Traceframe Info Format (Debugging with GDB)

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>