1 files changed, 43 insertions, 6 deletions

diff --git a/arch/ia64/kernel/kprobes.c b/arch/ia64/kernel/kprobes.c
index 41e80b42d3f..5978823d5c6 100644
--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -41,8 +41,8 @@ extern void jprobe_inst_return(void);
 #define KPROBE_HIT_ACTIVE       0x00000001
 #define KPROBE_HIT_SS           0x00000002
 
-static struct kprobe *current_kprobe;
-static unsigned long kprobe_status;
+static struct kprobe *current_kprobe, *kprobe_prev;
+static unsigned long kprobe_status, kprobe_status_prev;
 static struct pt_regs jprobe_saved_regs;
 
 enum instruction_type {A, I, M, F, B, L, X, u};
@@ -273,6 +273,23 @@ static int valid_kprobe_addr(int template, int slot, unsigned long addr)
         return 0;
 }
 
+static inline void save_previous_kprobe(void)
+{
+        kprobe_prev = current_kprobe;
+        kprobe_status_prev = kprobe_status;
+}
+
+static inline void restore_previous_kprobe(void)
+{
+        current_kprobe = kprobe_prev;
+        kprobe_status = kprobe_status_prev;
+}
+
+static inline void set_current_kprobe(struct kprobe *p)
+{
+        current_kprobe = p;
+}
+
 int arch_prepare_kprobe(struct kprobe *p)
 {
         unsigned long addr = (unsigned long) p->addr;
@@ -436,8 +453,18 @@ static int pre_kprobes_handler(struct die_args *args)
                                 unlock_kprobes();
                                 goto no_kprobe;
                         }
-                        arch_disarm_kprobe(p);
-                        ret = 1;
+                        /* We have reentered the pre_kprobe_handler(), since
+                         * another probe was hit while within the handler.
+                         * We here save the original kprobes variables and
+                         * just single step on the instruction of the new probe
+                         * without calling any user handlers.
+                         */
+                        save_previous_kprobe();
+                        set_current_kprobe(p);
+                        p->nmissed++;
+                        prepare_ss(p, regs);
+                        kprobe_status = KPROBE_REENTER;
+                        return 1;
                 } else if (args->err == __IA64_BREAK_JPROBE) {
                         /*
                          * jprobe instrumented function just completed
@@ -460,7 +487,7 @@ static int pre_kprobes_handler(struct die_args *args)
         }
 
         kprobe_status = KPROBE_HIT_ACTIVE;
-        current_kprobe = p;
+        set_current_kprobe(p);
 
         if (p->pre_handler && p->pre_handler(p, regs))
                 /*
@@ -485,12 +512,22 @@ static int post_kprobes_handler(struct pt_regs *regs)
         if (!kprobe_running())
                 return 0;
 
-        if (current_kprobe->post_handler)
+        if ((kprobe_status != KPROBE_REENTER) && current_kprobe->post_handler) {
+                kprobe_status = KPROBE_HIT_SSDONE;
                 current_kprobe->post_handler(current_kprobe, regs, 0);
+        }
 
         resume_execution(current_kprobe, regs);
 
+        /*Restore back the original saved kprobes variables and continue. */
+        if (kprobe_status == KPROBE_REENTER) {
+                restore_previous_kprobe();
+                goto out;
+        }
+
         unlock_kprobes();
+
+out:
         preempt_enable_no_resched();
         return 1;
 }