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=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 17AEEC433E0 for ; Fri, 26 Jun 2020 13:14:49 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id E61CA2080C for ; Fri, 26 Jun 2020 13:14:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E61CA2080C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jooBh-0001lE-VC; Fri, 26 Jun 2020 13:14:37 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1jooBg-0001l6-HX for xen-devel@lists.xenproject.org; Fri, 26 Jun 2020 13:14:36 +0000 X-Inumbo-ID: fb163750-b7ae-11ea-82bb-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id fb163750-b7ae-11ea-82bb-12813bfff9fa; Fri, 26 Jun 2020 13:14:35 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id AC611AC85; Fri, 26 Jun 2020 13:14:34 +0000 (UTC) Subject: Re: [PATCH v2 for-4.14] x86/livepatch: Make livepatching compatible with CET Shadow Stacks To: Andrew Cooper References: <20200626122408.19151-1-andrew.cooper3@citrix.com> From: Jan Beulich Message-ID: Date: Fri, 26 Jun 2020 15:14:36 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200626122408.19151-1-andrew.cooper3@citrix.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Wei Liu , Konrad Rzeszutek Wilk , Ross Lagerwall , Paul Durrant , Pawel Wieczorkiewicz , Xen-devel , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 26.06.2020 14:24, Andrew Cooper wrote: > Just like the alternatives infrastructure, the livepatch infrastructure > disables CR0.WP to perform patching, which is not permitted with CET active. > > Modify arch_livepatch_{quiesce,revive}() to disable CET before disabling WP, > and reset the dirty bits on all virtual regions before re-enabling CET. > > One complication is that arch_livepatch_revive() has to fix up the top of the > shadow stack. This depends on the functions not being inlined, even under > LTO. Another limitation is that reset_virtual_region_perms() may shatter the > final superpage of .text depending on alignment. > > This logic, and its downsides, are temporary until the patching infrastructure > can be adjusted to not use CR0.WP. In particular on this basis ... > Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich Jan