linux-kernel - Re: Tough Issue: kernel instruction corruption

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Date:	Sat, 5 Jul 2008 08:17:37 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	"Gavin Shan" <gshan@...atel-lucent.com>
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: Tough Issue: kernel instruction corruption

On Sat, 5 Jul 2008 22:20:46 +0800
"Gavin Shan" <gshan@...atel-lucent.com> wrote:

> Hello, I'm faced a tough issue recently: instructions of kernel
> were corrupted. There has 2 PCI buses on my board and lots
> of PCI devices with DMA capabality involved. I'm suspecting
> the kernel instructions were corrupted by DMA operations driving
> by those PCI devices with DMA capabality. 
> 
> Anybody have tried to protect kernel instructions from this case
> or have any ideas to protect kernel text section?

if you have a modern Intel board, you can enable the IOMMU on it that
will protect the kernel text (well, all of memory) from rogue DMA.
PPC generally has similar capabilities, as do some IBM x86 chipsets.

Without an IOMMU it's basically impossible to protect against such DMA.

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