3 ms·
Yes they do, but segmentation is practically non-existent and page tables distinguish only between rings 0 and rings 1-3. So no, they aren't very useful, but th
by zvrba 5y ago
Yes they do, but segmentation is practically non-existent and page tables distinguish only between rings 0 and rings 1-3. So no, they aren't very useful, but they do exist and, AFAIK, they're still checked in "far" control transfers.
- tzs 5y agoIt's too bad they have been made useless. I'm not fully sure about this, but I think that if you could have two rings for user code so that applications that want to run untrusted code in a sandbox could run the main application in ring 2 and the sandboxed code in ring 3, you could make the application safe from Spectre attacks from the sandboxed code without giving up performance.
- bonzini 5y agoThe point of Spectre attacks is that they use side channel to infer the target's data from communication between the target and the attacking userspace process. This is possible even over the network, so ring 2 wouldn't help much.