The IRQ handler has had a major changes to manage syscall, reschedule
and interrupt from user thread and stack guard.
Add userspace support:
- Use a global variable to know if the current execution is user or
machine. The location of this variable is read only for all user
thread and read/write for kernel thread.
- Memory shared is supported.
- Use dynamic allocation to optimize PMP slot usage. If the area size
is a power of 2, only one PMP slot is used, else 2 are used.
Add stack guard support:
- Use MPRV bit to force PMP rules to machine mode execution.
- IRQ stack have a locked stack guard to avoid re-write PMP
configuration registers for each interruption and then win some
cycle.
- The IRQ stack is used as "temporary" stack at the beginning of IRQ
handler to save current ESF. That avoid to trigger write fault on
thread stack during store ESF which that call IRQ handler to
infinity.
- A stack guard is also setup for privileged stack of a user thread.
Thread:
- A PMP setup is specific to each thread. PMP setup are saved in each
thread structure to improve reschedule performance.
Signed-off-by: Alexandre Mergnat <amergnat@baylibre.com>
Reviewed-by: Nicolas Royer <nroyer@baylibre.com>
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