Merge tag 'kbuild-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - remove headers_{install,check}_all targets

 - remove unreasonable 'depends on !UML' from CONFIG_SAMPLES

 - re-implement 'make headers_install' more cleanly

 - add new header-test-y syntax to compile-test headers

 - compile-test exported headers to ensure they are compilable in
   user-space

 - compile-test headers under include/ to ensure they are self-contained

 - remove -Waggregate-return, -Wno-uninitialized, -Wno-unused-value
   flags

 - add -Werror=unknown-warning-option for Clang

 - add 128-bit built-in types support to genksyms

 - fix missed rebuild of modules.builtin

 - propagate 'No space left on device' error in fixdep to Make

 - allow Clang to use its integrated assembler

 - improve some coccinelle scripts

 - add a new flag KBUILD_ABS_SRCTREE to request Kbuild to use absolute
   path for $(srctree).

 - do not ignore errors when compression utility is missing

 - misc cleanups

* tag 'kbuild-v5.3' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (49 commits)
  kbuild: use -- separater intead of $(filter-out ...) for cc-cross-prefix
  kbuild: Inform user to pass ARCH= for make mrproper
  kbuild: fix compression errors getting ignored
  kbuild: add a flag to force absolute path for srctree
  kbuild: replace KBUILD_SRCTREE with boolean building_out_of_srctree
  kbuild: remove src and obj from the top Makefile
  scripts/tags.sh: remove unused environment variables from comments
  scripts/tags.sh: drop SUBARCH support for ARM
  kbuild: compile-test kernel headers to ensure they are self-contained
  kheaders: include only headers into kheaders_data.tar.xz
  kheaders: remove meaningless -R option of 'ls'
  kbuild: support header-test-pattern-y
  kbuild: do not create wrappers for header-test-y
  kbuild: compile-test exported headers to ensure they are self-contained
  init/Kconfig: add CONFIG_CC_CAN_LINK
  kallsyms: exclude kasan local symbols on s390
  kbuild: add more hints about SUBDIRS replacement
  coccinelle: api/stream_open: treat all wait_.*() calls as blocking
  coccinelle: put_device: Add a cast to an expression for an assignment
  coccinelle: put_device: Adjust a message construction
  ...

Documentation/kbuild/headers_install.rst

@@ -40,12 +40,5 @@ INSTALL_HDR_PATH indicates where to install the headers. It defaults to
 An 'include' directory is automatically created inside INSTALL_HDR_PATH and
 headers are installed in 'INSTALL_HDR_PATH/include'.
 
-The command "make headers_install_all" exports headers for all architectures
-simultaneously.  (This is mostly of interest to distribution maintainers,
-who create an architecture-independent tarball from the resulting include
-directory.)  You also can use HDR_ARCH_LIST to specify list of architectures.
-Remember to provide the appropriate linux/asm directory via "mv" or "ln -s"
-before building a C library with headers exported this way.
-
 The kernel header export infrastructure is maintained by David Woodhouse
 <dwmw2@infradead.org>.

Documentation/kbuild/kbuild.rst

@@ -200,6 +200,15 @@ The output directory is often set using "O=..." on the commandline.
 
 The value can be overridden in which case the default value is ignored.
 
+KBUILD_ABS_SRCTREE
+--------------------------------------------------
+Kbuild uses a relative path to point to the tree when possible. For instance,
+when building in the source tree, the source tree path is '.'
+
+Setting this flag requests Kbuild to use absolute path to the source tree.
+There are some useful cases to do so, like when generating tag files with
+absolute path entries etc.
+
 KBUILD_SIGN_PIN
 ---------------
 This variable allows a passphrase or PIN to be passed to the sign-file

Documentation/kbuild/makefiles.rst

@@ -999,11 +999,7 @@ When kbuild executes, the following steps are followed (roughly):
 ------------------------------------
 
 	The archheaders: rule is used to generate header files that
-	may be installed into user space by "make header_install" or
-	"make headers_install_all".  In order to support
-	"make headers_install_all", this target has to be able to run
-	on an unconfigured tree, or a tree configured for another
-	architecture.
+	may be installed into user space by "make header_install".
 
 	It is run before "make archprepare" when run on the
 	architecture itself.
@@ -1140,6 +1136,22 @@ When kbuild executes, the following steps are followed (roughly):
 	In this example, extra-y is used to list object files that
 	shall be built, but shall not be linked as part of built-in.a.
 
+    header-test-y
+
+	header-test-y specifies headers (*.h) in the current directory that
+	should be compile tested to ensure they are self-contained,
+	i.e. compilable as standalone units. If CONFIG_HEADER_TEST is enabled,
+	this builds them as part of extra-y.
+
+    header-test-pattern-y
+
+	This works as a weaker version of header-test-y, and accepts wildcard
+	patterns. The typical usage is:
+
+		  header-test-pattern-y += *.h
+
+	This specifies all the files that matches to '*.h' in the current
+	directory, but the files in 'header-test-' are excluded.
 
 6.7 Commands useful for building a boot image
 ---------------------------------------------

Makefile

@@ -212,6 +212,13 @@ endif
 ifdef SUBDIRS
   $(warning ================= WARNING ================)
   $(warning 'SUBDIRS' will be removed after Linux 5.3)
+  $(warning )
+  $(warning If you are building an individual subdirectory)
+  $(warning in the kernel tree, you can do like this:)
+  $(warning $$ make path/to/dir/you/want/to/build/)
+  $(warning (Do not forget the trailing slash))
+  $(warning )
+  $(warning If you are building an external module,)
   $(warning Please use 'M=' or 'KBUILD_EXTMOD' instead)
   $(warning ==========================================)
   KBUILD_EXTMOD ?= $(SUBDIRS)
@@ -221,9 +228,12 @@ ifeq ("$(origin M)", "command line")
   KBUILD_EXTMOD := $(M)
 endif
 
+export KBUILD_CHECKSRC KBUILD_EXTMOD
+
 ifeq ($(abs_srctree),$(abs_objtree))
         # building in the source tree
         srctree := .
+	building_out_of_srctree :=
 else
         ifeq ($(abs_srctree)/,$(dir $(abs_objtree)))
                 # building in a subdirectory of the source tree
@@ -231,22 +241,17 @@ else
         else
                 srctree := $(abs_srctree)
         endif
-
-	# TODO:
-	# KBUILD_SRC is only used to distinguish in-tree/out-of-tree build.
-	# Replace it with $(srctree) or something.
-	KBUILD_SRC := $(abs_srctree)
+	building_out_of_srctree := 1
 endif
 
-export KBUILD_CHECKSRC KBUILD_EXTMOD KBUILD_SRC
+ifneq ($(KBUILD_ABS_SRCTREE),)
+srctree := $(abs_srctree)
+endif
 
 objtree		:= .
-src		:= $(srctree)
-obj		:= $(objtree)
-
 VPATH		:= $(srctree)
 
-export srctree objtree VPATH
+export building_out_of_srctree srctree objtree VPATH
 
 # To make sure we do not include .config for any of the *config targets
 # catch them early, and hand them over to scripts/kconfig/Makefile
@@ -262,7 +267,7 @@ old_version_h := include/linux/version.h
 clean-targets := %clean mrproper cleandocs
 no-dot-config-targets := $(clean-targets) \
 			 cscope gtags TAGS tags help% %docs check% coccicheck \
-			 $(version_h) headers_% archheaders archscripts \
+			 $(version_h) headers headers_% archheaders archscripts \
 			 %asm-generic kernelversion %src-pkg
 no-sync-config-targets := $(no-dot-config-targets) install %install \
 			   kernelrelease
@@ -449,7 +454,7 @@ USERINCLUDE    := \
 LINUXINCLUDE    := \
 		-I$(srctree)/arch/$(SRCARCH)/include \
 		-I$(objtree)/arch/$(SRCARCH)/include/generated \
-		$(if $(filter .,$(srctree)),,-I$(srctree)/include) \
+		$(if $(building_out_of_srctree),-I$(srctree)/include) \
 		-I$(objtree)/include \
 		$(USERINCLUDE)
 
@@ -510,7 +515,7 @@ PHONY += outputmakefile
 # At the same time when output Makefile generated, generate .gitignore to
 # ignore whole output directory
 outputmakefile:
-ifneq ($(srctree),.)
+ifdef building_out_of_srctree
 	$(Q)ln -fsn $(srctree) source
 	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkmakefile $(srctree)
 	$(Q)test -e .gitignore || \
@@ -527,7 +532,10 @@ endif
 ifneq ($(GCC_TOOLCHAIN),)
 CLANG_FLAGS	+= --gcc-toolchain=$(GCC_TOOLCHAIN)
 endif
+ifeq ($(shell $(AS) --version 2>&1 | head -n 1 | grep clang),)
 CLANG_FLAGS	+= -no-integrated-as
+endif
+CLANG_FLAGS	+= -Werror=unknown-warning-option
 KBUILD_CFLAGS	+= $(CLANG_FLAGS)
 KBUILD_AFLAGS	+= $(CLANG_FLAGS)
 export CLANG_FLAGS
@@ -608,6 +616,7 @@ ifeq ($(KBUILD_EXTMOD),)
 init-y		:= init/
 drivers-y	:= drivers/ sound/
 drivers-$(CONFIG_SAMPLES) += samples/
+drivers-$(CONFIG_KERNEL_HEADER_TEST) += include/
 net-y		:= net/
 libs-y		:= lib/
 core-y		:= usr/
@@ -1053,9 +1062,6 @@ vmlinux: scripts/link-vmlinux.sh autoksyms_recursive $(vmlinux-deps) FORCE
 
 targets := vmlinux
 
-# Some samples need headers_install.
-samples: headers_install
-
 # The actual objects are generated when descending,
 # make sure no implicit rule kicks in
 $(sort $(vmlinux-deps)): $(vmlinux-dirs) ;
@@ -1096,12 +1102,12 @@ PHONY += prepare archprepare prepare1 prepare3
 # and if so do:
 # 1) Check that make has not been executed in the kernel src $(srctree)
 prepare3: include/config/kernel.release
-ifneq ($(srctree),.)
+ifdef building_out_of_srctree
 	@$(kecho) '  Using $(srctree) as source for kernel'
 	$(Q)if [ -f $(srctree)/.config -o \
 		 -d $(srctree)/include/config -o \
 		 -d $(srctree)/arch/$(SRCARCH)/include/generated ]; then \
-		echo >&2 "  $(srctree) is not clean, please run 'make mrproper'"; \
+		echo >&2 "  $(srctree) is not clean, please run 'make ARCH=$(ARCH) mrproper'"; \
 		echo >&2 "  in the '$(srctree)' directory.";\
 		/bin/false; \
 	fi;
@@ -1181,39 +1187,44 @@ headerdep:
 #Default location for installed headers
 export INSTALL_HDR_PATH = $(objtree)/usr
 
-# If we do an all arch process set dst to include/arch-$(SRCARCH)
-hdr-dst = $(if $(KBUILD_HEADERS), dst=include/arch-$(SRCARCH), dst=include)
+quiet_cmd_headers_install = INSTALL $(INSTALL_HDR_PATH)/include
+      cmd_headers_install = \
+	mkdir -p $(INSTALL_HDR_PATH); \
+	rsync -mrl --include='*/' --include='*\.h' --exclude='*' \
+	usr/include $(INSTALL_HDR_PATH)
+
+PHONY += headers_install
+headers_install: headers
+	$(call cmd,headers_install)
 
 PHONY += archheaders archscripts
 
-PHONY += __headers
-__headers: $(version_h) scripts_basic uapi-asm-generic archheaders archscripts
-	$(Q)$(MAKE) $(build)=scripts build_unifdef
+hdr-inst := -f $(srctree)/scripts/Makefile.headersinst obj
 
-PHONY += headers_install_all
-headers_install_all:
-	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/headers.sh install
-
-PHONY += headers_install
-headers_install: __headers
+PHONY += headers
+headers: $(version_h) scripts_unifdef uapi-asm-generic archheaders archscripts
 	$(if $(wildcard $(srctree)/arch/$(SRCARCH)/include/uapi/asm/Kbuild),, \
 	  $(error Headers not exportable for the $(SRCARCH) architecture))
-	$(Q)$(MAKE) $(hdr-inst)=include/uapi dst=include
-	$(Q)$(MAKE) $(hdr-inst)=arch/$(SRCARCH)/include/uapi $(hdr-dst)
-
-PHONY += headers_check_all
-headers_check_all: headers_install_all
-	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/headers.sh check
+	$(Q)$(MAKE) $(hdr-inst)=include/uapi
+	$(Q)$(MAKE) $(hdr-inst)=arch/$(SRCARCH)/include/uapi
 
 PHONY += headers_check
-headers_check: headers_install
-	$(Q)$(MAKE) $(hdr-inst)=include/uapi dst=include HDRCHECK=1
-	$(Q)$(MAKE) $(hdr-inst)=arch/$(SRCARCH)/include/uapi $(hdr-dst) HDRCHECK=1
+headers_check: headers
+	$(Q)$(MAKE) $(hdr-inst)=include/uapi HDRCHECK=1
+	$(Q)$(MAKE) $(hdr-inst)=arch/$(SRCARCH)/include/uapi HDRCHECK=1
+
+ifdef CONFIG_HEADERS_INSTALL
+prepare: headers
+endif
 
 ifdef CONFIG_HEADERS_CHECK
 all: headers_check
 endif
 
+PHONY += scripts_unifdef
+scripts_unifdef: scripts_basic
+	$(Q)$(MAKE) $(build)=scripts scripts/unifdef
+
 # ---------------------------------------------------------------------------
 # Kernel selftest
 
@@ -1283,18 +1294,24 @@ all: modules
 # using awk while concatenating to the final file.
 
 PHONY += modules
-modules: $(vmlinux-dirs) $(if $(KBUILD_BUILTIN),vmlinux) modules.builtin
-	$(Q)$(AWK) '!x[$$0]++' $(vmlinux-dirs:%=$(objtree)/%/modules.order) > $(objtree)/modules.order
+modules: $(if $(KBUILD_BUILTIN),vmlinux) modules.order modules.builtin
 	@$(kecho) '  Building modules, stage 2.';
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
 	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/modules-check.sh
 
-modules.builtin: $(vmlinux-dirs:%=%/modules.builtin)
-	$(Q)$(AWK) '!x[$$0]++' $^ > $(objtree)/modules.builtin
+modules.order: $(vmlinux-dirs)
+	$(Q)$(AWK) '!x[$$0]++' $(addsuffix /$@, $(vmlinux-dirs)) > $@
 
-%/modules.builtin: include/config/auto.conf include/config/tristate.conf
-	$(Q)$(MAKE) $(modbuiltin)=$*
+modbuiltin-dirs := $(addprefix _modbuiltin_, $(vmlinux-dirs))
 
+modules.builtin: $(modbuiltin-dirs)
+	$(Q)$(AWK) '!x[$$0]++' $(addsuffix /$@, $(vmlinux-dirs)) > $@
+
+PHONY += $(modbuiltin-dirs)
+# tristate.conf is not included from this Makefile. Add it as a prerequisite
+# here to make it self-healing in case somebody accidentally removes it.
+$(modbuiltin-dirs): include/config/tristate.conf
+	$(Q)$(MAKE) $(modbuiltin)=$(patsubst _modbuiltin_%,%,$@)
 
 # Target to prepare building external modules
 PHONY += modules_prepare
@@ -1360,7 +1377,7 @@ CLEAN_DIRS  += $(MODVERDIR) include/ksym
 CLEAN_FILES += modules.builtin.modinfo
 
 # Directories & files removed with 'make mrproper'
-MRPROPER_DIRS  += include/config usr/include include/generated          \
+MRPROPER_DIRS  += include/config include/generated          \
 		  arch/$(SRCARCH)/include/generated .tmp_objdiff
 MRPROPER_FILES += .config .config.old .version \
 		  Module.symvers tags TAGS cscope* GPATH GTAGS GRTAGS GSYMS \
@@ -1551,7 +1568,7 @@ $(DOC_TARGETS): scripts_basic FORCE
 # ---------------------------------------------------------------------------
 
 PHONY += scripts_gdb
-scripts_gdb: prepare
+scripts_gdb: prepare0
 	$(Q)$(MAKE) $(build)=scripts/gdb
 	$(Q)ln -fsn $(abspath $(srctree)/scripts/gdb/vmlinux-gdb.py)
 
@@ -1698,7 +1715,7 @@ CHECKSTACK_ARCH := $(ARCH)
 endif
 checkstack:
 	$(OBJDUMP) -d vmlinux $$(find . -name '*.ko') | \
-	$(PERL) $(src)/scripts/checkstack.pl $(CHECKSTACK_ARCH)
+	$(PERL) $(srctree)/scripts/checkstack.pl $(CHECKSTACK_ARCH)
 
 kernelrelease:
 	@echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))"
@@ -1717,11 +1734,11 @@ endif
 
 tools/: FORCE
 	$(Q)mkdir -p $(objtree)/tools
-	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(src)/tools/
+	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/
 
 tools/%: FORCE
 	$(Q)mkdir -p $(objtree)/tools
-	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(src)/tools/ $*
+	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/ $*
 
 # Single targets
 # ---------------------------------------------------------------------------
@@ -1755,8 +1772,6 @@ build-dir = $(patsubst %/,%,$(dir $(build-target)))
 PHONY += /
 /: ./
 
-# Make sure the latest headers are built for Documentation
-Documentation/ samples/: headers_install
 %/: prepare FORCE
 	$(Q)$(MAKE) KBUILD_MODULES=1 $(build)=$(build-dir)
 

arch/arc/Makefile

@@ -19,7 +19,7 @@ ifdef CONFIG_ARC_CURR_IN_REG
 # any kernel headers, and missing the r25 global register
 # Can't do unconditionally because of recursive include issues
 # due to <linux/thread_info.h>
-LINUXINCLUDE	+=  -include ${src}/arch/arc/include/asm/current.h
+LINUXINCLUDE	+=  -include $(srctree)/arch/arc/include/asm/current.h
 endif
 
 cflags-y				+= -fsection-anchors

arch/arc/configs/tb10x_defconfig

@@ -94,6 +94,7 @@ CONFIG_CONFIGFS_FS=y
 CONFIG_DEBUG_INFO=y
 CONFIG_STRIP_ASM_SYMS=y
 CONFIG_DEBUG_FS=y
+CONFIG_HEADERS_INSTALL=y
 CONFIG_HEADERS_CHECK=y
 CONFIG_DEBUG_SECTION_MISMATCH=y
 CONFIG_MAGIC_SYSRQ=y

arch/nds32/configs/defconfig

@@ -92,6 +92,7 @@ CONFIG_DEBUG_INFO=y
 CONFIG_DEBUG_INFO_DWARF4=y
 CONFIG_GDB_SCRIPTS=y
 CONFIG_READABLE_ASM=y
+CONFIG_HEADERS_INSTALL=y
 CONFIG_HEADERS_CHECK=y
 CONFIG_DEBUG_SECTION_MISMATCH=y
 CONFIG_MAGIC_SYSRQ=y

arch/parisc/Makefile

@@ -120,8 +120,8 @@ PALO := $(shell if (which palo 2>&1); then : ; \
 	elif [ -x /sbin/palo ]; then echo /sbin/palo; \
 	fi)
 
-PALOCONF := $(shell if [ -f $(src)/palo.conf ]; then echo $(src)/palo.conf; \
-	else echo $(obj)/palo.conf; \
+PALOCONF := $(shell if [ -f $(srctree)/palo.conf ]; then echo $(srctree)/palo.conf; \
+	else echo $(objtree)/palo.conf; \
 	fi)
 
 palo lifimage: vmlinuz
@@ -131,8 +131,8 @@ palo lifimage: vmlinuz
 		false; \
 	fi
 	@if test ! -f "$(PALOCONF)"; then \
-		cp $(src)/arch/parisc/defpalo.conf $(obj)/palo.conf; \
-		echo 'A generic palo config file ($(obj)/palo.conf) has been created for you.'; \
+		cp $(srctree)/arch/parisc/defpalo.conf $(objtree)/palo.conf; \
+		echo 'A generic palo config file ($(objree)/palo.conf) has been created for you.'; \
 		echo 'You should check it and re-run "make palo".'; \
 		echo 'WARNING: the "lifimage" file is now placed in this directory by default!'; \
 		false; \
@@ -162,10 +162,10 @@ vmlinuz: vmlinux
 endif
 
 install:
-	$(CONFIG_SHELL) $(src)/arch/parisc/install.sh \
+	$(CONFIG_SHELL) $(srctree)/arch/parisc/install.sh \
 			$(KERNELRELEASE) vmlinux System.map "$(INSTALL_PATH)"
 zinstall:
-	$(CONFIG_SHELL) $(src)/arch/parisc/install.sh \
+	$(CONFIG_SHELL) $(srctree)/arch/parisc/install.sh \
 			$(KERNELRELEASE) vmlinuz System.map "$(INSTALL_PATH)"
 
 CLEAN_FILES	+= lifimage

arch/parisc/configs/a500_defconfig

@@ -166,6 +166,7 @@ CONFIG_NLS_ISO8859_1=m
 CONFIG_NLS_ISO8859_15=m
 CONFIG_NLS_UTF8=m
 CONFIG_DEBUG_FS=y
+CONFIG_HEADERS_INSTALL=y
 CONFIG_HEADERS_CHECK=y
 CONFIG_MAGIC_SYSRQ=y
 # CONFIG_DEBUG_BUGVERBOSE is not set

arch/parisc/configs/b180_defconfig

@@ -90,6 +90,7 @@ CONFIG_NLS_ASCII=m
 CONFIG_NLS_ISO8859_1=m
 CONFIG_NLS_ISO8859_15=m
 CONFIG_NLS_UTF8=m
+CONFIG_HEADERS_INSTALL=y
 CONFIG_HEADERS_CHECK=y
 CONFIG_MAGIC_SYSRQ=y
 CONFIG_DEBUG_KERNEL=y

arch/parisc/configs/c3000_defconfig

@@ -139,6 +139,7 @@ CONFIG_NLS_ISO8859_1=m
 CONFIG_NLS_ISO8859_15=m
 CONFIG_NLS_UTF8=m
 CONFIG_DEBUG_FS=y
+CONFIG_HEADERS_INSTALL=y
 CONFIG_HEADERS_CHECK=y
 CONFIG_MAGIC_SYSRQ=y
 CONFIG_DEBUG_MUTEXES=y

arch/parisc/configs/default_defconfig

@@ -183,6 +183,7 @@ CONFIG_NLS_KOI8_R=m
 CONFIG_NLS_KOI8_U=m
 CONFIG_NLS_UTF8=y
 CONFIG_DEBUG_FS=y
+CONFIG_HEADERS_INSTALL=y
 CONFIG_HEADERS_CHECK=y
 CONFIG_MAGIC_SYSRQ=y
 CONFIG_DEBUG_KERNEL=y

arch/powerpc/configs/ppc6xx_defconfig

@@ -1123,6 +1123,7 @@ CONFIG_NLS_KOI8_R=m
 CONFIG_NLS_KOI8_U=m
 CONFIG_DEBUG_INFO=y
 CONFIG_UNUSED_SYMBOLS=y
+CONFIG_HEADERS_INSTALL=y
 CONFIG_HEADERS_CHECK=y
 CONFIG_MAGIC_SYSRQ=y
 CONFIG_DEBUG_KERNEL=y

arch/s390/configs/debug_defconfig

@@ -588,6 +588,7 @@ CONFIG_GDB_SCRIPTS=y
 CONFIG_FRAME_WARN=1024
 CONFIG_READABLE_ASM=y
 CONFIG_UNUSED_SYMBOLS=y
+CONFIG_HEADERS_INSTALL=y
 CONFIG_HEADERS_CHECK=y
 CONFIG_DEBUG_SECTION_MISMATCH=y
 CONFIG_MAGIC_SYSRQ=y

arch/um/Makefile

@@ -73,7 +73,7 @@ KBUILD_AFLAGS += $(ARCH_INCLUDE)
 USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -I%,,$(KBUILD_CFLAGS))) \
 		$(ARCH_INCLUDE) $(MODE_INCLUDE) $(filter -I%,$(CFLAGS)) \
 		-D_FILE_OFFSET_BITS=64 -idirafter $(srctree)/include \
-		-idirafter $(obj)/include -D__KERNEL__ -D__UM_HOST__
+		-idirafter $(objtree)/include -D__KERNEL__ -D__UM_HOST__
 
 #This will adjust *FLAGS accordingly to the platform.
 include $(ARCH_DIR)/Makefile-os-$(OS)

drivers/gpu/drm/i915/.gitignore

@@ -1 +0,0 @@
-header_test_*.c

drivers/gpu/drm/i915/Makefile.header-test

@@ -2,7 +2,7 @@
 # Copyright © 2019 Intel Corporation
 
 # Test the headers are compilable as standalone units
-header_test := \
+header-test-$(CONFIG_DRM_I915_WERROR) := \
 	i915_active_types.h \
 	i915_gem_context_types.h \
 	i915_priolist_types.h \
@@ -35,13 +35,3 @@ header_test := \
 	intel_sprite.h \
 	intel_tv.h \
 	intel_workarounds_types.h
-
-quiet_cmd_header_test = HDRTEST $@
-      cmd_header_test = echo "\#include \"$(<F)\"" > $@
-
-header_test_%.c: %.h
-	$(call cmd,header_test)
-
-i915-$(CONFIG_DRM_I915_WERROR) += $(foreach h,$(header_test),$(patsubst %.h,header_test_%.o,$(h)))
-
-clean-files += $(foreach h,$(header_test),$(patsubst %.h,header_test_%.c,$(h)))

include/uapi/Kbuild

@@ -1,14 +1,14 @@
 # SPDX-License-Identifier: GPL-2.0
 ifeq ($(wildcard $(srctree)/arch/$(SRCARCH)/include/uapi/asm/a.out.h),)
-no-export-headers += a.out.h
+no-export-headers += linux/a.out.h
 endif
 
 ifeq ($(wildcard $(srctree)/arch/$(SRCARCH)/include/uapi/asm/kvm.h),)
-no-export-headers += kvm.h
+no-export-headers += linux/kvm.h
 endif
 
 ifeq ($(wildcard $(srctree)/arch/$(SRCARCH)/include/uapi/asm/kvm_para.h),)
 ifeq ($(wildcard $(objtree)/arch/$(SRCARCH)/include/generated/uapi/asm/kvm_para.h),)
-no-export-headers += kvm_para.h
+no-export-headers += linux/kvm_para.h
 endif
 endif

init/Kconfig

@@ -24,6 +24,9 @@ config CLANG_VERSION
 	int
 	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
 
+config CC_CAN_LINK
+	def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
+
 config CC_HAS_ASM_GOTO
 	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
 
@@ -96,6 +99,36 @@ config COMPILE_TEST
 	  here. If you are a user/distributor, say N here to exclude useless
 	  drivers to be distributed.
 
+config HEADER_TEST
+	bool "Compile test headers that should be standalone compilable"
+	help
+	  Compile test headers listed in header-test-y target to ensure they are
+	  self-contained, i.e. compilable as standalone units.
+
+	  If you are a developer or tester and want to ensure the requested
+	  headers are self-contained, say Y here. Otherwise, choose N.
+
+config KERNEL_HEADER_TEST
+	bool "Compile test kernel headers"
+	depends on HEADER_TEST
+	help
+	  Headers in include/ are used to build external moduls.
+	  Compile test them to ensure they are self-contained, i.e.
+	  compilable as standalone units.
+
+	  If you are a developer or tester and want to ensure the headers
+	  in include/ are self-contained, say Y here. Otherwise, choose N.
+
+config UAPI_HEADER_TEST
+	bool "Compile test UAPI headers"
+	depends on HEADER_TEST && HEADERS_INSTALL && CC_CAN_LINK
+	help
+	  Compile test headers exported to user-space to ensure they are
+	  self-contained, i.e. compilable as standalone units.
+
+	  If you are a developer or tester and want to ensure the exported
+	  headers are self-contained, say Y here. Otherwise, choose N.
+
 config LOCALVERSION
 	string "Local version - append to kernel release"
 	help