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APIAKeyLo_EL1, Pointer Authentication Key A for Instruction (bits[63:0])

The APIAKeyLo_EL1 characteristics are:

Purpose

Holds bits[63:0] of key A used for authentication of instruction pointer values.

Note

The term APIAKey_EL1 is used to describe the concatenation of APIAKeyHi_EL1: APIAKeyLo_EL1.

Configuration

This register is present only when FEAT_PAuth is implemented. Otherwise, direct accesses to APIAKeyLo_EL1 are UNDEFINED.

Attributes

APIAKeyLo_EL1 is a 64-bit register.

Field descriptions

The APIAKeyLo_EL1 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
64 bit value, bits[63:0] of the 128 bit pointer authentication key value
64 bit value, bits[63:0] of the 128 bit pointer authentication key value
313029282726252423222120191817161514131211109876543210

Bits [63:0]

64 bit value, bits[63:0] of the 128 bit pointer authentication key value.

This field resets to an architecturally UNKNOWN value.

Accessing the APIAKeyLo_EL1

Accesses to this register use the following encodings:

MRS <Xt>, APIAKeyLo_EL1

op0op1CRnCRmop2
0b110b0000b00100b00010b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && SCR_EL3.APK == '0' then
        UNDEFINED;
    elsif EL2Enabled() && HCR_EL2.APK == '0' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif EL2Enabled() && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGRTR_EL2.APIAKey == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif HaveEL(EL3) && SCR_EL3.APK == '0' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return APIAKeyLo_EL1;
elsif PSTATE.EL == EL2 then
    if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && SCR_EL3.APK == '0' then
        UNDEFINED;
    elsif HaveEL(EL3) && SCR_EL3.APK == '0' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return APIAKeyLo_EL1;
elsif PSTATE.EL == EL3 then
    return APIAKeyLo_EL1;
              

MSR APIAKeyLo_EL1, <Xt>

op0op1CRnCRmop2
0b110b0000b00100b00010b000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && SCR_EL3.APK == '0' then
        UNDEFINED;
    elsif EL2Enabled() && HCR_EL2.APK == '0' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif EL2Enabled() && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGWTR_EL2.APIAKey == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif HaveEL(EL3) && SCR_EL3.APK == '0' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        APIAKeyLo_EL1 = X[t];
elsif PSTATE.EL == EL2 then
    if Halted() && HaveEL(EL3) && EDSCR.SDD == '1' && boolean IMPLEMENTATION_DEFINED "EL3 trap priority when SDD == '1'" && SCR_EL3.APK == '0' then
        UNDEFINED;
    elsif HaveEL(EL3) && SCR_EL3.APK == '0' then
        if Halted() && EDSCR.SDD == '1' then
            UNDEFINED;
        else
            AArch64.SystemAccessTrap(EL3, 0x18);
    else
        APIAKeyLo_EL1 = X[t];
elsif PSTATE.EL == EL3 then
    APIAKeyLo_EL1 = X[t];