gdb/linux-fork.c

   1 /* GNU/Linux native-dependent code for debugging multiple forks.
   2
   3    Copyright (C) 2005-2015 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 <sys/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 /* Prevent warning from -Wmissing-prototypes.  */
  42 extern void _initialize_linux_fork (void);
  43
  44 /* Fork list data structure:  */
  45 struct fork_info
  46 {
  47   struct fork_info *next;
  48   ptid_t ptid;
  49   ptid_t parent_ptid;
  50   int num;                      /* Convenient handle (GDB fork id).  */
  51   struct regcache *savedregs;   /* Convenient for info fork, saves
  52                                    having to actually switch contexts.  */
  53   int clobber_regs;             /* True if we should restore saved regs.  */
  54   off_t *filepos;               /* Set of open file descriptors' offsets.  */
  55   int maxfd;
  56 };
  57
  58 /* Fork list methods:  */
  59
  60 int
  61 forks_exist_p (void)
  62 {
  63   return (fork_list != NULL);
  64 }
  65
  66 /* Add a fork to the internal fork list.  */
  67
  68 struct fork_info *
  69 add_fork (pid_t pid)
  70 {
  71   struct fork_info *fp;
  72
  73   if (fork_list == NULL && pid != ptid_get_pid (inferior_ptid))
  74     {
  75       /* Special case -- if this is the first fork in the list
  76          (the list is hitherto empty), and if this new fork is
  77          NOT the current inferior_ptid, then add inferior_ptid
  78          first, as a special zeroeth fork id.  */
  79       highest_fork_num = -1;
  80       add_fork (ptid_get_pid (inferior_ptid));  /* safe recursion */
  81     }
  82
  83   fp = XCNEW (struct fork_info);
  84   fp->ptid = ptid_build (pid, pid, 0);
  85   fp->num = ++highest_fork_num;
  86   fp->next = fork_list;
  87   fork_list = fp;
  88   return fp;
  89 }
  90
  91 static void
  92 free_fork (struct fork_info *fp)
  93 {
  94   /* Notes on step-resume breakpoints: since this is a concern for
  95      threads, let's convince ourselves that it's not a concern for
  96      forks.  There are two ways for a fork_info to be created.  First,
  97      by the checkpoint command, in which case we're at a gdb prompt
  98      and there can't be any step-resume breakpoint.  Second, by a fork
  99      in the user program, in which case we *may* have stepped into the
 100      fork call, but regardless of whether we follow the parent or the
 101      child, we will return to the same place and the step-resume
 102      breakpoint, if any, will take care of itself as usual.  And
 103      unlike threads, we do not save a private copy of the step-resume
 104      breakpoint -- so we're OK.  */
 105
 106   if (fp)
 107     {
 108       if (fp->savedregs)
 109         regcache_xfree (fp->savedregs);
 110       if (fp->filepos)
 111         xfree (fp->filepos);
 112       xfree (fp);
 113     }
 114 }
 115
 116 static void
 117 delete_fork (ptid_t ptid)
 118 {
 119   struct fork_info *fp, *fpprev;
 120
 121   fpprev = NULL;
 122
 123   linux_nat_forget_process (ptid_get_pid (ptid));
 124
 125   for (fp = fork_list; fp; fpprev = fp, fp = fp->next)
 126     if (ptid_equal (fp->ptid, ptid))
 127       break;
 128
 129   if (!fp)
 130     return;
 131
 132   if (fpprev)
 133     fpprev->next = fp->next;
 134   else
 135     fork_list = fp->next;
 136
 137   free_fork (fp);
 138
 139   /* Special case: if there is now only one process in the list,
 140      and if it is (hopefully!) the current inferior_ptid, then
 141      remove it, leaving the list empty -- we're now down to the
 142      default case of debugging a single process.  */
 143   if (fork_list != NULL && fork_list->next == NULL &&
 144       ptid_equal (fork_list->ptid, inferior_ptid))
 145     {
 146       /* Last fork -- delete from list and handle as solo process
 147          (should be a safe recursion).  */
 148       delete_fork (inferior_ptid);
 149     }
 150 }
 151
 152 /* Find a fork_info by matching PTID.  */
 153 static struct fork_info *
 154 find_fork_ptid (ptid_t ptid)
 155 {
 156   struct fork_info *fp;
 157
 158   for (fp = fork_list; fp; fp = fp->next)
 159     if (ptid_equal (fp->ptid, ptid))
 160       return fp;
 161
 162   return NULL;
 163 }
 164
 165 /* Find a fork_info by matching ID.  */
 166 static struct fork_info *
 167 find_fork_id (int num)
 168 {
 169   struct fork_info *fp;
 170
 171   for (fp = fork_list; fp; fp = fp->next)
 172     if (fp->num == num)
 173       return fp;
 174
 175   return NULL;
 176 }
 177
 178 /* Find a fork_info by matching pid.  */
 179 extern struct fork_info *
 180 find_fork_pid (pid_t pid)
 181 {
 182   struct fork_info *fp;
 183
 184   for (fp = fork_list; fp; fp = fp->next)
 185     if (pid == ptid_get_pid (fp->ptid))
 186       return fp;
 187
 188   return NULL;
 189 }
 190
 191 static ptid_t
 192 fork_id_to_ptid (int num)
 193 {
 194   struct fork_info *fork = find_fork_id (num);
 195   if (fork)
 196     return fork->ptid;
 197   else
 198     return pid_to_ptid (-1);
 199 }
 200
 201 static void
 202 init_fork_list (void)
 203 {
 204   struct fork_info *fp, *fpnext;
 205
 206   if (!fork_list)
 207     return;
 208
 209   for (fp = fork_list; fp; fp = fpnext)
 210     {
 211       fpnext = fp->next;
 212       free_fork (fp);
 213     }
 214
 215   fork_list = NULL;
 216 }
 217
 218 /* Fork list <-> gdb interface.  */
 219
 220 /* Utility function for fork_load/fork_save.
 221    Calls lseek in the (current) inferior process.  */
 222
 223 static off_t
 224 call_lseek (int fd, off_t offset, int whence)
 225 {
 226   char exp[80];
 227
 228   snprintf (&exp[0], sizeof (exp), "lseek (%d, %ld, %d)",
 229             fd, (long) offset, whence);
 230   return (off_t) parse_and_eval_long (&exp[0]);
 231 }
 232
 233 /* Load infrun state for the fork PTID.  */
 234
 235 static void
 236 fork_load_infrun_state (struct fork_info *fp)
 237 {
 238   extern void nullify_last_target_wait_ptid ();
 239   int i;
 240
 241   linux_nat_switch_fork (fp->ptid);
 242
 243   if (fp->savedregs && fp->clobber_regs)
 244     regcache_cpy (get_current_regcache (), fp->savedregs);
 245
 246   registers_changed ();
 247   reinit_frame_cache ();
 248
 249   stop_pc = regcache_read_pc (get_current_regcache ());
 250   nullify_last_target_wait_ptid ();
 251
 252   /* Now restore the file positions of open file descriptors.  */
 253   if (fp->filepos)
 254     {
 255       for (i = 0; i <= fp->maxfd; i++)
 256         if (fp->filepos[i] != (off_t) -1)
 257           call_lseek (i, fp->filepos[i], SEEK_SET);
 258       /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
 259          this is native-only.  If it ever has to be cross, we'll have
 260          to rethink this.  */
 261     }
 262 }
 263
 264 /* Save infrun state for the fork PTID.
 265    Exported for use by linux child_follow_fork.  */
 266
 267 static void
 268 fork_save_infrun_state (struct fork_info *fp, int clobber_regs)
 269 {
 270   char path[PATH_MAX];
 271   struct dirent *de;
 272   DIR *d;
 273
 274   if (fp->savedregs)
 275     regcache_xfree (fp->savedregs);
 276
 277   fp->savedregs = regcache_dup (get_current_regcache ());
 278   fp->clobber_regs = clobber_regs;
 279
 280   if (clobber_regs)
 281     {
 282       /* Now save the 'state' (file position) of all open file descriptors.
 283          Unfortunately fork does not take care of that for us...  */
 284       snprintf (path, PATH_MAX, "/proc/%ld/fd",
 285                 (long) ptid_get_pid (fp->ptid));
 286       if ((d = opendir (path)) != NULL)
 287         {
 288           long tmp;
 289
 290           fp->maxfd = 0;
 291           while ((de = readdir (d)) != NULL)
 292             {
 293               /* Count open file descriptors (actually find highest
 294                  numbered).  */
 295               tmp = strtol (&de->d_name[0], NULL, 10);
 296               if (fp->maxfd < tmp)
 297                 fp->maxfd = tmp;
 298             }
 299           /* Allocate array of file positions.  */
 300           fp->filepos = xrealloc (fp->filepos,
 301                                   (fp->maxfd + 1) * sizeof (*fp->filepos));
 302
 303           /* Initialize to -1 (invalid).  */
 304           for (tmp = 0; tmp <= fp->maxfd; tmp++)
 305             fp->filepos[tmp] = -1;
 306
 307           /* Now find actual file positions.  */
 308           rewinddir (d);
 309           while ((de = readdir (d)) != NULL)
 310             if (isdigit (de->d_name[0]))
 311               {
 312                 tmp = strtol (&de->d_name[0], NULL, 10);
 313                 fp->filepos[tmp] = call_lseek (tmp, 0, SEEK_CUR);
 314               }
 315           closedir (d);
 316         }
 317     }
 318 }
 319
 320 /* Kill 'em all, let God sort 'em out...  */
 321
 322 void
 323 linux_fork_killall (void)
 324 {
 325   /* Walk list and kill every pid.  No need to treat the
 326      current inferior_ptid as special (we do not return a
 327      status for it) -- however any process may be a child
 328      or a parent, so may get a SIGCHLD from a previously
 329      killed child.  Wait them all out.  */
 330   struct fork_info *fp;
 331   pid_t pid, ret;
 332   int status;
 333
 334   for (fp = fork_list; fp; fp = fp->next)
 335     {
 336       pid = ptid_get_pid (fp->ptid);
 337       do {
 338         /* Use SIGKILL instead of PTRACE_KILL because the former works even
 339            if the thread is running, while the later doesn't.  */
 340         kill (pid, SIGKILL);
 341         ret = waitpid (pid, &status, 0);
 342         /* We might get a SIGCHLD instead of an exit status.  This is
 343          aggravated by the first kill above - a child has just
 344          died.  MVS comment cut-and-pasted from linux-nat.  */
 345       } while (ret == pid && WIFSTOPPED (status));
 346     }
 347   init_fork_list ();    /* Clear list, prepare to start fresh.  */
 348 }
 349
 350 /* The current inferior_ptid has exited, but there are other viable
 351    forks to debug.  Delete the exiting one and context-switch to the
 352    first available.  */
 353
 354 void
 355 linux_fork_mourn_inferior (void)
 356 {
 357   /* Wait just one more time to collect the inferior's exit status.
 358      Do not check whether this succeeds though, since we may be
 359      dealing with a process that we attached to.  Such a process will
 360      only report its exit status to its original parent.  */
 361   int status;
 362
 363   waitpid (ptid_get_pid (inferior_ptid), &status, 0);
 364
 365   /* OK, presumably inferior_ptid is the one who has exited.
 366      We need to delete that one from the fork_list, and switch
 367      to the next available fork.  */
 368   delete_fork (inferior_ptid);
 369
 370   /* There should still be a fork - if there's only one left,
 371      delete_fork won't remove it, because we haven't updated
 372      inferior_ptid yet.  */
 373   gdb_assert (fork_list);
 374
 375   fork_load_infrun_state (fork_list);
 376   printf_filtered (_("[Switching to %s]\n"),
 377                    target_pid_to_str (inferior_ptid));
 378
 379   /* If there's only one fork, switch back to non-fork mode.  */
 380   if (fork_list->next == NULL)
 381     delete_fork (inferior_ptid);
 382 }
 383
 384 /* The current inferior_ptid is being detached, but there are other
 385    viable forks to debug.  Detach and delete it and context-switch to
 386    the first available.  */
 387
 388 void
 389 linux_fork_detach (const char *args, int from_tty)
 390 {
 391   /* OK, inferior_ptid is the one we are detaching from.  We need to
 392      delete it from the fork_list, and switch to the next available
 393      fork.  */
 394
 395   if (ptrace (PTRACE_DETACH, ptid_get_pid (inferior_ptid), 0, 0))
 396     error (_("Unable to detach %s"), target_pid_to_str (inferior_ptid));
 397
 398   delete_fork (inferior_ptid);
 399
 400   /* There should still be a fork - if there's only one left,
 401      delete_fork won't remove it, because we haven't updated
 402      inferior_ptid yet.  */
 403   gdb_assert (fork_list);
 404
 405   fork_load_infrun_state (fork_list);
 406
 407   if (from_tty)
 408     printf_filtered (_("[Switching to %s]\n"),
 409                      target_pid_to_str (inferior_ptid));
 410
 411   /* If there's only one fork, switch back to non-fork mode.  */
 412   if (fork_list->next == NULL)
 413     delete_fork (inferior_ptid);
 414 }
 415
 416 static void
 417 inferior_call_waitpid_cleanup (void *fp)
 418 {
 419   struct fork_info *oldfp = fp;
 420
 421   if (oldfp)
 422     {
 423       /* Switch back to inferior_ptid.  */
 424       remove_breakpoints ();
 425       fork_load_infrun_state (oldfp);
 426       insert_breakpoints ();
 427     }
 428 }
 429
 430 static int
 431 inferior_call_waitpid (ptid_t pptid, int pid)
 432 {
 433   struct objfile *waitpid_objf;
 434   struct value *waitpid_fn = NULL;
 435   struct value *argv[4], *retv;
 436   struct gdbarch *gdbarch = get_current_arch ();
 437   struct fork_info *oldfp = NULL, *newfp = NULL;
 438   struct cleanup *old_cleanup;
 439   int ret = -1;
 440
 441   if (!ptid_equal (pptid, inferior_ptid))
 442     {
 443       /* Switch to pptid.  */
 444       oldfp = find_fork_ptid (inferior_ptid);
 445       gdb_assert (oldfp != NULL);
 446       newfp = find_fork_ptid (pptid);
 447       gdb_assert (newfp != NULL);
 448       fork_save_infrun_state (oldfp, 1);
 449       remove_breakpoints ();
 450       fork_load_infrun_state (newfp);
 451       insert_breakpoints ();
 452     }
 453
 454   old_cleanup = make_cleanup (inferior_call_waitpid_cleanup, oldfp);
 455
 456   /* Get the waitpid_fn.  */
 457   if (lookup_minimal_symbol ("waitpid", NULL, NULL).minsym != NULL)
 458     waitpid_fn = find_function_in_inferior ("waitpid", &waitpid_objf);
 459   if (!waitpid_fn
 460       && lookup_minimal_symbol ("_waitpid", NULL, NULL).minsym != NULL)
 461     waitpid_fn = find_function_in_inferior ("_waitpid", &waitpid_objf);
 462   if (!waitpid_fn)
 463     goto out;
 464
 465   /* Get the argv.  */
 466   argv[0] = value_from_longest (builtin_type (gdbarch)->builtin_int, pid);
 467   argv[1] = value_from_pointer (builtin_type (gdbarch)->builtin_data_ptr, 0);
 468   argv[2] = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
 469   argv[3] = 0;
 470
 471   retv = call_function_by_hand (waitpid_fn, 3, argv);
 472   if (value_as_long (retv) < 0)
 473     goto out;
 474
 475   ret = 0;
 476
 477 out:
 478   do_cleanups (old_cleanup);
 479   return ret;
 480 }
 481
 482 /* Fork list <-> user interface.  */
 483
 484 static void
 485 delete_checkpoint_command (char *args, int from_tty)
 486 {
 487   ptid_t ptid, pptid;
 488   struct fork_info *fi;
 489
 490   if (!args || !*args)
 491     error (_("Requires argument (checkpoint id to delete)"));
 492
 493   ptid = fork_id_to_ptid (parse_and_eval_long (args));
 494   if (ptid_equal (ptid, minus_one_ptid))
 495     error (_("No such checkpoint id, %s"), args);
 496
 497   if (ptid_equal (ptid, inferior_ptid))
 498     error (_("\
 499 Please switch to another checkpoint before deleting the current one"));
 500
 501   if (ptrace (PTRACE_KILL, ptid_get_pid (ptid), 0, 0))
 502     error (_("Unable to kill pid %s"), target_pid_to_str (ptid));
 503
 504   fi = find_fork_ptid (ptid);
 505   gdb_assert (fi);
 506   pptid = fi->parent_ptid;
 507
 508   if (from_tty)
 509     printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid));
 510
 511   delete_fork (ptid);
 512
 513   /* If fi->parent_ptid is not a part of lwp but it's a part of checkpoint
 514      list, waitpid the ptid.
 515      If fi->parent_ptid is a part of lwp and it is stoped, waitpid the
 516      ptid.  */
 517   if ((!find_thread_ptid (pptid) && find_fork_ptid (pptid))
 518       || (find_thread_ptid (pptid) && is_stopped (pptid)))
 519     {
 520       if (inferior_call_waitpid (pptid, ptid_get_pid (ptid)))
 521         warning (_("Unable to wait pid %s"), target_pid_to_str (ptid));
 522     }
 523 }
 524
 525 static void
 526 detach_checkpoint_command (char *args, int from_tty)
 527 {
 528   ptid_t ptid;
 529
 530   if (!args || !*args)
 531     error (_("Requires argument (checkpoint id to detach)"));
 532
 533   ptid = fork_id_to_ptid (parse_and_eval_long (args));
 534   if (ptid_equal (ptid, minus_one_ptid))
 535     error (_("No such checkpoint id, %s"), args);
 536
 537   if (ptid_equal (ptid, inferior_ptid))
 538     error (_("\
 539 Please switch to another checkpoint before detaching the current one"));
 540
 541   if (ptrace (PTRACE_DETACH, ptid_get_pid (ptid), 0, 0))
 542     error (_("Unable to detach %s"), target_pid_to_str (ptid));
 543
 544   if (from_tty)
 545     printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid));
 546
 547   delete_fork (ptid);
 548 }
 549
 550 /* Print information about currently known checkpoints.  */
 551
 552 static void
 553 info_checkpoints_command (char *arg, int from_tty)
 554 {
 555   struct gdbarch *gdbarch = get_current_arch ();
 556   struct symtab_and_line sal;
 557   struct fork_info *fp;
 558   ULONGEST pc;
 559   int requested = -1;
 560   struct fork_info *printed = NULL;
 561
 562   if (arg && *arg)
 563     requested = (int) parse_and_eval_long (arg);
 564
 565   for (fp = fork_list; fp; fp = fp->next)
 566     {
 567       if (requested > 0 && fp->num != requested)
 568         continue;
 569
 570       printed = fp;
 571       if (ptid_equal (fp->ptid, inferior_ptid))
 572         {
 573           printf_filtered ("* ");
 574           pc = regcache_read_pc (get_current_regcache ());
 575         }
 576       else
 577         {
 578           printf_filtered ("  ");
 579           pc = regcache_read_pc (fp->savedregs);
 580         }
 581       printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));
 582       if (fp->num == 0)
 583         printf_filtered (_(" (main process)"));
 584       printf_filtered (_(" at "));
 585       fputs_filtered (paddress (gdbarch, pc), gdb_stdout);
 586
 587       sal = find_pc_line (pc, 0);
 588       if (sal.symtab)
 589         printf_filtered (_(", file %s"),
 590                          symtab_to_filename_for_display (sal.symtab));
 591       if (sal.line)
 592         printf_filtered (_(", line %d"), sal.line);
 593       if (!sal.symtab && !sal.line)
 594         {
 595           struct bound_minimal_symbol msym;
 596
 597           msym = lookup_minimal_symbol_by_pc (pc);
 598           if (msym.minsym)
 599             printf_filtered (", <%s>", MSYMBOL_LINKAGE_NAME (msym.minsym));
 600         }
 601
 602       putchar_filtered ('\n');
 603     }
 604   if (printed == NULL)
 605     {
 606       if (requested > 0)
 607         printf_filtered (_("No checkpoint number %d.\n"), requested);
 608       else
 609         printf_filtered (_("No checkpoints.\n"));
 610     }
 611 }
 612
 613 /* The PID of the process we're checkpointing.  */
 614 static int checkpointing_pid = 0;
 615
 616 int
 617 linux_fork_checkpointing_p (int pid)
 618 {
 619   return (checkpointing_pid == pid);
 620 }
 621
 622 /* Callback for iterate over threads.  Used to check whether
 623    the current inferior is multi-threaded.  Returns true as soon
 624    as it sees the second thread of the current inferior.  */
 625
 626 static int
 627 inf_has_multiple_thread_cb (struct thread_info *tp, void *data)
 628 {
 629   int *count_p = (int *) data;
 630
 631   if (current_inferior ()->pid == ptid_get_pid (tp->ptid))
 632     (*count_p)++;
 633
 634   /* Stop the iteration if multiple threads have been detected.  */
 635   return *count_p > 1;
 636 }
 637
 638 /* Return true if the current inferior is multi-threaded.  */
 639
 640 static int
 641 inf_has_multiple_threads (void)
 642 {
 643   int count = 0;
 644
 645   iterate_over_threads (inf_has_multiple_thread_cb, &count);
 646   return (count > 1);
 647 }
 648
 649 static void
 650 checkpoint_command (char *args, int from_tty)
 651 {
 652   struct objfile *fork_objf;
 653   struct gdbarch *gdbarch;
 654   struct target_waitstatus last_target_waitstatus;
 655   ptid_t last_target_ptid;
 656   struct value *fork_fn = NULL, *ret;
 657   struct fork_info *fp;
 658   pid_t retpid;
 659   struct cleanup *old_chain;
 660
 661   if (!target_has_execution)
 662     error (_("The program is not being run."));
 663
 664   /* Ensure that the inferior is not multithreaded.  */
 665   update_thread_list ();
 666   if (inf_has_multiple_threads ())
 667     error (_("checkpoint: can't checkpoint multiple threads."));
 668
 669   /* Make the inferior fork, record its (and gdb's) state.  */
 670
 671   if (lookup_minimal_symbol ("fork", NULL, NULL).minsym != NULL)
 672     fork_fn = find_function_in_inferior ("fork", &fork_objf);
 673   if (!fork_fn)
 674     if (lookup_minimal_symbol ("_fork", NULL, NULL).minsym != NULL)
 675       fork_fn = find_function_in_inferior ("fork", &fork_objf);
 676   if (!fork_fn)
 677     error (_("checkpoint: can't find fork function in inferior."));
 678
 679   gdbarch = get_objfile_arch (fork_objf);
 680   ret = value_from_longest (builtin_type (gdbarch)->builtin_int, 0);
 681
 682   /* Tell linux-nat.c that we're checkpointing this inferior.  */
 683   old_chain = make_cleanup_restore_integer (&checkpointing_pid);
 684   checkpointing_pid = ptid_get_pid (inferior_ptid);
 685
 686   ret = call_function_by_hand (fork_fn, 0, &ret);
 687   do_cleanups (old_chain);
 688   if (!ret)     /* Probably can't happen.  */
 689     error (_("checkpoint: call_function_by_hand returned null."));
 690
 691   retpid = value_as_long (ret);
 692   get_last_target_status (&last_target_ptid, &last_target_waitstatus);
 693
 694   fp = find_fork_pid (retpid);
 695
 696   if (from_tty)
 697     {
 698       int parent_pid;
 699
 700       printf_filtered (_("checkpoint %d: fork returned pid %ld.\n"),
 701                        fp != NULL ? fp->num : -1, (long) retpid);
 702       if (info_verbose)
 703         {
 704           parent_pid = ptid_get_lwp (last_target_ptid);
 705           if (parent_pid == 0)
 706             parent_pid = ptid_get_pid (last_target_ptid);
 707           printf_filtered (_("   gdb says parent = %ld.\n"),
 708                            (long) parent_pid);
 709         }
 710     }
 711
 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 }