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