genode/repos/os/src/server/lx_fs
Norman Feske 5ab1505d43 file system: enhanced file status info
This patch extends the 'File_system::Status',
'File_system::Directory_entry', and the related 'Vfs' types with
the following additional information:

- Distinction between continuous and transactional files (Node_type)
  (issue #3507)
- Readable, writeable, and executable attributes (Node_rwx),
  replacing the former 'mode' bits
  (issue #3030)

The types 'Node_rwx', 'Node_type' are defined twice,
once for the VFS (vfs/types.h) and once for the 'File_system'
session (file_system_session/file_system_session.h).
Similarly, there is a direct correspondance between
'Vfs::Directory_service::Dirent' and 'File_system::Directory_entry'.

This duplication of types follows the existing pattern of keeping the
VFS and file-system session independent from each other.
2019-11-19 14:23:56 +01:00
..
README
directory.h file system: enhanced file status info 2019-11-19 14:23:56 +01:00
file.h file system: enhanced file status info 2019-11-19 14:23:56 +01:00
lx_util.h
main.cc lx_fs: add modification time 2019-11-19 14:17:30 +01:00
node.h lx_fs: add modification time 2019-11-19 14:17:30 +01:00
open_node.h Follow practices suggested by "Effective C++" 2018-01-17 12:14:35 +01:00
symlink.h file system: use Id_space instead of Node_handle_registry 2017-08-17 10:59:43 +02:00
target.mk Build dynamically linked executables by default 2016-12-14 11:22:27 +01:00

README

This directory contains an Genode file-system service to Linux host fs
wrapper.

Configuration
~~~~~~~~~~~~~

Access to the file system can be tailored for each session depending on the
session's label. By default, no permissions are granted to any session.
To selectively permit access to (a part of) the file system, at least one
policy must be defined.

The following configuration illustates the way of how to express policy.

! <config>
!   <!-- constrain sessions according to their labels -->
!   <policy label="noux -> root" root="/" />
!   <policy label="noux -> home" root="/home/user" writeable="yes" />
!   <policy label="noux -> tmp"  root="/tmp"       writeable="yes" />
! </config>

Session-specific access-control policy is expressed via one or more '<policy>'
nodes. At session-creation time, each policy node is matched against the label
of the new session. If the label of a policy node matches, the defined policy
is applied. If multiple policies match, the one with the longest 'label'
attribute (the most specific one) is selected.

A policy node may contain the following attributes. The mandatory 'root'
attribute defines the viewport of the session onto the file system. The
optional 'writeable' attribute grants the permission to modify the file system.


Example
~~~~~~~

To illustrate the use of lx_fs, refer to the 'base-linux/run/lx_fs.run'
script.


Notes
~~~~~

If the Linux file system experiences changes from other processes
'inotify' may help to keep the servers cache up-to-date. This is not
implemented yet.