To: Amerigo Wang <xiyou.wangcong@gmail.com>
Cc: Tao Ma <tao.ma@oracle.com>, Andrew Morton <akpm@linux-foundation.org>,
       linux-kernel@vger.kernel.org, Alexey Dobriyan <adobriyan@gmail.com>
References: <4A292B0D.8030807@oracle.com> <4A295AFB.80909@kernel.org>
	<4A2A7F33.4030807@oracle.com> <4A2AEBE3.4000100@kernel.org>
	<20090608015242.GB2596@cr0.nay.redhat.com>
	<4A2CA96D.3090502@oracle.com>
	<2375c9f90906072341o2cded749m45bdddfdb499469@mail.gmail.com>
	<4A2CC52B.9010602@oracle.com>
	<2375c9f90906081743p77934f47n8ba1a018d333b95b@mail.gmail.com>
	<m1ab4i11zx.fsf@fess.ebiederm.org>
	<20090611050929.GA2706@cr0.nay.redhat.com>
From: ebiederm@xmission.com (Eric W. Biederman)
Date: Thu, 11 Jun 2009 07:12:14 -0700
In-Reply-To: <20090611050929.GA2706@cr0.nay.redhat.com> (Amerigo Wang's message of "Thu\, 11 Jun 2009 13\:09\:29 +0800")
Message-ID: <m11vpqvozl.fsf@fess.ebiederm.org>
User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.2 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8BIT
Subject: Re: /proc/kcore has a unreasonable size(281474974617600) in x86_64 2.6.30-rc8.
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1933
Lines: 59

Amerigo Wang <xiyou.wangcong@gmail.com> writes:

> On Mon, Jun 08, 2009 at 09:10:10PM -0700, Eric W. Biederman wrote:
>>Américo Wang <xiyou.wangcong@gmail.com> writes:
>>
>>> On Mon, Jun 8, 2009 at 4:00 PM, Tao Ma<tao.ma@oracle.com> wrote:
>>>>>>
>>>>>> But the result is the same
>>>>>
>>>>> Yes?
>>>>> Your printk() shows kcore size is: 5301604352, and in your subject it is
>>>>> 281474974617600...
>>>>>
>>>>> Or they happened in the same time?
>>>>
>>>> yes. the same box and the same linux version.
>>>> A bit strange.
>>>>
>>>> [taoma@ocfs2-test2 ~]$ dmesg|grep "high memory"
>>>> high memory ffff88013c000000, size 5301604352
>>>> [taoma@ocfs2-test2 ~]$ ll /proc/kcore
>>>> -r-------- 1 root root 281474974617600 Jun  8 15:20 /proc/kcore
>>>
>>> Really weird...
>>> They should be the same. This means we have some problem in our procfs.
>>>
>>> And, we have no problem on i386, I, myself, even can't reproduce this on my
>>> x86_64 box...
>>>
>>> Drop Cc to x86 people, add some Cc to proc people. :)
>>>
>>> Eric, Alexey, any ideas?
>>>
>>> Tao, would you like to send us your .config? Thanks.
>>
>>Short of some strange patch applied I would guess that a non-sense /proc/kcore
>>size is related to a kernel memory stomp, stepping on the high_memory variable.
>
> Hello, Eric.
>
> I see the problem now, I think the documentation of /proc/kcore
> is wrong, the size of kcore can be more than the size of physical
> memory, because it also contains the info of kernel modules which
> stay above the mapping of phy memory, see arch/x86/mm/init_64.c.
>
> What do you think?

I think that doesn't make any sense.

I was reading the code.

I smell a nasty problem somewhere.

Eric
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/