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Linux/kernel/panic.c

  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 #include <linux/bug.h>
 28 
 29 #define PANIC_TIMER_STEP 100
 30 #define PANIC_BLINK_SPD 18
 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 bool crash_kexec_post_notifiers;
 38 int panic_on_warn __read_mostly;
 39 
 40 int panic_timeout = CONFIG_PANIC_TIMEOUT;
 41 EXPORT_SYMBOL_GPL(panic_timeout);
 42 
 43 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
 44 
 45 EXPORT_SYMBOL(panic_notifier_list);
 46 
 47 static long no_blink(int state)
 48 {
 49         return 0;
 50 }
 51 
 52 /* Returns how long it waited in ms */
 53 long (*panic_blink)(int state);
 54 EXPORT_SYMBOL(panic_blink);
 55 
 56 /*
 57  * Stop ourself in panic -- architecture code may override this
 58  */
 59 void __weak panic_smp_self_stop(void)
 60 {
 61         while (1)
 62                 cpu_relax();
 63 }
 64 
 65 /*
 66  * Stop ourselves in NMI context if another CPU has already panicked. Arch code
 67  * may override this to prepare for crash dumping, e.g. save regs info.
 68  */
 69 void __weak nmi_panic_self_stop(struct pt_regs *regs)
 70 {
 71         panic_smp_self_stop();
 72 }
 73 
 74 /*
 75  * Stop other CPUs in panic.  Architecture dependent code may override this
 76  * with more suitable version.  For example, if the architecture supports
 77  * crash dump, it should save registers of each stopped CPU and disable
 78  * per-CPU features such as virtualization extensions.
 79  */
 80 void __weak crash_smp_send_stop(void)
 81 {
 82         static int cpus_stopped;
 83 
 84         /*
 85          * This function can be called twice in panic path, but obviously
 86          * we execute this only once.
 87          */
 88         if (cpus_stopped)
 89                 return;
 90 
 91         /*
 92          * Note smp_send_stop is the usual smp shutdown function, which
 93          * unfortunately means it may not be hardened to work in a panic
 94          * situation.
 95          */
 96         smp_send_stop();
 97         cpus_stopped = 1;
 98 }
 99 
100 atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
101 
102 /*
103  * A variant of panic() called from NMI context. We return if we've already
104  * panicked on this CPU. If another CPU already panicked, loop in
105  * nmi_panic_self_stop() which can provide architecture dependent code such
106  * as saving register state for crash dump.
107  */
108 void nmi_panic(struct pt_regs *regs, const char *msg)
109 {
110         int old_cpu, cpu;
111 
112         cpu = raw_smp_processor_id();
113         old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu);
114 
115         if (old_cpu == PANIC_CPU_INVALID)
116                 panic("%s", msg);
117         else if (old_cpu != cpu)
118                 nmi_panic_self_stop(regs);
119 }
120 EXPORT_SYMBOL(nmi_panic);
121 
122 /**
123  *      panic - halt the system
124  *      @fmt: The text string to print
125  *
126  *      Display a message, then perform cleanups.
127  *
128  *      This function never returns.
129  */
130 void panic(const char *fmt, ...)
131 {
132         static char buf[1024];
133         va_list args;
134         long i, i_next = 0;
135         int state = 0;
136         int old_cpu, this_cpu;
137         bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
138 
139         /*
140          * Disable local interrupts. This will prevent panic_smp_self_stop
141          * from deadlocking the first cpu that invokes the panic, since
142          * there is nothing to prevent an interrupt handler (that runs
143          * after setting panic_cpu) from invoking panic() again.
144          */
145         local_irq_disable();
146 
147         /*
148          * It's possible to come here directly from a panic-assertion and
149          * not have preempt disabled. Some functions called from here want
150          * preempt to be disabled. No point enabling it later though...
151          *
152          * Only one CPU is allowed to execute the panic code from here. For
153          * multiple parallel invocations of panic, all other CPUs either
154          * stop themself or will wait until they are stopped by the 1st CPU
155          * with smp_send_stop().
156          *
157          * `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which
158          * comes here, so go ahead.
159          * `old_cpu == this_cpu' means we came from nmi_panic() which sets
160          * panic_cpu to this CPU.  In this case, this is also the 1st CPU.
161          */
162         this_cpu = raw_smp_processor_id();
163         old_cpu  = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
164 
165         if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)
166                 panic_smp_self_stop();
167 
168         console_verbose();
169         bust_spinlocks(1);
170         va_start(args, fmt);
171         vsnprintf(buf, sizeof(buf), fmt, args);
172         va_end(args);
173         pr_emerg("Kernel panic - not syncing: %s\n", buf);
174 #ifdef CONFIG_DEBUG_BUGVERBOSE
175         /*
176          * Avoid nested stack-dumping if a panic occurs during oops processing
177          */
178         if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
179                 dump_stack();
180 #endif
181 
182         /*
183          * If we have crashed and we have a crash kernel loaded let it handle
184          * everything else.
185          * If we want to run this after calling panic_notifiers, pass
186          * the "crash_kexec_post_notifiers" option to the kernel.
187          *
188          * Bypass the panic_cpu check and call __crash_kexec directly.
189          */
190         if (!_crash_kexec_post_notifiers) {
191                 printk_nmi_flush_on_panic();
192                 __crash_kexec(NULL);
193 
194                 /*
195                  * Note smp_send_stop is the usual smp shutdown function, which
196                  * unfortunately means it may not be hardened to work in a
197                  * panic situation.
198                  */
199                 smp_send_stop();
200         } else {
201                 /*
202                  * If we want to do crash dump after notifier calls and
203                  * kmsg_dump, we will need architecture dependent extra
204                  * works in addition to stopping other CPUs.
205                  */
206                 crash_smp_send_stop();
207         }
208 
209         /*
210          * Run any panic handlers, including those that might need to
211          * add information to the kmsg dump output.
212          */
213         atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
214 
215         /* Call flush even twice. It tries harder with a single online CPU */
216         printk_nmi_flush_on_panic();
217         kmsg_dump(KMSG_DUMP_PANIC);
218 
219         /*
220          * If you doubt kdump always works fine in any situation,
221          * "crash_kexec_post_notifiers" offers you a chance to run
222          * panic_notifiers and dumping kmsg before kdump.
223          * Note: since some panic_notifiers can make crashed kernel
224          * more unstable, it can increase risks of the kdump failure too.
225          *
226          * Bypass the panic_cpu check and call __crash_kexec directly.
227          */
228         if (_crash_kexec_post_notifiers)
229                 __crash_kexec(NULL);
230 
231         bust_spinlocks(0);
232 
233         /*
234          * We may have ended up stopping the CPU holding the lock (in
235          * smp_send_stop()) while still having some valuable data in the console
236          * buffer.  Try to acquire the lock then release it regardless of the
237          * result.  The release will also print the buffers out.  Locks debug
238          * should be disabled to avoid reporting bad unlock balance when
239          * panic() is not being callled from OOPS.
240          */
241         debug_locks_off();
242         console_flush_on_panic();
243 
244         if (!panic_blink)
245                 panic_blink = no_blink;
246 
247         if (panic_timeout > 0) {
248                 /*
249                  * Delay timeout seconds before rebooting the machine.
250                  * We can't use the "normal" timers since we just panicked.
251                  */
252                 pr_emerg("Rebooting in %d seconds..\n", panic_timeout);
253 
254                 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
255                         touch_nmi_watchdog();
256                         if (i >= i_next) {
257                                 i += panic_blink(state ^= 1);
258                                 i_next = i + 3600 / PANIC_BLINK_SPD;
259                         }
260                         mdelay(PANIC_TIMER_STEP);
261                 }
262         }
263         if (panic_timeout != 0) {
264                 /*
265                  * This will not be a clean reboot, with everything
266                  * shutting down.  But if there is a chance of
267                  * rebooting the system it will be rebooted.
268                  */
269                 emergency_restart();
270         }
271 #ifdef __sparc__
272         {
273                 extern int stop_a_enabled;
274                 /* Make sure the user can actually press Stop-A (L1-A) */
275                 stop_a_enabled = 1;
276                 pr_emerg("Press Stop-A (L1-A) to return to the boot prom\n");
277         }
278 #endif
279 #if defined(CONFIG_S390)
280         {
281                 unsigned long caller;
282 
283                 caller = (unsigned long)__builtin_return_address(0);
284                 disabled_wait(caller);
285         }
286 #endif
287         pr_emerg("---[ end Kernel panic - not syncing: %s\n", buf);
288         local_irq_enable();
289         for (i = 0; ; i += PANIC_TIMER_STEP) {
290                 touch_softlockup_watchdog();
291                 if (i >= i_next) {
292                         i += panic_blink(state ^= 1);
293                         i_next = i + 3600 / PANIC_BLINK_SPD;
294                 }
295                 mdelay(PANIC_TIMER_STEP);
296         }
297 }
298 
299 EXPORT_SYMBOL(panic);
300 
301 /*
302  * TAINT_FORCED_RMMOD could be a per-module flag but the module
303  * is being removed anyway.
304  */
305 const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
306         { 'P', 'G', true },     /* TAINT_PROPRIETARY_MODULE */
307         { 'F', ' ', true },     /* TAINT_FORCED_MODULE */
308         { 'S', ' ', false },    /* TAINT_CPU_OUT_OF_SPEC */
309         { 'R', ' ', false },    /* TAINT_FORCED_RMMOD */
310         { 'M', ' ', false },    /* TAINT_MACHINE_CHECK */
311         { 'B', ' ', false },    /* TAINT_BAD_PAGE */
312         { 'U', ' ', false },    /* TAINT_USER */
313         { 'D', ' ', false },    /* TAINT_DIE */
314         { 'A', ' ', false },    /* TAINT_OVERRIDDEN_ACPI_TABLE */
315         { 'W', ' ', false },    /* TAINT_WARN */
316         { 'C', ' ', true },     /* TAINT_CRAP */
317         { 'I', ' ', false },    /* TAINT_FIRMWARE_WORKAROUND */
318         { 'O', ' ', true },     /* TAINT_OOT_MODULE */
319         { 'E', ' ', true },     /* TAINT_UNSIGNED_MODULE */
320         { 'L', ' ', false },    /* TAINT_SOFTLOCKUP */
321         { 'K', ' ', true },     /* TAINT_LIVEPATCH */
322 };
323 
324 /**
325  *      print_tainted - return a string to represent the kernel taint state.
326  *
327  *  'P' - Proprietary module has been loaded.
328  *  'F' - Module has been forcibly loaded.
329  *  'S' - SMP with CPUs not designed for SMP.
330  *  'R' - User forced a module unload.
331  *  'M' - System experienced a machine check exception.
332  *  'B' - System has hit bad_page.
333  *  'U' - Userspace-defined naughtiness.
334  *  'D' - Kernel has oopsed before
335  *  'A' - ACPI table overridden.
336  *  'W' - Taint on warning.
337  *  'C' - modules from drivers/staging are loaded.
338  *  'I' - Working around severe firmware bug.
339  *  'O' - Out-of-tree module has been loaded.
340  *  'E' - Unsigned module has been loaded.
341  *  'L' - A soft lockup has previously occurred.
342  *  'K' - Kernel has been live patched.
343  *
344  *      The string is overwritten by the next call to print_tainted().
345  */
346 const char *print_tainted(void)
347 {
348         static char buf[TAINT_FLAGS_COUNT + sizeof("Tainted: ")];
349 
350         if (tainted_mask) {
351                 char *s;
352                 int i;
353 
354                 s = buf + sprintf(buf, "Tainted: ");
355                 for (i = 0; i < TAINT_FLAGS_COUNT; i++) {
356                         const struct taint_flag *t = &taint_flags[i];
357                         *s++ = test_bit(i, &tainted_mask) ?
358                                         t->c_true : t->c_false;
359                 }
360                 *s = 0;
361         } else
362                 snprintf(buf, sizeof(buf), "Not tainted");
363 
364         return buf;
365 }
366 
367 int test_taint(unsigned flag)
368 {
369         return test_bit(flag, &tainted_mask);
370 }
371 EXPORT_SYMBOL(test_taint);
372 
373 unsigned long get_taint(void)
374 {
375         return tainted_mask;
376 }
377 
378 /**
379  * add_taint: add a taint flag if not already set.
380  * @flag: one of the TAINT_* constants.
381  * @lockdep_ok: whether lock debugging is still OK.
382  *
383  * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
384  * some notewortht-but-not-corrupting cases, it can be set to true.
385  */
386 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
387 {
388         if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
389                 pr_warn("Disabling lock debugging due to kernel taint\n");
390 
391         set_bit(flag, &tainted_mask);
392 }
393 EXPORT_SYMBOL(add_taint);
394 
395 static void spin_msec(int msecs)
396 {
397         int i;
398 
399         for (i = 0; i < msecs; i++) {
400                 touch_nmi_watchdog();
401                 mdelay(1);
402         }
403 }
404 
405 /*
406  * It just happens that oops_enter() and oops_exit() are identically
407  * implemented...
408  */
409 static void do_oops_enter_exit(void)
410 {
411         unsigned long flags;
412         static int spin_counter;
413 
414         if (!pause_on_oops)
415                 return;
416 
417         spin_lock_irqsave(&pause_on_oops_lock, flags);
418         if (pause_on_oops_flag == 0) {
419                 /* This CPU may now print the oops message */
420                 pause_on_oops_flag = 1;
421         } else {
422                 /* We need to stall this CPU */
423                 if (!spin_counter) {
424                         /* This CPU gets to do the counting */
425                         spin_counter = pause_on_oops;
426                         do {
427                                 spin_unlock(&pause_on_oops_lock);
428                                 spin_msec(MSEC_PER_SEC);
429                                 spin_lock(&pause_on_oops_lock);
430                         } while (--spin_counter);
431                         pause_on_oops_flag = 0;
432                 } else {
433                         /* This CPU waits for a different one */
434                         while (spin_counter) {
435                                 spin_unlock(&pause_on_oops_lock);
436                                 spin_msec(1);
437                                 spin_lock(&pause_on_oops_lock);
438                         }
439                 }
440         }
441         spin_unlock_irqrestore(&pause_on_oops_lock, flags);
442 }
443 
444 /*
445  * Return true if the calling CPU is allowed to print oops-related info.
446  * This is a bit racy..
447  */
448 int oops_may_print(void)
449 {
450         return pause_on_oops_flag == 0;
451 }
452 
453 /*
454  * Called when the architecture enters its oops handler, before it prints
455  * anything.  If this is the first CPU to oops, and it's oopsing the first
456  * time then let it proceed.
457  *
458  * This is all enabled by the pause_on_oops kernel boot option.  We do all
459  * this to ensure that oopses don't scroll off the screen.  It has the
460  * side-effect of preventing later-oopsing CPUs from mucking up the display,
461  * too.
462  *
463  * It turns out that the CPU which is allowed to print ends up pausing for
464  * the right duration, whereas all the other CPUs pause for twice as long:
465  * once in oops_enter(), once in oops_exit().
466  */
467 void oops_enter(void)
468 {
469         tracing_off();
470         /* can't trust the integrity of the kernel anymore: */
471         debug_locks_off();
472         do_oops_enter_exit();
473 }
474 
475 /*
476  * 64-bit random ID for oopses:
477  */
478 static u64 oops_id;
479 
480 static int init_oops_id(void)
481 {
482         if (!oops_id)
483                 get_random_bytes(&oops_id, sizeof(oops_id));
484         else
485                 oops_id++;
486 
487         return 0;
488 }
489 late_initcall(init_oops_id);
490 
491 void print_oops_end_marker(void)
492 {
493         init_oops_id();
494         pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id);
495 }
496 
497 /*
498  * Called when the architecture exits its oops handler, after printing
499  * everything.
500  */
501 void oops_exit(void)
502 {
503         do_oops_enter_exit();
504         print_oops_end_marker();
505         kmsg_dump(KMSG_DUMP_OOPS);
506 }
507 
508 struct warn_args {
509         const char *fmt;
510         va_list args;
511 };
512 
513 void __warn(const char *file, int line, void *caller, unsigned taint,
514             struct pt_regs *regs, struct warn_args *args)
515 {
516         disable_trace_on_warning();
517 
518         pr_warn("------------[ cut here ]------------\n");
519 
520         if (file)
521                 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
522                         raw_smp_processor_id(), current->pid, file, line,
523                         caller);
524         else
525                 pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
526                         raw_smp_processor_id(), current->pid, caller);
527 
528         if (args)
529                 vprintk(args->fmt, args->args);
530 
531         if (panic_on_warn) {
532                 /*
533                  * This thread may hit another WARN() in the panic path.
534                  * Resetting this prevents additional WARN() from panicking the
535                  * system on this thread.  Other threads are blocked by the
536                  * panic_mutex in panic().
537                  */
538                 panic_on_warn = 0;
539                 panic("panic_on_warn set ...\n");
540         }
541 
542         print_modules();
543 
544         if (regs)
545                 show_regs(regs);
546         else
547                 dump_stack();
548 
549         print_oops_end_marker();
550 
551         /* Just a warning, don't kill lockdep. */
552         add_taint(taint, LOCKDEP_STILL_OK);
553 }
554 
555 #ifdef WANT_WARN_ON_SLOWPATH
556 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
557 {
558         struct warn_args args;
559 
560         args.fmt = fmt;
561         va_start(args.args, fmt);
562         __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL,
563                &args);
564         va_end(args.args);
565 }
566 EXPORT_SYMBOL(warn_slowpath_fmt);
567 
568 void warn_slowpath_fmt_taint(const char *file, int line,
569                              unsigned taint, const char *fmt, ...)
570 {
571         struct warn_args args;
572 
573         args.fmt = fmt;
574         va_start(args.args, fmt);
575         __warn(file, line, __builtin_return_address(0), taint, NULL, &args);
576         va_end(args.args);
577 }
578 EXPORT_SYMBOL(warn_slowpath_fmt_taint);
579 
580 void warn_slowpath_null(const char *file, int line)
581 {
582         __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, NULL);
583 }
584 EXPORT_SYMBOL(warn_slowpath_null);
585 #endif
586 
587 #ifdef CONFIG_CC_STACKPROTECTOR
588 
589 /*
590  * Called when gcc's -fstack-protector feature is used, and
591  * gcc detects corruption of the on-stack canary value
592  */
593 __visible void __stack_chk_fail(void)
594 {
595         panic("stack-protector: Kernel stack is corrupted in: %p\n",
596                 __builtin_return_address(0));
597 }
598 EXPORT_SYMBOL(__stack_chk_fail);
599 
600 #endif
601 
602 core_param(panic, panic_timeout, int, 0644);
603 core_param(pause_on_oops, pause_on_oops, int, 0644);
604 core_param(panic_on_warn, panic_on_warn, int, 0644);
605 core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
606 
607 static int __init oops_setup(char *s)
608 {
609         if (!s)
610                 return -EINVAL;
611         if (!strcmp(s, "panic"))
612                 panic_on_oops = 1;
613         return 0;
614 }
615 early_param("oops", oops_setup);
616 

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