X-Git-Url: http://git.efficios.com/?a=blobdiff_plain;f=gdb%2Finflow.c;h=339b55c0bc69e3ef52cd96636c5b5ea63b84847f;hb=739b5c9c778dee9e2f54d864f83a81ecb0639535;hp=d46d6938e27d4e555a672a713f4793a62096a169;hpb=a94799ac1e430404fda5cbc181406cf5f3630108;p=deliverable%2Fbinutils-gdb.git

diff --git a/gdb/inflow.c b/gdb/inflow.c
index d46d6938e2..339b55c0bc 100644
--- a/gdb/inflow.c
+++ b/gdb/inflow.c
@@ -1,5 +1,5 @@
 /* Low level interface to ptrace, for GDB when running under Unix.
-   Copyright (C) 1986-2017 Free Software Foundation, Inc.
+   Copyright (C) 1986-2019 Free Software Foundation, Inc.
 
    This file is part of GDB.
 
@@ -24,7 +24,7 @@
 #include "terminal.h"
 #include "target.h"
 #include "gdbthread.h"
-#include "observer.h"
+#include "observable.h"
 #include <signal.h>
 #include <fcntl.h>
 #include "gdb_select.h"
@@ -34,7 +34,7 @@
 #ifdef HAVE_TERMIOS_H
 #include <termios.h>
 #endif
-#include "job-control.h"
+#include "common/job-control.h"
 
 #ifdef HAVE_SYS_IOCTL_H
 #include <sys/ioctl.h>
@@ -46,7 +46,7 @@
 
 static void pass_signal (int);
 
-static void child_terminal_ours_1 (int);
+static void child_terminal_ours_1 (target_terminal_state);
 
 /* Record terminal status separately for debugger and inferior.  */
 
@@ -54,25 +54,40 @@ 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.  */
+   corresponding inferior stops, and restore it to the terminal when
+   the inferior is resumed in the foreground.  */
 struct terminal_info
 {
+  terminal_info () = default;
+  ~terminal_info ();
+
   /* The name of the tty (from the `tty' command) that we gave to the
      inferior when it was started.  */
-  char *run_terminal;
+  char *run_terminal = nullptr;
 
   /* TTY state.  We save it whenever the inferior stops, and restore
-     it when it resumes.  */
-  serial_ttystate ttystate;
+     it when it resumes in the foreground.  */
+  serial_ttystate ttystate {};
 
 #ifdef HAVE_TERMIOS_H
-  /* Process group.  Saved and restored just like ttystate.  */
-  pid_t process_group;
+  /* The terminal's foreground process group.  Saved whenever the
+     inferior stops.  This is the pgrp displayed by "info terminal".
+     Note that this may be not the inferior's actual process group,
+     since each inferior that we spawn has its own process group, and
+     only one can be in the foreground at a time.  When the inferior
+     resumes, if we can determine the inferior's actual pgrp, then we
+     make that the foreground pgrp instead of what was saved here.
+     While it's a bit arbitrary which inferior's pgrp ends up in the
+     foreground when we resume several inferiors, this at least makes
+     'resume inf1+inf2' + 'stop all' + 'resume inf2' end up with
+     inf2's pgrp in the foreground instead of inf1's (which would be
+     problematic since it would be left stopped: Ctrl-C wouldn't work,
+     for example).  */
+  pid_t process_group = 0;
 #endif
 
   /* fcntl flags.  Saved and restored just like ttystate.  */
-  int tflags;
+  int tflags = 0;
 };
 
 /* Our own tty state, which we restore every time we need to deal with
@@ -91,16 +106,34 @@ static serial_ttystate initial_gdb_ttystate;
 
 static struct terminal_info *get_inflow_inferior_data (struct inferior *);
 
-#ifdef HAVE_TERMIOS_H
-
-/* Return the process group of the current inferior.  */
+/* RAII class used to ignore SIGTTOU in a scope.  */
 
-pid_t
-inferior_process_group (void)
+class scoped_ignore_sigttou
 {
-  return get_inflow_inferior_data (current_inferior ())->process_group;
-}
+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
+};
 
 /* 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,
@@ -108,7 +141,9 @@ inferior_process_group (void)
    to SIG_IGN.  */
 
 static sighandler_t sigint_ours;
+#ifdef SIGQUIT
 static sighandler_t sigquit_ours;
+#endif
 
 /* 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
@@ -117,11 +152,17 @@ static sighandler_t sigquit_ours;
    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
-   ().  */
+/* Track who owns GDB's terminal (is it GDB or some inferior?).  While
+   target_terminal::is_ours() etc. tracks the core's intention and is
+   independent of the target backend, this tracks the actual state of
+   GDB's own tty.  So for example,
 
-int terminal_is_ours;
+     (target_terminal::is_inferior () && gdb_tty_state == terminal_is_ours)
+
+   is true when the (native) inferior is not sharing a terminal with
+   GDB (e.g., because we attached to an inferior that is running on a
+   different terminal).  */
+static target_terminal_state gdb_tty_state = target_terminal_state::is_ours;
 
 /* See terminal.h.  */
 
@@ -165,29 +206,23 @@ gdb_has_a_terminal (void)
    before we actually run the inferior.  */
 
 void
-child_terminal_init_with_pgrp (int pgrp)
+child_terminal_init (struct target_ops *self)
 {
-  struct inferior *inf = current_inferior ();
-  struct terminal_info *tinfo = get_inflow_inferior_data (inf);
+  if (!gdb_has_a_terminal ())
+    return;
+
+  inferior *inf = current_inferior ();
+  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.  */
-  tinfo->process_group = pgrp;
+  /* 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;
-    }
+  xfree (tinfo->ttystate);
+  tinfo->ttystate = serial_copy_tty_state (stdin_serial, initial_gdb_ttystate);
 }
 
 /* Save the terminal settings again.  This is necessary for the TUI
@@ -204,45 +239,137 @@ gdb_save_tty_state (void)
     }
 }
 
-void
-child_terminal_init (struct target_ops *self)
+/* Try to determine whether TTY is GDB's input terminal.  Returns
+   TRIBOOL_UNKNOWN if we can't tell.  */
+
+static tribool
+is_gdb_terminal (const char *tty)
 {
-#ifdef HAVE_TERMIOS_H
-  /* This is for Lynx, and should be cleaned up by having Lynx be a
-     separate debugging target with a version of target_terminal::init
-     which passes in the process group to a generic routine which does
-     all the work (and the non-threaded child_terminal_init can just
-     pass in inferior_ptid to the same routine).  */
-  /* We assume INFERIOR_PID is also the child's process group.  */
-  child_terminal_init_with_pgrp (ptid_get_pid (inferior_ptid));
-#endif /* HAVE_TERMIOS_H */
+  struct stat gdb_tty;
+  struct stat other_tty;
+  int res;
+
+  res = stat (tty, &other_tty);
+  if (res == -1)
+    return TRIBOOL_UNKNOWN;
+
+  res = fstat (STDIN_FILENO, &gdb_tty);
+  if (res == -1)
+    return TRIBOOL_UNKNOWN;
+
+  return ((gdb_tty.st_dev == other_tty.st_dev
+	   && gdb_tty.st_ino == other_tty.st_ino)
+	  ? TRIBOOL_TRUE
+	  : TRIBOOL_FALSE);
 }
 
-/* Put the inferior's terminal settings into effect.
-   This is preparation for starting or resuming the inferior.
+/* Helper for sharing_input_terminal.  Try to determine whether
+   inferior INF is using the same TTY for input as GDB is.  Returns
+   TRIBOOL_UNKNOWN if we can't tell.  */
 
-   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.  */
+static tribool
+sharing_input_terminal_1 (inferior *inf)
+{
+  /* Using host-dependent code here is fine, because the
+     child_terminal_foo functions are meant to be used by child/native
+     targets.  */
+#if defined (__linux__) || defined (__sun__)
+  char buf[100];
+
+  xsnprintf (buf, sizeof (buf), "/proc/%d/fd/0", inf->pid);
+  return is_gdb_terminal (buf);
+#else
+  return TRIBOOL_UNKNOWN;
+#endif
+}
+
+/* Return true if the inferior is using the same TTY for input as GDB
+   is.  If this is true, then we save/restore terminal flags/state.
+
+   This is necessary because if inf->attach_flag is set, we don't
+   offhand 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.
+
+   If we can't determine, we assume the TTY is being shared.  This
+   works OK if you're only debugging one inferior.  However, if you're
+   debugging more than one inferior, and e.g., one is spawned by GDB
+   with "run" (sharing terminal with GDB), and another is attached to
+   (and running on a different terminal, as is most common), then it
+   matters, because we can only restore the terminal settings of one
+   of the inferiors, and in that scenario, we want to restore the
+   settings of the "run"'ed inferior.
+
+   Note, this is not the same as determining whether GDB and the
+   inferior are in the same session / connected to the same
+   controlling tty.  An inferior (fork child) may call setsid,
+   disconnecting itself from the ctty, while still leaving
+   stdin/stdout/stderr associated with the original terminal.  If
+   we're debugging that process, we should also save/restore terminal
+   settings.  */
+
+static bool
+sharing_input_terminal (inferior *inf)
+{
+  terminal_info *tinfo = get_inflow_inferior_data (inf);
+
+  tribool res = sharing_input_terminal_1 (inf);
+
+  if (res == TRIBOOL_UNKNOWN)
+    {
+      /* As fallback, if we can't determine by stat'ing the inferior's
+	 tty directly (because it's not supported on this host) and
+	 the child was spawned, check whether run_terminal is our tty.
+	 This isn't ideal, since this is checking the child's
+	 controlling terminal, not the input terminal (which may have
+	 been redirected), but is still better than nothing.  A false
+	 positive ("set inferior-tty" points to our terminal, but I/O
+	 was redirected) is much more likely than a false negative
+	 ("set inferior-tty" points to some other terminal, and then
+	 output was redirected to our terminal), and with a false
+	 positive we just end up trying to save/restore terminal
+	 settings when we didn't need to or we actually can't.  */
+      if (tinfo->run_terminal != NULL)
+	res = is_gdb_terminal (tinfo->run_terminal);
+
+      /* If we still can't determine, assume yes.  */
+      if (res == TRIBOOL_UNKNOWN)
+	return true;
+    }
+
+  return res == TRIBOOL_TRUE;
+}
+
+/* Put the inferior's terminal settings into effect.  This is
+   preparation for starting or resuming the inferior.  */
 
 void
 child_terminal_inferior (struct target_ops *self)
 {
-  struct inferior *inf;
-  struct terminal_info *tinfo;
-
-  if (!terminal_is_ours)
+  /* If we resume more than one inferior in the foreground on GDB's
+     terminal, then the first inferior's terminal settings "win".
+     Note that every child process is put in its own process group, so
+     the first process that ends up resumed ends up determining which
+     process group the kernel forwards Ctrl-C/Ctrl-Z (SIGINT/SIGTTOU)
+     to.  */
+  if (gdb_tty_state == target_terminal_state::is_inferior)
     return;
 
-  inf = current_inferior ();
-  tinfo = get_inflow_inferior_data (inf);
+  inferior *inf = current_inferior ();
+  terminal_info *tinfo = get_inflow_inferior_data (inf);
 
   if (gdb_has_a_terminal ()
       && tinfo->ttystate != NULL
-      && tinfo->run_terminal == NULL)
+      && sharing_input_terminal (inf))
     {
       int result;
 
+      /* Ignore SIGTTOU since it will happen when we try to set the
+	 terminal's state (if gdb_tty_state is currently
+	 ours_for_output).  */
+      scoped_ignore_sigttou ignore_sigttou;
+
 #ifdef F_GETFL
       result = fcntl (0, F_SETFL, tinfo->tflags);
       OOPSY ("fcntl F_SETFL");
@@ -259,28 +386,40 @@ child_terminal_inferior (struct target_ops *self)
 #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
+	  /* If we can't tell the inferior's actual process group,
+	     then restore whatever was the foreground pgrp the last
+	     time the inferior was running.  See also comments
+	     describing terminal_state::process_group.  */
+#ifdef HAVE_GETPGID
+	  result = tcsetpgrp (0, getpgid (inf->pid));
+#else
 	  result = tcsetpgrp (0, tinfo->process_group);
-	  if (!inf->attach_flag)
-	    OOPSY ("tcsetpgrp");
+#endif
+	  if (result == -1)
+	    {
+#if 0
+	      /* This fails if either GDB has no controlling terminal,
+		 e.g., running under 'setsid(1)', or if the inferior
+		 is not attached to GDB's controlling terminal.  E.g.,
+		 if it called setsid to create a new session or used
+		 the TIOCNOTTY ioctl, or simply if we've attached to a
+		 process running on another terminal and we couldn't
+		 tell whether it was sharing GDB's terminal (and so
+		 assumed yes).  */
+	      fprintf_unfiltered
+		(gdb_stderr,
+		 "[tcsetpgrp failed in child_terminal_inferior: %s]\n",
+		 safe_strerror (errno));
+#endif
+	    }
 #endif
 	}
+
+      gdb_tty_state = target_terminal_state::is_inferior;
     }
-  terminal_is_ours = 0;
 }
 
 /* Put some of our terminal settings into effect,
@@ -297,7 +436,7 @@ child_terminal_inferior (struct target_ops *self)
 void
 child_terminal_ours_for_output (struct target_ops *self)
 {
-  child_terminal_ours_1 (1);
+  child_terminal_ours_1 (target_terminal_state::is_ours_for_output);
 }
 
 /* Put our terminal settings into effect.
@@ -311,63 +450,66 @@ child_terminal_ours_for_output (struct target_ops *self)
 void
 child_terminal_ours (struct target_ops *self)
 {
-  child_terminal_ours_1 (0);
+  child_terminal_ours_1 (target_terminal_state::is_ours);
 }
 
-/* output_only is not used, and should not be used unless we introduce
-   separate terminal_is_ours and terminal_is_ours_for_output
-   flags.  */
+/* Save the current terminal settings in the inferior's terminal_info
+   cache.  */
 
-static void
-child_terminal_ours_1 (int output_only)
+void
+child_terminal_save_inferior (struct target_ops *self)
 {
-  struct inferior *inf;
-  struct terminal_info *tinfo;
-
-  if (terminal_is_ours)
+  /* Avoid attempting all the ioctl's when running in batch.  */
+  if (!gdb_has_a_terminal ())
     return;
 
-  terminal_is_ours = 1;
+  inferior *inf = current_inferior ();
+  terminal_info *tinfo = get_inflow_inferior_data (inf);
 
-  /* 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.  */
+  /* No need to save/restore if the inferior is not sharing GDB's
+     tty.  */
+  if (!sharing_input_terminal (inf))
+    return;
 
-  inf = current_inferior ();
-  tinfo = get_inflow_inferior_data (inf);
+  xfree (tinfo->ttystate);
+  tinfo->ttystate = serial_get_tty_state (stdin_serial);
 
-  if (tinfo->run_terminal != NULL || gdb_has_a_terminal () == 0)
-    return;
-  else
-    {
-#ifdef SIGTTOU
-      /* Ignore this signal since it will happen when we try to set the
-         pgrp.  */
-      sighandler_t osigttou = NULL;
+#ifdef HAVE_TERMIOS_H
+  tinfo->process_group = tcgetpgrp (0);
 #endif
-      int result ATTRIBUTE_UNUSED;
 
-#ifdef SIGTTOU
-      if (job_control)
-	osigttou = signal (SIGTTOU, SIG_IGN);
+#ifdef F_GETFL
+  tinfo->tflags = fcntl (0, F_GETFL, 0);
 #endif
+}
 
-      xfree (tinfo->ttystate);
-      tinfo->ttystate = serial_get_tty_state (stdin_serial);
+/* Switch terminal state to DESIRED_STATE, either is_ours, or
+   is_ours_for_output.  */
 
-#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
+static void
+child_terminal_ours_1 (target_terminal_state desired_state)
+{
+  gdb_assert (desired_state != target_terminal_state::is_inferior);
+
+  /* Avoid attempting all the ioctl's when running in batch.  */
+  if (!gdb_has_a_terminal ())
+    return;
+
+  if (gdb_tty_state != desired_state)
+    {
+      int result ATTRIBUTE_UNUSED;
+
+      /* Ignore SIGTTOU since it will happen when we try to set the
+	 terminal's pgrp.  */
+      scoped_ignore_sigttou ignore_sigttou;
 
       /* Set tty state to our_ttystate.  */
       serial_set_tty_state (stdin_serial, our_terminal_info.ttystate);
 
-      if (job_control)
+      /* If we only want output, then leave the inferior's pgrp in the
+	 foreground, so that Ctrl-C/Ctrl-Z reach the inferior
+	 directly.  */
+      if (job_control && desired_state == target_terminal_state::is_ours)
 	{
 #ifdef HAVE_TERMIOS_H
 	  result = tcsetpgrp (0, our_terminal_info.process_group);
@@ -384,12 +526,7 @@ child_terminal_ours_1 (int output_only)
 #endif /* termios */
 	}
 
-#ifdef SIGTTOU
-      if (job_control)
-	signal (SIGTTOU, osigttou);
-#endif
-
-      if (!job_control)
+      if (!job_control && desired_state == target_terminal_state::is_ours)
 	{
 	  signal (SIGINT, sigint_ours);
 #ifdef SIGQUIT
@@ -398,23 +535,103 @@ child_terminal_ours_1 (int output_only)
 	}
 
 #ifdef F_GETFL
-      tinfo->tflags = fcntl (0, F_GETFL, 0);
       result = fcntl (0, F_SETFL, our_terminal_info.tflags);
 #endif
+
+      gdb_tty_state = desired_state;
     }
 }
 
-/* Per-inferior data key.  */
-static const struct inferior_data *inflow_inferior_data;
+/* Interrupt the inferior.  Implementation of target_interrupt for
+   child/native targets.  */
 
-static void
-inflow_inferior_data_cleanup (struct inferior *inf, void *arg)
+void
+child_interrupt (struct target_ops *self)
 {
-  struct terminal_info *info = (struct terminal_info *) arg;
+  /* Interrupt the first inferior that has a resumed thread.  */
+  thread_info *resumed = NULL;
+  for (thread_info *thr : all_non_exited_threads ())
+    {
+      if (thr->executing)
+	{
+	  resumed = thr;
+	  break;
+	}
+      if (thr->suspend.waitstatus_pending_p)
+	resumed = thr;
+    }
 
-  xfree (info->run_terminal);
-  xfree (info->ttystate);
-  xfree (info);
+  if (resumed != NULL)
+    {
+      /* Note that unlike pressing Ctrl-C on the controlling terminal,
+	 here we only interrupt one process, not the whole process
+	 group.  This is because interrupting a process group (with
+	 either Ctrl-C or with kill(3) with negative PID) sends a
+	 SIGINT to each process in the process group, and we may not
+	 be debugging all processes in the process group.  */
+#ifndef _WIN32
+      kill (resumed->inf->pid, SIGINT);
+#endif
+    }
+}
+
+/* Pass a Ctrl-C to the inferior as-if a Ctrl-C was pressed while the
+   inferior was in the foreground.  Implementation of
+   target_pass_ctrlc for child/native targets.  */
+
+void
+child_pass_ctrlc (struct target_ops *self)
+{
+  gdb_assert (!target_terminal::is_ours ());
+
+#ifdef HAVE_TERMIOS_H
+  if (job_control)
+    {
+      pid_t term_pgrp = tcgetpgrp (0);
+
+      /* If there's any inferior sharing our terminal, pass the SIGINT
+	 to the terminal's foreground process group.  This acts just
+	 like the user typed a ^C on the terminal while the inferior
+	 was in the foreground.  Note that using a negative process
+	 number in kill() is a System V-ism.  The proper BSD interface
+	 is killpg().  However, all modern BSDs support the System V
+	 interface too.  */
+
+      if (term_pgrp != -1 && term_pgrp != our_terminal_info.process_group)
+	{
+	  kill (-term_pgrp, SIGINT);
+	  return;
+	}
+    }
+#endif
+
+  /* Otherwise, pass the Ctrl-C to the first inferior that was resumed
+     in the foreground.  */
+  for (inferior *inf : all_inferiors ())
+    {
+      if (inf->terminal_state != target_terminal_state::is_ours)
+	{
+	  gdb_assert (inf->pid != 0);
+
+#ifndef _WIN32
+	  kill (inf->pid, SIGINT);
+#endif
+	  return;
+	}
+    }
+
+  /* If no inferior was resumed in the foreground, then how did the
+     !is_ours assert above pass?  */
+  gdb_assert_not_reached ("no inferior resumed in the fg found");
+}
+
+/* Per-inferior data key.  */
+static const struct inferior_key<terminal_info> inflow_inferior_data;
+
+terminal_info::~terminal_info ()
+{
+  xfree (run_terminal);
+  xfree (ttystate);
 }
 
 /* Get the current svr4 data.  If none is found yet, add it now.  This
@@ -425,12 +642,9 @@ get_inflow_inferior_data (struct inferior *inf)
 {
   struct terminal_info *info;
 
-  info = (struct terminal_info *) inferior_data (inf, inflow_inferior_data);
+  info = inflow_inferior_data.get (inf);
   if (info == NULL)
-    {
-      info = XCNEW (struct terminal_info);
-      set_inferior_data (inf, inflow_inferior_data, info);
-    }
+    info = inflow_inferior_data.emplace (inf);
 
   return info;
 }
@@ -444,16 +658,8 @@ get_inflow_inferior_data (struct inferior *inf)
 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);
-    }
+  inf->terminal_state = target_terminal_state::is_ours;
+  inflow_inferior_data.clear (inf);
 }
 
 void
@@ -476,10 +682,26 @@ copy_terminal_info (struct inferior *to, struct inferior *from)
   if (tinfo_from->ttystate)
     tinfo_to->ttystate
       = serial_copy_tty_state (stdin_serial, tinfo_from->ttystate);
+
+  to->terminal_state = from->terminal_state;
 }
 
+/* See terminal.h.  */
+
 void
-info_terminal_command (char *arg, int from_tty)
+swap_terminal_info (inferior *a, inferior *b)
+{
+  terminal_info *info_a = inflow_inferior_data.get (a);
+  terminal_info *info_b = inflow_inferior_data.get (b);
+
+  inflow_inferior_data.set (a, info_b);
+  inflow_inferior_data.set (b, info_a);
+
+  std::swap (a->terminal_state, b->terminal_state);
+}
+
+void
+info_terminal_command (const char *arg, int from_tty)
 {
   target_terminal::info (arg, from_tty);
 }
@@ -496,7 +718,7 @@ child_terminal_info (struct target_ops *self, const char *args, int from_tty)
       return;
     }
 
-  if (ptid_equal (inferior_ptid, null_ptid))
+  if (inferior_ptid == null_ptid)
     return;
 
   inf = current_inferior ();
@@ -603,11 +825,11 @@ check_syscall (const char *msg, int result)
 void
 new_tty (void)
 {
-  int tty;
-
   if (inferior_thisrun_terminal == 0)
     return;
 #if !defined(__GO32__) && !defined(_WIN32)
+  int tty;
+
 #ifdef TIOCNOTTY
   /* Disconnect the child process from our controlling terminal.  On some
      systems (SVR4 for example), this may cause a SIGTTOU, so temporarily
@@ -615,12 +837,10 @@ new_tty (void)
   tty = open ("/dev/tty", O_RDWR);
   if (tty > 0)
     {
-      sighandler_t osigttou;
+      scoped_ignore_sigttou ignore_sigttou;
 
-      osigttou = signal (SIGTTOU, SIG_IGN);
       ioctl (tty, TIOCNOTTY, 0);
       close (tty);
-      signal (SIGTTOU, osigttou);
     }
 #endif
 
@@ -688,7 +908,7 @@ static void
 pass_signal (int signo)
 {
 #ifndef _WIN32
-  kill (ptid_get_pid (inferior_ptid), SIGINT);
+  kill (inferior_ptid.pid (), SIGINT);
 #endif
 }
 
@@ -766,13 +986,8 @@ _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);
+  gdb::observers::inferior_exit.attach (inflow_inferior_exit);
 }