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