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Date:   Thu, 24 Sep 2020 18:01:33 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Song Liu <songliubraving@...com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Cc:     kernel-team@...com, ast@...nel.org, daniel@...earbox.net,
        john.fastabend@...il.com, kpsingh@...omium.org,
        Song Liu <songliubraving@...com>
Subject: RE: [PATCH v5 bpf-next 3/3] selftests/bpf: add raw_tp_test_run

Song Liu wrote:
> This test runs test_run for raw_tracepoint program. The test covers ctx
> input, retval output, and running on correct cpu.
> 
> Signed-off-by: Song Liu <songliubraving@...com>
> ---

[...]

> +void test_raw_tp_test_run(void)
> +{
> +	struct bpf_prog_test_run_attr test_attr = {};
> +	int comm_fd = -1, err, nr_online, i, prog_fd;
> +	__u64 args[2] = {0x1234ULL, 0x5678ULL};
> +	int expected_retval = 0x1234 + 0x5678;
> +	struct test_raw_tp_test_run *skel;
> +	char buf[] = "new_name";
> +	bool *online = NULL;
> +
> +	err = parse_cpu_mask_file("/sys/devices/system/cpu/online", &online,
> +				  &nr_online);
> +	if (CHECK(err, "parse_cpu_mask_file", "err %d\n", err))
> +		return;
> +
> +	skel = test_raw_tp_test_run__open_and_load();
> +	if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
> +		goto cleanup;
> +
> +	err = test_raw_tp_test_run__attach(skel);
> +	if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
> +		goto cleanup;
> +
> +	comm_fd = open("/proc/self/comm", O_WRONLY|O_TRUNC);
> +	if (CHECK(comm_fd < 0, "open /proc/self/comm", "err %d\n", errno))
> +		goto cleanup;
> +
> +	err = write(comm_fd, buf, sizeof(buf));
> +	CHECK(err < 0, "task rename", "err %d", errno);
> +
> +	CHECK(skel->bss->count == 0, "check_count", "didn't increase\n");
> +	CHECK(skel->data->on_cpu != 0xffffffff, "check_on_cpu", "got wrong value\n");
> +
> +	prog_fd = bpf_program__fd(skel->progs.rename);
> +	test_attr.prog_fd = prog_fd;
> +	test_attr.ctx_in = args;
> +	test_attr.ctx_size_in = sizeof(__u64);
> +
> +	err = bpf_prog_test_run_xattr(&test_attr);
> +	CHECK(err == 0, "test_run", "should fail for too small ctx\n");
> +
> +	test_attr.ctx_size_in = sizeof(args);
> +	err = bpf_prog_test_run_xattr(&test_attr);
> +	CHECK(err < 0, "test_run", "err %d\n", errno);
> +	CHECK(test_attr.retval != expected_retval, "check_retval",
> +	      "expect 0x%x, got 0x%x\n", expected_retval, test_attr.retval);
> +
> +	for (i = 0; i < nr_online; i++) {
> +		if (online[i]) {
> +			DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts,
> +				.ctx_in = args,
> +				.ctx_size_in = sizeof(args),
> +				.flags = BPF_F_TEST_RUN_ON_CPU,
> +				.retval = 0,
> +				.cpu = i,
> +			);
> +
> +			err = bpf_prog_test_run_opts(prog_fd, &opts);
> +			CHECK(err < 0, "test_run_opts", "err %d\n", errno);
> +			CHECK(skel->data->on_cpu != i, "check_on_cpu",
> +			      "expect %d got %d\n", i, skel->data->on_cpu);
> +			CHECK(opts.retval != expected_retval,
> +			      "check_retval", "expect 0x%x, got 0x%x\n",
> +			      expected_retval, opts.retval);
> +
> +			if (i == 0) {
> +				/* invalid cpu ID should fail with ENXIO */
> +				opts.cpu = 0xffffffff;
> +				err = bpf_prog_test_run_opts(prog_fd, &opts);
> +				CHECK(err != -1 || errno != ENXIO,
> +				      "test_run_opts_fail",
> +				      "should failed with ENXIO\n");
> +			} else {

One more request...

How about pull this if/else branch out of the for loop here? It feels a bit
clumsy as-is imo. Also is it worthwhile to bang on the else branch for evey
cpu I would think testing for any non-zero value should be sufficient.

> +				/* non-zero cpu w/o BPF_F_TEST_RUN_ON_CPU
> +				 * should fail with EINVAL
> +				 */
> +				opts.flags = 0;
> +				err = bpf_prog_test_run_opts(prog_fd, &opts);
> +				CHECK(err != -1 || errno != EINVAL,
> +				      "test_run_opts_fail",
> +				      "should failed with EINVAL\n");
> +			}
> +		}
> +	}
> +cleanup:
> +	close(comm_fd);
> +	test_raw_tp_test_run__destroy(skel);
> +	free(online);
> +}

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