gdb/inflow.c

/* Low level interface to ptrace, for GDB when running under Unix.
   Copyright (C) 1986-2018 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"
#include "frame.h"
#include "inferior.h"
#include "command.h"
#include "serial.h"
#include "terminal.h"
#include "target.h"
#include "gdbthread.h"
#include "observer.h"
#include <signal.h>
#include <fcntl.h>
#include "gdb_select.h"

#include "inflow.h"
#include "gdbcmd.h"
#ifdef HAVE_TERMIOS_H
#include <termios.h>
#endif
#include "job-control.h"

#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif

#ifndef O_NOCTTY
#define O_NOCTTY 0
#endif

static void pass_signal (int);

static void child_terminal_ours_1 (int);

/* Record terminal status separately for debugger and inferior.  */

static struct serial *stdin_serial;

/* Terminal related info we need to keep track of.  Each inferior
   holds an instance of this structure --- we save it whenever the
   corresponding inferior stops, and restore it to the foreground
   inferior when it resumes.  */
struct terminal_info
{
  /* The name of the tty (from the `tty' command) that we gave to the
     inferior when it was started.  */
  char *run_terminal;

  /* TTY state.  We save it whenever the inferior stops, and restore
     it when it resumes.  */
  serial_ttystate ttystate;

#ifdef HAVE_TERMIOS_H
  /* Process group.  Saved and restored just like ttystate.  */
  pid_t process_group;
#endif

  /* fcntl flags.  Saved and restored just like ttystate.  */
  int tflags;
};

/* Our own tty state, which we restore every time we need to deal with
   the terminal.  This is set once, when GDB first starts, and then
   whenever we enter/leave TUI mode (gdb_save_tty_state).  The
   settings of flags which readline saves and restores are
   unimportant.  */
static struct terminal_info our_terminal_info;

/* Snapshot of the initial tty state taken during initialization of
   GDB, before readline/ncurses have had a chance to change it.  This
   is used as the initial tty state given to each new spawned
   inferior.  Unlike our_terminal_info, this is only ever set
   once.  */
static serial_ttystate initial_gdb_ttystate;

static struct terminal_info *get_inflow_inferior_data (struct inferior *);

/* RAII class used to ignore SIGTTOU in a scope.  */

class scoped_ignore_sigttou
{
public:
  scoped_ignore_sigttou ()
  {
#ifdef SIGTTOU
    if (job_control)
      m_osigttou = signal (SIGTTOU, SIG_IGN);
#endif
  }

  ~scoped_ignore_sigttou ()
  {
#ifdef SIGTTOU
    if (job_control)
      signal (SIGTTOU, m_osigttou);
#endif
  }

  DISABLE_COPY_AND_ASSIGN (scoped_ignore_sigttou);

private:
#ifdef SIGTTOU
  sighandler_t m_osigttou = NULL;
#endif
};

#ifdef HAVE_TERMIOS_H

/* Return the process group of the current inferior.  */

pid_t
inferior_process_group (void)
{
  return get_inflow_inferior_data (current_inferior ())->process_group;
}
#endif

/* While the inferior is running, we want SIGINT and SIGQUIT to go to the
   inferior only.  If we have job control, that takes care of it.  If not,
   we save our handlers in these two variables and set SIGINT and SIGQUIT
   to SIG_IGN.  */

static sighandler_t sigint_ours;
static sighandler_t sigquit_ours;

/* The name of the tty (from the `tty' command) that we're giving to
   the inferior when starting it up.  This is only (and should only
   be) used as a transient global by new_tty_prefork,
   create_tty_session, new_tty and new_tty_postfork, all called from
   fork_inferior, while forking a new child.  */
static const char *inferior_thisrun_terminal;

/* Nonzero if our terminal settings are in effect.  Zero if the
   inferior's settings are in effect.  Ignored if !gdb_has_a_terminal
   ().  */

int terminal_is_ours;

/* See terminal.h.  */

void
set_initial_gdb_ttystate (void)
{
  /* Note we can't do any of this in _initialize_inflow because at
     that point stdin_serial has not been created yet.  */

  initial_gdb_ttystate = serial_get_tty_state (stdin_serial);

  if (initial_gdb_ttystate != NULL)
    {
      our_terminal_info.ttystate
	= serial_copy_tty_state (stdin_serial, initial_gdb_ttystate);
#ifdef F_GETFL
      our_terminal_info.tflags = fcntl (0, F_GETFL, 0);
#endif
#ifdef HAVE_TERMIOS_H
      our_terminal_info.process_group = tcgetpgrp (0);
#endif
    }
}

/* Does GDB have a terminal (on stdin)?  */

static int
gdb_has_a_terminal (void)
{
  return initial_gdb_ttystate != NULL;
}

/* Macro for printing errors from ioctl operations */

#define	OOPSY(what)	\
  if (result == -1)	\
    fprintf_unfiltered(gdb_stderr, "[%s failed in terminal_inferior: %s]\n", \
	    what, safe_strerror (errno))

/* Initialize the terminal settings we record for the inferior,
   before we actually run the inferior.  */

void
child_terminal_init (struct target_ops *self)
{
  struct inferior *inf = current_inferior ();
  struct terminal_info *tinfo = get_inflow_inferior_data (inf);

#ifdef HAVE_TERMIOS_H
  /* Store the process group even without a terminal as it is used not
     only to reset the tty foreground process group, but also to
     interrupt the inferior.  A child we spawn should be a process
     group leader (PGID==PID) at this point, though that may not be
     true if we're attaching to an existing process.  */
  tinfo->process_group = inf->pid;
#endif

  if (gdb_has_a_terminal ())
    {
      xfree (tinfo->ttystate);
      tinfo->ttystate = serial_copy_tty_state (stdin_serial,
					       initial_gdb_ttystate);

      /* Make sure that next time we call terminal_inferior (which will be
         before the program runs, as it needs to be), we install the new
         process group.  */
      terminal_is_ours = 1;
    }
}

/* Save the terminal settings again.  This is necessary for the TUI
   when it switches to TUI or non-TUI mode;  curses changes the terminal
   and gdb must be able to restore it correctly.  */

void
gdb_save_tty_state (void)
{
  if (gdb_has_a_terminal ())
    {
      xfree (our_terminal_info.ttystate);
      our_terminal_info.ttystate = serial_get_tty_state (stdin_serial);
    }
}

/* Put the inferior's terminal settings into effect.
   This is preparation for starting or resuming the inferior.

   N.B. Targets that want to use this with async support must build that
   support on top of this (e.g., the caller still needs to remove stdin
   from the event loop).  E.g., see linux_nat_terminal_inferior.  */

void
child_terminal_inferior (struct target_ops *self)
{
  struct inferior *inf;
  struct terminal_info *tinfo;

  if (!terminal_is_ours)
    return;

  inf = current_inferior ();
  tinfo = get_inflow_inferior_data (inf);

  if (gdb_has_a_terminal ()
      && tinfo->ttystate != NULL
      && tinfo->run_terminal == NULL)
    {
      int result;

#ifdef F_GETFL
      result = fcntl (0, F_SETFL, tinfo->tflags);
      OOPSY ("fcntl F_SETFL");
#endif

      result = serial_set_tty_state (stdin_serial, tinfo->ttystate);
      OOPSY ("setting tty state");

      if (!job_control)
	{
	  sigint_ours = signal (SIGINT, SIG_IGN);
#ifdef SIGQUIT
	  sigquit_ours = signal (SIGQUIT, SIG_IGN);
#endif
	}

      /* If attach_flag is set, we don't know whether we are sharing a
         terminal with the inferior or not.  (attaching a process
         without a terminal is one case where we do not; attaching a
         process which we ran from the same shell as GDB via `&' is
         one case where we do, I think (but perhaps this is not
         `sharing' in the sense that we need to save and restore tty
         state)).  I don't know if there is any way to tell whether we
         are sharing a terminal.  So what we do is to go through all
         the saving and restoring of the tty state, but ignore errors
         setting the process group, which will happen if we are not
         sharing a terminal).  */

      if (job_control)
	{
#ifdef HAVE_TERMIOS_H
	  result = tcsetpgrp (0, tinfo->process_group);
	  if (!inf->attach_flag)
	    OOPSY ("tcsetpgrp");
#endif
	}
    }
  terminal_is_ours = 0;
}

/* Put some of our terminal settings into effect,
   enough to get proper results from our output,
   but do not change into or out of RAW mode
   so that no input is discarded.

   After doing this, either terminal_ours or terminal_inferior
   should be called to get back to a normal state of affairs.

   N.B. The implementation is (currently) no different than
   child_terminal_ours.  See child_terminal_ours_1.  */

void
child_terminal_ours_for_output (struct target_ops *self)
{
  child_terminal_ours_1 (1);
}

/* Put our terminal settings into effect.
   First record the inferior's terminal settings
   so they can be restored properly later.

   N.B. Targets that want to use this with async support must build that
   support on top of this (e.g., the caller still needs to add stdin to the
   event loop).  E.g., see linux_nat_terminal_ours.  */

void
child_terminal_ours (struct target_ops *self)
{
  child_terminal_ours_1 (0);
}

/* output_only is not used, and should not be used unless we introduce
   separate terminal_is_ours and terminal_is_ours_for_output
   flags.  */

static void
child_terminal_ours_1 (int output_only)
{
  struct inferior *inf;
  struct terminal_info *tinfo;

  if (terminal_is_ours)
    return;

  terminal_is_ours = 1;

  /* Checking inferior->run_terminal is necessary so that
     if GDB is running in the background, it won't block trying
     to do the ioctl()'s below.  Checking gdb_has_a_terminal
     avoids attempting all the ioctl's when running in batch.  */

  inf = current_inferior ();
  tinfo = get_inflow_inferior_data (inf);

  if (tinfo->run_terminal != NULL || gdb_has_a_terminal () == 0)
    return;
  else
    {
      int result ATTRIBUTE_UNUSED;

      /* Ignore SIGTTOU since it will happen when we try to set the
	 terminal's pgrp.  */
      scoped_ignore_sigttou ignore_sigttou;

      xfree (tinfo->ttystate);
      tinfo->ttystate = serial_get_tty_state (stdin_serial);

#ifdef HAVE_TERMIOS_H
      if (!inf->attach_flag)
	/* If tcsetpgrp failed in terminal_inferior, this would give us
	   our process group instead of the inferior's.  See
	   terminal_inferior for details.  */
	tinfo->process_group = tcgetpgrp (0);
#endif

      /* Set tty state to our_ttystate.  */
      serial_set_tty_state (stdin_serial, our_terminal_info.ttystate);

      if (job_control)
	{
#ifdef HAVE_TERMIOS_H
	  result = tcsetpgrp (0, our_terminal_info.process_group);
#if 0
	  /* This fails on Ultrix with EINVAL if you run the testsuite
	     in the background with nohup, and then log out.  GDB never
	     used to check for an error here, so perhaps there are other
	     such situations as well.  */
	  if (result == -1)
	    fprintf_unfiltered (gdb_stderr,
				"[tcsetpgrp failed in child_terminal_ours: %s]\n",
				safe_strerror (errno));
#endif
#endif /* termios */
	}

      if (!job_control)
	{
	  signal (SIGINT, sigint_ours);
#ifdef SIGQUIT
	  signal (SIGQUIT, sigquit_ours);
#endif
	}

#ifdef F_GETFL
      tinfo->tflags = fcntl (0, F_GETFL, 0);
      result = fcntl (0, F_SETFL, our_terminal_info.tflags);
#endif
    }
}

/* Per-inferior data key.  */
static const struct inferior_data *inflow_inferior_data;

static void
inflow_inferior_data_cleanup (struct inferior *inf, void *arg)
{
  struct terminal_info *info = (struct terminal_info *) arg;

  xfree (info->run_terminal);
  xfree (info->ttystate);
  xfree (info);
}

/* Get the current svr4 data.  If none is found yet, add it now.  This
   function always returns a valid object.  */

static struct terminal_info *
get_inflow_inferior_data (struct inferior *inf)
{
  struct terminal_info *info;

  info = (struct terminal_info *) inferior_data (inf, inflow_inferior_data);
  if (info == NULL)
    {
      info = XCNEW (struct terminal_info);
      set_inferior_data (inf, inflow_inferior_data, info);
    }

  return info;
}

/* This is a "inferior_exit" observer.  Releases the TERMINAL_INFO member
   of the inferior structure.  This field is private to inflow.c, and
   its type is opaque to the rest of GDB.  PID is the target pid of
   the inferior that is about to be removed from the inferior
   list.  */

static void
inflow_inferior_exit (struct inferior *inf)
{
  struct terminal_info *info;

  info = (struct terminal_info *) inferior_data (inf, inflow_inferior_data);
  if (info != NULL)
    {
      xfree (info->run_terminal);
      xfree (info->ttystate);
      xfree (info);
      set_inferior_data (inf, inflow_inferior_data, NULL);
    }
}

void
copy_terminal_info (struct inferior *to, struct inferior *from)
{
  struct terminal_info *tinfo_to, *tinfo_from;

  tinfo_to = get_inflow_inferior_data (to);
  tinfo_from = get_inflow_inferior_data (from);

  xfree (tinfo_to->run_terminal);
  xfree (tinfo_to->ttystate);

  *tinfo_to = *tinfo_from;

  if (tinfo_from->run_terminal)
    tinfo_to->run_terminal
      = xstrdup (tinfo_from->run_terminal);

  if (tinfo_from->ttystate)
    tinfo_to->ttystate
      = serial_copy_tty_state (stdin_serial, tinfo_from->ttystate);
}

void
info_terminal_command (const char *arg, int from_tty)
{
  target_terminal::info (arg, from_tty);
}

void
child_terminal_info (struct target_ops *self, const char *args, int from_tty)
{
  struct inferior *inf;
  struct terminal_info *tinfo;

  if (!gdb_has_a_terminal ())
    {
      printf_filtered (_("This GDB does not control a terminal.\n"));
      return;
    }

  if (ptid_equal (inferior_ptid, null_ptid))
    return;

  inf = current_inferior ();
  tinfo = get_inflow_inferior_data (inf);

  printf_filtered (_("Inferior's terminal status "
		     "(currently saved by GDB):\n"));

  /* First the fcntl flags.  */
  {
    int flags;

    flags = tinfo->tflags;

    printf_filtered ("File descriptor flags = ");

#ifndef O_ACCMODE
#define O_ACCMODE (O_RDONLY | O_WRONLY | O_RDWR)
#endif
    /* (O_ACCMODE) parens are to avoid Ultrix header file bug.  */
    switch (flags & (O_ACCMODE))
      {
      case O_RDONLY:
	printf_filtered ("O_RDONLY");
	break;
      case O_WRONLY:
	printf_filtered ("O_WRONLY");
	break;
      case O_RDWR:
	printf_filtered ("O_RDWR");
	break;
      }
    flags &= ~(O_ACCMODE);

#ifdef O_NONBLOCK
    if (flags & O_NONBLOCK)
      printf_filtered (" | O_NONBLOCK");
    flags &= ~O_NONBLOCK;
#endif

#if defined (O_NDELAY)
    /* If O_NDELAY and O_NONBLOCK are defined to the same thing, we will
       print it as O_NONBLOCK, which is good cause that is what POSIX
       has, and the flag will already be cleared by the time we get here.  */
    if (flags & O_NDELAY)
      printf_filtered (" | O_NDELAY");
    flags &= ~O_NDELAY;
#endif

    if (flags & O_APPEND)
      printf_filtered (" | O_APPEND");
    flags &= ~O_APPEND;

#if defined (O_BINARY)
    if (flags & O_BINARY)
      printf_filtered (" | O_BINARY");
    flags &= ~O_BINARY;
#endif

    if (flags)
      printf_filtered (" | 0x%x", flags);
    printf_filtered ("\n");
  }

#ifdef HAVE_TERMIOS_H
  printf_filtered ("Process group = %d\n", (int) tinfo->process_group);
#endif

  serial_print_tty_state (stdin_serial, tinfo->ttystate, gdb_stdout);
}

/* NEW_TTY_PREFORK is called before forking a new child process,
   so we can record the state of ttys in the child to be formed.
   TTYNAME is null if we are to share the terminal with gdb;
   or points to a string containing the name of the desired tty.

   NEW_TTY is called in new child processes under Unix, which will
   become debugger target processes.  This actually switches to
   the terminal specified in the NEW_TTY_PREFORK call.  */

void
new_tty_prefork (const char *ttyname)
{
  /* Save the name for later, for determining whether we and the child
     are sharing a tty.  */
  inferior_thisrun_terminal = ttyname;
}

#if !defined(__GO32__) && !defined(_WIN32)
/* If RESULT, assumed to be the return value from a system call, is
   negative, print the error message indicated by errno and exit.
   MSG should identify the operation that failed.  */
static void
check_syscall (const char *msg, int result)
{
  if (result < 0)
    {
      print_sys_errmsg (msg, errno);
      _exit (1);
    }
}
#endif

void
new_tty (void)
{
  int tty;

  if (inferior_thisrun_terminal == 0)
    return;
#if !defined(__GO32__) && !defined(_WIN32)
#ifdef TIOCNOTTY
  /* Disconnect the child process from our controlling terminal.  On some
     systems (SVR4 for example), this may cause a SIGTTOU, so temporarily
     ignore SIGTTOU.  */
  tty = open ("/dev/tty", O_RDWR);
  if (tty > 0)
    {
      scoped_ignore_sigttou ignore_sigttou;

      ioctl (tty, TIOCNOTTY, 0);
      close (tty);
    }
#endif

  /* Now open the specified new terminal.  */
  tty = open (inferior_thisrun_terminal, O_RDWR | O_NOCTTY);
  check_syscall (inferior_thisrun_terminal, tty);

  /* Avoid use of dup2; doesn't exist on all systems.  */
  if (tty != 0)
    {
      close (0);
      check_syscall ("dup'ing tty into fd 0", dup (tty));
    }
  if (tty != 1)
    {
      close (1);
      check_syscall ("dup'ing tty into fd 1", dup (tty));
    }
  if (tty != 2)
    {
      close (2);
      check_syscall ("dup'ing tty into fd 2", dup (tty));
    }

#ifdef TIOCSCTTY
  /* Make tty our new controlling terminal.  */
  if (ioctl (tty, TIOCSCTTY, 0) == -1)
    /* Mention GDB in warning because it will appear in the inferior's
       terminal instead of GDB's.  */
    warning (_("GDB: Failed to set controlling terminal: %s"),
	     safe_strerror (errno));
#endif

  if (tty > 2)
    close (tty);
#endif /* !go32 && !win32 */
}

/* NEW_TTY_POSTFORK is called after forking a new child process, and
   adding it to the inferior table, to store the TTYNAME being used by
   the child, or null if it sharing the terminal with gdb.  */

void
new_tty_postfork (void)
{
  /* Save the name for later, for determining whether we and the child
     are sharing a tty.  */

  if (inferior_thisrun_terminal)
    {
      struct inferior *inf = current_inferior ();
      struct terminal_info *tinfo = get_inflow_inferior_data (inf);

      tinfo->run_terminal = xstrdup (inferior_thisrun_terminal);
    }

  inferior_thisrun_terminal = NULL;
}


/* Call set_sigint_trap when you need to pass a signal on to an attached
   process when handling SIGINT.  */

static void
pass_signal (int signo)
{
#ifndef _WIN32
  kill (ptid_get_pid (inferior_ptid), SIGINT);
#endif
}

static sighandler_t osig;
static int osig_set;

void
set_sigint_trap (void)
{
  struct inferior *inf = current_inferior ();
  struct terminal_info *tinfo = get_inflow_inferior_data (inf);

  if (inf->attach_flag || tinfo->run_terminal)
    {
      osig = signal (SIGINT, pass_signal);
      osig_set = 1;
    }
  else
    osig_set = 0;
}

void
clear_sigint_trap (void)
{
  if (osig_set)
    {
      signal (SIGINT, osig);
      osig_set = 0;
    }
}


/* Create a new session if the inferior will run in a different tty.
   A session is UNIX's way of grouping processes that share a controlling
   terminal, so a new one is needed if the inferior terminal will be
   different from GDB's.

   Returns the session id of the new session, 0 if no session was created
   or -1 if an error occurred.  */
pid_t
create_tty_session (void)
{
#ifdef HAVE_SETSID
  pid_t ret;

  if (!job_control || inferior_thisrun_terminal == 0)
    return 0;

  ret = setsid ();
  if (ret == -1)
    warning (_("Failed to create new terminal session: setsid: %s"),
	     safe_strerror (errno));

  return ret;
#else
  return 0;
#endif /* HAVE_SETSID */
}

/* Get all the current tty settings (including whether we have a
   tty at all!).  We can't do this in _initialize_inflow because
   serial_fdopen() won't work until the serial_ops_list is
   initialized, but we don't want to do it lazily either, so
   that we can guarantee stdin_serial is opened if there is
   a terminal.  */
void
initialize_stdin_serial (void)
{
  stdin_serial = serial_fdopen (0);
}

void
_initialize_inflow (void)
{
  add_info ("terminal", info_terminal_command,
	    _("Print inferior's saved terminal status."));

  terminal_is_ours = 1;

  /* OK, figure out whether we have job control.  */
  have_job_control ();

  observer_attach_inferior_exit (inflow_inferior_exit);

  inflow_inferior_data
    = register_inferior_data_with_cleanup (NULL, inflow_inferior_data_cleanup);
}