Re: [Qemu-devel] [PATCH v15 6/9] module: implement module loading

[Fam Zheng]

On Tue, 01/14 15:45, Daniel P. Berrange wrote:
> On Tue, Jan 14, 2014 at 04:19:41PM +0100, Paolo Bonzini wrote:
> > Il 14/01/2014 15:47, Richard Henderson ha scritto:
> > >>>> +echo "CONFIG_STAMP=`date +%s`_$$_$RANDOM" >> $config_host_mak
> > >>> >>
> > >>> >> I really really don't like random numbers that make for 
> > >>> >> non-repeatable builds.
> > >>> >>  It's a quality-assurance nightmare.
> > >> > 
> > >> > Can you elaborate this, please?
> > > Build systems like we use at Red Hat want to be able to produce 
> > > bit-for-bit
> > > identical binaries when given the exact same input.  Using random numbers
> > > during the build process prevents that.
> > 
> > I totally agree, but AIUI people wanted the symbol to be something that
> > you couldn't know in advance (e.g. when compiling an out-of-tree
> > module).  For some definition of "couldn't" and "in advance".
> 
> You can't stop a determined person. The goal is really just to make sure
> they have to jump through painful hoops if they're going to delibrately
> ignore our policy that this is not for 3rd party out of tree modules to
> use.
> 
> When doing RHEL / Fedora builds, we *do* want this to change each time
> the RPM is rebuilt for a new release. eg any time we add a new patch
> to the RPM we want it to change, but if you're just rebuilding an
> src.rpm without making changes we don't need it to be different.
> 
> You could use a sha256 sum of  'configure content + version + pkgversion'
> to get something that'd change each time distros did a formal new build,
> but would still allow reproducible builds.

This sounds like a nice solution, I'll adopt. Thanks.

Fam