1 // SPDX-License-Identifier: GPL-2.0-only
5 * Copyright (C) 1991, 1992 Linus Torvalds
9 * This function is used through-out the kernel (including mm and fs)
10 * to indicate a major problem.
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/sysrq.h>
29 #include <linux/init.h>
30 #include <linux/nmi.h>
31 #include <linux/console.h>
32 #include <linux/bug.h>
33 #include <linux/ratelimit.h>
34 #include <linux/debugfs.h>
35 #include <asm/sections.h>
37 #define PANIC_TIMER_STEP 100
38 #define PANIC_BLINK_SPD 18
42 * Should we dump all CPUs backtraces in an oops event?
43 * Defaults to 0, can be changed via sysctl.
45 static unsigned int __read_mostly sysctl_oops_all_cpu_backtrace;
47 #define sysctl_oops_all_cpu_backtrace 0
48 #endif /* CONFIG_SMP */
50 int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
51 static unsigned long tainted_mask =
52 IS_ENABLED(CONFIG_GCC_PLUGIN_RANDSTRUCT) ? (1 << TAINT_RANDSTRUCT) : 0;
53 static int pause_on_oops;
54 static int pause_on_oops_flag;
55 static DEFINE_SPINLOCK(pause_on_oops_lock);
56 bool crash_kexec_post_notifiers;
57 int panic_on_warn __read_mostly;
58 unsigned long panic_on_taint;
59 bool panic_on_taint_nousertaint = false;
60 static unsigned int warn_limit __read_mostly;
62 int panic_timeout = CONFIG_PANIC_TIMEOUT;
63 EXPORT_SYMBOL_GPL(panic_timeout);
65 #define PANIC_PRINT_TASK_INFO 0x00000001
66 #define PANIC_PRINT_MEM_INFO 0x00000002
67 #define PANIC_PRINT_TIMER_INFO 0x00000004
68 #define PANIC_PRINT_LOCK_INFO 0x00000008
69 #define PANIC_PRINT_FTRACE_INFO 0x00000010
70 #define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020
71 unsigned long panic_print;
73 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
75 EXPORT_SYMBOL(panic_notifier_list);
78 static struct ctl_table kern_panic_table[] = {
81 .procname = "oops_all_cpu_backtrace",
82 .data = &sysctl_oops_all_cpu_backtrace,
83 .maxlen = sizeof(int),
85 .proc_handler = proc_dointvec_minmax,
86 .extra1 = SYSCTL_ZERO,
91 .procname = "warn_limit",
93 .maxlen = sizeof(warn_limit),
95 .proc_handler = proc_douintvec,
100 static __init int kernel_panic_sysctls_init(void)
102 register_sysctl_init("kernel", kern_panic_table);
105 late_initcall(kernel_panic_sysctls_init);
108 static long no_blink(int state)
113 /* Returns how long it waited in ms */
114 long (*panic_blink)(int state);
115 EXPORT_SYMBOL(panic_blink);
118 * Stop ourself in panic -- architecture code may override this
120 void __weak panic_smp_self_stop(void)
127 * Stop ourselves in NMI context if another CPU has already panicked. Arch code
128 * may override this to prepare for crash dumping, e.g. save regs info.
130 void __weak nmi_panic_self_stop(struct pt_regs *regs)
132 panic_smp_self_stop();
136 * Stop other CPUs in panic. Architecture dependent code may override this
137 * with more suitable version. For example, if the architecture supports
138 * crash dump, it should save registers of each stopped CPU and disable
139 * per-CPU features such as virtualization extensions.
141 void __weak crash_smp_send_stop(void)
143 static int cpus_stopped;
146 * This function can be called twice in panic path, but obviously
147 * we execute this only once.
153 * Note smp_send_stop is the usual smp shutdown function, which
154 * unfortunately means it may not be hardened to work in a panic
161 atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
164 * A variant of panic() called from NMI context. We return if we've already
165 * panicked on this CPU. If another CPU already panicked, loop in
166 * nmi_panic_self_stop() which can provide architecture dependent code such
167 * as saving register state for crash dump.
169 void nmi_panic(struct pt_regs *regs, const char *msg)
173 cpu = raw_smp_processor_id();
174 old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu);
176 if (old_cpu == PANIC_CPU_INVALID)
178 else if (old_cpu != cpu)
179 nmi_panic_self_stop(regs);
181 EXPORT_SYMBOL(nmi_panic);
183 static void panic_print_sys_info(void)
185 if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG)
186 console_flush_on_panic(CONSOLE_REPLAY_ALL);
188 if (panic_print & PANIC_PRINT_TASK_INFO)
191 if (panic_print & PANIC_PRINT_MEM_INFO)
194 if (panic_print & PANIC_PRINT_TIMER_INFO)
195 sysrq_timer_list_show();
197 if (panic_print & PANIC_PRINT_LOCK_INFO)
198 debug_show_all_locks();
200 if (panic_print & PANIC_PRINT_FTRACE_INFO)
201 ftrace_dump(DUMP_ALL);
204 void check_panic_on_warn(const char *origin)
206 static atomic_t warn_count = ATOMIC_INIT(0);
209 panic("%s: panic_on_warn set ...\n", origin);
211 if (atomic_inc_return(&warn_count) >= READ_ONCE(warn_limit) && warn_limit)
212 panic("%s: system warned too often (kernel.warn_limit is %d)",
217 * panic - halt the system
218 * @fmt: The text string to print
220 * Display a message, then perform cleanups.
222 * This function never returns.
224 void panic(const char *fmt, ...)
226 static char buf[1024];
228 long i, i_next = 0, len;
230 int old_cpu, this_cpu;
231 bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
235 * This thread may hit another WARN() in the panic path.
236 * Resetting this prevents additional WARN() from panicking the
237 * system on this thread. Other threads are blocked by the
238 * panic_mutex in panic().
244 * Disable local interrupts. This will prevent panic_smp_self_stop
245 * from deadlocking the first cpu that invokes the panic, since
246 * there is nothing to prevent an interrupt handler (that runs
247 * after setting panic_cpu) from invoking panic() again.
250 preempt_disable_notrace();
253 * It's possible to come here directly from a panic-assertion and
254 * not have preempt disabled. Some functions called from here want
255 * preempt to be disabled. No point enabling it later though...
257 * Only one CPU is allowed to execute the panic code from here. For
258 * multiple parallel invocations of panic, all other CPUs either
259 * stop themself or will wait until they are stopped by the 1st CPU
260 * with smp_send_stop().
262 * `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which
263 * comes here, so go ahead.
264 * `old_cpu == this_cpu' means we came from nmi_panic() which sets
265 * panic_cpu to this CPU. In this case, this is also the 1st CPU.
267 this_cpu = raw_smp_processor_id();
268 old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
270 if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)
271 panic_smp_self_stop();
276 len = vscnprintf(buf, sizeof(buf), fmt, args);
279 if (len && buf[len - 1] == '\n')
282 pr_emerg("Kernel panic - not syncing: %s\n", buf);
283 #ifdef CONFIG_DEBUG_BUGVERBOSE
285 * Avoid nested stack-dumping if a panic occurs during oops processing
287 if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
292 * If kgdb is enabled, give it a chance to run before we stop all
293 * the other CPUs or else we won't be able to debug processes left
299 * If we have crashed and we have a crash kernel loaded let it handle
301 * If we want to run this after calling panic_notifiers, pass
302 * the "crash_kexec_post_notifiers" option to the kernel.
304 * Bypass the panic_cpu check and call __crash_kexec directly.
306 if (!_crash_kexec_post_notifiers) {
310 * Note smp_send_stop is the usual smp shutdown function, which
311 * unfortunately means it may not be hardened to work in a
317 * If we want to do crash dump after notifier calls and
318 * kmsg_dump, we will need architecture dependent extra
319 * works in addition to stopping other CPUs.
321 crash_smp_send_stop();
325 * Run any panic handlers, including those that might need to
326 * add information to the kmsg dump output.
328 atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
330 kmsg_dump(KMSG_DUMP_PANIC);
333 * If you doubt kdump always works fine in any situation,
334 * "crash_kexec_post_notifiers" offers you a chance to run
335 * panic_notifiers and dumping kmsg before kdump.
336 * Note: since some panic_notifiers can make crashed kernel
337 * more unstable, it can increase risks of the kdump failure too.
339 * Bypass the panic_cpu check and call __crash_kexec directly.
341 if (_crash_kexec_post_notifiers)
350 * We may have ended up stopping the CPU holding the lock (in
351 * smp_send_stop()) while still having some valuable data in the console
352 * buffer. Try to acquire the lock then release it regardless of the
353 * result. The release will also print the buffers out. Locks debug
354 * should be disabled to avoid reporting bad unlock balance when
355 * panic() is not being callled from OOPS.
358 console_flush_on_panic(CONSOLE_FLUSH_PENDING);
360 panic_print_sys_info();
363 panic_blink = no_blink;
365 if (panic_timeout > 0) {
367 * Delay timeout seconds before rebooting the machine.
368 * We can't use the "normal" timers since we just panicked.
370 pr_emerg("Rebooting in %d seconds..\n", panic_timeout);
372 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
373 touch_nmi_watchdog();
375 i += panic_blink(state ^= 1);
376 i_next = i + 3600 / PANIC_BLINK_SPD;
378 mdelay(PANIC_TIMER_STEP);
381 if (panic_timeout != 0) {
383 * This will not be a clean reboot, with everything
384 * shutting down. But if there is a chance of
385 * rebooting the system it will be rebooted.
387 if (panic_reboot_mode != REBOOT_UNDEFINED)
388 reboot_mode = panic_reboot_mode;
393 extern int stop_a_enabled;
394 /* Make sure the user can actually press Stop-A (L1-A) */
396 pr_emerg("Press Stop-A (L1-A) from sun keyboard or send break\n"
397 "twice on console to return to the boot prom\n");
400 #if defined(CONFIG_S390)
403 pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
405 /* Do not scroll important messages printed above */
408 for (i = 0; ; i += PANIC_TIMER_STEP) {
409 touch_softlockup_watchdog();
411 i += panic_blink(state ^= 1);
412 i_next = i + 3600 / PANIC_BLINK_SPD;
414 mdelay(PANIC_TIMER_STEP);
418 EXPORT_SYMBOL(panic);
421 * TAINT_FORCED_RMMOD could be a per-module flag but the module
422 * is being removed anyway.
424 const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
425 [ TAINT_PROPRIETARY_MODULE ] = { 'P', 'G', true },
426 [ TAINT_FORCED_MODULE ] = { 'F', ' ', true },
427 [ TAINT_CPU_OUT_OF_SPEC ] = { 'S', ' ', false },
428 [ TAINT_FORCED_RMMOD ] = { 'R', ' ', false },
429 [ TAINT_MACHINE_CHECK ] = { 'M', ' ', false },
430 [ TAINT_BAD_PAGE ] = { 'B', ' ', false },
431 [ TAINT_USER ] = { 'U', ' ', false },
432 [ TAINT_DIE ] = { 'D', ' ', false },
433 [ TAINT_OVERRIDDEN_ACPI_TABLE ] = { 'A', ' ', false },
434 [ TAINT_WARN ] = { 'W', ' ', false },
435 [ TAINT_CRAP ] = { 'C', ' ', true },
436 [ TAINT_FIRMWARE_WORKAROUND ] = { 'I', ' ', false },
437 [ TAINT_OOT_MODULE ] = { 'O', ' ', true },
438 [ TAINT_UNSIGNED_MODULE ] = { 'E', ' ', true },
439 [ TAINT_SOFTLOCKUP ] = { 'L', ' ', false },
440 [ TAINT_LIVEPATCH ] = { 'K', ' ', true },
441 [ TAINT_AUX ] = { 'X', ' ', true },
442 [ TAINT_RANDSTRUCT ] = { 'T', ' ', true },
446 * print_tainted - return a string to represent the kernel taint state.
448 * For individual taint flag meanings, see Documentation/admin-guide/sysctl/kernel.rst
450 * The string is overwritten by the next call to print_tainted(),
451 * but is always NULL terminated.
453 const char *print_tainted(void)
455 static char buf[TAINT_FLAGS_COUNT + sizeof("Tainted: ")];
457 BUILD_BUG_ON(ARRAY_SIZE(taint_flags) != TAINT_FLAGS_COUNT);
463 s = buf + sprintf(buf, "Tainted: ");
464 for (i = 0; i < TAINT_FLAGS_COUNT; i++) {
465 const struct taint_flag *t = &taint_flags[i];
466 *s++ = test_bit(i, &tainted_mask) ?
467 t->c_true : t->c_false;
471 snprintf(buf, sizeof(buf), "Not tainted");
476 int test_taint(unsigned flag)
478 return test_bit(flag, &tainted_mask);
480 EXPORT_SYMBOL(test_taint);
482 unsigned long get_taint(void)
488 * add_taint: add a taint flag if not already set.
489 * @flag: one of the TAINT_* constants.
490 * @lockdep_ok: whether lock debugging is still OK.
492 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
493 * some notewortht-but-not-corrupting cases, it can be set to true.
495 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
497 if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
498 pr_warn("Disabling lock debugging due to kernel taint\n");
500 set_bit(flag, &tainted_mask);
502 if (tainted_mask & panic_on_taint) {
504 panic("panic_on_taint set ...");
507 EXPORT_SYMBOL(add_taint);
509 static void spin_msec(int msecs)
513 for (i = 0; i < msecs; i++) {
514 touch_nmi_watchdog();
520 * It just happens that oops_enter() and oops_exit() are identically
523 static void do_oops_enter_exit(void)
526 static int spin_counter;
531 spin_lock_irqsave(&pause_on_oops_lock, flags);
532 if (pause_on_oops_flag == 0) {
533 /* This CPU may now print the oops message */
534 pause_on_oops_flag = 1;
536 /* We need to stall this CPU */
538 /* This CPU gets to do the counting */
539 spin_counter = pause_on_oops;
541 spin_unlock(&pause_on_oops_lock);
542 spin_msec(MSEC_PER_SEC);
543 spin_lock(&pause_on_oops_lock);
544 } while (--spin_counter);
545 pause_on_oops_flag = 0;
547 /* This CPU waits for a different one */
548 while (spin_counter) {
549 spin_unlock(&pause_on_oops_lock);
551 spin_lock(&pause_on_oops_lock);
555 spin_unlock_irqrestore(&pause_on_oops_lock, flags);
559 * Return true if the calling CPU is allowed to print oops-related info.
560 * This is a bit racy..
562 bool oops_may_print(void)
564 return pause_on_oops_flag == 0;
568 * Called when the architecture enters its oops handler, before it prints
569 * anything. If this is the first CPU to oops, and it's oopsing the first
570 * time then let it proceed.
572 * This is all enabled by the pause_on_oops kernel boot option. We do all
573 * this to ensure that oopses don't scroll off the screen. It has the
574 * side-effect of preventing later-oopsing CPUs from mucking up the display,
577 * It turns out that the CPU which is allowed to print ends up pausing for
578 * the right duration, whereas all the other CPUs pause for twice as long:
579 * once in oops_enter(), once in oops_exit().
581 void oops_enter(void)
584 /* can't trust the integrity of the kernel anymore: */
586 do_oops_enter_exit();
588 if (sysctl_oops_all_cpu_backtrace)
589 trigger_all_cpu_backtrace();
593 * 64-bit random ID for oopses:
597 static int init_oops_id(void)
600 get_random_bytes(&oops_id, sizeof(oops_id));
606 late_initcall(init_oops_id);
608 static void print_oops_end_marker(void)
611 pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id);
615 * Called when the architecture exits its oops handler, after printing
620 do_oops_enter_exit();
621 print_oops_end_marker();
622 kmsg_dump(KMSG_DUMP_OOPS);
630 void __warn(const char *file, int line, void *caller, unsigned taint,
631 struct pt_regs *regs, struct warn_args *args)
633 disable_trace_on_warning();
636 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
637 raw_smp_processor_id(), current->pid, file, line,
640 pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
641 raw_smp_processor_id(), current->pid, caller);
644 vprintk(args->fmt, args->args);
651 check_panic_on_warn("kernel");
656 print_irqtrace_events(current);
658 print_oops_end_marker();
660 /* Just a warning, don't kill lockdep. */
661 add_taint(taint, LOCKDEP_STILL_OK);
665 void warn_slowpath_fmt(const char *file, int line, unsigned taint,
666 const char *fmt, ...)
668 struct warn_args args;
673 __warn(file, line, __builtin_return_address(0), taint,
679 va_start(args.args, fmt);
680 __warn(file, line, __builtin_return_address(0), taint, NULL, &args);
683 EXPORT_SYMBOL(warn_slowpath_fmt);
685 void __warn_printk(const char *fmt, ...)
695 EXPORT_SYMBOL(__warn_printk);
700 /* Support resetting WARN*_ONCE state */
702 static int clear_warn_once_set(void *data, u64 val)
704 generic_bug_clear_once();
705 memset(__start_once, 0, __end_once - __start_once);
709 DEFINE_DEBUGFS_ATTRIBUTE(clear_warn_once_fops, NULL, clear_warn_once_set,
712 static __init int register_warn_debugfs(void)
714 /* Don't care about failure */
715 debugfs_create_file_unsafe("clear_warn_once", 0200, NULL, NULL,
716 &clear_warn_once_fops);
720 device_initcall(register_warn_debugfs);
723 #ifdef CONFIG_STACKPROTECTOR
726 * Called when gcc's -fstack-protector feature is used, and
727 * gcc detects corruption of the on-stack canary value
729 __visible noinstr void __stack_chk_fail(void)
731 instrumentation_begin();
732 panic("stack-protector: Kernel stack is corrupted in: %pB",
733 __builtin_return_address(0));
734 instrumentation_end();
736 EXPORT_SYMBOL(__stack_chk_fail);
740 core_param(panic, panic_timeout, int, 0644);
741 core_param(panic_print, panic_print, ulong, 0644);
742 core_param(pause_on_oops, pause_on_oops, int, 0644);
743 core_param(panic_on_warn, panic_on_warn, int, 0644);
744 core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
746 static int __init oops_setup(char *s)
750 if (!strcmp(s, "panic"))
754 early_param("oops", oops_setup);
756 static int __init panic_on_taint_setup(char *s)
763 taint_str = strsep(&s, ",");
764 if (kstrtoul(taint_str, 16, &panic_on_taint))
767 /* make sure panic_on_taint doesn't hold out-of-range TAINT flags */
768 panic_on_taint &= TAINT_FLAGS_MAX;
773 if (s && !strcmp(s, "nousertaint"))
774 panic_on_taint_nousertaint = true;
776 pr_info("panic_on_taint: bitmask=0x%lx nousertaint_mode=%sabled\n",
777 panic_on_taint, panic_on_taint_nousertaint ? "en" : "dis");
781 early_param("panic_on_taint", panic_on_taint_setup);