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

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

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.
>
> 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.

Frediano