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# 8cflags-$(CONFIG_X86_32) := -march=i386 9cflags-$(CONFIG_X86_64) := -mcmodel=small 10cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \ 11 -fPIC -fno-strict-aliasing -mno-red-zone \ 12 -mno-mmx -mno-sse -fshort-wchar \ 13 -Wno-pointer-sign \ 14 $(call cc-disable-warning, address-of-packed-member) \ 15 $(call cc-disable-warning, gnu) \ 16 -fno-asynchronous-unwind-tables \ 17 $(CLANG_FLAGS) 18 19# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly 20# disable the stackleak plugin 21cflags-$(CONFIG_ARM64) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 22 -fpie $(DISABLE_STACKLEAK_PLUGIN) \ 23 $(call cc-option,-mbranch-protection=none) 24cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 25 -fno-builtin -fpic \ 26 $(call cc-option,-mno-single-pic-base) 27cflags-$(CONFIG_RISCV) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 28 -fpic 29cflags-$(CONFIG_LOONGARCH) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 30 -fpie 31 32cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt 33 34KBUILD_CFLAGS := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \ 35 -include $(srctree)/include/linux/hidden.h \ 36 -D__NO_FORTIFY \ 37 -ffreestanding \ 38 -fno-stack-protector \ 39 $(call cc-option,-fno-addrsig) \ 40 -D__DISABLE_EXPORTS 41 42# remove SCS flags from all objects in this directory 43KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) 44# disable LTO 45KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS)) 46 47GCOV_PROFILE := n 48# Sanitizer runtimes are unavailable and cannot be linked here. 49KASAN_SANITIZE := n 50KCSAN_SANITIZE := n 51UBSAN_SANITIZE := n 52OBJECT_FILES_NON_STANDARD := y 53 54# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. 55KCOV_INSTRUMENT := n 56 57lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 58 file.o mem.o random.o randomalloc.o pci.o \ 59 skip_spaces.o lib-cmdline.o lib-ctype.o \ 60 alignedmem.o relocate.o vsprintf.o 61 62# include the stub's generic dependencies from lib/ when building for ARM/arm64 63efi-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c 64 65$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 66 $(call if_changed_rule,cc_o_c) 67 68lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o fdt.o string.o \ 69 $(patsubst %.c,lib-%.o,$(efi-deps-y)) 70 71lib-$(CONFIG_ARM) += arm32-stub.o 72lib-$(CONFIG_ARM64) += arm64-stub.o 73lib-$(CONFIG_X86) += x86-stub.o 74lib-$(CONFIG_RISCV) += riscv-stub.o 75lib-$(CONFIG_LOONGARCH) += loongarch-stub.o 76 77CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 78 79# Even when -mbranch-protection=none is set, Clang will generate a 80# .note.gnu.property for code-less object files (like lib/ctype.c), 81# so work around this by explicitly removing the unwanted section. 82# https://bugs.llvm.org/show_bug.cgi?id=46480 83STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property 84 85# 86# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the 87# .bss section, so the .bss section of the EFI stub needs to be included in the 88# .data section of the compressed kernel to ensure initialization. Rename the 89# .bss section here so it's easy to pick out in the linker script. 90# 91STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc 92STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32 93STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64 94 95# 96# ARM discards the .data section because it disallows r/w data in the 97# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub, 98# which are preserved explicitly by the decompressor linker script. 99# 100STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ 101 --rename-section .bss=.bss.efistub,load,alloc 102STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 103 104# 105# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 106# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 107# So let's apply the __init annotations at the section level, by prefixing 108# the section names directly. This will ensure that even all the inline string 109# literals are covered. 110# The fact that the stub and the kernel proper are essentially the same binary 111# also means that we need to be extra careful to make sure that the stub does 112# not rely on any absolute symbol references, considering that the virtual 113# kernel mapping that the linker uses is not active yet when the stub is 114# executing. So build all C dependencies of the EFI stub into libstub, and do 115# a verification pass to see if any absolute relocations exist in any of the 116# object files. 117# 118extra-y := $(lib-y) 119lib-y := $(patsubst %.o,%.stub.o,$(lib-y)) 120 121STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 122 --prefix-symbols=__efistub_ 123STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 124 125# For RISC-V, we don't need anything special other than arm64. Keep all the 126# symbols in .init section and make sure that no absolute symbols references 127# doesn't exist. 128STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \ 129 --prefix-symbols=__efistub_ 130STUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20 131 132# For LoongArch, keep all the symbols in .init section and make sure that no 133# absolute symbols references exist. 134STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \ 135 --prefix-symbols=__efistub_ 136STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA 137 138$(obj)/%.stub.o: $(obj)/%.o FORCE 139 $(call if_changed,stubcopy) 140 141# 142# Strip debug sections and some other sections that may legally contain 143# absolute relocations, so that we can inspect the remaining sections for 144# such relocations. If none are found, regenerate the output object, but 145# this time, use objcopy and leave all sections in place. 146# 147quiet_cmd_stubcopy = STUBCPY $@ 148 cmd_stubcopy = \ 149 $(STRIP) --strip-debug -o $@ $<; \ 150 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 151 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 152 /bin/false; \ 153 fi; \ 154 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 155