1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/kernel/panic.c
4 *
5 * Copyright (C) 1991, 1992 Linus Torvalds
6 */
7
8/*
9 * This function is used through-out the kernel (including mm and fs)
10 * to indicate a major problem.
11 */
12#include <linux/debug_locks.h>
13#include <linux/sched/debug.h>
14#include <linux/interrupt.h>
15#include <linux/kgdb.h>
16#include <linux/kmsg_dump.h>
17#include <linux/kallsyms.h>
18#include <linux/notifier.h>
19#include <linux/vt_kern.h>
20#include <linux/module.h>
21#include <linux/random.h>
22#include <linux/ftrace.h>
23#include <linux/reboot.h>
24#include <linux/delay.h>
25#include <linux/kexec.h>
26#include <linux/panic_notifier.h>
27#include <linux/sched.h>
28#include <linux/string_helpers.h>
29#include <linux/sysrq.h>
30#include <linux/init.h>
31#include <linux/nmi.h>
32#include <linux/console.h>
33#include <linux/bug.h>
34#include <linux/ratelimit.h>
35#include <linux/debugfs.h>
36#include <linux/sysfs.h>
37#include <linux/context_tracking.h>
38#include <trace/events/error_report.h>
39#include <asm/sections.h>
40
41#define PANIC_TIMER_STEP 100
42#define PANIC_BLINK_SPD 18
43
44#ifdef CONFIG_SMP
45/*
46 * Should we dump all CPUs backtraces in an oops event?
47 * Defaults to 0, can be changed via sysctl.
48 */
49static unsigned int __read_mostly sysctl_oops_all_cpu_backtrace;
50#else
51#define sysctl_oops_all_cpu_backtrace 0
52#endif /* CONFIG_SMP */
53
54int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
55static unsigned long tainted_mask =
56 IS_ENABLED(CONFIG_RANDSTRUCT) ? (1 << TAINT_RANDSTRUCT) : 0;
57static int pause_on_oops;
58static int pause_on_oops_flag;
59static DEFINE_SPINLOCK(pause_on_oops_lock);
60bool crash_kexec_post_notifiers;
61int panic_on_warn __read_mostly;
62unsigned long panic_on_taint;
63bool panic_on_taint_nousertaint = false;
64static unsigned int warn_limit __read_mostly;
65
66int panic_timeout = CONFIG_PANIC_TIMEOUT;
67EXPORT_SYMBOL_GPL(panic_timeout);
68
69#define PANIC_PRINT_TASK_INFO 0x00000001
70#define PANIC_PRINT_MEM_INFO 0x00000002
71#define PANIC_PRINT_TIMER_INFO 0x00000004
72#define PANIC_PRINT_LOCK_INFO 0x00000008
73#define PANIC_PRINT_FTRACE_INFO 0x00000010
74#define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020
75#define PANIC_PRINT_ALL_CPU_BT 0x00000040
76#define PANIC_PRINT_BLOCKED_TASKS 0x00000080
77unsigned long panic_print;
78
79ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
80
81EXPORT_SYMBOL(panic_notifier_list);
82
83#ifdef CONFIG_SYSCTL
84static struct ctl_table kern_panic_table[] = {
85#ifdef CONFIG_SMP
86 {
87 .procname = "oops_all_cpu_backtrace",
88 .data = &sysctl_oops_all_cpu_backtrace,
89 .maxlen = sizeof(int),
90 .mode = 0644,
91 .proc_handler = proc_dointvec_minmax,
92 .extra1 = SYSCTL_ZERO,
93 .extra2 = SYSCTL_ONE,
94 },
95#endif
96 {
97 .procname = "warn_limit",
98 .data = &warn_limit,
99 .maxlen = sizeof(warn_limit),
100 .mode = 0644,
101 .proc_handler = proc_douintvec,
102 },
103 { }
104};
105
106static __init int kernel_panic_sysctls_init(void)
107{
108 register_sysctl_init("kernel", kern_panic_table);
109 return 0;
110}
111late_initcall(kernel_panic_sysctls_init);
112#endif
113
114static atomic_t warn_count = ATOMIC_INIT(0);
115
116#ifdef CONFIG_SYSFS
117static ssize_t warn_count_show(struct kobject *kobj, struct kobj_attribute *attr,
118 char *page)
119{
120 return sysfs_emit(buf: page, fmt: "%d\n", atomic_read(v: &warn_count));
121}
122
123static struct kobj_attribute warn_count_attr = __ATTR_RO(warn_count);
124
125static __init int kernel_panic_sysfs_init(void)
126{
127 sysfs_add_file_to_group(kobj: kernel_kobj, attr: &warn_count_attr.attr, NULL);
128 return 0;
129}
130late_initcall(kernel_panic_sysfs_init);
131#endif
132
133static long no_blink(int state)
134{
135 return 0;
136}
137
138/* Returns how long it waited in ms */
139long (*panic_blink)(int state);
140EXPORT_SYMBOL(panic_blink);
141
142/*
143 * Stop ourself in panic -- architecture code may override this
144 */
145void __weak __noreturn panic_smp_self_stop(void)
146{
147 while (1)
148 cpu_relax();
149}
150
151/*
152 * Stop ourselves in NMI context if another CPU has already panicked. Arch code
153 * may override this to prepare for crash dumping, e.g. save regs info.
154 */
155void __weak __noreturn nmi_panic_self_stop(struct pt_regs *regs)
156{
157 panic_smp_self_stop();
158}
159
160/*
161 * Stop other CPUs in panic. Architecture dependent code may override this
162 * with more suitable version. For example, if the architecture supports
163 * crash dump, it should save registers of each stopped CPU and disable
164 * per-CPU features such as virtualization extensions.
165 */
166void __weak crash_smp_send_stop(void)
167{
168 static int cpus_stopped;
169
170 /*
171 * This function can be called twice in panic path, but obviously
172 * we execute this only once.
173 */
174 if (cpus_stopped)
175 return;
176
177 /*
178 * Note smp_send_stop is the usual smp shutdown function, which
179 * unfortunately means it may not be hardened to work in a panic
180 * situation.
181 */
182 smp_send_stop();
183 cpus_stopped = 1;
184}
185
186atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
187
188/*
189 * A variant of panic() called from NMI context. We return if we've already
190 * panicked on this CPU. If another CPU already panicked, loop in
191 * nmi_panic_self_stop() which can provide architecture dependent code such
192 * as saving register state for crash dump.
193 */
194void nmi_panic(struct pt_regs *regs, const char *msg)
195{
196 int old_cpu, this_cpu;
197
198 old_cpu = PANIC_CPU_INVALID;
199 this_cpu = raw_smp_processor_id();
200
201 /* atomic_try_cmpxchg updates old_cpu on failure */
202 if (atomic_try_cmpxchg(v: &panic_cpu, old: &old_cpu, new: this_cpu))
203 panic(fmt: "%s", msg);
204 else if (old_cpu != this_cpu)
205 nmi_panic_self_stop(regs);
206}
207EXPORT_SYMBOL(nmi_panic);
208
209static void panic_print_sys_info(bool console_flush)
210{
211 if (console_flush) {
212 if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG)
213 console_flush_on_panic(mode: CONSOLE_REPLAY_ALL);
214 return;
215 }
216
217 if (panic_print & PANIC_PRINT_TASK_INFO)
218 show_state();
219
220 if (panic_print & PANIC_PRINT_MEM_INFO)
221 show_mem();
222
223 if (panic_print & PANIC_PRINT_TIMER_INFO)
224 sysrq_timer_list_show();
225
226 if (panic_print & PANIC_PRINT_LOCK_INFO)
227 debug_show_all_locks();
228
229 if (panic_print & PANIC_PRINT_FTRACE_INFO)
230 ftrace_dump(oops_dump_mode: DUMP_ALL);
231
232 if (panic_print & PANIC_PRINT_BLOCKED_TASKS)
233 show_state_filter(TASK_UNINTERRUPTIBLE);
234}
235
236void check_panic_on_warn(const char *origin)
237{
238 unsigned int limit;
239
240 if (panic_on_warn)
241 panic(fmt: "%s: panic_on_warn set ...\n", origin);
242
243 limit = READ_ONCE(warn_limit);
244 if (atomic_inc_return(v: &warn_count) >= limit && limit)
245 panic(fmt: "%s: system warned too often (kernel.warn_limit is %d)",
246 origin, limit);
247}
248
249/*
250 * Helper that triggers the NMI backtrace (if set in panic_print)
251 * and then performs the secondary CPUs shutdown - we cannot have
252 * the NMI backtrace after the CPUs are off!
253 */
254static void panic_other_cpus_shutdown(bool crash_kexec)
255{
256 if (panic_print & PANIC_PRINT_ALL_CPU_BT)
257 trigger_all_cpu_backtrace();
258
259 /*
260 * Note that smp_send_stop() is the usual SMP shutdown function,
261 * which unfortunately may not be hardened to work in a panic
262 * situation. If we want to do crash dump after notifier calls
263 * and kmsg_dump, we will need architecture dependent extra
264 * bits in addition to stopping other CPUs, hence we rely on
265 * crash_smp_send_stop() for that.
266 */
267 if (!crash_kexec)
268 smp_send_stop();
269 else
270 crash_smp_send_stop();
271}
272
273/**
274 * panic - halt the system
275 * @fmt: The text string to print
276 *
277 * Display a message, then perform cleanups.
278 *
279 * This function never returns.
280 */
281void panic(const char *fmt, ...)
282{
283 static char buf[1024];
284 va_list args;
285 long i, i_next = 0, len;
286 int state = 0;
287 int old_cpu, this_cpu;
288 bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
289
290 if (panic_on_warn) {
291 /*
292 * This thread may hit another WARN() in the panic path.
293 * Resetting this prevents additional WARN() from panicking the
294 * system on this thread. Other threads are blocked by the
295 * panic_mutex in panic().
296 */
297 panic_on_warn = 0;
298 }
299
300 /*
301 * Disable local interrupts. This will prevent panic_smp_self_stop
302 * from deadlocking the first cpu that invokes the panic, since
303 * there is nothing to prevent an interrupt handler (that runs
304 * after setting panic_cpu) from invoking panic() again.
305 */
306 local_irq_disable();
307 preempt_disable_notrace();
308
309 /*
310 * It's possible to come here directly from a panic-assertion and
311 * not have preempt disabled. Some functions called from here want
312 * preempt to be disabled. No point enabling it later though...
313 *
314 * Only one CPU is allowed to execute the panic code from here. For
315 * multiple parallel invocations of panic, all other CPUs either
316 * stop themself or will wait until they are stopped by the 1st CPU
317 * with smp_send_stop().
318 *
319 * cmpxchg success means this is the 1st CPU which comes here,
320 * so go ahead.
321 * `old_cpu == this_cpu' means we came from nmi_panic() which sets
322 * panic_cpu to this CPU. In this case, this is also the 1st CPU.
323 */
324 old_cpu = PANIC_CPU_INVALID;
325 this_cpu = raw_smp_processor_id();
326
327 /* atomic_try_cmpxchg updates old_cpu on failure */
328 if (atomic_try_cmpxchg(v: &panic_cpu, old: &old_cpu, new: this_cpu)) {
329 /* go ahead */
330 } else if (old_cpu != this_cpu)
331 panic_smp_self_stop();
332
333 console_verbose();
334 bust_spinlocks(yes: 1);
335 va_start(args, fmt);
336 len = vscnprintf(buf, size: sizeof(buf), fmt, args);
337 va_end(args);
338
339 if (len && buf[len - 1] == '\n')
340 buf[len - 1] = '\0';
341
342 pr_emerg("Kernel panic - not syncing: %s\n", buf);
343#ifdef CONFIG_DEBUG_BUGVERBOSE
344 /*
345 * Avoid nested stack-dumping if a panic occurs during oops processing
346 */
347 if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
348 dump_stack();
349#endif
350
351 /*
352 * If kgdb is enabled, give it a chance to run before we stop all
353 * the other CPUs or else we won't be able to debug processes left
354 * running on them.
355 */
356 kgdb_panic(msg: buf);
357
358 /*
359 * If we have crashed and we have a crash kernel loaded let it handle
360 * everything else.
361 * If we want to run this after calling panic_notifiers, pass
362 * the "crash_kexec_post_notifiers" option to the kernel.
363 *
364 * Bypass the panic_cpu check and call __crash_kexec directly.
365 */
366 if (!_crash_kexec_post_notifiers)
367 __crash_kexec(NULL);
368
369 panic_other_cpus_shutdown(crash_kexec: _crash_kexec_post_notifiers);
370
371 /*
372 * Run any panic handlers, including those that might need to
373 * add information to the kmsg dump output.
374 */
375 atomic_notifier_call_chain(nh: &panic_notifier_list, val: 0, v: buf);
376
377 panic_print_sys_info(console_flush: false);
378
379 kmsg_dump(reason: KMSG_DUMP_PANIC);
380
381 /*
382 * If you doubt kdump always works fine in any situation,
383 * "crash_kexec_post_notifiers" offers you a chance to run
384 * panic_notifiers and dumping kmsg before kdump.
385 * Note: since some panic_notifiers can make crashed kernel
386 * more unstable, it can increase risks of the kdump failure too.
387 *
388 * Bypass the panic_cpu check and call __crash_kexec directly.
389 */
390 if (_crash_kexec_post_notifiers)
391 __crash_kexec(NULL);
392
393 console_unblank();
394
395 /*
396 * We may have ended up stopping the CPU holding the lock (in
397 * smp_send_stop()) while still having some valuable data in the console
398 * buffer. Try to acquire the lock then release it regardless of the
399 * result. The release will also print the buffers out. Locks debug
400 * should be disabled to avoid reporting bad unlock balance when
401 * panic() is not being callled from OOPS.
402 */
403 debug_locks_off();
404 console_flush_on_panic(mode: CONSOLE_FLUSH_PENDING);
405
406 panic_print_sys_info(console_flush: true);
407
408 if (!panic_blink)
409 panic_blink = no_blink;
410
411 if (panic_timeout > 0) {
412 /*
413 * Delay timeout seconds before rebooting the machine.
414 * We can't use the "normal" timers since we just panicked.
415 */
416 pr_emerg("Rebooting in %d seconds..\n", panic_timeout);
417
418 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
419 touch_nmi_watchdog();
420 if (i >= i_next) {
421 i += panic_blink(state ^= 1);
422 i_next = i + 3600 / PANIC_BLINK_SPD;
423 }
424 mdelay(PANIC_TIMER_STEP);
425 }
426 }
427 if (panic_timeout != 0) {
428 /*
429 * This will not be a clean reboot, with everything
430 * shutting down. But if there is a chance of
431 * rebooting the system it will be rebooted.
432 */
433 if (panic_reboot_mode != REBOOT_UNDEFINED)
434 reboot_mode = panic_reboot_mode;
435 emergency_restart();
436 }
437#ifdef __sparc__
438 {
439 extern int stop_a_enabled;
440 /* Make sure the user can actually press Stop-A (L1-A) */
441 stop_a_enabled = 1;
442 pr_emerg("Press Stop-A (L1-A) from sun keyboard or send break\n"
443 "twice on console to return to the boot prom\n");
444 }
445#endif
446#if defined(CONFIG_S390)
447 disabled_wait();
448#endif
449 pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
450
451 /* Do not scroll important messages printed above */
452 suppress_printk = 1;
453
454 /*
455 * The final messages may not have been printed if in a context that
456 * defers printing (such as NMI) and irq_work is not available.
457 * Explicitly flush the kernel log buffer one last time.
458 */
459 console_flush_on_panic(mode: CONSOLE_FLUSH_PENDING);
460
461 local_irq_enable();
462 for (i = 0; ; i += PANIC_TIMER_STEP) {
463 touch_softlockup_watchdog();
464 if (i >= i_next) {
465 i += panic_blink(state ^= 1);
466 i_next = i + 3600 / PANIC_BLINK_SPD;
467 }
468 mdelay(PANIC_TIMER_STEP);
469 }
470}
471
472EXPORT_SYMBOL(panic);
473
474/*
475 * TAINT_FORCED_RMMOD could be a per-module flag but the module
476 * is being removed anyway.
477 */
478const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
479 [ TAINT_PROPRIETARY_MODULE ] = { .c_true: 'P', .c_false: 'G', .module: true },
480 [ TAINT_FORCED_MODULE ] = { 'F', ' ', true },
481 [ TAINT_CPU_OUT_OF_SPEC ] = { 'S', ' ', false },
482 [ TAINT_FORCED_RMMOD ] = { 'R', ' ', false },
483 [ TAINT_MACHINE_CHECK ] = { 'M', ' ', false },
484 [ TAINT_BAD_PAGE ] = { 'B', ' ', false },
485 [ TAINT_USER ] = { 'U', ' ', false },
486 [ TAINT_DIE ] = { 'D', ' ', false },
487 [ TAINT_OVERRIDDEN_ACPI_TABLE ] = { 'A', ' ', false },
488 [ TAINT_WARN ] = { 'W', ' ', false },
489 [ TAINT_CRAP ] = { 'C', ' ', true },
490 [ TAINT_FIRMWARE_WORKAROUND ] = { 'I', ' ', false },
491 [ TAINT_OOT_MODULE ] = { 'O', ' ', true },
492 [ TAINT_UNSIGNED_MODULE ] = { 'E', ' ', true },
493 [ TAINT_SOFTLOCKUP ] = { 'L', ' ', false },
494 [ TAINT_LIVEPATCH ] = { 'K', ' ', true },
495 [ TAINT_AUX ] = { 'X', ' ', true },
496 [ TAINT_RANDSTRUCT ] = { 'T', ' ', true },
497 [ TAINT_TEST ] = { 'N', ' ', true },
498};
499
500/**
501 * print_tainted - return a string to represent the kernel taint state.
502 *
503 * For individual taint flag meanings, see Documentation/admin-guide/sysctl/kernel.rst
504 *
505 * The string is overwritten by the next call to print_tainted(),
506 * but is always NULL terminated.
507 */
508const char *print_tainted(void)
509{
510 static char buf[TAINT_FLAGS_COUNT + sizeof("Tainted: ")];
511
512 BUILD_BUG_ON(ARRAY_SIZE(taint_flags) != TAINT_FLAGS_COUNT);
513
514 if (tainted_mask) {
515 char *s;
516 int i;
517
518 s = buf + sprintf(buf, fmt: "Tainted: ");
519 for (i = 0; i < TAINT_FLAGS_COUNT; i++) {
520 const struct taint_flag *t = &taint_flags[i];
521 *s++ = test_bit(i, &tainted_mask) ?
522 t->c_true : t->c_false;
523 }
524 *s = 0;
525 } else
526 snprintf(buf, size: sizeof(buf), fmt: "Not tainted");
527
528 return buf;
529}
530
531int test_taint(unsigned flag)
532{
533 return test_bit(flag, &tainted_mask);
534}
535EXPORT_SYMBOL(test_taint);
536
537unsigned long get_taint(void)
538{
539 return tainted_mask;
540}
541
542/**
543 * add_taint: add a taint flag if not already set.
544 * @flag: one of the TAINT_* constants.
545 * @lockdep_ok: whether lock debugging is still OK.
546 *
547 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
548 * some notewortht-but-not-corrupting cases, it can be set to true.
549 */
550void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
551{
552 if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
553 pr_warn("Disabling lock debugging due to kernel taint\n");
554
555 set_bit(nr: flag, addr: &tainted_mask);
556
557 if (tainted_mask & panic_on_taint) {
558 panic_on_taint = 0;
559 panic("panic_on_taint set ...");
560 }
561}
562EXPORT_SYMBOL(add_taint);
563
564static void spin_msec(int msecs)
565{
566 int i;
567
568 for (i = 0; i < msecs; i++) {
569 touch_nmi_watchdog();
570 mdelay(1);
571 }
572}
573
574/*
575 * It just happens that oops_enter() and oops_exit() are identically
576 * implemented...
577 */
578static void do_oops_enter_exit(void)
579{
580 unsigned long flags;
581 static int spin_counter;
582
583 if (!pause_on_oops)
584 return;
585
586 spin_lock_irqsave(&pause_on_oops_lock, flags);
587 if (pause_on_oops_flag == 0) {
588 /* This CPU may now print the oops message */
589 pause_on_oops_flag = 1;
590 } else {
591 /* We need to stall this CPU */
592 if (!spin_counter) {
593 /* This CPU gets to do the counting */
594 spin_counter = pause_on_oops;
595 do {
596 spin_unlock(lock: &pause_on_oops_lock);
597 spin_msec(MSEC_PER_SEC);
598 spin_lock(lock: &pause_on_oops_lock);
599 } while (--spin_counter);
600 pause_on_oops_flag = 0;
601 } else {
602 /* This CPU waits for a different one */
603 while (spin_counter) {
604 spin_unlock(lock: &pause_on_oops_lock);
605 spin_msec(msecs: 1);
606 spin_lock(lock: &pause_on_oops_lock);
607 }
608 }
609 }
610 spin_unlock_irqrestore(lock: &pause_on_oops_lock, flags);
611}
612
613/*
614 * Return true if the calling CPU is allowed to print oops-related info.
615 * This is a bit racy..
616 */
617bool oops_may_print(void)
618{
619 return pause_on_oops_flag == 0;
620}
621
622/*
623 * Called when the architecture enters its oops handler, before it prints
624 * anything. If this is the first CPU to oops, and it's oopsing the first
625 * time then let it proceed.
626 *
627 * This is all enabled by the pause_on_oops kernel boot option. We do all
628 * this to ensure that oopses don't scroll off the screen. It has the
629 * side-effect of preventing later-oopsing CPUs from mucking up the display,
630 * too.
631 *
632 * It turns out that the CPU which is allowed to print ends up pausing for
633 * the right duration, whereas all the other CPUs pause for twice as long:
634 * once in oops_enter(), once in oops_exit().
635 */
636void oops_enter(void)
637{
638 tracing_off();
639 /* can't trust the integrity of the kernel anymore: */
640 debug_locks_off();
641 do_oops_enter_exit();
642
643 if (sysctl_oops_all_cpu_backtrace)
644 trigger_all_cpu_backtrace();
645}
646
647static void print_oops_end_marker(void)
648{
649 pr_warn("---[ end trace %016llx ]---\n", 0ULL);
650}
651
652/*
653 * Called when the architecture exits its oops handler, after printing
654 * everything.
655 */
656void oops_exit(void)
657{
658 do_oops_enter_exit();
659 print_oops_end_marker();
660 kmsg_dump(reason: KMSG_DUMP_OOPS);
661}
662
663struct warn_args {
664 const char *fmt;
665 va_list args;
666};
667
668void __warn(const char *file, int line, void *caller, unsigned taint,
669 struct pt_regs *regs, struct warn_args *args)
670{
671 disable_trace_on_warning();
672
673 if (file)
674 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
675 raw_smp_processor_id(), current->pid, file, line,
676 caller);
677 else
678 pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
679 raw_smp_processor_id(), current->pid, caller);
680
681#pragma GCC diagnostic push
682#ifndef __clang__
683#pragma GCC diagnostic ignored "-Wsuggest-attribute=format"
684#endif
685 if (args)
686 vprintk(fmt: args->fmt, args: args->args);
687#pragma GCC diagnostic pop
688
689 print_modules();
690
691 if (regs)
692 show_regs(regs);
693
694 check_panic_on_warn(origin: "kernel");
695
696 if (!regs)
697 dump_stack();
698
699 print_irqtrace_events(current);
700
701 print_oops_end_marker();
702 trace_error_report_end(error_detector: ERROR_DETECTOR_WARN, id: (unsigned long)caller);
703
704 /* Just a warning, don't kill lockdep. */
705 add_taint(taint, LOCKDEP_STILL_OK);
706}
707
708#ifdef CONFIG_BUG
709#ifndef __WARN_FLAGS
710void warn_slowpath_fmt(const char *file, int line, unsigned taint,
711 const char *fmt, ...)
712{
713 bool rcu = warn_rcu_enter();
714 struct warn_args args;
715
716 pr_warn(CUT_HERE);
717
718 if (!fmt) {
719 __warn(file, line, __builtin_return_address(0), taint,
720 NULL, NULL);
721 warn_rcu_exit(rcu);
722 return;
723 }
724
725 args.fmt = fmt;
726 va_start(args.args, fmt);
727 __warn(file, line, __builtin_return_address(0), taint, NULL, &args);
728 va_end(args.args);
729 warn_rcu_exit(rcu);
730}
731EXPORT_SYMBOL(warn_slowpath_fmt);
732#else
733void __warn_printk(const char *fmt, ...)
734{
735 bool rcu = warn_rcu_enter();
736 va_list args;
737
738 pr_warn(CUT_HERE);
739
740 va_start(args, fmt);
741 vprintk(fmt, args);
742 va_end(args);
743 warn_rcu_exit(rcu);
744}
745EXPORT_SYMBOL(__warn_printk);
746#endif
747
748/* Support resetting WARN*_ONCE state */
749
750static int clear_warn_once_set(void *data, u64 val)
751{
752 generic_bug_clear_once();
753 memset(__start_once, 0, __end_once - __start_once);
754 return 0;
755}
756
757DEFINE_DEBUGFS_ATTRIBUTE(clear_warn_once_fops, NULL, clear_warn_once_set,
758 "%lld\n");
759
760static __init int register_warn_debugfs(void)
761{
762 /* Don't care about failure */
763 debugfs_create_file_unsafe(name: "clear_warn_once", mode: 0200, NULL, NULL,
764 fops: &clear_warn_once_fops);
765 return 0;
766}
767
768device_initcall(register_warn_debugfs);
769#endif
770
771#ifdef CONFIG_STACKPROTECTOR
772
773/*
774 * Called when gcc's -fstack-protector feature is used, and
775 * gcc detects corruption of the on-stack canary value
776 */
777__visible noinstr void __stack_chk_fail(void)
778{
779 instrumentation_begin();
780 panic("stack-protector: Kernel stack is corrupted in: %pB",
781 __builtin_return_address(0));
782 instrumentation_end();
783}
784EXPORT_SYMBOL(__stack_chk_fail);
785
786#endif
787
788core_param(panic, panic_timeout, int, 0644);
789core_param(panic_print, panic_print, ulong, 0644);
790core_param(pause_on_oops, pause_on_oops, int, 0644);
791core_param(panic_on_warn, panic_on_warn, int, 0644);
792core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
793
794static int __init oops_setup(char *s)
795{
796 if (!s)
797 return -EINVAL;
798 if (!strcmp(s, "panic"))
799 panic_on_oops = 1;
800 return 0;
801}
802early_param("oops", oops_setup);
803
804static int __init panic_on_taint_setup(char *s)
805{
806 char *taint_str;
807
808 if (!s)
809 return -EINVAL;
810
811 taint_str = strsep(&s, ",");
812 if (kstrtoul(s: taint_str, base: 16, res: &panic_on_taint))
813 return -EINVAL;
814
815 /* make sure panic_on_taint doesn't hold out-of-range TAINT flags */
816 panic_on_taint &= TAINT_FLAGS_MAX;
817
818 if (!panic_on_taint)
819 return -EINVAL;
820
821 if (s && !strcmp(s, "nousertaint"))
822 panic_on_taint_nousertaint = true;
823
824 pr_info("panic_on_taint: bitmask=0x%lx nousertaint_mode=%s\n",
825 panic_on_taint, str_enabled_disabled(panic_on_taint_nousertaint));
826
827 return 0;
828}
829early_param("panic_on_taint", panic_on_taint_setup);
830

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source code of linux/kernel/panic.c