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=-5.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 9D77FC433E1 for ; Wed, 26 Aug 2020 17:05:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 751372078D for ; Wed, 26 Aug 2020 17:05:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598461510; bh=Fp4rNpiuId6Zd1SRZaw++Fjp3anMdRDaszmTeS7uFZQ=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=cNr/Adq9/BJTCJlFq2ym2cSsFZ46eDL5ldtjpJInnTHtOh/RlxaPOjCaOMl43ockA xbf1vG7R8Q/jwYRoAZnTXRANcQoTWw1B44Fm2SbjyKWVHNzmrEAF7poocmIh7S2VT7 nFGa0HJx+RMKrtS5qZG0Btl8JnOgwTQwtzsbbEl8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726995AbgHZRFJ (ORCPT ); Wed, 26 Aug 2020 13:05:09 -0400 Received: from mail.kernel.org ([198.145.29.99]:33390 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726854AbgHZRFH (ORCPT ); Wed, 26 Aug 2020 13:05:07 -0400 Received: from mail-wr1-f48.google.com (mail-wr1-f48.google.com [209.85.221.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 4355C22CA0 for ; Wed, 26 Aug 2020 17:05:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598461506; bh=Fp4rNpiuId6Zd1SRZaw++Fjp3anMdRDaszmTeS7uFZQ=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=IXsZbehfS9rUMHIUdoa09eOQCVQ3Gh0ntq3FHoKtDEBmxNo4m64QNUZgFCYV/FBvm pA0iOF4Eb1d4wGL5f7juoUUApYPt8PaUV0XRtuZ1fvkTFHbKiaCRhCTKGYqTqFGDje m7p05GH9gD2W5ZWdl9vtHaNQM1v4gDB8YxzDl5VE= Received: by mail-wr1-f48.google.com with SMTP id c15so2543954wrs.11 for ; Wed, 26 Aug 2020 10:05:06 -0700 (PDT) X-Gm-Message-State: AOAM53144j71HPLuo7Gemv4xWvrx3nPNYzueJGF+EWXVyQf2FCP8T2sv xdJU+sCyELxDtO0NKGXTUwdAktbA2IbOMfzX8i18IA== X-Google-Smtp-Source: ABdhPJxT1whGlvFPDBPqTZxg6JBM1ZNVE0c8Sb8po9BtCcEYhiPPubL7pcyJ9YiMCYEcuPYkefPEyiGW6FbklL+xVTI= X-Received: by 2002:a5d:570e:: with SMTP id a14mr1919991wrv.70.1598461504645; Wed, 26 Aug 2020 10:05:04 -0700 (PDT) MIME-Version: 1.0 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> <73c2211f-8811-2d9f-1930-1c5035e6129c@intel.com> <20200826164604.GW6642@arm.com> <87ft892vvf.fsf@oldenburg2.str.redhat.com> In-Reply-To: <87ft892vvf.fsf@oldenburg2.str.redhat.com> From: Andy Lutomirski Date: Wed, 26 Aug 2020 10:04:53 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v11 25/25] x86/cet/shstk: Add arch_prctl functions for shadow stack To: Florian Weimer Cc: Dave Martin , "Yu, Yu-cheng" , Dave Hansen , Andy Lutomirski , 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 , "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 , Weijiang Yang Content-Type: text/plain; charset="UTF-8" Sender: linux-arch-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Wed, Aug 26, 2020 at 9:52 AM Florian Weimer wrote: > > * Dave Martin: > > > On Tue, Aug 25, 2020 at 04:34:27PM -0700, Yu, Yu-cheng wrote: > >> On 8/25/2020 4:20 PM, Dave Hansen wrote: > >> >On 8/25/20 2:04 PM, Yu, Yu-cheng wrote: > >> >>>>I think this is more arch-specific. Even if it becomes a new syscall, > >> >>>>we still need to pass the same parameters. > >> >>> > >> >>>Right, but without the copying in and out of memory. > >> >>> > >> >>Linux-api is already on the Cc list. Do we need to add more people to > >> >>get some agreements for the syscall? > >> >What kind of agreement are you looking for? I'd suggest just coding it > >> >up and posting the patches. Adding syscalls really is really pretty > >> >straightforward and isn't much code at all. > >> > > >> > >> Sure, I will do that. > > > > Alternatively, would a regular prctl() work here? > > Is this something appliation code has to call, or just the dynamic > loader? > > prctl in glibc is a variadic function, so if there's a mismatch between > the kernel/userspace syscall convention and the userspace calling > convention (for variadic functions) for specific types, it can't be made > to work in a generic way. > > The loader can use inline assembly for system calls and does not have > this issue, but applications would be implcated by it. > I would expect things like Go and various JITs to call it directly. If we wanted to be fancy and add a potentially more widely useful syscall, how about: mmap_special(void *addr, size_t length, int prot, int flags, int type); Where type is something like MMAP_SPECIAL_X86_SHSTK. Fundamentally, this is really just mmap() except that we want to map something a bit magical, and we don't want to require opening a device node to do it. --Andy