[OpenWrt-Devel] [PATCH 09/13] build system: have tar use $SOURCE_DATE_EPOCH for --mtime

[Alexander Couzens]

From: bryan newbold <bnewbold at robocracy.org>

The --mtime argument to 'tar' sets the modification time for all files within
the archive, which determines the timestamp files will get when they are
extracted. In this case, rootfs and other tarballs will get mtimes which
correspond to the last commit timestamp of the build system, as reported by
git/subversion.

This is a step towards reproducible image builds.

Signed-off-by: bryan newbold <bnewbold at robocracy.org>
Signed-off-by: Alexander Couzens <lynxis at fe80.eu>
---
 include/image.mk           | 8 ++++++--
 include/kernel-build.mk    | 6 +++++-
 scripts/sysupgrade-nand.sh | 7 ++++++-
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/image.mk b/include/image.mk
index a53bea8..d471788 100644
--- a/include/image.mk
+++ b/include/image.mk
@@ -187,7 +187,8 @@ ifneq ($(CONFIG_NAND_SUPPORT),)
 	[ -z "$(2)" ] || $(CP) "$(KDIR)/root.$(2)" "$(KDIR_TMP)/sysupgrade-$(1)/root"
 	[ -z "$(3)" ] || $(CP) "$(3)" "$(KDIR_TMP)/sysupgrade-$(1)/kernel"
 	(cd "$(KDIR_TMP)"; $(TAR) cvf \
-		"$(BIN_DIR)/$(IMG_PREFIX)-$(1)-$(2)-sysupgrade.tar" sysupgrade-$(1))
+		"$(BIN_DIR)/$(IMG_PREFIX)-$(1)-$(2)-sysupgrade.tar" sysupgrade-$(1) \
+			$(if $(SOURCE_DATE_EPOCH),--mtime="$(SOURCE_DATE_EPOCH)")
    endef
 
 # $(1) board name
@@ -249,7 +250,10 @@ define Image/mkfs/cpiogz
 endef
 
 define Image/mkfs/targz
-	$(TAR) -czpf $(BIN_DIR)/$(IMG_PREFIX)$(if $(PROFILE_SANITIZED),-$(PROFILE_SANITIZED))-rootfs.tar.gz --numeric-owner --owner=0 --group=0 --sort=name -C $(TARGET_DIR)/ .
+	$(TAR) -czpf $(BIN_DIR)/$(IMG_PREFIX)$(if $(PROFILE_SANITIZED),-$(PROFILE_SANITIZED))-rootfs.tar.gz \
+		--numeric-owner --owner=0 --group=0 --sort=name \
+		$(if $(SOURCE_DATE_EPOCH),--mtime="$(SOURCE_DATE_EPOCH)") \
+		-C $(TARGET_DIR)/ .
 endef
 
 E2SIZE=$(shell echo $$(($(CONFIG_TARGET_ROOTFS_PARTSIZE)*1024*1024)))
diff --git a/include/kernel-build.mk b/include/kernel-build.mk
index 9abfd54..39bdd01 100644
--- a/include/kernel-build.mk
+++ b/include/kernel-build.mk
@@ -18,6 +18,8 @@ include $(INCLUDE_DIR)/download.mk
 include $(INCLUDE_DIR)/quilt.mk
 include $(INCLUDE_DIR)/kernel-defaults.mk
 
+SOURCE_DATE_EPOCH:=$(shell $(TOPDIR)/scripts/getsource_date_epoch.sh)
+
 define Kernel/Prepare
 	$(call Kernel/Prepare/Default)
 endef
@@ -54,7 +56,9 @@ ifdef CONFIG_COLLECT_KERNEL_DEBUG
 		$(STAGING_DIR_ROOT)/lib/modules/$(LINUX_VERSION)/* \
 		$(KERNEL_BUILD_DIR)/debug/modules/
 	$(FIND) $(KERNEL_BUILD_DIR)/debug -type f | $(XARGS) $(KERNEL_CROSS)strip --only-keep-debug
-	$(TAR) c -C $(KERNEL_BUILD_DIR) debug | bzip2 -c -9 > $(BIN_DIR)/kernel-debug.tar.bz2
+	$(TAR) c -C $(KERNEL_BUILD_DIR) debug \
+		$(if $(SOURCE_DATE_EPOCH),--mtime="$(SOURCE_DATE_EPOCH)") \
+		| bzip2 -c -9 > $(BIN_DIR)/kernel-debug.tar.bz2
   endef
 endif
 
diff --git a/scripts/sysupgrade-nand.sh b/scripts/sysupgrade-nand.sh
index 92b326c..73881e0 100755
--- a/scripts/sysupgrade-nand.sh
+++ b/scripts/sysupgrade-nand.sh
@@ -56,7 +56,12 @@ echo "BOARD=${board}" > "${tmpdir}/sysupgrade-${board}/CONTROL"
 [ -z "${rootfs}" ] || cp "${rootfs}" "${tmpdir}/sysupgrade-${board}/root"
 [ -z "${kernel}" ] || cp "${kernel}" "${tmpdir}/sysupgrade-${board}/kernel"
 
-(cd "$tmpdir"; tar cvf sysupgrade.tar sysupgrade-${board})
+mtime=""
+if [ -n "$SOURCE_DATE_EPOCH" ]; then
+	mtime="--mtime=${SOURCE_DATE_EPOCH}"
+fi
+
+(cd "$tmpdir"; tar cvf sysupgrade.tar sysupgrade-${board} ${mtime})
 err="$?"
 if [ -e "$tmpdir/sysupgrade.tar" ]; then
 	cp "$tmpdir/sysupgrade.tar" "$outfile"
-- 
2.7.0
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