From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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=-5.8 required=3.0 tests=BAYES_00,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 5EB2FC4361B for ; Mon, 7 Dec 2020 22:20:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BF6423976 for ; Mon, 7 Dec 2020 22:20:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727940AbgLGWUN (ORCPT ); Mon, 7 Dec 2020 17:20:13 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:42857 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726231AbgLGWUN (ORCPT ); Mon, 7 Dec 2020 17:20:13 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1607379526; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Fth5ZshA4w8bE9b8/qiWSCrkxogy+LVVKUmgi5NsXks=; b=G+cV/Zg+zBZIi2k4E3xqKFun8Olpn/Q8rIsaDnv+J9Lxuekm8qDp1w1oGFyRt+PpmIIt1H vdfQYaZlSjXXpg2AwjBip/lJuC2bqZvp1F/SvLhMWo8HlGCKw2V95CFKL86g+ThoCJXRd+ eqlJ4p8cQm/O7yoVJquQdd7wo+25Yu8= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-214-P9WEY0ytMKqDQeJhlj40qg-1; Mon, 07 Dec 2020 17:18:44 -0500 X-MC-Unique: P9WEY0ytMKqDQeJhlj40qg-1 Received: by mail-wr1-f71.google.com with SMTP id 91so5261206wrk.17 for ; Mon, 07 Dec 2020 14:18:44 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version:content-transfer-encoding; bh=Fth5ZshA4w8bE9b8/qiWSCrkxogy+LVVKUmgi5NsXks=; b=gLanZvCtaEnFiZN9J0KZ8EjLRnb/TyYFyp7rynA7Y6u/ZXcvCHVIfC4RFVlDYW066Z oEIZgPbPsLsQRoqHJe40NN+R/QjERDTQQUglTaNskPsQJFP1T7G6jloVus8ZVJQ4qvaR alwmVI2+8Q+UDMlXqHmnMlWDOfcIAVAYHkIS+7rJ5RfPCfImlE5AG1q2r/JaBWEpI6hG BaFyKGaj6DW2Lk+rvrKlW7qaWnCFOZXTGwXu8kamVUWnIpCnOOACo/esL+ebE4W4+3VX gXnY5UjHnhiT8kZzjMfHx4bXovnVm8ibg6q5hOSXoOC9Q4LwgLhtz0LNDoIUbATEiGBi Kbyg== X-Gm-Message-State: AOAM530e6MLJmd51fnEWIGLpzfF/JVXa5tTxzxxBHlrCitA9CAeDVAGD WhO5WAJddETCBsF2cchcFXBQvN1uGJhGdCqmwBpoTabH3sj+0A/BHaoAvDYuU0AwDi5ON9q/I08 50rtm+r72UZfL X-Received: by 2002:adf:a3c1:: with SMTP id m1mr22792772wrb.28.1607379523682; Mon, 07 Dec 2020 14:18:43 -0800 (PST) X-Google-Smtp-Source: ABdhPJwXVT4WVwHnS2nuJVQ67PRhP411hbaf27RH3LB3A8/yPJvHHfgEqMoLeiz7LptG4SV7tj9IrQ== X-Received: by 2002:adf:a3c1:: with SMTP id m1mr22792762wrb.28.1607379523502; Mon, 07 Dec 2020 14:18:43 -0800 (PST) Received: from alrua-x1.borgediget.toke.dk ([45.145.92.2]) by smtp.gmail.com with ESMTPSA id h83sm803798wmf.9.2020.12.07.14.18.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Dec 2020 14:18:42 -0800 (PST) Received: by alrua-x1.borgediget.toke.dk (Postfix, from userid 1000) id 64A5E1843F5; Mon, 7 Dec 2020 23:18:42 +0100 (CET) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= To: Alexei Starovoitov Cc: Andrii Nakryiko , Yonghong Song , bpf Subject: Re: Latest libbpf fails to load programs compiled with old LLVM In-Reply-To: References: <87lfeebwpu.fsf@toke.dk> <10679e62-50a2-4c01-31d2-cb79c01e4cbf@fb.com> <87r1o59aoc.fsf@toke.dk> <6801fcdb-932e-c185-22db-89987099b553@fb.com> <875z5d7ufl.fsf@toke.dk> <878sa9619d.fsf@toke.dk> <874kkx5zl5.fsf@toke.dk> X-Clacks-Overhead: GNU Terry Pratchett Date: Mon, 07 Dec 2020 23:18:42 +0100 Message-ID: <87tusxi7jx.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Alexei Starovoitov writes: > On Mon, Dec 7, 2020 at 8:51 AM Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> >> Alexei Starovoitov writes: >> >> > On Mon, Dec 7, 2020 at 8:15 AM Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> >> >> >> Alexei Starovoitov writes: >> >> >> >> > On Mon, Dec 7, 2020 at 3:03 AM Toke H=C3=B8iland-J=C3=B8rgensen wrote: >> >> >> >> >> >> Wait, what? This is a regression that *breaks people's programs* on >> >> >> compiler versions that are still very much in the wild! I mean, fi= ne if >> >> >> you don't want to support new features on such files, but then sur= ely we >> >> >> can at least revert back to the old behaviour? >> >> > >> >> > Those folks that care about compiling with old llvm would have to s= tick >> >> > to whatever loader they have instead of using libbpf. >> >> > It's not a backward compatibility breakage. >> >> >> >> What? It's a change in libbpf that breaks loading of existing BPF obj= ect >> >> files that were working (with libbpf) before. If that's not a backward >> >> compatibility break then that term has lost all meaning. >> > >> > The user space library is not a kernel. >> > The library will change its interface. It will remove functions, featu= res, etc. >> > That's what .map is for. >> >> Right, OK, so how do I use .map to get the old behaviour here? That's >> all I'm asking for, really... > > Fix old llvm. The users would have to upgrade either from llvm 7.x to > 7.x+1 or to llvm 10+. Right, so by "we keep a stable interface" you mean "we expect you to upgrade your entire toolchain every time you update the library". Gotcha! I'll rectify my newspeak dictionary straight away - doubleplusgood! -Toke