Userland components in Ring 1/2 (where kernel is in ring 0) to provide protection from less trusted components

18 Sep 2020

      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.

Isaac Beckett

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