From patchwork Sun Aug 19 02:56:51 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andi Kleen X-Patchwork-Id: 1343351 Return-Path: X-Original-To: patchwork-linux-kbuild@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork2.kernel.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by patchwork2.kernel.org (Postfix) with ESMTP id AF1C6DF25A for ; Sun, 19 Aug 2012 03:12:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754995Ab2HSC7l (ORCPT ); Sat, 18 Aug 2012 22:59:41 -0400 Received: from mga02.intel.com ([134.134.136.20]:64945 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753990Ab2HSC5q (ORCPT ); Sat, 18 Aug 2012 22:57:46 -0400 Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga101.jf.intel.com with ESMTP; 18 Aug 2012 19:57:26 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.77,792,1336374000"; d="scan'208";a="182422075" Received: from tassilo.jf.intel.com ([10.7.201.151]) by orsmga001.jf.intel.com with ESMTP; 18 Aug 2012 19:57:25 -0700 Received: by tassilo.jf.intel.com (Postfix, from userid 501) id F0BA824198D; Sat, 18 Aug 2012 19:57:25 -0700 (PDT) From: Andi Kleen To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, mmarek@suse.cz, linux-kbuild@vger.kernel.org, JBeulich@suse.com, akpm@linux-foundation.org, Andi Kleen Subject: [PATCH 55/74] lto, workaround: Add workaround for initcall reordering Date: Sat, 18 Aug 2012 19:56:51 -0700 Message-Id: <1345345030-22211-56-git-send-email-andi@firstfloor.org> X-Mailer: git-send-email 1.7.7.6 In-Reply-To: <1345345030-22211-1-git-send-email-andi@firstfloor.org> References: <1345345030-22211-1-git-send-email-andi@firstfloor.org> Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org From: Andi Kleen Work around a LTO gcc problem: when there is no reference to a variable in a module it will be moved to the end of the program. This causes reordering of initcalls which the kernel does not like. Add a dummy reference function to avoid this. The function is deleted by the linker. This replaces a previous much slower workaround. Thanks to Honza Hubicka for suggesting this technique. Signed-off-by: Andi Kleen --- include/linux/init.h | 20 +++++++++++++++++++- 1 files changed, 19 insertions(+), 1 deletions(-) diff --git a/include/linux/init.h b/include/linux/init.h index c2f06b3..e425800 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -176,6 +176,23 @@ extern bool initcall_debug; #ifndef __ASSEMBLY__ +#ifdef CONFIG_LTO +/* Work around a LTO gcc problem: when there is no reference to a variable + * in a module it will be moved to the end of the program. This causes + * reordering of initcalls which the kernel does not like. + * Add a dummy reference function to avoid this. The function is + * deleted by the linker. + */ +#define LTO_REFERENCE_INITCALL(x) \ + ; /* yes this is needed */ \ + static __used __exit void *reference_##x(void) \ + { \ + return &x; \ + } +#else +#define LTO_REFERENCE_INITCALL(x) +#endif + /* initcalls are now grouped by functionality into separate * subsections. Ordering inside the subsections is determined * by link order. @@ -188,7 +205,8 @@ extern bool initcall_debug; #define __define_initcall(level,fn,id) \ static initcall_t __initcall_##fn##id __used \ - __attribute__((__section__(".initcall" level ".init"))) = fn + __attribute__((__section__(".initcall" level ".init"))) = fn \ + LTO_REFERENCE_INITCALL(__initcall_##fn##id) /* * Early initcalls run before initializing SMP.