kmodloader: add basic support for builtin modules

Enable parsing of 'modules.builtin' if present, for improved handling of
loadable and builtin modules similar to most other distros. In particular,
this allows 'modprobe' to return success whether a module is loadable or
built-in, a useful feature for consistent presence-testing. For example:

  root@OpenWrt:/# rmmod sch_fq_codel
  module is builtin

  root@OpenWrt:/# modinfo sch_cake
  filename:       /lib/modules/6.1.65/sch_cake.ko
  license:        Dual BSD/GPL
  depends:
  intree:         Y
  name:           sch_cake
  vermagic:       6.1.65 SMP mod_unload MIPS32_R2 32BIT

  root@OpenWrt:/# modprobe sch_fq_codel && echo SUCCESS || echo FAIL
  SUCCESS
  root@OpenWrt:/# modprobe sch_cake && echo SUCCESS || echo FAIL
  SUCCESS

Signed-off-by: Tony Ambardar <itugrok@yahoo.com>

diff --git a/kmodloader.c b/kmodloader.c
index 8d06ff15a5fa2dadda8fcda3ea69b6e7350f9f18..179517edd21bdb1dc51a206222a2042d1f7f7afd 100644 (file)
--- a/kmodloader.c
+++ b/kmodloader.c
@@ -40,6 +40,7 @@
 #include <libubox/list.h>
 
 #define DEF_MOD_PATH "/modules/%s/"
+#define MOD_BUILTIN "modules.builtin"
 /* duplicated from in-kernel include/linux/module.h */
 #define MODULE_NAME_LEN (64 - sizeof(unsigned long))
 
@@ -51,6 +52,7 @@ struct param {
 };
 
 enum {
+       BUILTIN,
        SCANNED,
        PROBE,
        LOADED,
@@ -439,6 +441,57 @@ out:
        return m;
 }
 
+static int scan_builtin_modules(void)
+{
+       char **p, path[350];
+       size_t buf_len = 0;
+       char *buf = NULL;
+       struct stat st;
+       FILE *fp = NULL;
+       int rv = -1;
+
+       if (!module_folders && init_module_folders())
+               goto err;
+       for (p = module_folders; *p; p++) {
+               snprintf(path, sizeof(path), "%s%s", *p, MOD_BUILTIN);
+               if (!stat(path, &st) && S_ISREG(st.st_mode)) {
+                       fp = fopen(path, "r");
+                       if (fp)
+                               break;
+               }
+       }
+       if (!fp)
+               goto out;       /* OK if modules.builtin unavailable */
+
+       while (getline(&buf, &buf_len, fp) > 0) {
+               struct module *m;
+               char *name;
+
+               name = get_module_name(buf);
+               if (!name)
+                       continue;
+               m = find_module(name);
+               if (m && !strcmp(m->name, name)) {
+                       ULOG_WARN("found duplicate builtin module %s\n", name);
+                       continue;
+               }
+               m = alloc_module(name, NULL, 0, NULL, 0);
+               if (!m) {
+                       ULOG_ERR("failed to allocate memory for module\n");
+                       goto err;
+               }
+
+               m->state = BUILTIN;
+       }
+out:
+       rv = 0;
+err:
+       free(buf);
+       fclose(fp);
+
+       return rv;
+}
+
 static int scan_module_folder(const char *dir)
 {
        int gl_flags = GLOB_NOESCAPE | GLOB_MARK;
@@ -856,12 +909,19 @@ static int main_rmmod(int argc, char **argv)
        if (scan_loaded_modules())
                return -1;
 
+       if (scan_builtin_modules())
+               return -1;
+
        name = get_module_name(argv[1]);
        m = find_module(name);
        if (!m) {
                ULOG_ERR("module is not loaded\n");
                return -1;
        }
+       if (m->state == BUILTIN) {
+               ULOG_ERR("module is builtin\n");
+               return -1;
+       }
        ret = syscall(__NR_delete_module, m->name, 0);
 
        if (ret)
@@ -975,6 +1035,9 @@ static int main_modprobe(int argc, char **argv)
        if (scan_loaded_modules())
                return -1;
 
+       if (scan_builtin_modules())
+               return -1;
+
        do {
                char *name;
 
@@ -987,6 +1050,9 @@ static int main_modprobe(int argc, char **argv)
                } else if (m && m->state == LOADED) {
                        if (!quiet)
                                ULOG_INFO("%s is already loaded\n", name);
+               } else if (m && m->state == BUILTIN) {
+                       if (!quiet)
+                               ULOG_INFO("%s is builtin\n", name);
                } else if (!m) {
                        if (!quiet)
                                ULOG_ERR("failed to find a module named %s\n", name);