Re: [PATCH v2 6/6] selftests/bpf: add tests for the page_owner bpf_iter target

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] bpf/selftests: hardcoded errno values break architecture portability
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commit d63d4254b64f243f696e8d9b4ca8b07f371d8139
Author: Zhen Ni <zhen.ni@easystack.cn>

selftests/bpf: add tests for the page_owner bpf_iter target

This commit adds a sleepable BPF program and a userspace runner to test
the seq_file and open-coded page_owner iterators. It verifies iterator
parity, output matching, and kfunc contracts including memcg classification.

> diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_page_owner.c b/tools/testing/selftests/bpf/progs/bpf_iter_page_owner.c
> new file mode 100644
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/bpf_iter_page_owner.c
[ ... ]
> +char memcg_pathbuf[4096];
> +char memcg_first_path[4096];
> +char memcg_first_name[80];
> +
> +#define MEMCG_ENODATA 61
> +#define MEMCG_EOPNOTSUPP 95
> +
> +#define MEMCG_F_ONLINE	(1 << 0)
> +#define MEMCG_F_OBJCG	(1 << 1)

[Severity: Medium]
Will these hardcoded errno values cause a regression in the selftests on
certain architectures?

The bpf_page_owner_get_memcg_info() kfunc returns standard kernel error
codes like -ENODATA and -EOPNOTSUPP. However, these error codes vary by
architecture. For example, ENODATA is 111 on SPARC and 86 on Alpha, while
EOPNOTSUPP is 122 on MIPS.

When the test runs on these architectures, the kfunc will return the
architecture-specific error code. This will fail the hardcoded comparison
in check_memcg(), incorrectly incrementing memcg_bad and causing the
selftest to fail.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261013122125.843451-1-zhen.ni@easystack.cn?part=6