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 -fshort-wchar \
13				   -Wno-pointer-sign \
14				   $(call cc-disable-warning, address-of-packed-member) \
15				   $(call cc-disable-warning, gnu)
16
17# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
18# disable the stackleak plugin
19cflags-$(CONFIG_ARM64)		:= $(subst -pg,,$(KBUILD_CFLAGS)) -fpie \
20				   $(DISABLE_STACKLEAK_PLUGIN)
21cflags-$(CONFIG_ARM)		:= $(subst -pg,,$(KBUILD_CFLAGS)) \
22				   -fno-builtin -fpic \
23				   $(call cc-option,-mno-single-pic-base)
24
25cflags-$(CONFIG_EFI_ARMSTUB)	+= -I$(srctree)/scripts/dtc/libfdt
26
27KBUILD_CFLAGS			:= $(cflags-y) -DDISABLE_BRANCH_PROFILING \
28				   -D__NO_FORTIFY \
29				   $(call cc-option,-ffreestanding) \
30				   $(call cc-option,-fno-stack-protector) \
31				   -D__DISABLE_EXPORTS
32
33GCOV_PROFILE			:= n
34KASAN_SANITIZE			:= n
35UBSAN_SANITIZE			:= n
36OBJECT_FILES_NON_STANDARD	:= y
37
38# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
39KCOV_INSTRUMENT			:= n
40
41lib-y				:= efi-stub-helper.o gop.o secureboot.o tpm.o
42
43# include the stub's generic dependencies from lib/ when building for ARM/arm64
44arm-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c
45arm-deps-$(CONFIG_ARM64) += sort.c
46
47$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
48	$(call if_changed_rule,cc_o_c)
49
50lib-$(CONFIG_EFI_ARMSTUB)	+= arm-stub.o fdt.o string.o random.o \
51				   $(patsubst %.c,lib-%.o,$(arm-deps-y))
52
53lib-$(CONFIG_ARM)		+= arm32-stub.o
54lib-$(CONFIG_ARM64)		+= arm64-stub.o
55CFLAGS_arm64-stub.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)
56
57#
58# arm64 puts the stub in the kernel proper, which will unnecessarily retain all
59# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
60# So let's apply the __init annotations at the section level, by prefixing
61# the section names directly. This will ensure that even all the inline string
62# literals are covered.
63# The fact that the stub and the kernel proper are essentially the same binary
64# also means that we need to be extra careful to make sure that the stub does
65# not rely on any absolute symbol references, considering that the virtual
66# kernel mapping that the linker uses is not active yet when the stub is
67# executing. So build all C dependencies of the EFI stub into libstub, and do
68# a verification pass to see if any absolute relocations exist in any of the
69# object files.
70#
71extra-$(CONFIG_EFI_ARMSTUB)	:= $(lib-y)
72lib-$(CONFIG_EFI_ARMSTUB)	:= $(patsubst %.o,%.stub.o,$(lib-y))
73
74STUBCOPY_RM-y			:= -R *ksymtab* -R *kcrctab*
75STUBCOPY_FLAGS-$(CONFIG_ARM64)	+= --prefix-alloc-sections=.init \
76				   --prefix-symbols=__efistub_
77STUBCOPY_RELOC-$(CONFIG_ARM64)	:= R_AARCH64_ABS
78
79$(obj)/%.stub.o: $(obj)/%.o FORCE
80	$(call if_changed,stubcopy)
81
82#
83# Strip debug sections and some other sections that may legally contain
84# absolute relocations, so that we can inspect the remaining sections for
85# such relocations. If none are found, regenerate the output object, but
86# this time, use objcopy and leave all sections in place.
87#
88quiet_cmd_stubcopy = STUBCPY $@
89      cmd_stubcopy = if $(STRIP) --strip-debug $(STUBCOPY_RM-y) -o $@ $<; \
90		     then if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); \
91		     then (echo >&2 "$@: absolute symbol references not allowed in the EFI stub"; \
92			   rm -f $@; /bin/false);			  \
93		     else $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@; fi	  \
94		     else /bin/false; fi
95
96#
97# ARM discards the .data section because it disallows r/w data in the
98# decompressor. So move our .data to .data.efistub, which is preserved
99# explicitly by the decompressor linker script.
100#
101STUBCOPY_FLAGS-$(CONFIG_ARM)	+= --rename-section .data=.data.efistub
102STUBCOPY_RELOC-$(CONFIG_ARM)	:= R_ARM_ABS
103