linux/kernel/notifier.c

// 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>

#define CREATE_TRACE_POINTS
#include <trace/events/notifier.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(…) …;

/*
 *	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,
				   bool unique_priority)
{ … }

static int notifier_chain_unregister(struct notifier_block **nl,
		struct notifier_block *n)
{ … }

/**
 * 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.
 *	Return:		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)
{ … }
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.
 *
 * Return:	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)
{ … }

/*
 *	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.
 *
 *	Returns 0 on success, %-EEXIST on error.
 */
int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
		struct notifier_block *n)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	atomic_notifier_chain_register_unique_prio - 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 if there is no other
 *	notifier registered using the same priority.
 *
 *	Returns 0 on success, %-EEXIST or %-EBUSY on error.
 */
int atomic_notifier_chain_register_unique_prio(struct atomic_notifier_head *nh,
					       struct notifier_block *n)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	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)
{ … }
EXPORT_SYMBOL_GPL(…);
NOKPROBE_SYMBOL(atomic_notifier_call_chain);

/**
 *	atomic_notifier_call_chain_is_empty - Check whether notifier chain is empty
 *	@nh: Pointer to head of the atomic notifier chain
 *
 *	Checks whether notifier chain is empty.
 *
 *	Returns true is notifier chain is empty, false otherwise.
 */
bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh)
{ … }

/*
 *	Blocking notifier chain routines.  All access to the chain is
 *	synchronized by an rwsem.
 */

static int __blocking_notifier_chain_register(struct blocking_notifier_head *nh,
					      struct notifier_block *n,
					      bool unique_priority)
{ … }

/**
 *	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.
 *
 *	Returns 0 on success, %-EEXIST on error.
 */
int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
		struct notifier_block *n)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	blocking_notifier_chain_register_unique_prio - 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 an blocking notifier chain if there is no other
 *	notifier registered using the same priority.
 *
 *	Returns 0 on success, %-EEXIST or %-EBUSY on error.
 */
int blocking_notifier_chain_register_unique_prio(struct blocking_notifier_head *nh,
						 struct notifier_block *n)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	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)
{ … }
EXPORT_SYMBOL_GPL(…);

int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh,
		unsigned long val_up, unsigned long val_down, void *v)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	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)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 *	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.
 *
 *	Returns 0 on success, %-EEXIST on error.
 */
int raw_notifier_chain_register(struct raw_notifier_head *nh,
		struct notifier_block *n)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	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)
{ … }
EXPORT_SYMBOL_GPL(…);

int raw_notifier_call_chain_robust(struct raw_notifier_head *nh,
		unsigned long val_up, unsigned long val_down, void *v)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	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)
{ … }
EXPORT_SYMBOL_GPL(…);

/*
 *	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.
 *
 *	Returns 0 on success, %-EEXIST on error.
 */
int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
		struct notifier_block *n)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	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)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 *	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)
{ … }
EXPORT_SYMBOL_GPL(…);

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)
{ … }
NOKPROBE_SYMBOL(notify_die);

int register_die_notifier(struct notifier_block *nb)
{ … }
EXPORT_SYMBOL_GPL(…);

int unregister_die_notifier(struct notifier_block *nb)
{ … }
EXPORT_SYMBOL_GPL(…);