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__ $(CC_FLAGS_DIALECT) \ 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 -fno-asynchronous-unwind-tables \ 20 $(CLANG_FLAGS) 21 22# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly 23# disable the stackleak plugin 24cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_KSTACK_ERASE) \ 25 -fno-unwind-tables -fno-asynchronous-unwind-tables 26cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \ 27 -DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \ 28 -DEFI_HAVE_STRCMP -fno-builtin -fpic \ 29 $(call cc-option,-mno-single-pic-base) \ 30 $(DISABLE_KSTACK_ERASE) 31cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax \ 32 $(DISABLE_KSTACK_ERASE) 33cflags-$(CONFIG_LOONGARCH) += -fpie $(DISABLE_KSTACK_ERASE) 34 35cflags-$(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 60# The .data section would be renamed to .data.efistub, therefore, remove 61# `-fdata-sections` flag from KBUILD_CFLAGS_KERNEL 62KBUILD_CFLAGS_KERNEL := $(filter-out -fdata-sections, $(KBUILD_CFLAGS_KERNEL)) 63 64KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ 65 66lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 67 file.o mem.o random.o randomalloc.o pci.o \ 68 skip_spaces.o lib-cmdline.o lib-ctype.o \ 69 alignedmem.o relocate.o printk.o vsprintf.o 70 71# include the stub's libfdt dependencies from lib/ when needed 72libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \ 73 fdt_empty_tree.c fdt_sw.c 74 75lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \ 76 $(patsubst %.c,lib-%.o,$(libfdt-deps)) 77 78$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 79 $(call if_changed_rule,cc_o_c) 80 81lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \ 82 primary_display.o efi-stub-entry.o 83 84lib-$(CONFIG_ARM) += arm32-stub.o 85lib-$(CONFIG_ARM64) += kaslr.o arm64.o arm64-stub.o smbios.o 86lib-$(CONFIG_X86) += x86-stub.o smbios.o 87lib-$(CONFIG_X86_64) += x86-5lvl.o 88lib-$(CONFIG_RISCV) += kaslr.o riscv.o riscv-stub.o 89lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o 90 91CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 92 93zboot-obj-y := zboot-decompress-gzip.o 94CFLAGS_zboot-decompress-gzip.o += -I$(srctree)/lib/zlib_inflate 95zboot-obj-$(CONFIG_KERNEL_ZSTD) := zboot-decompress-zstd.o lib-xxhash.o 96CFLAGS_zboot-decompress-zstd.o += -I$(srctree)/lib/zstd 97 98zboot-obj-$(CONFIG_RISCV) += lib-clz_ctz.o lib-ashldi3.o 99lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y) 100 101lib-$(CONFIG_UNACCEPTED_MEMORY) += unaccepted_memory.o bitmap.o find.o 102 103targets := $(lib-y) 104lib-y := $(patsubst %.o,%.stub.o,$(lib-y)) 105 106# Even when -mbranch-protection=none is set, Clang will generate a 107# .note.gnu.property for code-less object files (like lib/ctype.c), 108# so work around this by explicitly removing the unwanted section. 109# https://llvm.org/pr46480 110STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property 111 112STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32 113STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64 114 115# 116# ARM discards the .data section because it disallows r/w data in the 117# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub, 118# which are preserved explicitly by the decompressor linker script. 119# 120STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ 121 --rename-section .bss=.bss.efistub,load,alloc 122STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 123 124# 125# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 126# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 127# So let's apply the __init annotations at the section level, by prefixing 128# the section names directly. This will ensure that even all the inline string 129# literals are covered. 130# The fact that the stub and the kernel proper are essentially the same binary 131# also means that we need to be extra careful to make sure that the stub does 132# not rely on any absolute symbol references, considering that the virtual 133# kernel mapping that the linker uses is not active yet when the stub is 134# executing. So build all C dependencies of the EFI stub into libstub, and do 135# a verification pass to see if any absolute relocations exist in any of the 136# object files. 137# 138STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 139 --prefix-symbols=__efistub_ 140STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 141 142# For RISC-V, we don't need anything special other than arm64. Keep all the 143# symbols in .init section and make sure that no absolute symbols references 144# exist. 145STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \ 146 --prefix-symbols=__efistub_ 147STUBCOPY_RELOC-$(CONFIG_RISCV) := -E R_RISCV_HI20\|R_RISCV_$(BITS)\|R_RISCV_RELAX 148 149# For LoongArch, keep all the symbols in .init section and make sure that no 150# absolute symbols references exist. 151STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \ 152 --prefix-symbols=__efistub_ 153STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA 154 155$(obj)/%.stub.o: $(obj)/%.o FORCE 156 $(call if_changed,stubcopy) 157 158# 159# Strip debug sections and some other sections that may legally contain 160# absolute relocations, so that we can inspect the remaining sections for 161# such relocations. If none are found, regenerate the output object, but 162# this time, use objcopy and leave all sections in place. 163# 164quiet_cmd_stubcopy = STUBCPY $@ 165 cmd_stubcopy = \ 166 $(STRIP) --strip-debug -o $@ $<; \ 167 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 168 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 169 /bin/false; \ 170 fi; \ 171 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 172