Re: [ptxdist] [PATCH 2/3] barebox: add option for building barebox reproducibly

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Tue, Oct 16, 2018 at 11:06:19AM +0000, Baeuerle, Florian wrote:
> Am Dienstag, den 16.10.2018, 10:59 +0200 schrieb Michael Olbrich:
> > On Fri, Oct 12, 2018 at 12:28:19PM +0000, Baeuerle, Florian wrote:
> > > Am Freitag, den 12.10.2018, 14:01 +0200 schrieb Michael Olbrich:
> > > > On Thu, Oct 11, 2018 at 02:19:17PM +0000, Baeuerle, Florian wrote:
> > > > > Inject fake timestamps into the build via faketime to produce the exact
> > > > > same binaries.
> > > > > 
> > > > > Signed-off-by: Florian Bäuerle <florian.baeuerle@allegion.com>
> > > > > ---
> > > > >  platforms/barebox.in | 10 ++++++++++
> > > > >  rules/barebox.make   | 16 +++++++++++++++-
> > > > >  2 files changed, 25 insertions(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/platforms/barebox.in b/platforms/barebox.in
> > > > > index 645366e93..5bc2f08b6 100644
> > > > > --- a/platforms/barebox.in
> > > > > +++ b/platforms/barebox.in
> > > > > @@ -13,6 +13,7 @@ menuconfig BAREBOX
> > > > >  	select HOST_OPENSSL if BAREBOX_NEEDS_HOST_OPENSSL
> > > > >  	select HOST_IMX_CST if BAREBOX_NEEDS_HOST_IMX_CST
> > > > >  	select HOST_LZOP if BAREBOX_NEEDS_HOST_LZOP
> > > > > +	select HOST_FAKETIME if BAREBOX_REPRODUCIBLE
> > > > >  	prompt "barebox                       "
> > > > >  	bool
> > > > >  	help
> > > > > @@ -50,6 +51,15 @@ config BAREBOX_EXTRA_ENV_PATH
> > > > >  	  Directories and files to add to the builtin barebox
> > > > > environment.
> > > > >  	  Relative paths must be relative to the platformconfigdir.
> > > > >  
> > > > > +config BAREBOX_REPRODUCIBLE
> > > > > +	prompt "build reproducibly"
> > > > > +	bool
> > > > > +	default n
> > > > > +	help
> > > > > +	  With this, fake timestamps are injected to the barebox build,
> > > > > so the
> > > > > +	  resulting barebox images are identical when the sources
> > > > > haven't been
> > > > > +	  changed.
> > > > > +
> > > > >  config BAREBOX_BAREBOXENV
> > > > >  	prompt "install 'bareboxenv'"
> > > > >  	bool
> > > > > diff --git a/rules/barebox.make b/rules/barebox.make
> > > > > index a6ec3c394..ad160b3ba 100644
> > > > > --- a/rules/barebox.make
> > > > > +++ b/rules/barebox.make
> > > > > @@ -45,6 +45,20 @@ BAREBOX_ENV := \
> > > > >  	KCONFIG_NOTIMESTAMP=1 \
> > > > >  	pkg_wrapper_blacklist="$(BAREBOX_WRAPPER_BLACKLIST)"
> > > > >  
> > > > > +ifdef PTXCONF_BAREBOX_REPRODUCIBLE
> > > > > +BAREBOX_FAKE_TIMESTAMP := \
> > > > > +	$(shell echo $(BAREBOX_VERSION) | \
> > > > > +		sed -E "s/([0-9]{4})\.([0-9]{1,2}).*/\1-\2-01
> > > > > 00:00:00/")
> > > > > +BAREBOX_FAKETIME := faketime -f "$(BAREBOX_FAKE_TIMESTAMP)"
> > > > > +BAREBOX_ENV := $(BAREBOX_ENV) \
> > > > > +	KBUILD_BUILD_TIMESTAMP="$(BAREBOX_FAKE_TIMESTAMP)" \
> > > > > +	KBUILD_BUILD_VERSION="0" \
> > > > > +	KBUILD_BUILD_USER="ptxdist" \
> > > > > +	KBUILD_BUILD_HOST="ptxdist"
> > > 
> > > For the sake of completeness: the _USER and _HOST variables are *not yet*
> > > incorporated into the resulting binaries by barebox (at least with my
> > > configuration).
> > 
> > Hmm, then something is wrong here. scripts/mkcompile_h has always used
> > these variables.
> 
> Yes, it generates #defines, but apparently these are not used anywhere in the
> barebox source tree, thus they do not end up in the binary.

Ok, not used as in no user/host in the binary at all. That's ok then.

> > > > What is not covered by the KBUILD_BUILD_* variables? faketime is a big
> > > > hammer that can cause other problems. I'd like to understand what happens
> > > > here first.
> > > 
> > > It's an opt-in hammer at least. One annoyance that I observed is, that
> > > menuconfig barebox also does build host-faketime and a bunch of other things
> > > that are not a dependency of the host-faketime package.
> > 
> > That's the usual early build stuff, right? host-pkg-config and things like
> > that.
> > 
> 
> I guess so. It's host-chrpath, host-pkg-config, kernel-header, host-attr, host-
> autotools-*, host-acl, host-fakeroot, host-m4 to name a few.

Hmmm, I applied the patches and did some quick checks, and I'm not seeing
the issue. If you run ptxdist with '-d' you might get a hint where the
dependency is coming from.

Michael

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