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

[Andrew Fish <afish@apple.com>]

> On Sep 13, 2016, at 10:49 AM, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> 
> 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.
> 

I think all my pain has been the inconsistency on i386/IA32, but it left a mark. :). 

Thanks,

Andrew Fish

> -- 
> Ard.
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel