Re: [Xen-devel] [PATCH v3 13/23] XENVER_build_id: Provide ld-embedded build-ids (v10)

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 12/02/16 13:05, Konrad Rzeszutek Wilk wrote:
> The mechanism to get this is via the XENVER hypercall and
> we add a new sub-command to retrieve the binary build-id
> called XENVER_build_id. The sub-hypercall parameter
> allows an arbitrary size (the buffer and len is provided
> to the hypervisor). A NULL parameter will probe the hypervisor
> for the length of the build-id.
>
> One can also retrieve the value of the build-id by doing
> 'readelf -n xen-syms'.
>
> For EFI builds we re-use the same build-id that the xen-syms
> was built with.
>
> The version of ld that first implemented --build-id is v2.18.
> Hence we check for that or later version - if older version
> found we do not build the hypervisor with the build-id
> (and the return code is -ENODATA for that case).
>
> For x86 we have two binaries - the xen-syms and the xen - an
> smaller version with lots of sections removed. To make it possible
> for readelf -n xen we also modify mkelf32 and xen.lds.S to include
> the PT_NOTE ELF section.
>
> The EFI binary is more complicated. Having any non-recognizable
> sections (.note, .data.note, etc) causes the boot to hang.
> Moving the .note in the .data section makes it work. It is also
> worth noting that the PE/COFF does not have any "comment"
> sections to the author.
>
> Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Martin Pohlack <mpohlack@xxxxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Acked-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>

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