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