DSPSR_EL0, Debug Saved Program Status Register

The DSPSR_EL0 characteristics are:

Purpose

Holds the saved process state for Debug state. On entering Debug state, PSTATE information is written to this register. On exiting Debug state, values are copied from this register to PSTATE.

Configuration

AArch64 System register DSPSR_EL0 bits [31:0] are architecturally mapped to AArch32 System register DSPSR[31:0] .

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

DSPSR_EL0 is a 64-bit register.

Field descriptions

The DSPSR_EL0 bit assignments are:

When exiting Debug state to AArch32 state:

63	62	61	60	59	58	57	56	55	54	53	52	51	50	49	48	47	46	45	44	43	42	41	40	39	38	37	36	35	34	33	32
RES0
N	Z	C	V	Q	IT[1:0]		DIT	SSBS	PAN	SS	IL	GE				IT[7:2]						E	A	I	F	T	M[4]	M[3:0]

Bits [63:32]

Reserved, RES0.

N, bit [31]

Negative Condition flag. Copied to PSTATE.N on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Z, bit [30]

Zero Condition flag. Copied to PSTATE.Z on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

C, bit [29]

Carry Condition flag. Copied to PSTATE.C on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

V, bit [28]

Overflow Condition flag. Copied to PSTATE.V on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Q, bit [27]

Overflow or saturation flag. Copied to PSTATE.Q on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

IT[1:0], bits [26:25]

If-Then. Copied to PSTATE.IT[1:0] on exiting Debug state.

On exiting Debug state DSPSR_EL0.IT must contain a value that is valid for the instruction being returned to.

This field resets to an architecturally UNKNOWN value.

DIT, bit [24]

When ARMv8.4-DIT is implemented:

Data Independent Timing. Copied to PSTATE.DIT on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

SSBS, bit [23]

When ARMv8.0-SSBS is implemented:

Speculative Store Bypass. Copied to PSTATE.SSBS on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

PAN, bit [22]

When ARMv8.1-PAN is implemented:

Privileged Access Never. Copied to PSTATE.PAN on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

SS, bit [21]

Software Step. Copied to PSTATE.SS on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

IL, bit [20]

Illegal Execution state. Copied to PSTATE.IL on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

GE, bits [19:16]

Greater than or Equal flags. Copied to PSTATE.GE on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

IT[7:2], bits [15:10]

If-Then. Copied to PSTATE.IT[7:2] on exiting Debug state.

DSPSR_EL0.IT must contain a value that is valid for the instruction being returned to.

This field resets to an architecturally UNKNOWN value.

E, bit [9]

Endianness. Copied to PSTATE.E on exiting Debug state.

If the implementation does not support big-endian operation, DSPSR_EL0.E is RES0. If the implementation does not support little-endian operation, DSPSR_EL0.E is RES1. On exiting Debug state, if the implementation does not support big-endian operation at the Exception level being returned to, DSPSR_EL0.E is RES0, and if the implementation does not support little-endian operation at the Exception level being returned to, DSPSR_EL0.E is RES1.

This field resets to an architecturally UNKNOWN value.

A, bit [8]

SError interrupt mask. Copied to PSTATE.A on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

I, bit [7]

IRQ interrupt mask. Copied to PSTATE.I on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

F, bit [6]

FIQ interrupt mask. Copied to PSTATE.F on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

T, bit [5]

T32 Instruction set state. Copied to PSTATE.T on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

M[4], bit [4]

Execution state. Copied to PSTATE.nRW on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

M[3:0], bits [3:0]

AArch32 Mode. Copied to PSTATE.M[3:0] on exiting Debug state.

Other values are reserved. If DSPSR_EL0.M[3:0] has a Reserved value, or a value for an unimplemented Exception level, exiting Debug state is an illegal return event, as described in 'Illegal return events from AArch64 state' in the Arm®Architecture Reference Manual, Armv8, for Armv8-A architecture profile.

This field resets to an architecturally UNKNOWN value.

When entering Debug state from AArch64 state and exiting Debug state to AArch64 state:

63	62	61	60	59	58	57	56	55	54	53	52	51	50	49	48	47	46	45	44	43	42	41	40	39	38	37	36	35	34	33	32
RES0
N	Z	C	V	RES0		TCO	DIT	UAO	PAN	SS	IL	RES0							SSBS	BTYPE		D	A	I	F	RES0	M[4]	M[3:0]
31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0

Bits [63:32]

Reserved, RES0.

N, bit [31]

Negative Condition flag. Set to the value of PSTATE.N on entering Debug state, and copied to PSTATE.N on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Z, bit [30]

Zero Condition flag. Set to the value of PSTATE.Z on entering Debug state, and copied to PSTATE.Z on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

C, bit [29]

Carry Condition flag. Set to the value of PSTATE.C on entering Debug state, and copied to PSTATE.C on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

V, bit [28]

Overflow Condition flag. Set to the value of PSTATE.V on entering Debug state, and copied to PSTATE.V on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Bits [27:26]

Reserved, RES0.

TCO, bit [25]

When ARMv8.5-MemTag is implemented:

Tag Check Override. Set to the value of PSTATE.TCO on entering Debug state, and copied to PSTATE.TCO on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

DIT, bit [24]

When ARMv8.4-DIT is implemented:

Data Independent Timing. Set to the value of PSTATE.DIT on entering Debug state, and copied to PSTATE.DIT on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

UAO, bit [23]

When ARMv8.2-UAO is implemented:

User Access Override. Set to the value of PSTATE.UAO on entering Debug state, and copied to PSTATE.UAO on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

PAN, bit [22]

When ARMv8.1-PAN is implemented:

Privileged Access Never. Set to the value of PSTATE.PAN on entering Debug state, and copied to PSTATE.PAN on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

SS, bit [21]

Software Step. Set to the value of PSTATE.SS on entering Debug state, and conditionally copied to PSTATE.SS on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

IL, bit [20]

Illegal Execution state. Set to the value of PSTATE.IL on entering Debug state, and copied to PSTATE.IL on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Bits [19:13]

Reserved, RES0.

SSBS, bit [12]

When ARMv8.0-SSBS is implemented:

Speculative Store Bypass. Set to the value of PSTATE.SSBS on entering Debug state, and copied to PSTATE.SSBS on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

BTYPE, bits [11:10]

When ARMv8.5-BTI is implemented:

Branch Type Indicator. Set to the value of PSTATE.BTYPE on entering Debug state, and copied to PSTATE.BTYPE on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Otherwise:

Reserved, RES0.

D, bit [9]

Debug exception mask. Set to the value of PSTATE.D on entering Debug state, and copied to PSTATE.D on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

A, bit [8]

SError interrupt mask. Set to the value of PSTATE.A on entering Debug state, and copied to PSTATE.A on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

I, bit [7]

IRQ interrupt mask. Set to the value of PSTATE.I on entering Debug state, and copied to PSTATE.I on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

F, bit [6]

FIQ interrupt mask. Set to the value of PSTATE.F on entering Debug state, and copied to PSTATE.F on exiting Debug state.

This field resets to an architecturally UNKNOWN value.

Bit [5]

Reserved, RES0.

M[4], bit [4]

Execution state. Set to 0b0, the value of PSTATE.nRW, on entering Debug state from AArch64 state, and copied to PSTATE.nRW on exiting Debug state.

If AArch32 is not supported at any Exception level, this bit is RES0.

This field resets to an architecturally UNKNOWN value.

M[3:0], bits [3:0]

AArch64 Exception level and selected Stack Pointer.

Other values are reserved. If DSPSR_EL0.M[3:0] has a Reserved value, or a value for an unimplemented Exception level, exiting Debug state is an illegal return event, as described in 'Illegal return events from AArch64 state' in the Arm®Architecture Reference Manual, Armv8, for Armv8-A architecture profile.

The bits in this field are interpreted as follows:

• M[3:2] is set to the value of PSTATE.EL on entering Debug state and copied to PSTATE.EL on exiting Debug state.
• M[1] is unused and is 0 for all non-reserved values.
• M[0] is set to the value of PSTATE.SP on entering Debug state and copied to PSTATE.SP on exiting Debug state

This field resets to an architecturally UNKNOWN value.

if !Halted() then
    UNDEFINED;
else
    return DSPSR_EL0;
              

if !Halted() then
    UNDEFINED;
else
    DSPSR_EL0 = X[t];