initramfs: pass contents using an attrset

This commit significantly cleans up the assembly of the initramfs by
specifying and manipulating its contents using an attrset (in { dest
= src; } form) rather than chunks of bash script.

src/initramfs/default.nix

@@ -12,6 +12,31 @@
 # files which should be included in the initrd
 , modules ? [ ]
 
+# An attrset containing additional files to include in the initramfs
+# image.  Each attrname in this set is a path relative to the root
+# of the initramfs (e.g. "bin/signify") and the corresponding value is
+# the file to be copied to that location (e.g. "${signify}/bin/signify).
+#
+# - If the attrvalue has a trailing "/" then both the source and
+#   destination are considered to be directories; the source will be
+#   copied recursively, and symbolic links therein will be preserved
+#   (i.e. not dereferenced).  See `withBusybox` below for an example.
+#
+# - If the attrvalue does NOT have a trailing "/" then both the
+#   source and destination are considered to be files.  If the
+#   source is a symbolic link it will be dereferenced before copying.
+#
+# After copying, `chmod -R u+w` is performed, since the contents are
+# likely to be coming from /nix/store where Nix clears the u-w bit.
+#
+, contents ? {}
+
+# cause usr/{bin,sbin} to be symlinks to {bin/sbin}
+, withMergedUsr ? true
+
+# cause sbin to be a symlink to bin
+, withMergedBinSbin ? true
+
 , withBusybox ? true
 , withSignify ? true
 # Inclusion of these is temporarily disabled.  I had a bunch of
@@ -31,46 +56,55 @@ let
   nvramtool = nixpkgsOnBuildForHost.pkgsStatic.nvramtool.overrideAttrs(a: {
     NIX_CFLAGS_COMPILE = "-D__GLIBC__";
   });
+  contents' = (lib.pipe modules [
+    (map (m: let name = "${kernel.version}/kernel/${m}";
+             in {
+               name = "lib/modules/${name}";            # dest
+               value = "${kernel}/lib/modules/${name}"; # source
+             }))
+    lib.listToAttrs
+  ]) // lib.optionalAttrs withBusybox {
+    "bin" = "${busybox}/bin/";
+  } // lib.optionalAttrs withSignify {
+    "bin/signify" = "${signify}/bin/signify";
+  } // lib.optionalAttrs withLvm {
+    "bin/lvm" = "${lib.getBin lvm2}/bin/lvm";
+    "bin/dmsetup" = "${lib.getBin lvm2}/bin/dmsetup";
+  } // lib.optionalAttrs withCryptsetup {
+    "bin/cryptsetup" = "${cryptsetup}/bin/cryptsetup";
+  } // lib.optionalAttrs withKexec {
+    "bin/kexec" = "${kexec-tools}/bin/kexec";
+  } // lib.optionalAttrs withNvramTool {
+    "bin/nvramtool" = "${nvramtool}/bin/nvramtool";
+  } // lib.optionalAttrs (bootScript != null) {
+    "sbin/init" = "${bootScript}";
+  } // contents;
+
 in stdenv.mkDerivation {
   name = "initramfs.cpio";
   dontUnpack = true;
   dontFixup = true;
 
-  modulesList = (lib.concatMapStringsSep "\n" (m: "${kernel.version}/kernel/" + m) modules)+"\n";
-  passAsFile = [ "modulesList" ];
-
   buildPhase = ''
     runHook preBuild
-
-    mkdir -p $NIX_BUILD_TOP/lib/modules
-    pushd ${kernel}/lib/modules/
-      cat $modulesListPath | ${cpio}/bin/cpio -p -d $NIX_BUILD_TOP/lib/modules
-      popd
-
-    mkdir -p $NIX_BUILD_TOP/usr
-    ln -s bin $NIX_BUILD_TOP/sbin
-    ln -s ../bin $NIX_BUILD_TOP/usr/bin
-    ln -s ../sbin $NIX_BUILD_TOP/usr/sbin
-  '' + lib.optionalString withBusybox ''
-    cp -r ${busybox}/bin              $NIX_BUILD_TOP/bin
-    chmod -R u+w $NIX_BUILD_TOP/bin
-  '' + lib.optionalString (bootScript != null) ''
-    cp    ${bootScript} $NIX_BUILD_TOP/boot.sh
-    chmod +x $NIX_BUILD_TOP/boot.sh
-    ln -s boot.sh $NIX_BUILD_TOP/init
-    chmod +x $NIX_BUILD_TOP/sbin/init
-  '' + lib.optionalString withSignify ''
-    cp    ${signify}/bin/signify      $NIX_BUILD_TOP/bin/
-  '' + lib.optionalString withLvm ''
-    cp ${lib.getBin lvm2}/bin/lvm $NIX_BUILD_TOP/bin/
-    cp ${lib.getBin lvm2}/bin/dmsetup $NIX_BUILD_TOP/bin/
-  '' + lib.optionalString withCryptsetup ''
-    cp ${cryptsetup}/bin/cryptsetup $NIX_BUILD_TOP/bin/
-  '' + lib.optionalString withKexec ''
-    cp ${kexec-tools}/bin/kexec $NIX_BUILD_TOP/bin/
-  '' + lib.optionalString withNvramTool ''
-    cp ${nvramtool}/bin/nvramtool $NIX_BUILD_TOP/bin/
-  '' + ''
+  '' + lib.optionalString withMergedBinSbin ''
+    ln -s bin sbin
+  '' + lib.optionalString withMergedUsr ''
+    mkdir -p usr
+    ln -s ../bin usr/bin
+    ln -s ../sbin usr/sbin
+  '' + (lib.pipe contents' [
+        (lib.mapAttrsToList (dest: src:
+          if lib.hasSuffix "/" src then ''
+            mkdir -p ${lib.escapeShellArg (builtins.dirOf dest)}
+            cp -Tr ${lib.escapeShellArg src} ${lib.escapeShellArg dest}
+            chmod -R u+w ${lib.escapeShellArg dest}
+          '' else ''
+            install -vDT ${lib.escapeShellArg src} ${lib.escapeShellArg dest}
+          ''))
+        lib.concatStrings
+      ]) +
+  ''
     runHook postBuild
   '';
 

src/platform/kgpe/default.nix

@@ -17,12 +17,11 @@
         '';
       });
 
-    initramfs = prev.initramfs.overrideAttrs (a: {
-      postBuild = (a.postBuild or "") + ''
-        mkdir -p $NIX_BUILD_TOP/etc
-        cp ${final.image.src}/src/mainboard/asus/kgpe-d16/cmos.layout $NIX_BUILD_TOP/etc/
-        cp ${final.image.src}/src/mainboard/asus/kgpe-d16/cmos.default $NIX_BUILD_TOP/etc/
-      '';
+    initramfs = prev.initramfs.override (previousArgs: {
+      contents = (previousArgs.contents or {}) // {
+        "etc/cmos.layout"  = "${final.image.src}/src/mainboard/asus/kgpe-d16/cmos.layout";
+        "etc/cmos.default" = "${final.image.src}/src/mainboard/asus/kgpe-d16/cmos.default";
+      };
     });
 
     # microcode updates are needed only for Opteron 63xx