From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752555AbdHQKZY (ORCPT ); Thu, 17 Aug 2017 06:25:24 -0400 Received: from terminus.zytor.com ([65.50.211.136]:58175 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752417AbdHQKZJ (ORCPT ); Thu, 17 Aug 2017 06:25:09 -0400 Date: Thu, 17 Aug 2017 03:19:26 -0700 From: tip-bot for Matthias Kaehlcke Message-ID: Cc: linux-kernel@vger.kernel.org, arnd@arndb.de, ndesaulniers@google.com, keescook@chromium.org, srhines@google.com, ghackmann@google.com, mingo@kernel.org, mka@chromium.org, hpa@zytor.com, yamada.masahiro@socionext.com, tglx@linutronix.de, peterz@infradead.org, md@google.com, torvalds@linux-foundation.org Reply-To: hpa@zytor.com, yamada.masahiro@socionext.com, tglx@linutronix.de, mka@chromium.org, mingo@kernel.org, peterz@infradead.org, torvalds@linux-foundation.org, md@google.com, keescook@chromium.org, srhines@google.com, linux-kernel@vger.kernel.org, arnd@arndb.de, ndesaulniers@google.com, ghackmann@google.com In-Reply-To: <20170817004740.170588-1-mka@chromium.org> References: <20170817004740.170588-1-mka@chromium.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/build] x86/build: Fix stack alignment for CLang Git-Commit-ID: 8f91869766c00622b2eaa8ee567db4f333b78c1a 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 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 8f91869766c00622b2eaa8ee567db4f333b78c1a Gitweb: http://git.kernel.org/tip/8f91869766c00622b2eaa8ee567db4f333b78c1a Author: Matthias Kaehlcke AuthorDate: Wed, 16 Aug 2017 17:47:40 -0700 Committer: Ingo Molnar CommitDate: Thu, 17 Aug 2017 10:27:19 +0200 x86/build: Fix stack alignment for CLang Commit: d77698df39a5 ("x86/build: Specify stack alignment for clang") intended to use the same stack alignment for clang as with gcc. The two compilers use different options to configure the stack alignment (gcc: -mpreferred-stack-boundary=n, clang: -mstack-alignment=n). The above commit assumes that the clang option uses the same parameter type as gcc, i.e. that the alignment is specified as 2^n. However clang interprets the value of this option literally to use an alignment of n, in consequence the stack remains misaligned. Change the values used with -mstack-alignment to be the actual alignment instead of a power of two. cc-option isn't used here with the typical pattern of KBUILD_CFLAGS += $(call cc-option ...). The reason is that older gcc versions don't support the -mpreferred-stack-boundary option, since cc-option doesn't verify whether the alternative option is valid it would incorrectly select the clang option -mstack-alignment.. Signed-off-by: Matthias Kaehlcke Cc: Arnd Bergmann Cc: Bernhard.Rosenkranzer@linaro.org Cc: Greg Hackmann Cc: Kees Cook Cc: Linus Torvalds Cc: Masahiro Yamada Cc: Michael Davidson Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Stephen Hines Cc: Thomas Gleixner Cc: dianders@chromium.org Link: http://lkml.kernel.org/r/20170817004740.170588-1-mka@chromium.org Signed-off-by: Ingo Molnar --- arch/x86/Makefile | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 70b3aa9..48f3ae7 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -14,9 +14,11 @@ endif # For gcc stack alignment is specified with -mpreferred-stack-boundary, # clang has the option -mstack-alignment for that purpose. ifneq ($(call cc-option, -mpreferred-stack-boundary=4),) - cc_stack_align_opt := -mpreferred-stack-boundary -else ifneq ($(call cc-option, -mstack-alignment=4),) - cc_stack_align_opt := -mstack-alignment + cc_stack_align4 := -mpreferred-stack-boundary=2 + cc_stack_align8 := -mpreferred-stack-boundary=3 +else ifneq ($(call cc-option, -mstack-alignment=16),) + cc_stack_align4 := -mstack-alignment=4 + cc_stack_align8 := -mstack-alignment=8 endif # How to compile the 16-bit code. Note we always compile for -march=i386; @@ -36,7 +38,7 @@ REALMODE_CFLAGS := $(M16_CFLAGS) -g -Os -D__KERNEL__ \ REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -ffreestanding) REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -fno-stack-protector) -REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), $(cc_stack_align_opt)=2) +REALMODE_CFLAGS += $(cc_stack_align4) export REALMODE_CFLAGS # BITS is used as extension for files which are available in a 32 bit @@ -76,7 +78,7 @@ ifeq ($(CONFIG_X86_32),y) # Align the stack to the register width instead of using the default # alignment of 16 bytes. This reduces stack usage and the number of # alignment instructions. - KBUILD_CFLAGS += $(call cc-option,$(cc_stack_align_opt)=2) + KBUILD_CFLAGS += $(cc_stack_align4) # Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use # a lot more stack due to the lack of sharing of stacklots: @@ -115,7 +117,7 @@ else # default alignment which keep the stack *mis*aligned. # Furthermore an alignment to the register width reduces stack usage # and the number of alignment instructions. - KBUILD_CFLAGS += $(call cc-option,$(cc_stack_align_opt)=3) + KBUILD_CFLAGS += $(cc_stack_align8) # Use -mskip-rax-setup if supported. KBUILD_CFLAGS += $(call cc-option,-mskip-rax-setup)