[PATCH 4/4] Serve mounts node with a passive translator record

[Justus Winter]

Make mounts a node with a passive translator record so that the mtab
translator is started on access if it is available.

* rootdir.c (MTAB_TRANSLATOR): New macro.
(rootdir_mounts_get_translator): New function.
(mtab_translator_state): New enum.
(rootdir_mounts_exists): New function.
(rootdir_translator_make_node): Likewise.
(rootdir_entries): Add "mounts" node.
---
 rootdir.c |   53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/rootdir.c b/rootdir.c
index 31e2d8c..c8ff01d 100644
--- a/rootdir.c
+++ b/rootdir.c
@@ -404,6 +404,37 @@ rootdir_gc_fakeself (void *hook, char **contents, ssize_t 
*contents_len)
   return 0;
 }
 
+/* The mtab translator to use by default for the "mounts" node.  */
+#define MTAB_TRANSLATOR "/hurd/mtab"
+
+static error_t
+rootdir_mounts_get_translator (void *hook, char **argz, size_t *argz_len)
+{
+  static char mtab_argz[] = MTAB_TRANSLATOR "\0/";
+
+  *argz = malloc(sizeof mtab_argz);
+  if (! *argz)
+    return ENOMEM;
+
+  memcpy (*argz, mtab_argz, sizeof mtab_argz);
+  *argz_len = sizeof mtab_argz;
+  return 0;
+}
+
+enum mtab_translator_state {
+  MTAB_FALSE = FALSE,
+  MTAB_TRUE = TRUE,
+  MTAB_UNINITIALIZED,
+};
+
+static int
+rootdir_mounts_exists ()
+{
+  static enum mtab_translator_state state = MTAB_UNINITIALIZED;
+  if (state == MTAB_UNINITIALIZED)
+    state = access(MTAB_TRANSLATOR, F_OK|X_OK) == 0;
+  return state;
+}
 
 /* Glue logic and entries table */
 
@@ -426,6 +457,18 @@ rootdir_symlink_make_node (void *dir_hook, const void 
*entry_hook)
   return np;
 }
 
+static struct node *
+rootdir_translator_make_node (void *dir_hook, const void *entry_hook)
+{
+  struct node *np = procfs_make_node (entry_hook, dir_hook);
+  if (np)
+    {
+      procfs_node_chtype (np, S_IFREG | S_IPTRANS);
+      procfs_node_chmod (np, 0444);
+    }
+  return np;
+}
+
 static const struct procfs_dir_entry rootdir_entries[] = {
   {
     .name = "self",
@@ -487,6 +530,16 @@ static const struct procfs_dir_entry rootdir_entries[] = {
       .cleanup_contents = procfs_cleanup_contents_with_free,
     },
   },
+  {
+    .name = "mounts",
+    .hook = & (struct procfs_node_ops) {
+      .get_translator = rootdir_mounts_get_translator,
+    },
+    .ops = {
+      .make_node = rootdir_translator_make_node,
+      .exists = rootdir_mounts_exists,
+    }
+  },
 #ifdef PROFILE
   /* In order to get a usable gmon.out file, we must apparently use exit(). */
   {
-- 
1.7.10.4