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=-5.2 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 D7365C2D0FC for ; Wed, 13 May 2020 14:13:44 +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 8919E204EF for ; Wed, 13 May 2020 14:13:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8919E204EF 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 1jYs8a-00010E-LM; Wed, 13 May 2020 14:13:32 +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 1jYs8a-000109-0p for xen-devel@lists.xenproject.org; Wed, 13 May 2020 14:13:32 +0000 X-Inumbo-ID: ebeec59c-9523-11ea-a384-12813bfff9fa Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id ebeec59c-9523-11ea-a384-12813bfff9fa; Wed, 13 May 2020 14:13:30 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 4B8B4AC90; Wed, 13 May 2020 14:13:32 +0000 (UTC) Subject: Re: [PATCH] x86/build: Unilaterally disable -fcf-protection To: Andrew Cooper References: <20200513135552.24329-1-andrew.cooper3@citrix.com> <20200513135552.24329-3-andrew.cooper3@citrix.com> From: Jan Beulich Message-ID: Date: Wed, 13 May 2020 16:13:28 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200513135552.24329-3-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: Xen-devel , Jason Andryuk , Stefan Bader , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 13.05.2020 15:55, Andrew Cooper wrote: > Xen doesn't support CET-IBT yet. At a minimum, logic is required to enable it > for supervisor use, but the livepatch functionality needs to learn not to > overwrite ENDBR64 instructions. > > Furthermore, Ubuntu enables -fcf-protection by default, along with a buggy > version of GCC-9 which objects to it in combination with > -mindirect-branch=thunk-extern (Fixed in GCC 10, 9.4). > > Various objects (Xen boot path, Rombios 32 stubs) require .text to be at the > beginning of the object. These paths explode when .note.gnu.properties gets > put ahead of .text and we end up executing the notes data. > > Disable -fcf-protection for all embedded objects. > > Reported-by: Jason Andryuk > Signed-off-by: Andrew Cooper For the immediate purpose Reviewed-by: Jan Beulich I wonder however ... > --- a/Config.mk > +++ b/Config.mk > @@ -205,6 +205,7 @@ APPEND_CFLAGS += $(foreach i, $(APPEND_INCLUDES), -I$(i)) > > EMBEDDED_EXTRA_CFLAGS := -nopie -fno-stack-protector -fno-stack-protector-all > EMBEDDED_EXTRA_CFLAGS += -fno-exceptions -fno-asynchronous-unwind-tables > +EMBEDDED_EXTRA_CFLAGS += -fcf-protection=none ... whether this isn't going to bite us once some of the consumers of this variable want to enable some different mode. Jan