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 13 14cflags-$(CONFIG_ARM64) := $(subst -pg,,$(KBUILD_CFLAGS)) -fpie 15cflags-$(CONFIG_ARM) := $(subst -pg,,$(KBUILD_CFLAGS)) \ 16 -fno-builtin -fpic \ 17 $(call cc-option,-mno-single-pic-base) 18 19cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt 20 21KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ 22 -D__NO_FORTIFY \ 23 $(call cc-option,-ffreestanding) \ 24 $(call cc-option,-fno-stack-protector) \ 25 $(DISABLE_LTO) 26 27GCOV_PROFILE := n 28KASAN_SANITIZE := n 29UBSAN_SANITIZE := n 30OBJECT_FILES_NON_STANDARD := y 31 32# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. 33KCOV_INSTRUMENT := n 34 35lib-y := efi-stub-helper.o gop.o secureboot.o 36lib-$(CONFIG_RESET_ATTACK_MITIGATION) += tpm.o 37 38# include the stub's generic dependencies from lib/ when building for ARM/arm64 39arm-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c 40arm-deps-$(CONFIG_ARM64) += sort.c 41 42$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 43 $(call if_changed_rule,cc_o_c) 44 45lib-$(CONFIG_EFI_ARMSTUB) += arm-stub.o fdt.o string.o random.o \ 46 $(patsubst %.c,lib-%.o,$(arm-deps-y)) 47 48lib-$(CONFIG_ARM) += arm32-stub.o 49lib-$(CONFIG_ARM64) += arm64-stub.o 50CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 51 52# 53# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 54# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 55# So let's apply the __init annotations at the section level, by prefixing 56# the section names directly. This will ensure that even all the inline string 57# literals are covered. 58# The fact that the stub and the kernel proper are essentially the same binary 59# also means that we need to be extra careful to make sure that the stub does 60# not rely on any absolute symbol references, considering that the virtual 61# kernel mapping that the linker uses is not active yet when the stub is 62# executing. So build all C dependencies of the EFI stub into libstub, and do 63# a verification pass to see if any absolute relocations exist in any of the 64# object files. 65# 66extra-$(CONFIG_EFI_ARMSTUB) := $(lib-y) 67lib-$(CONFIG_EFI_ARMSTUB) := $(patsubst %.o,%.stub.o,$(lib-y)) 68 69STUBCOPY_RM-y := -R *ksymtab* -R *kcrctab* 70STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 71 --prefix-symbols=__efistub_ 72STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 73 74$(obj)/%.stub.o: $(obj)/%.o FORCE 75 $(call if_changed,stubcopy) 76 77# 78# Strip debug sections and some other sections that may legally contain 79# absolute relocations, so that we can inspect the remaining sections for 80# such relocations. If none are found, regenerate the output object, but 81# this time, use objcopy and leave all sections in place. 82# 83quiet_cmd_stubcopy = STUBCPY $@ 84 cmd_stubcopy = if $(STRIP) --strip-debug $(STUBCOPY_RM-y) -o $@ $<; \ 85 then if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); \ 86 then (echo >&2 "$@: absolute symbol references not allowed in the EFI stub"; \ 87 rm -f $@; /bin/false); \ 88 else $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@; fi \ 89 else /bin/false; fi 90 91# 92# ARM discards the .data section because it disallows r/w data in the 93# decompressor. So move our .data to .data.efistub, which is preserved 94# explicitly by the decompressor linker script. 95# 96STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub 97STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 98