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/reboot.h>
  19 #include <linux/delay.h>
  20 #include <linux/kexec.h>
  21 #include <linux/sched.h>
  22 #include <linux/sysrq.h>
  23 #include <linux/init.h>
  24 #include <linux/nmi.h>
  25
  26 #define PANIC_TIMER_STEP 100
  27 #define PANIC_BLINK_SPD 18
  28
  29 int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;
  30 static unsigned long tainted_mask;
  31 static int pause_on_oops;
  32 static int pause_on_oops_flag;
  33 static DEFINE_SPINLOCK(pause_on_oops_lock);
  34
  35 int panic_timeout;
  36 EXPORT_SYMBOL_GPL(panic_timeout);
  37
  38 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
  39
  40 EXPORT_SYMBOL(panic_notifier_list);
  41
  42 static long no_blink(int state)
  43 {
  44         return 0;
  45 }
  46
  47 /* Returns how long it waited in ms */
  48 long (*panic_blink)(int state);
  49 EXPORT_SYMBOL(panic_blink);
  50
  51 /*
  52  * Stop ourself in panic -- architecture code may override this
  53  */
  54 void __weak panic_smp_self_stop(void)
  55 {
  56         while (1)
  57                 cpu_relax();
  58 }
  59
  60 /**
  61  *      panic - halt the system
  62  *      @fmt: The text string to print
  63  *
  64  *      Display a message, then perform cleanups.
  65  *
  66  *      This function never returns.
  67  */
  68 void panic(const char *fmt, ...)
  69 {
  70         static DEFINE_SPINLOCK(panic_lock);
  71         static char buf[1024];
  72         va_list args;
  73         long i, i_next = 0;
  74         int state = 0;
  75
  76         /*
  77          * Disable local interrupts. This will prevent panic_smp_self_stop
  78          * from deadlocking the first cpu that invokes the panic, since
  79          * there is nothing to prevent an interrupt handler (that runs
  80          * after the panic_lock is acquired) from invoking panic again.
  81          */
  82         local_irq_disable();
  83
  84         /*
  85          * It's possible to come here directly from a panic-assertion and
  86          * not have preempt disabled. Some functions called from here want
  87          * preempt to be disabled. No point enabling it later though...
  88          *
  89          * Only one CPU is allowed to execute the panic code from here. For
  90          * multiple parallel invocations of panic, all other CPUs either
  91          * stop themself or will wait until they are stopped by the 1st CPU
  92          * with smp_send_stop().
  93          */
  94         if (!spin_trylock(&panic_lock))
  95                 panic_smp_self_stop();
  96
  97         console_verbose();
  98         bust_spinlocks(1);
  99         va_start(args, fmt);
 100         vsnprintf(buf, sizeof(buf), fmt, args);
 101         va_end(args);
 102         printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
 103 #ifdef CONFIG_DEBUG_BUGVERBOSE
 104         /*
 105          * Avoid nested stack-dumping if a panic occurs during oops processing
 106          */
 107         if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)
 108                 dump_stack();
 109 #endif
 110
 111         /*
 112          * If we have crashed and we have a crash kernel loaded let it handle
 113          * everything else.
 114          * Do we want to call this before we try to display a message?
 115          */
 116         crash_kexec(NULL);
 117
 118         /*
 119          * Note smp_send_stop is the usual smp shutdown function, which
 120          * unfortunately means it may not be hardened to work in a panic
 121          * situation.
 122          */
 123         smp_send_stop();
 124
 125         kmsg_dump(KMSG_DUMP_PANIC);
 126
 127         atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
 128
 129         bust_spinlocks(0);
 130
 131         if (!panic_blink)
 132                 panic_blink = no_blink;
 133
 134         if (panic_timeout > 0) {
 135                 /*
 136                  * Delay timeout seconds before rebooting the machine.
 137                  * We can't use the "normal" timers since we just panicked.
 138                  */
 139                 printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
 140
 141                 for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
 142                         touch_nmi_watchdog();
 143                         if (i >= i_next) {
 144                                 i += panic_blink(state ^= 1);
 145                                 i_next = i + 3600 / PANIC_BLINK_SPD;
 146                         }
 147                         mdelay(PANIC_TIMER_STEP);
 148                 }
 149         }
 150         if (panic_timeout != 0) {
 151                 /*
 152                  * This will not be a clean reboot, with everything
 153                  * shutting down.  But if there is a chance of
 154                  * rebooting the system it will be rebooted.
 155                  */
 156                 emergency_restart();
 157         }
 158 #ifdef __sparc__
 159         {
 160                 extern int stop_a_enabled;
 161                 /* Make sure the user can actually press Stop-A (L1-A) */
 162                 stop_a_enabled = 1;
 163                 printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
 164         }
 165 #endif
 166 #if defined(CONFIG_S390)
 167         {
 168                 unsigned long caller;
 169
 170                 caller = (unsigned long)__builtin_return_address(0);
 171                 disabled_wait(caller);
 172         }
 173 #endif
 174         local_irq_enable();
 175         for (i = 0; ; i += PANIC_TIMER_STEP) {
 176                 touch_softlockup_watchdog();
 177                 if (i >= i_next) {
 178                         i += panic_blink(state ^= 1);
 179                         i_next = i + 3600 / PANIC_BLINK_SPD;
 180                 }
 181                 mdelay(PANIC_TIMER_STEP);
 182         }
 183 }
 184
 185 EXPORT_SYMBOL(panic);
 186
 187
 188 struct tnt {
 189         u8      bit;
 190         char    true;
 191         char    false;
 192 };
 193
 194 static const struct tnt tnts[] = {
 195         { TAINT_PROPRIETARY_MODULE,     'P', 'G' },
 196         { TAINT_FORCED_MODULE,          'F', ' ' },
 197         { TAINT_UNSAFE_SMP,             'S', ' ' },
 198         { TAINT_FORCED_RMMOD,           'R', ' ' },
 199         { TAINT_MACHINE_CHECK,          'M', ' ' },
 200         { TAINT_BAD_PAGE,               'B', ' ' },
 201         { TAINT_USER,                   'U', ' ' },
 202         { TAINT_DIE,                    'D', ' ' },
 203         { TAINT_OVERRIDDEN_ACPI_TABLE,  'A', ' ' },
 204         { TAINT_WARN,                   'W', ' ' },
 205         { TAINT_CRAP,                   'C', ' ' },
 206         { TAINT_FIRMWARE_WORKAROUND,    'I', ' ' },
 207         { TAINT_OOT_MODULE,             'O', ' ' },
 208 };
 209
 210 /**
 211  *      print_tainted - return a string to represent the kernel taint state.
 212  *
 213  *  'P' - Proprietary module has been loaded.
 214  *  'F' - Module has been forcibly loaded.
 215  *  'S' - SMP with CPUs not designed for SMP.
 216  *  'R' - User forced a module unload.
 217  *  'M' - System experienced a machine check exception.
 218  *  'B' - System has hit bad_page.
 219  *  'U' - Userspace-defined naughtiness.
 220  *  'D' - Kernel has oopsed before
 221  *  'A' - ACPI table overridden.
 222  *  'W' - Taint on warning.
 223  *  'C' - modules from drivers/staging are loaded.
 224  *  'I' - Working around severe firmware bug.
 225  *  'O' - Out-of-tree module has been loaded.
 226  *
 227  *      The string is overwritten by the next call to print_tainted().
 228  */
 229 const char *print_tainted(void)
 230 {
 231         static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
 232
 233         if (tainted_mask) {
 234                 char *s;
 235                 int i;
 236
 237                 s = buf + sprintf(buf, "Tainted: ");
 238                 for (i = 0; i < ARRAY_SIZE(tnts); i++) {
 239                         const struct tnt *t = &tnts[i];
 240                         *s++ = test_bit(t->bit, &tainted_mask) ?
 241                                         t->true : t->false;
 242                 }
 243                 *s = 0;
 244         } else
 245                 snprintf(buf, sizeof(buf), "Not tainted");
 246
 247         return buf;
 248 }
 249
 250 int test_taint(unsigned flag)
 251 {
 252         return test_bit(flag, &tainted_mask);
 253 }
 254 EXPORT_SYMBOL(test_taint);
 255
 256 unsigned long get_taint(void)
 257 {
 258         return tainted_mask;
 259 }
 260
 261 /**
 262  * add_taint: add a taint flag if not already set.
 263  * @flag: one of the TAINT_* constants.
 264  * @lockdep_ok: whether lock debugging is still OK.
 265  *
 266  * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
 267  * some notewortht-but-not-corrupting cases, it can be set to true.
 268  */
 269 void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)
 270 {
 271         if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())
 272                 printk(KERN_WARNING
 273                        "Disabling lock debugging due to kernel taint\n");
 274
 275         set_bit(flag, &tainted_mask);
 276 }
 277 EXPORT_SYMBOL(add_taint);
 278
 279 static void spin_msec(int msecs)
 280 {
 281         int i;
 282
 283         for (i = 0; i < msecs; i++) {
 284                 touch_nmi_watchdog();
 285                 mdelay(1);
 286         }
 287 }
 288
 289 /*
 290  * It just happens that oops_enter() and oops_exit() are identically
 291  * implemented...
 292  */
 293 static void do_oops_enter_exit(void)
 294 {
 295         unsigned long flags;
 296         static int spin_counter;
 297
 298         if (!pause_on_oops)
 299                 return;
 300
 301         spin_lock_irqsave(&pause_on_oops_lock, flags);
 302         if (pause_on_oops_flag == 0) {
 303                 /* This CPU may now print the oops message */
 304                 pause_on_oops_flag = 1;
 305         } else {
 306                 /* We need to stall this CPU */
 307                 if (!spin_counter) {
 308                         /* This CPU gets to do the counting */
 309                         spin_counter = pause_on_oops;
 310                         do {
 311                                 spin_unlock(&pause_on_oops_lock);
 312                                 spin_msec(MSEC_PER_SEC);
 313                                 spin_lock(&pause_on_oops_lock);
 314                         } while (--spin_counter);
 315                         pause_on_oops_flag = 0;
 316                 } else {
 317                         /* This CPU waits for a different one */
 318                         while (spin_counter) {
 319                                 spin_unlock(&pause_on_oops_lock);
 320                                 spin_msec(1);
 321                                 spin_lock(&pause_on_oops_lock);
 322                         }
 323                 }
 324         }
 325         spin_unlock_irqrestore(&pause_on_oops_lock, flags);
 326 }
 327
 328 /*
 329  * Return true if the calling CPU is allowed to print oops-related info.
 330  * This is a bit racy..
 331  */
 332 int oops_may_print(void)
 333 {
 334         return pause_on_oops_flag == 0;
 335 }
 336
 337 /*
 338  * Called when the architecture enters its oops handler, before it prints
 339  * anything.  If this is the first CPU to oops, and it's oopsing the first
 340  * time then let it proceed.
 341  *
 342  * This is all enabled by the pause_on_oops kernel boot option.  We do all
 343  * this to ensure that oopses don't scroll off the screen.  It has the
 344  * side-effect of preventing later-oopsing CPUs from mucking up the display,
 345  * too.
 346  *
 347  * It turns out that the CPU which is allowed to print ends up pausing for
 348  * the right duration, whereas all the other CPUs pause for twice as long:
 349  * once in oops_enter(), once in oops_exit().
 350  */
 351 void oops_enter(void)
 352 {
 353         tracing_off();
 354         /* can't trust the integrity of the kernel anymore: */
 355         debug_locks_off();
 356         do_oops_enter_exit();
 357 }
 358
 359 /*
 360  * 64-bit random ID for oopses:
 361  */
 362 static u64 oops_id;
 363
 364 static int init_oops_id(void)
 365 {
 366         if (!oops_id)
 367                 get_random_bytes(&oops_id, sizeof(oops_id));
 368         else
 369                 oops_id++;
 370
 371         return 0;
 372 }
 373 late_initcall(init_oops_id);
 374
 375 void print_oops_end_marker(void)
 376 {
 377         init_oops_id();
 378         printk(KERN_WARNING "---[ end trace %016llx ]---\n",
 379                 (unsigned long long)oops_id);
 380 }
 381
 382 /*
 383  * Called when the architecture exits its oops handler, after printing
 384  * everything.
 385  */
 386 void oops_exit(void)
 387 {
 388         do_oops_enter_exit();
 389         print_oops_end_marker();
 390         kmsg_dump(KMSG_DUMP_OOPS);
 391 }
 392
 393 #ifdef WANT_WARN_ON_SLOWPATH
 394 struct slowpath_args {
 395         const char *fmt;
 396         va_list args;
 397 };
 398
 399 static void warn_slowpath_common(const char *file, int line, void *caller,
 400                                  unsigned taint, struct slowpath_args *args)
 401 {
 402         printk(KERN_WARNING "------------[ cut here ]------------\n");
 403         printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
 404
 405         if (args)
 406                 vprintk(args->fmt, args->args);
 407
 408         print_modules();
 409         dump_stack();
 410         print_oops_end_marker();
 411         /* Just a warning, don't kill lockdep. */
 412         add_taint(taint, LOCKDEP_STILL_OK);
 413 }
 414
 415 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
 416 {
 417         struct slowpath_args args;
 418
 419         args.fmt = fmt;
 420         va_start(args.args, fmt);
 421         warn_slowpath_common(file, line, __builtin_return_address(0),
 422                              TAINT_WARN, &args);
 423         va_end(args.args);
 424 }
 425 EXPORT_SYMBOL(warn_slowpath_fmt);
 426
 427 void warn_slowpath_fmt_taint(const char *file, int line,
 428                              unsigned taint, const char *fmt, ...)
 429 {
 430         struct slowpath_args args;
 431
 432         args.fmt = fmt;
 433         va_start(args.args, fmt);
 434         warn_slowpath_common(file, line, __builtin_return_address(0),
 435                              taint, &args);
 436         va_end(args.args);
 437 }
 438 EXPORT_SYMBOL(warn_slowpath_fmt_taint);
 439
 440 void warn_slowpath_null(const char *file, int line)
 441 {
 442         warn_slowpath_common(file, line, __builtin_return_address(0),
 443                              TAINT_WARN, NULL);
 444 }
 445 EXPORT_SYMBOL(warn_slowpath_null);
 446 #endif
 447
 448 #ifdef CONFIG_CC_STACKPROTECTOR
 449
 450 /*
 451  * Called when gcc's -fstack-protector feature is used, and
 452  * gcc detects corruption of the on-stack canary value
 453  */
 454 void __stack_chk_fail(void)
 455 {
 456         panic("stack-protector: Kernel stack is corrupted in: %p\n",
 457                 __builtin_return_address(0));
 458 }
 459 EXPORT_SYMBOL(__stack_chk_fail);
 460
 461 #endif
 462
 463 core_param(panic, panic_timeout, int, 0644);
 464 core_param(pause_on_oops, pause_on_oops, int, 0644);
 465
 466 static int __init oops_setup(char *s)
 467 {
 468         if (!s)
 469                 return -EINVAL;
 470         if (!strcmp(s, "panic"))
 471                 panic_on_oops = 1;
 472         return 0;
 473 }
 474 early_param("oops", oops_setup);