[Reproducible-builds] Bug#769844: linux: please make linux build reproducibly

[Bastian Blank]

On Mon, Jan 05, 2015 at 06:56:10PM +0100, Jérémy Bobbio wrote:
> We are currently experimenting with fixing mtimes in `dh_builddeb`
> instead of requiring a new helper. I have also done my latest
> experiments without `dh_strip_nondeterminism`. The attached patch adds
> the `-n` flag to gzip to compensate.

Okay.

> That's how the experimental toolchain now works: the .buildinfo is
> generated by dpkg-genbuildinfo, called by dpkg-buildpackage.

Thanks

> > > >  * linux-source: mtimes of many files differ. Would it be ok to just
> > > >    create the tarball with a single timestamp (`tar --mtime=`)?
> I've used find+touch instead. See attached patch.

Why?

> I also stumbled on a variation of the Installed-Size field in one of the
> .deb. But this is a different topic.

Is this value computed in a stable way?

> +@@ -301,7 +301,9 @@ if [ ! -z ${output_file} ]; then
> + 	if [ -z ${cpio_file} ]; then
> + 		timestamp=
> + 		if test -n "$KBUILD_BUILD_TIMESTAMP"; then
> +-			timestamp="$(date -d"$KBUILD_BUILD_TIMESTAMP" +%s || :)"
> ++			source_date=$(echo "$KBUILD_BUILD_TIMESTAMP" |
> ++					sed -e 's/.*(\([0-9-]\+\)).*/\1/')
> ++			timestamp="$(date -d"$source_date" +%s || :)"

This solution may not work.  The patched source can be built with a
normal timestamp override, via linux-source.

> @@ -87,6 +87,8 @@
>  	rm -rf '$@' '$(DIR)'
>  	$(call copy_source,$(DIR))
>  	chmod -R u+rw,go=rX '$(DIR)'
> +	find '$(DIR)' -depth -newermt '$(SOURCE_DATE)' -print0 | \
> +		xargs -0r touch --no-dereference --date='$(SOURCE_DATE)'

-newermt?  This does not look really stable.  

Bastian

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