gdb/python/py-finishbreakpoint.c

   1 /* Python interface to finish breakpoints
   2
   3    Copyright (C) 2011-2020 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20
  21
  22 #include "defs.h"
  23 #include "python-internal.h"
  24 #include "breakpoint.h"
  25 #include "frame.h"
  26 #include "gdbthread.h"
  27 #include "arch-utils.h"
  28 #include "language.h"
  29 #include "observable.h"
  30 #include "inferior.h"
  31 #include "block.h"
  32 #include "location.h"
  33
  34 /* Function that is called when a Python finish bp is found out of scope.  */
  35 static const char outofscope_func[] = "out_of_scope";
  36
  37 /* struct implementing the gdb.FinishBreakpoint object by extending
  38    the gdb.Breakpoint class.  */
  39 struct finish_breakpoint_object
  40 {
  41   /* gdb.Breakpoint base class.  */
  42   gdbpy_breakpoint_object py_bp;
  43   /* gdb.Type object of the value return by the breakpointed function.
  44      May be NULL if no debug information was available or return type
  45      was VOID.  */
  46   PyObject *return_type;
  47   /* gdb.Value object of the function finished by this breakpoint.  Will be
  48      NULL if return_type is NULL.  */
  49   PyObject *function_value;
  50   /* When stopped at this FinishBreakpoint, gdb.Value object returned by
  51      the function; Py_None if the value is not computable; NULL if GDB is
  52      not stopped at a FinishBreakpoint.  */
  53   PyObject *return_value;
  54 };
  55
  56 extern PyTypeObject finish_breakpoint_object_type
  57     CPYCHECKER_TYPE_OBJECT_FOR_TYPEDEF ("finish_breakpoint_object");
  58
  59 /* Python function to get the 'return_value' attribute of
  60    FinishBreakpoint.  */
  61
  62 static PyObject *
  63 bpfinishpy_get_returnvalue (PyObject *self, void *closure)
  64 {
  65   struct finish_breakpoint_object *self_finishbp =
  66       (struct finish_breakpoint_object *) self;
  67
  68   if (!self_finishbp->return_value)
  69     Py_RETURN_NONE;
  70
  71   Py_INCREF (self_finishbp->return_value);
  72   return self_finishbp->return_value;
  73 }
  74
  75 /* Deallocate FinishBreakpoint object.  */
  76
  77 static void
  78 bpfinishpy_dealloc (PyObject *self)
  79 {
  80   struct finish_breakpoint_object *self_bpfinish =
  81         (struct finish_breakpoint_object *) self;
  82
  83   Py_XDECREF (self_bpfinish->function_value);
  84   Py_XDECREF (self_bpfinish->return_type);
  85   Py_XDECREF (self_bpfinish->return_value);
  86   Py_TYPE (self)->tp_free (self);
  87 }
  88
  89 /* Triggered when gdbpy_should_stop is about to execute the `stop' callback
  90    of the gdb.FinishBreakpoint object BP_OBJ.  Will compute and cache the
  91    `return_value', if possible.  */
  92
  93 void
  94 bpfinishpy_pre_stop_hook (struct gdbpy_breakpoint_object *bp_obj)
  95 {
  96   struct finish_breakpoint_object *self_finishbp =
  97         (struct finish_breakpoint_object *) bp_obj;
  98
  99   /* Can compute return_value only once.  */
 100   gdb_assert (!self_finishbp->return_value);
 101
 102   if (!self_finishbp->return_type)
 103     return;
 104
 105   try
 106     {
 107       struct value *function =
 108         value_object_to_value (self_finishbp->function_value);
 109       struct type *value_type =
 110         type_object_to_type (self_finishbp->return_type);
 111       struct value *ret = get_return_value (function, value_type);
 112
 113       if (ret)
 114         {
 115           self_finishbp->return_value = value_to_value_object (ret);
 116           if (!self_finishbp->return_value)
 117               gdbpy_print_stack ();
 118         }
 119       else
 120         {
 121           Py_INCREF (Py_None);
 122           self_finishbp->return_value = Py_None;
 123         }
 124     }
 125   catch (const gdb_exception &except)
 126     {
 127       gdbpy_convert_exception (except);
 128       gdbpy_print_stack ();
 129     }
 130 }
 131
 132 /* Triggered when gdbpy_should_stop has triggered the `stop' callback
 133    of the gdb.FinishBreakpoint object BP_OBJ.  */
 134
 135 void
 136 bpfinishpy_post_stop_hook (struct gdbpy_breakpoint_object *bp_obj)
 137 {
 138
 139   try
 140     {
 141       /* Can't delete it here, but it will be removed at the next stop.  */
 142       disable_breakpoint (bp_obj->bp);
 143       gdb_assert (bp_obj->bp->disposition == disp_del);
 144     }
 145   catch (const gdb_exception &except)
 146     {
 147       gdbpy_convert_exception (except);
 148       gdbpy_print_stack ();
 149     }
 150 }
 151
 152 /* Python function to create a new breakpoint.  */
 153
 154 static int
 155 bpfinishpy_init (PyObject *self, PyObject *args, PyObject *kwargs)
 156 {
 157   static const char *keywords[] = { "frame", "internal", NULL };
 158   struct finish_breakpoint_object *self_bpfinish =
 159       (struct finish_breakpoint_object *) self;
 160   PyObject *frame_obj = NULL;
 161   int thread;
 162   struct frame_info *frame = NULL; /* init for gcc -Wall */
 163   struct frame_info *prev_frame = NULL;
 164   struct frame_id frame_id;
 165   PyObject *internal = NULL;
 166   int internal_bp = 0;
 167   CORE_ADDR pc;
 168   struct symbol *function;
 169
 170   if (!gdb_PyArg_ParseTupleAndKeywords (args, kwargs, "|OO", keywords,
 171                                         &frame_obj, &internal))
 172     return -1;
 173
 174   try
 175     {
 176       /* Default frame to newest frame if necessary.  */
 177       if (frame_obj == NULL)
 178         frame = get_current_frame ();
 179       else
 180         frame = frame_object_to_frame_info (frame_obj);
 181
 182       if (frame == NULL)
 183         {
 184           PyErr_SetString (PyExc_ValueError,
 185                            _("Invalid ID for the `frame' object."));
 186         }
 187       else
 188         {
 189           prev_frame = get_prev_frame (frame);
 190           if (prev_frame == 0)
 191             {
 192               PyErr_SetString (PyExc_ValueError,
 193                                _("\"FinishBreakpoint\" not "
 194                                  "meaningful in the outermost "
 195                                  "frame."));
 196             }
 197           else if (get_frame_type (prev_frame) == DUMMY_FRAME)
 198             {
 199               PyErr_SetString (PyExc_ValueError,
 200                                _("\"FinishBreakpoint\" cannot "
 201                                  "be set on a dummy frame."));
 202             }
 203           else
 204             {
 205               frame_id = get_frame_id (prev_frame);
 206               if (frame_id_eq (frame_id, null_frame_id))
 207                 PyErr_SetString (PyExc_ValueError,
 208                                  _("Invalid ID for the `frame' object."));
 209             }
 210         }
 211     }
 212   catch (const gdb_exception &except)
 213     {
 214       gdbpy_convert_exception (except);
 215       return -1;
 216     }
 217
 218   if (PyErr_Occurred ())
 219     return -1;
 220
 221   if (inferior_ptid == null_ptid)
 222     {
 223       PyErr_SetString (PyExc_ValueError,
 224                        _("No thread currently selected."));
 225       return -1;
 226     }
 227
 228   thread = inferior_thread ()->global_num;
 229
 230   if (internal)
 231     {
 232       internal_bp = PyObject_IsTrue (internal);
 233       if (internal_bp == -1)
 234         {
 235           PyErr_SetString (PyExc_ValueError,
 236                            _("The value of `internal' must be a boolean."));
 237           return -1;
 238         }
 239     }
 240
 241   /* Find the function we will return from.  */
 242   self_bpfinish->return_type = NULL;
 243   self_bpfinish->function_value = NULL;
 244
 245   try
 246     {
 247       if (get_frame_pc_if_available (frame, &pc))
 248         {
 249           function = find_pc_function (pc);
 250           if (function != NULL)
 251             {
 252               struct type *ret_type =
 253                 check_typedef (TYPE_TARGET_TYPE (SYMBOL_TYPE (function)));
 254
 255               /* Remember only non-void return types.  */
 256               if (TYPE_CODE (ret_type) != TYPE_CODE_VOID)
 257                 {
 258                   struct value *func_value;
 259
 260                   /* Ignore Python errors at this stage.  */
 261                   self_bpfinish->return_type = type_to_type_object (ret_type);
 262                   PyErr_Clear ();
 263                   func_value = read_var_value (function, NULL, frame);
 264                   self_bpfinish->function_value =
 265                       value_to_value_object (func_value);
 266                   PyErr_Clear ();
 267                 }
 268             }
 269         }
 270     }
 271   catch (const gdb_exception &except)
 272     {
 273       /* Just swallow.  Either the return type or the function value
 274          remain NULL.  */
 275     }
 276
 277   if (self_bpfinish->return_type == NULL || self_bpfinish->function_value == NULL)
 278     {
 279       /* Won't be able to compute return value.  */
 280       Py_XDECREF (self_bpfinish->return_type);
 281       Py_XDECREF (self_bpfinish->function_value);
 282
 283       self_bpfinish->return_type = NULL;
 284       self_bpfinish->function_value = NULL;
 285     }
 286
 287   bppy_pending_object = &self_bpfinish->py_bp;
 288   bppy_pending_object->number = -1;
 289   bppy_pending_object->bp = NULL;
 290
 291   try
 292     {
 293       /* Set a breakpoint on the return address.  */
 294       event_location_up location
 295         = new_address_location (get_frame_pc (prev_frame), NULL, 0);
 296       create_breakpoint (python_gdbarch,
 297                          location.get (), NULL, thread, NULL,
 298                          0,
 299                          1 /*temp_flag*/,
 300                          bp_breakpoint,
 301                          0,
 302                          AUTO_BOOLEAN_TRUE,
 303                          &bkpt_breakpoint_ops,
 304                          0, 1, internal_bp, 0);
 305     }
 306   catch (const gdb_exception &except)
 307     {
 308       GDB_PY_SET_HANDLE_EXCEPTION (except);
 309     }
 310
 311   self_bpfinish->py_bp.bp->frame_id = frame_id;
 312   self_bpfinish->py_bp.is_finish_bp = 1;
 313
 314   /* Bind the breakpoint with the current program space.  */
 315   self_bpfinish->py_bp.bp->pspace = current_program_space;
 316
 317   return 0;
 318 }
 319
 320 /* Called when GDB notices that the finish breakpoint BP_OBJ is out of
 321    the current callstack.  Triggers the method OUT_OF_SCOPE if implemented,
 322    then delete the breakpoint.  */
 323
 324 static void
 325 bpfinishpy_out_of_scope (struct finish_breakpoint_object *bpfinish_obj)
 326 {
 327   gdbpy_breakpoint_object *bp_obj = (gdbpy_breakpoint_object *) bpfinish_obj;
 328   PyObject *py_obj = (PyObject *) bp_obj;
 329
 330   if (bpfinish_obj->py_bp.bp->enable_state == bp_enabled
 331       && PyObject_HasAttrString (py_obj, outofscope_func))
 332     {
 333       gdbpy_ref<> meth_result (PyObject_CallMethod (py_obj, outofscope_func,
 334                                                     NULL));
 335       if (meth_result == NULL)
 336         gdbpy_print_stack ();
 337     }
 338
 339   delete_breakpoint (bpfinish_obj->py_bp.bp);
 340 }
 341
 342 /* Callback for `bpfinishpy_detect_out_scope'.  Triggers Python's
 343    `B->out_of_scope' function if B is a FinishBreakpoint out of its scope.  */
 344
 345 static bool
 346 bpfinishpy_detect_out_scope_cb (struct breakpoint *b,
 347                                 struct breakpoint *bp_stopped)
 348 {
 349   PyObject *py_bp = (PyObject *) b->py_bp_object;
 350
 351   /* Trigger out_of_scope if this is a FinishBreakpoint and its frame is
 352      not anymore in the current callstack.  */
 353   if (py_bp != NULL && b->py_bp_object->is_finish_bp)
 354     {
 355       struct finish_breakpoint_object *finish_bp =
 356           (struct finish_breakpoint_object *) py_bp;
 357
 358       /* Check scope if not currently stopped at the FinishBreakpoint.  */
 359       if (b != bp_stopped)
 360         {
 361           try
 362             {
 363               if (b->pspace == current_inferior ()->pspace
 364                   && (!target_has_registers
 365                       || frame_find_by_id (b->frame_id) == NULL))
 366                 bpfinishpy_out_of_scope (finish_bp);
 367             }
 368           catch (const gdb_exception &except)
 369             {
 370               gdbpy_convert_exception (except);
 371               gdbpy_print_stack ();
 372             }
 373         }
 374     }
 375
 376   return 0;
 377 }
 378
 379 /* Attached to `stop' notifications, check if the execution has run
 380    out of the scope of any FinishBreakpoint before it has been hit.  */
 381
 382 static void
 383 bpfinishpy_handle_stop (struct bpstats *bs, int print_frame)
 384 {
 385   gdbpy_enter enter_py (get_current_arch (), current_language);
 386
 387   iterate_over_breakpoints ([&] (breakpoint *bp)
 388     {
 389       return bpfinishpy_detect_out_scope_cb
 390         (bp, bs == NULL ? NULL : bs->breakpoint_at);
 391     });
 392 }
 393
 394 /* Attached to `exit' notifications, triggers all the necessary out of
 395    scope notifications.  */
 396
 397 static void
 398 bpfinishpy_handle_exit (struct inferior *inf)
 399 {
 400   gdbpy_enter enter_py (target_gdbarch (), current_language);
 401
 402   iterate_over_breakpoints ([&] (breakpoint *bp)
 403     {
 404       return bpfinishpy_detect_out_scope_cb (bp, nullptr);
 405     });
 406 }
 407
 408 /* Initialize the Python finish breakpoint code.  */
 409
 410 int
 411 gdbpy_initialize_finishbreakpoints (void)
 412 {
 413   if (PyType_Ready (&finish_breakpoint_object_type) < 0)
 414     return -1;
 415
 416   if (gdb_pymodule_addobject (gdb_module, "FinishBreakpoint",
 417                               (PyObject *) &finish_breakpoint_object_type) < 0)
 418     return -1;
 419
 420   gdb::observers::normal_stop.attach (bpfinishpy_handle_stop);
 421   gdb::observers::inferior_exit.attach (bpfinishpy_handle_exit);
 422
 423   return 0;
 424 }
 425
 426 static gdb_PyGetSetDef finish_breakpoint_object_getset[] = {
 427   { "return_value", bpfinishpy_get_returnvalue, NULL,
 428   "gdb.Value object representing the return value, if any. \
 429 None otherwise.", NULL },
 430     { NULL }  /* Sentinel.  */
 431 };
 432
 433 PyTypeObject finish_breakpoint_object_type =
 434 {
 435   PyVarObject_HEAD_INIT (NULL, 0)
 436   "gdb.FinishBreakpoint",         /*tp_name*/
 437   sizeof (struct finish_breakpoint_object),  /*tp_basicsize*/
 438   0,                              /*tp_itemsize*/
 439   bpfinishpy_dealloc,             /*tp_dealloc*/
 440   0,                              /*tp_print*/
 441   0,                              /*tp_getattr*/
 442   0,                              /*tp_setattr*/
 443   0,                              /*tp_compare*/
 444   0,                              /*tp_repr*/
 445   0,                              /*tp_as_number*/
 446   0,                              /*tp_as_sequence*/
 447   0,                              /*tp_as_mapping*/
 448   0,                              /*tp_hash */
 449   0,                              /*tp_call*/
 450   0,                              /*tp_str*/
 451   0,                              /*tp_getattro*/
 452   0,                              /*tp_setattro */
 453   0,                              /*tp_as_buffer*/
 454   Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
 455   "GDB finish breakpoint object", /* tp_doc */
 456   0,                              /* tp_traverse */
 457   0,                              /* tp_clear */
 458   0,                              /* tp_richcompare */
 459   0,                              /* tp_weaklistoffset */
 460   0,                              /* tp_iter */
 461   0,                              /* tp_iternext */
 462   0,                              /* tp_methods */
 463   0,                              /* tp_members */
 464   finish_breakpoint_object_getset,/* tp_getset */
 465   &breakpoint_object_type,        /* tp_base */
 466   0,                              /* tp_dict */
 467   0,                              /* tp_descr_get */
 468   0,                              /* tp_descr_set */
 469   0,                              /* tp_dictoffset */
 470   bpfinishpy_init,                /* tp_init */
 471   0,                              /* tp_alloc */
 472   0                               /* tp_new */
 473 };