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