From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752391AbaHDLgr (ORCPT ); Mon, 4 Aug 2014 07:36:47 -0400 Received: from mail-we0-f178.google.com ([74.125.82.178]:37805 "EHLO mail-we0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751698AbaHDLgq (ORCPT ); Mon, 4 Aug 2014 07:36:46 -0400 Date: Mon, 4 Aug 2014 13:36:36 +0200 From: Ingo Molnar To: Linus Torvalds Cc: linux-kernel@vger.kernel.org, "H. Peter Anvin" , Thomas Gleixner , Andrew Morton Subject: [GIT PULL] x86/build change for v3.17 Message-ID: <20140804113636.GA25578@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus, Please pull the latest x86-build-for-linus git tree from: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86-build-for-linus # HEAD: a9cfccee6604854aebc70215610b9788667f4fec x86, build: Change code16gcc.h from a C header to an assembly header Robustify the build process with a quirk to avoid GCC reordering related bugs. Thanks, Ingo ------------------> H. Peter Anvin (1): x86, build: Change code16gcc.h from a C header to an assembly header arch/x86/Makefile | 9 +++------ arch/x86/boot/code16gcc.h | 24 ++++++++++-------------- 2 files changed, 13 insertions(+), 20 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 602f57e..a98cc90 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -15,12 +15,9 @@ endif # that way we can complain to the user if the CPU is insufficient. # # The -m16 option is supported by GCC >= 4.9 and clang >= 3.5. For -# older versions of GCC, we need to play evil and unreliable tricks to -# attempt to ensure that our asm(".code16gcc") is first in the asm -# output. -CODE16GCC_CFLAGS := -m32 -include $(srctree)/arch/x86/boot/code16gcc.h \ - $(call cc-option, -fno-toplevel-reorder,\ - $(call cc-option, -fno-unit-at-a-time)) +# older versions of GCC, include an *assembly* header to make sure that +# gcc doesn't play any games behind our back. +CODE16GCC_CFLAGS := -m32 -Wa,$(srctree)/arch/x86/boot/code16gcc.h M16_CFLAGS := $(call cc-option, -m16, $(CODE16GCC_CFLAGS)) REALMODE_CFLAGS := $(M16_CFLAGS) -g -Os -D__KERNEL__ \ diff --git a/arch/x86/boot/code16gcc.h b/arch/x86/boot/code16gcc.h index d93e480..5ff4265 100644 --- a/arch/x86/boot/code16gcc.h +++ b/arch/x86/boot/code16gcc.h @@ -1,15 +1,11 @@ -/* - * code16gcc.h - * - * This file is -include'd when compiling 16-bit C code. - * Note: this asm() needs to be emitted before gcc emits any code. - * Depending on gcc version, this requires -fno-unit-at-a-time or - * -fno-toplevel-reorder. - * - * Hopefully gcc will eventually have a real -m16 option so we can - * drop this hack long term. - */ +# +# code16gcc.h +# +# This file is added to the assembler via -Wa when compiling 16-bit C code. +# This is done this way instead via asm() to make sure gcc does not reorder +# things around us. +# +# gcc 4.9+ has a real -m16 option so we can drop this hack long term. +# -#ifndef __ASSEMBLY__ -asm(".code16gcc"); -#endif + .code16gcc