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

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

On Thu, Jun 05, 2025 at 02:02:21PM +0200, Jan Beulich wrote:
> On 05.06.2025 13:16, 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>
> 
> I'll pick this up without a Fixes: tag, but I think it ought to have one. (I
> didn't check whether MB2 or build-id support came later, hence introducing the
> issue.)
> 
> > --- 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 )
> 
> Instead of dropping the efi_enabled(), I think you want to replace EFI_LOADER
> by EFI_BOOT.

Part of the motivation for MB2 entry point in xen.efi is using the
same binary in all boot modes, including legacy boot - in which case
none of EFI_* checks would be appropriate here. The grub series adds
support for loading PE binaries, and IIUC it isn't tied to booting via
EFI.

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

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