2 # The stub may be linked into the kernel proper or into a separate boot binary,
3 # but in either case, it executes before the kernel does (with MMU disabled) so
4 # things like ftrace and stack-protector are likely to cause trouble if left
5 # enabled, even if doing so doesn't break the build.
7 cflags-$(CONFIG_X86_32) := -march=i386
8 cflags-$(CONFIG_X86_64) := -mcmodel=small
9 cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ -O2 \
10 -fPIC -fno-strict-aliasing -mno-red-zone \
13 cflags-$(CONFIG_ARM64) := $(subst -pg,,$(KBUILD_CFLAGS))
14 cflags-$(CONFIG_ARM) := $(subst -pg,,$(KBUILD_CFLAGS)) \
15 -fno-builtin -fpic -mno-single-pic-base
17 cflags-$(CONFIG_EFI_ARMSTUB) += -I$(srctree)/scripts/dtc/libfdt
19 KBUILD_CFLAGS := $(cflags-y) -DDISABLE_BRANCH_PROFILING \
20 $(call cc-option,-ffreestanding) \
21 $(call cc-option,-fno-stack-protector)
26 OBJECT_FILES_NON_STANDARD := y
28 # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
31 lib-y := efi-stub-helper.o gop.o secureboot.o
33 # include the stub's generic dependencies from lib/ when building for ARM/arm64
34 arm-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c sort.c
36 $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
37 $(call if_changed_rule,cc_o_c)
39 lib-$(CONFIG_EFI_ARMSTUB) += arm-stub.o fdt.o string.o random.o \
40 $(patsubst %.c,lib-%.o,$(arm-deps))
42 lib-$(CONFIG_ARM) += arm32-stub.o
43 lib-$(CONFIG_ARM64) += arm64-stub.o
44 CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
47 # arm64 puts the stub in the kernel proper, which will unnecessarily retain all
48 # code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
49 # So let's apply the __init annotations at the section level, by prefixing
50 # the section names directly. This will ensure that even all the inline string
51 # literals are covered.
52 # The fact that the stub and the kernel proper are essentially the same binary
53 # also means that we need to be extra careful to make sure that the stub does
54 # not rely on any absolute symbol references, considering that the virtual
55 # kernel mapping that the linker uses is not active yet when the stub is
56 # executing. So build all C dependencies of the EFI stub into libstub, and do
57 # a verification pass to see if any absolute relocations exist in any of the
60 extra-$(CONFIG_EFI_ARMSTUB) := $(lib-y)
61 lib-$(CONFIG_EFI_ARMSTUB) := $(patsubst %.o,%.stub.o,$(lib-y))
63 STUBCOPY_RM-y := -R *ksymtab* -R *kcrctab*
64 STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
65 --prefix-symbols=__efistub_
66 STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS
68 $(obj)/%.stub.o: $(obj)/%.o FORCE
69 $(call if_changed,stubcopy)
72 # Strip debug sections and some other sections that may legally contain
73 # absolute relocations, so that we can inspect the remaining sections for
74 # such relocations. If none are found, regenerate the output object, but
75 # this time, use objcopy and leave all sections in place.
77 quiet_cmd_stubcopy = STUBCPY $@
78 cmd_stubcopy = if $(STRIP) --strip-debug $(STUBCOPY_RM-y) -o $@ $<; \
79 then if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); \
80 then (echo >&2 "$@: absolute symbol references not allowed in the EFI stub"; \
81 rm -f $@; /bin/false); \
82 else $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@; fi \
86 # ARM discards the .data section because it disallows r/w data in the
87 # decompressor. So move our .data to .data.efistub, which is preserved
88 # explicitly by the decompressor linker script.
90 STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub
91 STUBCOPY_RM-$(CONFIG_ARM) += -R ___ksymtab+sort -R ___kcrctab+sort
92 STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS