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/module.h>
  12 #include <linux/sched.h>
  13 #include <linux/delay.h>
  14 #include <linux/reboot.h>
  15 #include <linux/notifier.h>
  16 #include <linux/init.h>
  17 #include <linux/sysrq.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/nmi.h>
  20 #include <linux/kexec.h>
  21 #include <linux/debug_locks.h>
  22 #include <linux/random.h>
  23 #include <linux/kallsyms.h>
  24
  25 int panic_on_oops;
  26 static unsigned long tainted_mask;
  27 static int pause_on_oops;
  28 static int pause_on_oops_flag;
  29 static DEFINE_SPINLOCK(pause_on_oops_lock);
  30
  31 int panic_timeout;
  32
  33 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
  34
  35 EXPORT_SYMBOL(panic_notifier_list);
  36
  37 static int __init panic_setup(char *str)
  38 {
  39         panic_timeout = simple_strtoul(str, NULL, 0);
  40         return 1;
  41 }
  42 __setup("panic=", panic_setup);
  43
  44 static long no_blink(long time)
  45 {
  46         return 0;
  47 }
  48
  49 /* Returns how long it waited in ms */
  50 long (*panic_blink)(long time);
  51 EXPORT_SYMBOL(panic_blink);
  52
  53 /**
  54  *      panic - halt the system
  55  *      @fmt: The text string to print
  56  *
  57  *      Display a message, then perform cleanups.
  58  *
  59  *      This function never returns.
  60  */
  61
  62 NORET_TYPE void panic(const char * fmt, ...)
  63 {
  64         long i;
  65         static char buf[1024];
  66         va_list args;
  67 #if defined(CONFIG_S390)
  68         unsigned long caller = (unsigned long) __builtin_return_address(0);
  69 #endif
  70
  71         /*
  72          * It's possible to come here directly from a panic-assertion and not
  73          * have preempt disabled. Some functions called from here want
  74          * preempt to be disabled. No point enabling it later though...
  75          */
  76         preempt_disable();
  77
  78         bust_spinlocks(1);
  79         va_start(args, fmt);
  80         vsnprintf(buf, sizeof(buf), fmt, args);
  81         va_end(args);
  82         printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
  83         bust_spinlocks(0);
  84
  85         /*
  86          * If we have crashed and we have a crash kernel loaded let it handle
  87          * everything else.
  88          * Do we want to call this before we try to display a message?
  89          */
  90         crash_kexec(NULL);
  91
  92 #ifdef CONFIG_SMP
  93         /*
  94          * Note smp_send_stop is the usual smp shutdown function, which
  95          * unfortunately means it may not be hardened to work in a panic
  96          * situation.
  97          */
  98         smp_send_stop();
  99 #endif
 100
 101         atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
 102
 103         if (!panic_blink)
 104                 panic_blink = no_blink;
 105
 106         if (panic_timeout > 0) {
 107                 /*
 108                  * Delay timeout seconds before rebooting the machine.
 109                  * We can't use the "normal" timers since we just panicked..
 110                  */
 111                 printk(KERN_EMERG "Rebooting in %d seconds..",panic_timeout);
 112                 for (i = 0; i < panic_timeout*1000; ) {
 113                         touch_nmi_watchdog();
 114                         i += panic_blink(i);
 115                         mdelay(1);
 116                         i++;
 117                 }
 118                 /*      This will not be a clean reboot, with everything
 119                  *      shutting down.  But if there is a chance of
 120                  *      rebooting the system it will be rebooted.
 121                  */
 122                 emergency_restart();
 123         }
 124 #ifdef __sparc__
 125         {
 126                 extern int stop_a_enabled;
 127                 /* Make sure the user can actually press Stop-A (L1-A) */
 128                 stop_a_enabled = 1;
 129                 printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
 130         }
 131 #endif
 132 #if defined(CONFIG_S390)
 133         disabled_wait(caller);
 134 #endif
 135         local_irq_enable();
 136         for (i = 0;;) {
 137                 touch_softlockup_watchdog();
 138                 i += panic_blink(i);
 139                 mdelay(1);
 140                 i++;
 141         }
 142 }
 143
 144 EXPORT_SYMBOL(panic);
 145
 146
 147 struct tnt {
 148         u8 bit;
 149         char true;
 150         char false;
 151 };
 152
 153 static const struct tnt tnts[] = {
 154         { TAINT_PROPRIETARY_MODULE, 'P', 'G' },
 155         { TAINT_FORCED_MODULE, 'F', ' ' },
 156         { TAINT_UNSAFE_SMP, 'S', ' ' },
 157         { TAINT_FORCED_RMMOD, 'R', ' ' },
 158         { TAINT_MACHINE_CHECK, 'M', ' ' },
 159         { TAINT_BAD_PAGE, 'B', ' ' },
 160         { TAINT_USER, 'U', ' ' },
 161         { TAINT_DIE, 'D', ' ' },
 162         { TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },
 163         { TAINT_WARN, 'W', ' ' },
 164 };
 165
 166 /**
 167  *      print_tainted - return a string to represent the kernel taint state.
 168  *
 169  *  'P' - Proprietary module has been loaded.
 170  *  'F' - Module has been forcibly loaded.
 171  *  'S' - SMP with CPUs not designed for SMP.
 172  *  'R' - User forced a module unload.
 173  *  'M' - System experienced a machine check exception.
 174  *  'B' - System has hit bad_page.
 175  *  'U' - Userspace-defined naughtiness.
 176  *  'A' - ACPI table overridden.
 177  *  'W' - Taint on warning.
 178  *
 179  *      The string is overwritten by the next call to print_taint().
 180  */
 181 const char *print_tainted(void)
 182 {
 183         static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
 184
 185         if (tainted_mask) {
 186                 char *s;
 187                 int i;
 188
 189                 s = buf + sprintf(buf, "Tainted: ");
 190                 for (i = 0; i < ARRAY_SIZE(tnts); i++) {
 191                         const struct tnt *t = &tnts[i];
 192                         *s++ = test_bit(t->bit, &tainted_mask) ?
 193                                         t->true : t->false;
 194                 }
 195                 *s = 0;
 196         } else
 197                 snprintf(buf, sizeof(buf), "Not tainted");
 198         return(buf);
 199 }
 200
 201 int test_taint(unsigned flag)
 202 {
 203         return test_bit(flag, &tainted_mask);
 204 }
 205 EXPORT_SYMBOL(test_taint);
 206
 207 unsigned long get_taint(void)
 208 {
 209         return tainted_mask;
 210 }
 211
 212 void add_taint(unsigned flag)
 213 {
 214         debug_locks = 0; /* can't trust the integrity of the kernel anymore */
 215         set_bit(flag, &tainted_mask);
 216 }
 217 EXPORT_SYMBOL(add_taint);
 218
 219 static int __init pause_on_oops_setup(char *str)
 220 {
 221         pause_on_oops = simple_strtoul(str, NULL, 0);
 222         return 1;
 223 }
 224 __setup("pause_on_oops=", pause_on_oops_setup);
 225
 226 static void spin_msec(int msecs)
 227 {
 228         int i;
 229
 230         for (i = 0; i < msecs; i++) {
 231                 touch_nmi_watchdog();
 232                 mdelay(1);
 233         }
 234 }
 235
 236 /*
 237  * It just happens that oops_enter() and oops_exit() are identically
 238  * implemented...
 239  */
 240 static void do_oops_enter_exit(void)
 241 {
 242         unsigned long flags;
 243         static int spin_counter;
 244
 245         if (!pause_on_oops)
 246                 return;
 247
 248         spin_lock_irqsave(&pause_on_oops_lock, flags);
 249         if (pause_on_oops_flag == 0) {
 250                 /* This CPU may now print the oops message */
 251                 pause_on_oops_flag = 1;
 252         } else {
 253                 /* We need to stall this CPU */
 254                 if (!spin_counter) {
 255                         /* This CPU gets to do the counting */
 256                         spin_counter = pause_on_oops;
 257                         do {
 258                                 spin_unlock(&pause_on_oops_lock);
 259                                 spin_msec(MSEC_PER_SEC);
 260                                 spin_lock(&pause_on_oops_lock);
 261                         } while (--spin_counter);
 262                         pause_on_oops_flag = 0;
 263                 } else {
 264                         /* This CPU waits for a different one */
 265                         while (spin_counter) {
 266                                 spin_unlock(&pause_on_oops_lock);
 267                                 spin_msec(1);
 268                                 spin_lock(&pause_on_oops_lock);
 269                         }
 270                 }
 271         }
 272         spin_unlock_irqrestore(&pause_on_oops_lock, flags);
 273 }
 274
 275 /*
 276  * Return true if the calling CPU is allowed to print oops-related info.  This
 277  * is a bit racy..
 278  */
 279 int oops_may_print(void)
 280 {
 281         return pause_on_oops_flag == 0;
 282 }
 283
 284 /*
 285  * Called when the architecture enters its oops handler, before it prints
 286  * anything.  If this is the first CPU to oops, and it's oopsing the first time
 287  * then let it proceed.
 288  *
 289  * This is all enabled by the pause_on_oops kernel boot option.  We do all this
 290  * to ensure that oopses don't scroll off the screen.  It has the side-effect
 291  * of preventing later-oopsing CPUs from mucking up the display, too.
 292  *
 293  * It turns out that the CPU which is allowed to print ends up pausing for the
 294  * right duration, whereas all the other CPUs pause for twice as long: once in
 295  * oops_enter(), once in oops_exit().
 296  */
 297 void oops_enter(void)
 298 {
 299         debug_locks_off(); /* can't trust the integrity of the kernel anymore */
 300         do_oops_enter_exit();
 301 }
 302
 303 /*
 304  * 64-bit random ID for oopses:
 305  */
 306 static u64 oops_id;
 307
 308 static int init_oops_id(void)
 309 {
 310         if (!oops_id)
 311                 get_random_bytes(&oops_id, sizeof(oops_id));
 312
 313         return 0;
 314 }
 315 late_initcall(init_oops_id);
 316
 317 static void print_oops_end_marker(void)
 318 {
 319         init_oops_id();
 320         printk(KERN_WARNING "---[ end trace %016llx ]---\n",
 321                 (unsigned long long)oops_id);
 322 }
 323
 324 /*
 325  * Called when the architecture exits its oops handler, after printing
 326  * everything.
 327  */
 328 void oops_exit(void)
 329 {
 330         do_oops_enter_exit();
 331         print_oops_end_marker();
 332 }
 333
 334 #ifdef WANT_WARN_ON_SLOWPATH
 335 void warn_on_slowpath(const char *file, int line)
 336 {
 337         char function[KSYM_SYMBOL_LEN];
 338         unsigned long caller = (unsigned long) __builtin_return_address(0);
 339         sprint_symbol(function, caller);
 340
 341         printk(KERN_WARNING "------------[ cut here ]------------\n");
 342         printk(KERN_WARNING "WARNING: at %s:%d %s()\n", file,
 343                 line, function);
 344         print_modules();
 345         dump_stack();
 346         print_oops_end_marker();
 347         add_taint(TAINT_WARN);
 348 }
 349 EXPORT_SYMBOL(warn_on_slowpath);
 350
 351
 352 void warn_slowpath(const char *file, int line, const char *fmt, ...)
 353 {
 354         va_list args;
 355         char function[KSYM_SYMBOL_LEN];
 356         unsigned long caller = (unsigned long)__builtin_return_address(0);
 357         sprint_symbol(function, caller);
 358
 359         printk(KERN_WARNING "------------[ cut here ]------------\n");
 360         printk(KERN_WARNING "WARNING: at %s:%d %s()\n", file,
 361                 line, function);
 362         va_start(args, fmt);
 363         vprintk(fmt, args);
 364         va_end(args);
 365
 366         print_modules();
 367         dump_stack();
 368         print_oops_end_marker();
 369         add_taint(TAINT_WARN);
 370 }
 371 EXPORT_SYMBOL(warn_slowpath);
 372 #endif
 373
 374 #ifdef CONFIG_CC_STACKPROTECTOR
 375 /*
 376  * Called when gcc's -fstack-protector feature is used, and
 377  * gcc detects corruption of the on-stack canary value
 378  */
 379 void __stack_chk_fail(void)
 380 {
 381         panic("stack-protector: Kernel stack is corrupted");
 382 }
 383 EXPORT_SYMBOL(__stack_chk_fail);
 384 #endif