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

Pull Kbuild fixes from Masahiro Yamada:

 - revive single target %.ko

 - do not create built-in.a where it is unneeded

 - do not create modules.order where it is unneeded

 - show a warning if subdir-y/m is used to visit a module Makefile

* tag 'kbuild-fixes-v5.3-3' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: show hint if subdir-y/m is used to visit module Makefile
  kbuild: generate modules.order only in directories visited by obj-y/m
  kbuild: fix false-positive need-builtin calculation
  kbuild: revive single target %.ko

Makefile

@@ -1003,6 +1003,8 @@ endif
 
 PHONY += prepare0
 
+export MODORDER := $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)modules.order
+
 ifeq ($(KBUILD_EXTMOD),)
 core-y		+= kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ block/
 
@@ -1772,13 +1774,22 @@ build-dir = $(patsubst %/,%,$(dir $(build-target)))
 	$(Q)$(MAKE) $(build)=$(build-dir) $(build-target)
 %.symtypes: prepare FORCE
 	$(Q)$(MAKE) $(build)=$(build-dir) $(build-target)
+ifeq ($(KBUILD_EXTMOD),)
+# For the single build of an in-tree module, use a temporary file to avoid
+# the situation of modules_install installing an invalid modules.order.
+%.ko: MODORDER := .modules.tmp
+endif
+%.ko: prepare FORCE
+	$(Q)$(MAKE) $(build)=$(build-dir) $(build-target:.ko=.mod)
+	$(Q)echo $(build-target) > $(MODORDER)
+	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
 
 # Modules
 PHONY += /
 /: ./
 
 %/: prepare FORCE
-	$(Q)$(MAKE) KBUILD_MODULES=1 $(build)=$(build-dir)
+	$(Q)$(MAKE) KBUILD_MODULES=1 $(build)=$(build-dir) need-modorder=1
 
 # FIXME Should go into a make.lib or something
 # ===========================================================================

scripts/Makefile.build

@@ -52,6 +52,13 @@ ifndef obj
 $(warning kbuild: Makefile.build is included improperly)
 endif
 
+ifeq ($(MAKECMDGOALS)$(need-modorder),)
+ifneq ($(obj-m),)
+$(warning $(patsubst %.o,'%.ko',$(obj-m)) will not be built even though obj-m is specified.)
+$(warning You cannot use subdir-y/m to visit a module Makefile. Use obj-y/m instead.)
+endif
+endif
+
 # ===========================================================================
 
 ifneq ($(strip $(lib-y) $(lib-m) $(lib-)),)
@@ -487,7 +494,9 @@ targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
 
 PHONY += $(subdir-ym)
 $(subdir-ym):
-	$(Q)$(MAKE) $(build)=$@ need-builtin=$(if $(findstring $@,$(subdir-obj-y)),1)
+	$(Q)$(MAKE) $(build)=$@ \
+	need-builtin=$(if $(filter $@/built-in.a, $(subdir-obj-y)),1) \
+	need-modorder=$(if $(need-modorder),$(if $(filter $@/modules.order, $(modorder)),1))
 
 # Add FORCE to the prequisites of a target to force it to be always rebuilt.
 # ---------------------------------------------------------------------------

scripts/Makefile.modpost

@@ -85,10 +85,8 @@ endif
 
 include scripts/Makefile.lib
 
-modorder := $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)modules.order
-
 # find all modules listed in modules.order
-modules := $(sort $(shell cat $(modorder)))
+modules := $(sort $(shell cat $(MODORDER)))
 
 # Stop after building .o files if NOFINAL is set. Makes compile tests quicker
 __modpost: $(if $(KBUILD_MODPOST_NOFINAL), $(modules:.ko:.o),$(modules))
@@ -98,7 +96,7 @@ 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 $(modules)) modules
-      cmd_modpost = sed 's/ko$$/o/' $(modorder) | $(MODPOST)
+      cmd_modpost = sed 's/ko$$/o/' $(MODORDER) | $(MODPOST)
 
 PHONY += modules-modpost
 modules-modpost: