Re: [PATCH bpf-next v3 1/2] bpf: Support struct btf_struct_meta via KF_IMPLICIT_ARGS

[Jiri Olsa <olsajiri@gmail.com>]

On Wed, Mar 18, 2026 at 04:42:09PM -0700, Ihor Solodrai wrote:

SNIP

>  
> +/*
> + * A kfunc with KF_IMPLICIT_ARGS has two prototypes in BTF:
> + *   - the _impl prototype with full arg list (this is meta->func_proto)
> + *   - the BPF API prototype w/o implicit args (func->type in BTF)
> + * To determine whether an argument is implicit, we compare its position
> + * against the number of arguments of both prototypes.
> + */
> +static bool is_kfunc_arg_implicit(const struct bpf_kfunc_call_arg_meta *meta, u32 arg_idx)
> +{
> +	const struct btf_type *func, *func_proto;
> +	u32 argn, full_argn;
> +
> +	if (!(meta->kfunc_flags & KF_IMPLICIT_ARGS))
> +		return false;
> +
> +	full_argn = btf_type_vlen(meta->func_proto);
> +
> +	func = btf_type_by_id(meta->btf, meta->func_id);
> +	func_proto = btf_type_by_id(meta->btf, func->type);
> +	argn = btf_type_vlen(func_proto);
> +
> +	return argn <= arg_idx && arg_idx < full_argn;

hi,
I understand above is faster, but should we rather check for exact
types with something like:

__is_kfunc_ptr_arg_type(btf, arg, KF_ARG_PROG_AUX_ID ||
__is_kfunc_ptr_arg_type(btf, arg, KF_ARG_BTF_STRUCT_META

jirka