On Thu, Sep 17, 2020, at 12:44 PM, Isaac Beckett wrote: > Hey all, > > I was wondering if it makes sense for someone building a system on seL4 to > run certain drivers or other critical components in a more privileged > environment, but still outside the kernel. Does using a different CPU mode > in this context make sense? My hunch is that the case is no, because x86 > has those extra rings, but ARM only has two modes, Supervisor/System and > User mode, which would make it hard to provide any mechanism for the kernel > to manage privileged components, because of the differences between > platforms.
Other people have commented on the least authority implications but I need to point out that rings 1 and 2 _don't actually do anything_ on modern x86 systems, and by modern I mean since the 386 - they are only used for segment-based protection, page table translation treats 1/2 as equivalent to 0. Since ring 1/2 code can freely overwrite ring 0 code, the IOPL is not relevant either. -s _______________________________________________ Devel mailing list Devel@sel4.systems https://sel4.systems/lists/listinfo/devel
