gdb/linux-fork.c

   1 /* GNU/Linux native-dependent code for debugging multiple forks.
   2
   3    Copyright (C) 2005-2018 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 "arch-utils.h"
  22 #include "inferior.h"
  23 #include "infrun.h"
  24 #include "regcache.h"
  25 #include "gdbcmd.h"
  26 #include "infcall.h"
  27 #include "objfiles.h"
  28 #include "linux-fork.h"
  29 #include "linux-nat.h"
  30 #include "gdbthread.h"
  31 #include "source.h"
  32
  33 #include "nat/gdb_ptrace.h"
  34 #include "gdb_wait.h"
  35 #include <dirent.h>
  36 #include <ctype.h>
  37
  38 struct fork_info *fork_list;
  39 static int highest_fork_num;
  40
  41 /* Fork list data structure:  */
  42 struct fork_info
  43 {
  44   struct fork_info *next;
  45   ptid_t ptid;
  46   ptid_t parent_ptid;
  47   int num;                      /* Convenient handle (GDB fork id).  */
  48   readonly_detached_regcache *savedregs;        /* Convenient for info fork, saves
  49                                    having to actually switch contexts.  */
  50   CORE_ADDR pc;
  51   int clobber_regs;             /* True if we should restore saved regs.  */
  52   off_t *filepos;               /* Set of open file descriptors' offsets.  */
  53   int maxfd;
  54 };
  55
  56 /* Fork list methods:  */
  57
  58 int
  59 forks_exist_p (void)
  60 {
  61   return (fork_list != NULL);
  62 }
  63
  64 /* Return the last fork in the list.  */
  65
  66 static struct fork_info *
  67 find_last_fork (void)
  68 {
  69   struct fork_info *last;
  70
  71   if (fork_list == NULL)
  72     return NULL;
  73
  74   for (last = fork_list; last->next != NULL; last = last->next)
  75     ;
  76   return last;
  77 }
  78
  79 /* Add a fork to the internal fork list.  */
  80
  81 struct fork_info *
  82 add_fork (pid_t pid)
  83 {
  84   struct fork_info *fp;
  85
  86   if (fork_list == NULL && pid != ptid_get_pid (inferior_ptid))
  87     {
  88       /* Special case -- if this is the first fork in the list
  89          (the list is hitherto empty), and if this new fork is
  90          NOT the current inferior_ptid, then add inferior_ptid
  91          first, as a special zeroeth fork id.  */
  92       highest_fork_num = -1;
  93       add_fork (ptid_get_pid (inferior_ptid));  /* safe recursion */
  94     }
  95
  96   fp = XCNEW (struct fork_info);
  97   fp->ptid = ptid_build (pid, pid, 0);
  98   fp->num = ++highest_fork_num;
  99
 100   if (fork_list == NULL)
 101     fork_list = fp;
 102   else
 103     {
 104       struct fork_info *last = find_last_fork ();
 105
 106       last->next = fp;
 107     }
 108
 109   return fp;
 110 }
 111
 112 static void
 113 free_fork (struct fork_info *fp)
 114 {
 115   /* Notes on step-resume breakpoints: since this is a concern for
 116      threads, let's convince ourselves that it's not a concern for
 117      forks.  There are two ways for a fork_info to be created.  First,
 118      by the checkpoint command, in which case we're at a gdb prompt
 119      and there can't be any step-resume breakpoint.  Second, by a fork
 120      in the user program, in which case we *may* have stepped into the
 121      fork call, but regardless of whether we follow the parent or the
 122      child, we will return to the same place and the step-resume
 123      breakpoint, if any, will take care of itself as usual.  And
 124      unlike threads, we do not save a private copy of the step-resume
 125      breakpoint -- so we're OK.  */
 126
 127   if (fp)
 128     {
 129       if (fp->savedregs)
 130         delete fp->savedregs;
 131       if (fp->filepos)
 132         xfree (fp->filepos);
 133       xfree (fp);
 134     }
 135 }
 136
 137 static void
 138 delete_fork (ptid_t ptid)
 139 {
 140   struct fork_info *fp, *fpprev;
 141
 142   fpprev = NULL;
 143
 144   linux_target->low_forget_process (ptid_get_pid (ptid));
 145
 146   for (fp = fork_list; fp; fpprev = fp, fp = fp->next)
 147     if (ptid_equal (fp->ptid, ptid))
 148       break;
 149
 150   if (!fp)
 151     return;
 152
 153   if (fpprev)
 154     fpprev->next = fp->next;
 155   else
 156     fork_list = fp->next;
 157
 158   free_fork (fp);
 159
 160   /* Special case: if there is now only one process in the list,
 161      and if it is (hopefully!) the current inferior_ptid, then
 162      remove it, leaving the list empty -- we're now down to the
 163      default case of debugging a single process.  */
 164   if (fork_list != NULL && fork_list->next == NULL &&
 165       ptid_equal (fork_list->ptid, inferior_ptid))
 166     {
 167       /* Last fork -- delete from list and handle as solo process
 168          (should be a safe recursion).  */
 169       delete_fork (inferior_ptid);
 170     }
 171 }
 172
 173 /* Find a fork_info by matching PTID.  */
 174 static struct fork_info *
 175 find_fork_ptid (ptid_t ptid)
 176 {
 177   struct fork_info *fp;
 178
 179   for (fp = fork_list; fp; fp = fp->next)
 180     if (ptid_equal (fp->ptid, ptid))
 181       return fp;
 182
 183   return NULL;
 184 }
 185
 186 /* Find a fork_info by matching ID.  */
 187 static struct fork_info *
 188 find_fork_id (int num)
 189 {
 190   struct fork_info *fp;
 191
 192   for (fp = fork_list; fp; fp = fp->next)
 193     if (fp->num == num)
 194       return fp;
 195
 196   return NULL;
 197 }
 198
 199 /* Find a fork_info by matching pid.  */
 200 extern struct fork_info *
 201 find_fork_pid (pid_t pid)
 202 {
 203   struct fork_info *fp;
 204
 205   for (fp = fork_list; fp; fp = fp->next)
 206     if (pid == ptid_get_pid (fp->ptid))
 207       return fp;
 208
 209   return NULL;
 210 }
 211
 212 static ptid_t
 213 fork_id_to_ptid (int num)
 214 {
 215   struct fork_info *fork = find_fork_id (num);
 216   if (fork)
 217     return fork->ptid;
 218   else
 219     return pid_to_ptid (-1);
 220 }
 221
 222 static void
 223 init_fork_list (void)
 224 {
 225   struct fork_info *fp, *fpnext;
 226
 227   if (!fork_list)
 228     return;
 229
 230   for (fp = fork_list; fp; fp = fpnext)
 231     {
 232       fpnext = fp->next;
 233       free_fork (fp);
 234     }
 235
 236   fork_list = NULL;
 237 }
 238
 239 /* Fork list <-> gdb interface.  */
 240
 241 /* Utility function for fork_load/fork_save.
 242    Calls lseek in the (current) inferior process.  */
 243
 244 static off_t
 245 call_lseek (int fd, off_t offset, int whence)
 246 {
 247   char exp[80];
 248
 249   snprintf (&exp[0], sizeof (exp), "(long) lseek (%d, %ld, %d)",
 250             fd, (long) offset, whence);
 251   return (off_t) parse_and_eval_long (&exp[0]);
 252 }
 253
 254 /* Load infrun state for the fork PTID.  */
 255
 256 static void
 257 fork_load_infrun_state (struct fork_info *fp)
 258 {
 259   extern void nullify_last_target_wait_ptid ();
 260   int i;
 261
 262   linux_nat_switch_fork (fp->ptid);
 263
 264   if (fp->savedregs && fp->clobber_regs)
 265     get_current_regcache ()->restore (fp->savedregs);
 266
 267   registers_changed ();
 268   reinit_frame_cache ();
 269
 270   stop_pc = regcache_read_pc (get_current_regcache ());
 271   nullify_last_target_wait_ptid ();
 272
 273   /* Now restore the file positions of open file descriptors.  */
 274   if (fp->filepos)
 275     {
 276       for (i = 0; i <= fp->maxfd; i++)
 277         if (fp->filepos[i] != (off_t) -1)
 278           call_lseek (i, fp->filepos[i], SEEK_SET);
 279       /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
 280          this is native-only.  If it ever has to be cross, we'll have
 281          to rethink this.  */
 282     }
 283 }
 284
 285 /* Save infrun state for the fork PTID.
 286    Exported for use by linux child_follow_fork.  */
 287
 288 static void
 289 fork_save_infrun_state (struct fork_info *fp, int clobber_regs)
 290 {
 291   char path[PATH_MAX];
 292   struct dirent *de;
 293   DIR *d;
 294
 295   if (fp->savedregs)
 296     delete fp->savedregs;
 297
 298   fp->savedregs = new readonly_detached_regcache (*get_current_regcache ());
 299   fp->pc = regcache_read_pc (get_current_regcache ());
 300   fp->clobber_regs = clobber_regs;
 301
 302   if (clobber_regs)
 303     {
 304       /* Now save the 'state' (file position) of all open file descriptors.
 305          Unfortunately fork does not take care of that for us...  */
 306       snprintf (path, PATH_MAX, "/proc/%ld/fd",
 307                 (long) ptid_get_pid (fp->ptid));
 308       if ((d = opendir (path)) != NULL)
 309         {
 310           long tmp;
 311
 312           fp->maxfd = 0;
 313           while ((de = readdir (d)) != NULL)
 314             {
 315               /* Count open file descriptors (actually find highest
 316                  numbered).  */
 317               tmp = strtol (&de->d_name[0], NULL, 10);
 318               if (fp->maxfd < tmp)
 319                 fp->maxfd = tmp;
 320             }
 321           /* Allocate array of file positions.  */
 322           fp->filepos = XRESIZEVEC (off_t, fp->filepos, fp->maxfd + 1);
 323
 324           /* Initialize to -1 (invalid).  */
 325           for (tmp = 0; tmp <= fp->maxfd; tmp++)
 326             fp->filepos[tmp] = -1;
 327
 328           /* Now find actual file positions.  */
 329           rewinddir (d);
 330           while ((de = readdir (d)) != NULL)
 331             if (isdigit (de->d_name[0]))
 332               {
 333                 tmp = strtol (&de->d_name[0], NULL, 10);
 334                 fp->filepos[tmp] = call_lseek (tmp, 0, SEEK_CUR);
 335               }
 336           closedir (d);
 337         }
 338     }
 339 }
 340
 341 /* Kill 'em all, let God sort 'em out...  */
 342
 343 void
 344 linux_fork_killall (void)
 345 {
 346   /* Walk list and kill every pid.  No need to treat the
 347      current inferior_ptid as special (we do not return a
 348      status for it) -- however any process may be a child
 349      or a parent, so may get a SIGCHLD from a previously
 350      killed child.  Wait them all out.  */
 351   struct fork_info *fp;
 352   pid_t pid, ret;
 353   int status;
 354
 355   for (fp = fork_list; fp; fp = fp->next)
 356     {
 357       pid = ptid_get_pid (fp->ptid);
 358       do {
 359         /* Use SIGKILL instead of PTRACE_KILL because the former works even
 360            if the thread is running, while the later doesn't.  */
 361         kill (pid, SIGKILL);
 362         ret = waitpid (pid, &status, 0);
 363         /* We might get a SIGCHLD instead of an exit status.  This is
 364          aggravated by the first kill above - a child has just
 365          died.  MVS comment cut-and-pasted from linux-nat.  */
 366       } while (ret == pid && WIFSTOPPED (status));
 367     }
 368   init_fork_list ();    /* Clear list, prepare to start fresh.  */
 369 }
 370
 371 /* The current inferior_ptid has exited, but there are other viable
 372    forks to debug.  Delete the exiting one and context-switch to the
 373    first available.  */
 374
 375 void
 376 linux_fork_mourn_inferior (void)
 377 {
 378   struct fork_info *last;
 379   int status;
 380
 381   /* Wait just one more time to collect the inferior's exit status.
 382      Do not check whether this succeeds though, since we may be
 383      dealing with a process that we attached to.  Such a process will
 384      only report its exit status to its original parent.  */
 385   waitpid (ptid_get_pid (inferior_ptid), &status, 0);
 386
 387   /* OK, presumably inferior_ptid is the one who has exited.
 388      We need to delete that one from the fork_list, and switch
 389      to the next available fork.  */
 390   delete_fork (inferior_ptid);
 391
 392   /* There should still be a fork - if there's only one left,
 393      delete_fork won't remove it, because we haven't updated
 394      inferior_ptid yet.  */
 395   gdb_assert (fork_list);
 396
 397   last = find_last_fork ();
 398   fork_load_infrun_state (last);
 399   printf_filtered (_("[Switching to %s]\n"),
 400                    target_pid_to_str (inferior_ptid));
 401
 402   /* If there's only one fork, switch back to non-fork mode.  */
 403   if (fork_list->next == NULL)
 404     delete_fork (inferior_ptid);
 405 }
 406
 407 /* The current inferior_ptid is being detached, but there are other
 408    viable forks to debug.  Detach and delete it and context-switch to
 409    the first available.  */
 410
 411 void
 412 linux_fork_detach (int from_tty)
 413 {
 414   /* OK, inferior_ptid is the one we are detaching from.  We need to
 415      delete it from the fork_list, and switch to the next available
 416      fork.  */
 417
 418   if (ptrace (PTRACE_DETACH, ptid_get_pid (inferior_ptid), 0, 0))
 419     error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid));
 420
 421   delete_fork (inferior_ptid);
 422
 423   /* There should still be a fork - if there's only one left,
 424      delete_fork won't remove it, because we haven't updated
 425      inferior_ptid yet.  */
 426   gdb_assert (fork_list);
 427
 428   fork_load_infrun_state (fork_list);
 429
 430   if (from_tty)
 431     printf_filtered (_("[Switching to %s]\n"),
 432                      target_pid_to_str (inferior_ptid));
 433
 434   /* If there's only one fork, switch back to non-fork mode.  */
 435   if (fork_list->next == NULL)
 436     delete_fork (inferior_ptid);
 437 }
 438
 439 static void
 440 inferior_call_waitpid_cleanup (void *fp)
 441 {
 442   struct fork_info *oldfp = (struct fork_info *) fp;
 443
 444   if (oldfp)
 445     {
 446       /* Switch back to inferior_ptid.  */
 447       remove_breakpoints ();
 448       fork_load_infrun_state (oldfp);
 449       insert_breakpoints ();
 450     }
 451 }
 452
 453 static int
 454 inferior_call_waitpid (ptid_t pptid, int pid)
 455 {
 456   struct objfile *waitpid_objf;
 457   struct value *waitpid_fn = NULL;
 458   struct value *argv[4], *retv;
 459   struct gdbarch *gdbarch = get_current_arch ();
 460   struct fork_info *oldfp = NULL, *newfp = NULL;
 461   struct cleanup *old_cleanup;
 462   int ret = -1;
 463
 464   if (!ptid_equal (pptid, inferior_ptid))
 465     {
 466       /* Switch to pptid.  */
 467       oldfp = find_fork_ptid (inferior_ptid);
 468       gdb_assert (oldfp != NULL);
 469       newfp = find_fork_ptid (pptid);
 470       gdb_assert (newfp != NULL);
 471       fork_save_infrun_state (oldfp, 1);
 472       remove_breakpoints ();
 473       fork_load_infrun_state (newfp);
 474       insert_breakpoints ();
 475     }
 476
 477   old_cleanup = make_cleanup (inferior_call_waitpid_cleanup, oldfp);
 478
 479   /* Get the waitpid_fn.  */
 480   if (lookup_minimal_symbol ("waitpid", NULL, NULL).minsym != NULL)
 481     waitpid_fn = find_function_in_inferior ("waitpid", &waitpid_objf);
 482   if (!waitpid_fn
 483       && lookup_minimal_symbol ("_waitpid", NULL, NULL).minsym != NULL)
 484     waitpid_fn = find_function_in_inferior ("_waitpid", &waitpid_objf);
 485   if (!waitpid_fn)
 486     goto out;
 487
 488   /* Get the argv.  */
 489   argv[0] = value_from_longest (builtin_type (gdbarch)->builtin_int, pid);
 490   argv[1] = value_from_pointer (builtin_type (gdbarch)->builtin_data_ptr, 0);
 491   argv[2] = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
 492   argv[3] = 0;
 493
 494   retv = call_function_by_hand (waitpid_fn, NULL, 3, argv);
 495   if (value_as_long (retv) < 0)
 496     goto out;
 497
 498   ret = 0;
 499
 500 out:
 501   do_cleanups (old_cleanup);
 502   return ret;
 503 }
 504
 505 /* Fork list <-> user interface.  */
 506
 507 static void
 508 delete_checkpoint_command (const char *args, int from_tty)
 509 {
 510   ptid_t ptid, pptid;
 511   struct fork_info *fi;
 512
 513   if (!args || !*args)
 514     error (_("Requires argument (checkpoint id to delete)"));
 515
 516   ptid = fork_id_to_ptid (parse_and_eval_long (args));
 517   if (ptid_equal (ptid, minus_one_ptid))
 518     error (_("No such checkpoint id, %s"), args);
 519
 520   if (ptid_equal (ptid, inferior_ptid))
 521     error (_("\
 522 Please switch to another checkpoint before deleting the current one"));
 523
 524   if (ptrace (PTRACE_KILL, ptid_get_pid (ptid), 0, 0))
 525     error (_("Unable to kill pid %s"), target_pid_to_str (ptid));
 526
 527   fi = find_fork_ptid (ptid);
 528   gdb_assert (fi);
 529   pptid = fi->parent_ptid;
 530
 531   if (from_tty)
 532     printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid));
 533
 534   delete_fork (ptid);
 535
 536   /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
 537      list, waitpid the ptid.
 538      If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
 539      ptid.  */
 540   if ((!find_thread_ptid (pptid) && find_fork_ptid (pptid))
 541       || (find_thread_ptid (pptid) && is_stopped (pptid)))
 542     {
 543       if (inferior_call_waitpid (pptid, ptid_get_pid (ptid)))
 544         warning (_("Unable to wait pid %s"), target_pid_to_str (ptid));
 545     }
 546 }
 547
 548 static void
 549 detach_checkpoint_command (const char *args, int from_tty)
 550 {
 551   ptid_t ptid;
 552
 553   if (!args || !*args)
 554     error (_("Requires argument (checkpoint id to detach)"));
 555
 556   ptid = fork_id_to_ptid (parse_and_eval_long (args));
 557   if (ptid_equal (ptid, minus_one_ptid))
 558     error (_("No such checkpoint id, %s"), args);
 559
 560   if (ptid_equal (ptid, inferior_ptid))
 561     error (_("\
 562 Please switch to another checkpoint before detaching the current one"));
 563
 564   if (ptrace (PTRACE_DETACH, ptid_get_pid (ptid), 0, 0))
 565     error (_("Unable to detach %s"), target_pid_to_str (ptid));
 566
 567   if (from_tty)
 568     printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid));
 569
 570   delete_fork (ptid);
 571 }
 572
 573 /* Print information about currently known checkpoints.  */
 574
 575 static void
 576 info_checkpoints_command (const char *arg, int from_tty)
 577 {
 578   struct gdbarch *gdbarch = get_current_arch ();
 579   struct symtab_and_line sal;
 580   struct fork_info *fp;
 581   ULONGEST pc;
 582   int requested = -1;
 583   struct fork_info *printed = NULL;
 584
 585   if (arg && *arg)
 586     requested = (int) parse_and_eval_long (arg);
 587
 588   for (fp = fork_list; fp; fp = fp->next)
 589     {
 590       if (requested > 0 && fp->num != requested)
 591         continue;
 592
 593       printed = fp;
 594       if (ptid_equal (fp->ptid, inferior_ptid))
 595         printf_filtered ("* ");
 596       else
 597         printf_filtered ("  ");
 598
 599       pc = fp->pc;
 600       printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));
 601       if (fp->num == 0)
 602         printf_filtered (_(" (main process)"));
 603       printf_filtered (_(" at "));
 604       fputs_filtered (paddress (gdbarch, pc), gdb_stdout);
 605
 606       sal = find_pc_line (pc, 0);
 607       if (sal.symtab)
 608         printf_filtered (_(", file %s"),
 609                          symtab_to_filename_for_display (sal.symtab));
 610       if (sal.line)
 611         printf_filtered (_(", line %d"), sal.line);
 612       if (!sal.symtab && !sal.line)
 613         {
 614           struct bound_minimal_symbol msym;
 615
 616           msym = lookup_minimal_symbol_by_pc (pc);
 617           if (msym.minsym)
 618             printf_filtered (", <%s>", MSYMBOL_LINKAGE_NAME (msym.minsym));
 619         }
 620
 621       putchar_filtered ('\n');
 622     }
 623   if (printed == NULL)
 624     {
 625       if (requested > 0)
 626         printf_filtered (_("No checkpoint number %d.\n"), requested);
 627       else
 628         printf_filtered (_("No checkpoints.\n"));
 629     }
 630 }
 631
 632 /* The PID of the process we're checkpointing.  */
 633 static int checkpointing_pid = 0;
 634
 635 int
 636 linux_fork_checkpointing_p (int pid)
 637 {
 638   return (checkpointing_pid == pid);
 639 }
 640
 641 /* Callback for iterate over threads.  Used to check whether
 642    the current inferior is multi-threaded.  Returns true as soon
 643    as it sees the second thread of the current inferior.  */
 644
 645 static int
 646 inf_has_multiple_thread_cb (struct thread_info *tp, void *data)
 647 {
 648   int *count_p = (int *) data;
 649
 650   if (current_inferior ()->pid == ptid_get_pid (tp->ptid))
 651     (*count_p)++;
 652
 653   /* Stop the iteration if multiple threads have been detected.  */
 654   return *count_p > 1;
 655 }
 656
 657 /* Return true if the current inferior is multi-threaded.  */
 658
 659 static int
 660 inf_has_multiple_threads (void)
 661 {
 662   int count = 0;
 663
 664   iterate_over_threads (inf_has_multiple_thread_cb, &count);
 665   return (count > 1);
 666 }
 667
 668 static void
 669 checkpoint_command (const char *args, int from_tty)
 670 {
 671   struct objfile *fork_objf;
 672   struct gdbarch *gdbarch;
 673   struct target_waitstatus last_target_waitstatus;
 674   ptid_t last_target_ptid;
 675   struct value *fork_fn = NULL, *ret;
 676   struct fork_info *fp;
 677   pid_t retpid;
 678
 679   if (!target_has_execution)
 680     error (_("The program is not being run."));
 681
 682   /* Ensure that the inferior is not multithreaded.  */
 683   update_thread_list ();
 684   if (inf_has_multiple_threads ())
 685     error (_("checkpoint: can't checkpoint multiple threads."));
 686
 687   /* Make the inferior fork, record its (and gdb's) state.  */
 688
 689   if (lookup_minimal_symbol ("fork", NULL, NULL).minsym != NULL)
 690     fork_fn = find_function_in_inferior ("fork", &fork_objf);
 691   if (!fork_fn)
 692     if (lookup_minimal_symbol ("_fork", NULL, NULL).minsym != NULL)
 693       fork_fn = find_function_in_inferior ("fork", &fork_objf);
 694   if (!fork_fn)
 695     error (_("checkpoint: can't find fork function in inferior."));
 696
 697   gdbarch = get_objfile_arch (fork_objf);
 698   ret = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
 699
 700   /* Tell linux-nat.c that we're checkpointing this inferior.  */
 701   {
 702     scoped_restore save_pid
 703       = make_scoped_restore (&checkpointing_pid, ptid_get_pid (inferior_ptid));
 704
 705     ret = call_function_by_hand (fork_fn, NULL, 0, &ret);
 706   }
 707
 708   if (!ret)     /* Probably can't happen.  */
 709     error (_("checkpoint: call_function_by_hand returned null."));
 710
 711   retpid = value_as_long (ret);
 712   get_last_target_status (&last_target_ptid, &last_target_waitstatus);
 713
 714   fp = find_fork_pid (retpid);
 715
 716   if (from_tty)
 717     {
 718       int parent_pid;
 719
 720       printf_filtered (_("checkpoint %d: fork returned pid %ld.\n"),
 721                        fp != NULL ? fp->num : -1, (long) retpid);
 722       if (info_verbose)
 723         {
 724           parent_pid = ptid_get_lwp (last_target_ptid);
 725           if (parent_pid == 0)
 726             parent_pid = ptid_get_pid (last_target_ptid);
 727           printf_filtered (_("   gdb says parent = %ld.\n"),
 728                            (long) parent_pid);
 729         }
 730     }
 731
 732   if (!fp)
 733     error (_("Failed to find new fork"));
 734   fork_save_infrun_state (fp, 1);
 735   fp->parent_ptid = last_target_ptid;
 736 }
 737
 738 static void
 739 linux_fork_context (struct fork_info *newfp, int from_tty)
 740 {
 741   /* Now we attempt to switch processes.  */
 742   struct fork_info *oldfp;
 743
 744   gdb_assert (newfp != NULL);
 745
 746   oldfp = find_fork_ptid (inferior_ptid);
 747   gdb_assert (oldfp != NULL);
 748
 749   fork_save_infrun_state (oldfp, 1);
 750   remove_breakpoints ();
 751   fork_load_infrun_state (newfp);
 752   insert_breakpoints ();
 753
 754   printf_filtered (_("Switching to %s\n"),
 755                    target_pid_to_str (inferior_ptid));
 756
 757   print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC, 1);
 758 }
 759
 760 /* Switch inferior process (checkpoint) context, by checkpoint id.  */
 761 static void
 762 restart_command (const char *args, int from_tty)
 763 {
 764   struct fork_info *fp;
 765
 766   if (!args || !*args)
 767     error (_("Requires argument (checkpoint id to restart)"));
 768
 769   if ((fp = find_fork_id (parse_and_eval_long (args))) == NULL)
 770     error (_("Not found: checkpoint id %s"), args);
 771
 772   linux_fork_context (fp, from_tty);
 773 }
 774
 775 void
 776 _initialize_linux_fork (void)
 777 {
 778   init_fork_list ();
 779
 780   /* Checkpoint command: create a fork of the inferior process
 781      and set it aside for later debugging.  */
 782
 783   add_com ("checkpoint", class_obscure, checkpoint_command, _("\
 784 Fork a duplicate process (experimental)."));
 785
 786   /* Restart command: restore the context of a specified checkpoint
 787      process.  */
 788
 789   add_com ("restart", class_obscure, restart_command, _("\
 790 restart N: restore program context from a checkpoint.\n\
 791 Argument N is checkpoint ID, as displayed by 'info checkpoints'."));
 792
 793   /* Delete checkpoint command: kill the process and remove it from
 794      the fork list.  */
 795
 796   add_cmd ("checkpoint", class_obscure, delete_checkpoint_command, _("\
 797 Delete a checkpoint (experimental)."),
 798            &deletelist);
 799
 800   /* Detach checkpoint command: release the process to run independently,
 801      and remove it from the fork list.  */
 802
 803   add_cmd ("checkpoint", class_obscure, detach_checkpoint_command, _("\
 804 Detach from a checkpoint (experimental)."),
 805            &detachlist);
 806
 807   /* Info checkpoints command: list all forks/checkpoints
 808      currently under gdb's control.  */
 809
 810   add_info ("checkpoints", info_checkpoints_command,
 811             _("IDs of currently known checkpoints."));
 812 }