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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 002FAC2D0D1 for ; Thu, 19 Dec 2019 17:06:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA184222C2 for ; Thu, 19 Dec 2019 17:06:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Vx83zgmg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727078AbfLSRGI (ORCPT ); Thu, 19 Dec 2019 12:06:08 -0500 Received: from mail-pl1-f194.google.com ([209.85.214.194]:37021 "EHLO mail-pl1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726760AbfLSRGI (ORCPT ); Thu, 19 Dec 2019 12:06:08 -0500 Received: by mail-pl1-f194.google.com with SMTP id c23so2831917plz.4; Thu, 19 Dec 2019 09:06:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=XA55rnPiD5VnRa+mIp3j0LMWkAaLQc68hKMnHswUhU4=; b=Vx83zgmgCS0J6uG2ryd0wXh7MG6w+jAPCHg0iNJ7cos7v1rOAlTiNXyIA9dM9QwERc SMlNhFtMtHWSyTG38mjwLYQtZfHSUIjun7l1rdCgy72dcgJO6BPj+cDDKd5dLw5hD+Zs cq9EqolL3ah8iLRWH7Ys+gt2/vvTtm2oqtq/EMazxfsxXVBS6VoPfwpsRxSnBv0eAPuc LFgJ5rEiyqQt4/S+gXKSMlMwqqQFyri2sSGibSz7KO1k+KzCDoC4tezMtxON10RJInah cDxCCC+DKFrhcK9jqiLdiMS0dI/uUdoajNKkJKIZO+UADJ25bzY0Bnp2l+HWGePychFv ZXuA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=XA55rnPiD5VnRa+mIp3j0LMWkAaLQc68hKMnHswUhU4=; b=V6I1eMeG6z76IJmNDUiWQgKnKknuM7wtHROcnH9yYLO2qtJyXkYtTy4RV8hMle7REu weERScmFcO+pD5XaqgcZzpp5ARGued5U6IwuhqFXz4xA0AEi10dssicgUokD2iUHeseH bWqAZxD44fBbQe1WdTUuOd+sQz3QRgQgRS0FFRFz/1xB/yZwO9PNSdcY3Yv9MsgcvFv+ CAazVpeRJheSlmo65SXBDyYtmTC0u/oH5j2dOf0nvyMeenm9b66vhbj4XF8ib45uLY5l rt79ZiwKctxe8/N7Wa2afSU+bhKrdf3iXEocXCo2qGzXjx+U+nwp2PusgsCDP565afrn BthA== X-Gm-Message-State: APjAAAXeMeJNu8yWlZ2/rtt4R/8djv5J/EDs/benT2NbrU3dLmy5M9a/ T0Vb+3gVyv8e6TZJxoURDjw= X-Google-Smtp-Source: APXvYqyBSosMeJSZI0uU5VE5Up6x6lhN/AF6DOuokbHul/Qbi/lBms9M4kzQ+6X9Wzzb1kBX4Tl1vA== X-Received: by 2002:a17:90a:660d:: with SMTP id l13mr9325220pjj.23.1576775167245; Thu, 19 Dec 2019 09:06:07 -0800 (PST) Received: from ast-mbp.dhcp.thefacebook.com ([2620:10d:c090:180::6b48]) by smtp.gmail.com with ESMTPSA id u26sm8682977pfn.46.2019.12.19.09.06.05 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 19 Dec 2019 09:06:05 -0800 (PST) Date: Thu, 19 Dec 2019 09:06:04 -0800 From: Alexei Starovoitov To: Andrii Nakryiko Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, ast@fb.com, daniel@iogearbox.net, andrii.nakryiko@gmail.com, kernel-team@fb.com Subject: Re: [PATCH bpf-next 1/3] bpftool: add extra CO-RE mode to btf dump command Message-ID: <20191219170602.4xkljpjowi4i2e3q@ast-mbp.dhcp.thefacebook.com> References: <20191219070659.424273-1-andriin@fb.com> <20191219070659.424273-2-andriin@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191219070659.424273-2-andriin@fb.com> User-Agent: NeoMutt/20180223 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Dec 18, 2019 at 11:06:56PM -0800, Andrii Nakryiko wrote: > + if (core_mode) { > + printf("#if defined(__has_attribute) && __has_attribute(preserve_access_index)\n"); > + printf("#define __CLANG_BPF_CORE_SUPPORTED\n"); > + printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n"); > + printf("#endif\n\n"); I think it's dangerous to automatically opt-out when clang is not new enough. bpf prog will compile fine, but it will be missing co-re relocations. How about doing something like: printf("#ifdef NEEDS_CO_RE\n"); printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n"); printf("#endif\n\n"); and emit it always when 'format c'. Then on the program side it will look: #define NEEDS_CO_RE #include "vmlinux.h" If clang is too old there will be a compile time error which is a good thing. Future features will have different NEEDS_ macros.