From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:57328 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726708AbeKZVsl (ORCPT ); Mon, 26 Nov 2018 16:48:41 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Matthias Kaehlcke , Arnd Bergmann , Bernhard.Rosenkranzer@linaro.org, Greg Hackmann , Kees Cook , Linus Torvalds , Masahiro Yamada , Michael Davidson , Nick Desaulniers , Peter Zijlstra , Stephen Hines , Thomas Gleixner , dianders@chromium.org, Ingo Molnar , Nathan Chancellor Subject: [PATCH 4.4 36/70] x86/build: Fix stack alignment for CLang Date: Mon, 26 Nov 2018 11:50:51 +0100 Message-Id: <20181126105050.235366120@linuxfoundation.org> In-Reply-To: <20181126105046.722096341@linuxfoundation.org> References: <20181126105046.722096341@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Matthias Kaehlcke commit 8f91869766c00622b2eaa8ee567db4f333b78c1a upstream. 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 += $(call cc-option ...). The reason is that older gcc versions don't support the -mpreferred-stack-boundary option, since cc-option doesn't verify whether the alternative option is valid it would incorrectly select the clang option -mstack-alignment.. Signed-off-by: Matthias Kaehlcke Cc: Arnd Bergmann Cc: Bernhard.Rosenkranzer@linaro.org Cc: Greg Hackmann Cc: Kees Cook Cc: Linus Torvalds Cc: Masahiro Yamada Cc: Michael Davidson Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Stephen Hines Cc: Thomas Gleixner Cc: dianders@chromium.org Link: http://lkml.kernel.org/r/20170817004740.170588-1-mka@chromium.org Signed-off-by: Ingo Molnar Signed-off-by: Nathan Chancellor Signed-off-by: Greg Kroah-Hartman --- arch/x86/Makefile | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -14,9 +14,11 @@ endif # For gcc stack alignment is specified with -mpreferred-stack-boundary, # clang has the option -mstack-alignment for that purpose. ifneq ($(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 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)