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