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# 8cflags-$(CONFIG_X86_32) := -march=i386 9cflags-$(CONFIG_X86_64) := -mcmodel=small 10cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \ 11 -fPIC -fno-strict-aliasing -mno-red-zone \ 12 -mno-mmx -mno-sse -fshort-wchar \ 13 -Wno-pointer-sign \ 14 $(call cc-disable-warning, address-of-packed-member) \ 15 $(call cc-disable-warning, gnu) \ 16 -fno-asynchronous-unwind-tables 17 18# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly 19# disable the stackleak plugin 20cflags-$(CONFIG_ARM64) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 21 -fpie $(DISABLE_STACKLEAK_PLUGIN) 22cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \ 23 -fno-builtin -fpic \ 24 $(call cc-option,-mno-single-pic-base) 25 26cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt 27 28KBUILD_CFLAGS := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \ 29 -include $(srctree)/drivers/firmware/efi/libstub/hidden.h \ 30 -D__NO_FORTIFY \ 31 $(call cc-option,-ffreestanding) \ 32 $(call cc-option,-fno-stack-protector) \ 33 $(call cc-option,-fno-addrsig) \ 34 -D__DISABLE_EXPORTS 35 36# remove SCS flags from all objects in this directory 37KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) 38 39GCOV_PROFILE := n 40KASAN_SANITIZE := n 41UBSAN_SANITIZE := n 42OBJECT_FILES_NON_STANDARD := y 43 44# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in. 45KCOV_INSTRUMENT := n 46 47lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \ 48 file.o mem.o random.o randomalloc.o pci.o \ 49 skip_spaces.o lib-cmdline.o lib-ctype.o \ 50 alignedmem.o relocate.o vsprintf.o 51 52# include the stub's generic dependencies from lib/ when building for ARM/arm64 53efi-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c 54 55$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE 56 $(call if_changed_rule,cc_o_c) 57 58lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o fdt.o string.o \ 59 $(patsubst %.c,lib-%.o,$(efi-deps-y)) 60 61lib-$(CONFIG_ARM) += arm32-stub.o 62lib-$(CONFIG_ARM64) += arm64-stub.o 63lib-$(CONFIG_X86) += x86-stub.o 64CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 65CFLAGS_arm64-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET) 66 67# 68# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the 69# .bss section, so the .bss section of the EFI stub needs to be included in the 70# .data section of the compressed kernel to ensure initialization. Rename the 71# .bss section here so it's easy to pick out in the linker script. 72# 73STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc 74STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32 75STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64 76 77# 78# ARM discards the .data section because it disallows r/w data in the 79# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub, 80# which are preserved explicitly by the decompressor linker script. 81# 82STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \ 83 --rename-section .bss=.bss.efistub,load,alloc 84STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS 85 86# 87# arm64 puts the stub in the kernel proper, which will unnecessarily retain all 88# code indefinitely unless it is annotated as __init/__initdata/__initconst etc. 89# So let's apply the __init annotations at the section level, by prefixing 90# the section names directly. This will ensure that even all the inline string 91# literals are covered. 92# The fact that the stub and the kernel proper are essentially the same binary 93# also means that we need to be extra careful to make sure that the stub does 94# not rely on any absolute symbol references, considering that the virtual 95# kernel mapping that the linker uses is not active yet when the stub is 96# executing. So build all C dependencies of the EFI stub into libstub, and do 97# a verification pass to see if any absolute relocations exist in any of the 98# object files. 99# 100extra-y := $(lib-y) 101lib-y := $(patsubst %.o,%.stub.o,$(lib-y)) 102 103STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \ 104 --prefix-symbols=__efistub_ 105STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS 106 107$(obj)/%.stub.o: $(obj)/%.o FORCE 108 $(call if_changed,stubcopy) 109 110# 111# Strip debug sections and some other sections that may legally contain 112# absolute relocations, so that we can inspect the remaining sections for 113# such relocations. If none are found, regenerate the output object, but 114# this time, use objcopy and leave all sections in place. 115# 116quiet_cmd_stubcopy = STUBCPY $@ 117 cmd_stubcopy = \ 118 $(STRIP) --strip-debug -o $@ $<; \ 119 if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \ 120 echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \ 121 /bin/false; \ 122 fi; \ 123 $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@ 124