nixos: persistent file-system storage

nixos-modules/genode-core.nix

@@ -253,6 +253,26 @@ in {
               usb = rumpExt2;
             }.${config.genode.boot.storeBackend};
 
+            persistencePolicies = lib.mapAttrsToList (name: _: ''
+              , Init.Config.Policy::{
+                  , service = "File_system"
+                  , label = Genode.Init.LabelSelector.prefix
+                      "nixos -> ${name}"
+                  , attributes = toMap { root = "/services", writeable = "yes" }
+                  }
+            '') (filterAttrs (_: child: child.fsPersistence)
+              config.genode.init.children);
+
+            storePolicies = map (name: ''
+              , Init.Config.Policy::{
+                , service = "File_system"
+                , label =
+                    Init.LabelSelector.Type.Partial
+                      { prefix = Some "nixos -> ${name}", suffix = Some "nix-store" }
+                , attributes = toMap { root = "/nix/store", writeable = "no" }
+                }
+            '') (builtins.attrNames config.genode.init.children);
+
           in builtins.toFile "store_fs.dhall" ''
             let Genode = env:DHALL_GENODE
 
@@ -260,6 +280,14 @@ in {
 
             let VFS = Genode.VFS
 
+            let persistencePolicies = [ ${
+              toString persistencePolicies
+            } ] : List Init.Config.Policy.Type
+
+            let storePolicies = [ ${
+              toString storePolicies
+            } ] : List Init.Config.Policy.Type
+
             in  Init.Child.flat
                   Init.Child.Attributes::{
                   , binary = "vfs"
@@ -269,16 +297,11 @@ in {
                     , content = [ ${storeVfsConfig} ]
                     , policies =
                       [ Init.Config.Policy::{
-                        , service = "File_system"
-                        , label = Init.LabelSelector.suffix "nix-store"
-                        , attributes = toMap { root = "/nix/store" }
-                        }
-                      , Init.Config.Policy::{
                         , service = "File_system"
                         , label = Init.LabelSelector.prefix "store_rom"
                         , attributes = toMap { root = "/" }
                         }
-                      ]
+                      ] # persistencePolicies # storePolicies
                     }
                   }
           '';

nixos-modules/genode-init.nix

@@ -68,6 +68,16 @@ in {
               '';
             };
 
+            fsPersistence = lib.mkOption {
+              type = types.bool;
+              default = false;
+              description = ''
+                Whether this child will have access to mutable and persistent storage.
+                This space is shared among all components for which this option is available
+                and UNIX permission bits are not honored.
+              '';
+            };
+
             configFile = mkOption {
               type = types.path;
               description = ''

nixos-modules/systemd-runner.dhall

@@ -20,6 +20,7 @@ in  λ ( params
         , binary : Text
         , coreutils : Text
         , extraVfs : List XML.Type
+        , fsPersistence : Bool
         , interface : Optional Text
         , ramQuotaMiB : Natural
         }
@@ -90,10 +91,20 @@ in  λ ( params
                                               [ VFS.fs
                                                   VFS.FS::{
                                                   , label = "nix-store"
+                                                  , writeable = "no"
                                                   }
                                               ]
                                           ]
                                       ]
+                                    # ( if    params.fsPersistence
+                                        then  [ VFS.fs
+                                                  VFS.FS::{
+                                                  , label = "peristence"
+                                                  , writeable = "yes"
+                                                  }
+                                              ]
+                                        else  [ VFS.leaf "ram" ]
+                                      )
                                     # params.extraVfs
                                   )
                               ]

nixos-modules/systemd.nix

@@ -5,7 +5,8 @@ with lib; {
     type = types.attrsOf (types.submodule ({ name, config, ... }: {
       options.genode = {
 
-        enable = lib.mkEnableOption "systemd unit to a Genode subsystem translation";
+        enable =
+          lib.mkEnableOption "systemd unit to a Genode subsystem translation";
 
         interface = lib.mkOption {
           type = with types; nullOr str;
@@ -32,6 +33,16 @@ with lib; {
           description = "RAM quota in MiB";
         };
 
+        fsPersistence = lib.mkOption {
+          type = types.bool;
+          default = false;
+          description = ''
+            Whether this service will have access to mutable and persistent storage.
+            This space is shared among all services for which this option is available
+            and UNIX permission bits are not honored.
+          '';
+        };
+
       };
     }));
   };
@@ -56,6 +67,7 @@ with lib; {
               vfs
               vfs_pipe
             ];
+          inherit (service.genode) fsPersistence;
           configFile = let
             args = lib.strings.splitString " "
               (toString service.serviceConfig.ExecStart);
@@ -66,6 +78,7 @@ with lib; {
               "None Text"
             else
               ''Some "${service.genode.interface}"'';
+            toBool = cond: if cond then "True" else "False";
           in pkgs.writeText "${name'}.dhall" ''
             ${./systemd-runner.dhall} {
             , args = ${args'}
@@ -73,10 +86,11 @@ with lib; {
             , coreutils = "${pkgs.coreutils}"
             , extraVfs = ${
               if service.genode.extraVfs == null then
-                "[] : List (env:DHALL_PRELUDE).XML.Type"
+                "[] : List (env:DHALL_GENODE).Prelude.XML.Type"
               else
                 service.genode.extraVfs
             }
+            , fsPersistence = ${toBool service.genode.fsPersistence}
             , interface = ${interface}
             , ramQuotaMiB = ${toString service.genode.ramQuota}
             }