On 15/10/15 14:02, Will Deacon wrote:
> On Thu, Oct 15, 2015 at 10:17:47AM +0100, Vladimir Murzin wrote:
>> We might need the same change for arm64 counterpart (see
>> arch/arm64/kernel/armv8_deprecated.c).
>
> Something like below?
Looks good. Should these two go to stable?
Vladimir
>
> Will
>
>>From 63c3e83073cfac2e011adf0ed6f335275cc977a7 Mon Sep 17 00:00:00 2001
> From: Will Deacon <will.dea...@arm.com>
> Date: Thu, 15 Oct 2015 13:55:53 +0100
> Subject: [PATCH] arm64: compat: fix stxr failure case in SWP emulation
>
> If the STXR instruction fails in the SWP emulation code, we leave *data
> overwritten with the loaded value, therefore corrupting the data written
> by a subsequent, successful attempt.
>
> This patch re-jigs the code so that we only write back to *data once we
> know that the update has happened.
>
> Reported-by: Shengjiu Wang <shengjiu.w...@freescale.com>
> Reported-by: Vladimir Murzin <vladimir.mur...@arm.com>
> Signed-off-by: Will Deacon <will.dea...@arm.com>
> ---
> arch/arm64/kernel/armv8_deprecated.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/kernel/armv8_deprecated.c
> b/arch/arm64/kernel/armv8_deprecated.c
> index bcee7abac68e..6039d1eb5912 100644
> --- a/arch/arm64/kernel/armv8_deprecated.c
> +++ b/arch/arm64/kernel/armv8_deprecated.c
> @@ -284,12 +284,12 @@ static void register_insn_emulation_sysctl(struct
> ctl_table *table)
> __asm__ __volatile__( \
> ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN, \
> CONFIG_ARM64_PAN) \
> - " mov %w2, %w1\n" \
> - "0: ldxr"B" %w1, [%3]\n" \
> - "1: stxr"B" %w0, %w2, [%3]\n" \
> + "0: ldxr"B" %w2, [%3]\n" \
> + "1: stxr"B" %w0, %w1, [%3]\n" \
> " cbz %w0, 2f\n" \
> " mov %w0, %w4\n" \
> "2:\n" \
> + " mov %w1, %w2\n" \
> " .pushsection .fixup,\"ax\"\n" \
> " .align 2\n" \
> "3: mov %w0, %w5\n" \
>
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