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 \ 27 $(call cc-option,-mbranch-protection=none) 28cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \ 29 -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \ 30 -DEFI_HAVE_STRCMP -fno-builtin -fpic \ 31 $(call cc-option,-mno-single-pic-base) 32cflags-$(CONFIG_RISCV) += -fpic 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), $(KBUILD_CFLAGS)) 59 60GCOV_PROFILE := n 61# Sanitizer runtimes are unavailable and cannot be linked here. 62KASAN_SANITIZE := n 63KCSAN_SANITIZE := n 64KMSAN_SANITIZE := n 65UBSAN_SANITIZE := n 66OBJECT_FILES_NON_STANDARD := y 67 68# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. 69KCOV_INSTRUMENT := n 70 71lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 72 file.o mem.o random.o randomalloc.o pci.o \ 73 skip_spaces.o lib-cmdline.o lib-ctype.o \ 74 alignedmem.o relocate.o printk.o vsprintf.o 75 76# include the stub's libfdt dependencies from lib/ when needed 77libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \ 78 fdt_empty_tree.c fdt_sw.c 79 80lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \ 81 $(patsubst %.c,lib-%.o,$(libfdt-deps)) 82 83$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 84 $(call if_changed_rule,cc_o_c) 85 86lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \ 87 screen_info.o efi-stub-entry.o 88 89lib-$(CONFIG_ARM) += arm32-stub.o 90lib-$(CONFIG_ARM64) += arm64.o arm64-stub.o arm64-entry.o smbios.o 91lib-$(CONFIG_X86) += x86-stub.o 92lib-$(CONFIG_RISCV) += riscv.o riscv-stub.o 93lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o 94 95CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 96 97zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o 98lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y) 99 100extra-y := $(lib-y) 101lib-y := $(patsubst %.o,%.stub.o,$(lib-y)) 102 103# Even when -mbranch-protection=none is set, Clang will generate a 104# .note.gnu.property for code-less object files (like lib/ctype.c), 105# so work around this by explicitly removing the unwanted section. 106# https://bugs.llvm.org/show_bug.cgi?id=46480 107STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property 108 109# 110# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the 111# .bss section, so the .bss section of the EFI stub needs to be included in the 112# .data section of the compressed kernel to ensure initialization. Rename the 113# .bss section here so it's easy to pick out in the linker script. 114# 115STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc 116STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32 117STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64 118 119# 120# ARM discards the .data section because it disallows r/w data in the 121# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub, 122# which are preserved explicitly by the decompressor linker script. 123# 124STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ 125 --rename-section .bss=.bss.efistub,load,alloc 126STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 127 128# 129# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 130# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 131# So let's apply the __init annotations at the section level, by prefixing 132# the section names directly. This will ensure that even all the inline string 133# literals are covered. 134# The fact that the stub and the kernel proper are essentially the same binary 135# also means that we need to be extra careful to make sure that the stub does 136# not rely on any absolute symbol references, considering that the virtual 137# kernel mapping that the linker uses is not active yet when the stub is 138# executing. So build all C dependencies of the EFI stub into libstub, and do 139# a verification pass to see if any absolute relocations exist in any of the 140# object files. 141# 142STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 143 --prefix-symbols=__efistub_ 144STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS64 145 146# For RISC-V, we don't need anything special other than arm64. Keep all the 147# symbols in .init section and make sure that no absolute symbols references 148# doesn't exist. 149STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \ 150 --prefix-symbols=__efistub_ 151STUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20 152 153# For LoongArch, keep all the symbols in .init section and make sure that no 154# absolute symbols references exist. 155STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \ 156 --prefix-symbols=__efistub_ 157STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA 158 159$(obj)/%.stub.o: $(obj)/%.o FORCE 160 $(call if_changed,stubcopy) 161 162# 163# Strip debug sections and some other sections that may legally contain 164# absolute relocations, so that we can inspect the remaining sections for 165# such relocations. If none are found, regenerate the output object, but 166# this time, use objcopy and leave all sections in place. 167# 168quiet_cmd_stubcopy = STUBCPY $@ 169 cmd_stubcopy = \ 170 $(STRIP) --strip-debug -o $@ $<; \ 171 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 172 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 173 /bin/false; \ 174 fi; \ 175 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 176