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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 
 27 #define PANIC_TIMER_STEP 100
 28 #define PANIC_BLINK_SPD 18
 29 
 30 int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
 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 static bool crash_kexec_post_notifiers;
 36 int panic_on_warn __read_mostly;
 37 
 38 int panic_timeout = CONFIG_PANIC_TIMEOUT;
 39 EXPORT_SYMBOL_GPL(panic_timeout);
 40 
 41 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
 42 
 43 EXPORT_SYMBOL(panic_notifier_list);
 44 
 45 static long no_blink(int state)
 46 {
 47         return 0;
 48 }
 49 
 50 /* Returns how long it waited in ms */
 51 long (*panic_blink)(int state);
 52 EXPORT_SYMBOL(panic_blink);
 53 
 54 /*
 55  * Stop ourself in panic -- architecture code may override this
 56  */
 57 void __weak panic_smp_self_stop(void)
 58 {
 59         while (1)
 60                 cpu_relax();
 61 }
 62 
 63 /**
 64  *      panic - halt the system
 65  *      @fmt: The text string to print
 66  *
 67  *      Display a message, then perform cleanups.
 68  *
 69  *      This function never returns.
 70  */
 71 void panic(const char *fmt, ...)
 72 {
 73         static DEFINE_SPINLOCK(panic_lock);
 74         static char buf[1024];
 75         va_list args;
 76         long i, i_next = 0;
 77         int state = 0;
 78 
 79         /*
 80          * Disable local interrupts. This will prevent panic_smp_self_stop
 81          * from deadlocking the first cpu that invokes the panic, since
 82          * there is nothing to prevent an interrupt handler (that runs
 83          * after the panic_lock is acquired) from invoking panic again.
 84          */
 85         local_irq_disable();
 86 
 87         /*
 88          * It's possible to come here directly from a panic-assertion and
 89          * not have preempt disabled. Some functions called from here want
 90          * preempt to be disabled. No point enabling it later though...
 91          *
 92          * Only one CPU is allowed to execute the panic code from here. For
 93          * multiple parallel invocations of panic, all other CPUs either
 94          * stop themself or will wait until they are stopped by the 1st CPU
 95          * with smp_send_stop().
 96          */
 97         if (!spin_trylock(&panic_lock))
 98                 panic_smp_self_stop();
 99 
100         console_verbose();
101         bust_spinlocks(1);
102         va_start(args, fmt);
103         vsnprintf(buf, sizeof(buf), fmt, args);
104         va_end(args);
105         pr_emerg("Kernel panic - not syncing: %s\n", buf);
106 #ifdef CONFIG_DEBUG_BUGVERBOSE
107         /*
108          * Avoid nested stack-dumping if a panic occurs during oops processing
109          */
110         if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
111                 dump_stack();
112 #endif
113 
114         /*
115          * If we have crashed and we have a crash kernel loaded let it handle
116          * everything else.
117          * If we want to run this after calling panic_notifiers, pass
118          * the "crash_kexec_post_notifiers" option to the kernel.
119          */
120         if (!crash_kexec_post_notifiers)
121                 crash_kexec(NULL);
122 
123         /*
124          * Note smp_send_stop is the usual smp shutdown function, which
125          * unfortunately means it may not be hardened to work in a panic
126          * situation.
127          */
128         smp_send_stop();
129 
130         /*
131          * Run any panic handlers, including those that might need to
132          * add information to the kmsg dump output.
133          */
134         atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
135 
136         kmsg_dump(KMSG_DUMP_PANIC);
137 
138         /*
139          * If you doubt kdump always works fine in any situation,
140          * "crash_kexec_post_notifiers" offers you a chance to run
141          * panic_notifiers and dumping kmsg before kdump.
142          * Note: since some panic_notifiers can make crashed kernel
143          * more unstable, it can increase risks of the kdump failure too.
144          */
145         crash_kexec(NULL);
146 
147         bust_spinlocks(0);
148 
149         if (!panic_blink)
150                 panic_blink = no_blink;
151 
152         if (panic_timeout > 0) {
153                 /*
154                  * Delay timeout seconds before rebooting the machine.
155                  * We can't use the "normal" timers since we just panicked.
156                  */
157                 pr_emerg("Rebooting in %d seconds..", panic_timeout);
158 
159                 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
160                         touch_nmi_watchdog();
161                         if (i >= i_next) {
162                                 i += panic_blink(state ^= 1);
163                                 i_next = i + 3600 / PANIC_BLINK_SPD;
164                         }
165                         mdelay(PANIC_TIMER_STEP);
166                 }
167         }
168         if (panic_timeout != 0) {
169                 /*
170                  * This will not be a clean reboot, with everything
171                  * shutting down.  But if there is a chance of
172                  * rebooting the system it will be rebooted.
173                  */
174                 emergency_restart();
175         }
176 #ifdef __sparc__
177         {
178                 extern int stop_a_enabled;
179                 /* Make sure the user can actually press Stop-A (L1-A) */
180                 stop_a_enabled = 1;
181                 pr_emerg("Press Stop-A (L1-A) to return to the boot prom\n");
182         }
183 #endif
184 #if defined(CONFIG_S390)
185         {
186                 unsigned long caller;
187 
188                 caller = (unsigned long)__builtin_return_address(0);
189                 disabled_wait(caller);
190         }
191 #endif
192         pr_emerg("---[ end Kernel panic - not syncing: %s\n", buf);
193         local_irq_enable();
194         for (i = 0; ; i += PANIC_TIMER_STEP) {
195                 touch_softlockup_watchdog();
196                 if (i >= i_next) {
197                         i += panic_blink(state ^= 1);
198                         i_next = i + 3600 / PANIC_BLINK_SPD;
199                 }
200                 mdelay(PANIC_TIMER_STEP);
201         }
202 }
203 
204 EXPORT_SYMBOL(panic);
205 
206 
207 struct tnt {
208         u8      bit;
209         char    true;
210         char    false;
211 };
212 
213 static const struct tnt tnts[] = {
214         { TAINT_PROPRIETARY_MODULE,     'P', 'G' },
215         { TAINT_FORCED_MODULE,          'F', ' ' },
216         { TAINT_CPU_OUT_OF_SPEC,        'S', ' ' },
217         { TAINT_FORCED_RMMOD,           'R', ' ' },
218         { TAINT_MACHINE_CHECK,          'M', ' ' },
219         { TAINT_BAD_PAGE,               'B', ' ' },
220         { TAINT_USER,                   'U', ' ' },
221         { TAINT_DIE,                    'D', ' ' },
222         { TAINT_OVERRIDDEN_ACPI_TABLE,  'A', ' ' },
223         { TAINT_WARN,                   'W', ' ' },
224         { TAINT_CRAP,                   'C', ' ' },
225         { TAINT_FIRMWARE_WORKAROUND,    'I', ' ' },
226         { TAINT_OOT_MODULE,             'O', ' ' },
227         { TAINT_UNSIGNED_MODULE,        'E', ' ' },
228         { TAINT_SOFTLOCKUP,             'L', ' ' },
229         { TAINT_LIVEPATCH,              'K', ' ' },
230 };
231 
232 /**
233  *      print_tainted - return a string to represent the kernel taint state.
234  *
235  *  'P' - Proprietary module has been loaded.
236  *  'F' - Module has been forcibly loaded.
237  *  'S' - SMP with CPUs not designed for SMP.
238  *  'R' - User forced a module unload.
239  *  'M' - System experienced a machine check exception.
240  *  'B' - System has hit bad_page.
241  *  'U' - Userspace-defined naughtiness.
242  *  'D' - Kernel has oopsed before
243  *  'A' - ACPI table overridden.
244  *  'W' - Taint on warning.
245  *  'C' - modules from drivers/staging are loaded.
246  *  'I' - Working around severe firmware bug.
247  *  'O' - Out-of-tree module has been loaded.
248  *  'E' - Unsigned module has been loaded.
249  *  'L' - A soft lockup has previously occurred.
250  *  'K' - Kernel has been live patched.
251  *
252  *      The string is overwritten by the next call to print_tainted().
253  */
254 const char *print_tainted(void)
255 {
256         static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ")];
257 
258         if (tainted_mask) {
259                 char *s;
260                 int i;
261 
262                 s = buf + sprintf(buf, "Tainted: ");
263                 for (i = 0; i < ARRAY_SIZE(tnts); i++) {
264                         const struct tnt *t = &tnts[i];
265                         *s++ = test_bit(t->bit, &tainted_mask) ?
266                                         t->true : t->false;
267                 }
268                 *s = 0;
269         } else
270                 snprintf(buf, sizeof(buf), "Not tainted");
271 
272         return buf;
273 }
274 
275 int test_taint(unsigned flag)
276 {
277         return test_bit(flag, &tainted_mask);
278 }
279 EXPORT_SYMBOL(test_taint);
280 
281 unsigned long get_taint(void)
282 {
283         return tainted_mask;
284 }
285 
286 /**
287  * add_taint: add a taint flag if not already set.
288  * @flag: one of the TAINT_* constants.
289  * @lockdep_ok: whether lock debugging is still OK.
290  *
291  * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
292  * some notewortht-but-not-corrupting cases, it can be set to true.
293  */
294 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
295 {
296         if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
297                 pr_warn("Disabling lock debugging due to kernel taint\n");
298 
299         set_bit(flag, &tainted_mask);
300 }
301 EXPORT_SYMBOL(add_taint);
302 
303 static void spin_msec(int msecs)
304 {
305         int i;
306 
307         for (i = 0; i < msecs; i++) {
308                 touch_nmi_watchdog();
309                 mdelay(1);
310         }
311 }
312 
313 /*
314  * It just happens that oops_enter() and oops_exit() are identically
315  * implemented...
316  */
317 static void do_oops_enter_exit(void)
318 {
319         unsigned long flags;
320         static int spin_counter;
321 
322         if (!pause_on_oops)
323                 return;
324 
325         spin_lock_irqsave(&pause_on_oops_lock, flags);
326         if (pause_on_oops_flag == 0) {
327                 /* This CPU may now print the oops message */
328                 pause_on_oops_flag = 1;
329         } else {
330                 /* We need to stall this CPU */
331                 if (!spin_counter) {
332                         /* This CPU gets to do the counting */
333                         spin_counter = pause_on_oops;
334                         do {
335                                 spin_unlock(&pause_on_oops_lock);
336                                 spin_msec(MSEC_PER_SEC);
337                                 spin_lock(&pause_on_oops_lock);
338                         } while (--spin_counter);
339                         pause_on_oops_flag = 0;
340                 } else {
341                         /* This CPU waits for a different one */
342                         while (spin_counter) {
343                                 spin_unlock(&pause_on_oops_lock);
344                                 spin_msec(1);
345                                 spin_lock(&pause_on_oops_lock);
346                         }
347                 }
348         }
349         spin_unlock_irqrestore(&pause_on_oops_lock, flags);
350 }
351 
352 /*
353  * Return true if the calling CPU is allowed to print oops-related info.
354  * This is a bit racy..
355  */
356 int oops_may_print(void)
357 {
358         return pause_on_oops_flag == 0;
359 }
360 
361 /*
362  * Called when the architecture enters its oops handler, before it prints
363  * anything.  If this is the first CPU to oops, and it's oopsing the first
364  * time then let it proceed.
365  *
366  * This is all enabled by the pause_on_oops kernel boot option.  We do all
367  * this to ensure that oopses don't scroll off the screen.  It has the
368  * side-effect of preventing later-oopsing CPUs from mucking up the display,
369  * too.
370  *
371  * It turns out that the CPU which is allowed to print ends up pausing for
372  * the right duration, whereas all the other CPUs pause for twice as long:
373  * once in oops_enter(), once in oops_exit().
374  */
375 void oops_enter(void)
376 {
377         tracing_off();
378         /* can't trust the integrity of the kernel anymore: */
379         debug_locks_off();
380         do_oops_enter_exit();
381 }
382 
383 /*
384  * 64-bit random ID for oopses:
385  */
386 static u64 oops_id;
387 
388 static int init_oops_id(void)
389 {
390         if (!oops_id)
391                 get_random_bytes(&oops_id, sizeof(oops_id));
392         else
393                 oops_id++;
394 
395         return 0;
396 }
397 late_initcall(init_oops_id);
398 
399 void print_oops_end_marker(void)
400 {
401         init_oops_id();
402         pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id);
403 }
404 
405 /*
406  * Called when the architecture exits its oops handler, after printing
407  * everything.
408  */
409 void oops_exit(void)
410 {
411         do_oops_enter_exit();
412         print_oops_end_marker();
413         kmsg_dump(KMSG_DUMP_OOPS);
414 }
415 
416 #ifdef WANT_WARN_ON_SLOWPATH
417 struct slowpath_args {
418         const char *fmt;
419         va_list args;
420 };
421 
422 static void warn_slowpath_common(const char *file, int line, void *caller,
423                                  unsigned taint, struct slowpath_args *args)
424 {
425         disable_trace_on_warning();
426 
427         pr_warn("------------[ cut here ]------------\n");
428         pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS()\n",
429                 raw_smp_processor_id(), current->pid, file, line, caller);
430 
431         if (args)
432                 vprintk(args->fmt, args->args);
433 
434         if (panic_on_warn) {
435                 /*
436                  * This thread may hit another WARN() in the panic path.
437                  * Resetting this prevents additional WARN() from panicking the
438                  * system on this thread.  Other threads are blocked by the
439                  * panic_mutex in panic().
440                  */
441                 panic_on_warn = 0;
442                 panic("panic_on_warn set ...\n");
443         }
444 
445         print_modules();
446         dump_stack();
447         print_oops_end_marker();
448         /* Just a warning, don't kill lockdep. */
449         add_taint(taint, LOCKDEP_STILL_OK);
450 }
451 
452 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
453 {
454         struct slowpath_args args;
455 
456         args.fmt = fmt;
457         va_start(args.args, fmt);
458         warn_slowpath_common(file, line, __builtin_return_address(0),
459                              TAINT_WARN, &args);
460         va_end(args.args);
461 }
462 EXPORT_SYMBOL(warn_slowpath_fmt);
463 
464 void warn_slowpath_fmt_taint(const char *file, int line,
465                              unsigned taint, const char *fmt, ...)
466 {
467         struct slowpath_args args;
468 
469         args.fmt = fmt;
470         va_start(args.args, fmt);
471         warn_slowpath_common(file, line, __builtin_return_address(0),
472                              taint, &args);
473         va_end(args.args);
474 }
475 EXPORT_SYMBOL(warn_slowpath_fmt_taint);
476 
477 void warn_slowpath_null(const char *file, int line)
478 {
479         warn_slowpath_common(file, line, __builtin_return_address(0),
480                              TAINT_WARN, NULL);
481 }
482 EXPORT_SYMBOL(warn_slowpath_null);
483 #endif
484 
485 #ifdef CONFIG_CC_STACKPROTECTOR
486 
487 /*
488  * Called when gcc's -fstack-protector feature is used, and
489  * gcc detects corruption of the on-stack canary value
490  */
491 __visible void __stack_chk_fail(void)
492 {
493         panic("stack-protector: Kernel stack is corrupted in: %p\n",
494                 __builtin_return_address(0));
495 }
496 EXPORT_SYMBOL(__stack_chk_fail);
497 
498 #endif
499 
500 core_param(panic, panic_timeout, int, 0644);
501 core_param(pause_on_oops, pause_on_oops, int, 0644);
502 core_param(panic_on_warn, panic_on_warn, int, 0644);
503 
504 static int __init setup_crash_kexec_post_notifiers(char *s)
505 {
506         crash_kexec_post_notifiers = true;
507         return 0;
508 }
509 early_param("crash_kexec_post_notifiers", setup_crash_kexec_post_notifiers);
510 
511 static int __init oops_setup(char *s)
512 {
513         if (!s)
514                 return -EINVAL;
515         if (!strcmp(s, "panic"))
516                 panic_on_oops = 1;
517         return 0;
518 }
519 early_param("oops", oops_setup);
520 

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