Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751439AbaLEKkL (ORCPT ); Fri, 5 Dec 2014 05:40:11 -0500 Received: from mout.kundenserver.de ([212.227.17.10]:59255 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750823AbaLEKkJ (ORCPT ); Fri, 5 Dec 2014 05:40:09 -0500 From: Arnd Bergmann To: linux-arm-kernel@lists.infradead.org Cc: Olof Johansson , Alexander Graf , Catalin Marinas , Will Deacon , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] arm64: Enable CONFIG_COMPAT also for 64k page size Date: Fri, 05 Dec 2014 11:39:40 +0100 Message-ID: <3551792.oHatG1W6W1@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: References: <1417707993-82290-1-git-send-email-agraf@suse.de> <5480F12D.90007@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:Bxw1mBxYNO+UXpNDEt8DNf8plZQb3Vidcy+vlCuta4SDI3WbtQQ MH3ACAFje057Ec9CG0lYRGyxlwPXQB9+VN5FnEQUzYu/o9xzkuvaIEXOqqq3EdfxLyKZ7ly u/tZ1B+upllIj652ekukWg/hp+sA4P7JU+VnWvDaXAS3oF491KXIeyEsTlXSQt2P4p9pGtX I6dKbtZO55WUUJEGHw/IQ== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 04 December 2014 15:48:50 Olof Johansson wrote: > On Thu, Dec 4, 2014 at 3:41 PM, Alexander Graf wrote: > > On 04.12.14 22:15, Olof Johansson wrote: > >> On Thu, Dec 4, 2014 at 7:46 AM, Alexander Graf wrote: > >>> With binutils 2.25 the default alignment for 32bit arm sections changed to > >>> have everything 64k aligned. Armv7 binaries built with this binutils version > >>> run successfully on an arm64 system. > >>> > >>> Since effectively there is now the chance to run armv7 code on arm64 even > >>> with 64k page size, it doesn't make sense to block people from enabling > >>> CONFIG_COMPAT on those configurations. > >>> > >>> Signed-off-by: Alexander Graf > >>> --- > >>> arch/arm64/Kconfig | 1 - > >>> 1 file changed, 1 deletion(-) > >>> > >>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > >>> index 9532f8d..3cf4f238 100644 > >>> --- a/arch/arm64/Kconfig > >>> +++ b/arch/arm64/Kconfig > >>> @@ -409,7 +409,6 @@ source "fs/Kconfig.binfmt" > >>> > >>> config COMPAT > >>> bool "Kernel support for 32-bit EL0" > >>> - depends on !ARM64_64K_PAGES > >>> select COMPAT_BINFMT_ELF > >>> select HAVE_UID16 > >>> select OLD_SIGSUSPEND3 > >> > >> This is hardly "compat". Sure, it's great to have a new binutils that > >> has larger alignment, but practically not a single existing binary > >> will work today if someone tries to do this. > > > > Yes, but IMHO that's an implementation detail. The same applies for > > 32bit PPC binaries if you use 4k aligned segments. If your applications > > are not aligned for your page size, you can't run them. The only > > platform that managed nevertheless FWIW was IA64 ;). > > Yes, but there the binutils change happened early enough that by the > time the kernel change went in, all major distros had binaries that > were compatible. What is the exact symptom you see when running an unaligned user space binary on 64k-pages? Do we at least print a helpful error message somewhere or does it just crash? Should we add support for 64k-pages in the arm32 kernel as well now? Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/