1 /*
2 * linux/kernel/panic.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 */
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/ftrace.h>
19 #include <linux/reboot.h>
20 #include <linux/delay.h>
21 #include <linux/kexec.h>
22 #include <linux/sched.h>
23 #include <linux/sysrq.h>
24 #include <linux/init.h>
25 #include <linux/nmi.h>
27 #define PANIC_TIMER_STEP 100
28 #define PANIC_BLINK_SPD 18
30 /* Machine specific panic information string */
31 char *mach_panic_string;
33 int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
34 static unsigned long tainted_mask;
35 static int pause_on_oops;
36 static int pause_on_oops_flag;
37 static DEFINE_SPINLOCK(pause_on_oops_lock);
39 int panic_timeout = CONFIG_PANIC_TIMEOUT;
40 EXPORT_SYMBOL_GPL(panic_timeout);
42 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
44 EXPORT_SYMBOL(panic_notifier_list);
46 static long no_blink(int state)
47 {
48 return 0;
49 }
51 /* Returns how long it waited in ms */
52 long (*panic_blink)(int state);
53 EXPORT_SYMBOL(panic_blink);
55 /*
56 * Stop ourself in panic -- architecture code may override this
57 */
58 void __weak panic_smp_self_stop(void)
59 {
60 while (1)
61 cpu_relax();
62 }
64 /**
65 * panic - halt the system
66 * @fmt: The text string to print
67 *
68 * Display a message, then perform cleanups.
69 *
70 * This function never returns.
71 */
72 void panic(const char *fmt, ...)
73 {
74 static DEFINE_SPINLOCK(panic_lock);
75 static char buf[1024];
76 va_list args;
77 long i, i_next = 0;
78 int state = 0;
80 /*
81 * Disable local interrupts. This will prevent panic_smp_self_stop
82 * from deadlocking the first cpu that invokes the panic, since
83 * there is nothing to prevent an interrupt handler (that runs
84 * after the panic_lock is acquired) from invoking panic again.
85 */
86 local_irq_disable();
88 /*
89 * It's possible to come here directly from a panic-assertion and
90 * not have preempt disabled. Some functions called from here want
91 * preempt to be disabled. No point enabling it later though...
92 *
93 * Only one CPU is allowed to execute the panic code from here. For
94 * multiple parallel invocations of panic, all other CPUs either
95 * stop themself or will wait until they are stopped by the 1st CPU
96 * with smp_send_stop().
97 */
98 if (!spin_trylock(&panic_lock))
99 panic_smp_self_stop();
101 console_verbose();
102 bust_spinlocks(1);
103 va_start(args, fmt);
104 vsnprintf(buf, sizeof(buf), fmt, args);
105 va_end(args);
106 printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
107 #ifdef CONFIG_DEBUG_BUGVERBOSE
108 /*
109 * Avoid nested stack-dumping if a panic occurs during oops processing
110 */
111 if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
112 dump_stack();
113 #endif
115 /*
116 * If we have crashed and we have a crash kernel loaded let it handle
117 * everything else.
118 * Do we want to call this before we try to display a message?
119 */
120 crash_kexec(NULL);
122 /*
123 * Note smp_send_stop is the usual smp shutdown function, which
124 * unfortunately means it may not be hardened to work in a panic
125 * situation.
126 */
127 smp_send_stop();
129 /*
130 * Run any panic handlers, including those that might need to
131 * add information to the kmsg dump output.
132 */
133 atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
135 kmsg_dump(KMSG_DUMP_PANIC);
137 bust_spinlocks(0);
139 if (!panic_blink)
140 panic_blink = no_blink;
142 if (panic_timeout > 0) {
143 /*
144 * Delay timeout seconds before rebooting the machine.
145 * We can't use the "normal" timers since we just panicked.
146 */
147 printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
149 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
150 touch_nmi_watchdog();
151 if (i >= i_next) {
152 i += panic_blink(state ^= 1);
153 i_next = i + 3600 / PANIC_BLINK_SPD;
154 }
155 mdelay(PANIC_TIMER_STEP);
156 }
157 }
158 if (panic_timeout != 0) {
159 /*
160 * This will not be a clean reboot, with everything
161 * shutting down. But if there is a chance of
162 * rebooting the system it will be rebooted.
163 */
164 emergency_restart();
165 }
166 #ifdef __sparc__
167 {
168 extern int stop_a_enabled;
169 /* Make sure the user can actually press Stop-A (L1-A) */
170 stop_a_enabled = 1;
171 printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
172 }
173 #endif
174 #if defined(CONFIG_S390)
175 {
176 unsigned long caller;
178 caller = (unsigned long)__builtin_return_address(0);
179 disabled_wait(caller);
180 }
181 #endif
182 local_irq_enable();
183 for (i = 0; ; i += PANIC_TIMER_STEP) {
184 touch_softlockup_watchdog();
185 if (i >= i_next) {
186 i += panic_blink(state ^= 1);
187 i_next = i + 3600 / PANIC_BLINK_SPD;
188 }
189 mdelay(PANIC_TIMER_STEP);
190 }
191 }
193 EXPORT_SYMBOL(panic);
196 struct tnt {
197 u8 bit;
198 char true;
199 char false;
200 };
202 static const struct tnt tnts[] = {
203 { TAINT_PROPRIETARY_MODULE, 'P', 'G' },
204 { TAINT_FORCED_MODULE, 'F', ' ' },
205 { TAINT_UNSAFE_SMP, 'S', ' ' },
206 { TAINT_FORCED_RMMOD, 'R', ' ' },
207 { TAINT_MACHINE_CHECK, 'M', ' ' },
208 { TAINT_BAD_PAGE, 'B', ' ' },
209 { TAINT_USER, 'U', ' ' },
210 { TAINT_DIE, 'D', ' ' },
211 { TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },
212 { TAINT_WARN, 'W', ' ' },
213 { TAINT_CRAP, 'C', ' ' },
214 { TAINT_FIRMWARE_WORKAROUND, 'I', ' ' },
215 { TAINT_OOT_MODULE, 'O', ' ' },
216 };
218 /**
219 * print_tainted - return a string to represent the kernel taint state.
220 *
221 * 'P' - Proprietary module has been loaded.
222 * 'F' - Module has been forcibly loaded.
223 * 'S' - SMP with CPUs not designed for SMP.
224 * 'R' - User forced a module unload.
225 * 'M' - System experienced a machine check exception.
226 * 'B' - System has hit bad_page.
227 * 'U' - Userspace-defined naughtiness.
228 * 'D' - Kernel has oopsed before
229 * 'A' - ACPI table overridden.
230 * 'W' - Taint on warning.
231 * 'C' - modules from drivers/staging are loaded.
232 * 'I' - Working around severe firmware bug.
233 * 'O' - Out-of-tree module has been loaded.
234 *
235 * The string is overwritten by the next call to print_tainted().
236 */
237 const char *print_tainted(void)
238 {
239 static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ")];
241 if (tainted_mask) {
242 char *s;
243 int i;
245 s = buf + sprintf(buf, "Tainted: ");
246 for (i = 0; i < ARRAY_SIZE(tnts); i++) {
247 const struct tnt *t = &tnts[i];
248 *s++ = test_bit(t->bit, &tainted_mask) ?
249 t->true : t->false;
250 }
251 *s = 0;
252 } else
253 snprintf(buf, sizeof(buf), "Not tainted");
255 return buf;
256 }
258 int test_taint(unsigned flag)
259 {
260 return test_bit(flag, &tainted_mask);
261 }
262 EXPORT_SYMBOL(test_taint);
264 unsigned long get_taint(void)
265 {
266 return tainted_mask;
267 }
269 /**
270 * add_taint: add a taint flag if not already set.
271 * @flag: one of the TAINT_* constants.
272 * @lockdep_ok: whether lock debugging is still OK.
273 *
274 * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
275 * some notewortht-but-not-corrupting cases, it can be set to true.
276 */
277 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
278 {
279 if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
280 printk(KERN_WARNING
281 "Disabling lock debugging due to kernel taint\n");
283 set_bit(flag, &tainted_mask);
284 }
285 EXPORT_SYMBOL(add_taint);
287 static void spin_msec(int msecs)
288 {
289 int i;
291 for (i = 0; i < msecs; i++) {
292 touch_nmi_watchdog();
293 mdelay(1);
294 }
295 }
297 /*
298 * It just happens that oops_enter() and oops_exit() are identically
299 * implemented...
300 */
301 static void do_oops_enter_exit(void)
302 {
303 unsigned long flags;
304 static int spin_counter;
306 if (!pause_on_oops)
307 return;
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 }
336 /*
337 * Return true if the calling CPU is allowed to print oops-related info.
338 * This is a bit racy..
339 */
340 int oops_may_print(void)
341 {
342 return pause_on_oops_flag == 0;
343 }
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 */
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 }
367 /*
368 * 64-bit random ID for oopses:
369 */
370 static u64 oops_id;
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++;
379 return 0;
380 }
381 late_initcall(init_oops_id);
383 void print_oops_end_marker(void)
384 {
385 init_oops_id();
387 if (mach_panic_string)
388 printk(KERN_WARNING "Board Information: %s\n",
389 mach_panic_string);
391 printk(KERN_WARNING "---[ end trace %016llx ]---\n",
392 (unsigned long long)oops_id);
393 }
395 /*
396 * Called when the architecture exits its oops handler, after printing
397 * everything.
398 */
399 void oops_exit(void)
400 {
401 do_oops_enter_exit();
402 print_oops_end_marker();
403 kmsg_dump(KMSG_DUMP_OOPS);
404 }
406 #ifdef WANT_WARN_ON_SLOWPATH
407 struct slowpath_args {
408 const char *fmt;
409 va_list args;
410 };
412 static void warn_slowpath_common(const char *file, int line, void *caller,
413 unsigned taint, struct slowpath_args *args)
414 {
415 disable_trace_on_warning();
417 pr_warn("------------[ cut here ]------------\n");
418 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS()\n",
419 raw_smp_processor_id(), current->pid, file, line, caller);
421 if (args)
422 vprintk(args->fmt, args->args);
424 print_modules();
425 dump_stack();
426 print_oops_end_marker();
427 /* Just a warning, don't kill lockdep. */
428 add_taint(taint, LOCKDEP_STILL_OK);
429 }
431 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
432 {
433 struct slowpath_args args;
435 args.fmt = fmt;
436 va_start(args.args, fmt);
437 warn_slowpath_common(file, line, __builtin_return_address(0),
438 TAINT_WARN, &args);
439 va_end(args.args);
440 }
441 EXPORT_SYMBOL(warn_slowpath_fmt);
443 void warn_slowpath_fmt_taint(const char *file, int line,
444 unsigned taint, const char *fmt, ...)
445 {
446 struct slowpath_args args;
448 args.fmt = fmt;
449 va_start(args.args, fmt);
450 warn_slowpath_common(file, line, __builtin_return_address(0),
451 taint, &args);
452 va_end(args.args);
453 }
454 EXPORT_SYMBOL(warn_slowpath_fmt_taint);
456 void warn_slowpath_null(const char *file, int line)
457 {
458 warn_slowpath_common(file, line, __builtin_return_address(0),
459 TAINT_WARN, NULL);
460 }
461 EXPORT_SYMBOL(warn_slowpath_null);
462 #endif
464 #ifdef CONFIG_CC_STACKPROTECTOR
466 /*
467 * Called when gcc's -fstack-protector feature is used, and
468 * gcc detects corruption of the on-stack canary value
469 */
470 void __stack_chk_fail(void)
471 {
472 panic("stack-protector: Kernel stack is corrupted in: %p\n",
473 __builtin_return_address(0));
474 }
475 EXPORT_SYMBOL(__stack_chk_fail);
477 #endif
479 core_param(panic, panic_timeout, int, 0644);
480 core_param(pause_on_oops, pause_on_oops, int, 0644);
482 static int __init oops_setup(char *s)
483 {
484 if (!s)
485 return -EINVAL;
486 if (!strcmp(s, "panic"))
487 panic_on_oops = 1;
488 return 0;
489 }
490 early_param("oops", oops_setup);