linux-kernel - [PATCH 5.15 006/171] ARM: 9180/1: Thumb2: align ALT

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Date:   Mon, 31 Jan 2022 11:54:31 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
Subject: [PATCH 5.15 006/171] ARM: 9180/1: Thumb2: align ALT_UP() sections in modules sufficiently

From: Ard Biesheuvel <ardb@...nel.org>

commit 9f80ccda53b9417236945bc7ece4b519037df74d upstream.

When building for Thumb2, the .alt.smp.init sections that are emitted by
the ALT_UP() patching code may not be 32-bit aligned, even though the
fixup_smp_on_up() routine expects that. This results in alignment faults
at module load time, which need to be fixed up by the fault handler.

So let's align those sections explicitly, and prevent this from occurring.

Cc: <stable@...r.kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm/include/asm/assembler.h |    2 ++
 arch/arm/include/asm/processor.h |    1 +
 2 files changed, 3 insertions(+)

--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -259,6 +259,7 @@
  */
 #define ALT_UP(instr...)					\
 	.pushsection ".alt.smp.init", "a"			;\
+	.align	2						;\
 	.long	9998b - .					;\
 9997:	instr							;\
 	.if . - 9997b == 2					;\
@@ -270,6 +271,7 @@
 	.popsection
 #define ALT_UP_B(label)					\
 	.pushsection ".alt.smp.init", "a"			;\
+	.align	2						;\
 	.long	9998b - .					;\
 	W(b)	. + (label - 9998b)					;\
 	.popsection
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -96,6 +96,7 @@ unsigned long get_wchan(struct task_stru
 #define __ALT_SMP_ASM(smp, up)						\
 	"9998:	" smp "\n"						\
 	"	.pushsection \".alt.smp.init\", \"a\"\n"		\
+	"	.align	2\n"						\
 	"	.long	9998b - .\n"					\
 	"	" up "\n"						\
 	"	.popsection\n"