From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 21825 invoked by alias); 26 Jun 2017 10:13:19 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 21808 invoked by uid 89); 26 Jun 2017 10:13:18 -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 autolearn=ham version=3.3.2 spammy=H*r:4.76, safest, UD:org.uk, H*r:sk:4.82_1- X-HELO: pandora.armlinux.org.uk Date: Mon, 26 Jun 2017 10:13:00 -0000 From: Russell King - ARM Linux To: Dave Martin Cc: linux-arm-kernel@lists.infradead.org, Edmund Grimley-Evans , libc-alpha@sourceware.org, gdb@sourceware.org Subject: Re: [RFC PATCH 0/2] ARM: Fix unparseable signal frame with CONFIG_IWMMXT Message-ID: <20170626101304.GG4902@n2100.armlinux.org.uk> References: <1498059983-13438-1-git-send-email-Dave.Martin@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1498059983-13438-1-git-send-email-Dave.Martin@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-SW-Source: 2017-06/txt/msg01275.txt.bz2 On Wed, Jun 21, 2017 at 04:46:01PM +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. > > I don't know whether any userspace has implemented any sort of > workaround for this, but the ABI by itself is insufficient anyway. > > This series attempts to omit the spurious iWMMXt record when > appropriate. > > Not extensively tested, and the ABI impact is unknown for now. Hmm, I would actually suggest that we poke in a correct size for the missing iWMMXt record, and an invalid magic number as the "simple" solution for this - that doesn't make any layout changes to the data structures, and is probably the safest solution for backporting. Going forward, I think something along the lines of your proposal is okay. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.