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