152 lines
6.1 KiB
Makefile
152 lines
6.1 KiB
Makefile
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# SPDX-License-Identifier: GPL-2.0
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#
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# The stub may be linked into the kernel proper or into a separate boot binary,
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# but in either case, it executes before the kernel does (with MMU disabled) so
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# things like ftrace and stack-protector are likely to cause trouble if left
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# enabled, even if doing so doesn't break the build.
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#
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cflags-$(CONFIG_X86_32) := -march=i386
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cflags-$(CONFIG_X86_64) := -mcmodel=small
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cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \
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-fPIC -fno-strict-aliasing -mno-red-zone \
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-mno-mmx -mno-sse -fshort-wchar \
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-Wno-pointer-sign \
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$(call cc-disable-warning, address-of-packed-member) \
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$(call cc-disable-warning, gnu) \
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-fno-asynchronous-unwind-tables \
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$(CLANG_FLAGS)
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# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
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# disable the stackleak plugin
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cflags-$(CONFIG_ARM64) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
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-fpie $(DISABLE_STACKLEAK_PLUGIN) \
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$(call cc-option,-mbranch-protection=none)
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cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
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-fno-builtin -fpic \
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$(call cc-option,-mno-single-pic-base)
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cflags-$(CONFIG_RISCV) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
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-fpic
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cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt
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KBUILD_CFLAGS := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \
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-include $(srctree)/include/linux/hidden.h \
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-D__NO_FORTIFY \
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-ffreestanding \
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-fno-stack-protector \
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$(call cc-option,-fno-addrsig) \
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-D__DISABLE_EXPORTS
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#
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# struct randomization only makes sense for Linux internal types, which the EFI
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# stub code never touches, so let's turn off struct randomization for the stub
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# altogether
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#
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KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS))
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# remove SCS flags from all objects in this directory
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KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
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# disable LTO
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KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
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GCOV_PROFILE := n
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# Sanitizer runtimes are unavailable and cannot be linked here.
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KASAN_SANITIZE := n
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KCSAN_SANITIZE := n
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UBSAN_SANITIZE := n
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OBJECT_FILES_NON_STANDARD := y
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# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
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KCOV_INSTRUMENT := n
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lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \
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file.o mem.o random.o randomalloc.o pci.o \
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skip_spaces.o lib-cmdline.o lib-ctype.o \
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alignedmem.o relocate.o vsprintf.o
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# include the stub's generic dependencies from lib/ when building for ARM/arm64
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efi-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c
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$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
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$(call if_changed_rule,cc_o_c)
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lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o fdt.o string.o \
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$(patsubst %.c,lib-%.o,$(efi-deps-y))
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lib-$(CONFIG_ARM) += arm32-stub.o
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lib-$(CONFIG_ARM64) += arm64-stub.o
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lib-$(CONFIG_X86) += x86-stub.o
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lib-$(CONFIG_RISCV) += riscv-stub.o
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CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
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# Even when -mbranch-protection=none is set, Clang will generate a
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# .note.gnu.property for code-less object files (like lib/ctype.c),
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# so work around this by explicitly removing the unwanted section.
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# https://bugs.llvm.org/show_bug.cgi?id=46480
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STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property
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#
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# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the
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# .bss section, so the .bss section of the EFI stub needs to be included in the
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# .data section of the compressed kernel to ensure initialization. Rename the
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# .bss section here so it's easy to pick out in the linker script.
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#
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STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc
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STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32
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STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64
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#
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# ARM discards the .data section because it disallows r/w data in the
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# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub,
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# which are preserved explicitly by the decompressor linker script.
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#
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STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
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--rename-section .bss=.bss.efistub,load,alloc
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STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
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#
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# arm64 puts the stub in the kernel proper, which will unnecessarily retain all
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# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
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# So let's apply the __init annotations at the section level, by prefixing
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# the section names directly. This will ensure that even all the inline string
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# literals are covered.
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# The fact that the stub and the kernel proper are essentially the same binary
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# also means that we need to be extra careful to make sure that the stub does
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# not rely on any absolute symbol references, considering that the virtual
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# kernel mapping that the linker uses is not active yet when the stub is
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# executing. So build all C dependencies of the EFI stub into libstub, and do
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# a verification pass to see if any absolute relocations exist in any of the
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# object files.
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#
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extra-y := $(lib-y)
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lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
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STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
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--prefix-symbols=__efistub_
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STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS
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# For RISC-V, we don't need anything special other than arm64. Keep all the
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# symbols in .init section and make sure that no absolute symbols references
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# doesn't exist.
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STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \
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--prefix-symbols=__efistub_
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STUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20
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$(obj)/%.stub.o: $(obj)/%.o FORCE
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$(call if_changed,stubcopy)
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#
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# Strip debug sections and some other sections that may legally contain
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# absolute relocations, so that we can inspect the remaining sections for
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# such relocations. If none are found, regenerate the output object, but
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# this time, use objcopy and leave all sections in place.
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#
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quiet_cmd_stubcopy = STUBCPY $@
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cmd_stubcopy = \
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$(STRIP) --strip-debug -o $@ $<; \
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if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \
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echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \
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/bin/false; \
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fi; \
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$(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@
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