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

Re: [Xen-devel] [PATCH v5 19/28] build_id: Provide ld-embedded build-ids

On 04/07/2016 03:58 AM, Konrad Rzeszutek Wilk wrote:
On Mon, Apr 04, 2016 at 06:46:24AM -0600, Jan Beulich wrote:
On 24.03.16 at 21:00, <konrad.wilk@xxxxxxxxxx> wrote:
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 xen_build_id() call).

This appears to be stale.

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.

I'm afraid this is too vague: What exactly is happening there? And
is this due to binutils doing something wrong, or an issue with the
firmware on the box you've tried? While the placement of .note is
not really a big deal, any unusual placement needs a source
comment attached explaining the whys, to prevent people down
the road moving the section back into the "expected" place. But
see also below.

I will have to dig in this more. I know I tried it on TianoCore but
that seems to have some other issues at the moment so I will
try it out on real hardware.

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.

Would this also be a problem if you place the notes segment/section
last in the binary?

I am not sure. Ross, you are the one who observed this?

Yes, that would probably solve the problem.

Ross Lagerwall

Xen-devel mailing list



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