title: Why use Push/Pop instead of Mov to put a number in a register in shellcode?
body: <p>I have some sample code from a shell code payload showing a for loop and using push/pop to set the counter:</p>
  
  <pre><code>push 9
  pop ecx
  </code></pre>
  
  <p>Why can it not just use mov?</p>
  
  <pre><code>mov ecx, 9
  </code></pre>