powerpc/kprobes: Remove resume_execution() in kprobes

emulate_step() in kprobe_handler() would've already determined if the
probed instruction can be emulated. We single-step in hardware only if
the instruction couldn't be emulated. resume_execution() therefore is
superfluous -- all we need is to fix up the instruction pointer after
single-stepping.

Thanks to Paul Mackerras for catching this.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 2 insertions, 12 deletions

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index c533525ca56a..bc47352deb1f 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -378,17 +378,6 @@ static int __kprobes trampoline_probe_handler(struct kprobe *p,
  * single-stepped a copy of the instruction.  The address of this
  * copy is p->ainsn.insn.
  */
-static void __kprobes resume_execution(struct kprobe *p, struct pt_regs *regs)
-{
-        int ret;
-        unsigned int insn = *p->ainsn.insn;
-
-        regs->nip = (unsigned long)p->addr;
-        ret = emulate_step(regs, insn);
-        if (ret == 0)
-                regs->nip = (unsigned long)p->addr + 4;
-}
-
 static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 {
         struct kprobe *cur = kprobe_running();
@@ -406,7 +395,8 @@ static int __kprobes post_kprobe_handler(struct pt_regs *regs)
                 cur->post_handler(cur, regs, 0);
         }
 
-        resume_execution(cur, regs);
+        /* Adjust nip to after the single-stepped instruction */
+        regs->nip = (unsigned long)cur->addr + 4;
         regs->msr |= kcb->kprobe_saved_msr;
 
         /*Restore back the original saved kprobes variables and continue. */