Definition canonicalPMap fn n m : Maps.PMap.t (Z -> perm_kind -> option permission) :=
let l := mkBlockList n in
(fun _ _ => None, canonicalPTree (PList fn l m)).

Lemma canonicalPMap_default :
forall n k m fn
(Hkn : k >= n),
(canonicalPMap fn n m) !! (Pos.of_nat k) = fun _ _ => None.