Definition AccessMap_EI_FUN (j:meminj) (m1 m1' m2 : mem) (b2:block):
           Z -> perm_kind -> option permission :=
  if plt b2 (Mem.nextblock m2)
  then (fun ofs2 k =>
       match j b2 with
         None => PMap.get b2 m2.(Mem.mem_access) ofs2 k
       | Some (b3,d3) =>
          if Mem.perm_dec m1 b2 ofs2 Max Nonempty
          then PMap.get b2 m1'.(Mem.mem_access) ofs2 k
          else PMap.get b2 m2.(Mem.mem_access) ofs2 k
        end)
  else (fun ofs2 k =>
         if Mem.perm_dec m1' b2 ofs2 Max Nonempty
         then PMap.get b2 m1'.(Mem.mem_access) ofs2 k
         else None).

(* Specifications: *)
Lemma mkAccessMap_EI_existsT: forall j (m1 m1' m2:Mem.mem) (VB : (Mem.nextblock m2 <= Mem.nextblock m1')%positive), { M : PMap.t (Z -> perm_kind -> option permission) | fst M = (fun k ofs => None) /\ forall b, PMap.get b M = AccessMap_EI_FUN j m1 m1' m2 b}.