1 files changed, 17 insertions, 13 deletions

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index ca5d5a081e75..e4c5bf33970b 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -455,29 +455,33 @@ static int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 	}
 
 	kretprobe_assert(ri, orig_ret_address, trampoline_address);
-	regs->nip = orig_ret_address;
+
 	/*
-	 * Make LR point to the orig_ret_address.
-	 * When the 'nop' inside the kretprobe_trampoline
-	 * is optimized, we can do a 'blr' after executing the
-	 * detour buffer code.
+	 * We get here through one of two paths:
+	 * 1. by taking a trap -> kprobe_handler() -> here
+	 * 2. by optprobe branch -> optimized_callback() -> opt_pre_handler() -> here
+	 *
+	 * When going back through (1), we need regs->nip to be setup properly
+	 * as it is used to determine the return address from the trap.
+	 * For (2), since nip is not honoured with optprobes, we instead setup
+	 * the link register properly so that the subsequent 'blr' in
+	 * kretprobe_trampoline jumps back to the right instruction.
+	 *
+	 * For nip, we should set the address to the previous instruction since
+	 * we end up emulating it in kprobe_handler(), which increments the nip
+	 * again.
 	 */
+	regs->nip = orig_ret_address - 4;
 	regs->link = orig_ret_address;
 
-	reset_current_kprobe();
 	kretprobe_hash_unlock(current, &flags);
-	preempt_enable_no_resched();
 
 	hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
 		hlist_del(&ri->hlist);
 		kfree(ri);
 	}
-	/*
-	 * By returning a non-zero value, we are telling
-	 * kprobe_handler() that we don't want the post_handler
-	 * to run (and have re-enabled preemption)
-	 */
-	return 1;
+
+	return 0;
 }
 NOKPROBE_SYMBOL(trampoline_probe_handler);