1*4882a593Smuzhiyun# SPDX-License-Identifier: GPL-2.0 2*4882a593Smuzhiyun# 3*4882a593Smuzhiyun# The stub may be linked into the kernel proper or into a separate boot binary, 4*4882a593Smuzhiyun# but in either case, it executes before the kernel does (with MMU disabled) so 5*4882a593Smuzhiyun# things like ftrace and stack-protector are likely to cause trouble if left 6*4882a593Smuzhiyun# enabled, even if doing so doesn't break the build. 7*4882a593Smuzhiyun# 8*4882a593Smuzhiyuncflags-$(CONFIG_X86_32) := -march=i386 9*4882a593Smuzhiyuncflags-$(CONFIG_X86_64) := -mcmodel=small 10*4882a593Smuzhiyuncflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \ 11*4882a593Smuzhiyun -fPIC -fno-strict-aliasing -mno-red-zone \ 12*4882a593Smuzhiyun -mno-mmx -mno-sse -fshort-wchar \ 13*4882a593Smuzhiyun -Wno-pointer-sign \ 14*4882a593Smuzhiyun $(call cc-disable-warning, address-of-packed-member) \ 15*4882a593Smuzhiyun $(call cc-disable-warning, gnu) \ 16*4882a593Smuzhiyun -fno-asynchronous-unwind-tables \ 17*4882a593Smuzhiyun $(CLANG_FLAGS) 18*4882a593Smuzhiyun 19*4882a593Smuzhiyun# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly 20*4882a593Smuzhiyun# disable the stackleak plugin 21*4882a593Smuzhiyuncflags-$(CONFIG_ARM64) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 22*4882a593Smuzhiyun -fpie $(DISABLE_STACKLEAK_PLUGIN) \ 23*4882a593Smuzhiyun $(call cc-option,-mbranch-protection=none) 24*4882a593Smuzhiyuncflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 25*4882a593Smuzhiyun -fno-builtin -fpic \ 26*4882a593Smuzhiyun $(call cc-option,-mno-single-pic-base) 27*4882a593Smuzhiyuncflags-$(CONFIG_RISCV) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 28*4882a593Smuzhiyun -fpic 29*4882a593Smuzhiyun 30*4882a593Smuzhiyuncflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt 31*4882a593Smuzhiyun 32*4882a593SmuzhiyunKBUILD_CFLAGS := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \ 33*4882a593Smuzhiyun -include $(srctree)/include/linux/hidden.h \ 34*4882a593Smuzhiyun -D__NO_FORTIFY \ 35*4882a593Smuzhiyun -ffreestanding \ 36*4882a593Smuzhiyun -fno-stack-protector \ 37*4882a593Smuzhiyun $(call cc-option,-fno-addrsig) \ 38*4882a593Smuzhiyun -D__DISABLE_EXPORTS 39*4882a593Smuzhiyun 40*4882a593Smuzhiyun# 41*4882a593Smuzhiyun# struct randomization only makes sense for Linux internal types, which the EFI 42*4882a593Smuzhiyun# stub code never touches, so let's turn off struct randomization for the stub 43*4882a593Smuzhiyun# altogether 44*4882a593Smuzhiyun# 45*4882a593SmuzhiyunKBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS)) 46*4882a593Smuzhiyun 47*4882a593Smuzhiyun# remove SCS flags from all objects in this directory 48*4882a593SmuzhiyunKBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) 49*4882a593Smuzhiyun# disable LTO 50*4882a593SmuzhiyunKBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS)) 51*4882a593Smuzhiyun 52*4882a593SmuzhiyunGCOV_PROFILE := n 53*4882a593Smuzhiyun# Sanitizer runtimes are unavailable and cannot be linked here. 54*4882a593SmuzhiyunKASAN_SANITIZE := n 55*4882a593SmuzhiyunKCSAN_SANITIZE := n 56*4882a593SmuzhiyunUBSAN_SANITIZE := n 57*4882a593SmuzhiyunOBJECT_FILES_NON_STANDARD := y 58*4882a593Smuzhiyun 59*4882a593Smuzhiyun# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. 60*4882a593SmuzhiyunKCOV_INSTRUMENT := n 61*4882a593Smuzhiyun 62*4882a593Smuzhiyunlib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 63*4882a593Smuzhiyun file.o mem.o random.o randomalloc.o pci.o \ 64*4882a593Smuzhiyun skip_spaces.o lib-cmdline.o lib-ctype.o \ 65*4882a593Smuzhiyun alignedmem.o relocate.o vsprintf.o 66*4882a593Smuzhiyun 67*4882a593Smuzhiyun# include the stub's generic dependencies from lib/ when building for ARM/arm64 68*4882a593Smuzhiyunefi-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c 69*4882a593Smuzhiyun 70*4882a593Smuzhiyun$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 71*4882a593Smuzhiyun $(call if_changed_rule,cc_o_c) 72*4882a593Smuzhiyun 73*4882a593Smuzhiyunlib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o fdt.o string.o \ 74*4882a593Smuzhiyun $(patsubst %.c,lib-%.o,$(efi-deps-y)) 75*4882a593Smuzhiyun 76*4882a593Smuzhiyunlib-$(CONFIG_ARM) += arm32-stub.o 77*4882a593Smuzhiyunlib-$(CONFIG_ARM64) += arm64-stub.o 78*4882a593Smuzhiyunlib-$(CONFIG_X86) += x86-stub.o 79*4882a593Smuzhiyunlib-$(CONFIG_RISCV) += riscv-stub.o 80*4882a593SmuzhiyunCFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 81*4882a593Smuzhiyun 82*4882a593Smuzhiyun# Even when -mbranch-protection=none is set, Clang will generate a 83*4882a593Smuzhiyun# .note.gnu.property for code-less object files (like lib/ctype.c), 84*4882a593Smuzhiyun# so work around this by explicitly removing the unwanted section. 85*4882a593Smuzhiyun# https://bugs.llvm.org/show_bug.cgi?id=46480 86*4882a593SmuzhiyunSTUBCOPY_FLAGS-y += --remove-section=.note.gnu.property 87*4882a593Smuzhiyun 88*4882a593Smuzhiyun# 89*4882a593Smuzhiyun# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the 90*4882a593Smuzhiyun# .bss section, so the .bss section of the EFI stub needs to be included in the 91*4882a593Smuzhiyun# .data section of the compressed kernel to ensure initialization. Rename the 92*4882a593Smuzhiyun# .bss section here so it's easy to pick out in the linker script. 93*4882a593Smuzhiyun# 94*4882a593SmuzhiyunSTUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc 95*4882a593SmuzhiyunSTUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32 96*4882a593SmuzhiyunSTUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64 97*4882a593Smuzhiyun 98*4882a593Smuzhiyun# 99*4882a593Smuzhiyun# ARM discards the .data section because it disallows r/w data in the 100*4882a593Smuzhiyun# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub, 101*4882a593Smuzhiyun# which are preserved explicitly by the decompressor linker script. 102*4882a593Smuzhiyun# 103*4882a593SmuzhiyunSTUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ 104*4882a593Smuzhiyun --rename-section .bss=.bss.efistub,load,alloc 105*4882a593SmuzhiyunSTUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 106*4882a593Smuzhiyun 107*4882a593Smuzhiyun# 108*4882a593Smuzhiyun# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 109*4882a593Smuzhiyun# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 110*4882a593Smuzhiyun# So let's apply the __init annotations at the section level, by prefixing 111*4882a593Smuzhiyun# the section names directly. This will ensure that even all the inline string 112*4882a593Smuzhiyun# literals are covered. 113*4882a593Smuzhiyun# The fact that the stub and the kernel proper are essentially the same binary 114*4882a593Smuzhiyun# also means that we need to be extra careful to make sure that the stub does 115*4882a593Smuzhiyun# not rely on any absolute symbol references, considering that the virtual 116*4882a593Smuzhiyun# kernel mapping that the linker uses is not active yet when the stub is 117*4882a593Smuzhiyun# executing. So build all C dependencies of the EFI stub into libstub, and do 118*4882a593Smuzhiyun# a verification pass to see if any absolute relocations exist in any of the 119*4882a593Smuzhiyun# object files. 120*4882a593Smuzhiyun# 121*4882a593Smuzhiyunextra-y := $(lib-y) 122*4882a593Smuzhiyunlib-y := $(patsubst %.o,%.stub.o,$(lib-y)) 123*4882a593Smuzhiyun 124*4882a593SmuzhiyunSTUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 125*4882a593Smuzhiyun --prefix-symbols=__efistub_ 126*4882a593SmuzhiyunSTUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 127*4882a593Smuzhiyun 128*4882a593Smuzhiyun# For RISC-V, we don't need anything special other than arm64. Keep all the 129*4882a593Smuzhiyun# symbols in .init section and make sure that no absolute symbols references 130*4882a593Smuzhiyun# doesn't exist. 131*4882a593SmuzhiyunSTUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \ 132*4882a593Smuzhiyun --prefix-symbols=__efistub_ 133*4882a593SmuzhiyunSTUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20 134*4882a593Smuzhiyun 135*4882a593Smuzhiyun$(obj)/%.stub.o: $(obj)/%.o FORCE 136*4882a593Smuzhiyun $(call if_changed,stubcopy) 137*4882a593Smuzhiyun 138*4882a593Smuzhiyun# 139*4882a593Smuzhiyun# Strip debug sections and some other sections that may legally contain 140*4882a593Smuzhiyun# absolute relocations, so that we can inspect the remaining sections for 141*4882a593Smuzhiyun# such relocations. If none are found, regenerate the output object, but 142*4882a593Smuzhiyun# this time, use objcopy and leave all sections in place. 143*4882a593Smuzhiyun# 144*4882a593Smuzhiyunquiet_cmd_stubcopy = STUBCPY $@ 145*4882a593Smuzhiyun cmd_stubcopy = \ 146*4882a593Smuzhiyun $(STRIP) --strip-debug -o $@ $<; \ 147*4882a593Smuzhiyun if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 148*4882a593Smuzhiyun echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 149*4882a593Smuzhiyun /bin/false; \ 150*4882a593Smuzhiyun fi; \ 151*4882a593Smuzhiyun $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 152