From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751132AbbCMEpT (ORCPT ); Fri, 13 Mar 2015 00:45:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51369 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750853AbbCMEpP (ORCPT ); Fri, 13 Mar 2015 00:45:15 -0400 Message-ID: <55026B3B.8050507@redhat.com> Date: Fri, 13 Mar 2015 00:44:43 -0400 From: Jon Masters Organization: Red Hat, Inc. User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Catalin Marinas , Olof Johansson CC: "agraf@suse.de" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Will Deacon Subject: Re: [PATCH] arm64: Enable CONFIG_COMPAT also for 64k page size References: <1417707993-82290-1-git-send-email-agraf@suse.de> <20141205111455.GC28339@e104818-lin.cambridge.arm.com> In-Reply-To: <20141205111455.GC28339@e104818-lin.cambridge.arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/05/2014 06:14 AM, Catalin Marinas wrote: > On Thu, Dec 04, 2014 at 09:15:12PM +0000, 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. >> >> So, it seems very premature to take this off. At the very least >> document it like Will requested, and make it depend on !ARM_64K_PAGES >> || EXPERT. > > That would work for me. We need to be clear that most existing 32-bit > binaries will fail. Agreed. Btw we intend to ensure that a future Fedora mass rebuild incorporates this change in alignment on 32-bit to allow 32-bit Fedora userspace to exist inside a (32-bit personality) chroot on AArch64. This will allow us to migrate to 64-bit native builders both for 32 and 64-bit in advance of the eventual plan for KVM based build guests. Jon.