SVA: Secure Virtual Architecture

Introduction:

This is the open-source release of the Secure Virtual Architecture (SVA). SVA creates an extended version of the LLVM IR that is capable of supporting a commodity operating system kernel (such as FreeBSD and Linux). By controlling the expression of operating system code, SVA can reliably control operating system kernel behavior through compiler instrumentation.

This release is the second version of SVA that works on 64-bit x86 systems and supports FreeBSD 9.0. It contains the source code for KCoFI (for enforcing control-flow integrity) and Virtual Ghost (which protects applications from a compromised operating system kernel).

License:

The file LICENSE.TXT describes the licenses under which the source code is covered.

Authors:

The file CREDITS.TXT lists individual authors of the SVA source code.

Source Code Layout:

SVAOS: The source code for the SVA-OS run-time library that implements the SVA-OS instructions.

llvm: The source code for the modified version of LLVM used for compiling the SVA-OS run-time library and the FreeBSD kernel.

freebsd9_patch: A patch that will modify the FreeBSD 9.0 kernel source code to work on SVA.

autoconf: The source code to the AutoConf configure script.

How to Compile SVA:

Given that $SRC_ROOT is the absolute pathname to the SVA source code, do the following:

o Run the configure script in the source tree to create make.conf. If you want to enable the Virtual Ghost features, add the --enable-vg option.

• cd $SRC_ROOT

• ./configure --enable-targets=host --enable-vg

o Change directory to the llvm directory and Build the modified Clang/LLVM compiler. Be sure to use GNU Make (gmake):

• cd llvm ; gmake

o Change directory to the SVA-OS subdirectory and Build the SVA-OS run-time library

• cd ../SVA ; make

o If you do not have write access to /usr/obj, create a directory for storing object files created during the kernel build and set the MAKEOBJDIRPREFIX variable to refer to this directory:

• cd $SRC_ROOT ; mkdir obj

• MAKEOBJDIRPREFIX=$SRC_ROOT/obj

o Download and extract the FreeBSD 9.0 source code:

• fetch ftp://ftp-archive.freebsd.org/pub/FreeBSD-Archive/old-releases/amd64/9.0-RELEASE/src.txz

• xzcat src.txz | tar -xvf -

o Apply the SVA patches to the FreeBSD source code

• cd usr/src

• patch -p1 < ../../freebsd9_patch

o Build the kernel, setting INSTKERNNAME to the name of the kernel

• make buildkernel INSTKERNNAME=svaKernel __MAKE_CONF=$SRC_ROOT/make.conf

o As the root user, install the kernel

• make installkernel INSTKERNNAME=svaKernel __MAKE_CONF=$SRC_ROOT/make.conf

o Build the C library with Ghost Memory support

• cd lib/libc
• make

o As the root user, install the new C library

• make install

o As the root user, compile the programs in the sbin directory and install them

• cd ../..
• cd sbin
• make
• make install

Incremental Kernel Compiles

Once the FreeBSD SVA kernel has been compiled, you can add the following four lines in make.conf to avoid reconfiguring the kernel and to prevent the kernel from being rebuilt from scratch:

NO_KERNELCLEAN=true

NO_KERNELCONFIG=true

NO_KERNELDEPEND=true

NO_KERNELOBJ=true

Note that the FreeBSD Makefiles do not detect when the SVA Clang compiler has been modified. If you modify the compiler, you will need to rebuild the kernel from scratch.

Running the SVA FreeBSD Kernel

The SVA FreeBSD kernel only runs in single-user mode at present. When booting, exit to the boot loader prompt (option 2 by default in the FreeBSD boot loader) and use "boot -s" to boot in single user mode. The name in the examples above is svaKernel.