BPF_SRC
if (BPF_SRC(b->s.code) == BPF_K)
if (BPF_SRC(c) == BPF_X)
if (vmap[val].is_const && BPF_SRC(b->s.code) == BPF_K) {
if (BPF_SRC(p->code) == BPF_K && p->k == 0)