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SPSR_EL1, Saved Program Status Register (EL1)

The SPSR_EL1 characteristics are:

Purpose

Holds the saved process state when an exception is taken to EL1.

Configuration

AArch64 System register SPSR_EL1 bits [31:0] are architecturally mapped to AArch32 System register SPSR_svc[31:0] .

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

SPSR_EL1 is a 64-bit register.

Field descriptions

The SPSR_EL1 bit assignments are:

When exception taken from AArch32 state:
6362616059585756555453525150494847464544434241403938373635343332
00000000000000000000000000000000
NZCVQIT[1:0]DITSSBSPANSSILGEIT[7:2]EAIFTM[4]M[3:0]

An exception return from EL1 using AArch64 makes SPSR_EL1 become UNKNOWN.

Bits [63:32]

Reserved, RES0.

N, bit [31]

Negative Condition flag. Set to the value of PSTATE.N on taking an exception to EL1, and copied to PSTATE.N on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

Z, bit [30]

Zero Condition flag. Set to the value of PSTATE.Z on taking an exception to EL1, and copied to PSTATE.Z on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

C, bit [29]

Carry Condition flag. Set to the value of PSTATE.C on taking an exception to EL1, and copied to PSTATE.C on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

V, bit [28]

Overflow Condition flag. Set to the value of PSTATE.V on taking an exception to EL1, and copied to PSTATE.V on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

Q, bit [27]

Overflow or saturation flag. Set to the value of PSTATE.Q on taking an exception to EL1, and copied to PSTATE.Q on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

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

If-Then. Set to the value of PSTATE.IT[1:0] on taking an exception to EL1, and copied to PSTATE.IT[1:0] on executing an exception return operation in EL1.

On executing an exception return operation in EL1 SPSR_EL1.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. Set to the value of PSTATE.DIT on taking an exception to EL1, and copied to PSTATE.DIT on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.


Otherwise:

Reserved, RES0.

SSBS, bit [23]

When ARMv8.0-SSBS is implemented:

Speculative Store Bypass. Set to the value of PSTATE.SSBS on taking an exception to EL1, and copied to PSTATE.SSBS on executing an exception return operation in EL1.

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 taking an exception to EL1, and copied to PSTATE.PAN on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.


Otherwise:

Reserved, RES0.

SS, bit [21]

Software Step. Set to the value of PSTATE.SS on taking an exception to EL1, and conditionally copied to PSTATE.SS on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

IL, bit [20]

Illegal Execution state. Set to the value of PSTATE.IL on taking an exception to EL1, and copied to PSTATE.IL on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

GE, bits [19:16]

Greater than or Equal flags. Set to the value of PSTATE.GE on taking an exception to EL1, and copied to PSTATE.GE on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

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

If-Then. Set to the value of PSTATE.IT[7:2] on taking an exception to EL1, and copied to PSTATE.IT[7:2] on executing an exception return operation in EL1.

SPSR_EL1.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. Set to the value of PSTATE.E on taking an exception to EL1, and copied to PSTATE.E on executing an exception return operation in EL1.

If the implementation does not support big-endian operation, SPSR_EL1.E is RES0. If the implementation does not support little-endian operation, SPSR_EL1.E is RES1. On executing an exception return operation in EL1, if the implementation does not support big-endian operation at the Exception level being returned to, SPSR_EL1.E is RES0, and if the implementation does not support little-endian operation at the Exception level being returned to, SPSR_EL1.E is RES1.

This field resets to an architecturally UNKNOWN value.

A, bit [8]

SError interrupt mask. Set to the value of PSTATE.A on taking an exception to EL1, and copied to PSTATE.A on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

I, bit [7]

IRQ interrupt mask. Set to the value of PSTATE.I on taking an exception to EL1, and copied to PSTATE.I on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

F, bit [6]

FIQ interrupt mask. Set to the value of PSTATE.F on taking an exception to EL1, and copied to PSTATE.F on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

T, bit [5]

T32 Instruction set state. Set to the value of PSTATE.T on taking an exception to EL1, and copied to PSTATE.T on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

M[4], bit [4]

Execution state. Set to 0b1, the value of PSTATE.nRW, on taking an exception to EL1 from AArch32 state, and copied to PSTATE.nRW on executing an exception return operation in EL1.

M[4]Meaning
0b1

AArch32 execution state.

This field resets to an architecturally UNKNOWN value.

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

AArch32 Mode. Set to the value of PSTATE.M[3:0] on taking an exception to EL1, and copied to PSTATE.M[3:0] on executing an exception return operation in EL1.

M[3:0]Meaning
0b0000

User.

0b0001

FIQ.

0b0010

IRQ.

0b0011

Supervisor.

0b0111

Abort.

0b1011

Undefined.

0b1111

System.

Other values are reserved. If SPSR_EL1.M[3:0] has a Reserved value, or a value for an unimplemented Exception level, executing an exception return operation in EL1 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 exception taken from AArch64 state:
6362616059585756555453525150494847464544434241403938373635343332
00000000000000000000000000000000
NZCV00TCODITUAOPANSSIL0000000SSBSBTYPEDAIF0M[4]M[3:0]
313029282726252423222120191817161514131211109876543210
313029282726252423222120191817161514131211109876543210

An exception return from EL1 using AArch64 makes SPSR_EL1 become UNKNOWN.

Bits [63:32]

Reserved, RES0.

N, bit [31]

Negative Condition flag. Set to the value of PSTATE.N on taking an exception to EL1, and copied to PSTATE.N on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

Z, bit [30]

Zero Condition flag. Set to the value of PSTATE.Z on taking an exception to EL1, and copied to PSTATE.Z on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

C, bit [29]

Carry Condition flag. Set to the value of PSTATE.C on taking an exception to EL1, and copied to PSTATE.C on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

V, bit [28]

Overflow Condition flag. Set to the value of PSTATE.V on taking an exception to EL1, and copied to PSTATE.V on executing an exception return operation in EL1.

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 taking an exception to EL1, and copied to PSTATE.TCO on executing an exception return operation in EL1.

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 taking an exception to EL1, and copied to PSTATE.DIT on executing an exception return operation in EL1.

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 taking an exception to EL1, and copied to PSTATE.UAO on executing an exception return operation in EL1.

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 taking an exception to EL1, and copied to PSTATE.PAN on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.


Otherwise:

Reserved, RES0.

SS, bit [21]

Software Step. Set to the value of PSTATE.SS on taking an exception to EL1, and conditionally copied to PSTATE.SS on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

IL, bit [20]

Illegal Execution state. Set to the value of PSTATE.IL on taking an exception to EL1, and copied to PSTATE.IL on executing an exception return operation in EL1.

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 taking an exception to EL1, and copied to PSTATE.SSBS on executing an exception return operation in EL1.

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 taking an exception to EL1, and copied to PSTATE.BTYPE on executing an exception return operation in EL1.

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 taking an exception to EL1, and copied to PSTATE.D on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

A, bit [8]

SError interrupt mask. Set to the value of PSTATE.A on taking an exception to EL1, and copied to PSTATE.A on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

I, bit [7]

IRQ interrupt mask. Set to the value of PSTATE.I on taking an exception to EL1, and copied to PSTATE.I on executing an exception return operation in EL1.

This field resets to an architecturally UNKNOWN value.

F, bit [6]

FIQ interrupt mask. Set to the value of PSTATE.F on taking an exception to EL1, and copied to PSTATE.F on executing an exception return operation in EL1.

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 taking an exception to EL1 from AArch64 state, and copied to PSTATE.nRW on executing an exception return operation in EL1.

M[4]Meaning
0b0

AArch64 execution 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.

M[3:0]Meaning
0b0000

EL0t.

0b0100

EL1t.

0b0101

EL1h.

Other values are reserved. If SPSR_EL1.M[3:0] has a Reserved value, or a value for an unimplemented Exception level, executing an exception return operation in EL1 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 taking an exception to EL1 and copied to PSTATE.EL on executing an exception return operation in EL1.
  • M[1] is unused and is 0 for all non-reserved values.
  • M[0] is set to the value of PSTATE.SP on taking an exception to EL1 and copied to PSTATE.SP on executing an exception return operation in EL1

This field resets to an architecturally UNKNOWN value.

Accessing the SPSR_EL1

When HCR_EL2.E2H is 1, without explicit synchronization, access from EL3 using the mnemonic SPSR_EL1 or SPSR_EL12 are not guaranteed to be ordered with respect to accesses using the other mnemonic.

Accesses to this register use the following encodings:

MRS <Xt>, SPSR_EL1

op0CRnop1op2CRm
0b110b01000b0000b0000b0000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV1> == '01' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.<NV2,NV1,NV> == '111' then
        return NVMem[0x160];
    else
        return SPSR_EL1;
elsif PSTATE.EL == EL2 then
    if HCR_EL2.E2H == '1' then
        return SPSR_EL2;
    else
        return SPSR_EL1;
elsif PSTATE.EL == EL3 then
    return SPSR_EL1;
              

MSR SPSR_EL1, <Xt>

op0CRnop1op2CRm
0b110b01000b0000b0000b0000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV1> == '01' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.<NV2,NV1,NV> == '111' then
        NVMem[0x160] = X[t];
    else
        SPSR_EL1 = X[t];
elsif PSTATE.EL == EL2 then
    if HCR_EL2.E2H == '1' then
        SPSR_EL2 = X[t];
    else
        SPSR_EL1 = X[t];
elsif PSTATE.EL == EL3 then
    SPSR_EL1 = X[t];
              

MRS <Xt>, SPSR_EL12

op0CRnop1op2CRm
0b110b01000b1010b0000b0000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV1,NV> == '101' then
        return NVMem[0x160];
    elsif EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
elsif EL2Enabled() && HCR_EL2.E2H == '1' then
    if PSTATE.EL == EL2 then
        return SPSR_EL1;
    elsif PSTATE.EL == EL3 then
        return SPSR_EL1;
else
    UNDEFINED;
              

MSR SPSR_EL12, <Xt>

op0CRnop1op2CRm
0b110b01000b1010b0000b0000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV1,NV> == '101' then
        NVMem[0x160] = X[t];
    elsif EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
elsif EL2Enabled() && HCR_EL2.E2H == '1' then
    if PSTATE.EL == EL2 then
        SPSR_EL1 = X[t];
    elsif PSTATE.EL == EL3 then
        SPSR_EL1 = X[t];
else
    UNDEFINED;
              

MRS <Xt>, SPSR_EL2

op0CRnop1op2CRm
0b110b01000b1000b0000b0000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then
        return SPSR_EL1;
    elsif EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    return SPSR_EL2;
elsif PSTATE.EL == EL3 then
    return SPSR_EL2;
              

MSR SPSR_EL2, <Xt>

op0CRnop1op2CRm
0b110b01000b1000b0000b0000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then
        SPSR_EL1 = X[t];
    elsif EL2Enabled() && HCR_EL2.NV == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    SPSR_EL2 = X[t];
elsif PSTATE.EL == EL3 then
    SPSR_EL2 = X[t];
              


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