The VFS trace plugin offers access to Genode's trace session by providing a
file-system that can be mounted at arbitrary location within the VFS of a
component. The file system forms a directory structure that recursively
represents the parent-child relationship of running component. The leave
directories represent the threads within a component. Currently there are three
files for each thread that can be accessed:

:'enable': Start or stops tracing of a thread by write "true" or "false" into
           file.

:'buffer_size': Allows the configuration of the trace-buffer size for the
                thread in the usual Genode format (e.g. 5M, 512K, 1024).

:'trace_buffer': This read only file contains the current content of the trace
                 buffer. Every trace entry can only be read once, after that
                 only new entries appear. "tail -f" can also be used in order to
                 display continuous output.

In order to mount the file system configure the <vfs> of your component as
follow:

! <vfs>
!   <trace ram="16M"/>
! </vfs>

The "ram" attribute is mandatory and configures the quota of the trace-session
in the plugin. It limits the number of thread that can be traced at once.

Limitations:

The plugin retrieves up to 128 running components at load time. There is
currently no support to add or remove components once the plugin has been
started. This implies that components that are started at a later stage will not
appear within the file system.
