bpf: tracing session supporting

[kernel-patches-daemon-bpf]

Pull request for series with
subject: bpf: tracing session supporting
version: 4
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1034110

[kernel-patches-daemon-bpf]

Upstream branch: ec439c3
series: https://patchwork.kernel.org/project/netdevbpf/list/?series=1034110
version: 4

[kernel-patches-review-bot]

commit 3e46e186375c051803d246cb7d90dff0bca64069
Author: Menglong Dong <menglong8.dong@gmail.com>

selftests/bpf: add testcases for tracing session

This commit adds BPF selftests for the new fsession tracing feature,
including tests for function arguments, return values, bpf_get_func_ip(),
and session cookies.

> 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..f7c96ef1c7a9
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/fsession_test.c
> @@ -0,0 +1,192 @@
> +// 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 test8_entry_result = 0;
> +__u64 test8_exit_result = 0;
> +SEC("fsession/bpf_fentry_test1")
> +int BPF_PROG(test8, int a)
> +{
> +	__u64 addr = bpf_get_func_ip(ctx);
> +
> +	if (bpf_fsession_is_return(ctx))
> +		test8_exit_result = (const void *) addr == &bpf_fentry_test1;
> +	else
> +		test8_entry_result = (const void *) addr == &bpf_fentry_test1;
> +	return 0;
> +}

In test8, the code uses &bpf_fentry_test1 without declaring it. Looking at
similar tests like kprobe_multi.c and kprobe_multi_session.c, they include:

    extern const void bpf_fentry_test1 __ksym;

at the top of the file before taking the address of kernel symbols.
Without the __ksym declaration, does the comparison work correctly, or
would this cause the test to fail during compilation or at runtime?

---

AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

In-Reply-To-Subject: selftests/bpf: add testcases for tracing session
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/20299185010

[kernel-patches-review-bot]

commit 96bff41b996dafe2f94690adca80ca543b511d39
Author: Menglong Dong <menglong8.dong@gmail.com>

selftests/bpf: test fsession mixed with fentry and fexit

This commit adds three new test functions to verify that fsession BPF
programs work correctly when mixed with fentry and fexit programs on the
same tracing target (bpf_fentry_test1).

> diff --git a/tools/testing/selftests/bpf/progs/fsession_test.c b/tools/testing/selftests/bpf/progs/fsession_test.c
> index f7c96ef1c7a9..223a6ea47888 100644
> --- a/tools/testing/selftests/bpf/progs/fsession_test.c
> +++ b/tools/testing/selftests/bpf/progs/fsession_test.c
> @@ -190,3 +190,37 @@ int BPF_PROG(test10, int a)
>  		test10_exit_ok = *cookie == 0x1111222233334444ull;
>  	return 0;
>  }
> +
> +__u64 test11_entry_result = 0;
> +__u64 test11_exit_result = 0;
> +
> +SEC("fsession/bpf_fentry_test1")
> +int BPF_PROG(test11, int a, int ret)
> +{
> +	__u64 *cookie = bpf_fsession_cookie(ctx);
> +
> +	if (!bpf_fsession_is_return(ctx)) {
> +		test11_entry_result = a == 1 && ret == 0;
> +		*cookie = 0x123456ULL;

Should the cookie pointer be checked for NULL before dereferencing?

Looking at the existing tests in this file, both test9 and test10 (which
also call bpf_fsession_cookie) explicitly check if the cookie pointer is
NULL before dereferencing it:

  test9: if (cookie) { *cookie = 0xAAAA...; }
  test10: if (cookie) { *cookie = 0x1111...; }

test11 dereferences cookie without this check. If cookie were NULL or
invalid, test11 would crash rather than fail gracefully like test9/test10
do. While the BPF verifier likely ensures cookie is valid when the
program is loaded, following the established pattern would make the test
more robust.

The same issue occurs in the exit path:

> +		return 0;
> +	}
> +
> +	test11_exit_result = a == 1 && ret == 2 && *cookie == 0x123456ULL;
                                                    ^^^^^^^

> +	return 0;
> +}
> +
> +__u64 test12_result = 0;
> +SEC("fexit/bpf_fentry_test1")
> +int BPF_PROG(test12, int a, int ret)
> +{
> +	test12_result = a == 1 && ret == 2;
> +	return 0;
> +}
> +
> +__u64 test13_result = 0;
> +SEC("fentry/bpf_fentry_test1")
> +int BPF_PROG(test13, int a)
> +{
> +	test13_result = a == 1;
> +	return 0;
> +}

---

AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

In-Reply-To-Subject: selftests/bpf: test fsession mixed with fentry and fexit
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/20299185010

[kernel-patches-daemon-bpf]

Forwarding comment 3664660532 via email
In-Reply-To: 20251217095445.218428-9-dongml2@chinatelecom.cn
Patch: https://patchwork.kernel.org/project/netdevbpf/patch/20251217095445.218428-9-dongml2@chinatelecom.cn/

[kernel-patches-daemon-bpf]

Forwarding comment 3664678284 via email
In-Reply-To: 20251217095445.218428-10-dongml2@chinatelecom.cn
Patch: https://patchwork.kernel.org/project/netdevbpf/patch/20251217095445.218428-10-dongml2@chinatelecom.cn/