arch: arm64: Enable safe exception stack
This commit mainly enable the safe exception stack including the stack
switch. Init the safe exception stack by calling
z_arm64_safe_exception_stack during the boot stage on every core. Also,
tweaks several files to properly switch the mode with different cases.
1) The same as before, when executing in userspace, SP_EL0 holds the
user stack and SP_EL1 holds the privileged stack, using EL1h mode.
2) When entering exception from EL0 then SP_EL0 will be saved in the
_esf_t structure. SP_EL1 will be the current SP, then retrieves the safe
exception stack to SP_EL0, making sure the always pointing to safe
exception stack as long as the system running in kernel space.
3) When exiting exception from EL1 to EL0 then SP_EL0 will be restored
from the stack value previously saved in the _esf_t structure. Still at
EL1h mode.
4) Either entering or exiting exception from EL1 to EL1, SP_EL0 will
keep holding the safe exception stack unchanged as memtioned above.
5) Do a quick stack check every time entering the exception from EL1 to
EL1. If check fail, set SP_EL1 to safe exception stack, and then handle
the fatal error.
Overall, the exception from user mode will be handled with kernel stack
at the assumption that it is impossible the stackoverflow happens at the
entry of exception from EL0 to EL1. However the exception from kernel
mode will be firstly checked with the safe exception stack to see if the
kernel stack overflows, because the exception might be triggered by
stack invalid accessing.
Signed-off-by: Jaxson Han <jaxson.han@arm.com>
2 files changed
