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linux-next/arch/s390/Makefile
Martin Schwidefsky f19fbd5ed6 s390: introduce execute-trampolines for branches 
Add CONFIG_EXPOLINE to enable the use of the new -mindirect-branch= and
-mfunction_return= compiler options to create a kernel fortified against
the specte v2 attack.

With CONFIG_EXPOLINE=y all indirect branches will be issued with an
execute type instruction. For z10 or newer the EXRL instruction will
be used, for older machines the EX instruction. The typical indirect
call

	basr	%r14,%r1

is replaced with a PC relative call to a new thunk

	brasl	%r14,__s390x_indirect_jump_r1

The thunk contains the EXRL/EX instruction to the indirect branch

__s390x_indirect_jump_r1:
	exrl	0,0f
	j	.
0:	br	%r1

The detour via the execute type instruction has a performance impact.
To get rid of the detour the new kernel parameter "nospectre_v2" and
"spectre_v2=[on,off,auto]" can be used. If the parameter is specified
the kernel and module code will be patched at runtime.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2018-02-07 15:57:02 +01:00

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Makefile
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# SPDX-License-Identifier: GPL-2.0
#
# s390/Makefile
#
# This file is included by the global makefile so that you can add your own
# architecture-specific flags and dependencies. Remember to do have actions
# for "archclean" and "archdep" for cleaning up and making dependencies for
# this architecture
#
# Copyright (C) 1994 by Linus Torvalds
#
LD_BFD := elf64-s390
LDFLAGS := -m elf64_s390
KBUILD_AFLAGS_MODULE += -fPIC
KBUILD_CFLAGS_MODULE += -fPIC
KBUILD_CFLAGS += -m64
KBUILD_AFLAGS += -m64
UTS_MACHINE := s390x
STACK_SIZE := 16384
CHECKFLAGS += -D__s390__ -D__s390x__ -mbig-endian
export LD_BFD
mflags-$(CONFIG_MARCH_Z900) := -march=z900
mflags-$(CONFIG_MARCH_Z990) := -march=z990
mflags-$(CONFIG_MARCH_Z9_109) := -march=z9-109
mflags-$(CONFIG_MARCH_Z10) := -march=z10
mflags-$(CONFIG_MARCH_Z196) := -march=z196
mflags-$(CONFIG_MARCH_ZEC12) := -march=zEC12
mflags-$(CONFIG_MARCH_Z13) := -march=z13
mflags-$(CONFIG_MARCH_Z14) := -march=z14
export CC_FLAGS_MARCH := $(mflags-y)
aflags-y += $(mflags-y)
cflags-y += $(mflags-y)
cflags-$(CONFIG_MARCH_Z900_TUNE) += -mtune=z900
cflags-$(CONFIG_MARCH_Z990_TUNE) += -mtune=z990
cflags-$(CONFIG_MARCH_Z9_109_TUNE) += -mtune=z9-109
cflags-$(CONFIG_MARCH_Z10_TUNE) += -mtune=z10
cflags-$(CONFIG_MARCH_Z196_TUNE) += -mtune=z196
cflags-$(CONFIG_MARCH_ZEC12_TUNE) += -mtune=zEC12
cflags-$(CONFIG_MARCH_Z13_TUNE) += -mtune=z13
cflags-$(CONFIG_MARCH_Z14_TUNE) += -mtune=z14
cflags-y += -Wa,-I$(srctree)/arch/$(ARCH)/include
#KBUILD_IMAGE is necessary for make rpm
KBUILD_IMAGE :=arch/s390/boot/image
#
# Prevent tail-call optimizations, to get clearer backtraces:
#
cflags-$(CONFIG_FRAME_POINTER) += -fno-optimize-sibling-calls
# old style option for packed stacks
ifeq ($(call cc-option-yn,-mkernel-backchain),y)
cflags-$(CONFIG_PACK_STACK) += -mkernel-backchain -D__PACK_STACK
aflags-$(CONFIG_PACK_STACK) += -D__PACK_STACK
endif
# new style option for packed stacks
ifeq ($(call cc-option-yn,-mpacked-stack),y)
cflags-$(CONFIG_PACK_STACK) += -mpacked-stack -D__PACK_STACK
aflags-$(CONFIG_PACK_STACK) += -D__PACK_STACK
endif
ifeq ($(call cc-option-yn,-mstack-size=8192 -mstack-guard=128),y)
cflags-$(CONFIG_CHECK_STACK) += -mstack-size=$(STACK_SIZE)
ifneq ($(call cc-option-yn,-mstack-size=8192),y)
cflags-$(CONFIG_CHECK_STACK) += -mstack-guard=$(CONFIG_STACK_GUARD)
endif
endif
ifeq ($(call cc-option-yn,-mwarn-dynamicstack),y)
cflags-$(CONFIG_WARN_DYNAMIC_STACK) += -mwarn-dynamicstack
endif
ifdef CONFIG_EXPOLINE
ifeq ($(call cc-option-yn,$(CC_FLAGS_MARCH) -mindirect-branch=thunk),y)
CC_FLAGS_EXPOLINE := -mindirect-branch=thunk
CC_FLAGS_EXPOLINE += -mfunction-return=thunk
CC_FLAGS_EXPOLINE += -mindirect-branch-table
export CC_FLAGS_EXPOLINE
cflags-y += $(CC_FLAGS_EXPOLINE)
endif
endif
ifdef CONFIG_FUNCTION_TRACER
# make use of hotpatch feature if the compiler supports it
cc_hotpatch := -mhotpatch=0,3
ifeq ($(call cc-option-yn,$(cc_hotpatch)),y)
CC_FLAGS_FTRACE := $(cc_hotpatch)
KBUILD_AFLAGS += -DCC_USING_HOTPATCH
KBUILD_CFLAGS += -DCC_USING_HOTPATCH
endif
endif
# Test CFI features of binutils
cfi := $(call as-instr,.cfi_startproc\n.cfi_val_offset 15$(comma)-160\n.cfi_endproc,-DCONFIG_AS_CFI_VAL_OFFSET=1)
KBUILD_CFLAGS += -mbackchain -msoft-float $(cflags-y)
KBUILD_CFLAGS += -pipe -fno-strength-reduce -Wno-sign-compare
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables $(cfi)
KBUILD_AFLAGS += $(aflags-y) $(cfi)
OBJCOPYFLAGS := -O binary
head-y := arch/s390/kernel/head.o
head-y += arch/s390/kernel/head64.o
# See arch/s390/Kbuild for content of core part of the kernel
core-y += arch/s390/
libs-y += arch/s390/lib/
drivers-y += drivers/s390/
# must be linked after kernel
drivers-$(CONFIG_OPROFILE) += arch/s390/oprofile/
boot := arch/s390/boot
syscalls := arch/s390/kernel/syscalls
tools := arch/s390/tools
all: image bzImage
install: vmlinux
$(Q)$(MAKE) $(build)=$(boot) $@
image bzImage: vmlinux
$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
zfcpdump:
$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
vdso_install:
$(Q)$(MAKE) $(build)=arch/$(ARCH)/kernel/vdso64 $@
$(Q)$(MAKE) $(build)=arch/$(ARCH)/kernel/vdso32 $@
archclean:
$(Q)$(MAKE) $(clean)=$(boot)
$(Q)$(MAKE) $(clean)=$(tools)
archheaders:
$(Q)$(MAKE) $(build)=$(syscalls) uapi
archprepare:
$(Q)$(MAKE) $(build)=$(syscalls) kapi
$(Q)$(MAKE) $(build)=$(tools) kapi
# Don't use tabs in echo arguments
define archhelp
echo '* image - Kernel image for IPL ($(boot)/image)'
echo '* bzImage - Compressed kernel image for IPL ($(boot)/bzImage)'
echo ' install - Install kernel using'
echo ' (your) ~/bin/$(INSTALLKERNEL) or'
echo ' (distribution) /sbin/$(INSTALLKERNEL) or'
echo ' install to $$(INSTALL_PATH)'
endef
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