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TOMOYO Linux Cross Reference
Linux/kernel/panic.c

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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/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>
 26 #include <linux/console.h>
 27 
 28 #define PANIC_TIMER_STEP 100
 29 #define PANIC_BLINK_SPD 18
 30 
 31 int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
 32 static unsigned long tainted_mask;
 33 static int pause_on_oops;
 34 static int pause_on_oops_flag;
 35 static DEFINE_SPINLOCK(pause_on_oops_lock);
 36 static bool crash_kexec_post_notifiers;
 37 int panic_on_warn __read_mostly;
 38 
 39 int panic_timeout = CONFIG_PANIC_TIMEOUT;
 40 EXPORT_SYMBOL_GPL(panic_timeout);
 41 
 42 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
 43 
 44 EXPORT_SYMBOL(panic_notifier_list);
 45 
 46 static long no_blink(int state)
 47 {
 48         return 0;
 49 }
 50 
 51 /* Returns how long it waited in ms */
 52 long (*panic_blink)(int state);
 53 EXPORT_SYMBOL(panic_blink);
 54 
 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 }
 63 
 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;
 79 
 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();
 87 
 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();
100 
101         console_verbose();
102         bust_spinlocks(1);
103         va_start(args, fmt);
104         vsnprintf(buf, sizeof(buf), fmt, args);
105         va_end(args);
106         pr_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
114 
115         /*
116          * If we have crashed and we have a crash kernel loaded let it handle
117          * everything else.
118          * If we want to run this after calling panic_notifiers, pass
119          * the "crash_kexec_post_notifiers" option to the kernel.
120          */
121         if (!crash_kexec_post_notifiers)
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         /*
132          * Run any panic handlers, including those that might need to
133          * add information to the kmsg dump output.
134          */
135         atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
136 
137         kmsg_dump(KMSG_DUMP_PANIC);
138 
139         /*
140          * If you doubt kdump always works fine in any situation,
141          * "crash_kexec_post_notifiers" offers you a chance to run
142          * panic_notifiers and dumping kmsg before kdump.
143          * Note: since some panic_notifiers can make crashed kernel
144          * more unstable, it can increase risks of the kdump failure too.
145          */
146         crash_kexec(NULL);
147 
148         bust_spinlocks(0);
149 
150         /*
151          * We may have ended up stopping the CPU holding the lock (in
152          * smp_send_stop()) while still having some valuable data in the console
153          * buffer.  Try to acquire the lock then release it regardless of the
154          * result.  The release will also print the buffers out.  Locks debug
155          * should be disabled to avoid reporting bad unlock balance when
156          * panic() is not being callled from OOPS.
157          */
158         debug_locks_off();
159         console_flush_on_panic();
160 
161         if (!panic_blink)
162                 panic_blink = no_blink;
163 
164         if (panic_timeout > 0) {
165                 /*
166                  * Delay timeout seconds before rebooting the machine.
167                  * We can't use the "normal" timers since we just panicked.
168                  */
169                 pr_emerg("Rebooting in %d seconds..\n", panic_timeout);
170 
171                 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
172                         touch_nmi_watchdog();
173                         if (i >= i_next) {
174                                 i += panic_blink(state ^= 1);
175                                 i_next = i + 3600 / PANIC_BLINK_SPD;
176                         }
177                         mdelay(PANIC_TIMER_STEP);
178                 }
179         }
180         if (panic_timeout != 0) {
181                 /*
182                  * This will not be a clean reboot, with everything
183                  * shutting down.  But if there is a chance of
184                  * rebooting the system it will be rebooted.
185                  */
186                 emergency_restart();
187         }
188 #ifdef __sparc__
189         {
190                 extern int stop_a_enabled;
191                 /* Make sure the user can actually press Stop-A (L1-A) */
192                 stop_a_enabled = 1;
193                 pr_emerg("Press Stop-A (L1-A) to return to the boot prom\n");
194         }
195 #endif
196 #if defined(CONFIG_S390)
197         {
198                 unsigned long caller;
199 
200                 caller = (unsigned long)__builtin_return_address(0);
201                 disabled_wait(caller);
202         }
203 #endif
204         pr_emerg("---[ end Kernel panic - not syncing: %s\n", buf);
205         local_irq_enable();
206         for (i = 0; ; i += PANIC_TIMER_STEP) {
207                 touch_softlockup_watchdog();
208                 if (i >= i_next) {
209                         i += panic_blink(state ^= 1);
210                         i_next = i + 3600 / PANIC_BLINK_SPD;
211                 }
212                 mdelay(PANIC_TIMER_STEP);
213         }
214 }
215 
216 EXPORT_SYMBOL(panic);
217 
218 
219 struct tnt {
220         u8      bit;
221         char    true;
222         char    false;
223 };
224 
225 static const struct tnt tnts[] = {
226         { TAINT_PROPRIETARY_MODULE,     'P', 'G' },
227         { TAINT_FORCED_MODULE,          'F', ' ' },
228         { TAINT_CPU_OUT_OF_SPEC,        'S', ' ' },
229         { TAINT_FORCED_RMMOD,           'R', ' ' },
230         { TAINT_MACHINE_CHECK,          'M', ' ' },
231         { TAINT_BAD_PAGE,               'B', ' ' },
232         { TAINT_USER,                   'U', ' ' },
233         { TAINT_DIE,                    'D', ' ' },
234         { TAINT_OVERRIDDEN_ACPI_TABLE,  'A', ' ' },
235         { TAINT_WARN,                   'W', ' ' },
236         { TAINT_CRAP,                   'C', ' ' },
237         { TAINT_FIRMWARE_WORKAROUND,    'I', ' ' },
238         { TAINT_OOT_MODULE,             'O', ' ' },
239         { TAINT_UNSIGNED_MODULE,        'E', ' ' },
240         { TAINT_SOFTLOCKUP,             'L', ' ' },
241         { TAINT_LIVEPATCH,              'K', ' ' },
242 };
243 
244 /**
245  *      print_tainted - return a string to represent the kernel taint state.
246  *
247  *  'P' - Proprietary module has been loaded.
248  *  'F' - Module has been forcibly loaded.
249  *  'S' - SMP with CPUs not designed for SMP.
250  *  'R' - User forced a module unload.
251  *  'M' - System experienced a machine check exception.
252  *  'B' - System has hit bad_page.
253  *  'U' - Userspace-defined naughtiness.
254  *  'D' - Kernel has oopsed before
255  *  'A' - ACPI table overridden.
256  *  'W' - Taint on warning.
257  *  'C' - modules from drivers/staging are loaded.
258  *  'I' - Working around severe firmware bug.
259  *  'O' - Out-of-tree module has been loaded.
260  *  'E' - Unsigned module has been loaded.
261  *  'L' - A soft lockup has previously occurred.
262  *  'K' - Kernel has been live patched.
263  *
264  *      The string is overwritten by the next call to print_tainted().
265  */
266 const char *print_tainted(void)
267 {
268         static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ")];
269 
270         if (tainted_mask) {
271                 char *s;
272                 int i;
273 
274                 s = buf + sprintf(buf, "Tainted: ");
275                 for (i = 0; i < ARRAY_SIZE(tnts); i++) {
276                         const struct tnt *t = &tnts[i];
277                         *s++ = test_bit(t->bit, &tainted_mask) ?
278                                         t->true : t->false;
279                 }
280                 *s = 0;
281         } else
282                 snprintf(buf, sizeof(buf), "Not tainted");
283 
284         return buf;
285 }
286 
287 int test_taint(unsigned flag)
288 {
289         return test_bit(flag, &tainted_mask);
290 }
291 EXPORT_SYMBOL(test_taint);
292 
293 unsigned long get_taint(void)
294 {
295         return tainted_mask;
296 }
297 
298 /**
299  * add_taint: add a taint flag if not already set.
300  * @flag: one of the TAINT_* constants.
301  * @lockdep_ok: whether lock debugging is still OK.
302  *
303  * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
304  * some notewortht-but-not-corrupting cases, it can be set to true.
305  */
306 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
307 {
308         if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
309                 pr_warn("Disabling lock debugging due to kernel taint\n");
310 
311         set_bit(flag, &tainted_mask);
312 }
313 EXPORT_SYMBOL(add_taint);
314 
315 static void spin_msec(int msecs)
316 {
317         int i;
318 
319         for (i = 0; i < msecs; i++) {
320                 touch_nmi_watchdog();
321                 mdelay(1);
322         }
323 }
324 
325 /*
326  * It just happens that oops_enter() and oops_exit() are identically
327  * implemented...
328  */
329 static void do_oops_enter_exit(void)
330 {
331         unsigned long flags;
332         static int spin_counter;
333 
334         if (!pause_on_oops)
335                 return;
336 
337         spin_lock_irqsave(&pause_on_oops_lock, flags);
338         if (pause_on_oops_flag == 0) {
339                 /* This CPU may now print the oops message */
340                 pause_on_oops_flag = 1;
341         } else {
342                 /* We need to stall this CPU */
343                 if (!spin_counter) {
344                         /* This CPU gets to do the counting */
345                         spin_counter = pause_on_oops;
346                         do {
347                                 spin_unlock(&pause_on_oops_lock);
348                                 spin_msec(MSEC_PER_SEC);
349                                 spin_lock(&pause_on_oops_lock);
350                         } while (--spin_counter);
351                         pause_on_oops_flag = 0;
352                 } else {
353                         /* This CPU waits for a different one */
354                         while (spin_counter) {
355                                 spin_unlock(&pause_on_oops_lock);
356                                 spin_msec(1);
357                                 spin_lock(&pause_on_oops_lock);
358                         }
359                 }
360         }
361         spin_unlock_irqrestore(&pause_on_oops_lock, flags);
362 }
363 
364 /*
365  * Return true if the calling CPU is allowed to print oops-related info.
366  * This is a bit racy..
367  */
368 int oops_may_print(void)
369 {
370         return pause_on_oops_flag == 0;
371 }
372 
373 /*
374  * Called when the architecture enters its oops handler, before it prints
375  * anything.  If this is the first CPU to oops, and it's oopsing the first
376  * time then let it proceed.
377  *
378  * This is all enabled by the pause_on_oops kernel boot option.  We do all
379  * this to ensure that oopses don't scroll off the screen.  It has the
380  * side-effect of preventing later-oopsing CPUs from mucking up the display,
381  * too.
382  *
383  * It turns out that the CPU which is allowed to print ends up pausing for
384  * the right duration, whereas all the other CPUs pause for twice as long:
385  * once in oops_enter(), once in oops_exit().
386  */
387 void oops_enter(void)
388 {
389         tracing_off();
390         /* can't trust the integrity of the kernel anymore: */
391         debug_locks_off();
392         do_oops_enter_exit();
393 }
394 
395 /*
396  * 64-bit random ID for oopses:
397  */
398 static u64 oops_id;
399 
400 static int init_oops_id(void)
401 {
402         if (!oops_id)
403                 get_random_bytes(&oops_id, sizeof(oops_id));
404         else
405                 oops_id++;
406 
407         return 0;
408 }
409 late_initcall(init_oops_id);
410 
411 void print_oops_end_marker(void)
412 {
413         init_oops_id();
414         pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id);
415 }
416 
417 /*
418  * Called when the architecture exits its oops handler, after printing
419  * everything.
420  */
421 void oops_exit(void)
422 {
423         do_oops_enter_exit();
424         print_oops_end_marker();
425         kmsg_dump(KMSG_DUMP_OOPS);
426 }
427 
428 #ifdef WANT_WARN_ON_SLOWPATH
429 struct slowpath_args {
430         const char *fmt;
431         va_list args;
432 };
433 
434 static void warn_slowpath_common(const char *file, int line, void *caller,
435                                  unsigned taint, struct slowpath_args *args)
436 {
437         disable_trace_on_warning();
438 
439         pr_warn("------------[ cut here ]------------\n");
440         pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS()\n",
441                 raw_smp_processor_id(), current->pid, file, line, caller);
442 
443         if (args)
444                 vprintk(args->fmt, args->args);
445 
446         if (panic_on_warn) {
447                 /*
448                  * This thread may hit another WARN() in the panic path.
449                  * Resetting this prevents additional WARN() from panicking the
450                  * system on this thread.  Other threads are blocked by the
451                  * panic_mutex in panic().
452                  */
453                 panic_on_warn = 0;
454                 panic("panic_on_warn set ...\n");
455         }
456 
457         print_modules();
458         dump_stack();
459         print_oops_end_marker();
460         /* Just a warning, don't kill lockdep. */
461         add_taint(taint, LOCKDEP_STILL_OK);
462 }
463 
464 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
465 {
466         struct slowpath_args args;
467 
468         args.fmt = fmt;
469         va_start(args.args, fmt);
470         warn_slowpath_common(file, line, __builtin_return_address(0),
471                              TAINT_WARN, &args);
472         va_end(args.args);
473 }
474 EXPORT_SYMBOL(warn_slowpath_fmt);
475 
476 void warn_slowpath_fmt_taint(const char *file, int line,
477                              unsigned taint, const char *fmt, ...)
478 {
479         struct slowpath_args args;
480 
481         args.fmt = fmt;
482         va_start(args.args, fmt);
483         warn_slowpath_common(file, line, __builtin_return_address(0),
484                              taint, &args);
485         va_end(args.args);
486 }
487 EXPORT_SYMBOL(warn_slowpath_fmt_taint);
488 
489 void warn_slowpath_null(const char *file, int line)
490 {
491         warn_slowpath_common(file, line, __builtin_return_address(0),
492                              TAINT_WARN, NULL);
493 }
494 EXPORT_SYMBOL(warn_slowpath_null);
495 #endif
496 
497 #ifdef CONFIG_CC_STACKPROTECTOR
498 
499 /*
500  * Called when gcc's -fstack-protector feature is used, and
501  * gcc detects corruption of the on-stack canary value
502  */
503 __visible void __stack_chk_fail(void)
504 {
505         panic("stack-protector: Kernel stack is corrupted in: %p\n",
506                 __builtin_return_address(0));
507 }
508 EXPORT_SYMBOL(__stack_chk_fail);
509 
510 #endif
511 
512 core_param(panic, panic_timeout, int, 0644);
513 core_param(pause_on_oops, pause_on_oops, int, 0644);
514 core_param(panic_on_warn, panic_on_warn, int, 0644);
515 
516 static int __init setup_crash_kexec_post_notifiers(char *s)
517 {
518         crash_kexec_post_notifiers = true;
519         return 0;
520 }
521 early_param("crash_kexec_post_notifiers", setup_crash_kexec_post_notifiers);
522 
523 static int __init oops_setup(char *s)
524 {
525         if (!s)
526                 return -EINVAL;
527         if (!strcmp(s, "panic"))
528                 panic_on_oops = 1;
529         return 0;
530 }
531 early_param("oops", oops_setup);
532 

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