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1d2ad08480
linux/arch/s390/Makefile
Vasily Gorbik 1d2ad08480 s390/nospec: add an option to use thunk-extern 
Currently with -mindirect-branch=thunk and -mfunction-return=thunk compiler
options expoline thunks are put into individual COMDAT group sections. s390
is the only architecture which has group sections and it has implications
for kpatch and objtool tools support.

Using -mindirect-branch=thunk-extern and -mfunction-return=thunk-extern
is an alternative, which comes with a need to generate all required
expoline thunks manually. Unfortunately modules area is too far away from
the kernel image, and expolines from the kernel image cannon be used.
But since all new distributions (except Debian) build kernels for machine
generations newer than z10, where "exrl" instruction is available, that
leaves only 16 expolines thunks possible.

Provide an option to build the kernel with
-mindirect-branch=thunk-extern and -mfunction-return=thunk-extern for
z10 or newer. This also requires to postlink expoline thunks into all
modules explicitly. Currently modules already contain most expolines
anyhow.

Unfortunately -mindirect-branch=thunk-extern and
-mfunction-return=thunk-extern options support is broken in gcc <= 11.2.
Additional compile test is required to verify proper gcc support.

Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Co-developed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
2022-03-10 15:58:17 +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.
#
# Copyright (C) 1994 by Linus Torvalds
#
LD_BFD := elf64-s390
KBUILD_LDFLAGS := -m elf64_s390
KBUILD_AFLAGS_MODULE += -fPIC
KBUILD_CFLAGS_MODULE += -fPIC
KBUILD_AFLAGS += -m64
KBUILD_CFLAGS += -m64
ifeq ($(CONFIG_RELOCATABLE),y)
KBUILD_CFLAGS += -fPIE
LDFLAGS_vmlinux := -pie
endif
aflags_dwarf := -Wa,-gdwarf-2
KBUILD_AFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -D__ASSEMBLY__
KBUILD_AFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),$(aflags_dwarf))
KBUILD_CFLAGS_DECOMPRESSOR := $(CLANG_FLAGS) -m64 -O2 -mpacked-stack
KBUILD_CFLAGS_DECOMPRESSOR += -DDISABLE_BRANCH_PROFILING -D__NO_FORTIFY
KBUILD_CFLAGS_DECOMPRESSOR += -fno-delete-null-pointer-checks -msoft-float -mbackchain
KBUILD_CFLAGS_DECOMPRESSOR += -fno-asynchronous-unwind-tables
KBUILD_CFLAGS_DECOMPRESSOR += -ffreestanding
KBUILD_CFLAGS_DECOMPRESSOR += -fno-stack-protector
KBUILD_CFLAGS_DECOMPRESSOR += $(call cc-disable-warning, address-of-packed-member)
KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),-g)
KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO_DWARF4), $(call cc-option, -gdwarf-4,))
UTS_MACHINE := s390x
STACK_SIZE := $(if $(CONFIG_KASAN),65536,16384)
CHECKFLAGS += -D__s390__ -D__s390x__
export LD_BFD
mflags-$(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-$(CONFIG_MARCH_Z14) := -march=z14
mflags-$(CONFIG_MARCH_Z15) := -march=z15
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-$(CONFIG_MARCH_Z14_TUNE) += -mtune=z14
cflags-$(CONFIG_MARCH_Z15_TUNE) += -mtune=z15
cflags-y += -Wa,-I$(srctree)/arch/$(ARCH)/include
#
# Prevent tail-call optimizations, to get clearer backtraces:
#
cflags-$(CONFIG_FRAME_POINTER) += -fno-optimize-sibling-calls
KBUILD_AFLAGS_DECOMPRESSOR += $(aflags-y)
KBUILD_CFLAGS_DECOMPRESSOR += $(cflags-y)
ifneq ($(call cc-option,-mstack-size=8192 -mstack-guard=128),)
CC_FLAGS_CHECK_STACK := -mstack-size=$(STACK_SIZE)
ifeq ($(call cc-option,-mstack-size=8192),)
CC_FLAGS_CHECK_STACK += -mstack-guard=$(CONFIG_STACK_GUARD)
endif
export CC_FLAGS_CHECK_STACK
cflags-$(CONFIG_CHECK_STACK) += $(CC_FLAGS_CHECK_STACK)
endif
ifdef CONFIG_EXPOLINE
ifdef CONFIG_EXPOLINE_EXTERN
KBUILD_LDFLAGS_MODULE += arch/s390/lib/expoline.o
CC_FLAGS_EXPOLINE := -mindirect-branch=thunk-extern
CC_FLAGS_EXPOLINE += -mfunction-return=thunk-extern
else
CC_FLAGS_EXPOLINE := -mindirect-branch=thunk
CC_FLAGS_EXPOLINE += -mfunction-return=thunk
endif
CC_FLAGS_EXPOLINE += -mindirect-branch-table
export CC_FLAGS_EXPOLINE
cflags-y += $(CC_FLAGS_EXPOLINE) -DCC_USING_EXPOLINE
aflags-y += -DCC_USING_EXPOLINE
endif
ifdef CONFIG_FUNCTION_TRACER
ifeq ($(call cc-option,-mfentry -mnop-mcount),)
# make use of hotpatch feature if the compiler supports it
cc_hotpatch := -mhotpatch=0,3
ifneq ($(call cc-option,$(cc_hotpatch)),)
CC_FLAGS_FTRACE := $(cc_hotpatch)
KBUILD_AFLAGS += -DCC_USING_HOTPATCH
KBUILD_CFLAGS += -DCC_USING_HOTPATCH
endif
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 += -mpacked-stack -mbackchain -msoft-float $(cflags-y)
KBUILD_CFLAGS += -pipe -Wno-sign-compare
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables $(cfi)
KBUILD_AFLAGS += $(aflags-y) $(cfi)
export KBUILD_AFLAGS_DECOMPRESSOR
export KBUILD_CFLAGS_DECOMPRESSOR
OBJCOPYFLAGS := -O binary
head-y := arch/s390/kernel/head64.o
libs-y += arch/s390/lib/
drivers-y += drivers/s390/
boot := arch/s390/boot
syscalls := arch/s390/kernel/syscalls
tools := arch/s390/tools
all: bzImage
#KBUILD_IMAGE is necessary for packaging targets like rpm-pkg, deb-pkg...
KBUILD_IMAGE := $(boot)/bzImage
install:
sh -x $(srctree)/$(boot)/install.sh $(KERNELRELEASE) $(KBUILD_IMAGE) \
System.map "$(INSTALL_PATH)"
bzImage: vmlinux
$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
zfcpdump:
$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
vdso_install:
$(Q)$(MAKE) $(build)=arch/$(ARCH)/kernel/vdso64 $@
archheaders:
$(Q)$(MAKE) $(build)=$(syscalls) uapi
archprepare:
$(Q)$(MAKE) $(build)=$(syscalls) kapi
$(Q)$(MAKE) $(build)=$(tools) kapi
ifeq ($(KBUILD_EXTMOD),)
# We need to generate vdso-offsets.h before compiling certain files in kernel/.
# In order to do that, we should use the archprepare target, but we can't since
# asm-offsets.h is included in some files used to generate vdso-offsets.h, and
# asm-offsets.h is built in prepare0, for which archprepare is a dependency.
# Therefore we need to generate the header after prepare0 has been made, hence
# this hack.
prepare: vdso_prepare
vdso_prepare: prepare0
$(Q)$(MAKE) $(build)=arch/s390/kernel/vdso64 include/generated/vdso64-offsets.h
$(if $(CONFIG_COMPAT),$(Q)$(MAKE) \
$(build)=arch/s390/kernel/vdso32 include/generated/vdso32-offsets.h)
endif
# Don't use tabs in echo arguments
define archhelp
echo '* bzImage - Kernel image for IPL ($(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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