Cygwin: console: Make the console accessible from other terminals.

Previously, the console device could not be accessed from other terminals.
Due to this limitation, GNU screen and tmux cannot be opened in console.
With this patch, console device can be accessed from other TTYs, such as
other consoles or ptys. Thanks to this patch, screen and tmux get working
in console.

Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>

winsup/cygwin/devices.cc

@@ -69,6 +69,21 @@ exists_ntdev_silent (const device& dev)
   return exists_ntdev (dev) ? -1 : false;
 }
 
+static BOOL CALLBACK
+enum_cons_dev (HWND hw, LPARAM lp)
+{
+  unsigned long *bitmask = (unsigned long *) lp;
+  HANDLE h = NULL;
+  fhandler_console::console_state *cs;
+  if ((cs = fhandler_console::open_shared_console (hw, h)))
+    {
+      *bitmask |= (1UL << cs->tty_min_state.getntty ());
+      UnmapViewOfFile ((void *) cs);
+      CloseHandle (h);
+    }
+  return TRUE;
+}
+
 static int
 exists_console (const device& dev)
 {
@@ -81,8 +96,13 @@ exists_console (const device& dev)
       return cygheap && cygheap->ctty && cygheap->ctty->is_console ()
 	&& fhandler_console::exists ();
     default:
-      /* Only show my own console device (for now?) */
-      return iscons_dev (myself->ctty) && myself->ctty == devn;
+      if (dev.get_minor () < MAX_CONS_DEV)
+	{
+	  unsigned long bitmask = 0;
+	  EnumWindows (enum_cons_dev, (LPARAM) &bitmask);
+	  return bitmask & (1UL << dev.get_minor ());
+	}
+      return false;
     }
 }
 

winsup/cygwin/devices.in

@@ -65,6 +65,21 @@ exists_ntdev_silent (const device& dev)
   return exists_ntdev (dev) ? -1 : false;
 }
 
+static BOOL CALLBACK
+enum_cons_dev (HWND hw, LPARAM lp)
+{
+  unsigned long *bitmask = (unsigned long *) lp;
+  HANDLE h = NULL;
+  fhandler_console::console_state *cs;
+  if ((cs = fhandler_console::open_shared_console (hw, h)))
+    {
+      *bitmask |= (1UL << cs->tty_min_state.getntty ());
+      UnmapViewOfFile ((void *) cs);
+      CloseHandle (h);
+    }
+  return TRUE;
+}
+
 static int
 exists_console (const device& dev)
 {
@@ -77,8 +92,13 @@ exists_console (const device& dev)
       return cygheap && cygheap->ctty && cygheap->ctty->is_console ()
 	&& fhandler_console::exists ();
     default:
-      /* Only show my own console device (for now?) */
-      return iscons_dev (myself->ctty) && myself->ctty == devn;
+      if (dev.get_minor () < MAX_CONS_DEV)
+	{
+	  unsigned long bitmask = 0;
+	  EnumWindows (enum_cons_dev, (LPARAM) &bitmask);
+	  return bitmask & (1UL << dev.get_minor ());
+	}
+      return false;
     }
 }