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 $(call cc-option,-mno-single-pic-base) 31cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax \ 32 $(DISABLE_STACKLEAK_PLUGIN) 33cflags-$(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), $(KBUILD_CFLAGS)) 59 60lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 61 file.o mem.o random.o randomalloc.o pci.o \ 62 skip_spaces.o lib-cmdline.o lib-ctype.o \ 63 alignedmem.o relocate.o printk.o vsprintf.o 64 65# include the stub's libfdt dependencies from lib/ when needed 66libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \ 67 fdt_empty_tree.c fdt_sw.c 68 69lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \ 70 $(patsubst %.c,lib-%.o,$(libfdt-deps)) 71 72$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 73 $(call if_changed_rule,cc_o_c) 74 75lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \ 76 screen_info.o efi-stub-entry.o 77 78lib-$(CONFIG_ARM) += arm32-stub.o 79lib-$(CONFIG_ARM64) += kaslr.o arm64.o arm64-stub.o smbios.o 80lib-$(CONFIG_X86) += x86-stub.o smbios.o 81lib-$(CONFIG_X86_64) += x86-5lvl.o 82lib-$(CONFIG_RISCV) += kaslr.o riscv.o riscv-stub.o 83lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o 84 85CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 86 87zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o 88lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y) 89 90lib-$(CONFIG_UNACCEPTED_MEMORY) += unaccepted_memory.o bitmap.o find.o 91 92extra-y := $(lib-y) 93lib-y := $(patsubst %.o,%.stub.o,$(lib-y)) 94 95# Even when -mbranch-protection=none is set, Clang will generate a 96# .note.gnu.property for code-less object files (like lib/ctype.c), 97# so work around this by explicitly removing the unwanted section. 98# https://llvm.org/pr46480 99STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property 100 101STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32 102STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64 103 104# 105# ARM discards the .data section because it disallows r/w data in the 106# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub, 107# which are preserved explicitly by the decompressor linker script. 108# 109STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ 110 --rename-section .bss=.bss.efistub,load,alloc 111STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 112 113# 114# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 115# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 116# So let's apply the __init annotations at the section level, by prefixing 117# the section names directly. This will ensure that even all the inline string 118# literals are covered. 119# The fact that the stub and the kernel proper are essentially the same binary 120# also means that we need to be extra careful to make sure that the stub does 121# not rely on any absolute symbol references, considering that the virtual 122# kernel mapping that the linker uses is not active yet when the stub is 123# executing. So build all C dependencies of the EFI stub into libstub, and do 124# a verification pass to see if any absolute relocations exist in any of the 125# object files. 126# 127STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 128 --prefix-symbols=__efistub_ 129STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 130 131# For RISC-V, we don't need anything special other than arm64. Keep all the 132# symbols in .init section and make sure that no absolute symbols references 133# exist. 134STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \ 135 --prefix-symbols=__efistub_ 136STUBCOPY_RELOC-$(CONFIG_RISCV) := -E R_RISCV_HI20\|R_RISCV_$(BITS)\|R_RISCV_RELAX 137 138# For LoongArch, keep all the symbols in .init section and make sure that no 139# absolute symbols references exist. 140STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \ 141 --prefix-symbols=__efistub_ 142STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA 143 144$(obj)/%.stub.o: $(obj)/%.o FORCE 145 $(call if_changed,stubcopy) 146 147# 148# Strip debug sections and some other sections that may legally contain 149# absolute relocations, so that we can inspect the remaining sections for 150# such relocations. If none are found, regenerate the output object, but 151# this time, use objcopy and leave all sections in place. 152# 153quiet_cmd_stubcopy = STUBCPY $@ 154 cmd_stubcopy = \ 155 $(STRIP) --strip-debug -o $@ $<; \ 156 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 157 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 158 /bin/false; \ 159 fi; \ 160 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 161