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);