Have the GDB backend handle ExecutionController cancellation properly

pwndbg/dbg/gdb.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import re
+from asyncio import CancelledError
 from contextlib import nullcontext
 from typing import Any
 from typing import Coroutine
@@ -835,7 +836,7 @@ class GDBProcess(pwndbg.dbg_mod.Process):
                 # We don't need to bother communicating with the coroutine, as
                 # it doesn't yield anything we care about.
                 coroutine.send(None)
-            except StopIteration:
+            except (StopIteration, CancelledError):
                 # We're done.
                 break
 
@@ -845,10 +846,25 @@ class GDBExecutionController(pwndbg.dbg_mod.ExecutionController):
     async def single_step(self):
         gdb.execute("si")
 
+        # Check if the program stopped because of the step we just took. If it
+        # stopped for any other reason, we should propagate a cancellation error
+        # to the task and give it a chance to respond.
+        if "It stopped after being stepped" not in gdb.execute("info program", to_string=True):
+            raise CancelledError()
+
     @override
     async def cont(self, until: pwndbg.dbg_mod.StopPoint):
         gdb.execute("continue")
 
+        # Check if the program stopped because of the breakpoint we were given,
+        # and, just like for the single step, propagate a cancellation error if
+        # it stopped for any other reason.
+        assert isinstance(until, GDBStopPoint)
+        if f"It stopped at breakpoint {until.inner.number}" not in gdb.execute(
+            "info program", to_string=True
+        ):
+            raise CancelledError()
+
 
 # Like in LLDB, we only need a single instance of the execution controller.
 EXECUTION_CONTROLLER = GDBExecutionController()