[PATCH v3 10/12] btrace, python: Enable calling the ptwrite listener.

[Felix Willgerodt <felix.willgerodt@intel.com>]

Adding a new function to btinfo that allows to call the python ptwrite listener
from inside GDB.

gdb/ChangeLog:
2021-06-14  Felix Willgerodt  <felix.willgerodt@intel.com>

	* btrace.h (btrace_thread_info): New member ptw_callback_fun.
	* python/py-record-btrace.c (recpy_call_listener): New function.
	(recpy_initialize_listener): Save recpy_call_listener in btinfo.
---
 gdb/btrace.h                  |  8 +++++
 gdb/python/py-record-btrace.c | 67 +++++++++++++++++++++++++++++++++++
 gdb/python/py-record-btrace.h |  5 +++
 3 files changed, 80 insertions(+)

diff --git a/gdb/btrace.h b/gdb/btrace.h
index b15efcd147c..7ca71277372 100644
--- a/gdb/btrace.h
+++ b/gdb/btrace.h
@@ -352,6 +352,14 @@ struct btrace_thread_info
      stepping through the execution history.  */
   std::vector<std::string> aux_data;
 
+  /* Function pointer to the ptwrite callback.  Returns the string returned
+     by the ptwrite listener function or nullptr if no string is supposed to
+     be printed.  */
+  gdb::unique_xmalloc_ptr<char> (*ptw_callback_fun) (
+						const uint64_t *payload,
+						const uint64_t *ip,
+						const void *ptw_listener);
+
   /* PyObject pointer to the ptwrite listener function.  */
   void *ptw_listener = nullptr;
 
diff --git a/gdb/python/py-record-btrace.c b/gdb/python/py-record-btrace.c
index 82f0e00d675..6ca94168655 100644
--- a/gdb/python/py-record-btrace.c
+++ b/gdb/python/py-record-btrace.c
@@ -776,6 +776,72 @@ recpy_bt_function_call_history (PyObject *self, void *closure)
   return btpy_list_new (tinfo, first, last, 1, &recpy_func_type);
 }
 
+/* Helper function that calls the ptwrite listener PTW_LISTENER with
+   PAYLOAD and IP as arguments.  Returns a pointer to the string that will
+   be printed or nullptr if nothing should be printed.  IP can be nullptr,
+   PAYLOAD must point to a valid integer.  */
+gdb::unique_xmalloc_ptr<char>
+recpy_call_listener (const uint64_t *payload, const uint64_t *ip,
+		     const void *ptw_listener)
+{
+  if ((PyObject *) ptw_listener == Py_None)
+    return nullptr;
+  else if ((PyObject *) ptw_listener == nullptr)
+    error (_("No valid ptwrite listener."));
+
+  /* As Python is started as a seperate thread, we need to
+     acquire the GIL to safely call the listener function.  */
+  PyGILState_STATE gstate = PyGILState_Ensure ();
+
+  PyObject *py_payload = PyLong_FromUnsignedLongLong (*payload);
+  PyObject *py_ip;
+
+  if (ip == nullptr)
+    {
+      py_ip = Py_None;
+      Py_INCREF (Py_None);
+    }
+  else
+    py_ip = PyLong_FromUnsignedLongLong (*ip);
+
+  PyObject *py_result = PyObject_CallFunctionObjArgs ((PyObject *) ptw_listener,
+						      py_payload, py_ip, NULL);
+
+  if (PyErr_Occurred ())
+    {
+      gdbpy_print_stack ();
+      gdb_Py_DECREF (py_ip);
+      gdb_Py_DECREF (py_payload);
+      PyGILState_Release (gstate);
+      error (_("Error while executing Python code."));
+    }
+
+  gdb_Py_DECREF (py_ip);
+  gdb_Py_DECREF (py_payload);
+
+  if (py_result == Py_None)
+    {
+      gdb_Py_DECREF (py_result);
+      PyGILState_Release (gstate);
+      return nullptr;
+    }
+
+  gdb::unique_xmalloc_ptr<char> resultstring = gdbpy_obj_to_string (py_result);
+
+  if (PyErr_Occurred ())
+    {
+      gdbpy_print_stack ();
+      gdb_Py_DECREF (py_result);
+      PyGILState_Release (gstate);
+      error (_("Error while executing Python code."));
+    }
+
+  gdb_Py_DECREF (py_result);
+  PyGILState_Release (gstate);
+
+  return resultstring;
+}
+
 /* Helper function returning the current ptwrite listener.  Returns nullptr
    in case of errors.  */
 
@@ -810,6 +876,7 @@ recpy_initialize_listener (ptid_t inferior_ptid)
   process_stratum_target *proc_target = current_inferior ()->process_target ();
   struct thread_info * const tinfo = find_thread_ptid (proc_target, inferior_ptid);
 
+  tinfo->btrace.ptw_callback_fun = &recpy_call_listener;
   tinfo->btrace.ptw_listener = get_ptwrite_listener ();
 
   return (PyObject *) tinfo->btrace.ptw_listener;
diff --git a/gdb/python/py-record-btrace.h b/gdb/python/py-record-btrace.h
index 36389e99ab8..098d6701e97 100644
--- a/gdb/python/py-record-btrace.h
+++ b/gdb/python/py-record-btrace.h
@@ -97,4 +97,9 @@ extern PyObject *recpy_initialize_listener (ptid_t inferior_ptid);
 /* Helper function returning the current ptwrite listener.  */
 extern PyObject *get_ptwrite_listener ();
 
+/* Callback function for the ptwrite listener.  */
+extern gdb::unique_xmalloc_ptr<char>
+recpy_call_listener (const uint64_t *payload, const uint64_t *ip,
+                     const void *ptw_listener);
+
 #endif /* PYTHON_PY_RECORD_BTRACE_H */
-- 
2.25.4

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