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
  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);