[PATCH] Kprobe: multi kprobe posthandler for booster

If there are multi kprobes on the same probepoint, there will be one extra
aggr_kprobe on the head of kprobe list.  The aggr_kprobe has
aggr_post_handler/aggr_break_handler whether the other kprobe
post_hander/break_handler is NULL or not.  This patch modifies this, only
when there is one or more kprobe in the list whose post_handler is not
NULL, post_handler of aggr_kprobe will be set as aggr_post_handler.

[soshima@redhat.com: !CONFIG_PREEMPT fix]
Signed-off-by: Nbibo, mao <bibo.mao@intel.com>
Cc: Masami Hiramatsu <hiramatu@sdl.hitachi.co.jp>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: "Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Yumiko Sugita <sugita@sdl.hitachi.co.jp>
Cc: Hideo Aoki <haoki@redhat.com>
Signed-off-by: NSatoshi Oshima <soshima@redhat.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/i386/kernel/kprobes.c

@@ -259,7 +259,9 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 	struct kprobe_ctlblk *kcb;
 #ifdef CONFIG_PREEMPT
 	unsigned pre_preempt_count = preempt_count();
-#endif /* CONFIG_PREEMPT */
+#else
+	unsigned pre_preempt_count = 1;
+#endif
 
 	addr = (kprobe_opcode_t *)(regs->eip - sizeof(kprobe_opcode_t));
 
@@ -336,22 +338,14 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 		/* handler has already set things up, so skip ss setup */
 		return 1;
 
-	if (p->ainsn.boostable == 1 &&
-#ifdef CONFIG_PREEMPT
-	    !(pre_preempt_count) && /*
-				       * This enables booster when the direct
-				       * execution path aren't preempted.
-				       */
-#endif /* CONFIG_PREEMPT */
-	    !p->post_handler && !p->break_handler ) {
+ss_probe:
+	if (pre_preempt_count && p->ainsn.boostable == 1 && !p->post_handler){
 		/* Boost up -- we can execute copied instructions directly */
 		reset_current_kprobe();
 		regs->eip = (unsigned long)p->ainsn.insn;
 		preempt_enable_no_resched();
 		return 1;
 	}
-
-ss_probe:
 	prepare_singlestep(p, regs);
 	kcb->kprobe_status = KPROBE_HIT_SS;
 	return 1;

kernel/kprobes.c

@@ -368,16 +368,15 @@ static inline void copy_kprobe(struct kprobe *old_p, struct kprobe *p)
 */
 static int __kprobes add_new_kprobe(struct kprobe *old_p, struct kprobe *p)
 {
-        struct kprobe *kp;
-
 	if (p->break_handler) {
-		list_for_each_entry_rcu(kp, &old_p->list, list) {
-			if (kp->break_handler)
-				return -EEXIST;
-		}
+		if (old_p->break_handler)
+			return -EEXIST;
 		list_add_tail_rcu(&p->list, &old_p->list);
+		old_p->break_handler = aggr_break_handler;
 	} else
 		list_add_rcu(&p->list, &old_p->list);
+	if (p->post_handler && !old_p->post_handler)
+		old_p->post_handler = aggr_post_handler;
 	return 0;
 }
 
@@ -390,9 +389,11 @@ static inline void add_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
 	copy_kprobe(p, ap);
 	ap->addr = p->addr;
 	ap->pre_handler = aggr_pre_handler;
-	ap->post_handler = aggr_post_handler;
 	ap->fault_handler = aggr_fault_handler;
-	ap->break_handler = aggr_break_handler;
+	if (p->post_handler)
+		ap->post_handler = aggr_post_handler;
+	if (p->break_handler)
+		ap->break_handler = aggr_break_handler;
 
 	INIT_LIST_HEAD(&ap->list);
 	list_add_rcu(&p->list, &ap->list);
@@ -536,6 +537,21 @@ void __kprobes unregister_kprobe(struct kprobe *p)
 			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;
+		}
+		mutex_unlock(&kprobe_mutex);
 	}
 }