This commit aligns the programming of the privileged stack MPU
guard with that of the default stack guard (i.e of supervisor
threads). In particular:
- the guard is programmed BELOW the address indicated in
arch.priv_stack_start; it is, therefore, similar to the
default guard that is programmed BELOW stack_info.start.
An ASSERT is added to confirm that the guard is programmed
inside the thread privilege stack area.
- the stack fail check is updated accordningly
- arch.priv_stack_start is adjusted in arch_userspace_enter(),
to make sure we account for a (possible) guard requirement,
that is, if building with CONFIG_MPU_STACK_GUARD=y.
Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
639eb76729