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

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Fri, Jun 27, 2025 at 02:08:00PM +0100, Frediano Ziglio wrote:
> On Thu, Jun 5, 2025 at 12:17 PM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 
> 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>
> > ---
> > 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.

Besides the ARM issue, it would also make it harder to follow different
boot paths.

> >
> > Binutils 2.25 is now the minimum, and the makefiles can be cleaned up
> > somewhat, but I need to backport this patch, internally at least.
> > ---
> >  xen/common/version.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/xen/common/version.c b/xen/common/version.c
> > index 5474b8e385be..56b51c81d2fc 100644
> > --- a/xen/common/version.c
> > +++ b/xen/common/version.c
> > @@ -203,8 +203,11 @@ void __init xen_build_init(void)
> >      rc = xen_build_id_check(n, sz, &build_id_p, &build_id_len);
> >
> >  #ifdef CONFIG_X86
> > -    /* Alternatively we may have a CodeView record from an EFI build. */
> > -    if ( rc && efi_enabled(EFI_LOADER) )
> > +    /*
> > +     * xen.efi built with a new enough toolchain will have a CodeView 
> > record,
> > +     * not an ELF note.
> > +     */
> > +    if ( rc )
> >      {
> >          const struct pe_external_debug_directory *dir = (const void *)n;
> >
> 
> Reviewed-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>
> 
> I cannot see a better proposal in the discussion, but I prefer this
> fixed than keep it broken.

Yeah, I agree.

Acked-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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