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 0F245C282C2 for ; Wed, 13 Feb 2019 17:32:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D2BD120838 for ; Wed, 13 Feb 2019 17:32:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393073AbfBMRcl (ORCPT ); Wed, 13 Feb 2019 12:32:41 -0500 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:57814 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390079AbfBMRcl (ORCPT ); Wed, 13 Feb 2019 12:32:41 -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 9E10DA78; Wed, 13 Feb 2019 09:32:40 -0800 (PST) Received: from [10.1.197.21] (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D81F63F675; Wed, 13 Feb 2019 09:32:38 -0800 (PST) From: Kristina Martsenko Subject: Re: [PATCH v5 1/5] arm64: Add utilities to save restore pointer authentication keys To: James Morse , Amit Daniel Kachhap Cc: linux-arm-kernel@lists.infradead.org, Marc Zyngier , Catalin Marinas , Will Deacon , 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> <88ccd568-f027-6cdf-b4f1-6709d76102c1@arm.com> Message-ID: Date: Wed, 13 Feb 2019 17:32:37 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <88ccd568-f027-6cdf-b4f1-6709d76102c1@arm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 31/01/2019 16:20, James Morse wrote: > 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?) Yes, I don't think this should be in this series, since we're not building the kernel with pointer auth yet. > > ('noptrauth' would fit with 'notrace' slightly better) (But worse with e.g. __noreturn, __notrace_funcgraph, __init, __always_inline, __exception. Not sure what the pattern is. Would __noptrauth be better?) Thanks, Kristina > > [0] > https://gcc.gnu.org/onlinedocs/gcc/AArch64-Function-Attributes.html#AArch64-Function-Attributes >