diff --git a/common/hw-file.ads b/common/hw-file.ads
new file mode 100644
index 0000000..9f5e452
--- /dev/null
+++ b/common/hw-file.ads
@@ -0,0 +1,36 @@
+--
+-- Copyright (C) 2017 Nico Huber <nico.h@gmx.de>
+--
+-- This program is free software; you can redistribute it and/or modify
+-- it under the terms of the GNU General Public License as published by
+-- the Free Software Foundation; either version 2 of the License, or
+-- (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU General Public License for more details.
+--
+
+package HW.File is
+
+   -- Map a file's content into our address space
+   --
+   -- If `Map_Copy` is `False`, `Len` bytes from the start of the file
+   -- given by `Path` shall be mapped into the application's address
+   -- space at `Addr` using mmap(). If `Map_Copy` is `True`, anonymous
+   -- memory should be mapped instead and be filled with a copy of the
+   -- file's content using read().
+   procedure Map
+     (Path     : in     String;
+      Addr     : in     Word64;
+      Len      : in     Natural;
+      Readable : in     Boolean := False;
+      Writable : in     Boolean := False;
+      Map_Copy : in     Boolean := False;
+      Success  :    out Boolean)
+   with
+      Pre => (Readable or Writable) and
+             (if Map_Copy then Readable and not Writable);
+
+end HW.File;