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