gdb/bsd-uthread.c

   1 /* BSD user-level threads support.
   2
   3    Copyright (C) 2005-2024 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 "inferior.h"
  24 #include "objfiles.h"
  25 #include "observable.h"
  26 #include "regcache.h"
  27 #include "solib.h"
  28 #include "solist.h"
  29 #include "symfile.h"
  30 #include "target.h"
  31
  32 #include "gdbsupport/gdb_obstack.h"
  33
  34 #include "bsd-uthread.h"
  35
  36 static const target_info bsd_uthread_target_info = {
  37   "bsd-uthreads",
  38   N_("BSD user-level threads"),
  39   N_("BSD user-level threads")
  40 };
  41
  42 struct bsd_uthread_target final : public target_ops
  43 {
  44   const target_info &info () const override
  45   { return bsd_uthread_target_info; }
  46
  47   strata stratum () const override { return thread_stratum; }
  48
  49   void close () override;
  50
  51   void mourn_inferior () override;
  52
  53   void fetch_registers (struct regcache *, int) override;
  54   void store_registers (struct regcache *, int) override;
  55
  56   ptid_t wait (ptid_t, struct target_waitstatus *, target_wait_flags) override;
  57   void resume (ptid_t, int, enum gdb_signal) override;
  58
  59   bool thread_alive (ptid_t ptid) override;
  60
  61   void update_thread_list () override;
  62
  63   const char *extra_thread_info (struct thread_info *) override;
  64
  65   std::string pid_to_str (ptid_t) override;
  66 };
  67
  68 static bsd_uthread_target bsd_uthread_ops;
  69 \f
  70
  71 /* Architecture-specific operations.  */
  72
  73 struct bsd_uthread_ops
  74 {
  75   /* Supply registers for an inactive thread to a register cache.  */
  76   void (*supply_uthread)(struct regcache *, int, CORE_ADDR) = nullptr;
  77
  78   /* Collect registers for an inactive thread from a register cache.  */
  79   void (*collect_uthread)(const struct regcache *, int, CORE_ADDR) = nullptr;
  80 };
  81
  82 /* Per-architecture data key.  */
  83 static const registry<gdbarch>::key<struct bsd_uthread_ops> bsd_uthread_data;
  84
  85 static struct bsd_uthread_ops *
  86 get_bsd_uthread (struct gdbarch *gdbarch)
  87 {
  88   struct bsd_uthread_ops *ops = bsd_uthread_data.get (gdbarch);
  89   if (ops == nullptr)
  90     ops = bsd_uthread_data.emplace (gdbarch);
  91   return ops;
  92 }
  93
  94 /* Set the function that supplies registers from an inactive thread
  95    for architecture GDBARCH to SUPPLY_UTHREAD.  */
  96
  97 void
  98 bsd_uthread_set_supply_uthread (struct gdbarch *gdbarch,
  99                                 void (*supply_uthread) (struct regcache *,
 100                                                         int, CORE_ADDR))
 101 {
 102   struct bsd_uthread_ops *ops = get_bsd_uthread (gdbarch);
 103
 104   ops->supply_uthread = supply_uthread;
 105 }
 106
 107 /* Set the function that collects registers for an inactive thread for
 108    architecture GDBARCH to SUPPLY_UTHREAD.  */
 109
 110 void
 111 bsd_uthread_set_collect_uthread (struct gdbarch *gdbarch,
 112                          void (*collect_uthread) (const struct regcache *,
 113                                                   int, CORE_ADDR))
 114 {
 115   struct bsd_uthread_ops *ops = get_bsd_uthread (gdbarch);
 116
 117   ops->collect_uthread = collect_uthread;
 118 }
 119
 120 /* Magic number to help recognize a valid thread structure.  */
 121 #define BSD_UTHREAD_PTHREAD_MAGIC       0xd09ba115
 122
 123 /* Check whether the thread structure at ADDR is valid.  */
 124
 125 static void
 126 bsd_uthread_check_magic (CORE_ADDR addr)
 127 {
 128   bfd_endian byte_order = gdbarch_byte_order (current_inferior ()->arch ());
 129   ULONGEST magic = read_memory_unsigned_integer (addr, 4, byte_order);
 130
 131   if (magic != BSD_UTHREAD_PTHREAD_MAGIC)
 132     error (_("Bad magic"));
 133 }
 134
 135 /* Thread states.  */
 136 #define BSD_UTHREAD_PS_RUNNING  0
 137 #define BSD_UTHREAD_PS_DEAD     18
 138
 139 /* Address of the pointer to the thread structure for the running
 140    thread.  */
 141 static CORE_ADDR bsd_uthread_thread_run_addr;
 142
 143 /* Address of the list of all threads.  */
 144 static CORE_ADDR bsd_uthread_thread_list_addr;
 145
 146 /* Offsets of various "interesting" bits in the thread structure.  */
 147 static int bsd_uthread_thread_state_offset = -1;
 148 static int bsd_uthread_thread_next_offset = -1;
 149 static int bsd_uthread_thread_ctx_offset;
 150
 151 /* Name of shared threads library.  */
 152 static std::string bsd_uthread_solib_name;
 153
 154 /* Non-zero if the thread stratum implemented by this module is active.  */
 155 static int bsd_uthread_active;
 156
 157 static CORE_ADDR
 158 bsd_uthread_lookup_address (const char *name, struct objfile *objfile)
 159 {
 160   struct bound_minimal_symbol sym;
 161
 162   sym = lookup_minimal_symbol (name, NULL, objfile);
 163   if (sym.minsym)
 164     return sym.value_address ();
 165
 166   return 0;
 167 }
 168
 169 static int
 170 bsd_uthread_lookup_offset (const char *name, struct objfile *objfile)
 171 {
 172   bfd_endian byte_order = gdbarch_byte_order (current_inferior ()->arch ());
 173   CORE_ADDR addr;
 174
 175   addr = bsd_uthread_lookup_address (name, objfile);
 176   if (addr == 0)
 177     return 0;
 178
 179   return read_memory_unsigned_integer (addr, 4, byte_order);
 180 }
 181
 182 static CORE_ADDR
 183 bsd_uthread_read_memory_address (CORE_ADDR addr)
 184 {
 185   type *ptr_type
 186     = builtin_type (current_inferior ()->arch ())->builtin_data_ptr;
 187   return read_memory_typed_address (addr, ptr_type);
 188 }
 189
 190 /* If OBJFILE contains the symbols corresponding to one of the
 191    supported user-level threads libraries, activate the thread stratum
 192    implemented by this module.  */
 193
 194 static int
 195 bsd_uthread_activate (struct objfile *objfile)
 196 {
 197   gdbarch *gdbarch = current_inferior ()->arch ();
 198   struct bsd_uthread_ops *ops = get_bsd_uthread (gdbarch);
 199
 200   /* Skip if the thread stratum has already been activated.  */
 201   if (bsd_uthread_active)
 202     return 0;
 203
 204   /* There's no point in enabling this module if no
 205      architecture-specific operations are provided.  */
 206   if (!ops->supply_uthread)
 207     return 0;
 208
 209   bsd_uthread_thread_run_addr =
 210     bsd_uthread_lookup_address ("_thread_run", objfile);
 211   if (bsd_uthread_thread_run_addr == 0)
 212     return 0;
 213
 214   bsd_uthread_thread_list_addr =
 215     bsd_uthread_lookup_address ("_thread_list", objfile);
 216   if (bsd_uthread_thread_list_addr == 0)
 217     return 0;
 218
 219   bsd_uthread_thread_state_offset =
 220     bsd_uthread_lookup_offset ("_thread_state_offset", objfile);
 221   if (bsd_uthread_thread_state_offset == 0)
 222     return 0;
 223
 224   bsd_uthread_thread_next_offset =
 225     bsd_uthread_lookup_offset ("_thread_next_offset", objfile);
 226   if (bsd_uthread_thread_next_offset == 0)
 227     return 0;
 228
 229   bsd_uthread_thread_ctx_offset =
 230     bsd_uthread_lookup_offset ("_thread_ctx_offset", objfile);
 231
 232   current_inferior ()->push_target (&bsd_uthread_ops);
 233   bsd_uthread_active = 1;
 234   return 1;
 235 }
 236
 237 /* Cleanup due to deactivation.  */
 238
 239 void
 240 bsd_uthread_target::close ()
 241 {
 242   bsd_uthread_active = 0;
 243   bsd_uthread_thread_run_addr = 0;
 244   bsd_uthread_thread_list_addr = 0;
 245   bsd_uthread_thread_state_offset = 0;
 246   bsd_uthread_thread_next_offset = 0;
 247   bsd_uthread_thread_ctx_offset = 0;
 248   bsd_uthread_solib_name.clear ();
 249 }
 250
 251 /* Deactivate the thread stratum implemented by this module.  */
 252
 253 static void
 254 bsd_uthread_deactivate (void)
 255 {
 256   /* Skip if the thread stratum has already been deactivated.  */
 257   if (!bsd_uthread_active)
 258     return;
 259
 260   current_inferior ()->unpush_target (&bsd_uthread_ops);
 261 }
 262
 263 static void
 264 bsd_uthread_inferior_created (inferior *inf)
 265 {
 266   bsd_uthread_activate (NULL);
 267 }
 268
 269 /* Likely candidates for the threads library.  */
 270 static const char * const bsd_uthread_solib_names[] =
 271 {
 272   "/usr/lib/libc_r.so",         /* FreeBSD */
 273   "/usr/lib/libpthread.so",     /* OpenBSD */
 274   NULL
 275 };
 276
 277 static void
 278 bsd_uthread_solib_loaded (shobj &so)
 279 {
 280   const char * const *names = bsd_uthread_solib_names;
 281
 282   for (names = bsd_uthread_solib_names; *names; names++)
 283     {
 284       if (startswith (so.so_original_name, *names))
 285         {
 286           solib_read_symbols (so, 0);
 287
 288           if (bsd_uthread_activate (so.objfile))
 289             {
 290               bsd_uthread_solib_name = so.so_original_name;
 291               return;
 292             }
 293         }
 294     }
 295 }
 296
 297 static void
 298 bsd_uthread_solib_unloaded (program_space *pspace, const shobj &so)
 299 {
 300   if (bsd_uthread_solib_name.empty ())
 301     return;
 302
 303   if (so.so_original_name == bsd_uthread_solib_name)
 304     bsd_uthread_deactivate ();
 305 }
 306
 307 void
 308 bsd_uthread_target::mourn_inferior ()
 309 {
 310   beneath ()->mourn_inferior ();
 311   bsd_uthread_deactivate ();
 312 }
 313
 314 void
 315 bsd_uthread_target::fetch_registers (struct regcache *regcache, int regnum)
 316 {
 317   struct gdbarch *gdbarch = regcache->arch ();
 318   struct bsd_uthread_ops *uthread_ops = get_bsd_uthread (gdbarch);
 319   ptid_t ptid = regcache->ptid ();
 320   CORE_ADDR addr = ptid.tid ();
 321   CORE_ADDR active_addr;
 322   scoped_restore save_inferior_ptid = make_scoped_restore (&inferior_ptid);
 323
 324   /* We are doing operations (e.g. reading memory) that rely on
 325      inferior_ptid.  */
 326   inferior_ptid = ptid;
 327
 328   /* Always fetch the appropriate registers from the layer beneath.  */
 329   beneath ()->fetch_registers (regcache, regnum);
 330
 331   /* FIXME: That might have gotten us more than we asked for.  Make
 332      sure we overwrite all relevant registers with values from the
 333      thread structure.  This can go once we fix the underlying target.  */
 334   regnum = -1;
 335
 336   active_addr = bsd_uthread_read_memory_address (bsd_uthread_thread_run_addr);
 337   if (addr != 0 && addr != active_addr)
 338     {
 339       bsd_uthread_check_magic (addr);
 340       uthread_ops->supply_uthread (regcache, regnum,
 341                                    addr + bsd_uthread_thread_ctx_offset);
 342     }
 343 }
 344
 345 void
 346 bsd_uthread_target::store_registers (struct regcache *regcache, int regnum)
 347 {
 348   struct gdbarch *gdbarch = regcache->arch ();
 349   struct bsd_uthread_ops *uthread_ops = get_bsd_uthread (gdbarch);
 350   ptid_t ptid = regcache->ptid ();
 351   CORE_ADDR addr = ptid.tid ();
 352   CORE_ADDR active_addr;
 353   scoped_restore save_inferior_ptid = make_scoped_restore (&inferior_ptid);
 354
 355   /* We are doing operations (e.g. reading memory) that rely on
 356      inferior_ptid.  */
 357   inferior_ptid = ptid;
 358
 359   active_addr = bsd_uthread_read_memory_address (bsd_uthread_thread_run_addr);
 360   if (addr != 0 && addr != active_addr)
 361     {
 362       bsd_uthread_check_magic (addr);
 363       uthread_ops->collect_uthread (regcache, regnum,
 364                                     addr + bsd_uthread_thread_ctx_offset);
 365     }
 366   else
 367     {
 368       /* Updating the thread that is currently running; pass the
 369          request to the layer beneath.  */
 370       beneath ()->store_registers (regcache, regnum);
 371     }
 372 }
 373
 374 ptid_t
 375 bsd_uthread_target::wait (ptid_t ptid, struct target_waitstatus *status,
 376                           target_wait_flags options)
 377 {
 378   bfd_endian byte_order = gdbarch_byte_order (current_inferior ()->arch ());
 379   CORE_ADDR addr;
 380   process_stratum_target *beneath
 381     = as_process_stratum_target (this->beneath ());
 382
 383   /* Pass the request to the layer beneath.  */
 384   ptid = beneath->wait (ptid, status, options);
 385
 386   /* If the process is no longer alive, there's no point in figuring
 387      out the thread ID.  It will fail anyway.  */
 388   if (status->kind () == TARGET_WAITKIND_SIGNALLED
 389       || status->kind () == TARGET_WAITKIND_EXITED)
 390     return ptid;
 391
 392   /* Fetch the corresponding thread ID, and augment the returned
 393      process ID with it.  */
 394   addr = bsd_uthread_read_memory_address (bsd_uthread_thread_run_addr);
 395   if (addr != 0)
 396     {
 397       gdb_byte buf[4];
 398
 399       /* FIXME: For executables linked statically with the threads
 400          library, we end up here before the program has actually been
 401          executed.  In that case ADDR will be garbage since it has
 402          been read from the wrong virtual memory image.  */
 403       if (target_read_memory (addr, buf, 4) == 0)
 404         {
 405           ULONGEST magic = extract_unsigned_integer (buf, 4, byte_order);
 406           if (magic == BSD_UTHREAD_PTHREAD_MAGIC)
 407             ptid = ptid_t (ptid.pid (), 0, addr);
 408         }
 409     }
 410
 411   /* If INFERIOR_PTID doesn't have a tid member yet, and we now have a
 412      ptid with tid set, then ptid is still the initial thread of
 413      the process.  Notify GDB core about it.  */
 414   if (inferior_ptid.tid () == 0
 415       && ptid.tid () != 0 && !in_thread_list (beneath, ptid))
 416     thread_change_ptid (beneath, inferior_ptid, ptid);
 417
 418   /* Don't let the core see a ptid without a corresponding thread.  */
 419   thread_info *thread = beneath->find_thread (ptid);
 420   if (thread == NULL || thread->state == THREAD_EXITED)
 421     add_thread (beneath, ptid);
 422
 423   return ptid;
 424 }
 425
 426 void
 427 bsd_uthread_target::resume (ptid_t ptid, int step, enum gdb_signal sig)
 428 {
 429   /* Pass the request to the layer beneath.  */
 430   beneath ()->resume (ptid, step, sig);
 431 }
 432
 433 bool
 434 bsd_uthread_target::thread_alive (ptid_t ptid)
 435 {
 436   bfd_endian byte_order = gdbarch_byte_order (current_inferior ()->arch ());
 437   CORE_ADDR addr = ptid.tid ();
 438
 439   if (addr != 0)
 440     {
 441       int offset = bsd_uthread_thread_state_offset;
 442       ULONGEST state;
 443
 444       bsd_uthread_check_magic (addr);
 445
 446       state = read_memory_unsigned_integer (addr + offset, 4, byte_order);
 447       if (state == BSD_UTHREAD_PS_DEAD)
 448         return false;
 449     }
 450
 451   return beneath ()->thread_alive (ptid);
 452 }
 453
 454 void
 455 bsd_uthread_target::update_thread_list ()
 456 {
 457   pid_t pid = inferior_ptid.pid ();
 458   int offset = bsd_uthread_thread_next_offset;
 459   CORE_ADDR addr;
 460
 461   prune_threads ();
 462
 463   addr = bsd_uthread_read_memory_address (bsd_uthread_thread_list_addr);
 464   while (addr != 0)
 465     {
 466       ptid_t ptid = ptid_t (pid, 0, addr);
 467
 468       process_stratum_target *proc_target
 469         = as_process_stratum_target (this->beneath ());
 470       thread_info *thread = proc_target->find_thread (ptid);
 471       if (thread == nullptr || thread->state == THREAD_EXITED)
 472         {
 473           /* If INFERIOR_PTID doesn't have a tid member yet, then ptid
 474              is still the initial thread of the process.  Notify GDB
 475              core about it.  */
 476           if (inferior_ptid.tid () == 0)
 477             thread_change_ptid (proc_target, inferior_ptid, ptid);
 478           else
 479             add_thread (proc_target, ptid);
 480         }
 481
 482       addr = bsd_uthread_read_memory_address (addr + offset);
 483     }
 484 }
 485
 486 /* Possible states a thread can be in.  */
 487 static const char * const bsd_uthread_state[] =
 488 {
 489   "RUNNING",
 490   "SIGTHREAD",
 491   "MUTEX_WAIT",
 492   "COND_WAIT",
 493   "FDLR_WAIT",
 494   "FDLW_WAIT",
 495   "FDR_WAIT",
 496   "FDW_WAIT",
 497   "FILE_WAIT",
 498   "POLL_WAIT",
 499   "SELECT_WAIT",
 500   "SLEEP_WAIT",
 501   "WAIT_WAIT",
 502   "SIGSUSPEND",
 503   "SIGWAIT",
 504   "SPINBLOCK",
 505   "JOIN",
 506   "SUSPENDED",
 507   "DEAD",
 508   "DEADLOCK"
 509 };
 510
 511 /* Return a string describing th state of the thread specified by
 512    INFO.  */
 513
 514 const char *
 515 bsd_uthread_target::extra_thread_info (thread_info *info)
 516 {
 517   bfd_endian byte_order = gdbarch_byte_order (current_inferior ()->arch ());
 518   CORE_ADDR addr = info->ptid.tid ();
 519
 520   if (addr != 0)
 521     {
 522       int offset = bsd_uthread_thread_state_offset;
 523       ULONGEST state;
 524
 525       state = read_memory_unsigned_integer (addr + offset, 4, byte_order);
 526       if (state < ARRAY_SIZE (bsd_uthread_state))
 527         return bsd_uthread_state[state];
 528     }
 529
 530   return NULL;
 531 }
 532
 533 std::string
 534 bsd_uthread_target::pid_to_str (ptid_t ptid)
 535 {
 536   if (ptid.tid () != 0)
 537     return string_printf ("process %d, thread 0x%s",
 538                           ptid.pid (),
 539                           phex_nz (ptid.tid (), sizeof (ULONGEST)));
 540
 541   return normal_pid_to_str (ptid);
 542 }
 543
 544 void _initialize_bsd_uthread ();
 545 void
 546 _initialize_bsd_uthread ()
 547 {
 548   gdb::observers::inferior_created.attach (bsd_uthread_inferior_created,
 549                                            "bsd-uthread");
 550   gdb::observers::solib_loaded.attach (bsd_uthread_solib_loaded,
 551                                        "bsd-uthread");
 552   gdb::observers::solib_unloaded.attach (bsd_uthread_solib_unloaded,
 553                                          "bsd-uthread");
 554 }