(** Effect of [alloc] on permissions. *)

Axiom perm_alloc_inv:
forall m1 lo hi m2 b, alloc m1 lo hi = (m2, b) ->
forall b' ofs k p,
perm m2 b' ofs k p ->
if eq_block b' b then lo <= ofs < hi else perm m1 b' ofs k p.