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<a name="AArch64"></a>
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<a name="AArch64-1"></a>
<h4 class="subsection">21.4.1 AArch64</h4>
<a name="index-AArch64-support"></a>

<p>When <small>GDB</small> is debugging the AArch64 architecture, it provides the
following special commands:
</p>
<dl compact="compact">
<dt><code>set debug aarch64</code></dt>
<dd><a name="index-set-debug-aarch64"></a>
<p>This command determines whether AArch64 architecture-specific debugging
messages are to be displayed.
</p>
</dd>
<dt><code>show debug aarch64</code></dt>
<dd><p>Show whether AArch64 debugging messages are displayed.
</p>
</dd>
</dl>

<a name="AArch64-SVE_002e"></a>
<h4 class="subsubsection">21.4.1.1 AArch64 SVE.</h4>
<a name="index-AArch64-SVE_002e"></a>

<p>When <small>GDB</small> is debugging the AArch64 architecture, if the Scalable Vector
Extension (SVE) is present, then <small>GDB</small> will provide the vector registers
<code>$z0</code> through <code>$z31</code>, vector predicate registers <code>$p0</code> through
<code>$p15</code>, and the <code>$ffr</code> register.  In addition, the pseudo register
<code>$vg</code> will be provided.  This is the vector granule for the current thread
and represents the number of 64-bit chunks in an SVE <code>z</code> register.
</p>
<p>If the vector length changes, then the <code>$vg</code> register will be updated,
but the lengths of the <code>z</code> and <code>p</code> registers will not change.  This
is a known limitation of <small>GDB</small> and does not affect the execution of the
target process.
</p>
<a name="AArch64-Pointer-Authentication_002e"></a>
<h4 class="subsubsection">21.4.1.2 AArch64 Pointer Authentication.</h4>
<a name="index-AArch64-Pointer-Authentication_002e"></a>

<p>When <small>GDB</small> is debugging the AArch64 architecture, and the program is
using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
register <code>$lr</code> is pointing to an PAC function its value will be masked.
When GDB prints a backtrace, any addresses that required unmasking will be
postfixed with the marker [PAC].  When using the MI, this is printed as part
of the <code>addr_flags</code> field.
</p>


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