2 files changed, 62 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index 808550986f30..89ff704e9dad 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -683,11 +683,69 @@ static const struct argp_option opts[] = {
 	{},
 };
 
+static FILE *libbpf_capture_stream;
+
+static struct {
+	char *buf;
+	size_t buf_sz;
+} libbpf_output_capture;
+
+/* Creates a global memstream capturing INFO and WARN level 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)
+{
+	if (libbpf_capture_stream) {
+		PRINT_FAIL("%s: libbpf_capture_stream != NULL\n", __func__);
+		return -EINVAL;
+	}
+
+	libbpf_capture_stream = open_memstream(&libbpf_output_capture.buf,
+					       &libbpf_output_capture.buf_sz);
+	if (!libbpf_capture_stream) {
+		PRINT_FAIL("%s: open_memstream failed errno=%d\n", __func__, errno);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/* 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;
+	memset(&libbpf_output_capture, 0, sizeof(libbpf_output_capture));
+	return buf;
+}
+
 static int libbpf_print_fn(enum libbpf_print_level level,
 			   const char *format, va_list args)
 {
+	if (libbpf_capture_stream && level != LIBBPF_DEBUG) {
+		va_list args2;
+
+		va_copy(args2, args);
+		vfprintf(libbpf_capture_stream, format, args2);
+	}
+
 	if (env.verbosity < VERBOSE_VERY && level == LIBBPF_DEBUG)
 		return 0;
+
 	vfprintf(stdout, format, args);
 	return 0;
 }
@@ -1081,6 +1139,7 @@ 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;