[PATCH v2 10/12] btrace, python: Enable calling the ptwrite listener.

Felix Willgerodt via Gdb-patches
2021-06-14T15:09:16Z

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 */