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 $(call cc-option,-mbranch-protection=none) 27cflags-$(CONFIG_ARM) += -fno-builtin -fpic \ 28 $(call cc-option,-mno-single-pic-base) 29cflags-$(CONFIG_RISCV) += -fpic 30cflags-$(CONFIG_LOONGARCH) += -fpie 31 32cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt 33 34KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \ 35 -Os -DDISABLE_BRANCH_PROFILING \ 36 -include $(srctree)/include/linux/hidden.h \ 37 -D__NO_FORTIFY \ 38 -ffreestanding \ 39 -fno-stack-protector \ 40 $(call cc-option,-fno-addrsig) \ 41 -D__DISABLE_EXPORTS 42 43# 44# struct randomization only makes sense for Linux internal types, which the EFI 45# stub code never touches, so let's turn off struct randomization for the stub 46# altogether 47# 48KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS)) 49 50# remove SCS flags from all objects in this directory 51KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) 52# disable CFI 53KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS)) 54# disable LTO 55KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS)) 56 57GCOV_PROFILE := n 58# Sanitizer runtimes are unavailable and cannot be linked here. 59KASAN_SANITIZE := n 60KCSAN_SANITIZE := n 61KMSAN_SANITIZE := n 62UBSAN_SANITIZE := n 63OBJECT_FILES_NON_STANDARD := y 64 65# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. 66KCOV_INSTRUMENT := n 67 68lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 69 file.o mem.o random.o randomalloc.o pci.o \ 70 skip_spaces.o lib-cmdline.o lib-ctype.o \ 71 alignedmem.o relocate.o vsprintf.o 72 73# include the stub's libfdt dependencies from lib/ when needed 74libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \ 75 fdt_empty_tree.c fdt_sw.c 76 77lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \ 78 $(patsubst %.c,lib-%.o,$(libfdt-deps)) 79 80$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 81 $(call if_changed_rule,cc_o_c) 82 83lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o 84 85lib-$(CONFIG_ARM) += arm32-stub.o 86lib-$(CONFIG_ARM64) += arm64-stub.o arm64-entry.o 87lib-$(CONFIG_X86) += x86-stub.o 88lib-$(CONFIG_RISCV) += riscv-stub.o 89lib-$(CONFIG_LOONGARCH) += loongarch-stub.o 90 91CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 92 93zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o 94lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y) 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://bugs.llvm.org/show_bug.cgi?id=46480 103STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property 104 105# 106# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the 107# .bss section, so the .bss section of the EFI stub needs to be included in the 108# .data section of the compressed kernel to ensure initialization. Rename the 109# .bss section here so it's easy to pick out in the linker script. 110# 111STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc 112STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32 113STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64 114 115# 116# ARM discards the .data section because it disallows r/w data in the 117# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub, 118# which are preserved explicitly by the decompressor linker script. 119# 120STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ 121 --rename-section .bss=.bss.efistub,load,alloc 122STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 123 124# 125# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 126# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 127# So let's apply the __init annotations at the section level, by prefixing 128# the section names directly. This will ensure that even all the inline string 129# literals are covered. 130# The fact that the stub and the kernel proper are essentially the same binary 131# also means that we need to be extra careful to make sure that the stub does 132# not rely on any absolute symbol references, considering that the virtual 133# kernel mapping that the linker uses is not active yet when the stub is 134# executing. So build all C dependencies of the EFI stub into libstub, and do 135# a verification pass to see if any absolute relocations exist in any of the 136# object files. 137# 138STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 139 --prefix-symbols=__efistub_ 140STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS64 141 142# For RISC-V, we don't need anything special other than arm64. Keep all the 143# symbols in .init section and make sure that no absolute symbols references 144# doesn't exist. 145STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \ 146 --prefix-symbols=__efistub_ 147STUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20 148 149# For LoongArch, keep all the symbols in .init section and make sure that no 150# absolute symbols references exist. 151STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \ 152 --prefix-symbols=__efistub_ 153STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA 154 155$(obj)/%.stub.o: $(obj)/%.o FORCE 156 $(call if_changed,stubcopy) 157 158# 159# Strip debug sections and some other sections that may legally contain 160# absolute relocations, so that we can inspect the remaining sections for 161# such relocations. If none are found, regenerate the output object, but 162# this time, use objcopy and leave all sections in place. 163# 164quiet_cmd_stubcopy = STUBCPY $@ 165 cmd_stubcopy = \ 166 $(STRIP) --strip-debug -o $@ $<; \ 167 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 168 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 169 /bin/false; \ 170 fi; \ 171 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 172