gdb/linux-fork.c

   1 /* GNU/Linux native-dependent code for debugging multiple forks.
   2
   3    Copyright (C) 2005-2012 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 "regcache.h"
  24 #include "gdbcmd.h"
  25 #include "infcall.h"
  26 #include "objfiles.h"
  27 #include "gdb_assert.h"
  28 #include "gdb_string.h"
  29 #include "linux-fork.h"
  30 #include "linux-nat.h"
  31 #include "gdbthread.h"
  32
  33 #include <sys/ptrace.h>
  34 #include "gdb_wait.h"
  35 #include <sys/param.h>
  36 #include "gdb_dirent.h"
  37 #include <ctype.h>
  38
  39 struct fork_info *fork_list;
  40 static int highest_fork_num;
  41
  42 /* Prevent warning from -Wmissing-prototypes.  */
  43 extern void _initialize_linux_fork (void);
  44
  45 /* Fork list data structure:  */
  46 struct fork_info
  47 {
  48   struct fork_info *next;
  49   ptid_t ptid;
  50   ptid_t parent_ptid;
  51   int num;                      /* Convenient handle (GDB fork id).  */
  52   struct regcache *savedregs;   /* Convenient for info fork, saves
  53                                    having to actually switch contexts.  */
  54   int clobber_regs;             /* True if we should restore saved regs.  */
  55   off_t *filepos;               /* Set of open file descriptors' offsets.  */
  56   int maxfd;
  57 };
  58
  59 /* Fork list methods:  */
  60
  61 int
  62 forks_exist_p (void)
  63 {
  64   return (fork_list != NULL);
  65 }
  66
  67 /* Add a fork to the internal fork list.  */
  68
  69 struct fork_info *
  70 add_fork (pid_t pid)
  71 {
  72   struct fork_info *fp;
  73
  74   if (fork_list == NULL && pid != PIDGET (inferior_ptid))
  75     {
  76       /* Special case -- if this is the first fork in the list
  77          (the list is hitherto empty), and if this new fork is
  78          NOT the current inferior_ptid, then add inferior_ptid
  79          first, as a special zeroeth fork id.  */
  80       highest_fork_num = -1;
  81       add_fork (PIDGET (inferior_ptid));        /* safe recursion */
  82     }
  83
  84   fp = XZALLOC (struct fork_info);
  85   fp->ptid = ptid_build (pid, pid, 0);
  86   fp->num = ++highest_fork_num;
  87   fp->next = fork_list;
  88   fork_list = fp;
  89   return fp;
  90 }
  91
  92 static void
  93 free_fork (struct fork_info *fp)
  94 {
  95   /* Notes on step-resume breakpoints: since this is a concern for
  96      threads, let's convince ourselves that it's not a concern for
  97      forks.  There are two ways for a fork_info to be created.  First,
  98      by the checkpoint command, in which case we're at a gdb prompt
  99      and there can't be any step-resume breakpoint.  Second, by a fork
 100      in the user program, in which case we *may* have stepped into the
 101      fork call, but regardless of whether we follow the parent or the
 102      child, we will return to the same place and the step-resume
 103      breakpoint, if any, will take care of itself as usual.  And
 104      unlike threads, we do not save a private copy of the step-resume
 105      breakpoint -- so we're OK.  */
 106
 107   if (fp)
 108     {
 109       if (fp->savedregs)
 110         regcache_xfree (fp->savedregs);
 111       if (fp->filepos)
 112         xfree (fp->filepos);
 113       xfree (fp);
 114     }
 115 }
 116
 117 static void
 118 delete_fork (ptid_t ptid)
 119 {
 120   struct fork_info *fp, *fpprev;
 121
 122   fpprev = NULL;
 123
 124   for (fp = fork_list; fp; fpprev = fp, fp = fp->next)
 125     if (ptid_equal (fp->ptid, ptid))
 126       break;
 127
 128   if (!fp)
 129     return;
 130
 131   if (fpprev)
 132     fpprev->next = fp->next;
 133   else
 134     fork_list = fp->next;
 135
 136   free_fork (fp);
 137
 138   /* Special case: if there is now only one process in the list,
 139      and if it is (hopefully!) the current inferior_ptid, then
 140      remove it, leaving the list empty -- we're now down to the
 141      default case of debugging a single process.  */
 142   if (fork_list != NULL && fork_list->next == NULL &&
 143       ptid_equal (fork_list->ptid, inferior_ptid))
 144     {
 145       /* Last fork -- delete from list and handle as solo process
 146          (should be a safe recursion).  */
 147       delete_fork (inferior_ptid);
 148     }
 149 }
 150
 151 /* Find a fork_info by matching PTID.  */
 152 static struct fork_info *
 153 find_fork_ptid (ptid_t ptid)
 154 {
 155   struct fork_info *fp;
 156
 157   for (fp = fork_list; fp; fp = fp->next)
 158     if (ptid_equal (fp->ptid, ptid))
 159       return fp;
 160
 161   return NULL;
 162 }
 163
 164 /* Find a fork_info by matching ID.  */
 165 static struct fork_info *
 166 find_fork_id (int num)
 167 {
 168   struct fork_info *fp;
 169
 170   for (fp = fork_list; fp; fp = fp->next)
 171     if (fp->num == num)
 172       return fp;
 173
 174   return NULL;
 175 }
 176
 177 /* Find a fork_info by matching pid.  */
 178 extern struct fork_info *
 179 find_fork_pid (pid_t pid)
 180 {
 181   struct fork_info *fp;
 182
 183   for (fp = fork_list; fp; fp = fp->next)
 184     if (pid == ptid_get_pid (fp->ptid))
 185       return fp;
 186
 187   return NULL;
 188 }
 189
 190 static ptid_t
 191 fork_id_to_ptid (int num)
 192 {
 193   struct fork_info *fork = find_fork_id (num);
 194   if (fork)
 195     return fork->ptid;
 196   else
 197     return pid_to_ptid (-1);
 198 }
 199
 200 static void
 201 init_fork_list (void)
 202 {
 203   struct fork_info *fp, *fpnext;
 204
 205   if (!fork_list)
 206     return;
 207
 208   for (fp = fork_list; fp; fp = fpnext)
 209     {
 210       fpnext = fp->next;
 211       free_fork (fp);
 212     }
 213
 214   fork_list = NULL;
 215 }
 216
 217 /* Fork list <-> gdb interface.  */
 218
 219 /* Utility function for fork_load/fork_save.
 220    Calls lseek in the (current) inferior process.  */
 221
 222 static off_t
 223 call_lseek (int fd, off_t offset, int whence)
 224 {
 225   char exp[80];
 226
 227   snprintf (&exp[0], sizeof (exp), "lseek (%d, %ld, %d)",
 228             fd, (long) offset, whence);
 229   return (off_t) parse_and_eval_long (&exp[0]);
 230 }
 231
 232 /* Load infrun state for the fork PTID.  */
 233
 234 static void
 235 fork_load_infrun_state (struct fork_info *fp)
 236 {
 237   extern void nullify_last_target_wait_ptid ();
 238   int i;
 239
 240   linux_nat_switch_fork (fp->ptid);
 241
 242   if (fp->savedregs && fp->clobber_regs)
 243     regcache_cpy (get_current_regcache (), fp->savedregs);
 244
 245   registers_changed ();
 246   reinit_frame_cache ();
 247
 248   stop_pc = regcache_read_pc (get_current_regcache ());
 249   nullify_last_target_wait_ptid ();
 250
 251   /* Now restore the file positions of open file descriptors.  */
 252   if (fp->filepos)
 253     {
 254       for (i = 0; i <= fp->maxfd; i++)
 255         if (fp->filepos[i] != (off_t) -1)
 256           call_lseek (i, fp->filepos[i], SEEK_SET);
 257       /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
 258          this is native-only.  If it ever has to be cross, we'll have
 259          to rethink this.  */
 260     }
 261 }
 262
 263 /* Save infrun state for the fork PTID.
 264    Exported for use by linux child_follow_fork.  */
 265
 266 static void
 267 fork_save_infrun_state (struct fork_info *fp, int clobber_regs)
 268 {
 269   char path[MAXPATHLEN];
 270   struct dirent *de;
 271   DIR *d;
 272
 273   if (fp->savedregs)
 274     regcache_xfree (fp->savedregs);
 275
 276   fp->savedregs = regcache_dup (get_current_regcache ());
 277   fp->clobber_regs = clobber_regs;
 278
 279   if (clobber_regs)
 280     {
 281       /* Now save the 'state' (file position) of all open file descriptors.
 282          Unfortunately fork does not take care of that for us...  */
 283       snprintf (path, MAXPATHLEN, "/proc/%ld/fd", (long) PIDGET (fp->ptid));
 284       if ((d = opendir (path)) != NULL)
 285         {
 286           long tmp;
 287
 288           fp->maxfd = 0;
 289           while ((de = readdir (d)) != NULL)
 290             {
 291               /* Count open file descriptors (actually find highest
 292                  numbered).  */
 293               tmp = strtol (&de->d_name[0], NULL, 10);
 294               if (fp->maxfd < tmp)
 295                 fp->maxfd = tmp;
 296             }
 297           /* Allocate array of file positions.  */
 298           fp->filepos = xrealloc (fp->filepos,
 299                                   (fp->maxfd + 1) * sizeof (*fp->filepos));
 300
 301           /* Initialize to -1 (invalid).  */
 302           for (tmp = 0; tmp <= fp->maxfd; tmp++)
 303             fp->filepos[tmp] = -1;
 304
 305           /* Now find actual file positions.  */
 306           rewinddir (d);
 307           while ((de = readdir (d)) != NULL)
 308             if (isdigit (de->d_name[0]))
 309               {
 310                 tmp = strtol (&de->d_name[0], NULL, 10);
 311                 fp->filepos[tmp] = call_lseek (tmp, 0, SEEK_CUR);
 312               }
 313           closedir (d);
 314         }
 315     }
 316 }
 317
 318 /* Kill 'em all, let God sort 'em out...  */
 319
 320 void
 321 linux_fork_killall (void)
 322 {
 323   /* Walk list and kill every pid.  No need to treat the
 324      current inferior_ptid as special (we do not return a
 325      status for it) -- however any process may be a child
 326      or a parent, so may get a SIGCHLD from a previously
 327      killed child.  Wait them all out.  */
 328   struct fork_info *fp;
 329   pid_t pid, ret;
 330   int status;
 331
 332   for (fp = fork_list; fp; fp = fp->next)
 333     {
 334       pid = PIDGET (fp->ptid);
 335       do {
 336         /* Use SIGKILL instead of PTRACE_KILL because the former works even
 337            if the thread is running, while the later doesn't.  */
 338         kill (pid, SIGKILL);
 339         ret = waitpid (pid, &status, 0);
 340         /* We might get a SIGCHLD instead of an exit status.  This is
 341          aggravated by the first kill above - a child has just
 342          died.  MVS comment cut-and-pasted from linux-nat.  */
 343       } while (ret == pid && WIFSTOPPED (status));
 344     }
 345   init_fork_list ();    /* Clear list, prepare to start fresh.  */
 346 }
 347
 348 /* The current inferior_ptid has exited, but there are other viable
 349    forks to debug.  Delete the exiting one and context-switch to the
 350    first available.  */
 351
 352 void
 353 linux_fork_mourn_inferior (void)
 354 {
 355   /* Wait just one more time to collect the inferior's exit status.
 356      Do not check whether this succeeds though, since we may be
 357      dealing with a process that we attached to.  Such a process will
 358      only report its exit status to its original parent.  */
 359   int status;
 360
 361   waitpid (ptid_get_pid (inferior_ptid), &status, 0);
 362
 363   /* OK, presumably inferior_ptid is the one who has exited.
 364      We need to delete that one from the fork_list, and switch
 365      to the next available fork.  */
 366   delete_fork (inferior_ptid);
 367
 368   /* There should still be a fork - if there's only one left,
 369      delete_fork won't remove it, because we haven't updated
 370      inferior_ptid yet.  */
 371   gdb_assert (fork_list);
 372
 373   fork_load_infrun_state (fork_list);
 374   printf_filtered (_("[Switching to %s]\n"),
 375                    target_pid_to_str (inferior_ptid));
 376
 377   /* If there's only one fork, switch back to non-fork mode.  */
 378   if (fork_list->next == NULL)
 379     delete_fork (inferior_ptid);
 380 }
 381
 382 /* The current inferior_ptid is being detached, but there are other
 383    viable forks to debug.  Detach and delete it and context-switch to
 384    the first available.  */
 385
 386 void
 387 linux_fork_detach (char *args, int from_tty)
 388 {
 389   /* OK, inferior_ptid is the one we are detaching from.  We need to
 390      delete it from the fork_list, and switch to the next available
 391      fork.  */
 392
 393   if (ptrace (PTRACE_DETACH, PIDGET (inferior_ptid), 0, 0))
 394     error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid));
 395
 396   delete_fork (inferior_ptid);
 397
 398   /* There should still be a fork - if there's only one left,
 399      delete_fork won't remove it, because we haven't updated
 400      inferior_ptid yet.  */
 401   gdb_assert (fork_list);
 402
 403   fork_load_infrun_state (fork_list);
 404
 405   if (from_tty)
 406     printf_filtered (_("[Switching to %s]\n"),
 407                      target_pid_to_str (inferior_ptid));
 408
 409   /* If there's only one fork, switch back to non-fork mode.  */
 410   if (fork_list->next == NULL)
 411     delete_fork (inferior_ptid);
 412 }
 413
 414 static void
 415 inferior_call_waitpid_cleanup (void *fp)
 416 {
 417   struct fork_info *oldfp = fp;
 418
 419   if (oldfp)
 420     {
 421       /* Switch back to inferior_ptid.  */
 422       remove_breakpoints ();
 423       fork_load_infrun_state (oldfp);
 424       insert_breakpoints ();
 425     }
 426 }
 427
 428 static int
 429 inferior_call_waitpid (ptid_t pptid, int pid)
 430 {
 431   struct objfile *waitpid_objf;
 432   struct value *waitpid_fn = NULL;
 433   struct value *argv[4], *retv;
 434   struct gdbarch *gdbarch = get_current_arch ();
 435   struct fork_info *oldfp = NULL, *newfp = NULL;
 436   struct cleanup *old_cleanup;
 437   int ret = -1;
 438
 439   if (!ptid_equal (pptid, inferior_ptid))
 440     {
 441       /* Switch to pptid.  */
 442       oldfp = find_fork_ptid (inferior_ptid);
 443       gdb_assert (oldfp != NULL);
 444       newfp = find_fork_ptid (pptid);
 445       gdb_assert (newfp != NULL);
 446       fork_save_infrun_state (oldfp, 1);
 447       remove_breakpoints ();
 448       fork_load_infrun_state (newfp);
 449       insert_breakpoints ();
 450     }
 451
 452   old_cleanup = make_cleanup (inferior_call_waitpid_cleanup, oldfp);
 453
 454   /* Get the waitpid_fn.  */
 455   if (lookup_minimal_symbol ("waitpid", NULL, NULL) != NULL)
 456     waitpid_fn = find_function_in_inferior ("waitpid", &waitpid_objf);
 457   if (!waitpid_fn && lookup_minimal_symbol ("_waitpid", NULL, NULL) != NULL)
 458     waitpid_fn = find_function_in_inferior ("_waitpid", &waitpid_objf);
 459   if (!waitpid_fn)
 460     goto out;
 461
 462   /* Get the argv.  */
 463   argv[0] = value_from_longest (builtin_type (gdbarch)->builtin_int, pid);
 464   argv[1] = value_from_pointer (builtin_type (gdbarch)->builtin_data_ptr, 0);
 465   argv[2] = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
 466   argv[3] = 0;
 467
 468   retv = call_function_by_hand (waitpid_fn, 3, argv);
 469   if (value_as_long (retv) < 0)
 470     goto out;
 471
 472   ret = 0;
 473
 474 out:
 475   do_cleanups (old_cleanup);
 476   return ret;
 477 }
 478
 479 /* Fork list <-> user interface.  */
 480
 481 static void
 482 delete_checkpoint_command (char *args, int from_tty)
 483 {
 484   ptid_t ptid, pptid;
 485   struct fork_info *fi;
 486
 487   if (!args || !*args)
 488     error (_("Requires argument (checkpoint id to delete)"));
 489
 490   ptid = fork_id_to_ptid (parse_and_eval_long (args));
 491   if (ptid_equal (ptid, minus_one_ptid))
 492     error (_("No such checkpoint id, %s"), args);
 493
 494   if (ptid_equal (ptid, inferior_ptid))
 495     error (_("\
 496 Please switch to another checkpoint before deleting the current one"));
 497
 498   if (ptrace (PTRACE_KILL, PIDGET (ptid), 0, 0))
 499     error (_("Unable to kill pid %s"), target_pid_to_str (ptid));
 500
 501   fi = find_fork_ptid (ptid);
 502   gdb_assert (fi);
 503   pptid = fi->parent_ptid;
 504
 505   if (from_tty)
 506     printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid));
 507
 508   delete_fork (ptid);
 509
 510   /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
 511      list, waitpid the ptid.
 512      If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
 513      ptid.  */
 514   if ((!find_thread_ptid (pptid) && find_fork_ptid (pptid))
 515       || (find_thread_ptid (pptid) && is_stopped (pptid)))
 516     {
 517       if (inferior_call_waitpid (pptid, PIDGET (ptid)))
 518         warning (_("Unable to wait pid %s"), target_pid_to_str (ptid));
 519     }
 520 }
 521
 522 static void
 523 detach_checkpoint_command (char *args, int from_tty)
 524 {
 525   ptid_t ptid;
 526
 527   if (!args || !*args)
 528     error (_("Requires argument (checkpoint id to detach)"));
 529
 530   ptid = fork_id_to_ptid (parse_and_eval_long (args));
 531   if (ptid_equal (ptid, minus_one_ptid))
 532     error (_("No such checkpoint id, %s"), args);
 533
 534   if (ptid_equal (ptid, inferior_ptid))
 535     error (_("\
 536 Please switch to another checkpoint before detaching the current one"));
 537
 538   if (ptrace (PTRACE_DETACH, PIDGET (ptid), 0, 0))
 539     error (_("Unable to detach %s"), target_pid_to_str (ptid));
 540
 541   if (from_tty)
 542     printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid));
 543
 544   delete_fork (ptid);
 545 }
 546
 547 /* Print information about currently known checkpoints.  */
 548
 549 static void
 550 info_checkpoints_command (char *arg, int from_tty)
 551 {
 552   struct gdbarch *gdbarch = get_current_arch ();
 553   struct symtab_and_line sal;
 554   struct fork_info *fp;
 555   ULONGEST pc;
 556   int requested = -1;
 557   struct fork_info *printed = NULL;
 558
 559   if (arg && *arg)
 560     requested = (int) parse_and_eval_long (arg);
 561
 562   for (fp = fork_list; fp; fp = fp->next)
 563     {
 564       if (requested > 0 && fp->num != requested)
 565         continue;
 566
 567       printed = fp;
 568       if (ptid_equal (fp->ptid, inferior_ptid))
 569         {
 570           printf_filtered ("* ");
 571           pc = regcache_read_pc (get_current_regcache ());
 572         }
 573       else
 574         {
 575           printf_filtered ("  ");
 576           pc = regcache_read_pc (fp->savedregs);
 577         }
 578       printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));
 579       if (fp->num == 0)
 580         printf_filtered (_(" (main process)"));
 581       printf_filtered (_(" at "));
 582       fputs_filtered (paddress (gdbarch, pc), gdb_stdout);
 583
 584       sal = find_pc_line (pc, 0);
 585       if (sal.symtab)
 586         printf_filtered (_(", file %s"), lbasename (sal.symtab->filename));
 587       if (sal.line)
 588         printf_filtered (_(", line %d"), sal.line);
 589       if (!sal.symtab && !sal.line)
 590         {
 591           struct minimal_symbol *msym;
 592
 593           msym = lookup_minimal_symbol_by_pc (pc);
 594           if (msym)
 595             printf_filtered (", <%s>", SYMBOL_LINKAGE_NAME (msym));
 596         }
 597
 598       putchar_filtered ('\n');
 599     }
 600   if (printed == NULL)
 601     {
 602       if (requested > 0)
 603         printf_filtered (_("No checkpoint number %d.\n"), requested);
 604       else
 605         printf_filtered (_("No checkpoints.\n"));
 606     }
 607 }
 608
 609 /* The PID of the process we're checkpointing.  */
 610 static int checkpointing_pid = 0;
 611
 612 int
 613 linux_fork_checkpointing_p (int pid)
 614 {
 615   return (checkpointing_pid == pid);
 616 }
 617
 618 /* Callback for iterate over threads.  Used to check whether
 619    the current inferior is multi-threaded.  Returns true as soon
 620    as it sees the second thread of the current inferior.  */
 621
 622 static int
 623 inf_has_multiple_thread_cb (struct thread_info *tp, void *data)
 624 {
 625   int *count_p = (int *) data;
 626
 627   if (current_inferior ()->pid == ptid_get_pid (tp->ptid))
 628     (*count_p)++;
 629
 630   /* Stop the iteration if multiple threads have been detected.  */
 631   return *count_p > 1;
 632 }
 633
 634 /* Return true if the current inferior is multi-threaded.  */
 635
 636 static int
 637 inf_has_multiple_threads (void)
 638 {
 639   int count = 0;
 640
 641   iterate_over_threads (inf_has_multiple_thread_cb, &count);
 642   return (count > 1);
 643 }
 644
 645 static void
 646 checkpoint_command (char *args, int from_tty)
 647 {
 648   struct objfile *fork_objf;
 649   struct gdbarch *gdbarch;
 650   struct target_waitstatus last_target_waitstatus;
 651   ptid_t last_target_ptid;
 652   struct value *fork_fn = NULL, *ret;
 653   struct fork_info *fp;
 654   pid_t retpid;
 655   struct cleanup *old_chain;
 656
 657   if (!target_has_execution)
 658     error (_("The program is not being run."));
 659
 660   /* Ensure that the inferior is not multithreaded.  */
 661   update_thread_list ();
 662   if (inf_has_multiple_threads ())
 663     error (_("checkpoint: can't checkpoint multiple threads."));
 664
 665   /* Make the inferior fork, record its (and gdb's) state.  */
 666
 667   if (lookup_minimal_symbol ("fork", NULL, NULL) != NULL)
 668     fork_fn = find_function_in_inferior ("fork", &fork_objf);
 669   if (!fork_fn)
 670     if (lookup_minimal_symbol ("_fork", NULL, NULL) != NULL)
 671       fork_fn = find_function_in_inferior ("fork", &fork_objf);
 672   if (!fork_fn)
 673     error (_("checkpoint: can't find fork function in inferior."));
 674
 675   gdbarch = get_objfile_arch (fork_objf);
 676   ret = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
 677
 678   /* Tell linux-nat.c that we're checkpointing this inferior.  */
 679   old_chain = make_cleanup_restore_integer (&checkpointing_pid);
 680   checkpointing_pid = PIDGET (inferior_ptid);
 681
 682   ret = call_function_by_hand (fork_fn, 0, &ret);
 683   do_cleanups (old_chain);
 684   if (!ret)     /* Probably can't happen.  */
 685     error (_("checkpoint: call_function_by_hand returned null."));
 686
 687   retpid = value_as_long (ret);
 688   get_last_target_status (&last_target_ptid, &last_target_waitstatus);
 689   if (from_tty)
 690     {
 691       int parent_pid;
 692
 693       printf_filtered (_("checkpoint: fork returned pid %ld.\n"),
 694                        (long) retpid);
 695       if (info_verbose)
 696         {
 697           parent_pid = ptid_get_lwp (last_target_ptid);
 698           if (parent_pid == 0)
 699             parent_pid = ptid_get_pid (last_target_ptid);
 700           printf_filtered (_("   gdb says parent = %ld.\n"),
 701                            (long) parent_pid);
 702         }
 703     }
 704
 705   fp = find_fork_pid (retpid);
 706   if (!fp)
 707     error (_("Failed to find new fork"));
 708   fork_save_infrun_state (fp, 1);
 709   fp->parent_ptid = last_target_ptid;
 710 }
 711
 712 static void
 713 linux_fork_context (struct fork_info *newfp, int from_tty)
 714 {
 715   /* Now we attempt to switch processes.  */
 716   struct fork_info *oldfp;
 717
 718   gdb_assert (newfp != NULL);
 719
 720   oldfp = find_fork_ptid (inferior_ptid);
 721   gdb_assert (oldfp != NULL);
 722
 723   fork_save_infrun_state (oldfp, 1);
 724   remove_breakpoints ();
 725   fork_load_infrun_state (newfp);
 726   insert_breakpoints ();
 727
 728   printf_filtered (_("Switching to %s\n"),
 729                    target_pid_to_str (inferior_ptid));
 730
 731   print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC);
 732 }
 733
 734 /* Switch inferior process (checkpoint) context, by checkpoint id.  */
 735 static void
 736 restart_command (char *args, int from_tty)
 737 {
 738   struct fork_info *fp;
 739
 740   if (!args || !*args)
 741     error (_("Requires argument (checkpoint id to restart)"));
 742
 743   if ((fp = find_fork_id (parse_and_eval_long (args))) == NULL)
 744     error (_("Not found: checkpoint id %s"), args);
 745
 746   linux_fork_context (fp, from_tty);
 747 }
 748
 749 void
 750 _initialize_linux_fork (void)
 751 {
 752   init_fork_list ();
 753
 754   /* Checkpoint command: create a fork of the inferior process
 755      and set it aside for later debugging.  */
 756
 757   add_com ("checkpoint", class_obscure, checkpoint_command, _("\
 758 Fork a duplicate process (experimental)."));
 759
 760   /* Restart command: restore the context of a specified checkpoint
 761      process.  */
 762
 763   add_com ("restart", class_obscure, restart_command, _("\
 764 restart <n>: restore program context from a checkpoint.\n\
 765 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
 766
 767   /* Delete checkpoint command: kill the process and remove it from
 768      the fork list.  */
 769
 770   add_cmd ("checkpoint", class_obscure, delete_checkpoint_command, _("\
 771 Delete a checkpoint (experimental)."),
 772            &deletelist);
 773
 774   /* Detach checkpoint command: release the process to run independently,
 775      and remove it from the fork list.  */
 776
 777   add_cmd ("checkpoint", class_obscure, detach_checkpoint_command, _("\
 778 Detach from a checkpoint (experimental)."),
 779            &detachlist);
 780
 781   /* Info checkpoints command: list all forks/checkpoints
 782      currently under gdb's control.  */
 783
 784   add_info ("checkpoints", info_checkpoints_command,
 785             _("IDs of currently known checkpoints."));
 786 }