gdb/ravenscar-thread.c

   1 /* Ada Ravenscar thread support.
   2
   3    Copyright (C) 2004-2019 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 #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 "observable.h"
  29 #include "gdbcmd.h"
  30 #include "top.h"
  31 #include "regcache.h"
  32 #include "objfiles.h"
  33
  34 /* This module provides support for "Ravenscar" tasks (Ada) when
  35    debugging on bare-metal targets.
  36
  37    The typical situation is when debugging a bare-metal target over
  38    the remote protocol. In that situation, the system does not know
  39    about high-level concepts such as threads, only about some code
  40    running on one or more CPUs. And since the remote protocol does not
  41    provide any handling for CPUs, the de facto standard for handling
  42    them is to have one thread per CPU, where the thread's ptid has
  43    its lwp field set to the CPU number (eg: 1 for the first CPU,
  44    2 for the second one, etc).  This module will make that assumption.
  45
  46    This module then creates and maintains the list of threads based
  47    on the list of Ada tasks, with one thread per Ada task. The convention
  48    is that threads corresponding to the CPUs (see assumption above)
  49    have a ptid_t of the form (PID, LWP, 0), while threads corresponding
  50    to our Ada tasks have a ptid_t of the form (PID, 0, TID) where TID
  51    is the Ada task's ID as extracted from Ada runtime information.
  52
  53    Switching to a given Ada task (or its underlying thread) is performed
  54    by fetching the registers of that task from the memory area where
  55    the registers were saved.  For any of the other operations, the
  56    operation is performed by first finding the CPU on which the task
  57    is running, switching to its corresponding ptid, and then performing
  58    the operation on that ptid using the target beneath us.  */
  59
  60 /* If non-null, ravenscar task support is enabled.  */
  61 static int ravenscar_task_support = 1;
  62
  63 /* PTID of the last thread that received an event.
  64    This can be useful to determine the associated task that received
  65    the event, to make it the current task.  */
  66 static ptid_t base_ptid;
  67
  68 static const char running_thread_name[] = "__gnat_running_thread_table";
  69
  70 static const char known_tasks_name[] = "system__tasking__debug__known_tasks";
  71 static const char first_task_name[] = "system__tasking__debug__first_task";
  72
  73 static const char ravenscar_runtime_initializer[] =
  74   "system__bb__threads__initialize";
  75
  76 static const target_info ravenscar_target_info = {
  77   "ravenscar",
  78   N_("Ravenscar tasks."),
  79   N_("Ravenscar tasks support.")
  80 };
  81
  82 struct ravenscar_thread_target final : public target_ops
  83 {
  84   const target_info &info () const override
  85   { return ravenscar_target_info; }
  86
  87   strata stratum () const override { return thread_stratum; }
  88
  89   ptid_t wait (ptid_t, struct target_waitstatus *, int) override;
  90   void resume (ptid_t, int, enum gdb_signal) override;
  91
  92   void fetch_registers (struct regcache *, int) override;
  93   void store_registers (struct regcache *, int) override;
  94
  95   void prepare_to_store (struct regcache *) override;
  96
  97   bool stopped_by_sw_breakpoint () override;
  98
  99   bool stopped_by_hw_breakpoint () override;
 100
 101   bool stopped_by_watchpoint () override;
 102
 103   bool stopped_data_address (CORE_ADDR *) override;
 104
 105   bool thread_alive (ptid_t ptid) override;
 106
 107   int core_of_thread (ptid_t ptid) override;
 108
 109   void update_thread_list () override;
 110
 111   const char *extra_thread_info (struct thread_info *) override;
 112
 113   const char *pid_to_str (ptid_t) override;
 114
 115   ptid_t get_ada_task_ptid (long lwp, long thread) override;
 116
 117   void mourn_inferior () override;
 118 };
 119
 120 /* This module's target-specific operations.  */
 121 static ravenscar_thread_target ravenscar_ops;
 122
 123 static ptid_t ravenscar_active_task (int cpu);
 124 static void ravenscar_update_inferior_ptid (void);
 125 static int has_ravenscar_runtime (void);
 126 static int ravenscar_runtime_initialized (void);
 127 static void ravenscar_inferior_created (struct target_ops *target,
 128                                         int from_tty);
 129
 130 /* Return nonzero iff PTID corresponds to a ravenscar task.  */
 131
 132 static int
 133 is_ravenscar_task (ptid_t ptid)
 134 {
 135   /* By construction, ravenscar tasks have their LWP set to zero.
 136      Also make sure that the TID is nonzero, as some remotes, when
 137      asked for the list of threads, will return the first thread
 138      as having its TID set to zero.  For instance, TSIM version
 139      2.0.48 for LEON3 sends 'm0' as a reply to the 'qfThreadInfo'
 140      query, which the remote protocol layer then treats as a thread
 141      whose TID is 0.  This is obviously not a ravenscar task.  */
 142   return ptid.lwp () == 0 && ptid.tid () != 0;
 143 }
 144
 145 /* Given PTID, which can be either a ravenscar task or a CPU thread,
 146    return which CPU that ptid is running on.
 147
 148    This assume that PTID is a valid ptid_t.  Otherwise, a gdb_assert
 149    will be triggered.  */
 150
 151 static int
 152 ravenscar_get_thread_base_cpu (ptid_t ptid)
 153 {
 154   int base_cpu;
 155
 156   if (is_ravenscar_task (ptid))
 157     {
 158       struct ada_task_info *task_info = ada_get_task_info_from_ptid (ptid);
 159
 160       gdb_assert (task_info != NULL);
 161       base_cpu = task_info->base_cpu;
 162     }
 163   else
 164     {
 165       /* We assume that the LWP of the PTID is equal to the CPU number.  */
 166       base_cpu = ptid.lwp ();
 167     }
 168
 169   return base_cpu;
 170 }
 171
 172 /* Given a ravenscar task (identified by its ptid_t PTID), return nonzero
 173    if this task is the currently active task on the cpu that task is
 174    running on.
 175
 176    In other words, this function determine which CPU this task is
 177    currently running on, and then return nonzero if the CPU in question
 178    is executing the code for that task.  If that's the case, then
 179    that task's registers are in the CPU bank.  Otherwise, the task
 180    is currently suspended, and its registers have been saved in memory.  */
 181
 182 static int
 183 ravenscar_task_is_currently_active (ptid_t ptid)
 184 {
 185   ptid_t active_task_ptid
 186     = ravenscar_active_task (ravenscar_get_thread_base_cpu (ptid));
 187
 188   return ptid == active_task_ptid;
 189 }
 190
 191 /* Return the CPU thread (as a ptid_t) on which the given ravenscar
 192    task is running.
 193
 194    This is the thread that corresponds to the CPU on which the task
 195    is running.  */
 196
 197 static ptid_t
 198 get_base_thread_from_ravenscar_task (ptid_t ptid)
 199 {
 200   int base_cpu;
 201
 202   if (!is_ravenscar_task (ptid))
 203     return ptid;
 204
 205   base_cpu = ravenscar_get_thread_base_cpu (ptid);
 206   return ptid_t (ptid.pid (), base_cpu, 0);
 207 }
 208
 209 /* Fetch the ravenscar running thread from target memory and
 210    update inferior_ptid accordingly.  */
 211
 212 static void
 213 ravenscar_update_inferior_ptid (void)
 214 {
 215   int base_cpu;
 216
 217   base_ptid = inferior_ptid;
 218
 219   gdb_assert (!is_ravenscar_task (inferior_ptid));
 220   base_cpu = ravenscar_get_thread_base_cpu (base_ptid);
 221
 222   /* If the runtime has not been initialized yet, the inferior_ptid is
 223      the only ptid that there is.  */
 224   if (!ravenscar_runtime_initialized ())
 225     return;
 226
 227   /* Make sure we set base_ptid before calling ravenscar_active_task
 228      as the latter relies on it.  */
 229   inferior_ptid = ravenscar_active_task (base_cpu);
 230   gdb_assert (inferior_ptid != null_ptid);
 231
 232   /* The running thread may not have been added to
 233      system.tasking.debug's list yet; so ravenscar_update_thread_list
 234      may not always add it to the thread list.  Add it here.  */
 235   if (!find_thread_ptid (inferior_ptid))
 236     add_thread (inferior_ptid);
 237 }
 238
 239 /* The Ravenscar Runtime exports a symbol which contains the ID of
 240    the thread that is currently running.  Try to locate that symbol
 241    and return its associated minimal symbol.
 242    Return NULL if not found.  */
 243
 244 static struct bound_minimal_symbol
 245 get_running_thread_msymbol (void)
 246 {
 247   struct bound_minimal_symbol msym;
 248
 249   msym = lookup_minimal_symbol (running_thread_name, NULL, NULL);
 250   if (!msym.minsym)
 251     /* Older versions of the GNAT runtime were using a different
 252        (less ideal) name for the symbol where the active thread ID
 253        is stored.  If we couldn't find the symbol using the latest
 254        name, then try the old one.  */
 255     msym = lookup_minimal_symbol ("running_thread", NULL, NULL);
 256
 257   return msym;
 258 }
 259
 260 /* Return True if the Ada Ravenscar run-time can be found in the
 261    application.  */
 262
 263 static int
 264 has_ravenscar_runtime (void)
 265 {
 266   struct bound_minimal_symbol msym_ravenscar_runtime_initializer =
 267     lookup_minimal_symbol (ravenscar_runtime_initializer, NULL, NULL);
 268   struct bound_minimal_symbol msym_known_tasks =
 269     lookup_minimal_symbol (known_tasks_name, NULL, NULL);
 270   struct bound_minimal_symbol msym_first_task =
 271     lookup_minimal_symbol (first_task_name, NULL, NULL);
 272   struct bound_minimal_symbol msym_running_thread
 273     = get_running_thread_msymbol ();
 274
 275   return (msym_ravenscar_runtime_initializer.minsym
 276           && (msym_known_tasks.minsym || msym_first_task.minsym)
 277           && msym_running_thread.minsym);
 278 }
 279
 280 /* Return True if the Ada Ravenscar run-time can be found in the
 281    application, and if it has been initialized on target.  */
 282
 283 static int
 284 ravenscar_runtime_initialized (void)
 285 {
 286   return (!(ravenscar_active_task (1) == null_ptid));
 287 }
 288
 289 /* Return the ID of the thread that is currently running.
 290    Return 0 if the ID could not be determined.  */
 291
 292 static CORE_ADDR
 293 get_running_thread_id (int cpu)
 294 {
 295   struct bound_minimal_symbol object_msym = get_running_thread_msymbol ();
 296   int object_size;
 297   int buf_size;
 298   gdb_byte *buf;
 299   CORE_ADDR object_addr;
 300   struct type *builtin_type_void_data_ptr =
 301     builtin_type (target_gdbarch ())->builtin_data_ptr;
 302
 303   if (!object_msym.minsym)
 304     return 0;
 305
 306   object_size = TYPE_LENGTH (builtin_type_void_data_ptr);
 307   object_addr = (BMSYMBOL_VALUE_ADDRESS (object_msym)
 308                  + (cpu - 1) * object_size);
 309   buf_size = object_size;
 310   buf = (gdb_byte *) alloca (buf_size);
 311   read_memory (object_addr, buf, buf_size);
 312   return extract_typed_address (buf, builtin_type_void_data_ptr);
 313 }
 314
 315 void
 316 ravenscar_thread_target::resume (ptid_t ptid, int step, enum gdb_signal siggnal)
 317 {
 318   inferior_ptid = base_ptid;
 319   beneath ()->resume (base_ptid, step, siggnal);
 320 }
 321
 322 ptid_t
 323 ravenscar_thread_target::wait (ptid_t ptid,
 324                                struct target_waitstatus *status,
 325                                int options)
 326 {
 327   ptid_t event_ptid;
 328
 329   inferior_ptid = base_ptid;
 330   event_ptid = beneath ()->wait (base_ptid, status, 0);
 331   /* Find any new threads that might have been created, and update
 332      inferior_ptid to the active thread.
 333
 334      Only do it if the program is still alive, though.  Otherwise,
 335      this causes problems when debugging through the remote protocol,
 336      because we might try switching threads (and thus sending packets)
 337      after the remote has disconnected.  */
 338   if (status->kind != TARGET_WAITKIND_EXITED
 339       && status->kind != TARGET_WAITKIND_SIGNALLED)
 340     {
 341       inferior_ptid = event_ptid;
 342       this->update_thread_list ();
 343       ravenscar_update_inferior_ptid ();
 344     }
 345   return inferior_ptid;
 346 }
 347
 348 /* Add the thread associated to the given TASK to the thread list
 349    (if the thread has already been added, this is a no-op).  */
 350
 351 static void
 352 ravenscar_add_thread (struct ada_task_info *task)
 353 {
 354   if (find_thread_ptid (task->ptid) == NULL)
 355     add_thread (task->ptid);
 356 }
 357
 358 void
 359 ravenscar_thread_target::update_thread_list ()
 360 {
 361   ada_build_task_list ();
 362
 363   /* Do not clear the thread list before adding the Ada task, to keep
 364      the thread that the process stratum has included into it
 365      (base_ptid) and the running thread, that may not have been included
 366      to system.tasking.debug's list yet.  */
 367
 368   iterate_over_live_ada_tasks (ravenscar_add_thread);
 369 }
 370
 371 static ptid_t
 372 ravenscar_active_task (int cpu)
 373 {
 374   CORE_ADDR tid = get_running_thread_id (cpu);
 375
 376   if (tid == 0)
 377     return null_ptid;
 378   else
 379     return ptid_t (base_ptid.pid (), 0, tid);
 380 }
 381
 382 const char *
 383 ravenscar_thread_target::extra_thread_info (thread_info *tp)
 384 {
 385   return "Ravenscar task";
 386 }
 387
 388 bool
 389 ravenscar_thread_target::thread_alive (ptid_t ptid)
 390 {
 391   /* Ravenscar tasks are non-terminating.  */
 392   return true;
 393 }
 394
 395 const char *
 396 ravenscar_thread_target::pid_to_str (ptid_t ptid)
 397 {
 398   static char buf[30];
 399
 400   snprintf (buf, sizeof (buf), "Thread %#x", (int) ptid.tid ());
 401   return buf;
 402 }
 403
 404 void
 405 ravenscar_thread_target::fetch_registers (struct regcache *regcache, int regnum)
 406 {
 407   ptid_t ptid = regcache->ptid ();
 408
 409   if (ravenscar_runtime_initialized ()
 410       && is_ravenscar_task (ptid)
 411       && !ravenscar_task_is_currently_active (ptid))
 412     {
 413       struct gdbarch *gdbarch = regcache->arch ();
 414       struct ravenscar_arch_ops *arch_ops
 415         = gdbarch_ravenscar_ops (gdbarch);
 416
 417       arch_ops->to_fetch_registers (regcache, regnum);
 418     }
 419   else
 420     beneath ()->fetch_registers (regcache, regnum);
 421 }
 422
 423 void
 424 ravenscar_thread_target::store_registers (struct regcache *regcache,
 425                                           int regnum)
 426 {
 427   ptid_t ptid = regcache->ptid ();
 428
 429   if (ravenscar_runtime_initialized ()
 430       && is_ravenscar_task (ptid)
 431       && !ravenscar_task_is_currently_active (ptid))
 432     {
 433       struct gdbarch *gdbarch = regcache->arch ();
 434       struct ravenscar_arch_ops *arch_ops
 435         = gdbarch_ravenscar_ops (gdbarch);
 436
 437       arch_ops->to_store_registers (regcache, regnum);
 438     }
 439   else
 440     beneath ()->store_registers (regcache, regnum);
 441 }
 442
 443 void
 444 ravenscar_thread_target::prepare_to_store (struct regcache *regcache)
 445 {
 446   ptid_t ptid = regcache->ptid ();
 447
 448   if (ravenscar_runtime_initialized ()
 449       && is_ravenscar_task (ptid)
 450       && !ravenscar_task_is_currently_active (ptid))
 451     {
 452       struct gdbarch *gdbarch = regcache->arch ();
 453       struct ravenscar_arch_ops *arch_ops
 454         = gdbarch_ravenscar_ops (gdbarch);
 455
 456       arch_ops->to_prepare_to_store (regcache);
 457     }
 458   else
 459     beneath ()->prepare_to_store (regcache);
 460 }
 461
 462 /* Implement the to_stopped_by_sw_breakpoint target_ops "method".  */
 463
 464 bool
 465 ravenscar_thread_target::stopped_by_sw_breakpoint ()
 466 {
 467   ptid_t saved_ptid = inferior_ptid;
 468   bool result;
 469
 470   inferior_ptid = get_base_thread_from_ravenscar_task (saved_ptid);
 471   result = beneath ()->stopped_by_sw_breakpoint ();
 472   inferior_ptid = saved_ptid;
 473   return result;
 474 }
 475
 476 /* Implement the to_stopped_by_hw_breakpoint target_ops "method".  */
 477
 478 bool
 479 ravenscar_thread_target::stopped_by_hw_breakpoint ()
 480 {
 481   ptid_t saved_ptid = inferior_ptid;
 482   bool result;
 483
 484   inferior_ptid = get_base_thread_from_ravenscar_task (saved_ptid);
 485   result = beneath ()->stopped_by_hw_breakpoint ();
 486   inferior_ptid = saved_ptid;
 487   return result;
 488 }
 489
 490 /* Implement the to_stopped_by_watchpoint target_ops "method".  */
 491
 492 bool
 493 ravenscar_thread_target::stopped_by_watchpoint ()
 494 {
 495   ptid_t saved_ptid = inferior_ptid;
 496   bool result;
 497
 498   inferior_ptid = get_base_thread_from_ravenscar_task (saved_ptid);
 499   result = beneath ()->stopped_by_watchpoint ();
 500   inferior_ptid = saved_ptid;
 501   return result;
 502 }
 503
 504 /* Implement the to_stopped_data_address target_ops "method".  */
 505
 506 bool
 507 ravenscar_thread_target::stopped_data_address (CORE_ADDR *addr_p)
 508 {
 509   ptid_t saved_ptid = inferior_ptid;
 510   bool result;
 511
 512   inferior_ptid = get_base_thread_from_ravenscar_task (saved_ptid);
 513   result = beneath ()->stopped_data_address (addr_p);
 514   inferior_ptid = saved_ptid;
 515   return result;
 516 }
 517
 518 void
 519 ravenscar_thread_target::mourn_inferior ()
 520 {
 521   base_ptid = null_ptid;
 522   beneath ()->mourn_inferior ();
 523   unpush_target (&ravenscar_ops);
 524 }
 525
 526 /* Implement the to_core_of_thread target_ops "method".  */
 527
 528 int
 529 ravenscar_thread_target::core_of_thread (ptid_t ptid)
 530 {
 531   ptid_t saved_ptid = inferior_ptid;
 532   int result;
 533
 534   inferior_ptid = get_base_thread_from_ravenscar_task (saved_ptid);
 535   result = beneath ()->core_of_thread (inferior_ptid);
 536   inferior_ptid = saved_ptid;
 537   return result;
 538 }
 539
 540 /* Observer on inferior_created: push ravenscar thread stratum if needed.  */
 541
 542 static void
 543 ravenscar_inferior_created (struct target_ops *target, int from_tty)
 544 {
 545   const char *err_msg;
 546
 547   if (!ravenscar_task_support
 548       || gdbarch_ravenscar_ops (target_gdbarch ()) == NULL
 549       || !has_ravenscar_runtime ())
 550     return;
 551
 552   err_msg = ada_get_tcb_types_info ();
 553   if (err_msg != NULL)
 554     {
 555       warning (_("%s. Task/thread support disabled."), err_msg);
 556       return;
 557     }
 558
 559   ravenscar_update_inferior_ptid ();
 560   push_target (&ravenscar_ops);
 561 }
 562
 563 ptid_t
 564 ravenscar_thread_target::get_ada_task_ptid (long lwp, long thread)
 565 {
 566   return ptid_t (base_ptid.pid (), 0, thread);
 567 }
 568
 569 /* Command-list for the "set/show ravenscar" prefix command.  */
 570 static struct cmd_list_element *set_ravenscar_list;
 571 static struct cmd_list_element *show_ravenscar_list;
 572
 573 /* Implement the "set ravenscar" prefix command.  */
 574
 575 static void
 576 set_ravenscar_command (const char *arg, int from_tty)
 577 {
 578   printf_unfiltered (_(\
 579 "\"set ravenscar\" must be followed by the name of a setting.\n"));
 580   help_list (set_ravenscar_list, "set ravenscar ", all_commands, gdb_stdout);
 581 }
 582
 583 /* Implement the "show ravenscar" prefix command.  */
 584
 585 static void
 586 show_ravenscar_command (const char *args, int from_tty)
 587 {
 588   cmd_show_list (show_ravenscar_list, from_tty, "");
 589 }
 590
 591 /* Implement the "show ravenscar task-switching" command.  */
 592
 593 static void
 594 show_ravenscar_task_switching_command (struct ui_file *file, int from_tty,
 595                                        struct cmd_list_element *c,
 596                                        const char *value)
 597 {
 598   if (ravenscar_task_support)
 599     fprintf_filtered (file, _("\
 600 Support for Ravenscar task/thread switching is enabled\n"));
 601   else
 602     fprintf_filtered (file, _("\
 603 Support for Ravenscar task/thread switching is disabled\n"));
 604 }
 605
 606 /* Module startup initialization function, automagically called by
 607    init.c.  */
 608
 609 void
 610 _initialize_ravenscar (void)
 611 {
 612   base_ptid = null_ptid;
 613
 614   /* Notice when the inferior is created in order to push the
 615      ravenscar ops if needed.  */
 616   gdb::observers::inferior_created.attach (ravenscar_inferior_created);
 617
 618   add_prefix_cmd ("ravenscar", no_class, set_ravenscar_command,
 619                   _("Prefix command for changing Ravenscar-specific settings"),
 620                   &set_ravenscar_list, "set ravenscar ", 0, &setlist);
 621
 622   add_prefix_cmd ("ravenscar", no_class, show_ravenscar_command,
 623                   _("Prefix command for showing Ravenscar-specific settings"),
 624                   &show_ravenscar_list, "show ravenscar ", 0, &showlist);
 625
 626   add_setshow_boolean_cmd ("task-switching", class_obscure,
 627                            &ravenscar_task_support, _("\
 628 Enable or disable support for GNAT Ravenscar tasks"), _("\
 629 Show whether support for GNAT Ravenscar tasks is enabled"),
 630                            _("\
 631 Enable or disable support for task/thread switching with the GNAT\n\
 632 Ravenscar run-time library for bareboard configuration."),
 633                            NULL, show_ravenscar_task_switching_command,
 634                            &set_ravenscar_list, &show_ravenscar_list);
 635 }