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DCPS3

Debug Change PE State to EL3 allows the debugger to move the PE into EL3 from a lower Exception Level or to a specific mode at the current Exception Level.

DCPS3 is undefined if any of:

  • The PE is in Non-debug state.
  • EL3 is not implemented.
  • EDSCR.SDD is set to 1.

When the PE executes DCPS3:

  • If EL3 is using AArch32, the PE enters Monitor mode and LR_mon, SPSR_mon, DLR and DSPSR become UNKNOWN. If DCPS3 is executed in Monitor mode, SCR.NS is cleared to 0.
  • If EL3 is using AArch64, the PE enters EL3 using AArch64, selects SP_EL3, and ELR_EL3, ESR_EL3, SPSR_EL3, DLR_EL0 and DSPSR_EL0 become UNKNOWN.

For more information on the operation of this instruction, see DCPS.

T1

15141312111098765432101514131211109876543210
11110111100011111000000000000011

T1

DCPS3

if !HaveEL(EL3) then UNDEFINED;

Operation

if !Halted() || EDSCR.SDD == '1' then UNDEFINED;

if ELUsingAArch32(EL3) then
    from_secure = IsSecure();
    if PSTATE.M == M32_Monitor then SCR.NS = '0';
    AArch32.WriteMode(M32_Monitor);
    if HavePANExt() then
        if !from_secure then
            PSTATE.PAN = '0';
        elsif SCTLR.SPAN == '0' then
            PSTATE.PAN = '1';
    PSTATE.E = SCTLR.EE;

    LR_mon = bits(32) UNKNOWN;
    SPSR_mon = bits(32) UNKNOWN;

    DLR = bits(32) UNKNOWN;
    DSPSR = bits(32) UNKNOWN;
else                                        // Targeting EL3 using AArch64
    AArch64.MaybeZeroRegisterUppers();
    MaybeZeroSVEUppers(EL3);
    PSTATE.nRW = '0';
    PSTATE.SP = '1';
    PSTATE.EL = EL3;
    if HaveUAOExt() then PSTATE.UAO = '0';

    ELR_EL3 = bits(64) UNKNOWN;
    ESR_EL3 = bits(32) UNKNOWN;
    SPSR_EL3 = bits(32) UNKNOWN;

    DLR_EL0 = bits(64) UNKNOWN;
    DSPSR_EL0 = bits(32) UNKNOWN;

    sync_errors = HaveIESB() && SCTLR_EL3.IESB == '1';
    if HaveDoubleFaultExt() && SCR_EL3.EA == '1' && SCR_EL3.NMEA == '1' then
        sync_errors = TRUE;
    // SCTLR_EL3.IESB might be ignored in Debug state.
    if !ConstrainUnpredictableBool(Unpredictable_IESBinDebug) then
        sync_errors = FALSE;
    if sync_errors then SynchronizeErrors();

UpdateEDSCRFields();                        // Update EDSCR PE state flags
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