linux-kernel - Re: [PATCH] Input: serport: Add compat_ioctl routine to support 32bit inputtattach in 64bit systems

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Date:	Mon, 8 Sep 2014 14:28:57 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	John Sung <penmount.touch@...il.com>
Cc:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: serport: Add compat_ioctl routine to support
 32bit inputtattach in 64bit systems

Hi John,

On Fri, Sep 05, 2014 at 09:04:37PM +0800, John Sung wrote:
> When running a 32-bit inputattach utility in a 64-bit system, there will be error code "inputattach: can't set device type". This is caused by the serport device driver not supporting compat_ioctl, so that SPIOCSTYPE ioctl fails.
> 
> Signed-off-by: John Sung <penmount.touch@...il.com>
> ---
>  drivers/input/serio/serport.c |   24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/input/serio/serport.c b/drivers/input/serio/serport.c
> index 0cb7ef5..4b68c29 100644
> --- a/drivers/input/serio/serport.c
> +++ b/drivers/input/serio/serport.c
> @@ -22,6 +22,8 @@
>  #include <linux/serio.h>
>  #include <linux/tty.h>
>  
> +#include <asm/compat.h>
> +
>  MODULE_AUTHOR("Vojtech Pavlik <vojtech@....cz>");
>  MODULE_DESCRIPTION("Input device TTY line discipline");
>  MODULE_LICENSE("GPL");
> @@ -31,6 +33,8 @@ MODULE_ALIAS_LDISC(N_MOUSE);
>  #define SERPORT_ACTIVE	2
>  #define SERPORT_DEAD	3
>  
> +#define SPIOCSTYPE32 (_IOW('q', 0x01, compat_ulong_t))
> +
>  struct serport {
>  	struct tty_struct *tty;
>  	wait_queue_head_t wait;
> @@ -221,6 +225,25 @@ static int serport_ldisc_ioctl(struct tty_struct * tty, struct file * file, unsi
>  	return -EINVAL;
>  }
>  
> +static long serport_ldisc_compat_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg)
> +{
> +	struct serport *serport = (struct serport*) tty->disc_data;
> +	unsigned long type;
> +
> +	if (cmd == SPIOCSTYPE32) {
> +		if (get_user(type, (unsigned long __user *) arg))
> +			return -EFAULT;
> +
> +		serport->id.proto = type & 0x000000ff;
> +		serport->id.id	  = (type & 0x0000ff00) >> 8;
> +		serport->id.extra = (type & 0x00ff0000) >> 16;
> +
> +		return 0;
> +	}
> +
> +	return -EINVAL;
> +}
> +
>  static void serport_ldisc_write_wakeup(struct tty_struct * tty)
>  {
>  	struct serport *serport = (struct serport *) tty->disc_data;
> @@ -243,6 +266,7 @@ static struct tty_ldisc_ops serport_ldisc = {
>  	.close =	serport_ldisc_close,
>  	.read =		serport_ldisc_read,
>  	.ioctl =	serport_ldisc_ioctl,
> +	.compat_ioctl =	serport_ldisc_compat_ioctl,

I think this, and serport_ldisc_compat_ioctl definition, should be
protected by #ifdef OCNFIG_COMPAT. Also, instea dof replicating the
ioctl definition and parsing, could we combine the code a bit?

Thanks.

-- 
Dmitry
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