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 $(call cc-disable-warning, gnu) \ 16 -fno-asynchronous-unwind-tables 17 18# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly 19# disable the stackleak plugin 20cflags-$(CONFIG_ARM64) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 21 -fpie $(DISABLE_STACKLEAK_PLUGIN) 22cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 23 -fno-builtin -fpic \ 24 $(call cc-option,-mno-single-pic-base) 25cflags-$(CONFIG_RISCV) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 26 -fpic 27 28cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt 29 30KBUILD_CFLAGS := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \ 31 -include $(srctree)/drivers/firmware/efi/libstub/hidden.h \ 32 -D__NO_FORTIFY \ 33 -ffreestanding \ 34 -fno-stack-protector \ 35 $(call cc-option,-fno-addrsig) \ 36 -D__DISABLE_EXPORTS 37 38# remove SCS flags from all objects in this directory 39KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) 40 41GCOV_PROFILE := n 42# Sanitizer runtimes are unavailable and cannot be linked here. 43KASAN_SANITIZE := n 44KCSAN_SANITIZE := n 45UBSAN_SANITIZE := n 46OBJECT_FILES_NON_STANDARD := y 47 48# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. 49KCOV_INSTRUMENT := n 50 51lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 52 file.o mem.o random.o randomalloc.o pci.o \ 53 skip_spaces.o lib-cmdline.o lib-ctype.o \ 54 alignedmem.o relocate.o vsprintf.o 55 56# include the stub's generic dependencies from lib/ when building for ARM/arm64 57efi-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c 58 59$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 60 $(call if_changed_rule,cc_o_c) 61 62lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o fdt.o string.o \ 63 $(patsubst %.c,lib-%.o,$(efi-deps-y)) 64 65lib-$(CONFIG_ARM) += arm32-stub.o 66lib-$(CONFIG_ARM64) += arm64-stub.o 67lib-$(CONFIG_X86) += x86-stub.o 68lib-$(CONFIG_RISCV) += riscv-stub.o 69CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 70CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 71 72# 73# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the 74# .bss section, so the .bss section of the EFI stub needs to be included in the 75# .data section of the compressed kernel to ensure initialization. Rename the 76# .bss section here so it's easy to pick out in the linker script. 77# 78STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc 79STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32 80STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64 81 82# 83# ARM discards the .data section because it disallows r/w data in the 84# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub, 85# which are preserved explicitly by the decompressor linker script. 86# 87STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ 88 --rename-section .bss=.bss.efistub,load,alloc 89STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 90 91# 92# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 93# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 94# So let's apply the __init annotations at the section level, by prefixing 95# the section names directly. This will ensure that even all the inline string 96# literals are covered. 97# The fact that the stub and the kernel proper are essentially the same binary 98# also means that we need to be extra careful to make sure that the stub does 99# not rely on any absolute symbol references, considering that the virtual 100# kernel mapping that the linker uses is not active yet when the stub is 101# executing. So build all C dependencies of the EFI stub into libstub, and do 102# a verification pass to see if any absolute relocations exist in any of the 103# object files. 104# 105extra-y := $(lib-y) 106lib-y := $(patsubst %.o,%.stub.o,$(lib-y)) 107 108STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 109 --prefix-symbols=__efistub_ 110STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 111 112# For RISC-V, we don't need anything special other than arm64. Keep all the 113# symbols in .init section and make sure that no absolute symbols references 114# doesn't exist. 115STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \ 116 --prefix-symbols=__efistub_ 117STUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20 118 119$(obj)/%.stub.o: $(obj)/%.o FORCE 120 $(call if_changed,stubcopy) 121 122# 123# Strip debug sections and some other sections that may legally contain 124# absolute relocations, so that we can inspect the remaining sections for 125# such relocations. If none are found, regenerate the output object, but 126# this time, use objcopy and leave all sections in place. 127# 128quiet_cmd_stubcopy = STUBCPY $@ 129 cmd_stubcopy = \ 130 $(STRIP) --strip-debug -o $@ $<; \ 131 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 132 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 133 /bin/false; \ 134 fi; \ 135 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 136