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