PTO-ARCH-SYSTEM-REGISTERS-ACCESS-CONTROL

1// PTO-UNIT: {"id":"PTO-ARCH-SYSTEM-REGISTERS-ACCESS-CONTROL","surface":"arch","classification":["system-registers","access-control"],"depends_on":["PTO-ARCH-PROGRAMMING-MODEL-EXECUTION-CONTEXT"]}2readonly func CurrentACR() => AccessControlRing3begin4    return _CurrentACR;5end;6
7pure func AccessControlRingBits(ring: AccessControlRing) => bits(4)8begin9    case ring of10        when 0 => return '0000';11        when 1 => return '0001';12        when 2 => return '0010';13        when 3 => return '0011';14        when 4 => return '0100';15        when 5 => return '0101';16        when 6 => return '0110';17        when 7 => return '0111';18        when 8 => return '1000';19        when 9 => return '1001';20        when 10 => return '1010';21        when 11 => return '1011';22        when 12 => return '1100';23        when 13 => return '1101';24        when 14 => return '1110';25        when 15 => return '1111';26    end;27end;28
29func SetCurrentACR(ring: AccessControlRing)30begin31    _CurrentACR = ring;32    _SystemRegisters.core_state[3:0] = AccessControlRingBits(ring);33end;34
35pure func TrapTargetForFault(source: AccessControlRing) => AccessControlRing36begin37    if source == 0 then return 0; else return 1; end;38end;39
40pure func TrapTargetForInterrupt(source: AccessControlRing) => AccessControlRing41begin42    return TrapTargetForFault(source);43end;44
45pure func ServiceRequestPermitted(source: AccessControlRing,46                                  request_type: bits(4)) => boolean47begin48    if source == 1 then49        return request_type == '0000' || request_type == '0010';50    elsif source >= 2 then51        return UInt(request_type) <= 2;52    else53        return FALSE;54    end;55end;56
57pure func ServiceRequestTarget(source: AccessControlRing,58                               request_type: bits(4)) => AccessControlRing59begin60    assert ServiceRequestPermitted(source, request_type);61    if request_type == '0001' then return 1; else return 0; end;62end;63
64readonly func TrapVectorEntry(target: AccessControlRing,65                              fault_address: Word) => Word66begin67    let index = ((target * 4096) + 0x0f01) as SystemRegisterFileIndex;68    let vector_base = _ExtendedSystemRegisters[[index]];69    if vector_base == Zeros{PTO_XLEN} then return fault_address;70    else return vector_base;71    end;72end;73