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

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

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

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