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/interrupt.h>
13 #include <linux/kmsg_dump.h>
14 #include <linux/kallsyms.h>
15 #include <linux/notifier.h>
16 #include <linux/module.h>
17 #include <linux/random.h>
18 #include <linux/reboot.h>
19 #include <linux/delay.h>
20 #include <linux/kexec.h>
21 #include <linux/sched.h>
22 #include <linux/sysrq.h>
23 #include <linux/init.h>
24 #include <linux/nmi.h>
25 #include <linux/dmi.h>
26 
27 #define PANIC_TIMER_STEP 100
28 #define PANIC_BLINK_SPD 18
29 
30 int panic_on_oops;
31 static unsigned long tainted_mask;
32 static int pause_on_oops;
33 static int pause_on_oops_flag;
34 static DEFINE_SPINLOCK(pause_on_oops_lock);
35 
36 int panic_timeout;
37 EXPORT_SYMBOL_GPL(panic_timeout);
38 
39 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
40 
41 EXPORT_SYMBOL(panic_notifier_list);
42 
no_blink(int state)43 static long no_blink(int state)
44 {
45 	return 0;
46 }
47 
48 /* Returns how long it waited in ms */
49 long (*panic_blink)(int state);
50 EXPORT_SYMBOL(panic_blink);
51 
52 /*
53  * Stop ourself in panic -- architecture code may override this
54  */
panic_smp_self_stop(void)55 void __weak panic_smp_self_stop(void)
56 {
57 	while (1)
58 		cpu_relax();
59 }
60 
61 /**
62  *	panic - halt the system
63  *	@fmt: The text string to print
64  *
65  *	Display a message, then perform cleanups.
66  *
67  *	This function never returns.
68  */
panic(const char * fmt,...)69 void panic(const char *fmt, ...)
70 {
71 	static DEFINE_SPINLOCK(panic_lock);
72 	static char buf[1024];
73 	va_list args;
74 	long i, i_next = 0;
75 	int state = 0;
76 
77 	/*
78 	 * Disable local interrupts. This will prevent panic_smp_self_stop
79 	 * from deadlocking the first cpu that invokes the panic, since
80 	 * there is nothing to prevent an interrupt handler (that runs
81 	 * after the panic_lock is acquired) from invoking panic again.
82 	 */
83 	local_irq_disable();
84 
85 	/*
86 	 * It's possible to come here directly from a panic-assertion and
87 	 * not have preempt disabled. Some functions called from here want
88 	 * preempt to be disabled. No point enabling it later though...
89 	 *
90 	 * Only one CPU is allowed to execute the panic code from here. For
91 	 * multiple parallel invocations of panic, all other CPUs either
92 	 * stop themself or will wait until they are stopped by the 1st CPU
93 	 * with smp_send_stop().
94 	 */
95 	if (!spin_trylock(&panic_lock))
96 		panic_smp_self_stop();
97 
98 	console_verbose();
99 	bust_spinlocks(1);
100 	va_start(args, fmt);
101 	vsnprintf(buf, sizeof(buf), fmt, args);
102 	va_end(args);
103 	printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
104 #ifdef CONFIG_DEBUG_BUGVERBOSE
105 	/*
106 	 * Avoid nested stack-dumping if a panic occurs during oops processing
107 	 */
108 	if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
109 		dump_stack();
110 #endif
111 
112 	/*
113 	 * If we have crashed and we have a crash kernel loaded let it handle
114 	 * everything else.
115 	 * Do we want to call this before we try to display a message?
116 	 */
117 	crash_kexec(NULL);
118 
119 	/*
120 	 * Note smp_send_stop is the usual smp shutdown function, which
121 	 * unfortunately means it may not be hardened to work in a panic
122 	 * situation.
123 	 */
124 	smp_send_stop();
125 
126 	kmsg_dump(KMSG_DUMP_PANIC);
127 
128 	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
129 
130 	bust_spinlocks(0);
131 
132 	if (!panic_blink)
133 		panic_blink = no_blink;
134 
135 	if (panic_timeout > 0) {
136 		/*
137 		 * Delay timeout seconds before rebooting the machine.
138 		 * We can't use the "normal" timers since we just panicked.
139 		 */
140 		printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
141 
142 		for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
143 			touch_nmi_watchdog();
144 			if (i >= i_next) {
145 				i += panic_blink(state ^= 1);
146 				i_next = i + 3600 / PANIC_BLINK_SPD;
147 			}
148 			mdelay(PANIC_TIMER_STEP);
149 		}
150 	}
151 	if (panic_timeout != 0) {
152 		/*
153 		 * This will not be a clean reboot, with everything
154 		 * shutting down.  But if there is a chance of
155 		 * rebooting the system it will be rebooted.
156 		 */
157 		emergency_restart();
158 	}
159 #ifdef __sparc__
160 	{
161 		extern int stop_a_enabled;
162 		/* Make sure the user can actually press Stop-A (L1-A) */
163 		stop_a_enabled = 1;
164 		printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
165 	}
166 #endif
167 #if defined(CONFIG_S390)
168 	{
169 		unsigned long caller;
170 
171 		caller = (unsigned long)__builtin_return_address(0);
172 		disabled_wait(caller);
173 	}
174 #endif
175 	local_irq_enable();
176 	for (i = 0; ; i += PANIC_TIMER_STEP) {
177 		touch_softlockup_watchdog();
178 		if (i >= i_next) {
179 			i += panic_blink(state ^= 1);
180 			i_next = i + 3600 / PANIC_BLINK_SPD;
181 		}
182 		mdelay(PANIC_TIMER_STEP);
183 	}
184 }
185 
186 EXPORT_SYMBOL(panic);
187 
188 
189 struct tnt {
190 	u8	bit;
191 	char	true;
192 	char	false;
193 };
194 
195 static const struct tnt tnts[] = {
196 	{ TAINT_PROPRIETARY_MODULE,	'P', 'G' },
197 	{ TAINT_FORCED_MODULE,		'F', ' ' },
198 	{ TAINT_UNSAFE_SMP,		'S', ' ' },
199 	{ TAINT_FORCED_RMMOD,		'R', ' ' },
200 	{ TAINT_MACHINE_CHECK,		'M', ' ' },
201 	{ TAINT_BAD_PAGE,		'B', ' ' },
202 	{ TAINT_USER,			'U', ' ' },
203 	{ TAINT_DIE,			'D', ' ' },
204 	{ TAINT_OVERRIDDEN_ACPI_TABLE,	'A', ' ' },
205 	{ TAINT_WARN,			'W', ' ' },
206 	{ TAINT_CRAP,			'C', ' ' },
207 	{ TAINT_FIRMWARE_WORKAROUND,	'I', ' ' },
208 	{ TAINT_OOT_MODULE,		'O', ' ' },
209 };
210 
211 /**
212  *	print_tainted - return a string to represent the kernel taint state.
213  *
214  *  'P' - Proprietary module has been loaded.
215  *  'F' - Module has been forcibly loaded.
216  *  'S' - SMP with CPUs not designed for SMP.
217  *  'R' - User forced a module unload.
218  *  'M' - System experienced a machine check exception.
219  *  'B' - System has hit bad_page.
220  *  'U' - Userspace-defined naughtiness.
221  *  'D' - Kernel has oopsed before
222  *  'A' - ACPI table overridden.
223  *  'W' - Taint on warning.
224  *  'C' - modules from drivers/staging are loaded.
225  *  'I' - Working around severe firmware bug.
226  *  'O' - Out-of-tree module has been loaded.
227  *
228  *	The string is overwritten by the next call to print_tainted().
229  */
print_tainted(void)230 const char *print_tainted(void)
231 {
232 	static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
233 
234 	if (tainted_mask) {
235 		char *s;
236 		int i;
237 
238 		s = buf + sprintf(buf, "Tainted: ");
239 		for (i = 0; i < ARRAY_SIZE(tnts); i++) {
240 			const struct tnt *t = &tnts[i];
241 			*s++ = test_bit(t->bit, &tainted_mask) ?
242 					t->true : t->false;
243 		}
244 		*s = 0;
245 	} else
246 		snprintf(buf, sizeof(buf), "Not tainted");
247 
248 	return buf;
249 }
250 
test_taint(unsigned flag)251 int test_taint(unsigned flag)
252 {
253 	return test_bit(flag, &tainted_mask);
254 }
255 EXPORT_SYMBOL(test_taint);
256 
get_taint(void)257 unsigned long get_taint(void)
258 {
259 	return tainted_mask;
260 }
261 
add_taint(unsigned flag)262 void add_taint(unsigned flag)
263 {
264 	/*
265 	 * Can't trust the integrity of the kernel anymore.
266 	 * We don't call directly debug_locks_off() because the issue
267 	 * is not necessarily serious enough to set oops_in_progress to 1
268 	 * Also we want to keep up lockdep for staging/out-of-tree
269 	 * development and post-warning case.
270 	 */
271 	switch (flag) {
272 	case TAINT_CRAP:
273 	case TAINT_OOT_MODULE:
274 	case TAINT_WARN:
275 	case TAINT_FIRMWARE_WORKAROUND:
276 		break;
277 
278 	default:
279 		if (__debug_locks_off())
280 			printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
281 	}
282 
283 	set_bit(flag, &tainted_mask);
284 }
285 EXPORT_SYMBOL(add_taint);
286 
spin_msec(int msecs)287 static void spin_msec(int msecs)
288 {
289 	int i;
290 
291 	for (i = 0; i < msecs; i++) {
292 		touch_nmi_watchdog();
293 		mdelay(1);
294 	}
295 }
296 
297 /*
298  * It just happens that oops_enter() and oops_exit() are identically
299  * implemented...
300  */
do_oops_enter_exit(void)301 static void do_oops_enter_exit(void)
302 {
303 	unsigned long flags;
304 	static int spin_counter;
305 
306 	if (!pause_on_oops)
307 		return;
308 
309 	spin_lock_irqsave(&pause_on_oops_lock, flags);
310 	if (pause_on_oops_flag == 0) {
311 		/* This CPU may now print the oops message */
312 		pause_on_oops_flag = 1;
313 	} else {
314 		/* We need to stall this CPU */
315 		if (!spin_counter) {
316 			/* This CPU gets to do the counting */
317 			spin_counter = pause_on_oops;
318 			do {
319 				spin_unlock(&pause_on_oops_lock);
320 				spin_msec(MSEC_PER_SEC);
321 				spin_lock(&pause_on_oops_lock);
322 			} while (--spin_counter);
323 			pause_on_oops_flag = 0;
324 		} else {
325 			/* This CPU waits for a different one */
326 			while (spin_counter) {
327 				spin_unlock(&pause_on_oops_lock);
328 				spin_msec(1);
329 				spin_lock(&pause_on_oops_lock);
330 			}
331 		}
332 	}
333 	spin_unlock_irqrestore(&pause_on_oops_lock, flags);
334 }
335 
336 /*
337  * Return true if the calling CPU is allowed to print oops-related info.
338  * This is a bit racy..
339  */
oops_may_print(void)340 int oops_may_print(void)
341 {
342 	return pause_on_oops_flag == 0;
343 }
344 
345 /*
346  * Called when the architecture enters its oops handler, before it prints
347  * anything.  If this is the first CPU to oops, and it's oopsing the first
348  * time then let it proceed.
349  *
350  * This is all enabled by the pause_on_oops kernel boot option.  We do all
351  * this to ensure that oopses don't scroll off the screen.  It has the
352  * side-effect of preventing later-oopsing CPUs from mucking up the display,
353  * too.
354  *
355  * It turns out that the CPU which is allowed to print ends up pausing for
356  * the right duration, whereas all the other CPUs pause for twice as long:
357  * once in oops_enter(), once in oops_exit().
358  */
oops_enter(void)359 void oops_enter(void)
360 {
361 	tracing_off();
362 	/* can't trust the integrity of the kernel anymore: */
363 	debug_locks_off();
364 	do_oops_enter_exit();
365 }
366 
367 /*
368  * 64-bit random ID for oopses:
369  */
370 static u64 oops_id;
371 
init_oops_id(void)372 static int init_oops_id(void)
373 {
374 	if (!oops_id)
375 		get_random_bytes(&oops_id, sizeof(oops_id));
376 	else
377 		oops_id++;
378 
379 	return 0;
380 }
381 late_initcall(init_oops_id);
382 
print_oops_end_marker(void)383 void print_oops_end_marker(void)
384 {
385 	init_oops_id();
386 	printk(KERN_WARNING "---[ end trace %016llx ]---\n",
387 		(unsigned long long)oops_id);
388 }
389 
390 /*
391  * Called when the architecture exits its oops handler, after printing
392  * everything.
393  */
oops_exit(void)394 void oops_exit(void)
395 {
396 	do_oops_enter_exit();
397 	print_oops_end_marker();
398 	kmsg_dump(KMSG_DUMP_OOPS);
399 }
400 
401 #ifdef WANT_WARN_ON_SLOWPATH
402 struct slowpath_args {
403 	const char *fmt;
404 	va_list args;
405 };
406 
warn_slowpath_common(const char * file,int line,void * caller,unsigned taint,struct slowpath_args * args)407 static void warn_slowpath_common(const char *file, int line, void *caller,
408 				 unsigned taint, struct slowpath_args *args)
409 {
410 	const char *board;
411 
412 	printk(KERN_WARNING "------------[ cut here ]------------\n");
413 	printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
414 	board = dmi_get_system_info(DMI_PRODUCT_NAME);
415 	if (board)
416 		printk(KERN_WARNING "Hardware name: %s\n", board);
417 
418 	if (args)
419 		vprintk(args->fmt, args->args);
420 
421 	print_modules();
422 	dump_stack();
423 	print_oops_end_marker();
424 	add_taint(taint);
425 }
426 
warn_slowpath_fmt(const char * file,int line,const char * fmt,...)427 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
428 {
429 	struct slowpath_args args;
430 
431 	args.fmt = fmt;
432 	va_start(args.args, fmt);
433 	warn_slowpath_common(file, line, __builtin_return_address(0),
434 			     TAINT_WARN, &args);
435 	va_end(args.args);
436 }
437 EXPORT_SYMBOL(warn_slowpath_fmt);
438 
warn_slowpath_fmt_taint(const char * file,int line,unsigned taint,const char * fmt,...)439 void warn_slowpath_fmt_taint(const char *file, int line,
440 			     unsigned taint, const char *fmt, ...)
441 {
442 	struct slowpath_args args;
443 
444 	args.fmt = fmt;
445 	va_start(args.args, fmt);
446 	warn_slowpath_common(file, line, __builtin_return_address(0),
447 			     taint, &args);
448 	va_end(args.args);
449 }
450 EXPORT_SYMBOL(warn_slowpath_fmt_taint);
451 
warn_slowpath_null(const char * file,int line)452 void warn_slowpath_null(const char *file, int line)
453 {
454 	warn_slowpath_common(file, line, __builtin_return_address(0),
455 			     TAINT_WARN, NULL);
456 }
457 EXPORT_SYMBOL(warn_slowpath_null);
458 #endif
459 
460 #ifdef CONFIG_CC_STACKPROTECTOR
461 
462 /*
463  * Called when gcc's -fstack-protector feature is used, and
464  * gcc detects corruption of the on-stack canary value
465  */
__stack_chk_fail(void)466 void __stack_chk_fail(void)
467 {
468 	panic("stack-protector: Kernel stack is corrupted in: %p\n",
469 		__builtin_return_address(0));
470 }
471 EXPORT_SYMBOL(__stack_chk_fail);
472 
473 #endif
474 
475 core_param(panic, panic_timeout, int, 0644);
476 core_param(pause_on_oops, pause_on_oops, int, 0644);
477 
oops_setup(char * s)478 static int __init oops_setup(char *s)
479 {
480 	if (!s)
481 		return -EINVAL;
482 	if (!strcmp(s, "panic"))
483 		panic_on_oops = 1;
484 	return 0;
485 }
486 early_param("oops", oops_setup);
487