From f0193d3ea73b966b5dbfa272c8228d743b8856ef Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 13 Sep 2018 22:12:15 -0400 Subject: 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 --- include/linux/tty_ldisc.h | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/tty_ldisc.h b/include/linux/tty_ldisc.h index 840894ca3fc0..b1e6043e9917 100644 --- a/include/linux/tty_ldisc.h +++ b/include/linux/tty_ldisc.h @@ -54,11 +54,17 @@ * 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); * * This function notifies the line discpline that a change has @@ -184,7 +190,7 @@ struct tty_ldisc_ops { 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 *, -- cgit