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From: Ard Biesheuvel <ardb@kernel.org>
To: linux@armlinux.org.uk
Cc: linux-arm-kernel@lists.infradead.org, arnd@arndb.de,
	linus.walleij@linaro.org, Ard Biesheuvel <ardb@kernel.org>,
	stable@vger.kernel.org
Subject: [PATCH] ARM: Thumb2: align ALT_UP() sections sufficiently
Date: Tue, 18 Jan 2022 11:27:56 +0100	[thread overview]
Message-ID: <20220118102756.1259149-1-ardb@kernel.org> (raw)

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 avoid this from occurring.

Cc: <stable@vger.kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm/include/asm/assembler.h | 2 ++
 arch/arm/include/asm/processor.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 5a530e25ea1a..51ae4674ca49 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -261,6 +261,7 @@ THUMB(	fpreg	.req	r7	)
  */
 #define ALT_UP(instr...)					\
 	.pushsection ".alt.smp.init", "a"			;\
+	.align	2						;\
 	.long	9998b - .					;\
 9997:	instr							;\
 	.if . - 9997b == 2					;\
@@ -272,6 +273,7 @@ THUMB(	fpreg	.req	r7	)
 	.popsection
 #define ALT_UP_B(label)					\
 	.pushsection ".alt.smp.init", "a"			;\
+	.align	2						;\
 	.long	9998b - .					;\
 	W(b)	. + (label - 9998b)					;\
 	.popsection
diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 6af68edfa53a..bdc35c0e8dfb 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -96,6 +96,7 @@ unsigned long __get_wchan(struct task_struct *p);
 #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"
-- 
2.30.2


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             reply	other threads:[~2022-01-18 10:29 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-18 10:27 Ard Biesheuvel [this message]
2022-01-18 11:21 ` [PATCH] ARM: Thumb2: align ALT_UP() sections sufficiently Russell King (Oracle)
2022-01-18 11:32   ` Ard Biesheuvel
2022-01-18 11:35     ` Russell King (Oracle)

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