ELR_EL3, Exception Link Register (EL3)

The ELR_EL3 characteristics are:

Purpose

When taking an exception to EL3, holds the address to return to.

Configuration

This register is present only when HaveEL(EL3). Otherwise, direct accesses to ELR_EL3 are UNDEFINED.

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

ELR_EL3 is a 129-bit register.

Field descriptions

The ELR_EL3 bit assignments are:

When Morello is implemented and Capability access at EL3 is not trapped:

Bits [128:0]

Return address.

An exception return from EL3 using AArch64 makes ELR_EL3 become UNKNOWN.

This field resets to an architecturally UNKNOWN value.

When Morello is implemented and Capability access at EL3 is trapped:

Bits [128:64]

Reserved, RES0.

Bits [63:0]

Return address.

An exception return from EL3 using AArch64 makes ELR_EL3 become UNKNOWN.

This field resets to an architecturally UNKNOWN value.

When Morello is not implemented:

6362616059585756555453525150494847464544434241403938373635343332
Return address
Return address
313029282726252423222120191817161514131211109876543210

Bits [63:0]

Return address.

An exception return from EL3 using AArch64 makes ELR_EL3 become UNKNOWN.

This field resets to an architecturally UNKNOWN value.

Accessing the ELR_EL3

Accesses to this register use the following encodings:

MRS <Xt>, ELR_EL3

op0op1CRnCRmop2
0b110b1100b01000b00000b001

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then return ELR_EL3<63:0>;

MSR ELR_EL3, <Xt>

op0op1CRnCRmop2
0b110b1100b01000b00000b001

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then ELR_EL3 = ZeroExtend(X[t]);

MRS <Ct>, CELR_EL3

op0op1CRnCRmop2
0b110b1100b01000b00000b001

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then if CPTR_EL3.EC == '0' then AArch64.SystemAccessTrap(EL3, 0x29); else return ELR_EL3;

MSR CELR_EL3, <Ct>

op0op1CRnCRmop2
0b110b1100b01000b00000b001

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then UNDEFINED; elsif PSTATE.EL == EL2 then UNDEFINED; elsif PSTATE.EL == EL3 then if CPTR_EL3.EC == '0' then AArch64.SystemAccessTrap(EL3, 0x29); else ELR_EL3 = C[t];




12/01/2022 09:56; 05a4944b4b04e7ab50def8c126b479d22136f35b

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