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.
9 # non-x86 reuses KBUILD_CFLAGS, x86 does not
10 cflags-y := $(KBUILD_CFLAGS)
12 cflags-$(CONFIG_X86_32) := -march=i386
13 cflags-$(CONFIG_X86_64) := -mcmodel=small
14 cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \
15 -fPIC -fno-strict-aliasing -mno-red-zone \
16 -mno-mmx -mno-sse -fshort-wchar \
18 $(call cc-disable-warning, address-of-packed-member) \
19 $(call cc-disable-warning, gnu) \
20 -fno-asynchronous-unwind-tables \
23 # arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
24 # disable the stackleak plugin
25 cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_STACKLEAK_PLUGIN) \
26 -fno-unwind-tables -fno-asynchronous-unwind-tables
27 cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \
28 -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \
29 -DEFI_HAVE_STRCMP -fno-builtin -fpic \
30 $(call cc-option,-mno-single-pic-base)
31 cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE
32 cflags-$(CONFIG_LOONGARCH) += -fpie
34 cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt
36 KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \
37 -Os -DDISABLE_BRANCH_PROFILING \
38 -include $(srctree)/include/linux/hidden.h \
41 -fno-stack-protector \
42 $(call cc-option,-fno-addrsig) \
46 # struct randomization only makes sense for Linux internal types, which the EFI
47 # stub code never touches, so let's turn off struct randomization for the stub
50 KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS))
52 # remove SCS flags from all objects in this directory
53 KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
55 KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS))
57 KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
60 # Sanitizer runtimes are unavailable and cannot be linked here.
65 OBJECT_FILES_NON_STANDARD := y
67 # Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
70 lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \
71 file.o mem.o random.o randomalloc.o pci.o \
72 skip_spaces.o lib-cmdline.o lib-ctype.o \
73 alignedmem.o relocate.o printk.o vsprintf.o
75 # include the stub's libfdt dependencies from lib/ when needed
76 libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \
77 fdt_empty_tree.c fdt_sw.c
79 lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \
80 $(patsubst %.c,lib-%.o,$(libfdt-deps))
82 $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
83 $(call if_changed_rule,cc_o_c)
85 lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \
86 screen_info.o efi-stub-entry.o
88 lib-$(CONFIG_ARM) += arm32-stub.o
89 lib-$(CONFIG_ARM64) += kaslr.o arm64.o arm64-stub.o smbios.o
90 lib-$(CONFIG_X86) += x86-stub.o
91 lib-$(CONFIG_X86_64) += x86-5lvl.o
92 lib-$(CONFIG_RISCV) += kaslr.o riscv.o riscv-stub.o
93 lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o
95 CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
97 zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o
98 lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y)
100 lib-$(CONFIG_UNACCEPTED_MEMORY) += unaccepted_memory.o bitmap.o find.o
103 lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
105 # Even when -mbranch-protection=none is set, Clang will generate a
106 # .note.gnu.property for code-less object files (like lib/ctype.c),
107 # so work around this by explicitly removing the unwanted section.
108 # https://bugs.llvm.org/show_bug.cgi?id=46480
109 STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property
111 STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32
112 STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64
115 # ARM discards the .data section because it disallows r/w data in the
116 # decompressor. So move our .data to .data.efistub and .bss to .bss.efistub,
117 # which are preserved explicitly by the decompressor linker script.
119 STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
120 --rename-section .bss=.bss.efistub,load,alloc
121 STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
124 # arm64 puts the stub in the kernel proper, which will unnecessarily retain all
125 # code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
126 # So let's apply the __init annotations at the section level, by prefixing
127 # the section names directly. This will ensure that even all the inline string
128 # literals are covered.
129 # The fact that the stub and the kernel proper are essentially the same binary
130 # also means that we need to be extra careful to make sure that the stub does
131 # not rely on any absolute symbol references, considering that the virtual
132 # kernel mapping that the linker uses is not active yet when the stub is
133 # executing. So build all C dependencies of the EFI stub into libstub, and do
134 # a verification pass to see if any absolute relocations exist in any of the
137 STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
138 --prefix-symbols=__efistub_
139 STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS
141 # For RISC-V, we don't need anything special other than arm64. Keep all the
142 # symbols in .init section and make sure that no absolute symbols references
144 STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \
145 --prefix-symbols=__efistub_
146 STUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20
148 # For LoongArch, keep all the symbols in .init section and make sure that no
149 # absolute symbols references exist.
150 STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \
151 --prefix-symbols=__efistub_
152 STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA
154 $(obj)/%.stub.o: $(obj)/%.o FORCE
155 $(call if_changed,stubcopy)
158 # Strip debug sections and some other sections that may legally contain
159 # absolute relocations, so that we can inspect the remaining sections for
160 # such relocations. If none are found, regenerate the output object, but
161 # this time, use objcopy and leave all sections in place.
163 quiet_cmd_stubcopy = STUBCPY $@
165 $(STRIP) --strip-debug -o $@ $<; \
166 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \
167 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \
170 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@