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 Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BD288C433F5 for ; Fri, 10 Dec 2021 14:20:36 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.243956.422088 (Exim 4.92) (envelope-from ) id 1mvgkw-0007gJ-Gj; Fri, 10 Dec 2021 14:20:14 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 243956.422088; Fri, 10 Dec 2021 14:20:14 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mvgkw-0007gC-Dh; Fri, 10 Dec 2021 14:20:14 +0000 Received: by outflank-mailman (input) for mailman id 243956; Fri, 10 Dec 2021 14:20:13 +0000 Received: from se1-gles-flk1-in.inumbo.com ([94.247.172.50] helo=se1-gles-flk1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1mvgkv-0007g5-HM for xen-devel@lists.xenproject.org; Fri, 10 Dec 2021 14:20:13 +0000 Received: from ppsw-43.csi.cam.ac.uk (ppsw-43.csi.cam.ac.uk [131.111.8.143]) by se1-gles-flk1.inumbo.com (Halon) with ESMTPS id 481872d2-59c4-11ec-a831-37629979565c; Fri, 10 Dec 2021 15:20:10 +0100 (CET) Received: from hades.srcf.societies.cam.ac.uk ([131.111.179.67]:41522) by ppsw-43.csi.cam.ac.uk (ppsw.cam.ac.uk [131.111.8.139]:25) with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) id 1mvgkr-0007EV-p0 (Exim 4.95) (return-path ); Fri, 10 Dec 2021 14:20:09 +0000 Received: from [192.168.1.10] (host-92-12-61-86.as13285.net [92.12.61.86]) (Authenticated sender: amc96) by hades.srcf.societies.cam.ac.uk (Postfix) with ESMTPSA id 67F3C1FDB9; Fri, 10 Dec 2021 14:20:09 +0000 (GMT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 481872d2-59c4-11ec-a831-37629979565c X-Cam-AntiVirus: no malware found X-Cam-ScannerInfo: https://help.uis.cam.ac.uk/email-scanner-virus Message-ID: <44707bed-ceb3-377b-f2b3-9864b7fa4e97@srcf.net> Date: Fri, 10 Dec 2021 14:20:09 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Content-Language: en-GB To: Jan Beulich , Andrew Cooper Cc: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Wei Liu , Xen-devel References: <20211126123446.32324-1-andrew.cooper3@citrix.com> <20211126123446.32324-2-andrew.cooper3@citrix.com> <69d1b4a3-a042-c2c4-2f59-ea897886ae1d@suse.com> <566dbf20-2881-80ac-eafd-57ac4b217f0f@suse.com> From: Andrew Cooper Subject: Re: [PATCH 01/65] x86: Introduce support for CET-IBT In-Reply-To: <566dbf20-2881-80ac-eafd-57ac4b217f0f@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 29/11/2021 09:21, Jan Beulich wrote: > On 26.11.2021 16:21, Andrew Cooper wrote: >> On 26/11/2021 14:10, Jan Beulich wrote: >>> On 26.11.2021 13:33, Andrew Cooper wrote: >>>> @@ -124,6 +129,18 @@ config XEN_SHSTK >>>> When CET-SS is active, 32bit PV guests cannot be used. Backwards >>>> compatiblity can be provided via the PV Shim mechanism. >>>> >>>> +config XEN_IBT >>>> + bool "Supervisor Indirect Branch Tracking" >>>> + depends on HAS_CC_CET_IBT >>>> + default y >>>> + help >>>> + Control-flow Enforcement Technology (CET) is a set of features in >>>> + hardware designed to combat Return-oriented Programming (ROP, also >>>> + call/jump COP/JOP) attacks. Indirect Branch Tracking is one CET >>>> + feature designed to provide function pointer protection. >>>> + >>>> + This option arranges for Xen to use CET-IBT for its own protection. >>> Shouldn't this depend on BROKEN until it's actually functional? >> It compiles fine right from now, and making it BROKEN would inhibit >> bisection through the series. >> >> Nothing actually matters until patch 65 turns on MSR_S_CET.ENDBR_EN. > "Nothing" except that until then the promised extra security isn't > there. The series is very likely to be committed in one fell swoop, but even that aside, it really doesn't matter until 4.17-rc1 As it stands, this is ~65 patches of incremental changes to the binary, and oughtn't to be 65 nops and a massive switch at the end. ~Andrew