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| <h3 class="section">E.19 Branch Trace Format</h3> |
| |
| <p><a name="index-branch-trace-format-3636"></a> |
| In order to display the branch trace of an inferior thread, |
| <span class="sc">gdb</span> needs to obtain the list of branches. This list is |
| represented as list of sequential code blocks that are connected via |
| branches. The code in each block has been executed sequentially. |
| |
| <p>This list is obtained using the ‘<samp><span class="samp">qXfer:btrace:read</span></samp>’ |
| (see <a href="qXfer-btrace-read.html#qXfer-btrace-read">qXfer btrace read</a>) packet and is an XML document. |
| |
| <p><span class="sc">gdb</span> must be linked with the Expat library to support XML |
| traceframe info discovery. See <a href="Expat.html#Expat">Expat</a>. |
| |
| <p>The top-level structure of the document is shown below: |
| |
| <pre class="smallexample"> <?xml version="1.0"?> |
| <!DOCTYPE btrace |
| PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN" |
| "http://sourceware.org/gdb/gdb-btrace.dtd"> |
| <btrace> |
| block... |
| </btrace> |
| </pre> |
| <ul> |
| <li>A block of sequentially executed instructions starting at <var>begin</var> |
| and ending at <var>end</var>: |
| |
| <pre class="smallexample"> <block begin="<var>begin</var>" end="<var>end</var>"/> |
| </pre> |
| </ul> |
| |
| <p>The formal DTD for the branch trace format is given below: |
| |
| <pre class="smallexample"> <!ELEMENT btrace (block* | pt) > |
| <!ATTLIST btrace version CDATA #FIXED "1.0"> |
| |
| <!ELEMENT block EMPTY> |
| <!ATTLIST block begin CDATA #REQUIRED |
| end CDATA #REQUIRED> |
| |
| <!ELEMENT pt (pt-config?, raw?)> |
| |
| <!ELEMENT pt-config (cpu?)> |
| |
| <!ELEMENT cpu EMPTY> |
| <!ATTLIST cpu vendor CDATA #REQUIRED |
| family CDATA #REQUIRED |
| model CDATA #REQUIRED |
| stepping CDATA #REQUIRED> |
| |
| <!ELEMENT raw (#PCDATA)> |
| </pre> |
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