linux-kernel - Re: [PATCH RFC bpf-next 5/5] selftests/bpf: add testcases for tracing session

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Message-ID: <aPXwo0puQI3t0CXC@krava>
Date: Mon, 20 Oct 2025 10:19:47 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Menglong Dong <menglong8.dong@...il.com>
Cc: ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
	andrii@...nel.org, martin.lau@...ux.dev, eddyz87@...il.com,
	song@...nel.org, yonghong.song@...ux.dev, kpsingh@...nel.org,
	sdf@...ichev.me, haoluo@...gle.com, mattbobrowski@...gle.com,
	rostedt@...dmis.org, mhiramat@...nel.org,
	mathieu.desnoyers@...icios.com, leon.hwang@...ux.dev,
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH RFC bpf-next 5/5] selftests/bpf: add testcases for
 tracing session

On Sat, Oct 18, 2025 at 10:21:24PM +0800, Menglong Dong wrote:

SNIP

> +static void test_fsession_reattach(void)
> +{
> +	struct fsession_test *skel = NULL;
> +	int err, prog_fd;
> +	LIBBPF_OPTS(bpf_test_run_opts, topts);
> +
> +	skel = fsession_test__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "fsession_test__open_and_load"))
> +		goto cleanup;
> +
> +	/* First attach */
> +	err = fsession_test__attach(skel);
> +	if (!ASSERT_OK(err, "fsession_first_attach"))
> +		goto cleanup;
> +
> +	/* Trigger test function calls */
> +	prog_fd = bpf_program__fd(skel->progs.test1);
> +	err = bpf_prog_test_run_opts(prog_fd, &topts);
> +	if (!ASSERT_OK(err, "test_run_opts err"))
> +		return;

goto cleanup

> +	if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
> +		return;

goto cleanup

> +
> +	/* Verify first call */
> +	ASSERT_EQ(skel->bss->test1_entry_called, 1, "test1_entry_first");
> +	ASSERT_EQ(skel->bss->test1_exit_called, 1, "test1_exit_first");
> +
> +	/* Detach */
> +	fsession_test__detach(skel);
> +
> +	/* Reset counters */
> +	memset(skel->bss, 0, sizeof(*skel->bss));
> +
> +	/* Second attach */
> +	err = fsession_test__attach(skel);
> +	if (!ASSERT_OK(err, "fsession_second_attach"))
> +		goto cleanup;
> +
> +	err = bpf_prog_test_run_opts(prog_fd, &topts);
> +	if (!ASSERT_OK(err, "test_run_opts err"))
> +		return;

goto cleanup

> +	if (!ASSERT_OK(topts.retval, "test_run_opts retval"))
> +		return;

goto cleanup

> +
> +	/* Verify second call */
> +	ASSERT_EQ(skel->bss->test1_entry_called, 1, "test1_entry_second");
> +	ASSERT_EQ(skel->bss->test1_exit_called, 1, "test1_exit_second");
> +
> +cleanup:
> +	fsession_test__destroy(skel);
> +}
> +
> +void test_fsession_test(void)
> +{
> +#if !defined(__x86_64__)
> +	test__skip();
> +	return;
> +#endif
> +	if (test__start_subtest("fsession_basic"))
> +		test_fsession_basic();
> +	if (test__start_subtest("fsession_reattach"))
> +		test_fsession_reattach();
> +}
> diff --git a/tools/testing/selftests/bpf/progs/fsession_test.c b/tools/testing/selftests/bpf/progs/fsession_test.c
> new file mode 100644
> index 000000000000..cce2b32f7c2c
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/fsession_test.c
> @@ -0,0 +1,178 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2025 ChinaTelecom */
> +#include <vmlinux.h>
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_tracing.h>
> +
> +char _license[] SEC("license") = "GPL";
> +
> +__u64 test1_entry_result = 0;
> +__u64 test1_exit_result = 0;
> +__u64 test1_entry_called = 0;
> +__u64 test1_exit_called = 0;
> +
> +SEC("fsession/bpf_fentry_test1")
> +int BPF_PROG(test1, int a)
> +{

I guess we can access return argument directly but it makes sense only
for exit session program, or we could use bpf_get_func_ret

jirka


> +	bool is_exit = bpf_tracing_is_exit(ctx);
> +
> +	if (!is_exit) {
> +		/* This is entry */
> +		test1_entry_called = 1;
> +		test1_entry_result = a == 1;
> +		return 0; /* Return 0 to allow exit to be called */
> +	}
> +
> +	/* This is exit */
> +	test1_exit_called = 1;
> +	test1_exit_result = a == 1;
> +	return 0;
> +}
> +
> +__u64 test2_entry_result = 0;
> +__u64 test2_exit_result = 0;
> +__u64 test2_entry_called = 0;
> +__u64 test2_exit_called = 0;
> +

SNIP