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=-8.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 75AB3C433DF for ; Thu, 8 Oct 2020 18:21:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 224D322203 for ; Thu, 8 Oct 2020 18:21:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728268AbgJHSVg (ORCPT ); Thu, 8 Oct 2020 14:21:36 -0400 Received: from foss.arm.com ([217.140.110.172]:42906 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725616AbgJHSVg (ORCPT ); Thu, 8 Oct 2020 14:21:36 -0400 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 91CC4D6E; Thu, 8 Oct 2020 11:21:35 -0700 (PDT) Received: from [10.37.12.22] (unknown [10.37.12.22]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2D4F63F802; Thu, 8 Oct 2020 11:21:31 -0700 (PDT) Subject: Re: [PATCH v4 29/39] arm64: mte: Switch GCR_EL1 in kernel entry and exit To: Catalin Marinas , Andrey Konovalov Cc: Dmitry Vyukov , kasan-dev@googlegroups.com, Andrey Ryabinin , Alexander Potapenko , Marco Elver , Evgenii Stepanov , Elena Petrova , Branislav Rankov , Kevin Brodsky , Will Deacon , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1f2681fdff1aa1096df949cb8634a9be6bf4acc4.1601593784.git.andreyknvl@google.com> <20201002140652.GG7034@gaia> From: Vincenzo Frascino Message-ID: <1b2327ee-5f30-e412-7359-32a7a38b4c8d@arm.com> Date: Thu, 8 Oct 2020 19:24:12 +0100 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: <20201002140652.GG7034@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 Hi Catalin, On 10/2/20 3:06 PM, Catalin Marinas wrote: > On Fri, Oct 02, 2020 at 01:10:30AM +0200, Andrey Konovalov wrote: >> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c >> index 7c67ac6f08df..d1847f29f59b 100644 >> --- a/arch/arm64/kernel/mte.c >> +++ b/arch/arm64/kernel/mte.c >> @@ -23,6 +23,8 @@ >> #include >> #include >> >> +u64 gcr_kernel_excl __ro_after_init; >> + >> static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap) >> { >> pte_t old_pte = READ_ONCE(*ptep); >> @@ -120,6 +122,13 @@ void *mte_set_mem_tag_range(void *addr, size_t size, u8 tag) >> return ptr; >> } >> >> +void mte_init_tags(u64 max_tag) >> +{ >> + u64 incl = GENMASK(max_tag & MTE_TAG_MAX, 0); > > Nitpick: it's not obvious that MTE_TAG_MAX is a mask, so better write > this as GENMASK(min(max_tag, MTE_TAG_MAX), 0). > The two things do not seem equivalent because the format of the tags in KASAN is 0xFF and in MTE is 0xF, hence if extract the minimum whatever is the tag passed by KASAN it will always be MTE_TAG_MAX. To make it cleaner I propose: GENMASK(FIELD_GET(MTE_TAG_MAX, max_tag), 0); > Otherwise it looks fine. > > Reviewed-by: Catalin Marinas > -- Regards, Vincenzo