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__ -O2 \ 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 $(call cc-disable-warning, gnu) 16 17# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly 18# disable the stackleak plugin 19cflags-$(CONFIG_ARM64) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 20 -fpie $(DISABLE_STACKLEAK_PLUGIN) 21cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 22 -fno-builtin -fpic \ 23 $(call cc-option,-mno-single-pic-base) 24 25cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt 26 27KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ 28 -D__NO_FORTIFY \ 29 $(call cc-option,-ffreestanding) \ 30 $(call cc-option,-fno-stack-protector) \ 31 -D__DISABLE_EXPORTS 32 33GCOV_PROFILE := n 34KASAN_SANITIZE := n 35UBSAN_SANITIZE := n 36OBJECT_FILES_NON_STANDARD := y 37 38# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. 39KCOV_INSTRUMENT := n 40 41lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 42 random.o pci.o 43 44# include the stub's generic dependencies from lib/ when building for ARM/arm64 45arm-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c 46arm-deps-$(CONFIG_ARM64) += sort.c 47 48$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 49 $(call if_changed_rule,cc_o_c) 50 51lib-$(CONFIG_EFI_ARMSTUB) += arm-stub.o fdt.o string.o \ 52 $(patsubst %.c,lib-%.o,$(arm-deps-y)) 53 54lib-$(CONFIG_ARM) += arm32-stub.o 55lib-$(CONFIG_ARM64) += arm64-stub.o 56CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 57CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 58 59# 60# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 61# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 62# So let's apply the __init annotations at the section level, by prefixing 63# the section names directly. This will ensure that even all the inline string 64# literals are covered. 65# The fact that the stub and the kernel proper are essentially the same binary 66# also means that we need to be extra careful to make sure that the stub does 67# not rely on any absolute symbol references, considering that the virtual 68# kernel mapping that the linker uses is not active yet when the stub is 69# executing. So build all C dependencies of the EFI stub into libstub, and do 70# a verification pass to see if any absolute relocations exist in any of the 71# object files. 72# 73extra-$(CONFIG_EFI_ARMSTUB) := $(lib-y) 74lib-$(CONFIG_EFI_ARMSTUB) := $(patsubst %.o,%.stub.o,$(lib-y)) 75 76STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 77 --prefix-symbols=__efistub_ 78STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 79 80$(obj)/%.stub.o: $(obj)/%.o FORCE 81 $(call if_changed,stubcopy) 82 83# 84# Strip debug sections and some other sections that may legally contain 85# absolute relocations, so that we can inspect the remaining sections for 86# such relocations. If none are found, regenerate the output object, but 87# this time, use objcopy and leave all sections in place. 88# 89quiet_cmd_stubcopy = STUBCPY $@ 90 cmd_stubcopy = \ 91 $(STRIP) --strip-debug -o $@ $<; \ 92 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 93 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 94 /bin/false; \ 95 fi; \ 96 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 97 98# 99# ARM discards the .data section because it disallows r/w data in the 100# decompressor. So move our .data to .data.efistub, which is preserved 101# explicitly by the decompressor linker script. 102# 103STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub 104STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 105