linux-kernel - [PATCH 3/3] xtensa: fix a7 clobbering in coprocessor context load/store

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Message-Id: <20220420061611.4103443-4-jcmvbkbc@gmail.com>
Date:   Tue, 19 Apr 2022 23:16:11 -0700
From:   Max Filippov <jcmvbkbc@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>, stable@...r.kernel.org
Subject: [PATCH 3/3] xtensa: fix a7 clobbering in coprocessor context load/store

Fast coprocessor exception handler saves a3..a6, but coprocessor context
load/store code uses a4..a7 as temporaries, potentially clobbering a7.
'Potentially' because coprocessor state load/store macros may not use
all four temporary registers (and neither FPU nor HiFi macros do).
Use a3..a6 as intended.

Cc: stable@...r.kernel.org
Fixes: c658eac628aa ("[XTENSA] Add support for configurable registers and coprocessors")
Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
---
 arch/xtensa/kernel/coprocessor.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/xtensa/kernel/coprocessor.S b/arch/xtensa/kernel/coprocessor.S
index 45cc0ae0af6f..c7b9f12896f2 100644
--- a/arch/xtensa/kernel/coprocessor.S
+++ b/arch/xtensa/kernel/coprocessor.S
@@ -29,7 +29,7 @@
 	.if XTENSA_HAVE_COPROCESSOR(x);					\
 		.align 4;						\
 	.Lsave_cp_regs_cp##x:						\
-		xchal_cp##x##_store a2 a4 a5 a6 a7;			\
+		xchal_cp##x##_store a2 a3 a4 a5 a6;			\
 		jx	a0;						\
 	.endif
 
@@ -46,7 +46,7 @@
 	.if XTENSA_HAVE_COPROCESSOR(x);					\
 		.align 4;						\
 	.Lload_cp_regs_cp##x:						\
-		xchal_cp##x##_load a2 a4 a5 a6 a7;			\
+		xchal_cp##x##_load a2 a3 a4 a5 a6;			\
 		jx	a0;						\
 	.endif
 
-- 
2.30.2