linux-yocto/arch/x86/Makefile

SPDX-License-Identifier: GPL-2.0

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

ifdef CONFIG_CC_IS_GCC RETPOLINE_CFLAGS := $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register) RETPOLINE_CFLAGS += $(call cc-option,-mindirect-branch-cs-prefix) RETPOLINE_VDSO_CFLAGS := $(call cc-option,-mindirect-branch=thunk-inline -mindirect-branch-register) endif ifdef CONFIG_CC_IS_CLANG RETPOLINE_CFLAGS := -mretpoline-external-thunk RETPOLINE_VDSO_CFLAGS := -mretpoline endif

ifdef CONFIG_RETHUNK RETHUNK_CFLAGS := -mfunction-return=thunk-extern RETPOLINE_CFLAGS += $(RETHUNK_CFLAGS) endif

export RETHUNK_CFLAGS export RETPOLINE_CFLAGS export RETPOLINE_VDSO_CFLAGS

For gcc stack alignment is specified with -mpreferred-stack-boundary,

clang has the option -mstack-alignment for that purpose.

ifneq ($(call cc-option, -mpreferred-stack-boundary=4),) cc_stack_align4 := -mpreferred-stack-boundary=2 cc_stack_align8 := -mpreferred-stack-boundary=3 else ifneq ($(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;

that way we can complain to the user if the CPU is insufficient.

REALMODE_CFLAGS := -m16 -g -Os -DDISABLE_BRANCH_PROFILING -D__DISABLE_EXPORTS
-Wall -Wstrict-prototypes -march=i386 -mregparm=3
-fno-strict-aliasing -fomit-frame-pointer -fno-pic
-mno-mmx -mno-sse $(call cc-option,-fcf-protection=none)

REALMODE_CFLAGS += -ffreestanding REALMODE_CFLAGS += -fno-stack-protector REALMODE_CFLAGS += -Wno-address-of-packed-member REALMODE_CFLAGS += $(cc_stack_align4) REALMODE_CFLAGS += $(CLANG_FLAGS) 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

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 -mno-avx KBUILD_RUSTFLAGS += -Ctarget-feature=-sse,-sse2,-sse3,-ssse3,-sse4.1,-sse4.2,-avx,-avx2

ifeq ($(CONFIG_X86_KERNEL_IBT),y)

Kernel IBT has S_CET.NOTRACK_EN=0, as such the compilers must not generate

NOTRACK prefixes. Current generation compilers unconditionally employ NOTRACK

for jump-tables, as such, disable jump-tables for now.

(jump-tables are implicitly disabled by RETPOLINE)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104816

KBUILD_CFLAGS += $(call cc-option,-fcf-protection=branch -fno-jump-tables) else KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none) endif

ifeq ($(CONFIG_X86_32),y) BITS := 32 UTS_MACHINE := i386 CHECKFLAGS += -D__i386__

    KBUILD_AFLAGS += -m32
    KBUILD_CFLAGS += -m32

    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

    # 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 += $(cc_stack_align4)

    # CPU-specific tuning. Anything which can be shared with UML should go here.
    include $(srctree)/arch/x86/Makefile_32.cpu
    KBUILD_CFLAGS += $(cflags-y)

    # temporary until string.h is fixed
    KBUILD_CFLAGS += -ffreestanding

ifeq ($(CONFIG_STACKPROTECTOR),y)
	ifeq ($(CONFIG_SMP),y)
		KBUILD_CFLAGS += -mstack-protector-guard-reg=fs -mstack-protector-guard-symbol=__stack_chk_guard
	else
		KBUILD_CFLAGS += -mstack-protector-guard=global
	endif
endif

else BITS := 64 UTS_MACHINE := x86_64 CHECKFLAGS += -D__x86_64__

    KBUILD_AFLAGS += -m64
    KBUILD_CFLAGS += -m64

    # Align jump targets to 1 byte, not the default 16 bytes:
    KBUILD_CFLAGS += $(call cc-option,-falign-jumps=1)

    # Pack loops tightly as well:
    KBUILD_CFLAGS += $(call cc-option,-falign-loops=1)

    # Don't autogenerate traditional x87 instructions
    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.
    # However the standard kernel entry on x86-64 leaves the stack on an
    # 8-byte boundary. If the compiler isn't informed about the actual
    # alignment it will generate extra alignment instructions for the
    # 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 += $(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-$(CONFIG_MK8)		+= -march=k8
    cflags-$(CONFIG_MPSC)		+= -march=nocona
    cflags-$(CONFIG_MCORE2)		+= -march=core2
    cflags-$(CONFIG_MATOM)		+= -march=atom
    cflags-$(CONFIG_GENERIC_CPU)	+= -mtune=generic
    KBUILD_CFLAGS += $(cflags-y)

    rustflags-$(CONFIG_MK8)		+= -Ctarget-cpu=k8
    rustflags-$(CONFIG_MPSC)	+= -Ctarget-cpu=nocona
    rustflags-$(CONFIG_MCORE2)	+= -Ctarget-cpu=core2
    rustflags-$(CONFIG_MATOM)	+= -Ctarget-cpu=atom
    rustflags-$(CONFIG_GENERIC_CPU)	+= -Ztune-cpu=generic
    KBUILD_RUSTFLAGS += $(rustflags-y)

    KBUILD_CFLAGS += -mno-red-zone
    KBUILD_CFLAGS += -mcmodel=kernel
    KBUILD_RUSTFLAGS += -Cno-redzone=y
    KBUILD_RUSTFLAGS += -Ccode-model=kernel

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 endif endif

ifeq ($(ACCUMULATE_OUTGOING_ARGS), 1) # This compiler flag is not supported by Clang: KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args,) endif

Workaround for a gcc prelease that unfortunately was shipped in a suse release

KBUILD_CFLAGS += -Wno-sign-compare

KBUILD_CFLAGS += -fno-asynchronous-unwind-tables

Avoid indirect branches in kernel to deal with Spectre

ifdef CONFIG_RETPOLINE KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)

Additionally, avoid generating expensive indirect jumps which

are subject to retpolines for small number of switch cases.

clang turns off jump table generation by default when under

retpoline builds, however, gcc does not for x86. This has

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 += -fno-jump-tables endif endif

ifdef CONFIG_SLS KBUILD_CFLAGS += -mharden-sls=all endif

KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE)

ifdef CONFIG_LTO_CLANG ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo ?),0) KBUILD_LDFLAGS += -plugin-opt=-stack-alignment=$(if $(CONFIG_X86_32),4,8) endif endif

ifdef CONFIG_X86_NEED_RELOCS LDFLAGS_vmlinux := --emit-relocs --discard-none else LDFLAGS_vmlinux := endif

The 64-bit kernel must be aligned to 2MB. Pass -z max-page-size=0x200000 to

the linker to force 2MB page size regardless of the default page size used

by the linker.

ifdef CONFIG_X86_64 LDFLAGS_vmlinux += -z max-page-size=0x200000 endif

archscripts: scripts_basic $(Q)$(MAKE) $(build)=arch/x86/tools relocs

Syscall table generation

archheaders: $(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all

Kernel objects

libs-y += arch/x86/lib/

drivers-y are linked after core-y

drivers-$(CONFIG_MATH_EMULATION) += arch/x86/math-emu/ drivers-$(CONFIG_PCI) += arch/x86/pci/

suspend and hibernation support

drivers-$(CONFIG_PM) += arch/x86/power/

drivers-$(CONFIG_FB) += arch/x86/video/

boot loader support. Several targets are kept for legacy purposes

boot := arch/x86/boot

BOOT_TARGETS = bzdisk fdimage fdimage144 fdimage288 hdimage 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: $(call cmd,install)

PHONY += vdso_install vdso_install: $(Q)$(MAKE) $(build)=arch/x86/entry/vdso $@

archprepare: checkbin checkbin: ifdef CONFIG_RETPOLINE ifeq ($(RETPOLINE_CFLAGS),) @echo "You are building kernel with non-retpoline compiler." >&2 @echo "Please update your compiler." >&2 @false endif endif

archclean: $(Q)rm -rf $(objtree)/arch/i386 $(Q)rm -rf $(objtree)/arch/x86_64

define archhelp echo '* bzImage - Compressed kernel image (arch/x86/boot/bzImage)' echo ' install - Install kernel using (your) ~/bin/$(INSTALLKERNEL) or' echo ' (distribution) /sbin/$(INSTALLKERNEL) or install to ' echo ' $$(INSTALL_PATH) and run lilo' echo '' 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 ' hdimage - Create a BIOS/EFI hard disk image (arch/x86/boot/hdimage)' echo ' isoimage - Create a boot CD-ROM image (arch/x86/boot/image.iso)' echo ' bzdisk/fdimage*/hdimage/isoimage also accept:' echo ' FDARGS="..." arguments for the booted kernel' echo ' FDINITRD=file initrd for the booted kernel' echo '' echo ' kvm_guest.config - Enable Kconfig items for running this kernel as a KVM guest' echo ' xen.config - Enable Kconfig items for running this kernel as a Xen guest' echo ' x86_debug.config - Enable tip tree debugging options for testing'

endef