image-builder: Add NSDAX_BIN for passing in compiled nsdax tool

In Fedora we are running the osbuilder scripts on the client machine,
to generate an initrd for the running host kernel. In this setup,
there's currently a runtime dependency on gcc for compiling the nsdax
tool, which is suboptimal.

Add NSDAX_BIN environment variable; if specified, image-builder.sh
will use that path as the nsdax tool. This let's ship a compiled
nsdax tool to users and drop the runtime gcc dependency

Fixes: #417

Signed-off-by: Cole Robinson <crobinso@redhat.com>

image-builder/image_builder.sh

@@ -88,6 +88,7 @@ Options:
 Extra environment variables:
 	AGENT_BIN:  Use it to change the expected agent binary name
 	AGENT_INIT: Use kata agent as init process
+	NSDAX_BIN:  Use to specify path to pre-compiled 'nsdax' tool.
 	FS_TYPE:    Filesystem type to use. Only xfs and ext4 are supported.
 	USE_DOCKER: If set will build image in a Docker Container (requries docker)
 		    DEFAULT: not set
@@ -130,6 +131,8 @@ build_with_container() {
 	local root_free_space="$5"
 	local agent_bin="$6"
 	local agent_init="$7"
+	local container_engine="$8"
+	local nsdax_bin="$9"
 	local container_image_name="image-builder-osbuilder"
 	local shared_files=""
 
@@ -158,6 +161,7 @@ build_with_container() {
 		   --env FS_TYPE="${fs_type}" \
 		   --env BLOCK_SIZE="${block_size}" \
 		   --env ROOT_FREE_SPACE="${root_free_space}" \
+		   --env NSDAX_BIN="${nsdax_bin}" \
 		   --env DEBUG="${DEBUG}" \
 		   -v /dev:/dev \
 		   -v "${script_dir}":"/osbuilder" \
@@ -411,6 +415,7 @@ set_dax_header() {
 	local image="$1"
 	local img_size="$2"
 	local fs_type="$3"
+	local nsdax_bin="$4"
 
 	# rootfs start + DAX header size
 	local rootfs_offset=$((rootfs_start + dax_header_sz))
@@ -425,9 +430,12 @@ set_dax_header() {
 	info "Set DAX metadata"
 	# Set metadata header
 	# Issue: https://github.com/kata-containers/osbuilder/issues/240
-	gcc -O2 "${script_dir}/nsdax.gpl.c" -o "${script_dir}/nsdax"
+	if [ -z "${nsdax_bin}" ] ; then
-	"${script_dir}/nsdax" "${header_image}" "${dax_header_bytes}" "${dax_alignment_bytes}"
+		nsdax_bin="${script_dir}/nsdax"
-	rm -f "${script_dir}/nsdax"
+		gcc -O2 "${script_dir}/nsdax.gpl.c" -o "${nsdax_bin}"
+		trap "rm ${nsdax_bin}" EXIT
+	fi
+	"${nsdax_bin}" "${header_image}" "${dax_header_bytes}" "${dax_alignment_bytes}"
 	sync
 
 	touch "${dax_image}"
@@ -452,6 +460,7 @@ main() {
 	local image="${IMAGE:-kata-containers.img}"
 	local block_size="${BLOCK_SIZE:-4096}"
 	local root_free_space="${ROOT_FREE_SPACE:-}"
+	local nsdax_bin="${NSDAX_BIN:-}"
 
 	while getopts "ho:r:f:" opt
 	do
@@ -471,6 +480,7 @@ main() {
 		exit 0
 	fi
 
+	local container_engine
 	if [ -n "${USE_DOCKER}" ]; then
 		container_engine="docker"
 	elif [ -n "${USE_PODMAN}" ]; then
@@ -478,8 +488,11 @@ main() {
 	fi
 
 	if [ -n "$container_engine" ]; then
-		build_with_container "${rootfs}" "${image}" "${fs_type}" "${block_size}" \
+		build_with_container "${rootfs}" \
-						  "${root_free_space}" "${agent_bin}" "${agent_init}" "${container_engine}"
+			"${image}" "${fs_type}" "${block_size}" \
+			"${root_free_space}" "${agent_bin}" \
+			"${agent_init}" "${container_engine}" \
+			"${nsdax_bin}"
 		exit $?
 	fi
 
@@ -496,7 +509,7 @@ main() {
 						"${fs_type}" "${block_size}"
 
 	# insert at the beginning of the image the MBR + DAX header
-	set_dax_header "${image}" "${img_size}" "${fs_type}"
+	set_dax_header "${image}" "${img_size}" "${fs_type}" "${nsdax_bin}"
 }
 
 main "$@"