[PATCH] Notify page fault call chain
[linux-2.6.git] / kernel / kprobes.c
index 507f26e7ae7cff796f8f7e3a40d7f9b78bb9864e..64aab081153b8345649710623b12704f5a87aec6 100644 (file)
 
 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;
 }