From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by sourceware.org (Postfix) with ESMTPS id 26B50385040C for ; Fri, 18 Sep 2020 08:30:55 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 26B50385040C Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 15F0920789; Fri, 18 Sep 2020 08:30:51 +0000 (UTC) Date: Fri, 18 Sep 2020 09:30:48 +0100 From: Will Deacon To: Dave Martin Cc: Catalin Marinas , 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: <20200918083046.GA30709@willie-the-truck> References: <20200904103029.32083-1-catalin.marinas@arm.com> <20200904103029.32083-30-catalin.marinas@arm.com> <20200917081107.GA29031@willie-the-truck> <20200917090229.GA10662@gaia> <20200917161550.GA6642@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200917161550.GA6642@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Spam-Status: No, score=-8.1 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 18 Sep 2020 08:30:56 -0000 On Thu, Sep 17, 2020 at 05:15:53PM +0100, Dave Martin wrote: > 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? I think so, yes. I'm hoping to queue it for 5.10, once I have an Ack from the Android tools side on the per-thread ABI. Will