Add workaround for gdbserver weird bug (#2577)

* add workaround for gdbserver, exception: Remote 'g' packet reply is too long

* Fix workaround for gdbserver, for single events

* cleanup redundant class

* cleanup _inner_handler

pwndbg/gdblib/events.py

@@ -8,12 +8,14 @@ from __future__ import annotations
 
 import sys
 from collections import defaultdict
+from collections import deque
 from enum import Enum
 from enum import auto
 from functools import partial
 from functools import wraps
 from typing import Any
 from typing import Callable
+from typing import Deque
 from typing import Dict
 from typing import List
 from typing import TypeVar
@@ -74,6 +76,61 @@ class StartEvent:
 gdb.events.start = StartEvent()
 
 
+def _is_safe_event_packet():
+    try:
+        gdb.selected_frame()
+    except gdb.error as e:
+        if "Remote 'g' packet reply is too long" in str(e):
+            return False
+    return True
+
+
+def _is_safe_event_thread():
+    try:
+        gdb.newest_frame()
+    except gdb.error as e:
+        if "Selected thread is running" in str(e):
+            return False
+    return True
+
+
+def wrap_safe_event_handler(event_handler: Callable[P, T]) -> Callable[P, T]:
+    """
+    Wraps an event handler to ensure it is only executed when the event is safe.
+    Invalid events are queued and executed later when safe.
+
+    Note: Avoid using `gdb.post_event` because of another bug in gdbserver
+    where the `gdb.newest_frame` function may not work properly.
+
+    Workaround to fix bug in gdbserver: https://github.com/pwndbg/pwndbg/issues/2576
+    """
+    queued_invalid_events: Deque[Callable[..., Any]] = deque()
+
+    def _loop_until_thread_ok():
+        if not queued_invalid_events:
+            return
+
+        if not _is_safe_event_thread():
+            gdb.post_event(_loop_until_thread_ok)
+            return
+
+        while queued_invalid_events:
+            queued_invalid_events.popleft()()
+
+    @wraps(event_handler)
+    def _inner_handler(*a: P.args, **kw: P.kwargs):
+        if _is_safe_event_packet():
+            while queued_invalid_events:
+                queued_invalid_events.popleft()()
+            event_handler(*a, **kw)
+            return
+
+        queued_invalid_events.append(lambda: event_handler(*a, **kw))
+        gdb.post_event(_loop_until_thread_ok)
+
+    return _inner_handler
+
+
 class HandlerPriority(Enum):
     """
     A priority level for an event handler, ordered from highest to lowest priority.
@@ -143,6 +200,10 @@ def connect(
     registered[event_handler].setdefault(priority, []).append(caller)
     if event_handler not in connected:
         handle = partial(invoke_event, event_handler)
+
+        if event_handler == gdb.events.new_objfile:
+            handle = wrap_safe_event_handler(handle)
+
         event_handler.connect(handle)
         connected[event_handler] = handle
     return func