Messages in this thread | | | Date | Thu, 11 Jul 2013 14:36:38 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 1/2 v3] x86: introduce int3-based instruction patching |
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On 07/11/2013 02:04 PM, Borislav Petkov wrote: > On Thu, Jul 11, 2013 at 01:53:16PM -0700, H. Peter Anvin wrote: >> Has anyone talked to AMD or VIA about this at all? > > I guess I can try to take care of the AMD part. Just to confirm, is this > the exact sequence we're interested in: > > 1. Setup int3 handler for fixup. > > 2. Put a breakpoint (int3) on the first byte of modifying region, and > synchronize code on all CPUs. > > 3. Modify other bytes of modifying region. > > 4. Modify the first byte of modifying region, and synchronize code on > all CPUs. > > 5. Clear int3 handler. > > If a suitable int3 handler is left permanently in place then the > synchronization in step 4 is unnecessary. >
Correct.
-hpa
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