Re: [PATCH 1/3] x86/EFI: Fix detection of buildid

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Jun 05, 2025 at 12:16:36PM +0100, Andrew Cooper wrote:
> The format of the buildid is a property of the binary, not a property of how
> it was loaded.  This fixes buildid recognition when starting xen.efi from it's
> MB2 entrypoint.
> 
> Suggested-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Some possibly useless rants below.

> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
> CC: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> CC: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> 
> I don't like this patch and tried hard to do it in a better way, but the EFI
> aspects of the build system are too intractable.
> 
> While on x86 I can in principle pull the same common-stubs.o trick, split on
> XEN_BUILD_PE rather than XEN_BUILD_EFI, that doesn't work on ARM which
> hand-codes it's PE-ness.  Also, it's really not EFI related, other than as a
> consequence of that being the only reason we use PE32+ binaries.

Since this is already gated on CONFIG_X86 you could pass XEN_BUILD_PE
as a define in CFLAGS, and use it together with the CONFIG_X86 check?

That however would still put the code in the .gz binary, as the object
file would be the same for both builds.  Otherwise we would need to
compile this twice and use the different object files for the PE vs
ELF images, which seems extremely cumbersome for a little benefit, as
this is init-only code that would be gone once booted.

Thanks, Roger.