linux-kernel - Re: Wanted: simple, safe x86 stack overflow detection

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Message-ID: <Pine.LNX.4.64.0703061937450.19813@blonde.wat.veritas.com>
Date:	Tue, 6 Mar 2007 19:43:41 +0000 (GMT)
From:	Hugh Dickins <hugh@...itas.com>
To:	Chuck Ebbert <cebbert@...hat.com>
cc:	Bill Irwin <bill.irwin@...cle.com>,
	Andi Kleen <andi@...stfloor.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Wanted: simple, safe x86 stack overflow detection

On Tue, 6 Mar 2007, Chuck Ebbert wrote:
> 
> In the 4k/4k stack i386 kernel, is there any fundamental reason it
> can't be 4k/8k? We seem to be mostly hitting problems in overflowing
> the IRQ stack... I think. Overhead would only be 4k per CPU for that.

For all of history prior to 2.6.20, there's been the fundamental
reason that even interrupt stacks need to access current_thread_info,
and that involved the (THREAD_SIZE - 1) mask.  But 2.6.20's read_pda
using %gs gets away from that: my guess is that it's now possible
for i386 to use different sized stacks.

Hugh
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