From patchwork Sat Feb 8 08:01:08 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andi Kleen X-Patchwork-Id: 3609701 Return-Path: X-Original-To: patchwork-linux-kbuild@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id E405EC02E3 for ; Sat, 8 Feb 2014 08:06:17 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 25D0420172 for ; Sat, 8 Feb 2014 08:06:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4ABCD2017E for ; Sat, 8 Feb 2014 08:06:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751557AbaBHICI (ORCPT ); Sat, 8 Feb 2014 03:02:08 -0500 Received: from mga01.intel.com ([192.55.52.88]:35074 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750907AbaBHICG (ORCPT ); Sat, 8 Feb 2014 03:02:06 -0500 Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga101.fm.intel.com with ESMTP; 08 Feb 2014 00:02:05 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,805,1384329600"; d="scan'208";a="477990119" Received: from laut.jf.intel.com (HELO localhost) ([10.23.232.94]) by fmsmga002.fm.intel.com with ESMTP; 08 Feb 2014 00:02:05 -0800 Received: by localhost (Postfix, from userid 1000) id 091FB124AC1; Sat, 8 Feb 2014 09:01:26 +0100 (CET) From: Andi Kleen To: linux-kernel@vger.kernel.org Cc: linux-kbuild@vger.kernel.org, x86@kernel.org, Andi Kleen Subject: [PATCH 04/17] lto, workaround: Add workaround for initcall reordering Date: Sat, 8 Feb 2014 09:01:08 +0100 Message-Id: <1391846481-31491-4-git-send-email-ak@linux.intel.com> X-Mailer: git-send-email 1.8.5.2 In-Reply-To: <1391846481-31491-1-git-send-email-ak@linux.intel.com> References: <1391846481-31491-1-git-send-email-ak@linux.intel.com> Sender: linux-kbuild-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org X-Spam-Status: No, score=-7.4 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 file changed, 19 insertions(+), 1 deletion(-) diff --git a/include/linux/init.h b/include/linux/init.h index e168880..a3ba270 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -163,6 +163,23 @@ 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. @@ -175,7 +192,8 @@ extern bool initcall_debug; #define __define_initcall(fn, id) \ static initcall_t __initcall_##fn##id __used \ - __attribute__((__section__(".initcall" #id ".init"))) = fn + __attribute__((__section__(".initcall" #id ".init"))) = fn; \ + LTO_REFERENCE_INITCALL(__initcall_##fn##id) /* * Early initcalls run before initializing SMP.