Re: [PATCH bpf-next v7 1/2] libbpf: support selective kernel module BTF loading via bpf_object_open_opts

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, Sep 07, 2026 at 01:38:46PM +0800, Fuyu Zhao wrote:

SNIP

>  static int load_module_btfs(struct bpf_object *obj)
>  {
>  	struct bpf_btf_info info;
> @@ -5825,6 +5842,9 @@ static int load_module_btfs(struct bpf_object *obj)
>  	if (!kernel_supports(obj, FEAT_MODULE_BTF))
>  		return 0;
>  
> +	if (obj->btf_module_allowlist_cnt == 0)
> +		return 0;
> +
>  	while (true) {
>  		err = bpf_btf_get_next_id(id, &id);
>  		if (err && errno == ENOENT)
> @@ -5867,6 +5887,11 @@ static int load_module_btfs(struct bpf_object *obj)
>  			continue;
>  		}
>  
> +		if (!is_btf_mod_allowed(obj, name)) {
> +			close(fd);
> +			continue;
> +		}
> +
>  		btf = btf_get_from_fd(fd, obj->btf_vmlinux);
>  		err = libbpf_get_error(btf);
>  		if (err) {
> @@ -5891,6 +5916,10 @@ static int load_module_btfs(struct bpf_object *obj)
>  			break;
>  		}
>  		obj->btf_module_cnt++;
> +
> +		if (obj->btf_module_allowlist &&

IIUC you don't need to check obj->btf_module_allowlist,
because obj->btf_module_allowlist_cnt is -1 by default?

> +		    obj->btf_module_allowlist_cnt == obj->btf_module_cnt)
> +			break;
>  	}
>  
>  	if (err) {
> @@ -8426,8 +8455,10 @@ static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf,
>  					  const struct bpf_object_open_opts *opts)
>  {
>  	const char *kconfig, *btf_tmp_path, *token_path;
> +	const char **mod_allow;
> +	int mod_allow_cnt;
>  	struct bpf_object *obj;
> -	int err;
> +	int err, i, j;
>  	char *log_buf;
>  	size_t log_size;
>  	__u32 log_level;
> @@ -8470,6 +8501,22 @@ static struct bpf_object *bpf_object_open(const char *path, const void *obj_buf,
>  	if (token_path && strlen(token_path) >= PATH_MAX)
>  		return ERR_PTR(-ENAMETOOLONG);
>  
> +	mod_allow = OPTS_GET(opts, btf_module_allowlist, NULL);
> +	mod_allow_cnt = OPTS_GET(opts, btf_module_allowlist_cnt, 0);
> +
> +	if ((!mod_allow && mod_allow_cnt > 0) || mod_allow_cnt < 0)
> +		return ERR_PTR(-EINVAL);
> +
> +	for (i = 0; i < mod_allow_cnt; i++) {
> +		if (!mod_allow[i] || !mod_allow[i][0])
> +			return ERR_PTR(-EINVAL);
> +
> +		for (j = 0; j < i; j++) {
> +			if (strcmp(mod_allow[i], mod_allow[j]) == 0)
> +				return ERR_PTR(-EINVAL);
> +		}

do we care if user supplied same name multiple times?

thanks,
jirka

> +	}
> +
>  	obj = bpf_object__new(path, obj_buf, obj_buf_sz, obj_name);
>  	if (IS_ERR(obj))
>  		return obj;