[PATCH 3/3] [pending] kbuild: make forbid sharing objects among multiple modules

[Masahiro Yamada <masahiroy@kernel.org>]

 *** This patch is applicable after all the warnings are fixed.
 *** It may take a couple of development cycles.

Now that all the warnings are fixed, the warning can be promoted to
an error.

Simplify the modules.builtin rule because modname always consists of
a single word.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 scripts/Makefile.build     | 6 ------
 scripts/Makefile.lib       | 8 ++++----
 scripts/Makefile.vmlinux_o | 5 +----
 3 files changed, 5 insertions(+), 14 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 799df12b53f3..37cf88d076e8 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -222,10 +222,6 @@ endif
 
 cmd_check_local_export = $(srctree)/scripts/check-local-export $@
 
-ifneq ($(findstring 1, $(KBUILD_EXTRA_WARN)),)
-cmd_warn_shared_object = $(if $(word 2, $(modname-multi)),$(warning $(kbuild-file): $*.o is added to multiple modules: $(modname-multi)))
-endif
-
 define rule_cc_o_c
 	$(call cmd_and_fixdep,cc_o_c)
 	$(call cmd,gen_ksymdeps)
@@ -235,7 +231,6 @@ define rule_cc_o_c
 	$(call cmd,gen_objtooldep)
 	$(call cmd,gen_symversions_c)
 	$(call cmd,record_mcount)
-	$(call cmd,warn_shared_object)
 endef
 
 define rule_as_o_S
@@ -244,7 +239,6 @@ define rule_as_o_S
 	$(call cmd,check_local_export)
 	$(call cmd,gen_objtooldep)
 	$(call cmd,gen_symversions_S)
-	$(call cmd,warn_shared_object)
 endef
 
 # Built-in and composite module parts
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 3aa384cec76b..d73bfe0fabda 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -106,13 +106,13 @@ endif
 
 # Finds the multi-part object the current object will be linked into.
 # If the object belongs to two or more multi-part objects, list them all.
-modname-multi = $(sort $(foreach m,$(multi-obj-ym),\
+__modname-multi = $(sort $(foreach m,$(multi-obj-ym),\
 		$(if $(filter $*.o, $(call suffix-search, $m, .o, -objs -y -m)),$(m:.o=))))
 
-__modname = $(or $(modname-multi),$(basetarget))
+modname-multi = $(if $(word 2, $(__modname-multi)), $(error $(kbuild-file): $*.o is added to multiple modules: $(__modname-multi)))$(__modname-multi)
 
-modname = $(subst $(space),:,$(__modname))
-modfile = $(addprefix $(obj)/,$(__modname))
+modname = $(or $(modname-multi),$(basetarget))
+modfile = $(addprefix $(obj)/,$(modname))
 
 # target with $(obj)/ and its suffix stripped
 target-stem = $(basename $(patsubst $(obj)/%,%,$@))
diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o
index 0edfdb40364b..2faf4960aa7a 100644
--- a/scripts/Makefile.vmlinux_o
+++ b/scripts/Makefile.vmlinux_o
@@ -74,13 +74,10 @@ modules.builtin.modinfo: vmlinux.o FORCE
 # module.builtin
 # ---------------------------------------------------------------------------
 
-# The second line aids cases where multiple modules share the same object.
-
 quiet_cmd_modules_builtin = GEN     $@
       cmd_modules_builtin = \
 	tr '\0' '\n' < $< | \
-	sed -n 's/^[[:alnum:]:_]*\.file=//p' | \
-	tr ' ' '\n' | uniq | sed -e 's:^:kernel/:' -e 's/$$/.ko/' > $@
+	sed -n 's@^[[:alnum:]:_]*\.file=\(.*\)@kernel/\1.ko@p' | uniq > $@
 
 targets += modules.builtin
 modules.builtin: modules.builtin.modinfo FORCE
-- 
2.34.1