Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752158AbdFPWza (ORCPT ); Fri, 16 Jun 2017 18:55:30 -0400 Received: from gate.crashing.org ([63.228.1.57]:60530 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752026AbdFPWz3 (ORCPT ); Fri, 16 Jun 2017 18:55:29 -0400 Message-ID: <1497653684.2897.104.camel@kernel.crashing.org> Subject: Re: [RFC PATCH 7/7 v1]powerpc: Deliver SEGV signal on protection key violation. From: Benjamin Herrenschmidt To: Ram Pai Cc: Anshuman Khandual , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, dave.hansen@intel.com, paulus@samba.org, aneesh.kumar@linux.vnet.ibm.com Date: Sat, 17 Jun 2017 08:54:44 +1000 In-Reply-To: <20170616191537.GB17588@ram.oc3035372033.ibm.com> References: <1496711109-4968-1-git-send-email-linuxram@us.ibm.com> <1496711109-4968-8-git-send-email-linuxram@us.ibm.com> <622d7abf-3d99-8897-5afb-ef8c4f950fc0@linux.vnet.ibm.com> <1497609181.2897.100.camel@kernel.crashing.org> <20170616191537.GB17588@ram.oc3035372033.ibm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-2.fc25) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 530 Lines: 14 On Fri, 2017-06-16 at 12:15 -0700, Ram Pai wrote: > gp_regs size is not changed, nor is the layout. A unused field in > the gp_regs is used to fill in the AMR contents. Old binaries will not > be knowing about this unused field, and hence should not break. > > New binaries can leverage this already existing but newly defined > field; to read the contents of AMR. > > Is it still a concern? Calls to sys_swapcontext with a made-up context will end up with a crap AMR if done by code who didn't know about that register. Ben.