linux-kernel - [PATCH v2 06/14] powerpc/40x: Reorder a few instructions in critical exception prolog

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Message-Id: <434c69e46655d79f3d26e8ab114dcc40b8274af6.1611309841.git.christophe.leroy@csgroup.eu>
Date:   Fri, 22 Jan 2021 10:05:29 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, npiggin@...il.com
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 06/14] powerpc/40x: Reorder a few instructions in critical
 exception prolog

In order to ease preparation for CONFIG_VMAP_STACK, reorder
a few instruction, especially save r1 into stack frame earlier.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/kernel/head_40x.S | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 6394040bbaba..b7caaa09c860 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -119,6 +119,9 @@ _ENTRY(saved_ksp_limit)
 	lwz	r11,TASK_STACK-THREAD(r11) /* this thread's kernel stack */
 1:	addi	r11,r11,THREAD_SIZE-INT_FRAME_SIZE /* Alloc an excpt frm  */
 	tophys(r11,r11)
+	stw	r1,GPR1(r11)
+	stw	r1,0(r11)
+	tovirt(r1,r11)
 	stw	r10,_CCR(r11)		/* save various registers	   */
 	stw	r12,GPR12(r11)
 	stw	r9,GPR9(r11)
@@ -129,14 +132,11 @@ _ENTRY(saved_ksp_limit)
 	stw	r10,GPR10(r11)
 	stw	r12,GPR11(r11)
 	mfspr	r12,SPRN_DEAR		/* save DEAR and ESR in the frame  */
-	stw	r12,_DEAR(r11)		/* since they may have had stuff   */
 	mfspr	r9,SPRN_ESR		/* in them at the point where the  */
+	stw	r12,_DEAR(r11)		/* since they may have had stuff   */
 	stw	r9,_ESR(r11)		/* exception was taken		   */
 	mfspr	r12,SPRN_SRR2
-	stw	r1,GPR1(r11)
 	mfspr	r9,SPRN_SRR3
-	stw	r1,0(r11)
-	tovirt(r1,r11)
 	rlwinm	r9,r9,0,14,12		/* clear MSR_WE (necessary?)	   */
 	stw	r0,GPR0(r11)
 	lis	r10, STACK_FRAME_REGS_MARKER@ha /* exception frame marker */
-- 
2.25.0