1# SPDX-License-Identifier: GPL-2.0 2# 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) so 5# things like ftrace and stack-protector are likely to cause trouble if left 6# enabled, even if doing so doesn't break the build. 7# 8 9# non-x86 reuses KBUILD_CFLAGS, x86 does not 10cflags-y := $(KBUILD_CFLAGS) 11 12cflags-$(CONFIG_X86_32) := -march=i386 13cflags-$(CONFIG_X86_64) := -mcmodel=small 14cflags-$(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 $(CLANG_FLAGS) 22 23# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly 24# disable the stackleak plugin 25cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_STACKLEAK_PLUGIN) \ 26 -fno-unwind-tables -fno-asynchronous-unwind-tables 27cflags-$(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 33cflags-$(CONFIG_LOONGARCH) += -fpie 34 35cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt 36 37KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \ 38 -Os -DDISABLE_BRANCH_PROFILING \ 39 -include $(srctree)/include/linux/hidden.h \ 40 -D__NO_FORTIFY \ 41 -ffreestanding \ 42 -fno-stack-protector \ 43 $(call cc-option,-fno-addrsig) \ 44 -D__DISABLE_EXPORTS 45 46# 47# struct randomization only makes sense for Linux internal types, which the EFI 48# stub code never touches, so let's turn off struct randomization for the stub 49# altogether 50# 51KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS)) 52 53# remove SCS flags from all objects in this directory 54KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) 55# disable CFI 56KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS)) 57# disable LTO 58KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS)) 59 60# The .data section would be renamed to .data.efistub, therefore, remove 61# `-fdata-sections` flag from KBUILD_CFLAGS_KERNEL 62KBUILD_CFLAGS_KERNEL := $(filter-out -fdata-sections, $(KBUILD_CFLAGS_KERNEL)) 63 64lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 65 file.o mem.o random.o randomalloc.o pci.o \ 66 skip_spaces.o lib-cmdline.o lib-ctype.o \ 67 alignedmem.o relocate.o printk.o vsprintf.o 68 69# include the stub's libfdt dependencies from lib/ when needed 70libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \ 71 fdt_empty_tree.c fdt_sw.c 72 73lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \ 74 $(patsubst %.c,lib-%.o,$(libfdt-deps)) 75 76$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 77 $(call if_changed_rule,cc_o_c) 78 79lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \ 80 screen_info.o efi-stub-entry.o 81 82lib-$(CONFIG_ARM) += arm32-stub.o 83lib-$(CONFIG_ARM64) += kaslr.o arm64.o arm64-stub.o smbios.o 84lib-$(CONFIG_X86) += x86-stub.o 85lib-$(CONFIG_X86_64) += x86-5lvl.o 86lib-$(CONFIG_RISCV) += kaslr.o riscv.o riscv-stub.o 87lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o 88 89CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 90 91zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o 92lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y) 93 94lib-$(CONFIG_UNACCEPTED_MEMORY) += unaccepted_memory.o bitmap.o find.o 95 96extra-y := $(lib-y) 97lib-y := $(patsubst %.o,%.stub.o,$(lib-y)) 98 99# Even when -mbranch-protection=none is set, Clang will generate a 100# .note.gnu.property for code-less object files (like lib/ctype.c), 101# so work around this by explicitly removing the unwanted section. 102# https://llvm.org/pr46480 103STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property 104 105STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32 106STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64 107 108# 109# ARM discards the .data section because it disallows r/w data in the 110# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub, 111# which are preserved explicitly by the decompressor linker script. 112# 113STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ 114 --rename-section .bss=.bss.efistub,load,alloc 115STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 116 117# 118# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 119# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 120# So let's apply the __init annotations at the section level, by prefixing 121# the section names directly. This will ensure that even all the inline string 122# literals are covered. 123# The fact that the stub and the kernel proper are essentially the same binary 124# also means that we need to be extra careful to make sure that the stub does 125# not rely on any absolute symbol references, considering that the virtual 126# kernel mapping that the linker uses is not active yet when the stub is 127# executing. So build all C dependencies of the EFI stub into libstub, and do 128# a verification pass to see if any absolute relocations exist in any of the 129# object files. 130# 131STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 132 --prefix-symbols=__efistub_ 133STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 134 135# For RISC-V, we don't need anything special other than arm64. Keep all the 136# symbols in .init section and make sure that no absolute symbols references 137# exist. 138STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \ 139 --prefix-symbols=__efistub_ 140STUBCOPY_RELOC-$(CONFIG_RISCV) := -E R_RISCV_HI20\|R_RISCV_$(BITS)\|R_RISCV_RELAX 141 142# For LoongArch, keep all the symbols in .init section and make sure that no 143# absolute symbols references exist. 144STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \ 145 --prefix-symbols=__efistub_ 146STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA 147 148$(obj)/%.stub.o: $(obj)/%.o FORCE 149 $(call if_changed,stubcopy) 150 151# 152# Strip debug sections and some other sections that may legally contain 153# absolute relocations, so that we can inspect the remaining sections for 154# such relocations. If none are found, regenerate the output object, but 155# this time, use objcopy and leave all sections in place. 156# 157quiet_cmd_stubcopy = STUBCPY $@ 158 cmd_stubcopy = \ 159 $(STRIP) --strip-debug -o $@ $<; \ 160 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 161 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 162 /bin/false; \ 163 fi; \ 164 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 165