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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/sched/debug.h>
 13 #include <linux/interrupt.h>
 14 #include <linux/kmsg_dump.h>
 15 #include <linux/kallsyms.h>
 16 #include <linux/notifier.h>
 17 #include <linux/vt_kern.h>
 18 #include <linux/module.h>
 19 #include <linux/random.h>
 20 #include <linux/ftrace.h>
 21 #include <linux/reboot.h>
 22 #include <linux/delay.h>
 23 #include <linux/kexec.h>
 24 #include <linux/sched.h>
 25 #include <linux/sysrq.h>
 26 #include <linux/init.h>
 27 #include <linux/nmi.h>
 28 #include <linux/console.h>
 29 #include <linux/bug.h>
 30 #include <linux/ratelimit.h>
 31 #include <linux/debugfs.h>
 32 #include <asm/sections.h>
 33 
 34 #define PANIC_TIMER_STEP 100
 35 #define PANIC_BLINK_SPD 18
 36 
 37 int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
 38 static unsigned long tainted_mask =
 39         IS_ENABLED(CONFIG_GCC_PLUGIN_RANDSTRUCT) ? (1 << TAINT_RANDSTRUCT) : 0;
 40 static int pause_on_oops;
 41 static int pause_on_oops_flag;
 42 static DEFINE_SPINLOCK(pause_on_oops_lock);
 43 bool crash_kexec_post_notifiers;
 44 int panic_on_warn __read_mostly;
 45 
 46 int panic_timeout = CONFIG_PANIC_TIMEOUT;
 47 EXPORT_SYMBOL_GPL(panic_timeout);
 48 
 49 #define PANIC_PRINT_TASK_INFO           0x00000001
 50 #define PANIC_PRINT_MEM_INFO            0x00000002
 51 #define PANIC_PRINT_TIMER_INFO          0x00000004
 52 #define PANIC_PRINT_LOCK_INFO           0x00000008
 53 #define PANIC_PRINT_FTRACE_INFO         0x00000010
 54 unsigned long panic_print;
 55 
 56 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
 57 
 58 EXPORT_SYMBOL(panic_notifier_list);
 59 
 60 static long no_blink(int state)
 61 {
 62         return 0;
 63 }
 64 
 65 /* Returns how long it waited in ms */
 66 long (*panic_blink)(int state);
 67 EXPORT_SYMBOL(panic_blink);
 68 
 69 /*
 70  * Stop ourself in panic -- architecture code may override this
 71  */
 72 void __weak panic_smp_self_stop(void)
 73 {
 74         while (1)
 75                 cpu_relax();
 76 }
 77 
 78 /*
 79  * Stop ourselves in NMI context if another CPU has already panicked. Arch code
 80  * may override this to prepare for crash dumping, e.g. save regs info.
 81  */
 82 void __weak nmi_panic_self_stop(struct pt_regs *regs)
 83 {
 84         panic_smp_self_stop();
 85 }
 86 
 87 /*
 88  * Stop other CPUs in panic.  Architecture dependent code may override this
 89  * with more suitable version.  For example, if the architecture supports
 90  * crash dump, it should save registers of each stopped CPU and disable
 91  * per-CPU features such as virtualization extensions.
 92  */
 93 void __weak crash_smp_send_stop(void)
 94 {
 95         static int cpus_stopped;
 96 
 97         /*
 98          * This function can be called twice in panic path, but obviously
 99          * we execute this only once.
100          */
101         if (cpus_stopped)
102                 return;
103 
104         /*
105          * Note smp_send_stop is the usual smp shutdown function, which
106          * unfortunately means it may not be hardened to work in a panic
107          * situation.
108          */
109         smp_send_stop();
110         cpus_stopped = 1;
111 }
112 
113 atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);
114 
115 /*
116  * A variant of panic() called from NMI context. We return if we've already
117  * panicked on this CPU. If another CPU already panicked, loop in
118  * nmi_panic_self_stop() which can provide architecture dependent code such
119  * as saving register state for crash dump.
120  */
121 void nmi_panic(struct pt_regs *regs, const char *msg)
122 {
123         int old_cpu, cpu;
124 
125         cpu = raw_smp_processor_id();
126         old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu);
127 
128         if (old_cpu == PANIC_CPU_INVALID)
129                 panic("%s", msg);
130         else if (old_cpu != cpu)
131                 nmi_panic_self_stop(regs);
132 }
133 EXPORT_SYMBOL(nmi_panic);
134 
135 static void panic_print_sys_info(void)
136 {
137         if (panic_print & PANIC_PRINT_TASK_INFO)
138                 show_state();
139 
140         if (panic_print & PANIC_PRINT_MEM_INFO)
141                 show_mem(0, NULL);
142 
143         if (panic_print & PANIC_PRINT_TIMER_INFO)
144                 sysrq_timer_list_show();
145 
146         if (panic_print & PANIC_PRINT_LOCK_INFO)
147                 debug_show_all_locks();
148 
149         if (panic_print & PANIC_PRINT_FTRACE_INFO)
150                 ftrace_dump(DUMP_ALL);
151 }
152 
153 /**
154  *      panic - halt the system
155  *      @fmt: The text string to print
156  *
157  *      Display a message, then perform cleanups.
158  *
159  *      This function never returns.
160  */
161 void panic(const char *fmt, ...)
162 {
163         static char buf[1024];
164         va_list args;
165         long i, i_next = 0, len;
166         int state = 0;
167         int old_cpu, this_cpu;
168         bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;
169 
170         /*
171          * Disable local interrupts. This will prevent panic_smp_self_stop
172          * from deadlocking the first cpu that invokes the panic, since
173          * there is nothing to prevent an interrupt handler (that runs
174          * after setting panic_cpu) from invoking panic() again.
175          */
176         local_irq_disable();
177 
178         /*
179          * It's possible to come here directly from a panic-assertion and
180          * not have preempt disabled. Some functions called from here want
181          * preempt to be disabled. No point enabling it later though...
182          *
183          * Only one CPU is allowed to execute the panic code from here. For
184          * multiple parallel invocations of panic, all other CPUs either
185          * stop themself or will wait until they are stopped by the 1st CPU
186          * with smp_send_stop().
187          *
188          * `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which
189          * comes here, so go ahead.
190          * `old_cpu == this_cpu' means we came from nmi_panic() which sets
191          * panic_cpu to this CPU.  In this case, this is also the 1st CPU.
192          */
193         this_cpu = raw_smp_processor_id();
194         old_cpu  = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
195 
196         if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)
197                 panic_smp_self_stop();
198 
199         console_verbose();
200         bust_spinlocks(1);
201         va_start(args, fmt);
202         len = vscnprintf(buf, sizeof(buf), fmt, args);
203         va_end(args);
204 
205         if (len && buf[len - 1] == '\n')
206                 buf[len - 1] = '\0';
207 
208         pr_emerg("Kernel panic - not syncing: %s\n", buf);
209 #ifdef CONFIG_DEBUG_BUGVERBOSE
210         /*
211          * Avoid nested stack-dumping if a panic occurs during oops processing
212          */
213         if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
214                 dump_stack();
215 #endif
216 
217         /*
218          * If we have crashed and we have a crash kernel loaded let it handle
219          * everything else.
220          * If we want to run this after calling panic_notifiers, pass
221          * the "crash_kexec_post_notifiers" option to the kernel.
222          *
223          * Bypass the panic_cpu check and call __crash_kexec directly.
224          */
225         if (!_crash_kexec_post_notifiers) {
226                 printk_safe_flush_on_panic();
227                 __crash_kexec(NULL);
228 
229                 /*
230                  * Note smp_send_stop is the usual smp shutdown function, which
231                  * unfortunately means it may not be hardened to work in a
232                  * panic situation.
233                  */
234                 smp_send_stop();
235         } else {
236                 /*
237                  * If we want to do crash dump after notifier calls and
238                  * kmsg_dump, we will need architecture dependent extra
239                  * works in addition to stopping other CPUs.
240                  */
241                 crash_smp_send_stop();
242         }
243 
244         /*
245          * Run any panic handlers, including those that might need to
246          * add information to the kmsg dump output.
247          */
248         atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
249 
250         /* Call flush even twice. It tries harder with a single online CPU */
251         printk_safe_flush_on_panic();
252         kmsg_dump(KMSG_DUMP_PANIC);
253 
254         /*
255          * If you doubt kdump always works fine in any situation,
256          * "crash_kexec_post_notifiers" offers you a chance to run
257          * panic_notifiers and dumping kmsg before kdump.
258          * Note: since some panic_notifiers can make crashed kernel
259          * more unstable, it can increase risks of the kdump failure too.
260          *
261          * Bypass the panic_cpu check and call __crash_kexec directly.
262          */
263         if (_crash_kexec_post_notifiers)
264                 __crash_kexec(NULL);
265 
266 #ifdef CONFIG_VT
267         unblank_screen();
268 #endif
269         console_unblank();
270 
271         /*
272          * We may have ended up stopping the CPU holding the lock (in
273          * smp_send_stop()) while still having some valuable data in the console
274          * buffer.  Try to acquire the lock then release it regardless of the
275          * result.  The release will also print the buffers out.  Locks debug
276          * should be disabled to avoid reporting bad unlock balance when
277          * panic() is not being callled from OOPS.
278          */
279         debug_locks_off();
280         console_flush_on_panic();
281 
282         panic_print_sys_info();
283 
284         if (!panic_blink)
285                 panic_blink = no_blink;
286 
287         if (panic_timeout > 0) {
288                 /*
289                  * Delay timeout seconds before rebooting the machine.
290                  * We can't use the "normal" timers since we just panicked.
291                  */
292                 pr_emerg("Rebooting in %d seconds..\n", panic_timeout);
293 
294                 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
295                         touch_nmi_watchdog();
296                         if (i >= i_next) {
297                                 i += panic_blink(state ^= 1);
298                                 i_next = i + 3600 / PANIC_BLINK_SPD;
299                         }
300                         mdelay(PANIC_TIMER_STEP);
301                 }
302         }
303         if (panic_timeout != 0) {
304                 /*
305                  * This will not be a clean reboot, with everything
306                  * shutting down.  But if there is a chance of
307                  * rebooting the system it will be rebooted.
308                  */
309                 emergency_restart();
310         }
311 #ifdef __sparc__
312         {
313                 extern int stop_a_enabled;
314                 /* Make sure the user can actually press Stop-A (L1-A) */
315                 stop_a_enabled = 1;
316                 pr_emerg("Press Stop-A (L1-A) from sun keyboard or send break\n"
317                          "twice on console to return to the boot prom\n");
318         }
319 #endif
320 #if defined(CONFIG_S390)
321         {
322                 unsigned long caller;
323 
324                 caller = (unsigned long)__builtin_return_address(0);
325                 disabled_wait(caller);
326         }
327 #endif
328         pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
329         local_irq_enable();
330         for (i = 0; ; i += PANIC_TIMER_STEP) {
331                 touch_softlockup_watchdog();
332                 if (i >= i_next) {
333                         i += panic_blink(state ^= 1);
334                         i_next = i + 3600 / PANIC_BLINK_SPD;
335                 }
336                 mdelay(PANIC_TIMER_STEP);
337         }
338 }
339 
340 EXPORT_SYMBOL(panic);
341 
342 /*
343  * TAINT_FORCED_RMMOD could be a per-module flag but the module
344  * is being removed anyway.
345  */
346 const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
347         [ TAINT_PROPRIETARY_MODULE ]    = { 'P', 'G', true },
348         [ TAINT_FORCED_MODULE ]         = { 'F', ' ', true },
349         [ TAINT_CPU_OUT_OF_SPEC ]       = { 'S', ' ', false },
350         [ TAINT_FORCED_RMMOD ]          = { 'R', ' ', false },
351         [ TAINT_MACHINE_CHECK ]         = { 'M', ' ', false },
352         [ TAINT_BAD_PAGE ]              = { 'B', ' ', false },
353         [ TAINT_USER ]                  = { 'U', ' ', false },
354         [ TAINT_DIE ]                   = { 'D', ' ', false },
355         [ TAINT_OVERRIDDEN_ACPI_TABLE ] = { 'A', ' ', false },
356         [ TAINT_WARN ]                  = { 'W', ' ', false },
357         [ TAINT_CRAP ]                  = { 'C', ' ', true },
358         [ TAINT_FIRMWARE_WORKAROUND ]   = { 'I', ' ', false },
359         [ TAINT_OOT_MODULE ]            = { 'O', ' ', true },
360         [ TAINT_UNSIGNED_MODULE ]       = { 'E', ' ', true },
361         [ TAINT_SOFTLOCKUP ]            = { 'L', ' ', false },
362         [ TAINT_LIVEPATCH ]             = { 'K', ' ', true },
363         [ TAINT_AUX ]                   = { 'X', ' ', true },
364         [ TAINT_RANDSTRUCT ]            = { 'T', ' ', true },
365 };
366 
367 /**
368  * print_tainted - return a string to represent the kernel taint state.
369  *
370  * For individual taint flag meanings, see Documentation/sysctl/kernel.txt
371  *
372  * The string is overwritten by the next call to print_tainted(),
373  * but is always NULL terminated.
374  */
375 const char *print_tainted(void)
376 {
377         static char buf[TAINT_FLAGS_COUNT + sizeof("Tainted: ")];
378 
379         BUILD_BUG_ON(ARRAY_SIZE(taint_flags) != TAINT_FLAGS_COUNT);
380 
381         if (tainted_mask) {
382                 char *s;
383                 int i;
384 
385                 s = buf + sprintf(buf, "Tainted: ");
386                 for (i = 0; i < TAINT_FLAGS_COUNT; i++) {
387                         const struct taint_flag *t = &taint_flags[i];
388                         *s++ = test_bit(i, &tainted_mask) ?
389                                         t->c_true : t->c_false;
390                 }
391                 *s = 0;
392         } else
393                 snprintf(buf, sizeof(buf), "Not tainted");
394 
395         return buf;
396 }
397 
398 int test_taint(unsigned flag)
399 {
400         return test_bit(flag, &tainted_mask);
401 }
402 EXPORT_SYMBOL(test_taint);
403 
404 unsigned long get_taint(void)
405 {
406         return tainted_mask;
407 }
408 
409 /**
410  * add_taint: add a taint flag if not already set.
411  * @flag: one of the TAINT_* constants.
412  * @lockdep_ok: whether lock debugging is still OK.
413  *
414  * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
415  * some notewortht-but-not-corrupting cases, it can be set to true.
416  */
417 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
418 {
419         if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
420                 pr_warn("Disabling lock debugging due to kernel taint\n");
421 
422         set_bit(flag, &tainted_mask);
423 }
424 EXPORT_SYMBOL(add_taint);
425 
426 static void spin_msec(int msecs)
427 {
428         int i;
429 
430         for (i = 0; i < msecs; i++) {
431                 touch_nmi_watchdog();
432                 mdelay(1);
433         }
434 }
435 
436 /*
437  * It just happens that oops_enter() and oops_exit() are identically
438  * implemented...
439  */
440 static void do_oops_enter_exit(void)
441 {
442         unsigned long flags;
443         static int spin_counter;
444 
445         if (!pause_on_oops)
446                 return;
447 
448         spin_lock_irqsave(&pause_on_oops_lock, flags);
449         if (pause_on_oops_flag == 0) {
450                 /* This CPU may now print the oops message */
451                 pause_on_oops_flag = 1;
452         } else {
453                 /* We need to stall this CPU */
454                 if (!spin_counter) {
455                         /* This CPU gets to do the counting */
456                         spin_counter = pause_on_oops;
457                         do {
458                                 spin_unlock(&pause_on_oops_lock);
459                                 spin_msec(MSEC_PER_SEC);
460                                 spin_lock(&pause_on_oops_lock);
461                         } while (--spin_counter);
462                         pause_on_oops_flag = 0;
463                 } else {
464                         /* This CPU waits for a different one */
465                         while (spin_counter) {
466                                 spin_unlock(&pause_on_oops_lock);
467                                 spin_msec(1);
468                                 spin_lock(&pause_on_oops_lock);
469                         }
470                 }
471         }
472         spin_unlock_irqrestore(&pause_on_oops_lock, flags);
473 }
474 
475 /*
476  * Return true if the calling CPU is allowed to print oops-related info.
477  * This is a bit racy..
478  */
479 int oops_may_print(void)
480 {
481         return pause_on_oops_flag == 0;
482 }
483 
484 /*
485  * Called when the architecture enters its oops handler, before it prints
486  * anything.  If this is the first CPU to oops, and it's oopsing the first
487  * time then let it proceed.
488  *
489  * This is all enabled by the pause_on_oops kernel boot option.  We do all
490  * this to ensure that oopses don't scroll off the screen.  It has the
491  * side-effect of preventing later-oopsing CPUs from mucking up the display,
492  * too.
493  *
494  * It turns out that the CPU which is allowed to print ends up pausing for
495  * the right duration, whereas all the other CPUs pause for twice as long:
496  * once in oops_enter(), once in oops_exit().
497  */
498 void oops_enter(void)
499 {
500         tracing_off();
501         /* can't trust the integrity of the kernel anymore: */
502         debug_locks_off();
503         do_oops_enter_exit();
504 }
505 
506 /*
507  * 64-bit random ID for oopses:
508  */
509 static u64 oops_id;
510 
511 static int init_oops_id(void)
512 {
513         if (!oops_id)
514                 get_random_bytes(&oops_id, sizeof(oops_id));
515         else
516                 oops_id++;
517 
518         return 0;
519 }
520 late_initcall(init_oops_id);
521 
522 void print_oops_end_marker(void)
523 {
524         init_oops_id();
525         pr_warn("---[ end trace %016llx ]---\n", (unsigned long long)oops_id);
526 }
527 
528 /*
529  * Called when the architecture exits its oops handler, after printing
530  * everything.
531  */
532 void oops_exit(void)
533 {
534         do_oops_enter_exit();
535         print_oops_end_marker();
536         kmsg_dump(KMSG_DUMP_OOPS);
537 }
538 
539 struct warn_args {
540         const char *fmt;
541         va_list args;
542 };
543 
544 void __warn(const char *file, int line, void *caller, unsigned taint,
545             struct pt_regs *regs, struct warn_args *args)
546 {
547         disable_trace_on_warning();
548 
549         if (args)
550                 pr_warn(CUT_HERE);
551 
552         if (file)
553                 pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS\n",
554                         raw_smp_processor_id(), current->pid, file, line,
555                         caller);
556         else
557                 pr_warn("WARNING: CPU: %d PID: %d at %pS\n",
558                         raw_smp_processor_id(), current->pid, caller);
559 
560         if (args)
561                 vprintk(args->fmt, args->args);
562 
563         if (panic_on_warn) {
564                 /*
565                  * This thread may hit another WARN() in the panic path.
566                  * Resetting this prevents additional WARN() from panicking the
567                  * system on this thread.  Other threads are blocked by the
568                  * panic_mutex in panic().
569                  */
570                 panic_on_warn = 0;
571                 panic("panic_on_warn set ...\n");
572         }
573 
574         print_modules();
575 
576         if (regs)
577                 show_regs(regs);
578         else
579                 dump_stack();
580 
581         print_irqtrace_events(current);
582 
583         print_oops_end_marker();
584 
585         /* Just a warning, don't kill lockdep. */
586         add_taint(taint, LOCKDEP_STILL_OK);
587 }
588 
589 #ifdef WANT_WARN_ON_SLOWPATH
590 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
591 {
592         struct warn_args args;
593 
594         args.fmt = fmt;
595         va_start(args.args, fmt);
596         __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL,
597                &args);
598         va_end(args.args);
599 }
600 EXPORT_SYMBOL(warn_slowpath_fmt);
601 
602 void warn_slowpath_fmt_taint(const char *file, int line,
603                              unsigned taint, const char *fmt, ...)
604 {
605         struct warn_args args;
606 
607         args.fmt = fmt;
608         va_start(args.args, fmt);
609         __warn(file, line, __builtin_return_address(0), taint, NULL, &args);
610         va_end(args.args);
611 }
612 EXPORT_SYMBOL(warn_slowpath_fmt_taint);
613 
614 void warn_slowpath_null(const char *file, int line)
615 {
616         pr_warn(CUT_HERE);
617         __warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, NULL);
618 }
619 EXPORT_SYMBOL(warn_slowpath_null);
620 #else
621 void __warn_printk(const char *fmt, ...)
622 {
623         va_list args;
624 
625         pr_warn(CUT_HERE);
626 
627         va_start(args, fmt);
628         vprintk(fmt, args);
629         va_end(args);
630 }
631 EXPORT_SYMBOL(__warn_printk);
632 #endif
633 
634 #ifdef CONFIG_BUG
635 
636 /* Support resetting WARN*_ONCE state */
637 
638 static int clear_warn_once_set(void *data, u64 val)
639 {
640         generic_bug_clear_once();
641         memset(__start_once, 0, __end_once - __start_once);
642         return 0;
643 }
644 
645 DEFINE_DEBUGFS_ATTRIBUTE(clear_warn_once_fops, NULL, clear_warn_once_set,
646                          "%lld\n");
647 
648 static __init int register_warn_debugfs(void)
649 {
650         /* Don't care about failure */
651         debugfs_create_file_unsafe("clear_warn_once", 0200, NULL, NULL,
652                                    &clear_warn_once_fops);
653         return 0;
654 }
655 
656 device_initcall(register_warn_debugfs);
657 #endif
658 
659 #ifdef CONFIG_STACKPROTECTOR
660 
661 /*
662  * Called when gcc's -fstack-protector feature is used, and
663  * gcc detects corruption of the on-stack canary value
664  */
665 __visible void __stack_chk_fail(void)
666 {
667         panic("stack-protector: Kernel stack is corrupted in: %pB",
668                 __builtin_return_address(0));
669 }
670 EXPORT_SYMBOL(__stack_chk_fail);
671 
672 #endif
673 
674 #ifdef CONFIG_ARCH_HAS_REFCOUNT
675 void refcount_error_report(struct pt_regs *regs, const char *err)
676 {
677         WARN_RATELIMIT(1, "refcount_t %s at %pB in %s[%d], uid/euid: %u/%u\n",
678                 err, (void *)instruction_pointer(regs),
679                 current->comm, task_pid_nr(current),
680                 from_kuid_munged(&init_user_ns, current_uid()),
681                 from_kuid_munged(&init_user_ns, current_euid()));
682 }
683 #endif
684 
685 core_param(panic, panic_timeout, int, 0644);
686 core_param(panic_print, panic_print, ulong, 0644);
687 core_param(pause_on_oops, pause_on_oops, int, 0644);
688 core_param(panic_on_warn, panic_on_warn, int, 0644);
689 core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 0644);
690 
691 static int __init oops_setup(char *s)
692 {
693         if (!s)
694                 return -EINVAL;
695         if (!strcmp(s, "panic"))
696                 panic_on_oops = 1;
697         return 0;
698 }
699 early_param("oops", oops_setup);
700 

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