[PATCH v3] Add decoding for evdev ioctls.

[Dmitry V. Levin]

On Fri, Feb 13, 2015 at 04:41:25PM +0100, Etienne Gemsa wrote:
[...]
> Oops, the last patch was not the one I intended to send. Please check this one instead,
> thank you.

This one fails to build, too.

> > > +		if (_IOC_DIR(code) != _IOC_WRITE)
> > > +			return 0;
> 
> > It's not easy to implement correctly this way.
> > sys_ioctl() uses return code of this function only on exit of syscall,
> > so extra case should be taken to return proper code on exit of _IOW ioctls.
> >
> > I'd invert the checks for syscall state and ioctl direction:
> 
> Sorry, I do not understand why it would be better to invert the checks.

Inverted checks are easier to implement correctly: there is no much
difference with _IOR ioctls that are decoded on exit, but it's a bit more
tricky with _IOW ioctls - they are decoded on enter but the return code that
matters is the one that is returned on exit.

[...]
> +		/* On exiting, we should only decode _IOR ioctls */
> +		if (syserror(tcp)) {
> +			if (_IOC_DIR(code) != _IOC_READ)
> +				return 1;
> +			else
> +				return 0;
> +		}
> +		/* Write ioctls are already decoded */
> +		if (_IOC_DIR(code) != _IOC_READ)
> +			return 1;

This is a good illustration:  evdev_ioctl returns 1 on exit of any
non-_IOR ioctl, including those ioctls for which it returned 0 on enter.


-- 
ldv
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