fgetvp
error = fgetvp(td, uap->fd, &cap_pread_rights, &vp);
error = fgetvp(td, args->fd, &cap_fsync_rights, &vp);
ret = -fgetvp(curthread, cmd.fd, &cap_no_rights, &vnode);
error = fgetvp(td, dirfd, cap_rights_init(&rights), &cdir);
int fgetvp(struct thread *td, int fd, const cap_rights_t *rightsp,