Re: [PATCH bpf-next v10 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_global_percpu_data_subskel` selftest fails unconditionally because it asserts `var_cnt > 0` on a subskeleton that is generated with zero variables.
--

--- Patch [6]: [PATCH bpf-next v10 6/9] selftests/bpf: Add tests to verify global percpu data ---
commit c5a32c0630bc8d9b3aedfc264c75289a1f8e6d98
Author: Leon Hwang <leon.hwang@linux.dev>

selftests/bpf: Add tests to verify global percpu data

This commit adds selftests to verify operations on global percpu data in BPF
programs. It tests various libbpf APIs and skeleton behaviors for percpu
maps. It also adds a test to ensure live variables of a subskeleton do not
include 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
> @@ -0,0 +1,37 @@

[ ... ]

> +	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]
Since test_global_percpu_data.c only contains variables in .percpu* sections,
and the subskeleton generator skips percpu array variables, will var_cnt
always be exactly 0 here, causing this test to unconditionally fail?

Would it make sense to either add a standard global variable to
test_global_percpu_data.c (e.g. in .bss or .data), or adjust this assertion?

> +
> +	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");
> +	}
> +
> +out:
> +	test_global_percpu_data__destroy(subskel);
> +	bpf_object__close(obj);
> +}

> diff --git a/tools/testing/selftests/bpf/progs/test_global_percpu_data.c b/tools/testing/selftests/bpf/progs/test_global_percpu_data.c
> new file mode 100644
> index 0000000000000..54380dfb11a5a
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_global_percpu_data.c
> @@ -0,0 +1,33 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <vmlinux.h>
> +#include <bpf/bpf_helpers.h>
> +#include "bpf_misc.h"
> +
> +int unused SEC(".percpu.looooooooong");
> +int data2 SEC(".percpu.data");
> +int data SEC(".percpu") = -1;
> +int nums[7] SEC(".percpu");
> +char run SEC(".percpu") = 0;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260715153254.92010-1-leon.hwang@linux.dev?part=6