Messages in this thread | | | Date | Tue, 6 Mar 2018 09:38:17 +0100 | From | Joerg Roedel <> | Subject | Re: [PATCH 07/34] x86/entry/32: Restore segments before int registers |
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On Mon, Mar 05, 2018 at 01:58:32PM -0800, Linus Torvalds wrote: > On Mon, Mar 5, 2018 at 1:35 PM, Joerg Roedel <joro@8bytes.org> wrote: > > I could probably add some debug instrumentation to check for that in my > > future testing, as there is no NX protection in the user address-range > > for the kernel-cr3. > > Does not NX work with PAE? > > Oh, it looks like the NX bit is marked as "RSVD (must be 0)" in the > PDPDT. Oh well.
I had a version of these patches running which implemented NX on the PDE level by allocating 8k PMD pages. But that ended up needing 5 order-1 allocations for each page-table, which I got to fail pretty easily after some time. So I abandoned this approach for now.
Maybe it can be implemented with order-0 allocations for PMD pages, the open problem is how to link the user and kernel PMD page-pairs together then.
Regards,
Joerg
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