Re: using segmentation in the kernel

From: Brian Gerst
Date: Tue Oct 11 2005 - 16:15:53 EST

Alon Bar-Lev wrote:
Brian Gerst wrote:

Jonathan M. McCune wrote:


Why send the kernel back to the 2.0 days? There is no valid reason for doing this with they way x86 segmentation works, which is why it was done away with in 2.1.

But with segmentation you can set code to be read-only, disallow execution from stack, separate modules so that they will not affect kernel and more...

The main problem with segmentation is that it is x86 specific...

Too much pain for for not enough gain. Segments are not fine-grained enough to work well. Look at the PaX and execshield hacks for userspace. You are far better off working at the page-table level (RO and NX pages) which has the advantage of being portable.

Brian Gerst
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