Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
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__ -std=gnu11 -fms-extensions \
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 $(if $(CONFIG_CC_IS_CLANG),-Wno-gnu -Wno-microsoft-anon-tag) \
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 $(DISABLE_KSTACK_ERASE) \
26 -fno-unwind-tables -fno-asynchronous-unwind-tables
27cflags-$(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) \
31 $(DISABLE_KSTACK_ERASE)
32cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax \
33 $(DISABLE_KSTACK_ERASE)
34cflags-$(CONFIG_LOONGARCH) += -fpie $(DISABLE_KSTACK_ERASE)
35
36cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt
37
38KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \
39 -Os -DDISABLE_BRANCH_PROFILING \
40 -include $(srctree)/include/linux/hidden.h \
41 -D__NO_FORTIFY \
42 -ffreestanding \
43 -fno-stack-protector \
44 $(call cc-option,-fno-addrsig) \
45 -D__DISABLE_EXPORTS
46
47#
48# struct randomization only makes sense for Linux internal types, which the EFI
49# stub code never touches, so let's turn off struct randomization for the stub
50# altogether
51#
52KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS))
53
54# remove SCS flags from all objects in this directory
55KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
56# disable CFI
57KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS))
58# disable LTO
59KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
60
61# The .data section would be renamed to .data.efistub, therefore, remove
62# `-fdata-sections` flag from KBUILD_CFLAGS_KERNEL
63KBUILD_CFLAGS_KERNEL := $(filter-out -fdata-sections, $(KBUILD_CFLAGS_KERNEL))
64
65KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__
66
67lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \
68 file.o mem.o random.o randomalloc.o pci.o \
69 skip_spaces.o lib-cmdline.o lib-ctype.o \
70 alignedmem.o relocate.o printk.o vsprintf.o
71
72# include the stub's libfdt dependencies from lib/ when needed
73libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \
74 fdt_empty_tree.c fdt_sw.c
75
76lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \
77 $(patsubst %.c,lib-%.o,$(libfdt-deps))
78
79$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
80 $(call if_changed_rule,cc_o_c)
81
82lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \
83 screen_info.o efi-stub-entry.o
84
85lib-$(CONFIG_ARM) += arm32-stub.o
86lib-$(CONFIG_ARM64) += kaslr.o arm64.o arm64-stub.o smbios.o
87lib-$(CONFIG_X86) += x86-stub.o smbios.o
88lib-$(CONFIG_X86_64) += x86-5lvl.o
89lib-$(CONFIG_RISCV) += kaslr.o riscv.o riscv-stub.o
90lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o
91
92CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
93
94zboot-obj-y := zboot-decompress-gzip.o
95CFLAGS_zboot-decompress-gzip.o += -I$(srctree)/lib/zlib_inflate
96zboot-obj-$(CONFIG_KERNEL_ZSTD) := zboot-decompress-zstd.o lib-xxhash.o
97CFLAGS_zboot-decompress-zstd.o += -I$(srctree)/lib/zstd
98
99zboot-obj-$(CONFIG_RISCV) += lib-clz_ctz.o lib-ashldi3.o
100lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y)
101
102lib-$(CONFIG_UNACCEPTED_MEMORY) += unaccepted_memory.o bitmap.o find.o
103
104targets := $(lib-y)
105lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
106
107# Even when -mbranch-protection=none is set, Clang will generate a
108# .note.gnu.property for code-less object files (like lib/ctype.c),
109# so work around this by explicitly removing the unwanted section.
110# https://llvm.org/pr46480
111STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property
112
113STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32
114STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64
115
116#
117# ARM discards the .data section because it disallows r/w data in the
118# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub,
119# which are preserved explicitly by the decompressor linker script.
120#
121STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
122 --rename-section .bss=.bss.efistub,load,alloc
123STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
124
125#
126# arm64 puts the stub in the kernel proper, which will unnecessarily retain all
127# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
128# So let's apply the __init annotations at the section level, by prefixing
129# the section names directly. This will ensure that even all the inline string
130# literals are covered.
131# The fact that the stub and the kernel proper are essentially the same binary
132# also means that we need to be extra careful to make sure that the stub does
133# not rely on any absolute symbol references, considering that the virtual
134# kernel mapping that the linker uses is not active yet when the stub is
135# executing. So build all C dependencies of the EFI stub into libstub, and do
136# a verification pass to see if any absolute relocations exist in any of the
137# object files.
138#
139STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
140 --prefix-symbols=__efistub_
141STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS
142
143# For RISC-V, we don't need anything special other than arm64. Keep all the
144# symbols in .init section and make sure that no absolute symbols references
145# exist.
146STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \
147 --prefix-symbols=__efistub_
148STUBCOPY_RELOC-$(CONFIG_RISCV) := -E R_RISCV_HI20\|R_RISCV_$(BITS)\|R_RISCV_RELAX
149
150# For LoongArch, keep all the symbols in .init section and make sure that no
151# absolute symbols references exist.
152STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \
153 --prefix-symbols=__efistub_
154STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA
155
156$(obj)/%.stub.o: $(obj)/%.o FORCE
157 $(call if_changed,stubcopy)
158
159#
160# Strip debug sections and some other sections that may legally contain
161# absolute relocations, so that we can inspect the remaining sections for
162# such relocations. If none are found, regenerate the output object, but
163# this time, use objcopy and leave all sections in place.
164#
165quiet_cmd_stubcopy = STUBCPY $@
166 cmd_stubcopy = \
167 $(STRIP) --strip-debug -o $@ $<; \
168 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \
169 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \
170 /bin/false; \
171 fi; \
172 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@