Add shared subtree support, suggested by Vladimir Dronnikov. Also break out a

few new (unfinished) config options, which I intend to make hidden (but
enabled) when CONFIG_NITPICK is disabled.  Getting the .config infrastructure
to do that is non-obvious, it seems...

5 files changed, 107 insertions, 57 deletions

diff --git a/include/libbb.h b/include/libbb.h
index 745f8372b..963a0290c 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -407,7 +407,7 @@ extern const char * const bb_default_login_shell;
 #define DEFAULT_SHELL_SHORT_NAME     (bb_default_login_shell+6)
 
 
-extern const char bb_path_mtab_file[];
+extern char bb_path_mtab_file[];
 
 extern int bb_default_error_retval;
 
diff --git a/include/platform.h b/include/platform.h
index 8890d4ffd..ca6f3634f 100644
--- a/include/platform.h
+++ b/include/platform.h
@@ -228,6 +228,35 @@ typedef unsigned long long int  uintmax_t;
 
 #if defined(__linux__)
 #include <sys/mount.h>
+// Make sure we have all the new mount flags we actually try to use.
+#ifndef MS_BIND
+#define MS_BIND        (1<<12)
+#endif
+#ifndef MS_MOVE
+#define MS_MOVE        (1<<13)
+#endif
+#ifndef MS_RECURSIVE
+#define MS_RECURSIVE   (1<<14)
+#endif
+#ifndef MS_SILENT
+#define MS_SILENT      (1<<15)
+#endif
+
+// The shared subtree stuff, which went in around 2.6.15
+#ifndef MS_UNBINDABLE
+#define MS_UNBINDABLE  (1<<17)
+#endif
+#ifndef MS_PRIVATE
+#define MS_PRIVATE     (1<<18)
+#endif
+#ifndef MS_SLAVE
+#define MS_SLAVE       (1<<19)
+#endif
+#ifndef MS_SHARED
+#define MS_SHARED      (1<<20)
+#endif
+
+ 
 #if !defined(BLKSSZGET)
 #define BLKSSZGET _IO(0x12, 104)
 #endif
diff --git a/libbb/mtab_file.c b/libbb/mtab_file.c
index 3821a6806..92bd2394f 100644
--- a/libbb/mtab_file.c
+++ b/libbb/mtab_file.c
@@ -13,8 +13,5 @@
 
 /* Busybox mount uses either /proc/mounts or /etc/mtab to
  * get the list of currently mounted filesystems */
-#if defined(CONFIG_FEATURE_MTAB_SUPPORT)
-const char bb_path_mtab_file[] = "/etc/mtab";
-#else
-const char bb_path_mtab_file[] = "/proc/mounts";
-#endif
+char bb_path_mtab_file[] =      USE_FEATURE_MTAB_SUPPORT("/etc/mtab")
+                                                        SKIP_FEATURE_MTAB_SUPPORT("/proc/mounts");
diff --git a/util-linux/Config.in b/util-linux/Config.in
index 65d670824..2222e5c38 100644
--- a/util-linux/Config.in
+++ b/util-linux/Config.in
@@ -370,7 +370,24 @@ config CONFIG_FEATURE_MOUNT_NFS
         default n
         depends on CONFIG_MOUNT
         help
-         Enable mounting of NFS file systems.
+          Enable mounting of NFS file systems.
+
+config CONFIG_FEATURE_MOUNT_FLAGS
+        depends on CONFIG_MOUNT
+        bool "Support lots of -o flags in mount."
+        default y
+        help
+          Without this, mount only supports ro/rw/remount.  With this, it
+          supports nosuid, suid, dev, nodev, exec, noexec, sync, async, atime,
+          noatime, diratime, nodiratime, loud, bind, move, shared, slave,
+          private, unbindable, rshared, rslave, rprivate, and runbindable.
+
+config CONFIG_FEATURE_MOUNT_FSTAB
+        depends on CONFIG_MOUNT
+        bool "Support /etc/fstab and -a"
+        default y
+        help
+          Support mount all and looking for files in /etc/fstab.
 
 config CONFIG_PIVOT_ROOT
         bool "pivot_root"
diff --git a/util-linux/mount.c b/util-linux/mount.c
index d5d3eae17..5d5f487c2 100644
--- a/util-linux/mount.c
+++ b/util-linux/mount.c
@@ -25,17 +25,6 @@
 #include "busybox.h"
 #include <mntent.h>
 
-// These two aren't always defined in old headers
-#ifndef MS_BIND
-#define MS_BIND         4096
-#endif
-#ifndef MS_MOVE
-#define MS_MOVE         8192
-#endif
-#ifndef MS_SILENT
-#define MS_SILENT       32768
-#endif
-
 // Not real flags, but we want to be able to check for this.
 #define MOUNT_NOAUTO    (1<<29)
 #define MOUNT_SWAP      (1<<30)
@@ -43,40 +32,59 @@
  * flags */
 
 struct {
-        const char *name;
+        char *name;
         long flags;
-} static const mount_options[] = {
-        // NOP flags.
-
-        {"loop", 0},
-        {"defaults", 0},
-        {"quiet", 0},
-
-        // vfs flags
-
-        {"ro", MS_RDONLY},
-        {"rw", ~MS_RDONLY},
-        {"nosuid", MS_NOSUID},
-        {"suid", ~MS_NOSUID},
-        {"dev", ~MS_NODEV},
-        {"nodev", MS_NODEV},
-        {"exec", ~MS_NOEXEC},
-        {"noexec", MS_NOEXEC},
-        {"sync", MS_SYNCHRONOUS},
-        {"async", ~MS_SYNCHRONOUS},
-        {"atime", ~MS_NOATIME},
-        {"noatime", MS_NOATIME},
-        {"diratime", ~MS_NODIRATIME},
-        {"nodiratime", MS_NODIRATIME},
-        {"loud", ~MS_SILENT},
-
-        // action flags
-
-        {"remount", MS_REMOUNT},
-        {"bind", MS_BIND},
-        {"move", MS_MOVE},
-        {"noauto",MOUNT_NOAUTO},
-        {"swap",MOUNT_SWAP}
+} static mount_options[] = {
+        // MS_FLAGS set a bit.  ~MS_FLAGS disable that bit.  0 flags are NOPs.
+
+        USE_FEATURE_MOUNT_LOOP(
+                {"loop", 0},
+        )
+
+        USE_FEATURE_MOUNT_FSTAB(
+                {"defaults", 0},
+                {"quiet", 0},
+                {"noauto",MOUNT_NOAUTO},
+                {"swap",MOUNT_SWAP},
+        )
+
+        USE_FEATURE_MOUNT_FLAGS(
+                // vfs flags
+                {"nosuid", MS_NOSUID},
+                {"suid", ~MS_NOSUID},
+                {"dev", ~MS_NODEV},
+                {"nodev", MS_NODEV},
+                {"exec", ~MS_NOEXEC},
+                {"noexec", MS_NOEXEC},
+                {"sync", MS_SYNCHRONOUS},
+                {"async", ~MS_SYNCHRONOUS},
+                {"atime", ~MS_NOATIME},
+                {"noatime", MS_NOATIME},
+                {"diratime", ~MS_NODIRATIME},
+                {"nodiratime", MS_NODIRATIME},
+                {"loud", ~MS_SILENT},
+
+                // action flags
+
+                {"bind", MS_BIND},
+                {"move", MS_MOVE},
+                {"shared", MS_SHARED},
+                {"slave", MS_SLAVE},
+                {"private", MS_PRIVATE},
+                {"unbindable", MS_UNBINDABLE},
+                {"rshared", MS_SHARED|MS_RECURSIVE},
+                {"rslave", MS_SLAVE|MS_RECURSIVE},
+                {"rprivate", MS_SLAVE|MS_RECURSIVE},
+                {"runbindable", MS_UNBINDABLE|MS_RECURSIVE},
+        )
+
+        // Always understood.
+
+        {"ro", MS_RDONLY},        // vfs flag
+        {"rw", ~MS_RDONLY},       // vfs flag
+        {"remount", MS_REMOUNT},  // action flag
+
+
 };
 
 /* Append mount options to string */
@@ -225,9 +233,8 @@ static int mount_it_now(struct mntent *mp, int vfsflags, char *filteropts)
 
                 for(i=0; mount_options[i].flags != MS_REMOUNT; i++)
                         if (mount_options[i].flags > 0)
-                                append_mount_options(&(mp->mnt_opts),
-// Shut up about the darn const.  It's not important.  I don't care.
-                                                (char *)mount_options[i].name);
+// Shut up about the darn const.  It's not important.  I don't care.  (char *)
+                                append_mount_options(&(mp->mnt_opts), mount_options[i].name);
 
                 // Remove trailing / (if any) from directory we mounted on
 
@@ -285,8 +292,8 @@ static int singlemount(struct mntent *mp, int ignore_busy)
         // Look at the file.  (Not found isn't a failure for remount, or for
         // a synthetic filesystem like proc or sysfs.)
 
-        if (stat(mp->mnt_fsname, &st));
-        else if (!(vfsflags & (MS_REMOUNT | MS_BIND | MS_MOVE))) {
+        if (!lstat(mp->mnt_fsname, &st) && !(vfsflags & (MS_REMOUNT | MS_BIND | MS_MOVE | MS_SHARED | MS_PRIVATE || MS_SLAVE | MS_UNBINDABLE)))
+        {
                 // Do we need to allocate a loopback device for it?
 
                 if (ENABLE_FEATURE_MOUNT_LOOP && S_ISREG(st.st_mode)) {
@@ -456,7 +463,7 @@ int mount_main(int argc, char **argv)
         // Open either fstab or mtab
 
         if (parse_mount_options(cmdopts,0) & MS_REMOUNT)
-                fstabname = (char *)bb_path_mtab_file;  // Again with the evil const.
+                fstabname = bb_path_mtab_file;  // Again with the evil const (char *).
         else fstabname="/etc/fstab";
 
         if (!(fstab=setmntent(fstabname,"r")))