Re: git: a60e7e6ff0ec - main - stand: compile ia32 EFI loader with -malign-double

On Sun, Feb 15, 2026 at 8:56 AM Ahmad Khalifa <ahmadkhalifa570@gmail.com>
wrote:

> On Sun Feb 15, 2026 at 4:27 PM +0200, Ahmad Khalifa wrote:
> > On Sun Feb 15, 2026 at 4:02 PM +0200, Jessica Clarke wrote:
> >> On 15 Feb 2026, at 13:56, Ahmad Khalifa <vexeduxr@FreeBSD.org> wrote:
> >>>
> >>> The branch main has been updated by vexeduxr:
> >>>
> >>> URL:
> https://cgit.FreeBSD.org/src/commit/?id=a60e7e6ff0ec1fdd66c2568ac6c03b843dbb3c9d
> >>>
> >>> commit a60e7e6ff0ec1fdd66c2568ac6c03b843dbb3c9d
> >>> Author:     Ahmad Khalifa <vexeduxr@FreeBSD.org>
> >>> AuthorDate: 2026-02-15 12:23:26 +0000
> >>> Commit:     Ahmad Khalifa <vexeduxr@FreeBSD.org>
> >>> CommitDate: 2026-02-15 13:30:06 +0000
> >>>
> >>>    stand: compile ia32 EFI loader with -malign-double
> >>>
> >>>    The UEFI spec says:
> >>>> Structures are aligned on boundaries equal to the largest internal
> >>>> datum of the structure and internal data are implicitly padded to
> >>>> achieve natural alignment.
> >>>
> >>>    By default, structs containing members of type "long long" have 4
> byte
> >>>    alignment on i386. This caused some EFI structures to be subtly
> wrong.
> >>>
> >>>    Fix this by compiling the ia32 EFI loader with -malign-double, which
> >>>    bumps the alignment up to 8 if such members are present.
> >>
> >> This seems like a dangerously big hammer. Are there any types shared
> >> with libsa or the kernel itself that would change layout? (I suppose
> >> for the latter they already need to be aligned as the kernel is 64-bit?)
> >
> > For the kernel, any shared types would have already needed to be
> > aligned, yes. I didn't consider shared types with either libsa or libefi
> > though, I'll look into it now. Nice catch.
> >
>
> Okay, so libsa, libefi, liblua and ficl all share types with the loader.
> Quite obvious in hindsight... I'll back this out until I come up with
> something better.
>

Yea, EFI lives in two worlds: The world of having to make UEFI calls,
which has one calling convention and ABI (including structures), and then
it also lives in the world of creating some binary structs for the kernel.
These
have to agree somehow.

It's even worse, since the 32-bit loader code is also shared with the BIOS
loader, which has some different layout conventions...

If we have to do this, we'd likely need another libsa32 etc for the new
conventions.

I'm curious, which structures does this affect. UEFI / EDK2 tries hard to
make details
like this not matter.


> >>
> >> Annotating just the EFI types would seem more appropriate, like how we
> >> annotate function pointers to use the Microsoft calling convention.
> >
> > They're all under contrib unfortunately. Not sure if we want to
> > introduce that big of a diff with upstream.
> >
> >>
> >> Jessica
>
>