kbuild: warn about duplicate exported symbols

In modpost introduce a check for symbols exported twice.
This check caught only one victim (inet_bind_bucket_create) for
which a patch is already sent to netdev.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

1 files changed, 13 insertions, 3 deletions

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 976adf152db3..d901095ea8b7 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -117,6 +117,7 @@ struct symbol {
         unsigned int vmlinux:1;    /* 1 if symbol is defined in vmlinux */
         unsigned int kernel:1;     /* 1 if symbol is from kernel
                                     *  (only for external modules) **/
+        unsigned int preloaded:1;  /* 1 if symbol from Module.symvers */
         char name[0];
 };
 
@@ -186,9 +187,17 @@ static struct symbol *sym_add_exported(const char *name, struct module *mod)
 {
         struct symbol *s = find_symbol(name);
 
-        if (!s)
+        if (!s) {
                 s = new_symbol(name, mod);
-
+        } else {
+                if (!s->preloaded) {
+                        warn("%s: duplicate symbol '%s' previous definition "
+                             "was in %s%s\n", mod->name, name,
+                             s->module->name,
+                             is_vmlinux(s->module->name) ?"":".ko");
+                }
+        }
+        s->preloaded = 0;
         s->vmlinux   = is_vmlinux(mod->name);
         s->kernel    = 0;
         return s;
@@ -706,7 +715,8 @@ static void read_dump(const char *fname, unsigned int kernel)
                         mod->skip = 1;
                 }
                 s = sym_add_exported(symname, mod);
-                s->kernel = kernel;
+                s->kernel    = kernel;
+                s->preloaded = 1;
                 sym_update_crc(symname, mod, crc);
         }
         return;