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