Re: [RFC bpf-next v1 1/8] bpf: add a get_helper_proto() utility function

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On Sat, Jun 29, 2024 at 2:48 AM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote:
>
> Extract the part of check_helper_call() as a utility function allowing
> to query 'struct bpf_func_proto' for a specific helper function id.
>
> Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
> ---
>  kernel/bpf/verifier.c | 37 ++++++++++++++++++++++++++-----------
>  1 file changed, 26 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index d3927d819465..8dd3385cf925 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -10261,6 +10261,24 @@ static void update_loop_inline_state(struct bpf_verifier_env *env, u32 subprogno
>                                  state->callback_subprogno == subprogno);
>  }
>
> +static int get_helper_proto(struct bpf_verifier_env *env, int func_id,
> +                           const struct bpf_func_proto **ptr)
> +{
> +       const struct bpf_func_proto *result = NULL;
> +
> +       if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID)
> +               return -ERANGE;
> +
> +       if (env->ops->get_func_proto)
> +               result = env->ops->get_func_proto(func_id, env->prog);
> +
> +       if (!result)
> +               return -EINVAL;
> +
> +       *ptr = result;
> +       return 0;
> +}
> +
>  static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
>                              int *insn_idx_p)
>  {
> @@ -10277,17 +10295,14 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
>
>         /* find function prototype */
>         func_id = insn->imm;
> -       if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
> -               verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
> -                       func_id);
> -               return -EINVAL;
> -       }
> -
> -       if (env->ops->get_func_proto)
> -               fn = env->ops->get_func_proto(func_id, env->prog);
> -       if (!fn) {
> -               verbose(env, "program of this type cannot use helper %s#%d\n",
> -                       func_id_name(func_id), func_id);
> +       err = get_helper_proto(env, insn->imm, &fn);
> +       if (err) {
> +               if (err == -ERANGE)
> +                       verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
> +                               func_id);
> +               else
> +                       verbose(env, "program of this type cannot use helper %s#%d\n",
> +                               func_id_name(func_id), func_id);
>                 return -EINVAL;
>         }

subjective, but this might be cleaner and will keep first verbose() on
a single line:

err = get_helper_proto(...);
if (err == -ERANGE) {
    verbose(...);
    return -EINVAL;
} else if (err) {
    verbose(...);
    return err;
}


>
> --
> 2.45.2
>





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