ARM processor mode, kernel startup, Hyp / secure state

[Ian Jackson]

Dave Martin writes ("Re: ARM processor mode, kernel startup, Hyp / secure state"):
> There may be a safe way to do this check -- for example, on ARM1176
> and Cortex-A8 there is a CP14 debug status/control register that you can
> read which includes a flag indicating which world you're in.  This isn't part
> of the architecture though and may be different/not possible on some
> CPUs.

Yes.  I don't think we can write this into a boot protocol spec unless
we have some architectural way of doing it.

> All in all, it's better to engineer things so that the check doesn't need to
> be done at all.

Yes, in principle.

> Note that in real deployments, the kernel is not an ELF image and
> therefore cannot have notes.

Yes.  But in the future it will do, surely ?  I mean, we're working on
bootloader protocols and this part (to do with startup cpu states and
ownership of the various privilege levels) is only part of it.

Ian.