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=-2.3 required=3.0 tests=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 0935CC433E0 for ; Tue, 19 May 2020 16:11:08 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 CEBA52075F for ; Tue, 19 May 2020 16:11:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="DYd0BU0j" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CEBA52075F 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+infradead-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=bombadil.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=+4EEG+eDROOLaVZWgivVrgsZ7xAwWLndhZ5kddAb7Ww=; b=DYd0BU0jlF8Ef+ mIwgXP/zrMMgsmSaE8XvS1VCikyA6CBhNTqQX1ds37Chwv9NzvqClgxo03utHxP+J5NKaT8IiIKe0 vuuSTaR9HmNcsyZPCWabqQ0ZLJ6uFGbjrM3jD2vwejBanJblh01LH6pWlZn4FWNKN0VwINvxtIt2k AucKQ2ZxwM7FHkcdFNYwTx63A3pcAx9e3ClM5eeNcTMtMHwwuO6a+QMIROrH8lZtP4sekNUvjhAYV +q/tu72JfqPvn/DC/dclg/e+fuG8wNlTV/6tGRSgwmagsyzg71wEoLBV1CJxtD6eFQYLrDwJkL7br CG7X3Ks9HMm5DIi/3YpA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jb4pf-0007KH-Gv; Tue, 19 May 2020 16:11:07 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jb4pb-0007Fa-Eq for linux-arm-kernel@lists.infradead.org; Tue, 19 May 2020 16:11:05 +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 6BCB830E; Tue, 19 May 2020 09:11:02 -0700 (PDT) Received: from gaia (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 60C603F305; Tue, 19 May 2020 09:11:00 -0700 (PDT) Date: Tue, 19 May 2020 17:10:58 +0100 From: Catalin Marinas To: Luis Machado Subject: Re: [PATCH v3 19/23] arm64: mte: Add PTRACE_{PEEK,POKE}MTETAGS support Message-ID: <20200519161057.GE20313@gaia> References: <20200421142603.3894-1-catalin.marinas@arm.com> <20200421142603.3894-20-catalin.marinas@arm.com> <20200513104849.GC2719@gaia> <3d2621ac-9d08-53ea-6c22-c62532911377@linaro.org> <20200513141147.GD2719@gaia> <20200518164723.GA5031@arm.com> <55fe4d37-23ae-a6b7-8db1-884aaf4a9b9c@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <55fe4d37-23ae-a6b7-8db1-884aaf4a9b9c@linaro.org> 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-20200519_091103_550044_7FAAC918 X-CRM114-Status: GOOD ( 16.08 ) 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, Richard Earnshaw , Omair Javaid , Szabolcs Nagy , Andrey Konovalov , Kevin Brodsky , Peter Collingbourne , linux-mm@kvack.org, Alan Hayward , Vincenzo Frascino , Will Deacon , Dave 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+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, May 18, 2020 at 02:12:24PM -0300, Luis Machado wrote: > On 5/18/20 1:47 PM, Dave Martin wrote: > > Wrinkle: just because MTE is "off", pages might still be mapped with > > PROT_MTE and have arbitrary tags set on them, and the debugger perhaps > > needs a way to know that. Currently grubbing around in /proc is the > > only way to discover that. Dunno whether it matters. > > That is the sort of thing that may confused the debugger. > > If MTE is "off" (and thus the debugger doesn't need to validate tags), then > the pages mapped with PROT_MTE that show up in /proc//smaps should be > ignored? There is no such thing as global MTE "off". If the HWCAP is present, a user program can map an address with PROT_MTE and access tags. Maybe it uses it for extra storage, you never know, doesn't have to be heap allocation related. > I'm looking for a precise way to tell if MTE is being used or not for a > particular process/thread. This, in turn, will tell debuggers when to look > for PROT_MTE mappings in /proc//smaps and when to validate tagged > addresses. > > So far my assumption was that MTE will always be "on" when HWCAP2_MTE is > present. So having HWCAP2_MTE means we have the NT_ARM_MTE regset and that > PROT_MTE pages have to be checked. Yes. I haven't figured out what to put in the regset yet, most likely the prctl value as it has other software-only controls like the tagged address ABI. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel