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