Messages in this thread Patch in this message | | | Date | Tue, 18 Jul 2017 03:44:08 -0700 | From | tip-bot for Matthias Kaehlcke <> | Subject | [tip:x86/urgent] x86/build: Fix stack alignment for CLang |
| |
Commit-ID: 79e6b917e69a34d45e83e72f1e9bb7487d5f5832 Gitweb: http://git.kernel.org/tip/79e6b917e69a34d45e83e72f1e9bb7487d5f5832 Author: Matthias Kaehlcke <mka@chromium.org> AuthorDate: Tue, 11 Jul 2017 14:29:40 -0700 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Tue, 18 Jul 2017 11:02:53 +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.
Signed-off-by: Matthias Kaehlcke <mka@chromium.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Bernhard.Rosenkranzer@linaro.org Cc: Greg Hackmann <ghackmann@google.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masahiro Yamada <yamada.masahiro@socionext.com> Cc: Michael Davidson <md@google.com> Cc: Michal Marek <mmarek@suse.com> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephen Hines <srhines@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dianders@chromium.org Cc: linux-kbuild@vger.kernel.org Link: http://lkml.kernel.org/r/20170711212940.101416-1-mka@chromium.org Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/Makefile | 15 ++++----------- 1 file changed, 4 insertions(+), 11 deletions(-)
diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 1e902f9..9c6f11e 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -11,14 +11,6 @@ else KBUILD_DEFCONFIG := $(ARCH)_defconfig endif -# For gcc stack alignment is specified with -mpreferred-stack-boundary, -# clang has the option -mstack-alignment for that purpose. -ifneq ($(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 -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. # @@ -36,7 +28,8 @@ 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 += $(call __cc-option, $(CC), $(REALMODE_CFLAGS),\ + -mpreferred-stack-boundary=2,-mstack-alignment=4) export REALMODE_CFLAGS # BITS is used as extension for files which are available in a 32 bit @@ -76,7 +69,7 @@ ifeq ($(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 += $(call cc-option,-mpreferred-stack-boundary=2,-mstack-alignment=4) # 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 +108,7 @@ 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 += $(call cc-option,-mpreferred-stack-boundary=3,-mstack-alignment=8) # Use -mskip-rax-setup if supported. KBUILD_CFLAGS += $(call cc-option,-mskip-rax-setup)
| |