Definition FLIP mu :=
  match mu with
    Build_SM_Injection locBSrc locBTgt pSrc pTgt local extBSrc extBTgt fSrc fTgt extern =>
    Build_SM_Injection extBSrc extBTgt fSrc fTgt extern locBSrc locBTgt pSrc pTgt local
  end.

Lemma unchanged_on_perm: forall (P:block -> Z -> Prop) m m' (Unch: Mem.unchanged_on P m m'), Mem.unchanged_on (fun b z => P b z /\ Mem.perm m b z Max Nonempty) m m'.