From 8df6943f7df17b5cf0187a987d6f33bab92cb119 Mon Sep 17 00:00:00 2001
From: Lars Wikman <lars@underjord.io>
Date: Wed, 8 Jan 2025 14:44:23 +0100
Subject: [PATCH] Add option to rel2fw.sh to allow post-processing

This would typically be invoked by `mix firmware` further up the
stack. It is at the right moment to allow operating on the squashfs
file system before it is packed up into the fw file.

The primary purpose is to allow signing the root filesystem for use
with dm-verity.
---
 scripts/rel2fw.sh | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/scripts/rel2fw.sh b/scripts/rel2fw.sh
index 3b1a5994..8b50372e 100755
--- a/scripts/rel2fw.sh
+++ b/scripts/rel2fw.sh
@@ -28,6 +28,7 @@ usage() {
     echo "  -f <firmware output file>  Default is $PROJECT_DIR.fw"
     echo "  -o <image output file>     Default is $PROJECT_DIR.img"
     echo "  -p <file priorities>       The ordering of files in the rootfs (may be specified more than once)"
+    echo "  -s <script path>           Post-processing script for rootfs (optional)"
     echo
     echo "Barring errors, the firmware file is always created. The raw image is only"
     echo "created if specified."
@@ -48,7 +49,7 @@ sbin/init 32764
 etc/erlinit.config 32763
 END
 
-while getopts "a:c:f:o:p:" opt; do
+while getopts "a:c:f:o:p:s:" opt; do
     case $opt in
         a)
             ROOTFS_OVERLAYS="$ROOTFS_OVERLAYS $OPTARG"
@@ -66,6 +67,9 @@ while getopts "a:c:f:o:p:" opt; do
             # Append priorities to the master list
             cat "$OPTARG" >> "$SQUASHFS_PRIORITIES"
             ;;
+        s)
+            POST_PROCESSING_SCRIPT="$OPTARG"
+            ;;
         \?)
             echo "$SCRIPT_NAME: ERROR: Invalid option: -$OPTARG"
             usage
@@ -157,6 +161,12 @@ fi
 # Merge the Erlang/OTP release onto the base image
 "$NERVES_SYSTEM/scripts/merge-squashfs" "$NERVES_SDK_IMAGES/rootfs.squashfs" "$TMP_DIR/combined.squashfs" "$TMP_DIR/rootfs_overlay" "$SQUASHFS_PRIORITIES"
 
+# If a post processing script for the final rootfs was specified, run it
+if [ ! -z "${POST_PROCESSING_SCRIPT}" ]; then
+    echo "Running post-processing script: ${POST_PROCESSING_SCRIPT}"
+    ${POST_PROCESSING_SCRIPT} "$TMP_DIR/combined.squashfs";
+fi
+
 # Build the firmware image
 echo "Building $FW_FILENAME..."
 ROOTFS="$TMP_DIR/combined.squashfs" $FWUP -c -f "$FWUP_CONFIG" \