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,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 11E1BC433E0 for ; Wed, 5 Aug 2020 09:25:45 +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 D22BA20792 for ; Wed, 5 Aug 2020 09:25:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="DQovJdOv" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D22BA20792 Authentication-Results: mail.kernel.org; dmarc=none (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:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=wysaPg/lf/BOdEQThkPkFpjhWNwjEGMbMYd6RRPQ0Z8=; b=DQovJdOvamMYndFqeKJ9yVYEM L+GMyxscKergQwwKapNB8MFC6aELyG3zLt+gyiD8rSmck1JWFVCHl/d+yPJwInFDPBIUfB+t81N81 dlsyc4aGPqp2igg7bRzIeVXI1/yndS67mUC5737jTmrNXeSZpG2lddCdFPoTXufNc+eJ5n4SR6+Gt bsqFdpi4rJNUmVekQ2i5Ey1gL1LlSrOME56lNFeUQRqwb3jnxb+5TrmZmZofWblc/ryisrdNz/tG3 1jqkKfSzFFrTnMf8TmUzz2VoZzzOUnm8CTi44KypUm8Epo4QeyR7CnpAi1ka2xEa0fT4GEaKOwZZ6 oDLf0azVA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1k3Fes-0000MW-LY; Wed, 05 Aug 2020 09:24:26 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k3Fep-0000LZ-Ml for linux-arm-kernel@lists.infradead.org; Wed, 05 Aug 2020 09:24:24 +0000 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 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-Disposition: inline In-Reply-To: <9342a080-9450-c01a-54a0-9ddebfe45613@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200805_052423_845949_652DA1E6 X-CRM114-Status: GOOD ( 19.68 ) 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: linux-arch@vger.kernel.org, Szabolcs Nagy , Andrey Konovalov , Peter Collingbourne , linux-mm@kvack.org, Andrew Morton , Vincenzo Frascino , Will Deacon , Dave P Martin , linux-arm-kernel@lists.infradead.org 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 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel