gdb/linux-fork.c

   1 /* GNU/Linux native-dependent code for debugging multiple forks.
   2
   3    Copyright (C) 2005-2014 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 "gdb_assert.h"
  29 #include <string.h>
  30 #include "linux-fork.h"
  31 #include "linux-nat.h"
  32 #include "gdbthread.h"
  33 #include "source.h"
  34
  35 #include <sys/ptrace.h>
  36 #include "gdb_wait.h"
  37 #include <dirent.h>
  38 #include <ctype.h>
  39
  40 struct fork_info *fork_list;
  41 static int highest_fork_num;
  42
  43 /* Prevent warning from -Wmissing-prototypes.  */
  44 extern void _initialize_linux_fork (void);
  45
  46 /* Fork list data structure:  */
  47 struct fork_info
  48 {
  49   struct fork_info *next;
  50   ptid_t ptid;
  51   ptid_t parent_ptid;
  52   int num;                      /* Convenient handle (GDB fork id).  */
  53   struct regcache *savedregs;   /* Convenient for info fork, saves
  54                                    having to actually switch contexts.  */
  55   int clobber_regs;             /* True if we should restore saved regs.  */
  56   off_t *filepos;               /* Set of open file descriptors' offsets.  */
  57   int maxfd;
  58 };
  59
  60 /* Fork list methods:  */
  61
  62 int
  63 forks_exist_p (void)
  64 {
  65   return (fork_list != NULL);
  66 }
  67
  68 /* Add a fork to the internal fork list.  */
  69
  70 struct fork_info *
  71 add_fork (pid_t pid)
  72 {
  73   struct fork_info *fp;
  74
  75   if (fork_list == NULL && pid != ptid_get_pid (inferior_ptid))
  76     {
  77       /* Special case -- if this is the first fork in the list
  78          (the list is hitherto empty), and if this new fork is
  79          NOT the current inferior_ptid, then add inferior_ptid
  80          first, as a special zeroeth fork id.  */
  81       highest_fork_num = -1;
  82       add_fork (ptid_get_pid (inferior_ptid));  /* safe recursion */
  83     }
  84
  85   fp = XCNEW (struct fork_info);
  86   fp->ptid = ptid_build (pid, pid, 0);
  87   fp->num = ++highest_fork_num;
  88   fp->next = fork_list;
  89   fork_list = fp;
  90   return fp;
  91 }
  92
  93 static void
  94 free_fork (struct fork_info *fp)
  95 {
  96   /* Notes on step-resume breakpoints: since this is a concern for
  97      threads, let's convince ourselves that it's not a concern for
  98      forks.  There are two ways for a fork_info to be created.  First,
  99      by the checkpoint command, in which case we're at a gdb prompt
 100      and there can't be any step-resume breakpoint.  Second, by a fork
 101      in the user program, in which case we *may* have stepped into the
 102      fork call, but regardless of whether we follow the parent or the
 103      child, we will return to the same place and the step-resume
 104      breakpoint, if any, will take care of itself as usual.  And
 105      unlike threads, we do not save a private copy of the step-resume
 106      breakpoint -- so we're OK.  */
 107
 108   if (fp)
 109     {
 110       if (fp->savedregs)
 111         regcache_xfree (fp->savedregs);
 112       if (fp->filepos)
 113         xfree (fp->filepos);
 114       xfree (fp);
 115     }
 116 }
 117
 118 static void
 119 delete_fork (ptid_t ptid)
 120 {
 121   struct fork_info *fp, *fpprev;
 122
 123   fpprev = NULL;
 124
 125   linux_nat_forget_process (ptid_get_pid (ptid));
 126
 127   for (fp = fork_list; fp; fpprev = fp, fp = fp->next)
 128     if (ptid_equal (fp->ptid, ptid))
 129       break;
 130
 131   if (!fp)
 132     return;
 133
 134   if (fpprev)
 135     fpprev->next = fp->next;
 136   else
 137     fork_list = fp->next;
 138
 139   free_fork (fp);
 140
 141   /* Special case: if there is now only one process in the list,
 142      and if it is (hopefully!) the current inferior_ptid, then
 143      remove it, leaving the list empty -- we're now down to the
 144      default case of debugging a single process.  */
 145   if (fork_list != NULL && fork_list->next == NULL &&
 146       ptid_equal (fork_list->ptid, inferior_ptid))
 147     {
 148       /* Last fork -- delete from list and handle as solo process
 149          (should be a safe recursion).  */
 150       delete_fork (inferior_ptid);
 151     }
 152 }
 153
 154 /* Find a fork_info by matching PTID.  */
 155 static struct fork_info *
 156 find_fork_ptid (ptid_t ptid)
 157 {
 158   struct fork_info *fp;
 159
 160   for (fp = fork_list; fp; fp = fp->next)
 161     if (ptid_equal (fp->ptid, ptid))
 162       return fp;
 163
 164   return NULL;
 165 }
 166
 167 /* Find a fork_info by matching ID.  */
 168 static struct fork_info *
 169 find_fork_id (int num)
 170 {
 171   struct fork_info *fp;
 172
 173   for (fp = fork_list; fp; fp = fp->next)
 174     if (fp->num == num)
 175       return fp;
 176
 177   return NULL;
 178 }
 179
 180 /* Find a fork_info by matching pid.  */
 181 extern struct fork_info *
 182 find_fork_pid (pid_t pid)
 183 {
 184   struct fork_info *fp;
 185
 186   for (fp = fork_list; fp; fp = fp->next)
 187     if (pid == ptid_get_pid (fp->ptid))
 188       return fp;
 189
 190   return NULL;
 191 }
 192
 193 static ptid_t
 194 fork_id_to_ptid (int num)
 195 {
 196   struct fork_info *fork = find_fork_id (num);
 197   if (fork)
 198     return fork->ptid;
 199   else
 200     return pid_to_ptid (-1);
 201 }
 202
 203 static void
 204 init_fork_list (void)
 205 {
 206   struct fork_info *fp, *fpnext;
 207
 208   if (!fork_list)
 209     return;
 210
 211   for (fp = fork_list; fp; fp = fpnext)
 212     {
 213       fpnext = fp->next;
 214       free_fork (fp);
 215     }
 216
 217   fork_list = NULL;
 218 }
 219
 220 /* Fork list <-> gdb interface.  */
 221
 222 /* Utility function for fork_load/fork_save.
 223    Calls lseek in the (current) inferior process.  */
 224
 225 static off_t
 226 call_lseek (int fd, off_t offset, int whence)
 227 {
 228   char exp[80];
 229
 230   snprintf (&exp[0], sizeof (exp), "lseek (%d, %ld, %d)",
 231             fd, (long) offset, whence);
 232   return (off_t) parse_and_eval_long (&exp[0]);
 233 }
 234
 235 /* Load infrun state for the fork PTID.  */
 236
 237 static void
 238 fork_load_infrun_state (struct fork_info *fp)
 239 {
 240   extern void nullify_last_target_wait_ptid ();
 241   int i;
 242
 243   linux_nat_switch_fork (fp->ptid);
 244
 245   if (fp->savedregs && fp->clobber_regs)
 246     regcache_cpy (get_current_regcache (), fp->savedregs);
 247
 248   registers_changed ();
 249   reinit_frame_cache ();
 250
 251   stop_pc = regcache_read_pc (get_current_regcache ());
 252   nullify_last_target_wait_ptid ();
 253
 254   /* Now restore the file positions of open file descriptors.  */
 255   if (fp->filepos)
 256     {
 257       for (i = 0; i <= fp->maxfd; i++)
 258         if (fp->filepos[i] != (off_t) -1)
 259           call_lseek (i, fp->filepos[i], SEEK_SET);
 260       /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
 261          this is native-only.  If it ever has to be cross, we'll have
 262          to rethink this.  */
 263     }
 264 }
 265
 266 /* Save infrun state for the fork PTID.
 267    Exported for use by linux child_follow_fork.  */
 268
 269 static void
 270 fork_save_infrun_state (struct fork_info *fp, int clobber_regs)
 271 {
 272   char path[PATH_MAX];
 273   struct dirent *de;
 274   DIR *d;
 275
 276   if (fp->savedregs)
 277     regcache_xfree (fp->savedregs);
 278
 279   fp->savedregs = regcache_dup (get_current_regcache ());
 280   fp->clobber_regs = clobber_regs;
 281
 282   if (clobber_regs)
 283     {
 284       /* Now save the 'state' (file position) of all open file descriptors.
 285          Unfortunately fork does not take care of that for us...  */
 286       snprintf (path, PATH_MAX, "/proc/%ld/fd",
 287                 (long) ptid_get_pid (fp->ptid));
 288       if ((d = opendir (path)) != NULL)
 289         {
 290           long tmp;
 291
 292           fp->maxfd = 0;
 293           while ((de = readdir (d)) != NULL)
 294             {
 295               /* Count open file descriptors (actually find highest
 296                  numbered).  */
 297               tmp = strtol (&de->d_name[0], NULL, 10);
 298               if (fp->maxfd < tmp)
 299                 fp->maxfd = tmp;
 300             }
 301           /* Allocate array of file positions.  */
 302           fp->filepos = xrealloc (fp->filepos,
 303                                   (fp->maxfd + 1) * sizeof (*fp->filepos));
 304
 305           /* Initialize to -1 (invalid).  */
 306           for (tmp = 0; tmp <= fp->maxfd; tmp++)
 307             fp->filepos[tmp] = -1;
 308
 309           /* Now find actual file positions.  */
 310           rewinddir (d);
 311           while ((de = readdir (d)) != NULL)
 312             if (isdigit (de->d_name[0]))
 313               {
 314                 tmp = strtol (&de->d_name[0], NULL, 10);
 315                 fp->filepos[tmp] = call_lseek (tmp, 0, SEEK_CUR);
 316               }
 317           closedir (d);
 318         }
 319     }
 320 }
 321
 322 /* Kill 'em all, let God sort 'em out...  */
 323
 324 void
 325 linux_fork_killall (void)
 326 {
 327   /* Walk list and kill every pid.  No need to treat the
 328      current inferior_ptid as special (we do not return a
 329      status for it) -- however any process may be a child
 330      or a parent, so may get a SIGCHLD from a previously
 331      killed child.  Wait them all out.  */
 332   struct fork_info *fp;
 333   pid_t pid, ret;
 334   int status;
 335
 336   for (fp = fork_list; fp; fp = fp->next)
 337     {
 338       pid = ptid_get_pid (fp->ptid);
 339       do {
 340         /* Use SIGKILL instead of PTRACE_KILL because the former works even
 341            if the thread is running, while the later doesn't.  */
 342         kill (pid, SIGKILL);
 343         ret = waitpid (pid, &status, 0);
 344         /* We might get a SIGCHLD instead of an exit status.  This is
 345          aggravated by the first kill above - a child has just
 346          died.  MVS comment cut-and-pasted from linux-nat.  */
 347       } while (ret == pid && WIFSTOPPED (status));
 348     }
 349   init_fork_list ();    /* Clear list, prepare to start fresh.  */
 350 }
 351
 352 /* The current inferior_ptid has exited, but there are other viable
 353    forks to debug.  Delete the exiting one and context-switch to the
 354    first available.  */
 355
 356 void
 357 linux_fork_mourn_inferior (void)
 358 {
 359   /* Wait just one more time to collect the inferior's exit status.
 360      Do not check whether this succeeds though, since we may be
 361      dealing with a process that we attached to.  Such a process will
 362      only report its exit status to its original parent.  */
 363   int status;
 364
 365   waitpid (ptid_get_pid (inferior_ptid), &status, 0);
 366
 367   /* OK, presumably inferior_ptid is the one who has exited.
 368      We need to delete that one from the fork_list, and switch
 369      to the next available fork.  */
 370   delete_fork (inferior_ptid);
 371
 372   /* There should still be a fork - if there's only one left,
 373      delete_fork won't remove it, because we haven't updated
 374      inferior_ptid yet.  */
 375   gdb_assert (fork_list);
 376
 377   fork_load_infrun_state (fork_list);
 378   printf_filtered (_("[Switching to %s]\n"),
 379                    target_pid_to_str (inferior_ptid));
 380
 381   /* If there's only one fork, switch back to non-fork mode.  */
 382   if (fork_list->next == NULL)
 383     delete_fork (inferior_ptid);
 384 }
 385
 386 /* The current inferior_ptid is being detached, but there are other
 387    viable forks to debug.  Detach and delete it and context-switch to
 388    the first available.  */
 389
 390 void
 391 linux_fork_detach (const char *args, int from_tty)
 392 {
 393   /* OK, inferior_ptid is the one we are detaching from.  We need to
 394      delete it from the fork_list, and switch to the next available
 395      fork.  */
 396
 397   if (ptrace (PTRACE_DETACH, ptid_get_pid (inferior_ptid), 0, 0))
 398     error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid));
 399
 400   delete_fork (inferior_ptid);
 401
 402   /* There should still be a fork - if there's only one left,
 403      delete_fork won't remove it, because we haven't updated
 404      inferior_ptid yet.  */
 405   gdb_assert (fork_list);
 406
 407   fork_load_infrun_state (fork_list);
 408
 409   if (from_tty)
 410     printf_filtered (_("[Switching to %s]\n"),
 411                      target_pid_to_str (inferior_ptid));
 412
 413   /* If there's only one fork, switch back to non-fork mode.  */
 414   if (fork_list->next == NULL)
 415     delete_fork (inferior_ptid);
 416 }
 417
 418 static void
 419 inferior_call_waitpid_cleanup (void *fp)
 420 {
 421   struct fork_info *oldfp = fp;
 422
 423   if (oldfp)
 424     {
 425       /* Switch back to inferior_ptid.  */
 426       remove_breakpoints ();
 427       fork_load_infrun_state (oldfp);
 428       insert_breakpoints ();
 429     }
 430 }
 431
 432 static int
 433 inferior_call_waitpid (ptid_t pptid, int pid)
 434 {
 435   struct objfile *waitpid_objf;
 436   struct value *waitpid_fn = NULL;
 437   struct value *argv[4], *retv;
 438   struct gdbarch *gdbarch = get_current_arch ();
 439   struct fork_info *oldfp = NULL, *newfp = NULL;
 440   struct cleanup *old_cleanup;
 441   int ret = -1;
 442
 443   if (!ptid_equal (pptid, inferior_ptid))
 444     {
 445       /* Switch to pptid.  */
 446       oldfp = find_fork_ptid (inferior_ptid);
 447       gdb_assert (oldfp != NULL);
 448       newfp = find_fork_ptid (pptid);
 449       gdb_assert (newfp != NULL);
 450       fork_save_infrun_state (oldfp, 1);
 451       remove_breakpoints ();
 452       fork_load_infrun_state (newfp);
 453       insert_breakpoints ();
 454     }
 455
 456   old_cleanup = make_cleanup (inferior_call_waitpid_cleanup, oldfp);
 457
 458   /* Get the waitpid_fn.  */
 459   if (lookup_minimal_symbol ("waitpid", NULL, NULL).minsym != NULL)
 460     waitpid_fn = find_function_in_inferior ("waitpid", &waitpid_objf);
 461   if (!waitpid_fn
 462       && lookup_minimal_symbol ("_waitpid", NULL, NULL).minsym != NULL)
 463     waitpid_fn = find_function_in_inferior ("_waitpid", &waitpid_objf);
 464   if (!waitpid_fn)
 465     goto out;
 466
 467   /* Get the argv.  */
 468   argv[0] = value_from_longest (builtin_type (gdbarch)->builtin_int, pid);
 469   argv[1] = value_from_pointer (builtin_type (gdbarch)->builtin_data_ptr, 0);
 470   argv[2] = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
 471   argv[3] = 0;
 472
 473   retv = call_function_by_hand (waitpid_fn, 3, argv);
 474   if (value_as_long (retv) < 0)
 475     goto out;
 476
 477   ret = 0;
 478
 479 out:
 480   do_cleanups (old_cleanup);
 481   return ret;
 482 }
 483
 484 /* Fork list <-> user interface.  */
 485
 486 static void
 487 delete_checkpoint_command (char *args, int from_tty)
 488 {
 489   ptid_t ptid, pptid;
 490   struct fork_info *fi;
 491
 492   if (!args || !*args)
 493     error (_("Requires argument (checkpoint id to delete)"));
 494
 495   ptid = fork_id_to_ptid (parse_and_eval_long (args));
 496   if (ptid_equal (ptid, minus_one_ptid))
 497     error (_("No such checkpoint id, %s"), args);
 498
 499   if (ptid_equal (ptid, inferior_ptid))
 500     error (_("\
 501 Please switch to another checkpoint before deleting the current one"));
 502
 503   if (ptrace (PTRACE_KILL, ptid_get_pid (ptid), 0, 0))
 504     error (_("Unable to kill pid %s"), target_pid_to_str (ptid));
 505
 506   fi = find_fork_ptid (ptid);
 507   gdb_assert (fi);
 508   pptid = fi->parent_ptid;
 509
 510   if (from_tty)
 511     printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid));
 512
 513   delete_fork (ptid);
 514
 515   /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
 516      list, waitpid the ptid.
 517      If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
 518      ptid.  */
 519   if ((!find_thread_ptid (pptid) && find_fork_ptid (pptid))
 520       || (find_thread_ptid (pptid) && is_stopped (pptid)))
 521     {
 522       if (inferior_call_waitpid (pptid, ptid_get_pid (ptid)))
 523         warning (_("Unable to wait pid %s"), target_pid_to_str (ptid));
 524     }
 525 }
 526
 527 static void
 528 detach_checkpoint_command (char *args, int from_tty)
 529 {
 530   ptid_t ptid;
 531
 532   if (!args || !*args)
 533     error (_("Requires argument (checkpoint id to detach)"));
 534
 535   ptid = fork_id_to_ptid (parse_and_eval_long (args));
 536   if (ptid_equal (ptid, minus_one_ptid))
 537     error (_("No such checkpoint id, %s"), args);
 538
 539   if (ptid_equal (ptid, inferior_ptid))
 540     error (_("\
 541 Please switch to another checkpoint before detaching the current one"));
 542
 543   if (ptrace (PTRACE_DETACH, ptid_get_pid (ptid), 0, 0))
 544     error (_("Unable to detach %s"), target_pid_to_str (ptid));
 545
 546   if (from_tty)
 547     printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid));
 548
 549   delete_fork (ptid);
 550 }
 551
 552 /* Print information about currently known checkpoints.  */
 553
 554 static void
 555 info_checkpoints_command (char *arg, int from_tty)
 556 {
 557   struct gdbarch *gdbarch = get_current_arch ();
 558   struct symtab_and_line sal;
 559   struct fork_info *fp;
 560   ULONGEST pc;
 561   int requested = -1;
 562   struct fork_info *printed = NULL;
 563
 564   if (arg && *arg)
 565     requested = (int) parse_and_eval_long (arg);
 566
 567   for (fp = fork_list; fp; fp = fp->next)
 568     {
 569       if (requested > 0 && fp->num != requested)
 570         continue;
 571
 572       printed = fp;
 573       if (ptid_equal (fp->ptid, inferior_ptid))
 574         {
 575           printf_filtered ("* ");
 576           pc = regcache_read_pc (get_current_regcache ());
 577         }
 578       else
 579         {
 580           printf_filtered ("  ");
 581           pc = regcache_read_pc (fp->savedregs);
 582         }
 583       printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));
 584       if (fp->num == 0)
 585         printf_filtered (_(" (main process)"));
 586       printf_filtered (_(" at "));
 587       fputs_filtered (paddress (gdbarch, pc), gdb_stdout);
 588
 589       sal = find_pc_line (pc, 0);
 590       if (sal.symtab)
 591         printf_filtered (_(", file %s"),
 592                          symtab_to_filename_for_display (sal.symtab));
 593       if (sal.line)
 594         printf_filtered (_(", line %d"), sal.line);
 595       if (!sal.symtab && !sal.line)
 596         {
 597           struct bound_minimal_symbol msym;
 598
 599           msym = lookup_minimal_symbol_by_pc (pc);
 600           if (msym.minsym)
 601             printf_filtered (", <%s>", MSYMBOL_LINKAGE_NAME (msym.minsym));
 602         }
 603
 604       putchar_filtered ('\n');
 605     }
 606   if (printed == NULL)
 607     {
 608       if (requested > 0)
 609         printf_filtered (_("No checkpoint number %d.\n"), requested);
 610       else
 611         printf_filtered (_("No checkpoints.\n"));
 612     }
 613 }
 614
 615 /* The PID of the process we're checkpointing.  */
 616 static int checkpointing_pid = 0;
 617
 618 int
 619 linux_fork_checkpointing_p (int pid)
 620 {
 621   return (checkpointing_pid == pid);
 622 }
 623
 624 /* Callback for iterate over threads.  Used to check whether
 625    the current inferior is multi-threaded.  Returns true as soon
 626    as it sees the second thread of the current inferior.  */
 627
 628 static int
 629 inf_has_multiple_thread_cb (struct thread_info *tp, void *data)
 630 {
 631   int *count_p = (int *) data;
 632
 633   if (current_inferior ()->pid == ptid_get_pid (tp->ptid))
 634     (*count_p)++;
 635
 636   /* Stop the iteration if multiple threads have been detected.  */
 637   return *count_p > 1;
 638 }
 639
 640 /* Return true if the current inferior is multi-threaded.  */
 641
 642 static int
 643 inf_has_multiple_threads (void)
 644 {
 645   int count = 0;
 646
 647   iterate_over_threads (inf_has_multiple_thread_cb, &count);
 648   return (count > 1);
 649 }
 650
 651 static void
 652 checkpoint_command (char *args, int from_tty)
 653 {
 654   struct objfile *fork_objf;
 655   struct gdbarch *gdbarch;
 656   struct target_waitstatus last_target_waitstatus;
 657   ptid_t last_target_ptid;
 658   struct value *fork_fn = NULL, *ret;
 659   struct fork_info *fp;
 660   pid_t retpid;
 661   struct cleanup *old_chain;
 662
 663   if (!target_has_execution)
 664     error (_("The program is not being run."));
 665
 666   /* Ensure that the inferior is not multithreaded.  */
 667   update_thread_list ();
 668   if (inf_has_multiple_threads ())
 669     error (_("checkpoint: can't checkpoint multiple threads."));
 670
 671   /* Make the inferior fork, record its (and gdb's) state.  */
 672
 673   if (lookup_minimal_symbol ("fork", NULL, NULL).minsym != NULL)
 674     fork_fn = find_function_in_inferior ("fork", &fork_objf);
 675   if (!fork_fn)
 676     if (lookup_minimal_symbol ("_fork", NULL, NULL).minsym != NULL)
 677       fork_fn = find_function_in_inferior ("fork", &fork_objf);
 678   if (!fork_fn)
 679     error (_("checkpoint: can't find fork function in inferior."));
 680
 681   gdbarch = get_objfile_arch (fork_objf);
 682   ret = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
 683
 684   /* Tell linux-nat.c that we're checkpointing this inferior.  */
 685   old_chain = make_cleanup_restore_integer (&checkpointing_pid);
 686   checkpointing_pid = ptid_get_pid (inferior_ptid);
 687
 688   ret = call_function_by_hand (fork_fn, 0, &ret);
 689   do_cleanups (old_chain);
 690   if (!ret)     /* Probably can't happen.  */
 691     error (_("checkpoint: call_function_by_hand returned null."));
 692
 693   retpid = value_as_long (ret);
 694   get_last_target_status (&last_target_ptid, &last_target_waitstatus);
 695   if (from_tty)
 696     {
 697       int parent_pid;
 698
 699       printf_filtered (_("checkpoint: fork returned pid %ld.\n"),
 700                        (long) retpid);
 701       if (info_verbose)
 702         {
 703           parent_pid = ptid_get_lwp (last_target_ptid);
 704           if (parent_pid == 0)
 705             parent_pid = ptid_get_pid (last_target_ptid);
 706           printf_filtered (_("   gdb says parent = %ld.\n"),
 707                            (long) parent_pid);
 708         }
 709     }
 710
 711   fp = find_fork_pid (retpid);
 712   if (!fp)
 713     error (_("Failed to find new fork"));
 714   fork_save_infrun_state (fp, 1);
 715   fp->parent_ptid = last_target_ptid;
 716 }
 717
 718 static void
 719 linux_fork_context (struct fork_info *newfp, int from_tty)
 720 {
 721   /* Now we attempt to switch processes.  */
 722   struct fork_info *oldfp;
 723
 724   gdb_assert (newfp != NULL);
 725
 726   oldfp = find_fork_ptid (inferior_ptid);
 727   gdb_assert (oldfp != NULL);
 728
 729   fork_save_infrun_state (oldfp, 1);
 730   remove_breakpoints ();
 731   fork_load_infrun_state (newfp);
 732   insert_breakpoints ();
 733
 734   printf_filtered (_("Switching to %s\n"),
 735                    target_pid_to_str (inferior_ptid));
 736
 737   print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC, 1);
 738 }
 739
 740 /* Switch inferior process (checkpoint) context, by checkpoint id.  */
 741 static void
 742 restart_command (char *args, int from_tty)
 743 {
 744   struct fork_info *fp;
 745
 746   if (!args || !*args)
 747     error (_("Requires argument (checkpoint id to restart)"));
 748
 749   if ((fp = find_fork_id (parse_and_eval_long (args))) == NULL)
 750     error (_("Not found: checkpoint id %s"), args);
 751
 752   linux_fork_context (fp, from_tty);
 753 }
 754
 755 void
 756 _initialize_linux_fork (void)
 757 {
 758   init_fork_list ();
 759
 760   /* Checkpoint command: create a fork of the inferior process
 761      and set it aside for later debugging.  */
 762
 763   add_com ("checkpoint", class_obscure, checkpoint_command, _("\
 764 Fork a duplicate process (experimental)."));
 765
 766   /* Restart command: restore the context of a specified checkpoint
 767      process.  */
 768
 769   add_com ("restart", class_obscure, restart_command, _("\
 770 restart <n>: restore program context from a checkpoint.\n\
 771 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
 772
 773   /* Delete checkpoint command: kill the process and remove it from
 774      the fork list.  */
 775
 776   add_cmd ("checkpoint", class_obscure, delete_checkpoint_command, _("\
 777 Delete a checkpoint (experimental)."),
 778            &deletelist);
 779
 780   /* Detach checkpoint command: release the process to run independently,
 781      and remove it from the fork list.  */
 782
 783   add_cmd ("checkpoint", class_obscure, detach_checkpoint_command, _("\
 784 Detach from a checkpoint (experimental)."),
 785            &detachlist);
 786
 787   /* Info checkpoints command: list all forks/checkpoints
 788      currently under gdb's control.  */
 789
 790   add_info ("checkpoints", info_checkpoints_command,
 791             _("IDs of currently known checkpoints."));
 792 }