change semantics of ldisc ->compat_ioctl()

First of all, make it return int. Returning long when native method
had never allowed that is ridiculous and inconvenient.

More importantly, change the caller; if ldisc ->compat_ioctl() is NULL
or returns -ENOIOCTLCMD, tty_compat_ioctl() will try to feed cmd and
compat_ptr(arg) to ldisc's native ->ioctl().

That simplifies ->compat_ioctl() instances quite a bit - they only
need to deal with ioctls that are neither generic tty ones (those
would get shunted off to tty_ioctl()) nor simple compat pointer ones.

Note that something like TCFLSH won't reach ->compat_ioctl(),
even if ldisc ->ioctl() does handle it - it will be recognized
earlier and passed to tty_ioctl() (and ultimately - ldisc ->ioctl()).

For many ldiscs it means that NULL ->compat_ioctl() does the
right thing. Those where it won't serve (see e.g. n_r3964.c) are
also easily dealt with - we need to handle the numeric-argument
ioctls (calling the native instance) and, if such would exist,
the ioctls that need layout conversion, etc.

All in-tree ldiscs dealt with.

Signed-off-by: Al Viro <[e-mail]>

drivers/bluetooth/hci_ldisc.c

···
 	hci_uart_ldisc.read		= hci_uart_tty_read;
 	hci_uart_ldisc.write		= hci_uart_tty_write;
 	hci_uart_ldisc.ioctl		= hci_uart_tty_ioctl;
+	hci_uart_ldisc.compat_ioctl	= hci_uart_tty_ioctl;
 	hci_uart_ldisc.poll		= hci_uart_tty_poll;
 	hci_uart_ldisc.receive_buf	= hci_uart_tty_receive;
 	hci_uart_ldisc.write_wakeup	= hci_uart_tty_wakeup;

drivers/input/serio/serport.c

···
 
 #ifdef CONFIG_COMPAT
 #define COMPAT_SPIOCSTYPE	_IOW('q', 0x01, compat_ulong_t)
-static long serport_ldisc_compat_ioctl(struct tty_struct *tty,
+static int serport_ldisc_compat_ioctl(struct tty_struct *tty,
 				       struct file *file,
 				       unsigned int cmd, unsigned long arg)
 {

drivers/net/hamradio/6pack.c

···
 #include <linux/ip.h>
 #include <linux/tcp.h>
 #include <linux/semaphore.h>
-#include <linux/compat.h>
 #include <linux/refcount.h>
 
 #define SIXPACK_VERSION    "Revision: 0.3.0"
···
 	return err;
 }
 
-#ifdef CONFIG_COMPAT
-static long sixpack_compat_ioctl(struct tty_struct * tty, struct file * file,
-				unsigned int cmd, unsigned long arg)
-{
-	switch (cmd) {
-	case SIOCGIFNAME:
-	case SIOCGIFENCAP:
-	case SIOCSIFENCAP:
-	case SIOCSIFHWADDR:
-		return sixpack_ioctl(tty, file, cmd,
-				(unsigned long)compat_ptr(arg));
-	}
-
-	return -ENOIOCTLCMD;
-}
-#endif
-
 static struct tty_ldisc_ops sp_ldisc = {
 	.owner		= THIS_MODULE,
 	.magic		= TTY_LDISC_MAGIC,
···
 	.open		= sixpack_open,
 	.close		= sixpack_close,
 	.ioctl		= sixpack_ioctl,
-#ifdef CONFIG_COMPAT
-	.compat_ioctl	= sixpack_compat_ioctl,
-#endif
 	.receive_buf	= sixpack_receive_buf,
 	.write_wakeup	= sixpack_write_wakeup,
 };

drivers/net/hamradio/mkiss.c

···
 #include <linux/skbuff.h>
 #include <linux/if_arp.h>
 #include <linux/jiffies.h>
-#include <linux/compat.h>
 
 #include <net/ax25.h>
 
···
 	return err;
 }
 
-#ifdef CONFIG_COMPAT
-static long mkiss_compat_ioctl(struct tty_struct *tty, struct file *file,
-	unsigned int cmd, unsigned long arg)
-{
-	switch (cmd) {
-	case SIOCGIFNAME:
-	case SIOCGIFENCAP:
-	case SIOCSIFENCAP:
-	case SIOCSIFHWADDR:
-		return mkiss_ioctl(tty, file, cmd,
-				   (unsigned long)compat_ptr(arg));
-	}
-
-	return -ENOIOCTLCMD;
-}
-#endif
-
 /*
  * Handle the 'receiver data ready' interrupt.
  * This function is called by the 'tty_io' module in the kernel when
···
 	.open		= mkiss_open,
 	.close		= mkiss_close,
 	.ioctl		= mkiss_ioctl,
-#ifdef CONFIG_COMPAT
-	.compat_ioctl	= mkiss_compat_ioctl,
-#endif
 	.receive_buf	= mkiss_receive_buf,
 	.write_wakeup	= mkiss_write_wakeup
 };

drivers/net/slip/slip.c

···
 #include <linux/rtnetlink.h>
 #include <linux/if_arp.h>
 #include <linux/if_slip.h>
-#include <linux/compat.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/slab.h>
···
 	}
 }
 
-#ifdef CONFIG_COMPAT
-static long slip_compat_ioctl(struct tty_struct *tty, struct file *file,
-					unsigned int cmd, unsigned long arg)
-{
-	switch (cmd) {
-	case SIOCGIFNAME:
-	case SIOCGIFENCAP:
-	case SIOCSIFENCAP:
-	case SIOCSIFHWADDR:
-	case SIOCSKEEPALIVE:
-	case SIOCGKEEPALIVE:
-	case SIOCSOUTFILL:
-	case SIOCGOUTFILL:
-		return slip_ioctl(tty, file, cmd,
-				  (unsigned long)compat_ptr(arg));
-	}
-
-	return -ENOIOCTLCMD;
-}
-#endif
-
 /* VSV changes start here */
 #ifdef CONFIG_SLIP_SMART
 /* function do_ioctl called from net/core/dev.c
···
 	.close	 	= slip_close,
 	.hangup	 	= slip_hangup,
 	.ioctl		= slip_ioctl,
-#ifdef CONFIG_COMPAT
-	.compat_ioctl	= slip_compat_ioctl,
-#endif
 	.receive_buf	= slip_receive_buf,
 	.write_wakeup	= slip_write_wakeup,
 };

drivers/net/wan/x25_asy.c

···
 #include <linux/lapb.h>
 #include <linux/init.h>
 #include <linux/rtnetlink.h>
-#include <linux/compat.h>
 #include <linux/slab.h>
 #include <net/x25device.h>
 #include "x25_asy.h"
···
 	}
 }
 
-#ifdef CONFIG_COMPAT
-static long x25_asy_compat_ioctl(struct tty_struct *tty, struct file *file,
-			 unsigned int cmd,  unsigned long arg)
-{
-	switch (cmd) {
-	case SIOCGIFNAME:
-	case SIOCSIFHWADDR:
-		return x25_asy_ioctl(tty, file, cmd,
-				     (unsigned long)compat_ptr(arg));
-	}
-
-	return -ENOIOCTLCMD;
-}
-#endif
-
 static int x25_asy_open_dev(struct net_device *dev)
 {
 	struct x25_asy *sl = netdev_priv(dev);
···
 	.open		= x25_asy_open_tty,
 	.close		= x25_asy_close_tty,
 	.ioctl		= x25_asy_ioctl,
-#ifdef CONFIG_COMPAT
-	.compat_ioctl	= x25_asy_compat_ioctl,
-#endif
 	.receive_buf	= x25_asy_receive_buf,
 	.write_wakeup	= x25_asy_write_wakeup,
 };

drivers/tty/n_gsm.c

···
 	}
 }
 
-#ifdef CONFIG_COMPAT
-static long gsmld_compat_ioctl(struct tty_struct *tty, struct file *file,
-		       unsigned int cmd, unsigned long arg)
-{
-	return gsmld_ioctl(tty, file, cmd, arg);
-}
-#endif
-
 /*
  *	Network interface
  *
···
 	.flush_buffer    = gsmld_flush_buffer,
 	.read            = gsmld_read,
 	.write           = gsmld_write,
-#ifdef CONFIG_COMPAT
-	.compat_ioctl    = gsmld_compat_ioctl,
-#endif
 	.ioctl           = gsmld_ioctl,
 	.poll            = gsmld_poll,
 	.receive_buf     = gsmld_receive_buf,

drivers/tty/n_r3964.c

···
 		const unsigned char *buf, size_t nr);
 static int r3964_ioctl(struct tty_struct *tty, struct file *file,
 		unsigned int cmd, unsigned long arg);
+#ifdef CONFIG_COMPAT
+static int r3964_compat_ioctl(struct tty_struct *tty, struct file *file,
+		unsigned int cmd, unsigned long arg);
+#endif
 static void r3964_set_termios(struct tty_struct *tty, struct ktermios *old);
 static __poll_t r3964_poll(struct tty_struct *tty, struct file *file,
 		struct poll_table_struct *wait);
···
 	.read = r3964_read,
 	.write = r3964_write,
 	.ioctl = r3964_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = r3964_compat_ioctl,
+#endif
 	.set_termios = r3964_set_termios,
 	.poll = r3964_poll,
 	.receive_buf = r3964_receive_buf,
···
 		return -ENOIOCTLCMD;
 	}
 }
+
+#ifdef CONFIG_COMPAT
+static int r3964_compat_ioctl(struct tty_struct *tty, struct file *file,
+		unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	case R3964_ENABLE_SIGNALS:
+	case R3964_SETPRIORITY:
+	case R3964_USE_BCC:
+		return r3964_ioctl(tty, file, cmd, arg);
+	default:
+		return -ENOIOCTLCMD;
+	}
+}
+#endif
 
 static void r3964_set_termios(struct tty_struct *tty, struct ktermios *old)
 {

drivers/tty/tty_io.c

···
 		return hung_up_tty_compat_ioctl(file, cmd, arg);
 	if (ld->ops->compat_ioctl)
 		retval = ld->ops->compat_ioctl(tty, file, cmd, arg);
+	if (retval == -ENOIOCTLCMD && ld->ops->ioctl)
+		retval = ld->ops->ioctl(tty, file,
+				(unsigned long)compat_ptr(cmd), arg);
 	tty_ldisc_deref(ld);
 
 	return retval;

include/linux/tty_ldisc.h

···
  *	low-level driver can "grab" an ioctl request before the line
  *	discpline has a chance to see it.
  *
- * long	(*compat_ioctl)(struct tty_struct * tty, struct file * file,
+ * int	(*compat_ioctl)(struct tty_struct * tty, struct file * file,
  *		        unsigned int cmd, unsigned long arg);
  *
  *	Process ioctl calls from 32-bit process on 64-bit system
+ *
+ *	NOTE: only ioctls that are neither "pointer to compatible
+ *	structure" nor tty-generic.  Something private that takes
+ *	an integer or a pointer to wordsize-sensitive structure
+ *	belongs here, but most of ldiscs will happily leave
+ *	it NULL.
  *
  * void	(*set_termios)(struct tty_struct *tty, struct ktermios * old);
  *
···
 			 const unsigned char *buf, size_t nr);
 	int	(*ioctl)(struct tty_struct *tty, struct file *file,
 			 unsigned int cmd, unsigned long arg);
-	long	(*compat_ioctl)(struct tty_struct *tty, struct file *file,
+	int	(*compat_ioctl)(struct tty_struct *tty, struct file *file,
 				unsigned int cmd, unsigned long arg);
 	void	(*set_termios)(struct tty_struct *tty, struct ktermios *old);
 	__poll_t (*poll)(struct tty_struct *, struct file *,

net/nfc/nci/uart.c

···
 	.receive_buf	= nci_uart_tty_receive,
 	.write_wakeup	= nci_uart_tty_wakeup,
 	.ioctl		= nci_uart_tty_ioctl,
+	.compat_ioctl	= nci_uart_tty_ioctl,
 };
 
 static int __init nci_uart_init(void)