Re: [PATCH bpf-next v9 6/9] 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 test `test_global_percpu_data_subskel` unconditionally asserts that `var_cnt > 0`, but the compiled BPF object contains no non-percpu global variables, meaning `var_cnt` will always be exactly 0 and the test will reliably fail.
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--- Patch [6]: [PATCH bpf-next v9 6/9] selftests/bpf: Add tests to verify global percpu data ---
commit 3e1db5f1fcec57a130c30e415035e1b1944b5e17
Author: Leon Hwang <leon.hwang@linux.dev>

selftests/bpf: Add tests to verify global percpu data

This commit introduces tests for BPF global percpu data, verifying APIs like
bpf_map__set_initial_value() and bpf_map__initial_value(). It also adds a
subskeleton test to ensure that the live variables of a subskeleton do not
include those 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
[ ... ]
> +	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 test unconditionally fail here?

Since all global variables in test_global_percpu_data.c are placed in .percpu
sections:

int unused SEC(".percpu.looooooooong");
int data2 SEC(".percpu.data");
int data SEC(".percpu") = -1;

bpftool generates a subskeleton with a variable count of 0, because maps of type
BPF_MAP_TYPE_PERCPU_ARRAY are skipped during subskeleton generation.

Thus, subskel->subskel->var_cnt should be exactly 0, which would cause this
assertion to fail.

> +
> +	for (i = 0; i < subskel->subskel->var_cnt; i++) {
> +		const struct bpf_var_skeleton *var;
> +
> +		var = (void *) subskel->subskel->vars + i * subskel->subskel->var_skel_sz;
> +		ASSERT_NEQ(var->map, &subskel->maps.percpu, "var");
> +	}
> +

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260713154024.30851-1-leon.hwang@linux.dev?part=6