[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: bibo, 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: Satoshi Oshima <soshima@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 29 insertions, 19 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 37f86234bdd7..727e419ad78a 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/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;
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 1fbf466a29aa..f095178e48c3 100644
--- a/kernel/kprobes.c
+++ b/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 @@ valid_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);
         }
 }