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Commit 9e8730b1 authored by Matthias Kaehlcke's avatar Matthias Kaehlcke Committed by Ingo Molnar
Browse files

x86/build: Use cc-option to validate stack alignment parameter 



With the following commit:

  8f918697 ("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
<option>=N is valid in combination with the other CFLAGS.

This causes problems (as reported by the kbuild robot) with older GCC versions
which only support stack alignment on a boundary of 16 bytes or higher.

Also use (__)cc_option to add the stack alignment option to CFLAGS to
make sure only valid options are added.

Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
Signed-off-by: default avatarMatthias 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: 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
Fixes: 8f918697 ("x86/build: Fix stack alignment for CLang")
Link: http://lkml.kernel.org/r/20170817182047.176752-1-mka@chromium.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 8f918697

arch/x86/Makefile

+3 −3
Original line number Original line Diff line number Diff line
@@ -38,7 +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), -ffreestanding)

REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -fno-stack-protector)

REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -fno-stack-protector)

REALMODE_CFLAGS += $(cc_stack_align4)

REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), $(cc_stack_align4))

export REALMODE_CFLAGS

export REALMODE_CFLAGS





# BITS is used as extension for files which are available in a 32 bit

# BITS is used as extension for files which are available in a 32 bit
@@ -78,7 +78,7 @@ ifeq ($(CONFIG_X86_32),y) 
        # Align the stack to the register width instead of using the default

        # 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 of 16 bytes. This reduces stack usage and the number of

        # alignment instructions.

        # alignment instructions.

        KBUILD_CFLAGS += $(cc_stack_align4)

        KBUILD_CFLAGS += $(call cc-option,$(cc_stack_align4))





        # Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use

        # 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:

        # a lot more stack due to the lack of sharing of stacklots:
@@ -117,7 +117,7 @@ else 
        # default alignment which keep the stack *mis*aligned.

        # default alignment which keep the stack *mis*aligned.

        # Furthermore an alignment to the register width reduces stack usage

        # Furthermore an alignment to the register width reduces stack usage

        # and the number of alignment instructions.

        # and the number of alignment instructions.

        KBUILD_CFLAGS += $(cc_stack_align8)

        KBUILD_CFLAGS += $(call cc-option,$(cc_stack_align8))





	# Use -mskip-rax-setup if supported.

	# Use -mskip-rax-setup if supported.

	KBUILD_CFLAGS += $(call cc-option,-mskip-rax-setup)

	KBUILD_CFLAGS += $(call cc-option,-mskip-rax-setup)