1 # SPDX-License-Identifier: GPL-2.0
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.
8 cflags-$(CONFIG_X86_32) := -march=i386
9 cflags-$(CONFIG_X86_64) := -mcmodel=small
10 cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ -O2 \
11 -fPIC -fno-strict-aliasing -mno-red-zone \
12 -mno-mmx -mno-sse -fshort-wchar \
14 $(call cc-disable-warning, address-of-packed-member) \
15 $(call cc-disable-warning, gnu)
17 # arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
18 # disable the stackleak plugin
19 cflags-$(CONFIG_ARM64) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
20 -fpie $(DISABLE_STACKLEAK_PLUGIN)
21 cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
23 $(call cc-option,-mno-single-pic-base)
25 cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt
27 KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \
28 -include $(srctree)/drivers/firmware/efi/libstub/hidden.h \
30 $(call cc-option,-ffreestanding) \
31 $(call cc-option,-fno-stack-protector) \
37 OBJECT_FILES_NON_STANDARD := y
39 # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
42 lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \
43 file.o mem.o random.o randomalloc.o pci.o
45 # include the stub's generic dependencies from lib/ when building for ARM/arm64
46 arm-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c
48 $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
49 $(call if_changed_rule,cc_o_c)
51 lib-$(CONFIG_EFI_ARMSTUB) += arm-stub.o fdt.o string.o \
52 $(patsubst %.c,lib-%.o,$(arm-deps-y))
54 lib-$(CONFIG_ARM) += arm32-stub.o
55 lib-$(CONFIG_ARM64) += arm64-stub.o
56 lib-$(CONFIG_X86) += x86-stub.o
57 CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
58 CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
61 # arm64 puts the stub in the kernel proper, which will unnecessarily retain all
62 # code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
63 # So let's apply the __init annotations at the section level, by prefixing
64 # the section names directly. This will ensure that even all the inline string
65 # literals are covered.
66 # The fact that the stub and the kernel proper are essentially the same binary
67 # also means that we need to be extra careful to make sure that the stub does
68 # not rely on any absolute symbol references, considering that the virtual
69 # kernel mapping that the linker uses is not active yet when the stub is
70 # executing. So build all C dependencies of the EFI stub into libstub, and do
71 # a verification pass to see if any absolute relocations exist in any of the
74 extra-$(CONFIG_EFI_ARMSTUB) := $(lib-y)
75 lib-$(CONFIG_EFI_ARMSTUB) := $(patsubst %.o,%.stub.o,$(lib-y))
77 STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
78 --prefix-symbols=__efistub_
79 STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS
81 $(obj)/%.stub.o: $(obj)/%.o FORCE
82 $(call if_changed,stubcopy)
85 # Strip debug sections and some other sections that may legally contain
86 # absolute relocations, so that we can inspect the remaining sections for
87 # such relocations. If none are found, regenerate the output object, but
88 # this time, use objcopy and leave all sections in place.
90 quiet_cmd_stubcopy = STUBCPY $@
92 $(STRIP) --strip-debug -o $@ $<; \
93 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \
94 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \
97 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@
100 # ARM discards the .data section because it disallows r/w data in the
101 # decompressor. So move our .data to .data.efistub, which is preserved
102 # explicitly by the decompressor linker script.
104 STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub
105 STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS