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				   $(call cc-disable-warning, gnu) \
16				   -fno-asynchronous-unwind-tables
17
18# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
19# disable the stackleak plugin
20cflags-$(CONFIG_ARM64)		:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
21				   -fpie $(DISABLE_STACKLEAK_PLUGIN)
22cflags-$(CONFIG_ARM)		:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
23				   -fno-builtin -fpic \
24				   $(call cc-option,-mno-single-pic-base)
25
26cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt
27
28KBUILD_CFLAGS			:= $(cflags-y) -DDISABLE_BRANCH_PROFILING \
29				   -include $(srctree)/drivers/firmware/efi/libstub/hidden.h \
30				   -D__NO_FORTIFY \
31				   $(call cc-option,-ffreestanding) \
32				   $(call cc-option,-fno-stack-protector) \
33				   -D__DISABLE_EXPORTS
34
35GCOV_PROFILE			:= n
36KASAN_SANITIZE			:= n
37UBSAN_SANITIZE			:= n
38OBJECT_FILES_NON_STANDARD	:= y
39
40# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
41KCOV_INSTRUMENT			:= n
42
43lib-y				:= efi-stub-helper.o gop.o secureboot.o tpm.o \
44				   file.o mem.o random.o randomalloc.o pci.o \
45				   skip_spaces.o lib-cmdline.o lib-ctype.o \
46				   alignedmem.o
47
48# include the stub's generic dependencies from lib/ when building for ARM/arm64
49efi-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c
50
51$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
52	$(call if_changed_rule,cc_o_c)
53
54lib-$(CONFIG_EFI_GENERIC_STUB)	+= efi-stub.o fdt.o string.o \
55				   $(patsubst %.c,lib-%.o,$(efi-deps-y))
56
57lib-$(CONFIG_ARM)		+= arm32-stub.o
58lib-$(CONFIG_ARM64)		+= arm64-stub.o
59lib-$(CONFIG_X86)		+= x86-stub.o
60CFLAGS_arm32-stub.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)
61CFLAGS_arm64-stub.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)
62
63#
64# arm64 puts the stub in the kernel proper, which will unnecessarily retain all
65# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
66# So let's apply the __init annotations at the section level, by prefixing
67# the section names directly. This will ensure that even all the inline string
68# literals are covered.
69# The fact that the stub and the kernel proper are essentially the same binary
70# also means that we need to be extra careful to make sure that the stub does
71# not rely on any absolute symbol references, considering that the virtual
72# kernel mapping that the linker uses is not active yet when the stub is
73# executing. So build all C dependencies of the EFI stub into libstub, and do
74# a verification pass to see if any absolute relocations exist in any of the
75# object files.
76#
77extra-$(CONFIG_EFI_GENERIC_STUB) := $(lib-y)
78lib-$(CONFIG_EFI_GENERIC_STUB)	:= $(patsubst %.o,%.stub.o,$(lib-y))
79
80STUBCOPY_FLAGS-$(CONFIG_ARM64)	+= --prefix-alloc-sections=.init \
81				   --prefix-symbols=__efistub_
82STUBCOPY_RELOC-$(CONFIG_ARM64)	:= R_AARCH64_ABS
83
84$(obj)/%.stub.o: $(obj)/%.o FORCE
85	$(call if_changed,stubcopy)
86
87#
88# Strip debug sections and some other sections that may legally contain
89# absolute relocations, so that we can inspect the remaining sections for
90# such relocations. If none are found, regenerate the output object, but
91# this time, use objcopy and leave all sections in place.
92#
93quiet_cmd_stubcopy = STUBCPY $@
94      cmd_stubcopy =							\
95	$(STRIP) --strip-debug -o $@ $<;				\
96	if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then		\
97		echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \
98		/bin/false;						\
99	fi;								\
100	$(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@
101
102#
103# ARM discards the .data section because it disallows r/w data in the
104# decompressor. So move our .data to .data.efistub, which is preserved
105# explicitly by the decompressor linker script.
106#
107STUBCOPY_FLAGS-$(CONFIG_ARM)	+= --rename-section .data=.data.efistub
108STUBCOPY_RELOC-$(CONFIG_ARM)	:= R_ARM_ABS
109