[Buildroot] BR2_REPRODUCIBLE issues
Yann E. MORIN
yann.morin.1998 at free.fr
Sun Nov 5 08:46:30 UTC 2017
Arnout, All,
On 2017-11-04 20:53 +0100, Arnout Vandecappelle spake thusly:
> On 03-11-17 21:15, Peter Korsgaard wrote:
> >>>>>> "Einar" == Einar Jón Gunnarsson <tolvupostur at gmail.com> writes:
> >
> > > Hello all.
> > > I've been using BR2_REPRODUCIBLE, and it mostly works.
> >
> > > But when it is using a git repo, I have the following issues with creating
> > > SOURCE_DATE_EPOCH:
> > > 1) It uses $(GIT), but the GIT variable is only defined in line 487:
> > > "include package/Makefile.in".
> > > Note that this is done around line 250 in $(TOPDIR)/Makefile, so sometimes
> > > $(GIT) is unset then getting BR2_VERSION_GIT_EPOCH
> >
> > What make version (and buildroot version) are you using? It works here:
> >
> > strace -s 100 -f -e execve make BR2_REPRODUCIBLE=y printvars VARS=SOURCE_DATE_EPOCH 2>&1 | grep log
> > [pid 9504] execve("/bin/bash", ["/bin/bash", "-c", "GIT_DIR=/home/peko/source/buildroot/.git git log -1 --format=%at"], [/* 46 vars */]) = 0
> > [pid 9504] execve("/usr/bin/git", ["git", "log", "-1", "--format=%at"], [/* 47 vars */]) = 0
> > [pid 9505] execve("/bin/bash", ["/bin/bash", "-c", "GIT_DIR=/home/peko/source/buildroot/.git git log -1 --format=%at"], [/* 46 vars */]) = 0
> > [pid 9505] execve("/usr/bin/git", ["git", "log", "-1", "--format=%at"], [/* 47 vars */]) = 0
> >
> > It uses the BR2_GIT setting, E.G.:
> >
> > strace -s 100 -f -e execve make BR2_REPRODUCIBLE=y printvars VARS=SOURCE_DATE_EPOCH BR2_GIT=foot 2>&1 | grep log
> > [pid 9880] execve("/bin/bash", ["/bin/bash", "-c", "GIT_DIR=/home/peko/source/buildroot/.git foot log -1 --format=%at"], [/* 46 vars */]) = 0
> > [pid 9881] execve("/bin/bash", ["/bin/bash", "-c", "GIT_DIR=/home/peko/source/buildroot/.git foot log -1 --format=%at"], [/* 46 vars */]) = 0
> >
> > This is with current master and make 4.1.
>
> But not when there is no .config file:
>
> $ make O=/tmp/brtest BR2_REPRODUCIBLE=y printvars VARS=SOURCE_DATE_EPOCH
> /bin/sh: log: command not found
> SOURCE_DATE_EPOCH=
> /bin/sh: log: command not found
Uh? Why you want to do that?
> $ make O=/tmp/brtest BR2_REPRODUCIBLE=y printvars VARS=SOURCE_DATE_EPOCH GIT=git
> SOURCE_DATE_EPOCH=1509720578
If anything, SOURCE_DATE_EPOCH should come from the environment, as
specified in the spec (see below).
> Solution: move the GIT definition to top-level Makefile.
That would not solve anything, because it is still defined from BR2_GIT
that comes... from .config .
> >> 2) It always uses the last git commit to calculate the date. So any commit
> > > changes the timestamp, while the non-git timestamp stays the same.
> > > This makes the whole thing almost useless.
> > > If the git log command could take a parameter, you could make reproducible
> > > builds based on e.g. tag 2017.08, which would be much more useful.
> >
> > Well, SOURCE_DATE_EPOCH is meant to refer to the date of the last source
> > code change rather than the build time (E.G. so repeated builds of the
> > same sources would give the same results, but builds of changed sources
> > would return a newer timestamp).
> >
> > So I don't really agree that it useless. What we could perhaps do is to
> > only export our value for SOURCE_DATE_EPOCH if not already set in the
> > enviroment, so you can set it outside Buildroot if you want a different
> > behaviour.
>
> Well, the proposed solution of using a config variable sounds OK. Only, I think
> it would make more sense to have a config variable with a date, rather than a
> commit ID.
Or let the user define SOURCE_DATE_EPOCH in the environment, as this is
what would be used and is how SOURCE_DATE_EPOCH is specified;
https://reproducible-builds.org/specs/source-date-epoch/
Build systems MUST NOT overwrite this variable for child processes
to consume if it is already present.
I still fail to see what is wrong with the current situation...
Regards,
Yann E. MORIN.
> Regards,
> Arnout
>
>
> --
> Arnout Vandecappelle arnout at mind be
> Senior Embedded Software Architect +32-16-286500
> Essensium/Mind http://www.mind.be
> G.Geenslaan 9, 3001 Leuven, Belgium BE 872 984 063 RPR Leuven
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