dcps1

Debug Change PE State to EL1 (A32)

DCPS1

Switches execution to EL1 (Debug).

Pseudocode Operation

DebugChangeEL(EL1); // Changes exception level and branches to debug handler

Encoding

Binary Layout

111101111000

31:20

1111

19:16

1000

15:12

0000000000

11:2

01

1:0

 

Format System

Opcode 0xF78F8001

Extension A32 (System)

Operands

Related

Other forms of dcps1

• dcps1 Debug Change PE State to EL1

More in A32 (System)

Reference

View in Arm A64 ISA Reference ↗ Arm AArch32 ISA

Instruction Forms

Encoding	Instruction		ISA		Bit pattern
0xF78F8001	DCPS1		T32		111101111000 | 1111 | 1000 | 0000000000 | 01

Description

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: When the PE executes DCPS1 at EL0, EL1 or EL3: 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 the DCPS<n> instructions, see DCPS.

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(64) UNKNOWN;
    SPSR_EL1 = bits(64) UNKNOWN;

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