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    /*
     *  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/debug_locks.h>
    #include <linux/interrupt.h>
    
    #include <linux/kmsg_dump.h>
    
    #include <linux/kallsyms.h>
    #include <linux/notifier.h>
    
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    #include <linux/module.h>
    
    #include <linux/random.h>
    
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    #include <linux/reboot.h>
    
    #include <linux/delay.h>
    #include <linux/kexec.h>
    #include <linux/sched.h>
    
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    #include <linux/sysrq.h>
    
    #include <linux/init.h>
    
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    #include <linux/nmi.h>
    
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    #define PANIC_TIMER_STEP 100
    #define PANIC_BLINK_SPD 18
    
    
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    int panic_on_oops;
    
    static unsigned long tainted_mask;
    
    static int pause_on_oops;
    static int pause_on_oops_flag;
    static DEFINE_SPINLOCK(pause_on_oops_lock);
    
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    int panic_timeout;
    
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    ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
    
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    EXPORT_SYMBOL(panic_notifier_list);
    
    
    static long no_blink(int state)
    
    /* Returns how long it waited in ms */
    long (*panic_blink)(int state);
    EXPORT_SYMBOL(panic_blink);
    
    
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    /**
     *	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, ...)
    {
    	static char buf[1024];
    	va_list args;
    
    	long i, i_next = 0;
    	int state = 0;
    
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    	 * 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();
    
    
    	console_verbose();
    
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    	bust_spinlocks(1);
    	va_start(args, fmt);
    	vsnprintf(buf, sizeof(buf), fmt, args);
    	va_end(args);
    	printk(KERN_EMERG "Kernel panic - not syncing: %s\n",buf);
    
    #ifdef CONFIG_DEBUG_BUGVERBOSE
    	dump_stack();
    #endif
    
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    	/*
    	 * 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?
    	 */
    
    	kmsg_dump(KMSG_DUMP_PANIC);
    
    
    	/*
    	 * Note smp_send_stop is the usual smp shutdown function, which
    	 * unfortunately means it may not be hardened to work in a panic
    	 * situation.
    	 */
    
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    	smp_send_stop();
    
    
    	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);
    
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    	if (!panic_blink)
    		panic_blink = no_blink;
    
    
    	if (panic_timeout > 0) {
    
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    		/*
    
    		 * 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; i += PANIC_TIMER_STEP) {
    
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    			touch_nmi_watchdog();
    
    			if (i >= i_next) {
    				i += panic_blink(state ^= 1);
    				i_next = i + 3600 / PANIC_BLINK_SPD;
    			}
    			mdelay(PANIC_TIMER_STEP);
    
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    		}
    
    	}
    	if (panic_timeout != 0) {
    
    		/*
    		 * 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.
    
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    		 */
    
    		emergency_restart();
    
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    	}
    #ifdef __sparc__
    	{
    		extern int stop_a_enabled;
    
    		/* Make sure the user can actually press Stop-A (L1-A) */
    
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    		stop_a_enabled = 1;
    
    		printk(KERN_EMERG "Press Stop-A (L1-A) to return to the boot prom\n");
    
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    	}
    #endif
    
    #if defined(CONFIG_S390)
    
    	{
    		unsigned long caller;
    
    		caller = (unsigned long)__builtin_return_address(0);
    		disabled_wait(caller);
    	}
    
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    #endif
    	local_irq_enable();
    
    	for (i = 0; ; i += PANIC_TIMER_STEP) {
    
    		touch_softlockup_watchdog();
    
    		if (i >= i_next) {
    			i += panic_blink(state ^= 1);
    			i_next = i + 3600 / PANIC_BLINK_SPD;
    		}
    		mdelay(PANIC_TIMER_STEP);
    
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    	}
    }
    
    EXPORT_SYMBOL(panic);
    
    
    struct tnt {
    
    	u8	bit;
    	char	true;
    	char	false;
    
    };
    
    static const struct tnt tnts[] = {
    
    	{ TAINT_PROPRIETARY_MODULE,	'P', 'G' },
    	{ TAINT_FORCED_MODULE,		'F', ' ' },
    	{ TAINT_UNSAFE_SMP,		'S', ' ' },
    	{ TAINT_FORCED_RMMOD,		'R', ' ' },
    	{ TAINT_MACHINE_CHECK,		'M', ' ' },
    	{ TAINT_BAD_PAGE,		'B', ' ' },
    	{ TAINT_USER,			'U', ' ' },
    	{ TAINT_DIE,			'D', ' ' },
    	{ TAINT_OVERRIDDEN_ACPI_TABLE,	'A', ' ' },
    	{ TAINT_WARN,			'W', ' ' },
    	{ TAINT_CRAP,			'C', ' ' },
    
    	{ TAINT_FIRMWARE_WORKAROUND,	'I', ' ' },
    
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    /**
     *	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' - System experienced a machine check exception.
    
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     *  'B' - System has hit bad_page.
    
     *  'U' - Userspace-defined naughtiness.
    
     *  'D' - Kernel has oopsed before
    
     *  'A' - ACPI table overridden.
     *  'W' - Taint on warning.
    
     *  'C' - modules from drivers/staging are loaded.
    
     *  'I' - Working around severe firmware bug.
    
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     *
    
     *	The string is overwritten by the next call to print_tainted().
    
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     */
    const char *print_tainted(void)
    {
    
    	static char buf[ARRAY_SIZE(tnts) + sizeof("Tainted: ") + 1];
    
    	if (tainted_mask) {
    		char *s;
    		int i;
    
    		s = buf + sprintf(buf, "Tainted: ");
    		for (i = 0; i < ARRAY_SIZE(tnts); i++) {
    			const struct tnt *t = &tnts[i];
    			*s++ = test_bit(t->bit, &tainted_mask) ?
    					t->true : t->false;
    		}
    		*s = 0;
    	} else
    
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    		snprintf(buf, sizeof(buf), "Not tainted");
    
    
    	return buf;
    
    int test_taint(unsigned flag)
    
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    {
    
    	return test_bit(flag, &tainted_mask);
    }
    EXPORT_SYMBOL(test_taint);
    
    unsigned long get_taint(void)
    {
    	return tainted_mask;
    
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    }
    
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    void add_taint(unsigned flag)
    
    	/*
    	 * Can't trust the integrity of the kernel anymore.
    	 * We don't call directly debug_locks_off() because the issue
    	 * is not necessarily serious enough to set oops_in_progress to 1
    
    	 * Also we want to keep up lockdep for staging development and
    	 * post-warning case.
    
    	if (flag != TAINT_CRAP && flag != TAINT_WARN && __debug_locks_off())
    
    		printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
    
    	set_bit(flag, &tainted_mask);
    
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    EXPORT_SYMBOL(add_taint);
    
    
    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)
    {
    
    	tracing_off();
    
    	/* can't trust the integrity of the kernel anymore: */
    	debug_locks_off();
    
    	do_oops_enter_exit();
    }
    
    
    /*
     * 64-bit random ID for oopses:
     */
    static u64 oops_id;
    
    static int init_oops_id(void)
    {
    	if (!oops_id)
    		get_random_bytes(&oops_id, sizeof(oops_id));
    
    
    	return 0;
    }
    late_initcall(init_oops_id);
    
    
    void print_oops_end_marker(void)
    
    {
    	init_oops_id();
    	printk(KERN_WARNING "---[ end trace %016llx ]---\n",
    		(unsigned long long)oops_id);
    }
    
    
    /*
     * Called when the architecture exits its oops handler, after printing
     * everything.
     */
    void oops_exit(void)
    {
    	do_oops_enter_exit();
    
    #ifdef WANT_WARN_ON_SLOWPATH
    
    struct slowpath_args {
    	const char *fmt;
    
    static void warn_slowpath_common(const char *file, int line, void *caller,
    				 unsigned taint, struct slowpath_args *args)
    
    
    	printk(KERN_WARNING "------------[ cut here ]------------\n");
    
    	printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
    
    	board = dmi_get_system_info(DMI_PRODUCT_NAME);
    	if (board)
    		printk(KERN_WARNING "Hardware name: %s\n", board);
    
    	if (args)
    		vprintk(args->fmt, args->args);
    
    
    	print_modules();
    	dump_stack();
    	print_oops_end_marker();
    
    
    void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
    {
    	struct slowpath_args args;
    
    	args.fmt = fmt;
    	va_start(args.args, fmt);
    
    	warn_slowpath_common(file, line, __builtin_return_address(0),
    			     TAINT_WARN, &args);
    
    EXPORT_SYMBOL(warn_slowpath_fmt);
    
    
    void warn_slowpath_fmt_taint(const char *file, int line,
    			     unsigned taint, const char *fmt, ...)
    {
    	struct slowpath_args args;
    
    	args.fmt = fmt;
    	va_start(args.args, fmt);
    	warn_slowpath_common(file, line, __builtin_return_address(0),
    			     taint, &args);
    	va_end(args.args);
    }
    EXPORT_SYMBOL(warn_slowpath_fmt_taint);
    
    
    void warn_slowpath_null(const char *file, int line)
    {
    
    	warn_slowpath_common(file, line, __builtin_return_address(0),
    			     TAINT_WARN, NULL);
    
    }
    EXPORT_SYMBOL(warn_slowpath_null);
    
    #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 in: %p\n",
    		__builtin_return_address(0));
    
    }
    EXPORT_SYMBOL(__stack_chk_fail);
    
    
    core_param(panic, panic_timeout, int, 0644);
    core_param(pause_on_oops, pause_on_oops, int, 0644);
    
    
    static int __init oops_setup(char *s)
    {
    	if (!s)
    		return -EINVAL;
    	if (!strcmp(s, "panic"))
    		panic_on_oops = 1;
    	return 0;
    }
    early_param("oops", oops_setup);