title: Difference betwee vsdo and vsyscall
body: <p>I am try to understand the mechanism used by Linux to invoke a system call. In particular, I am struggling to understand the VSDO mechanism. Can it be used to invoke all system calls? And what the difference between the vsdo  page and vsyscall page within the process memory? are they always there? </p>
  
  <p>For example using cat /proc/self/maps : </p>
  
  <pre><code>7fff32938000-7fff32939000 r-xp 00000000 00:00 0                          [vdso]
  ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
  </code></pre>
  
  <p>Best, </p>