Merge tag 'kbuild-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Add new environment variables, USERCFLAGS and USERLDFLAGS to allow
   additional flags to be passed to user-space programs.

 - Fix missing fflush() bugs in Kconfig and fixdep

 - Fix a minor bug in the comment format of the .config file

 - Make kallsyms ignore llvm's local labels, .L*

 - Fix UAPI compile-test for cross-compiling with Clang

 - Extend the LLVM= syntax to support LLVM=<suffix> form for using a
   particular version of LLVm, and LLVM=<prefix> form for using custom
   LLVM in a particular directory path.

 - Clean up Makefiles

* tag 'kbuild-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: Make $(LLVM) more flexible
  kbuild: add --target to correctly cross-compile UAPI headers with Clang
  fixdep: use fflush() and ferror() to ensure successful write to files
  arch: syscalls: simplify uapi/kapi directory creation
  usr/include: replace extra-y with always-y
  certs: simplify empty certs creation in certs/Makefile
  certs: include certs/signing_key.x509 unconditionally
  kallsyms: ignore all local labels prefixed by '.L'
  kconfig: fix missing '# end of' for empty menu
  kconfig: add fflush() before ferror() check
  kbuild: replace $(if A,A,B) with $(or A,B)
  kbuild: Add environment variables for userprogs flags
  kbuild: unify cmd_copy and cmd_shipped

Author: torvalds

Documentation/kbuild/kbuild.rst

@@ -77,6 +77,17 @@ HOSTLDLIBS
 ----------
 Additional libraries to link against when building host programs.
 
+.. _userkbuildflags:
+
+USERCFLAGS
+----------
+Additional options used for $(CC) when compiling userprogs.
+
+USERLDFLAGS
+-----------
+Additional options used for $(LD) when linking userprogs. userprogs are linked
+with CC, so $(USERLDFLAGS) should include "-Wl," prefix as applicable.
+
 KBUILD_KCONFIG
 --------------
 Set the top-level Kconfig file to the value of this environment

Documentation/kbuild/llvm.rst

@@ -49,17 +49,36 @@ example: ::
 LLVM Utilities
 --------------
 
-LLVM has substitutes for GNU binutils utilities. Kbuild supports ``LLVM=1``
-to enable them. ::
-
-	make LLVM=1
-
-They can be enabled individually. The full list of the parameters: ::
+LLVM has substitutes for GNU binutils utilities. They can be enabled individually.
+The full list of supported make variables::
 
 	make CC=clang LD=ld.lld AR=llvm-ar NM=llvm-nm STRIP=llvm-strip \
 	  OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump READELF=llvm-readelf \
 	  HOSTCC=clang HOSTCXX=clang++ HOSTAR=llvm-ar HOSTLD=ld.lld
 
+To simplify the above command, Kbuild supports the ``LLVM`` variable::
+
+	make LLVM=1
+
+If your LLVM tools are not available in your PATH, you can supply their
+location using the LLVM variable with a trailing slash::
+
+	make LLVM=/path/to/llvm/
+
+which will use ``/path/to/llvm/clang``, ``/path/to/llvm/ld.lld``, etc.
+
+If your LLVM tools have a version suffix and you want to test with that
+explicit version rather than the unsuffixed executables like ``LLVM=1``, you
+can pass the suffix using the ``LLVM`` variable::
+
+	make LLVM=-14
+
+which will use ``clang-14``, ``ld.lld-14``, etc.
+
+``LLVM=0`` is not the same as omitting ``LLVM`` altogether, it will behave like
+``LLVM=1``. If you only wish to use certain LLVM utilities, use their respective
+make variables.
+
 The integrated assembler is enabled by default. You can pass ``LLVM_IAS=0`` to
 disable it.
 

Documentation/kbuild/makefiles.rst

@@ -982,6 +982,8 @@ The syntax is quite similar. The difference is to use "userprogs" instead of
 
 	When linking bpfilter_umh, it will be passed the extra option -static.
 
+	From command line, :ref:`USERCFLAGS and USERLDFLAGS <userkbuildflags>` will also be used.
+
 5.4 When userspace programs are actually built
 ----------------------------------------------
 

Makefile

@@ -424,34 +424,41 @@ HOST_LFS_LDFLAGS := $(shell getconf LFS_LDFLAGS 2>/dev/null)
 HOST_LFS_LIBS := $(shell getconf LFS_LIBS 2>/dev/null)
 
 ifneq ($(LLVM),)
-HOSTCC	= clang
-HOSTCXX	= clang++
+ifneq ($(filter %/,$(LLVM)),)
+LLVM_PREFIX := $(LLVM)
+else ifneq ($(filter -%,$(LLVM)),)
+LLVM_SUFFIX := $(LLVM)
+endif
+
+HOSTCC	= $(LLVM_PREFIX)clang$(LLVM_SUFFIX)
+HOSTCXX	= $(LLVM_PREFIX)clang++$(LLVM_SUFFIX)
 else
 HOSTCC	= gcc
 HOSTCXX	= g++
 endif
 
-export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
-			      -O2 -fomit-frame-pointer -std=gnu11 \
-			      -Wdeclaration-after-statement
-export KBUILD_USERLDFLAGS :=
+KBUILD_USERHOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
+			 -O2 -fomit-frame-pointer -std=gnu11 \
+			 -Wdeclaration-after-statement
+KBUILD_USERCFLAGS  := $(KBUILD_USERHOSTCFLAGS) $(USERCFLAGS)
+KBUILD_USERLDFLAGS := $(USERLDFLAGS)
 
-KBUILD_HOSTCFLAGS   := $(KBUILD_USERCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
+KBUILD_HOSTCFLAGS   := $(KBUILD_USERHOSTCFLAGS) $(HOST_LFS_CFLAGS) $(HOSTCFLAGS)
 KBUILD_HOSTCXXFLAGS := -Wall -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
 KBUILD_HOSTLDFLAGS  := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
 KBUILD_HOSTLDLIBS   := $(HOST_LFS_LIBS) $(HOSTLDLIBS)
 
 # Make variables (CC, etc...)
 CPP		= $(CC) -E
 ifneq ($(LLVM),)
-CC		= clang
-LD		= ld.lld
-AR		= llvm-ar
-NM		= llvm-nm
-OBJCOPY		= llvm-objcopy
-OBJDUMP		= llvm-objdump
-READELF		= llvm-readelf
-STRIP		= llvm-strip
+CC		= $(LLVM_PREFIX)clang$(LLVM_SUFFIX)
+LD		= $(LLVM_PREFIX)ld.lld$(LLVM_SUFFIX)
+AR		= $(LLVM_PREFIX)llvm-ar$(LLVM_SUFFIX)
+NM		= $(LLVM_PREFIX)llvm-nm$(LLVM_SUFFIX)
+OBJCOPY		= $(LLVM_PREFIX)llvm-objcopy$(LLVM_SUFFIX)
+OBJDUMP		= $(LLVM_PREFIX)llvm-objdump$(LLVM_SUFFIX)
+READELF		= $(LLVM_PREFIX)llvm-readelf$(LLVM_SUFFIX)
+STRIP		= $(LLVM_PREFIX)llvm-strip$(LLVM_SUFFIX)
 else
 CC		= $(CROSS_COMPILE)gcc
 LD		= $(CROSS_COMPILE)ld
@@ -531,6 +538,7 @@ export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AW
 export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
 export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD
 export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
+export KBUILD_USERCFLAGS KBUILD_USERLDFLAGS
 
 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS
 export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
@@ -1237,8 +1245,8 @@ define filechk_version.h
 	echo \#define LINUX_VERSION_SUBLEVEL $(SUBLEVEL)
 endef
 
-$(version_h): PATCHLEVEL := $(if $(PATCHLEVEL), $(PATCHLEVEL), 0)
-$(version_h): SUBLEVEL := $(if $(SUBLEVEL), $(SUBLEVEL), 0)
+$(version_h): PATCHLEVEL := $(or $(PATCHLEVEL), 0)
+$(version_h): SUBLEVEL := $(or $(SUBLEVEL), 0)
 $(version_h): FORCE
 	$(call filechk,version.h)
 
@@ -1621,7 +1629,7 @@ help:
 	@$(MAKE) -f $(srctree)/Documentation/Makefile dochelp
 	@echo  ''
 	@echo  'Architecture specific targets ($(SRCARCH)):'
-	@$(if $(archhelp),$(archhelp),\
+	@$(or $(archhelp),\
 		echo '  No architecture specific help defined for $(SRCARCH)')
 	@echo  ''
 	@$(if $(boards), \
@@ -1838,7 +1846,7 @@ $(clean-dirs):
 
 clean: $(clean-dirs)
 	$(call cmd,rmfiles)
-	@find $(if $(KBUILD_EXTMOD), $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
+	@find $(or $(KBUILD_EXTMOD), .) $(RCS_FIND_IGNORE) \
 		\( -name '*.[aios]' -o -name '*.ko' -o -name '.*.cmd' \
 		-o -name '*.ko.*' \
 		-o -name '*.dtb' -o -name '*.dtbo' -o -name '*.dtb.S' -o -name '*.dt.yaml' \

arch/alpha/kernel/syscalls/Makefile

@@ -2,8 +2,7 @@
 kapi := arch/$(SRCARCH)/include/generated/asm
 uapi := arch/$(SRCARCH)/include/generated/uapi/asm
 
-_dummy := $(shell [ -d '$(uapi)' ] || mkdir -p '$(uapi)')	\
-	  $(shell [ -d '$(kapi)' ] || mkdir -p '$(kapi)')
+$(shell mkdir -p $(uapi) $(kapi))
 
 syscall := $(src)/syscall.tbl
 syshdr := $(srctree)/scripts/syscallhdr.sh

arch/arm/tools/Makefile

@@ -29,8 +29,7 @@ kapi:	$(kapi-hdrs-y) $(gen-y)
 uapi:	$(uapi-hdrs-y)
 
 # Create output directory if not already present
-_dummy := $(shell [ -d '$(kapi)' ] || mkdir -p '$(kapi)') \
-          $(shell [ -d '$(uapi)' ] || mkdir -p '$(uapi)')
+$(shell mkdir -p $(kapi) $(uapi))
 
 quiet_cmd_gen_mach = GEN     $@
       cmd_gen_mach = $(AWK) -f $(real-prereqs) > $@

arch/ia64/kernel/syscalls/Makefile

@@ -2,8 +2,7 @@
 kapi := arch/$(SRCARCH)/include/generated/asm
 uapi := arch/$(SRCARCH)/include/generated/uapi/asm
 
-_dummy := $(shell [ -d '$(uapi)' ] || mkdir -p '$(uapi)')	\
-	  $(shell [ -d '$(kapi)' ] || mkdir -p '$(kapi)')
+$(shell mkdir -p $(uapi) $(kapi))
 
 syscall := $(src)/syscall.tbl
 syshdr := $(srctree)/scripts/syscallhdr.sh

arch/m68k/kernel/syscalls/Makefile

@@ -2,8 +2,7 @@
 kapi := arch/$(SRCARCH)/include/generated/asm
 uapi := arch/$(SRCARCH)/include/generated/uapi/asm
 
-_dummy := $(shell [ -d '$(uapi)' ] || mkdir -p '$(uapi)')	\
-	  $(shell [ -d '$(kapi)' ] || mkdir -p '$(kapi)')
+$(shell mkdir -p $(uapi) $(kapi))
 
 syscall := $(src)/syscall.tbl
 syshdr := $(srctree)/scripts/syscallhdr.sh

arch/microblaze/boot/Makefile

@@ -29,7 +29,7 @@ $(obj)/simpleImage.$(DTB).ub: $(obj)/simpleImage.$(DTB) FORCE
 	$(call if_changed,uimage)
 
 $(obj)/simpleImage.$(DTB).unstrip: vmlinux FORCE
-	$(call if_changed,shipped)
+	$(call if_changed,copy)
 
 $(obj)/simpleImage.$(DTB).strip: vmlinux FORCE
 	$(call if_changed,strip)

arch/microblaze/boot/dts/Makefile

@@ -12,7 +12,7 @@ $(obj)/linked_dtb.o: $(obj)/system.dtb
 # Generate system.dtb from $(DTB).dtb
 ifneq ($(DTB),system)
 $(obj)/system.dtb: $(obj)/$(DTB).dtb
-	$(call if_changed,shipped)
+	$(call if_changed,copy)
 endif
 endif