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<h2 class="appendix">Appendix F Trace File Format</h2>

<p><a name="index-trace-file-format-2534"></a>
The trace file comes in three parts: a header, a textual description
section, and a trace frame section with binary data.

   <p>The header has the form <code>\x7fTRACE0\n</code>.  The first byte is
<code>0x7f</code> so as to indicate that the file contains binary data,
while the <code>0</code> is a version number that may have different values
in the future.

   <p>The description section consists of multiple lines of <span class="sc">ascii</span> text
separated by newline characters (<code>0xa</code>).  The lines may include a
variety of optional descriptive or context-setting information, such
as tracepoint definitions or register set size.  <span class="sc">gdb</span> will
ignore any line that it does not recognize.  An empty line marks the end
of this section.

<!-- FIXME add some specific types of data -->
   <p>The trace frame section consists of a number of consecutive frames. 
Each frame begins with a two-byte tracepoint number, followed by a
four-byte size giving the amount of data in the frame.  The data in
the frame consists of a number of blocks, each introduced by a
character indicating its type (at least register, memory, and trace
state variable).  The data in this section is raw binary, not a
hexadecimal or other encoding; its endianness matches the target's
endianness.

<!-- FIXME bi-arch may require endianness/arch info in description section -->
     <dl>
<dt><code>R </code><var>bytes</var><dd>Register block.  The number and ordering of bytes matches that of a
<code>g</code> packet in the remote protocol.  Note that these are the
actual bytes, in target order and <span class="sc">gdb</span> register order, not a
hexadecimal encoding.

     <br><dt><code>M </code><var>address</var> <var>length</var> <var>bytes</var><code>...</code><dd>Memory block.  This is a contiguous block of memory, at the 8-byte
address <var>address</var>, with a 2-byte length <var>length</var>, followed by
<var>length</var> bytes.

     <br><dt><code>V </code><var>number</var> <var>value</var><dd>Trace state variable block.  This records the 8-byte signed value
<var>value</var> of trace state variable numbered <var>number</var>.

   </dl>

   <p>Future enhancements of the trace file format may include additional types
of blocks.

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