Re: [RFC PATCH v3 bpf-next 5/5] selftests/bpf: add tests for the numab kfuncs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] selftests/bpf: missing kfunc BTF skip check in test_bpf_numab()
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commit 07e4c14213f29b11a7ce19b88e46e524dc48e78d
Author: Yafang Shao <laoar.shao@gmail.com>

selftests/bpf: add tests for the numab kfuncs

This commit adds BPF selftests exercising the bpf_numab_set_mode() and
bpf_numab_get_mode() kfuncs across set/get roundtrips, mode validation,
invalid cgroup IDs, and cgroup hierarchy combinations.

> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_numab.c b/tools/testing/selftests/bpf/prog_tests/bpf_numab.c
> new file mode 100644
> index 0000000000000..7ce4b8153c42f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_numab.c
> @@ -0,0 +1,227 @@
[ ... ]
> +static void test_set_get(void)
> +{
> +	struct bpf_numab *skel;
> +	int cgroup_fd;
> +	u64 cgid;
> +
> +	cgroup_fd = test__join_cgroup(CGROUP_PATH);
> +	if (!ASSERT_GE(cgroup_fd, 0, "join_cgroup"))
> +		return;
> +
> +	skel = bpf_numab__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "open_and_load"))
> +		goto cleanup;
[ ... ]
> +void test_bpf_numab(void)
> +{
> +	if (test__start_subtest("set_get"))
> +		test_set_get();
> +	if (test__start_subtest("invalid_mode"))
> +		test_invalid_mode();
> +	if (test__start_subtest("bad_cgid"))
> +		test_bad_cgid();
> +	if (test__start_subtest("hierarchy"))
> +		test_hierarchy();
> +}

[Severity: Medium]
What happens when test_bpf_numab() runs on a kernel built without
CONFIG_BPF_NUMAB=y (for example when CONFIG_NUMA_BALANCING is disabled or on
non-x86_64 selftest configs where CONFIG_NUMA_BALANCING is not enabled)?

Because tools/testing/selftests/bpf/progs/bpf_numab.c declares
bpf_numab_set_mode and bpf_numab_get_mode as strong __ksym externs:

    extern int bpf_numab_set_mode(u64 cgid, s64 mode) __ksym;
    extern s64 bpf_numab_get_mode(u64 cgid) __ksym;

calling test_bpf_numab() -> test_set_get() -> bpf_numab__open_and_load()
(as well as test_invalid_mode(), test_bad_cgid(), and test_hierarchy())
fails in bpf_object__resolve_ksym_func_btf_id() with -ESRCH and trips
ASSERT_OK_PTR(skel, "open_and_load").

Should test_bpf_numab() check vmlinux BTF for bpf_numab_set_mode and
bpf_numab_get_mode via btf__find_by_name_kind(..., BTF_KIND_FUNC) and call
test__skip() when the kfuncs are not present?

> diff --git a/tools/testing/selftests/bpf/progs/bpf_numab.c b/tools/testing/selftests/bpf/progs/bpf_numab.c
[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261019064157.29885-1-laoar.shao@gmail.com?part=5