kbuild: fail kernel compilation in case of unresolved module symbols

At stage 2 modpost utility is used to check modules.  In case of unresolved
symbols modpost only prints warning.

IMHO it is a good idea to fail compilation process in case of unresolved
symbols (at least in modules coming with kernel), since usually such errors
are left unnoticed, but kernel modules are broken.

- new option '-w' is added to modpost:
  if option is specified, modpost only warns about unresolved symbols

- modpost is called with '-w' for external modules in Makefile.modpost

Signed-off-by: Andrey Mirkin <amirkin@sw.ru>
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

2 files changed, 20 insertions, 6 deletions

diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 9137df2f9290..4b2721ca97da 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -58,6 +58,7 @@ quiet_cmd_modpost = MODPOST $(words $(filter-out vmlinux FORCE, $^)) modules
         $(if $(KBUILD_EXTMOD),-i,-o) $(kernelsymfile) \
         $(if $(KBUILD_EXTMOD),-I $(modulesymfile)) \
         $(if $(KBUILD_EXTMOD),-o $(modulesymfile)) \
+        $(if $(KBUILD_EXTMOD),-w) \
         $(wildcard vmlinux) $(filter-out FORCE,$^)
 
 PHONY += __modpost
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 16a19353c67f..41277963f47a 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -23,6 +23,8 @@ int have_vmlinux = 0;
 static int all_versions = 0;
 /* If we are modposting external module set to 1 */
 static int external_module = 0;
+/* Only warn about unresolved symbols */
+static int warn_unresolved = 0;
 /* How a symbol is exported */
 enum export {
         export_plain,      export_unused,     export_gpl,
@@ -1196,16 +1198,19 @@ static void add_header(struct buffer *b, struct module *mod)
 /**
  * Record CRCs for unresolved symbols
  **/
-static void add_versions(struct buffer *b, struct module *mod)
+static int add_versions(struct buffer *b, struct module *mod)
 {
         struct symbol *s, *exp;
+        int err = 0;
 
         for (s = mod->unres; s; s = s->next) {
                 exp = find_symbol(s->name);
                 if (!exp || exp->module == mod) {
-                        if (have_vmlinux && !s->weak)
+                        if (have_vmlinux && !s->weak) {
                                 warn("\"%s\" [%s.ko] undefined!\n",
                                      s->name, mod->name);
+                                err = warn_unresolved ? 0 : 1;
+                        }
                         continue;
                 }
                 s->module = exp->module;
@@ -1214,7 +1219,7 @@ static void add_versions(struct buffer *b, struct module *mod)
         }
 
         if (!modversions)
-                return;
+                return err;
 
         buf_printf(b, "\n");
         buf_printf(b, "static const struct modversion_info ____versions[]\n");
@@ -1234,6 +1239,8 @@ static void add_versions(struct buffer *b, struct module *mod)
         }
 
         buf_printf(b, "};\n");
+
+        return err;
 }
 
 static void add_depends(struct buffer *b, struct module *mod,
@@ -1411,8 +1418,9 @@ int main(int argc, char **argv)
         char *kernel_read = NULL, *module_read = NULL;
         char *dump_write = NULL;
         int opt;
+        int err;
 
-        while ((opt = getopt(argc, argv, "i:I:mo:a")) != -1) {
+        while ((opt = getopt(argc, argv, "i:I:mo:aw")) != -1) {
                 switch(opt) {
                         case 'i':
                                 kernel_read = optarg;
@@ -1430,6 +1438,9 @@ int main(int argc, char **argv)
                         case 'a':
                                 all_versions = 1;
                                 break;
+                        case 'w':
+                                warn_unresolved = 1;
+                                break;
                         default:
                                 exit(1);
                 }
@@ -1450,6 +1461,8 @@ int main(int argc, char **argv)
                 check_exports(mod);
         }
 
+        err = 0;
+
         for (mod = modules; mod; mod = mod->next) {
                 if (mod->skip)
                         continue;
@@ -1457,7 +1470,7 @@ int main(int argc, char **argv)
                 buf.pos = 0;
 
                 add_header(&buf, mod);
-                add_versions(&buf, mod);
+                err |= add_versions(&buf, mod);
                 add_depends(&buf, mod, modules);
                 add_moddevtable(&buf, mod);
                 add_srcversion(&buf, mod);
@@ -1469,5 +1482,5 @@ int main(int argc, char **argv)
         if (dump_write)
                 write_dump(dump_write);
 
-        return 0;
+        return err;
 }