/*
   *  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/sched/debug.h>

  #include <linux/interrupt.h>

  #include <linux/kmsg_dump.h>

  #include <linux/kallsyms.h>
  #include <linux/notifier.h>

  #include <linux/vt_kern.h>

  #include <linux/module.h>

  #include <linux/random.h>

  #include <linux/ftrace.h>

  #include <linux/reboot.h>

  #include <linux/delay.h>
  #include <linux/kexec.h>
  #include <linux/sched.h>

  #include <linux/sysrq.h>

  #include <linux/init.h>

  #include <linux/nmi.h>

  #include <linux/console.h>

  #include <linux/bug.h>

  #include <linux/ratelimit.h>

  #define PANIC_TIMER_STEP 100
  #define PANIC_BLINK_SPD 18

  int panic_on_oops = CONFIG_PANIC_ON_OOPS_VALUE;

  static unsigned long tainted_mask;

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

  bool crash_kexec_post_notifiers;

  int panic_on_warn __read_mostly;

  int panic_timeout = CONFIG_PANIC_TIMEOUT;

  EXPORT_SYMBOL_GPL(panic_timeout);

  ATOMIC_NOTIFIER_HEAD(panic_notifier_list);

  
  EXPORT_SYMBOL(panic_notifier_list);

  static long no_blink(int state)

  {

  	return 0;

  }

  /* Returns how long it waited in ms */
  long (*panic_blink)(int state);
  EXPORT_SYMBOL(panic_blink);

  /*
   * Stop ourself in panic -- architecture code may override this
   */
  void __weak panic_smp_self_stop(void)
  {
  	while (1)
  		cpu_relax();
  }

  /*
   * Stop ourselves in NMI context if another CPU has already panicked. Arch code
   * may override this to prepare for crash dumping, e.g. save regs info.
   */
  void __weak nmi_panic_self_stop(struct pt_regs *regs)
  {
  	panic_smp_self_stop();
  }

  /*
   * Stop other CPUs in panic.  Architecture dependent code may override this
   * with more suitable version.  For example, if the architecture supports
   * crash dump, it should save registers of each stopped CPU and disable
   * per-CPU features such as virtualization extensions.
   */
  void __weak crash_smp_send_stop(void)
  {
  	static int cpus_stopped;
  
  	/*
  	 * This function can be called twice in panic path, but obviously
  	 * we execute this only once.
  	 */
  	if (cpus_stopped)
  		return;
  
  	/*
  	 * 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();
  	cpus_stopped = 1;
  }

  atomic_t panic_cpu = ATOMIC_INIT(PANIC_CPU_INVALID);

  /*
   * A variant of panic() called from NMI context. We return if we've already
   * panicked on this CPU. If another CPU already panicked, loop in
   * nmi_panic_self_stop() which can provide architecture dependent code such
   * as saving register state for crash dump.
   */
  void nmi_panic(struct pt_regs *regs, const char *msg)
  {
  	int old_cpu, cpu;
  
  	cpu = raw_smp_processor_id();
  	old_cpu = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, cpu);
  
  	if (old_cpu == PANIC_CPU_INVALID)
  		panic("%s", msg);
  	else if (old_cpu != cpu)
  		nmi_panic_self_stop(regs);
  }
  EXPORT_SYMBOL(nmi_panic);

  /**
   *	panic - halt the system
   *	@fmt: The text string to print
   *
   *	Display a message, then perform cleanups.
   *
   *	This function never returns.
   */

  void panic(const char *fmt, ...)

  {

  	static char buf[1024];
  	va_list args;

  	long i, i_next = 0;
  	int state = 0;

  	int old_cpu, this_cpu;

  	bool _crash_kexec_post_notifiers = crash_kexec_post_notifiers;

  	/*

  	 * Disable local interrupts. This will prevent panic_smp_self_stop
  	 * from deadlocking the first cpu that invokes the panic, since
  	 * there is nothing to prevent an interrupt handler (that runs

  	 * after setting panic_cpu) from invoking panic() again.

  	 */
  	local_irq_disable();
  
  	/*

  	 * 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...

  	 *
  	 * Only one CPU is allowed to execute the panic code from here. For
  	 * multiple parallel invocations of panic, all other CPUs either
  	 * stop themself or will wait until they are stopped by the 1st CPU
  	 * with smp_send_stop().

  	 *
  	 * `old_cpu == PANIC_CPU_INVALID' means this is the 1st CPU which
  	 * comes here, so go ahead.
  	 * `old_cpu == this_cpu' means we came from nmi_panic() which sets
  	 * panic_cpu to this CPU.  In this case, this is also the 1st CPU.

  	 */

  	this_cpu = raw_smp_processor_id();
  	old_cpu  = atomic_cmpxchg(&panic_cpu, PANIC_CPU_INVALID, this_cpu);
  
  	if (old_cpu != PANIC_CPU_INVALID && old_cpu != this_cpu)

  		panic_smp_self_stop();

  	console_verbose();

  	bust_spinlocks(1);
  	va_start(args, fmt);
  	vsnprintf(buf, sizeof(buf), fmt, args);
  	va_end(args);

  	pr_emerg("Kernel panic - not syncing: %s
  ", buf);

  #ifdef CONFIG_DEBUG_BUGVERBOSE

  	/*
  	 * Avoid nested stack-dumping if a panic occurs during oops processing
  	 */

  	if (!test_taint(TAINT_DIE) && oops_in_progress <= 1)

  		dump_stack();

  #endif

  	/*
  	 * If we have crashed and we have a crash kernel loaded let it handle
  	 * everything else.

  	 * If we want to run this after calling panic_notifiers, pass
  	 * the "crash_kexec_post_notifiers" option to the kernel.

  	 *
  	 * Bypass the panic_cpu check and call __crash_kexec directly.

  	 */

  	if (!_crash_kexec_post_notifiers) {

  		printk_safe_flush_on_panic();

  		__crash_kexec(NULL);

  		/*
  		 * 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();
  	} else {
  		/*
  		 * If we want to do crash dump after notifier calls and
  		 * kmsg_dump, we will need architecture dependent extra
  		 * works in addition to stopping other CPUs.
  		 */
  		crash_smp_send_stop();
  	}

  	/*
  	 * Run any panic handlers, including those that might need to
  	 * add information to the kmsg dump output.
  	 */

  	atomic_notifier_call_chain(&panic_notifier_list, 0, buf);

  	/* Call flush even twice. It tries harder with a single online CPU */

  	printk_safe_flush_on_panic();

  	kmsg_dump(KMSG_DUMP_PANIC);

  	/*
  	 * If you doubt kdump always works fine in any situation,
  	 * "crash_kexec_post_notifiers" offers you a chance to run
  	 * panic_notifiers and dumping kmsg before kdump.
  	 * Note: since some panic_notifiers can make crashed kernel
  	 * more unstable, it can increase risks of the kdump failure too.

  	 *
  	 * Bypass the panic_cpu check and call __crash_kexec directly.

  	 */

  	if (_crash_kexec_post_notifiers)

  		__crash_kexec(NULL);

  #ifdef CONFIG_VT
  	unblank_screen();
  #endif
  	console_unblank();

  	/*
  	 * We may have ended up stopping the CPU holding the lock (in
  	 * smp_send_stop()) while still having some valuable data in the console
  	 * buffer.  Try to acquire the lock then release it regardless of the

  	 * result.  The release will also print the buffers out.  Locks debug
  	 * should be disabled to avoid reporting bad unlock balance when
  	 * panic() is not being callled from OOPS.

  	 */

  	debug_locks_off();

  	console_flush_on_panic();

  	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.
  		 */

  		pr_emerg("Rebooting in %d seconds..
  ", panic_timeout);

  		for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {

  			touch_nmi_watchdog();

  			if (i >= i_next) {
  				i += panic_blink(state ^= 1);
  				i_next = i + 3600 / PANIC_BLINK_SPD;
  			}
  			mdelay(PANIC_TIMER_STEP);

  		}

  	}
  	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.

  		 */

  		emergency_restart();

  	}
  #ifdef __sparc__
  	{
  		extern int stop_a_enabled;

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

  		stop_a_enabled = 1;

  		pr_emerg("Press Stop-A (L1-A) from sun keyboard or send break
  "
  			 "twice on console to return to the boot prom
  ");

  	}
  #endif

  #if defined(CONFIG_S390)

  	{
  		unsigned long caller;
  
  		caller = (unsigned long)__builtin_return_address(0);
  		disabled_wait(caller);
  	}

  #endif

  	pr_emerg("---[ end Kernel panic - not syncing: %s
  ", buf);

  	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);

  	}
  }
  
  EXPORT_SYMBOL(panic);

  /*
   * TAINT_FORCED_RMMOD could be a per-module flag but the module
   * is being removed anyway.
   */
  const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
  	{ 'P', 'G', true },	/* TAINT_PROPRIETARY_MODULE */
  	{ 'F', ' ', true },	/* TAINT_FORCED_MODULE */
  	{ 'S', ' ', false },	/* TAINT_CPU_OUT_OF_SPEC */
  	{ 'R', ' ', false },	/* TAINT_FORCED_RMMOD */
  	{ 'M', ' ', false },	/* TAINT_MACHINE_CHECK */
  	{ 'B', ' ', false },	/* TAINT_BAD_PAGE */
  	{ 'U', ' ', false },	/* TAINT_USER */
  	{ 'D', ' ', false },	/* TAINT_DIE */
  	{ 'A', ' ', false },	/* TAINT_OVERRIDDEN_ACPI_TABLE */
  	{ 'W', ' ', false },	/* TAINT_WARN */
  	{ 'C', ' ', true },	/* TAINT_CRAP */
  	{ 'I', ' ', false },	/* TAINT_FIRMWARE_WORKAROUND */
  	{ 'O', ' ', true },	/* TAINT_OOT_MODULE */
  	{ 'E', ' ', true },	/* TAINT_UNSIGNED_MODULE */
  	{ 'L', ' ', false },	/* TAINT_SOFTLOCKUP */
  	{ 'K', ' ', true },	/* TAINT_LIVEPATCH */

  };

  /**
   *	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.

   *  '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.

   *  'O' - Out-of-tree module has been loaded.

   *  'E' - Unsigned module has been loaded.

   *  'L' - A soft lockup has previously occurred.

   *  'K' - Kernel has been live patched.

   *

   *	The string is overwritten by the next call to print_tainted().

   */

  const char *print_tainted(void)
  {

  	static char buf[TAINT_FLAGS_COUNT + sizeof("Tainted: ")];

  
  	if (tainted_mask) {
  		char *s;
  		int i;
  
  		s = buf + sprintf(buf, "Tainted: ");

  		for (i = 0; i < TAINT_FLAGS_COUNT; i++) {
  			const struct taint_flag *t = &taint_flags[i];
  			*s++ = test_bit(i, &tainted_mask) ?

  					t->c_true : t->c_false;

  		}
  		*s = 0;
  	} else

  		snprintf(buf, sizeof(buf), "Not tainted");

  
  	return buf;

  }

  int test_taint(unsigned flag)

  {

  	return test_bit(flag, &tainted_mask);
  }
  EXPORT_SYMBOL(test_taint);
  
  unsigned long get_taint(void)
  {
  	return tainted_mask;

  }

  /**
   * add_taint: add a taint flag if not already set.
   * @flag: one of the TAINT_* constants.
   * @lockdep_ok: whether lock debugging is still OK.
   *
   * If something bad has gone wrong, you'll want @lockdebug_ok = false, but for
   * some notewortht-but-not-corrupting cases, it can be set to true.
   */
  void add_taint(unsigned flag, enum lockdep_ok lockdep_ok)

  {

  	if (lockdep_ok == LOCKDEP_NOW_UNRELIABLE && __debug_locks_off())

  		pr_warn("Disabling lock debugging due to kernel taint
  ");

  	set_bit(flag, &tainted_mask);

  }

  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));

  	else
  		oops_id++;

  
  	return 0;
  }
  late_initcall(init_oops_id);

  void print_oops_end_marker(void)

  {
  	init_oops_id();

  	pr_warn("---[ end trace %016llx ]---
  ", (unsigned long long)oops_id);

  }

  /*

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

  	print_oops_end_marker();

  	kmsg_dump(KMSG_DUMP_OOPS);

  }

  struct warn_args {

  	const char *fmt;

  	va_list args;

  };

  void __warn(const char *file, int line, void *caller, unsigned taint,
  	    struct pt_regs *regs, struct warn_args *args)

  {

  	disable_trace_on_warning();

  	pr_warn("------------[ cut here ]------------
  ");

  
  	if (file)
  		pr_warn("WARNING: CPU: %d PID: %d at %s:%d %pS
  ",
  			raw_smp_processor_id(), current->pid, file, line,
  			caller);
  	else
  		pr_warn("WARNING: CPU: %d PID: %d at %pS
  ",
  			raw_smp_processor_id(), current->pid, caller);

  	if (args)
  		vprintk(args->fmt, args->args);

  	if (panic_on_warn) {
  		/*
  		 * This thread may hit another WARN() in the panic path.
  		 * Resetting this prevents additional WARN() from panicking the
  		 * system on this thread.  Other threads are blocked by the
  		 * panic_mutex in panic().
  		 */
  		panic_on_warn = 0;
  		panic("panic_on_warn set ...
  ");
  	}

  	print_modules();

  
  	if (regs)
  		show_regs(regs);
  	else
  		dump_stack();

  	print_oops_end_marker();

  	/* Just a warning, don't kill lockdep. */
  	add_taint(taint, LOCKDEP_STILL_OK);

  }

  #ifdef WANT_WARN_ON_SLOWPATH

  void warn_slowpath_fmt(const char *file, int line, const char *fmt, ...)
  {

  	struct warn_args args;

  
  	args.fmt = fmt;
  	va_start(args.args, fmt);

  	__warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL,
  	       &args);

  	va_end(args.args);
  }

  EXPORT_SYMBOL(warn_slowpath_fmt);

  void warn_slowpath_fmt_taint(const char *file, int line,
  			     unsigned taint, const char *fmt, ...)
  {

  	struct warn_args args;

  
  	args.fmt = fmt;
  	va_start(args.args, fmt);

  	__warn(file, line, __builtin_return_address(0), taint, NULL, &args);

  	va_end(args.args);
  }
  EXPORT_SYMBOL(warn_slowpath_fmt_taint);

  void warn_slowpath_null(const char *file, int line)
  {

  	__warn(file, line, __builtin_return_address(0), TAINT_WARN, NULL, NULL);

  }
  EXPORT_SYMBOL(warn_slowpath_null);

  #endif

  #ifdef CONFIG_CC_STACKPROTECTOR

  /*
   * Called when gcc's -fstack-protector feature is used, and
   * gcc detects corruption of the on-stack canary value
   */

  __visible void __stack_chk_fail(void)

  {

  	panic("stack-protector: Kernel stack is corrupted in: %p
  ",
  		__builtin_return_address(0));

  }
  EXPORT_SYMBOL(__stack_chk_fail);

  #endif

  #ifdef CONFIG_ARCH_HAS_REFCOUNT
  void refcount_error_report(struct pt_regs *regs, const char *err)
  {
  	WARN_RATELIMIT(1, "refcount_t %s at %pB in %s[%d], uid/euid: %u/%u
  ",
  		err, (void *)instruction_pointer(regs),
  		current->comm, task_pid_nr(current),
  		from_kuid_munged(&init_user_ns, current_uid()),
  		from_kuid_munged(&init_user_ns, current_euid()));
  }
  #endif

  core_param(panic, panic_timeout, int, 0644);
  core_param(pause_on_oops, pause_on_oops, int, 0644);

  core_param(panic_on_warn, panic_on_warn, int, 0644);

  core_param(crash_kexec_post_notifiers, crash_kexec_post_notifiers, bool, 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);