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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: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://github.com/ClangBuiltLinux/linux/issues/1436 Link: https://lkml.kernel.org/r/20210812183848.1519994-1-ndesaulniers@google.com
307 lines
9.7 KiB
Makefile
307 lines
9.7 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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# Unified Makefile for i386 and x86_64
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# select defconfig based on actual architecture
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ifeq ($(ARCH),x86)
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ifeq ($(shell uname -m),x86_64)
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KBUILD_DEFCONFIG := x86_64_defconfig
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else
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KBUILD_DEFCONFIG := i386_defconfig
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endif
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else
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KBUILD_DEFCONFIG := $(ARCH)_defconfig
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endif
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# For gcc stack alignment is specified with -mpreferred-stack-boundary,
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# clang has the option -mstack-alignment for that purpose.
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ifneq ($(call cc-option, -mpreferred-stack-boundary=4),)
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cc_stack_align4 := -mpreferred-stack-boundary=2
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cc_stack_align8 := -mpreferred-stack-boundary=3
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else ifneq ($(call cc-option, -mstack-alignment=16),)
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cc_stack_align4 := -mstack-alignment=4
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cc_stack_align8 := -mstack-alignment=8
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endif
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# How to compile the 16-bit code. Note we always compile for -march=i386;
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# that way we can complain to the user if the CPU is insufficient.
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REALMODE_CFLAGS := -m16 -g -Os -DDISABLE_BRANCH_PROFILING \
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-Wall -Wstrict-prototypes -march=i386 -mregparm=3 \
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-fno-strict-aliasing -fomit-frame-pointer -fno-pic \
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-mno-mmx -mno-sse $(call cc-option,-fcf-protection=none)
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REALMODE_CFLAGS += -ffreestanding
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REALMODE_CFLAGS += -fno-stack-protector
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REALMODE_CFLAGS += -Wno-address-of-packed-member
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REALMODE_CFLAGS += $(cc_stack_align4)
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REALMODE_CFLAGS += $(CLANG_FLAGS)
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export REALMODE_CFLAGS
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# BITS is used as extension for files which are available in a 32 bit
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# and a 64 bit version to simplify shared Makefiles.
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# e.g.: obj-y += foo_$(BITS).o
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export BITS
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#
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# Prevent GCC from generating any FP code by mistake.
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#
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# This must happen before we try the -mpreferred-stack-boundary, see:
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#
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# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
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#
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KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow -mno-avx
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# Intel CET isn't enabled in the kernel
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KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none)
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ifeq ($(CONFIG_X86_32),y)
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BITS := 32
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UTS_MACHINE := i386
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CHECKFLAGS += -D__i386__
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KBUILD_AFLAGS += -m32
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KBUILD_CFLAGS += -m32
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KBUILD_CFLAGS += -msoft-float -mregparm=3 -freg-struct-return
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# Never want PIC in a 32-bit kernel, prevent breakage with GCC built
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# with nonstandard options
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KBUILD_CFLAGS += -fno-pic
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# Align the stack to the register width instead of using the default
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# alignment of 16 bytes. This reduces stack usage and the number of
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# alignment instructions.
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KBUILD_CFLAGS += $(cc_stack_align4)
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# CPU-specific tuning. Anything which can be shared with UML should go here.
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include arch/x86/Makefile_32.cpu
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KBUILD_CFLAGS += $(cflags-y)
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# temporary until string.h is fixed
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KBUILD_CFLAGS += -ffreestanding
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ifeq ($(CONFIG_STACKPROTECTOR),y)
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ifeq ($(CONFIG_SMP),y)
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KBUILD_CFLAGS += -mstack-protector-guard-reg=fs -mstack-protector-guard-symbol=__stack_chk_guard
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else
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KBUILD_CFLAGS += -mstack-protector-guard=global
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endif
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endif
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else
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BITS := 64
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UTS_MACHINE := x86_64
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CHECKFLAGS += -D__x86_64__
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KBUILD_AFLAGS += -m64
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KBUILD_CFLAGS += -m64
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# Align jump targets to 1 byte, not the default 16 bytes:
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KBUILD_CFLAGS += $(call cc-option,-falign-jumps=1)
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# Pack loops tightly as well:
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KBUILD_CFLAGS += $(call cc-option,-falign-loops=1)
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# Don't autogenerate traditional x87 instructions
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KBUILD_CFLAGS += -mno-80387
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KBUILD_CFLAGS += $(call cc-option,-mno-fp-ret-in-387)
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# By default gcc and clang use a stack alignment of 16 bytes for x86.
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# However the standard kernel entry on x86-64 leaves the stack on an
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# 8-byte boundary. If the compiler isn't informed about the actual
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# alignment it will generate extra alignment instructions for the
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# default alignment which keep the stack *mis*aligned.
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# Furthermore an alignment to the register width reduces stack usage
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# and the number of alignment instructions.
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KBUILD_CFLAGS += $(cc_stack_align8)
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# Use -mskip-rax-setup if supported.
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KBUILD_CFLAGS += $(call cc-option,-mskip-rax-setup)
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# FIXME - should be integrated in Makefile.cpu (Makefile_32.cpu)
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cflags-$(CONFIG_MK8) += -march=k8
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cflags-$(CONFIG_MPSC) += -march=nocona
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cflags-$(CONFIG_MCORE2) += -march=core2
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cflags-$(CONFIG_MATOM) += -march=atom
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cflags-$(CONFIG_GENERIC_CPU) += -mtune=generic
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KBUILD_CFLAGS += $(cflags-y)
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KBUILD_CFLAGS += -mno-red-zone
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KBUILD_CFLAGS += -mcmodel=kernel
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endif
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ifdef CONFIG_X86_X32
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x32_ld_ok := $(call try-run,\
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/bin/echo -e '1: .quad 1b' | \
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$(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" - && \
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$(OBJCOPY) -O elf32-x86-64 "$$TMP" "$$TMP.o" && \
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$(LD) -m elf32_x86_64 "$$TMP.o" -o "$$TMP",y,n)
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ifeq ($(x32_ld_ok),y)
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CONFIG_X86_X32_ABI := y
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KBUILD_AFLAGS += -DCONFIG_X86_X32_ABI
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KBUILD_CFLAGS += -DCONFIG_X86_X32_ABI
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else
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$(warning CONFIG_X86_X32 enabled but no binutils support)
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endif
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endif
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export CONFIG_X86_X32_ABI
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#
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# If the function graph tracer is used with mcount instead of fentry,
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# '-maccumulate-outgoing-args' is needed to prevent a GCC bug
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# (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42109)
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#
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ifdef CONFIG_FUNCTION_GRAPH_TRACER
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ifndef CONFIG_HAVE_FENTRY
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ACCUMULATE_OUTGOING_ARGS := 1
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endif
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endif
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ifeq ($(ACCUMULATE_OUTGOING_ARGS), 1)
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# This compiler flag is not supported by Clang:
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KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args,)
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endif
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# Workaround for a gcc prelease that unfortunately was shipped in a suse release
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KBUILD_CFLAGS += -Wno-sign-compare
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#
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KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
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# Avoid indirect branches in kernel to deal with Spectre
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ifdef CONFIG_RETPOLINE
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KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
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# Additionally, avoid generating expensive indirect jumps which
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# are subject to retpolines for small number of switch cases.
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# clang turns off jump table generation by default when under
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# retpoline builds, however, gcc does not for x86. This has
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# only been fixed starting from gcc stable version 8.4.0 and
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# onwards, but not for older ones. See gcc bug #86952.
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ifndef CONFIG_CC_IS_CLANG
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KBUILD_CFLAGS += -fno-jump-tables
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endif
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endif
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KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE)
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ifdef CONFIG_LTO_CLANG
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ifeq ($(shell test $(CONFIG_LLD_VERSION) -lt 130000; echo $$?),0)
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KBUILD_LDFLAGS += -plugin-opt=-stack-alignment=$(if $(CONFIG_X86_32),4,8)
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endif
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endif
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ifdef CONFIG_X86_NEED_RELOCS
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LDFLAGS_vmlinux := --emit-relocs --discard-none
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else
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LDFLAGS_vmlinux :=
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endif
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#
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# The 64-bit kernel must be aligned to 2MB. Pass -z max-page-size=0x200000 to
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# the linker to force 2MB page size regardless of the default page size used
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# by the linker.
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#
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ifdef CONFIG_X86_64
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LDFLAGS_vmlinux += -z max-page-size=0x200000
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endif
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archscripts: scripts_basic
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$(Q)$(MAKE) $(build)=arch/x86/tools relocs
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###
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# Syscall table generation
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archheaders:
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$(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
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###
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# Kernel objects
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head-y := arch/x86/kernel/head_$(BITS).o
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head-y += arch/x86/kernel/head$(BITS).o
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head-y += arch/x86/kernel/ebda.o
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head-y += arch/x86/kernel/platform-quirks.o
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libs-y += arch/x86/lib/
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# drivers-y are linked after core-y
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drivers-$(CONFIG_MATH_EMULATION) += arch/x86/math-emu/
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drivers-$(CONFIG_PCI) += arch/x86/pci/
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# suspend and hibernation support
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drivers-$(CONFIG_PM) += arch/x86/power/
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drivers-$(CONFIG_FB) += arch/x86/video/
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####
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# boot loader support. Several targets are kept for legacy purposes
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boot := arch/x86/boot
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BOOT_TARGETS = bzdisk fdimage fdimage144 fdimage288 hdimage isoimage
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PHONY += bzImage $(BOOT_TARGETS)
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# Default kernel to build
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all: bzImage
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# KBUILD_IMAGE specify target image being built
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KBUILD_IMAGE := $(boot)/bzImage
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bzImage: vmlinux
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ifeq ($(CONFIG_X86_DECODER_SELFTEST),y)
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$(Q)$(MAKE) $(build)=arch/x86/tools posttest
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endif
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$(Q)$(MAKE) $(build)=$(boot) $(KBUILD_IMAGE)
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$(Q)mkdir -p $(objtree)/arch/$(UTS_MACHINE)/boot
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$(Q)ln -fsn ../../x86/boot/bzImage $(objtree)/arch/$(UTS_MACHINE)/boot/$@
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$(BOOT_TARGETS): vmlinux
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$(Q)$(MAKE) $(build)=$(boot) $@
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PHONY += install bzlilo
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install bzlilo:
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$(Q)$(MAKE) $(build)=$(boot) $@
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PHONY += vdso_install
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vdso_install:
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$(Q)$(MAKE) $(build)=arch/x86/entry/vdso $@
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archprepare: checkbin
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checkbin:
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ifndef CONFIG_CC_HAS_ASM_GOTO
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@echo Compiler lacks asm-goto support.
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@exit 1
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endif
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ifdef CONFIG_RETPOLINE
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ifeq ($(RETPOLINE_CFLAGS),)
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@echo "You are building kernel with non-retpoline compiler." >&2
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@echo "Please update your compiler." >&2
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@false
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endif
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endif
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archclean:
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$(Q)rm -rf $(objtree)/arch/i386
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$(Q)rm -rf $(objtree)/arch/x86_64
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$(Q)$(MAKE) $(clean)=$(boot)
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$(Q)$(MAKE) $(clean)=arch/x86/tools
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define archhelp
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echo '* bzImage - Compressed kernel image (arch/x86/boot/bzImage)'
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echo ' install - Install kernel using (your) ~/bin/$(INSTALLKERNEL) or'
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echo ' (distribution) /sbin/$(INSTALLKERNEL) or install to '
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echo ' $$(INSTALL_PATH) and run lilo'
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echo ''
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echo ' fdimage - Create 1.4MB boot floppy image (arch/x86/boot/fdimage)'
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echo ' fdimage144 - Create 1.4MB boot floppy image (arch/x86/boot/fdimage)'
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echo ' fdimage288 - Create 2.8MB boot floppy image (arch/x86/boot/fdimage)'
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echo ' hdimage - Create a BIOS/EFI hard disk image (arch/x86/boot/hdimage)'
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echo ' isoimage - Create a boot CD-ROM image (arch/x86/boot/image.iso)'
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echo ' bzdisk/fdimage*/hdimage/isoimage also accept:'
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echo ' FDARGS="..." arguments for the booted kernel'
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echo ' FDINITRD=file initrd for the booted kernel'
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echo ''
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echo ' kvm_guest.config - Enable Kconfig items for running this kernel as a KVM guest'
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echo ' xen.config - Enable Kconfig items for running this kernel as a Xen guest'
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endef
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