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=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 766F6C433E0 for ; Wed, 24 Jun 2020 17:17:58 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3C4A920823 for ; Wed, 24 Jun 2020 17:17:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="AhPxl50r" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3C4A920823 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=tlvV2rJf7zCTlnepaEFk3ElUOLTbXj+KMNplhVCWlnU=; b=AhPxl50rmacvbcyWMiEbF1h0/ 3Rw/pKyf/pYjQO7QBetAhUI/JcLZqV2mEi/p3zWSxSHkyzrcSj7kTSEz2E3u1svWWzS27fcctjIAR /LNAmDmrh/cIW1tcXPbmSK3hPBiid2eD7XPOz1tzaCRNUaPFPhpLEsfHLMSzp6NESzh65kihspLcJ 58aObLsoZBgi7Vt2i3F1qqGdCa2PzRjZxKmKAUdpKEn+gHk6Mjbxb3gG9ym1snprdG9w2IRjgK6YO 0YfLO3SZOxk45npt03kSH8/3SFjo6u3jxBVQqiry/wcZmWFWRa0PaxwkL4HEvCio3X5lymJEY9GWW Le6qVccbQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jo90c-0005Xr-2Z; Wed, 24 Jun 2020 17:16:26 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jo90V-0005V6-F8 for linux-arm-kernel@lists.infradead.org; Wed, 24 Jun 2020 17:16:22 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B1C8B1FB; Wed, 24 Jun 2020 10:16:18 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F027B3F71E; Wed, 24 Jun 2020 10:16:15 -0700 (PDT) Date: Wed, 24 Jun 2020 18:16:13 +0100 From: Dave Martin To: Ard Biesheuvel Subject: Re: [PATCH v3 3/9] efi/libstub: Remove .note.gnu.property Message-ID: <20200624171613.GJ25945@arm.com> References: <20200624033142.cinvg6rbg252j46d@google.com> <202006232143.66828CD3@keescook> <20200624104356.GA6134@willie-the-truck> <202006240820.A3468F4@keescook> <202006240844.7BE48D2B5@keescook> <20200624162919.GH25945@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , linux-efi , Catalin Marinas , Arvind Sankar , Will Deacon , Thomas Gleixner , linux-arch , Fangrui Song , Masahiro Yamada , X86 ML , Russell King , clang-built-linux , Ingo Molnar , Borislav Petkov , Kees Cook , Arnd Bergmann , Nathan Chancellor , Peter Collingbourne , Linux ARM , Nick Desaulniers , Linux Kernel Mailing List , James Morse Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jun 24, 2020 at 06:40:48PM +0200, Ard Biesheuvel wrote: > On Wed, 24 Jun 2020 at 18:29, Dave Martin wrote: > > > > On Wed, Jun 24, 2020 at 05:48:41PM +0200, Ard Biesheuvel wrote: > > > On Wed, 24 Jun 2020 at 17:45, Kees Cook wrote: > > > > > > > > On Wed, Jun 24, 2020 at 05:31:06PM +0200, Ard Biesheuvel wrote: > > > > > On Wed, 24 Jun 2020 at 17:21, Kees Cook wrote: > > > > > > > > > > > > On Wed, Jun 24, 2020 at 12:46:32PM +0200, Ard Biesheuvel wrote: > > > > > > > I'm not sure if there is a point to having PAC and/or BTI in the EFI > > > > > > > stub, given that it runs under the control of the firmware, with its > > > > > > > memory mappings and PAC configuration etc. > > > > > > > > > > > > Is BTI being ignored when the firmware runs? > > > > > > > > > > Given that it requires the 'guarded' attribute to be set in the page > > > > > tables, and the fact that the UEFI spec does not require it for > > > > > executables that it invokes, nor describes any means of annotating > > > > > such executables as having been built with BTI annotations, I think we > > > > > can safely assume that the EFI stub will execute with BTI disabled in > > > > > the foreseeable future. > > > > > > > > yaaaaaay. *sigh* How long until EFI catches up? > > > > > > > > That said, BTI shouldn't _hurt_, right? If EFI ever decides to enable > > > > it, we'll be ready? > > > > > > > > > > Sure. Although I anticipate that we'll need to set some flag in the > > > PE/COFF header to enable it, and so any BTI opcodes we emit without > > > that will never take effect in practice. > > > > In the meantime, it is possible to build all the in-tree parts of EFI > > for BTI, and just turn it off for out-of-tree EFI binaries? > > > > Not sure I understand the question. What do you mean by out-of-tree > EFI binaries? And how would the firmware (which is out of tree itself, > and is in charge of the page tables, vector table, timer interrupt etc > when the EFI stub executes) distinguish such binaries from the EFI > stub? I'm not an EFI expert, but I'm guessing that you configure EFI with certain compiler flags and build it. Possibly some standalone EFI executables are built out of the same tree and shipped with the firmware from the same build, but I'm speculating. If not, we can just run all EFI executables with BTI off. > > If there's no easy way to do this though, I guess we should wait for / > > push for a PE/COFF flag to describe this properly. > > > > Yeah good point. I will take this to the forum. In the interim, we could set the GP bit in EFI's page tables for the executable code from the firmware image if we want this protection, but turn it off in pages mapping the executable code of EFI executables. This is better than nothing. Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel