8f012745e7
The linker routines that we rely on to produce a relocatable PIE binary treat it as a shared ELF object in some ways, i.e., it emits symbol based R_AARCH64_ABS64 relocations into the final binary since doing so would be appropriate when linking a shared library that is subject to symbol preemption. (This means that an executable can override certain symbols that are exported by a shared library it is linked with, and that the shared library *must* update all its internal references as well, and point them to the version provided by the executable.) Symbol preemption does not occur for OS hosted PIE executables, let alone for vmlinux, and so we would prefer to get rid of these symbol based relocations. This would allow us to simplify the relocation routines, and to strip the .dynsym, .dynstr and .hash sections from the binary. (Note that these are tiny, and are placed in the .init segment, but they clutter up the vmlinux binary.) Note that these R_AARCH64_ABS64 relocations are only emitted for absolute references to symbols defined in the linker script, all other relocatable quantities are covered by anonymous R_AARCH64_RELATIVE relocations that simply list the offsets to all 64-bit values in the binary that need to be fixed up based on the offset between the link time and run time addresses. Fortunately, GNU ld has a -Bsymbolic option, which is intended for shared libraries to allow them to ignore symbol preemption, and unconditionally bind all internal symbol references to its own definitions. So set it for our PIE binary as well, and get rid of the asoociated sections and the relocation code that processes them. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> [will: fixed conflict with __dynsym_offset linker script entry] Signed-off-by: Will Deacon <will.deacon@arm.com> Note: This backport only adds -Bsymbolic to LDFLAGS_vmlinux, but doesn't remove R_AARCH64_ABS64 relocation handling, because those changes depend on later refactoring of the code that we don't need in android-4.4. Bug: 66932127 Change-Id: I56f664e02bc8d2fa3e5f496fb041bc3a8e1a4094 (cherry picked from commit 08cc55b2afd97a654f71b3bebf8bb0ec89fdc498) Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
166 lines
4.8 KiB
Makefile
166 lines
4.8 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 :=-p --no-undefined -X
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CPPFLAGS_vmlinux.lds = -DTEXT_OFFSET=$(TEXT_OFFSET)
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OBJCOPYFLAGS :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
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GZFLAGS :=-9
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ifneq ($(CONFIG_RELOCATABLE),)
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LDFLAGS_vmlinux += -pie -Bsymbolic
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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 ($(cc-name),clang)
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# This is a workaround for https://bugs.llvm.org/show_bug.cgi?id=30792.
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# TODO: revert when this is fixed in LLVM.
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KBUILD_CFLAGS += -mno-implicit-float
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else
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KBUILD_CFLAGS += -mgeneral-regs-only
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endif
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KBUILD_CFLAGS += $(lseinstr)
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KBUILD_CFLAGS += -fno-pic
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KBUILD_CFLAGS += $(call cc-option, -mpc-relative-literal-loads)
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KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
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KBUILD_AFLAGS += $(lseinstr)
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ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
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KBUILD_CPPFLAGS += -mbig-endian
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AS += -EB
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LD += -EB
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else
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KBUILD_CPPFLAGS += -mlittle-endian
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AS += -EL
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LD += -EL
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endif
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CHECKFLAGS += -D__aarch64__
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ifeq ($(CONFIG_ARM64_MODULE_CMODEL_LARGE), y)
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KBUILD_CFLAGS_MODULE += -mcmodel=large
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endif
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ifeq ($(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 := $(shell awk 'BEGIN {srand(); printf "0x%03x000\n", int(512 * rand())}')
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else
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TEXT_OFFSET := 0x00080000
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endif
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ifeq ($(cc-name),clang)
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KBUILD_CFLAGS += $(call cc-disable-warning, asm-operand-widths)
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endif
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# KASAN_SHADOW_OFFSET = VA_START + (1 << (VA_BITS - 3)) - (1 << 61)
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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 - 3)) \
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- (1 << (64 - 32 - 3)) )) )
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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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ifeq ($(CONFIG_BUILD_ARM64_APPENDED_DTB_IMAGE),y)
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KBUILD_IMAGE := $(subst $\",,$(CONFIG_BUILD_ARM64_APPENDED_KERNEL_IMAGE_NAME))
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else
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KBUILD_IMAGE := Image.gz
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endif
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KBUILD_DTBS := dtbs
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ifeq ($(CONFIG_BUILD_ARM64_DT_OVERLAY),y)
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export DTC_FLAGS := -@
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endif
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all: $(KBUILD_IMAGE) $(KBUILD_DTBS)
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boot := arch/arm64/boot
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Image: vmlinux
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$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
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Image.%: vmlinux
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$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
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zinstall install: vmlinux
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$(Q)$(MAKE) $(build)=$(boot) $@
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%.dtb: scripts
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$(Q)$(MAKE) $(build)=$(boot)/dts $(boot)/dts/$@
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PHONY += dtbs dtbs_install
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dtbs: prepare scripts
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$(Q)$(MAKE) $(build)=$(boot)/dts
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dtbs_install:
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$(Q)$(MAKE) $(dtbinst)=$(boot)/dts
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Image-dtb Image.gz-dtb: vmlinux scripts dtbs
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$(Q)$(MAKE) $(build)=$(boot) $(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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$(Q)$(MAKE) $(clean)=$(boot)/dts
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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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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 '* dtbs - Build device tree blobs for enabled boards'
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echo ' dtbs_install - Install dtbs to $(INSTALL_DTBS_PATH)'
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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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