gdb/linux-fork.c

   1 /* GNU/Linux native-dependent code for debugging multiple forks.
   2
   3    Copyright (C) 2005, 2006 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 2 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, write to the Free Software
  19    Foundation, Inc., 51 Franklin Street, Fifth Floor,
  20    Boston, MA 02110-1301, USA.  */
  21
  22 #include "defs.h"
  23 #include "inferior.h"
  24 #include "regcache.h"
  25 #include "gdbcmd.h"
  26 #include "infcall.h"
  27 #include "gdb_assert.h"
  28 #include "gdb_string.h"
  29 #include "linux-fork.h"
  30 #include "linux-nat.h"
  31
  32 #include <sys/ptrace.h>
  33 #include <sys/wait.h>
  34 #include <sys/param.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 int detach_fork = 1;            /* Default behavior is to detach
  45                                    newly forked processes (legacy).  */
  46
  47 /* Fork list data structure:  */
  48 struct fork_info
  49 {
  50   struct fork_info *next;
  51   ptid_t 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   ULONGEST pc;                  /* PC for info fork.  */
  57   off_t *filepos;               /* Set of open file descriptors' offsets.  */
  58   int maxfd;
  59 };
  60
  61 /* Fork list methods:  */
  62
  63 extern int
  64 forks_exist_p (void)
  65 {
  66   return (fork_list != NULL);
  67 }
  68
  69 /* Add a fork to internal fork list.
  70    Called from linux child_follow_fork.  */
  71
  72 extern struct fork_info *
  73 add_fork (pid_t pid)
  74 {
  75   struct fork_info *fp;
  76
  77   if (fork_list == NULL && pid != PIDGET (inferior_ptid))
  78     {
  79       /* Special case -- if this is the first fork in the list
  80          (the list is hitherto empty), and if this new fork is
  81          NOT the current inferior_ptid, then add inferior_ptid
  82          first, as a special zeroeth fork id.  */
  83       highest_fork_num = -1;
  84       add_fork (PIDGET (inferior_ptid));        /* safe recursion */
  85     }
  86
  87   fp = XZALLOC (struct fork_info);
  88   fp->ptid = ptid_build (pid, pid, 0);
  89   fp->num = ++highest_fork_num;
  90   fp->next = fork_list;
  91   fork_list = fp;
  92   return fp;
  93 }
  94
  95 static void
  96 free_fork (struct fork_info *fp)
  97 {
  98   /* Notes on step-resume breakpoints: since this is a concern for
  99      threads, let's convince ourselves that it's not a concern for
 100      forks.  There are two ways for a fork_info to be created.  First,
 101      by the checkpoint command, in which case we're at a gdb prompt
 102      and there can't be any step-resume breakpoint.  Second, by a fork
 103      in the user program, in which case we *may* have stepped into the
 104      fork call, but regardless of whether we follow the parent or the
 105      child, we will return to the same place and the step-resume
 106      breakpoint, if any, will take care of itself as usual.  And
 107      unlike threads, we do not save a private copy of the step-resume
 108      breakpoint -- so we're OK.  */
 109
 110   if (fp)
 111     {
 112       if (fp->savedregs)
 113         regcache_xfree (fp->savedregs);
 114       if (fp->filepos)
 115         xfree (fp->filepos);
 116       xfree (fp);
 117     }
 118 }
 119
 120 static void
 121 delete_fork (ptid_t ptid)
 122 {
 123   struct fork_info *fp, *fpprev;
 124
 125   fpprev = NULL;
 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   inferior_ptid = fp->ptid;
 244
 245   linux_nat_switch_fork (inferior_ptid);
 246
 247   if (fp->savedregs && fp->clobber_regs)
 248     regcache_cpy (current_regcache, fp->savedregs);
 249
 250   registers_changed ();
 251   reinit_frame_cache ();
 252
 253   /* We must select a new frame before making any inferior calls to
 254      avoid warnings.  */
 255   select_frame (get_current_frame ());
 256
 257   stop_pc = read_pc ();
 258   nullify_last_target_wait_ptid ();
 259
 260   /* Now restore the file positions of open file descriptors.  */
 261   if (fp->filepos)
 262     {
 263       for (i = 0; i <= fp->maxfd; i++)
 264         if (fp->filepos[i] != (off_t) -1)
 265           call_lseek (i, fp->filepos[i], SEEK_SET);
 266       /* NOTE: I can get away with using SEEK_SET and SEEK_CUR because
 267          this is native-only.  If it ever has to be cross, we'll have
 268          to rethink this.  */
 269     }
 270 }
 271
 272 /* Save infrun state for the fork PTID.
 273    Exported for use by linux child_follow_fork.  */
 274
 275 extern void
 276 fork_save_infrun_state (struct fork_info *fp, int clobber_regs)
 277 {
 278   char path[MAXPATHLEN];
 279   struct dirent *de;
 280   DIR *d;
 281
 282   if (fp->savedregs)
 283     regcache_xfree (fp->savedregs);
 284
 285   fp->savedregs = regcache_dup (current_regcache);
 286   fp->clobber_regs = clobber_regs;
 287   fp->pc = read_pc ();
 288
 289   if (clobber_regs)
 290     {
 291       /* Now save the 'state' (file position) of all open file descriptors.
 292          Unfortunately fork does not take care of that for us...  */
 293       snprintf (path, MAXPATHLEN, "/proc/%ld/fd", (long) PIDGET (fp->ptid));
 294       if ((d = opendir (path)) != NULL)
 295         {
 296           long tmp;
 297
 298           fp->maxfd = 0;
 299           while ((de = readdir (d)) != NULL)
 300             {
 301               /* Count open file descriptors (actually find highest
 302                  numbered).  */
 303               tmp = strtol (&de->d_name[0], NULL, 10);
 304               if (fp->maxfd < tmp)
 305                 fp->maxfd = tmp;
 306             }
 307           /* Allocate array of file positions.  */
 308           fp->filepos = xrealloc (fp->filepos,
 309                                   (fp->maxfd + 1) * sizeof (*fp->filepos));
 310
 311           /* Initialize to -1 (invalid).  */
 312           for (tmp = 0; tmp <= fp->maxfd; tmp++)
 313             fp->filepos[tmp] = -1;
 314
 315           /* Now find actual file positions.  */
 316           rewinddir (d);
 317           while ((de = readdir (d)) != NULL)
 318             if (isdigit (de->d_name[0]))
 319               {
 320                 tmp = strtol (&de->d_name[0], NULL, 10);
 321                 fp->filepos[tmp] = call_lseek (tmp, 0, SEEK_CUR);
 322               }
 323           closedir (d);
 324         }
 325     }
 326 }
 327
 328 /* Kill 'em all, let God sort 'em out...  */
 329
 330 extern void
 331 linux_fork_killall (void)
 332 {
 333   /* Walk list and kill every pid.  No need to treat the
 334      current inferior_ptid as special (we do not return a
 335      status for it) -- however any process may be a child
 336      or a parent, so may get a SIGCHLD from a previously
 337      killed child.  Wait them all out.  */
 338   struct fork_info *fp;
 339   pid_t pid, ret;
 340   int status;
 341
 342   for (fp = fork_list; fp; fp = fp->next)
 343     {
 344       pid = PIDGET (fp->ptid);
 345       do {
 346         ptrace (PT_KILL, pid, 0, 0);
 347         ret = waitpid (pid, &status, 0);
 348         /* We might get a SIGCHLD instead of an exit status.  This is
 349          aggravated by the first kill above - a child has just
 350          died.  MVS comment cut-and-pasted from linux-nat.  */
 351       } while (ret == pid && WIFSTOPPED (status));
 352     }
 353   init_fork_list ();    /* Clear list, prepare to start fresh.  */
 354 }
 355
 356 /* The current inferior_ptid has exited, but there are other viable
 357    forks to debug.  Delete the exiting one and context-switch to the
 358    first available.  */
 359
 360 extern void
 361 linux_fork_mourn_inferior (void)
 362 {
 363   /* Wait just one more time to collect the inferior's exit status.
 364      Do not check whether this succeeds though, since we may be
 365      dealing with a process that we attached to.  Such a process will
 366      only report its exit status to its original parent.  */
 367   int status;
 368
 369   waitpid (ptid_get_pid (inferior_ptid), &status, 0);
 370
 371   /* OK, presumably inferior_ptid is the one who has exited.
 372      We need to delete that one from the fork_list, and switch
 373      to the next available fork.  */
 374   delete_fork (inferior_ptid);
 375
 376   /* There should still be a fork - if there's only one left,
 377      delete_fork won't remove it, because we haven't updated
 378      inferior_ptid yet.  */
 379   gdb_assert (fork_list);
 380
 381   fork_load_infrun_state (fork_list);
 382   printf_filtered (_("[Switching to %s]\n"),
 383                    target_pid_to_str (inferior_ptid));
 384
 385   /* If there's only one fork, switch back to non-fork mode.  */
 386   if (fork_list->next == NULL)
 387     delete_fork (inferior_ptid);
 388 }
 389
 390 /* Fork list <-> user interface.  */
 391
 392 static void
 393 delete_fork_command (char *args, int from_tty)
 394 {
 395   ptid_t ptid;
 396
 397   if (!args || !*args)
 398     error (_("Requires argument (fork/checkpoint id to delete)"));
 399
 400   ptid = fork_id_to_ptid (parse_and_eval_long (args));
 401   if (ptid_equal (ptid, minus_one_ptid))
 402     error (_("No such fork/checkpoint id, %s"), args);
 403
 404   if (ptid_equal (ptid, inferior_ptid))
 405     error (_("Please switch to another fork/checkpoint before deleting the current one"));
 406
 407   if (ptrace (PTRACE_KILL, PIDGET (ptid), 0, 0))
 408     error (_("Unable to kill pid %s"), target_tid_to_str (ptid));
 409
 410   if (from_tty)
 411     printf_filtered (_("Killed %s\n"), target_pid_to_str (ptid));
 412
 413   delete_fork (ptid);
 414 }
 415
 416 static void
 417 detach_fork_command (char *args, int from_tty)
 418 {
 419   ptid_t ptid;
 420
 421   if (!args || !*args)
 422     error (_("Requires argument (fork id to detach)"));
 423
 424   ptid = fork_id_to_ptid (parse_and_eval_long (args));
 425   if (ptid_equal (ptid, minus_one_ptid))
 426     error (_("No such fork id, %s"), args);
 427
 428   if (ptid_equal (ptid, inferior_ptid))
 429     error (_("Please switch to another fork before detaching the current one"));
 430
 431   if (ptrace (PTRACE_DETACH, PIDGET (ptid), 0, 0))
 432     error (_("Unable to detach %s"), target_pid_to_str (ptid));
 433
 434   if (from_tty)
 435     printf_filtered (_("Detached %s\n"), target_pid_to_str (ptid));
 436
 437   delete_fork (ptid);
 438 }
 439
 440 /* Print information about currently known forks.  */
 441
 442 static void
 443 info_forks_command (char *arg, int from_tty)
 444 {
 445   struct frame_info *cur_frame;
 446   struct symtab_and_line sal;
 447   struct symtab *cur_symtab;
 448   struct fork_info *fp;
 449   int cur_line;
 450   ULONGEST pc;
 451
 452   for (fp = fork_list; fp; fp = fp->next)
 453     {
 454       if (ptid_equal (fp->ptid, inferior_ptid))
 455         {
 456           printf_filtered ("* ");
 457           pc = read_pc ();
 458         }
 459       else
 460         {
 461           printf_filtered ("  ");
 462           pc = fp->pc;
 463         }
 464       printf_filtered ("%d %s", fp->num, target_pid_to_str (fp->ptid));
 465       if (fp->num == 0)
 466         printf_filtered (_(" (main process)"));
 467       printf_filtered (_(" at "));
 468       deprecated_print_address_numeric (pc, 1, gdb_stdout);
 469
 470       sal = find_pc_line (pc, 0);
 471       if (sal.symtab)
 472         {
 473           char *tmp = strrchr (sal.symtab->filename, '/');
 474
 475           if (tmp)
 476             printf_filtered (_(", file %s"), tmp + 1);
 477           else
 478             printf_filtered (_(", file %s"), sal.symtab->filename);
 479         }
 480       if (sal.line)
 481         printf_filtered (_(", line %d"), sal.line);
 482       if (!sal.symtab && !sal.line)
 483         {
 484           struct minimal_symbol *msym;
 485
 486           msym = lookup_minimal_symbol_by_pc (pc);
 487           if (msym)
 488             printf_filtered (", <%s>", SYMBOL_LINKAGE_NAME (msym));
 489         }
 490
 491       putchar_filtered ('\n');
 492     }
 493 }
 494
 495 /* Save/restore mode variable 'detach_fork':
 496    We need to temporarily take over this mode variable, while
 497    preserving the user-specified state, and make sure that it
 498    gets restored in case of error.
 499
 500    The int pointer that we use comes from the caller, so we can
 501    be called more than once (even though currently we don't need to).  */
 502
 503 static void
 504 restore_detach_fork (void *arg)
 505 {
 506   detach_fork = *(int *) arg;
 507 }
 508
 509 static struct cleanup *
 510 save_detach_fork (int *saved_val)
 511 {
 512   *saved_val = detach_fork;
 513   return make_cleanup (restore_detach_fork, (void *) saved_val);
 514 }
 515
 516 static void
 517 checkpoint_command (char *args, int from_tty)
 518 {
 519   struct target_waitstatus last_target_waitstatus;
 520   ptid_t last_target_ptid;
 521   struct value *fork_fn = NULL, *ret;
 522   struct fork_info *fp;
 523   pid_t retpid;
 524   struct cleanup *old_chain;
 525   long i;
 526   /* Make this temp var static, 'cause it's used in the error context.  */
 527   static int temp_detach_fork;
 528
 529   /* Make the inferior fork, record its (and gdb's) state.  */
 530
 531   if (lookup_minimal_symbol ("fork", NULL, NULL) != NULL)
 532     fork_fn = find_function_in_inferior ("fork");
 533   if (!fork_fn)
 534     if (lookup_minimal_symbol ("_fork", NULL, NULL) != NULL)
 535       fork_fn = find_function_in_inferior ("fork");
 536   if (!fork_fn)
 537     error (_("checkpoint: can't find fork function in inferior."));
 538
 539   ret = value_from_longest (builtin_type_int, 0);
 540   old_chain = save_detach_fork (&temp_detach_fork);
 541   detach_fork = 0;
 542   ret = call_function_by_hand (fork_fn, 0, &ret);
 543   do_cleanups (old_chain);
 544   if (!ret)     /* Probably can't happen.  */
 545     error (_("checkpoint: call_function_by_hand returned null."));
 546
 547   retpid = value_as_long (ret);
 548   get_last_target_status (&last_target_ptid, &last_target_waitstatus);
 549   if (from_tty)
 550     {
 551       int parent_pid;
 552
 553       printf_filtered (_("checkpoint: fork returned pid %ld.\n"),
 554                        (long) retpid);
 555       if (info_verbose)
 556         {
 557           parent_pid = ptid_get_lwp (last_target_ptid);
 558           if (parent_pid == 0)
 559             parent_pid = ptid_get_pid (last_target_ptid);
 560           printf_filtered (_("   gdb says parent = %ld.\n"),
 561                            (long) parent_pid);
 562         }
 563     }
 564
 565   fp = find_fork_pid (retpid);
 566   if (!fp)
 567     error (_("Failed to find new fork"));
 568   fork_save_infrun_state (fp, 1);
 569 }
 570
 571 static void
 572 linux_fork_context (struct fork_info *newfp, int from_tty)
 573 {
 574   /* Now we attempt to switch processes.  */
 575   struct fork_info *oldfp = find_fork_ptid (inferior_ptid);
 576   ptid_t ptid;
 577   int id, i;
 578
 579   if (!newfp)
 580     error (_("No such fork/process"));
 581
 582   if (!oldfp)
 583     oldfp = add_fork (ptid_get_pid (inferior_ptid));
 584
 585   fork_save_infrun_state (oldfp, 1);
 586   fork_load_infrun_state (newfp);
 587
 588   printf_filtered (_("Switching to %s\n"),
 589                    target_pid_to_str (inferior_ptid));
 590
 591   print_stack_frame (get_selected_frame (NULL), 1, SRC_AND_LOC);
 592 }
 593
 594 /* Switch inferior process (fork) context, by process id.  */
 595 static void
 596 process_command (char *args, int from_tty)
 597 {
 598   struct fork_info *fp;
 599
 600   if (!args || !*args)
 601     error (_("Requires argument (process id to switch to)"));
 602
 603   if ((fp = find_fork_pid (parse_and_eval_long (args))) == NULL)
 604     error (_("Not found: process id %s"), args);
 605
 606   linux_fork_context (fp, from_tty);
 607 }
 608
 609 /* Switch inferior process (fork) context, by fork id.  */
 610 static void
 611 fork_command (char *args, int from_tty)
 612 {
 613   struct fork_info *fp;
 614
 615   if (!args || !*args)
 616     error (_("Requires argument (fork id to switch to)"));
 617
 618   if ((fp = find_fork_id (parse_and_eval_long (args))) == NULL)
 619     error (_("Not found: fork id %s"), args);
 620
 621   linux_fork_context (fp, from_tty);
 622 }
 623
 624 /* Switch inferior process (fork) context, by checkpoint id.  */
 625 static void
 626 restart_command (char *args, int from_tty)
 627 {
 628   struct fork_info *fp;
 629
 630   if (!args || !*args)
 631     error (_("Requires argument (checkpoint id to restart)"));
 632
 633   if ((fp = find_fork_id (parse_and_eval_long (args))) == NULL)
 634     error (_("Not found: checkpoint id %s"), args);
 635
 636   linux_fork_context (fp, from_tty);
 637 }
 638
 639 void
 640 _initialize_linux_fork (void)
 641 {
 642   init_fork_list ();
 643
 644   /* Set/show detach-on-fork: user-settable mode.  */
 645
 646   add_setshow_boolean_cmd ("detach-on-fork", class_obscure, &detach_fork, _("\
 647 Set whether gdb will detach the child of a fork."), _("\
 648 Show whether gdb will detach the child of a fork."), _("\
 649 Tells gdb whether to detach the child of a fork."),
 650                            NULL, NULL, &setlist, &showlist);
 651
 652   /* Set/show restart-auto-finish: user-settable count.  Causes the
 653      first "restart" of a fork to do some number of "finish" commands
 654      before returning to user.
 655
 656      Useful because otherwise the virgin fork process will be stopped
 657      somewhere in the un-interesting fork system call.  */
 658
 659   /* Checkpoint command: create a fork of the inferior process
 660      and set it aside for later debugging.  */
 661
 662   add_com ("checkpoint", class_obscure, checkpoint_command, _("\
 663 Fork a duplicate process (experimental)."));
 664
 665   /* Restart command: restore the context of a specified fork
 666      process.  May be used for "program forks" as well as for
 667      "debugger forks" (checkpoints).  */
 668
 669   add_com ("restart", class_obscure, restart_command, _("\
 670 restart <n>: restore program context from a checkpoint.\n\
 671 Argument 'n' is checkpoint ID, as displayed by 'info checkpoints'."));
 672
 673   /* Delete-checkpoint command: kill the process and remove it from
 674      fork list.  */
 675
 676   add_com ("delete-checkpoint", class_obscure, delete_fork_command, _("\
 677 Delete a fork/checkpoint (experimental)."));
 678
 679   /* Detach-checkpoint command: release the process to run independantly,
 680      and remove it from the fork list.  */
 681
 682   add_com ("detach-checkpoint", class_obscure, detach_fork_command, _("\
 683 Detach from a fork/checkpoint (experimental)."));
 684
 685   /* Info checkpoints command: list all forks/checkpoints
 686      currently under gdb's control.  */
 687
 688   add_info ("checkpoints", info_forks_command,
 689             _("IDs of currently known forks/checkpoints."));
 690
 691   /* Command aliases (let "fork" and "checkpoint" be used
 692      interchangeably).  */
 693
 694   add_com_alias ("delete-fork", "delete-checkpoint", class_obscure, 1);
 695   add_com_alias ("detach-fork", "detach-checkpoint", class_obscure, 1);
 696   add_info_alias ("forks", "checkpoints", 0);
 697
 698   /* "fork <n>" (by analogy to "thread <n>").  */
 699   add_com ("fork", class_obscure, fork_command, _("\
 700 fork <n>: Switch between forked processes.\n\
 701 Argument 'n' is fork ID, as displayed by 'info forks'."));
 702
 703   /* "process <proc id>" as opposed to "fork <fork id>".  */
 704   add_com ("process", class_obscure, process_command, _("\
 705 process <pid>: Switch between forked processes.\n\
 706 Argument 'pid' is process ID, as displayed by 'info forks' or 'shell ps'."));
 707 }