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

On 8/19/2026 5:12 PM, [email protected] wrote:
> 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 <[email protected]>
> 
> 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?
> 

I don't consider this a problem since the test runs serially and the callback
only affects the kmod_btfs test.

However, I can forward unmatched logs to the original callback through
old_print_cb to preserve the original logging behavior.