auditon_udata
void audit_arg_auditon(union auditon_udata *udata);
union auditon_udata;
audit_arg_auditon(union auditon_udata *udata)
union auditon_udata ar_arg_auditon;
union auditon_udata udata;
if ((uap->length <= 0) || (uap->length > sizeof(union auditon_udata)))