Re: [PATCH 4/7] x86: Add support for rd/wr fs/gs base

Andi Kleen
2014-05-01T21:15:57Z

> If usergs == kernelgs, then ebx will always be 1 and we'll never end
> up in paranoid_userspace.

You may miss a reschedule in this obscure case. It shouldn't really
happen because loading a kernel pointer is not useful for user space.

Doesn't seem like a real issue to me.

We only happen need to handle it to avoid crashing.

> Alternatively, what if the paranoid entry checked whether we're coming
> from userspace at the very beginning and, if so, just jumped to the
> non-paranoid entry?

That would work, but I doubt it would be worth it.

-Andi