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, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 8B5F9C43441 for ; Wed, 14 Nov 2018 18:11:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5848022419 for ; Wed, 14 Nov 2018 18:11:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5848022419 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731394AbeKOEP7 (ORCPT ); Wed, 14 Nov 2018 23:15:59 -0500 Received: from foss.arm.com ([217.140.101.70]:49118 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727576AbeKOEP6 (ORCPT ); Wed, 14 Nov 2018 23:15:58 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 875A4A78; Wed, 14 Nov 2018 10:11:43 -0800 (PST) Received: from brain-police (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B85593F718; Wed, 14 Nov 2018 10:11:40 -0800 (PST) Date: Wed, 14 Nov 2018 18:11:39 +0000 From: Will Deacon To: Catalin Marinas Cc: Kristina Martsenko , linux-arm-kernel@lists.infradead.org, Mark Rutland , linux-arch@vger.kernel.org, Andrew Jones , Jacob Bramley , Arnd Bergmann , Ard Biesheuvel , Marc Zyngier , Adam Wallis , "Suzuki K . Poulose" , Christoffer Dall , kvmarm@lists.cs.columbia.edu, Ramana Radhakrishnan , Amit Kachhap , Dave P Martin , linux-kernel@vger.kernel.org, Kees Cook , gorcunov@openvz.org Subject: Re: [PATCH v5 07/17] arm64: add basic pointer authentication support Message-ID: <20181114181138.GB2580@brain-police> References: <20181005084754.20950-1-kristina.martsenko@arm.com> <20181005084754.20950-8-kristina.martsenko@arm.com> <20181019111542.6wrvjguirglzg7vg@mbp> <20181019112404.GD14246@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181019112404.GD14246@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, On Fri, Oct 19, 2018 at 12:24:04PM +0100, Will Deacon wrote: > On Fri, Oct 19, 2018 at 12:15:43PM +0100, Catalin Marinas wrote: > > On Fri, Oct 05, 2018 at 09:47:44AM +0100, Kristina Martsenko wrote: > > > diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h > > > new file mode 100644 > > > index 000000000000..2aefedc31d9e > > > --- /dev/null > > > +++ b/arch/arm64/include/asm/pointer_auth.h > > > @@ -0,0 +1,63 @@ > > > +// SPDX-License-Identifier: GPL-2.0 > > > +#ifndef __ASM_POINTER_AUTH_H > > > +#define __ASM_POINTER_AUTH_H > > > + > > > +#include > > > + > > > +#include > > > +#include > > > + > > > +#ifdef CONFIG_ARM64_PTR_AUTH > > > +/* > > > + * Each key is a 128-bit quantity which is split across a pair of 64-bit > > > + * registers (Lo and Hi). > > > + */ > > > +struct ptrauth_key { > > > + unsigned long lo, hi; > > > +}; > > > + > > > +/* > > > + * We give each process its own instruction A key (APIAKey), which is shared by > > > + * all threads. This is inherited upon fork(), and reinitialised upon exec*(). > > > + * All other keys are currently unused, with APIBKey, APDAKey, and APBAKey > > > + * instructions behaving as NOPs. > > > + */ > > > > I don't remember the past discussions but I assume the tools guys are ok > > with a single key shared by multiple threads. Ramana, could you ack this > > part, FTR? > > > > (and it would help if someone from the Android and Chrome camps can > > confirm) > > FWIW: I think we should be entertaining a prctl() interface to use a new > key on a per-thread basis. Obviously, this would need to be used with care > (e.g. you'd fork(); use the prctl() and then you'd better not return from > the calling function!). > > Assuming we want this (Kees -- I was under the impression that everything in > Android would end up with the same key otherwise?), then the question is > do we want: > > - prctl() get/set operations for the key, or > - prctl() set_random_key operation, or > - both of the above? > > Part of the answer to that may lie in the requirements of CRIU, where I > strongly suspect they need explicit get/set operations, although these > could be gated on CONFIG_CHECKPOINT_RESTORE=y. I managed to speak to the CRIU developers at LPC. The good news is that their preference is for a ptrace()-based interface for getting and setting the keys, so the only prctl() operation we need is to set a random key (separately for A and B). Will