Move ptmx into pty(4).

Now that pty(4) is a loadable kernel module, I'd better move /dev/ptmx
in there as well. This means that pty(4) now provides almost all
pseudo-terminal compatibility code. This means it's very easy to test
whether applications use the proper library interfaces when allocating
pseudo-terminals (namely posix_openpt and openpty).

share/man/man4/pts.4

@@ -147,15 +147,6 @@ The files used by this
 pseudo-terminals implementation are:
 .Pp
 .Bl -tag -width ".Pa /dev/pts/[num]"
-.It Pa /dev/ptmx
-Control device, returns a file descriptor to a new master
-pseudo-terminal when opened.
-This device should not be opened directly.
-It's only available for binary compatibility.
-New devices should only be allocated with
-.Xr posix_openpt 2
-and
-.Xr openpty 3 .
 .It Pa /dev/pts/[num]
 Pseudo-terminal slave devices.
 .El

share/man/man4/pty.4

@@ -32,7 +32,7 @@
 .Os
 .Sh NAME
 .Nm pty
-.Nd BSD-style compatibility pseudo-terminal driver
+.Nd BSD-style and System V-style compatibility pseudo-terminal driver
 .Sh SYNOPSIS
 .Cd "device pty"
 .Sh DESCRIPTION
@@ -48,6 +48,12 @@ driver.
 A device node for this terminal shall be created, which has the name
 .Pa /dev/ttyXX .
 .Pp
+The
+.Nm
+driver also provides a cloning System V
+.Pa /dev/ptmx
+device.
+.Pp
 New code should not try to allocate pseudo-terminals using this
 interface.
 It is only provided for compatibility with older C libraries
@@ -63,6 +69,9 @@ device names:
 Pseudo-terminal master devices.
 .It Pa /dev/tty[l-sL-S][0-9a-v]
 Pseudo-terminal slave devices.
+.It Pa /dev/ptmx
+Control device, returns a file descriptor to a new master
+pseudo-terminal when opened.
 .El
 .Sh DIAGNOSTICS
 None.
@@ -75,7 +84,7 @@ A
 pseudo-terminal driver appeared in
 .Bx 4.2 .
 .Sh BUGS
-Unlike previous implementations, the master slave device nodes are
+Unlike previous implementations, the master and slave device nodes are
 destroyed when the PTY becomes unused.
 A call to
 .Xr stat 2

sys/dev/pty/pty.c

@@ -47,6 +47,9 @@ __FBSDID("$FreeBSD$");
  * the pts(4) driver. We just call into pts(4) to create the actual PTY.
  * To make sure we don't use the same PTY multiple times, we abuse
  * si_drv1 inside the cdev to mark whether the PTY is in use.
+ *
+ * It also implements a /dev/ptmx device node, which is useful for Linux
+ * binary emulation.
  */
 
 static unsigned int pty_warningcnt = 1;
@@ -118,6 +121,20 @@ pty_clone(void *arg, struct ucred *cr, char *name, int namelen,
 	    NULL, UID_ROOT, GID_WHEEL, 0666, "%s", name);
 }
 
+static int
+ptmx_fdopen(struct cdev *dev __unused, int fflags, struct thread *td,
+    struct file *fp)
+{
+
+	return (pts_alloc(fflags & (FREAD|FWRITE), td, fp));
+}
+
+static struct cdevsw ptmx_cdevsw = {
+	.d_version	= D_VERSION,
+	.d_fdopen	= ptmx_fdopen,
+	.d_name		= "ptmx",
+};
+
 static int
 pty_modevent(module_t mod, int type, void *data)
 {
@@ -125,6 +142,7 @@ pty_modevent(module_t mod, int type, void *data)
         switch(type) {
         case MOD_LOAD: 
 		EVENTHANDLER_REGISTER(dev_clone, pty_clone, 0, 1000);
+		make_dev(&ptmx_cdevsw, 0, UID_ROOT, GID_WHEEL, 0666, "ptmx");
 		break;
 	case MOD_SHUTDOWN:
 		break;

sys/kern/tty_pts.c

@@ -32,7 +32,7 @@ __FBSDID("$FreeBSD$");
 
 /* Add compatibility bits for FreeBSD. */
 #define PTS_COMPAT
-/* Add /dev/ptyXX compat bits. */
+/* Add pty(4) compat bits. */
 #define PTS_EXTERNAL
 /* Add bits to make Linux binaries work. */
 #define PTS_LINUX
@@ -694,7 +694,10 @@ static struct ttydevsw pts_class = {
 	.tsw_free	= ptsdrv_free,
 };
 
-static int
+#ifndef PTS_EXTERNAL
+static
+#endif /* !PTS_EXTERNAL */
+int
 pts_alloc(int fflags, struct thread *td, struct file *fp)
 {
 	int unit, ok;
@@ -815,29 +818,11 @@ posix_openpt(struct thread *td, struct posix_openpt_args *uap)
 	return (0);
 }
 
-#if defined(PTS_COMPAT) || defined(PTS_LINUX)
-static int
-ptmx_fdopen(struct cdev *dev, int fflags, struct thread *td, struct file *fp)
-{
-
-	return (pts_alloc(fflags & (FREAD|FWRITE), td, fp));
-}
-
-static struct cdevsw ptmx_cdevsw = {
-	.d_version	= D_VERSION,
-	.d_fdopen	= ptmx_fdopen,
-	.d_name		= "ptmx",
-};
-#endif /* PTS_COMPAT || PTS_LINUX */
-
 static void
 pts_init(void *unused)
 {
 
 	pts_pool = new_unrhdr(0, INT_MAX, NULL);
-#if defined(PTS_COMPAT) || defined(PTS_LINUX)
-	make_dev(&ptmx_cdevsw, 0, UID_ROOT, GID_WHEEL, 0666, "ptmx");
-#endif /* PTS_COMPAT || PTS_LINUX */
 }
 
 SYSINIT(pts, SI_SUB_DRIVERS, SI_ORDER_MIDDLE, pts_init, NULL);

sys/sys/tty.h

@@ -202,6 +202,7 @@ void	tty_info(struct tty *tp);
 void	ttyconsdev_select(const char *name);
 
 /* Pseudo-terminal hooks. */
+int	pts_alloc(int fflags, struct thread *td, struct file *fp);
 int	pts_alloc_external(int fd, struct thread *td, struct file *fp,
     struct cdev *dev, const char *name);