pkg/driver/flatcar: Update the script

It was taken straight from the old driver loader bash script, but now
it's a separate script, so some constructs like `local` make no sense
there. A result was that no kernel tools were patched, thus they could
fail to run if they were built against a newer glibc than the one
provided by the falco-driver-loader image.

Also print both standard output and standard error on failure, so we
may have some idea about what's going on here.

Signed-off-by: Krzesimir Nowak <knowak@microsoft.com>

pkg/driver/distro/flatcar.go

@@ -28,29 +28,57 @@ import (
 )
 
 const flatcarRelocateScript = `
-local -a tools=(
-		scripts/basic/fixdep
-		scripts/mod/modpost
-		tools/objtool/objtool
-	)
-local -r hostld=$(ls /host/usr/lib64/ld-linux-*.so.*)
-local -r kdir=/lib/modules/$(ls /lib/modules/)/build
-echo "** Found host dl interpreter: ${hostld}"
-for host_tool in ${tools[@]}; do
-	t=${host_tool}
-	tool=$(basename $t)
-	tool_dir=$(dirname $t)
-	host_tool=${kdir}/${host_tool}
-	if [ ! -f ${host_tool} ]; then
+set -euo pipefail
+
+shopt -s nullglob
+
+hostlds=( /host/usr/lib64/ld-linux-*.so.* )
+if [[ ${#hostlds[@]} -eq 0 ]]; then
+	echo "** no dynamic loaders found"
+	exit 1
+fi
+if [[ ${#hostlds[@]} -gt 1 ]]; then
+	echo "** more than one fitting dynamic loader found, picking first"
+fi
+hostld=${hostlds[0]}
+echo "** Found host dynamic loader: ${hostld}"
+
+kdirs=( /host/lib/modules/*/build )
+if [[ ${#kdirs[@]} -eq 0 ]]; then
+	echo "** no kernel module tools directories found"
+	exit 1
+fi
+if [[ ${#kdirs[@]} -gt 1 ]]; then
+	echo "** more than one fitting kernel module tools directory found, picking first"
+fi
+kdir=${kdirs[0]}
+echo "** Found kernel tools directory: ${kdir}"
+
+tools=(
+	scripts/basic/fixdep
+	scripts/mod/modpost
+	tools/objtool/objtool
+)
+
+tmp_dir=$(mktemp -d)
+for tool in "${tools[@]}"; do
+	host_tool=${kdir}/${tool}
+	if [[ ! -f ${host_tool} ]]; then
+		echo "${tool@Q} not found in ${kdir@Q}, not patching"
 		continue
 	fi
-	umount ${host_tool} 2>/dev/null || true
-	mkdir -p /tmp/${tool_dir}/
-	cp -a ${host_tool} /tmp/${tool_dir}/
-	echo "** Setting host dl interpreter for $host_tool"
-	patchelf --set-interpreter ${hostld} --set-rpath /host/usr/lib64 /tmp/${tool_dir}/${tool}
-	mount -o bind /tmp/${tool_dir}/${tool} ${host_tool}
+	umount "${host_tool}" 2>/dev/null || true
+	tmp_tool=${tmp_dir}/${tool}
+	mkdir -p "$(dirname "${tmp_tool}")"
+	cp -a "${host_tool}" "${tmp_tool}"
+	echo "** Setting host dynamic loader for ${tool@Q}"
+	patchelf \
+		--set-interpreter "${hostld}" \
+		--set-rpath /host/usr/lib64 \
+		"${tmp_tool}"
+	mount -o bind "${tmp_tool}" "${host_tool}"
 done
+rm -rf "${tmp_dir}"
 `
 
 func init() {
@@ -94,7 +122,7 @@ func (f *flatcar) customizeBuild(ctx context.Context,
 		return nil, nil
 	}
 	printer.Logger.Info("Flatcar detected; relocating kernel tools.", printer.Logger.Args("version", f.versionID))
-	out, err := exec.CommandContext(ctx, "/bin/bash", "-c", flatcarRelocateScript).Output()
+	out, err := exec.CommandContext(ctx, "/bin/bash", "-c", flatcarRelocateScript).CombinedOutput()
 	if err != nil {
 		printer.DefaultText.Print(string(out))
 	}