x86 NX support [LWN.net]

x86 NX support

Posted Jun 3, 2004 5:02 UTC (Thu) by rfunk (subscriber, #4054)
Parent article: x86 NX support

<blockquote><i>a longstanding x86 security weakness will be no
more.</i></blockquote>

Well, at least for those running x86-64 machines. The masses of us still
running plain old 32-bit x86 machines get no joy.

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x86 NX support

Posted Jun 3, 2004 9:47 UTC (Thu) by hansl (subscriber, #5086) [Link]

> Well, at least for those running x86-64 machines. The masses of us
> still running plain old 32-bit x86 machines get no joy.

No, as I understand it a 32bit x86 processor with PAE support
(which is what most people run) is supported. But it is somewhat
of a hack since PAE needs to be turned on even with small amounts
(less than 4GB) of memory and it does come at a certain performance
cost.

PAE needs to be turned on because only then there is extra room in
the processors page tables (just 1 bit per page) to mark memory
non-executable.

-Hans

x86 NX support

Posted Jun 3, 2004 14:32 UTC (Thu) by knobunc (subscriber, #4678) [Link]

The quickstart document cited in the article says:

- make sure you have a CPU that has the NX feature. Such CPUs are:
  all 64-bit variants of AMD (Athlon64, Opteron), future CPUs of
  Intel, Transmeta and VIA. (NOTE: 64-bit x86_64 kernels already
  make use of the 64-bit variant of the NX feature - this patch
  is only meant for 32-bit x86 kernels and distributions.)

So you do have to have a compatible processor. This change adds protection when you are running a 32-bit kernel.
-ben