On Thu, Jul 30, 2020 at 11:18 PM Jianlin Lv <Jianlin.Lv@xxxxxxx> wrote:
>
> Clang compiler version: 12.0.0
> The following warning appears during the selftests/bpf compilation:
>
> prog_tests/send_signal.c:51:3: warning: ignoring return value of ‘write’,
> declared with attribute warn_unused_result [-Wunused-result]
> 51 | write(pipe_c2p[1], buf, 1);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~
> prog_tests/send_signal.c:54:3: warning: ignoring return value of ‘read’,
> declared with attribute warn_unused_result [-Wunused-result]
> 54 | read(pipe_p2c[0], buf, 1);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~
> ......
>
> prog_tests/stacktrace_build_id_nmi.c:13:2: warning: ignoring return value
> of ‘fscanf’,declared with attribute warn_unused_result [-Wunused-resul]
> 13 | fscanf(f, "%llu", &sample_freq);
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> test_tcpnotify_user.c:133:2: warning:ignoring return value of ‘system’,
> declared with attribute warn_unused_result [-Wunused-result]
> 133 | system(test_script);
> | ^~~~~~~~~~~~~~~~~~~
> test_tcpnotify_user.c:138:2: warning:ignoring return value of ‘system’,
> declared with attribute warn_unused_result [-Wunused-result]
> 138 | system(test_script);
> | ^~~~~~~~~~~~~~~~~~~
> test_tcpnotify_user.c:143:2: warning:ignoring return value of ‘system’,
> declared with attribute warn_unused_result [-Wunused-result]
> 143 | system(test_script);
> | ^~~~~~~~~~~~~~~~~~~
>
> Add code that fix compilation warning about ignoring return value and
> handles any errors; Check return value of library`s API make the code
> more secure.
>
> Signed-off-by: Jianlin Lv <Jianlin.Lv@xxxxxxx>
> ---
> .../selftests/bpf/prog_tests/send_signal.c | 37 ++++++++++++++-----
> .../bpf/prog_tests/stacktrace_build_id_nmi.c | 3 +-
> .../selftests/bpf/test_tcpnotify_user.c | 15 ++++++--
> 3 files changed, 41 insertions(+), 14 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal.c b/tools/testing/selftests/bpf/prog_tests/send_signal.c
> index 504abb7bfb95..7a5272e4e810 100644
> --- a/tools/testing/selftests/bpf/prog_tests/send_signal.c
> +++ b/tools/testing/selftests/bpf/prog_tests/send_signal.c
> @@ -48,22 +48,31 @@ static void test_send_signal_common(struct perf_event_attr *attr,
> close(pipe_p2c[1]); /* close write */
>
> /* notify parent signal handler is installed */
> - write(pipe_c2p[1], buf, 1);
> + if (CHECK_FAIL(write(pipe_c2p[1], buf, 1) != 1)) {
> + perror("Child: write pipe error");
> + goto close_out;
> + }
Please don't use CHECK_FAIL. Using CHECK is better for many reasons,
but it will also be shorter here (while still recording failure):
CHECK(write(pipe_c2p[1], buf, 1) != 1, "pipe_write", "err %d\n", -errno);
>
> /* make sure parent enabled bpf program to send_signal */
> - read(pipe_p2c[0], buf, 1);
> + if (CHECK_FAIL(read(pipe_p2c[0], buf, 1) != 1)) {
> + perror("Child: read pipe error");
> + goto close_out;
> + }
>
[...]
