ss_get_value
int ss_get_value(struct lwp *, vaddr_t, u_int *);
error = ss_get_value(l, l->l_md.md_bpva, &l->l_md.md_bpsave[0]);
error = ss_get_value(l, l->l_md.md_bpva + 4, &l->l_md.md_bpsave[1]);