Merge tag 'kbuild-v5.7' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:
 "Build system:

   - add CONFIG_UNUSED_KSYMS_WHITELIST, which will be useful to define a
     fixed set of export symbols for Generic Kernel Image (GKI)

   - allow to run 'make dt_binding_check' without .config

   - use full schema for checking DT examples in *.yaml files

   - make modpost fail for missing MODULE_IMPORT_NS(), which makes more
     sense because we know the produced modules are never loadable

   - Remove unused 'AS' variable

  Kconfig:

   - sanitize DEFCONFIG_LIST, and remove ARCH_DEFCONFIG from Kconfig
     files

   - relax the 'imply' behavior so that symbols implied by 'y' can
     become 'm'

   - make 'imply' obey 'depends on' in order to make 'imply' really weak

  Misc:

   - add documentation on building the kernel with Clang/LLVM

   - revive __HAVE_ARCH_STRLEN for 32bit sparc to use optimized strlen()

   - fix warning from deb-pkg builds when CONFIG_DEBUG_INFO=n

   - various script and Makefile cleanups"

* tag 'kbuild-v5.7' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (34 commits)
  Makefile: Update kselftest help information
  kbuild: deb-pkg: fix warning when CONFIG_DEBUG_INFO is unset
  kbuild: add outputmakefile to no-dot-config-targets
  kbuild: remove AS variable
  net: wan: wanxl: refactor the firmware rebuild rule
  net: wan: wanxl: use $(M68KCC) instead of $(M68KAS) for rebuilding firmware
  net: wan: wanxl: use allow to pass CROSS_COMPILE_M68k for rebuilding firmware
  kbuild: add comment about grouped target
  kbuild: add -Wall to KBUILD_HOSTCXXFLAGS
  kconfig: remove unused variable in qconf.cc
  sparc: revive __HAVE_ARCH_STRLEN for 32bit sparc
  kbuild: refactor Makefile.dtbinst more
  kbuild: compute the dtbs_install destination more simply
  Makefile: disallow data races on gcc-10 as well
  kconfig: make 'imply' obey the direct dependency
  kconfig: allow symbols implied by y to become m
  net: drop_monitor: use IS_REACHABLE() to guard net_dm_hw_report()
  modpost: return error if module is missing ns imports and MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=n
  modpost: rework and consolidate logging interface
  kbuild: allow to run dt_binding_check without kernel configuration
  ...

Makefile

@@ -255,7 +255,8 @@ clean-targets := %clean mrproper cleandocs
 no-dot-config-targets := $(clean-targets) \
 			 cscope gtags TAGS tags help% %docs check% coccicheck \
 			 $(version_h) headers headers_% archheaders archscripts \
-			 %asm-generic kernelversion %src-pkg
+			 %asm-generic kernelversion %src-pkg dt_binding_check \
+			 outputmakefile
 no-sync-config-targets := $(no-dot-config-targets) install %install \
 			   kernelrelease
 single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.s %.symtypes %/
@@ -388,6 +389,9 @@ endif
 KCONFIG_CONFIG	?= .config
 export KCONFIG_CONFIG
 
+# Default file for 'make defconfig'. This may be overridden by arch-Makefile.
+export KBUILD_DEFCONFIG := defconfig
+
 # SHELL used by kbuild
 CONFIG_SHELL := sh
 
@@ -400,12 +404,11 @@ HOSTCXX      = g++
 KBUILD_HOSTCFLAGS   := -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 \
 		-fomit-frame-pointer -std=gnu89 $(HOST_LFS_CFLAGS) \
 		$(HOSTCFLAGS)
-KBUILD_HOSTCXXFLAGS := -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
+KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
 KBUILD_HOSTLDFLAGS  := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
 KBUILD_HOSTLDLIBS   := $(HOST_LFS_LIBS) $(HOSTLDLIBS)
 
 # Make variables (CC, etc...)
-AS		= $(CROSS_COMPILE)as
 LD		= $(CROSS_COMPILE)ld
 CC		= $(CROSS_COMPILE)gcc
 CPP		= $(CC) -E
@@ -472,7 +475,7 @@ KBUILD_LDFLAGS :=
 GCC_PLUGINS_CFLAGS :=
 CLANG_FLAGS :=
 
-export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
+export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC
 export CPP AR NM STRIP OBJCOPY OBJDUMP OBJSIZE READELF PAHOLE LEX YACC AWK INSTALLKERNEL
 export PERL PYTHON PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
 export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
@@ -535,7 +538,7 @@ endif
 ifneq ($(GCC_TOOLCHAIN),)
 CLANG_FLAGS	+= --gcc-toolchain=$(GCC_TOOLCHAIN)
 endif
-ifeq ($(shell $(AS) --version 2>&1 | head -n 1 | grep clang),)
+ifeq ($(if $(AS),$(shell $(AS) --version 2>&1 | head -n 1 | grep clang)),)
 CLANG_FLAGS	+= -no-integrated-as
 endif
 CLANG_FLAGS	+= -Werror=unknown-warning-option
@@ -674,6 +677,7 @@ $(KCONFIG_CONFIG):
 #
 # This exploits the 'multi-target pattern rule' trick.
 # The syncconfig should be executed only once to make all the targets.
+# (Note: use the grouped target '&:' when we bump to GNU Make 4.3)
 %/auto.conf %/auto.conf.cmd: $(KCONFIG_CONFIG)
 	$(Q)$(MAKE) -f $(srctree)/Makefile syncconfig
 else # !may-sync-config
@@ -714,6 +718,7 @@ endif
 
 # Tell gcc to never replace conditional load with a non-conditional one
 KBUILD_CFLAGS	+= $(call cc-option,--param=allow-store-data-races=0)
+KBUILD_CFLAGS	+= $(call cc-option,-fno-allow-store-data-races)
 
 include scripts/Makefile.kcov
 include scripts/Makefile.gcc-plugins
@@ -729,7 +734,7 @@ KBUILD_CFLAGS += $(call cc-option,-fno-reorder-blocks,) \
 endif
 
 ifneq ($(CONFIG_FRAME_WARN),0)
-KBUILD_CFLAGS += $(call cc-option,-Wframe-larger-than=${CONFIG_FRAME_WARN})
+KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
 endif
 
 stackp-flags-$(CONFIG_CC_HAS_STACKPROTECTOR_NONE) := -fno-stack-protector
@@ -1063,9 +1068,12 @@ endif
 
 autoksyms_h := $(if $(CONFIG_TRIM_UNUSED_KSYMS), include/generated/autoksyms.h)
 
+quiet_cmd_autoksyms_h = GEN     $@
+      cmd_autoksyms_h = mkdir -p $(dir $@); \
+			$(CONFIG_SHELL) $(srctree)/scripts/gen_autoksyms.sh $@
+
 $(autoksyms_h):
-	$(Q)mkdir -p $(dir $@)
-	$(Q)touch $@
+	$(call cmd,autoksyms_h)
 
 ARCH_POSTLINK := $(wildcard $(srctree)/arch/$(SRCARCH)/Makefile.postlink)
 
@@ -1240,14 +1248,18 @@ ifneq ($(dtstree),)
 	$(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
 
 PHONY += dtbs dtbs_install dtbs_check
-dtbs dtbs_check: include/config/kernel.release scripts_dtc
+dtbs: include/config/kernel.release scripts_dtc
 	$(Q)$(MAKE) $(build)=$(dtstree)
 
-dtbs_check: export CHECK_DTBS=1
-dtbs_check: dt_binding_check
+ifneq ($(filter dtbs_check, $(MAKECMDGOALS)),)
+export CHECK_DTBS=y
+dtbs: dt_binding_check
+endif
+
+dtbs_check: dtbs
 
 dtbs_install:
-	$(Q)$(MAKE) $(dtbinst)=$(dtstree)
+	$(Q)$(MAKE) $(dtbinst)=$(dtstree) dst=$(INSTALL_DTBS_PATH)
 
 ifdef CONFIG_OF_EARLY_FLATTREE
 all: dtbs
@@ -1259,6 +1271,10 @@ PHONY += scripts_dtc
 scripts_dtc: scripts_basic
 	$(Q)$(MAKE) $(build)=scripts/dtc
 
+ifneq ($(filter dt_binding_check, $(MAKECMDGOALS)),)
+export CHECK_DT_BINDING=y
+endif
+
 PHONY += dt_binding_check
 dt_binding_check: scripts_dtc
 	$(Q)$(MAKE) $(build)=Documentation/devicetree/bindings
@@ -1470,12 +1486,15 @@ help:
 	@echo  '  nsdeps          - Generate missing symbol namespace dependencies'
 	@echo  ''
 	@echo  'Kernel selftest:'
-	@echo  '  kselftest       - Build and run kernel selftest (run as root)'
-	@echo  '                    Build, install, and boot kernel before'
-	@echo  '                    running kselftest on it'
-	@echo  '  kselftest-clean - Remove all generated kselftest files'
-	@echo  '  kselftest-merge - Merge all the config dependencies of kselftest to existing'
-	@echo  '                    .config.'
+	@echo  '  kselftest         - Build and run kernel selftest'
+	@echo  '                      Build, install, and boot kernel before'
+	@echo  '                      running kselftest on it'
+	@echo  '                      Run as root for full coverage'
+	@echo  '  kselftest-all     - Build kernel selftest'
+	@echo  '  kselftest-install - Build and install kernel selftest'
+	@echo  '  kselftest-clean   - Remove all generated kselftest files'
+	@echo  '  kselftest-merge   - Merge all the config dependencies of'
+	@echo  '		      kselftest to existing .config.'
 	@echo  ''
 	@$(if $(dtstree), \
 		echo 'Devicetree:'; \