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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#
8
9# non-x86 reuses KBUILD_CFLAGS, x86 does not
10cflags-y := $(KBUILD_CFLAGS)
11
12cflags-$(CONFIG_X86_32) := -march=i386
13cflags-$(CONFIG_X86_64) := -mcmodel=small
14cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \
15 -fPIC -fno-strict-aliasing -mno-red-zone \
16 -mno-mmx -mno-sse -fshort-wchar \
17 -Wno-pointer-sign \
18 $(call cc-disable-warning, address-of-packed-member) \
19 $(call cc-disable-warning, gnu) \
20 -fno-asynchronous-unwind-tables \
21 $(CLANG_FLAGS)
22
23# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
24# disable the stackleak plugin
25cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_STACKLEAK_PLUGIN) \
26 -fno-unwind-tables -fno-asynchronous-unwind-tables
27cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \
28 -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \
29 -DEFI_HAVE_STRCMP -fno-builtin -fpic \
30 $(call cc-option,-mno-single-pic-base)
31cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax
32cflags-$(CONFIG_LOONGARCH) += -fpie
33
34cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt
35
36KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \
37 -Os -DDISABLE_BRANCH_PROFILING \
38 -include $(srctree)/include/linux/hidden.h \
39 -D__NO_FORTIFY \
40 -ffreestanding \
41 -fno-stack-protector \
42 $(call cc-option,-fno-addrsig) \
43 -D__DISABLE_EXPORTS
44
45#
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
48# altogether
49#
50KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS))
51
52# remove SCS flags from all objects in this directory
53KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
54# disable CFI
55KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS))
56# disable LTO
57KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
58
59GCOV_PROFILE := n
60# Sanitizer runtimes are unavailable and cannot be linked here.
61KASAN_SANITIZE := n
62KCSAN_SANITIZE := n
63KMSAN_SANITIZE := n
64UBSAN_SANITIZE := n
65OBJECT_FILES_NON_STANDARD := y
66
67# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
68KCOV_INSTRUMENT := n
69
70lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \
71 file.o mem.o random.o randomalloc.o pci.o \
72 skip_spaces.o lib-cmdline.o lib-ctype.o \
73 alignedmem.o relocate.o printk.o vsprintf.o
74
75# include the stub's libfdt dependencies from lib when needed
76libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \
77 fdt_empty_tree.c fdt_sw.c
78
79lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \
80 $(patsubst %.c,lib-%.o,$(libfdt-deps))
81
82$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
83 $(call if_changed_rule,cc_o_c)
84
85lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \
86 screen_info.o efi-stub-entry.o
87
88lib-$(CONFIG_ARM) += arm32-stub.o
89lib-$(CONFIG_ARM64) += kaslr.o arm64.o arm64-stub.o smbios.o
90lib-$(CONFIG_X86) += x86-stub.o
91lib-$(CONFIG_X86_64) += x86-5lvl.o
92lib-$(CONFIG_RISCV) += kaslr.o riscv.o riscv-stub.o
93lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o
94
95CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
96
97zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o
98lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y)
99
100lib-$(CONFIG_UNACCEPTED_MEMORY) += unaccepted_memory.o bitmap.o find.o
101
102extra-y := $(lib-y)
103lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
104
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://llvm.org/pr46480
109STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property
110
111STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32
112STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64
113
114#
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.
118#
119STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
120 --rename-section .bss=.bss.efistub,load,alloc
121STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
122
123#
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
135# object files.
136#
137STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
138 --prefix-symbols=__efistub_
139STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS
140
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
143# exist.
144STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \
145 --prefix-symbols=__efistub_
146STUBCOPY_RELOC-$(CONFIG_RISCV) := -E R_RISCV_HI20\|R_RISCV_$(BITS)\|R_RISCV_RELAX
147
148# For LoongArch, keep all the symbols in .init section and make sure that no
149# absolute symbols references exist.
150STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \
151 --prefix-symbols=__efistub_
152STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA
153
154$(obj)/%.stub.o: $(obj)/%.o FORCE
155 $(call if_changed,stubcopy)
156
157#
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.
162#
163quiet_cmd_stubcopy = STUBCPY $@
164 cmd_stubcopy = \
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; \
168 /bin/false; \
169 fi; \
170 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@
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#
8
9# non-x86 reuses KBUILD_CFLAGS, x86 does not
10cflags-y := $(KBUILD_CFLAGS)
11
12cflags-$(CONFIG_X86_32) := -march=i386
13cflags-$(CONFIG_X86_64) := -mcmodel=small
14cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \
15 -fPIC -fno-strict-aliasing -mno-red-zone \
16 -mno-mmx -mno-sse -fshort-wchar \
17 -Wno-pointer-sign \
18 $(call cc-disable-warning, address-of-packed-member) \
19 $(call cc-disable-warning, gnu) \
20 -fno-asynchronous-unwind-tables \
21 $(CLANG_FLAGS)
22
23# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
24# disable the stackleak plugin
25cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_STACKLEAK_PLUGIN) \
26 -fno-unwind-tables -fno-asynchronous-unwind-tables \
27 $(call cc-option,-mbranch-protection=none)
28cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \
29 -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \
30 -DEFI_HAVE_STRCMP -fno-builtin -fpic \
31 $(call cc-option,-mno-single-pic-base)
32cflags-$(CONFIG_RISCV) += -fpic
33cflags-$(CONFIG_LOONGARCH) += -fpie
34
35cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt
36
37KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \
38 -Os -DDISABLE_BRANCH_PROFILING \
39 -include $(srctree)/include/linux/hidden.h \
40 -D__NO_FORTIFY \
41 -ffreestanding \
42 -fno-stack-protector \
43 $(call cc-option,-fno-addrsig) \
44 -D__DISABLE_EXPORTS
45
46#
47# struct randomization only makes sense for Linux internal types, which the EFI
48# stub code never touches, so let's turn off struct randomization for the stub
49# altogether
50#
51KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS))
52
53# remove SCS flags from all objects in this directory
54KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
55# disable CFI
56KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS))
57# disable LTO
58KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
59
60GCOV_PROFILE := n
61# Sanitizer runtimes are unavailable and cannot be linked here.
62KASAN_SANITIZE := n
63KCSAN_SANITIZE := n
64KMSAN_SANITIZE := n
65UBSAN_SANITIZE := n
66OBJECT_FILES_NON_STANDARD := y
67
68# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
69KCOV_INSTRUMENT := n
70
71lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \
72 file.o mem.o random.o randomalloc.o pci.o \
73 skip_spaces.o lib-cmdline.o lib-ctype.o \
74 alignedmem.o relocate.o printk.o vsprintf.o
75
76# include the stub's libfdt dependencies from lib when needed
77libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \
78 fdt_empty_tree.c fdt_sw.c
79
80lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \
81 $(patsubst %.c,lib-%.o,$(libfdt-deps))
82
83$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
84 $(call if_changed_rule,cc_o_c)
85
86lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \
87 screen_info.o efi-stub-entry.o
88
89lib-$(CONFIG_ARM) += arm32-stub.o
90lib-$(CONFIG_ARM64) += arm64.o arm64-stub.o arm64-entry.o smbios.o
91lib-$(CONFIG_X86) += x86-stub.o
92lib-$(CONFIG_RISCV) += riscv.o riscv-stub.o
93lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o
94
95CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
96
97zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o
98lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y)
99
100extra-y := $(lib-y)
101lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
102
103# Even when -mbranch-protection=none is set, Clang will generate a
104# .note.gnu.property for code-less object files (like lib/ctype.c),
105# so work around this by explicitly removing the unwanted section.
106# https://bugs.llvm.org/show_bug.cgi?id=46480
107STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property
108
109#
110# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the
111# .bss section, so the .bss section of the EFI stub needs to be included in the
112# .data section of the compressed kernel to ensure initialization. Rename the
113# .bss section here so it's easy to pick out in the linker script.
114#
115STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc
116STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32
117STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64
118
119#
120# ARM discards the .data section because it disallows r/w data in the
121# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub,
122# which are preserved explicitly by the decompressor linker script.
123#
124STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
125 --rename-section .bss=.bss.efistub,load,alloc
126STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
127
128#
129# arm64 puts the stub in the kernel proper, which will unnecessarily retain all
130# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
131# So let's apply the __init annotations at the section level, by prefixing
132# the section names directly. This will ensure that even all the inline string
133# literals are covered.
134# The fact that the stub and the kernel proper are essentially the same binary
135# also means that we need to be extra careful to make sure that the stub does
136# not rely on any absolute symbol references, considering that the virtual
137# kernel mapping that the linker uses is not active yet when the stub is
138# executing. So build all C dependencies of the EFI stub into libstub, and do
139# a verification pass to see if any absolute relocations exist in any of the
140# object files.
141#
142STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
143 --prefix-symbols=__efistub_
144STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS64
145
146# For RISC-V, we don't need anything special other than arm64. Keep all the
147# symbols in .init section and make sure that no absolute symbols references
148# doesn't exist.
149STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \
150 --prefix-symbols=__efistub_
151STUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20
152
153# For LoongArch, keep all the symbols in .init section and make sure that no
154# absolute symbols references exist.
155STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \
156 --prefix-symbols=__efistub_
157STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA
158
159$(obj)/%.stub.o: $(obj)/%.o FORCE
160 $(call if_changed,stubcopy)
161
162#
163# Strip debug sections and some other sections that may legally contain
164# absolute relocations, so that we can inspect the remaining sections for
165# such relocations. If none are found, regenerate the output object, but
166# this time, use objcopy and leave all sections in place.
167#
168quiet_cmd_stubcopy = STUBCPY $@
169 cmd_stubcopy = \
170 $(STRIP) --strip-debug -o $@ $<; \
171 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \
172 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \
173 /bin/false; \
174 fi; \
175 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@