gdb/inflow.c

   1 /* Low level interface to ptrace, for GDB when running under Unix.
   2    Copyright (C) 1986-2014 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include "defs.h"
  20 #include "frame.h"
  21 #include "inferior.h"
  22 #include "command.h"
  23 #include "serial.h"
  24 #include "terminal.h"
  25 #include "target.h"
  26 #include "gdbthread.h"
  27 #include "observer.h"
  28 #include <signal.h>
  29 #include <fcntl.h>
  30 #include "gdb_select.h"
  31
  32 #include "inflow.h"
  33 #include "gdbcmd.h"
  34
  35 #ifdef HAVE_SYS_IOCTL_H
  36 #include <sys/ioctl.h>
  37 #endif
  38
  39 #ifndef O_NOCTTY
  40 #define O_NOCTTY 0
  41 #endif
  42
  43 extern void _initialize_inflow (void);
  44
  45 static void pass_signal (int);
  46
  47 static void child_terminal_ours_1 (int);
  48 \f
  49 /* Record terminal status separately for debugger and inferior.  */
  50
  51 static struct serial *stdin_serial;
  52
  53 /* Terminal related info we need to keep track of.  Each inferior
  54    holds an instance of this structure --- we save it whenever the
  55    corresponding inferior stops, and restore it to the foreground
  56    inferior when it resumes.  */
  57 struct terminal_info
  58 {
  59   /* The name of the tty (from the `tty' command) that we gave to the
  60      inferior when it was started.  */
  61   char *run_terminal;
  62
  63   /* TTY state.  We save it whenever the inferior stops, and restore
  64      it when it resumes.  */
  65   serial_ttystate ttystate;
  66
  67 #ifdef PROCESS_GROUP_TYPE
  68   /* Process group.  Saved and restored just like ttystate.  */
  69   PROCESS_GROUP_TYPE process_group;
  70 #endif
  71
  72   /* fcntl flags.  Saved and restored just like ttystate.  */
  73   int tflags;
  74 };
  75
  76 /* Our own tty state, which we restore every time we need to deal with
  77    the terminal.  This is only set once, when GDB first starts.  The
  78    settings of flags which readline saves and restores and
  79    unimportant.  */
  80 static struct terminal_info our_terminal_info;
  81
  82 static struct terminal_info *get_inflow_inferior_data (struct inferior *);
  83
  84 #ifdef PROCESS_GROUP_TYPE
  85
  86 /* Return the process group of the current inferior.  */
  87
  88 PROCESS_GROUP_TYPE
  89 inferior_process_group (void)
  90 {
  91   return get_inflow_inferior_data (current_inferior ())->process_group;
  92 }
  93 #endif
  94
  95 /* While the inferior is running, we want SIGINT and SIGQUIT to go to the
  96    inferior only.  If we have job control, that takes care of it.  If not,
  97    we save our handlers in these two variables and set SIGINT and SIGQUIT
  98    to SIG_IGN.  */
  99
 100 static void (*sigint_ours) ();
 101 static void (*sigquit_ours) ();
 102
 103 /* The name of the tty (from the `tty' command) that we're giving to
 104    the inferior when starting it up.  This is only (and should only
 105    be) used as a transient global by new_tty_prefork,
 106    create_tty_session, new_tty and new_tty_postfork, all called from
 107    fork_inferior, while forking a new child.  */
 108 static const char *inferior_thisrun_terminal;
 109
 110 /* Nonzero if our terminal settings are in effect.  Zero if the
 111    inferior's settings are in effect.  Ignored if !gdb_has_a_terminal
 112    ().  */
 113
 114 int terminal_is_ours;
 115
 116 #ifdef PROCESS_GROUP_TYPE
 117 static PROCESS_GROUP_TYPE
 118 gdb_getpgrp (void)
 119 {
 120   int process_group = -1;
 121
 122 #ifdef HAVE_TERMIOS
 123   process_group = tcgetpgrp (0);
 124 #endif
 125 #ifdef HAVE_TERMIO
 126   process_group = getpgrp ();
 127 #endif
 128 #ifdef HAVE_SGTTY
 129   ioctl (0, TIOCGPGRP, &process_group);
 130 #endif
 131   return process_group;
 132 }
 133 #endif
 134
 135 enum
 136   {
 137     yes, no, have_not_checked
 138   }
 139 gdb_has_a_terminal_flag = have_not_checked;
 140
 141 /* The value of the "interactive-mode" setting.  */
 142 static enum auto_boolean interactive_mode = AUTO_BOOLEAN_AUTO;
 143
 144 /* Implement the "show interactive-mode" option.  */
 145
 146 static void
 147 show_interactive_mode (struct ui_file *file, int from_tty,
 148                        struct cmd_list_element *c,
 149                        const char *value)
 150 {
 151   if (interactive_mode == AUTO_BOOLEAN_AUTO)
 152     fprintf_filtered (file, "Debugger's interactive mode "
 153                             "is %s (currently %s).\n",
 154                       value, gdb_has_a_terminal () ? "on" : "off");
 155   else
 156     fprintf_filtered (file, "Debugger's interactive mode is %s.\n", value);
 157 }
 158
 159 /* Does GDB have a terminal (on stdin)?  */
 160 int
 161 gdb_has_a_terminal (void)
 162 {
 163   if (interactive_mode != AUTO_BOOLEAN_AUTO)
 164     return interactive_mode == AUTO_BOOLEAN_TRUE;
 165
 166   switch (gdb_has_a_terminal_flag)
 167     {
 168     case yes:
 169       return 1;
 170     case no:
 171       return 0;
 172     case have_not_checked:
 173       /* Get all the current tty settings (including whether we have a
 174          tty at all!).  Can't do this in _initialize_inflow because
 175          serial_fdopen() won't work until the serial_ops_list is
 176          initialized.  */
 177
 178 #ifdef F_GETFL
 179       our_terminal_info.tflags = fcntl (0, F_GETFL, 0);
 180 #endif
 181
 182       gdb_has_a_terminal_flag = no;
 183       if (stdin_serial != NULL)
 184         {
 185           our_terminal_info.ttystate = serial_get_tty_state (stdin_serial);
 186
 187           if (our_terminal_info.ttystate != NULL)
 188             {
 189               gdb_has_a_terminal_flag = yes;
 190 #ifdef PROCESS_GROUP_TYPE
 191               our_terminal_info.process_group = gdb_getpgrp ();
 192 #endif
 193             }
 194         }
 195
 196       return gdb_has_a_terminal_flag == yes;
 197     default:
 198       /* "Can't happen".  */
 199       return 0;
 200     }
 201 }
 202
 203 /* Macro for printing errors from ioctl operations */
 204
 205 #define OOPSY(what)     \
 206   if (result == -1)     \
 207     fprintf_unfiltered(gdb_stderr, "[%s failed in terminal_inferior: %s]\n", \
 208             what, safe_strerror (errno))
 209
 210 /* Initialize the terminal settings we record for the inferior,
 211    before we actually run the inferior.  */
 212
 213 void
 214 child_terminal_init_with_pgrp (int pgrp)
 215 {
 216   struct inferior *inf = current_inferior ();
 217   struct terminal_info *tinfo = get_inflow_inferior_data (inf);
 218
 219 #ifdef PROCESS_GROUP_TYPE
 220   /* Store the process group even without a terminal as it is used not
 221      only to reset the tty foreground process group, but also to
 222      interrupt the inferior.  */
 223   tinfo->process_group = pgrp;
 224 #endif
 225
 226   if (gdb_has_a_terminal ())
 227     {
 228       xfree (tinfo->ttystate);
 229       tinfo->ttystate = serial_copy_tty_state (stdin_serial,
 230                                                our_terminal_info.ttystate);
 231
 232       /* Make sure that next time we call terminal_inferior (which will be
 233          before the program runs, as it needs to be), we install the new
 234          process group.  */
 235       terminal_is_ours = 1;
 236     }
 237 }
 238
 239 /* Save the terminal settings again.  This is necessary for the TUI
 240    when it switches to TUI or non-TUI mode;  curses changes the terminal
 241    and gdb must be able to restore it correctly.  */
 242
 243 void
 244 gdb_save_tty_state (void)
 245 {
 246   if (gdb_has_a_terminal ())
 247     {
 248       xfree (our_terminal_info.ttystate);
 249       our_terminal_info.ttystate = serial_get_tty_state (stdin_serial);
 250     }
 251 }
 252
 253 void
 254 child_terminal_init (struct target_ops *self)
 255 {
 256 #ifdef PROCESS_GROUP_TYPE
 257   /* This is for Lynx, and should be cleaned up by having Lynx be a
 258      separate debugging target with a version of target_terminal_init
 259      which passes in the process group to a generic routine which does
 260      all the work (and the non-threaded child_terminal_init can just
 261      pass in inferior_ptid to the same routine).  */
 262   /* We assume INFERIOR_PID is also the child's process group.  */
 263   child_terminal_init_with_pgrp (ptid_get_pid (inferior_ptid));
 264 #endif /* PROCESS_GROUP_TYPE */
 265 }
 266
 267 /* Put the inferior's terminal settings into effect.
 268    This is preparation for starting or resuming the inferior.
 269
 270    N.B. Targets that want to use this with async support must build that
 271    support on top of this (e.g., the caller still needs to remove stdin
 272    from the event loop).  E.g., see linux_nat_terminal_inferior.  */
 273
 274 void
 275 child_terminal_inferior (struct target_ops *self)
 276 {
 277   struct inferior *inf;
 278   struct terminal_info *tinfo;
 279
 280   if (!terminal_is_ours)
 281     return;
 282
 283   inf = current_inferior ();
 284   tinfo = get_inflow_inferior_data (inf);
 285
 286   if (gdb_has_a_terminal ()
 287       && tinfo->ttystate != NULL
 288       && tinfo->run_terminal == NULL)
 289     {
 290       int result;
 291
 292 #ifdef F_GETFL
 293       /* Is there a reason this is being done twice?  It happens both
 294          places we use F_SETFL, so I'm inclined to think perhaps there
 295          is some reason, however perverse.  Perhaps not though...  */
 296       result = fcntl (0, F_SETFL, tinfo->tflags);
 297       result = fcntl (0, F_SETFL, tinfo->tflags);
 298       OOPSY ("fcntl F_SETFL");
 299 #endif
 300
 301       /* Because we were careful to not change in or out of raw mode in
 302          terminal_ours, we will not change in our out of raw mode with
 303          this call, so we don't flush any input.  */
 304       result = serial_set_tty_state (stdin_serial,
 305                                      tinfo->ttystate);
 306       OOPSY ("setting tty state");
 307
 308       if (!job_control)
 309         {
 310           sigint_ours = (void (*)()) signal (SIGINT, SIG_IGN);
 311 #ifdef SIGQUIT
 312           sigquit_ours = (void (*)()) signal (SIGQUIT, SIG_IGN);
 313 #endif
 314         }
 315
 316       /* If attach_flag is set, we don't know whether we are sharing a
 317          terminal with the inferior or not.  (attaching a process
 318          without a terminal is one case where we do not; attaching a
 319          process which we ran from the same shell as GDB via `&' is
 320          one case where we do, I think (but perhaps this is not
 321          `sharing' in the sense that we need to save and restore tty
 322          state)).  I don't know if there is any way to tell whether we
 323          are sharing a terminal.  So what we do is to go through all
 324          the saving and restoring of the tty state, but ignore errors
 325          setting the process group, which will happen if we are not
 326          sharing a terminal).  */
 327
 328       if (job_control)
 329         {
 330 #ifdef HAVE_TERMIOS
 331           result = tcsetpgrp (0, tinfo->process_group);
 332           if (!inf->attach_flag)
 333             OOPSY ("tcsetpgrp");
 334 #endif
 335
 336 #ifdef HAVE_SGTTY
 337           result = ioctl (0, TIOCSPGRP, &tinfo->process_group);
 338           if (!inf->attach_flag)
 339             OOPSY ("TIOCSPGRP");
 340 #endif
 341         }
 342
 343     }
 344   terminal_is_ours = 0;
 345 }
 346
 347 /* Put some of our terminal settings into effect,
 348    enough to get proper results from our output,
 349    but do not change into or out of RAW mode
 350    so that no input is discarded.
 351
 352    After doing this, either terminal_ours or terminal_inferior
 353    should be called to get back to a normal state of affairs.
 354
 355    N.B. The implementation is (currently) no different than
 356    child_terminal_ours.  See child_terminal_ours_1.  */
 357
 358 void
 359 child_terminal_ours_for_output (struct target_ops *self)
 360 {
 361   child_terminal_ours_1 (1);
 362 }
 363
 364 /* Put our terminal settings into effect.
 365    First record the inferior's terminal settings
 366    so they can be restored properly later.
 367
 368    N.B. Targets that want to use this with async support must build that
 369    support on top of this (e.g., the caller still needs to add stdin to the
 370    event loop).  E.g., see linux_nat_terminal_ours.  */
 371
 372 void
 373 child_terminal_ours (struct target_ops *self)
 374 {
 375   child_terminal_ours_1 (0);
 376 }
 377
 378 /* output_only is not used, and should not be used unless we introduce
 379    separate terminal_is_ours and terminal_is_ours_for_output
 380    flags.  */
 381
 382 static void
 383 child_terminal_ours_1 (int output_only)
 384 {
 385   struct inferior *inf;
 386   struct terminal_info *tinfo;
 387
 388   if (terminal_is_ours)
 389     return;
 390
 391   terminal_is_ours = 1;
 392
 393   /* Checking inferior->run_terminal is necessary so that
 394      if GDB is running in the background, it won't block trying
 395      to do the ioctl()'s below.  Checking gdb_has_a_terminal
 396      avoids attempting all the ioctl's when running in batch.  */
 397
 398   inf = current_inferior ();
 399   tinfo = get_inflow_inferior_data (inf);
 400
 401   if (tinfo->run_terminal != NULL || gdb_has_a_terminal () == 0)
 402     return;
 403
 404     {
 405 #ifdef SIGTTOU
 406       /* Ignore this signal since it will happen when we try to set the
 407          pgrp.  */
 408       void (*osigttou) () = NULL;
 409 #endif
 410       int result;
 411
 412 #ifdef SIGTTOU
 413       if (job_control)
 414         osigttou = (void (*)()) signal (SIGTTOU, SIG_IGN);
 415 #endif
 416
 417       xfree (tinfo->ttystate);
 418       tinfo->ttystate = serial_get_tty_state (stdin_serial);
 419
 420 #ifdef PROCESS_GROUP_TYPE
 421       if (!inf->attach_flag)
 422         /* If setpgrp failed in terminal_inferior, this would give us
 423            our process group instead of the inferior's.  See
 424            terminal_inferior for details.  */
 425         tinfo->process_group = gdb_getpgrp ();
 426 #endif
 427
 428       /* Here we used to set ICANON in our ttystate, but I believe this
 429          was an artifact from before when we used readline.  Readline sets
 430          the tty state when it needs to.
 431          FIXME-maybe: However, query() expects non-raw mode and doesn't
 432          use readline.  Maybe query should use readline (on the other hand,
 433          this only matters for HAVE_SGTTY, not termio or termios, I think).  */
 434
 435       /* Set tty state to our_ttystate.  We don't change in our out of raw
 436          mode, to avoid flushing input.  We need to do the same thing
 437          regardless of output_only, because we don't have separate
 438          terminal_is_ours and terminal_is_ours_for_output flags.  It's OK,
 439          though, since readline will deal with raw mode when/if it needs
 440          to.  */
 441
 442       serial_noflush_set_tty_state (stdin_serial, our_terminal_info.ttystate,
 443                                     tinfo->ttystate);
 444
 445       if (job_control)
 446         {
 447 #ifdef HAVE_TERMIOS
 448           result = tcsetpgrp (0, our_terminal_info.process_group);
 449 #if 0
 450           /* This fails on Ultrix with EINVAL if you run the testsuite
 451              in the background with nohup, and then log out.  GDB never
 452              used to check for an error here, so perhaps there are other
 453              such situations as well.  */
 454           if (result == -1)
 455             fprintf_unfiltered (gdb_stderr,
 456                                 "[tcsetpgrp failed in child_terminal_ours: %s]\n",
 457                                 safe_strerror (errno));
 458 #endif
 459 #endif /* termios */
 460
 461 #ifdef HAVE_SGTTY
 462           result = ioctl (0, TIOCSPGRP, &our_terminal_info.process_group);
 463 #endif
 464         }
 465
 466 #ifdef SIGTTOU
 467       if (job_control)
 468         signal (SIGTTOU, osigttou);
 469 #endif
 470
 471       if (!job_control)
 472         {
 473           signal (SIGINT, sigint_ours);
 474 #ifdef SIGQUIT
 475           signal (SIGQUIT, sigquit_ours);
 476 #endif
 477         }
 478
 479 #ifdef F_GETFL
 480       tinfo->tflags = fcntl (0, F_GETFL, 0);
 481
 482       /* Is there a reason this is being done twice?  It happens both
 483          places we use F_SETFL, so I'm inclined to think perhaps there
 484          is some reason, however perverse.  Perhaps not though...  */
 485       result = fcntl (0, F_SETFL, our_terminal_info.tflags);
 486       result = fcntl (0, F_SETFL, our_terminal_info.tflags);
 487 #endif
 488     }
 489 }
 490
 491 /* Per-inferior data key.  */
 492 static const struct inferior_data *inflow_inferior_data;
 493
 494 static void
 495 inflow_inferior_data_cleanup (struct inferior *inf, void *arg)
 496 {
 497   struct terminal_info *info = arg;
 498
 499   xfree (info->run_terminal);
 500   xfree (info->ttystate);
 501   xfree (info);
 502 }
 503
 504 /* Get the current svr4 data.  If none is found yet, add it now.  This
 505    function always returns a valid object.  */
 506
 507 static struct terminal_info *
 508 get_inflow_inferior_data (struct inferior *inf)
 509 {
 510   struct terminal_info *info;
 511
 512   info = inferior_data (inf, inflow_inferior_data);
 513   if (info == NULL)
 514     {
 515       info = XCNEW (struct terminal_info);
 516       set_inferior_data (inf, inflow_inferior_data, info);
 517     }
 518
 519   return info;
 520 }
 521
 522 /* This is a "inferior_exit" observer.  Releases the TERMINAL_INFO member
 523    of the inferior structure.  This field is private to inflow.c, and
 524    its type is opaque to the rest of GDB.  PID is the target pid of
 525    the inferior that is about to be removed from the inferior
 526    list.  */
 527
 528 static void
 529 inflow_inferior_exit (struct inferior *inf)
 530 {
 531   struct terminal_info *info;
 532
 533   info = inferior_data (inf, inflow_inferior_data);
 534   if (info != NULL)
 535     {
 536       xfree (info->run_terminal);
 537       xfree (info->ttystate);
 538       xfree (info);
 539       set_inferior_data (inf, inflow_inferior_data, NULL);
 540     }
 541 }
 542
 543 void
 544 copy_terminal_info (struct inferior *to, struct inferior *from)
 545 {
 546   struct terminal_info *tinfo_to, *tinfo_from;
 547
 548   tinfo_to = get_inflow_inferior_data (to);
 549   tinfo_from = get_inflow_inferior_data (from);
 550
 551   xfree (tinfo_to->run_terminal);
 552   xfree (tinfo_to->ttystate);
 553
 554   *tinfo_to = *tinfo_from;
 555
 556   if (tinfo_from->run_terminal)
 557     tinfo_to->run_terminal
 558       = xstrdup (tinfo_from->run_terminal);
 559
 560   if (tinfo_from->ttystate)
 561     tinfo_to->ttystate
 562       = serial_copy_tty_state (stdin_serial, tinfo_from->ttystate);
 563 }
 564
 565 void
 566 term_info (char *arg, int from_tty)
 567 {
 568   target_terminal_info (arg, from_tty);
 569 }
 570
 571 void
 572 child_terminal_info (struct target_ops *self, const char *args, int from_tty)
 573 {
 574   struct inferior *inf;
 575   struct terminal_info *tinfo;
 576
 577   if (!gdb_has_a_terminal ())
 578     {
 579       printf_filtered (_("This GDB does not control a terminal.\n"));
 580       return;
 581     }
 582
 583   if (ptid_equal (inferior_ptid, null_ptid))
 584     return;
 585
 586   inf = current_inferior ();
 587   tinfo = get_inflow_inferior_data (inf);
 588
 589   printf_filtered (_("Inferior's terminal status "
 590                      "(currently saved by GDB):\n"));
 591
 592   /* First the fcntl flags.  */
 593   {
 594     int flags;
 595
 596     flags = tinfo->tflags;
 597
 598     printf_filtered ("File descriptor flags = ");
 599
 600 #ifndef O_ACCMODE
 601 #define O_ACCMODE (O_RDONLY | O_WRONLY | O_RDWR)
 602 #endif
 603     /* (O_ACCMODE) parens are to avoid Ultrix header file bug.  */
 604     switch (flags & (O_ACCMODE))
 605       {
 606       case O_RDONLY:
 607         printf_filtered ("O_RDONLY");
 608         break;
 609       case O_WRONLY:
 610         printf_filtered ("O_WRONLY");
 611         break;
 612       case O_RDWR:
 613         printf_filtered ("O_RDWR");
 614         break;
 615       }
 616     flags &= ~(O_ACCMODE);
 617
 618 #ifdef O_NONBLOCK
 619     if (flags & O_NONBLOCK)
 620       printf_filtered (" | O_NONBLOCK");
 621     flags &= ~O_NONBLOCK;
 622 #endif
 623
 624 #if defined (O_NDELAY)
 625     /* If O_NDELAY and O_NONBLOCK are defined to the same thing, we will
 626        print it as O_NONBLOCK, which is good cause that is what POSIX
 627        has, and the flag will already be cleared by the time we get here.  */
 628     if (flags & O_NDELAY)
 629       printf_filtered (" | O_NDELAY");
 630     flags &= ~O_NDELAY;
 631 #endif
 632
 633     if (flags & O_APPEND)
 634       printf_filtered (" | O_APPEND");
 635     flags &= ~O_APPEND;
 636
 637 #if defined (O_BINARY)
 638     if (flags & O_BINARY)
 639       printf_filtered (" | O_BINARY");
 640     flags &= ~O_BINARY;
 641 #endif
 642
 643     if (flags)
 644       printf_filtered (" | 0x%x", flags);
 645     printf_filtered ("\n");
 646   }
 647
 648 #ifdef PROCESS_GROUP_TYPE
 649   printf_filtered ("Process group = %d\n", (int) tinfo->process_group);
 650 #endif
 651
 652   serial_print_tty_state (stdin_serial, tinfo->ttystate, gdb_stdout);
 653 }
 654 \f
 655 /* NEW_TTY_PREFORK is called before forking a new child process,
 656    so we can record the state of ttys in the child to be formed.
 657    TTYNAME is null if we are to share the terminal with gdb;
 658    or points to a string containing the name of the desired tty.
 659
 660    NEW_TTY is called in new child processes under Unix, which will
 661    become debugger target processes.  This actually switches to
 662    the terminal specified in the NEW_TTY_PREFORK call.  */
 663
 664 void
 665 new_tty_prefork (const char *ttyname)
 666 {
 667   /* Save the name for later, for determining whether we and the child
 668      are sharing a tty.  */
 669   inferior_thisrun_terminal = ttyname;
 670 }
 671
 672 #if !defined(__GO32__) && !defined(_WIN32)
 673 /* If RESULT, assumed to be the return value from a system call, is
 674    negative, print the error message indicated by errno and exit.
 675    MSG should identify the operation that failed.  */
 676 static void
 677 check_syscall (const char *msg, int result)
 678 {
 679   if (result < 0)
 680     {
 681       print_sys_errmsg (msg, errno);
 682       _exit (1);
 683     }
 684 }
 685 #endif
 686
 687 void
 688 new_tty (void)
 689 {
 690   int tty;
 691
 692   if (inferior_thisrun_terminal == 0)
 693     return;
 694 #if !defined(__GO32__) && !defined(_WIN32)
 695 #ifdef TIOCNOTTY
 696   /* Disconnect the child process from our controlling terminal.  On some
 697      systems (SVR4 for example), this may cause a SIGTTOU, so temporarily
 698      ignore SIGTTOU.  */
 699   tty = open ("/dev/tty", O_RDWR);
 700   if (tty > 0)
 701     {
 702       void (*osigttou) ();
 703
 704       osigttou = (void (*)()) signal (SIGTTOU, SIG_IGN);
 705       ioctl (tty, TIOCNOTTY, 0);
 706       close (tty);
 707       signal (SIGTTOU, osigttou);
 708     }
 709 #endif
 710
 711   /* Now open the specified new terminal.  */
 712   tty = open (inferior_thisrun_terminal, O_RDWR | O_NOCTTY);
 713   check_syscall (inferior_thisrun_terminal, tty);
 714
 715   /* Avoid use of dup2; doesn't exist on all systems.  */
 716   if (tty != 0)
 717     {
 718       close (0);
 719       check_syscall ("dup'ing tty into fd 0", dup (tty));
 720     }
 721   if (tty != 1)
 722     {
 723       close (1);
 724       check_syscall ("dup'ing tty into fd 1", dup (tty));
 725     }
 726   if (tty != 2)
 727     {
 728       close (2);
 729       check_syscall ("dup'ing tty into fd 2", dup (tty));
 730     }
 731
 732 #ifdef TIOCSCTTY
 733   /* Make tty our new controlling terminal.  */
 734   if (ioctl (tty, TIOCSCTTY, 0) == -1)
 735     /* Mention GDB in warning because it will appear in the inferior's
 736        terminal instead of GDB's.  */
 737     warning (_("GDB: Failed to set controlling terminal: %s"),
 738              safe_strerror (errno));
 739 #endif
 740
 741   if (tty > 2)
 742     close (tty);
 743 #endif /* !go32 && !win32 */
 744 }
 745
 746 /* NEW_TTY_POSTFORK is called after forking a new child process, and
 747    adding it to the inferior table, to store the TTYNAME being used by
 748    the child, or null if it sharing the terminal with gdb.  */
 749
 750 void
 751 new_tty_postfork (void)
 752 {
 753   /* Save the name for later, for determining whether we and the child
 754      are sharing a tty.  */
 755
 756   if (inferior_thisrun_terminal)
 757     {
 758       struct inferior *inf = current_inferior ();
 759       struct terminal_info *tinfo = get_inflow_inferior_data (inf);
 760
 761       tinfo->run_terminal = xstrdup (inferior_thisrun_terminal);
 762     }
 763
 764   inferior_thisrun_terminal = NULL;
 765 }
 766
 767 \f
 768 /* Call set_sigint_trap when you need to pass a signal on to an attached
 769    process when handling SIGINT.  */
 770
 771 static void
 772 pass_signal (int signo)
 773 {
 774 #ifndef _WIN32
 775   kill (ptid_get_pid (inferior_ptid), SIGINT);
 776 #endif
 777 }
 778
 779 static void (*osig) ();
 780 static int osig_set;
 781
 782 void
 783 set_sigint_trap (void)
 784 {
 785   struct inferior *inf = current_inferior ();
 786   struct terminal_info *tinfo = get_inflow_inferior_data (inf);
 787
 788   if (inf->attach_flag || tinfo->run_terminal)
 789     {
 790       osig = (void (*)()) signal (SIGINT, pass_signal);
 791       osig_set = 1;
 792     }
 793   else
 794     osig_set = 0;
 795 }
 796
 797 void
 798 clear_sigint_trap (void)
 799 {
 800   if (osig_set)
 801     {
 802       signal (SIGINT, osig);
 803       osig_set = 0;
 804     }
 805 }
 806 \f
 807
 808 /* Create a new session if the inferior will run in a different tty.
 809    A session is UNIX's way of grouping processes that share a controlling
 810    terminal, so a new one is needed if the inferior terminal will be
 811    different from GDB's.
 812
 813    Returns the session id of the new session, 0 if no session was created
 814    or -1 if an error occurred.  */
 815 pid_t
 816 create_tty_session (void)
 817 {
 818 #ifdef HAVE_SETSID
 819   pid_t ret;
 820
 821   if (!job_control || inferior_thisrun_terminal == 0)
 822     return 0;
 823
 824   ret = setsid ();
 825   if (ret == -1)
 826     warning (_("Failed to create new terminal session: setsid: %s"),
 827              safe_strerror (errno));
 828
 829   return ret;
 830 #else
 831   return 0;
 832 #endif /* HAVE_SETSID */
 833 }
 834
 835 /* This is here because this is where we figure out whether we (probably)
 836    have job control.  Just using job_control only does part of it because
 837    setpgid or setpgrp might not exist on a system without job control.
 838    It might be considered misplaced (on the other hand, process groups and
 839    job control are closely related to ttys).
 840
 841    For a more clean implementation, in libiberty, put a setpgid which merely
 842    calls setpgrp and a setpgrp which does nothing (any system with job control
 843    will have one or the other).  */
 844 int
 845 gdb_setpgid (void)
 846 {
 847   int retval = 0;
 848
 849   if (job_control)
 850     {
 851 #if defined (HAVE_TERMIOS) || defined (TIOCGPGRP)
 852 #ifdef HAVE_SETPGID
 853       /* The call setpgid (0, 0) is supposed to work and mean the same
 854          thing as this, but on Ultrix 4.2A it fails with EPERM (and
 855          setpgid (getpid (), getpid ()) succeeds).  */
 856       retval = setpgid (getpid (), getpid ());
 857 #else
 858 #ifdef HAVE_SETPGRP
 859 #ifdef SETPGRP_VOID
 860       retval = setpgrp ();
 861 #else
 862       retval = setpgrp (getpid (), getpid ());
 863 #endif
 864 #endif /* HAVE_SETPGRP */
 865 #endif /* HAVE_SETPGID */
 866 #endif /* defined (HAVE_TERMIOS) || defined (TIOCGPGRP) */
 867     }
 868
 869   return retval;
 870 }
 871
 872 /* Get all the current tty settings (including whether we have a
 873    tty at all!).  We can't do this in _initialize_inflow because
 874    serial_fdopen() won't work until the serial_ops_list is
 875    initialized, but we don't want to do it lazily either, so
 876    that we can guarantee stdin_serial is opened if there is
 877    a terminal.  */
 878 void
 879 initialize_stdin_serial (void)
 880 {
 881   stdin_serial = serial_fdopen (0);
 882 }
 883
 884 void
 885 _initialize_inflow (void)
 886 {
 887   add_info ("terminal", term_info,
 888             _("Print inferior's saved terminal status."));
 889
 890   add_setshow_auto_boolean_cmd ("interactive-mode", class_support,
 891                                 &interactive_mode, _("\
 892 Set whether GDB's standard input is a terminal."), _("\
 893 Show whether GDB's standard input is a terminal."), _("\
 894 If on, GDB assumes that standard input is a terminal.  In practice, it\n\
 895 means that GDB should wait for the user to answer queries associated to\n\
 896 commands entered at the command prompt.  If off, GDB assumes that standard\n\
 897 input is not a terminal, and uses the default answer to all queries.\n\
 898 If auto (the default), determine which mode to use based on the standard\n\
 899 input settings."),
 900                         NULL,
 901                         show_interactive_mode,
 902                         &setlist, &showlist);
 903
 904   terminal_is_ours = 1;
 905
 906   /* OK, figure out whether we have job control.  If neither termios nor
 907      sgtty (i.e. termio or go32), leave job_control 0.  */
 908
 909 #if defined (HAVE_TERMIOS)
 910   /* Do all systems with termios have the POSIX way of identifying job
 911      control?  I hope so.  */
 912 #ifdef _POSIX_JOB_CONTROL
 913   job_control = 1;
 914 #else
 915 #ifdef _SC_JOB_CONTROL
 916   job_control = sysconf (_SC_JOB_CONTROL);
 917 #else
 918   job_control = 0;              /* Have to assume the worst.  */
 919 #endif /* _SC_JOB_CONTROL */
 920 #endif /* _POSIX_JOB_CONTROL */
 921 #endif /* HAVE_TERMIOS */
 922
 923 #ifdef HAVE_SGTTY
 924 #ifdef TIOCGPGRP
 925   job_control = 1;
 926 #else
 927   job_control = 0;
 928 #endif /* TIOCGPGRP */
 929 #endif /* sgtty */
 930
 931   observer_attach_inferior_exit (inflow_inferior_exit);
 932
 933   inflow_inferior_data
 934     = register_inferior_data_with_cleanup (NULL, inflow_inferior_data_cleanup);
 935 }