fget_cap
error = fget_cap(td, fd_fd, &cap_no_rights, NULL, &fp, NULL);
error = fget_cap(td, ndp->ni_dirfd, &rights, &flags, &fp,
error = fget_cap(td, fd, needrightsp, NULL, &fp, &caps);
error = fget_cap(td, fd, rightsp, NULL, &fp, havecapsp);
int fget_cap(struct thread *td, int fd, const cap_rights_t *needrightsp,