Commit c8617e8b authored by Eduard Zingerman's avatar Eduard Zingerman Committed by Andrii Nakryiko
Browse files

selftests/bpf: Utility functions to capture libbpf log in test_progs 



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 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)

    /* 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: default avatarEduard Zingerman <eddyz87@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240306104529.6453-6-eddyz87@gmail.com
parent 5bab7a27

tools/testing/selftests/bpf/test_progs.c

+59 −0
Original line number Diff line number Diff line
@@ -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);

}

tools/testing/selftests/bpf/test_progs.h

+3 −0
Original line number Diff line number Diff line
@@ -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;