compat_ioctl: move tape handling into drivers

MTIOCPOS and MTIOCGET are incompatible between 32-bit and 64-bit user
space, and traditionally have been translated in fs/compat_ioctl.c.

To get rid of that translation handler, move a corresponding
implementation into each of the four drivers implementing those commands.

The interesting part of that is now in a new linux/mtio.h header that
wraps the existing uapi/linux/mtio.h header and provides an abstraction
to let drivers handle both cases easily. Using an in_compat_syscall()
check, the caller does not have to keep track of whether this was
called through .unlocked_ioctl() or .compat_ioctl().

Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "Kai Mäkisara" <Kai.Makisara@kolumbus.fi>
Cc: linux-scsi@vger.kernel.org
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 21 insertions, 6 deletions

diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
index db1a65f4b490..3e7482695f77 100644
--- a/drivers/ide/ide-tape.c
+++ b/drivers/ide/ide-tape.c
@@ -19,6 +19,7 @@
 
 #define IDETAPE_VERSION "1.20"
 
+#include <linux/compat.h>
 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/string.h>
@@ -1407,14 +1408,10 @@ static long do_idetape_chrdev_ioctl(struct file *file,
 		if (tape->drv_write_prot)
 			mtget.mt_gstat |= GMT_WR_PROT(0xffffffff);
 
-		if (copy_to_user(argp, &mtget, sizeof(struct mtget)))
-			return -EFAULT;
-		return 0;
+		return put_user_mtget(argp, &mtget);
 	case MTIOCPOS:
 		mtpos.mt_blkno = position / tape->user_bs_factor - block_offset;
-		if (copy_to_user(argp, &mtpos, sizeof(struct mtpos)))
-			return -EFAULT;
-		return 0;
+		return put_user_mtpos(argp, &mtpos);
 	default:
 		if (tape->chrdev_dir == IDETAPE_DIR_READ)
 			ide_tape_discard_merge_buffer(drive, 1);
@@ -1432,6 +1429,22 @@ static long idetape_chrdev_ioctl(struct file *file,
 	return ret;
 }
 
+static long idetape_chrdev_compat_ioctl(struct file *file,
+				unsigned int cmd, unsigned long arg)
+{
+	long ret;
+
+	if (cmd == MTIOCPOS32)
+		cmd = MTIOCPOS;
+	else if (cmd == MTIOCGET32)
+		cmd = MTIOCGET;
+
+	mutex_lock(&ide_tape_mutex);
+	ret = do_idetape_chrdev_ioctl(file, cmd, arg);
+	mutex_unlock(&ide_tape_mutex);
+	return ret;
+}
+
 /*
  * Do a mode sense page 0 with block descriptor and if it succeeds set the tape
  * block size with the reported value.
@@ -1886,6 +1899,8 @@ static const struct file_operations idetape_fops = {
 	.read		= idetape_chrdev_read,
 	.write		= idetape_chrdev_write,
 	.unlocked_ioctl	= idetape_chrdev_ioctl,
+	.compat_ioctl	= IS_ENABLED(CONFIG_COMPAT) ?
+			  idetape_chrdev_compat_ioctl : NULL,
 	.open		= idetape_chrdev_open,
 	.release	= idetape_chrdev_release,
 	.llseek		= noop_llseek,