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1# SPDX-License-Identifier: GPL-2.02#3# The stub may be linked into the kernel proper or into a separate boot binary,4# but in either case, it executes before the kernel does (with MMU disabled) so5# things like ftrace and stack-protector are likely to cause trouble if left6# enabled, even if doing so doesn't break the build.7#8 9# non-x86 reuses KBUILD_CFLAGS, x86 does not10cflags-y := $(KBUILD_CFLAGS)11 12cflags-$(CONFIG_X86_32) := -march=i38613cflags-$(CONFIG_X86_64) := -mcmodel=small14cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \15 -fPIC -fno-strict-aliasing -mno-red-zone \16 -mno-mmx -mno-sse -fshort-wchar \17 -Wno-pointer-sign \18 $(call cc-disable-warning, address-of-packed-member) \19 $(call cc-disable-warning, gnu) \20 -fno-asynchronous-unwind-tables \21 $(CLANG_FLAGS)22 23# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly24# disable the stackleak plugin25cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_STACKLEAK_PLUGIN) \26 -fno-unwind-tables -fno-asynchronous-unwind-tables27cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \28 -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \29 -DEFI_HAVE_STRCMP -fno-builtin -fpic \30 $(call cc-option,-mno-single-pic-base) \31 $(DISABLE_STACKLEAK_PLUGIN)32cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax \33 $(DISABLE_STACKLEAK_PLUGIN)34cflags-$(CONFIG_LOONGARCH) += -fpie35 36cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt37 38KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \39 -Os -DDISABLE_BRANCH_PROFILING \40 -include $(srctree)/include/linux/hidden.h \41 -D__NO_FORTIFY \42 -ffreestanding \43 -fno-stack-protector \44 $(call cc-option,-fno-addrsig) \45 -D__DISABLE_EXPORTS46 47#48# struct randomization only makes sense for Linux internal types, which the EFI49# stub code never touches, so let's turn off struct randomization for the stub50# altogether51#52KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS))53 54# remove SCS flags from all objects in this directory55KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))56# disable CFI57KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS))58# disable LTO59KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))60 61# The .data section would be renamed to .data.efistub, therefore, remove62# `-fdata-sections` flag from KBUILD_CFLAGS_KERNEL63KBUILD_CFLAGS_KERNEL := $(filter-out -fdata-sections, $(KBUILD_CFLAGS_KERNEL))64 65lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \66 file.o mem.o random.o randomalloc.o pci.o \67 skip_spaces.o lib-cmdline.o lib-ctype.o \68 alignedmem.o relocate.o printk.o vsprintf.o69 70# include the stub's libfdt dependencies from lib/ when needed71libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \72 fdt_empty_tree.c fdt_sw.c73 74lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \75 $(patsubst %.c,lib-%.o,$(libfdt-deps))76 77$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE78 $(call if_changed_rule,cc_o_c)79 80lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \81 screen_info.o efi-stub-entry.o82 83lib-$(CONFIG_ARM) += arm32-stub.o84lib-$(CONFIG_ARM64) += kaslr.o arm64.o arm64-stub.o smbios.o85lib-$(CONFIG_X86) += x86-stub.o smbios.o86lib-$(CONFIG_X86_64) += x86-5lvl.o87lib-$(CONFIG_RISCV) += kaslr.o riscv.o riscv-stub.o88lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o89 90CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)91 92zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o93lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y)94 95lib-$(CONFIG_UNACCEPTED_MEMORY) += unaccepted_memory.o bitmap.o find.o96 97extra-y := $(lib-y)98lib-y := $(patsubst %.o,%.stub.o,$(lib-y))99 100# Even when -mbranch-protection=none is set, Clang will generate a101# .note.gnu.property for code-less object files (like lib/ctype.c),102# so work around this by explicitly removing the unwanted section.103# https://llvm.org/pr46480104STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property105 106STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32107STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64108 109#110# ARM discards the .data section because it disallows r/w data in the111# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub,112# which are preserved explicitly by the decompressor linker script.113#114STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \115 --rename-section .bss=.bss.efistub,load,alloc116STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS117 118#119# arm64 puts the stub in the kernel proper, which will unnecessarily retain all120# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.121# So let's apply the __init annotations at the section level, by prefixing122# the section names directly. This will ensure that even all the inline string123# literals are covered.124# The fact that the stub and the kernel proper are essentially the same binary125# also means that we need to be extra careful to make sure that the stub does126# not rely on any absolute symbol references, considering that the virtual127# kernel mapping that the linker uses is not active yet when the stub is128# executing. So build all C dependencies of the EFI stub into libstub, and do129# a verification pass to see if any absolute relocations exist in any of the130# object files.131#132STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \133 --prefix-symbols=__efistub_134STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS135 136# For RISC-V, we don't need anything special other than arm64. Keep all the137# symbols in .init section and make sure that no absolute symbols references138# exist.139STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \140 --prefix-symbols=__efistub_141STUBCOPY_RELOC-$(CONFIG_RISCV) := -E R_RISCV_HI20\|R_RISCV_$(BITS)\|R_RISCV_RELAX142 143# For LoongArch, keep all the symbols in .init section and make sure that no144# absolute symbols references exist.145STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \146 --prefix-symbols=__efistub_147STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA148 149$(obj)/%.stub.o: $(obj)/%.o FORCE150 $(call if_changed,stubcopy)151 152#153# Strip debug sections and some other sections that may legally contain154# absolute relocations, so that we can inspect the remaining sections for155# such relocations. If none are found, regenerate the output object, but156# this time, use objcopy and leave all sections in place.157#158quiet_cmd_stubcopy = STUBCPY $@159 cmd_stubcopy = \160 $(STRIP) --strip-debug -o $@ $<; \161 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \162 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \163 /bin/false; \164 fi; \165 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@166