Section X86Context.
Context {initU: seq.seq nat}
{the_program: Asm.program}.
Notation the_ge := (@the_ge the_program).
Context {Hsafe : safe_genv the_ge}.
Instance X86Sem: Semantics := @X86Sem the_program Hsafe.

Lemma corestep_unchanged_on:
forall c m
c' m' b (ofs : Z),
corestep semSem c m c' m' ->
Memory.Mem.valid_block m b ->
~ Memory.Mem.perm m b ofs Memtype.Cur Memtype.Writable ->
ZMap.get ofs (Memory.Mem.mem_contents m) !! b =
ZMap.get ofs (Memory.Mem.mem_contents m') !! b.