gdb/python/py-finishbreakpoint.c

   1 /* Python interface to finish breakpoints
   2
   3    Copyright (C) 2011-2019 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 }
  87
  88 /* Triggered when gdbpy_should_stop is about to execute the `stop' callback
  89    of the gdb.FinishBreakpoint object BP_OBJ.  Will compute and cache the
  90    `return_value', if possible.  */
  91
  92 void
  93 bpfinishpy_pre_stop_hook (struct gdbpy_breakpoint_object *bp_obj)
  94 {
  95   struct finish_breakpoint_object *self_finishbp =
  96         (struct finish_breakpoint_object *) bp_obj;
  97
  98   /* Can compute return_value only once.  */
  99   gdb_assert (!self_finishbp->return_value);
 100
 101   if (!self_finishbp->return_type)
 102     return;
 103
 104   TRY
 105     {
 106       struct value *function =
 107         value_object_to_value (self_finishbp->function_value);
 108       struct type *value_type =
 109         type_object_to_type (self_finishbp->return_type);
 110       struct value *ret = get_return_value (function, value_type);
 111
 112       if (ret)
 113         {
 114           self_finishbp->return_value = value_to_value_object (ret);
 115           if (!self_finishbp->return_value)
 116               gdbpy_print_stack ();
 117         }
 118       else
 119         {
 120           Py_INCREF (Py_None);
 121           self_finishbp->return_value = Py_None;
 122         }
 123     }
 124   CATCH (except, RETURN_MASK_ALL)
 125     {
 126       gdbpy_convert_exception (except);
 127       gdbpy_print_stack ();
 128     }
 129   END_CATCH
 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 (except, RETURN_MASK_ALL)
 146     {
 147       gdbpy_convert_exception (except);
 148       gdbpy_print_stack ();
 149     }
 150   END_CATCH
 151 }
 152
 153 /* Python function to create a new breakpoint.  */
 154
 155 static int
 156 bpfinishpy_init (PyObject *self, PyObject *args, PyObject *kwargs)
 157 {
 158   static const char *keywords[] = { "frame", "internal", NULL };
 159   struct finish_breakpoint_object *self_bpfinish =
 160       (struct finish_breakpoint_object *) self;
 161   PyObject *frame_obj = NULL;
 162   int thread;
 163   struct frame_info *frame = NULL; /* init for gcc -Wall */
 164   struct frame_info *prev_frame = NULL;
 165   struct frame_id frame_id;
 166   PyObject *internal = NULL;
 167   int internal_bp = 0;
 168   CORE_ADDR pc;
 169   struct symbol *function;
 170
 171   if (!gdb_PyArg_ParseTupleAndKeywords (args, kwargs, "|OO", keywords,
 172                                         &frame_obj, &internal))
 173     return -1;
 174
 175   TRY
 176     {
 177       /* Default frame to newest frame if necessary.  */
 178       if (frame_obj == NULL)
 179         frame = get_current_frame ();
 180       else
 181         frame = frame_object_to_frame_info (frame_obj);
 182
 183       if (frame == NULL)
 184         {
 185           PyErr_SetString (PyExc_ValueError,
 186                            _("Invalid ID for the `frame' object."));
 187         }
 188       else
 189         {
 190           prev_frame = get_prev_frame (frame);
 191           if (prev_frame == 0)
 192             {
 193               PyErr_SetString (PyExc_ValueError,
 194                                _("\"FinishBreakpoint\" not "
 195                                  "meaningful in the outermost "
 196                                  "frame."));
 197             }
 198           else if (get_frame_type (prev_frame) == DUMMY_FRAME)
 199             {
 200               PyErr_SetString (PyExc_ValueError,
 201                                _("\"FinishBreakpoint\" cannot "
 202                                  "be set on a dummy frame."));
 203             }
 204           else
 205             {
 206               frame_id = get_frame_id (prev_frame);
 207               if (frame_id_eq (frame_id, null_frame_id))
 208                 PyErr_SetString (PyExc_ValueError,
 209                                  _("Invalid ID for the `frame' object."));
 210             }
 211         }
 212     }
 213   CATCH (except, RETURN_MASK_ALL)
 214     {
 215       gdbpy_convert_exception (except);
 216       return -1;
 217     }
 218   END_CATCH
 219
 220   if (PyErr_Occurred ())
 221     return -1;
 222
 223   if (inferior_ptid == null_ptid)
 224     {
 225       PyErr_SetString (PyExc_ValueError,
 226                        _("No thread currently selected."));
 227       return -1;
 228     }
 229
 230   thread = inferior_thread ()->global_num;
 231
 232   if (internal)
 233     {
 234       internal_bp = PyObject_IsTrue (internal);
 235       if (internal_bp == -1)
 236         {
 237           PyErr_SetString (PyExc_ValueError,
 238                            _("The value of `internal' must be a boolean."));
 239           return -1;
 240         }
 241     }
 242
 243   /* Find the function we will return from.  */
 244   self_bpfinish->return_type = NULL;
 245   self_bpfinish->function_value = NULL;
 246
 247   TRY
 248     {
 249       if (get_frame_pc_if_available (frame, &pc))
 250         {
 251           function = find_pc_function (pc);
 252           if (function != NULL)
 253             {
 254               struct type *ret_type =
 255                 check_typedef (TYPE_TARGET_TYPE (SYMBOL_TYPE (function)));
 256
 257               /* Remember only non-void return types.  */
 258               if (TYPE_CODE (ret_type) != TYPE_CODE_VOID)
 259                 {
 260                   struct value *func_value;
 261
 262                   /* Ignore Python errors at this stage.  */
 263                   self_bpfinish->return_type = type_to_type_object (ret_type);
 264                   PyErr_Clear ();
 265                   func_value = read_var_value (function, NULL, frame);
 266                   self_bpfinish->function_value =
 267                       value_to_value_object (func_value);
 268                   PyErr_Clear ();
 269                 }
 270             }
 271         }
 272     }
 273   CATCH (except, RETURN_MASK_ALL)
 274     {
 275       /* Just swallow.  Either the return type or the function value
 276          remain NULL.  */
 277     }
 278   END_CATCH
 279
 280   if (self_bpfinish->return_type == NULL || self_bpfinish->function_value == NULL)
 281     {
 282       /* Won't be able to compute return value.  */
 283       Py_XDECREF (self_bpfinish->return_type);
 284       Py_XDECREF (self_bpfinish->function_value);
 285
 286       self_bpfinish->return_type = NULL;
 287       self_bpfinish->function_value = NULL;
 288     }
 289
 290   bppy_pending_object = &self_bpfinish->py_bp;
 291   bppy_pending_object->number = -1;
 292   bppy_pending_object->bp = NULL;
 293
 294   TRY
 295     {
 296       /* Set a breakpoint on the return address.  */
 297       event_location_up location
 298         = new_address_location (get_frame_pc (prev_frame), NULL, 0);
 299       create_breakpoint (python_gdbarch,
 300                          location.get (), NULL, thread, NULL,
 301                          0,
 302                          1 /*temp_flag*/,
 303                          bp_breakpoint,
 304                          0,
 305                          AUTO_BOOLEAN_TRUE,
 306                          &bkpt_breakpoint_ops,
 307                          0, 1, internal_bp, 0);
 308     }
 309   CATCH (except, RETURN_MASK_ALL)
 310     {
 311       GDB_PY_SET_HANDLE_EXCEPTION (except);
 312     }
 313   END_CATCH
 314
 315   self_bpfinish->py_bp.bp->frame_id = frame_id;
 316   self_bpfinish->py_bp.is_finish_bp = 1;
 317
 318   /* Bind the breakpoint with the current program space.  */
 319   self_bpfinish->py_bp.bp->pspace = current_program_space;
 320
 321   return 0;
 322 }
 323
 324 /* Called when GDB notices that the finish breakpoint BP_OBJ is out of
 325    the current callstack.  Triggers the method OUT_OF_SCOPE if implemented,
 326    then delete the breakpoint.  */
 327
 328 static void
 329 bpfinishpy_out_of_scope (struct finish_breakpoint_object *bpfinish_obj)
 330 {
 331   gdbpy_breakpoint_object *bp_obj = (gdbpy_breakpoint_object *) bpfinish_obj;
 332   PyObject *py_obj = (PyObject *) bp_obj;
 333
 334   if (bpfinish_obj->py_bp.bp->enable_state == bp_enabled
 335       && PyObject_HasAttrString (py_obj, outofscope_func))
 336     {
 337       gdbpy_ref<> meth_result (PyObject_CallMethod (py_obj, outofscope_func,
 338                                                     NULL));
 339       if (meth_result == NULL)
 340         gdbpy_print_stack ();
 341     }
 342
 343   delete_breakpoint (bpfinish_obj->py_bp.bp);
 344 }
 345
 346 /* Callback for `bpfinishpy_detect_out_scope'.  Triggers Python's
 347    `B->out_of_scope' function if B is a FinishBreakpoint out of its scope.  */
 348
 349 static int
 350 bpfinishpy_detect_out_scope_cb (struct breakpoint *b, void *args)
 351 {
 352   struct breakpoint *bp_stopped = (struct breakpoint *) args;
 353   PyObject *py_bp = (PyObject *) b->py_bp_object;
 354
 355   /* Trigger out_of_scope if this is a FinishBreakpoint and its frame is
 356      not anymore in the current callstack.  */
 357   if (py_bp != NULL && b->py_bp_object->is_finish_bp)
 358     {
 359       struct finish_breakpoint_object *finish_bp =
 360           (struct finish_breakpoint_object *) py_bp;
 361
 362       /* Check scope if not currently stopped at the FinishBreakpoint.  */
 363       if (b != bp_stopped)
 364         {
 365           TRY
 366             {
 367               if (b->pspace == current_inferior ()->pspace
 368                   && (!target_has_registers
 369                       || frame_find_by_id (b->frame_id) == NULL))
 370                 bpfinishpy_out_of_scope (finish_bp);
 371             }
 372           CATCH (except, RETURN_MASK_ALL)
 373             {
 374               gdbpy_convert_exception (except);
 375               gdbpy_print_stack ();
 376             }
 377           END_CATCH
 378         }
 379     }
 380
 381   return 0;
 382 }
 383
 384 /* Attached to `stop' notifications, check if the execution has run
 385    out of the scope of any FinishBreakpoint before it has been hit.  */
 386
 387 static void
 388 bpfinishpy_handle_stop (struct bpstats *bs, int print_frame)
 389 {
 390   gdbpy_enter enter_py (get_current_arch (), current_language);
 391
 392   iterate_over_breakpoints (bpfinishpy_detect_out_scope_cb,
 393                             bs == NULL ? NULL : bs->breakpoint_at);
 394 }
 395
 396 /* Attached to `exit' notifications, triggers all the necessary out of
 397    scope notifications.  */
 398
 399 static void
 400 bpfinishpy_handle_exit (struct inferior *inf)
 401 {
 402   gdbpy_enter enter_py (target_gdbarch (), current_language);
 403
 404   iterate_over_breakpoints (bpfinishpy_detect_out_scope_cb, NULL);
 405 }
 406
 407 /* Initialize the Python finish breakpoint code.  */
 408
 409 int
 410 gdbpy_initialize_finishbreakpoints (void)
 411 {
 412   if (PyType_Ready (&finish_breakpoint_object_type) < 0)
 413     return -1;
 414
 415   if (gdb_pymodule_addobject (gdb_module, "FinishBreakpoint",
 416                               (PyObject *) &finish_breakpoint_object_type) < 0)
 417     return -1;
 418
 419   gdb::observers::normal_stop.attach (bpfinishpy_handle_stop);
 420   gdb::observers::inferior_exit.attach (bpfinishpy_handle_exit);
 421
 422   return 0;
 423 }
 424
 425 static gdb_PyGetSetDef finish_breakpoint_object_getset[] = {
 426   { "return_value", bpfinishpy_get_returnvalue, NULL,
 427   "gdb.Value object representing the return value, if any. \
 428 None otherwise.", NULL },
 429     { NULL }  /* Sentinel.  */
 430 };
 431
 432 PyTypeObject finish_breakpoint_object_type =
 433 {
 434   PyVarObject_HEAD_INIT (NULL, 0)
 435   "gdb.FinishBreakpoint",         /*tp_name*/
 436   sizeof (struct finish_breakpoint_object),  /*tp_basicsize*/
 437   0,                              /*tp_itemsize*/
 438   bpfinishpy_dealloc,             /*tp_dealloc*/
 439   0,                              /*tp_print*/
 440   0,                              /*tp_getattr*/
 441   0,                              /*tp_setattr*/
 442   0,                              /*tp_compare*/
 443   0,                              /*tp_repr*/
 444   0,                              /*tp_as_number*/
 445   0,                              /*tp_as_sequence*/
 446   0,                              /*tp_as_mapping*/
 447   0,                              /*tp_hash */
 448   0,                              /*tp_call*/
 449   0,                              /*tp_str*/
 450   0,                              /*tp_getattro*/
 451   0,                              /*tp_setattro */
 452   0,                              /*tp_as_buffer*/
 453   Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
 454   "GDB finish breakpoint object", /* tp_doc */
 455   0,                              /* tp_traverse */
 456   0,                              /* tp_clear */
 457   0,                              /* tp_richcompare */
 458   0,                              /* tp_weaklistoffset */
 459   0,                              /* tp_iter */
 460   0,                              /* tp_iternext */
 461   0,                              /* tp_methods */
 462   0,                              /* tp_members */
 463   finish_breakpoint_object_getset,/* tp_getset */
 464   &breakpoint_object_type,        /* tp_base */
 465   0,                              /* tp_dict */
 466   0,                              /* tp_descr_get */
 467   0,                              /* tp_descr_set */
 468   0,                              /* tp_dictoffset */
 469   bpfinishpy_init,                /* tp_init */
 470   0,                              /* tp_alloc */
 471   0                               /* tp_new */
 472 };