From 89bbe4c798bc3a43c882179adb5222c1a972ac70 Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Thu, 11 Jun 2020 22:11:19 +1000
Subject: [PATCH] powerpc/64: indirect function call use bctrl rather than blrl
 in ret_from_kernel_thread

References: jsc#SLE-9246
Patch-mainline: v5.9-rc1
Git-commit: 89bbe4c798bc3a43c882179adb5222c1a972ac70

blrl is not recommended to use as an indirect function call, as it may
corrupt the link stack predictor.

This is not a performance critical path but this should be fixed for
consistency.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200611121119.1015740-1-npiggin@gmail.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/kernel/entry_64.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 9d49338e0c85..1013adc9acfb 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -233,12 +233,12 @@ _GLOBAL(ret_from_fork)
 _GLOBAL(ret_from_kernel_thread)
 	bl	schedule_tail
 	REST_NVGPRS(r1)
-	mtlr	r14
+	mtctr	r14
 	mr	r3,r15
 #ifdef PPC64_ELF_ABI_v2
 	mr	r12,r14
 #endif
-	blrl
+	bctrl
 	li	r3,0
 	b	.Lsyscall_exit
 
-- 
2.28.0