[RFC PATCH] image.bbclass: create separate task for creating reproducible image

[venkata.pyla@toshiba-tsip.com]

From: venkata pyla <venkata.pyla@toshiba-tsip.com>

Currently the reproducible fix for setting same file timestamps across
builds is present in the function `do_rootfs_finalize` and this fix may
be skipped for the tasks that are added after this task or `do_rootfs`
 for e.g. in one of the child project(CIP) for swupdate target it adds
 additional task `do_generate_image_uuid` that is added after `do_rootfs`
 this task is updating some contents in the rootfs which is skipping the
 reproducible fix was applied in `do_rootfs_finalize`.

For this reason a separate task `do_image_make_reproducible` is created
which should call before the final target image is created [tar, wic,
squashfs] so that it applies reproducible fixes just before image
creation.

RFC:
In this patch I tried below dependency[1] for the function to solve the
above problem, it works now but I am not sure whether it guarantee
always this task `do_image_make_reproducible` will run just before
`do_image_[tar,wic,squashfs]` tasks or does it need more changes to make
it guarantee, any suggestions?

[1] addtask image_make_reprodcible after do_rootfs before do_image

Signed-off-by: venkata pyla <venkata.pyla@toshiba-tsip.com>
---
 meta/classes/image.bbclass | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
index ef7d5a2..c3a3d45 100644
--- a/meta/classes/image.bbclass
+++ b/meta/classes/image.bbclass
@@ -446,19 +446,6 @@ do_rootfs_finalize() {
         fi
 EOSUDO
 
-    # Set same time-stamps to the newly generated file/folders in the
-    # rootfs image for the purpose of reproducible builds.
-    if [ -n "${SOURCE_DATE_EPOCH}" ]; then
-        fn="${DEPLOY_DIR_IMAGE}/files.modified_timestamps"
-        if sudo find ${ROOTFSDIR} -newermt "$(date -d@${SOURCE_DATE_EPOCH} '+%Y-%m-%d %H:%M:%S')" \
-            -printf "%y %p\n" -exec touch '{}' -h -d@${SOURCE_DATE_EPOCH} ';' | egrep ^f >"$fn"; then
-            if [ -e "$fn" ]; then
-                bbwarn "modified timestamp (${SOURCE_DATE_EPOCH}) of $(cat "$fn" | wc -l) files for image reproducibly." \
-                       "List of files modified can be found in: .${DEPLOY_DIR_IMAGE}/files.modified_timestamps"
-            fi
-        fi
-    fi
-
 }
 do_rootfs_finalize[network] = "${TASK_USE_SUDO}"
 addtask rootfs_finalize before do_rootfs after do_rootfs_postprocess
@@ -502,3 +489,23 @@ do_rootfs_quality_check() {
 do_rootfs_quality_check[network] = "${TASK_USE_SUDO}"
 
 addtask rootfs_quality_check after do_rootfs_finalize before do_rootfs
+
+# Run this task just before final image creation of different image types
+#     i.e do_image_tar, do_image_squashfs, do_image_wic etc.
+#     to avoid modification of image contents that leads to non-reproducible
+#     image
+do_image_make_reproducible() {
+    # Set same time-stamps to the newly generated file/folders in the
+    # rootfs image for the purpose of reproducible builds.
+    if [ -n "${SOURCE_DATE_EPOCH}" ]; then
+        fn="${DEPLOY_DIR_IMAGE}/files.modified_timestamps"
+        if sudo find ${ROOTFSDIR} -newermt "$(date -d@${SOURCE_DATE_EPOCH} '+%Y-%m-%d %H:%M:%S')" \
+            -printf "%y %p\n" -exec touch '{}' -h -d@${SOURCE_DATE_EPOCH} ';' | egrep ^f >"$fn"; then
+            if [ -e "$fn" ]; then
+                bbwarn "modified timestamp (${SOURCE_DATE_EPOCH}) of $(cat "$fn" | wc -l) files for image reproducibly." \
+                       "List of files modified can be found in: .${DEPLOY_DIR_IMAGE}/files.modified_timestamps"
+            fi
+        fi
+    fi
+}
+addtask image_make_reprodcible after do_rootfs before do_image
-- 
2.20.1