecture code may override this
59 */
60void __weak panic_smp_self_stop(void)
61{
62 while (1)
63 cpu_relax();
64}
65
66/*
67 * Stop ourselves in NMI context if another CPU has already panicked. Arch code
68 * may override this to prepare for crash dumping, e.g. save regs info.
69 */
70void __weak nmi_panic_self_stop(struct pt_regs *regs)
71{
72 panic_smp_self_stop();
73}
74
75/*
76 * Stop other CPUs in panic. Architecture dependent code may override this
77 * with more suitable version. For example, if the architecture supports
78 * crash dump, it should save registers of each stopped CPU and disable
79 * per-CPU features such as virtualization extensions.
80 */
81void __weak crash_smp_send_stop(void)
82{
83 static int cpus_stopped;
84
85 /*
86 * This function can be called twice in panic path, but obviously
87 * we execute this only once.
88 */
89 if (cpus_stopped)
90 return;
91
92 /*
93 * Note smp_send_stop is the usual smp shutdown function, which
94 * unfortunately means it may not be hardened to work in a panic
95 * situation.
96 */
97 smp_send_stop();
98 cpus_stopped = 1;
99}
100
101atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
102
103/*
104 * A variant of panic() called from NMI context. We return if we've already
105 * panicked on this CPU. If another CPU already panicked, loop in
106 * nmi_panic_self_stop() which can provide architecture dependent code such
107 * as saving register state for crash dump.
108 */
109void nmi_panic(struct pt_regs *regs, const char *msg)
110{
111 int old_cpu, cpu;
112
113 cpu = raw_smp_processor_id();
114 old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu);
115
116 if (old_cpu == PANIC_CPU_INVALID)
117 panic("%s", msg);
118 else if (old_cpu != cpu)
119 nmi_panic_self_stop(regs);
120}
121EXPORT_SYMBOL(nmi_panic);
122
123/**
124 * panic - halt the system
125 * @fmt: The text string to print
126 *
127 * Display a message, then perform cleanups.
128 *
129 * This function never returns.
130 */
131void panic(const char *fmt, ...)
132{
133 static char buf[1024];
134 va_list args;
135 long i, i_next = 0;
136 int state = 0;
137 int old_cpu, this_cpu;
138 bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
139
140 /*
141 * Disable local interrupts. This will prevent panic_smp_self_stop
142 * from deadlocking the first cpu that invokes the panic, since
143 * there is nothing to prevent an interrupt handler (that runs
144 * after setting panic_cpu) from invoking panic() again.
145 */
146 local_irq_disable();
147
148 /*
149 * It's possible to come here directly from a panic-assertion and
150 * not have preempt disabled. Some functions called from here want
151 * preempt to be disabled. No point enabling it later though...
152 *
153 * Only one CPU is allowed to execute the panic code from here. For
154 * multiple parallel invocations of panic, all other CPUs either
155 * stop themself or will wait until they are stopped by the 1st CPU
156 * with smp_send_stop().
157 *
158 * `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which
159 * comes here, so go ahead.
160 * `old_cpu == this_cpu' means we came from nmi_panic() which sets
161 * panic_cpu to this CPU. In this case, this is also the 1st CPU.
162 */
163 this_cpu = raw_smp_processor_id();
164 old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
165
166 if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)
167 panic_smp_self_stop();
168
169 console_verbose();
170 bust_spinlocks(1);
171 va_start(args, fmt);
172 vsnprintf(buf, sizeof(buf), fmt, args);
173 va_end(args);
174 pr_emerg("Kernel panic - not syncing: %s\n", buf);
175#ifdef CONFIG_DEBUG_BUGVERBOSE
176 /*
177 * Avoid nested stack-dumping if a panic occurs during oops processing
178 */
179 if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
180 dump_stack();
181#endif
182
183 /*
184 * If we have crashed and we have a crash kernel loaded let it handle
185 * everything else.
186 * If we want to run this after calling panic_notifiers, pass
187 * the "crash_kexec_post_notifiers" option to the kernel.
188 *
189 * Bypass the panic_cpu check and call __crash_kexec directly.
190 */
191 if (!_crash_kexec_post_notifiers) {
192 printk_safe_flush_on_panic();
193 __crash_kexec(NULL);
194
195 /*
196 * Note smp_send_stop is the usual smp shutdown function, which
197 * unfortunately means it may not be hardened to work in a
198 * panic situation.
199 */
200 smp_send_stop();
201 } else {
202 /*
203 * If we want to do crash dump after notifier calls and
204 * kmsg_dump, we will need architecture dependent extra
205 * works in addition to stopping other CPUs.
206 */
207 crash_smp_send_stop();
208 }
209
210 /*
211 * Run any panic handlers, including those that might need to
212 * add information to the kmsg dump output.
213 */
214 atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
215
216 /* Call flush even twice. It tries harder with a single online CPU */
217 printk_safe_flush_on_panic();
218 kmsg_dump(KMSG_DUMP_PANIC);
219
220 /*
221 * If you doubt kdump always works fine in any situation,
222 * "crash_kexec_post_notifiers" offers you a chance to run
223 * panic_notifiers and dumping kmsg before kdump.
224 * Note: since some panic_notifiers can make crashed kernel
225 * more unstable, it can increase risks of the kdump failure too.
226 *
227 * Bypass the panic_cpu check and call __crash_kexec directly.
228 */
229 if (_crash_kexec_post_notifiers)
230 __crash_kexec(NULL);
231
232 bust_spinlocks(0);
233
234 /*
235 * We may have ended up stopping the CPU holding the lock (in
236 * smp_send_stop()) while still having some valuable data in the console
237 * buffer. Try to acquire the lock then release it regardless of the
238 * result. The release will also print the buffers out. Locks debug
239 * should be disabled to avoid reporting bad unlock balance when
240 * panic() is not being callled from OOPS.
241 */
242 debug_locks_off();
243 console_flush_on_panic();
244
245 if (!panic_blink)
246 panic_blink = no_blink;
247
248 if (panic_timeout > 0) {
249 /*
250 * Delay timeout seconds before rebooting the machine.
251 * We can't use the "normal" timers since we just panicked.
252 */
253 pr_emerg("Rebooting in %d seconds..\n", panic_timeout);
254
255 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
256 touch_nmi_watchdog();
257 if (i >= i_next) {
258 i += panic_blink(state ^= 1);
259 i_next = i + 3600 / PANIC_BLINK_SPD;
260 }
261 mdelay(PANIC_TIMER_STEP);
262 }
263 }
264 if (panic_timeout != 0) {
265 /*
266 * This will not be a clean reboot, with everything
267 * shutting down. But if there is a chance of
268 * rebooting the system it will be rebooted.
269 */
270 emergency_restart();
271 }
272#ifdef __sparc__
273 {
274 extern int stop_a_enabled;
275 /* Make sure the user can actually press Stop-A (L1-A) */
276 stop_a_enabled = 1;
277 pr_emerg("Press Stop-A (L1-A) from sun keyboard or send break\n"
278 "twice on console to return to the boot prom\n");
279 }
280#endif
281#if defined(CONFIG_S390)
282 {
283 unsigned long caller;
284
285 caller = (unsigned long)__builtin_return_address(0);
286 disabled_wait(caller);
287 }
288#endif
289 pr_emerg("---[ end Kernel panic - not syncing: %s\n", buf);
290 local_irq_enable();
291 for (i = 0; ; i += PANIC_TIMER_STEP) {
292 touch_softlockup_watchdog();
293 if (i >= i_next) {
294 i += panic_blink(state ^= 1);
295 i_next = i + 3600 / PANIC_BLINK_SPD;
296 }
297 mdelay(PANIC_TIMER_STEP);
298 }
299}
300
301EXPORT_SYMBOL(panic);
302
303/*
304 * TAINT_FORCED_RMMOD could be a per-module flag but the module
305 * is being removed anyway.
306 */
307const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
308 { 'P', 'G', true }, /* TAINT_PROPRIETARY_MODULE */
309 { 'F', ' ', true }, /* TAINT_FORCED_MODULE */
310 { 'S', ' ', false }, /* TAINT_CPU_OUT_OF_SPEC */
311 { 'R', ' ', false }, /* TAINT_FORCED_RMMOD */
312 { 'M', ' ', false }, /* TAINT_MACHINE_CHECK */
313 { 'B', ' ', false }, /* TAINT_BAD_PAGE */
314 { 'U', ' ', false }, /* TAINT_USER */
315 { 'D', ' ', false }, /* TAINT_DIE */
316 { 'A', ' ', false }, /* TAINT_OVERRIDDEN_ACPI_TABLE */
317 { 'W', ' ', false }, /* TAINT_WARN */
318 { 'C', ' ', true }, /* TAINT_CRAP */
319 { 'I', ' ', false }, /* TAINT_FIRMWARE_WORKAROUND */
320 { 'O', ' ', true }, /* TAINT_OOT_MODULE */
321 { 'E', ' ', true }, /* TAINT_UNSIGNED_MODULE */
322 { 'L', ' ', false }, /* TAINT_SOFTLOCKUP */
323 { 'K', ' ', true }, /* TAINT_LIVEPATCH */
324};
325
326/**
327 * print_tainted - return a string to represent the kernel taint state.
328 *
329 * 'P' - Proprietary module has been loaded.
330 * 'F' - Module has been forcibly loaded.
331 * 'S' - SMP with CPUs not designed for SMP.
332 * 'R' - User forced a module unload.
333 * 'M' - System experienced a machine check exception.
334 * 'B' - System has hit bad_page.
335 * 'U' - Userspace-defined naughtiness.
336 * 'D' - Kernel has oopsed before
337 * 'A' - ACPI table overridden.
338 * 'W' - Taint on warning.
339 * 'C' - modules from drivers/staging are loaded.
340 * 'I' - Working around severe firmware bug.
341 * 'O' - Out-of-tree module has been loaded.
342 * 'E' - Unsigned module has been loaded.
343 * 'L' - A soft lockup has previously occurred.
344 * 'K' - Kernel has been live patched.
345 *
346 * The string is overwritten by the next call to print_tainted().
347 */
348const char *print_tainted(void)
349{
350 static char buf[TAINT_FLAGS_COUNT + sizeof("Tainted: ")];
351
352 if (tainted_mask) {
353 char *s;
354 int i;
355
356 s = buf + sprintf(buf, "Tainted: ");
357 for (i = 0; i < TAINT_FLAGS_COUNT; i++) {
358 const struct taint_flag *t = &taint_flags[i];
359 *s++ = test_bit(i, &tainted_mask) ?
360 t->c_true : t->c_false;
361 }
362 *s = 0;
363 } else
364 snprintf(buf, sizeof(buf), "Not tainted");
365
366 return buf;
367}
368
369int test_taint(unsigned flag)
370{
371 return test_bit(flag, &tainted_mask);
372}
373EXPORT_SYMBOL(test_taint);
374
375unsigned long get_taint(void)
376{
377 return tainted_mask;
378}
379
380/**
381 * add_taint: add a taint flag if not already set.
382 * @flag: one of the TAINT_* constants.
383 * @lockdep_ok: whether lock debugging is still OK.
384 *
385 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
386 * some notewortht-but-not-corrupting cases, it can be set to true.
387 */
388void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
389{
390 if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
391 pr_warn("Disabling lock debugging due to kernel taint\n");
392
393 set_bit(flag, &tainted_mask);
394}
395EXPORT_SYMBOL(add_taint);
396
397static void spin_msec(int msecs)
398{
399 int i;
400
401 for (i = 0; i < msecs; i++) {
402 touch_nmi_watchdog();
403 mdelay(1);
404 }
405}
406
407/*
408 * It just happens that oops_enter() and oops_exit() are identically
409 * implemented...
410 */
411static void do_oops_enter_exit(void)
412{
413 unsigned long flags;
414 static int spin_counter;
415
416 if (!pause_on_oops)
417 return;
418
419 spin_lock_irqsave(&pause_on_oops_lock, flags);
420 if (pause_on_oops_flag == 0) {
421 /* This CPU may now print the oops message */
422 pause_on_oops_flag = 1;
423 } else {
424 /* We need to stall this CPU */
425 if (!spin_counter) {
426 /* This CPU gets to do the counting */
427 spin_counter = pause_on_oops;
428 do {
429 spin_unlock(&pause_on_oops_lock);
430 spin_msec(MSEC_PER_SEC);
431 spin_lock(&pause_on_oops_lock);
432 } while (--spin_counter);
433 pause_on_oops_flag = 0;
434 } else {
435 /* This CPU waits for a different one */
436 while (spin_counter) {
437 spin_unlock(&pause_on_oops_lock);
438 spin_msec(1);
439 spin_lock(&pause_on_oops_lock);
440 }
441 }
442 }
443 spin_unlock_irqrestore(&pause_on_oops_lock, flags);
444}
445
446/*
447 * Return true if the calling CPU is allowed to print oops-related info.
448 * This is a bit racy..
449 */
450int oops_may_print(void)
451{
452 return pause_on_oops_flag == 0;
453}
454
455/*
456 * Called when the architecture enters its oops handler, before it prints
457 * anything. If this is the first CPU to oops, and it's oopsing the first
458 * time then let it proceed.
459 *
460 * This is all enabled by the pause_on_oops kernel boot option. We do all
461 * this to ensure that oopses don't scroll off the screen. It has the
462 * side-effect of preventing later-oopsing CPUs from mucking up the display,
463 * too.
464 *
465 * It turns out that the CPU which is allowed to print ends up pausing for
466 * the right duration, whereas all the other CPUs pause for twice as long:
467 * once in oops_enter(), once in oops_exit().
468 */
469void oops_enter(void)
470{
471 tracing_off();
472 /* can't trust the integrity of the kernel anymore: */
473 debug_locks_off();
474 do_oops_enter_exit();
475}
476
477/*
478 * 64-bit random ID for oopses:
479 */
480static u64 oops_id;
481
482static int init_oops_id(void)
483{
484 if (!oops_id)
485 get_random_bytes(&oops_id, sizeof(oops_id));
486 else
487 oops_id++;
488
489 return 0;
490}
491late_initcall(init_oops_id);
492
493void print_oops_end_marker(void)
494{
495 init_oops_id();
496 pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id);
497}
498
499/*
500 * Called when the architecture exits its oops handler, after printing
501 * everything.
502 */
503void oops_exit(void)
504{
505 do_oops_enter_exit();
506 print_oops_end_marker();
507 kmsg_dump(KMSG_DUMP_OOPS);
508}
509
510struct warn_args {
511 const char *fmt;
512 va_list args;
513};
514
515void __warn(const char *file, int line, void *caller, unsigned taint,
516 struct pt_regs *regs, struct warn_args *args)
517{
518 disable_trace_on_warning();
519
520 pr_warn("------------[ cut here ]------------\n");
521
522 if (file)
523 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
524 raw_smp_processor_id(), current->pid, file, line,
525 caller);
526 else
527 pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
528 raw_smp_processor_id(), current->pid, caller);
529
530 if (args)
531 vprintk(args->fmt, args->args);
532
533 if (panic_on_warn) {
534 /*
535 * This thread may hit another WARN() in the panic path.
536 * Resetting this prevents additional WARN() from panicking the
537 * system on this thread. Other threads are blocked by the
538 * panic_mutex in panic().
539 */
540 panic_on_warn = 0;
541 panic("panic_on_warn set ...\n");
542 }
543
544 print_modules();
545
546 if (regs)
547 show_regs(regs);
548 else
549 dump_stack();
550
551 print_oops_end_marker();
552
553 /* Just a warning, don't kill lockdep. */
554 add_taint(taint, LOCKDEP_STILL_OK);
555}
556
557#ifdef WANT_WARN_ON_SLOWPATH
558void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
559{
560 struct warn_args args;
561
562 args.fmt = fmt;
563 va_start(args.args, fmt);
564 __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL,
565 &args);
566 va_end(args.args);
567}
568EXPORT_SYMBOL(warn_slowpath_fmt);
569
570void warn_slowpath_fmt_taint(const char *file, int line,
571 unsigned taint, const char *fmt, ...)
572{
573 struct warn_args args;
574
575 args.fmt = fmt;
576 va_start(args.args, fmt);
577 __warn(file, line, __builtin_return_address(0), taint, NULL, &args);
578 va_end(args.args);
579}
580EXPORT_SYMBOL(warn_slowpath_fmt_taint);
581
582void warn_slowpath_null(const char *file, int line)
583{
584 __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, NULL);
585}
586EXPORT_SYMBOL(warn_slowpath_null);
587#endif
588
589#ifdef CONFIG_CC_STACKPROTECTOR
590
591/*
592 * Called when gcc's -fstack-protector feature is used, and
593 * gcc detects corruption of the on-stack canary value
594 */
595__visible void __stack_chk_fail(void)
596{
597 panic("stack-protector: Kernel stack is corrupted in: %p\n",
598 __builtin_return_address(0));
599}
600EXPORT_SYMBOL(__stack_chk_fail);
601
602#endif
603
604core_param(panic, panic_timeout, int, 0644);
605core_param(pause_on_oops, pause_on_oops, int, 0644);
606core_param(panic_on_warn, panic_on_warn, int, 0644);
607core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
608
609static int __init oops_setup(char *s)
610{
611 if (!s)
612 return -EINVAL;
613 if (!strcmp(s, "panic"))
614 panic_on_oops = 1;
615 return 0;
616}
617early_param("oops", oops_setup);