Module MemoryWD.
(** Valid memories are the ones that do not contain any dangling pointers*)
Definition valid_mem m :=
forall b,
Mem.valid_block m b ->
forall ofs mv,
Maps.ZMap.get ofs (Mem.mem_contents m) # b = mv ->
match mv with
| Fragment v q n =>
mem_wd.val_valid v m
| _ => True
end.

Lemma restrPermMap_mem_valid :
forall m p (Hlt: permMapLt p (getMaxPerm m)),
valid_mem m <-> valid_mem (restrPermMap Hlt).