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 long no_blink(long time)
  38 {
  39         return 0;
  40 }
  41
  42 /* Returns how long it waited in ms */
  43 long (*panic_blink)(long time);
  44 EXPORT_SYMBOL(panic_blink);
  45
  46 /**
  47  *      panic - halt the system
  48  *      @fmt: The text string to print
  49  *
  50  *      Display a message, then perform cleanups.
  51  *
  52  *      This function never returns.
  53  */
  54
  55 NORET_TYPE void panic(const char * fmt, ...)
  56 {
  57         long i;
  58         static char buf[1024];
  59         va_list args;
  60 #if defined(CONFIG_S390)
  61         unsigned long caller = (unsigned long) __builtin_return_address(0);
  62 #endif
  63
  64         /*
  65          * It's possible to come here directly from a panic-assertion and not
  66          * have preempt disabled. Some functions called from here want
  67          * preempt to be disabled. No point enabling it later though...
  68          */
  69         preempt_disable();
  70
  71         bust_spinlocks(1);
  72         va_start(args, fmt);
  73         vsnprintf(buf, sizeof(buf), fmt, args);
  74         va_end(args);
  75         printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
  76         bust_spinlocks(0);
  77
  78         /*
  79          * If we have crashed and we have a crash kernel loaded let it handle
  80          * everything else.
  81          * Do we want to call this before we try to display a message?
  82          */
  83         crash_kexec(NULL);
  84
  85 #ifdef CONFIG_SMP
  86         /*
  87          * Note smp_send_stop is the usual smp shutdown function, which
  88          * unfortunately means it may not be hardened to work in a panic
  89          * situation.
  90          */
  91         smp_send_stop();
  92 #endif
  93
  94         atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
  95
  96         if (!panic_blink)
  97                 panic_blink = no_blink;
  98
  99         if (panic_timeout > 0) {
 100                 /*
 101                  * Delay timeout seconds before rebooting the machine.
 102                  * We can't use the "normal" timers since we just panicked..
 103                  */
 104                 printk(KERN_EMERG "Rebooting in %d seconds..",panic_timeout);
 105                 for (i = 0; i < panic_timeout*1000; ) {
 106                         touch_nmi_watchdog();
 107                         i += panic_blink(i);
 108                         mdelay(1);
 109                         i++;
 110                 }
 111                 /*      This will not be a clean reboot, with everything
 112                  *      shutting down.  But if there is a chance of
 113                  *      rebooting the system it will be rebooted.
 114                  */
 115                 emergency_restart();
 116         }
 117 #ifdef __sparc__
 118         {
 119                 extern int stop_a_enabled;
 120                 /* Make sure the user can actually press Stop-A (L1-A) */
 121                 stop_a_enabled = 1;
 122                 printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
 123         }
 124 #endif
 125 #if defined(CONFIG_S390)
 126         disabled_wait(caller);
 127 #endif
 128         local_irq_enable();
 129         for (i = 0;;) {
 130                 touch_softlockup_watchdog();
 131                 i += panic_blink(i);
 132                 mdelay(1);
 133                 i++;
 134         }
 135 }
 136
 137 EXPORT_SYMBOL(panic);
 138
 139
 140 struct tnt {
 141         u8 bit;
 142         char true;
 143         char false;
 144 };
 145
 146 static const struct tnt tnts[] = {
 147         { TAINT_PROPRIETARY_MODULE, 'P', 'G' },
 148         { TAINT_FORCED_MODULE, 'F', ' ' },
 149         { TAINT_UNSAFE_SMP, 'S', ' ' },
 150         { TAINT_FORCED_RMMOD, 'R', ' ' },
 151         { TAINT_MACHINE_CHECK, 'M', ' ' },
 152         { TAINT_BAD_PAGE, 'B', ' ' },
 153         { TAINT_USER, 'U', ' ' },
 154         { TAINT_DIE, 'D', ' ' },
 155         { TAINT_OVERRIDDEN_ACPI_TABLE, 'A', ' ' },
 156         { TAINT_WARN, 'W', ' ' },
 157         { TAINT_CRAP, 'C', ' ' },
 158 };
 159
 160 /**
 161  *      print_tainted - return a string to represent the kernel taint state.
 162  *
 163  *  'P' - Proprietary module has been loaded.
 164  *  'F' - Module has been forcibly loaded.
 165  *  'S' - SMP with CPUs not designed for SMP.
 166  *  'R' - User forced a module unload.
 167  *  'M' - System experienced a machine check exception.
 168  *  'B' - System has hit bad_page.
 169  *  'U' - Userspace-defined naughtiness.
 170  *  'D' - Kernel has oopsed before
 171  *  'A' - ACPI table overridden.
 172  *  'W' - Taint on warning.
 173  *  'C' - modules from drivers/staging are loaded.
 174  *
 175  *      The string is overwritten by the next call to print_taint().
 176  */
 177 const char *print_tainted(void)
 178 {
 179         static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
 180
 181         if (tainted_mask) {
 182                 char *s;
 183                 int i;
 184
 185                 s = buf + sprintf(buf, "Tainted: ");
 186                 for (i = 0; i < ARRAY_SIZE(tnts); i++) {
 187                         const struct tnt *t = &tnts[i];
 188                         *s++ = test_bit(t->bit, &tainted_mask) ?
 189                                         t->true : t->false;
 190                 }
 191                 *s = 0;
 192         } else
 193                 snprintf(buf, sizeof(buf), "Not tainted");
 194         return(buf);
 195 }
 196
 197 int test_taint(unsigned flag)
 198 {
 199         return test_bit(flag, &tainted_mask);
 200 }
 201 EXPORT_SYMBOL(test_taint);
 202
 203 unsigned long get_taint(void)
 204 {
 205         return tainted_mask;
 206 }
 207
 208 void add_taint(unsigned flag)
 209 {
 210         debug_locks = 0; /* can't trust the integrity of the kernel anymore */
 211         set_bit(flag, &tainted_mask);
 212 }
 213 EXPORT_SYMBOL(add_taint);
 214
 215 static void spin_msec(int msecs)
 216 {
 217         int i;
 218
 219         for (i = 0; i < msecs; i++) {
 220                 touch_nmi_watchdog();
 221                 mdelay(1);
 222         }
 223 }
 224
 225 /*
 226  * It just happens that oops_enter() and oops_exit() are identically
 227  * implemented...
 228  */
 229 static void do_oops_enter_exit(void)
 230 {
 231         unsigned long flags;
 232         static int spin_counter;
 233
 234         if (!pause_on_oops)
 235                 return;
 236
 237         spin_lock_irqsave(&pause_on_oops_lock, flags);
 238         if (pause_on_oops_flag == 0) {
 239                 /* This CPU may now print the oops message */
 240                 pause_on_oops_flag = 1;
 241         } else {
 242                 /* We need to stall this CPU */
 243                 if (!spin_counter) {
 244                         /* This CPU gets to do the counting */
 245                         spin_counter = pause_on_oops;
 246                         do {
 247                                 spin_unlock(&pause_on_oops_lock);
 248                                 spin_msec(MSEC_PER_SEC);
 249                                 spin_lock(&pause_on_oops_lock);
 250                         } while (--spin_counter);
 251                         pause_on_oops_flag = 0;
 252                 } else {
 253                         /* This CPU waits for a different one */
 254                         while (spin_counter) {
 255                                 spin_unlock(&pause_on_oops_lock);
 256                                 spin_msec(1);
 257                                 spin_lock(&pause_on_oops_lock);
 258                         }
 259                 }
 260         }
 261         spin_unlock_irqrestore(&pause_on_oops_lock, flags);
 262 }
 263
 264 /*
 265  * Return true if the calling CPU is allowed to print oops-related info.  This
 266  * is a bit racy..
 267  */
 268 int oops_may_print(void)
 269 {
 270         return pause_on_oops_flag == 0;
 271 }
 272
 273 /*
 274  * Called when the architecture enters its oops handler, before it prints
 275  * anything.  If this is the first CPU to oops, and it's oopsing the first time
 276  * then let it proceed.
 277  *
 278  * This is all enabled by the pause_on_oops kernel boot option.  We do all this
 279  * to ensure that oopses don't scroll off the screen.  It has the side-effect
 280  * of preventing later-oopsing CPUs from mucking up the display, too.
 281  *
 282  * It turns out that the CPU which is allowed to print ends up pausing for the
 283  * right duration, whereas all the other CPUs pause for twice as long: once in
 284  * oops_enter(), once in oops_exit().
 285  */
 286 void oops_enter(void)
 287 {
 288         debug_locks_off(); /* can't trust the integrity of the kernel anymore */
 289         do_oops_enter_exit();
 290 }
 291
 292 /*
 293  * 64-bit random ID for oopses:
 294  */
 295 static u64 oops_id;
 296
 297 static int init_oops_id(void)
 298 {
 299         if (!oops_id)
 300                 get_random_bytes(&oops_id, sizeof(oops_id));
 301
 302         return 0;
 303 }
 304 late_initcall(init_oops_id);
 305
 306 static void print_oops_end_marker(void)
 307 {
 308         init_oops_id();
 309         printk(KERN_WARNING "---[ end trace %016llx ]---\n",
 310                 (unsigned long long)oops_id);
 311 }
 312
 313 /*
 314  * Called when the architecture exits its oops handler, after printing
 315  * everything.
 316  */
 317 void oops_exit(void)
 318 {
 319         do_oops_enter_exit();
 320         print_oops_end_marker();
 321 }
 322
 323 #ifdef WANT_WARN_ON_SLOWPATH
 324 void warn_on_slowpath(const char *file, int line)
 325 {
 326         char function[KSYM_SYMBOL_LEN];
 327         unsigned long caller = (unsigned long) __builtin_return_address(0);
 328         sprint_symbol(function, caller);
 329
 330         printk(KERN_WARNING "------------[ cut here ]------------\n");
 331         printk(KERN_WARNING "WARNING: at %s:%d %s()\n", file,
 332                 line, function);
 333         print_modules();
 334         dump_stack();
 335         print_oops_end_marker();
 336         add_taint(TAINT_WARN);
 337 }
 338 EXPORT_SYMBOL(warn_on_slowpath);
 339
 340
 341 void warn_slowpath(const char *file, int line, const char *fmt, ...)
 342 {
 343         va_list args;
 344         char function[KSYM_SYMBOL_LEN];
 345         unsigned long caller = (unsigned long)__builtin_return_address(0);
 346         sprint_symbol(function, caller);
 347
 348         printk(KERN_WARNING "------------[ cut here ]------------\n");
 349         printk(KERN_WARNING "WARNING: at %s:%d %s()\n", file,
 350                 line, function);
 351         va_start(args, fmt);
 352         vprintk(fmt, args);
 353         va_end(args);
 354
 355         print_modules();
 356         dump_stack();
 357         print_oops_end_marker();
 358         add_taint(TAINT_WARN);
 359 }
 360 EXPORT_SYMBOL(warn_slowpath);
 361 #endif
 362
 363 #ifdef CONFIG_CC_STACKPROTECTOR
 364 /*
 365  * Called when gcc's -fstack-protector feature is used, and
 366  * gcc detects corruption of the on-stack canary value
 367  */
 368 void __stack_chk_fail(void)
 369 {
 370         panic("stack-protector: Kernel stack is corrupted");
 371 }
 372 EXPORT_SYMBOL(__stack_chk_fail);
 373 #endif
 374
 375 core_param(panic, panic_timeout, int, 0644);
 376 core_param(pause_on_oops, pause_on_oops, int, 0644);