From patchwork Tue Feb 18 14:28:42 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andi Kleen X-Patchwork-Id: 3671561 Return-Path: X-Original-To: patchwork-linux-kbuild@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 969579F370 for ; Tue, 18 Feb 2014 14:36:56 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id BF10C201FE for ; Tue, 18 Feb 2014 14:36:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EB2F3201F7 for ; Tue, 18 Feb 2014 14:36:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756005AbaBRO3u (ORCPT ); Tue, 18 Feb 2014 09:29:50 -0500 Received: from mga11.intel.com ([192.55.52.93]:12903 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755977AbaBRO3r (ORCPT ); Tue, 18 Feb 2014 09:29:47 -0500 Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga102.fm.intel.com with ESMTP; 18 Feb 2014 06:29:46 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,502,1389772800"; d="scan'208";a="483436677" Received: from laut.jf.intel.com (HELO localhost) ([10.23.232.94]) by fmsmga002.fm.intel.com with ESMTP; 18 Feb 2014 06:29:45 -0800 Received: by localhost (Postfix, from userid 1000) id AF7DF124B07; Tue, 18 Feb 2014 15:29:06 +0100 (CET) From: Andi Kleen To: linux-kernel@vger.kernel.org Cc: sam@ravnborg.org, x86@kernel.org, linux-kbuild@vger.kernel.org, Andi Kleen Subject: [PATCH 04/20] lto, workaround: Add workaround for initcall reordering Date: Tue, 18 Feb 2014 15:28:42 +0100 Message-Id: <1392733738-8290-5-git-send-email-andi@firstfloor.org> X-Mailer: git-send-email 1.8.5.2 In-Reply-To: <1392733738-8290-1-git-send-email-andi@firstfloor.org> References: <1392733738-8290-1-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 X-Spam-Status: No, score=-7.5 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 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 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.