toolchain/share/doc/gdb/BSD-libkvm-Interface.html

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<h4 class="subsection">21.1.1 BSD libkvm Interface</h4>
<p><a name="index-libkvm-1439"></a><a name="index-kernel-memory-image-1440"></a><a name="index-kernel-crash-dump-1441"></a>
BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
interface that provides a uniform interface for accessing kernel virtual
memory images, including live systems and crash dumps. <span class="sc">gdb</span>
uses this interface to allow you to debug live kernels and kernel crash
dumps on many native BSD configurations. This is implemented as a
special <code>kvm</code> debugging target. For debugging a live system, load
the currently running kernel into <span class="sc">gdb</span> and connect to the
<code>kvm</code> target:
<pre class="smallexample"> (gdb) <b>target kvm</b>
</pre>
<p>For debugging crash dumps, provide the file name of the crash dump as an
argument:
<pre class="smallexample"> (gdb) <b>target kvm /var/crash/bsd.0</b>
</pre>
<p>Once connected to the <code>kvm</code> target, the following commands are
available:
<a name="index-kvm-1442"></a>
<dl><dt><code>kvm pcb</code><dd>Set current context from the <dfn>Process Control Block</dfn> (PCB) address.
<br><dt><code>kvm proc</code><dd>Set current context from proc address. This command isn't available on
modern FreeBSD systems.
</dl>
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