linux-kernel - Re: [PATCH 2/3] kernel.h: add u64_to_user

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Date:	Thu, 21 Apr 2016 10:36:12 -0300
From:	Gustavo Padovan <gustavo@...ovan.org>
To:	Joe Perches <joe@...ches.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org,
	dri-devel@...ts.freedesktop.org,
	Daniel Stone <daniels@...labora.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	Riley Andrews <riandrews@...roid.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Rob Clark <robdclark@...il.com>,
	Greg Hackmann <ghackmann@...gle.com>,
	John Harrison <John.C.Harrison@...el.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Airlie <airlied@...ux.ie>,
	Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH 2/3] kernel.h: add u64_to_user_ptr()

2016-04-20 Joe Perches <joe@...ches.com>:

> On Wed, 2016-04-20 at 16:18 -0300, Gustavo Padovan wrote:
> > From: Gustavo Padovan <gustavo.padovan@...labora.co.uk>
> > 
> > This function had copies in 3 different files. Unify them in kernel.h.
> []
> > diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> []
> > @@ -53,6 +53,12 @@
> > 
> >  #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
> >  
> > +static inline void __user *u64_to_user_ptr(u64 address)
> > +{
> > +	typecheck(u64, address);
> > +	return (void __user *)(uintptr_t)address;
> > +}
> > +
> 
> This won't work because by the time address is checked
> address is already u64
> 
> This would need to be something like
> 
> #define u64_to_user_ptr(x)	\
> ({				\
> 	typecheck(u64, x);	\
> 	u64_to_user_ptr(x);	\
> })

Indeed, thanks for noting and for the suggestion.

	Gustavo