title: Handling ARM TrustZones
body: <p>ARM has something called TrustZone.
  As per ARM documentation , it gives that a process can run in Secure / Non-Secure World.</p>
  
  <ol>
  <li>What does the Secure / Non-Secure World means.
  Is it related to Processor executing modes or it is related to setting the permissions of    memory regions or something else.</li>
  <li>Is there any relationship between the 7 operating modes of ARM and the Secure / Non-Secure         Worlds.</li>
  <li>How to enable the TrustZone in ARM.</li>
  <li>From Which version of ARM is this introduced.</li>
  <li>Is it mandatory to use this TrustZone.
  Does linux kernel uses this TrustZone extension.</li>
  </ol>
  
  <p>Kindly help me in understanding this.</p>