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ELR_EL1, Exception Link Register (EL1)

The ELR_EL1 characteristics are:

Purpose

When taking an exception to EL1, holds the address to return to.

Configuration

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

ELR_EL1 is a 64-bit register.

Field descriptions

The ELR_EL1 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
Return address
Return address
313029282726252423222120191817161514131211109876543210

Bits [63:0]

Return address.

An exception return from EL1 using AArch64 makes ELR_EL1 become UNKNOWN.

This field resets to an architecturally UNKNOWN value.

Accessing the ELR_EL1

An exception return from EL1 using AArch64 makes ELR_EL1 become UNKNOWN.

When HCR_EL2.E2H is 1, without explicit synchronization, access from EL3 using the mnemonic ELR_EL1 or ELR_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>, ELR_EL1

op0op1CRnCRmop2
op0CRnop1op2CRm
0b110b0000b01000b00000b001
0b110b01000b0000b0010b0000

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[0x230]; else return ELR_EL1; elsif PSTATE.EL == EL2 then if HCR_EL2.E2H == '1' then return ELR_EL2; else return ELR_EL1; elsif PSTATE.EL == EL3 then return ELR_EL1;

MSR ELR_EL1, <Xt>

op0op1CRnCRmop2
op0CRnop1op2CRm
0b110b0000b01000b00000b001
0b110b01000b0000b0010b0000

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[0x230] = X[t]; else ELR_EL1 = X[t]; elsif PSTATE.EL == EL2 then if HCR_EL2.E2H == '1' then ELR_EL2 = X[t]; else ELR_EL1 = X[t]; elsif PSTATE.EL == EL3 then ELR_EL1 = X[t];

MRS <Xt>, ELR_EL12

op0op1CRnCRmop2
op0CRnop1op2CRm
0b110b1010b01000b00000b001
0b110b01000b1010b0010b0000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.<NV2,NV1,NV> == '101' then return NVMem[0x230]; elsif EL2Enabled() && HCR_EL2.NV == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if EL2Enabled() && HCR_EL2.E2H == '1' then if PSTATE.EL == EL2 then return ELR_EL1; else UNDEFINED; elsif PSTATE.EL == EL3 then if EL2Enabled() && HCR_EL2.E2H == '1' then return ELR_EL1; else else UNDEFINED;

MSR ELR_EL12, <Xt>

op0op1CRnCRmop2
op0CRnop1op2CRm
0b110b1010b01000b00000b001
0b110b01000b1010b0010b0000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.<NV2,NV1,NV> == '101' then NVMem[0x230] = X[t]; elsif EL2Enabled() && HCR_EL2.NV == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then if EL2Enabled() && HCR_EL2.E2H == '1' then if PSTATE.EL == EL2 then ELR_EL1 = X[t]; else UNDEFINED; elsif PSTATE.EL == EL3 then if EL2Enabled() && HCR_EL2.E2H == '1' then ELR_EL1 = X[t]; else else UNDEFINED;

MRS <Xt>, ELR_EL2

op0op1CRnCRmop2
op0CRnop1op2CRm
0b110b1000b01000b00000b001
0b110b01000b1000b0010b0000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then return ELR_EL1; elsif EL2Enabled() && HCR_EL2.NV == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then return ELR_EL2; elsif PSTATE.EL == EL3 then return ELR_EL2;

MSR ELR_EL2, <Xt>

op0op1CRnCRmop2
op0CRnop1op2CRm
0b110b1000b01000b00000b001
0b110b01000b1000b0010b0000

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if EL2Enabled() && HCR_EL2.<NV2,NV> == '11' then ELR_EL1 = X[t]; elsif EL2Enabled() && HCR_EL2.NV == '1' then AArch64.SystemAccessTrap(EL2, 0x18); else UNDEFINED; elsif PSTATE.EL == EL2 then ELR_EL2 = X[t]; elsif PSTATE.EL == EL3 then ELR_EL2 = X[t];




2713/0312/20192018 2116:5942; e5e4db499bf9867a4b93324c4dbac985d3da93766379d01c197f1d40720d32d0f84c419c9187c009

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