E.18 Traceframe Info Format

To be able to know which objects in the inferior can be examined when inspecting a tracepoint hit, gdb needs to obtain the list of memory ranges, registers and trace state variables that have been collected in a traceframe.

This list is obtained using the ‘qXfer:traceframe-info:read’ (see qXfer traceframe info read) packet and is an XML document.

gdb must be linked with the Expat library to support XML traceframe info discovery. See Expat.

The top-level structure of the document is shown below:

     <?xml version="1.0"?>
     <!DOCTYPE traceframe-info
               PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
                      "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
     <traceframe-info>
        block...
     </traceframe-info>

Each traceframe block can be either:

• A region of collected memory starting at addr and extending for length bytes from there:

            <memory start="addr" length="length"/>
  

• A block indicating trace state variable numbered number has been collected:

            <tvar id="number"/>
  

The formal DTD for the traceframe info format is given below:

     <!ELEMENT traceframe-info  (memory | tvar)* >
     <!ATTLIST traceframe-info  version CDATA   #FIXED  "1.0">
     
     <!ELEMENT memory        EMPTY>
     <!ATTLIST memory        start   CDATA   #REQUIRED
                             length  CDATA   #REQUIRED>
     <!ELEMENT tvar>
     <!ATTLIST tvar          id      CDATA   #REQUIRED>