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In general, a thread refers to a unit of concurrent execution within a target. Typically, each thread carries its own execution context, so this window provides a means of navigating those contexts. Furthermore, this window provides a means of navigating and managing open traces, much like the static listing provides a means of navigating open programs. The window also plots a timeline showing thread lifespans, and displays a caret which can be used to navigate the current point in time. This window, the Stack window, and the Dynamic Listing window provide a complete trace navigation system.
The trace tab bar is displayed when at least one trace is open. It displays the name of each open trace in a button, where the "current" or "focused" trace is selected. Clicking a tab will select its trace and focus the tool onto it. A trace associated with a live target has a red "recording" icon at its left. If that icon is not present, or has disappeared, the trace is dead or terminated. A "dead" trace can still be manipulated and marked up, but it will not record any new target information.
In most cases, a trace is ephemeral, but occasionally, interesting behavior is observed that is difficult to store as static mark-up. When a trace is no longer needed, it can be closed by right-clicking the tab and selecting "Close Trace." Warning: closing a trace that has not been saved cannot be undone. If you accumulate many unwanted traces, use one of the "Close Others," "Close Dead," or "Close All" actions from the pop-up menu.
Selecting a thread in the table will navigate to (or "activate" or "focus") that thread. Windows which are sensitive to the current thread will update. Notably, the Registers window will display the activated thread's register values. Listing windows with configured location tracking will re-compute that location with the thread's context and navigate to it. The thread timeline plots all recorded threads. Threads which are alive will appear to extend "to the end of time." The threads table displays more detailed information in the following columns:
The user can navigate through time within the current trace by using the caret in the plot column header. There are also actions for "stepping the trace" forward and backward. See the Time window for a way to display and navigate to specific events in the trace's timeline. Note that stepping away from the present will prevent most windows from interacting with the live target. While some components and scripts may interact with the target and record things "into the present," such updates may not appear on screen until the user steps back to the present. Stepping the trace does not affect the target, except that viewing the present requires querying the live target, which can perturb its state.
This action is available when there exists a snapshot previous to the current. It steps the trace backward to the previous snapshot, causing most windows to display the recorded data from the new point in time.
This action is available when there exists a snapshot ahead of the current. It steps the trace forward to the next snapshot, causing most windows to display the recorded data from the new point in time.
This action is available when the current point in time includes emulated steps. It steps the trace backward to the previous tick.
This action is available when a thread is selected. It steps the current thread forward to the next tick, using emulation. Note that emulation does not affect the target. Furthermore, emulation may halt early if it encounters certain instructions or causes an exception.
This toggle is always available and is enabled by default. When first enabled, if the current trace is live, it immediately steps the trace to the present. Furthermore, as long as it is enabled and the current trace is live, whenever the recorder steps forward, the tool steps with it. In most cases, this option should remain on, otherwise stepping the target will not cause any windows to update. Toggling it off then on is a quick way to return to the present after browsing the past.
This toggle is always available and is enabled by default. While enabled, any changes in
navigation coordinates are translated, to the extent possible, and sent to the connected
debugger. This may, for example, issue thread
and/or frame
commands
to GDB so that commands typed into its CLI will refer to the same thread and frame as is
focused in Ghidra. Conversely, any debugger events which indicate a change in focus are
translated, to the extent possible, into navigation coordinates and activated in Ghidra. For
example, if the user issues a frame
command to the CLI of a GDB connection, then
Ghidra will navigate to that same frame.