dm-verity: save veritysetup args beside runtime environment

We already have this directory to save the environment variable settings
so they can be copied into the initramfs for runtime setup.

There are quite a few veritysetup args, and the nature of storing the
hash data after the filesystem data in an "oversized" partition can be
error prone due to rounding, fencepost errors, etc.

Save a copy of what we used for ease of debug inspection, and for basic
cut and paste use in experimentation and tweaking.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>

classes/dm-verity-img.bbclass

@@ -34,7 +34,6 @@ DM_VERITY_IMAGE_HASH_BLOCK_SIZE ?= "4096"
 # any useful info) and feed the rest to a script.
 process_verity() {
     local ENV="${STAGING_VERITY_DIR}/${IMAGE_BASENAME}.$TYPE.verity.env"
-    install -d ${STAGING_VERITY_DIR}
     rm -f $ENV
 
     # Each line contains a key and a value string delimited by ':'. Read the
@@ -59,6 +58,9 @@ verity_setup() {
     local SIZE=$(stat --printf="%s" $INPUT)
     local OUTPUT=$INPUT.verity
     local SETUP_ARGS=""
+    local SAVED_ARGS="${STAGING_VERITY_DIR}/${IMAGE_BASENAME}.$TYPE.verity.args"
+
+    install -d ${STAGING_VERITY_DIR}
 
     if [ ${DM_VERITY_IMAGE_DATA_BLOCK_SIZE} -ge ${DM_VERITY_IMAGE_HASH_BLOCK_SIZE} ]; then
         align=${DM_VERITY_IMAGE_DATA_BLOCK_SIZE}
@@ -75,6 +77,8 @@ verity_setup() {
         --hash-offset=$SIZE format $OUTPUT $OUTPUT \
     "
 
+    echo "veritysetup $SETUP_ARGS" > $SAVED_ARGS
+
     # Let's drop the first line of output (doesn't contain any useful info)
     # and feed the rest to another function.
     veritysetup $SETUP_ARGS | tail -n +2 | process_verity