kprobes: add (un)register_kprobes for batch registration

Introduce unregister_/register_kprobes() for kprobe batch registration.  This
can reduce waiting time for synchronized_sched() when a lot of probes have to
be unregistered at once.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: David Miller <davem@davemloft.net>
Cc: "Frank Ch. Eigler" <fche@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 87 insertions, 37 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index f02a4311768b..76275fc025a5 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -580,6 +580,7 @@ static int __kprobes __register_kprobe(struct kprobe *p,
         }
 
         p->nmissed = 0;
+        INIT_LIST_HEAD(&p->list);
         mutex_lock(&kprobe_mutex);
         old_p = get_kprobe(p->addr);
         if (old_p) {
@@ -606,35 +607,28 @@ out:
         return ret;
 }
 
-int __kprobes register_kprobe(struct kprobe *p)
-{
-        return __register_kprobe(p, (unsigned long)__builtin_return_address(0));
-}
-
-void __kprobes unregister_kprobe(struct kprobe *p)
+/*
+ * Unregister a kprobe without a scheduler synchronization.
+ */
+static int __kprobes __unregister_kprobe_top(struct kprobe *p)
 {
-        struct module *mod;
         struct kprobe *old_p, *list_p;
-        int cleanup_p;
 
-        mutex_lock(&kprobe_mutex);
         old_p = get_kprobe(p->addr);
-        if (unlikely(!old_p)) {
-                mutex_unlock(&kprobe_mutex);
-                return;
-        }
+        if (unlikely(!old_p))
+                return -EINVAL;
+
         if (p != old_p) {
                 list_for_each_entry_rcu(list_p, &old_p->list, list)
                         if (list_p == p)
                         /* kprobe p is a valid probe */
                                 goto valid_p;
-                mutex_unlock(&kprobe_mutex);
-                return;
+                return -EINVAL;
         }
 valid_p:
         if (old_p == p ||
             (old_p->pre_handler == aggr_pre_handler &&
-             p->list.next == &old_p->list && p->list.prev == &old_p->list)) {
+             list_is_singular(&old_p->list))) {
                 /*
                  * Only probe on the hash list. Disarm only if kprobes are
                  * enabled - otherwise, the breakpoint would already have
@@ -643,43 +637,97 @@ valid_p:
                 if (kprobe_enabled)
                         arch_disarm_kprobe(p);
                 hlist_del_rcu(&old_p->hlist);
-                cleanup_p = 1;
         } else {
+                if (p->break_handler)
+                        old_p->break_handler = NULL;
+                if (p->post_handler) {
+                        list_for_each_entry_rcu(list_p, &old_p->list, list) {
+                                if ((list_p != p) && (list_p->post_handler))
+                                        goto noclean;
+                        }
+                        old_p->post_handler = NULL;
+                }
+noclean:
                 list_del_rcu(&p->list);
-                cleanup_p = 0;
         }
+        return 0;
+}
 
-        mutex_unlock(&kprobe_mutex);
+static void __kprobes __unregister_kprobe_bottom(struct kprobe *p)
+{
+        struct module *mod;
+        struct kprobe *old_p;
 
-        synchronize_sched();
         if (p->mod_refcounted) {
                 mod = module_text_address((unsigned long)p->addr);
                 if (mod)
                         module_put(mod);
         }
 
-        if (cleanup_p) {
-                if (p != old_p) {
-                        list_del_rcu(&p->list);
+        if (list_empty(&p->list) || list_is_singular(&p->list)) {
+                if (!list_empty(&p->list)) {
+                        /* "p" is the last child of an aggr_kprobe */
+                        old_p = list_entry(p->list.next, struct kprobe, list);
+                        list_del(&p->list);
                         kfree(old_p);
                 }
                 arch_remove_kprobe(p);
-        } else {
-                mutex_lock(&kprobe_mutex);
-                if (p->break_handler)
-                        old_p->break_handler = NULL;
-                if (p->post_handler){
-                        list_for_each_entry_rcu(list_p, &old_p->list, list){
-                                if (list_p->post_handler){
-                                        cleanup_p = 2;
-                                        break;
-                                }
-                        }
-                        if (cleanup_p == 0)
-                                old_p->post_handler = NULL;
+        }
+}
+
+static int __register_kprobes(struct kprobe **kps, int num,
+        unsigned long called_from)
+{
+        int i, ret = 0;
+
+        if (num <= 0)
+                return -EINVAL;
+        for (i = 0; i < num; i++) {
+                ret = __register_kprobe(kps[i], called_from);
+                if (ret < 0 && i > 0) {
+                        unregister_kprobes(kps, i);
+                        break;
                 }
-                mutex_unlock(&kprobe_mutex);
         }
+        return ret;
+}
+
+/*
+ * Registration and unregistration functions for kprobe.
+ */
+int __kprobes register_kprobe(struct kprobe *p)
+{
+        return __register_kprobes(&p, 1,
+                                  (unsigned long)__builtin_return_address(0));
+}
+
+void __kprobes unregister_kprobe(struct kprobe *p)
+{
+        unregister_kprobes(&p, 1);
+}
+
+int __kprobes register_kprobes(struct kprobe **kps, int num)
+{
+        return __register_kprobes(kps, num,
+                                  (unsigned long)__builtin_return_address(0));
+}
+
+void __kprobes unregister_kprobes(struct kprobe **kps, int num)
+{
+        int i;
+
+        if (num <= 0)
+                return;
+        mutex_lock(&kprobe_mutex);
+        for (i = 0; i < num; i++)
+                if (__unregister_kprobe_top(kps[i]) < 0)
+                        kps[i]->addr = NULL;
+        mutex_unlock(&kprobe_mutex);
+
+        synchronize_sched();
+        for (i = 0; i < num; i++)
+                if (kps[i]->addr)
+                        __unregister_kprobe_bottom(kps[i]);
 }
 
 static struct notifier_block kprobe_exceptions_nb = {
@@ -1118,6 +1166,8 @@ module_init(init_kprobes);
 
 EXPORT_SYMBOL_GPL(register_kprobe);
 EXPORT_SYMBOL_GPL(unregister_kprobe);
+EXPORT_SYMBOL_GPL(register_kprobes);
+EXPORT_SYMBOL_GPL(unregister_kprobes);
 EXPORT_SYMBOL_GPL(register_jprobe);
 EXPORT_SYMBOL_GPL(unregister_jprobe);
 #ifdef CONFIG_KPROBES