Re: [PATCH dwarves] pahole: enable --reproducible_build when SOURCE_DATE_EPOCH is set

[Dominique Martinet <asmadeus@codewreck.org>]

Alan Maguire wrote on Mon, Jul 01, 2024 at 05:44:15PM +0100:
> >  - in theory, sure; this patch works. I say we can do this independantly
> > of any other effort. The propere way of setting reproducible build in
> > the kernel is not SOURCE_DATE_EPOCH but KBUILD_BUILD_TIMESTAMP and
> > handling it at kernel makefile level is sound.
> 
> Okay, so I propose we try and get the KBUILD_BUILD_TIMESTAMP-based
> change upstream. I'll send that later today. That doesn't mean we can't
> add the envvar-based method too, it just means we have something
> upstream that handles reproducible builds more explicitly.

Thanks.

> >  - in practice, (nixos hat) some modules won't set it but will only have
> > SOURCE_DATE_EPOCH available, and there are trees that won't be updated
> > for years (and that's being optimistic), so our local patch in pahole is
> > here to stay for a while and the benefits far outweight the rebasing
> > work.
> >  - (alpine hat) alpine doesn't seem to care as much about
> > reproducibility (the nixos patch wasn't in and nobody complained so far),
> > undecided at this point. Makefile.btf patch is probably good enough, but
> > since I'm maintaining the patch anyway it's no extra work to add it
> > there, undecided at this point.
> > 
> >
> 
> One thing I think would be worth doing in your patch would be adding
> debug logging (if in verbose mode) that we are enabling reproducible
> builds due to the presence of the SOURCE_DATE_EPOCH envvar. I don't
> think we can do this in the non-debug case because build logs would just
> be flooded with a few thousand of these messages for each module we add
> BTF to using pahole. With that small addition I'd be happy with the
> change. Can you send a v2 with that added? Thanks!

That makes sense, I'll send a v2 with a debug log message
tonight/tomorrow

-- 
Dominique Martinet | Asmadeus