From e20f7e5e7243008d507c3d2d2e02cd40eb94a8c0 Mon Sep 17 00:00:00 2001 From: Cao jin Date: Mon, 7 Aug 2017 19:29:44 +0800 Subject: [PATCH 1/3] x86/build: Drop unused mflags-y Subarchitecture support (mflags-y) was removed from x86 in this commit: 6bda2c8b32fe ("x86: remove subarchitecture support") So drop the mflags-y usage from the Makefile. Signed-off-by: Cao jin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1502105384-23214-1-git-send-email-caoj.fnst@cn.fujitsu.com Signed-off-by: Ingo Molnar --- arch/x86/Makefile | 3 --- 1 file changed, 3 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 1e902f926be3f..70b3aa9aa7184 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -232,9 +232,6 @@ KBUILD_CFLAGS += -Wno-sign-compare # KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -KBUILD_CFLAGS += $(mflags-y) -KBUILD_AFLAGS += $(mflags-y) - archscripts: scripts_basic $(Q)$(MAKE) $(build)=arch/x86/tools relocs From 8f91869766c00622b2eaa8ee567db4f333b78c1a Mon Sep 17 00:00:00 2001 From: Matthias Kaehlcke Date: Wed, 16 Aug 2017 17:47:40 -0700 Subject: [PATCH 2/3] 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 += $(call cc-option ...). The reason is that older gcc versions don't support the -mpreferred-stack-boundary option, since cc-option doesn't verify whether the alternative option is valid it would incorrectly select the clang option -mstack-alignment.. Signed-off-by: Matthias Kaehlcke Cc: Arnd Bergmann Cc: Bernhard.Rosenkranzer@linaro.org Cc: Greg Hackmann Cc: Kees Cook Cc: Linus Torvalds Cc: Masahiro Yamada Cc: Michael Davidson Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Stephen Hines Cc: Thomas Gleixner Cc: dianders@chromium.org Link: http://lkml.kernel.org/r/20170817004740.170588-1-mka@chromium.org Signed-off-by: Ingo Molnar --- arch/x86/Makefile | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 70b3aa9aa7184..48f3ae7897a00 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -14,9 +14,11 @@ endif # For gcc stack alignment is specified with -mpreferred-stack-boundary, # clang has the option -mstack-alignment for that purpose. ifneq ($(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) From 9e8730b178a2472fca3123e909d6e69cc8127778 Mon Sep 17 00:00:00 2001 From: Matthias Kaehlcke Date: Thu, 17 Aug 2017 11:20:47 -0700 Subject: [PATCH 3/3] x86/build: Use cc-option to validate stack alignment parameter With the following commit: 8f91869766c0 ("x86/build: Fix stack alignment for CLang") cc-option is only used to determine the name of the stack alignment option supported by the compiler, but not to verify that the actual parameter