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