Add kernel/notifier.c

There is separate notifier header, but no separate notifier .c file.

Extract notifier code out of kernel/sys.c which will remain for
misc syscalls I hope. Merge kernel/die_notifier.c into kernel/notifier.c.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 539 insertions, 0 deletions

diff --git a/kernel/notifier.c b/kernel/notifier.c
new file mode 100644
index 000000000000..4253f472f060
--- /dev/null
+++ b/kernel/notifier.c
@@ -0,0 +1,539 @@
+#include <linux/kdebug.h>
+#include <linux/kprobes.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/rcupdate.h>
+#include <linux/vmalloc.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 (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 __kprobes 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(*nl);
+
+	while (nb && nr_to_call) {
+		next_nb = rcu_dereference(nb->next);
+		ret = nb->notifier_call(nb, val, v);
+
+		if (nr_calls)
+			(*nr_calls)++;
+
+		if ((ret & NOTIFY_STOP_MASK) == NOTIFY_STOP_MASK)
+			break;
+		nb = next_nb;
+		nr_to_call--;
+	}
+	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
+ *	@nr_to_call: See the comment for notifier_call_chain.
+ *	@nr_calls: See the comment for notifier_call_chain.
+ *
+ *	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 __kprobes __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
+					unsigned long val, void *v,
+					int nr_to_call, int *nr_calls)
+{
+	int ret;
+
+	rcu_read_lock();
+	ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
+	rcu_read_unlock();
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
+
+int __kprobes atomic_notifier_call_chain(struct atomic_notifier_head *nh,
+		unsigned long val, void *v)
+{
+	return __atomic_notifier_call_chain(nh, val, v, -1, NULL);
+}
+EXPORT_SYMBOL_GPL(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);
+
+/**
+ *	__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
+ *	@nr_to_call: See comment for notifier_call_chain.
+ *	@nr_calls: See comment for notifier_call_chain.
+ *
+ *	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 nr_to_call, int *nr_calls)
+{
+	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_dereference(nh->head)) {
+		down_read(&nh->rwsem);
+		ret = notifier_call_chain(&nh->head, val, v, nr_to_call,
+					nr_calls);
+		up_read(&nh->rwsem);
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__blocking_notifier_call_chain);
+
+int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
+		unsigned long val, void *v)
+{
+	return __blocking_notifier_call_chain(nh, val, v, -1, NULL);
+}
+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);
+
+/**
+ *	__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
+ *	@nr_to_call: See comment for notifier_call_chain.
+ *	@nr_calls: See comment for notifier_call_chain
+ *
+ *	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,
+			      int nr_to_call, int *nr_calls)
+{
+	return notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
+}
+EXPORT_SYMBOL_GPL(__raw_notifier_call_chain);
+
+int raw_notifier_call_chain(struct raw_notifier_head *nh,
+		unsigned long val, void *v)
+{
+	return __raw_notifier_call_chain(nh, val, v, -1, NULL);
+}
+EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
+
+/*
+ *	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
+ *	@nr_to_call: See comment for notifier_call_chain.
+ *	@nr_calls: See comment for notifier_call_chain
+ *
+ *	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 nr_to_call, int *nr_calls)
+{
+	int ret;
+	int idx;
+
+	idx = srcu_read_lock(&nh->srcu);
+	ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
+	srcu_read_unlock(&nh->srcu, idx);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(__srcu_notifier_call_chain);
+
+int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
+		unsigned long val, void *v)
+{
+	return __srcu_notifier_call_chain(nh, val, v, -1, NULL);
+}
+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);
+
+/**
+ *	register_reboot_notifier - Register function to be called at reboot time
+ *	@nb: Info about notifier function to be called
+ *
+ *	Registers a function with the list of functions
+ *	to be called at reboot time.
+ *
+ *	Currently always returns zero, as blocking_notifier_chain_register()
+ *	always returns zero.
+ */
+int register_reboot_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&reboot_notifier_list, nb);
+}
+EXPORT_SYMBOL(register_reboot_notifier);
+
+/**
+ *	unregister_reboot_notifier - Unregister previously registered reboot notifier
+ *	@nb: Hook to be unregistered
+ *
+ *	Unregisters a previously registered reboot
+ *	notifier function.
+ *
+ *	Returns zero on success, or %-ENOENT on failure.
+ */
+int unregister_reboot_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&reboot_notifier_list, nb);
+}
+EXPORT_SYMBOL(unregister_reboot_notifier);
+
+static ATOMIC_NOTIFIER_HEAD(die_chain);
+
+int 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,
+
+	};
+	return atomic_notifier_call_chain(&die_chain, val, &args);
+}
+
+int register_die_notifier(struct notifier_block *nb)
+{
+	vmalloc_sync_all();
+	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);