From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=tVVj=AJ=vger.kernel.org=bpf-owner@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,
	SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 7D27CC433DF
	for <bpf@archiver.kernel.org>; Sun, 28 Jun 2020 21:20:31 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [23.128.96.18])
	by mail.kernel.org (Postfix) with ESMTP id 48B18206C3
	for <bpf@archiver.kernel.org>; Sun, 28 Jun 2020 21:20:31 +0000 (UTC)
Authentication-Results: mail.kernel.org;
	dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OlJSOD3j"
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1726188AbgF1VUa (ORCPT <rfc822;bpf@archiver.kernel.org>);
        Sun, 28 Jun 2020 17:20:30 -0400
Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:57250 "EHLO
        us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org
        with ESMTP id S1726104AbgF1VUa (ORCPT <rfc822;bpf@vger.kernel.org>);
        Sun, 28 Jun 2020 17:20:30 -0400
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;
        s=mimecast20190719; t=1593379229;
        h=from:from:reply-to:subject:subject:date:date:message-id:message-id:
         to:to:cc:cc:mime-version:mime-version:content-type:content-type:
         in-reply-to:in-reply-to:references:references;
        bh=PRgc2g0Ojg/UFEUY5mUxOQF8F4RTlNOReX7eEYTBsx0=;
        b=OlJSOD3jwzcOWGlzgQyCVv9ijcl6y9bRLVX/CPFMFN2Gn5MIgTwxZT8sZvDRLk/bujeS9t
        MksJagxhTsgzxjTNt4gwwLzzl7vaFxtwc7grNvEbMbQNC+zJp57LmA9DjJYRyKhqqfMP7Q
        OqNQJaBdD6P2JWtS3vToyNU5STssG50=
Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com
 [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id
 us-mta-199-kKf1MKz5MYKNWyxVqENnPw-1; Sun, 28 Jun 2020 17:20:26 -0400
X-MC-Unique: kKf1MKz5MYKNWyxVqENnPw-1
Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11])
        (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
        (No client certificate requested)
        by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B256818C35A0;
        Sun, 28 Jun 2020 21:20:24 +0000 (UTC)
Received: from krava (unknown [10.40.192.56])
        by smtp.corp.redhat.com (Postfix) with SMTP id 2ED6C7166A;
        Sun, 28 Jun 2020 21:20:20 +0000 (UTC)
Date:   Sun, 28 Jun 2020 23:20:19 +0200
From:   Jiri Olsa <jolsa@redhat.com>
To:     Yonghong Song <yhs@fb.com>
Cc:     Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>, netdev@vger.kernel.org,
        bpf@vger.kernel.org, Song Liu <songliubraving@fb.com>,
        Martin KaFai Lau <kafai@fb.com>,
        David Miller <davem@redhat.com>,
        John Fastabend <john.fastabend@gmail.com>,
        Wenbo Zhang <ethercflow@gmail.com>,
        KP Singh <kpsingh@chromium.org>,
        Andrii Nakryiko <andriin@fb.com>,
        Brendan Gregg <bgregg@netflix.com>,
        Florent Revest <revest@chromium.org>,
        Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v4 bpf-next 05/14] bpf: Remove btf_id helpers resolving
Message-ID: <20200628212019.GH2988321@krava>
References: <20200625221304.2817194-1-jolsa@kernel.org>
 <20200625221304.2817194-6-jolsa@kernel.org>
 <7480f7b2-01f0-f575-7e4f-cf3bde851c3f@fb.com>
 <20200628201608.GG2988321@krava>
 <7c0a5ea0-9425-071d-0f41-b7e5c5ef04f0@fb.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <7c0a5ea0-9425-071d-0f41-b7e5c5ef04f0@fb.com>
X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11
Sender: bpf-owner@vger.kernel.org
Precedence: bulk
List-ID: <bpf.vger.kernel.org>
X-Mailing-List: bpf@vger.kernel.org

On Sun, Jun 28, 2020 at 01:59:54PM -0700, Yonghong Song wrote:

SNIP

> > > 
> > > The corresponding BTF_ID definition here is:
> > >    BTF_ID_LIST(bpf_skb_output_btf_ids)
> > >    BTF_ID(struct, sk_buff)
> > > 
> > > The bpf helper writer needs to ensure proper declarations
> > > of BTF_IDs like the above matching helpers definition.
> > > Support we have arg1 and arg3 as BTF_ID. then the list
> > > definition may be
> > > 
> > >    BTF_ID_LIST(bpf_skb_output_btf_ids)
> > >    BTF_ID(struct, sk_buff)
> > >    BTF_ID(struct, __unused)
> > >    BTF_ID(struct, task_struct)
> > > 
> > > This probably okay, I guess.
> > 
> > right, AFAIK we don't have such case yet, but would be good
> > to be ready and have something like
> > 
> >    BTF_ID(struct, __unused)
> > 
> > maybe adding new type for that will be better:
> > 
> >    BTF_ID(none, unused)
> 
> Maybe we can have a separate macro BTF_ID_UNUSED macro
> which simply adds 4 bytes hole in the .btf_ids* section.

right, we don't need symbols for that

jirka