Definition A2P {A} :=
 (fun (pmap : access_map) (a : address * A) =>
      let (a0, _) := a in let (b0, ofs0) := a0 in setPermBlock (Some Writable) b0 ofs0 pmap LKSIZE_nat).

Lemma A2P_overwrite A : forall a b e, fst a = fst b -> PMap_eq (@A2P A (A2P e a) b) (@A2P A e a).