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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 7210DC433E0 for ; Mon, 21 Dec 2020 16:44:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2F22E22C9C for ; Mon, 21 Dec 2020 16:44:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725850AbgLUQoG convert rfc822-to-8bit (ORCPT ); Mon, 21 Dec 2020 11:44:06 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.86.151]:54377 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725777AbgLUQoF (ORCPT ); Mon, 21 Dec 2020 11:44:05 -0500 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mtapsc-5-b9x0mQY4PWebkGD87-Qp8A-1; Mon, 21 Dec 2020 16:42:26 +0000 X-MC-Unique: b9x0mQY4PWebkGD87-Qp8A-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 21 Dec 2020 16:42:23 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 21 Dec 2020 16:42:23 +0000 From: David Laight To: 'Segher Boessenkool' , Christophe Leroy CC: Xiaoming Ni , "ravi.bangoria@linux.ibm.com" , "mikey@neuling.org" , "yanaijie@huawei.com" , "haren@linux.ibm.com" , "linux-kernel@vger.kernel.org" , "npiggin@gmail.com" , "wangle6@huawei.com" , "paulus@samba.org" , "aneesh.kumar@linux.ibm.com" , "linuxppc-dev@lists.ozlabs.org" Subject: RE: [PATCH] powerpc:Don't print raw EIP/LR hex values in dump_stack() and show_regs() Thread-Topic: [PATCH] powerpc:Don't print raw EIP/LR hex values in dump_stack() and show_regs() Thread-Index: AQHW17dukx+1atuJ10yi7rVw0MWNE6oBwFGw Date: Mon, 21 Dec 2020 16:42:23 +0000 Message-ID: References: <20201221032758.12143-1-nixiaoming@huawei.com> <2279fc96-1f10-0c3f-64d9-734f18758620@csgroup.eu> <20201221163130.GZ2672@gate.crashing.org> In-Reply-To: <20201221163130.GZ2672@gate.crashing.org> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Segher Boessenkool > Sent: 21 December 2020 16:32 > > On Mon, Dec 21, 2020 at 04:17:21PM +0100, Christophe Leroy wrote: > > Le 21/12/2020 à 04:27, Xiaoming Ni a écrit : > > >Since the commit 2b0e86cc5de6 ("powerpc/fsl_booke/32: implement KASLR > > >infrastructure"), the powerpc system is ready to support KASLR. > > >To reduces the risk of invalidating address randomization, don't print the > > >EIP/LR hex values in dump_stack() and show_regs(). > > > I think your change is not enough to hide EIP address, see below a dump > > with you patch, you get "Faulting instruction address: 0xc03a0c14" > > As far as I can see the patch does nothing to the GPR printout. Often > GPRs contain code addresses. As one example, the LR is moved via a GPR > (often GPR0, but not always) for storing on the stack. > > So this needs more work. If the dump_stack() is from an oops you need the real EIP value on order to stand any chance of making headway. Otherwise you might just as well just print 'borked - tough luck'. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)