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
  ...

Author: torvalds

Documentation/Makefile

@@ -2,7 +2,8 @@
 # Makefile for Sphinx documentation
 #
 
-subdir-y := devicetree/bindings/
+# for cleaning
+subdir- := devicetree/bindings
 
 # Check for broken documentation file references
 ifeq ($(CONFIG_WARN_MISSING_DOCUMENTS),y)

Documentation/devicetree/bindings/.gitignore

@@ -1,2 +1,2 @@
 *.example.dts
-processed-schema.yaml
+processed-schema*.yaml

Documentation/devicetree/bindings/Makefile

@@ -2,7 +2,6 @@
 DT_DOC_CHECKER ?= dt-doc-validate
 DT_EXTRACT_EX ?= dt-extract-example
 DT_MK_SCHEMA ?= dt-mk-schema
-DT_MK_SCHEMA_FLAGS := $(if $(DT_SCHEMA_FILES), -u)
 
 quiet_cmd_chk_binding = CHKDT   $(patsubst $(srctree)/%,%,$<)
       cmd_chk_binding = $(DT_DOC_CHECKER) -u $(srctree)/$(src) $< ; \
@@ -11,26 +10,35 @@ quiet_cmd_chk_binding = CHKDT   $(patsubst $(srctree)/%,%,$<)
 $(obj)/%.example.dts: $(src)/%.yaml FORCE
 	$(call if_changed,chk_binding)
 
-DT_TMP_SCHEMA := processed-schema.yaml
+# Use full schemas when checking %.example.dts
+DT_TMP_SCHEMA := $(obj)/processed-schema-examples.yaml
 
 quiet_cmd_mk_schema = SCHEMA  $@
       cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(real-prereqs)
 
-DT_DOCS = $(shell \
+DT_DOCS = $(addprefix $(src)/, \
+	$(shell \
 	cd $(srctree)/$(src) && \
 	find * \( -name '*.yaml' ! \
-		-name $(DT_TMP_SCHEMA) ! \
+		-name 'processed-schema*' ! \
 		-name '*.example.dt.yaml' \) \
-	)
+	))
 
-DT_SCHEMA_FILES ?= $(addprefix $(src)/,$(DT_DOCS))
+DT_SCHEMA_FILES ?= $(DT_DOCS)
 
-ifeq ($(CHECK_DTBS),)
-extra-y += $(patsubst $(src)/%.yaml,%.example.dts, $(DT_SCHEMA_FILES))
-extra-y += $(patsubst $(src)/%.yaml,%.example.dt.yaml, $(DT_SCHEMA_FILES))
-endif
+extra-$(CHECK_DT_BINDING) += $(patsubst $(src)/%.yaml,%.example.dts, $(DT_SCHEMA_FILES))
+extra-$(CHECK_DT_BINDING) += $(patsubst $(src)/%.yaml,%.example.dt.yaml, $(DT_SCHEMA_FILES))
+extra-$(CHECK_DT_BINDING) += processed-schema-examples.yaml
 
-$(obj)/$(DT_TMP_SCHEMA): $(DT_SCHEMA_FILES) FORCE
+override DTC_FLAGS := \
+	-Wno-avoid_unnecessary_addr_size \
+	-Wno-graph_child_address
+
+$(obj)/processed-schema-examples.yaml: $(DT_DOCS) FORCE
+	$(call if_changed,mk_schema)
+
+$(obj)/processed-schema.yaml: DT_MK_SCHEMA_FLAGS := -u
+$(obj)/processed-schema.yaml: $(DT_SCHEMA_FILES) FORCE
 	$(call if_changed,mk_schema)
 
-extra-y += $(DT_TMP_SCHEMA)
+extra-y += processed-schema.yaml

Documentation/devicetree/writing-schema.rst

@@ -147,6 +147,10 @@ Note that ``dtbs_check`` will skip any binding schema files with errors. It is
 necessary to use ``dt_binding_check`` to get all the validation errors in the
 binding schema files.
 
+It is possible to run both in a single command::
+
+    make dt_binding_check dtbs_check
+
 It is also possible to run checks with a single schema file by setting the
 ``DT_SCHEMA_FILES`` variable to a specific schema file.
 

Documentation/kbuild/index.rst

@@ -20,6 +20,7 @@ Kernel Build System
     issues
     reproducible-builds
     gcc-plugins
+    llvm
 
 .. only::  subproject and html
 

Documentation/kbuild/kconfig-language.rst

@@ -159,11 +159,11 @@ applicable everywhere (see syntax).
   Given the following example::
 
     config FOO
-	tristate
+	tristate "foo"
 	imply BAZ
 
     config BAZ
-	tristate
+	tristate "baz"
 	depends on BAR
 
   The following values are possible:
@@ -173,14 +173,35 @@ applicable everywhere (see syntax).
 	===		===		=============	==============
 	n		y		n		N/m/y
 	m		y		m		M/y/n
-	y		y		y		Y/n
+	y		y		y		Y/m/n
+	n		m		n		N/m
+	m		m		m		M/n
+	y		m		n		M/n
 	y		n		*		N
 	===		===		=============	==============
 
   This is useful e.g. with multiple drivers that want to indicate their
   ability to hook into a secondary subsystem while allowing the user to
   configure that subsystem out without also having to unset these drivers.
 
+  Note: If the combination of FOO=y and BAR=m causes a link error,
+  you can guard the function call with IS_REACHABLE()::
+
+	foo_init()
+	{
+		if (IS_REACHABLE(CONFIG_BAZ))
+			baz_register(&foo);
+		...
+	}
+
+  Note: If the feature provided by BAZ is highly desirable for FOO,
+  FOO should imply not only BAZ, but also its dependency BAR::
+
+    config FOO
+	tristate "foo"
+	imply BAR
+	imply BAZ
+
 - limiting menu display: "visible if" <expr>
 
   This attribute is only applicable to menu blocks, if the condition is

Documentation/kbuild/llvm.rst

@@ -0,0 +1,80 @@
+==============================
+Building Linux with Clang/LLVM
+==============================
+
+This document covers how to build the Linux kernel with Clang and LLVM
+utilities.
+
+About
+-----
+
+The Linux kernel has always traditionally been compiled with GNU toolchains
+such as GCC and binutils. Ongoing work has allowed for `Clang
+<https://clang.llvm.org/>`_ and `LLVM <https://llvm.org/>`_ utilities to be
+used as viable substitutes. Distributions such as `Android
+<https://www.android.com/>`_, `ChromeOS
+<https://www.chromium.org/chromium-os>`_, and `OpenMandriva
+<https://www.openmandriva.org/>`_ use Clang built kernels.  `LLVM is a
+collection of toolchain components implemented in terms of C++ objects
+<https://www.aosabook.org/en/llvm.html>`_. Clang is a front-end to LLVM that
+supports C and the GNU C extensions required by the kernel, and is pronounced
+"klang," not "see-lang."
+
+Clang
+-----
+
+The compiler used can be swapped out via `CC=` command line argument to `make`.
+`CC=` should be set when selecting a config and during a build.
+
+	make CC=clang defconfig
+
+	make CC=clang
+
+Cross Compiling
+---------------
+
+A single Clang compiler binary will typically contain all supported backends,
+which can help simplify cross compiling.
+
+	ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- make CC=clang
+
+`CROSS_COMPILE` is not used to prefix the Clang compiler binary, instead
+`CROSS_COMPILE` is used to set a command line flag: `--target <triple>`. For
+example:
+
+	clang --target aarch64-linux-gnu foo.c
+
+LLVM Utilities
+--------------
+
+LLVM has substitutes for GNU binutils utilities. These can be invoked as
+additional parameters to `make`.
+
+	make CC=clang AS=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \\
+	  OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump OBJSIZE=llvm-objsize \\
+	  READELF=llvm-readelf HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar \\
+	  HOSTLD=ld.lld
+
+Getting Help
+------------
+
+- `Website <https://clangbuiltlinux.github.io/>`_
+- `Mailing List <https://groups.google.com/forum/#!forum/clang-built-linux>`_: <[email protected]>
+- `Issue Tracker <https://github.com/ClangBuiltLinux/linux/issues>`_
+- IRC: #clangbuiltlinux on chat.freenode.net
+- `Telegram <https://t.me/ClangBuiltLinux>`_: @ClangBuiltLinux
+- `Uncyclo <https://github.com/ClangBuiltLinux/linux/wiki>`_
+- `Beginner Bugs <https://github.com/ClangBuiltLinux/linux/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22>`_
+
+Getting LLVM
+-------------
+
+- http://releases.llvm.org/download.html
+- https://github.com/llvm/llvm-project
+- https://llvm.org/docs/GettingStarted.html
+- https://llvm.org/docs/CMake.html
+- https://apt.llvm.org/
+- https://www.archlinux.org/packages/extra/x86_64/llvm/
+- https://github.com/ClangBuiltLinux/tc-build
+- https://github.com/ClangBuiltLinux/linux/wiki/Building-Clang-from-source
+- https://android.googlesource.com/platform/prebuilts/clang/host/linux-x86/

MAINTAINERS

@@ -4139,6 +4139,7 @@ B:	https://github.com/ClangBuiltLinux/linux/issues
 C:	irc://chat.freenode.net/clangbuiltlinux
 S:	Supported
 K:	\b(?i:clang|llvm)\b
+F:	Documentation/kbuild/llvm.rst
 
 CLEANCACHE API
 M:	Konrad Rzeszutek Wilk <[email protected]>

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:'; \

arch/sh/Kconfig

@@ -87,11 +87,6 @@ config SUPERH64
 	select HAVE_EXIT_THREAD
 	select KALLSYMS
 
-config ARCH_DEFCONFIG
-	string
-	default "arch/sh/configs/shx3_defconfig" if SUPERH32
-	default "arch/sh/configs/cayman_defconfig" if SUPERH64
-
 config GENERIC_BUG
 	def_bool y
 	depends on BUG && SUPERH32

arch/sparc/Kconfig

@@ -96,11 +96,6 @@ config SPARC64
 	select PCI_DOMAINS if PCI
 	select ARCH_HAS_GIGANTIC_PAGE
 
-config ARCH_DEFCONFIG
-	string
-	default "arch/sparc/configs/sparc32_defconfig" if SPARC32
-	default "arch/sparc/configs/sparc64_defconfig" if SPARC64
-
 config ARCH_PROC_KCORE_TEXT
 	def_bool y