/*
   *  linux/kernel/panic.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   */
  
  /*
   * This function is used through-out the kernel (including mm and fs)
   * to indicate a major problem.
   */

  #include <linux/module.h>
  #include <linux/sched.h>
  #include <linux/delay.h>
  #include <linux/reboot.h>
  #include <linux/notifier.h>
  #include <linux/init.h>
  #include <linux/sysrq.h>
  #include <linux/interrupt.h>
  #include <linux/nmi.h>

  #include <linux/kexec.h>

  #include <linux/debug_locks.h>

  int panic_on_oops;
  int tainted;

  static int pause_on_oops;
  static int pause_on_oops_flag;
  static DEFINE_SPINLOCK(pause_on_oops_lock);

  int panic_timeout;

  ATOMIC_NOTIFIER_HEAD(panic_notifier_list);

  
  EXPORT_SYMBOL(panic_notifier_list);
  
  static int __init panic_setup(char *str)
  {
  	panic_timeout = simple_strtoul(str, NULL, 0);
  	return 1;
  }
  __setup("panic=", panic_setup);
  
  static long no_blink(long time)
  {
  	return 0;
  }
  
  /* Returns how long it waited in ms */
  long (*panic_blink)(long time);
  EXPORT_SYMBOL(panic_blink);
  
  /**
   *	panic - halt the system
   *	@fmt: The text string to print
   *
   *	Display a message, then perform cleanups.
   *
   *	This function never returns.
   */
   
  NORET_TYPE void panic(const char * fmt, ...)
  {
  	long i;
  	static char buf[1024];
  	va_list args;

  #if defined(CONFIG_S390)

          unsigned long caller = (unsigned long) __builtin_return_address(0);
  #endif

  	/*
  	 * It's possible to come here directly from a panic-assertion and not
  	 * have preempt disabled. Some functions called from here want
  	 * preempt to be disabled. No point enabling it later though...
  	 */
  	preempt_disable();

  	bust_spinlocks(1);
  	va_start(args, fmt);
  	vsnprintf(buf, sizeof(buf), fmt, args);
  	va_end(args);
  	printk(KERN_EMERG "Kernel panic - not syncing: %s
  ",buf);
  	bust_spinlocks(0);

  	/*
  	 * If we have crashed and we have a crash kernel loaded let it handle
  	 * everything else.
  	 * Do we want to call this before we try to display a message?
  	 */

  	crash_kexec(NULL);

  #ifdef CONFIG_SMP

  	/*
  	 * Note smp_send_stop is the usual smp shutdown function, which
  	 * unfortunately means it may not be hardened to work in a panic
  	 * situation.
  	 */

  	smp_send_stop();
  #endif

  	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

  
  	if (!panic_blink)
  		panic_blink = no_blink;

  	if (panic_timeout > 0) {

  		/*
  	 	 * Delay timeout seconds before rebooting the machine. 
  		 * We can't use the "normal" timers since we just panicked..
  	 	 */
  		printk(KERN_EMERG "Rebooting in %d seconds..",panic_timeout);
  		for (i = 0; i < panic_timeout*1000; ) {
  			touch_nmi_watchdog();
  			i += panic_blink(i);
  			mdelay(1);
  			i++;
  		}

  		/*	This will not be a clean reboot, with everything
  		 *	shutting down.  But if there is a chance of
  		 *	rebooting the system it will be rebooted.

  		 */

  		emergency_restart();

  	}
  #ifdef __sparc__
  	{
  		extern int stop_a_enabled;

  		/* Make sure the user can actually press Stop-A (L1-A) */

  		stop_a_enabled = 1;

  		printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom
  ");

  	}
  #endif

  #if defined(CONFIG_S390)

          disabled_wait(caller);
  #endif
  	local_irq_enable();
  	for (i = 0;;) {

  		touch_softlockup_watchdog();

  		i += panic_blink(i);
  		mdelay(1);
  		i++;
  	}
  }
  
  EXPORT_SYMBOL(panic);
  
  /**
   *	print_tainted - return a string to represent the kernel taint state.
   *
   *  'P' - Proprietary module has been loaded.
   *  'F' - Module has been forcibly loaded.
   *  'S' - SMP with CPUs not designed for SMP.
   *  'R' - User forced a module unload.
   *  'M' - Machine had a machine check experience.
   *  'B' - System has hit bad_page.

   *  'U' - Userspace-defined naughtiness.

   *
   *	The string is overwritten by the next call to print_taint().
   */
   
  const char *print_tainted(void)
  {
  	static char buf[20];
  	if (tainted) {

  		snprintf(buf, sizeof(buf), "Tainted: %c%c%c%c%c%c%c%c",

  			tainted & TAINT_PROPRIETARY_MODULE ? 'P' : 'G',
  			tainted & TAINT_FORCED_MODULE ? 'F' : ' ',
  			tainted & TAINT_UNSAFE_SMP ? 'S' : ' ',
  			tainted & TAINT_FORCED_RMMOD ? 'R' : ' ',
   			tainted & TAINT_MACHINE_CHECK ? 'M' : ' ',

  			tainted & TAINT_BAD_PAGE ? 'B' : ' ',

  			tainted & TAINT_USER ? 'U' : ' ',
  			tainted & TAINT_DIE ? 'D' : ' ');

  	}
  	else
  		snprintf(buf, sizeof(buf), "Not tainted");
  	return(buf);
  }
  
  void add_taint(unsigned flag)
  {

  	debug_locks = 0; /* can't trust the integrity of the kernel anymore */

  	tainted |= flag;
  }
  EXPORT_SYMBOL(add_taint);

  
  static int __init pause_on_oops_setup(char *str)
  {
  	pause_on_oops = simple_strtoul(str, NULL, 0);
  	return 1;
  }
  __setup("pause_on_oops=", pause_on_oops_setup);
  
  static void spin_msec(int msecs)
  {
  	int i;
  
  	for (i = 0; i < msecs; i++) {
  		touch_nmi_watchdog();
  		mdelay(1);
  	}
  }
  
  /*
   * It just happens that oops_enter() and oops_exit() are identically
   * implemented...
   */
  static void do_oops_enter_exit(void)
  {
  	unsigned long flags;
  	static int spin_counter;
  
  	if (!pause_on_oops)
  		return;
  
  	spin_lock_irqsave(&pause_on_oops_lock, flags);
  	if (pause_on_oops_flag == 0) {
  		/* This CPU may now print the oops message */
  		pause_on_oops_flag = 1;
  	} else {
  		/* We need to stall this CPU */
  		if (!spin_counter) {
  			/* This CPU gets to do the counting */
  			spin_counter = pause_on_oops;
  			do {
  				spin_unlock(&pause_on_oops_lock);
  				spin_msec(MSEC_PER_SEC);
  				spin_lock(&pause_on_oops_lock);
  			} while (--spin_counter);
  			pause_on_oops_flag = 0;
  		} else {
  			/* This CPU waits for a different one */
  			while (spin_counter) {
  				spin_unlock(&pause_on_oops_lock);
  				spin_msec(1);
  				spin_lock(&pause_on_oops_lock);
  			}
  		}
  	}
  	spin_unlock_irqrestore(&pause_on_oops_lock, flags);
  }
  
  /*
   * Return true if the calling CPU is allowed to print oops-related info.  This
   * is a bit racy..
   */
  int oops_may_print(void)
  {
  	return pause_on_oops_flag == 0;
  }
  
  /*
   * Called when the architecture enters its oops handler, before it prints
   * anything.  If this is the first CPU to oops, and it's oopsing the first time
   * then let it proceed.
   *
   * This is all enabled by the pause_on_oops kernel boot option.  We do all this
   * to ensure that oopses don't scroll off the screen.  It has the side-effect
   * of preventing later-oopsing CPUs from mucking up the display, too.
   *
   * It turns out that the CPU which is allowed to print ends up pausing for the
   * right duration, whereas all the other CPUs pause for twice as long: once in
   * oops_enter(), once in oops_exit().
   */
  void oops_enter(void)
  {

  	debug_locks_off(); /* can't trust the integrity of the kernel anymore */

  	do_oops_enter_exit();
  }
  
  /*
   * Called when the architecture exits its oops handler, after printing
   * everything.
   */
  void oops_exit(void)
  {
  	do_oops_enter_exit();
  }

  
  #ifdef CONFIG_CC_STACKPROTECTOR
  /*
   * Called when gcc's -fstack-protector feature is used, and
   * gcc detects corruption of the on-stack canary value
   */
  void __stack_chk_fail(void)
  {
  	panic("stack-protector: Kernel stack is corrupted");
  }
  EXPORT_SYMBOL(__stack_chk_fail);
  #endif