// SPDX-License-Identifier: GPL-2.0-only

  #include <linux/kdebug.h>
  #include <linux/kprobes.h>

  #include <linux/export.h>

  #include <linux/notifier.h>
  #include <linux/rcupdate.h>
  #include <linux/vmalloc.h>

  #include <linux/reboot.h>

  
  /*
   *	Notifier list for kernel code which wants to be called
   *	at shutdown. This is used to stop any idling DMA operations
   *	and the like.
   */
  BLOCKING_NOTIFIER_HEAD(reboot_notifier_list);
  
  /*
   *	Notifier chain core routines.  The exported routines below
   *	are layered on top of these, with appropriate locking added.
   */
  
  static int notifier_chain_register(struct notifier_block **nl,
  		struct notifier_block *n)
  {
  	while ((*nl) != NULL) {

  		if (unlikely((*nl) == n)) {
  			WARN(1, "double register detected");
  			return 0;
  		}

  		if (n->priority > (*nl)->priority)
  			break;
  		nl = &((*nl)->next);
  	}
  	n->next = *nl;
  	rcu_assign_pointer(*nl, n);
  	return 0;
  }
  
  static int notifier_chain_unregister(struct notifier_block **nl,
  		struct notifier_block *n)
  {
  	while ((*nl) != NULL) {
  		if ((*nl) == n) {
  			rcu_assign_pointer(*nl, n->next);
  			return 0;
  		}
  		nl = &((*nl)->next);
  	}
  	return -ENOENT;
  }
  
  /**
   * notifier_call_chain - Informs the registered notifiers about an event.
   *	@nl:		Pointer to head of the blocking notifier chain
   *	@val:		Value passed unmodified to notifier function
   *	@v:		Pointer passed unmodified to notifier function
   *	@nr_to_call:	Number of notifier functions to be called. Don't care
   *			value of this parameter is -1.
   *	@nr_calls:	Records the number of notifications sent. Don't care
   *			value of this field is NULL.
   *	@returns:	notifier_call_chain returns the value returned by the
   *			last notifier function called.
   */

  static int notifier_call_chain(struct notifier_block **nl,
  			       unsigned long val, void *v,
  			       int nr_to_call, int *nr_calls)

  {
  	int ret = NOTIFY_DONE;
  	struct notifier_block *nb, *next_nb;

  	nb = rcu_dereference_raw(*nl);

  
  	while (nb && nr_to_call) {

  		next_nb = rcu_dereference_raw(nb->next);

  
  #ifdef CONFIG_DEBUG_NOTIFIERS

  		if (unlikely(!func_ptr_is_kernel_text(nb->notifier_call))) {

  			WARN(1, "Invalid notifier called!");
  			nb = next_nb;
  			continue;
  		}
  #endif

  		ret = nb->notifier_call(nb, val, v);
  
  		if (nr_calls)
  			(*nr_calls)++;

  		if (ret & NOTIFY_STOP_MASK)

  			break;
  		nb = next_nb;
  		nr_to_call--;
  	}
  	return ret;
  }

  NOKPROBE_SYMBOL(notifier_call_chain);

  /**
   * notifier_call_chain_robust - Inform the registered notifiers about an event
   *                              and rollback on error.
   * @nl:		Pointer to head of the blocking notifier chain
   * @val_up:	Value passed unmodified to the notifier function
   * @val_down:	Value passed unmodified to the notifier function when recovering
   *              from an error on @val_up
   * @v		Pointer passed unmodified to the notifier function
   *
   * NOTE:	It is important the @nl chain doesn't change between the two
   *		invocations of notifier_call_chain() such that we visit the
   *		exact same notifier callbacks; this rules out any RCU usage.
   *
   * Returns:	the return value of the @val_up call.
   */
  static int notifier_call_chain_robust(struct notifier_block **nl,
  				     unsigned long val_up, unsigned long val_down,
  				     void *v)
  {
  	int ret, nr = 0;
  
  	ret = notifier_call_chain(nl, val_up, v, -1, &nr);
  	if (ret & NOTIFY_STOP_MASK)
  		notifier_call_chain(nl, val_down, v, nr-1, NULL);
  
  	return ret;
  }

  /*
   *	Atomic notifier chain routines.  Registration and unregistration
   *	use a spinlock, and call_chain is synchronized by RCU (no locks).
   */
  
  /**
   *	atomic_notifier_chain_register - Add notifier to an atomic notifier chain
   *	@nh: Pointer to head of the atomic notifier chain
   *	@n: New entry in notifier chain
   *
   *	Adds a notifier to an atomic notifier chain.
   *
   *	Currently always returns zero.
   */
  int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
  		struct notifier_block *n)
  {
  	unsigned long flags;
  	int ret;
  
  	spin_lock_irqsave(&nh->lock, flags);
  	ret = notifier_chain_register(&nh->head, n);
  	spin_unlock_irqrestore(&nh->lock, flags);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(atomic_notifier_chain_register);
  
  /**
   *	atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain
   *	@nh: Pointer to head of the atomic notifier chain
   *	@n: Entry to remove from notifier chain
   *
   *	Removes a notifier from an atomic notifier chain.
   *
   *	Returns zero on success or %-ENOENT on failure.
   */
  int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
  		struct notifier_block *n)
  {
  	unsigned long flags;
  	int ret;
  
  	spin_lock_irqsave(&nh->lock, flags);
  	ret = notifier_chain_unregister(&nh->head, n);
  	spin_unlock_irqrestore(&nh->lock, flags);
  	synchronize_rcu();
  	return ret;
  }
  EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
  
  /**

   *	atomic_notifier_call_chain - Call functions in an atomic notifier chain

   *	@nh: Pointer to head of the atomic notifier chain
   *	@val: Value passed unmodified to notifier function
   *	@v: Pointer passed unmodified to notifier function

   *
   *	Calls each function in a notifier chain in turn.  The functions
   *	run in an atomic context, so they must not block.
   *	This routine uses RCU to synchronize with changes to the chain.
   *
   *	If the return value of the notifier can be and'ed
   *	with %NOTIFY_STOP_MASK then atomic_notifier_call_chain()
   *	will return immediately, with the return value of
   *	the notifier function which halted execution.
   *	Otherwise the return value is the return value
   *	of the last notifier function called.
   */

  int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
  			       unsigned long val, void *v)

  {
  	int ret;
  
  	rcu_read_lock();

  	ret = notifier_call_chain(&nh->head, val, v, -1, NULL);

  	rcu_read_unlock();

  	return ret;

  }
  EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);

  NOKPROBE_SYMBOL(atomic_notifier_call_chain);

  
  /*
   *	Blocking notifier chain routines.  All access to the chain is
   *	synchronized by an rwsem.
   */
  
  /**
   *	blocking_notifier_chain_register - Add notifier to a blocking notifier chain
   *	@nh: Pointer to head of the blocking notifier chain
   *	@n: New entry in notifier chain
   *
   *	Adds a notifier to a blocking notifier chain.
   *	Must be called in process context.
   *
   *	Currently always returns zero.
   */
  int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
  		struct notifier_block *n)
  {
  	int ret;
  
  	/*
  	 * This code gets used during boot-up, when task switching is
  	 * not yet working and interrupts must remain disabled.  At
  	 * such times we must not call down_write().
  	 */
  	if (unlikely(system_state == SYSTEM_BOOTING))
  		return notifier_chain_register(&nh->head, n);
  
  	down_write(&nh->rwsem);
  	ret = notifier_chain_register(&nh->head, n);
  	up_write(&nh->rwsem);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
  
  /**
   *	blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
   *	@nh: Pointer to head of the blocking notifier chain
   *	@n: Entry to remove from notifier chain
   *
   *	Removes a notifier from a blocking notifier chain.
   *	Must be called from process context.
   *
   *	Returns zero on success or %-ENOENT on failure.
   */
  int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
  		struct notifier_block *n)
  {
  	int ret;
  
  	/*
  	 * This code gets used during boot-up, when task switching is
  	 * not yet working and interrupts must remain disabled.  At
  	 * such times we must not call down_write().
  	 */
  	if (unlikely(system_state == SYSTEM_BOOTING))
  		return notifier_chain_unregister(&nh->head, n);
  
  	down_write(&nh->rwsem);
  	ret = notifier_chain_unregister(&nh->head, n);
  	up_write(&nh->rwsem);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);

  int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh,
  		unsigned long val_up, unsigned long val_down, void *v)
  {
  	int ret = NOTIFY_DONE;
  
  	/*
  	 * We check the head outside the lock, but if this access is
  	 * racy then it does not matter what the result of the test
  	 * is, we re-check the list after having taken the lock anyway:
  	 */
  	if (rcu_access_pointer(nh->head)) {
  		down_read(&nh->rwsem);
  		ret = notifier_call_chain_robust(&nh->head, val_up, val_down, v);
  		up_read(&nh->rwsem);
  	}
  	return ret;
  }
  EXPORT_SYMBOL_GPL(blocking_notifier_call_chain_robust);

  /**

   *	blocking_notifier_call_chain - Call functions in a blocking notifier chain

   *	@nh: Pointer to head of the blocking notifier chain
   *	@val: Value passed unmodified to notifier function
   *	@v: Pointer passed unmodified to notifier function

   *
   *	Calls each function in a notifier chain in turn.  The functions
   *	run in a process context, so they are allowed to block.
   *
   *	If the return value of the notifier can be and'ed
   *	with %NOTIFY_STOP_MASK then blocking_notifier_call_chain()
   *	will return immediately, with the return value of
   *	the notifier function which halted execution.
   *	Otherwise the return value is the return value
   *	of the last notifier function called.
   */

  int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
  		unsigned long val, void *v)

  {
  	int ret = NOTIFY_DONE;
  
  	/*
  	 * We check the head outside the lock, but if this access is
  	 * racy then it does not matter what the result of the test
  	 * is, we re-check the list after having taken the lock anyway:
  	 */

  	if (rcu_access_pointer(nh->head)) {

  		down_read(&nh->rwsem);

  		ret = notifier_call_chain(&nh->head, val, v, -1, NULL);

  		up_read(&nh->rwsem);
  	}
  	return ret;
  }

  EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
  
  /*
   *	Raw notifier chain routines.  There is no protection;
   *	the caller must provide it.  Use at your own risk!
   */
  
  /**
   *	raw_notifier_chain_register - Add notifier to a raw notifier chain
   *	@nh: Pointer to head of the raw notifier chain
   *	@n: New entry in notifier chain
   *
   *	Adds a notifier to a raw notifier chain.
   *	All locking must be provided by the caller.
   *
   *	Currently always returns zero.
   */
  int raw_notifier_chain_register(struct raw_notifier_head *nh,
  		struct notifier_block *n)
  {
  	return notifier_chain_register(&nh->head, n);
  }
  EXPORT_SYMBOL_GPL(raw_notifier_chain_register);
  
  /**
   *	raw_notifier_chain_unregister - Remove notifier from a raw notifier chain
   *	@nh: Pointer to head of the raw notifier chain
   *	@n: Entry to remove from notifier chain
   *
   *	Removes a notifier from a raw notifier chain.
   *	All locking must be provided by the caller.
   *
   *	Returns zero on success or %-ENOENT on failure.
   */
  int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
  		struct notifier_block *n)
  {
  	return notifier_chain_unregister(&nh->head, n);
  }
  EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);

  int raw_notifier_call_chain_robust(struct raw_notifier_head *nh,
  		unsigned long val_up, unsigned long val_down, void *v)
  {
  	return notifier_call_chain_robust(&nh->head, val_up, val_down, v);
  }
  EXPORT_SYMBOL_GPL(raw_notifier_call_chain_robust);

  /**

   *	raw_notifier_call_chain - Call functions in a raw notifier chain

   *	@nh: Pointer to head of the raw notifier chain
   *	@val: Value passed unmodified to notifier function
   *	@v: Pointer passed unmodified to notifier function

   *
   *	Calls each function in a notifier chain in turn.  The functions
   *	run in an undefined context.
   *	All locking must be provided by the caller.
   *
   *	If the return value of the notifier can be and'ed
   *	with %NOTIFY_STOP_MASK then raw_notifier_call_chain()
   *	will return immediately, with the return value of
   *	the notifier function which halted execution.
   *	Otherwise the return value is the return value
   *	of the last notifier function called.
   */

  int raw_notifier_call_chain(struct raw_notifier_head *nh,
  		unsigned long val, void *v)
  {

  	return notifier_call_chain(&nh->head, val, v, -1, NULL);

  }
  EXPORT_SYMBOL_GPL(raw_notifier_call_chain);

  #ifdef CONFIG_SRCU

  /*
   *	SRCU notifier chain routines.    Registration and unregistration
   *	use a mutex, and call_chain is synchronized by SRCU (no locks).
   */
  
  /**
   *	srcu_notifier_chain_register - Add notifier to an SRCU notifier chain
   *	@nh: Pointer to head of the SRCU notifier chain
   *	@n: New entry in notifier chain
   *
   *	Adds a notifier to an SRCU notifier chain.
   *	Must be called in process context.
   *
   *	Currently always returns zero.
   */
  int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
  		struct notifier_block *n)
  {
  	int ret;
  
  	/*
  	 * This code gets used during boot-up, when task switching is
  	 * not yet working and interrupts must remain disabled.  At
  	 * such times we must not call mutex_lock().
  	 */
  	if (unlikely(system_state == SYSTEM_BOOTING))
  		return notifier_chain_register(&nh->head, n);
  
  	mutex_lock(&nh->mutex);
  	ret = notifier_chain_register(&nh->head, n);
  	mutex_unlock(&nh->mutex);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(srcu_notifier_chain_register);
  
  /**
   *	srcu_notifier_chain_unregister - Remove notifier from an SRCU notifier chain
   *	@nh: Pointer to head of the SRCU notifier chain
   *	@n: Entry to remove from notifier chain
   *
   *	Removes a notifier from an SRCU notifier chain.
   *	Must be called from process context.
   *
   *	Returns zero on success or %-ENOENT on failure.
   */
  int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
  		struct notifier_block *n)
  {
  	int ret;
  
  	/*
  	 * This code gets used during boot-up, when task switching is
  	 * not yet working and interrupts must remain disabled.  At
  	 * such times we must not call mutex_lock().
  	 */
  	if (unlikely(system_state == SYSTEM_BOOTING))
  		return notifier_chain_unregister(&nh->head, n);
  
  	mutex_lock(&nh->mutex);
  	ret = notifier_chain_unregister(&nh->head, n);
  	mutex_unlock(&nh->mutex);
  	synchronize_srcu(&nh->srcu);
  	return ret;
  }
  EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
  
  /**

   *	srcu_notifier_call_chain - Call functions in an SRCU notifier chain

   *	@nh: Pointer to head of the SRCU notifier chain
   *	@val: Value passed unmodified to notifier function
   *	@v: Pointer passed unmodified to notifier function

   *
   *	Calls each function in a notifier chain in turn.  The functions
   *	run in a process context, so they are allowed to block.
   *
   *	If the return value of the notifier can be and'ed
   *	with %NOTIFY_STOP_MASK then srcu_notifier_call_chain()
   *	will return immediately, with the return value of
   *	the notifier function which halted execution.
   *	Otherwise the return value is the return value
   *	of the last notifier function called.
   */

  int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
  		unsigned long val, void *v)

  {
  	int ret;
  	int idx;
  
  	idx = srcu_read_lock(&nh->srcu);

  	ret = notifier_call_chain(&nh->head, val, v, -1, NULL);

  	srcu_read_unlock(&nh->srcu, idx);
  	return ret;
  }

  EXPORT_SYMBOL_GPL(srcu_notifier_call_chain);
  
  /**
   *	srcu_init_notifier_head - Initialize an SRCU notifier head
   *	@nh: Pointer to head of the srcu notifier chain
   *
   *	Unlike other sorts of notifier heads, SRCU notifier heads require
   *	dynamic initialization.  Be sure to call this routine before
   *	calling any of the other SRCU notifier routines for this head.
   *
   *	If an SRCU notifier head is deallocated, it must first be cleaned
   *	up by calling srcu_cleanup_notifier_head().  Otherwise the head's
   *	per-cpu data (used by the SRCU mechanism) will leak.
   */
  void srcu_init_notifier_head(struct srcu_notifier_head *nh)
  {
  	mutex_init(&nh->mutex);
  	if (init_srcu_struct(&nh->srcu) < 0)
  		BUG();
  	nh->head = NULL;
  }
  EXPORT_SYMBOL_GPL(srcu_init_notifier_head);

  #endif /* CONFIG_SRCU */

  static ATOMIC_NOTIFIER_HEAD(die_chain);

  int notrace notify_die(enum die_val val, const char *str,

  	       struct pt_regs *regs, long err, int trap, int sig)
  {
  	struct die_args args = {
  		.regs	= regs,
  		.str	= str,
  		.err	= err,
  		.trapnr	= trap,
  		.signr	= sig,
  
  	};

  	RCU_LOCKDEP_WARN(!rcu_is_watching(),

  			   "notify_die called but RCU thinks we're quiescent");

  	return atomic_notifier_call_chain(&die_chain, val, &args);
  }

  NOKPROBE_SYMBOL(notify_die);

  
  int register_die_notifier(struct notifier_block *nb)
  {

  	return atomic_notifier_chain_register(&die_chain, nb);
  }
  EXPORT_SYMBOL_GPL(register_die_notifier);
  
  int unregister_die_notifier(struct notifier_block *nb)
  {
  	return atomic_notifier_chain_unregister(&die_chain, nb);
  }
  EXPORT_SYMBOL_GPL(unregister_die_notifier);