* Implemented support for chroot:

- Added a "root" vnode to the io_context. It is used for resolving
    paths and converting nodes to paths instead of sRoot. Some more
    passing around of io_context structures was necessary.
  - Introduced a new lock sIOContextRootLock to protect
    io_context::root. The current uses of io_context::io_mutex
    (put_vnode(), remove_vnode() while holding it) looked too suspicious
    to use that mutex in vnode_path_to_vnode().
  - Added _kern_change_root() syscall and chroot() libroot function.
  - Added chroot coreutils program to the image. Funnily it seems to be
    much easier to set up a little jail than under Linux (just copy
    bash and libroot.so into respective subdirs; mount another pipefs
    if you want pipe support).
    With Haiku allowing direct access to directories via inode IDs
    jailing is obviously not very secure at the moment.
  - Added /var/empty to the image. It will be the chroot target for ssh.
* Changed vfs.cpp:get_cwd() so that the io_context::io_mutex is no
  longer held when calling dir_vnode_to_path().


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@24673 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/fs/fd.h

@@ -16,6 +16,7 @@ extern "C" {
 #endif
 
 struct file_descriptor;
+struct io_context;
 struct selectsync;
 struct select_info;
 
@@ -28,7 +29,9 @@ struct fd_ops {
 						struct selectsync *sync);
 	status_t	(*fd_deselect)(struct file_descriptor *, uint8 event,
 						struct selectsync *sync);
-	status_t	(*fd_read_dir)(struct file_descriptor *, struct dirent *buffer, size_t bufferSize, uint32 *_count);
+	status_t	(*fd_read_dir)(struct io_context* ioContext,
+						struct file_descriptor *, struct dirent *buffer,
+						size_t bufferSize, uint32 *_count);
 	status_t	(*fd_rewind_dir)(struct file_descriptor *);
 	status_t	(*fd_read_stat)(struct file_descriptor *, struct stat *);
 	status_t	(*fd_write_stat)(struct file_descriptor *, const struct stat *, int statMask);