[v3,09/12] btrace, python: Enable ptwrite listener registration.

Message ID 20210616074205.1129553-10-felix.willgerodt@intel.com
State New
Headers show
Series
  • Extensions for PTWRITE
Related show

Commit Message

Tom Tromey via Gdb-patches June 16, 2021, 7:42 a.m.
With this patch a default ptwrite listener is registered upon start of GDB.
It prints the plain ptwrite payload as hex.  The default listener can be
overwritten by registering a custom listener in python or by registering
"None", for no output at all.  Registering a listener function creates per
thread copies to allow unique internal states per thread.

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

	* btrace.c (ftrace_add_pt): Add call to
	apply_ext_lang_ptwrite_listener.
	* btrace.h (btrace_thread_info): New member ptw_listener.
	* data-directory/Makefile.in: Add ptwrite.py.
	* extension-priv.h (struct extension_language_ops): New member
	apply_ptwrite_listener.
	* extension.c (apply_ext_lang_ptwrite_listener): New function.
	* extension.h (apply_ext_lang_ptwrite_listener): New declaration.
	* guile/guile.c (guile_extension_ops): Add
	gdbscm_load_ptwrite_listener.
	* python/lib/gdb/ptwrite.py: New file.
	* python/py-record-btrace.c (recpy_initialize_listener,
	get_ptwrite_listener): New function.
	* python/py-record-btrace.h (recpy_initialize_listener): New
	declaration.
	* python/py-record.c (gdbpy_load_ptwrite_listener): New function.
	* python/python-internal.h (gdbpy_load_ptwrite_listener): New
	declaration.
	* python/python.c (python_extension_ops): New member
	gdbpy_load_ptwrite_listener.
---
 gdb/btrace.c                   |  3 ++
 gdb/btrace.h                   |  3 ++
 gdb/data-directory/Makefile.in |  1 +
 gdb/extension-priv.h           |  4 ++
 gdb/extension.c                | 21 +++++++++
 gdb/extension.h                |  3 ++
 gdb/guile/guile.c              |  1 +
 gdb/python/lib/gdb/ptwrite.py  | 84 ++++++++++++++++++++++++++++++++++
 gdb/python/py-record-btrace.c  | 67 +++++++++++++++++++++++++++
 gdb/python/py-record-btrace.h  |  6 +++
 gdb/python/python-internal.h   |  3 ++
 gdb/python/python.c            |  2 +
 12 files changed, 198 insertions(+)
 create mode 100644 gdb/python/lib/gdb/ptwrite.py

-- 
2.25.4

Intel Deutschland GmbH
Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de <http://www.intel.de>
Managing Directors: Christin Eisenschmid, Sharon Heck, Tiffany Doon Silva  
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928

Comments

Tom Tromey via Gdb-patches Aug. 13, 2021, 10:36 a.m. | #1
Thanks, Felix,


>+  apply_ext_lang_ptwrite_listener (inferior_ptid);


Should this be called ptwrite_filter?


>+  /* PyObject pointer to the ptwrite listener function.  */

>+  void *ptw_listener = nullptr;

>+


The comment says that this is a PyObject.  Why is it declared void *?


>diff --git a/gdb/extension-priv.h b/gdb/extension-priv.h

>index 77f23e0f911..36da4211738 100644

>--- a/gdb/extension-priv.h

>+++ b/gdb/extension-priv.h

>@@ -183,6 +183,10 @@ struct extension_language_ops

>      enum ext_lang_frame_args args_type,

>      struct ui_out *out, int frame_low, int frame_high);

>

>+  /* Used for registering the ptwrite listener to the current thread.  */

>+  enum ext_lang_bt_status (*apply_ptwrite_listener)

>+    (const struct extension_language_defn *, ptid_t inferior_ptid);


There is a parameter name for the second but not for the first parameter.  Also, the name shadows a global variable.  Let's call it just 'ptid'.


>+/* Used for registering the ptwrite listener to the current thread.  */

>+

>+enum ext_lang_bt_status


This enum is specifically for frame filters.  We'd need to either generalize it or add our own for ptwrite filters.


>+apply_ext_lang_ptwrite_listener (ptid_t inferior_ptid)

>+{

>+  for (const struct extension_language_defn *extlang : extension_languages)

>+    {

>+      enum ext_lang_bt_status status;

>+

>+      if (extlang->ops == nullptr

>+	  || extlang->ops->apply_ptwrite_listener == NULL)

>+	continue;

>+      status = extlang->ops->apply_ptwrite_listener (extlang, inferior_ptid);

>+

>+      if (status != EXT_LANG_BT_NO_FILTERS)

>+	return status;


I would have inserted the empty line after the 'continue' from the if statement since obtaining the status and checking it belong together.

IIUC, this installs the ptwrite filter.  The code that actually calls it on a PTWRITE event is not part of this patch.  I think the installation of the filter and calling it should be inside one patch to make it clear how this works.


>+# Ptwrite utilities.

>+# Copyright (C) 2020 Free Software Foundation, Inc.


Year.


>+def default_listener(payload, ip):

>+    """Default listener that is active upon starting GDB."""

>+    return "{:x}".format(payload)

>+

>+# This dict contains the per thread copies of the listener function and the

>+# global template listener, from which the copies are created.

>+_ptwrite_listener = {"global" : default_listener}

>+

>+

>+def _update_listener_dict(thread_list):

>+    """Helper function to update the listener dict.

>+

>+    Discards listener copies of threads that already exited and registers

>+    copies of the listener for new threads."""

>+    # thread_list[x].ptid returns the tuple (pid, lwp, tid)

>+    lwp_list = [i.ptid[1] for i in thread_list]

>+

>+    # clean-up old listeners

>+    for key in _ptwrite_listener.keys():

>+      if key not in lwp_list and key != "global":

>+        _ptwrite_listener.pop(key)

>+

>+    # Register listener for new threads

>+    for key in lwp_list:

>+        if key not in _ptwrite_listener.keys():

>+            _ptwrite_listener[key] = deepcopy(_ptwrite_listener["global"])


So we can only update all at once?  In non-stop mode, I think we want to be able to update just the one for the current thread.

What's the purpose of this deepcopy?  For the default filter, this doesn't seem necessary.  For user-defined filters, this is initializing the per-thread filter from a template, correct?  Should 'global' be spelled 'template' in that case?

Should the template filter be part of the dict, at all?


>+def _clear_traces(thread_list):

>+    """Helper function to clear the trace of all threads."""


The comment doesn't match the code.  The function clears the recordings of threads in THREAD_LIST.


>+    current_thread = gdb.selected_thread()

>+

>+    recording = gdb.current_recording()

>+

>+    if (recording is not None):

>+        for thread in thread_list:

>+            thread.switch()

>+            recording.clear()

>+

>+        current_thread.switch()


Should there be a try around the above to ensure we switch back in case of exceptions?


>+def register_listener(listener):

>+    """Register the ptwrite listener function."""

>+    if listener is not None and not callable(listener):

>+        raise TypeError("Listener must be callable!")

>+

>+    thread_list = gdb.Inferior.threads(gdb.selected_inferior())

>+    _clear_traces(thread_list)


Please add a comment as to why we need to clear the recordings for all threads?


>+def get_listener():

>+    """Returns the listeners of the current thread."""


The comment says 'listeners' but there can be only one, correct?

>+    thread_list = gdb.Inferior.threads(gdb.selected_inferior())

>+    _update_listener_dict(thread_list)


Why do we need to update the filters for all threads?


>+/* Helper function returning the current ptwrite listener.  Returns nullptr

>+   in case of errors.  */

>+

>+PyObject *

>+get_ptwrite_listener ()

>+{

>+  PyObject *module = PyImport_ImportModule ("gdb.ptwrite");

>+

>+  if (PyErr_Occurred ())

>+  {

>+    gdbpy_print_stack ();

>+    return nullptr;

>+  }

>+

>+  PyObject *default_ptw_listener = PyObject_CallMethod (module,

>	"get_listener",

>+							NULL);

>+

>+  gdb_Py_DECREF (module);

>+

>+  if (PyErr_Occurred ())

>+    gdbpy_print_stack ();

>+

>+  return default_ptw_listener;


This is not necessarily the default listener, correct?


>+/* Helper function to initialize the ptwrite listener.  Returns nullptr in

>+   case of errors.  */

>+

>+PyObject *

>+recpy_initialize_listener (ptid_t inferior_ptid)


The argument name shadows a global variable.  Let's just call it 'ptid'.


>+  process_stratum_target *proc_target = current_inferior ()->process_target ();


Any chance we can get here without having a current inferior?


>+  struct thread_info * const tinfo = find_thread_ptid (proc_target, inferior_ptid);

>+

>+  tinfo->btrace.ptw_listener = get_ptwrite_listener ();


Let's check tinfo.  Or pass it in as parameter.


>+  return (PyObject *) tinfo->btrace.ptw_listener;


It is called only once and that call ignores the result.


>+/* Used for registering the default ptwrite listener to the current thread.  A

>+   pointer to this function is stored in the python extension interface.  */

>+

>+enum ext_lang_bt_status

>+gdbpy_load_ptwrite_listener (const struct extension_language_defn *extlang,

>+			     ptid_t inferior_ptid)

>+{

>+  struct gdbarch *gdbarch = NULL;

>+

>+  if (!gdb_python_initialized)

>+    return EXT_LANG_BT_NO_FILTERS;

>+

>+  try

>+    {

>+      gdbarch = target_gdbarch ();


Is this a precaution or did you run into cases where target_gdbarch() throws?  Should the rest also be done inside a try block?


Regards,
Markus.
Intel Deutschland GmbH
Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de <http://www.intel.de>
Managing Directors: Christin Eisenschmid, Sharon Heck, Tiffany Doon Silva  
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928

Patch

diff --git a/gdb/btrace.c b/gdb/btrace.c
index 2c4f3f67c6b..d66c3e21f11 100644
--- a/gdb/btrace.c
+++ b/gdb/btrace.c
@@ -34,6 +34,7 @@ 
 #include "gdbsupport/rsp-low.h"
 #include "gdbcmd.h"
 #include "cli/cli-utils.h"
+#include "extension.h"
 #include "gdbarch.h"
 
 /* For maintenance commands.  */
@@ -1311,6 +1312,8 @@  ftrace_add_pt (struct btrace_thread_info *btinfo,
   uint64_t offset;
   int status;
 
+  apply_ext_lang_ptwrite_listener (inferior_ptid);
+
   for (;;)
     {
       struct pt_insn insn;
diff --git a/gdb/btrace.h b/gdb/btrace.h
index e6694551c70..b15efcd147c 100644
--- a/gdb/btrace.h
+++ b/gdb/btrace.h
@@ -352,6 +352,9 @@  struct btrace_thread_info
      stepping through the execution history.  */
   std::vector<std::string> aux_data;
 
+  /* PyObject pointer to the ptwrite listener function.  */
+  void *ptw_listener = nullptr;
+
   /* The function level offset.  When added to each function's LEVEL,
      this normalizes the function levels such that the smallest level
      becomes zero.  */
diff --git a/gdb/data-directory/Makefile.in b/gdb/data-directory/Makefile.in
index 888325f974e..c759920a343 100644
--- a/gdb/data-directory/Makefile.in
+++ b/gdb/data-directory/Makefile.in
@@ -74,6 +74,7 @@  PYTHON_FILE_LIST = \
 	gdb/frames.py \
 	gdb/printing.py \
 	gdb/prompt.py \
+	gdb/ptwrite.py \
 	gdb/types.py \
 	gdb/unwinder.py \
 	gdb/xmethod.py \
diff --git a/gdb/extension-priv.h b/gdb/extension-priv.h
index 77f23e0f911..36da4211738 100644
--- a/gdb/extension-priv.h
+++ b/gdb/extension-priv.h
@@ -183,6 +183,10 @@  struct extension_language_ops
      enum ext_lang_frame_args args_type,
      struct ui_out *out, int frame_low, int frame_high);
 
+  /* Used for registering the ptwrite listener to the current thread.  */
+  enum ext_lang_bt_status (*apply_ptwrite_listener)
+    (const struct extension_language_defn *, ptid_t inferior_ptid);
+
   /* Update values held by the extension language when OBJFILE is discarded.
      New global types must be created for every such value, which must then be
      updated to use the new types.
diff --git a/gdb/extension.c b/gdb/extension.c
index 27dce9befa0..826cb0285c3 100644
--- a/gdb/extension.c
+++ b/gdb/extension.c
@@ -550,6 +550,27 @@  apply_ext_lang_frame_filter (struct frame_info *frame,
   return EXT_LANG_BT_NO_FILTERS;
 }
 
+/* Used for registering the ptwrite listener to the current thread.  */
+
+enum ext_lang_bt_status
+apply_ext_lang_ptwrite_listener (ptid_t inferior_ptid)
+{
+  for (const struct extension_language_defn *extlang : extension_languages)
+    {
+      enum ext_lang_bt_status status;
+
+      if (extlang->ops == nullptr
+	  || extlang->ops->apply_ptwrite_listener == NULL)
+	continue;
+      status = extlang->ops->apply_ptwrite_listener (extlang, inferior_ptid);
+
+      if (status != EXT_LANG_BT_NO_FILTERS)
+	return status;
+    }
+
+  return EXT_LANG_BT_NO_FILTERS;
+}
+
 /* Update values held by the extension language when OBJFILE is discarded.
    New global types must be created for every such value, which must then be
    updated to use the new types.
diff --git a/gdb/extension.h b/gdb/extension.h
index 56f57560de3..97562304ae4 100644
--- a/gdb/extension.h
+++ b/gdb/extension.h
@@ -295,6 +295,9 @@  extern enum ext_lang_bt_status apply_ext_lang_frame_filter
    enum ext_lang_frame_args args_type,
    struct ui_out *out, int frame_low, int frame_high);
 
+enum ext_lang_bt_status apply_ext_lang_ptwrite_listener
+  (ptid_t inferior_ptid);
+
 extern void preserve_ext_lang_values (struct objfile *, htab_t copied_types);
 
 extern const struct extension_language_defn *get_breakpoint_cond_ext_lang
diff --git a/gdb/guile/guile.c b/gdb/guile/guile.c
index a28dee37ed8..ef784885e87 100644
--- a/gdb/guile/guile.c
+++ b/gdb/guile/guile.c
@@ -124,6 +124,7 @@  static const struct extension_language_ops guile_extension_ops =
   gdbscm_apply_val_pretty_printer,
 
   NULL, /* gdbscm_apply_frame_filter, */
+  NULL, /* gdbscm_load_ptwrite_listener, */
 
   gdbscm_preserve_values,
 
diff --git a/gdb/python/lib/gdb/ptwrite.py b/gdb/python/lib/gdb/ptwrite.py
new file mode 100644
index 00000000000..f79463aefcf
--- /dev/null
+++ b/gdb/python/lib/gdb/ptwrite.py
@@ -0,0 +1,84 @@ 
+# Ptwrite utilities.
+# Copyright (C) 2020 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Utilities for working with ptwrite listeners."""
+
+import gdb
+from copy import deepcopy
+
+
+def default_listener(payload, ip):
+    """Default listener that is active upon starting GDB."""
+    return "{:x}".format(payload)
+
+# This dict contains the per thread copies of the listener function and the
+# global template listener, from which the copies are created.
+_ptwrite_listener = {"global" : default_listener}
+
+
+def _update_listener_dict(thread_list):
+    """Helper function to update the listener dict.
+
+    Discards listener copies of threads that already exited and registers
+    copies of the listener for new threads."""
+    # thread_list[x].ptid returns the tuple (pid, lwp, tid)
+    lwp_list = [i.ptid[1] for i in thread_list]
+
+    # clean-up old listeners
+    for key in _ptwrite_listener.keys():
+      if key not in lwp_list and key != "global":
+        _ptwrite_listener.pop(key)
+
+    # Register listener for new threads
+    for key in lwp_list:
+        if key not in _ptwrite_listener.keys():
+            _ptwrite_listener[key] = deepcopy(_ptwrite_listener["global"])
+
+
+def _clear_traces(thread_list):
+    """Helper function to clear the trace of all threads."""
+    current_thread = gdb.selected_thread()
+
+    recording = gdb.current_recording()
+
+    if (recording is not None):
+        for thread in thread_list:
+            thread.switch()
+            recording.clear()
+
+        current_thread.switch()
+
+
+def register_listener(listener):
+    """Register the ptwrite listener function."""
+    if listener is not None and not callable(listener):
+        raise TypeError("Listener must be callable!")
+
+    thread_list = gdb.Inferior.threads(gdb.selected_inferior())
+    _clear_traces(thread_list)
+
+    _ptwrite_listener.clear()
+    _ptwrite_listener["global"] = listener
+
+    _update_listener_dict(thread_list)
+
+
+def get_listener():
+    """Returns the listeners of the current thread."""
+    thread_list = gdb.Inferior.threads(gdb.selected_inferior())
+    _update_listener_dict(thread_list)
+
+    return _ptwrite_listener[gdb.selected_thread().ptid[1]]
diff --git a/gdb/python/py-record-btrace.c b/gdb/python/py-record-btrace.c
index 97649b206a5..82f0e00d675 100644
--- a/gdb/python/py-record-btrace.c
+++ b/gdb/python/py-record-btrace.c
@@ -776,6 +776,73 @@  recpy_bt_function_call_history (PyObject *self, void *closure)
   return btpy_list_new (tinfo, first, last, 1, &recpy_func_type);
 }
 
+/* Helper function returning the current ptwrite listener.  Returns nullptr
+   in case of errors.  */
+
+PyObject *
+get_ptwrite_listener ()
+{
+  PyObject *module = PyImport_ImportModule ("gdb.ptwrite");
+
+  if (PyErr_Occurred ())
+  {
+    gdbpy_print_stack ();
+    return nullptr;
+  }
+
+  PyObject *default_ptw_listener = PyObject_CallMethod (module,	"get_listener",
+							NULL);
+
+  gdb_Py_DECREF (module);
+
+  if (PyErr_Occurred ())
+    gdbpy_print_stack ();
+
+  return default_ptw_listener;
+}
+
+/* Helper function to initialize the ptwrite listener.  Returns nullptr in
+   case of errors.  */
+
+PyObject *
+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_listener = get_ptwrite_listener ();
+
+  return (PyObject *) tinfo->btrace.ptw_listener;
+}
+
+/* Used for registering the default ptwrite listener to the current thread.  A
+   pointer to this function is stored in the python extension interface.  */
+
+enum ext_lang_bt_status
+gdbpy_load_ptwrite_listener (const struct extension_language_defn *extlang,
+			     ptid_t inferior_ptid)
+{
+  struct gdbarch *gdbarch = NULL;
+
+  if (!gdb_python_initialized)
+    return EXT_LANG_BT_NO_FILTERS;
+
+  try
+    {
+      gdbarch = target_gdbarch ();
+    }
+  catch (const gdb_exception &except)
+    {
+      return EXT_LANG_BT_NO_FILTERS;
+    }
+
+  gdbpy_enter enter_py (gdbarch, current_language);
+
+  recpy_initialize_listener (inferior_ptid);
+
+  return EXT_LANG_BT_OK;
+}
+
 /* Implementation of BtraceRecord.goto (self, BtraceInstruction) -> None.  */
 
 PyObject *
diff --git a/gdb/python/py-record-btrace.h b/gdb/python/py-record-btrace.h
index adb03c5eab4..36389e99ab8 100644
--- a/gdb/python/py-record-btrace.h
+++ b/gdb/python/py-record-btrace.h
@@ -91,4 +91,10 @@  extern PyObject *recpy_bt_func_prev (PyObject *self, void *closure);
 /* Implementation of RecordFunctionSegment.next [RecordFunctionSegment].  */
 extern PyObject *recpy_bt_func_next (PyObject *self, void *closure);
 
+/* Helper function to initialize the ptwrite listener.  */
+extern PyObject *recpy_initialize_listener (ptid_t inferior_ptid);
+
+/* Helper function returning the current ptwrite listener.  */
+extern PyObject *get_ptwrite_listener ();
+
 #endif /* PYTHON_PY_RECORD_BTRACE_H */
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index 690d2fb43c0..fcbd7a0b1b8 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -392,6 +392,9 @@  extern enum ext_lang_rc gdbpy_apply_val_pretty_printer
    struct ui_file *stream, int recurse,
    const struct value_print_options *options,
    const struct language_defn *language);
+extern enum ext_lang_bt_status gdbpy_load_ptwrite_listener
+  (const struct extension_language_defn *extlang,
+   ptid_t inferior_ptid);
 extern enum ext_lang_bt_status gdbpy_apply_frame_filter
   (const struct extension_language_defn *,
    struct frame_info *frame, frame_filter_flags flags,
diff --git a/gdb/python/python.c b/gdb/python/python.c
index e42cbc4fd5e..ad23532f9d8 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -174,6 +174,8 @@  const struct extension_language_ops python_extension_ops =
 
   gdbpy_apply_frame_filter,
 
+  gdbpy_load_ptwrite_listener,
+
   gdbpy_preserve_values,
 
   gdbpy_breakpoint_has_cond,