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_INVALID,DKIM_SIGNED, 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 B071DC35669 for ; Fri, 21 Feb 2020 23:05:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 847D720722 for ; Fri, 21 Feb 2020 23:05:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZENXGE8+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729451AbgBUXFO (ORCPT ); Fri, 21 Feb 2020 18:05:14 -0500 Received: from mail-qk1-f196.google.com ([209.85.222.196]:40486 "EHLO mail-qk1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726802AbgBUXFN (ORCPT ); Fri, 21 Feb 2020 18:05:13 -0500 Received: by mail-qk1-f196.google.com with SMTP id b7so3445554qkl.7 for ; Fri, 21 Feb 2020 15:05:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:date:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=JoSFFpTYFiaHmH8ulMoTAh2gcF7SkvLOnEEsmrgnXy8=; b=ZENXGE8+LPDYeYrm7qYCxS6xLDib/gu7943oikNBP6fHJuCB0/3w8R3eGXbzaLq++Z Qh41kBK8ftSyqNGIx8WZnBiuduCLirxIylRpNwjYqs0Mq986x4pbeN8k65/uU0HmiOPq pCimpCmlVvuQTsNKANhNIcKdl98gK9he2u19uPZyNtM8poRfsvotTHMrolUeJMaYck/k /NFBKzhm4zWgoqqdcvsw/6Sd+osJjx31ecscxw+zGC0zS62IWC9FMczxYpSEMBv+VsH0 MfDehN4zjx+117b03RuK++j87aOZa2opFhnZ3mj0rIa24ce8zyzC8bE5By9Q2E+o2srm /UKg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:date:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=JoSFFpTYFiaHmH8ulMoTAh2gcF7SkvLOnEEsmrgnXy8=; b=YOnZr2Cy0TSkNMMu7TmudoEw41G/7vAOtg8LFsLHJzco4hsKyc7OoA834NDPfXQMUt 3CY1Jf1Jh+Wb0ehKuUCzri+yYvCezmUPJ6VnutUpycKfkIytzGD+dIUxfLYlUV36X3/0 gtV0G6eRrI62M51kYy73cppDUdw+o3zchtOiqWwVh+nGIYZDX4jUvta65t3RJrnUtJP1 m9csx6BW8O5fGI+X/aWhLnaa4p7L07TkMb2b25R5dCeh6xhwFBY4jmQmRze2dqddXQCf 3QXaRWaOKe78FiIhPZDaZCgT9X1hqIFEANj8GdqPJjutL7fK1xDyZ9yG9E9i/ZNSqAXF QtTA== X-Gm-Message-State: APjAAAUKKHeJfNx4vxlB985g9ZkNJrmBnjYQUMIzP5T14AjIs5/WxfqU y7S5lzchdrnGlAWGL+H84q8= X-Google-Smtp-Source: APXvYqwaVqfXbV7TqYDvUgFLvjqxwL2ExERchNv7petey3SAoxE3PYNiAidZ+Xp96mfnbQUVuky0rA== X-Received: by 2002:a37:6c5:: with SMTP id 188mr35749334qkg.277.1582326311881; Fri, 21 Feb 2020 15:05:11 -0800 (PST) Received: from rani.riverdale.lan ([2001:470:1f07:5f3::b55f]) by smtp.gmail.com with ESMTPSA id e3sm2243206qtb.65.2020.02.21.15.05.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Feb 2020 15:05:11 -0800 (PST) From: Arvind Sankar X-Google-Original-From: Arvind Sankar Date: Fri, 21 Feb 2020 18:05:09 -0500 To: Josh Poimboeuf Cc: Arvind Sankar , Arjan van de Ven , Peter Zijlstra , Kees Cook , Andy Lutomirski , Kristen Carlson Accardi , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, rick.p.edgecombe@intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: Re: [RFC PATCH 06/11] x86: make sure _etext includes function sections Message-ID: <20200221230504.GA3001063@rani.riverdale.lan> References: <75f0bd0365857ba4442ee69016b63764a8d2ad68.camel@linux.intel.com> <20200207092423.GC14914@hirez.programming.kicks-ass.net> <202002091742.7B1E6BF19@keescook> <20200210105117.GE14879@hirez.programming.kicks-ass.net> <43b7ba31-6dca-488b-8a0e-72d9fdfd1a6b@linux.intel.com> <20200210163627.GA1829035@rani.riverdale.lan> <20200221195039.dptvoerfez4r76ay@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200221195039.dptvoerfez4r76ay@treble> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 21, 2020 at 01:50:39PM -0600, Josh Poimboeuf wrote: > On Mon, Feb 10, 2020 at 11:36:29AM -0500, Arvind Sankar wrote: > > On Mon, Feb 10, 2020 at 07:54:58AM -0800, Arjan van de Ven wrote: > > > > > > > > I'll leave it to others to figure out the exact details. But afaict it > > > > should be possible to have fine-grained-randomization and preserve the > > > > workaround in the end. > > > > > > > > > > the most obvious "solution" is to compile with an alignment of 4 bytes (so tight packing) > > > and then in the randomizer preserve the offset within 32 bytes, no matter what it is > > > > > > that would get you an average padding of 16 bytes which is a bit more than now but not too insane > > > (queue Kees' argument that tiny bits of padding are actually good) > > > > > > > With the patchset for adding the mbranches-within-32B-boundaries option, > > the section alignment gets forced to 32. With function-sections that > > means function alignment has to be 32 too. > > We should be careful about enabling -mbranches-within-32B-boundaries. > It will hurt AMD, and presumably future Intel CPUs which don't need it. > > -- > Josh > And past Intel CPUs too :) As I understand it only appears from Skylake onwards.