[PATCH 1/2] kbuild: remove cc-option test of -fno-stack-protector

From: Masahiro Yamada
Date: Fri Jun 26 2020 - 15:00:23 EST

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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@xxxxxxxxxx>
---

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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