kernel/reproducibility: kernel modules need SOURCE_DATE_EPOCH export

If CONFIG_IKHEADERS is set to =m, then reproducibility issues creep
into the modules build, since the variables we are setting for the
main kernel build are not present.

Since the source code must be available for a possibly git query
on the timestamp, there didn't seem to be an easy way to move the
environment variable setting to a common routine. As such, we
duplicate the block of code that exports the required variables for
reproducible builds. There is a maintenance risk to this, but any
issues should be easy enough to catch.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

diff --git a/meta/classes/kernel.bbclass b/meta/classes/kernel.bbclass
index 6846d6040df6ac4380468cfa83d924b6b7f91736..0935196f6f618710beab8c4b88a9049d6d6a76b1 100644 (file)
--- a/meta/classes/kernel.bbclass
+++ b/meta/classes/kernel.bbclass
@@ -331,6 +331,21 @@ kernel_do_compile() {
 
 do_compile_kernelmodules() {
        unset CFLAGS CPPFLAGS CXXFLAGS LDFLAGS MACHINE
+       if [ "${BUILD_REPRODUCIBLE_BINARIES}" = "1" ]; then
+               # kernel sources do not use do_unpack, so SOURCE_DATE_EPOCH may not
+               # be set....
+               if [ "${SOURCE_DATE_EPOCH}" = "" -o "${SOURCE_DATE_EPOCH}" = "0" ]; then
+                       # The source directory is not necessarily a git repository, so we
+                       # specify the git-dir to ensure that git does not query a
+                       # repository in any parent directory.
+                       SOURCE_DATE_EPOCH=`git --git-dir="${S}/.git" log -1 --pretty=%ct 2>/dev/null || echo "${REPRODUCIBLE_TIMESTAMP_ROOTFS}"`
+               fi
+
+               ts=`LC_ALL=C date -d @$SOURCE_DATE_EPOCH`
+               export KBUILD_BUILD_TIMESTAMP="$ts"
+               export KCONFIG_NOTIMESTAMP=1
+               bbnote "KBUILD_BUILD_TIMESTAMP: $ts"
+       fi
        if (grep -q -i -e '^CONFIG_MODULES=y$' ${B}/.config); then
                cc_extra=$(get_cc_option)
                oe_runmake -C ${B} ${PARALLEL_MAKE} modules CC="${KERNEL_CC} $cc_extra " LD="${KERNEL_LD}" ${KERNEL_EXTRA_ARGS}