modpost: return error if module is missing ns imports and MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=n

Currently when CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=n, modpost
only warns when a module is missing namespace imports. Under this
configuration, such a module cannot be loaded into the kernel anyway, as
the module loader would reject it. We might as well return a build
error when a module is missing namespace imports under
CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=n, so that the build
warning does not go ignored/unnoticed.
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/Makefile.modpost

@@ -46,13 +46,14 @@ 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 $(KBUILD_EXTMOD),$(addprefix -e ,$(KBUILD_EXTRA_SYMBOLS)))	\
-	$(if $(KBUILD_EXTMOD),-o $(modulesymfile))			\
-	$(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)			\
+MODPOST = scripts/mod/modpost								\
+	$(if $(CONFIG_MODVERSIONS),-m)							\
+	$(if $(CONFIG_MODULE_SRCVERSION_ALL),-a)					\
+	$(if $(KBUILD_EXTMOD),-i,-o) $(kernelsymfile)					\
+	$(if $(KBUILD_EXTMOD),$(addprefix -e ,$(KBUILD_EXTRA_SYMBOLS)))			\
+	$(if $(KBUILD_EXTMOD),-o $(modulesymfile))					\
+	$(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E)					\
+	$(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-N) 	\
 	$(if $(KBUILD_MODPOST_WARN),-w)
 
 ifdef MODPOST_VMLINUX

scripts/mod/modpost.c

@@ -39,6 +39,8 @@ static int sec_mismatch_count = 0;
 static int sec_mismatch_fatal = 0;
 /* ignore missing files */
 static int ignore_missing_files;
+/* If set to 1, only warn (instead of error) about missing ns imports */
+static int allow_missing_ns_imports;
 
 enum export {
 	export_plain,      export_unused,     export_gpl,
@@ -2205,8 +2207,11 @@ static int check_exports(struct module *mod)
 
 		if (exp->namespace &&
 		    !module_imports_namespace(mod, exp->namespace)) {
-			warn("module %s uses symbol %s from namespace %s, but does not import it.\n",
-			     basename, exp->name, exp->namespace);
+			modpost_log(allow_missing_ns_imports ? LOG_WARN : LOG_ERROR,
+				    "module %s uses symbol %s from namespace %s, but does not import it.\n",
+				    basename, exp->name, exp->namespace);
+			if (!allow_missing_ns_imports)
+				err = 1;
 			add_namespace(&mod->missing_namespaces, exp->namespace);
 		}
 
@@ -2549,7 +2554,7 @@ int main(int argc, char **argv)
 	struct ext_sym_list *extsym_iter;
 	struct ext_sym_list *extsym_start = NULL;
 
-	while ((opt = getopt(argc, argv, "i:e:mnsT:o:awEd:")) != -1) {
+	while ((opt = getopt(argc, argv, "i:e:mnsT:o:awENd:")) != -1) {
 		switch (opt) {
 		case 'i':
 			kernel_read = optarg;
@@ -2587,6 +2592,9 @@ int main(int argc, char **argv)
 		case 'E':
 			sec_mismatch_fatal = 1;
 			break;
+		case 'N':
+			allow_missing_ns_imports = 1;
+			break;
 		case 'd':
 			missing_namespace_deps = optarg;
 			break;