samples/bpf/task_fd_query_user.c

234 	int err = -1, res, kfd, efd;
240 	kfd = open(buf, O_WRONLY | O_TRUNC, 0);
241 	CHECK_PERROR_RET(kfd < 0);
250 	CHECK_PERROR_RET(write(kfd, buf, strlen(buf)) < 0);
252 	close(kfd);
253 	kfd = -1;
270 	kfd = sys_perf_event_open(&attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
271 	link = bpf_program__attach_perf_event(progs[0], kfd);
275 		close(kfd);
280 	err = bpf_task_fd_query(getpid(), kfd, 0, buf, &len,