Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751800AbaBHICN (ORCPT ); Sat, 8 Feb 2014 03:02:13 -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 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.95,805,1384329600"; d="scan'208";a="477990119" 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-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- 1.8.5.2 -- 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/