initramfs: pass module list as a nix expression rather than a file

src/initramfs/default.nix

@@ -3,8 +3,13 @@
 # initramfs-formatted `cpio` archive from their contents.
 { nixpkgsOnBuildForHost
 , nixpkgsOnBuildForBuild
+, lib
 , userspace
 , kernel
+
+# a list of paths (relative to ${kernel}/lib/modules/*/kernel) to modules .ko
+# files which should be included in the initrd
+, modules ? [ ]
 }:
 
 nixpkgsOnBuildForHost.stdenv.mkDerivation {
@@ -12,20 +17,22 @@ nixpkgsOnBuildForHost.stdenv.mkDerivation {
   nativeBuildInputs = with nixpkgsOnBuildForBuild; [ findutils cpio ];
   srcs = [ ];
   dontUnpack = true;
+  modulesList = (lib.concatMapStringsSep "\n" (m: "${kernel.version}/kernel/" + m) modules)+"\n";
+  passAsFile = [ "modulesList" ];
   buildPhase = ''
     mkdir build
     mkdir -p build/lib/modules
     BUILD=$(pwd)/build
     pushd ${kernel}/lib/modules/
-    cat ${userspace}/modules-insmod.txt | cpio -p -d $BUILD/lib/modules
-    popd
+      cat $modulesListPath | cpio -p -d $BUILD/lib/modules
+      popd
     pushd ${userspace}
-    find . | cpio -p -d $BUILD/
-    popd
+      find . | cpio -p -d $BUILD/
+      popd
     chmod -R u+w $BUILD
     pushd $BUILD
-    find . | cpio --create -H newc -R +0:+0 > $out
-    popd
+      find . | cpio --create -H newc -R +0:+0 > $out
+      popd
   '';
   dontInstall = true;
 }

src/platform/kevin/default.nix

@@ -61,6 +61,10 @@ in {
       inherit modules_noinsmod;
     };
 
+    initramfs = prev.initramfs.override {
+      modules = modules_insmod ++ modules_noinsmod;
+    };
+
     coreboot =
       let atf = final.nixpkgsOnBuildForHost.callPackage (import ./atf) {
             buildArmTrustedFirmware = (final.nixpkgsOnBuildForHost.callPackage (import <nixpkgs/pkgs/misc/arm-trusted-firmware>) {