From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH v5 07/17] arm64: add basic pointer authentication support Date: Fri, 19 Oct 2018 12:24:04 +0100 Message-ID: <20181019112404.GD14246@arm.com> References: <20181005084754.20950-1-kristina.martsenko@arm.com> <20181005084754.20950-8-kristina.martsenko@arm.com> <20181019111542.6wrvjguirglzg7vg@mbp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20181019111542.6wrvjguirglzg7vg@mbp> Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: linux-arch.vger.kernel.org [+Cyrill Gorcunov for CRIU stuff] 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. Will From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from foss.arm.com ([217.140.101.70]:50704 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726609AbeJST3k (ORCPT ); Fri, 19 Oct 2018 15:29:40 -0400 Date: Fri, 19 Oct 2018 12:24:04 +0100 From: Will Deacon Subject: Re: [PATCH v5 07/17] arm64: add basic pointer authentication support Message-ID: <20181019112404.GD14246@arm.com> References: <20181005084754.20950-1-kristina.martsenko@arm.com> <20181005084754.20950-8-kristina.martsenko@arm.com> <20181019111542.6wrvjguirglzg7vg@mbp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181019111542.6wrvjguirglzg7vg@mbp> Sender: linux-arch-owner@vger.kernel.org List-ID: 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 Message-ID: <20181019112404.w9gAudQ2Vx38-wBrduQDOjuSAAVvflPRNe_KkoL1UNs@z> [+Cyrill Gorcunov for CRIU stuff] 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. Will