[OE-core][PATCH v2] classes/kernel: Generate reproducible kernel module tarball

["Joshua Watt" <JPEWhacker@gmail.com>]

If reproducible binaries are requested, generate the kernel modules
tarball in a reproducible way. Namely, sort the tarball contents, clamp
the mtime to the source date epoch, compress the archive with a
consistent compression level (9), and don't include the name and
timestamp in the compressed file.

[YOCTO #12719]

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
---
 meta/classes/kernel.bbclass | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/meta/classes/kernel.bbclass b/meta/classes/kernel.bbclass
index a724645466..6846d6040d 100644
--- a/meta/classes/kernel.bbclass
+++ b/meta/classes/kernel.bbclass
@@ -691,7 +691,13 @@ kernel_do_deploy() {
 
 	if [ ${MODULE_TARBALL_DEPLOY} = "1" ] && (grep -q -i -e '^CONFIG_MODULES=y$' .config); then
 		mkdir -p ${D}${root_prefix}/lib
-		tar -cvzf $deployDir/modules-${MODULE_TARBALL_NAME}.tgz -C ${D}${root_prefix} lib
+		if [ -n "${SOURCE_DATE_EPOCH}" ]; then
+			TAR_ARGS="--sort=name --clamp-mtime --mtime=@${SOURCE_DATE_EPOCH}"
+		else
+			TAR_ARGS=""
+		fi
+		tar $TAR_ARGS -cv -C ${D}${root_prefix} lib | gzip -9n > $deployDir/modules-${MODULE_TARBALL_NAME}.tgz
+
 		ln -sf modules-${MODULE_TARBALL_NAME}.tgz $deployDir/modules-${MODULE_TARBALL_LINK_NAME}.tgz
 	fi
 
-- 
2.17.1