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

[Jessica Yu <jeyu@kernel.org>]

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>
---
 scripts/Makefile.modpost |  1 +
 scripts/mod/modpost.c    | 19 +++++++++++++++----
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index b4d3f2d122ac..a53660f910a9 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -53,6 +53,7 @@ MODPOST = scripts/mod/modpost						\
 	$(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),,-N) 	\
 	$(if $(KBUILD_MODPOST_WARN),-w)
 
 ifdef MODPOST_VMLINUX
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 7edfdb2f4497..53e966f7d557 100644
--- a/scripts/mod/modpost.c
+++ b/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;
+/* Return an error when there are missing namespace imports */
+static int missing_ns_import_error = 0;
 
 enum export {
 	export_plain,      export_unused,     export_gpl,
@@ -2216,9 +2218,15 @@ 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);
-			add_namespace(&mod->missing_namespaces, exp->namespace);
+			if (missing_ns_import_error) {
+				merror("module %s uses symbol %s from namespace %s, but does not import it.\n",
+					basename, exp->name, exp->namespace);
+				err = 1;
+			} else {
+				warn("module %s uses symbol %s from namespace %s, but does not import it.\n",
+				     basename, exp->name, exp->namespace);
+			}
+				add_namespace(&mod->missing_namespaces, exp->namespace);
 		}
 
 		if (!mod->gpl_compatible)
@@ -2560,7 +2568,7 @@ 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;
@@ -2598,6 +2606,9 @@ int main(int argc, char **argv)
 		case 'E':
 			sec_mismatch_fatal = 1;
 			break;
+		case 'N':
+			missing_ns_import_error = 1;
+			break;
 		case 'd':
 			missing_namespace_deps = optarg;
 			break;
-- 
2.16.4