Date:   Sat, 27 Jun 2020 09:39:40 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        X86 ML <x86@...nel.org>, linux-efi <linux-efi@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] kbuild: remove cc-option test of -fno-stack-protector

On Fri, 26 Jun 2020 at 21:00, Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> Some Makefiles already pass -fno-stack-protector unconditionally.
> For example, arch/arm64/kernel/vdso/Makefile, arch/x86/xen/Makefile.
> No problem report so far about hard-coding this option. So, we can
> assume all supported compilers know -fno-stack-protector.
>
> GCC 4.8 and Clang support this option (https://godbolt.org/z/_HDGzN)
>
> Get rid of cc-option from -fno-stack-protector.
>
> Remove CONFIG_CC_HAS_STACKPROTECTOR_NONE, which should always be 'y'.
>
> Note:
> arch/mips/vdso/Makefile adds -fno-stack-protector twice, first
> unconditionally, and second conditionally. I removed the second one.
>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>

Acked-by: Ard Biesheuvel <ardb@...nel.org>

> ---
>
>  Documentation/kbuild/kconfig-language.rst | 4 ++--
>  Makefile                                  | 2 +-
>  arch/Kconfig                              | 3 ---
>  arch/arm/boot/compressed/Makefile         | 3 +--
>  arch/mips/vdso/Makefile                   | 3 +--
>  arch/powerpc/kernel/Makefile              | 2 +-
>  arch/powerpc/platforms/powermac/Makefile  | 2 +-
>  arch/sparc/vdso/Makefile                  | 4 ++--
>  arch/um/Makefile                          | 3 +--
>  arch/x86/Makefile                         | 2 +-
>  arch/x86/boot/compressed/Makefile         | 2 +-
>  arch/x86/entry/vdso/Makefile              | 4 ++--
>  arch/x86/kernel/cpu/Makefile              | 3 +--
>  arch/x86/lib/Makefile                     | 2 +-
>  arch/x86/mm/Makefile                      | 7 +++----
>  arch/x86/power/Makefile                   | 3 +--
>  arch/x86/purgatory/Makefile               | 2 +-
>  arch/x86/um/vdso/Makefile                 | 2 +-
>  arch/x86/xen/Makefile                     | 5 ++---
>  drivers/firmware/efi/libstub/Makefile     | 2 +-
>  drivers/xen/Makefile                      | 3 +--
>  kernel/kcsan/Makefile                     | 3 +--
>  lib/Makefile                              | 4 ++--
>  mm/kasan/Makefile                         | 2 +-
>  24 files changed, 30 insertions(+), 42 deletions(-)
>
> diff --git a/Documentation/kbuild/kconfig-language.rst b/Documentation/kbuild/kconfig-language.rst
> index a1601ec3317b..2538e7cb08e6 100644
> --- a/Documentation/kbuild/kconfig-language.rst
> +++ b/Documentation/kbuild/kconfig-language.rst
> @@ -540,8 +540,8 @@ followed by a test macro::
>  If you need to expose a compiler capability to makefiles and/or C source files,
>  `CC_HAS_` is the recommended prefix for the config option::
>
> -  config CC_HAS_STACKPROTECTOR_NONE
> -       def_bool $(cc-option,-fno-stack-protector)
> +  config CC_HAS_ASM_GOTO
> +       def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
>
>  Build as module only
>  ~~~~~~~~~~~~~~~~~~~~
> diff --git a/Makefile b/Makefile
> index 5496a32dffa6..73948798ce3f 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -762,7 +762,7 @@ ifneq ($(CONFIG_FRAME_WARN),0)
>  KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
>  endif
>
> -stackp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector
> +stackp-flags-y                                    := -fno-stack-protector
>  stackp-flags-$(CONFIG_STACKPROTECTOR)             := -fstack-protector
>  stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG)      := -fstack-protector-strong
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 8cc35dc556c7..1ea61290900a 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -478,9 +478,6 @@ config HAVE_STACKPROTECTOR
>           An arch should select this symbol if:
>           - it has implemented a stack canary (e.g. __stack_chk_guard)
>
> -config CC_HAS_STACKPROTECTOR_NONE
> -       def_bool $(cc-option,-fno-stack-protector)
> -
>  config STACKPROTECTOR
>         bool "Stack Protector buffer overflow detection"
>         depends on HAVE_STACKPROTECTOR
> diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> index 00602a6fba04..cb7a56c6723c 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -84,9 +84,8 @@ endif
>
>  # -fstack-protector-strong triggers protection checks in this code,
>  # but it is being used too early to link to meaningful stack_chk logic.
> -nossp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector
>  $(foreach o, $(libfdt_objs) atags_to_fdt.o, \
> -       $(eval CFLAGS_$(o) := -I $(srctree)/scripts/dtc/libfdt $(nossp-flags-y)))
> +       $(eval CFLAGS_$(o) := -I $(srctree)/scripts/dtc/libfdt -fno-stack-protector))
>
>  # These were previously generated C files. When you are building the kernel
>  # with O=, make sure to remove the stale files in the output tree. Otherwise,
> diff --git a/arch/mips/vdso/Makefile b/arch/mips/vdso/Makefile
> index 2e64c7600eea..57fe83235281 100644
> --- a/arch/mips/vdso/Makefile
> +++ b/arch/mips/vdso/Makefile
> @@ -35,8 +35,7 @@ cflags-vdso := $(ccflags-vdso) \
>         -O3 -g -fPIC -fno-strict-aliasing -fno-common -fno-builtin -G 0 \
>         -mrelax-pic-calls $(call cc-option, -mexplicit-relocs) \
>         -fno-stack-protector -fno-jump-tables -DDISABLE_BRANCH_PROFILING \
> -       $(call cc-option, -fno-asynchronous-unwind-tables) \
> -       $(call cc-option, -fno-stack-protector)
> +       $(call cc-option, -fno-asynchronous-unwind-tables)
>  aflags-vdso := $(ccflags-vdso) \
>         -D__ASSEMBLY__ -Wa,-gdwarf-2
>
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index 244542ae2a91..3a83f2b876a5 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -16,7 +16,7 @@ CFLAGS_prom_init.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
>  CFLAGS_btext.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
>  CFLAGS_prom.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
>
> -CFLAGS_prom_init.o += $(call cc-option, -fno-stack-protector)
> +CFLAGS_prom_init.o += -fno-stack-protector
>  CFLAGS_prom_init.o += -DDISABLE_BRANCH_PROFILING
>  CFLAGS_prom_init.o += -ffreestanding
>
> diff --git a/arch/powerpc/platforms/powermac/Makefile b/arch/powerpc/platforms/powermac/Makefile
> index f4247ade71ca..cf85f0662d0d 100644
> --- a/arch/powerpc/platforms/powermac/Makefile
> +++ b/arch/powerpc/platforms/powermac/Makefile
> @@ -1,6 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  CFLAGS_bootx_init.o            += -fPIC
> -CFLAGS_bootx_init.o            += $(call cc-option, -fno-stack-protector)
> +CFLAGS_bootx_init.o            += -fno-stack-protector
>
>  KASAN_SANITIZE_bootx_init.o := n
>
> diff --git a/arch/sparc/vdso/Makefile b/arch/sparc/vdso/Makefile
> index 708cb6304c2d..f44355e46f31 100644
> --- a/arch/sparc/vdso/Makefile
> +++ b/arch/sparc/vdso/Makefile
> @@ -54,7 +54,7 @@ $(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE
>  # optimize sibling calls.
>  #
>  CFL := $(PROFILING) -mcmodel=medlow -fPIC -O2 -fasynchronous-unwind-tables -m64 \
> -       $(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
> +       $(filter -g%,$(KBUILD_CFLAGS)) -fno-stack-protector \
>         -fno-omit-frame-pointer -foptimize-sibling-calls \
>         -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
>
> @@ -93,7 +93,7 @@ KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
>  KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))
>  KBUILD_CFLAGS_32 := $(filter-out $(SPARC_REG_CFLAGS),$(KBUILD_CFLAGS_32))
>  KBUILD_CFLAGS_32 += -m32 -msoft-float -fpic
> -KBUILD_CFLAGS_32 += $(call cc-option, -fno-stack-protector)
> +KBUILD_CFLAGS_32 += -fno-stack-protector
>  KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
>  KBUILD_CFLAGS_32 += -fno-omit-frame-pointer
>  KBUILD_CFLAGS_32 += -DDISABLE_BRANCH_PROFILING
> diff --git a/arch/um/Makefile b/arch/um/Makefile
> index 3f27aa3ec0a6..1cea46ff9bb7 100644
> --- a/arch/um/Makefile
> +++ b/arch/um/Makefile
> @@ -121,8 +121,7 @@ LINK-$(CONFIG_LD_SCRIPT_STATIC) += -static
>  LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib $(call cc-option, -no-pie)
>
>  CFLAGS_NO_HARDENING := $(call cc-option, -fno-PIC,) $(call cc-option, -fno-pic,) \
> -       $(call cc-option, -fno-stack-protector,) \
> -       $(call cc-option, -fno-stack-protector-all,)
> +       -fno-stack-protector $(call cc-option, -fno-stack-protector-all)
>
>  # Options used by linker script
>  export LDS_START      := $(START)
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 00e378de8bc0..89c3cdfba753 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -37,7 +37,7 @@ REALMODE_CFLAGS       := $(M16_CFLAGS) -g -Os -DDISABLE_BRANCH_PROFILING \
>                    -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 += -fno-stack-protector
>  REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), -Wno-address-of-packed-member)
>  REALMODE_CFLAGS += $(call __cc-option, $(CC), $(REALMODE_CFLAGS), $(cc_stack_align4))
>  export REALMODE_CFLAGS
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index 7619742f91c9..c88a31569a5e 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -36,7 +36,7 @@ cflags-$(CONFIG_X86_64) := -mcmodel=small
>  KBUILD_CFLAGS += $(cflags-y)
>  KBUILD_CFLAGS += -mno-mmx -mno-sse
>  KBUILD_CFLAGS += $(call cc-option,-ffreestanding)
> -KBUILD_CFLAGS += $(call cc-option,-fno-stack-protector)
> +KBUILD_CFLAGS += -fno-stack-protector
>  KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
>  KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
>  KBUILD_CFLAGS += -Wno-pointer-sign
> diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile
> index 04e65f0698f6..215376d975a2 100644
> --- a/arch/x86/entry/vdso/Makefile
> +++ b/arch/x86/entry/vdso/Makefile
> @@ -82,7 +82,7 @@ $(obj)/vdso-image-%.c: $(obj)/vdso%.so.dbg $(obj)/vdso%.so $(obj)/vdso2c FORCE
>  # optimize sibling calls.
>  #
>  CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
> -       $(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
> +       $(filter -g%,$(KBUILD_CFLAGS)) -fno-stack-protector \
>         -fno-omit-frame-pointer -foptimize-sibling-calls \
>         -DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
>
> @@ -151,7 +151,7 @@ KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
>  KBUILD_CFLAGS_32 := $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS_32))
>  KBUILD_CFLAGS_32 := $(filter-out $(RETPOLINE_CFLAGS),$(KBUILD_CFLAGS_32))
>  KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
> -KBUILD_CFLAGS_32 += $(call cc-option, -fno-stack-protector)
> +KBUILD_CFLAGS_32 += -fno-stack-protector
>  KBUILD_CFLAGS_32 += $(call cc-option, -foptimize-sibling-calls)
>  KBUILD_CFLAGS_32 += -fno-omit-frame-pointer
>  KBUILD_CFLAGS_32 += -DDISABLE_BRANCH_PROFILING
> diff --git a/arch/x86/kernel/cpu/Makefile b/arch/x86/kernel/cpu/Makefile
> index dba6a83bc349..93792b457b81 100644
> --- a/arch/x86/kernel/cpu/Makefile
> +++ b/arch/x86/kernel/cpu/Makefile
> @@ -17,8 +17,7 @@ KCOV_INSTRUMENT_perf_event.o := n
>  KCSAN_SANITIZE_common.o := n
>
>  # Make sure load_percpu_segment has no stackprotector
> -nostackp := $(call cc-option, -fno-stack-protector)
> -CFLAGS_common.o                := $(nostackp)
> +CFLAGS_common.o                := -fno-stack-protector
>
>  obj-y                  := cacheinfo.o scattered.o topology.o
>  obj-y                  += common.o
> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
> index 6110bce7237b..d46fff11f06f 100644
> --- a/arch/x86/lib/Makefile
> +++ b/arch/x86/lib/Makefile
> @@ -24,7 +24,7 @@ ifdef CONFIG_FUNCTION_TRACER
>  CFLAGS_REMOVE_cmdline.o = -pg
>  endif
>
> -CFLAGS_cmdline.o := $(call cc-option, -fno-stack-protector)
> +CFLAGS_cmdline.o := -fno-stack-protector
>  endif
>
>  inat_tables_script = $(srctree)/arch/x86/tools/gen-insn-attr-x86.awk
> diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
> index f7fd0e868c9c..5864219221ca 100644
> --- a/arch/x86/mm/Makefile
> +++ b/arch/x86/mm/Makefile
> @@ -22,10 +22,9 @@ obj-y                                :=  init.o init_$(BITS).o fault.o ioremap.o extable.o mmap.o \
>  obj-y                          += pat/
>
>  # Make sure __phys_addr has no stackprotector
> -nostackp := $(call cc-option, -fno-stack-protector)
> -CFLAGS_physaddr.o              := $(nostackp)
> -CFLAGS_setup_nx.o              := $(nostackp)
> -CFLAGS_mem_encrypt_identity.o  := $(nostackp)
> +CFLAGS_physaddr.o              := -fno-stack-protector
> +CFLAGS_setup_nx.o              := -fno-stack-protector
> +CFLAGS_mem_encrypt_identity.o  := -fno-stack-protector
>
>  CFLAGS_fault.o := -I $(srctree)/$(src)/../include/asm/trace
>
> diff --git a/arch/x86/power/Makefile b/arch/x86/power/Makefile
> index 37923d715741..6907b523e856 100644
> --- a/arch/x86/power/Makefile
> +++ b/arch/x86/power/Makefile
> @@ -3,8 +3,7 @@ OBJECT_FILES_NON_STANDARD_hibernate_asm_$(BITS).o := y
>
>  # __restore_processor_state() restores %gs after S3 resume and so should not
>  # itself be stack-protected
> -nostackp := $(call cc-option, -fno-stack-protector)
> -CFLAGS_cpu.o   := $(nostackp)
> +CFLAGS_cpu.o   := -fno-stack-protector
>
>  obj-$(CONFIG_PM_SLEEP)         += cpu.o
>  obj-$(CONFIG_HIBERNATION)      += hibernate_$(BITS).o hibernate_asm_$(BITS).o hibernate.o
> diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
> index 088bd764e0b7..183ac60e5990 100644
> --- a/arch/x86/purgatory/Makefile
> +++ b/arch/x86/purgatory/Makefile
> @@ -34,7 +34,7 @@ KCOV_INSTRUMENT := n
>  PURGATORY_CFLAGS_REMOVE := -mcmodel=kernel
>  PURGATORY_CFLAGS := -mcmodel=large -ffreestanding -fno-zero-initialized-in-bss
>  PURGATORY_CFLAGS += $(DISABLE_STACKLEAK_PLUGIN) -DDISABLE_BRANCH_PROFILING
> -PURGATORY_CFLAGS += $(call cc-option,-fno-stack-protector)
> +PURGATORY_CFLAGS += -fno-stack-protector
>
>  # Default KBUILD_CFLAGS can have -pg option set when FTRACE is enabled. That
>  # in turn leaves some undefined symbols like __fentry__ in purgatory and not
> diff --git a/arch/x86/um/vdso/Makefile b/arch/x86/um/vdso/Makefile
> index 0caddd6acb22..5943387e3f35 100644
> --- a/arch/x86/um/vdso/Makefile
> +++ b/arch/x86/um/vdso/Makefile
> @@ -42,7 +42,7 @@ $(obj)/%.so: $(obj)/%.so.dbg FORCE
>  # optimize sibling calls.
>  #
>  CFL := $(PROFILING) -mcmodel=small -fPIC -O2 -fasynchronous-unwind-tables -m64 \
> -       $(filter -g%,$(KBUILD_CFLAGS)) $(call cc-option, -fno-stack-protector) \
> +       $(filter -g%,$(KBUILD_CFLAGS)) -fno-stack-protector \
>         -fno-omit-frame-pointer -foptimize-sibling-calls
>
>  $(vobjs): KBUILD_CFLAGS += $(CFL)
> diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
> index 084de77a109e..5f1db522d06b 100644
> --- a/arch/x86/xen/Makefile
> +++ b/arch/x86/xen/Makefile
> @@ -9,9 +9,8 @@ CFLAGS_REMOVE_irq.o = -pg
>  endif
>
>  # Make sure early boot has no stackprotector
> -nostackp := $(call cc-option, -fno-stack-protector)
> -CFLAGS_enlighten_pv.o          := $(nostackp)
> -CFLAGS_mmu_pv.o                        := $(nostackp)
> +CFLAGS_enlighten_pv.o          := -fno-stack-protector
> +CFLAGS_mmu_pv.o                        := -fno-stack-protector
>
>  obj-y                          += enlighten.o
>  obj-y                          += mmu.o
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 75daaf20374e..f8418763cd79 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -29,7 +29,7 @@ KBUILD_CFLAGS                 := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \
>                                    -include $(srctree)/drivers/firmware/efi/libstub/hidden.h \
>                                    -D__NO_FORTIFY \
>                                    $(call cc-option,-ffreestanding) \
> -                                  $(call cc-option,-fno-stack-protector) \
> +                                  -fno-stack-protector \
>                                    $(call cc-option,-fno-addrsig) \
>                                    -D__DISABLE_EXPORTS
>
> diff --git a/drivers/xen/Makefile b/drivers/xen/Makefile
> index 0d322f3d90cd..c25c9a699b48 100644
> --- a/drivers/xen/Makefile
> +++ b/drivers/xen/Makefile
> @@ -5,8 +5,7 @@ obj-y   += mem-reservation.o
>  obj-y  += events/
>  obj-y  += xenbus/
>
> -nostackp := $(call cc-option, -fno-stack-protector)
> -CFLAGS_features.o                      := $(nostackp)
> +CFLAGS_features.o                      := -fno-stack-protector
>
>  dom0-$(CONFIG_ARM64) += arm-device.o
>  dom0-$(CONFIG_PCI) += pci.o
> diff --git a/kernel/kcsan/Makefile b/kernel/kcsan/Makefile
> index d4999b38d1be..d111f32bd5fd 100644
> --- a/kernel/kcsan/Makefile
> +++ b/kernel/kcsan/Makefile
> @@ -7,8 +7,7 @@ CFLAGS_REMOVE_core.o = $(CC_FLAGS_FTRACE)
>  CFLAGS_REMOVE_debugfs.o = $(CC_FLAGS_FTRACE)
>  CFLAGS_REMOVE_report.o = $(CC_FLAGS_FTRACE)
>
> -CFLAGS_core.o := $(call cc-option,-fno-conserve-stack,) \
> -       $(call cc-option,-fno-stack-protector,)
> +CFLAGS_core.o := $(call cc-option,-fno-conserve-stack,) -fno-stack-protector
>
>  obj-y := core.o debugfs.o report.o
>  obj-$(CONFIG_KCSAN_SELFTEST) += test.o
> diff --git a/lib/Makefile b/lib/Makefile
> index b1c42c10073b..0cda70649f1c 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -22,7 +22,7 @@ KCOV_INSTRUMENT_fault-inject.o := n
>  ifdef CONFIG_AMD_MEM_ENCRYPT
>  KASAN_SANITIZE_string.o := n
>
> -CFLAGS_string.o := $(call cc-option, -fno-stack-protector)
> +CFLAGS_string.o := -fno-stack-protector
>  endif
>
>  # Used by KCSAN while enabled, avoid recursion.
> @@ -300,7 +300,7 @@ endif
>  UBSAN_SANITIZE_ubsan.o := n
>  KASAN_SANITIZE_ubsan.o := n
>  KCSAN_SANITIZE_ubsan.o := n
> -CFLAGS_ubsan.o := $(call cc-option, -fno-stack-protector) $(DISABLE_STACKLEAK_PLUGIN)
> +CFLAGS_ubsan.o := -fno-stack-protector $(DISABLE_STACKLEAK_PLUGIN)
>
>  obj-$(CONFIG_SBITMAP) += sbitmap.o
>
> diff --git a/mm/kasan/Makefile b/mm/kasan/Makefile
> index d532c2587731..370d970e5ab5 100644
> --- a/mm/kasan/Makefile
> +++ b/mm/kasan/Makefile
> @@ -16,7 +16,7 @@ CFLAGS_REMOVE_tags_report.o = $(CC_FLAGS_FTRACE)
>  # Function splitter causes unnecessary splits in __asan_load1/__asan_store1
>  # see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
>  CC_FLAGS_KASAN_RUNTIME := $(call cc-option, -fno-conserve-stack)
> -CC_FLAGS_KASAN_RUNTIME += $(call cc-option, -fno-stack-protector)
> +CC_FLAGS_KASAN_RUNTIME += -fno-stack-protector
>  # Disable branch tracing to avoid recursion.
>  CC_FLAGS_KASAN_RUNTIME += -DDISABLE_BRANCH_PROFILING
>
> --
> 2.25.1
>

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