[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH v6 17/24] build_id: Provide ld-embedded build-ids

Hi Konrad,

On 07/04/16 04:49, Konrad Rzeszutek Wilk wrote:
This patch enables the Elf to be built with the build-id
and provide in the Xen hypervisor the code to extract it.

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.
We check for to see if the linker supports the --build-id
parameter and if so use it.

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.

Lastly, we MUST call --binary-id=sha1 on all linker invocation so that
symbol offsets don't changes (which means we have multiple binary
ids - except that the last one is the final one). Without this change,
the symbol table embedded in Xen are incorrect - some of the values it
contains are offset by the size of the included build id.
This obviously causes problems when resolving symbols.

Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Martin Pohlack <mpohlack@xxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

For the ARM bits:

Acked-by: Julien Grall <julien.grall@xxxxxxx>


Julien Grall

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.