Re: [XEN PATCH] tools/xenstore: Log xenstored build ID on startup

[Edwin Torok <edvin.torok@xxxxxxxxxx>]

On Fri, 2020-11-13 at 17:13 +0000, Andrew Cooper wrote:
> On 13/11/2020 16:56, Bjoern Doebel wrote:
> > On 13.11.20 16:36, Jürgen Groß wrote:
> > > On 13.11.20 15:18, Bjoern Doebel wrote:
> > > > Right now we do not have a mechanism to determine the version
> > > > of the
> > > > currently running xenstored at runtime. As xenstored runs
> > > > throughout
> > > > the
> > > > lifetime of a Xen host, this may lead to problems when newer
> > > > user space
> > > > builds are staged. Then, the running xenstored will no longer
> > > > match the
> > > > version of the installed xenstored.
> > > > 
> > > > To allow users to always identify the running version of
> > > > xenstored, add
> > > > a linker-generated unique build ID to every xenstored build.
> > > > Add
> > > > functionality to log this build ID into a file upon service
> > > > startup.
> > > > 
> > > > Signed-off-by: Bjoern Doebel <doebel@xxxxxxxxx>
> > > > Reviewed-by: Martin Mazein <amazein@xxxxxxxxx>
> > > > Reviewed-by: Paul Durrant <pdurrant@xxxxxxxxxxxx>
> > > 
> > > No support for oxenstored or xenstore-stubdom?
> > 
> > Your suggestion further down will apparently help for stubdom. I do
> > not speak ocaml at all - how do we address this?
> 
> CC'ing Edwin and Christian who have done the bulk of the oxenstored
> recently.
> 
> It sounds like it might not be possible right now, but would be
> possible
> with a future plan to switch the Ocaml build system over to dune (the
> new/preferred Ocaml upstream toolchain).

See here what is possible with Dune:
https://dune.readthedocs.io/en/stable/dune-libs.html#build-info

Would the output of 'git describe --always --dirty' (perhaps combined
with a build date) serve as a useful build ID?

> 
> If it does end up being an XS_CONTROL sub-op, we can implement it at
> a
> future point when we can usefully answer the question.

Wouldn't using readelf on /proc/<pid>/exe give you the running buildid?

readelf -a /usr/sbin/oxenstored /proc/$(pidof oxenstored)/exe | grep
'Build ID'
    Build ID: bdd5304c8984ed22570d51308ae8717d03fe60ae
    Build ID: bdd5304c8984ed22570d51308ae8717d03fe60ae

readelf -a /usr/sbin/oxenstored /proc/$(pidof oxenstored)/exe | grep
'Build ID'
    Build ID: b44ff99b216db7526e3ee7841068d584cc9c2b95
    Build ID: bdd5304c8984ed22570d51308ae8717d03fe60ae


When you're inside a stubdom it is probably not so easy though.

Best regards,
--Edwin

> 
> ~Andrew