Commit 989ceac7 authored by Nick Desaulniers's avatar Nick Desaulniers Committed by Ingo Molnar
Browse files

x86/build: Remove stale cc-option checks 



cc-option, __cc-option, cc-option-yn, and cc-disable-warning all invoke
the compiler during build time, and can slow down the build when these
checks become stale for our supported compilers, whose minimally
supported versions increases over time.

See Documentation/process/changes.rst for the current supported minimal
versions (GCC 4.9+, clang 10.0.1+). Compiler version support for these
flags may be verified on godbolt.org.

The following flags are supported by all supported versions of GCC and
Clang. Remove their cc-option, __cc-option, and cc-option-yn tests.

  -Wno-address-of-packed-member
  -mno-avx
  -m32
  -mno-80387
  -march=k8
  -march=nocona
  -march=core2
  -march=atom
  -mtune=generic
  -mfentry

[ mingo: Fixed regression on GCC, via partial revert of the stack-boundary changes.  ]

Signed-off-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/1436
Link: https://lkml.kernel.org/r/20210812183848.1519994-1-ndesaulniers@google.com
parent 36a21d51

arch/x86/Makefile

+14 −32
Original line number Diff line number Diff line
@@ -31,8 +31,8 @@ REALMODE_CFLAGS := -m16 -g -Os -DDISABLE_BRANCH_PROFILING \ 


REALMODE_CFLAGS += -ffreestanding

REALMODE_CFLAGS += -fno-stack-protector

REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -Wno-address-of-packed-member)

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

REALMODE_CFLAGS += -Wno-address-of-packed-member

REALMODE_CFLAGS += $(cc_stack_align4)

REALMODE_CFLAGS += $(CLANG_FLAGS)

export REALMODE_CFLAGS
@@ -48,8 +48,7 @@ export BITS 
#

#    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383

#

KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow

KBUILD_CFLAGS += $(call cc-option,-mno-avx,)

KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx



# Intel CET isn't enabled in the kernel

KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
@@ -59,9 +58,8 @@ ifeq ($(CONFIG_X86_32),y) 
        UTS_MACHINE := i386

        CHECKFLAGS += -D__i386__



        biarch := $(call cc-option,-m32)

        KBUILD_AFLAGS += $(biarch)

        KBUILD_CFLAGS += $(biarch)

        KBUILD_AFLAGS += -m32

        KBUILD_CFLAGS += -m32



        KBUILD_CFLAGS += -msoft-float -mregparm=3 -freg-struct-return
@@ -72,7 +70,7 @@ 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_align4))

        KBUILD_CFLAGS += $(cc_stack_align4)



        # CPU-specific tuning. Anything which can be shared with UML should go here.

        include arch/x86/Makefile_32.cpu
@@ -93,7 +91,6 @@ else 
        UTS_MACHINE := x86_64

        CHECKFLAGS += -D__x86_64__



        biarch := -m64

        KBUILD_AFLAGS += -m64

        KBUILD_CFLAGS += -m64
@@ -104,7 +101,7 @@ else 
        KBUILD_CFLAGS += $(call cc-option,-falign-loops=1)



        # Don't autogenerate traditional x87 instructions

        KBUILD_CFLAGS += $(call cc-option,-mno-80387)

        KBUILD_CFLAGS += -mno-80387

        KBUILD_CFLAGS += $(call cc-option,-mno-fp-ret-in-387)



        # By default gcc and clang use a stack alignment of 16 bytes for x86.
@@ -114,20 +111,17 @@ 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_align8))

        KBUILD_CFLAGS += $(cc_stack_align8)



	# Use -mskip-rax-setup if supported.

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



        # FIXME - should be integrated in Makefile.cpu (Makefile_32.cpu)

        cflags-$(CONFIG_MK8) += $(call cc-option,-march=k8)

        cflags-$(CONFIG_MPSC) += $(call cc-option,-march=nocona)



        cflags-$(CONFIG_MCORE2) += \

                $(call cc-option,-march=core2,$(call cc-option,-mtune=generic))

	cflags-$(CONFIG_MATOM) += $(call cc-option,-march=atom) \

		$(call cc-option,-mtune=atom,$(call cc-option,-mtune=generic))

        cflags-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=generic)

        cflags-$(CONFIG_MK8)		+= -march=k8

        cflags-$(CONFIG_MPSC)		+= -march=nocona

        cflags-$(CONFIG_MCORE2)		+= -march=core2

        cflags-$(CONFIG_MATOM)		+= -march=atom

        cflags-$(CONFIG_GENERIC_CPU)	+= -mtune=generic

        KBUILD_CFLAGS += $(cflags-y)



        KBUILD_CFLAGS += -mno-red-zone
@@ -158,18 +152,6 @@ export CONFIG_X86_X32_ABI 
ifdef CONFIG_FUNCTION_GRAPH_TRACER

  ifndef CONFIG_HAVE_FENTRY

	ACCUMULATE_OUTGOING_ARGS := 1

  else

    ifeq ($(call cc-option-yn, -mfentry), n)

	ACCUMULATE_OUTGOING_ARGS := 1



	# GCC ignores '-maccumulate-outgoing-args' when used with '-Os'.

	# If '-Os' is enabled, disable it and print a warning.

        ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE

          undefine CONFIG_CC_OPTIMIZE_FOR_SIZE

          $(warning Disabling CONFIG_CC_OPTIMIZE_FOR_SIZE.  Your compiler does not have -mfentry so you cannot optimize for size with CONFIG_FUNCTION_GRAPH_TRACER.)

        endif



    endif

  endif

endif
@@ -193,7 +175,7 @@ ifdef CONFIG_RETPOLINE 
  # only been fixed starting from gcc stable version 8.4.0 and

  # onwards, but not for older ones. See gcc bug #86952.

  ifndef CONFIG_CC_IS_CLANG

    KBUILD_CFLAGS += $(call cc-option,-fno-jump-tables)

    KBUILD_CFLAGS += -fno-jump-tables

  endif

endif