Add first draft of marshalling spec

[polintos/scott/priv.git] / idl / addrspace.idl

diff --git a/idl/addrspace.idl b/idl/addrspace.idl
index 14f4ae28f48e77a7a84f43192eeeb7445bfe8eb5..6b2e44b061de9ae4dce295697dad71c27fd6aced 100644 (file)
--- a/idl/addrspace.idl
+++ b/idl/addrspace.idl
@@ -177,8 +177,26 @@ bitfield MapFlags {
        CopyOnWrite,   // Share the mapped object only until it is written to;
                       // then, before the write takes place, copy the object. 
                       // It is undefined whether this mapping will receive
-                      // the copy or the original.  Ignored for alloc_and_map.
-       
+                      // the copy or the original.
+
+       Snapshot,      // The mapped object will also be made CopyOnWrite, so
+                      // that any writes to the mapped page via any mapping
+                      // will cause a fault.  Thus, after the snapshot, the
+                      // only changes that will be visible will be through
+                      // the new mapping.  This is ideal for things like fork()
+                      // and file versioning, and is used by AddrSpace.clone().
+                      //
+                      // If not set, then only the new mapping will be
+                      // CopyOnWrite, so if another mapping updates the page
+                      // before a write occurs through this mapping (thus
+                      // breaking CopyOnWrite), the change will be visible in
+                      // the new mapping.  This is ideal for private
+                      // mappings, where all that is desired is that the new
+                      // mapping cannot change the underlying object (while
+                      // keeping the mapping writeable).
+                      //
+                      // Ignored if CopyOnWrite is not set.
+
        AccessFlags access:3,
                       // These are the requested read/write/execute
                       // permissions on the mapping.  A missing permission (or
@@ -222,16 +240,17 @@ interface AddrSpace {
        // By default, the old address space continues to be backed by
        // whatever Mappables were in use, and pages in the new address space
        // are backed by anonymous memory when a page in either is written to. 
-       // If old_space_is_anon is true, though, this is reversed, which is useful
+       // If flags.Reverse is true, though, this is reversed, which is useful
        // when versioning a file to make the new version the one that gets
        // stored to disk.
+       //
+       // The upstream address space is also marked as copy-on
 
-       clone(AddrSpace addrspace out, bool clone_is_real);
+       clone(AddrSpace addrspace out, CloneFlags flags);
        
-       // Create an anonymous RAM mapping.     
-
-       alloc_and_map(ulong len, ulong vstart inout, 
-                     AllocFlags aflags, MapFlags mflags);
+       bitfield CloneFlags {
+               Reverse
+       };
        
        // Mappable must be implemented by the local kernel, and must hold
        // read/write/exec permissions appropriate for the MapFlags given.