Re: [RFC PATCH bpf-next v3 2/2] selftests/bpf: add tests for selective kmod BTF loading

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The custom libbpf print callback silently drops all non-matching libbpf logs, hiding crucial diagnostic information if the test fails.
--

--- Patch [2]: [RFC PATCH bpf-next v3 2/2] selftests/bpf: add tests for selective kmod BTF loading ---
commit 17f3a2340dd7be0947e3baabf30a8c7722ec91fe
Author: Fuyu Zhao <zhaofuyu@vivo.com>

selftests/bpf: add tests for selective kmod BTF loading

This commit adds tests for the selective kmod BTF loading feature. It
covers scenarios such as valid modules, non-existent modules, duplicate
names, unneeded modules, and missing count properties.

> diff --git a/tools/testing/selftests/bpf/prog_tests/kmod_btfs.c b/tools/testing/selftests/bpf/prog_tests/kmod_btfs.c
> new file mode 100644
> index 0000000000000..61d2845a731ff
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/kmod_btfs.c
> @@ -0,0 +1,196 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <test_progs.h>
> +#include "kmod_btfs.skel.h"

[ ... ]

> +static int libbpf_print_cb(enum libbpf_print_level level, const char *fmt,
> +			   va_list args)
> +{
> +	if (!strcmp(fmt, btf_skip_fmt)) {
> +		if (!strcmp(va_arg(args, char *), "bpf_test_no_cfi"))
> +			btf_skipped = true;
> +	} else if (!strcmp(fmt, dup_ignore_fmt)) {
> +		if (!strcmp(va_arg(args, char *), "bpf_testmod"))
> +			dup_ignored = true;
> +	}
> +
> +	return 0;
> +}

[Severity: Medium]
Does this unconditionally swallow all other libbpf debug, info, and error logs?

Since old_print_cb is stored as a local variable in the subtests (like
kmod_btfs_dup and kmod_btfs_skip) rather than globally, this callback has no
way to forward unmatched logs to the original handler. If a BPF program fails
to load during these tests, will the underlying verifier or libbpf errors be
completely hidden, making CI failures harder to debug?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260819090426.267-1-zhaofuyu@vivo.com?part=2