Kbuild fixes for v5.3 (2nd)

- detect missing missing "WITH Linux-syscall-note" for uapi headers
 
  - fix needless rebuild when using Clang
 
  - fix false-positive cc-option in Kconfig when using Clang
 
  - avoid including corrupted .*.cmd files in the modpost stage
 
  - fix warning of 'make vmlinux'
 
  - fix {m,n,x,g}config to not generate the broken .config on the second
    save operation.
 
  - some trivial Makefile fixes
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Merge tag 'kbuild-fixes-v5.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild fixes from Masahiro Yamada:

 - detect missing missing "WITH Linux-syscall-note" for uapi headers

 - fix needless rebuild when using Clang

 - fix false-positive cc-option in Kconfig when using Clang

 - avoid including corrupted .*.cmd files in the modpost stage

 - fix warning of 'make vmlinux'

 - fix {m,n,x,g}config to not generate the broken .config on the second
   save operation.

 - some trivial Makefile fixes

* tag 'kbuild-fixes-v5.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kconfig: Clear "written" flag to avoid data loss
  kbuild: Check for unknown options with cc-option usage in Kconfig and clang
  lib/raid6: fix unnecessary rebuild of vpermxor*.c
  kbuild: modpost: do not parse unnecessary rules for vmlinux modpost
  kbuild: modpost: remove unnecessary dependency for __modpost
  kbuild: modpost: handle KBUILD_EXTRA_SYMBOLS only for external modules
  kbuild: modpost: include .*.cmd files only when targets exist
  kbuild: initialize CLANG_FLAGS correctly in the top Makefile
  kbuild: detect missing "WITH Linux-syscall-note" for uapi headers

Makefile

@@ -472,6 +472,7 @@ KBUILD_CFLAGS_MODULE  := -DMODULE
 KBUILD_LDFLAGS_MODULE := -T $(srctree)/scripts/module-common.lds
 KBUILD_LDFLAGS :=
 GCC_PLUGINS_CFLAGS :=
+CLANG_FLAGS :=
 
 export ARCH SRCARCH CONFIG_SHELL HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE AS LD CC
 export CPP AR NM STRIP OBJCOPY OBJDUMP PAHOLE KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS
@@ -519,7 +520,7 @@ endif
 
 ifneq ($(shell $(CC) --version 2>&1 | head -n 1 | grep clang),)
 ifneq ($(CROSS_COMPILE),)
-CLANG_FLAGS	:= --target=$(notdir $(CROSS_COMPILE:%-=%))
+CLANG_FLAGS	+= --target=$(notdir $(CROSS_COMPILE:%-=%))
 GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
 CLANG_FLAGS	+= --prefix=$(GCC_TOOLCHAIN_DIR)
 GCC_TOOLCHAIN	:= $(realpath $(GCC_TOOLCHAIN_DIR)/..)

lib/raid6/Makefile

@@ -66,7 +66,7 @@ CFLAGS_vpermxor1.o += $(altivec_flags)
 CFLAGS_vpermxor2.o += $(altivec_flags)
 CFLAGS_vpermxor4.o += $(altivec_flags)
 CFLAGS_vpermxor8.o += $(altivec_flags)
-targets += vpermxor1.o vpermxor2.o vpermxor4.o vpermxor8.o
+targets += vpermxor1.c vpermxor2.c vpermxor4.c vpermxor8.c
 $(obj)/vpermxor%.c: $(src)/vpermxor.uc $(src)/unroll.awk FORCE
 	$(call if_changed,unroll)
 

scripts/Kconfig.include

@@ -25,7 +25,7 @@ failure = $(if-success,$(1),n,y)
 
 # $(cc-option,<flag>)
 # Return y if the compiler supports <flag>, n otherwise
-cc-option = $(success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null)
+cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -E -x c /dev/null -o /dev/null)
 
 # $(ld-option,<flag>)
 # Return y if the linker supports <flag>, n otherwise

scripts/Makefile.modpost

@@ -38,12 +38,39 @@
 # symbols in the final module linking stage
 # KBUILD_MODPOST_NOFINAL can be set to skip the final link of modules.
 # This is solely useful to speed up test compiles
-PHONY := _modpost
-_modpost: __modpost
+
+PHONY := __modpost
+__modpost:
 
 include include/config/auto.conf
 include scripts/Kbuild.include
 
+kernelsymfile := $(objtree)/Module.symvers
+modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers
+
+MODPOST = scripts/mod/modpost						\
+	$(if $(CONFIG_MODVERSIONS),-m)					\
+	$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a)			\
+	$(if $(KBUILD_EXTMOD),-i,-o) $(kernelsymfile)			\
+	$(if $(KBUILD_EXTMOD),-I $(modulesymfile))			\
+	$(if $(KBUILD_EXTMOD),$(addprefix -e ,$(KBUILD_EXTRA_SYMBOLS)))	\
+	$(if $(KBUILD_EXTMOD),-o $(modulesymfile))			\
+	$(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)			\
+	$(if $(KBUILD_MODPOST_WARN),-w)
+
+ifdef MODPOST_VMLINUX
+
+__modpost: vmlinux.o
+
+quiet_cmd_modpost = MODPOST $@
+      cmd_modpost = $(MODPOST) $@
+
+PHONY += vmlinux.o
+vmlinux.o:
+	$(call cmd,modpost)
+
+else
+
 # When building external modules load the Kbuild file to retrieve EXTRA_SYMBOLS info
 ifneq ($(KBUILD_EXTMOD),)
 
@@ -58,50 +85,27 @@ endif
 
 include scripts/Makefile.lib
 
-kernelsymfile := $(objtree)/Module.symvers
-modulesymfile := $(firstword $(KBUILD_EXTMOD))/Module.symvers
-
 modorder := $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)modules.order
 
-# Step 1), find all modules listed in modules.order
-ifdef CONFIG_MODULES
+# find all modules listed in modules.order
 modules := $(sort $(shell cat $(modorder)))
-endif
 
 # Stop after building .o files if NOFINAL is set. Makes compile tests quicker
-_modpost: $(if $(KBUILD_MODPOST_NOFINAL), $(modules:.ko:.o),$(modules))
+__modpost: $(if $(KBUILD_MODPOST_NOFINAL), $(modules:.ko:.o),$(modules))
+	@:
 
-# Step 2), invoke modpost
-#  Includes step 3,4
-modpost = scripts/mod/modpost                    \
- $(if $(CONFIG_MODVERSIONS),-m)                  \
- $(if $(CONFIG_MODULE_SRCVERSION_ALL),-a,)       \
- $(if $(KBUILD_EXTMOD),-i,-o) $(kernelsymfile)   \
- $(if $(KBUILD_EXTMOD),-I $(modulesymfile))      \
- $(if $(KBUILD_EXTRA_SYMBOLS), $(patsubst %, -e %,$(KBUILD_EXTRA_SYMBOLS))) \
- $(if $(KBUILD_EXTMOD),-o $(modulesymfile))      \
- $(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)  \
- $(if $(KBUILD_MODPOST_WARN),-w)
-
-MODPOST_OPT=$(subst -i,-n,$(filter -i,$(MAKEFLAGS)))
+MODPOST += $(subst -i,-n,$(filter -i,$(MAKEFLAGS))) -s -T - $(wildcard vmlinux)
 
 # We can go over command line length here, so be careful.
-quiet_cmd_modpost = MODPOST $(words $(filter-out vmlinux FORCE, $^)) modules
-      cmd_modpost = sed 's/ko$$/o/' $(modorder) | $(modpost) $(MODPOST_OPT) -s -T -
+quiet_cmd_modpost = MODPOST $(words $(modules)) modules
+      cmd_modpost = sed 's/ko$$/o/' $(modorder) | $(MODPOST)
 
-PHONY += __modpost
-__modpost: $(modules:.ko=.o) FORCE
-	$(call cmd,modpost) $(wildcard vmlinux)
-
-quiet_cmd_kernel-mod = MODPOST $@
-      cmd_kernel-mod = $(modpost) $@
-
-vmlinux.o: FORCE
-	$(call cmd,kernel-mod)
+PHONY += modules-modpost
+modules-modpost:
+	$(call cmd,modpost)
 
 # Declare generated files as targets for modpost
-$(modules:.ko=.mod.c): __modpost ;
-
+$(modules:.ko=.mod.c): modules-modpost
 
 # Step 5), compile all *.mod.c files
 
@@ -145,10 +149,10 @@ FORCE:
 # optimization, we don't need to read them if the target does not
 # exist, we will rebuild anyway in that case.
 
-cmd_files := $(wildcard $(foreach f,$(sort $(targets)),$(dir $(f)).$(notdir $(f)).cmd))
+existing-targets := $(wildcard $(sort $(targets)))
+
+-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
 
-ifneq ($(cmd_files),)
-  include $(cmd_files)
 endif
 
 .PHONY: $(PHONY)

scripts/headers_install.sh

@@ -23,6 +23,12 @@ TMPFILE=$OUTFILE.tmp
 
 trap 'rm -f $OUTFILE $TMPFILE' EXIT
 
+# SPDX-License-Identifier with GPL variants must have "WITH Linux-syscall-note"
+if [ -n "$(sed -n -e "/SPDX-License-Identifier:.*GPL-/{/WITH Linux-syscall-note/!p}" $INFILE)" ]; then
+	echo "error: $INFILE: missing \"WITH Linux-syscall-note\" for SPDX-License-Identifier" >&2
+	exit 1
+fi
+
 sed -E -e '
 	s/([[:space:](])(__user|__force|__iomem)[[:space:]]/\1/g
 	s/__attribute_const__([[:space:]]|$)/\1/g

scripts/kconfig/confdata.c

@@ -848,6 +848,7 @@ int conf_write(const char *name)
 	const char *str;
 	char tmpname[PATH_MAX + 1], oldname[PATH_MAX + 1];
 	char *env;
+	int i;
 	bool need_newline = false;
 
 	if (!name)
@@ -930,6 +931,9 @@ next:
 	}
 	fclose(out);
 
+	for_all_symbols(i, sym)
+		sym->flags &= ~SYMBOL_WRITTEN;
+
 	if (*tmpname) {
 		if (is_same(name, tmpname)) {
 			conf_message("No change to %s", name);

scripts/link-vmlinux.sh

@@ -210,7 +210,7 @@ info LD vmlinux.o
 modpost_link vmlinux.o
 
 # modpost vmlinux.o to check for section mismatches
-${MAKE} -f "${srctree}/scripts/Makefile.modpost" vmlinux.o
+${MAKE} -f "${srctree}/scripts/Makefile.modpost" MODPOST_VMLINUX=1
 
 info MODINFO modules.builtin.modinfo
 ${OBJCOPY} -j .modinfo -O binary vmlinux.o modules.builtin.modinfo