title: How does kbuild actually work?
body: <p>When i'm developing a linux driver, i've read about how to write linux kbuild makefile through this <a href="https://www.kernel.org/doc/Documentation/kbuild/makefiles.txt">document</a> </p>
  
  <p>I know kbuild system use makefile variables such as obj-y obj-m to determine what to build and how to build.</p>
  
  <p>But what i'm confused about is where does kbuild system really execute build process.In a word, if i have <code>obj-m = a.o</code>, then where does kbuild system parse <code>obj-m</code> and execute <code>gcc a.c</code> ?</p>