Re: [RFC][PATCH] Randomize kernel base address on boot

From: H. Peter Anvin
Date: Tue May 24 2011 - 19:07:31 EST


On 05/24/2011 02:16 PM, Ingo Molnar wrote:
>
> On some systems holes can be pretty low as well - you'd have to research e820
> maps submitted to lkml to see how common this is - but it's not terribly
> common.
>
> Some really old systems might have a hole between 15MB-16MB - but that's not an
> issue if we load at 16 MB or higher.
>

It definitely happens, and not just at 15-16 MiB either.

Doing this without actually consulting the memory map is dangerous as
hell; plus you have to verify that you're not clobbering anything else,
like the command line, initramfs or the linked list of data.

-hpa
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