[PATCH 2/2] 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 | 15 ++++++++-------
 scripts/mod/modpost.c    | 14 +++++++++++---
 2 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index b4d3f2d122ac..957eed6a17a5 100644
--- a/scripts/Makefile.modpost
+++ b/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
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index e2805fbeb99f..9ae2b1c9a870 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;
+/* If set to 1, only warn (instead of error) about missing ns imports */
+static int allow_missing_ns_imports = 0;
 
 enum export {
 	export_plain,      export_unused,     export_gpl,
@@ -2211,8 +2213,11 @@ 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);
+			warn_unless(!allow_missing_ns_imports,
+				    "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);
 		}
 
@@ -2555,7 +2560,7 @@ 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;
@@ -2593,6 +2598,9 @@ 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;
-- 
2.16.4