From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@armlinux.org.uk (Russell King - ARM Linux) Date: Tue, 27 Jun 2017 23:08:12 +0100 Subject: [RFC PATCH v2 2/2] ARM: signal: Fix unparseable iwmmxt_sigframe in uc_regspace[] In-Reply-To: <1498583067-14178-3-git-send-email-Dave.Martin@arm.com> References: <1498583067-14178-1-git-send-email-Dave.Martin@arm.com> <1498583067-14178-3-git-send-email-Dave.Martin@arm.com> Message-ID: <20170627220812.GT4902@n2100.armlinux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. -- 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.