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DCPS1

Debug Change PE State to EL1 allows the debugger to move the PE into EL1 from EL0 or to a specific mode at the current Exception Level.

DCPS1 is undefined if any of:

  • The PE is in Non-debug state.
  • EL2 is implemented, EL2 is implemented and enabled in the current Security state, and any of:
    • EL2 is using AArch32 and HCR.TGE is set to 1.
    • EL2 is using AArch64 and HCR_EL2.TGE is set to 1.

When the PE executes DCPS1 at EL0, EL1 or EL3:

  • If EL3 or EL1 is using AArch32, the PE enters SVC mode and LR_svc, SPSR_svc, DLR, and DSPSR become UNKNOWN. If DCPS1 is executed in Monitor mode, SCR.NS is cleared to 0.
  • If EL1 is using AArch64, the PE enters EL1 using AArch64, selects SP_EL1, and ELR_EL1, ESR_EL1, SPSR_EL1, DLR_EL0 and DSPSR_EL0 become UNKNOWN.

When the PE executes DCPS1 at EL2 the PE does not change mode, and ELR_hyp, HSR, SPSR_hyp, DLR and DSPSR become UNKNOWN.

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

T1

15141312111098765432101514131211109876543210
11110111100011111000000000000001

T1

DCPS1

// No additional decoding required.

Operation

if !Halted() then UNDEFINED;

if EL2Enabled() && PSTATE.EL == EL0 then
    tge = if ELUsingAArch32(EL2) then HCR.TGE else HCR_EL2.TGE;
    if tge == '1' then UNDEFINED;

if PSTATE.EL != EL0 || ELUsingAArch32(EL1) then
    if PSTATE.M == M32_Monitor then SCR.NS = '0';
    if PSTATE.EL != EL2 then
        AArch32.WriteMode(M32_Svc);
        PSTATE.E = SCTLR.EE;
        if HavePANExt() && SCTLR.SPAN == '0' then PSTATE.PAN = '1';
        LR_svc = bits(32) UNKNOWN;
        SPSR_svc = bits(32) UNKNOWN;
    else
        PSTATE.E = HSCTLR.EE;
        ELR_hyp = bits(32) UNKNOWN;
        HSR = bits(32) UNKNOWN;
        SPSR_hyp = bits(32) UNKNOWN;

    DLR = bits(32) UNKNOWN;
    DSPSR = bits(32) UNKNOWN;
else                                        // Targeting EL1 using AArch64
    AArch64.MaybeZeroRegisterUppers();
    MaybeZeroSVEUppers(EL1);
    PSTATE.nRW = '0';
    PSTATE.SP = '1';
    PSTATE.EL = EL1;
    if HavePANExt() && SCTLR_EL1.SPAN == '0' then PSTATE.PAN = '1';
    if HaveUAOExt() then PSTATE.UAO = '0';

    ELR_EL1 = bits(64) UNKNOWN;
    ESR_EL1 = bits(32) UNKNOWN;
    SPSR_EL1 = bits(32) UNKNOWN;

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

    // SCTLR_EL1.IESB might be ignored in Debug state.
    if HaveIESB() && SCTLR_EL1.IESB == '1' &&  !ConstrainUnpredictableBool(Unpredictable_IESBinDebug) then
        SynchronizeErrors();

UpdateEDSCRFields();                        // Update EDSCR PE state flags
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