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=-10.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 6A4C8C433DB for ; Thu, 14 Jan 2021 09:40:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2534B23A21 for ; Thu, 14 Jan 2021 09:40:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728558AbhANJkR (ORCPT ); Thu, 14 Jan 2021 04:40:17 -0500 Received: from foss.arm.com ([217.140.110.172]:46660 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728538AbhANJkN (ORCPT ); Thu, 14 Jan 2021 04:40:13 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id AE12A1FB; Thu, 14 Jan 2021 01:39:35 -0800 (PST) Received: from [10.0.0.31] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1EC303F70D; Thu, 14 Jan 2021 01:39:32 -0800 (PST) Subject: Re: [PATCH v2 2/4] arm64: mte: Add asynchronous mode support To: Catalin Marinas Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Will Deacon , Dmitry Vyukov , Andrey Ryabinin , Alexander Potapenko , Marco Elver , Evgenii Stepanov , Branislav Rankov , Andrey Konovalov References: <20210107172908.42686-1-vincenzo.frascino@arm.com> <20210107172908.42686-3-vincenzo.frascino@arm.com> <20210113172228.GE27045@gaia> From: Vincenzo Frascino Message-ID: <16a57293-37fa-4526-e6cd-61f80b93e12a@arm.com> Date: Thu, 14 Jan 2021 09:43:19 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210113172228.GE27045@gaia> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/13/21 5:22 PM, Catalin Marinas wrote: > On Thu, Jan 07, 2021 at 05:29:06PM +0000, Vincenzo Frascino wrote: >> MTE provides an asynchronous mode for detecting tag exceptions. In >> particular instead of triggering a fault the arm64 core updates a >> register which is checked by the kernel at the first entry after the tag >> exception has occurred. > > Just rephrase the "tag exception" here as there's no exception taken. > Also we don't check this only when the kernel is first entered after a > tag check fault, as per patch 3. > Ok, I will clarify it in v3. >> --- a/arch/arm64/kernel/mte.c >> +++ b/arch/arm64/kernel/mte.c >> @@ -153,8 +153,35 @@ void mte_init_tags(u64 max_tag) >> >> void mte_enable_kernel(enum kasan_arg_mode mode) >> { >> - /* Enable MTE Sync Mode for EL1. */ >> - sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_SYNC); >> + const char *m; >> + >> + /* Preset parameter values based on the mode. */ >> + switch (mode) { >> + case KASAN_ARG_MODE_OFF: >> + return; >> + case KASAN_ARG_MODE_LIGHT: >> + /* Enable MTE Async Mode for EL1. */ >> + sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_ASYNC); >> + m = "asynchronous"; >> + break; >> + case KASAN_ARG_MODE_DEFAULT: >> + case KASAN_ARG_MODE_PROD: >> + case KASAN_ARG_MODE_FULL: >> + /* Enable MTE Sync Mode for EL1. */ >> + sysreg_clear_set(sctlr_el1, SCTLR_ELx_TCF_MASK, SCTLR_ELx_TCF_SYNC); >> + m = "synchronous"; >> + break; >> + default: >> + /* >> + * kasan mode should be always set hence we should >> + * not reach this condition. >> + */ >> + WARN_ON_ONCE(1); >> + return; >> + } > > I guess the switch statement here will be re-written as we want kasan to > drive the actual sync/async modes as it sees fit rather than MTE > guessing what PROD/FULL/LIGHT means. > Yes, this is correct, it will present only sync/async mode. -- Regards, Vincenzo