linux-kernel - Re: /proc/kcore has a unreasonable size(281474974617600) in x86

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Message-ID: <m1ab4i11zx.fsf@fess.ebiederm.org>
Date:	Mon, 08 Jun 2009 21:10:10 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Américo Wang <xiyou.wangcong@...il.com>
Cc:	Tao Ma <tao.ma@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: /proc/kcore has a unreasonable size(281474974617600) in x86_64  2.6.30-rc8.

Américo Wang <xiyou.wangcong@...il.com> writes:

> On Mon, Jun 8, 2009 at 4:00 PM, Tao Ma<tao.ma@...cle.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@...s2-test2 ~]$ dmesg|grep "high memory"
>> high memory ffff88013c000000, size 5301604352
>> [taoma@...s2-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.

Eric

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