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>

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 6541166..dfde0e8 100644 (file)
--- 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 2b00c60..d398c61 100644 (file)
--- 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;