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17<title>Debugging with GDB: BSD libkvm Interface</title>
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64<a name="BSD-libkvm-Interface"></a>
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66<p>
67Next: <a href="Process-Information.html#Process-Information" accesskey="n" rel="next">Process Information</a>, Up: <a href="Native.html#Native" accesskey="u" rel="up">Native</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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70<a name="BSD-libkvm-Interface-1"></a>
71<h4 class="subsection">21.1.1 BSD libkvm Interface</h4>
72
73<a name="index-libkvm"></a>
74<a name="index-kernel-memory-image"></a>
75<a name="index-kernel-crash-dump"></a>
76
77<p>BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
78interface that provides a uniform interface for accessing kernel virtual
79memory images, including live systems and crash dumps.  <small>GDB</small>
80uses this interface to allow you to debug live kernels and kernel crash
81dumps on many native BSD configurations.  This is implemented as a
82special <code>kvm</code> debugging target.  For debugging a live system, load
83the currently running kernel into <small>GDB</small> and connect to the
84<code>kvm</code> target:
85</p>
86<div class="smallexample">
87<pre class="smallexample">(gdb) <b>target kvm</b>
88</pre></div>
89
90<p>For debugging crash dumps, provide the file name of the crash dump as an
91argument:
92</p>
93<div class="smallexample">
94<pre class="smallexample">(gdb) <b>target kvm /var/crash/bsd.0</b>
95</pre></div>
96
97<p>Once connected to the <code>kvm</code> target, the following commands are
98available:
99</p>
100<dl compact="compact">
101<dd><a name="index-kvm"></a>
102</dd>
103<dt><code>kvm pcb</code></dt>
104<dd><p>Set current context from the <em>Process Control Block</em> (PCB) address.
105</p>
106</dd>
107<dt><code>kvm proc</code></dt>
108<dd><p>Set current context from proc address.  This command isn&rsquo;t available on
109modern FreeBSD systems.
110</p></dd>
111</dl>
112
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