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=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 E94A3C3A5A2 for ; Fri, 23 Aug 2019 16:32:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id B966A22CEC for ; Fri, 23 Aug 2019 16:32:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B966A22CEC 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 41E376B04A9; Fri, 23 Aug 2019 12:32:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3CF476B04AB; Fri, 23 Aug 2019 12:32:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2E4A26B04AC; Fri, 23 Aug 2019 12:32:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0007.hostedemail.com [216.40.44.7]) by kanga.kvack.org (Postfix) with ESMTP id 07D646B04A9 for ; Fri, 23 Aug 2019 12:32:56 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id B12D882437D7 for ; Fri, 23 Aug 2019 16:32:56 +0000 (UTC) X-FDA: 75854236752.13.pull25_8dcb572fd0e55 X-HE-Tag: pull25_8dcb572fd0e55 X-Filterd-Recvd-Size: 3562 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf08.hostedemail.com (Postfix) with ESMTP for ; Fri, 23 Aug 2019 16:32:54 +0000 (UTC) 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 2435328; Fri, 23 Aug 2019 09:32:53 -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 7280E3F246; Fri, 23 Aug 2019 09:32:51 -0700 (PDT) Date: Fri, 23 Aug 2019 17:32:49 +0100 From: Dave Martin To: Catalin Marinas Cc: linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, Szabolcs Nagy , Andrey Konovalov , Kevin Brodsky , Will Deacon , linux-mm@kvack.org, Andrew Morton , Vincenzo Frascino , Will Deacon , Dave Hansen , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v9 3/3] arm64: Relax Documentation/arm64/tagged-pointers.rst Message-ID: <20190823163247.GG27757@arm.com> References: <20190821164730.47450-1-catalin.marinas@arm.com> <20190821164730.47450-4-catalin.marinas@arm.com> <20190821173352.yqfgaozi7nfhcofg@willie-the-truck> <20190821184649.GD27757@arm.com> <20190822155531.GB55798@arrakis.emea.arm.com> <20190822163723.GF27757@arm.com> <20190823161912.GJ29387@arrakis.emea.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190823161912.GJ29387@arrakis.emea.arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) 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 Fri, Aug 23, 2019 at 05:19:13PM +0100, Catalin Marinas wrote: > On Thu, Aug 22, 2019 at 05:37:23PM +0100, Dave P Martin wrote: > > On Thu, Aug 22, 2019 at 04:55:32PM +0100, Catalin Marinas wrote: > > > On Wed, Aug 21, 2019 at 07:46:51PM +0100, Dave P Martin wrote: [...] > > > > sigaltstack() is interesting, since we don't support tagged stacks. > > > > > > We should support tagged SP with the new ABI as they'll be required for > > > MTE. sigaltstack() and clone() are the two syscalls that come to mind > > > here. > > > > > > > Do we keep the ss_sp tag in the kernel, but squash it when delivering > > > > a signal to the alternate stack? > > > > > > We don't seem to be doing any untagging, so we just just use whatever > > > the caller asked for. We may need a small test to confirm. > > > > If we want to support tagged SP, then I guess we shouldn't be squashing > > the tag anywhere. A test for that would be sensible to have. > > I hacked the sas.c kselftest to use a tagged stack and works fine, the > SP register has a tagged address on the signal handler. Cool... [...] > > > > There is no foolproof rule, unless we can rewrite history... > > > > > > I would expect the norm to be the preservation of tags with a few > > > exceptions. The only ones I think where we won't preserve the tags are > > > mmap, mremap, brk (apart from the signal stuff already mentioned in the > > > current tagged-pointers.rst doc). > > > > > > So I can remove this paragraph altogether and add a note in part 3 of > > > the tagged-address-abi.rst document that mmap/mremap/brk do not preserve > > > the tag information. > > > > Deleting text is always a good idea ;) > > I'm going this route ;). [reply deleted] Cheers ---Dave