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