18 files changed, 591 insertions, 204 deletions

diff --git a/firmware/SOURCES b/firmware/SOURCES
index a68d10ec76..f1c7621244 100644
--- a/firmware/SOURCES
+++ b/firmware/SOURCES
@@ -238,6 +238,7 @@ common/dircache.c
 common/pathfuncs.c
 common/fdprintf.c
 common/linked_list.c
+common/rb_namespace.c
 common/strcasecmp.c
 common/strcasestr.c
 common/strnatcmp.c
diff --git a/firmware/common/dir.c b/firmware/common/dir.c
index f89129ae34..85e6ff316b 100644
--- a/firmware/common/dir.c
+++ b/firmware/common/dir.c
@@ -27,17 +27,14 @@
 #include "dir.h"
 #include "pathfuncs.h"
 #include "fileobj_mgr.h"
-#include "dircache_redirect.h"
+#include "rb_namespace.h"
 
 /* structure used for open directory streams */
 static struct dirstr_desc
 {
     struct filestr_base stream; /* basic stream info (first!) */
-    struct dirscan_info scan;   /* directory scan cursor */
+    struct ns_scan_info scan;   /* directory scan cursor */
     struct dirent       entry;  /* current parsed entry information */
-#ifdef HAVE_MULTIVOLUME
-    int                 volumecounter; /* counter for root volume entries */
-#endif
 } open_streams[MAX_OPEN_DIRS];
 
 /* check and return a struct dirstr_desc* from a DIR* */
@@ -47,7 +44,7 @@ static struct dirstr_desc * get_dirstr(DIR *dirp)
 
     if (!PTR_IN_ARRAY(open_streams, dir, MAX_OPEN_DIRS))
         dir = NULL;
-    else if (dir->stream.flags & FDO_BUSY)
+    else if (dir->stream.flags & (FDO_BUSY|FD_VALID))
         return dir;
 
     int errnum;
@@ -104,49 +101,6 @@ static struct dirstr_desc * alloc_dirstr(void)
     return NULL;
 }
 
-#ifdef HAVE_MULTIVOLUME
-static int readdir_volume_inner(struct dirstr_desc *dir, struct dirent *entry)
-{
-    /* Volumes (secondary file systems) get inserted into the system root
-     * directory. If the path specified volume 0, enumeration will not
-     * include other volumes, but just its own files and directories.
-     *
-     * Fake special directories, which don't really exist, that will get
-     * redirected upon opendir()
-     */
-    while (++dir->volumecounter < NUM_VOLUMES)
-    {
-        /* on the system root */
-        if (!fat_ismounted(dir->volumecounter))
-            continue;
-
-        get_volume_name(dir->volumecounter, entry->d_name);
-        dir->entry.info.attr    = ATTR_MOUNT_POINT;
-        dir->entry.info.size    = 0;
-        dir->entry.info.wrtdate = 0;
-        dir->entry.info.wrttime = 0;
-        return 1;
-    }
-
-    /* do normal directory entry fetching */
-    return 0;
-}
-#endif /* HAVE_MULTIVOLUME */
-
-static inline int readdir_volume(struct dirstr_desc *dir,
-                                 struct dirent *entry)
-{
-#ifdef HAVE_MULTIVOLUME
-    /* fetch virtual volume entries? */
-    if (dir->volumecounter < NUM_VOLUMES)
-        return readdir_volume_inner(dir, entry);
-#endif /* HAVE_MULTIVOLUME */
-
-    /* do normal directory entry fetching */
-    return 0;
-    (void)dir; (void)entry;
-}
-
 
 /** POSIX interface **/
 
@@ -165,21 +119,13 @@ DIR * opendir(const char *dirname)
     if (!dir)
         FILE_ERROR(EMFILE, RC);
 
-    rc = open_stream_internal(dirname, FF_DIR, &dir->stream, NULL);
+    rc = ns_open_stream(dirname, FF_DIR, &dir->stream, &dir->scan);
     if (rc < 0)
     {
         DEBUGF("Open failed: %d\n", rc);
         FILE_ERROR(ERRNO, RC);
     }
 
-#ifdef HAVE_MULTIVOLUME
-    /* volume counter is relevant only to the system root */
-    dir->volumecounter = rc > 1 ? 0 : INT_MAX;
-#endif /* HAVE_MULTIVOLUME */
-
-    fat_rewind(&dir->stream.fatstr);
-    rewinddir_dirent(&dir->scan);
-
     dirp = (DIR *)dir;
 file_error:
     file_internal_unlock_WRITER();
@@ -204,7 +150,7 @@ int closedir(DIR *dirp)
         FILE_ERROR(EBADF, -2);
     }
 
-    rc = close_stream_internal(&dir->stream);
+    rc = ns_close_stream(&dir->stream);
     if (rc < 0)
         FILE_ERROR(ERRNO, rc * 10 - 3);
 
@@ -222,16 +168,11 @@ struct dirent * readdir(DIR *dirp)
 
     struct dirent *res = NULL;
 
-    int rc = readdir_volume(dir, &dir->entry);
-    if (rc == 0)
-    {
-        rc = readdir_dirent(&dir->stream, &dir->scan, &dir->entry);
-        if (rc < 0)
-            FILE_ERROR(EIO, RC);
-    }
-
+    int rc = ns_readdir_dirent(&dir->stream, &dir->scan, &dir->entry);
     if (rc > 0)
         res = &dir->entry;
+    else if (rc < 0)
+        FILE_ERROR(EIO, RC);
 
 file_error:
     RELEASE_DIRSTR(READER, dir);
@@ -258,13 +199,9 @@ int readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result)
     if (!dir)
         FILE_ERROR_RETURN(ERRNO, -1);
 
-    int rc = readdir_volume(dir, entry);
-    if (rc == 0)
-    {
-        rc = readdir_dirent(&dir->stream, &dir->scan, entry);
-        if (rc < 0)
-            FILE_ERROR(EIO, rc * 10 - 4);
-    }
+    int rc = ns_readdir_dirent(&dir->stream, &dir->scan, entry);
+    if (rc < 0)
+        FILE_ERROR(EIO, rc * 10 - 4);
 
 file_error:
     RELEASE_DIRSTR(READER, dir);
@@ -288,12 +225,7 @@ void rewinddir(DIR *dirp)
     if (!dir)
         FILE_ERROR_RETURN(ERRNO);
 
-    rewinddir_dirent(&dir->scan);
-
-#ifdef HAVE_MULTIVOLUME
-    if (dir->volumecounter != INT_MAX)
-        dir->volumecounter = 0;
-#endif /* HAVE_MULTIVOLUME */
+    ns_dirscan_rewind(&dir->scan);
 
     RELEASE_DIRSTR(READER, dir);
 }
diff --git a/firmware/common/dircache.c b/firmware/common/dircache.c
index 0cdaf1bd4a..cc65d2d540 100644
--- a/firmware/common/dircache.c
+++ b/firmware/common/dircache.c
@@ -2541,13 +2541,10 @@ static ssize_t get_path_sub(int idx, struct get_path_sub_data *data)
         cename = "";
 
     #ifdef HAVE_MULTIVOLUME
+        /* prepend the volume specifier */
         int volume = IF_MV_VOL(-idx - 1);
-        if (volume > 0)
-        {
-            /* prepend the volume specifier for volumes > 0 */
-            cename = alloca(VOL_MAX_LEN+1);
-            get_volume_name(volume, cename);
-        }
+        cename = alloca(VOL_MAX_LEN+1);
+        get_volume_name(volume, cename);
     #endif /* HAVE_MULTIVOLUME */
 
         data->serialhash = dc_hash_serialnum(get_idx_dcvolp(idx)->serialnum,
diff --git a/firmware/common/disk.c b/firmware/common/disk.c
index 98c273b26d..3bd88f66a8 100644
--- a/firmware/common/disk.c
+++ b/firmware/common/disk.c
@@ -27,7 +27,7 @@
 #include "disk_cache.h"
 #include "fileobj_mgr.h"
 #include "dir.h"
-#include "dircache_redirect.h"
+#include "rb_namespace.h"
 #include "disk.h"
 
 
diff --git a/firmware/common/file.c b/firmware/common/file.c
index cb918c6eab..893e475a32 100644
--- a/firmware/common/file.c
+++ b/firmware/common/file.c
@@ -28,7 +28,7 @@
 #include "file.h"
 #include "fileobj_mgr.h"
 #include "disk_cache.h"
-#include "dircache_redirect.h"
+#include "rb_namespace.h"
 #include "string-extra.h"
 
 /**
diff --git a/firmware/common/file_internal.c b/firmware/common/file_internal.c
index fe18f90056..45f412e166 100644
--- a/firmware/common/file_internal.c
+++ b/firmware/common/file_internal.c
@@ -26,9 +26,7 @@
 #include "pathfuncs.h"
 #include "disk_cache.h"
 #include "fileobj_mgr.h"
-#include "dir.h"
-#include "dircache_redirect.h"
-#include "dircache.h"
+#include "rb_namespace.h"
 #include "string-extra.h"
 #include "rbunicode.h"
 
@@ -87,9 +85,10 @@ void file_cache_free(struct filestr_cache *cachep)
 
 /** Stream base APIs **/
 
-static inline void filestr_clear(struct filestr_base *stream)
+static inline void filestr_clear(struct filestr_base *stream,
+                                 unsigned int flags)
 {
-    stream->flags = 0;
+    stream->flags = flags;
     stream->bindp = NULL;
 #if 0
     stream->mtx   = NULL;
@@ -153,7 +152,7 @@ void filestr_discard_cache(struct filestr_base *stream)
 /* Initialize the base descriptor */
 void filestr_base_init(struct filestr_base *stream)
 {
-    filestr_clear(stream);
+    filestr_clear(stream, FD_VALID);
     file_cache_init(&stream->cache);
     stream->cachep = &stream->cache;
 }
@@ -161,7 +160,7 @@ void filestr_base_init(struct filestr_base *stream)
 /* free base descriptor resources */
 void filestr_base_destroy(struct filestr_base *stream)
 {
-    filestr_clear(stream);
+    filestr_clear(stream, 0);
     filestr_free_cache(stream);
 }
 
@@ -293,7 +292,7 @@ struct pathwalk_component
 
 #define WALK_RC_NOT_FOUND    0   /* successfully not found (aid for file creation) */
 #define WALK_RC_FOUND        1   /* found and opened */
-#define WALK_RC_FOUND_ROOT   2   /* found and opened sys/volume root */
+#define WALK_RC_FOUND_ROOT   2   /* found and opened sys root */
 #define WALK_RC_CONT_AT_ROOT 3   /* continue at root level */
 
 /* return another struct pathwalk_component from the pool, or NULL if the
@@ -397,10 +396,10 @@ static int walk_open_info(struct pathwalk *walkp,
 
     /* make open official if not simply probing for presence - must do it here
        or compp->info on stack will get destroyed before it was copied */
-    if (!(callflags & FF_PROBE))
+    if (!(callflags & (FF_PROBE|FF_NOFS)))
         fileop_onopen_internal(stream, &compp->info, callflags);
 
-    return compp->nextp ? WALK_RC_FOUND : WALK_RC_FOUND_ROOT;
+    return compp->attr == ATTR_SYSTEM_ROOT ? WALK_RC_FOUND_ROOT : WALK_RC_FOUND;
 }
 
 /* check the component against the prefix test info */
@@ -507,6 +506,10 @@ walk_path(struct pathwalk *walkp, struct pathwalk_component *compp,
         if (len > MAX_COMPNAME)
             return -ENAMETOOLONG;
 
+        /* no filesystem is mounted here */
+        if (walkp->callflags & FF_NOFS)
+            return -ENOENT;
+
         /* check for "." and ".." */
         if (name[0] == '.')
         {
@@ -575,7 +578,7 @@ int open_stream_internal(const char *path, unsigned int callflags,
         callflags &= ~(FF_INFO | FF_PARENTINFO | FF_CHECKPREFIX);
 
     /* This lets it be passed quietly to directory scanning */
-    stream->flags = callflags & FF_MASK;
+    stream->flags |= callflags & FF_MASK;
 
     struct pathwalk walk;
     walk.path      = path;
@@ -585,80 +588,36 @@ int open_stream_internal(const char *path, unsigned int callflags,
 
     struct pathwalk_component *rootp = pathwalk_comp_alloc(NULL);
     rootp->nextp = NULL;
-    rootp->attr  = ATTR_SYSTEM_ROOT;
-
-#ifdef HAVE_MULTIVOLUME
-    int volume = 0, rootrc = WALK_RC_FOUND;
-#endif /* HAVE_MULTIVOLUME */
 
     while (1)
     {
-        const char *pathptr = walk.path;
- 
-    #ifdef HAVE_MULTIVOLUME
-        /* this seamlessly integrates secondary filesystems into the
-           root namespace (e.g. "/<0>/../../<1>/../foo/." :<=> "/foo") */
-        const char *p;
-        volume = path_strip_volume(pathptr, &p, false);
-        if (!CHECK_VOL(volume))
-        {
-            DEBUGF("No such device or address: %d\n", volume);
-            FILE_ERROR(ENXIO, -2);
-        }
-
-        if (p == pathptr)
-        {
-            /* the root of this subpath is the system root */
-            rootp->attr = ATTR_SYSTEM_ROOT;
-            rootrc = WALK_RC_FOUND_ROOT;
-        }
-        else
-        {
-            /* this subpath specifies a mount point */
-            rootp->attr = ATTR_MOUNT_POINT;
-            rootrc = WALK_RC_FOUND;
-        }
-
-        walk.path = p;
-    #endif /* HAVE_MULTIVOLUME */
-
-        /* set name to start at last leading separator; names of volume
-           specifiers will be returned as "/<fooN>" */
-        rootp->name   = GOBBLE_PATH_SEPCH(pathptr) - 1;
-        rootp->length =
-            IF_MV( rootrc == WALK_RC_FOUND ? p - rootp->name : ) 1;
+        rc = ns_parse_root(walk.path, &rootp->name, &rootp->length);
+        if (rc < 0)
+            break;
 
-        rc = fat_open_rootdir(IF_MV(volume,) &rootp->info.fatfile);
+        rc = ns_open_root(IF_MV(rc,) &walk.callflags, &rootp->info, &rootp->attr);
         if (rc < 0)
-        {
-            /* not mounted */
-            DEBUGF("No such device or address: %d\n", IF_MV_VOL(volume));
-            rc = -ENXIO;
             break;
-        }
 
-        get_rootinfo_internal(&rootp->info);
+        walk.path = rootp->name + rootp->length;
+
         rc = walk_path(&walk, rootp, stream);
         if (rc != WALK_RC_CONT_AT_ROOT)
             break;
     }
 
-    switch (rc)
+    if (rc >= 0)
     {
-    case WALK_RC_FOUND_ROOT:
-        IF_MV( rc = rootrc; )
-    case WALK_RC_NOT_FOUND:
-    case WALK_RC_FOUND:
         /* FF_PROBE leaves nothing for caller to clean up */
-        if (callflags & FF_PROBE)
+        if (walk.callflags & FF_PROBE)
             filestr_base_destroy(stream);
-
-        break;
-
-    default: /* utter, abject failure :`( */
+    }
+    else
+    {
+        /* utter, abject failure :`( */
         DEBUGF("Open failed: rc=%d, errno=%d\n", rc, errno);
         filestr_base_destroy(stream);
-        FILE_ERROR(-rc, -3);
+        FILE_ERROR(-rc, -1);
     }
 
 file_error:
diff --git a/firmware/common/fileobj_mgr.c b/firmware/common/fileobj_mgr.c
index e34a460e10..37452fbbe1 100644
--- a/firmware/common/fileobj_mgr.c
+++ b/firmware/common/fileobj_mgr.c
@@ -20,12 +20,13 @@
  ****************************************************************************/
 #include "config.h"
 #include "system.h"
+#include <errno.h>
 #include "debug.h"
 #include "file.h"
 #include "dir.h"
 #include "disk_cache.h"
 #include "fileobj_mgr.h"
-#include "dircache_redirect.h"
+#include "rb_namespace.h"
 
 /**
  * Manages file and directory streams on all volumes
@@ -34,8 +35,8 @@
  */
 
 
-/* there will always be enough of these for all user handles, thus these
-   functions don't return failure codes */
+/* there will always be enough of these for all user handles, thus most of
+   these functions don't return failure codes */
 #define MAX_FILEOBJS (MAX_OPEN_HANDLES + AUX_FILEOBJS)
 
 /* describes the file as an image on the storage medium */
@@ -84,6 +85,15 @@ static struct ll_head busy_bindings[NUM_VOLUMES];
     for (struct filestr_base *s = STREAM_##what(start); \
          s; s = STREAM_NEXT(s))
 
+/* once a file/directory, always a file/directory; such a change
+   is a bug */
+#define CHECK_FO_DIRECTORY(callflags, fobp) \
+    if (((callflags) ^ (fobp)->flags) & FO_DIRECTORY) \
+    {                                                            \
+        DEBUGF("%s - FO_DIRECTORY flag does not match: %p %u\n", \
+               __func__, (fobp), (callflags));                   \
+    }
+
 
 /* syncs information for the stream's old and new parent directory if any are
    currently opened */
@@ -96,6 +106,10 @@ static void fileobj_sync_parent(const struct file_base_info *infop[],
             continue; /* not directory or removed can't be parent of anything */
 
         struct filestr_base *parentstrp = STREAM_FIRST(fobp);
+
+        if (!parentstrp)
+            continue;
+
         struct fat_file *parentfilep = &parentstrp->infop->fatfile;
 
         for (int i = 0; i < count; i++)
@@ -111,8 +125,7 @@ static void fileobj_sync_parent(const struct file_base_info *infop[],
 }
 
 /* see if this file has open streams and return that fileobj_binding if so,
-   else grab a new one from the free list; returns true if this stream is
-   the only open one */
+   else grab a new one from the free list; returns true if this is new */
 static bool binding_assign(const struct file_base_info *srcinfop,
                            struct fileobj_binding **fobpp)
 {
@@ -123,7 +136,7 @@ static bool binding_assign(const struct file_base_info *srcinfop,
 
         if (fat_file_is_same(&srcinfop->fatfile, &fobp->bind.info.fatfile))
         {
-            /* already has open streams */
+            /* already has open streams/mounts */
             *fobpp = fobp;
             return false;
         }
@@ -143,6 +156,23 @@ static void binding_add_to_free_list(struct fileobj_binding *fobp)
     ll_insert_last(FREE_BINDINGS(), &fobp->bind.node);
 }
 
+static void bind_source_info(const struct file_base_info *srcinfop,
+                             struct fileobj_binding **fobpp)
+{
+    if (!binding_assign(srcinfop, fobpp))
+        return; /* already in use */
+
+    /* is new */
+    (*fobpp)->bind.info = *srcinfop;
+    fileobj_bind_file(&(*fobpp)->bind);
+}
+
+static void release_binding(struct fileobj_binding *fobp)
+{
+    fileobj_unbind_file(&fobp->bind);
+    binding_add_to_free_list(fobp);
+}
+
 /** File and directory internal interface **/
 
 void file_binding_insert_last(struct file_base_binding *bindp)
@@ -169,6 +199,41 @@ void file_binding_remove_next(struct file_base_binding *prevp,
 }
 #endif /* HAVE_DIRCACHE */
 
+/* mounts a file object as a target from elsewhere */
+bool fileobj_mount(const struct file_base_info *srcinfop,
+                   unsigned int callflags,
+                   struct file_base_binding **bindpp)
+{
+    struct fileobj_binding *fobp;
+    bind_source_info(srcinfop, &fobp);
+
+    CHECK_FO_DIRECTORY(callflags, fobp);
+
+    if (fobp->flags & FO_MOUNTTARGET)
+        return false;           /* already mounted */
+
+    fobp->flags |= FDO_BUSY | FO_MOUNTTARGET |
+                   (callflags & FO_DIRECTORY);
+
+    *bindpp = &fobp->bind;
+
+    return true;
+}
+
+/* unmounts the file object and frees it if now unusued */
+void fileobj_unmount(struct file_base_binding *bindp)
+{
+    struct fileobj_binding *fobp = (struct fileobj_binding *)bindp;
+
+    if (!(fobp->flags & FO_MOUNTTARGET))
+        return;                /* not mounted */
+
+    if (STREAM_FIRST(fobp) == NULL)
+        release_binding(fobp); /* no longer in use */
+    else
+        fobp->flags &= ~FO_MOUNTTARGET;
+}
+
 /* opens the file object for a new stream and sets up the caches;
  * the stream must already be opened at the FS driver level and *stream
  * initialized.
@@ -180,10 +245,14 @@ void fileobj_fileop_open(struct filestr_base *stream,
                          const struct file_base_info *srcinfop,
                          unsigned int callflags)
 {
+    /* assign base file information */
     struct fileobj_binding *fobp;
-    bool first = binding_assign(srcinfop, &fobp);
+    bind_source_info(srcinfop, &fobp);
+
+    unsigned int foflags = fobp->flags;
 
     /* add stream to this file's list */
+    bool first = STREAM_FIRST(fobp) == NULL;
     ll_insert_last(&fobp->list, &stream->node);
 
     /* initiate the new stream into the enclave */
@@ -197,27 +266,16 @@ void fileobj_fileop_open(struct filestr_base *stream,
     if (first)
     {
         /* first stream for file */
-        fobp->bind.info = *srcinfop;
-        fobp->flags     = FDO_BUSY | FO_SINGLE |
-                          (callflags & (FO_DIRECTORY|FO_TRUNC));
-        fobp->writers   = 0;
-        fobp->size      = 0;
-
-        fileobj_bind_file(&fobp->bind);
+        fobp->flags   = foflags | FDO_BUSY | FO_SINGLE |
+                        (callflags & (FO_DIRECTORY|FO_TRUNC));
+        fobp->writers = 0;
+        fobp->size    = 0;
     }
     else
     {
         /* additional stream for file */
-        fobp->flags &= ~FO_SINGLE;
-        fobp->flags |= callflags & FO_TRUNC;
-
-        /* once a file/directory, always a file/directory; such a change
-           is a bug */
-        if ((callflags ^ fobp->flags) & FO_DIRECTORY)
-        {
-            DEBUGF("%s - FO_DIRECTORY flag does not match: %p %u\n",
-                   __func__, stream, callflags);
-        }
+        fobp->flags = (foflags & ~FO_SINGLE) | (callflags & FO_TRUNC);
+        CHECK_FO_DIRECTORY(callflags, fobp);
     }
 
     if ((callflags & FD_WRITE) && ++fobp->writers == 1)
@@ -257,12 +315,14 @@ void fileobj_fileop_close(struct filestr_base *stream)
     if (foflags & FO_SINGLE)
     {
        /* last stream for file; close everything */
-        fileobj_unbind_file(&fobp->bind);
-
         if (fobp->writers)
             file_cache_free(&fobp->cache);
 
-        binding_add_to_free_list(fobp); 
+        /* binding must stay valid if something is mounted to here */
+        if (foflags & FO_MOUNTTARGET)
+            fobp->flags = foflags & (FDO_BUSY|FO_DIRECTORY|FO_MOUNTTARGET);
+        else
+            release_binding(fobp);
     }
     else
     {
diff --git a/firmware/common/pathfuncs.c b/firmware/common/pathfuncs.c
index 0935a9a6e3..078c0b6938 100644
--- a/firmware/common/pathfuncs.c
+++ b/firmware/common/pathfuncs.c
@@ -105,7 +105,7 @@ static const unsigned char storage_dec_indexes[STORAGE_NUM_TYPES+1] =
  */
 int path_strip_volume(const char *name, const char **nameptr, bool greedy)
 {
-    int volume = 0;
+    int volume = ROOT_VOLUME;
     const char *t = name;
     int c, v = 0;
 
@@ -114,9 +114,16 @@ int path_strip_volume(const char *name, const char **nameptr, bool greedy)
      * digits within the brackets is parsed as the volume number and of
      * those, only the last ones VOL_MUM_MAX allows.
      */
-    c = *(t = GOBBLE_PATH_SEPCH(t)); /* skip all leading slashes */
+    t = GOBBLE_PATH_SEPCH(t);   /* skip all leading slashes */
+    if (t == name)
+    {
+        volume = -1;            /* relative path; don't know */
+        goto psv_out;
+    }
+
+    c = *t;
     if (c != VOL_START_TOK)     /* missing start token? no volume */
-        goto volume0;
+        goto psv_out;
 
     do
     {
@@ -127,7 +134,7 @@ int path_strip_volume(const char *name, const char **nameptr, bool greedy)
             break;
         case '\0':
         case PATH_SEPCH:        /* no closing bracket; no volume */
-            goto volume0;
+            goto psv_out;
         default:                /* something else; reset volume */
             v = 0;
         }
@@ -137,7 +144,7 @@ int path_strip_volume(const char *name, const char **nameptr, bool greedy)
     if (!(c = *++t))            /* no more path and no '/' is ok */
         ;
     else if (c != PATH_SEPCH)   /* more path and no separator after end */
-        goto volume0;
+        goto psv_out;
     else if (greedy)
         t = GOBBLE_PATH_SEPCH(++t); /* strip remaining separators */
 
@@ -146,7 +153,7 @@ int path_strip_volume(const char *name, const char **nameptr, bool greedy)
 
     volume = v;
     name = t;
-volume0:
+psv_out:
     if (nameptr)
         *nameptr = name;
     return volume;
@@ -157,10 +164,14 @@ volume0:
  */
 int get_volume_name(int volume, char *buffer)
 {
-    if (volume < 0)
+    if (volume < 0 || volume == ROOT_VOLUME)
     {
-        *buffer = '\0';
-        return 0;
+        char *t = buffer;
+        if (volume == ROOT_VOLUME)
+            *t++ = PATH_ROOTCHR;
+
+        *t = '\0';
+        return t - buffer;
     }
 
     volume %= VOL_NUM_MAX; /* as path parser would have it */
@@ -173,6 +184,20 @@ int get_volume_name(int volume, char *buffer)
     return snprintf(buffer, VOL_MAX_LEN + 1, "%c%s%d%c",
                     VOL_START_TOK, voldec, volume, VOL_END_TOK);
 }
+
+/* Returns volume name formatted with the root. Assumes buffer size is at
+ * least {VOL_MAX_LEN}+2 */
+int make_volume_root(int volume, char *buffer)
+{
+    char *t = buffer;
+
+    if (volume >= 0 && volume != ROOT_VOLUME)
+        *t++ = PATH_ROOTCHR;
+
+    t += get_volume_name(volume, t);
+
+    return t - buffer;
+}
 #endif /* HAVE_MULTIVOLUME */
 
 /* Just like path_strip_volume() but strips a leading drive specifier and
diff --git a/firmware/common/rb_namespace.c b/firmware/common/rb_namespace.c
new file mode 100644
index 0000000000..04f92e97af
--- /dev/null
+++ b/firmware/common/rb_namespace.c
@@ -0,0 +1,289 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2017 by Michael Sevakis
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include "config.h"
+#include <errno.h>
+#include "fileobj_mgr.h"
+#include "rb_namespace.h"
+
+#define ROOT_CONTENTS_INDEX  (NUM_VOLUMES)
+#define NUM_ROOT_ITEMS   (NUM_VOLUMES+1)
+
+static uint8_t root_entry_flags[NUM_VOLUMES+1];
+static struct file_base_binding *root_bindp;
+
+static inline unsigned int get_root_item_state(int item)
+{
+    return root_entry_flags[item];
+}
+
+static inline void set_root_item_state(int item, unsigned int state)
+{
+    root_entry_flags[item] = state;
+}
+
+static void get_mount_point_entry(IF_MV(int volume,) struct dirent *entry)
+{
+#ifdef HAVE_MULTIVOLUME
+    get_volume_name(volume, entry->d_name);
+#else /* */
+    strcpy(entry->d_name, PATH_ROOTSTR);
+#endif /* HAVE_MULTIVOLUME */
+
+    /* is dirinfo_native */
+    entry->info.attr    = ATTR_MOUNT_POINT;
+    entry->info.size    = 0;
+    entry->info.wrtdate = 0;
+    entry->info.wrttime = 0;
+}
+
+/* unmount the directory that enumerates into the root namespace */
+static void unmount_item(int item)
+{
+    unsigned int state = get_root_item_state(item);
+    if (!state)
+        return;
+
+    if (state & NSITEM_CONTENTS)
+    {
+        fileobj_unmount(root_bindp);
+        root_bindp = NULL;
+    }
+
+    set_root_item_state(item, 0);
+}
+
+/* mount the directory that enumerates into the root namespace */
+int root_mount_path(const char *path, unsigned int flags)
+{
+#ifdef HAVE_MULTIVOLUME
+    int volume = path_strip_volume(path, NULL, false);
+    if (volume == ROOT_VOLUME)
+        return -EINVAL;
+
+    if (!CHECK_VOL(volume))
+        return -ENOENT;
+#else
+    if (!path_is_absolute(path))
+        return -ENOENT;
+#endif /* HAVE_MULTIVOLUME */
+
+    bool contents = flags & NSITEM_CONTENTS;
+    int item = contents ? ROOT_CONTENTS_INDEX : IF_MV_VOL(volume);
+    unsigned int state = get_root_item_state(item);
+
+    if (state)
+        return -EBUSY;
+
+    if (contents)
+    {
+        /* cache information about the target */
+        struct filestr_base stream;
+        struct path_component_info compinfo;
+
+        int e = errno;
+        int rc = open_stream_internal(path, FF_DIR | FF_PROBE | FF_INFO |
+                                      FF_DEVPATH, &stream, &compinfo);
+        if (rc <= 0)
+        {
+            rc = rc ? -errno : -ENOENT;
+            errno = e;
+            return rc;
+        }
+
+        if (!fileobj_mount(&compinfo.info, FO_DIRECTORY, &root_bindp))
+            return -EBUSY;
+    }
+
+    state = NSITEM_MOUNTED | (flags & (NSITEM_HIDDEN|NSITEM_CONTENTS));
+    set_root_item_state(item, state);
+
+    return 0;
+}
+
+/* inform root that an entire volume is being unmounted */
+void root_unmount_volume(IF_MV_NONVOID(int volume))
+{
+    FOR_EACH_VOLUME(volume, item)
+    {
+    #ifdef HAVE_MULTIVOLUME
+        uint32_t state = get_root_item_state(item);
+        if (state && (volume < 0 || item == volume))
+    #endif /* HAVE_MULTIVOLUME */
+            unmount_item(item);
+    }
+
+    /* if the volume unmounted contains the root directory contents then
+       the contents must also be unmounted */
+#ifdef HAVE_MULTIVOLUME
+    uint32_t state = get_root_item_state(ROOT_CONTENTS_INDEX);
+    if (state && (volume < 0 || BASEINFO_VOL(&root_bindp->info) == volume))
+#endif
+        unmount_item(ROOT_CONTENTS_INDEX);
+}
+
+/* parse the root part of a path */
+int ns_parse_root(const char *path, const char **pathp, uint16_t *lenp)
+{
+    int volume = ROOT_VOLUME;
+
+#ifdef HAVE_MULTIVOLUME
+    /* this seamlessly integrates secondary filesystems into the
+       root namespace (e.g. "/<0>/../../<1>/../foo/." :<=> "/foo") */
+    const char *p;
+    volume = path_strip_volume(path, &p, false);
+    if (volume != ROOT_VOLUME && !CHECK_VOL(volume))
+        return -ENOENT;
+#endif /* HAVE_MULTIVOLUME */
+
+    /* set name to start at last leading separator; name of root will
+     * be returned as "/", volume specifiers as "/<fooN>" */
+    *pathp = GOBBLE_PATH_SEPCH(path) - 1;
+    *lenp  = IF_MV( volume < NUM_VOLUMES ? p - *pathp : ) 1;
+
+#ifdef HAVE_MULTIVOLUME
+    if (*lenp > MAX_COMPNAME+1)
+        return -ENAMETOOLONG;
+#endif
+
+    return volume;
+}
+
+/* open one of the items in the root */
+int ns_open_root(IF_MV(int volume,) unsigned int *callflagsp,
+                 struct file_base_info *infop, uint16_t *attrp)
+{
+    unsigned int callflags = *callflagsp;
+    bool devpath = !!(callflags & FF_DEVPATH);
+#ifdef HAVE_MULTIVOLUME
+    bool sysroot = volume == ROOT_VOLUME;
+    if (devpath && sysroot)
+        return -ENOENT;         /* devpath needs volume spec */
+#else
+    bool sysroot = !devpath;    /* always sysroot unless devpath */
+#endif
+
+    int item = sysroot ? ROOT_CONTENTS_INDEX : IF_MV_VOL(volume);
+    unsigned int state = get_root_item_state(item);
+
+    if (sysroot)
+    {
+        *attrp = ATTR_SYSTEM_ROOT;
+
+        if (state)
+            *infop = root_bindp->info;
+        else
+            *callflagsp = callflags | FF_NOFS;  /* contents not mounted */
+    }
+    else
+    {
+        *attrp = ATTR_MOUNT_POINT;
+
+        if (!devpath && !state)
+            return -ENOENT; /* regular open requires having been mounted */
+
+        if (fat_open_rootdir(IF_MV(volume,) &infop->fatfile) < 0)
+            return -ENOENT; /* not mounted */
+
+        get_rootinfo_internal(infop);
+    }
+
+    return 0;
+}
+
+/* read root directory entries */
+int root_readdir_dirent(struct filestr_base *stream,
+                        struct ns_scan_info *scanp, struct dirent *entry)
+{
+    int rc = 0;
+
+    int item = scanp->item;
+
+    /* skip any not-mounted or hidden items */
+    unsigned int state;
+    while (1)
+    {
+        if (item >= NUM_ROOT_ITEMS)
+            goto file_eod;
+
+        state = get_root_item_state(item);
+        if ((state & (NSITEM_MOUNTED|NSITEM_HIDDEN)) == NSITEM_MOUNTED)
+            break;
+
+        item++;
+    }
+
+    if (item == ROOT_CONTENTS_INDEX)
+    {
+        rc = readdir_dirent(stream, &scanp->scan, entry);
+        if (rc < 0)
+            FILE_ERROR(ERRNO, rc * 10 - 1);
+
+        if (rc == 0)
+            item++;
+    }
+    else
+    {
+        get_mount_point_entry(IF_MV(item,) entry);
+        item++;
+        rc = 1;
+    }
+
+    scanp->item = item;
+
+file_eod:
+    if (rc == 0)
+        empty_dirent(entry);
+
+file_error:
+    return rc;
+}
+
+/* opens a stream to enumerate items in a namespace container */
+int ns_open_stream(const char *path, unsigned int callflags,
+                   struct filestr_base *stream, struct ns_scan_info *scanp)
+{
+    /* stream still needs synchronization even if we don't have a stream */
+    static struct mutex no_contents_mtx SHAREDBSS_ATTR;
+
+    int rc = open_stream_internal(path, callflags, stream, NULL);
+    if (rc < 0)
+        FILE_ERROR(ERRNO, rc * 10 - 1);
+
+    scanp->item = rc > 1 ? 0 : -1;
+
+    if (stream->flags & FDO_BUSY)
+    {
+        /* root contents are mounted */
+        fat_rewind(&stream->fatstr);
+    }
+    else
+    {
+        /* root contents not mounted */
+        mutex_init(&no_contents_mtx);
+        stream->mtx = &no_contents_mtx;
+    }
+
+    ns_dirscan_rewind(scanp);
+
+    rc = 0;
+file_error:
+    return rc;
+}
diff --git a/firmware/export/mv.h b/firmware/export/mv.h
index ec7b2efdbd..5aa0ff8b4d 100644
--- a/firmware/export/mv.h
+++ b/firmware/export/mv.h
@@ -84,6 +84,10 @@
 #define VOL_MAX_LEN      (1 + VOL_DEC_MAX_LEN + 2 + 1)
 #define VOL_NUM_MAX      100
 
+#ifndef ROOT_VOLUME
+#define ROOT_VOLUME      INT_MAX
+#endif
+
 #else /* empty definitions if no multi-volume */
 #define IF_MV(x...)
 #define IF_MV_NONVOID(x...) void
diff --git a/firmware/export/pathfuncs.h b/firmware/export/pathfuncs.h
index 92539c54c1..8858d85d24 100644
--- a/firmware/export/pathfuncs.h
+++ b/firmware/export/pathfuncs.h
@@ -30,10 +30,15 @@
 /* useful char constants that could be reconfigured if desired */
 #define PATH_SEPCH    '/'
 #define PATH_SEPSTR   "/"
+#define PATH_ROOTCHR  '/'
 #define PATH_ROOTSTR  "/"
 #define PATH_BADSEPCH '\\'
 #define PATH_DRVSEPCH ':'
 
+#ifndef ROOT_VOLUME
+#define ROOT_VOLUME   INT_MAX
+#endif
+
 /* a nicer way to check for "." and ".." than two strcmp() calls */
 static inline bool is_dotdir_name(const char *name)
 {
@@ -75,6 +80,7 @@ static inline bool name_is_dot_dot(const char *name)
 #ifdef HAVE_MULTIVOLUME
 int path_strip_volume(const char *name, const char **nameptr, bool greedy);
 int get_volume_name(int volume, char *name);
+int make_volume_root(int volume, char *dst);
 #endif
 
 int path_strip_drive(const char *name, const char **nameptr, bool greedy);
diff --git a/firmware/export/rbpaths.h b/firmware/export/rbpaths.h
index de591f0ec1..458a070f92 100644
--- a/firmware/export/rbpaths.h
+++ b/firmware/export/rbpaths.h
@@ -64,6 +64,9 @@
 #define PLUGIN_DIR          ROCKBOX_DIR "/rocks"
 #define CODECS_DIR          ROCKBOX_DIR "/codecs"
 
+#define RB_ROOT_VOL_HIDDEN(v)   (IF_MV_VOL(v) == 0)
+#define RB_ROOT_CONTENTS_DIR    "/" IF_MV("<0>")
+
 #else /* APPLICATION */
 
 #define HOME_DIR "<HOME>" /* replaced at runtime */
diff --git a/firmware/include/dircache_redirect.h b/firmware/include/dircache_redirect.h
index 9fae16b551..9a8de2fecd 100644
--- a/firmware/include/dircache_redirect.h
+++ b/firmware/include/dircache_redirect.h
@@ -20,7 +20,10 @@
  ****************************************************************************/
 #ifndef _DIRCACHE_REDIRECT_H_
 
+#include "rbpaths.h"
+#include "pathfuncs.h"
 #include "dir.h"
+#include "dircache.h"
 
 /***
  ** Internal redirects that depend upon whether or not dircache is made
@@ -123,10 +126,20 @@ static inline void fileop_onsync_internal(struct filestr_base *stream)
 
 static inline void volume_onmount_internal(IF_MV_NONVOID(int volume))
 {
+#ifdef HAVE_MULTIVOLUME
+    char path[VOL_MAX_LEN+2];
+    make_volume_root(volume, path);
+#else
+    const char *path = PATH_ROOTSTR;
+#endif
+    root_mount_path(path, RB_ROOT_VOL_HIDDEN(volume) ? NSITEM_HIDDEN : 0);
+#ifdef HAVE_MULTIVOLUME
+    if (volume == path_strip_volume(RB_ROOT_CONTENTS_DIR, NULL, false))
+#endif
+        root_mount_path(RB_ROOT_CONTENTS_DIR, NSITEM_CONTENTS);
 #ifdef HAVE_DIRCACHE
     dircache_mount();
 #endif
-    IF_MV( (void)volume; )
 }
 
 static inline void volume_onunmount_internal(IF_MV_NONVOID(int volume))
@@ -135,6 +148,7 @@ static inline void volume_onunmount_internal(IF_MV_NONVOID(int volume))
     /* First, to avoid update of something about to be destroyed anyway */
     dircache_unmount(IF_MV(volume));
 #endif
+    root_unmount_volume(IF_MV(volume));
     fileobj_mgr_unmount(IF_MV(volume));
 }
 
diff --git a/firmware/include/file_internal.h b/firmware/include/file_internal.h
index d62b5a8541..f4bd8bb8c2 100644
--- a/firmware/include/file_internal.h
+++ b/firmware/include/file_internal.h
@@ -72,16 +72,18 @@ enum fildes_and_obj_flags
     /* used in descriptor and common */
     FDO_BUSY       = 0x0001,     /* descriptor/object is in use */
     /* only used in individual stream descriptor */
-    FD_WRITE       = 0x0002,     /* descriptor has write mode */
-    FD_WRONLY      = 0x0004,     /* descriptor is write mode only */
-    FD_APPEND      = 0x0008,     /* descriptor is append mode */
+    FD_VALID       = 0x0002,     /* descriptor is valid but not registered */
+    FD_WRITE       = 0x0004,     /* descriptor has write mode */
+    FD_WRONLY      = 0x0008,     /* descriptor is write mode only */
+    FD_APPEND      = 0x0010,     /* descriptor is append mode */
     FD_NONEXIST    = 0x8000,     /* closed but not freed (uncombined) */
     /* only used as common flags */
-    FO_DIRECTORY   = 0x0010,     /* fileobj is a directory */
-    FO_TRUNC       = 0x0020,     /* fileobj is opened to be truncated */
-    FO_REMOVED     = 0x0040,     /* fileobj was deleted while open */
-    FO_SINGLE      = 0x0080,     /* fileobj has only one stream open */
-    FDO_MASK       = 0x00ff,
+    FO_DIRECTORY   = 0x0020,     /* fileobj is a directory */
+    FO_TRUNC       = 0x0040,     /* fileobj is opened to be truncated */
+    FO_REMOVED     = 0x0080,     /* fileobj was deleted while open */
+    FO_SINGLE      = 0x0100,     /* fileobj has only one stream open */
+    FO_MOUNTTARGET = 0x0200,     /* fileobj kept open as a mount target */
+    FDO_MASK       = 0x03ff,
     FDO_CHG_MASK   = FO_TRUNC,   /* fileobj permitted external change */
     /* bitflags that instruct various 'open' functions how to behave;
      * saved in stream flags (only) but not used by manager */
@@ -95,7 +97,9 @@ enum fildes_and_obj_flags
     FF_CACHEONLY   = 0x00200000, /* succeed only if in dircache */
     FF_INFO        = 0x00400000, /* return info on self */
     FF_PARENTINFO  = 0x00800000, /* return info on parent */
-    FF_MASK        = 0x00ff0000,
+    FF_DEVPATH     = 0x01000000, /* path is a device path, not root-based */
+    FF_NOFS        = 0x02000000, /* no filesystem mounted here */
+    FF_MASK        = 0x03ff0000,
 };
 
 /** Common data structures used throughout **/
diff --git a/firmware/include/fileobj_mgr.h b/firmware/include/fileobj_mgr.h
index 627d2df341..0db3520d34 100644
--- a/firmware/include/fileobj_mgr.h
+++ b/firmware/include/fileobj_mgr.h
@@ -29,6 +29,11 @@ void file_binding_remove(struct file_base_binding *bindp);
 void file_binding_remove_next(struct file_base_binding *prevp,
                               struct file_base_binding *bindp);
 
+bool fileobj_mount(const struct file_base_info *srcinfop,
+                   unsigned int callflags,
+                   struct file_base_binding **bindpp);
+void fileobj_unmount(struct file_base_binding *bindp);
+
 void fileobj_fileop_open(struct filestr_base *stream,
                          const struct file_base_info *srcinfop,
                          unsigned int callflags);
diff --git a/firmware/include/fs_defines.h b/firmware/include/fs_defines.h
index 538c4b36cd..aee6daff6a 100644
--- a/firmware/include/fs_defines.h
+++ b/firmware/include/fs_defines.h
@@ -51,12 +51,19 @@
 /* internal functions open streams as well; make sure they don't fail if all
    user descs are busy; this needs to be at least the greatest quantity needed
    at once by all internal functions */
+/* internal functions open streams as well; make sure they don't fail if all
+   user descs are busy; this needs to be at least the greatest quantity needed
+   at once by all internal functions */
+#define MOUNT_AUX_FILEOBJS 1
+
 #ifdef HAVE_DIRCACHE
-#define AUX_FILEOBJS 3
+#define DIRCACHE_AUX_FILEOBJS 1
 #else
-#define AUX_FILEOBJS 2
+#define DIRCACHE_AUX_FILEOBJS 0
 #endif
 
+#define AUX_FILEOBJS (2+DIRCACHE_AUX_FILEOBJS+MOUNT_AUX_FILEOBJS)
+
 /* number of components statically allocated to handle the vast majority
    of path depths; should maybe be tuned for >= 90th percentile but for now,
    imma just guessing based on something like:
diff --git a/firmware/include/rb_namespace.h b/firmware/include/rb_namespace.h
new file mode 100644
index 0000000000..4d7a125c7b
--- /dev/null
+++ b/firmware/include/rb_namespace.h
@@ -0,0 +1,79 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2017 by Michael Sevakis
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#ifndef RB_NAMESPACE_H
+#define RB_NAMESPACE_H
+
+#include "file_internal.h"
+
+enum ns_item_flags
+{
+    NSITEM_MOUNTED   = 0x01, /* item is mounted */
+    NSITEM_HIDDEN    = 0x02, /* item is not enumerated */
+    NSITEM_CONTENTS  = 0x04, /* contents enumerate */
+};
+
+struct ns_scan_info
+{
+    struct dirscan_info scan; /* dirscan info - first! */
+    int                 item; /* current item in parent */
+};
+
+/* root functions */
+int root_mount_path(const char *path, unsigned int flags);
+void root_unmount_volume(IF_MV_NONVOID(int volume));
+int root_readdir_dirent(struct filestr_base *stream,
+                        struct ns_scan_info *scanp,
+                        struct dirent *entry);
+
+/* namespace functions */
+int ns_parse_root(const char *path, const char **pathp, uint16_t *lenp);
+int ns_open_root(IF_MV(int volume,) unsigned int *callflagsp,
+                 struct file_base_info *infop, uint16_t *attrp);
+int ns_open_stream(const char *path, unsigned int callflags,
+                   struct filestr_base *stream, struct ns_scan_info *scanp);
+
+/* closes the namespace stream */
+static inline int ns_close_stream(struct filestr_base *stream)
+{
+    return close_stream_internal(stream);
+}
+
+#include "dircache_redirect.h"
+
+static inline void ns_dirscan_rewind(struct ns_scan_info *scanp)
+{
+    rewinddir_dirent(&scanp->scan);
+    if (scanp->item != -1)
+        scanp->item = 0;
+}
+
+static inline int ns_readdir_dirent(struct filestr_base *stream,
+                                    struct ns_scan_info *scanp,
+                                    struct dirent *entry)
+
+{
+    if (scanp->item == -1)
+        return readdir_dirent(stream, &scanp->scan, entry);
+    else
+        return root_readdir_dirent(stream, scanp, entry);
+}
+
+#endif /* RB_NAMESPACE_H */
diff --git a/uisimulator/common/filesystem-sim.c b/uisimulator/common/filesystem-sim.c
index 766beb3fda..45483b7172 100644
--- a/uisimulator/common/filesystem-sim.c
+++ b/uisimulator/common/filesystem-sim.c
@@ -309,6 +309,8 @@ int sim_get_os_path(char *buffer, const char *path, size_t bufsize)
 
             const char *next;
             volume = path_strip_volume(p, &next, true);
+            if (volume == ROOT_VOLUME)
+                volume = 0; /* FIXME: root no longer implies volume 0 */
 
             if (next > p)
             {