On 15/10/15 14:25, Vladimir Murzin wrote:
> 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?
On the second thought looks like we still update *data in case stxr
fails (or I need more coffee).
Vladimir
>
> 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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