title: Eudyptula Challenge and kernel path
body: <p>I have decided to take the <a href="http://eudyptula-challenge.org/">Eudyptula Challenge</a>.
  After I submitted the first task which is to build a simple "Hello World!" module, I received the following answer.</p>
  
  <blockquote>
    <p>Please read the requirements for the Makefile and allow the module to be
    built against any kernel source tree on the filesystem, not just those
    kernels that happened to be installed in <code>/lib/</code> at some point in time.</p>
  </blockquote>
  
  <p>The requirements are:</p>
  
  <blockquote>
    <p>The Makefile should be able to build the kernel module against the
    source of the currently-running kernel as well as being able to accept
    an arbitrary kernel sources directory from an environment variable.</p>
  </blockquote>
  
  <p>What I am doing is checking whether the environment variable <code>KERNELRELEASE</code> is set. If it is I build the module against</p>
  
  <pre><code>$(KERNELRELEASE)/build  
  </code></pre>
  
  <p>and if it isn't against  </p>
  
  <pre><code>/lib/modules/$(shell uname -r)/build
  </code></pre>
  
  <p>I can't understand why this does not satisfy the requirements of this task.</p>