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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