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