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

[Jan Beulich <jbeulich@xxxxxxxx>]

On 05.06.2025 14:20, Marek Marczykowski-Górecki wrote:
> 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.

"The grub series" being which one? I didn't know xen.efi's non-EFI MB2 entry
point could be used; instead I was under the impression that someone was
having (half?) a patch eliminating the MB data from xen.efi, as being dead
code.

Jan