selftests/bpf: abstract away test log output

This patch changes how test output is printed out. By default, if test
had no errors, the only output will be a single line with test number,
name, and verdict at the end, e.g.:

  #31 xdp:OK

If test had any errors, all log output captured during test execution
will be output after test completes.

It's possible to force output of log with `-v` (`--verbose`) option, in
which case output won't be buffered and will be output immediately.

To support this, individual tests are required to use helper methods for
logging: `test__printf()` and `test__vprintf()`.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_noinline.c b/tools/testing/selftests/bpf/prog_tests/xdp_noinline.c
index 09e6b46f5515..b5404494b8aa 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_noinline.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_noinline.c
@@ -75,7 +75,8 @@ void test_xdp_noinline(void)
 	}
 	if (bytes != MAGIC_BYTES * NUM_ITER * 2 || pkts != NUM_ITER * 2) {
 		error_cnt++;
-		printf("test_xdp_noinline:FAIL:stats %lld %lld\n", bytes, pkts);
+		test__printf("test_xdp_noinline:FAIL:stats %lld %lld\n",
+			     bytes, pkts);
 	}
 out:
 	bpf_object__close(obj);