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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i1CUk-0000cV-S1; Fri, 23 Aug 2019 16:32:58 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i1CUh-0000Xs-Q8 for linux-arm-kernel@lists.infradead.org; Fri, 23 Aug 2019 16:32:57 +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 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 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-Disposition: inline In-Reply-To: <20190823161912.GJ29387@arrakis.emea.arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190823_093255_896396_001FC049 X-CRM114-Status: GOOD ( 21.06 ) 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, 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 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 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel