Messages in this thread | | | From | Andy Lutomirski <> | Date | Thu, 5 Jan 2017 12:18:34 -0800 | Subject | Re: [RFC] x86/mm/KASLR: Remap GDTs at fixed location |
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On Thu, Jan 5, 2017 at 11:03 AM, Thomas Garnier <thgarnie@google.com> wrote: > On Thu, Jan 5, 2017 at 10:58 AM, Arjan van de Ven <arjan@linux.intel.com> wrote: >> On 1/5/2017 9:54 AM, Thomas Garnier wrote: >> >>> >>> That's my goal too. I started by doing a RO remap and got couple >>> problems with hibernation. I can try again for the next iteration or >>> delay it for another patch. I also need to look at KVM GDT usage, I am >>> not familiar with it yet. >> >> >> don't we write to the GDT as part of the TLS segment stuff for glibc ? >> > > Not sure which glibc feature it is. > > In this design, you can write to the GDT per-cpu variable that will > remain read-write. You just need to make the remapping writeable when > we load task registers (ltr) then the processor use the current GDT > address. At least that the case I know, I might find more through > testing.
Hmm. I bet that if we preset the accessed bits in all the segments then we don't need it to be writable in general. But your point about set_thread_area (TLS) is well taken. However, I strongly suspect that we could make set_thread_area unconditionally set the accessed bit and no one would ever notice.
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