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

[Eduard Zingerman]

On Wed, 2026-08-19 at 17:04 +0800, Fuyu Zhao wrote:

...

> +++ 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 bool btf_skipped;
> +static bool dup_ignored;
> +
> +static const char btf_skip_fmt[] =
> +	"libbpf: skipping module BTF '%s', not in kmod_btf_names\n";
> +static const char dup_ignore_fmt[] =
> +	"libbpf: duplicate kmod BTF name '%s' ignored\n";
> +
> +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;
> +}

Idk what Andrii would say about this, but I'd rather add an internal
function akin to:

  size_t bpf_object_btf_module_cnt(const struct bpf_object *obj);

in libbpf.c and expose it via libbpf_internal.h (*not* via API),
instead of intercepting log messages.

...