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 32cflags-$(CONFIG_LOONGARCH) += -fpie 33 34cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt 35 36KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \ 37 -Os -DDISABLE_BRANCH_PROFILING \ 38 -include $(srctree)/include/linux/hidden.h \ 39 -D__NO_FORTIFY \ 40 -ffreestanding \ 41 -fno-stack-protector \ 42 $(call cc-option,-fno-addrsig) \ 43 -D__DISABLE_EXPORTS 44 45# 46# struct randomization only makes sense for Linux internal types, which the EFI 47# stub code never touches, so let's turn off struct randomization for the stub 48# altogether 49# 50KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS)) 51 52# remove SCS flags from all objects in this directory 53KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) 54# disable CFI 55KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS)) 56# disable LTO 57KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS)) 58 59GCOV_PROFILE := n 60# Sanitizer runtimes are unavailable and cannot be linked here. 61KASAN_SANITIZE := n 62KCSAN_SANITIZE := n 63KMSAN_SANITIZE := n 64UBSAN_SANITIZE := n 65OBJECT_FILES_NON_STANDARD := y 66 67# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. 68KCOV_INSTRUMENT := n 69 70lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 71 file.o mem.o random.o randomalloc.o pci.o \ 72 skip_spaces.o lib-cmdline.o lib-ctype.o \ 73 alignedmem.o relocate.o printk.o vsprintf.o 74 75# include the stub's libfdt dependencies from lib/ when needed 76libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \ 77 fdt_empty_tree.c fdt_sw.c 78 79lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \ 80 $(patsubst %.c,lib-%.o,$(libfdt-deps)) 81 82$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 83 $(call if_changed_rule,cc_o_c) 84 85lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \ 86 screen_info.o efi-stub-entry.o 87 88lib-$(CONFIG_ARM) += arm32-stub.o 89lib-$(CONFIG_ARM64) += arm64.o arm64-stub.o smbios.o 90lib-$(CONFIG_X86) += x86-stub.o 91lib-$(CONFIG_RISCV) += riscv.o riscv-stub.o 92lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o 93 94CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 95 96zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o 97lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y) 98 99extra-y := $(lib-y) 100lib-y := $(patsubst %.o,%.stub.o,$(lib-y)) 101 102# Even when -mbranch-protection=none is set, Clang will generate a 103# .note.gnu.property for code-less object files (like lib/ctype.c), 104# so work around this by explicitly removing the unwanted section. 105# https://bugs.llvm.org/show_bug.cgi?id=46480 106STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property 107 108# 109# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the 110# .bss section, so the .bss section of the EFI stub needs to be included in the 111# .data section of the compressed kernel to ensure initialization. Rename the 112# .bss section here so it's easy to pick out in the linker script. 113# 114STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc 115STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32 116STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64 117 118# 119# ARM discards the .data section because it disallows r/w data in the 120# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub, 121# which are preserved explicitly by the decompressor linker script. 122# 123STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ 124 --rename-section .bss=.bss.efistub,load,alloc 125STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 126 127# 128# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 129# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 130# So let's apply the __init annotations at the section level, by prefixing 131# the section names directly. This will ensure that even all the inline string 132# literals are covered. 133# The fact that the stub and the kernel proper are essentially the same binary 134# also means that we need to be extra careful to make sure that the stub does 135# not rely on any absolute symbol references, considering that the virtual 136# kernel mapping that the linker uses is not active yet when the stub is 137# executing. So build all C dependencies of the EFI stub into libstub, and do 138# a verification pass to see if any absolute relocations exist in any of the 139# object files. 140# 141STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 142 --prefix-symbols=__efistub_ 143STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 144 145# For RISC-V, we don't need anything special other than arm64. Keep all the 146# symbols in .init section and make sure that no absolute symbols references 147# doesn't exist. 148STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \ 149 --prefix-symbols=__efistub_ 150STUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20 151 152# For LoongArch, keep all the symbols in .init section and make sure that no 153# absolute symbols references exist. 154STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \ 155 --prefix-symbols=__efistub_ 156STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA 157 158$(obj)/%.stub.o: $(obj)/%.o FORCE 159 $(call if_changed,stubcopy) 160 161# 162# Strip debug sections and some other sections that may legally contain 163# absolute relocations, so that we can inspect the remaining sections for 164# such relocations. If none are found, regenerate the output object, but 165# this time, use objcopy and leave all sections in place. 166# 167quiet_cmd_stubcopy = STUBCPY $@ 168 cmd_stubcopy = \ 169 $(STRIP) --strip-debug -o $@ $<; \ 170 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 171 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 172 /bin/false; \ 173 fi; \ 174 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 175