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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,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 0039BC433DB for ; Thu, 7 Jan 2021 17:28:44 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7B42E233CE for ; Thu, 7 Jan 2021 17:28:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7B42E233CE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=iY7ZLpvKBb7+MZJkjmm+wqBcP4IwUa5cFUkKEegbiyo=; b=GPvvw1IvxFrAQ3plgh+AlrAuj pGo5JZ35ZB0arwy8lVu23sQxVy36Az+TCfUK1AI45aZub61nIc7jvpTiFttvxWnRAskwXIPzJJ9XJ kNeDrK+5DKogXs/QkZLv+WrDhqc4oybtLzPxlxOc3Qs82dB5D3Mi2a3cLrERKGROR5+9mPbZcxM2j rUBpg7NEN5QX/VeW1J/1TEpIMpdEZjWVZ0AGy1DBlHdXqoMAEly4rf0gJ/g/8vE3aBondu2uUCTPq I7Ktosbm05GO8qZj0aNA3GUVtVElDUccJnQYEqzVIWJR6dUHa9GDQzdMkHZfhg+B5pOqMaDaogWr3 436+vgg5A==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kxZ2p-0004mF-3y; Thu, 07 Jan 2021 17:25:55 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kxZ2m-0004lj-HQ for linux-arm-kernel@lists.infradead.org; Thu, 07 Jan 2021 17:25:53 +0000 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 1A85B31B; Thu, 7 Jan 2021 09:25:47 -0800 (PST) Received: from [10.37.8.33] (unknown [10.37.8.33]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6166C3F719; Thu, 7 Jan 2021 09:25:44 -0800 (PST) Subject: Re: [PATCH 2/4] arm64: mte: Add asynchronous mode support To: Andrey Konovalov References: <20210106115519.32222-1-vincenzo.frascino@arm.com> <20210106115519.32222-3-vincenzo.frascino@arm.com> From: Vincenzo Frascino Message-ID: Date: Thu, 7 Jan 2021 17:29:24 +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: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210107_122552_832177_0A3BD0EC X-CRM114-Status: GOOD ( 25.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Branislav Rankov , Marco Elver , Catalin Marinas , Evgenii Stepanov , Will Deacon , LKML , kasan-dev , Alexander Potapenko , Linux ARM , Andrey Ryabinin , Dmitry Vyukov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Andrey, On 1/7/21 4:29 PM, Andrey Konovalov wrote: > On Wed, Jan 6, 2021 at 12:56 PM 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. >> >> Add support for MTE asynchronous mode. >> >> The exception handling mechanism will be added with a future patch. >> >> Note: KASAN HW activates async mode via kasan.mode kernel parameter. >> The default mode is set to synchronous. >> >> Cc: Catalin Marinas >> Cc: Will Deacon >> Signed-off-by: Vincenzo Frascino >> --- >> arch/arm64/kernel/mte.c | 31 +++++++++++++++++++++++++++++-- >> 1 file changed, 29 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c >> index 24a273d47df1..5d992e16b420 100644 >> --- 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; >> + } >> + >> + pr_info_once("MTE: enabled in %s mode at EL1\n", m); >> + >> isb(); >> } >> >> -- >> 2.29.2 >> > > Hi Vincenzo, > > It would be cleaner to pass a bool to mte_enable_kernel() and have it > indicate sync/async mode. This way you don't have to pull all these > KASAN constants into the arm64 code. > Boolean arguments are generally bad for legibility, hence I tend to avoid them. In this case exposing the constants does not seem a big issue especially because the only user of this code is "KASAN_HW_TAGS" and definitely improves its legibility hence I would prefer to keep it as is. > Thanks! > -- Regards, Vincenzo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel