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2335c9cb83
Add the STACKLEAK gcc plugin to arm32 by adding the helper used by stackleak common code: on_thread_stack(). It initialize the stack with the poison value before returning from system calls which improves the kernel security. Additionally, this disables the plugin in EFI stub code and decompress code, which are out of scope for the protection. Before the test on Qemu versatilepb board: # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT lkdtm: Performing direct entry STACKLEAK_ERASING lkdtm: XFAIL: stackleak is not supported on this arch (HAVE_ARCH_STACKLEAK=n) After: # echo STACKLEAK_ERASING > /sys/kernel/debug/provoke-crash/DIRECT lkdtm: Performing direct entry STACKLEAK_ERASING lkdtm: stackleak stack usage: high offset: 80 bytes current: 280 bytes lowest: 696 bytes tracked: 696 bytes untracked: 192 bytes poisoned: 7220 bytes low offset: 4 bytes lkdtm: OK: the rest of the thread stack is properly erased Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> Acked-by: Ard Biesheuvel <ardb@kernel.org> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
165 lines
6.6 KiB
Makefile
165 lines
6.6 KiB
Makefile
# SPDX-License-Identifier: GPL-2.0
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#
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# The stub may be linked into the kernel proper or into a separate boot binary,
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# but in either case, it executes before the kernel does (with MMU disabled) so
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# things like ftrace and stack-protector are likely to cause trouble if left
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# enabled, even if doing so doesn't break the build.
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#
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# non-x86 reuses KBUILD_CFLAGS, x86 does not
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cflags-y := $(KBUILD_CFLAGS)
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cflags-$(CONFIG_X86_32) := -march=i386
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cflags-$(CONFIG_X86_64) := -mcmodel=small
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cflags-$(CONFIG_X86) += -m$(BITS) -D__KERNEL__ \
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-fPIC -fno-strict-aliasing -mno-red-zone \
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-mno-mmx -mno-sse -fshort-wchar \
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-Wno-pointer-sign \
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$(call cc-disable-warning, address-of-packed-member) \
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$(call cc-disable-warning, gnu) \
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-fno-asynchronous-unwind-tables \
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$(CLANG_FLAGS)
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# arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
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# disable the stackleak plugin
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cflags-$(CONFIG_ARM64) += -fpie $(DISABLE_STACKLEAK_PLUGIN) \
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-fno-unwind-tables -fno-asynchronous-unwind-tables
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cflags-$(CONFIG_ARM) += -DEFI_HAVE_STRLEN -DEFI_HAVE_STRNLEN \
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-DEFI_HAVE_MEMCHR -DEFI_HAVE_STRRCHR \
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-DEFI_HAVE_STRCMP -fno-builtin -fpic \
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$(call cc-option,-mno-single-pic-base) \
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$(DISABLE_STACKLEAK_PLUGIN)
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cflags-$(CONFIG_RISCV) += -fpic -DNO_ALTERNATIVE -mno-relax
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cflags-$(CONFIG_LOONGARCH) += -fpie
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cflags-$(CONFIG_EFI_PARAMS_FROM_FDT) += -I$(srctree)/scripts/dtc/libfdt
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KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(cflags-y)) \
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-Os -DDISABLE_BRANCH_PROFILING \
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-include $(srctree)/include/linux/hidden.h \
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-D__NO_FORTIFY \
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-ffreestanding \
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-fno-stack-protector \
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$(call cc-option,-fno-addrsig) \
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-D__DISABLE_EXPORTS
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#
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# struct randomization only makes sense for Linux internal types, which the EFI
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# stub code never touches, so let's turn off struct randomization for the stub
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# altogether
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#
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KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS), $(KBUILD_CFLAGS))
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# remove SCS flags from all objects in this directory
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KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS))
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# disable CFI
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KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_CFI), $(KBUILD_CFLAGS))
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# disable LTO
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KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_LTO), $(KBUILD_CFLAGS))
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# The .data section would be renamed to .data.efistub, therefore, remove
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# `-fdata-sections` flag from KBUILD_CFLAGS_KERNEL
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KBUILD_CFLAGS_KERNEL := $(filter-out -fdata-sections, $(KBUILD_CFLAGS_KERNEL))
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lib-y := efi-stub-helper.o gop.o secureboot.o tpm.o \
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file.o mem.o random.o randomalloc.o pci.o \
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skip_spaces.o lib-cmdline.o lib-ctype.o \
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alignedmem.o relocate.o printk.o vsprintf.o
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# include the stub's libfdt dependencies from lib/ when needed
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libfdt-deps := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c \
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fdt_empty_tree.c fdt_sw.c
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lib-$(CONFIG_EFI_PARAMS_FROM_FDT) += fdt.o \
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$(patsubst %.c,lib-%.o,$(libfdt-deps))
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$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
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$(call if_changed_rule,cc_o_c)
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lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o string.o intrinsics.o systable.o \
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screen_info.o efi-stub-entry.o
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lib-$(CONFIG_ARM) += arm32-stub.o
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lib-$(CONFIG_ARM64) += kaslr.o arm64.o arm64-stub.o smbios.o
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lib-$(CONFIG_X86) += x86-stub.o
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lib-$(CONFIG_X86_64) += x86-5lvl.o
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lib-$(CONFIG_RISCV) += kaslr.o riscv.o riscv-stub.o
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lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o
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CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
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zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o
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lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y)
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lib-$(CONFIG_UNACCEPTED_MEMORY) += unaccepted_memory.o bitmap.o find.o
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extra-y := $(lib-y)
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lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
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# Even when -mbranch-protection=none is set, Clang will generate a
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# .note.gnu.property for code-less object files (like lib/ctype.c),
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# so work around this by explicitly removing the unwanted section.
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# https://llvm.org/pr46480
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STUBCOPY_FLAGS-y += --remove-section=.note.gnu.property
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STUBCOPY_RELOC-$(CONFIG_X86_32) := R_386_32
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STUBCOPY_RELOC-$(CONFIG_X86_64) := R_X86_64_64
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#
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# ARM discards the .data section because it disallows r/w data in the
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# decompressor. So move our .data to .data.efistub and .bss to .bss.efistub,
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# which are preserved explicitly by the decompressor linker script.
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#
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STUBCOPY_FLAGS-$(CONFIG_ARM) += --rename-section .data=.data.efistub \
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--rename-section .bss=.bss.efistub,load,alloc
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STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
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#
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# arm64 puts the stub in the kernel proper, which will unnecessarily retain all
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# code indefinitely unless it is annotated as __init/__initdata/__initconst etc.
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# So let's apply the __init annotations at the section level, by prefixing
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# the section names directly. This will ensure that even all the inline string
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# literals are covered.
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# The fact that the stub and the kernel proper are essentially the same binary
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# also means that we need to be extra careful to make sure that the stub does
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# not rely on any absolute symbol references, considering that the virtual
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# kernel mapping that the linker uses is not active yet when the stub is
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# executing. So build all C dependencies of the EFI stub into libstub, and do
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# a verification pass to see if any absolute relocations exist in any of the
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# object files.
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#
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STUBCOPY_FLAGS-$(CONFIG_ARM64) += --prefix-alloc-sections=.init \
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--prefix-symbols=__efistub_
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STUBCOPY_RELOC-$(CONFIG_ARM64) := R_AARCH64_ABS
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# For RISC-V, we don't need anything special other than arm64. Keep all the
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# symbols in .init section and make sure that no absolute symbols references
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# exist.
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STUBCOPY_FLAGS-$(CONFIG_RISCV) += --prefix-alloc-sections=.init \
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--prefix-symbols=__efistub_
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STUBCOPY_RELOC-$(CONFIG_RISCV) := -E R_RISCV_HI20\|R_RISCV_$(BITS)\|R_RISCV_RELAX
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# For LoongArch, keep all the symbols in .init section and make sure that no
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# absolute symbols references exist.
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STUBCOPY_FLAGS-$(CONFIG_LOONGARCH) += --prefix-alloc-sections=.init \
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--prefix-symbols=__efistub_
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STUBCOPY_RELOC-$(CONFIG_LOONGARCH) := R_LARCH_MARK_LA
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$(obj)/%.stub.o: $(obj)/%.o FORCE
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$(call if_changed,stubcopy)
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#
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# Strip debug sections and some other sections that may legally contain
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# absolute relocations, so that we can inspect the remaining sections for
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# such relocations. If none are found, regenerate the output object, but
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# this time, use objcopy and leave all sections in place.
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#
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quiet_cmd_stubcopy = STUBCPY $@
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cmd_stubcopy = \
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$(STRIP) --strip-debug -o $@ $<; \
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if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \
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echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \
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/bin/false; \
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fi; \
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$(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@
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