From: "H. Peter Anvin" <hpa@zytor.com>
To: Andrew Morton <akpm@osdl.org>
Cc: Reinette Chatre <reinette.chatre@linux.intel.com>,
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: Wed, 04 Oct 2006 18:40:06 -0700 [thread overview]
Message-ID: <45246276.6000908@zytor.com> (raw)
In-Reply-To: <20061004181003.6dae6065.akpm@osdl.org>
Andrew Morton wrote:
> 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.
On some architectures, kernel and user space are separate, overlapping
address spaces.
If __bitmap_parse was an inline (and not exported), this would be okay;
as it is, you end up doing the test dynamically under all circumstances,
even though in most (if not all) cases the address space is know a priori.
-hpa
next prev parent reply other threads:[~2006-10-05 1:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-05 0:56 [PATCH] bitmap: separate bitmap parsing for user buffer and kernel buffer 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 ` H. Peter Anvin [this message]
2006-10-05 19:57 ` [PATCH] bitmap: separate bitmap parsing for user buffer and kernel buffer Andi Kleen
2006-10-05 20:38 ` Andrew Morton
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