[PATCH] Kprobes: Track kprobe on a per_cpu basis - base changes

Changes to the base kprobe infrastructure to track kprobe execution on a
per-cpu basis.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
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>

1 files changed, 28 insertions, 15 deletions

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index ce4915dd683a..6da8f9b33d1e 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -51,7 +51,7 @@ static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
 
 unsigned int kprobe_cpu = NR_CPUS;
 static DEFINE_SPINLOCK(kprobe_lock);
-static struct kprobe *curr_kprobe;
+static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
 
 /*
  * kprobe->ainsn.insn points to the copy of the instruction to be
@@ -188,6 +188,17 @@ void __kprobes unlock_kprobes(void)
         local_irq_restore(flags);
 }
 
+/* We have preemption disabled.. so it is safe to use __ versions */
+static inline void set_kprobe_instance(struct kprobe *kp)
+{
+        __get_cpu_var(kprobe_instance) = kp;
+}
+
+static inline void reset_kprobe_instance(void)
+{
+        __get_cpu_var(kprobe_instance) = NULL;
+}
+
 /* You have to be holding the kprobe_lock */
 struct kprobe __kprobes *get_kprobe(void *addr)
 {
@@ -213,11 +224,11 @@ static int __kprobes aggr_pre_handler(struct kprobe *p, struct pt_regs *regs)
 
         list_for_each_entry(kp, &p->list, list) {
                 if (kp->pre_handler) {
-                        curr_kprobe = kp;
+                        set_kprobe_instance(kp);
                         if (kp->pre_handler(kp, regs))
                                 return 1;
                 }
-                curr_kprobe = NULL;
+                reset_kprobe_instance();
         }
         return 0;
 }
@@ -229,9 +240,9 @@ static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
 
         list_for_each_entry(kp, &p->list, list) {
                 if (kp->post_handler) {
-                        curr_kprobe = kp;
+                        set_kprobe_instance(kp);
                         kp->post_handler(kp, regs, flags);
-                        curr_kprobe = NULL;
+                        reset_kprobe_instance();
                 }
         }
         return;
@@ -240,12 +251,14 @@ static void __kprobes aggr_post_handler(struct kprobe *p, struct pt_regs *regs,
 static int __kprobes aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
                                         int trapnr)
 {
+        struct kprobe *cur = __get_cpu_var(kprobe_instance);
+
         /*
          * if we faulted "during" the execution of a user specified
          * probe handler, invoke just that probe's fault handler
          */
-        if (curr_kprobe && curr_kprobe->fault_handler) {
-                if (curr_kprobe->fault_handler(curr_kprobe, regs, trapnr))
+        if (cur && cur->fault_handler) {
+                if (cur->fault_handler(cur, regs, trapnr))
                         return 1;
         }
         return 0;
@@ -253,15 +266,15 @@ static int __kprobes aggr_fault_handler(struct kprobe *p, struct pt_regs *regs,
 
 static int __kprobes aggr_break_handler(struct kprobe *p, struct pt_regs *regs)
 {
-        struct kprobe *kp = curr_kprobe;
-        if (curr_kprobe && kp->break_handler) {
-                if (kp->break_handler(kp, regs)) {
-                        curr_kprobe = NULL;
-                        return 1;
-                }
+        struct kprobe *cur = __get_cpu_var(kprobe_instance);
+        int ret = 0;
+
+        if (cur && cur->break_handler) {
+                if (cur->break_handler(cur, regs))
+                        ret = 1;
         }
-        curr_kprobe = NULL;
-        return 0;
+        reset_kprobe_instance();
+        return ret;
 }
 
 struct kretprobe_instance __kprobes *get_free_rp_inst(struct kretprobe *rp)