arm64: Implement Shadow Call Stack

This change implements shadow stack switching, initial SCS set-up,
and interrupt shadow stacks for arm64.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Will Deacon <will@kernel.org>
9 files changed