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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 14F7AC169C4 for ; Thu, 31 Jan 2019 16:20:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D5FEC218D3 for ; Thu, 31 Jan 2019 16:20:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388370AbfAaQUI (ORCPT ); Thu, 31 Jan 2019 11:20:08 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:47186 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731284AbfAaQUH (ORCPT ); Thu, 31 Jan 2019 11:20:07 -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 54929EBD; Thu, 31 Jan 2019 08:20:07 -0800 (PST) Received: from [10.1.196.105] (eglon.cambridge.arm.com [10.1.196.105]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AB2943F557; Thu, 31 Jan 2019 08:20:05 -0800 (PST) Subject: Re: [PATCH v5 1/5] arm64: Add utilities to save restore pointer authentication keys To: Amit Daniel Kachhap Cc: linux-arm-kernel@lists.infradead.org, Marc Zyngier , Catalin Marinas , Will Deacon , Kristina Martsenko , kvmarm@lists.cs.columbia.edu, Ramana Radhakrishnan , Dave Martin , linux-kernel@vger.kernel.org References: <1548658727-14271-1-git-send-email-amit.kachhap@arm.com> <1548658727-14271-2-git-send-email-amit.kachhap@arm.com> From: James Morse Message-ID: <88ccd568-f027-6cdf-b4f1-6709d76102c1@arm.com> Date: Thu, 31 Jan 2019 16:20:03 +0000 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <1548658727-14271-2-git-send-email-amit.kachhap@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Amit, On 28/01/2019 06:58, Amit Daniel Kachhap wrote: > The keys can be switched either inside an assembly or such > functions which do not have pointer authentication checks, so a GCC > attribute is added to enable it. > > A function ptrauth_keys_store is added which is similar to existing > function ptrauth_keys_switch but saves the key values in memory. > This may be useful for save/restore scenarios when CPU changes > privilege levels, suspend/resume etc. > diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h > index 15d4951..98441ce 100644 > --- a/arch/arm64/include/asm/pointer_auth.h > +++ b/arch/arm64/include/asm/pointer_auth.h > @@ -11,6 +11,13 @@ > > #ifdef CONFIG_ARM64_PTR_AUTH > /* > + * Compile the function without pointer authentication instructions. This > + * allows pointer authentication to be enabled/disabled within the function > + * (but leaves the function unprotected by pointer authentication). > + */ > +#define __no_ptrauth __attribute__((target("sign-return-address=none"))) The documentation[0] for this says 'none' is the default. Will this only take-effect once the kernel supports pointer-auth for the host? (Is this just documentation until then?) ('noptrauth' would fit with 'notrace' slightly better) Thanks, James [0] https://gcc.gnu.org/onlinedocs/gcc/AArch64-Function-Attributes.html#AArch64-Function-Attributes