Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752510AbaA2RwE (ORCPT ); Wed, 29 Jan 2014 12:52:04 -0500 Received: from terminus.zytor.com ([198.137.202.10]:45646 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750938AbaA2RwB (ORCPT ); Wed, 29 Jan 2014 12:52:01 -0500 Date: Wed, 29 Jan 2014 09:51:26 -0800 From: tip-bot for David Woodhouse Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, dwmw2@infradead.org, tglx@linutronix.de, hpa@linux.intel.com, David.Woodhouse@intel.com Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, dwmw2@infradead.org, tglx@linutronix.de, hpa@linux.intel.com, David.Woodhouse@intel.com In-Reply-To: <1390997807.20153.133.camel@i7.infradead.org> References: <1390997807.20153.133.camel@i7.infradead.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/build] x86, build: Build 16-bit code with -m16 where possible Git-Commit-ID: 372cb9eef903d1e18961d2c1a34c75f027f0bd8f X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.1 (terminus.zytor.com [127.0.0.1]); Wed, 29 Jan 2014 09:51:32 -0800 (PST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 372cb9eef903d1e18961d2c1a34c75f027f0bd8f Gitweb: http://git.kernel.org/tip/372cb9eef903d1e18961d2c1a34c75f027f0bd8f Author: David Woodhouse AuthorDate: Wed, 29 Jan 2014 12:16:47 +0000 Committer: H. Peter Anvin CommitDate: Wed, 29 Jan 2014 09:47:49 -0800 x86, build: Build 16-bit code with -m16 where possible Both clang 3.5 and GCC 4.9 will support this (as of r199754 and r207196 respectively). Both have been tested to produce booting kernels when the 16-bit code is built with -m16. (Modulo LLVM PR3997, at least.) Signed-off-by: David Woodhouse Link: http://lkml.kernel.org/r/1390997807.20153.133.camel@i7.infradead.org Signed-off-by: H. Peter Anvin --- arch/x86/Makefile | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 9ecbc1c..dbc9b2b 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -13,14 +13,22 @@ endif # How to compile the 16-bit code. Note we always compile for -march=i386; # that way we can complain to the user if the CPU is insufficient. -REALMODE_CFLAGS := -m32 -g -Os -D__KERNEL__ -DDISABLE_BRANCH_PROFILING \ +# +# 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)) +M16_CFLAGS := -m16 + +REALMODE_CFLAGS := -g -Os -D__KERNEL__ -DDISABLE_BRANCH_PROFILING \ + $(call cc-option, $(M16_CFLAGS), $(CODE16GCC_CFLAGS)) \ -Wall -Wstrict-prototypes -march=i386 -mregparm=3 \ - -include $(srctree)/arch/x86/boot/code16gcc.h \ -fno-strict-aliasing -fomit-frame-pointer -fno-pic \ -mno-mmx -mno-sse \ $(call cc-option, -ffreestanding) \ - $(call cc-option, -fno-toplevel-reorder,\ - $(call cc-option, -fno-unit-at-a-time)) \ $(call cc-option, -fno-stack-protector) \ $(call cc-option, -mpreferred-stack-boundary=2) export REALMODE_CFLAGS -- 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/