LibVMI: Simplified Virtual Machine Introspection

LibVMI is a virtual machine introspection library. This means that it helps you access the memory of a running virtual machine. LibVMI provides primatives for accessing this memory using physical or virtual addresses and kernel symbols. LibVMI also supports accessing memory from a physical memory snapshot, which is helpful for debugging or forensic analysis.

LibVMI is designed to run on Linux (file, Xen, or KVM access) or Mac OS X (file access only). The most used platform is Linux + Xen, but the others are well tested and worth exploring as well. LibVMI can provide access to physical memory for any operating system, and access to virtual memory and kernel symbols from Windows and Linux.

If you would like higher level semantic information, then we suggest using LibVMI with PyVMI (python wrapper, included with LibVMI) and Volatility. Volatility (http://code.google.com/p/volatility/) is a forensic memory analysis framework supporting both Linux and Windows systems that can aid significantly in performing useful memory analysis tasks. PyVMI includes a Volatility address space plugin that enables you to use Volatility on a live virtual machine.

This file contains very basic instructions to get you up and running. If you want more details about installation, or programming with LibVMI, then see the documentation included in the doc/ subdirectory of LibVMI, or view the documentation online at http://www.libvmi.com.

Dependencies

The following libraries are used in building this code:

• libxc (from Xen, the Xen Control library, required for Xen support)
• libxenstore (from Xen, access to the xenstore, required for Xen support)
• libvirt (from Red Hat, access to KVM guests, 0.8.7 or newer required for KVM support, MUST BE BUILT WITH QMP SUPPORT -- THIS REQUIRES yajl)
• qemu-kvm patch (option 1 for KVM memory access, optional for KVM support, still buggy but faster than alternative option, see Note 2)
• gdb enabled kvm VM (option 2 for KVM memory access, optional for KVM support, more stable than option 1 but slower, see Note 2)
• yacc OR bison (for reading the configuration file)
• lex OR flex (for reading the configuration file)
• glib (version 2.22 or better is required)

Note 1: If you are installing a packaged version of Xen, you will likely need to install something like 'xen-devel' to obtain the files needed from libxc and libxenstore in the dependencies listed above.

Note 2: If you want KVM support then you will need to build your own version of QEMU-KVM or enable GDB support for your VM. See the section on KVM support (below) for additional information.

Installation and Configuration

For complete details on installation and configuration, please see the related online documentation:

http://code.google.com/p/vmitools/wiki/LibVMIInstallation

Python Interface

LibVMI is written in C. If you would rather work with Python, then look at the tools/pyvmi/ directory after installing LibVMI. PyVMI provides a feature complete python interface to LibVMI with a relatively small performance overhead.

Xen Support

If you would like LibVMI to work on Xen domains, you must simply ensure that you have Xen installed along with any Xen development packages. LibVMI should effectively just work on any recent version of Xen.

KVM Support

If you would like LibVMI to work on KVM VM's, you must do some additional setup. This is because KVM doesn't have much built-in capability for introspection. For KVM support you need to do the following:

• Ensure that you have libvirt version 0.8.7 or newer

• Ensure that your libvirt installation supports QMP commands, most prepackaged versions do not support this by default so you may need to install libvirt from source yourself. To enable QMP support when installing from source, ensure that you have libyajl-dev (or the equivalent from your linux distro) installed, then run the configure script from libvirt. Ensure that the configure script reports that it found yajl. Then run make && make install.

• Choose a memory access technique:

  1. Patch QEMU-KVM with the provided patch. This technique will provide the fastest memory access, but is buggy and may cause your VM to crash / lose data / etc. To use this method, follow the instructions in the libvmi/tools/qemu-kvm-patch directory.

  2. Enable GDB access to your KVM VM. This is done by adding '-s' to the VM creation line or, by modifying the VM XML definition used by libvirt as follows:

     • Change:

       <domain type='kvm'>
       

       to:

       <domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
       

     • Add:

       <qemu:commandline>
         <qemu:arg value='-s'/>
       </qemu:commandline>
       

       under the <domain> level of the XML.

• You only need one memory access technique. LibVMI will first look for the QEMU-KVM patch and use that if it is installed. Otherwise it will fall back to using GDB. So if you want to use GDB, you should both enable GDB and ensure that QEMU-KVM does not have the LibVMI patch.

File / Snapshot Support

If you would like LibVMI to work on physical memory snapshots saved to a file, then you don't need any special setup.

Building

LibVMI uses the standard GNU build system. To compile this library, simply follow the steps below:

./autogen.sh
./configure
make

The example code will work without installing LibVMI. However, you may choose to install the library into the prefix specified to 'configure' by:

make install

The default installation prefix is /usr/local. You may need to run 'ldconfig' after performing a 'make install'.

Transition from XenAccess

If you are just making the transition form XenAccess, please see the transition documentation online:

http://code.google.com/p/vmitools/wiki/TransitionFromXenAccess