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
  23 int panic_on_oops;
  24 int panic_on_unrecovered_nmi;
  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' - Machine had a machine check experience.
 153  *  'B' - System has hit bad_page.
 154  *
 155  *      The string is overwritten by the next call to print_taint().
 156  */
 157
 158 const char *print_tainted(void)
 159 {
 160         static char buf[20];
 161         if (tainted) {
 162                 snprintf(buf, sizeof(buf), "Tainted: %c%c%c%c%c%c",
 163                         tainted & TAINT_PROPRIETARY_MODULE ? 'P' : 'G',
 164                         tainted & TAINT_FORCED_MODULE ? 'F' : ' ',
 165                         tainted & TAINT_UNSAFE_SMP ? 'S' : ' ',
 166                         tainted & TAINT_FORCED_RMMOD ? 'R' : ' ',
 167                         tainted & TAINT_MACHINE_CHECK ? 'M' : ' ',
 168                         tainted & TAINT_BAD_PAGE ? 'B' : ' ');
 169         }
 170         else
 171                 snprintf(buf, sizeof(buf), "Not tainted");
 172         return(buf);
 173 }
 174
 175 void add_taint(unsigned flag)
 176 {
 177         debug_locks = 0; /* can't trust the integrity of the kernel anymore */
 178         tainted |= flag;
 179 }
 180 EXPORT_SYMBOL(add_taint);
 181
 182 static int __init pause_on_oops_setup(char *str)
 183 {
 184         pause_on_oops = simple_strtoul(str, NULL, 0);
 185         return 1;
 186 }
 187 __setup("pause_on_oops=", pause_on_oops_setup);
 188
 189 static void spin_msec(int msecs)
 190 {
 191         int i;
 192
 193         for (i = 0; i < msecs; i++) {
 194                 touch_nmi_watchdog();
 195                 mdelay(1);
 196         }
 197 }
 198
 199 /*
 200  * It just happens that oops_enter() and oops_exit() are identically
 201  * implemented...
 202  */
 203 static void do_oops_enter_exit(void)
 204 {
 205         unsigned long flags;
 206         static int spin_counter;
 207
 208         if (!pause_on_oops)
 209                 return;
 210
 211         spin_lock_irqsave(&pause_on_oops_lock, flags);
 212         if (pause_on_oops_flag == 0) {
 213                 /* This CPU may now print the oops message */
 214                 pause_on_oops_flag = 1;
 215         } else {
 216                 /* We need to stall this CPU */
 217                 if (!spin_counter) {
 218                         /* This CPU gets to do the counting */
 219                         spin_counter = pause_on_oops;
 220                         do {
 221                                 spin_unlock(&pause_on_oops_lock);
 222                                 spin_msec(MSEC_PER_SEC);
 223                                 spin_lock(&pause_on_oops_lock);
 224                         } while (--spin_counter);
 225                         pause_on_oops_flag = 0;
 226                 } else {
 227                         /* This CPU waits for a different one */
 228                         while (spin_counter) {
 229                                 spin_unlock(&pause_on_oops_lock);
 230                                 spin_msec(1);
 231                                 spin_lock(&pause_on_oops_lock);
 232                         }
 233                 }
 234         }
 235         spin_unlock_irqrestore(&pause_on_oops_lock, flags);
 236 }
 237
 238 /*
 239  * Return true if the calling CPU is allowed to print oops-related info.  This
 240  * is a bit racy..
 241  */
 242 int oops_may_print(void)
 243 {
 244         return pause_on_oops_flag == 0;
 245 }
 246
 247 /*
 248  * Called when the architecture enters its oops handler, before it prints
 249  * anything.  If this is the first CPU to oops, and it's oopsing the first time
 250  * then let it proceed.
 251  *
 252  * This is all enabled by the pause_on_oops kernel boot option.  We do all this
 253  * to ensure that oopses don't scroll off the screen.  It has the side-effect
 254  * of preventing later-oopsing CPUs from mucking up the display, too.
 255  *
 256  * It turns out that the CPU which is allowed to print ends up pausing for the
 257  * right duration, whereas all the other CPUs pause for twice as long: once in
 258  * oops_enter(), once in oops_exit().
 259  */
 260 void oops_enter(void)
 261 {
 262         debug_locks_off(); /* can't trust the integrity of the kernel anymore */
 263         do_oops_enter_exit();
 264 }
 265
 266 /*
 267  * Called when the architecture exits its oops handler, after printing
 268  * everything.
 269  */
 270 void oops_exit(void)
 271 {
 272         do_oops_enter_exit();
 273 }
 274
 275 #ifdef CONFIG_CC_STACKPROTECTOR
 276 /*
 277  * Called when gcc's -fstack-protector feature is used, and
 278  * gcc detects corruption of the on-stack canary value
 279  */
 280 void __stack_chk_fail(void)
 281 {
 282         panic("stack-protector: Kernel stack is corrupted");
 283 }
 284 EXPORT_SYMBOL(__stack_chk_fail);
 285 #endif