To: linux-kernel@vger.kernel.org
From: hpa@zytor.com (H. Peter Anvin)
Subject: Re: __init poisoning for i386, too
Date: Thu, 7 Oct 2004 21:05:45 +0000 (UTC)
Organization: Mostly alphabetical, except Q, which We do not fancy
Message-ID: <ck4b39$fmp$1@terminus.zytor.com>
References: <20041006221854.GA1622@elf.ucw.cz> <20041007061610.GU9106@holomorphy.com>
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Followup to:  <20041007061610.GU9106@holomorphy.com>
By author:    William Lee Irwin III <wli@holomorphy.com>
In newsgroup: linux.dev.kernel
>
> On Thu, Oct 07, 2004 at 12:18:55AM +0200, Pavel Machek wrote:
> > Overwrite __init section so calls to __init functions from normal code
> > are catched, reliably. I wonder if this should be configurable... but
> > it is configurable on x86-64 so I copied it. Please apply,
> 
> Any chance we could:
> (a) set the stuff to 0x0f0b so illegal instructions come of it; jumps are
> 	most often aligned to something > 16 bits anyway
> (b) poison __initdata, memsetting to some bit pattern oopsable to dereference
> 

What's wrong with using 0xCC (breakpoint instruction)?

If you want an illegal instruction, 0xFF 0xFF is an illegal
instruction, so filling memory with 0xFF will do what you want.

	-hpa
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