Overview
========

Dune is a system that lets you safely run applications in Ring 0 by using
hardware virtualization.  This lets applications access privileged CPU features
and do things like change their own page table, register interrupt handlers and
more, while still being able to perform normal system calls.  More information
is available here:

	http://dune.scs.stanford.edu/

Dune has two components:

1.  A kernel module to enable virtualization (kern)
2.  A utility library to help with using Dune (libdune)

We also provide an optional patched glibc (eglibc-2.14). It slightly
improves system call performance by performing a VMCALL directly.
If used, it does not need to be installed globally.

Dune is enabled only on applications that call dune_init().  All other
applications on the system remain unaffected.

The directory layout of this archive is as follows:
kern/    -> the Dune kernel module
libdune/ -> the Dune library OS
bench/   -> a series of benchmarks to compare Dune and Linux performance
test/    -> simple test programs and examples
sandbox/ -> a generic implementation for sandboxing untrusted binaries

Requirements
============

* A 64-bit x86 Linux environment
* A recent Intel CPU (we use Nehalem and later) with VT-x support.
* A recent kernel version --- We use 3.0 and later, but earlier versions
  may also work.
* Kernel headers must be installed for the running kernel.

We provide a script called dune_req.sh that will attempt to verify
if these requirements are met.

Setup
=====

# make
# insmod kern/dune.ko
# test/hello

You'll need to be root to load the module. However, applications can use
Dune without running as root; simply change the permission of '/dev/dune'
accordingly.

Another program worth trying after Dune is setup is the Dune benchmark suite.
It can be run with the following command:

# bench/bench_dune

Run the following command to build a faster version of glibc (optional):

# make libc

If eglibc build fails some systems (e.g. Ubuntu) may have incompatible default
CFLAGS set.  Before running the libc build set the following flags.

# setenv CFLAGS "-U_FORTIFY_SOURCE -O2 -fno-stack-protector"

The alternate glibc can be used by prefixing dune apps with the
dune_env.sh script.

Limitations
===========

Dune is fairly far along, but could benefit from better support for signals
and more robust pthread support inside libdune. We're currently working on
these issues.

Programming
===========

1.  Call dune_init() to enter dune mode.  (Link to libdune.)
2.  The application will continue to function as normal.  You can use printf,
    use sockets, access files, etc.
3.  But you can then also perform privileged CPU instructions.

Questions?
==========

Contact us at dune@scs.stanford.edu.

Last edited: 10/05/12