From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753796AbbFAPuZ (ORCPT ); Mon, 1 Jun 2015 11:50:25 -0400 Received: from mail-la0-f48.google.com ([209.85.215.48]:35356 "EHLO mail-la0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753579AbbFAPtL (ORCPT ); Mon, 1 Jun 2015 11:49:11 -0400 MIME-Version: 1.0 In-Reply-To: References: <20150515103414.GA20518@intel.com> <20150601083214.GA381@x4> From: Andy Lutomirski Date: Mon, 1 Jun 2015 08:48:48 -0700 Message-ID: Subject: Re: [committed, PATCH] Add -mshared option to x86 ELF assembler To: "H.J. Lu" , X86 ML , "linux-kernel@vger.kernel.org" Cc: Markus Trippelsdorf , Binutils , Andy Lutomirski Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 1, 2015 at 4:05 AM, H.J. Lu wrote: > On Mon, Jun 1, 2015 at 1:32 AM, Markus Trippelsdorf > wrote: >> On 2015.05.15 at 03:34 -0700, H.J. Lu wrote: >>> This patch adds -mshared option to x86 ELF assembler. By default, >>> assembler will optimize out non-PLT relocations against defined non-weak >>> global branch targets with default visibility. The -mshared option tells >>> the assembler to generate code which may go into a shared library >>> where all non-weak global branch targets with default visibility can >>> be preempted. The resulting code is slightly bigger. This option >>> only affects the handling of branch instructions. >>> >>> This Linux kernel patch is needed to create a working x86 Linux kernel if >>> it hasn't been applied: >>> >>> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S >>> index ae6588b..b91a00c 100644 >>> --- a/arch/x86/kernel/head_64.S >>> +++ b/arch/x86/kernel/head_64.S >>> @@ -339,8 +339,8 @@ early_idt_handlers: >>> i = i + 1 >>> .endr >>> >>> -/* This is global to keep gas from relaxing the jumps */ >>> -ENTRY(early_idt_handler) >>> +/* This is weak to keep gas from relaxing the jumps */ >>> +WEAK(early_idt_handler) >>> cld >> >> Have you posted the patch to LKML already? >> (I hit this issue today and it took me a while to figure out the cause.) > > A kernel patch will be checked in soon. > It already is: https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/commit/?h=x86/asm&id=cdeb6048940fa4bfb429e2f1cba0d28a11e20cd5 It's currently queued for 4.2. Ingo, would it make sense to promote this to 4.1? It's definitely a violation of the "no development after the merge window" rule, but it's sort of a build fix. Alternatively, we could ask Greg et al to backport it. --Andy