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SubjectRe: using segmentation in the kernel
Alon Bar-Lev wrote:
> Brian Gerst wrote:
>
>> Jonathan M. McCune wrote:
>>
>>> Hello,
>>>
>> 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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