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__ $(LINUX_INCLUDE) -O2 \
10				   -fPIC -fno-strict-aliasing -mno-red-zone \
11				   -mno-mmx -mno-sse
12
13cflags-$(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				   $(call cc-option,-ffreestanding) \
21				   $(call cc-option,-fno-stack-protector)
22
23GCOV_PROFILE			:= n
24KASAN_SANITIZE			:= n
25UBSAN_SANITIZE			:= n
26
27lib-y				:= efi-stub-helper.o
28
29# include the stub's generic dependencies from lib/ when building for ARM/arm64
30arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c
31
32$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
33	$(call if_changed_rule,cc_o_c)
34
35lib-$(CONFIG_EFI_ARMSTUB)	+= arm-stub.o fdt.o string.o \
36				   $(patsubst %.c,lib-%.o,$(arm-deps))
37
38lib-$(CONFIG_ARM)		+= arm32-stub.o
39lib-$(CONFIG_ARM64)		+= arm64-stub.o
40CFLAGS_arm64-stub.o 		:= -DTEXT_OFFSET=$(TEXT_OFFSET)
41
42#
43# arm64 puts the stub in the kernel proper, which will unnecessarily retain all
44# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
45# So let's apply the __init annotations at the section level, by prefixing
46# the section names directly. This will ensure that even all the inline string
47# literals are covered.
48# The fact that the stub and the kernel proper are essentially the same binary
49# also means that we need to be extra careful to make sure that the stub does
50# not rely on any absolute symbol references, considering that the virtual
51# kernel mapping that the linker uses is not active yet when the stub is
52# executing. So build all C dependencies of the EFI stub into libstub, and do
53# a verification pass to see if any absolute relocations exist in any of the
54# object files.
55#
56extra-$(CONFIG_EFI_ARMSTUB)	:= $(lib-y)
57lib-$(CONFIG_EFI_ARMSTUB)	:= $(patsubst %.o,%.stub.o,$(lib-y))
58
59STUBCOPY_FLAGS-y		:= -R .debug* -R *ksymtab* -R *kcrctab*
60STUBCOPY_FLAGS-$(CONFIG_ARM64)	+= --prefix-alloc-sections=.init \
61				   --prefix-symbols=__efistub_
62STUBCOPY_RELOC-$(CONFIG_ARM64)	:= R_AARCH64_ABS
63
64$(obj)/%.stub.o: $(obj)/%.o FORCE
65	$(call if_changed,stubcopy)
66
67quiet_cmd_stubcopy = STUBCPY $@
68      cmd_stubcopy = if $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@; then	\
69		     $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y)	\
70		     && (echo >&2 "$@: absolute symbol references not allowed in the EFI stub"; \
71			 rm -f $@; /bin/false); else /bin/false; fi
72
73#
74# ARM discards the .data section because it disallows r/w data in the
75# decompressor. So move our .data to .data.efistub, which is preserved
76# explicitly by the decompressor linker script.
77#
78STUBCOPY_FLAGS-$(CONFIG_ARM)	+= --rename-section .data=.data.efistub
79STUBCOPY_RELOC-$(CONFIG_ARM)	:= R_ARM_ABS
80