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remarkable-linux/arch/x86/Makefile
Josh Poimboeuf 3f135e57a4 x86/build: Mostly disable '-maccumulate-outgoing-args' 
The GCC '-maccumulate-outgoing-args' flag is enabled for most configs,
mostly because of issues which are no longer relevant.  For most
configs, and with most recent versions of GCC, it's no longer needed.

Clarify which cases need it, and only enable it for those cases.  Also
produce a compile-time error for the ftrace graph + mcount + '-Os' case,
which will otherwise cause runtime failures.

The main benefit of '-maccumulate-outgoing-args' is that it prevents an
ugly prologue for functions which have aligned stacks.  But removing the
option also has some benefits: more readable argument saves, smaller
text size, and (presumably) slightly improved performance.

Here are the object size savings for 32-bit and 64-bit defconfig
kernels:

      text	   data	    bss	     dec	    hex	filename
  10006710	3543328	1773568	15323606	 e9d1d6	vmlinux.x86-32.before
   9706358	3547424	1773568	15027350	 e54c96	vmlinux.x86-32.after

      text	   data	    bss	     dec	    hex	filename
  10652105	4537576	 843776	16033457	 f4a6b1	vmlinux.x86-64.before
  10639629	4537576	 843776	16020981	 f475f5	vmlinux.x86-64.after

That comes out to a 3% text size improvement on x86-32 and a 0.1% text
size improvement on x86-64.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170316193133.zrj6gug53766m6nn@treble
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-03-30 11:53:04 +02:00

308 lines
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Makefile
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# Unified Makefile for i386 and x86_64
# select defconfig based on actual architecture
ifeq ($(ARCH),x86)
ifeq ($(shell uname -m),x86_64)
KBUILD_DEFCONFIG := x86_64_defconfig
else
KBUILD_DEFCONFIG := i386_defconfig
endif
else
KBUILD_DEFCONFIG := $(ARCH)_defconfig
endif
# How to compile the 16-bit code. Note we always compile for -march=i386;
# that way we can complain to the user if the CPU is insufficient.
#
# The -m16 option is supported by GCC >= 4.9 and clang >= 3.5. For
# older versions of GCC, include an *assembly* header to make sure that
# gcc doesn't play any games behind our back.
CODE16GCC_CFLAGS := -m32 -Wa,$(srctree)/arch/x86/boot/code16gcc.h
M16_CFLAGS := $(call cc-option, -m16, $(CODE16GCC_CFLAGS))
REALMODE_CFLAGS := $(M16_CFLAGS) -g -Os -D__KERNEL__ \
-DDISABLE_BRANCH_PROFILING \
-Wall -Wstrict-prototypes -march=i386 -mregparm=3 \
-fno-strict-aliasing -fomit-frame-pointer -fno-pic \
-mno-mmx -mno-sse \
$(call cc-option, -ffreestanding) \
$(call cc-option, -fno-stack-protector) \
$(call cc-option, -mpreferred-stack-boundary=2)
export REALMODE_CFLAGS
# BITS is used as extension for files which are available in a 32 bit
# and a 64 bit version to simplify shared Makefiles.
# e.g.: obj-y += foo_$(BITS).o
export BITS
ifdef CONFIG_X86_NEED_RELOCS
LDFLAGS_vmlinux := --emit-relocs
endif
#
# Prevent GCC from generating any FP code by mistake.
#
# This must happen before we try the -mpreferred-stack-boundary, see:
#
# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
#
KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow
KBUILD_CFLAGS += $(call cc-option,-mno-avx,)
ifeq ($(CONFIG_X86_32),y)
BITS := 32
UTS_MACHINE := i386
CHECKFLAGS += -D__i386__
biarch := $(call cc-option,-m32)
KBUILD_AFLAGS += $(biarch)
KBUILD_CFLAGS += $(biarch)
KBUILD_CFLAGS += -msoft-float -mregparm=3 -freg-struct-return
# Never want PIC in a 32-bit kernel, prevent breakage with GCC built
# with nonstandard options
KBUILD_CFLAGS += -fno-pic
# prevent gcc from keeping the stack 16 byte aligned
KBUILD_CFLAGS += $(call cc-option,-mpreferred-stack-boundary=2)
# 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:
KBUILD_CFLAGS += $(call cc-ifversion, -lt, 0400, \
$(call cc-option,-fno-unit-at-a-time))
# CPU-specific tuning. Anything which can be shared with UML should go here.
include arch/x86/Makefile_32.cpu
KBUILD_CFLAGS += $(cflags-y)
# temporary until string.h is fixed
KBUILD_CFLAGS += -ffreestanding
else
BITS := 64
UTS_MACHINE := x86_64
CHECKFLAGS += -D__x86_64__ -m64
biarch := -m64
KBUILD_AFLAGS += -m64
KBUILD_CFLAGS += -m64
# Align jump targets to 1 byte, not the default 16 bytes:
KBUILD_CFLAGS += -falign-jumps=1
# Pack loops tightly as well:
KBUILD_CFLAGS += -falign-loops=1
# Don't autogenerate traditional x87 instructions
KBUILD_CFLAGS += $(call cc-option,-mno-80387)
KBUILD_CFLAGS += $(call cc-option,-mno-fp-ret-in-387)
# Use -mpreferred-stack-boundary=3 if supported.
KBUILD_CFLAGS += $(call cc-option,-mpreferred-stack-boundary=3)
# 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)
KBUILD_CFLAGS += $(cflags-y)
KBUILD_CFLAGS += -mno-red-zone
KBUILD_CFLAGS += -mcmodel=kernel
# -funit-at-a-time shrinks the kernel .text considerably
# unfortunately it makes reading oopses harder.
KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time)
endif
ifdef CONFIG_X86_X32
x32_ld_ok := $(call try-run,\
/bin/echo -e '1: .quad 1b' | \
$(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" - && \
$(OBJCOPY) -O elf32-x86-64 "$$TMP" "$$TMPO" && \
$(LD) -m elf32_x86_64 "$$TMPO" -o "$$TMP",y,n)
ifeq ($(x32_ld_ok),y)
CONFIG_X86_X32_ABI := y
KBUILD_AFLAGS += -DCONFIG_X86_X32_ABI
KBUILD_CFLAGS += -DCONFIG_X86_X32_ABI
else
$(warning CONFIG_X86_X32 enabled but no binutils support)
endif
endif
export CONFIG_X86_X32_ABI
# Don't unroll struct assignments with kmemcheck enabled
ifeq ($(CONFIG_KMEMCHECK),y)
KBUILD_CFLAGS += $(call cc-option,-fno-builtin-memcpy)
endif
#
# If the function graph tracer is used with mcount instead of fentry,
# '-maccumulate-outgoing-args' is needed to prevent a GCC bug
# (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42109)
#
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
endif
endif
endif
#
# Jump labels need '-maccumulate-outgoing-args' for gcc < 4.5.2 to prevent a
# GCC bug (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46226). There's no way
# to test for this bug at compile-time because the test case needs to execute,
# which is a no-go for cross compilers. So check the GCC version instead.
#
ifdef CONFIG_JUMP_LABEL
ifneq ($(ACCUMULATE_OUTGOING_ARGS), 1)
ACCUMULATE_OUTGOING_ARGS = $(call cc-if-fullversion, -lt, 040502, 1)
endif
endif
ifeq ($(ACCUMULATE_OUTGOING_ARGS), 1)
KBUILD_CFLAGS += -maccumulate-outgoing-args
endif
# Stackpointer is addressed different for 32 bit and 64 bit x86
sp-$(CONFIG_X86_32) := esp
sp-$(CONFIG_X86_64) := rsp
# do binutils support CFI?
cfi := $(call as-instr,.cfi_startproc\n.cfi_rel_offset $(sp-y)$(comma)0\n.cfi_endproc,-DCONFIG_AS_CFI=1)
# is .cfi_signal_frame supported too?
cfi-sigframe := $(call as-instr,.cfi_startproc\n.cfi_signal_frame\n.cfi_endproc,-DCONFIG_AS_CFI_SIGNAL_FRAME=1)
cfi-sections := $(call as-instr,.cfi_sections .debug_frame,-DCONFIG_AS_CFI_SECTIONS=1)
# does binutils support specific instructions?
asinstr := $(call as-instr,fxsaveq (%rax),-DCONFIG_AS_FXSAVEQ=1)
asinstr += $(call as-instr,pshufb %xmm0$(comma)%xmm0,-DCONFIG_AS_SSSE3=1)
asinstr += $(call as-instr,crc32l %eax$(comma)%eax,-DCONFIG_AS_CRC32=1)
avx_instr := $(call as-instr,vxorps %ymm0$(comma)%ymm1$(comma)%ymm2,-DCONFIG_AS_AVX=1)
avx2_instr :=$(call as-instr,vpbroadcastb %xmm0$(comma)%ymm1,-DCONFIG_AS_AVX2=1)
avx512_instr :=$(call as-instr,vpmovm2b %k1$(comma)%zmm5,-DCONFIG_AS_AVX512=1)
sha1_ni_instr :=$(call as-instr,sha1msg1 %xmm0$(comma)%xmm1,-DCONFIG_AS_SHA1_NI=1)
sha256_ni_instr :=$(call as-instr,sha256msg1 %xmm0$(comma)%xmm1,-DCONFIG_AS_SHA256_NI=1)
KBUILD_AFLAGS += $(cfi) $(cfi-sigframe) $(cfi-sections) $(asinstr) $(avx_instr) $(avx2_instr) $(avx512_instr) $(sha1_ni_instr) $(sha256_ni_instr)
KBUILD_CFLAGS += $(cfi) $(cfi-sigframe) $(cfi-sections) $(asinstr) $(avx_instr) $(avx2_instr) $(avx512_instr) $(sha1_ni_instr) $(sha256_ni_instr)
LDFLAGS := -m elf_$(UTS_MACHINE)
# Speed up the build
KBUILD_CFLAGS += -pipe
# Workaround for a gcc prelease that unfortunately was shipped in a suse release
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
###
# Syscall table generation
archheaders:
$(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
archprepare:
ifeq ($(CONFIG_KEXEC_FILE),y)
$(Q)$(MAKE) $(build)=arch/x86/purgatory arch/x86/purgatory/kexec-purgatory.c
endif
###
# Kernel objects
head-y := arch/x86/kernel/head_$(BITS).o
head-y += arch/x86/kernel/head$(BITS).o
head-y += arch/x86/kernel/ebda.o
head-y += arch/x86/kernel/platform-quirks.o
libs-y += arch/x86/lib/
# See arch/x86/Kbuild for content of core part of the kernel
core-y += arch/x86/
# drivers-y are linked after core-y
drivers-$(CONFIG_MATH_EMULATION) += arch/x86/math-emu/
drivers-$(CONFIG_PCI) += arch/x86/pci/
# must be linked after kernel/
drivers-$(CONFIG_OPROFILE) += arch/x86/oprofile/
# suspend and hibernation support
drivers-$(CONFIG_PM) += arch/x86/power/
drivers-$(CONFIG_FB) += arch/x86/video/
drivers-$(CONFIG_RAS) += arch/x86/ras/
####
# boot loader support. Several targets are kept for legacy purposes
boot := arch/x86/boot
BOOT_TARGETS = bzlilo bzdisk fdimage fdimage144 fdimage288 isoimage
PHONY += bzImage $(BOOT_TARGETS)
# Default kernel to build
all: bzImage
# KBUILD_IMAGE specify target image being built
KBUILD_IMAGE := $(boot)/bzImage
bzImage: vmlinux
ifeq ($(CONFIG_X86_DECODER_SELFTEST),y)
$(Q)$(MAKE) $(build)=arch/x86/tools posttest
endif
$(Q)$(MAKE) $(build)=$(boot) $(KBUILD_IMAGE)
$(Q)mkdir -p $(objtree)/arch/$(UTS_MACHINE)/boot
$(Q)ln -fsn ../../x86/boot/bzImage $(objtree)/arch/$(UTS_MACHINE)/boot/$@
$(BOOT_TARGETS): vmlinux
$(Q)$(MAKE) $(build)=$(boot) $@
PHONY += install
install:
$(Q)$(MAKE) $(build)=$(boot) $@
PHONY += vdso_install
vdso_install:
$(Q)$(MAKE) $(build)=arch/x86/entry/vdso $@
archclean:
$(Q)rm -rf $(objtree)/arch/i386
$(Q)rm -rf $(objtree)/arch/x86_64
$(Q)$(MAKE) $(clean)=$(boot)
$(Q)$(MAKE) $(clean)=arch/x86/tools
$(Q)$(MAKE) $(clean)=arch/x86/purgatory
define archhelp
echo '* bzImage - Compressed kernel image (arch/x86/boot/bzImage)'
echo ' install - Install kernel using'
echo ' (your) ~/bin/$(INSTALLKERNEL) or'
echo ' (distribution) /sbin/$(INSTALLKERNEL) or'
echo ' install to $$(INSTALL_PATH) and run lilo'
echo ' fdimage - Create 1.4MB boot floppy image (arch/x86/boot/fdimage)'
echo ' fdimage144 - Create 1.4MB boot floppy image (arch/x86/boot/fdimage)'
echo ' fdimage288 - Create 2.8MB boot floppy image (arch/x86/boot/fdimage)'
echo ' isoimage - Create a boot CD-ROM image (arch/x86/boot/image.iso)'
echo ' bzdisk/fdimage*/isoimage also accept:'
echo ' FDARGS="..." arguments for the booted kernel'
echo ' FDINITRD=file initrd for the booted kernel'
endef
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