[PATCH v2 10/10] make custom linux-image bit-by-bit reproducible

[Felix Moessbauer <felix.moessbauer@siemens.com>]

This patch makes the build of custom linux kernels bit-by-bit
reproducible. By that, we can remove the dh_strip_nondeterminism step,
which significantly reduces the kernel build time.

The implementation is similar to how upstream debian builds their kernel
images and extracts all information from the changelog. As the
DISTRIBUTOR field is not part of the changelog, we inject it via a bb
variable which is defaulted to ISAR.

Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
---
 .../linux/files/debian/isar/build.tmpl             |  1 +
 meta/recipes-kernel/linux/files/debian/rules.tmpl  | 14 +++++++++++++-
 meta/recipes-kernel/linux/linux-custom.inc         |  2 ++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/meta/recipes-kernel/linux/files/debian/isar/build.tmpl b/meta/recipes-kernel/linux/files/debian/isar/build.tmpl
index 94cfbe0..e7e0479 100644
--- a/meta/recipes-kernel/linux/files/debian/isar/build.tmpl
+++ b/meta/recipes-kernel/linux/files/debian/isar/build.tmpl
@@ -34,6 +34,7 @@ print_settings() {
 # ---------------
 # ARCH=${ARCH}
 # CROSS_COMPILE=${CROSS_COMPILE}
+# KBUILD_BUILD_TIMESTAMP=${KBUILD_BUILD_TIMESTAMP}
 EOF
 }
 
diff --git a/meta/recipes-kernel/linux/files/debian/rules.tmpl b/meta/recipes-kernel/linux/files/debian/rules.tmpl
index 8063c49..e8ae3da 100755
--- a/meta/recipes-kernel/linux/files/debian/rules.tmpl
+++ b/meta/recipes-kernel/linux/files/debian/rules.tmpl
@@ -2,6 +2,11 @@
 
 CROSS_COMPILE:=$(DEB_HOST_GNU_TYPE)-
 
+MAINTAINER := $(shell sed -ne 's,^Maintainer: .[^<]*<\([^>]*\)>,\1,p' debian/control)
+DISTRIBUTOR := ${DISTRIBUTOR}
+SOURCE_DATE := $(shell dpkg-parsechangelog -SDate)
+SOURCE_DATE_UTC_ISO := $(shell date -u -d '$(SOURCE_DATE)' +%Y-%m-%d)
+
 O:=$(CURDIR)/${KERNEL_BUILD_DIR}
 S:=$(CURDIR)
 deb_top_dir:=$(S)/debian
@@ -14,7 +19,11 @@ isar_env=$(strip \
 	export MAKE='$(MAKE)' && \
 	export O='${O}' && \
 	export S='${S}' && \
-	export CURDIR='$(CURDIR)' \
+	export CURDIR='$(CURDIR)' && \
+	export KBUILD_BUILD_TIMESTAMP='$(SOURCE_DATE)' && \
+	export KBUILD_BUILD_VERSION_TIMESTAMP='$(DISTRIBUTOR) $(DEB_VERSION_UPSTREAM) ($(SOURCE_DATE_UTC_ISO))' && \
+	export KBUILD_BUILD_USER='$(word 1,$(subst @, ,$(MAINTAINER)))' && \
+	export KBUILD_BUILD_HOST='$(word 2,$(subst @, ,$(MAINTAINER)))' \
 )
 
 %:
@@ -35,5 +44,8 @@ override_dh_auto_install:
 override_dh_auto_test:
 	true
 
+override_dh_strip_nondeterminism:
+	true
+
 override_dh_strip:
 	unset DEB_HOST_GNU_TYPE && dh_strip -Xvmlinu --no-automatic-dbgsym
diff --git a/meta/recipes-kernel/linux/linux-custom.inc b/meta/recipes-kernel/linux/linux-custom.inc
index 447d4e8..6c539c0 100644
--- a/meta/recipes-kernel/linux/linux-custom.inc
+++ b/meta/recipes-kernel/linux/linux-custom.inc
@@ -12,6 +12,7 @@
 CHANGELOG_V = "${PV}+${PR}"
 DESCRIPTION ?= "Custom kernel"
 MAINTAINER ?= "isar-users <isar-users@googlegroups.com>"
+DISTRIBUTOR ?= "ISAR"
 
 KBUILD_DEPENDS ?= "build-essential:native, \
                    libelf-dev:native, \
@@ -79,6 +80,7 @@ TEMPLATE_VARS += "                \
     KERNEL_NAME_PROVIDED          \
     KERNEL_CONFIG_FRAGMENTS       \
     KCFLAGS                       \
+    DISTRIBUTOR                   \
 "
 
 inherit dpkg
-- 
2.34.1