
The LLVM linker (ld.lld) defaults to removing local relocations, which causes KASLR boot failures. ld.bfd and ld.gold already handle this correctly. This adds the explicit instruction "--discard-none" during the link phase. There is no change in output for ld.bfd and ld.gold, but ld.lld now produces an image with all the needed relocations. Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: clang-built-linux@googlegroups.com Cc: x86-ml <x86@kernel.org> Link: https://lkml.kernel.org/r/20190404214027.GA7324@beast Link: https://github.com/ClangBuiltLinux/linux/issues/404
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SPDX-License-Identifier: GPL-2.0
Unified Makefile for i386 and x86_64
select defconfig based on actual architecture
ifeq ($(ARCH),x86) ifeq ($(shell uname -m),x86_64) KBUILD_DEFCONFIG := x86_64_defconfig else KBUILD_DEFCONFIG := i386_defconfig endif else KBUILD_DEFCONFIG := $(ARCH)_defconfig endif
For gcc stack alignment is specified with -mpreferred-stack-boundary,
clang has the option -mstack-alignment for that purpose.
ifneq ($(call cc-option, -mpreferred-stack-boundary=4),) cc_stack_align4 := -mpreferred-stack-boundary=2 cc_stack_align8 := -mpreferred-stack-boundary=3 else ifneq ($(call cc-option, -mstack-alignment=16),) cc_stack_align4 := -mstack-alignment=4 cc_stack_align8 := -mstack-alignment=8 endif
How to compile the 16-bit code. Note we always compile for -march=i386;
that way we can complain to the user if the CPU is insufficient.
The -m16 option is supported by GCC >= 4.9 and clang >= 3.5. For
older versions of GCC, include an assembly header to make sure that
gcc doesn't play any games behind our back.
CODE16GCC_CFLAGS := -m32 -Wa,$(srctree)/arch/x86/boot/code16gcc.h M16_CFLAGS := $(call cc-option, -m16, $(CODE16GCC_CFLAGS))
REALMODE_CFLAGS := $(M16_CFLAGS) -g -Os -DDISABLE_BRANCH_PROFILING
-Wall -Wstrict-prototypes -march=i386 -mregparm=3
-fno-strict-aliasing -fomit-frame-pointer -fno-pic
-mno-mmx -mno-sse
REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -ffreestanding) REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -fno-stack-protector) REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), $(cc_stack_align4)) export REALMODE_CFLAGS
BITS is used as extension for files which are available in a 32 bit
and a 64 bit version to simplify shared Makefiles.
e.g.: obj-y += foo_$(BITS).o
export BITS
ifdef CONFIG_X86_NEED_RELOCS LDFLAGS_vmlinux := --emit-relocs --discard-none endif
Prevent GCC from generating any FP code by mistake.
This must happen before we try the -mpreferred-stack-boundary, see:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
KBUILD_CFLAGS += -mno-sse -mno-mmx -mno-sse2 -mno-3dnow KBUILD_CFLAGS += $(call cc-option,-mno-avx,)
ifeq ($(CONFIG_X86_32),y) BITS := 32 UTS_MACHINE := i386 CHECKFLAGS += -D__i386__
biarch := $(call cc-option,-m32)
KBUILD_AFLAGS += $(biarch)
KBUILD_CFLAGS += $(biarch)
KBUILD_CFLAGS += -msoft-float -mregparm=3 -freg-struct-return
# Never want PIC in a 32-bit kernel, prevent breakage with GCC built
# with nonstandard options
KBUILD_CFLAGS += -fno-pic
# Align the stack to the register width instead of using the default
# alignment of 16 bytes. This reduces stack usage and the number of
# alignment instructions.
KBUILD_CFLAGS += $(call cc-option,$(cc_stack_align4))
# CPU-specific tuning. Anything which can be shared with UML should go here.
include arch/x86/Makefile_32.cpu
KBUILD_CFLAGS += $(cflags-y)
# temporary until string.h is fixed
KBUILD_CFLAGS += -ffreestanding
else BITS := 64 UTS_MACHINE := x86_64 CHECKFLAGS += -D__x86_64__
biarch := -m64
KBUILD_AFLAGS += -m64
KBUILD_CFLAGS += -m64
# Align jump targets to 1 byte, not the default 16 bytes:
KBUILD_CFLAGS += $(call cc-option,-falign-jumps=1)
# Pack loops tightly as well:
KBUILD_CFLAGS += $(call cc-option,-falign-loops=1)
# Don't autogenerate traditional x87 instructions
KBUILD_CFLAGS += $(call cc-option,-mno-80387)
KBUILD_CFLAGS += $(call cc-option,-mno-fp-ret-in-387)
# By default gcc and clang use a stack alignment of 16 bytes for x86.
# However the standard kernel entry on x86-64 leaves the stack on an
# 8-byte boundary. If the compiler isn't informed about the actual
# alignment it will generate extra alignment instructions for the
# default alignment which keep the stack *mis*aligned.
# Furthermore an alignment to the register width reduces stack usage
# and the number of alignment instructions.
KBUILD_CFLAGS += $(call cc-option,$(cc_stack_align8))
# Use -mskip-rax-setup if supported.
KBUILD_CFLAGS += $(call cc-option,-mskip-rax-setup)
# FIXME - should be integrated in Makefile.cpu (Makefile_32.cpu)
cflags-$(CONFIG_MK8) += $(call cc-option,-march=k8)
cflags-$(CONFIG_MPSC) += $(call cc-option,-march=nocona)
cflags-$(CONFIG_MCORE2) += \
$(call cc-option,-march=core2,$(call cc-option,-mtune=generic))
cflags-$(CONFIG_MATOM) += $(call cc-option,-march=atom) \
$(call cc-option,-mtune=atom,$(call cc-option,-mtune=generic))
cflags-$(CONFIG_GENERIC_CPU) += $(call cc-option,-mtune=generic)
KBUILD_CFLAGS += $(cflags-y)
KBUILD_CFLAGS += -mno-red-zone
KBUILD_CFLAGS += -mcmodel=kernel
endif
ifdef CONFIG_X86_X32
x32_ld_ok := $(call try-run,
/bin/echo -e '1: .quad 1b' |
$(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" - &&
$(OBJCOPY) -O elf32-x86-64 "$$TMP" "$$TMPO" &&
$(LD) -m elf32_x86_64 "$$TMPO" -o "$$TMP",y,n)
ifeq ($(x32_ld_ok),y)
CONFIG_X86_X32_ABI := y
KBUILD_AFLAGS += -DCONFIG_X86_X32_ABI
KBUILD_CFLAGS += -DCONFIG_X86_X32_ABI
else
$(warning CONFIG_X86_X32 enabled but no binutils support)
endif
endif
export CONFIG_X86_X32_ABI
If the function graph tracer is used with mcount instead of fentry,
'-maccumulate-outgoing-args' is needed to prevent a GCC bug
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42109)
ifdef CONFIG_FUNCTION_GRAPH_TRACER ifndef CONFIG_HAVE_FENTRY ACCUMULATE_OUTGOING_ARGS := 1 else ifeq ($(call cc-option-yn, -mfentry), n) ACCUMULATE_OUTGOING_ARGS := 1
# GCC ignores '-maccumulate-outgoing-args' when used with '-Os'.
# If '-Os' is enabled, disable it and print a warning.
ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
undefine CONFIG_CC_OPTIMIZE_FOR_SIZE
$(warning Disabling CONFIG_CC_OPTIMIZE_FOR_SIZE. Your compiler does not have -mfentry so you cannot optimize for size with CONFIG_FUNCTION_GRAPH_TRACER.)
endif
endif
endif endif
ifeq ($(ACCUMULATE_OUTGOING_ARGS), 1) # This compiler flag is not supported by Clang: KBUILD_CFLAGS += $(call cc-option,-maccumulate-outgoing-args,) endif
Stackpointer is addressed different for 32 bit and 64 bit x86
sp-$(CONFIG_X86_32) := esp sp-$(CONFIG_X86_64) := rsp
do binutils support CFI?
cfi := $(call as-instr,.cfi_startproc\n.cfi_rel_offset $(sp-y)$(comma)0\n.cfi_endproc,-DCONFIG_AS_CFI=1)
is .cfi_signal_frame supported too?
cfi-sigframe := $(call as-instr,.cfi_startproc\n.cfi_signal_frame\n.cfi_endproc,-DCONFIG_AS_CFI_SIGNAL_FRAME=1) cfi-sections := $(call as-instr,.cfi_sections .debug_frame,-DCONFIG_AS_CFI_SECTIONS=1)
does binutils support specific instructions?
asinstr += $(call as-instr,pshufb %xmm0$(comma)%xmm0,-DCONFIG_AS_SSSE3=1) avx_instr := $(call as-instr,vxorps %ymm0$(comma)%ymm1$(comma)%ymm2,-DCONFIG_AS_AVX=1) avx2_instr :=$(call as-instr,vpbroadcastb %xmm0$(comma)%ymm1,-DCONFIG_AS_AVX2=1) avx512_instr :=$(call as-instr,vpmovm2b %k1$(comma)%zmm5,-DCONFIG_AS_AVX512=1) sha1_ni_instr :=$(call as-instr,sha1msg1 %xmm0$(comma)%xmm1,-DCONFIG_AS_SHA1_NI=1) sha256_ni_instr :=$(call as-instr,sha256msg1 %xmm0$(comma)%xmm1,-DCONFIG_AS_SHA256_NI=1)
KBUILD_AFLAGS += $(cfi) $(cfi-sigframe) $(cfi-sections) $(asinstr) $(avx_instr) $(avx2_instr) $(avx512_instr) $(sha1_ni_instr) $(sha256_ni_instr) KBUILD_CFLAGS += $(cfi) $(cfi-sigframe) $(cfi-sections) $(asinstr) $(avx_instr) $(avx2_instr) $(avx512_instr) $(sha1_ni_instr) $(sha256_ni_instr)
KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE)
The 64-bit kernel must be aligned to 2MB. Pass -z max-page-size=0x200000 to
the linker to force 2MB page size regardless of the default page size used
by the linker.
ifdef CONFIG_X86_64 KBUILD_LDFLAGS += $(call ld-option, -z max-page-size=0x200000) endif
Workaround for a gcc prelease that unfortunately was shipped in a suse release
KBUILD_CFLAGS += -Wno-sign-compare
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
Avoid indirect branches in kernel to deal with Spectre
ifdef CONFIG_RETPOLINE KBUILD_CFLAGS += $(RETPOLINE_CFLAGS)
Additionally, avoid generating expensive indirect jumps which
are subject to retpolines for small number of switch cases.
clang turns off jump table generation by default when under
retpoline builds, however, gcc does not for x86. This has
only been fixed starting from gcc stable version 8.4.0 and
onwards, but not for older ones. See gcc bug #86952.
ifndef CONFIG_CC_IS_CLANG KBUILD_CFLAGS += $(call cc-option,-fno-jump-tables) endif endif
archscripts: scripts_basic $(Q)$(MAKE) $(build)=arch/x86/tools relocs
Syscall table generation
archheaders: $(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
Kernel objects
head-y := arch/x86/kernel/head_$(BITS).o head-y += arch/x86/kernel/head$(BITS).o head-y += arch/x86/kernel/ebda.o head-y += arch/x86/kernel/platform-quirks.o
libs-y += arch/x86/lib/
See arch/x86/Kbuild for content of core part of the kernel
core-y += arch/x86/
drivers-y are linked after core-y
drivers-$(CONFIG_MATH_EMULATION) += arch/x86/math-emu/ drivers-$(CONFIG_PCI) += arch/x86/pci/
must be linked after kernel/
drivers-$(CONFIG_OPROFILE) += arch/x86/oprofile/
suspend and hibernation support
drivers-$(CONFIG_PM) += arch/x86/power/
drivers-$(CONFIG_FB) += arch/x86/video/
boot loader support. Several targets are kept for legacy purposes
boot := arch/x86/boot
BOOT_TARGETS = bzlilo bzdisk fdimage fdimage144 fdimage288 isoimage
PHONY += bzImage $(BOOT_TARGETS)
Default kernel to build
all: bzImage
KBUILD_IMAGE specify target image being built
KBUILD_IMAGE := $(boot)/bzImage
bzImage: vmlinux ifeq ($(CONFIG_X86_DECODER_SELFTEST),y) $(Q)$(MAKE) $(build)=arch/x86/tools posttest endif $(Q)$(MAKE) $(build)=$(boot) $(KBUILD_IMAGE) $(Q)mkdir -p $(objtree)/arch/$(UTS_MACHINE)/boot $(Q)ln -fsn ../../x86/boot/bzImage $(objtree)/arch/$(UTS_MACHINE)/boot/$@
$(BOOT_TARGETS): vmlinux $(Q)$(MAKE) $(build)=$(boot) $@
PHONY += install install: $(Q)$(MAKE) $(build)=$(boot) $@
PHONY += vdso_install vdso_install: $(Q)$(MAKE) $(build)=arch/x86/entry/vdso $@
archprepare: checkbin checkbin: ifndef CONFIG_CC_HAS_ASM_GOTO @echo Compiler lacks asm-goto support. @exit 1 endif ifdef CONFIG_RETPOLINE ifeq ($(RETPOLINE_CFLAGS),) @echo "You are building kernel with non-retpoline compiler." >&2 @echo "Please update your compiler." >&2 @false endif endif
archclean: $(Q)rm -rf $(objtree)/arch/i386 $(Q)rm -rf $(objtree)/arch/x86_64 $(Q)$(MAKE) $(clean)=$(boot) $(Q)$(MAKE) $(clean)=arch/x86/tools
define archhelp echo '* bzImage - Compressed kernel image (arch/x86/boot/bzImage)' echo ' install - Install kernel using' echo ' (your) ~/bin/$(INSTALLKERNEL) or' echo ' (distribution) /sbin/$(INSTALLKERNEL) or' echo ' install to $$(INSTALL_PATH) and run lilo' echo ' fdimage - Create 1.4MB boot floppy image (arch/x86/boot/fdimage)' echo ' fdimage144 - Create 1.4MB boot floppy image (arch/x86/boot/fdimage)' echo ' fdimage288 - Create 2.8MB boot floppy image (arch/x86/boot/fdimage)' echo ' isoimage - Create a boot CD-ROM image (arch/x86/boot/image.iso)' echo ' bzdisk/fdimage*/isoimage also accept:' echo ' FDARGS="..." arguments for the booted kernel' echo ' FDINITRD=file initrd for the booted kernel' endef