Instructions, while ARM uses SMC. Programmatically, they all achieve very
similar results.
-Read more about Trusted Execution Environments `here. <http://www.openvirtualization.org/open-source-arm-trustzone.html>`_
-
`NIST SP800-147 <http://csrc.nist.gov/publications/nistpubs/800-147/NIST-SP800-147-April2011.pdf>`_
, is a guidelines for firmware security, to ensure that the firmware itself is secure.