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<title>Debugging with GDB: Trace File Format</title>
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<a name="Trace-File-Format"></a>
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<p>
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Next: <a href="Index-Section-Format.html#Index-Section-Format" accesskey="n" rel="next">Index Section Format</a>, Previous: <a href="Operating-System-Information.html#Operating-System-Information" accesskey="p" rel="prev">Operating System Information</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<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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<a name="Trace-File-Format-1"></a>
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<h2 class="appendix">Appendix I Trace File Format</h2>
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<a name="index-trace-file-format"></a>
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<p>The trace file comes in three parts: a header, a textual description
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section, and a trace frame section with binary data.
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</p>
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<p>The header has the form <code>\x7fTRACE0\n</code>. The first byte is
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<code>0x7f</code> so as to indicate that the file contains binary data,
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while the <code>0</code> is a version number that may have different values
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in the future.
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</p>
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<p>The description section consists of multiple lines of <small>ASCII</small> text
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separated by newline characters (<code>0xa</code>). The lines may include a
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variety of optional descriptive or context-setting information, such
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as tracepoint definitions or register set size. <small>GDB</small> will
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ignore any line that it does not recognize. An empty line marks the end
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of this section.
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</p>
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<dl compact="compact">
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<dt><code>R <var>size</var></code></dt>
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<dd><p>Specifies the size of a register block in bytes. This is equal to the
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size of a <code>g</code> packet payload in the remote protocol. <var>size</var>
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is an ascii decimal number. There should be only one such line in
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a single trace file.
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</p>
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</dd>
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<dt><code>status <var>status</var></code></dt>
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<dd><p>Trace status. <var>status</var> has the same format as a <code>qTStatus</code>
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remote packet reply. There should be only one such line in a single trace
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file.
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</p>
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</dd>
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<dt><code>tp <var>payload</var></code></dt>
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<dd><p>Tracepoint definition. The <var>payload</var> has the same format as
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<code>qTfP</code>/<code>qTsP</code> remote packet reply payload. A single tracepoint
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may take multiple lines of definition, corresponding to the multiple
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reply packets.
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</p>
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</dd>
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<dt><code>tsv <var>payload</var></code></dt>
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<dd><p>Trace state variable definition. The <var>payload</var> has the same format as
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<code>qTfV</code>/<code>qTsV</code> remote packet reply payload. A single variable
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may take multiple lines of definition, corresponding to the multiple
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reply packets.
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</p>
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</dd>
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<dt><code>tdesc <var>payload</var></code></dt>
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<dd><p>Target description in XML format. The <var>payload</var> is a single line of
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the XML file. All such lines should be concatenated together to get
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the original XML file. This file is in the same format as <code>qXfer</code>
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<code>features</code> payload, and corresponds to the main <code>target.xml</code>
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file. Includes are not allowed.
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</p>
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</dd>
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</dl>
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<p>The trace frame section consists of a number of consecutive frames.
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Each frame begins with a two-byte tracepoint number, followed by a
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four-byte size giving the amount of data in the frame. The data in
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the frame consists of a number of blocks, each introduced by a
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character indicating its type (at least register, memory, and trace
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state variable). The data in this section is raw binary, not a
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hexadecimal or other encoding; its endianness matches the target’s
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endianness.
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</p>
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<dl compact="compact">
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<dt><code>R <var>bytes</var></code></dt>
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<dd><p>Register block. The number and ordering of bytes matches that of a
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<code>g</code> packet in the remote protocol. Note that these are the
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actual bytes, in target order, not a hexadecimal encoding.
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</p>
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</dd>
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<dt><code>M <var>address</var> <var>length</var> <var>bytes</var>...</code></dt>
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<dd><p>Memory block. This is a contiguous block of memory, at the 8-byte
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address <var>address</var>, with a 2-byte length <var>length</var>, followed by
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<var>length</var> bytes.
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</p>
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</dd>
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<dt><code>V <var>number</var> <var>value</var></code></dt>
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<dd><p>Trace state variable block. This records the 8-byte signed value
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<var>value</var> of trace state variable numbered <var>number</var>.
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</p>
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</dd>
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</dl>
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<p>Future enhancements of the trace file format may include additional types
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of blocks.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Index-Section-Format.html#Index-Section-Format" accesskey="n" rel="next">Index Section Format</a>, Previous: <a href="Operating-System-Information.html#Operating-System-Information" accesskey="p" rel="prev">Operating System Information</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<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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