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