From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932412AbdJ3Pum (ORCPT ); Mon, 30 Oct 2017 11:50:42 -0400 Received: from pandora.armlinux.org.uk ([78.32.30.218]:58716 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932313AbdJ3Pul (ORCPT ); Mon, 30 Oct 2017 11:50:41 -0400 Date: Mon, 30 Oct 2017 15:50:30 +0000 From: Russell King - ARM Linux To: Arnd Bergmann Cc: Gregory CLEMENT , Ard Biesheuvel , Romain Izard , Sven Schmidt <4sschmid@informatik.uni-hamburg.de>, LKML , Linux ARM , Petr Cvek , Aaro Koskinen , Andrea Adami , Robert Jarzmik Subject: Re: [PATCH] ARM: add a private asm/unaligned.h Message-ID: <20171030155029.GP20805@n2100.armlinux.org.uk> References: <20171020200231.1355569-1-arnd@arndb.de> <87wp3g39es.fsf@free-electrons.com> <20171027152743.GJ20805@n2100.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 30, 2017 at 04:09:43PM +0100, Arnd Bergmann wrote: > On Fri, Oct 27, 2017 at 5:27 PM, Russell King - ARM Linux > wrote: > > > > > There's three things wrong, all of which I have patches to address: > > > > 1. The decompressor code reading the image data sometimes issues unaligned > > reads. Some compilers get this wrong and cause an abort. Arnds patch > > addresses this. > > > > 2. Additional sections can appear in the zImage binary which adds extra > > bytes on the end of the image. Concatenating the zImage with the > > extra bytes onto a DTB is the same thing as doing this: > > > > cat zImage extrabytes foo.dtb > image > > > > and the decompressor tolerates no additional bytes between the > > _official_ end of the zImage and the DTB. I've added a patch which > > detects this situation and fails the kernel build when it happens. > > > > 3. Ard's patch "efi/libstub: arm: omit sorting of the UEFI memory map" > > gets rid of the additional sections that (a) change the alignment > > of the compressed data, and (b) add additional unexpected bytes on > > the end of zImage. > > It's possible that we still need yet another patch to address the gcc bug that > Alex Graf found, i.e. https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82445 > > Without the latest gcc, we might still get into a situation in which we get > an unaligned strd when compiling for armv5te or armv6 with gcc-7.[012]. > As someone mentioned in the bug report, that problem doesn't seem > to happen with gcc-6 or -mtune=xscale, or with gcc-7 -march=armv7-a. There is another solution which we've used in the past - we could detect these compiler versions and refuse to build with the broken compilers. -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up According to speedtest.net: 8.21Mbps down 510kbps up