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fa63da2ab0
This is a GCC only option, which warns about ABI changes within GCC, so
unconditionally adding it breaks Clang with tons of:
warning: unknown warning option '-Wno-psabi' [-Wunknown-warning-option]
and link time failures:
ld.lld: error: undefined symbol: __efistub___stack_chk_guard
>>> referenced by arm-stub.c:73
(/home/nathan/cbl/linux/drivers/firmware/efi/libstub/arm-stub.c:73)
>>> arm-stub.stub.o:(__efistub_install_memreserve_table)
in archive ./drivers/firmware/efi/libstub/lib.a
These failures come from the lack of -fno-stack-protector, which is
added via cc-option in drivers/firmware/efi/libstub/Makefile. When an
unknown flag is added to KBUILD_CFLAGS, clang will noisily warn that it
is ignoring the option like above, unlike gcc, who will just error.
$ echo "int main() { return 0; }" > tmp.c
$ clang -Wno-psabi tmp.c; echo $?
warning: unknown warning option '-Wno-psabi' [-Wunknown-warning-option]
1 warning generated.
0
$ gcc -Wsometimes-uninitialized tmp.c; echo $?
gcc: error: unrecognized command line option
‘-Wsometimes-uninitialized’; did you mean ‘-Wmaybe-uninitialized’?
1
For cc-option to work properly with clang and behave like gcc, -Werror
is needed, which was done in commit c3f0d0bc5b ("kbuild, LLVMLinux:
Add -Werror to cc-option to support clang").
$ clang -Werror -Wno-psabi tmp.c; echo $?
error: unknown warning option '-Wno-psabi'
[-Werror,-Wunknown-warning-option]
1
As a consequence of this, when an unknown flag is unconditionally added
to KBUILD_CFLAGS, it will cause cc-option to always fail and those flags
will never get added:
$ clang -Werror -Wno-psabi -fno-stack-protector tmp.c; echo $?
error: unknown warning option '-Wno-psabi'
[-Werror,-Wunknown-warning-option]
1
This can be seen when compiling the whole kernel as some warnings that
are normally disabled (see below) show up. The full list of flags
missing from drivers/firmware/efi/libstub are the following (gathered
from diffing .arm64-stub.o.cmd):
-fno-delete-null-pointer-checks
-Wno-address-of-packed-member
-Wframe-larger-than=2048
-Wno-unused-const-variable
-fno-strict-overflow
-fno-merge-all-constants
-fno-stack-check
-Werror=date-time
-Werror=incompatible-pointer-types
-ffreestanding
-fno-stack-protector
Use cc-disable-warning so that it gets disabled for GCC and does nothing
for Clang.
Fixes: ebcc5928c5 ("arm64: Silence gcc warnings about arch ABI drift")
Link: https://github.com/ClangBuiltLinux/linux/issues/511
Reported-by: Qian Cai <cai@lca.pw>
Acked-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
178 lines
5.8 KiB
Makefile
178 lines
5.8 KiB
Makefile
#
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# arch/arm64/Makefile
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#
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# This file is included by the global makefile so that you can add your own
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# architecture-specific flags and dependencies.
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#
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# This file is subject to the terms and conditions of the GNU General Public
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# License. See the file "COPYING" in the main directory of this archive
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# for more details.
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#
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# Copyright (C) 1995-2001 by Russell King
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LDFLAGS_vmlinux :=--no-undefined -X
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CPPFLAGS_vmlinux.lds = -DTEXT_OFFSET=$(TEXT_OFFSET)
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GZFLAGS :=-9
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ifeq ($(CONFIG_RELOCATABLE), y)
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# Pass --no-apply-dynamic-relocs to restore pre-binutils-2.27 behaviour
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# for relative relocs, since this leads to better Image compression
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# with the relocation offsets always being zero.
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LDFLAGS_vmlinux += -shared -Bsymbolic -z notext -z norelro \
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$(call ld-option, --no-apply-dynamic-relocs)
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endif
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ifeq ($(CONFIG_ARM64_ERRATUM_843419),y)
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ifeq ($(call ld-option, --fix-cortex-a53-843419),)
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$(warning ld does not support --fix-cortex-a53-843419; kernel may be susceptible to erratum)
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else
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LDFLAGS_vmlinux += --fix-cortex-a53-843419
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endif
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endif
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KBUILD_DEFCONFIG := defconfig
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# Check for binutils support for specific extensions
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lseinstr := $(call as-instr,.arch_extension lse,-DCONFIG_AS_LSE=1)
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ifeq ($(CONFIG_ARM64_LSE_ATOMICS), y)
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ifeq ($(lseinstr),)
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$(warning LSE atomics not supported by binutils)
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endif
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endif
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ifeq ($(CONFIG_ARM64), y)
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brokengasinst := $(call as-instr,1:\n.inst 0\n.rept . - 1b\n\nnop\n.endr\n,,-DCONFIG_BROKEN_GAS_INST=1)
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ifneq ($(brokengasinst),)
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$(warning Detected assembler with broken .inst; disassembly will be unreliable)
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endif
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endif
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KBUILD_CFLAGS += -mgeneral-regs-only $(lseinstr) $(brokengasinst)
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KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
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KBUILD_CFLAGS += $(call cc-disable-warning, psabi)
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KBUILD_AFLAGS += $(lseinstr) $(brokengasinst)
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KBUILD_CFLAGS += $(call cc-option,-mabi=lp64)
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KBUILD_AFLAGS += $(call cc-option,-mabi=lp64)
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ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y)
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prepare: stack_protector_prepare
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stack_protector_prepare: prepare0
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$(eval KBUILD_CFLAGS += -mstack-protector-guard=sysreg \
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-mstack-protector-guard-reg=sp_el0 \
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-mstack-protector-guard-offset=$(shell \
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awk '{if ($$2 == "TSK_STACK_CANARY") print $$3;}' \
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include/generated/asm-offsets.h))
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endif
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ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
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KBUILD_CPPFLAGS += -mbig-endian
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CHECKFLAGS += -D__AARCH64EB__
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AS += -EB
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# Prefer the baremetal ELF build target, but not all toolchains include
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# it so fall back to the standard linux version if needed.
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KBUILD_LDFLAGS += -EB $(call ld-option, -maarch64elfb, -maarch64linuxb)
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UTS_MACHINE := aarch64_be
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else
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KBUILD_CPPFLAGS += -mlittle-endian
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CHECKFLAGS += -D__AARCH64EL__
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AS += -EL
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# Same as above, prefer ELF but fall back to linux target if needed.
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KBUILD_LDFLAGS += -EL $(call ld-option, -maarch64elf, -maarch64linux)
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UTS_MACHINE := aarch64
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endif
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CHECKFLAGS += -D__aarch64__
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ifeq ($(CONFIG_ARM64_MODULE_PLTS),y)
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KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/arm64/kernel/module.lds
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endif
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# Default value
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head-y := arch/arm64/kernel/head.o
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# The byte offset of the kernel image in RAM from the start of RAM.
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ifeq ($(CONFIG_ARM64_RANDOMIZE_TEXT_OFFSET), y)
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TEXT_OFFSET := $(shell awk "BEGIN {srand(); printf \"0x%06x\n\", \
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int(2 * 1024 * 1024 / (2 ^ $(CONFIG_ARM64_PAGE_SHIFT)) * \
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rand()) * (2 ^ $(CONFIG_ARM64_PAGE_SHIFT))}")
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else
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TEXT_OFFSET := 0x00080000
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endif
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ifeq ($(CONFIG_KASAN_SW_TAGS), y)
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KASAN_SHADOW_SCALE_SHIFT := 4
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else
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KASAN_SHADOW_SCALE_SHIFT := 3
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endif
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KBUILD_CFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
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KBUILD_CPPFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
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KBUILD_AFLAGS += -DKASAN_SHADOW_SCALE_SHIFT=$(KASAN_SHADOW_SCALE_SHIFT)
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# KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - KASAN_SHADOW_SCALE_SHIFT))
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# - (1 << (64 - KASAN_SHADOW_SCALE_SHIFT))
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# in 32-bit arithmetic
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KASAN_SHADOW_OFFSET := $(shell printf "0x%08x00000000\n" $$(( \
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(0xffffffff & (-1 << ($(CONFIG_ARM64_VA_BITS) - 32))) \
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+ (1 << ($(CONFIG_ARM64_VA_BITS) - 32 - $(KASAN_SHADOW_SCALE_SHIFT))) \
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- (1 << (64 - 32 - $(KASAN_SHADOW_SCALE_SHIFT))) )) )
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export TEXT_OFFSET GZFLAGS
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core-y += arch/arm64/kernel/ arch/arm64/mm/
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core-$(CONFIG_NET) += arch/arm64/net/
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core-$(CONFIG_KVM) += arch/arm64/kvm/
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core-$(CONFIG_XEN) += arch/arm64/xen/
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core-$(CONFIG_CRYPTO) += arch/arm64/crypto/
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libs-y := arch/arm64/lib/ $(libs-y)
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core-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
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# Default target when executing plain make
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boot := arch/arm64/boot
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KBUILD_IMAGE := $(boot)/Image.gz
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all: Image.gz
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Image: vmlinux
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$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
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Image.%: Image
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$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
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zinstall install:
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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/arm64/kernel/vdso $@
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# We use MRPROPER_FILES and CLEAN_FILES now
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archclean:
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$(Q)$(MAKE) $(clean)=$(boot)
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ifeq ($(KBUILD_EXTMOD),)
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# We need to generate vdso-offsets.h before compiling certain files in kernel/.
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# In order to do that, we should use the archprepare target, but we can't since
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# asm-offsets.h is included in some files used to generate vdso-offsets.h, and
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# asm-offsets.h is built in prepare0, for which archprepare is a dependency.
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# Therefore we need to generate the header after prepare0 has been made, hence
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# this hack.
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prepare: vdso_prepare
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vdso_prepare: prepare0
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$(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso include/generated/vdso-offsets.h
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endif
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define archhelp
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echo '* Image.gz - Compressed kernel image (arch/$(ARCH)/boot/Image.gz)'
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echo ' Image - Uncompressed kernel image (arch/$(ARCH)/boot/Image)'
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echo ' install - Install uncompressed kernel'
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echo ' zinstall - Install compressed kernel'
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echo ' Install using (your) ~/bin/installkernel or'
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echo ' (distribution) /sbin/installkernel or'
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echo ' install to $$(INSTALL_PATH) and run lilo'
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endef
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