From 823e5d8afaaf9fff0cc2ab04e7fc0a62b1023c3e Mon Sep 17 00:00:00 2001
From: "Paul E. Murphy" <murp@ibm.com>
Date: Fri, 19 Aug 2022 09:20:02 -0500
Subject: [PATCH] [release-branch.go1.19] runtime: fix ppc64 startup on newer
 linux kernels

R0 needs to be cleared at startup as it may not always be cleared
by the kernel on newer kernels.

Fixes #54665

Change-Id: Id7055699aaa8d8b193b7e3e784f075ce29ac3f1d
Reviewed-on: https://go-review.googlesource.com/c/go/+/424927
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: David Chase <drchase@google.com>
Run-TryBot: Paul Murphy <murp@ibm.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/425394
Reviewed-by: Ian Lance Taylor <iant@google.com>
---
 src/runtime/rt0_linux_ppc64.s | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/runtime/rt0_linux_ppc64.s b/src/runtime/rt0_linux_ppc64.s
index 897d61052a..c9300a9caf 100644
--- a/src/runtime/rt0_linux_ppc64.s
+++ b/src/runtime/rt0_linux_ppc64.s
@@ -22,6 +22,7 @@ TEXT _main<>(SB),NOSPLIT,$-8
 	// There is no TLS base pointer.
 	//
 	// TODO(austin): Support ABI v1 dynamic linking entry point
+	XOR	R0, R0 // Note, newer kernels may not always set R0 to 0.
 	MOVD	$runtime·rt0_go(SB), R12
 	MOVD	R12, CTR
 	MOVBZ	runtime·iscgo(SB), R5
-- 
2.48.1