Merge tag 'kbuild-v4.18-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull more Kbuild updates from Masahiro Yamada:

- fix some bugs introduced by the recent Kconfig syntax extension

- add some symbols about compiler information in Kconfig, such as
CC_IS_GCC, CC_IS_CLANG, GCC_VERSION, etc.

- test compiler capability for the stack protector in Kconfig, and
clean-up Makefile

- test compiler capability for GCC-plugins in Kconfig, and clean-up
Makefile

- allow to enable GCC-plugins for COMPILE_TEST

- test compiler capability for KCOV in Kconfig and correct dependency

- remove auto-detect mode of the GCOV format, which is now more nicely
handled in Kconfig

- test compiler capability for mprofile-kernel on PowerPC, and clean-up
Makefile

- misc cleanups

* tag 'kbuild-v4.18-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
linux/linkage.h: replace VMLINUX_SYMBOL_STR() with __stringify()
kconfig: fix localmodconfig
sh: remove no-op macro VMLINUX_SYMBOL()
powerpc/kbuild: move -mprofile-kernel check to Kconfig
Documentation: kconfig: add recommended way to describe compiler support
gcc-plugins: disable GCC_PLUGIN_STRUCTLEAK_BYREF_ALL for COMPILE_TEST
gcc-plugins: allow to enable GCC_PLUGINS for COMPILE_TEST
gcc-plugins: test plugin support in Kconfig and clean up Makefile
gcc-plugins: move GCC version check for PowerPC to Kconfig
kcov: test compiler capability in Kconfig and correct dependency
gcov: remove CONFIG_GCOV_FORMAT_AUTODETECT
arm64: move GCC version check for ARCH_SUPPORTS_INT128 to Kconfig
kconfig: add CC_IS_CLANG and CLANG_VERSION
kconfig: add CC_IS_GCC and GCC_VERSION
stack-protector: test compiler capability in Kconfig and drop AUTO mode
kbuild: fix endless syncconfig in case arch Makefile sets CROSS_COMPILE

Documentation/kbuild/kconfig-language.txt

···
 The dependencies are moved to the symbol GENERIC_IOMAP and we avoid the
 situation where select forces a symbol equals to 'y'.
 
+Adding features that need compiler support
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+There are several features that need compiler support. The recommended way
+to describe the dependency on the compiler feature is to use "depends on"
+followed by a test macro.
+
+config CC_STACKPROTECTOR
+	bool "Stack Protector buffer overflow detection"
+	depends on $(cc-option,-fstack-protector)
+	...
+
+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)
+
 Build as module only
 ~~~~~~~~~~~~~~~~~~~~
 To restrict a component build to module-only, qualify its config symbol

Makefile

···
 export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
 export KBUILD_ARFLAGS
 
-export CC_VERSION_TEXT := $(shell $(CC) --version | head -n 1)
-
 # When compiling out-of-tree modules, put MODVERDIR in the module
 # tree rather than in the kernel tree. The kernel tree might
 # even be read-only.
···
   export CC_CAN_LINK
 endif
 
+# The expansion should be delayed until arch/$(SRCARCH)/Makefile is included.
+# Some architectures define CROSS_COMPILE in arch/$(SRCARCH)/Makefile.
+# CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
+# and from include/config/auto.conf.cmd to detect the compiler upgrade.
+CC_VERSION_TEXT = $(shell $(CC) --version | head -n 1)
+
 ifeq ($(config-targets),1)
 # ===========================================================================
 # *config targets only - make sure prerequisites are updated, and descend
···
 # KBUILD_DEFCONFIG may point out an alternative default configuration
 # used for 'make defconfig'
 include arch/$(SRCARCH)/Makefile
-export KBUILD_DEFCONFIG KBUILD_KCONFIG
+export KBUILD_DEFCONFIG KBUILD_KCONFIG CC_VERSION_TEXT
 
 config: scripts_basic outputmakefile FORCE
 	$(Q)$(MAKE) $(build)=scripts/kconfig $@
···
 endif # KBUILD_EXTMOD
 
 ifeq ($(dot-config),1)
-# Read in config
 -include include/config/auto.conf
+endif
 
+# The all: target is the default when no target is given on the
+# command line.
+# This allow a user to issue only 'make' to build a kernel including modules
+# Defaults to vmlinux, but the arch makefile usually adds further targets
+all: vmlinux
+
+CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage \
+	$(call cc-option,-fno-tree-loop-im) \
+	$(call cc-disable-warning,maybe-uninitialized,)
+export CFLAGS_GCOV
+
+# The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default
+# values of the respective KBUILD_* variables
+ARCH_CPPFLAGS :=
+ARCH_AFLAGS :=
+ARCH_CFLAGS :=
+include arch/$(SRCARCH)/Makefile
+
+ifeq ($(dot-config),1)
 ifeq ($(KBUILD_EXTMOD),)
-# Read in dependencies to all Kconfig* files, make sure to run
-# oldconfig if changes are detected.
+# Read in dependencies to all Kconfig* files, make sure to run syncconfig if
+# changes are detected. This should be included after arch/$(SRCARCH)/Makefile
+# because some architectures define CROSS_COMPILE there.
 -include include/config/auto.conf.cmd
 
 # To avoid any implicit rule to kick in, define an empty command
···
 # Dummy target needed, because used as prerequisite
 include/config/auto.conf: ;
 endif # $(dot-config)
-
-# The all: target is the default when no target is given on the
-# command line.
-# This allow a user to issue only 'make' to build a kernel including modules
-# Defaults to vmlinux, but the arch makefile usually adds further targets
-all: vmlinux
-
-CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage \
-	$(call cc-option,-fno-tree-loop-im) \
-	$(call cc-disable-warning,maybe-uninitialized,)
-export CFLAGS_GCOV CFLAGS_KCOV
-
-# The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default
-# values of the respective KBUILD_* variables
-ARCH_CPPFLAGS :=
-ARCH_AFLAGS :=
-ARCH_CFLAGS :=
-include arch/$(SRCARCH)/Makefile
 
 KBUILD_CFLAGS	+= $(call cc-option,-fno-delete-null-pointer-checks,)
 KBUILD_CFLAGS	+= $(call cc-disable-warning,frame-address,)
···
 KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
 endif
 
-# This selects the stack protector compiler flag. Testing it is delayed
-# until after .config has been reprocessed, in the prepare-compiler-check
-# target.
-ifdef CONFIG_CC_STACKPROTECTOR_AUTO
-  stackp-flag := $(call cc-option,-fstack-protector-strong,$(call cc-option,-fstack-protector))
-  stackp-name := AUTO
-else
-ifdef CONFIG_CC_STACKPROTECTOR_REGULAR
-  stackp-flag := -fstack-protector
-  stackp-name := REGULAR
-else
-ifdef CONFIG_CC_STACKPROTECTOR_STRONG
-  stackp-flag := -fstack-protector-strong
-  stackp-name := STRONG
-else
-  # If either there is no stack protector for this architecture or
-  # CONFIG_CC_STACKPROTECTOR_NONE is selected, we're done, and $(stackp-name)
-  # is empty, skipping all remaining stack protector tests.
-  #
-  # Force off for distro compilers that enable stack protector by default.
-  KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
-endif
-endif
-endif
-# Find arch-specific stack protector compiler sanity-checking script.
-ifdef stackp-name
-ifneq ($(stackp-flag),)
-  stackp-path := $(srctree)/scripts/gcc-$(SRCARCH)_$(BITS)-has-stack-protector.sh
-  stackp-check := $(wildcard $(stackp-path))
-  # If the wildcard test matches a test script, run it to check functionality.
-  ifdef stackp-check
-    ifneq ($(shell $(CONFIG_SHELL) $(stackp-check) $(CC) $(KBUILD_CPPFLAGS) $(biarch)),y)
-      stackp-broken := y
-    endif
-  endif
-  ifndef stackp-broken
-    # If the stack protector is functional, enable code that depends on it.
-    KBUILD_CPPFLAGS += -DCONFIG_CC_STACKPROTECTOR
-    # Either we've already detected the flag (for AUTO) or we'll fail the
-    # build in the prepare-compiler-check rule (for specific flag).
-    KBUILD_CFLAGS += $(stackp-flag)
-  else
-    # We have to make sure stack protector is unconditionally disabled if
-    # the compiler is broken (in case we're going to continue the build in
-    # AUTO mode).
-    KBUILD_CFLAGS += $(call cc-option, -fno-stack-protector)
-  endif
-endif
-endif
+stackp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector
+stackp-flags-$(CONFIG_CC_STACKPROTECTOR)          := -fstack-protector
+stackp-flags-$(CONFIG_CC_STACKPROTECTOR_STRONG)   := -fstack-protector-strong
+
+KBUILD_CFLAGS += $(stackp-flags-y)
 
 ifeq ($(cc-name),clang)
 KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
···
 # prepare2 creates a makefile if using a separate output directory.
 # From this point forward, .config has been reprocessed, so any rules
 # that need to depend on updated CONFIG_* values can be checked here.
-prepare2: prepare3 prepare-compiler-check outputmakefile asm-generic
+prepare2: prepare3 outputmakefile asm-generic
 
 prepare1: prepare2 $(version_h) $(autoksyms_h) include/generated/utsrelease.h \
                    include/config/auto.conf
···
 
 PHONY += prepare-objtool
 prepare-objtool: $(objtool_target)
-
-# Check for CONFIG flags that require compiler support. Abort the build
-# after .config has been processed, but before the kernel build starts.
-#
-# For security-sensitive CONFIG options, we don't want to fallback and/or
-# silently change which compiler flags will be used, since that leads to
-# producing kernels with different security feature characteristics
-# depending on the compiler used. (For example, "But I selected
-# CC_STACKPROTECTOR_STRONG! Why did it build with _REGULAR?!")
-PHONY += prepare-compiler-check
-prepare-compiler-check: FORCE
-# Make sure compiler supports requested stack protector flag.
-ifdef stackp-name
-  # Warn about CONFIG_CC_STACKPROTECTOR_AUTO having found no option.
-  ifeq ($(stackp-flag),)
-	@echo CONFIG_CC_STACKPROTECTOR_$(stackp-name): \
-		  Compiler does not support any known stack-protector >&2
-  else
-  # Fail if specifically requested stack protector is missing.
-  ifeq ($(call cc-option, $(stackp-flag)),)
-	@echo Cannot use CONFIG_CC_STACKPROTECTOR_$(stackp-name): \
-		  $(stackp-flag) not supported by compiler >&2 && exit 1
-  endif
-  endif
-endif
-# Make sure compiler does not have buggy stack-protector support. If a
-# specific stack-protector was requested, fail the build, otherwise warn.
-ifdef stackp-broken
-  ifeq ($(stackp-name),AUTO)
-	@echo CONFIG_CC_STACKPROTECTOR_$(stackp-name): \
-                  $(stackp-flag) available but compiler is broken: disabling >&2
-  else
-	@echo Cannot use CONFIG_CC_STACKPROTECTOR_$(stackp-name): \
-                  $(stackp-flag) available but compiler is broken >&2 && exit 1
-  endif
-endif
-	@:
 
 # Generate some files
 # ---------------------------------------------------------------------------

arch/Kconfig

···
 
 	  See Documentation/prctl/seccomp_filter.txt for details.
 
+preferred-plugin-hostcc := $(if-success,[ $(gcc-version) -ge 40800 ],$(HOSTCXX),$(HOSTCC))
+
+config PLUGIN_HOSTCC
+	string
+	default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")"
+	help
+	  Host compiler used to build GCC plugins.  This can be $(HOSTCXX),
+	  $(HOSTCC), or a null string if GCC plugin is unsupported.
+
 config HAVE_GCC_PLUGINS
 	bool
 	help
···
 menuconfig GCC_PLUGINS
 	bool "GCC plugins"
 	depends on HAVE_GCC_PLUGINS
-	depends on !COMPILE_TEST
+	depends on PLUGIN_HOSTCC != ""
 	help
 	  GCC plugins are loadable modules that provide extra features to the
 	  compiler. They are useful for runtime instrumentation and static analysis.
···
 config GCC_PLUGIN_CYC_COMPLEXITY
 	bool "Compute the cyclomatic complexity of a function" if EXPERT
 	depends on GCC_PLUGINS
-	depends on !COMPILE_TEST
+	depends on !COMPILE_TEST	# too noisy
 	help
 	  The complexity M of a function's control flow graph is defined as:
 	   M = E - N + 2P
···
 config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL
 	bool "Force initialize all struct type variables passed by reference"
 	depends on GCC_PLUGIN_STRUCTLEAK
+	depends on !COMPILE_TEST
 	help
 	  Zero initialize any struct type local variable that may be passed by
 	  reference without having been initialized.
···
 config GCC_PLUGIN_STRUCTLEAK_VERBOSE
 	bool "Report forcefully initialized variables"
 	depends on GCC_PLUGIN_STRUCTLEAK
-	depends on !COMPILE_TEST
+	depends on !COMPILE_TEST	# too noisy
 	help
 	  This option will cause a warning to be printed each time the
 	  structleak plugin finds a variable it thinks needs to be
···
 config GCC_PLUGIN_RANDSTRUCT_PERFORMANCE
 	bool "Use cacheline-aware structure randomization"
 	depends on GCC_PLUGIN_RANDSTRUCT
-	depends on !COMPILE_TEST
+	depends on !COMPILE_TEST	# do not reduce test coverage
 	help
 	  If you say Y here, the RANDSTRUCT randomization will make a
 	  best effort at restricting randomization to cacheline-sized
···
 	bool
 	help
 	  An arch should select this symbol if:
-	  - its compiler supports the -fstack-protector option
 	  - it has implemented a stack canary (e.g. __stack_chk_guard)
 
-choice
-	prompt "Stack Protector buffer overflow detection"
+config CC_HAS_STACKPROTECTOR_NONE
+	def_bool $(cc-option,-fno-stack-protector)
+
+config CC_STACKPROTECTOR
+	bool "Stack Protector buffer overflow detection"
 	depends on HAVE_CC_STACKPROTECTOR
-	default CC_STACKPROTECTOR_AUTO
+	depends on $(cc-option,-fstack-protector)
+	default y
 	help
 	  This option turns on the "stack-protector" GCC feature. This
 	  feature puts, at the beginning of functions, a canary value on
···
 	  overwrite the canary, which gets detected and the attack is then
 	  neutralized via a kernel panic.
 
-config CC_STACKPROTECTOR_NONE
-	bool "None"
-	help
-	  Disable "stack-protector" GCC feature.
-
-config CC_STACKPROTECTOR_REGULAR
-	bool "Regular"
-	help
 	  Functions will have the stack-protector canary logic added if they
 	  have an 8-byte or larger character array on the stack.
 
···
 	  by about 0.3%.
 
 config CC_STACKPROTECTOR_STRONG
-	bool "Strong"
+	bool "Strong Stack Protector"
+	depends on CC_STACKPROTECTOR
+	depends on $(cc-option,-fstack-protector-strong)
+	default y
 	help
 	  Functions will have the stack-protector canary logic added in any
 	  of the following conditions:
···
 	  On an x86 "defconfig" build, this feature adds canary checks to
 	  about 20% of all kernel functions, which increases the kernel code
 	  size by about 2%.
-
-config CC_STACKPROTECTOR_AUTO
-	bool "Automatic"
-	help
-	  If the compiler supports it, the best available stack-protector
-	  option will be chosen.
-
-endchoice
 
 config HAVE_ARCH_WITHIN_STACK_FRAMES
 	bool

arch/arm64/Kconfig

···
 	select ARCH_USE_QUEUED_RWLOCKS
 	select ARCH_SUPPORTS_MEMORY_FAILURE
 	select ARCH_SUPPORTS_ATOMIC_RMW
+	select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 50000 || CC_IS_CLANG
 	select ARCH_SUPPORTS_NUMA_BALANCING
 	select ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 	select ARCH_WANT_FRAME_POINTERS

arch/arm64/Makefile

···
 KBUILD_CFLAGS	+= $(call cc-option,-mabi=lp64)
 KBUILD_AFLAGS	+= $(call cc-option,-mabi=lp64)
 
-ifeq ($(cc-name),clang)
-KBUILD_CFLAGS	+= -DCONFIG_ARCH_SUPPORTS_INT128
-else
-KBUILD_CFLAGS	+= $(call cc-ifversion, -ge, 0500, -DCONFIG_ARCH_SUPPORTS_INT128)
-endif
-
 ifeq ($(CONFIG_CPU_BIG_ENDIAN), y)
 KBUILD_CPPFLAGS	+= -mbig-endian
 CHECKFLAGS	+= -D__AARCH64EB__

arch/powerpc/Kconfig

···
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER
-	select HAVE_GCC_PLUGINS
+	select HAVE_GCC_PLUGINS			if GCC_VERSION >= 50200   # plugin support on gcc <= 5.1 is buggy on PPC
 	select HAVE_GENERIC_GUP
 	select HAVE_HW_BREAKPOINT		if PERF_EVENTS && (PPC_BOOK3S || PPC_8xx)
 	select HAVE_IDE
···
 
 	  If unsure, say "N".
 
-config DISABLE_MPROFILE_KERNEL
-	bool "Disable use of mprofile-kernel for kernel tracing"
-	depends on PPC64 && CPU_LITTLE_ENDIAN
-	default y
-	help
-	  Selecting this options disables use of the mprofile-kernel ABI for
-	  kernel tracing. That will cause options such as live patching
-	  (CONFIG_LIVEPATCH) which depend on CONFIG_DYNAMIC_FTRACE_WITH_REGS to
-	  be disabled also.
-
-	  If you have a toolchain which supports mprofile-kernel, then you can
-	  disable this. Otherwise leave it enabled. If you're not sure, say
-	  "Y".
-
 config MPROFILE_KERNEL
 	depends on PPC64 && CPU_LITTLE_ENDIAN
-	def_bool !DISABLE_MPROFILE_KERNEL
+	def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC) -I$(srctree)/include -D__KERNEL__)
 
 config HOTPLUG_CPU
 	bool "Support for enabling/disabling CPUs"

arch/powerpc/Makefile

···
 endif
 
 ifdef CONFIG_MPROFILE_KERNEL
-    ifeq ($(shell $(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC) -I$(srctree)/include -D__KERNEL__),OK)
-        CC_FLAGS_FTRACE := -pg -mprofile-kernel
-        KBUILD_CPPFLAGS += -DCC_USING_MPROFILE_KERNEL
-    else
-        # If the user asked for mprofile-kernel but the toolchain doesn't
-        # support it, emit a warning and deliberately break the build later
-        # with mprofile-kernel-not-supported. We would prefer to make this an
-        # error right here, but then the user would never be able to run
-        # oldconfig to change their configuration.
-        $(warning Compiler does not support mprofile-kernel, set CONFIG_DISABLE_MPROFILE_KERNEL)
-        CC_FLAGS_FTRACE := -mprofile-kernel-not-supported
-    endif
+	CC_FLAGS_FTRACE := -pg -mprofile-kernel
 endif
 
 CFLAGS-$(CONFIG_CELL_CPU) += $(call cc-option,-mcpu=cell)

arch/powerpc/include/asm/module.h

···
 #include <asm-generic/module.h>
 
 
-#ifdef CC_USING_MPROFILE_KERNEL
+#ifdef CONFIG_MPROFILE_KERNEL
 #define MODULE_ARCH_VERMAGIC_FTRACE	"mprofile-kernel "
 #else
 #define MODULE_ARCH_VERMAGIC_FTRACE	""

arch/powerpc/kernel/module_64.c

···
 	return (unsigned long)&stubs[i];
 }
 
-#ifdef CC_USING_MPROFILE_KERNEL
+#ifdef CONFIG_MPROFILE_KERNEL
 static bool is_mprofile_mcount_callsite(const char *name, u32 *instruction)
 {
 	if (strcmp("_mcount", name))
···
 
 #ifdef CONFIG_DYNAMIC_FTRACE
 
-#ifdef CC_USING_MPROFILE_KERNEL
+#ifdef CONFIG_MPROFILE_KERNEL
 
 #define PACATOC offsetof(struct paca_struct, kernel_toc)
 

arch/powerpc/kernel/trace/ftrace.c

···
 		return -EINVAL;
 	}
 
-#ifdef CC_USING_MPROFILE_KERNEL
+#ifdef CONFIG_MPROFILE_KERNEL
 	/* When using -mkernel_profile there is no load to jump over */
 	pop = PPC_INST_NOP;
 
···
 		pr_err("Expected %08x found %08x\n", PPC_INST_LD_TOC, op);
 		return -EINVAL;
 	}
-#endif /* CC_USING_MPROFILE_KERNEL */
+#endif /* CONFIG_MPROFILE_KERNEL */
 
 	if (patch_instruction((unsigned int *)ip, pop)) {
 		pr_err("Patching NOP failed.\n");
···
  * They should effectively be a NOP, and follow formal constraints,
  * depending on the ABI. Return false if they don't.
  */
-#ifndef CC_USING_MPROFILE_KERNEL
+#ifndef CONFIG_MPROFILE_KERNEL
 static int
 expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
 {

arch/powerpc/tools/gcc-check-mprofile-kernel.sh

···
     2> /dev/null | grep -q "_mcount" && \
     exit 1
 
-echo "OK"
 exit 0

arch/sh/include/asm/vmlinux.lds.h

···
 #ifdef CONFIG_DWARF_UNWINDER
 #define DWARF_EH_FRAME							\
 	.eh_frame : AT(ADDR(.eh_frame) - LOAD_OFFSET) {			\
-		  VMLINUX_SYMBOL(__start_eh_frame) = .;			\
+		  __start_eh_frame = .;					\
 		  *(.eh_frame)						\
-		  VMLINUX_SYMBOL(__stop_eh_frame) = .;			\
+		  __stop_eh_frame = .;					\
 	}
 #else
 #define DWARF_EH_FRAME

arch/x86/Kconfig

···
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD if X86_64
 	select HAVE_ARCH_VMAP_STACK		if X86_64
 	select HAVE_ARCH_WITHIN_STACK_FRAMES
-	select HAVE_CC_STACKPROTECTOR
+	select HAVE_CC_STACKPROTECTOR		if CC_HAS_SANE_STACKPROTECTOR
 	select HAVE_CMPXCHG_DOUBLE
 	select HAVE_CMPXCHG_LOCAL
 	select HAVE_CONTEXT_TRACKING		if X86_64
···
 	default 2
 
 source "init/Kconfig"
+
+config CC_HAS_SANE_STACKPROTECTOR
+	bool
+	default $(success,$(srctree)/scripts/gcc-x86_64-has-stack-protector.sh $(CC)) if 64BIT
+	default $(success,$(srctree)/scripts/gcc-x86_32-has-stack-protector.sh $(CC))
+	help
+	   We have to make sure stack protector is unconditionally disabled if
+	   the compiler produces broken code.
+
 source "kernel/Kconfig.freezer"
 
 menu "Processor type and features"

include/linux/linkage.h

···
 
 #ifndef cond_syscall
 #define cond_syscall(x)	asm(				\
-	".weak " VMLINUX_SYMBOL_STR(x) "\n\t"		\
-	".set  " VMLINUX_SYMBOL_STR(x) ","		\
-		 VMLINUX_SYMBOL_STR(sys_ni_syscall))
+	".weak " __stringify(x) "\n\t"			\
+	".set  " __stringify(x) ","			\
+		 __stringify(sys_ni_syscall))
 #endif
 
 #ifndef SYSCALL_ALIAS
 #define SYSCALL_ALIAS(alias, name) asm(			\
-	".globl " VMLINUX_SYMBOL_STR(alias) "\n\t"	\
-	".set   " VMLINUX_SYMBOL_STR(alias) ","		\
-		  VMLINUX_SYMBOL_STR(name))
+	".globl " __stringify(alias) "\n\t"		\
+	".set   " __stringify(alias) ","		\
+		  __stringify(name))
 #endif
 
 #define __page_aligned_data	__section(.data..page_aligned) __aligned(PAGE_SIZE)

init/Kconfig

···
 	default ARCH_DEFCONFIG
 	default "arch/$(ARCH)/defconfig"
 
+config CC_IS_GCC
+	def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
+
+config GCC_VERSION
+	int
+	default $(shell,$(srctree)/scripts/gcc-version.sh -p $(CC) | sed 's/^0*//') if CC_IS_GCC
+	default 0
+
+config CC_IS_CLANG
+	def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
+
+config CLANG_VERSION
+	int
+	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
+
 config CONSTRUCTORS
 	bool
 	depends on !UML

kernel/gcov/Kconfig

···
 choice
 	prompt "Specify GCOV format"
 	depends on GCOV_KERNEL
-	default GCOV_FORMAT_AUTODETECT
 	---help---
-	The gcov format is usually determined by the GCC version, but there are
+	The gcov format is usually determined by the GCC version, and the
+	default is chosen according to your GCC version. However, there are
 	exceptions where format changes are integrated in lower-version GCCs.
-	In such a case use this option to adjust the format used in the kernel
-	accordingly.
-
-	If unsure, choose "Autodetect".
-
-config GCOV_FORMAT_AUTODETECT
-	bool "Autodetect"
-	---help---
-	Select this option to use the format that corresponds to your GCC
-	version.
+	In such a case, change this option to adjust the format used in the
+	kernel accordingly.
 
 config GCOV_FORMAT_3_4
 	bool "GCC 3.4 format"
+	depends on CC_IS_GCC && GCC_VERSION < 40700
 	---help---
 	Select this option to use the format defined by GCC 3.4.
 

kernel/gcov/Makefile

···
 obj-y := base.o fs.o
 obj-$(CONFIG_GCOV_FORMAT_3_4) += gcc_3_4.o
 obj-$(CONFIG_GCOV_FORMAT_4_7) += gcc_4_7.o
-obj-$(CONFIG_GCOV_FORMAT_AUTODETECT) += $(call cc-ifversion, -lt, 0407, \
-							gcc_3_4.o, gcc_4_7.o)

lib/Kconfig.debug

···
 	  only for x86_64. KCOV requires testing on other archs, and most likely
 	  disabling of instrumentation for some early boot code.
 
+config CC_HAS_SANCOV_TRACE_PC
+	def_bool $(cc-option,-fsanitize-coverage=trace-pc)
+
 config KCOV
 	bool "Code coverage for fuzzing"
 	depends on ARCH_HAS_KCOV
+	depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS
 	select DEBUG_FS
-	select GCC_PLUGINS if !COMPILE_TEST
-	select GCC_PLUGIN_SANCOV if !COMPILE_TEST
+	select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC
 	help
 	  KCOV exposes kernel code coverage information in a form suitable
 	  for coverage-guided fuzzing (randomized testing).
···
 config KCOV_ENABLE_COMPARISONS
 	bool "Enable comparison operands collection by KCOV"
 	depends on KCOV
-	default n
+	depends on $(cc-option,-fsanitize-coverage=trace-cmp)
 	help
 	  KCOV also exposes operands of every comparison in the instrumented
 	  code along with operand sizes and PCs of the comparison instructions.
···
 config KCOV_INSTRUMENT_ALL
 	bool "Instrument all code by default"
 	depends on KCOV
-	default y if KCOV
+	default y
 	help
 	  If you are doing generic system call fuzzing (like e.g. syzkaller),
 	  then you will want to instrument the whole kernel and you should

scripts/Kconfig.include

···
 # $(ld-option,<flag>)
 # Return y if the linker supports <flag>, n otherwise
 ld-option = $(success,$(LD) -v $(1))
+
+# gcc version including patch level
+gcc-version := $(shell,$(srctree)/scripts/gcc-version.sh -p $(CC) | sed 's/^0*//')

scripts/Makefile.gcc-plugins

···
 # SPDX-License-Identifier: GPL-2.0
-ifdef CONFIG_GCC_PLUGINS
-  __PLUGINCC := $(call cc-ifversion, -ge, 0408, $(HOSTCXX), $(HOSTCC))
-  PLUGINCC := $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-plugin.sh "$(__PLUGINCC)" "$(HOSTCXX)" "$(CC)")
+gcc-plugin-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY)	+= cyc_complexity_plugin.so
 
-  SANCOV_PLUGIN := -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so
-
-  gcc-plugin-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY)	+= cyc_complexity_plugin.so
-
-  gcc-plugin-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY)	+= latent_entropy_plugin.so
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY)	+= -DLATENT_ENTROPY_PLUGIN
-  ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
+gcc-plugin-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY)	+= latent_entropy_plugin.so
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY)	+= -DLATENT_ENTROPY_PLUGIN
+ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY
     DISABLE_LATENT_ENTROPY_PLUGIN			+= -fplugin-arg-latent_entropy_plugin-disable
-  endif
-
-  ifdef CONFIG_GCC_PLUGIN_SANCOV
-    ifeq ($(strip $(CFLAGS_KCOV)),)
-      # It is needed because of the gcc-plugin.sh and gcc version checks.
-      gcc-plugin-$(CONFIG_GCC_PLUGIN_SANCOV)           += sancov_plugin.so
-
-      ifneq ($(PLUGINCC),)
-        CFLAGS_KCOV := $(SANCOV_PLUGIN)
-      else
-        $(warning warning: cannot use CONFIG_KCOV: -fsanitize-coverage=trace-pc is not supported by compiler)
-      endif
-    endif
-  endif
-
-  gcc-plugin-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)	+= structleak_plugin.so
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE)	+= -fplugin-arg-structleak_plugin-verbose
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL)	+= -fplugin-arg-structleak_plugin-byref-all
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)	+= -DSTRUCTLEAK_PLUGIN
-
-  gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)	+= randomize_layout_plugin.so
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)	+= -DRANDSTRUCT_PLUGIN
-  gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE)	+= -fplugin-arg-randomize_layout_plugin-performance-mode
-
-  GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y))
-
-  export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR
-  export SANCOV_PLUGIN DISABLE_LATENT_ENTROPY_PLUGIN
-
-  ifneq ($(PLUGINCC),)
-    # SANCOV_PLUGIN can be only in CFLAGS_KCOV because avoid duplication.
-    GCC_PLUGINS_CFLAGS := $(filter-out $(SANCOV_PLUGIN), $(GCC_PLUGINS_CFLAGS))
-  endif
-
-  KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
-  GCC_PLUGIN := $(gcc-plugin-y)
-  GCC_PLUGIN_SUBDIR := $(gcc-plugin-subdir-y)
 endif
 
-# If plugins aren't supported, abort the build before hard-to-read compiler
-# errors start getting spewed by the main build.
-PHONY += gcc-plugins-check
-gcc-plugins-check: FORCE
-ifdef CONFIG_GCC_PLUGINS
-  ifeq ($(PLUGINCC),)
-    ifneq ($(GCC_PLUGINS_CFLAGS),)
-      # Various gccs between 4.5 and 5.1 have bugs on powerpc due to missing
-      # header files. gcc <= 4.6 doesn't work at all, gccs from 4.8 to 5.1 have
-      # issues with 64-bit targets.
-      ifeq ($(ARCH),powerpc)
-        ifeq ($(call cc-ifversion, -le, 0501, y), y)
-	  @echo "Cannot use CONFIG_GCC_PLUGINS: plugin support on gcc <= 5.1 is buggy on powerpc, please upgrade to gcc 5.2 or newer" >&2 && exit 1
-        endif
-      endif
-      ifeq ($(call cc-ifversion, -ge, 0405, y), y)
-	$(Q)$(srctree)/scripts/gcc-plugin.sh --show-error "$(__PLUGINCC)" "$(HOSTCXX)" "$(CC)" || true
-	@echo "Cannot use CONFIG_GCC_PLUGINS: your gcc installation does not support plugins, perhaps the necessary headers are missing?" >&2 && exit 1
-      else
-	@echo "Cannot use CONFIG_GCC_PLUGINS: your gcc version does not support plugins, you should upgrade it to at least gcc 4.5" >&2 && exit 1
-      endif
-    endif
-  endif
-endif
-	@:
+gcc-plugin-$(CONFIG_GCC_PLUGIN_SANCOV)		+= sancov_plugin.so
+gcc-plugin-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)	+= structleak_plugin.so
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE)	+= -fplugin-arg-structleak_plugin-verbose
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL)	+= -fplugin-arg-structleak_plugin-byref-all
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)	+= -DSTRUCTLEAK_PLUGIN
+
+gcc-plugin-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)	+= randomize_layout_plugin.so
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT)	+= -DRANDSTRUCT_PLUGIN
+gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_RANDSTRUCT_PERFORMANCE)	+= -fplugin-arg-randomize_layout_plugin-performance-mode
+
+GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y))
+
+export GCC_PLUGINS_CFLAGS GCC_PLUGIN GCC_PLUGIN_SUBDIR
+export DISABLE_LATENT_ENTROPY_PLUGIN
+
+# sancov_plugin.so can be only in CFLAGS_KCOV because avoid duplication.
+GCC_PLUGINS_CFLAGS := $(filter-out %/sancov_plugin.so, $(GCC_PLUGINS_CFLAGS))
+
+KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
+GCC_PLUGIN := $(gcc-plugin-y)
+GCC_PLUGIN_SUBDIR := $(gcc-plugin-subdir-y)
 
 # Actually do the build, if requested.
 PHONY += gcc-plugins
-gcc-plugins: scripts_basic gcc-plugins-check
+gcc-plugins: scripts_basic
 ifdef CONFIG_GCC_PLUGINS
 	$(Q)$(MAKE) $(build)=scripts/gcc-plugins
 endif

scripts/Makefile.kcov

···
 ifdef CONFIG_KCOV
-CFLAGS_KCOV	:= $(call cc-option,-fsanitize-coverage=trace-pc,)
-ifeq ($(CONFIG_KCOV_ENABLE_COMPARISONS),y)
-CFLAGS_KCOV += $(call cc-option,-fsanitize-coverage=trace-cmp,)
-endif
+
+kcov-flags-$(CONFIG_CC_HAS_SANCOV_TRACE_PC)	+= -fsanitize-coverage=trace-pc
+kcov-flags-$(CONFIG_KCOV_ENABLE_COMPARISONS)	+= -fsanitize-coverage=trace-cmp
+kcov-flags-$(CONFIG_GCC_PLUGIN_SANCOV)		+= -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so
+
+export CFLAGS_KCOV := $(kcov-flags-y)
 
 endif

scripts/clang-version.sh

···
 # clang-5.0.1 etc.
 #
 
-if [ "$1" = "-p" ] ; then
-	with_patchlevel=1;
-	shift;
-fi
-
 compiler="$*"
 
-if [ ${#compiler} -eq 0 ]; then
-	echo "Error: No compiler specified."
-	printf "Usage:\n\t$0 <clang-command>\n"
+if !( $compiler --version | grep -q clang) ; then
+	echo 0
 	exit 1
 fi
 
 MAJOR=$(echo __clang_major__ | $compiler -E -x c - | tail -n 1)
 MINOR=$(echo __clang_minor__ | $compiler -E -x c - | tail -n 1)
-if [ "x$with_patchlevel" != "x" ] ; then
-	PATCHLEVEL=$(echo __clang_patchlevel__ | $compiler -E -x c - | tail -n 1)
-	printf "%02d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL
-else
-	printf "%02d%02d\\n" $MAJOR $MINOR
-fi
+PATCHLEVEL=$(echo __clang_patchlevel__ | $compiler -E -x c - | tail -n 1)
+printf "%d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL

scripts/gcc-plugins/Makefile

···
 # SPDX-License-Identifier: GPL-2.0
+PLUGINCC := $(CONFIG_PLUGIN_HOSTCC:"%"=%)
 GCC_PLUGINS_DIR := $(shell $(CC) -print-file-name=plugin)
 
 ifeq ($(PLUGINCC),$(HOSTCC))
···
   HOST_EXTRACXXFLAGS += -fno-exceptions -fasynchronous-unwind-tables -ggdb
   HOST_EXTRACXXFLAGS += -Wno-narrowing -Wno-unused-variable
   export HOST_EXTRACXXFLAGS
-endif
-
-ifneq ($(CFLAGS_KCOV), $(SANCOV_PLUGIN))
-  GCC_PLUGIN := $(filter-out $(SANCOV_PLUGIN), $(GCC_PLUGIN))
 endif
 
 export HOSTLIBS

scripts/gcc-x86_32-has-stack-protector.sh

···
 #!/bin/sh
 # SPDX-License-Identifier: GPL-2.0
 
-echo "int foo(void) { char X[200]; return 3; }" | $* -S -x c -c -O0 -fstack-protector - -o - 2> /dev/null | grep -q "%gs"
-if [ "$?" -eq "0" ] ; then
-	echo y
-else
-	echo n
-fi
+echo "int foo(void) { char X[200]; return 3; }" | $* -S -x c -c -m32 -O0 -fstack-protector - -o - 2> /dev/null | grep -q "%gs"

scripts/gcc-x86_64-has-stack-protector.sh

···
 # SPDX-License-Identifier: GPL-2.0
 
 echo "int foo(void) { char X[200]; return 3; }" | $* -S -x c -c -O0 -mcmodel=kernel -fno-PIE -fstack-protector - -o - 2> /dev/null | grep -q "%gs"
-if [ "$?" -eq "0" ] ; then
-	echo y
-else
-	echo n
-fi

scripts/kconfig/streamline_config.pl

···
     my $last_source = "";
 
     # Check for any environment variables used
-    while ($source =~ /\$(\w+)/ && $last_source ne $source) {
+    while ($source =~ /\$\((\w+)\)/ && $last_source ne $source) {
 	my $env = $1;
 	$last_source = $source;
-	$source =~ s/\$$env/$ENV{$env}/;
+	$source =~ s/\$\($env\)/$ENV{$env}/;
     }
 
     open(my $kinfile, '<', $source) || die "Can't open $kconfig";