linux-kernel - Re: [PATCH] Fix _IOC

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Message-ID: <20140401142852.GA22576@leaf>
Date:	Tue, 1 Apr 2014 07:28:53 -0700
From:	Josh Triplett <josh@...htriplett.org>
To:	Hans Verkuil <hverkuil@...all.nl>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Sparse Mailing-list <linux-sparse@...r.kernel.org>,
	Linux Media Mailing List <linux-media@...r.kernel.org>,
	Christopher Li <sparse@...isli.org>
Subject: Re: [PATCH] Fix _IOC_TYPECHECK sparse error

On Tue, Apr 01, 2014 at 09:04:12AM +0200, Hans Verkuil wrote:
> When running sparse over drivers/media/v4l2-core/v4l2-ioctl.c I get these
> errors:
> 
> drivers/media/v4l2-core/v4l2-ioctl.c:2043:9: error: bad integer constant expression
> drivers/media/v4l2-core/v4l2-ioctl.c:2044:9: error: bad integer constant expression
> drivers/media/v4l2-core/v4l2-ioctl.c:2045:9: error: bad integer constant expression
> drivers/media/v4l2-core/v4l2-ioctl.c:2046:9: error: bad integer constant expression
> 
> etc.
> 
> The root cause of that turns out to be in include/asm-generic/ioctl.h:
> 
> #include <uapi/asm-generic/ioctl.h>
> 
> /* provoke compile error for invalid uses of size argument */
> extern unsigned int __invalid_size_argument_for_IOC;
> #define _IOC_TYPECHECK(t) \
>         ((sizeof(t) == sizeof(t[1]) && \
>           sizeof(t) < (1 << _IOC_SIZEBITS)) ? \
>           sizeof(t) : __invalid_size_argument_for_IOC)
> 
> If it is defined as this (as is already done if __KERNEL__ is not defined):
> 
> #define _IOC_TYPECHECK(t) (sizeof(t))
> 
> then all is well with the world.
> 
> This patch allows sparse to work correctly.
> 
> Signed-off-by: Hans Verkuil <hans.verkuil@...co.com>

Reviewed-by: Josh Triplett <josh@...htriplett.org>

> diff --git a/include/asm-generic/ioctl.h b/include/asm-generic/ioctl.h
> index d17295b..297fb0d 100644
> --- a/include/asm-generic/ioctl.h
> +++ b/include/asm-generic/ioctl.h
> @@ -3,10 +3,15 @@
>  
>  #include <uapi/asm-generic/ioctl.h>
>  
> +#ifdef __CHECKER__
> +#define _IOC_TYPECHECK(t) (sizeof(t))
> +#else
>  /* provoke compile error for invalid uses of size argument */
>  extern unsigned int __invalid_size_argument_for_IOC;
>  #define _IOC_TYPECHECK(t) \
>  	((sizeof(t) == sizeof(t[1]) && \
>  	  sizeof(t) < (1 << _IOC_SIZEBITS)) ? \
>  	  sizeof(t) : __invalid_size_argument_for_IOC)
> +#endif
> +
>  #endif /* _ASM_GENERIC_IOCTL_H */
> 
> --
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