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

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. */