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17<title>Debugging with GDB: AArch64</title>
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64<a name="AArch64"></a>
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66<p>
67Next: <a href="i386.html#i386" accesskey="n" rel="next">i386</a>, Up: <a href="Architectures.html#Architectures" accesskey="u" rel="up">Architectures</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="AArch64-1"></a>
71<h4 class="subsection">21.4.1 AArch64</h4>
72<a name="index-AArch64-support"></a>
73
74<p>When <small>GDB</small> is debugging the AArch64 architecture, it provides the
75following special commands:
76</p>
77<dl compact="compact">
78<dt><code>set debug aarch64</code></dt>
79<dd><a name="index-set-debug-aarch64"></a>
80<p>This command determines whether AArch64 architecture-specific debugging
81messages are to be displayed.
82</p>
83</dd>
84<dt><code>show debug aarch64</code></dt>
85<dd><p>Show whether AArch64 debugging messages are displayed.
86</p>
87</dd>
88</dl>
89
90<a name="AArch64-SVE"></a>
91<h4 class="subsubsection">21.4.1.1 AArch64 SVE</h4>
92<a name="index-AArch64-SVE"></a>
93
94<p>When <small>GDB</small> is debugging the AArch64 architecture, if the Scalable Vector
95Extension (SVE) is present, then <small>GDB</small> will provide the vector registers
96<code>$z0</code> through <code>$z31</code>, vector predicate registers <code>$p0</code> through
97<code>$p15</code>, and the <code>$ffr</code> register.  In addition, the pseudo register
98<code>$vg</code> will be provided.  This is the vector granule for the current thread
99and represents the number of 64-bit chunks in an SVE <code>z</code> register.
100</p>
101<p>If the vector length changes, then the <code>$vg</code> register will be updated,
102but the lengths of the <code>z</code> and <code>p</code> registers will not change.  This
103is a known limitation of <small>GDB</small> and does not affect the execution of the
104target process.
105</p>
106<a name="AArch64-Pointer-Authentication"></a>
107<h4 class="subsubsection">21.4.1.2 AArch64 Pointer Authentication</h4>
108<a name="index-AArch64-Pointer-Authentication_002e"></a>
109
110<p>When <small>GDB</small> is debugging the AArch64 architecture, and the program is
111using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
112register <code>$lr</code> is pointing to an PAC function its value will be masked.
113When GDB prints a backtrace, any addresses that required unmasking will be
114postfixed with the marker [PAC].  When using the MI, this is printed as part
115of the <code>addr_flags</code> field.
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