From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 24645 invoked by alias); 28 Jun 2017 13:09:25 -0000 Mailing-List: contact gdb-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-owner@sourceware.org Received: (qmail 24540 invoked by uid 89); 28 Jun 2017 13:09:24 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_PASS autolearn=ham version=3.3.2 spammy=manufacture, king X-Spam-User: qpsmtpd, 2 recipients X-HELO: foss.arm.com Received: from foss.arm.com (HELO foss.arm.com) (217.140.101.70) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 28 Jun 2017 13:09:22 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5741F344; Wed, 28 Jun 2017 06:09:21 -0700 (PDT) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 755473F557; Wed, 28 Jun 2017 06:09:20 -0700 (PDT) Date: Wed, 28 Jun 2017 13:09:00 -0000 From: Dave Martin To: Russell King - ARM Linux Cc: gdb@sourceware.org, Edmund Grimley-Evans , libc-alpha@sourceware.org, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC PATCH v2 2/2] ARM: signal: Fix unparseable iwmmxt_sigframe in uc_regspace[] Message-ID: <20170628130916.GM8543@e103592.cambridge.arm.com> References: <1498583067-14178-1-git-send-email-Dave.Martin@arm.com> <1498583067-14178-3-git-send-email-Dave.Martin@arm.com> <20170627220812.GT4902@n2100.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170627220812.GT4902@n2100.armlinux.org.uk> User-Agent: Mutt/1.5.23 (2014-03-12) X-SW-Source: 2017-06/txt/msg00040.txt.bz2 On Tue, Jun 27, 2017 at 11:08:12PM +0100, Russell King - ARM Linux wrote: > On Tue, Jun 27, 2017 at 06:04:07PM +0100, Dave Martin wrote: > > In kernels with CONFIG_IWMMXT=y running on non-iWMMXt hardware, the > > signal frame can be left partially uninitialised in such a way > > that userspace cannot parse uc_regspace[] safely. In particular, > > this means that the VFP registers cannot be located reliably in the > > signal frame when a multi_v7_defconfig kernel is run on the > > majority of platforms. > > > > The cause is that the uc_regspace[] is laid out statically based on > > the kernel config, but the decision of whether to save/restore the > > iWMMXt registers must be a runtime decision. > > > > To minimise breakage of software that may assume a fixed layout, > > this patch emits a dummy block of the same size as iwmmxt_sigframe, > > for non-iWMMXt threads. However, the magic and size of this block > > are now filled in to help parsers skip over it. A new DUMMY_MAGIC > > is defined for this purpose. > > > > It is probably legitimate (if non-portable) for userspace to > > manufacture its own sigframe for sigreturn, and there is no obvious > > reason why userspace should be required to insert a DUMMY_MAGIC > > block when running on non-iWMMXt hardware, when omitting it has > > worked just fine forever in other configurations. So in this case, > > sigreturn does not require this block to be present. > > > > Reported-by: Edmund Grimley-Evans > > Signed-off-by: Dave Martin > > This looks fine to me. Please drop it in the patch system, thanks. Do you have a view on whether I should Cc-stable on this? The patches seem to apply cleanly back to v3.4, but I'm not in a position to test that far back easily. As a reference point, Debian stretch seems to use v4.9.x for its multiplatform distro kernel, so it may be worth going at least that far back. (jessie uses v3.16.x.) Cheers ---Dave