94f0f30b2d
commit 1a3887924a7e6edd331be76da7bf4c1e8eab4b1e upstream. The EFI stub is a wrapper around the core kernel that makes it look like a EFI compatible PE/COFF application to the EFI firmware. EFI applications run on top of the EFI runtime, which is heavily based on so-called protocols, which are struct types consisting [mostly] of function pointer members that are instantiated and recorded in a protocol database. These structs look like the ideal randomization candidates to the randstruct plugin (as they only carry function pointers), but of course, these protocols are contracts between the firmware that exposes them, and the EFI applications (including our stubbed kernel) that invoke them. This means that struct randomization for EFI protocols is not a great idea, and given that the stub shares very little data with the core kernel that is represented as a randomizable struct, we're better off just disabling it completely here. Cc: <stable@vger.kernel.org> # v4.14+ Reported-by: Daniel Marth <daniel.marth@inso.tuwien.ac.at> Tested-by: Daniel Marth <daniel.marth@inso.tuwien.ac.at> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
150 lines
6.0 KiB
Makefile
150 lines
6.0 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
|
|
#
|
|
# The stub may be linked into the kernel proper or into a separate boot binary,
|
|
# but in either case, it executes before the kernel does (with MMU disabled) so
|
|
# things like ftrace and stack-protector are likely to cause trouble if left
|
|
# enabled, even if doing so doesn't break the build.
|
|
#
|
|
cflags-$(CONFIG_X86_32) := -march=i386
|
|
cflags-$(CONFIG_X86_64) := -mcmodel=small
|
|
cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \
|
|
-fPIC -fno-strict-aliasing -mno-red-zone \
|
|
-mno-mmx -mno-sse -fshort-wchar \
|
|
-Wno-pointer-sign \
|
|
$(call cc-disable-warning, address-of-packed-member) \
|
|
$(call cc-disable-warning, gnu) \
|
|
-fno-asynchronous-unwind-tables \
|
|
$(CLANG_FLAGS)
|
|
|
|
# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
|
|
# disable the stackleak plugin
|
|
cflags-$(CONFIG_ARM64) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
|
|
-fpie $(DISABLE_STACKLEAK_PLUGIN) \
|
|
$(call cc-option,-mbranch-protection=none)
|
|
cflags-$(CONFIG_ARM) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
|
|
-fno-builtin -fpic \
|
|
$(call cc-option,-mno-single-pic-base)
|
|
cflags-$(CONFIG_RISCV) := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
|
|
-fpic
|
|
|
|
cflags-$(CONFIG_EFI_GENERIC_STUB) += -I$(srctree)/scripts/dtc/libfdt
|
|
|
|
KBUILD_CFLAGS := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \
|
|
-include $(srctree)/include/linux/hidden.h \
|
|
-D__NO_FORTIFY \
|
|
-ffreestanding \
|
|
-fno-stack-protector \
|
|
$(call cc-option,-fno-addrsig) \
|
|
-D__DISABLE_EXPORTS
|
|
|
|
#
|
|
# struct randomization only makes sense for Linux internal types, which the EFI
|
|
# stub code never touches, so let's turn off struct randomization for the stub
|
|
# altogether
|
|
#
|
|
KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS))
|
|
|
|
# remove SCS flags from all objects in this directory
|
|
KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
|
|
|
|
GCOV_PROFILE := n
|
|
# Sanitizer runtimes are unavailable and cannot be linked here.
|
|
KASAN_SANITIZE := n
|
|
KCSAN_SANITIZE := n
|
|
UBSAN_SANITIZE := n
|
|
OBJECT_FILES_NON_STANDARD := y
|
|
|
|
# Prevents link failures: __sanitizer_cov_trace_pc() is not linked in.
|
|
KCOV_INSTRUMENT := n
|
|
|
|
lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \
|
|
file.o mem.o random.o randomalloc.o pci.o \
|
|
skip_spaces.o lib-cmdline.o lib-ctype.o \
|
|
alignedmem.o relocate.o vsprintf.o
|
|
|
|
# include the stub's generic dependencies from lib/ when building for ARM/arm64
|
|
efi-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c
|
|
|
|
$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
|
|
$(call if_changed_rule,cc_o_c)
|
|
|
|
lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o fdt.o string.o \
|
|
$(patsubst %.c,lib-%.o,$(efi-deps-y))
|
|
|
|
lib-$(CONFIG_ARM) += arm32-stub.o
|
|
lib-$(CONFIG_ARM64) += arm64-stub.o
|
|
lib-$(CONFIG_X86) += x86-stub.o
|
|
lib-$(CONFIG_RISCV) += riscv-stub.o
|
|
CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
|
|
|
|
# Even when -mbranch-protection=none is set, Clang will generate a
|
|
# .note.gnu.property for code-less object files (like lib/ctype.c),
|
|
# so work around this by explicitly removing the unwanted section.
|
|
# https://bugs.llvm.org/show_bug.cgi?id=46480
|
|
STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property
|
|
|
|
#
|
|
# For x86, bootloaders like systemd-boot or grub-efi do not zero-initialize the
|
|
# .bss section, so the .bss section of the EFI stub needs to be included in the
|
|
# .data section of the compressed kernel to ensure initialization. Rename the
|
|
# .bss section here so it's easy to pick out in the linker script.
|
|
#
|
|
STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc
|
|
STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32
|
|
STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64
|
|
|
|
#
|
|
# ARM discards the .data section because it disallows r/w data in the
|
|
# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub,
|
|
# which are preserved explicitly by the decompressor linker script.
|
|
#
|
|
STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
|
|
--rename-section .bss=.bss.efistub,load,alloc
|
|
STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
|
|
|
|
#
|
|
# arm64 puts the stub in the kernel proper, which will unnecessarily retain all
|
|
# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
|
|
# So let's apply the __init annotations at the section level, by prefixing
|
|
# the section names directly. This will ensure that even all the inline string
|
|
# literals are covered.
|
|
# The fact that the stub and the kernel proper are essentially the same binary
|
|
# also means that we need to be extra careful to make sure that the stub does
|
|
# not rely on any absolute symbol references, considering that the virtual
|
|
# kernel mapping that the linker uses is not active yet when the stub is
|
|
# executing. So build all C dependencies of the EFI stub into libstub, and do
|
|
# a verification pass to see if any absolute relocations exist in any of the
|
|
# object files.
|
|
#
|
|
extra-y := $(lib-y)
|
|
lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
|
|
|
|
STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
|
|
--prefix-symbols=__efistub_
|
|
STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS
|
|
|
|
# For RISC-V, we don't need anything special other than arm64. Keep all the
|
|
# symbols in .init section and make sure that no absolute symbols references
|
|
# doesn't exist.
|
|
STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \
|
|
--prefix-symbols=__efistub_
|
|
STUBCOPY_RELOC-$(CONFIG_RISCV) := R_RISCV_HI20
|
|
|
|
$(obj)/%.stub.o: $(obj)/%.o FORCE
|
|
$(call if_changed,stubcopy)
|
|
|
|
#
|
|
# Strip debug sections and some other sections that may legally contain
|
|
# absolute relocations, so that we can inspect the remaining sections for
|
|
# such relocations. If none are found, regenerate the output object, but
|
|
# this time, use objcopy and leave all sections in place.
|
|
#
|
|
quiet_cmd_stubcopy = STUBCPY $@
|
|
cmd_stubcopy = \
|
|
$(STRIP) --strip-debug -o $@ $<; \
|
|
if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \
|
|
echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \
|
|
/bin/false; \
|
|
fi; \
|
|
$(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@
|