Re: [PATCH bpf-next v7 08/11] selftests/bpf: Add tests to verify global percpu data

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The subskel test incorrectly asserts that `var_cnt > 0`, causing the test to reliably fail.
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commit 55ee2a40d2c9fa6afdbccf30892e0d5b8f148c44
Author: Leon Hwang <leon.hwang@linux.dev>

selftests/bpf: Add tests to verify global percpu data

This commit adds tests to verify global percpu data using libbpf APIs.
It also introduces a subskeleton test to ensure that the live variables
of a subskel do not include variables for global percpu data.

> diff --git a/tools/testing/selftests/bpf/prog_tests/global_percpu_subskel.c b/tools/testing/selftests/bpf/prog_tests/global_percpu_subskel.c
> new file mode 100644
> index 0000000000000..8aebd533d86b5
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/global_percpu_subskel.c
[ ... ]
> +void test_global_percpu_data_subskel(void)
> +{
> +	struct test_global_percpu_data *subskel = NULL;
> +	struct bpf_object *obj;
> +	int i;
[ ... ]
> +	if (!ASSERT_OK_PTR(subskel->subskel, "subskel"))
> +		goto out;
> +	if (!ASSERT_OK_PTR(subskel->maps.percpu, "maps.percpu"))
> +		goto out;
> +	ASSERT_EQ(bpf_map__type(subskel->maps.percpu), BPF_MAP_TYPE_PERCPU_ARRAY,
> +		  "percpu_map_type");
> +	ASSERT_GT(subskel->subskel->var_cnt, 0, "var_cnt");

[Severity: Medium]
Will this assertion cause the test to unconditionally fail?

Looking at test_global_percpu_data.c, all defined variables are placed
in the .percpu section. Since bpftool explicitly skips .percpu maps when
generating subskeletons, there appear to be no non-percpu maps with BTF
variables present.

If that is the case, subskel->subskel->var_cnt will be exactly 0, causing
this check to evaluate to ASSERT_GT(0, 0) and reliably fail the test.

> +
> +	for (i = 0; i < subskel->subskel->var_cnt; i++) {
> +		const struct bpf_var_skeleton *var;
[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260622143557.22955-1-leon.hwang@linux.dev?part=8