Re: [PATCH 1/2] ArmPkg/AsmMacroIoLibV8: Introduce ASM_FUNC_ALIGN()

["Marvin Häuser" <mhaeuser@posteo.de>]

> On 18. Apr 2023, at 10:10, Ard Biesheuvel <ardb@kernel.org> wrote:
> 
> On Tue, 18 Apr 2023 at 08:40, Marvin Häuser <mhaeuser@posteo.de> wrote:
>> 
>> 
>>> On 17. Apr 2023, at 23:18, Ard Biesheuvel <ardb@kernel.org> wrote:
>>> 
>>> Agree with all of this.
>>> 
>>> And thanks for tracking this down - must not have been fun :-)
>> 
>> No worries - it wasn’t. :) It was mere luck Vitaly discovered early it was an issue that triggered based on the binary layout rather than a bug in the mapping code itself…
>> 
>> Speaking of not fun to track down, I initially wanted to add ASSERTs (yes, runtime :( ) to check the alignment guarantee is actually met. Leif basically declined any form of regression-testing at runtime. Do you happen to have a simple(!) idea for how it could be checked at build-time? (It’s less about “which commands do I run?” and more about integration with the build process / BaseTools, cross-OS compatibility, etc.)
>> 
> 
> 
> I think we should just add another align to the code:
> 
> .align xx
> func:
> 
> < code >
> 
> .align xx
> .org func + xx
> 
> That way, if the code straddles a xx-aligned boundary, the .org will
> move backwards and force an error.

Wow, that's pretty fucking smart... I didn't even know that directive was a thing. I will try to toy with it soon. Do you want it as a separate series, separate commit in the current series, or squashed into the fix?