On Mon, Mar 4, 2024 at 2:52 PM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
>
> Several test_progs tests already capture libbpf log in order to check
> for some expected output, e.g bpf_tcp_ca.c, kfunc_dynptr_param.c,
> log_buf.c and a few others.
>
> This commit provides a, hopefully, simple API to capture libbpf log
> w/o necessity to define new print callback in each test:
>
> /* Creates a global memstream capturing all output passed to
> * libbpf_print_fn.
> * Returns 0 on success, negative value on failure.
> * On failure the description is printed using PRINT_FAIL and
> * current test case is marked as fail.
> */
> int start_libbpf_log_capture(void)
>
> /* Destroys global memstream created by start_libbpf_log_capture().
> * Returns a pointer to captured data which has to be freed.
> * Returned buffer is null terminated.
> */
> char *stop_libbpf_log_capture(void)
>
> The intended usage is as follows:
>
> if (start_libbpf_log_capture())
> return;
> use_libbpf();
> char *log = stop_libbpf_log_capture();
> ASSERT_HAS_SUBSTR(log, "... expected ...", "expected some message");
> free(log);
>
> As a safety measure, free(start_libbpf_log_capture()) is invoked in the
> epilogue of the test_progs.c:run_one_test().
>
> Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
> ---
> tools/testing/selftests/bpf/test_progs.c | 57 ++++++++++++++++++++++++
> tools/testing/selftests/bpf/test_progs.h | 3 ++
> 2 files changed, 60 insertions(+)
>
[...]
> +/* Destroys global memstream created by start_libbpf_log_capture().
> + * Returns a pointer to captured data which has to be freed.
> + * Returned buffer is null terminated.
> + */
> +char *stop_libbpf_log_capture(void)
> +{
> + char *buf;
> +
> + if (!libbpf_capture_stream)
> + return NULL;
> +
> + fputc(0, libbpf_capture_stream);
> + fclose(libbpf_capture_stream);
> + libbpf_capture_stream = NULL;
> + /* get 'buf' after fclose(), see open_memstream() documentation */
> + buf = libbpf_output_capture.buf;
> + bzero(&libbpf_output_capture, sizeof(libbpf_output_capture));
please use memset():
$ rg -w memset | wc -l
355
$ rg -w bzero | wc -l
12
> + return buf;
> +}
> +
> static int libbpf_print_fn(enum libbpf_print_level level,
> const char *format, va_list args)
> {
> + if (libbpf_capture_stream) {
> + va_list args2;
> +
> + va_copy(args2, args);
> + vfprintf(libbpf_capture_stream, format, args2);
> + }
should we take into account verbosity settings? capturing LIBBPF_DEBUG
logs probably isn't very useful (but will make debugging harder,
probably)
> +
> if (env.verbosity < VERBOSE_VERY && level == LIBBPF_DEBUG)
> return 0;
> vfprintf(stdout, format, args);
> @@ -1081,6 +1137,7 @@ static void run_one_test(int test_num)
> cleanup_cgroup_environment();
>
> stdio_restore();
> + free(stop_libbpf_log_capture());
>
> dump_test_log(test, state, false, false, NULL);
> }
> diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h
> index 80df51244886..0ba5a20b19ba 100644
> --- a/tools/testing/selftests/bpf/test_progs.h
> +++ b/tools/testing/selftests/bpf/test_progs.h
> @@ -397,6 +397,9 @@ int test__join_cgroup(const char *path);
> system(cmd); \
> })
>
> +int start_libbpf_log_capture(void);
> +char *stop_libbpf_log_capture(void);
> +
> static inline __u64 ptr_to_u64(const void *ptr)
> {
> return (__u64) (unsigned long) ptr;
> --
> 2.43.0
>
