gdb/ravenscar-thread.c

   1 /* Ada Ravenscar thread support.
   2
   3    Copyright (C) 2004-2017 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 #include "defs.h"
  21 #include "gdbcore.h"
  22 #include "gdbthread.h"
  23 #include "ada-lang.h"
  24 #include "target.h"
  25 #include "inferior.h"
  26 #include "command.h"
  27 #include "ravenscar-thread.h"
  28 #include "observer.h"
  29 #include "gdbcmd.h"
  30 #include "top.h"
  31 #include "regcache.h"
  32 #include "objfiles.h"
  33
  34 /* If non-null, ravenscar task support is enabled.  */
  35 static int ravenscar_task_support = 1;
  36
  37 /* This module's target-specific operations.  */
  38 static struct target_ops ravenscar_ops;
  39
  40 /* Some base target uses a special value for the null PID (exempli gratia
  41    remote).  */
  42 static ptid_t base_magic_null_ptid;
  43
  44 /* Ptid of the inferior as seen by the process stratum.  */
  45 static ptid_t base_ptid;
  46
  47 static const char running_thread_name[] = "__gnat_running_thread_table";
  48
  49 static const char known_tasks_name[] = "system__tasking__debug__known_tasks";
  50 static const char first_task_name[] = "system__tasking__debug__first_task";
  51
  52 static const char ravenscar_runtime_initializer[] =
  53   "system__bb__threads__initialize";
  54
  55 static void ravenscar_update_thread_list (struct target_ops *ops);
  56 static ptid_t ravenscar_running_thread (void);
  57 static char *ravenscar_extra_thread_info (struct target_ops *self,
  58                                           struct thread_info *tp);
  59 static int ravenscar_thread_alive (struct target_ops *ops, ptid_t ptid);
  60 static void ravenscar_fetch_registers (struct target_ops *ops,
  61                                        struct regcache *regcache, int regnum);
  62 static void ravenscar_store_registers (struct target_ops *ops,
  63                                        struct regcache *regcache, int regnum);
  64 static void ravenscar_prepare_to_store (struct target_ops *self,
  65                                         struct regcache *regcache);
  66 static void ravenscar_resume (struct target_ops *ops, ptid_t ptid, int step,
  67                               enum gdb_signal siggnal);
  68 static void ravenscar_mourn_inferior (struct target_ops *ops);
  69 static void ravenscar_update_inferior_ptid (void);
  70 static int has_ravenscar_runtime (void);
  71 static int ravenscar_runtime_initialized (void);
  72 static void ravenscar_inferior_created (struct target_ops *target,
  73                                         int from_tty);
  74
  75 /* Fetch the ravenscar running thread from target memory and
  76    update inferior_ptid accordingly.  */
  77
  78 static void
  79 ravenscar_update_inferior_ptid (void)
  80 {
  81   base_ptid = inferior_ptid;
  82
  83   /* If the runtime has not been initialized yet, the inferior_ptid is
  84      the only ptid that there is.  */
  85   if (!ravenscar_runtime_initialized ())
  86     return;
  87
  88   /* Make sure we set base_ptid before calling ravenscar_running_thread
  89      as the latter relies on it.  */
  90   inferior_ptid = ravenscar_running_thread ();
  91   gdb_assert (!ptid_equal (inferior_ptid, null_ptid));
  92
  93   /* The running thread may not have been added to
  94      system.tasking.debug's list yet; so ravenscar_update_thread_list
  95      may not always add it to the thread list.  Add it here.  */
  96   if (!find_thread_ptid (inferior_ptid))
  97     add_thread (inferior_ptid);
  98 }
  99
 100 /* The Ravenscar Runtime exports a symbol which contains the ID of
 101    the thread that is currently running.  Try to locate that symbol
 102    and return its associated minimal symbol.
 103    Return NULL if not found.  */
 104
 105 static struct bound_minimal_symbol
 106 get_running_thread_msymbol (void)
 107 {
 108   struct bound_minimal_symbol msym;
 109
 110   msym = lookup_minimal_symbol (running_thread_name, NULL, NULL);
 111   if (!msym.minsym)
 112     /* Older versions of the GNAT runtime were using a different
 113        (less ideal) name for the symbol where the active thread ID
 114        is stored.  If we couldn't find the symbol using the latest
 115        name, then try the old one.  */
 116     msym = lookup_minimal_symbol ("running_thread", NULL, NULL);
 117
 118   return msym;
 119 }
 120
 121 /* Return True if the Ada Ravenscar run-time can be found in the
 122    application.  */
 123
 124 static int
 125 has_ravenscar_runtime (void)
 126 {
 127   struct bound_minimal_symbol msym_ravenscar_runtime_initializer =
 128     lookup_minimal_symbol (ravenscar_runtime_initializer, NULL, NULL);
 129   struct bound_minimal_symbol msym_known_tasks =
 130     lookup_minimal_symbol (known_tasks_name, NULL, NULL);
 131   struct bound_minimal_symbol msym_first_task =
 132     lookup_minimal_symbol (first_task_name, NULL, NULL);
 133   struct bound_minimal_symbol msym_running_thread
 134     = get_running_thread_msymbol ();
 135
 136   return (msym_ravenscar_runtime_initializer.minsym
 137           && (msym_known_tasks.minsym || msym_first_task.minsym)
 138           && msym_running_thread.minsym);
 139 }
 140
 141 /* Return True if the Ada Ravenscar run-time can be found in the
 142    application, and if it has been initialized on target.  */
 143
 144 static int
 145 ravenscar_runtime_initialized (void)
 146 {
 147   return (!(ptid_equal (ravenscar_running_thread (), null_ptid)));
 148 }
 149
 150 /* Return the ID of the thread that is currently running.
 151    Return 0 if the ID could not be determined.  */
 152
 153 static CORE_ADDR
 154 get_running_thread_id (void)
 155 {
 156   struct bound_minimal_symbol object_msym = get_running_thread_msymbol ();
 157   int object_size;
 158   int buf_size;
 159   gdb_byte *buf;
 160   CORE_ADDR object_addr;
 161   struct type *builtin_type_void_data_ptr =
 162     builtin_type (target_gdbarch ())->builtin_data_ptr;
 163
 164   if (!object_msym.minsym)
 165     return 0;
 166
 167   object_addr = BMSYMBOL_VALUE_ADDRESS (object_msym);
 168   object_size = TYPE_LENGTH (builtin_type_void_data_ptr);
 169   buf_size = object_size;
 170   buf = (gdb_byte *) alloca (buf_size);
 171   read_memory (object_addr, buf, buf_size);
 172   return extract_typed_address (buf, builtin_type_void_data_ptr);
 173 }
 174
 175 static void
 176 ravenscar_resume (struct target_ops *ops, ptid_t ptid, int step,
 177                   enum gdb_signal siggnal)
 178 {
 179   struct target_ops *beneath = find_target_beneath (ops);
 180
 181   inferior_ptid = base_ptid;
 182   beneath->to_resume (beneath, base_ptid, step, siggnal);
 183 }
 184
 185 static ptid_t
 186 ravenscar_wait (struct target_ops *ops, ptid_t ptid,
 187                 struct target_waitstatus *status,
 188                 int options)
 189 {
 190   struct target_ops *beneath = find_target_beneath (ops);
 191
 192   inferior_ptid = base_ptid;
 193   beneath->to_wait (beneath, base_ptid, status, 0);
 194   /* Find any new threads that might have been created, and update
 195      inferior_ptid to the active thread.
 196
 197      Only do it if the program is still alive, though.  Otherwise,
 198      this causes problems when debugging through the remote protocol,
 199      because we might try switching threads (and thus sending packets)
 200      after the remote has disconnected.  */
 201   if (status->kind != TARGET_WAITKIND_EXITED
 202       && status->kind != TARGET_WAITKIND_SIGNALLED)
 203     {
 204       ravenscar_update_thread_list (ops);
 205       ravenscar_update_inferior_ptid ();
 206     }
 207   return inferior_ptid;
 208 }
 209
 210 /* Add the thread associated to the given TASK to the thread list
 211    (if the thread has already been added, this is a no-op).  */
 212
 213 static void
 214 ravenscar_add_thread (struct ada_task_info *task)
 215 {
 216   if (find_thread_ptid (task->ptid) == NULL)
 217     add_thread (task->ptid);
 218 }
 219
 220 static void
 221 ravenscar_update_thread_list (struct target_ops *ops)
 222 {
 223   ada_build_task_list ();
 224
 225   /* Do not clear the thread list before adding the Ada task, to keep
 226      the thread that the process stratum has included into it
 227      (base_ptid) and the running thread, that may not have been included
 228      to system.tasking.debug's list yet.  */
 229
 230   iterate_over_live_ada_tasks (ravenscar_add_thread);
 231 }
 232
 233 static ptid_t
 234 ravenscar_running_thread (void)
 235 {
 236   CORE_ADDR tid = get_running_thread_id ();
 237
 238   if (tid == 0)
 239     return null_ptid;
 240   else
 241     return ptid_build (ptid_get_pid (base_ptid), 0, tid);
 242 }
 243
 244 static char *
 245 ravenscar_extra_thread_info (struct target_ops *self, struct thread_info *tp)
 246 {
 247   return "Ravenscar task";
 248 }
 249
 250 static int
 251 ravenscar_thread_alive (struct target_ops *ops, ptid_t ptid)
 252 {
 253   /* Ravenscar tasks are non-terminating.  */
 254   return 1;
 255 }
 256
 257 static char *
 258 ravenscar_pid_to_str (struct target_ops *ops, ptid_t ptid)
 259 {
 260   static char buf[30];
 261
 262   snprintf (buf, sizeof (buf), "Thread %#x", (int) ptid_get_tid (ptid));
 263   return buf;
 264 }
 265
 266 static void
 267 ravenscar_fetch_registers (struct target_ops *ops,
 268                            struct regcache *regcache, int regnum)
 269 {
 270   struct target_ops *beneath = find_target_beneath (ops);
 271
 272   if (!ravenscar_runtime_initialized ()
 273       || ptid_equal (inferior_ptid, base_magic_null_ptid)
 274       || ptid_equal (inferior_ptid, ravenscar_running_thread ()))
 275     beneath->to_fetch_registers (beneath, regcache, regnum);
 276   else
 277     {
 278       struct gdbarch *gdbarch = get_regcache_arch (regcache);
 279       struct ravenscar_arch_ops *arch_ops
 280         = gdbarch_ravenscar_ops (gdbarch);
 281
 282       arch_ops->to_fetch_registers (regcache, regnum);
 283     }
 284 }
 285
 286 static void
 287 ravenscar_store_registers (struct target_ops *ops,
 288                            struct regcache *regcache, int regnum)
 289 {
 290   struct target_ops *beneath = find_target_beneath (ops);
 291
 292   if (!ravenscar_runtime_initialized ()
 293       || ptid_equal (inferior_ptid, base_magic_null_ptid)
 294       || ptid_equal (inferior_ptid, ravenscar_running_thread ()))
 295     beneath->to_store_registers (beneath, regcache, regnum);
 296   else
 297     {
 298       struct gdbarch *gdbarch = get_regcache_arch (regcache);
 299       struct ravenscar_arch_ops *arch_ops
 300         = gdbarch_ravenscar_ops (gdbarch);
 301
 302       arch_ops->to_store_registers (regcache, regnum);
 303     }
 304 }
 305
 306 static void
 307 ravenscar_prepare_to_store (struct target_ops *self,
 308                             struct regcache *regcache)
 309 {
 310   struct target_ops *beneath = find_target_beneath (self);
 311
 312   if (!ravenscar_runtime_initialized ()
 313       || ptid_equal (inferior_ptid, base_magic_null_ptid)
 314       || ptid_equal (inferior_ptid, ravenscar_running_thread ()))
 315     beneath->to_prepare_to_store (beneath, regcache);
 316   else
 317     {
 318       struct gdbarch *gdbarch = get_regcache_arch (regcache);
 319       struct ravenscar_arch_ops *arch_ops
 320         = gdbarch_ravenscar_ops (gdbarch);
 321
 322       arch_ops->to_prepare_to_store (regcache);
 323     }
 324 }
 325
 326 static void
 327 ravenscar_mourn_inferior (struct target_ops *ops)
 328 {
 329   struct target_ops *beneath = find_target_beneath (ops);
 330
 331   base_ptid = null_ptid;
 332   beneath->to_mourn_inferior (beneath);
 333   unpush_target (&ravenscar_ops);
 334 }
 335
 336 /* Observer on inferior_created: push ravenscar thread stratum if needed.  */
 337
 338 static void
 339 ravenscar_inferior_created (struct target_ops *target, int from_tty)
 340 {
 341
 342   if (!ravenscar_task_support
 343       || gdbarch_ravenscar_ops (target_gdbarch ()) == NULL
 344       || !has_ravenscar_runtime ())
 345     return;
 346
 347   base_magic_null_ptid = inferior_ptid;
 348   ravenscar_update_inferior_ptid ();
 349   push_target (&ravenscar_ops);
 350 }
 351
 352 static ptid_t
 353 ravenscar_get_ada_task_ptid (struct target_ops *self, long lwp, long thread)
 354 {
 355   return ptid_build (ptid_get_pid (base_ptid), 0, thread);
 356 }
 357
 358 static void
 359 init_ravenscar_thread_ops (void)
 360 {
 361   ravenscar_ops.to_shortname = "ravenscar";
 362   ravenscar_ops.to_longname = "Ravenscar tasks.";
 363   ravenscar_ops.to_doc = "Ravenscar tasks support.";
 364   ravenscar_ops.to_resume = ravenscar_resume;
 365   ravenscar_ops.to_wait = ravenscar_wait;
 366   ravenscar_ops.to_fetch_registers = ravenscar_fetch_registers;
 367   ravenscar_ops.to_store_registers = ravenscar_store_registers;
 368   ravenscar_ops.to_prepare_to_store = ravenscar_prepare_to_store;
 369   ravenscar_ops.to_thread_alive = ravenscar_thread_alive;
 370   ravenscar_ops.to_update_thread_list = ravenscar_update_thread_list;
 371   ravenscar_ops.to_pid_to_str = ravenscar_pid_to_str;
 372   ravenscar_ops.to_extra_thread_info = ravenscar_extra_thread_info;
 373   ravenscar_ops.to_get_ada_task_ptid = ravenscar_get_ada_task_ptid;
 374   ravenscar_ops.to_mourn_inferior = ravenscar_mourn_inferior;
 375   ravenscar_ops.to_has_all_memory = default_child_has_all_memory;
 376   ravenscar_ops.to_has_memory = default_child_has_memory;
 377   ravenscar_ops.to_has_stack = default_child_has_stack;
 378   ravenscar_ops.to_has_registers = default_child_has_registers;
 379   ravenscar_ops.to_has_execution = default_child_has_execution;
 380   ravenscar_ops.to_stratum = thread_stratum;
 381   ravenscar_ops.to_magic = OPS_MAGIC;
 382 }
 383
 384 /* Command-list for the "set/show ravenscar" prefix command.  */
 385 static struct cmd_list_element *set_ravenscar_list;
 386 static struct cmd_list_element *show_ravenscar_list;
 387
 388 /* Implement the "set ravenscar" prefix command.  */
 389
 390 static void
 391 set_ravenscar_command (char *arg, int from_tty)
 392 {
 393   printf_unfiltered (_(\
 394 "\"set ravenscar\" must be followed by the name of a setting.\n"));
 395   help_list (set_ravenscar_list, "set ravenscar ", all_commands, gdb_stdout);
 396 }
 397
 398 /* Implement the "show ravenscar" prefix command.  */
 399
 400 static void
 401 show_ravenscar_command (char *args, int from_tty)
 402 {
 403   cmd_show_list (show_ravenscar_list, from_tty, "");
 404 }
 405
 406 /* Implement the "show ravenscar task-switching" command.  */
 407
 408 static void
 409 show_ravenscar_task_switching_command (struct ui_file *file, int from_tty,
 410                                        struct cmd_list_element *c,
 411                                        const char *value)
 412 {
 413   if (ravenscar_task_support)
 414     fprintf_filtered (file, _("\
 415 Support for Ravenscar task/thread switching is enabled\n"));
 416   else
 417     fprintf_filtered (file, _("\
 418 Support for Ravenscar task/thread switching is disabled\n"));
 419 }
 420
 421 /* Provide a prototype to silence -Wmissing-prototypes.  */
 422 extern void _initialize_ravenscar (void);
 423
 424 /* Module startup initialization function, automagically called by
 425    init.c.  */
 426
 427 void
 428 _initialize_ravenscar (void)
 429 {
 430   init_ravenscar_thread_ops ();
 431   base_ptid = null_ptid;
 432
 433   /* Notice when the inferior is created in order to push the
 434      ravenscar ops if needed.  */
 435   observer_attach_inferior_created (ravenscar_inferior_created);
 436
 437   complete_target_initialization (&ravenscar_ops);
 438
 439   add_prefix_cmd ("ravenscar", no_class, set_ravenscar_command,
 440                   _("Prefix command for changing Ravenscar-specific settings"),
 441                   &set_ravenscar_list, "set ravenscar ", 0, &setlist);
 442
 443   add_prefix_cmd ("ravenscar", no_class, show_ravenscar_command,
 444                   _("Prefix command for showing Ravenscar-specific settings"),
 445                   &show_ravenscar_list, "show ravenscar ", 0, &showlist);
 446
 447   add_setshow_boolean_cmd ("task-switching", class_obscure,
 448                            &ravenscar_task_support, _("\
 449 Enable or disable support for GNAT Ravenscar tasks"), _("\
 450 Show whether support for GNAT Ravenscar tasks is enabled"),
 451                            _("\
 452 Enable or disable support for task/thread switching with the GNAT\n\
 453 Ravenscar run-time library for bareboard configuration."),
 454                            NULL, show_ravenscar_task_switching_command,
 455                            &set_ravenscar_list, &show_ravenscar_list);
 456 }