Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751119AbaLELfi (ORCPT ); Fri, 5 Dec 2014 06:35:38 -0500 Received: from foss-mx-na.foss.arm.com ([217.140.108.86]:45148 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750749AbaLELfg (ORCPT ); Fri, 5 Dec 2014 06:35:36 -0500 Date: Fri, 5 Dec 2014 11:35:42 +0000 From: Will Deacon To: Catalin Marinas Cc: Olof Johansson , "agraf@suse.de" , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH] arm64: Enable CONFIG_COMPAT also for 64k page size Message-ID: <20141205113541.GB1630@arm.com> References: <1417707993-82290-1-git-send-email-agraf@suse.de> <20141205111455.GC28339@e104818-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141205111455.GC28339@e104818-lin.cambridge.arm.com> 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 Fri, Dec 05, 2014 at 11:14:55AM +0000, 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. I'd still like to run some regression tests to make sure we don't back ourselves into corners with things like SHMLBA, which would now be less than a page size. Will -- 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/