kbuild: warn when a moduled uses a symbol marked UNUSED

We now have infrastructure in place to mark an EXPORTed symbol
as unused. So the natural next step is to warn during buildtime when
a module uses a symbol marked UNUSED.

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

2 files changed, 64 insertions, 23 deletions

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 65411665e13c..dfde0e87a765 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -24,7 +24,10 @@ static int all_versions = 0;
 /* If we are modposting external module set to 1 */
 static int external_module = 0;
 /* How a symbol is exported */
-enum export {export_plain, export_gpl, export_gpl_future, export_unknown};
+enum export {
+        export_plain,      export_unused,     export_gpl,
+        export_unused_gpl, export_gpl_future, export_unknown
+};
 
 void fatal(const char *fmt, ...)
 {
@@ -191,7 +194,9 @@ static struct {
         enum export export;
 } export_list[] = {
         { .str = "EXPORT_SYMBOL",            .export = export_plain },
+        { .str = "EXPORT_UNUSED_SYMBOL",     .export = export_unused },
         { .str = "EXPORT_SYMBOL_GPL",        .export = export_gpl },
+        { .str = "EXPORT_UNUSED_SYMBOL_GPL", .export = export_unused_gpl },
         { .str = "EXPORT_SYMBOL_GPL_FUTURE", .export = export_gpl_future },
         { .str = "(unknown)",                .export = export_unknown },
 };
@@ -218,8 +223,12 @@ static enum export export_from_sec(struct elf_info *elf, Elf_Section sec)
 {
         if (sec == elf->export_sec)
                 return export_plain;
+        else if (sec == elf->export_unused_sec)
+                return export_unused;
         else if (sec == elf->export_gpl_sec)
                 return export_gpl;
+        else if (sec == elf->export_unused_gpl_sec)
+                return export_unused_gpl;
         else if (sec == elf->export_gpl_future_sec)
                 return export_gpl_future;
         else
@@ -368,8 +377,12 @@ static void parse_elf(struct elf_info *info, const char *filename)
                         info->modinfo_len = sechdrs[i].sh_size;
                 } else if (strcmp(secname, "__ksymtab") == 0)
                         info->export_sec = i;
+                else if (strcmp(secname, "__ksymtab_unused") == 0)
+                        info->export_unused_sec = i;
                 else if (strcmp(secname, "__ksymtab_gpl") == 0)
                         info->export_gpl_sec = i;
+                else if (strcmp(secname, "__ksymtab_unused_gpl") == 0)
+                        info->export_unused_gpl_sec = i;
                 else if (strcmp(secname, "__ksymtab_gpl_future") == 0)
                         info->export_gpl_future_sec = i;
 
@@ -1087,38 +1100,64 @@ void buf_write(struct buffer *buf, const char *s, int len)
         buf->pos += len;
 }
 
-void check_license(struct module *mod)
+static void check_for_gpl_usage(enum export exp, const char *m, const char *s)
+{
+        const char *e = is_vmlinux(m) ?"":".ko";
+
+        switch (exp) {
+        case export_gpl:
+                fatal("modpost: GPL-incompatible module %s%s "
+                      "uses GPL-only symbol '%s'\n", m, e, s);
+                break;
+        case export_unused_gpl:
+                fatal("modpost: GPL-incompatible module %s%s "
+                      "uses GPL-only symbol marked UNUSED '%s'\n", m, e, s);
+                break;
+        case export_gpl_future:
+                warn("modpost: GPL-incompatible module %s%s "
+                      "uses future GPL-only symbol '%s'\n", m, e, s);
+                break;
+        case export_plain:
+        case export_unused:
+        case export_unknown:
+                /* ignore */
+                break;
+        }
+}
+
+static void check_for_unused(enum export exp, const char* m, const char* s)
+{
+        const char *e = is_vmlinux(m) ?"":".ko";
+
+        switch (exp) {
+        case export_unused:
+        case export_unused_gpl:
+                warn("modpost: module %s%s "
+                      "uses symbol '%s' marked UNUSED\n", m, e, s);
+                break;
+        default:
+                /* ignore */
+                break;
+        }
+}
+
+static void check_exports(struct module *mod)
 {
         struct symbol *s, *exp;
 
         for (s = mod->unres; s; s = s->next) {
                 const char *basename;
-                if (mod->gpl_compatible == 1) {
-                        /* GPL-compatible modules may use all symbols */
-                        continue;
-                }
                 exp = find_symbol(s->name);
                 if (!exp || exp->module == mod)
                         continue;
                 basename = strrchr(mod->name, '/');
                 if (basename)
                         basename++;
-                switch (exp->export) {
-                        case export_gpl:
-                                fatal("modpost: GPL-incompatible module %s "
-                                      "uses GPL-only symbol '%s'\n",
-                                 basename ? basename : mod->name,
-                                exp->name);
-                                break;
-                        case export_gpl_future:
-                                warn("modpost: GPL-incompatible module %s "
-                                      "uses future GPL-only symbol '%s'\n",
-                                      basename ? basename : mod->name,
-                                      exp->name);
-                                break;
-                        case export_plain: /* ignore */ break;
-                        case export_unknown: /* ignore */ break;
-                }
+                else
+                        basename = mod->name;
+                if (!mod->gpl_compatible)
+                        check_for_gpl_usage(exp->export, basename, exp->name);
+                check_for_unused(exp->export, basename, exp->name);
         }
 }
 
@@ -1399,7 +1438,7 @@ int main(int argc, char **argv)
         for (mod = modules; mod; mod = mod->next) {
                 if (mod->skip)
                         continue;
-                check_license(mod);
+                check_exports(mod);
         }
 
         for (mod = modules; mod; mod = mod->next) {
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 2b00c6062844..d398c61e55ef 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -117,7 +117,9 @@ struct elf_info {
         Elf_Sym      *symtab_start;
         Elf_Sym      *symtab_stop;
         Elf_Section  export_sec;
+        Elf_Section  export_unused_sec;
         Elf_Section  export_gpl_sec;
+        Elf_Section  export_unused_gpl_sec;
         Elf_Section  export_gpl_future_sec;
         const char   *strtab;
         char         *modinfo;