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 #include <linux/dmi.h>
  26
  27 int panic_on_oops;
  28 static unsigned long tainted_mask;
  29 static int pause_on_oops;
  30 static int pause_on_oops_flag;
  31 static DEFINE_SPINLOCK(pause_on_oops_lock);
  32
  33 int panic_timeout;
  34
  35 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
  36
  37 EXPORT_SYMBOL(panic_notifier_list);
  38
  39 /* Returns how long it waited in ms */
  40 long (*panic_blink)(long time);
  41 EXPORT_SYMBOL(panic_blink);
  42
  43 static void panic_blink_one_second(void)
  44 {
  45         static long i = 0, end;
  46
  47         if (panic_blink) {
  48                 end = i + MSEC_PER_SEC;
  49
  50                 while (i < end) {
  51                         i += panic_blink(i);
  52                         mdelay(1);
  53                         i++;
  54                 }
  55         } else {
  56                 /*
  57                  * When running under a hypervisor a small mdelay may get
  58                  * rounded up to the hypervisor timeslice. For example, with
  59                  * a 1ms in 10ms hypervisor timeslice we might inflate a
  60                  * mdelay(1) loop by 10x.
  61                  *
  62                  * If we have nothing to blink, spin on 1 second calls to
  63                  * mdelay to avoid this.
  64                  */
  65                 mdelay(MSEC_PER_SEC);
  66         }
  67 }
  68
  69 /**
  70  *      panic - halt the system
  71  *      @fmt: The text string to print
  72  *
  73  *      Display a message, then perform cleanups.
  74  *
  75  *      This function never returns.
  76  */
  77 NORET_TYPE void panic(const char * fmt, ...)
  78 {
  79         static char buf[1024];
  80         va_list args;
  81         long i;
  82
  83         /*
  84          * It's possible to come here directly from a panic-assertion and
  85          * not have preempt disabled. Some functions called from here want
  86          * preempt to be disabled. No point enabling it later though...
  87          */
  88         preempt_disable();
  89
  90         bust_spinlocks(1);
  91         va_start(args, fmt);
  92         vsnprintf(buf, sizeof(buf), fmt, args);
  93         va_end(args);
  94         printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
  95 #ifdef CONFIG_DEBUG_BUGVERBOSE
  96         dump_stack();
  97 #endif
  98
  99         /*
 100          * If we have crashed and we have a crash kernel loaded let it handle
 101          * everything else.
 102          * Do we want to call this before we try to display a message?
 103          */
 104         crash_kexec(NULL);
 105
 106         kmsg_dump(KMSG_DUMP_PANIC);
 107
 108         /*
 109          * Note smp_send_stop is the usual smp shutdown function, which
 110          * unfortunately means it may not be hardened to work in a panic
 111          * situation.
 112          */
 113         smp_send_stop();
 114
 115         atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
 116
 117         bust_spinlocks(0);
 118
 119         if (panic_timeout > 0) {
 120                 /*
 121                  * Delay timeout seconds before rebooting the machine.
 122                  * We can't use the "normal" timers since we just panicked.
 123                  */
 124                 printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
 125
 126                 for (i = 0; i < panic_timeout; i++) {
 127                         touch_nmi_watchdog();
 128                         panic_blink_one_second();
 129                 }
 130                 /*
 131                  * This will not be a clean reboot, with everything
 132                  * shutting down.  But if there is a chance of
 133                  * rebooting the system it will be rebooted.
 134                  */
 135                 emergency_restart();
 136         }
 137 #ifdef __sparc__
 138         {
 139                 extern int stop_a_enabled;
 140                 /* Make sure the user can actually press Stop-A (L1-A) */
 141                 stop_a_enabled = 1;
 142                 printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
 143         }
 144 #endif
 145 #if defined(CONFIG_S390)
 146         {
 147                 unsigned long caller;
 148
 149                 caller = (unsigned long)__builtin_return_address(0);
 150                 disabled_wait(caller);
 151         }
 152 #endif
 153         local_irq_enable();
 154         while (1) {
 155                 touch_softlockup_watchdog();
 156                 panic_blink_one_second();
 157         }
 158 }
 159
 160 EXPORT_SYMBOL(panic);
 161
 162
 163 struct tnt {
 164         u8      bit;
 165         char    true;
 166         char    false;
 167 };
 168
 169 static const struct tnt tnts[] = {
 170         { TAINT_PROPRIETARY_MODULE,     'P', 'G' },
 171         { TAINT_FORCED_MODULE,          'F', ' ' },
 172         { TAINT_UNSAFE_SMP,             'S', ' ' },
 173         { TAINT_FORCED_RMMOD,           'R', ' ' },
 174         { TAINT_MACHINE_CHECK,          'M', ' ' },
 175         { TAINT_BAD_PAGE,               'B', ' ' },
 176         { TAINT_USER,                   'U', ' ' },
 177         { TAINT_DIE,                    'D', ' ' },
 178         { TAINT_OVERRIDDEN_ACPI_TABLE,  'A', ' ' },
 179         { TAINT_WARN,                   'W', ' ' },
 180         { TAINT_CRAP,                   'C', ' ' },
 181 };
 182
 183 /**
 184  *      print_tainted - return a string to represent the kernel taint state.
 185  *
 186  *  'P' - Proprietary module has been loaded.
 187  *  'F' - Module has been forcibly loaded.
 188  *  'S' - SMP with CPUs not designed for SMP.
 189  *  'R' - User forced a module unload.
 190  *  'M' - System experienced a machine check exception.
 191  *  'B' - System has hit bad_page.
 192  *  'U' - Userspace-defined naughtiness.
 193  *  'D' - Kernel has oopsed before
 194  *  'A' - ACPI table overridden.
 195  *  'W' - Taint on warning.
 196  *  'C' - modules from drivers/staging are loaded.
 197  *
 198  *      The string is overwritten by the next call to print_tainted().
 199  */
 200 const char *print_tainted(void)
 201 {
 202         static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
 203
 204         if (tainted_mask) {
 205                 char *s;
 206                 int i;
 207
 208                 s = buf + sprintf(buf, "Tainted: ");
 209                 for (i = 0; i < ARRAY_SIZE(tnts); i++) {
 210                         const struct tnt *t = &tnts[i];
 211                         *s++ = test_bit(t->bit, &tainted_mask) ?
 212                                         t->true : t->false;
 213                 }
 214                 *s = 0;
 215         } else
 216                 snprintf(buf, sizeof(buf), "Not tainted");
 217
 218         return buf;
 219 }
 220
 221 int test_taint(unsigned flag)
 222 {
 223         return test_bit(flag, &tainted_mask);
 224 }
 225 EXPORT_SYMBOL(test_taint);
 226
 227 unsigned long get_taint(void)
 228 {
 229         return tainted_mask;
 230 }
 231
 232 void add_taint(unsigned flag)
 233 {
 234         /*
 235          * Can't trust the integrity of the kernel anymore.
 236          * We don't call directly debug_locks_off() because the issue
 237          * is not necessarily serious enough to set oops_in_progress to 1
 238          * Also we want to keep up lockdep for staging development and
 239          * post-warning case.
 240          */
 241         if (flag != TAINT_CRAP && flag != TAINT_WARN && __debug_locks_off())
 242                 printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
 243
 244         set_bit(flag, &tainted_mask);
 245 }
 246 EXPORT_SYMBOL(add_taint);
 247
 248 static void spin_msec(int msecs)
 249 {
 250         int i;
 251
 252         for (i = 0; i < msecs; i++) {
 253                 touch_nmi_watchdog();
 254                 mdelay(1);
 255         }
 256 }
 257
 258 /*
 259  * It just happens that oops_enter() and oops_exit() are identically
 260  * implemented...
 261  */
 262 static void do_oops_enter_exit(void)
 263 {
 264         unsigned long flags;
 265         static int spin_counter;
 266
 267         if (!pause_on_oops)
 268                 return;
 269
 270         spin_lock_irqsave(&pause_on_oops_lock, flags);
 271         if (pause_on_oops_flag == 0) {
 272                 /* This CPU may now print the oops message */
 273                 pause_on_oops_flag = 1;
 274         } else {
 275                 /* We need to stall this CPU */
 276                 if (!spin_counter) {
 277                         /* This CPU gets to do the counting */
 278                         spin_counter = pause_on_oops;
 279                         do {
 280                                 spin_unlock(&pause_on_oops_lock);
 281                                 spin_msec(MSEC_PER_SEC);
 282                                 spin_lock(&pause_on_oops_lock);
 283                         } while (--spin_counter);
 284                         pause_on_oops_flag = 0;
 285                 } else {
 286                         /* This CPU waits for a different one */
 287                         while (spin_counter) {
 288                                 spin_unlock(&pause_on_oops_lock);
 289                                 spin_msec(1);
 290                                 spin_lock(&pause_on_oops_lock);
 291                         }
 292                 }
 293         }
 294         spin_unlock_irqrestore(&pause_on_oops_lock, flags);
 295 }
 296
 297 /*
 298  * Return true if the calling CPU is allowed to print oops-related info.
 299  * This is a bit racy..
 300  */
 301 int oops_may_print(void)
 302 {
 303         return pause_on_oops_flag == 0;
 304 }
 305
 306 /*
 307  * Called when the architecture enters its oops handler, before it prints
 308  * anything.  If this is the first CPU to oops, and it's oopsing the first
 309  * time then let it proceed.
 310  *
 311  * This is all enabled by the pause_on_oops kernel boot option.  We do all
 312  * this to ensure that oopses don't scroll off the screen.  It has the
 313  * side-effect of preventing later-oopsing CPUs from mucking up the display,
 314  * too.
 315  *
 316  * It turns out that the CPU which is allowed to print ends up pausing for
 317  * the right duration, whereas all the other CPUs pause for twice as long:
 318  * once in oops_enter(), once in oops_exit().
 319  */
 320 void oops_enter(void)
 321 {
 322         tracing_off();
 323         /* can't trust the integrity of the kernel anymore: */
 324         debug_locks_off();
 325         do_oops_enter_exit();
 326 }
 327
 328 /*
 329  * 64-bit random ID for oopses:
 330  */
 331 static u64 oops_id;
 332
 333 static int init_oops_id(void)
 334 {
 335         if (!oops_id)
 336                 get_random_bytes(&oops_id, sizeof(oops_id));
 337         else
 338                 oops_id++;
 339
 340         return 0;
 341 }
 342 late_initcall(init_oops_id);
 343
 344 static void print_oops_end_marker(void)
 345 {
 346         init_oops_id();
 347         printk(KERN_WARNING "---[ end trace %016llx ]---\n",
 348                 (unsigned long long)oops_id);
 349 }
 350
 351 /*
 352  * Called when the architecture exits its oops handler, after printing
 353  * everything.
 354  */
 355 void oops_exit(void)
 356 {
 357         do_oops_enter_exit();
 358         print_oops_end_marker();
 359         kmsg_dump(KMSG_DUMP_OOPS);
 360 }
 361
 362 #ifdef WANT_WARN_ON_SLOWPATH
 363 struct slowpath_args {
 364         const char *fmt;
 365         va_list args;
 366 };
 367
 368 static void warn_slowpath_common(const char *file, int line, void *caller, struct slowpath_args *args)
 369 {
 370         const char *board;
 371
 372         printk(KERN_WARNING "------------[ cut here ]------------\n");
 373         printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
 374         board = dmi_get_system_info(DMI_PRODUCT_NAME);
 375         if (board)
 376                 printk(KERN_WARNING "Hardware name: %s\n", board);
 377
 378         if (args)
 379                 vprintk(args->fmt, args->args);
 380
 381         print_modules();
 382         dump_stack();
 383         print_oops_end_marker();
 384         add_taint(TAINT_WARN);
 385 }
 386
 387 void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
 388 {
 389         struct slowpath_args args;
 390
 391         args.fmt = fmt;
 392         va_start(args.args, fmt);
 393         warn_slowpath_common(file, line, __builtin_return_address(0), &args);
 394         va_end(args.args);
 395 }
 396 EXPORT_SYMBOL(warn_slowpath_fmt);
 397
 398 void warn_slowpath_null(const char *file, int line)
 399 {
 400         warn_slowpath_common(file, line, __builtin_return_address(0), NULL);
 401 }
 402 EXPORT_SYMBOL(warn_slowpath_null);
 403 #endif
 404
 405 #ifdef CONFIG_CC_STACKPROTECTOR
 406
 407 /*
 408  * Called when gcc's -fstack-protector feature is used, and
 409  * gcc detects corruption of the on-stack canary value
 410  */
 411 void __stack_chk_fail(void)
 412 {
 413         panic("stack-protector: Kernel stack is corrupted in: %p\n",
 414                 __builtin_return_address(0));
 415 }
 416 EXPORT_SYMBOL(__stack_chk_fail);
 417
 418 #endif
 419
 420 core_param(panic, panic_timeout, int, 0644);
 421 core_param(pause_on_oops, pause_on_oops, int, 0644);