1# 2# The stub may be linked into the kernel proper or into a separate boot binary, 3# but in either case, it executes before the kernel does (with MMU disabled) so 4# things like ftrace and stack-protector are likely to cause trouble if left 5# enabled, even if doing so doesn't break the build. 6# 7cflags-$(CONFIG_X86_32) := -march=i386 8cflags-$(CONFIG_X86_64) := -mcmodel=small 9cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ -O2 \ 10 -fPIC -fno-strict-aliasing -mno-red-zone \ 11 -mno-mmx -mno-sse 12 13cflags-$(CONFIG_ARM64) := $(subst -pg,,$(KBUILD_CFLAGS)) 14cflags-$(CONFIG_ARM) := $(subst -pg,,$(KBUILD_CFLAGS)) \ 15 -fno-builtin -fpic -mno-single-pic-base 16 17cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt 18 19KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \ 20 -D__NO_FORTIFY \ 21 $(call cc-option,-ffreestanding) \ 22 $(call cc-option,-fno-stack-protector) 23 24GCOV_PROFILE := n 25KASAN_SANITIZE := n 26UBSAN_SANITIZE := n 27OBJECT_FILES_NON_STANDARD := y 28 29# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. 30KCOV_INSTRUMENT := n 31 32lib-y := efi-stub-helper.o gop.o secureboot.o 33 34# include the stub's generic dependencies from lib/ when building for ARM/arm64 35arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c 36 37$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 38 $(call if_changed_rule,cc_o_c) 39 40lib-$(CONFIG_EFI_ARMSTUB) += arm-stub.o fdt.o string.o random.o \ 41 $(patsubst %.c,lib-%.o,$(arm-deps)) 42 43lib-$(CONFIG_ARM) += arm32-stub.o 44lib-$(CONFIG_ARM64) += arm64-stub.o 45CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 46 47# 48# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 49# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 50# So let's apply the __init annotations at the section level, by prefixing 51# the section names directly. This will ensure that even all the inline string 52# literals are covered. 53# The fact that the stub and the kernel proper are essentially the same binary 54# also means that we need to be extra careful to make sure that the stub does 55# not rely on any absolute symbol references, considering that the virtual 56# kernel mapping that the linker uses is not active yet when the stub is 57# executing. So build all C dependencies of the EFI stub into libstub, and do 58# a verification pass to see if any absolute relocations exist in any of the 59# object files. 60# 61extra-$(CONFIG_EFI_ARMSTUB) := $(lib-y) 62lib-$(CONFIG_EFI_ARMSTUB) := $(patsubst %.o,%.stub.o,$(lib-y)) 63 64STUBCOPY_RM-y := -R *ksymtab* -R *kcrctab* 65STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 66 --prefix-symbols=__efistub_ 67STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 68 69$(obj)/%.stub.o: $(obj)/%.o FORCE 70 $(call if_changed,stubcopy) 71 72# 73# Strip debug sections and some other sections that may legally contain 74# absolute relocations, so that we can inspect the remaining sections for 75# such relocations. If none are found, regenerate the output object, but 76# this time, use objcopy and leave all sections in place. 77# 78quiet_cmd_stubcopy = STUBCPY $@ 79 cmd_stubcopy = if $(STRIP) --strip-debug $(STUBCOPY_RM-y) -o $@ $<; \ 80 then if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); \ 81 then (echo >&2 "$@: absolute symbol references not allowed in the EFI stub"; \ 82 rm -f $@; /bin/false); \ 83 else $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@; fi \ 84 else /bin/false; fi 85 86# 87# ARM discards the .data section because it disallows r/w data in the 88# decompressor. So move our .data to .data.efistub, which is preserved 89# explicitly by the decompressor linker script. 90# 91STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub 92STUBCOPY_RM-$(CONFIG_ARM) += -R ___ksymtab+sort -R ___kcrctab+sort 93STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 94