Mark Rutland
8c213cc217
[ Upstream commit 9abe390e68 ]
Certain portions of code always need to be position-independent
regardless of CONFIG_RELOCATABLE, including code which is executed in an
idmap or which is executed before relocations are applied. In some
kernel configurations the LLD linker generates position-dependent
veneers for such code, and when executed these result in early boot-time
failures.
Marc Zyngier encountered a boot failure resulting from this when
building a (particularly cursed) configuration with LLVM, as he reported
to the list:
https://lore.kernel.org/linux-arm-kernel/86wmjwvatn.wl-maz@kernel.org/
In Marc's kernel configuration, the .head.text and .rodata.text sections
end up more than 128MiB apart, requiring a veneer to branch between the
two:
| [mark@lakrids:~/src/linux]% usekorg 14.1.0 aarch64-linux-objdump -t vmlinux | grep -w _text
| ffff800080000000 g .head.text 0000000000000000 _text
| [mark@lakrids:~/src/linux]% usekorg 14.1.0 aarch64-linux-objdump -t vmlinux | grep -w primary_entry
| ffff8000889df0e0 g .rodata.text 000000000000006c primary_entry,
... consequently, LLD inserts a position-dependent veneer for the branch
from _stext (in .head.text) to primary_entry (in .rodata.text):
| ffff800080000000 <_text>:
| ffff800080000000: fa405a4d ccmp x18, #0x0, #0xd, pl // pl = nfrst
| ffff800080000004: 14003fff b ffff800080010000 <__AArch64AbsLongThunk_primary_entry>
...
| ffff800080010000 <__AArch64AbsLongThunk_primary_entry>:
| ffff800080010000: 58000050 ldr x16, ffff800080010008 <__AArch64AbsLongThunk_primary_entry+0x8>
| ffff800080010004: d61f0200 br x16
| ffff800080010008: 889df0e0 .word 0x889df0e0
| ffff80008001000c: ffff8000 .word 0xffff8000
... and as this is executed early in boot before the kernel is mapped in
TTBR1 this results in a silent boot failure.
Fix this by passing '--pic-veneer' to the linker, which will cause the
linker to use position-independent veneers, e.g.
| ffff800080000000 <_text>:
| ffff800080000000: fa405a4d ccmp x18, #0x0, #0xd, pl // pl = nfrst
| ffff800080000004: 14003fff b ffff800080010000 <__AArch64ADRPThunk_primary_entry>
...
| ffff800080010000 <__AArch64ADRPThunk_primary_entry>:
| ffff800080010000: f004e3f0 adrp x16, ffff800089c8f000 <__idmap_text_start>
| ffff800080010004: 91038210 add x16, x16, #0xe0
| ffff800080010008: d61f0200 br x16
I've opted to pass '--pic-veneer' unconditionally, as:
* In addition to solving the boot failure, these sequences are generally
nicer as they require fewer instructions and don't need to perform
data accesses.
* While the position-independent veneer sequences have a limited +/-2GiB
range, this is not a new restriction. Even kernels built with
CONFIG_RELOCATABLE=n are limited to 2GiB in size as we have several
structues using 32-bit relative offsets and PPREL32 relocations, which
are similarly limited to +/-2GiB in range. These include extable
entries, jump table entries, and alt_instr entries.
* GNU LD defaults to using position-independent veneers, and supports
the same '--pic-veneer' option, so this change is not expected to
adversely affect GNU LD.
I've tested with GNU LD 2.30 to 2.42 inclusive and LLVM 13.0.1 to 19.1.0
inclusive, using the kernel.org binaries from:
* https://mirrors.edge.kernel.org/pub/tools/crosstool/
* https://mirrors.edge.kernel.org/pub/tools/llvm/
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Marc Zyngier <maz@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20240927101838.3061054-1-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
220 lines
7.2 KiB
Makefile
220 lines
7.2 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 --pic-veneer
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ifeq ($(CONFIG_RELOCATABLE), y)
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# Pass --no-apply-dynamic-relocs to restore pre-binutils-2.27 behaviour
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# for relative relocs, since this leads to better Image compression
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# with the relocation offsets always being zero.
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LDFLAGS_vmlinux += -shared -Bsymbolic -z notext \
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$(call ld-option, --no-apply-dynamic-relocs)
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endif
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ifeq ($(CONFIG_ARM64_ERRATUM_843419),y)
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ifeq ($(CONFIG_ARM64_LD_HAS_FIX_ERRATUM_843419),y)
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LDFLAGS_vmlinux += --fix-cortex-a53-843419
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endif
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endif
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cc_has_k_constraint := $(call try-run,echo \
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'int main(void) { \
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asm volatile("and w0, w0, %w0" :: "K" (4294967295)); \
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return 0; \
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}' | $(CC) -S -x c -o "$$TMP" -,,-DCONFIG_CC_HAS_K_CONSTRAINT=1)
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ifeq ($(CONFIG_BROKEN_GAS_INST),y)
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$(warning Detected assembler with broken .inst; disassembly will be unreliable)
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endif
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KBUILD_CFLAGS += -mgeneral-regs-only \
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$(compat_vdso) $(cc_has_k_constraint)
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KBUILD_CFLAGS += $(call cc-disable-warning, psabi)
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KBUILD_AFLAGS += $(compat_vdso)
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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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# Avoid generating .eh_frame* sections.
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ifneq ($(CONFIG_UNWIND_TABLES),y)
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KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
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KBUILD_AFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
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else
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KBUILD_CFLAGS += -fasynchronous-unwind-tables
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KBUILD_AFLAGS += -fasynchronous-unwind-tables
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endif
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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_ARM64_BTI_KERNEL),y)
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KBUILD_CFLAGS += -mbranch-protection=pac-ret+bti
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else ifeq ($(CONFIG_ARM64_PTR_AUTH_KERNEL),y)
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ifeq ($(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET),y)
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KBUILD_CFLAGS += -mbranch-protection=pac-ret
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else
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KBUILD_CFLAGS += -msign-return-address=non-leaf
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endif
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else
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KBUILD_CFLAGS += $(call cc-option,-mbranch-protection=none)
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endif
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# Tell the assembler to support instructions from the latest target
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# architecture.
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#
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# For non-integrated assemblers we'll pass this on the command line, and for
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# integrated assemblers we'll define ARM64_ASM_ARCH and ARM64_ASM_PREAMBLE for
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# inline usage.
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#
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# We cannot pass the same arch flag to the compiler as this would allow it to
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# freely generate instructions which are not supported by earlier architecture
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# versions, which would prevent a single kernel image from working on earlier
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# hardware.
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ifeq ($(CONFIG_AS_HAS_ARMV8_5), y)
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asm-arch := armv8.5-a
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else ifeq ($(CONFIG_AS_HAS_ARMV8_4), y)
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asm-arch := armv8.4-a
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else ifeq ($(CONFIG_AS_HAS_ARMV8_3), y)
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asm-arch := armv8.3-a
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else ifeq ($(CONFIG_AS_HAS_ARMV8_2), y)
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asm-arch := armv8.2-a
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endif
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ifdef asm-arch
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KBUILD_CFLAGS += -Wa,-march=$(asm-arch) \
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-DARM64_ASM_ARCH='"$(asm-arch)"'
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endif
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ifeq ($(CONFIG_SHADOW_CALL_STACK), y)
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KBUILD_CFLAGS += -ffixed-x18
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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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# 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 -z norelro)
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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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# 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 -z norelro)
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UTS_MACHINE := aarch64
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endif
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ifeq ($(CONFIG_LD_IS_LLD), y)
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KBUILD_LDFLAGS += -z norelro
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endif
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CHECKFLAGS += -D__aarch64__
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ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS),y)
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KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
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CC_FLAGS_FTRACE := -fpatchable-function-entry=4,2
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else ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_ARGS),y)
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KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
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CC_FLAGS_FTRACE := -fpatchable-function-entry=2
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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 ifeq ($(CONFIG_KASAN_GENERIC), y)
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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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libs-y := arch/arm64/lib/ $(libs-y)
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libs-$(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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ifeq ($(CONFIG_EFI_ZBOOT),)
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KBUILD_IMAGE := $(boot)/Image.gz
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else
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KBUILD_IMAGE := $(boot)/vmlinuz.efi
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endif
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all: $(notdir $(KBUILD_IMAGE))
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vmlinuz.efi: Image
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Image vmlinuz.efi: 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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install: KBUILD_IMAGE := $(boot)/Image
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install zinstall:
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$(call cmd,install)
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archprepare:
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$(Q)$(MAKE) $(build)=arch/arm64/tools kapi
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ifeq ($(CONFIG_ARM64_ERRATUM_843419),y)
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ifneq ($(CONFIG_ARM64_LD_HAS_FIX_ERRATUM_843419),y)
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@echo "warning: ld does not support --fix-cortex-a53-843419; kernel may be susceptible to erratum" >&2
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endif
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endif
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ifeq ($(CONFIG_ARM64_USE_LSE_ATOMICS),y)
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ifneq ($(CONFIG_ARM64_LSE_ATOMICS),y)
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@echo "warning: LSE atomics not supported by binutils" >&2
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endif
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endif
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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 \
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include/generated/vdso-offsets.h arch/arm64/kernel/vdso/vdso.so
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ifdef CONFIG_COMPAT_VDSO
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$(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso32 \
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include/generated/vdso32-offsets.h arch/arm64/kernel/vdso32/vdso.so
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endif
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endif
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vdso-install-y += arch/arm64/kernel/vdso/vdso.so.dbg
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vdso-install-$(CONFIG_COMPAT_VDSO) += arch/arm64/kernel/vdso32/vdso.so.dbg:vdso32.so
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include $(srctree)/scripts/Makefile.defconf
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PHONY += virtconfig
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virtconfig:
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$(call merge_into_defconfig_override,defconfig,virt)
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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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