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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 B4870C10F11 for ; Wed, 10 Apr 2019 15:52:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8CF3520830 for ; Wed, 10 Apr 2019 15:52:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729958AbfDJPwx (ORCPT ); Wed, 10 Apr 2019 11:52:53 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:34544 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727340AbfDJPww (ORCPT ); Wed, 10 Apr 2019 11:52:52 -0400 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x3AFowHF032713 for ; Wed, 10 Apr 2019 11:52:51 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2rsjd3m1cj-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 10 Apr 2019 11:52:50 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 10 Apr 2019 16:52:45 +0100 Received: from d06av24.portsmouth.uk.ibm.com (d06av24.portsmouth.uk.ibm.com [9.149.105.60]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3AFqiro59572270 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 10 Apr 2019 15:52:44 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B7B574204C; Wed, 10 Apr 2019 15:52:44 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7F76642042; Wed, 10 Apr 2019 15:52:44 +0000 (GMT) Received: from mschwideX1 (unknown [9.152.212.148]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 10 Apr 2019 15:52:44 +0000 (GMT) Date: Wed, 10 Apr 2019 17:52:43 +0200 From: Martin Schwidefsky To: Mathieu Desnoyers Cc: heiko carstens , gor , libc-alpha , linux-kernel , carlos Subject: Re: rseq/s390: choosing code signature In-Reply-To: <514609006.3159.1554911439933.JavaMail.zimbra@efficios.com> References: <1779981820.2626.1554838342731.JavaMail.zimbra@efficios.com> <20190410123258.37f182cf@mschwideX1> <514609006.3159.1554911439933.JavaMail.zimbra@efficios.com> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 19041015-0008-0000-0000-000002D8649E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19041015-0009-0000-0000-00002244893B Message-Id: <20190410175243.6fc3d16a@mschwideX1> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-10_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904100110 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 10 Apr 2019 11:50:39 -0400 (EDT) Mathieu Desnoyers wrote: > ----- On Apr 10, 2019, at 6:32 AM, schwidefsky schwidefsky@de.ibm.com wrote: > > > On Tue, 9 Apr 2019 15:32:22 -0400 (EDT) > > Mathieu Desnoyers wrote: > > > >> Hi, > >> > >> We are about to include the code signature required prior to restartable > >> sequences abort handlers into glibc, which will make this ABI choice final. > >> We need architecture maintainer input on that signature value. > >> > >> That code signature is placed before each abort handler, so the kernel can > >> validate that it is indeed jumping to an abort handler (and not some > >> arbitrary attacker-chosen code). The signature is never executed. > >> > >> The current discussion thread on the glibc mailing list leads us towards > >> using a trap with uncommon immediate operand, which simplifies integration > >> with disassemblers, emulators, makes it easier to debug if the control > >> flow gets redirected there by mistake, and is nicer for some architecture's > >> speculative execution. > >> > >> We can have different signatures for each sub-architecture, as long as they > >> don't have to co-exist within the same process. We can special-case with > >> #ifdef for each sub-architecture and endianness if need be. If the architecture > >> has instruction set extensions that can co-exist with the architecture > >> instruction set within the same process, we need to take into account to which > >> instruction the chosen signature value would map (and possibly decide if we > >> need to extend rseq to support many signatures). > >> > >> Here is an example of rseq signature definition template: > >> > >> /* > >> * TODO: document trap instruction objdump output on each sub-architecture > >> * instruction sets, as well as instruction set extensions. > >> */ > >> #define RSEQ_SIG 0x######## > >> > >> Ideally we'd need a patch on top of the Linux kernel > >> tools/testing/selftests/rseq/rseq-s390.h file that updates > >> the signature value, so I can then pick it up for the glibc > >> patchset. > > > > The trap4 instruction is a suitable one. The patch would look like this > > Great! I'm picking it up into my rseq tree if that's OK with you. Just added the patch to s390/linux:features for the next merge window as well. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.