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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 60EFEC43381 for ; Mon, 18 Jan 2021 13:02:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D83422571 for ; Mon, 18 Jan 2021 13:02:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391987AbhARNB0 (ORCPT ); Mon, 18 Jan 2021 08:01:26 -0500 Received: from mail.kernel.org ([198.145.29.99]:56386 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390479AbhARM6N (ORCPT ); Mon, 18 Jan 2021 07:58:13 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5710322B48; Mon, 18 Jan 2021 12:57:18 +0000 (UTC) Date: Mon, 18 Jan 2021 12:57:15 +0000 From: Catalin Marinas To: Vincenzo Frascino 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 Subject: Re: [PATCH v3 3/4] arm64: mte: Enable async tag check fault Message-ID: <20210118125715.GA4483@gaia> References: <20210115120043.50023-1-vincenzo.frascino@arm.com> <20210115120043.50023-4-vincenzo.frascino@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210115120043.50023-4-vincenzo.frascino@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 15, 2021 at 12:00:42PM +0000, Vincenzo Frascino wrote: > diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h > index d02aff9f493d..1a715963d909 100644 > --- a/arch/arm64/include/asm/mte.h > +++ b/arch/arm64/include/asm/mte.h > @@ -92,5 +92,26 @@ static inline void mte_assign_mem_tag_range(void *addr, size_t size) > > #endif /* CONFIG_ARM64_MTE */ > > +#ifdef CONFIG_KASAN_HW_TAGS > +void mte_check_tfsr_el1_no_sync(void); > +static inline void mte_check_tfsr_el1(void) > +{ > + mte_check_tfsr_el1_no_sync(); > + /* > + * The asynchronous faults are synch'ed automatically with > + * TFSR_EL1 on kernel entry but for exit an explicit dsb() > + * is required. > + */ > + dsb(ish); > +} Mark commented already, the barrier should be above mte_check_tfsr_el1_no_sync(). Regarding the ISB, we are waiting for confirmation from the architects. > diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c > index df7a1ae26d7c..6cb92e9d6ad1 100644 > --- a/arch/arm64/kernel/mte.c > +++ b/arch/arm64/kernel/mte.c > @@ -180,6 +180,32 @@ void mte_enable_kernel(enum kasan_hw_tags_mode mode) > isb(); > } > > +#ifdef CONFIG_KASAN_HW_TAGS > +void mte_check_tfsr_el1_no_sync(void) > +{ > + u64 tfsr_el1; > + > + if (!system_supports_mte()) > + return; > + > + tfsr_el1 = read_sysreg_s(SYS_TFSR_EL1); > + > + /* > + * The kernel should never hit the condition TF0 == 1 > + * at this point because for the futex code we set > + * PSTATE.TCO. > + */ > + WARN_ON(tfsr_el1 & SYS_TFSR_EL1_TF0); I'd change this to a WARN_ON_ONCE() in case we trip over this due to model bugs etc. and it floods the log. > + if (tfsr_el1 & SYS_TFSR_EL1_TF1) { > + write_sysreg_s(0, SYS_TFSR_EL1); > + isb(); While in general we use ISB after a sysreg update, I haven't convinced myself it's needed here. There's no side-effect to updating this reg and a subsequent TFSR access should see the new value. If a speculated load is allowed to update this reg, we'd probably need an ISB+DSB (I don't think it does, something to check with the architects). > + > + pr_err("MTE: Asynchronous tag exception detected!"); We discussed this already, I think we should replace this pr_err() with a call to kasan_report(). In principle, kasan already knows the mode as it asked for sync/async but we could make this explicit and expand the kasan API to take some argument (or have separate function like kasan_report_async()). -- Catalin