aboutsummaryrefslogtreecommitdiff
path: root/kernel/panic.c
blob: 4d8d6f906decede78600ef0767770dd713f8b225 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
/*
 *  linux/kernel/panic.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * This function is used through-out the kernel (including mm and fs)
 * to indicate a major problem.
 */
#include <linux/debug_locks.h>
#include <linux/interrupt.h>
#include <linux/kmsg_dump.h>
#include <linux/kallsyms.h>
#include <linux/notifier.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/ftrace.h>
#include <linux/reboot.h>
#include <linux/delay.h>
#include <linux/kexec.h>
#include <linux/sched.h>
#include <linux/sysrq.h>
#include <linux/init.h>
#include <linux/nmi.h>

#define PANIC_TIMER_STEP 100
#define PANIC_BLINK_SPD 18

int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
static unsigned long tainted_mask;
static int pause_on_oops;
static int pause_on_oops_flag;
static DEFINE_SPINLOCK(pause_on_oops_lock);
static bool crash_kexec_post_notifiers;
int panic_on_warn __read_mostly;

int panic_timeout = CONFIG_PANIC_TIMEOUT;
EXPORT_SYMBOL_GPL(panic_timeout);

ATOMIC_NOTIFIER_HEAD(panic_notifier_list);

EXPORT_SYMBOL(panic_notifier_list);

static long no_blink(int state)
{
	return 0;
}

/* Returns how long it waited in ms */
long (*panic_blink)(int state);
EXPORT_SYMBOL(panic_blink);

/*
 * Stop ourself in panic -- architecture code may override this
 */
void __weak panic_smp_self_stop(void)
{
	while (1)
		cpu_relax();
}

/**
 *	panic - halt the system
 *	@fmt: The text string to print
 *
 *	Display a message, then perform cleanups.
 *
 *	This function never returns.
 */
void panic(const char *fmt, ...)
{
	static DEFINE_SPINLOCK(panic_lock);
	static char buf[1024];
	va_list args;
	long i, i_next = 0;
	int state = 0;

	/*
	 * Disable local interrupts. This will prevent panic_smp_self_stop
	 * from deadlocking the first cpu that invokes the panic, since
	 * there is nothing to prevent an interrupt handler (that runs
	 * after the panic_lock is acquired) from invoking panic again.
	 */
	local_irq_disable();

	/*
	 * It's possible to come here directly from a panic-assertion and
	 * not have preempt disabled. Some functions called from here want
	 * preempt to be disabled. No point enabling it later though...
	 *
	 * Only one CPU is allowed to execute the panic code from here. For
	 * multiple parallel invocations of panic, all other CPUs either
	 * stop themself or will wait until they are stopped by the 1st CPU
	 * with smp_send_stop().
	 */
	if (!spin_trylock(&panic_lock))
		panic_smp_self_stop();

	console_verbose();
	bust_spinlocks(1);
	va_start(args, fmt);
	vsnprintf(buf, sizeof(buf), fmt, args);
	va_end(args);
	pr_emerg("Kernel panic - not syncing: %s\n", buf);
#ifdef CONFIG_DEBUG_BUGVERBOSE
	/*
	 * Avoid nested stack-dumping if a panic occurs during oops processing
	 */
	if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
		dump_stack();
#endif

	/*
	 * If we have crashed and we have a crash kernel loaded let it handle
	 * everything else.
	 * If we want to run this after calling panic_notifiers, pass
	 * the "crash_kexec_post_notifiers" option to the kernel.
	 */
	if (!crash_kexec_post_notifiers)
		crash_kexec(NULL);

	/*
	 * Note smp_send_stop is the usual smp shutdown function, which
	 * unfortunately means it may not be hardened to work in a panic
	 * situation.
	 */
	smp_send_stop();

	/*
	 * Run any panic handlers, including those that might need to
	 * add information to the kmsg dump output.
	 */
	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

	kmsg_dump(KMSG_DUMP_PANIC);

	/*
	 * If you doubt kdump always works fine in any situation,
	 * "crash_kexec_post_notifiers" offers you a chance to run
	 * panic_notifiers and dumping kmsg before kdump.
	 * Note: since some panic_notifiers can make crashed kernel
	 * more unstable, it can increase risks of the kdump failure too.
	 */
	crash_kexec(NULL);

	bust_spinlocks(0);

	if (!panic_blink)
		panic_blink = no_blink;

	if (panic_timeout > 0) {
		/*
		 * Delay timeout seconds before rebooting the machine.
		 * We can't use the "normal" timers since we just panicked.
		 */
		pr_emerg("Rebooting in %d seconds..", panic_timeout);

		for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
			touch_nmi_watchdog();
			if (i >= i_next) {
				i += panic_blink(state ^= 1);
				i_next = i + 3600 / PANIC_BLINK_SPD;
			}
			mdelay(PANIC_TIMER_STEP);
		}
	}
	if (panic_timeout != 0) {
		/*
		 * This will not be a clean reboot, with everything
		 * shutting down.  But if there is a chance of
		 * rebooting the system it will be rebooted.
		 */
		emergency_restart();
	}
#ifdef __sparc__
	{
		extern int stop_a_enabled;
		/* Make sure the user can actually press Stop-A (L1-A) */
		stop_a_enabled = 1;
		pr_emerg("Press Stop-A (L1-A) to return to the boot prom\n");
	}
#endif
#if defined(CONFIG_S390)
	{
		unsigned long caller;

		caller = (unsigned long)__builtin_return_address(0);
		disabled_wait(caller);
	}
#endif
	pr_emerg("---[ end Kernel panic - not syncing: %s\n", buf);
	local_irq_enable();
	for (i = 0; ; i += PANIC_TIMER_STEP) {
		touch_softlockup_watchdog();
		if (i >= i_next) {
			i += panic_blink(state ^= 1);
			i_next = i + 3600 / PANIC_BLINK_SPD;
		}
		mdelay(PANIC_TIMER_STEP);
	}
}

EXPORT_SYMBOL(panic);


struct tnt {
	u8	bit;
	char	true;
	char	false;
};

static const struct tnt tnts[] = {
	{ TAINT_PROPRIETARY_MODULE,	'P', 'G' },
	{ TAINT_FORCED_MODULE,		'F', ' ' },
	{ TAINT_CPU_OUT_OF_SPEC,	'S', ' ' },
	{ TAINT_FORCED_RMMOD,		'R', ' ' },
	{ TAINT_MACHINE_CHECK,		'M', ' ' },
	{ TAINT_BAD_PAGE,		'B', ' ' },
	{ TAINT_USER,			'U', ' ' },
	{ TAINT_DIE,			'D', ' ' },
	{ TAINT_OVERRIDDEN_ACPI_TABLE,	'A', ' ' },
	{ TAINT_WARN,			'W', ' ' },
	{ TAINT_CRAP,			'C', ' ' },
	{ TAINT_FIRMWARE_WORKAROUND,	'I', ' ' },
	{ TAINT_OOT_MODULE,		'O', ' ' },
	{ TAINT_UNSIGNED_MODULE,	'E', ' ' },
	{ TAINT_SOFTLOCKUP,		'L', ' ' },
};

/**
 *	print_tainted - return a string to represent the kernel taint state.
 *
 *  'P' - Proprietary module has been loaded.
 *  'F' - Module has been forcibly loaded.
 *  'S' - SMP with CPUs not designed for SMP.
 *  'R' - User forced a module unload.
 *  'M' - System experienced a machine check exception.
 *  'B' - System has hit bad_page.
 *  'U' - Userspace-defined naughtiness.
 *  'D' - Kernel has oopsed before
 *  'A' - ACPI table overridden.
 *  'W' - Taint on warning.
 *  'C' - modules from drivers/staging are loaded.
 *  'I' - Working around severe firmware bug.
 *  'O' - Out-of-tree module has been loaded.
 *  'E' - Unsigned module has been loaded.
 *  'L' - A soft lockup has previously occurred.
 *
 *	The string is overwritten by the next call to print_tainted().
 */
const char *print_tainted(void)
{
	static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ")];

	if (tainted_mask) {
		char *s;
		int i;

		s = buf + sprintf(buf, "Tainted: ");
		for (i = 0; i < ARRAY_SIZE(tnts); i++) {
			const struct tnt *t = &tnts[i];
			*s++ = test_bit(t->bit, &tainted_mask) ?
					t->true : t->false;
		}
		*s = 0;
	} else
		snprintf(buf, sizeof(buf), "Not tainted");

	return buf;
}

int test_taint(unsigned flag)
{
	return test_bit(flag, &tainted_mask);
}
EXPORT_SYMBOL(test_taint);

unsigned long get_taint(void)
{
	return tainted_mask;
}

/**
 * add_taint: add a taint flag if not already set.
 * @flag: one of the TAINT_* constants.
 * @lockdep_ok: whether lock debugging is still OK.
 *
 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
 * some notewortht-but-not-corrupting cases, it can be set to true.
 */
void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
{
	if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
		pr_warn("Disabling lock debugging due to kernel taint\n");

	set_bit(flag, &tainted_mask);
}
EXPORT_SYMBOL(add_taint);

static void spin_msec(int msecs)
{
	int i;

	for (i = 0; i < msecs; i++) {
		touch_nmi_watchdog();
		mdelay(1);
	}
}

/*
 * It just happens that oops_enter() and oops_exit() are identically
 * implemented...
 */
static void do_oops_enter_exit(void)
{
	unsigned long flags;
	static int spin_counter;

	if (!pause_on_oops)
		return;

	spin_lock_irqsave(&pause_on_oops_lock, flags);
	if (pause_on_oops_flag == 0) {
		/* This CPU may now print the oops message */
		pause_on_oops_flag = 1;
	} else {
		/* We need to stall this CPU */
		if (!spin_counter) {
			/* This CPU gets to do the counting */
			spin_counter = pause_on_oops;
			do {
				spin_unlock(&pause_on_oops_lock);
				spin_msec(MSEC_PER_SEC);
				spin_lock(&pause_on_oops_lock);
			} while (--spin_counter);
			pause_on_oops_flag = 0;
		} else {
			/* This CPU waits for a different one */
			while (spin_counter) {
				spin_unlock(&pause_on_oops_lock);
				spin_msec(1);
				spin_lock(&pause_on_oops_lock);
			}
		}
	}
	spin_unlock_irqrestore(&pause_on_oops_lock, flags);
}

/*
 * Return true if the calling CPU is allowed to print oops-related info.
 * This is a bit racy..
 */
int oops_may_print(void)
{
	return pause_on_oops_flag == 0;
}

/*
 * Called when the architecture enters its oops handler, before it prints
 * anything.  If this is the first CPU to oops, and it's oopsing the first
 * time then let it proceed.
 *
 * This is all enabled by the pause_on_oops kernel boot option.  We do all
 * this to ensure that oopses don't scroll off the screen.  It has the
 * side-effect of preventing later-oopsing CPUs from mucking up the display,
 * too.
 *
 * It turns out that the CPU which is allowed to print ends up pausing for
 * the right duration, whereas all the other CPUs pause for twice as long:
 * once in oops_enter(), once in oops_exit().
 */
void oops_enter(void)
{
	tracing_off();
	/* can't trust the integrity of the kernel anymore: */
	debug_locks_off();
	do_oops_enter_exit();
}

/*
 * 64-bit random ID for oopses:
 */
static u64 oops_id;

static int init_oops_id(void)
{
	if (!oops_id)
		get_random_bytes(&oops_id, sizeof(oops_id));
	else
		oops_id++;

	return 0;
}
late_initcall(init_oops_id);

void print_oops_end_marker(void)
{
	init_oops_id();
	pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id);
}

/*
 * Called when the architecture exits its oops handler, after printing
 * everything.
 */
void oops_exit(void)
{
	do_oops_enter_exit();
	print_oops_end_marker();
	kmsg_dump(KMSG_DUMP_OOPS);
}

#ifdef WANT_WARN_ON_SLOWPATH
struct slowpath_args {
	const char *fmt;
	va_list args;
};

static void warn_slowpath_common(const char *file, int line, void *caller,
				 unsigned taint, struct slowpath_args *args)
{
	disable_trace_on_warning();

	pr_warn("------------[ cut here ]------------\n");
	pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS()\n",
		raw_smp_processor_id(), current->pid, file, line, caller);

	if (args)
		vprintk(args->fmt, args->args);

	if (panic_on_warn) {
		/*
		 * This thread may hit another WARN() in the panic path.
		 * Resetting this prevents additional WARN() from panicking the
		 * system on this thread.  Other threads are blocked by the
		 * panic_mutex in panic().
		 */
		panic_on_warn = 0;
		panic("panic_on_warn set ...\n");
	}

	print_modules();
	dump_stack();
	print_oops_end_marker();
	/* Just a warning, don't kill lockdep. */
	add_taint(taint, LOCKDEP_STILL_OK);
}

void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
{
	struct slowpath_args args;

	args.fmt = fmt;
	va_start(args.args, fmt);
	warn_slowpath_common(file, line, __builtin_return_address(0),
			     TAINT_WARN, &args);
	va_end(args.args);
}
EXPORT_SYMBOL(warn_slowpath_fmt);

void warn_slowpath_fmt_taint(const char *file, int line,
			     unsigned taint, const char *fmt, ...)
{
	struct slowpath_args args;

	args.fmt = fmt;
	va_start(args.args, fmt);
	warn_slowpath_common(file, line, __builtin_return_address(0),
			     taint, &args);
	va_end(args.args);
}
EXPORT_SYMBOL(warn_slowpath_fmt_taint);

void warn_slowpath_null(const char *file, int line)
{
	warn_slowpath_common(file, line, __builtin_return_address(0),
			     TAINT_WARN, NULL);
}
EXPORT_SYMBOL(warn_slowpath_null);
#endif

#ifdef CONFIG_CC_STACKPROTECTOR

/*
 * Called when gcc's -fstack-protector feature is used, and
 * gcc detects corruption of the on-stack canary value
 */
__visible void __stack_chk_fail(void)
{
	panic("stack-protector: Kernel stack is corrupted in: %p\n",
		__builtin_return_address(0));
}
EXPORT_SYMBOL(__stack_chk_fail);

#endif

core_param(panic, panic_timeout, int, 0644);
core_param(pause_on_oops, pause_on_oops, int, 0644);
core_param(panic_on_warn, panic_on_warn, int, 0644);

static int __init setup_crash_kexec_post_notifiers(char *s)
{
	crash_kexec_post_notifiers = true;
	return 0;
}
early_param("crash_kexec_post_notifiers", setup_crash_kexec_post_notifiers);

static int __init oops_setup(char *s)
{
	if (!s)
		return -EINVAL;
	if (!strcmp(s, "panic"))
		panic_on_oops = 1;
	return 0;
}
early_param("oops", oops_setup);