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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 20339C433E0 for ; Wed, 5 Aug 2020 09:24:26 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id DE67F22CA0 for ; Wed, 5 Aug 2020 09:24:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DE67F22CA0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 61A3A6B0002; Wed, 5 Aug 2020 05:24:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5C87C6B0005; Wed, 5 Aug 2020 05:24:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 4DE056B0006; Wed, 5 Aug 2020 05:24:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0181.hostedemail.com [216.40.44.181]) by kanga.kvack.org (Postfix) with ESMTP id 364CB6B0002 for ; Wed, 5 Aug 2020 05:24:25 -0400 (EDT) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B27D28248047 for ; Wed, 5 Aug 2020 09:24:24 +0000 (UTC) X-FDA: 77115979248.19.chain75_3a13dfc26fad Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin19.hostedemail.com (Postfix) with ESMTP id 7ECAC1AD1B5 for ; Wed, 5 Aug 2020 09:24:24 +0000 (UTC) X-HE-Tag: chain75_3a13dfc26fad X-Filterd-Recvd-Size: 2758 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf06.hostedemail.com (Postfix) with ESMTP for ; Wed, 5 Aug 2020 09:24:24 +0000 (UTC) Received: from gaia (unknown [95.146.230.158]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 045B122B40; Wed, 5 Aug 2020 09:24:20 +0000 (UTC) Date: Wed, 5 Aug 2020 10:24:18 +0100 From: Catalin Marinas To: Kevin Brodsky Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, Will Deacon , Dave P Martin , Vincenzo Frascino , Szabolcs Nagy , Andrey Konovalov , Peter Collingbourne , Andrew Morton Subject: Re: [PATCH v7 18/29] arm64: mte: Allow user control of the tag check mode via prctl() Message-ID: <20200805092418.GB13391@gaia> References: <20200715170844.30064-1-catalin.marinas@arm.com> <20200715170844.30064-19-catalin.marinas@arm.com> <9342a080-9450-c01a-54a0-9ddebfe45613@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9342a080-9450-c01a-54a0-9ddebfe45613@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: 7ECAC1AD1B5 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Aug 04, 2020 at 08:34:42PM +0100, Kevin Brodsky wrote: > On 15/07/2020 18:08, Catalin Marinas wrote: > > By default, even if PROT_MTE is set on a memory range, there is no tag > > check fault reporting (SIGSEGV). Introduce a set of option to the > > exiting prctl(PR_SET_TAGGED_ADDR_CTRL) to allow user control of the tag > > check fault mode: > > > > PR_MTE_TCF_NONE - no reporting (default) > > PR_MTE_TCF_SYNC - synchronous tag check fault reporting > > PR_MTE_TCF_ASYNC - asynchronous tag check fault reporting > > > > These options translate into the corresponding SCTLR_EL1.TCF0 bitfield, > > context-switched by the kernel. Note that uaccess done by the kernel is > > not checked and cannot be configured by the user. > > The last sentence is outdated, it should probably say that uaccess is only > checked in in synchronous mode. Thanks, I forgot about the commit log. The documentation was updated to: **Note**: Kernel accesses to the user address space (e.g. ``read()`` system call) are not checked if the user thread tag checking mode is ``PR_MTE_TCF_NONE`` or ``PR_MTE_TCF_ASYNC``. If the tag checking mode is ``PR_MTE_TCF_SYNC``, the kernel makes a best effort to check its user address accesses, however it cannot always guarantee it. -- Catalin