[PATCH 5/5] powerpc: kprobes: emulate instructions on kprobe handler re-entry

[Naveen N. Rao]

On kprobe handler re-entry, try to emulate the instruction rather than
single stepping always.

As a related change, remove the duplicate saving of msr as that is
already done in set_current_kprobe()

Acked-by: Ananth N Mavinakayanahalli <ana...@linux.vnet.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/kprobes.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 8b48f7d046bd..005bd4a75902 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -273,10 +273,17 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
                         */
                        save_previous_kprobe(kcb);
                        set_current_kprobe(p, regs, kcb);
-                       kcb->kprobe_saved_msr = regs->msr;
                        kprobes_inc_nmissed_count(p);
                        prepare_singlestep(p, regs);
                        kcb->kprobe_status = KPROBE_REENTER;
+                       if (p->ainsn.boostable >= 0) {
+                               ret = try_to_emulate(p, regs);
+
+                               if (ret > 0) {
+                                       restore_previous_kprobe(kcb);
+                                       return 1;
+                               }
+                       }
                        return 1;
                } else {
                        if (*addr != BREAKPOINT_INSTRUCTION) {
-- 
2.11.0