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<title>Architecture of Linux Kernel | garhve&#x27;s gibberish</title>


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  <div class="title_postpage">Architecture of Linux Kernel</div>
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  <div class="date_postpage">2022-09-03</div>
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      &emsp;<a href="https://blog.garhve.com/tags/linux/">#linux</a>
      
  
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<p>Modern microcontrollers nowadays support at least two privilege levels. Intel/AMD x86-64 family supports 4 levels, whilst ARM (32bit) microcontrollers support up to 7 levels (6 privileged, 1 non-privileged).</p>
<p>Modern operating systems support at least 2 levels:</p>
<ul>
<li><strong>User space</strong>: For applications to run in unprivileged user mode</li>
<li><strong>Kernel space</strong>: For the kernel (and all its components) to run in privileged mode – kernel mode</li>
</ul>
<p>Address of these 2 spaces are separate.</p>
<p>Applications in user mode will auto-linked to glibc(the GNU standard C library). Libraries only available in user mode, kernel mode doesn't have this conception. An application only can through <strong>System call</strong> to access kernel. On the other hand, system calls are the only legal entry point into the kernel space.</p>
<blockquote>
<p>Libraries APIs: man section 3
System calls APIs: man section 2</p>
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<p>to be continue...</p>

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