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authorAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>2006-06-26 00:25:29 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-26 09:58:22 -0700
commite6f47f978bcd5413fff610613b18e9e0eab9bc1b (patch)
treebf9e698cb76a0e958a8c9157fba74fb6d8255298 /kernel/kprobes.c
parent3d5631e0631a11633c649bc995a6537ec21b67b4 (diff)
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[PATCH] Notify page fault call chain
With this patch Kprobes now registers for page fault notifications only when their is an active probe registered. Once all the active probes are unregistered their is no need to be notified of page faults and kprobes unregisters itself from the page fault notifications. Hence we will have ZERO side effects when no probes are active. Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/kprobes.c')
-rw-r--r--kernel/kprobes.c30
1 files changed, 23 insertions, 7 deletions
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 507f26e7ae7c..64aab081153b 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -47,11 +47,17 @@
static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
+static atomic_t kprobe_count;
DEFINE_MUTEX(kprobe_mutex); /* Protects kprobe_table */
DEFINE_SPINLOCK(kretprobe_lock); /* Protects kretprobe_inst_table */
static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
+static struct notifier_block kprobe_page_fault_nb = {
+ .notifier_call = kprobe_exceptions_notify,
+ .priority = 0x7fffffff /* we need to notified first */
+};
+
#ifdef __ARCH_WANT_KPROBES_INSN_SLOT
/*
* kprobe->ainsn.insn points to the copy of the instruction to be
@@ -465,6 +471,8 @@ static int __kprobes __register_kprobe(struct kprobe *p,
old_p = get_kprobe(p->addr);
if (old_p) {
ret = register_aggr_kprobe(old_p, p);
+ if (!ret)
+ atomic_inc(&kprobe_count);
goto out;
}
@@ -475,6 +483,10 @@ static int __kprobes __register_kprobe(struct kprobe *p,
hlist_add_head_rcu(&p->hlist,
&kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]);
+ if (atomic_add_return(1, &kprobe_count) == \
+ (ARCH_INACTIVE_KPROBE_COUNT + 1))
+ register_page_fault_notifier(&kprobe_page_fault_nb);
+
arch_arm_kprobe(p);
out:
@@ -553,6 +565,16 @@ valid_p:
}
mutex_unlock(&kprobe_mutex);
}
+
+ /* Call unregister_page_fault_notifier()
+ * if no probes are active
+ */
+ mutex_lock(&kprobe_mutex);
+ if (atomic_add_return(-1, &kprobe_count) == \
+ ARCH_INACTIVE_KPROBE_COUNT)
+ unregister_page_fault_notifier(&kprobe_page_fault_nb);
+ mutex_unlock(&kprobe_mutex);
+ return;
}
static struct notifier_block kprobe_exceptions_nb = {
@@ -560,10 +582,6 @@ static struct notifier_block kprobe_exceptions_nb = {
.priority = 0x7fffffff /* we need to be notified first */
};
-static struct notifier_block kprobe_page_fault_nb = {
- .notifier_call = kprobe_exceptions_notify,
- .priority = 0x7fffffff /* we need to notified first */
-};
int __kprobes register_jprobe(struct jprobe *jp)
{
@@ -673,14 +691,12 @@ static int __init init_kprobes(void)
INIT_HLIST_HEAD(&kprobe_table[i]);
INIT_HLIST_HEAD(&kretprobe_inst_table[i]);
}
+ atomic_set(&kprobe_count, 0);
err = arch_init_kprobes();
if (!err)
err = register_die_notifier(&kprobe_exceptions_nb);
- if (!err)
- err = register_page_fault_notifier(&kprobe_page_fault_nb);
-
return err;
}