From: Andrew Morton <akpm@osdl.org>
To: Andi Kleen <ak@suse.de>
Cc: Joe Korty <joe.korty@ccur.com>,
Inaky Perez-Gonzalez <inaky@linux.intel.com>,
Paul Jackson <pj@sgi.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] bitmap: separate bitmap parsing for user buffer and kernel buffer
Date: Thu, 5 Oct 2006 13:38:07 -0700 [thread overview]
Message-ID: <20061005133807.97827533.akpm@osdl.org> (raw)
In-Reply-To: <p73odsqzgbz.fsf@verdi.suse.de>
On 05 Oct 2006 21:57:04 +0200
Andi Kleen <ak@suse.de> wrote:
> Andrew Morton <akpm@osdl.org> writes:
>
> > On Wed, 4 Oct 2006 17:56:30 -0700
> > Reinette Chatre <reinette.chatre@linux.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.
>
> It is needed on lots of architectures that use separate address spaces
> like sparc64, m68k, s390 (and on x86 with 4:4 patches)
>
It needs set_fs(KERNEL_DS) if we're going to use __get_user() on both
callpaths.
I think we'll stick with the `is_user' version - less tricky, clearer.
prev parent reply other threads:[~2006-10-05 20:39 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-05 0:56 Reinette Chatre
2006-10-05 1:10 ` Andrew Morton
2006-10-05 1:33 ` Inaky Perez-Gonzalez
2006-10-05 1:57 ` Andrew Morton
2006-10-05 19:49 ` [PATCH] bitmap: parse kernel and user buffers Reinette Chatre
2006-10-05 21:48 ` [PATCH] bitmap: parse input from " Reinette Chatre
2006-10-05 22:32 ` Inaky Perez-Gonzalez
2006-10-05 1:40 ` [PATCH] bitmap: separate bitmap parsing for user buffer and kernel buffer H. Peter Anvin
2006-10-05 19:57 ` Andi Kleen
2006-10-05 20:38 ` Andrew Morton [this message]
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