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=-8.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 D4E0DC43461 for ; Thu, 17 Sep 2020 16:26:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A1A6A20795 for ; Thu, 17 Sep 2020 16:26:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728302AbgIQQ0B (ORCPT ); Thu, 17 Sep 2020 12:26:01 -0400 Received: from foss.arm.com ([217.140.110.172]:48810 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728496AbgIQQZZ (ORCPT ); Thu, 17 Sep 2020 12:25:25 -0400 X-Greylist: delayed 561 seconds by postgrey-1.27 at vger.kernel.org; Thu, 17 Sep 2020 12:25:25 EDT 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 76B0D11D4; Thu, 17 Sep 2020 09:15:57 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AAA243F68F; Thu, 17 Sep 2020 09:15:55 -0700 (PDT) Date: Thu, 17 Sep 2020 17:15:53 +0100 From: Dave Martin To: Catalin Marinas Cc: Will Deacon , linux-arch@vger.kernel.org, libc-alpha@sourceware.org, Szabolcs Nagy , Andrey Konovalov , Kevin Brodsky , linux-mm@kvack.org, Andrew Morton , Vincenzo Frascino , Peter Collingbourne , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v9 29/29] arm64: mte: Add Memory Tagging Extension documentation Message-ID: <20200917161550.GA6642@arm.com> References: <20200904103029.32083-1-catalin.marinas@arm.com> <20200904103029.32083-30-catalin.marinas@arm.com> <20200917081107.GA29031@willie-the-truck> <20200917090229.GA10662@gaia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200917090229.GA10662@gaia> User-Agent: Mutt/1.5.23 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Thu, Sep 17, 2020 at 10:02:30AM +0100, Catalin Marinas wrote: > On Thu, Sep 17, 2020 at 09:11:08AM +0100, Will Deacon wrote: > > On Fri, Sep 04, 2020 at 11:30:29AM +0100, Catalin Marinas wrote: > > > From: Vincenzo Frascino > > > > > > Memory Tagging Extension (part of the ARMv8.5 Extensions) provides > > > a mechanism to detect the sources of memory related errors which > > > may be vulnerable to exploitation, including bounds violations, > > > use-after-free, use-after-return, use-out-of-scope and use before > > > initialization errors. > > > > > > Add Memory Tagging Extension documentation for the arm64 linux > > > kernel support. > > > > > > Signed-off-by: Vincenzo Frascino > > > Co-developed-by: Catalin Marinas > > > Signed-off-by: Catalin Marinas > > > Acked-by: Szabolcs Nagy > > > > I'm taking this to mean that Szabolcs is happy with the proposed ABI -- > > please shout if that's not the case! > > I think Szabolcs is still on holiday. To summarise the past threads, > AFAICT he's happy with this per-thread control ABI but the discussion > went on whether to expand it in the future (with a new bit) to > synchronise the tag checking mode across all threads of a process. This > adds some complications for the kernel as it needs an IPI to the other > CPUs to set SCTLR_EL1 and it's also racy with multiple threads > requesting different modes. > > Now, in the glibc land, if the tag check mode is controlled via > environment variables, the dynamic loader can set this at process start > while still in single-threaded mode and not touch it at run-time. The > MTE checking can still be enabled at run-time, per mapped memory range > via the PROT_MTE flag. This approach doesn't require any additional > changes to the current patches. But it's for Szabolcs to confirm once > he's back. > > > Wasn't there a man page kicking around too? Would be good to see that > > go upstream (to the manpages project, of course). > > Dave started writing one for the tagged address ABI, not sure where that > is. For the MTE additions, we are waiting for the ABI to be upstreamed. The tagged address ABI control stuff is upstream in the man-pages-5.08 release. I don't think anyone drafted anything for MTE yet. Do we consider the MTE ABI to be sufficiently stable now for it to be worth starting drafting something? Cheers ---Dave