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=-7.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 EE2FFC433E1 for ; Tue, 25 Aug 2020 21:04:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9066620665 for ; Tue, 25 Aug 2020 21:04:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9066620665 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E1E216B0006; Tue, 25 Aug 2020 17:04:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id DCE826B0007; Tue, 25 Aug 2020 17:04:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CE4786B0008; Tue, 25 Aug 2020 17:04:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0228.hostedemail.com [216.40.44.228]) by kanga.kvack.org (Postfix) with ESMTP id B7DA46B0006 for ; Tue, 25 Aug 2020 17:04:08 -0400 (EDT) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 64FD2180AD807 for ; Tue, 25 Aug 2020 21:04:08 +0000 (UTC) X-FDA: 77190318576.04.magic40_570e42d2705e Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin04.hostedemail.com (Postfix) with ESMTP id 3730A800CD1B for ; Tue, 25 Aug 2020 21:04:08 +0000 (UTC) X-HE-Tag: magic40_570e42d2705e X-Filterd-Recvd-Size: 4257 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by imf11.hostedemail.com (Postfix) with ESMTP for ; Tue, 25 Aug 2020 21:04:06 +0000 (UTC) IronPort-SDR: HXSOrIMFCSMkz9UizkfKHJSryheND8Vb8bQLnMWMDFkL742Mmk1665uL3phCr6nA7XrZVnEtH9 KP+tooJbRvSA== X-IronPort-AV: E=McAfee;i="6000,8403,9724"; a="156186297" X-IronPort-AV: E=Sophos;i="5.76,354,1592895600"; d="scan'208";a="156186297" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2020 14:04:03 -0700 IronPort-SDR: WoRGvY0PoRGbOXpqpJzl8Xjzeiomd80lkvcS9rWmmRwQORlx7kbHU7liFPi0L8I1jnFtU4A5EK gSD7dSjmypQQ== X-IronPort-AV: E=Sophos;i="5.76,354,1592895600"; d="scan'208";a="474507675" Received: from yyu32-mobl1.amr.corp.intel.com (HELO [10.213.162.112]) ([10.213.162.112]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2020 14:04:01 -0700 Subject: Re: [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for shadow stack To: Dave Hansen , Andy Lutomirski Cc: X86 ML , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , LKML , "open list:DOCUMENTATION" , Linux-MM , linux-arch , Linux API , Arnd Bergmann , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H.J. Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V. Shankar" , Vedvyas Shanbhogue , Dave Martin , Weijiang Yang References: <20200825002540.3351-1-yu-cheng.yu@intel.com> <20200825002540.3351-26-yu-cheng.yu@intel.com> <2d253891-9393-44d0-35e0-4b9a2da23cec@intel.com> <086c73d8-9b06-f074-e315-9964eb666db9@intel.com> From: "Yu, Yu-cheng" Message-ID: <73c2211f-8811-2d9f-1930-1c5035e6129c@intel.com> Date: Tue, 25 Aug 2020 14:04:00 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <086c73d8-9b06-f074-e315-9964eb666db9@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Rspamd-Queue-Id: 3730A800CD1B X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 8/25/2020 12:19 PM, Dave Hansen wrote: > On 8/25/20 11:43 AM, Yu, Yu-cheng wrote: >>>> arch_prctl(ARCH_X86_CET_MMAP_SHSTK, u64 *args) >>>> =C2=A0=C2=A0=C2=A0=C2=A0 Allocate a new shadow stack. >>>> >>>> =C2=A0=C2=A0=C2=A0=C2=A0 The parameter 'args' is a pointer to a use= r buffer. >>>> >>>> =C2=A0=C2=A0=C2=A0=C2=A0 *args =3D desired size >>>> =C2=A0=C2=A0=C2=A0=C2=A0 *(args + 1) =3D MAP_32BIT or MAP_POPULATE >>>> >>>> =C2=A0=C2=A0=C2=A0=C2=A0 On returning, *args is the allocated shado= w stack address. >>> >>> This is hideous.=C2=A0 Would this be better as a new syscall? >> >> Could you point out why this is hideous, so that I can modify the >> arch_prctl? >=20 > Passing values in memory is hideous when we don't have to. A syscall > would let you have separate arguments for size and flags and would also > let you have a nice return value instead of needing to do that in memor= y > too. That is a good justification. >=20 >> I think this is more arch-specific.=C2=A0 Even if it becomes a new sys= call, >> we still need to pass the same parameters. >=20 > Right, but without the copying in and out of memory. >=20 Linux-api is already on the Cc list. Do we need to add more people to=20 get some agreements for the syscall?