linux-kernel - Re: [PATCH] bitmap: separate bitmap parsing for user buffer and kernel buffer

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Message-Id: <200610041833.40866.inaky@linux.intel.com>
Date:	Wed, 4 Oct 2006 18:33:37 -0700
From:	Inaky Perez-Gonzalez <inaky@...ux.intel.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	Reinette Chatre <reinette.chatre@...ux.intel.com>,
	Joe Korty <joe.korty@...r.com>, Paul Jackson <pj@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bitmap: separate bitmap parsing for user buffer and kernel buffer

On Wednesday 04 October 2006 18:10, Andrew Morton wrote:
> On Wed, 4 Oct 2006 17:56:30 -0700
> Reinette Chatre <reinette.chatre@...ux.intel.com> wrote:
> > +			if (is_user) {
> > +				if (__get_user(c, buf++))
> > +					return -EFAULT;
> > +			}
> > +			else
> > +				c = *buf++;
>
> Is this actually needed?  __get_user(kernel_address) works OK and (believe
> it or not, given all the stuff it involves) boils down to a single
> instruction.

We weren't too sure if that'd be true in all kinds of arches and
memory models. If it works for kernel space too, then we can fold
out a lot of code...

Your call, you are the expert :)

--
Inaky
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