1998-04-04 Roland McGrath <roland@baalperazim.frob.com>

	Add support for a "virtual root directory" specified at startup.
	* priv.h (_diskfs_chroot_directory): Declare new variable.
	* opts-std-startup.c (startup_options, parse_startup_opt): New
	string-valued option -C/--directory/--virtual-root/--chroot sets
	_diskfs_chroot_directory.
	* init-startup.c (_diskfs_chroot_directory): New variable.
	(diskfs_startup_diskfs): If that's set, look up the name and
	warp us to that as a virtual root directory.
	* fsys-getroot.c (diskfs_S_fsys_getroot): Initialize new peropen's
	shadow_root_parent to null, and shadow_root to either null or,
	if _diskfs_chroot_directory is set, to diskfs_root_node.

1 files changed, 60 insertions, 15 deletions

diff --git a/libdiskfs/init-startup.c b/libdiskfs/init-startup.c
index d2802db5..3573f8ff 100644
--- a/libdiskfs/init-startup.c
+++ b/libdiskfs/init-startup.c
@@ -1,5 +1,5 @@
 /* diskfs_startup_diskfs -- advertise our fsys control port to our parent FS.
-   Copyright (C) 1994, 1995, 1996 Free Software Foundation
+   Copyright (C) 1994, 1995, 1996, 1998 Free Software Foundation
 
 This file is part of the GNU Hurd.
 
@@ -8,7 +8,7 @@ it under the terms of the GNU General Public License as published by
 the Free Software Foundation; either version 2, or (at your option)
 any later version.
 
-The GNU Hurd is distributed in the hope that it will be useful, 
+The GNU Hurd is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
@@ -22,15 +22,62 @@ the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
 #include "priv.h"
 #include <stdio.h>
 #include <string.h>
+#include <fcntl.h>
+#include <error.h>
 #include <hurd/fsys.h>
 #include <hurd/startup.h>
 
+const char *_diskfs_chroot_directory;
+
 mach_port_t
 diskfs_startup_diskfs (mach_port_t bootstrap, int flags)
 {
   mach_port_t realnode;
   struct port_info *newpi;
-  
+
+  if (_diskfs_chroot_directory != NULL)
+    {
+      /* The boot options requested we change to a subdirectory
+	 and treat that as the root of the filesystem.  */
+      error_t err;
+      struct node *np, *old;
+      struct protid *rootpi;
+
+      mutex_lock (&diskfs_root_node->lock);
+
+      /* Create a protid we can use in diskfs_lookup.  */
+      err = diskfs_create_protid (diskfs_make_peropen (diskfs_root_node,
+						       O_READ|O_EXEC, 0),
+				  0, &rootpi);
+      assert_perror (err);
+
+      /* Look up the directory name.  */
+      err = diskfs_lookup (diskfs_root_node, _diskfs_chroot_directory,
+			   LOOKUP, &np, NULL, rootpi);
+      mutex_unlock (&diskfs_root_node->lock);
+      ports_port_deref (rootpi);
+
+      if (err == EAGAIN)
+	error (1, 0, "`--virtual-root=%s' specifies the real root directory",
+	       _diskfs_chroot_directory);
+      else if (err)
+	error (1, err, "`%s' not found", _diskfs_chroot_directory);
+
+      if (!S_ISDIR (np->dn_stat.st_mode))
+	{
+	  mutex_unlock (&np->lock);
+	  error (1, ENOTDIR, "%s", _diskfs_chroot_directory);
+	}
+
+      /* Install this node as the new root, forgetting about the real root
+	 node.  The last essential piece that makes the virtual root work
+	 is in fsys-getroot.c, which sets the first peropen's shadow_root
+	 if _diskfs_chroot_directory is non-null.  */
+      old = diskfs_root_node;
+      diskfs_root_node = np;
+      ports_port_deref (old);
+    }
+
   if (bootstrap != MACH_PORT_NULL)
     {
       errno = ports_create_port (diskfs_control_class, diskfs_port_bucket,
@@ -70,22 +117,22 @@ error_t
 diskfs_S_startup_dosync (mach_port_t handle)
 {
   error_t err = 0;
-  struct port_info *pi 
+  struct port_info *pi
     = ports_lookup_port (diskfs_port_bucket, handle,
 			 diskfs_shutdown_notification_class);
 
   if (!pi)
     return EOPNOTSUPP;
-  
+
   if (! diskfs_readonly)
     {
       /* First start a sync so that if something goes wrong
 	 we at least get this much done. */
       diskfs_sync_everything (0);
       diskfs_set_hypermetadata (0, 0);
-  
+
       rwlock_writer_lock (&diskfs_fsys_lock);
-  
+
       /* Permit all the current RPC's to finish, and then suspend new ones */
       err = ports_inhibit_class_rpcs (diskfs_protid_class);
       if (! err)
@@ -107,7 +154,7 @@ diskfs_S_startup_dosync (mach_port_t handle)
 
 /* This is called when we have an ordinary environment, complete
    with proc and auth ports. */
-void 
+void
 _diskfs_init_completed ()
 {
   startup_t init;
@@ -117,12 +164,12 @@ _diskfs_init_completed ()
   mach_port_t notify;
   char *name;
 
-  /* Contact the startup server and register our shutdown request. 
+  /* Contact the startup server and register our shutdown request.
      If we get an error, print an informational message. */
 
   proc = getproc ();
   assert (proc);
-  
+
   err = ports_create_port (diskfs_shutdown_notification_class,
 			   diskfs_port_bucket, sizeof (struct port_info),
 			   &pi);
@@ -133,17 +180,17 @@ _diskfs_init_completed ()
   mach_port_deallocate (mach_task_self (), proc);
   if (err)
     goto errout;
-  
+
   notify = ports_get_right (pi);
   ports_port_deref (pi);
   asprintf (&name,
 	    "%s %s", program_invocation_short_name, diskfs_disk_name ?: "-");
-  err = startup_request_notification (init, notify, 
+  err = startup_request_notification (init, notify,
 				      MACH_MSG_TYPE_MAKE_SEND, name);
   free (name);
   if (err)
     goto errout;
-  
+
   mach_port_deallocate (mach_task_self (), init);
   return;
 
@@ -151,5 +198,3 @@ _diskfs_init_completed ()
   fprintf (stderr, "Cannot request shutdown notification: %s\n",
 	   strerror (err));
 }
-
-