In ARC's SecureShield, a new secure mode (currently only em) is added.
The secure/normal mode is orthogonal to kernel/user mode. The
differences between secure mode and normal mode are following:
* different irq stack frame. so need to change the definition of
_irq_stack_frame, assembly code.
* new aux regs, e.g, secure status(SEC_STAT), secure vector base
(VECT_BASE_S)
* interrupts and exceptions, secure mode has its own vector base;
interrupt can be configured as secure or normal through the
interrupt priority aux reg.
* secure timers. Two secure timers (secure timer 0 and timer 1) are
added.Here, for simplicity and backwards compatibility original
internal timers (timer 0 and timer1) are used as sys clock of zephyr
* on reset, the processor is in secure mode and secure vector base is
used.
Note: the mix of secure and normal mode is not supported, i.e. it's
assumed that the processor is always in secure mode.
Signed-off-by: Wayne Ren <wei.ren@synopsys.com>
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