Re: [PATCH 2/2] ArmPkg/AsmMacroIoLib: force word alignment for functions

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 13 September 2016 at 18:45, Andrew Fish <afish@apple.com> wrote:
>
>> On Sep 13, 2016, at 10:27 AM, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>>
>> Without an explicit .align directive, the Clang assembler defaults to
>> no alignment, which may result in instructions appearing misaligned in
>> the final executable. So use word alignment in all cases.
>>
>> Contributed-under: TianoCore Contribution Agreement 1.0
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>> ArmPkg/Include/AsmMacroIoLib.h | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/ArmPkg/Include/AsmMacroIoLib.h b/ArmPkg/Include/AsmMacroIoLib.h
>> index fb73ea9a4694..5e4de1f269c8 100644
>> --- a/ArmPkg/Include/AsmMacroIoLib.h
>> +++ b/ArmPkg/Include/AsmMacroIoLib.h
>> @@ -56,6 +56,7 @@
>>   .global   Name                  ; \
>>   .section  #Section, "ax"        ; \
>>   .type     Name, %function       ; \
>> +  .align    2                     ; \
>
> Ard,
>
> I've been burned in the past by as .align is bytes or power of 2 based on what the native assembler defaults to (over simplification). I'm not sure if that issues exists in the ARM world?
>

The GNU assembler for ARM interprets this as power-of-2, and so does
Clang, according to my testing. Both support the .p2align directive as
well, which makes it 100% unambiguous, so I suppose I could use that
instead.

-- 
Ard.