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 #include <linux/ratelimit.h>
30 #include <linux/debugfs.h>
31 #include <asm/sections.h>
32
33 #define PANIC_TIMER_STEP 100
34 #define PANIC_BLINK_SPD 18
35
36 int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
37 static unsigned long tainted_mask =
38 IS_ENABLED(CONFIG_GCC_PLUGIN_RANDSTRUCT) ? (1 << TAINT_RANDSTRUCT) : 0;
39 static int pause_on_oops;
40 static int pause_on_oops_flag;
41 static DEFINE_SPINLOCK(pause_on_oops_lock);
42 bool crash_kexec_post_notifiers;
43 int panic_on_warn __read_mostly;
44
45 int panic_timeout = CONFIG_PANIC_TIMEOUT;
46 EXPORT_SYMBOL_GPL(panic_timeout);
47
48 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
49
50 EXPORT_SYMBOL(panic_notifier_list);
51
no_blink(int state)52 static long no_blink(int state)
53 {
54 return 0;
55 }
56
57 /* Returns how long it waited in ms */
58 long (*panic_blink)(int state);
59 EXPORT_SYMBOL(panic_blink);
60
61 /*
62 * Stop ourself in panic -- architecture code may override this
63 */
panic_smp_self_stop(void)64 void __weak panic_smp_self_stop(void)
65 {
66 while (1)
67 cpu_relax();
68 }
69
70 /*
71 * Stop ourselves in NMI context if another CPU has already panicked. Arch code
72 * may override this to prepare for crash dumping, e.g. save regs info.
73 */
nmi_panic_self_stop(struct pt_regs * regs)74 void __weak nmi_panic_self_stop(struct pt_regs *regs)
75 {
76 panic_smp_self_stop();
77 }
78
79 /*
80 * Stop other CPUs in panic. Architecture dependent code may override this
81 * with more suitable version. For example, if the architecture supports
82 * crash dump, it should save registers of each stopped CPU and disable
83 * per-CPU features such as virtualization extensions.
84 */
crash_smp_send_stop(void)85 void __weak crash_smp_send_stop(void)
86 {
87 static int cpus_stopped;
88
89 /*
90 * This function can be called twice in panic path, but obviously
91 * we execute this only once.
92 */
93 if (cpus_stopped)
94 return;
95
96 /*
97 * Note smp_send_stop is the usual smp shutdown function, which
98 * unfortunately means it may not be hardened to work in a panic
99 * situation.
100 */
101 smp_send_stop();
102 cpus_stopped = 1;
103 }
104
105 atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
106
107 /*
108 * A variant of panic() called from NMI context. We return if we've already
109 * panicked on this CPU. If another CPU already panicked, loop in
110 * nmi_panic_self_stop() which can provide architecture dependent code such
111 * as saving register state for crash dump.
112 */
nmi_panic(struct pt_regs * regs,const char * msg)113 void nmi_panic(struct pt_regs *regs, const char *msg)
114 {
115 int old_cpu, cpu;
116
117 cpu = raw_smp_processor_id();
118 old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu);
119
120 if (old_cpu == PANIC_CPU_INVALID)
121 panic("%s", msg);
122 else if (old_cpu != cpu)
123 nmi_panic_self_stop(regs);
124 }
125 EXPORT_SYMBOL(nmi_panic);
126
127 /**
128 * panic - halt the system
129 * @fmt: The text string to print
130 *
131 * Display a message, then perform cleanups.
132 *
133 * This function never returns.
134 */
panic(const char * fmt,...)135 void panic(const char *fmt, ...)
136 {
137 static char buf[1024];
138 va_list args;
139 long i, i_next = 0;
140 int state = 0;
141 int old_cpu, this_cpu;
142 bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
143
144 /*
145 * Disable local interrupts. This will prevent panic_smp_self_stop
146 * from deadlocking the first cpu that invokes the panic, since
147 * there is nothing to prevent an interrupt handler (that runs
148 * after setting panic_cpu) from invoking panic() again.
149 */
150 local_irq_disable();
151
152 /*
153 * It's possible to come here directly from a panic-assertion and
154 * not have preempt disabled. Some functions called from here want
155 * preempt to be disabled. No point enabling it later though...
156 *
157 * Only one CPU is allowed to execute the panic code from here. For
158 * multiple parallel invocations of panic, all other CPUs either
159 * stop themself or will wait until they are stopped by the 1st CPU
160 * with smp_send_stop().
161 *
162 * `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which
163 * comes here, so go ahead.
164 * `old_cpu == this_cpu' means we came from nmi_panic() which sets
165 * panic_cpu to this CPU. In this case, this is also the 1st CPU.
166 */
167 this_cpu = raw_smp_processor_id();
168 old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
169
170 if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)
171 panic_smp_self_stop();
172
173 console_verbose();
174 bust_spinlocks(1);
175 va_start(args, fmt);
176 vsnprintf(buf, sizeof(buf), fmt, args);
177 va_end(args);
178 pr_emerg("Kernel panic - not syncing: %s\n", buf);
179 #ifdef CONFIG_DEBUG_BUGVERBOSE
180 /*
181 * Avoid nested stack-dumping if a panic occurs during oops processing
182 */
183 if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
184 dump_stack();
185 #endif
186
187 /*
188 * If we have crashed and we have a crash kernel loaded let it handle
189 * everything else.
190 * If we want to run this after calling panic_notifiers, pass
191 * the "crash_kexec_post_notifiers" option to the kernel.
192 *
193 * Bypass the panic_cpu check and call __crash_kexec directly.
194 */
195 if (!_crash_kexec_post_notifiers) {
196 printk_safe_flush_on_panic();
197 __crash_kexec(NULL);
198
199 /*
200 * Note smp_send_stop is the usual smp shutdown function, which
201 * unfortunately means it may not be hardened to work in a
202 * panic situation.
203 */
204 smp_send_stop();
205 } else {
206 /*
207 * If we want to do crash dump after notifier calls and
208 * kmsg_dump, we will need architecture dependent extra
209 * works in addition to stopping other CPUs.
210 */
211 crash_smp_send_stop();
212 }
213
214 /*
215 * Run any panic handlers, including those that might need to
216 * add information to the kmsg dump output.
217 */
218 atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
219
220 /* Call flush even twice. It tries harder with a single online CPU */
221 printk_safe_flush_on_panic();
222 kmsg_dump(KMSG_DUMP_PANIC);
223
224 /*
225 * If you doubt kdump always works fine in any situation,
226 * "crash_kexec_post_notifiers" offers you a chance to run
227 * panic_notifiers and dumping kmsg before kdump.
228 * Note: since some panic_notifiers can make crashed kernel
229 * more unstable, it can increase risks of the kdump failure too.
230 *
231 * Bypass the panic_cpu check and call __crash_kexec directly.
232 */
233 if (_crash_kexec_post_notifiers)
234 __crash_kexec(NULL);
235
236 bust_spinlocks(0);
237
238 /*
239 * We may have ended up stopping the CPU holding the lock (in
240 * smp_send_stop()) while still having some valuable data in the console
241 * buffer. Try to acquire the lock then release it regardless of the
242 * result. The release will also print the buffers out. Locks debug
243 * should be disabled to avoid reporting bad unlock balance when
244 * panic() is not being callled from OOPS.
245 */
246 debug_locks_off();
247 console_flush_on_panic();
248
249 if (!panic_blink)
250 panic_blink = no_blink;
251
252 if (panic_timeout > 0) {
253 /*
254 * Delay timeout seconds before rebooting the machine.
255 * We can't use the "normal" timers since we just panicked.
256 */
257 pr_emerg("Rebooting in %d seconds..\n", panic_timeout);
258
259 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
260 touch_nmi_watchdog();
261 if (i >= i_next) {
262 i += panic_blink(state ^= 1);
263 i_next = i + 3600 / PANIC_BLINK_SPD;
264 }
265 mdelay(PANIC_TIMER_STEP);
266 }
267 }
268 if (panic_timeout != 0) {
269 /*
270 * This will not be a clean reboot, with everything
271 * shutting down. But if there is a chance of
272 * rebooting the system it will be rebooted.
273 */
274 emergency_restart();
275 }
276 #ifdef __sparc__
277 {
278 extern int stop_a_enabled;
279 /* Make sure the user can actually press Stop-A (L1-A) */
280 stop_a_enabled = 1;
281 pr_emerg("Press Stop-A (L1-A) from sun keyboard or send break\n"
282 "twice on console to return to the boot prom\n");
283 }
284 #endif
285 #if defined(CONFIG_S390)
286 {
287 unsigned long caller;
288
289 caller = (unsigned long)__builtin_return_address(0);
290 disabled_wait(caller);
291 }
292 #endif
293 pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
294 local_irq_enable();
295 for (i = 0; ; i += PANIC_TIMER_STEP) {
296 touch_softlockup_watchdog();
297 if (i >= i_next) {
298 i += panic_blink(state ^= 1);
299 i_next = i + 3600 / PANIC_BLINK_SPD;
300 }
301 mdelay(PANIC_TIMER_STEP);
302 }
303 }
304
305 EXPORT_SYMBOL(panic);
306
307 /*
308 * TAINT_FORCED_RMMOD could be a per-module flag but the module
309 * is being removed anyway.
310 */
311 const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
312 [ TAINT_PROPRIETARY_MODULE ] = { 'P', 'G', true },
313 [ TAINT_FORCED_MODULE ] = { 'F', ' ', true },
314 [ TAINT_CPU_OUT_OF_SPEC ] = { 'S', ' ', false },
315 [ TAINT_FORCED_RMMOD ] = { 'R', ' ', false },
316 [ TAINT_MACHINE_CHECK ] = { 'M', ' ', false },
317 [ TAINT_BAD_PAGE ] = { 'B', ' ', false },
318 [ TAINT_USER ] = { 'U', ' ', false },
319 [ TAINT_DIE ] = { 'D', ' ', false },
320 [ TAINT_OVERRIDDEN_ACPI_TABLE ] = { 'A', ' ', false },
321 [ TAINT_WARN ] = { 'W', ' ', false },
322 [ TAINT_CRAP ] = { 'C', ' ', true },
323 [ TAINT_FIRMWARE_WORKAROUND ] = { 'I', ' ', false },
324 [ TAINT_OOT_MODULE ] = { 'O', ' ', true },
325 [ TAINT_UNSIGNED_MODULE ] = { 'E', ' ', true },
326 [ TAINT_SOFTLOCKUP ] = { 'L', ' ', false },
327 [ TAINT_LIVEPATCH ] = { 'K', ' ', true },
328 [ TAINT_AUX ] = { 'X', ' ', true },
329 [ TAINT_RANDSTRUCT ] = { 'T', ' ', true },
330 };
331
332 /**
333 * print_tainted - return a string to represent the kernel taint state.
334 *
335 * For individual taint flag meanings, see Documentation/sysctl/kernel.txt
336 *
337 * The string is overwritten by the next call to print_tainted(),
338 * but is always NULL terminated.
339 */
print_tainted(void)340 const char *print_tainted(void)
341 {
342 static char buf[TAINT_FLAGS_COUNT + sizeof("Tainted: ")];
343
344 BUILD_BUG_ON(ARRAY_SIZE(taint_flags) != TAINT_FLAGS_COUNT);
345
346 if (tainted_mask) {
347 char *s;
348 int i;
349
350 s = buf + sprintf(buf, "Tainted: ");
351 for (i = 0; i < TAINT_FLAGS_COUNT; i++) {
352 const struct taint_flag *t = &taint_flags[i];
353 *s++ = test_bit(i, &tainted_mask) ?
354 t->c_true : t->c_false;
355 }
356 *s = 0;
357 } else
358 snprintf(buf, sizeof(buf), "Not tainted");
359
360 return buf;
361 }
362
test_taint(unsigned flag)363 int test_taint(unsigned flag)
364 {
365 return test_bit(flag, &tainted_mask);
366 }
367 EXPORT_SYMBOL(test_taint);
368
get_taint(void)369 unsigned long get_taint(void)
370 {
371 return tainted_mask;
372 }
373
374 /**
375 * add_taint: add a taint flag if not already set.
376 * @flag: one of the TAINT_* constants.
377 * @lockdep_ok: whether lock debugging is still OK.
378 *
379 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
380 * some notewortht-but-not-corrupting cases, it can be set to true.
381 */
add_taint(unsigned flag,enum lockdep_ok lockdep_ok)382 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
383 {
384 if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
385 pr_warn("Disabling lock debugging due to kernel taint\n");
386
387 set_bit(flag, &tainted_mask);
388 }
389 EXPORT_SYMBOL(add_taint);
390
spin_msec(int msecs)391 static void spin_msec(int msecs)
392 {
393 int i;
394
395 for (i = 0; i < msecs; i++) {
396 touch_nmi_watchdog();
397 mdelay(1);
398 }
399 }
400
401 /*
402 * It just happens that oops_enter() and oops_exit() are identically
403 * implemented...
404 */
do_oops_enter_exit(void)405 static void do_oops_enter_exit(void)
406 {
407 unsigned long flags;
408 static int spin_counter;
409
410 if (!pause_on_oops)
411 return;
412
413 spin_lock_irqsave(&pause_on_oops_lock, flags);
414 if (pause_on_oops_flag == 0) {
415 /* This CPU may now print the oops message */
416 pause_on_oops_flag = 1;
417 } else {
418 /* We need to stall this CPU */
419 if (!spin_counter) {
420 /* This CPU gets to do the counting */
421 spin_counter = pause_on_oops;
422 do {
423 spin_unlock(&pause_on_oops_lock);
424 spin_msec(MSEC_PER_SEC);
425 spin_lock(&pause_on_oops_lock);
426 } while (--spin_counter);
427 pause_on_oops_flag = 0;
428 } else {
429 /* This CPU waits for a different one */
430 while (spin_counter) {
431 spin_unlock(&pause_on_oops_lock);
432 spin_msec(1);
433 spin_lock(&pause_on_oops_lock);
434 }
435 }
436 }
437 spin_unlock_irqrestore(&pause_on_oops_lock, flags);
438 }
439
440 /*
441 * Return true if the calling CPU is allowed to print oops-related info.
442 * This is a bit racy..
443 */
oops_may_print(void)444 int oops_may_print(void)
445 {
446 return pause_on_oops_flag == 0;
447 }
448
449 /*
450 * Called when the architecture enters its oops handler, before it prints
451 * anything. If this is the first CPU to oops, and it's oopsing the first
452 * time then let it proceed.
453 *
454 * This is all enabled by the pause_on_oops kernel boot option. We do all
455 * this to ensure that oopses don't scroll off the screen. It has the
456 * side-effect of preventing later-oopsing CPUs from mucking up the display,
457 * too.
458 *
459 * It turns out that the CPU which is allowed to print ends up pausing for
460 * the right duration, whereas all the other CPUs pause for twice as long:
461 * once in oops_enter(), once in oops_exit().
462 */
oops_enter(void)463 void oops_enter(void)
464 {
465 tracing_off();
466 /* can't trust the integrity of the kernel anymore: */
467 debug_locks_off();
468 do_oops_enter_exit();
469 }
470
471 /*
472 * 64-bit random ID for oopses:
473 */
474 static u64 oops_id;
475
init_oops_id(void)476 static int init_oops_id(void)
477 {
478 if (!oops_id)
479 get_random_bytes(&oops_id, sizeof(oops_id));
480 else
481 oops_id++;
482
483 return 0;
484 }
485 late_initcall(init_oops_id);
486
print_oops_end_marker(void)487 void print_oops_end_marker(void)
488 {
489 init_oops_id();
490 pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id);
491 }
492
493 /*
494 * Called when the architecture exits its oops handler, after printing
495 * everything.
496 */
oops_exit(void)497 void oops_exit(void)
498 {
499 do_oops_enter_exit();
500 print_oops_end_marker();
501 kmsg_dump(KMSG_DUMP_OOPS);
502 }
503
504 struct warn_args {
505 const char *fmt;
506 va_list args;
507 };
508
__warn(const char * file,int line,void * caller,unsigned taint,struct pt_regs * regs,struct warn_args * args)509 void __warn(const char *file, int line, void *caller, unsigned taint,
510 struct pt_regs *regs, struct warn_args *args)
511 {
512 disable_trace_on_warning();
513
514 if (args)
515 pr_warn(CUT_HERE);
516
517 if (file)
518 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
519 raw_smp_processor_id(), current->pid, file, line,
520 caller);
521 else
522 pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
523 raw_smp_processor_id(), current->pid, caller);
524
525 if (args)
526 vprintk(args->fmt, args->args);
527
528 if (panic_on_warn) {
529 /*
530 * This thread may hit another WARN() in the panic path.
531 * Resetting this prevents additional WARN() from panicking the
532 * system on this thread. Other threads are blocked by the
533 * panic_mutex in panic().
534 */
535 panic_on_warn = 0;
536 panic("panic_on_warn set ...\n");
537 }
538
539 print_modules();
540
541 if (regs)
542 show_regs(regs);
543 else
544 dump_stack();
545
546 print_irqtrace_events(current);
547
548 print_oops_end_marker();
549
550 /* Just a warning, don't kill lockdep. */
551 add_taint(taint, LOCKDEP_STILL_OK);
552 }
553
554 #ifdef WANT_WARN_ON_SLOWPATH
warn_slowpath_fmt(const char * file,int line,const char * fmt,...)555 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
556 {
557 struct warn_args args;
558
559 args.fmt = fmt;
560 va_start(args.args, fmt);
561 __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL,
562 &args);
563 va_end(args.args);
564 }
565 EXPORT_SYMBOL(warn_slowpath_fmt);
566
warn_slowpath_fmt_taint(const char * file,int line,unsigned taint,const char * fmt,...)567 void warn_slowpath_fmt_taint(const char *file, int line,
568 unsigned taint, const char *fmt, ...)
569 {
570 struct warn_args args;
571
572 args.fmt = fmt;
573 va_start(args.args, fmt);
574 __warn(file, line, __builtin_return_address(0), taint, NULL, &args);
575 va_end(args.args);
576 }
577 EXPORT_SYMBOL(warn_slowpath_fmt_taint);
578
warn_slowpath_null(const char * file,int line)579 void warn_slowpath_null(const char *file, int line)
580 {
581 pr_warn(CUT_HERE);
582 __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, NULL);
583 }
584 EXPORT_SYMBOL(warn_slowpath_null);
585 #else
__warn_printk(const char * fmt,...)586 void __warn_printk(const char *fmt, ...)
587 {
588 va_list args;
589
590 pr_warn(CUT_HERE);
591
592 va_start(args, fmt);
593 vprintk(fmt, args);
594 va_end(args);
595 }
596 EXPORT_SYMBOL(__warn_printk);
597 #endif
598
599 #ifdef CONFIG_BUG
600
601 /* Support resetting WARN*_ONCE state */
602
clear_warn_once_set(void * data,u64 val)603 static int clear_warn_once_set(void *data, u64 val)
604 {
605 generic_bug_clear_once();
606 memset(__start_once, 0, __end_once - __start_once);
607 return 0;
608 }
609
610 DEFINE_SIMPLE_ATTRIBUTE(clear_warn_once_fops,
611 NULL,
612 clear_warn_once_set,
613 "%lld\n");
614
register_warn_debugfs(void)615 static __init int register_warn_debugfs(void)
616 {
617 /* Don't care about failure */
618 debugfs_create_file("clear_warn_once", 0200, NULL,
619 NULL, &clear_warn_once_fops);
620 return 0;
621 }
622
623 device_initcall(register_warn_debugfs);
624 #endif
625
626 #ifdef CONFIG_STACKPROTECTOR
627
628 /*
629 * Called when gcc's -fstack-protector feature is used, and
630 * gcc detects corruption of the on-stack canary value
631 */
__stack_chk_fail(void)632 __visible void __stack_chk_fail(void)
633 {
634 panic("stack-protector: Kernel stack is corrupted in: %pB\n",
635 __builtin_return_address(0));
636 }
637 EXPORT_SYMBOL(__stack_chk_fail);
638
639 #endif
640
641 #ifdef CONFIG_ARCH_HAS_REFCOUNT
refcount_error_report(struct pt_regs * regs,const char * err)642 void refcount_error_report(struct pt_regs *regs, const char *err)
643 {
644 WARN_RATELIMIT(1, "refcount_t %s at %pB in %s[%d], uid/euid: %u/%u\n",
645 err, (void *)instruction_pointer(regs),
646 current->comm, task_pid_nr(current),
647 from_kuid_munged(&init_user_ns, current_uid()),
648 from_kuid_munged(&init_user_ns, current_euid()));
649 }
650 #endif
651
652 core_param(panic, panic_timeout, int, 0644);
653 core_param(pause_on_oops, pause_on_oops, int, 0644);
654 core_param(panic_on_warn, panic_on_warn, int, 0644);
655 core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
656
oops_setup(char * s)657 static int __init oops_setup(char *s)
658 {
659 if (!s)
660 return -EINVAL;
661 if (!strcmp(s, "panic"))
662 panic_on_oops = 1;
663 return 0;
664 }
665 early_param("oops", oops_setup);
666
