(* TODO those definitions are also in sync_preds_defs, see if we can include without changing the dep DAG too badly *)
(* The TT branch of the jam below might seem too weak, but we already keep enough control over joining with other rmaps that it should be enough *)
Definition LKspec_ext (R: pred rmap) lksize : spec :=
fun (sh: Share.t) (l: AV.address)  =>
allp (jam (adr_range_dec l lksize)
(fun l' => yesat (SomeP rmaps.Mpred (fun _ => R)) (LK lksize (snd l' - snd l)) sh l')
(fun _ => TT)).
Definition LK_at R lksize sh :=
LKspec_ext R lksize sh.

Lemma data_at_rmap_makelock CS sh b ofs R phi length :
0 < length ->
writable0_share sh ->
app_pred (@data_at_ CS sh (Tarray (Tpointer Tvoid noattr) length noattr) (Vptr b ofs)) phi ->
exists phi',
rmap_makelock phi phi' (b, Ptrofs.unsigned ofs) R (size_chunk Mptr * length) /\
LK_at R (size_chunk Mptr * length) sh (b, Ptrofs.unsigned ofs) phi'.