linux-kernel - Re: [PATCH] use canary at end of stack to indicate overruns at oops time

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Date:	Mon, 21 Apr 2008 21:20:58 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	linux-kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] use canary at end of stack to indicate overruns at oops
 time

On Mon, 21 Apr 2008 22:44:39 -0500
Eric Sandeen <sandeen@...hat.com> wrote:

> Use a canary at the end of the stack to clearly indicate
> at oops time whether the stack has ever overflowed.
> 
> This is a very simple implementation with a couple of
> drawbacks:
> 
> 1) a thread may legitimately use exactly up to the last 
>    word on the stack
> 
>  -- but the chances of doing this and then oopsing later seem slim
> 
> 2) it's possible that the stack usage isn't dense enough
>    that the canary location could get skipped over
> 
>  -- but the worst that happens is that we don't flag the overrun
> 
> With the code in place, an intentionally-bloated stack oops does:
> 
> BUG: unable to handle kernel paging request at ffff8103f84cc680
> IP: [<ffffffff810253df>] update_curr+0x9a/0xa8
> PGD 8063 PUD 0 
> Thread overran stack or stack corrupted
> Oops: 0000 [1] SMP 
> CPU 0 

I like this but I wonder if it's useful to do this for the irq stacks too;

either way

Acked-by: Arjan van de Ven <arjan@...ux.intel.com>

(I'll also add detection of your printk to the kerneloops.org website)
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