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 #include <linux/kallsyms.h>
  24
  25 int panic_on_oops;
  26 int tainted;
  27 static int pause_on_oops;
  28 static int pause_on_oops_flag;
  29 static DEFINE_SPINLOCK(pause_on_oops_lock);
  30
  31 int panic_timeout;
  32
  33 ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
  34
  35 EXPORT_SYMBOL(panic_notifier_list);
  36
  37 static int __init panic_setup(char *str)
  38 {
  39         panic_timeout = simple_strtoul(str, NULL, 0);
  40         return 1;
  41 }
  42 __setup("panic=", panic_setup);
  43
  44 static long no_blink(long time)
  45 {
  46         return 0;
  47 }
  48
  49 /* Returns how long it waited in ms */
  50 long (*panic_blink)(long time);
  51 EXPORT_SYMBOL(panic_blink);
  52
  53 /**
  54  *      panic - halt the system
  55  *      @fmt: The text string to print
  56  *
  57  *      Display a message, then perform cleanups.
  58  *
  59  *      This function never returns.
  60  */
  61
  62 NORET_TYPE void panic(const char * fmt, ...)
  63 {
  64         long i;
  65         static char buf[1024];
  66         va_list args;
  67 #if defined(CONFIG_S390)
  68         unsigned long caller = (unsigned long) __builtin_return_address(0);
  69 #endif
  70
  71         /*
  72          * It's possible to come here directly from a panic-assertion and not
  73          * have preempt disabled. Some functions called from here want
  74          * preempt to be disabled. No point enabling it later though...
  75          */
  76         preempt_disable();
  77
  78         bust_spinlocks(1);
  79         va_start(args, fmt);
  80         vsnprintf(buf, sizeof(buf), fmt, args);
  81         va_end(args);
  82         printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
  83         bust_spinlocks(0);
  84
  85         /*
  86          * If we have crashed and we have a crash kernel loaded let it handle
  87          * everything else.
  88          * Do we want to call this before we try to display a message?
  89          */
  90         crash_kexec(NULL);
  91
  92 #ifdef CONFIG_SMP
  93         /*
  94          * Note smp_send_stop is the usual smp shutdown function, which
  95          * unfortunately means it may not be hardened to work in a panic
  96          * situation.
  97          */
  98         smp_send_stop();
  99 #endif
 100
 101         atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
 102
 103         if (!panic_blink)
 104                 panic_blink = no_blink;
 105
 106         if (panic_timeout > 0) {
 107                 /*
 108                  * Delay timeout seconds before rebooting the machine.
 109                  * We can't use the "normal" timers since we just panicked..
 110                  */
 111                 printk(KERN_EMERG "Rebooting in %d seconds..",panic_timeout);
 112                 for (i = 0; i < panic_timeout*1000; ) {
 113                         touch_nmi_watchdog();
 114                         i += panic_blink(i);
 115                         mdelay(1);
 116                         i++;
 117                 }
 118                 /*      This will not be a clean reboot, with everything
 119                  *      shutting down.  But if there is a chance of
 120                  *      rebooting the system it will be rebooted.
 121                  */
 122                 emergency_restart();
 123         }
 124 #ifdef __sparc__
 125         {
 126                 extern int stop_a_enabled;
 127                 /* Make sure the user can actually press Stop-A (L1-A) */
 128                 stop_a_enabled = 1;
 129                 printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
 130         }
 131 #endif
 132 #if defined(CONFIG_S390)
 133         disabled_wait(caller);
 134 #endif
 135         local_irq_enable();
 136         for (i = 0;;) {
 137                 touch_softlockup_watchdog();
 138                 i += panic_blink(i);
 139                 mdelay(1);
 140                 i++;
 141         }
 142 }
 143
 144 EXPORT_SYMBOL(panic);
 145
 146 /**
 147  *      print_tainted - return a string to represent the kernel taint state.
 148  *
 149  *  'P' - Proprietary module has been loaded.
 150  *  'F' - Module has been forcibly loaded.
 151  *  'S' - SMP with CPUs not designed for SMP.
 152  *  'R' - User forced a module unload.
 153  *  'M' - System experienced a machine check exception.
 154  *  'B' - System has hit bad_page.
 155  *  'U' - Userspace-defined naughtiness.
 156  *
 157  *      The string is overwritten by the next call to print_taint().
 158  */
 159
 160 const char *print_tainted(void)
 161 {
 162         static char buf[20];
 163         if (tainted) {
 164                 snprintf(buf, sizeof(buf), "Tainted: %c%c%c%c%c%c%c%c",
 165                         tainted & TAINT_PROPRIETARY_MODULE ? 'P' : 'G',
 166                         tainted & TAINT_FORCED_MODULE ? 'F' : ' ',
 167                         tainted & TAINT_UNSAFE_SMP ? 'S' : ' ',
 168                         tainted & TAINT_FORCED_RMMOD ? 'R' : ' ',
 169                         tainted & TAINT_MACHINE_CHECK ? 'M' : ' ',
 170                         tainted & TAINT_BAD_PAGE ? 'B' : ' ',
 171                         tainted & TAINT_USER ? 'U' : ' ',
 172                         tainted & TAINT_DIE ? 'D' : ' ');
 173         }
 174         else
 175                 snprintf(buf, sizeof(buf), "Not tainted");
 176         return(buf);
 177 }
 178
 179 void add_taint(unsigned flag)
 180 {
 181         debug_locks = 0; /* can't trust the integrity of the kernel anymore */
 182         tainted |= flag;
 183 }
 184 EXPORT_SYMBOL(add_taint);
 185
 186 static int __init pause_on_oops_setup(char *str)
 187 {
 188         pause_on_oops = simple_strtoul(str, NULL, 0);
 189         return 1;
 190 }
 191 __setup("pause_on_oops=", pause_on_oops_setup);
 192
 193 static void spin_msec(int msecs)
 194 {
 195         int i;
 196
 197         for (i = 0; i < msecs; i++) {
 198                 touch_nmi_watchdog();
 199                 mdelay(1);
 200         }
 201 }
 202
 203 /*
 204  * It just happens that oops_enter() and oops_exit() are identically
 205  * implemented...
 206  */
 207 static void do_oops_enter_exit(void)
 208 {
 209         unsigned long flags;
 210         static int spin_counter;
 211
 212         if (!pause_on_oops)
 213                 return;
 214
 215         spin_lock_irqsave(&pause_on_oops_lock, flags);
 216         if (pause_on_oops_flag == 0) {
 217                 /* This CPU may now print the oops message */
 218                 pause_on_oops_flag = 1;
 219         } else {
 220                 /* We need to stall this CPU */
 221                 if (!spin_counter) {
 222                         /* This CPU gets to do the counting */
 223                         spin_counter = pause_on_oops;
 224                         do {
 225                                 spin_unlock(&pause_on_oops_lock);
 226                                 spin_msec(MSEC_PER_SEC);
 227                                 spin_lock(&pause_on_oops_lock);
 228                         } while (--spin_counter);
 229                         pause_on_oops_flag = 0;
 230                 } else {
 231                         /* This CPU waits for a different one */
 232                         while (spin_counter) {
 233                                 spin_unlock(&pause_on_oops_lock);
 234                                 spin_msec(1);
 235                                 spin_lock(&pause_on_oops_lock);
 236                         }
 237                 }
 238         }
 239         spin_unlock_irqrestore(&pause_on_oops_lock, flags);
 240 }
 241
 242 /*
 243  * Return true if the calling CPU is allowed to print oops-related info.  This
 244  * is a bit racy..
 245  */
 246 int oops_may_print(void)
 247 {
 248         return pause_on_oops_flag == 0;
 249 }
 250
 251 /*
 252  * Called when the architecture enters its oops handler, before it prints
 253  * anything.  If this is the first CPU to oops, and it's oopsing the first time
 254  * then let it proceed.
 255  *
 256  * This is all enabled by the pause_on_oops kernel boot option.  We do all this
 257  * to ensure that oopses don't scroll off the screen.  It has the side-effect
 258  * of preventing later-oopsing CPUs from mucking up the display, too.
 259  *
 260  * It turns out that the CPU which is allowed to print ends up pausing for the
 261  * right duration, whereas all the other CPUs pause for twice as long: once in
 262  * oops_enter(), once in oops_exit().
 263  */
 264 void oops_enter(void)
 265 {
 266         debug_locks_off(); /* can't trust the integrity of the kernel anymore */
 267         do_oops_enter_exit();
 268 }
 269
 270 /*
 271  * 64-bit random ID for oopses:
 272  */
 273 static u64 oops_id;
 274
 275 static int init_oops_id(void)
 276 {
 277         if (!oops_id)
 278                 get_random_bytes(&oops_id, sizeof(oops_id));
 279
 280         return 0;
 281 }
 282 late_initcall(init_oops_id);
 283
 284 static void print_oops_end_marker(void)
 285 {
 286         init_oops_id();
 287         printk(KERN_WARNING "---[ end trace %016llx ]---\n",
 288                 (unsigned long long)oops_id);
 289 }
 290
 291 /*
 292  * Called when the architecture exits its oops handler, after printing
 293  * everything.
 294  */
 295 void oops_exit(void)
 296 {
 297         do_oops_enter_exit();
 298         print_oops_end_marker();
 299 }
 300
 301 #ifdef WANT_WARN_ON_SLOWPATH
 302 void warn_on_slowpath(const char *file, int line)
 303 {
 304         char function[KSYM_SYMBOL_LEN];
 305         unsigned long caller = (unsigned long) __builtin_return_address(0);
 306         sprint_symbol(function, caller);
 307
 308         printk(KERN_WARNING "------------[ cut here ]------------\n");
 309         printk(KERN_WARNING "WARNING: at %s:%d %s()\n", file,
 310                 line, function);
 311         print_modules();
 312         dump_stack();
 313         print_oops_end_marker();
 314 }
 315 EXPORT_SYMBOL(warn_on_slowpath);
 316 #endif
 317
 318 #ifdef CONFIG_CC_STACKPROTECTOR
 319 /*
 320  * Called when gcc's -fstack-protector feature is used, and
 321  * gcc detects corruption of the on-stack canary value
 322  */
 323 void __stack_chk_fail(void)
 324 {
 325         panic("stack-protector: Kernel stack is corrupted");
 326 }
 327 EXPORT_SYMBOL(__stack_chk_fail);
 328 #endif