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This is a great question! What this means is that a software patch cannot fix the speculative execution behavior that causes the PACMAN issue since it is built
by jprx 4y ago
This is a great question! What this means is that a software patch cannot fix the speculative execution behavior that causes the PACMAN issue since it is built directly into how the hardware operates.
- adamsmith143 4y agoSo there is no possible set of instructions that could block the particular behavior in the exploit?
- jprx 4y agoYou could maybe do it with lots of fences or just a ridiculous chain of NOPs after each branch such that the ROB is cleared before you have time to try to load a pointer speculatively. In practice, both of these would probably kill performance, so I don't think either of these are great solutions. Recall we are targeting the kernel where everything needs to be as fast as possible.
- fulafel 4y agoThis gets into the turing completeness tarpit. Yes, it's possible to make a vulnerable implementation emulate a chip that is not vulnerable. And maybe even detect when you don't need to emulate and run natively some of the time.