Messages in this thread | | | Date | Thu, 18 Sep 2003 20:48:00 +0100 | From | Jamie Lokier <> | Subject | Re: [PATCH] Athlon/Opteron Prefetch Fix for 2.6.0test5 + numbers |
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Andi Kleen wrote: > > My point is simply that non-zero base GDT segments are possible in > > userspace, and whatever code you add later to add the base should > > be aware of that. > > I don't see how a non standard GDT is possible in user space. The GDT > is only managed by the kernel. 2.6 offers to change it for NPTL, but > that only applies to data segments.
I don't see anything in set_thread_area() which restricts them to data segments. Btw, NPTL isn't the only userspace code which uses this function.
Admittedly it would be quite odd to use set_thread_area() to create and use a GDT code segment - but given that you can do it, it would be _really_ odd if prefetch instructions gave spurious faults in these segments yet were fixed up elsewhere.
> In vm86 mode the user can load a different base without LDT, but that > should not matter here (although it may be better to check for VM86 mode > too)
Shouldn't spurious faults in prefetch instructions in vm86 mode be fixed up too?
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