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# APIBKeyLo_EL1, Pointer Authentication Key B for Instruction (bits[63:0])

The APIBKeyLo_EL1 characteristics are:

## Purpose

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

Note

The term APIBKey_EL1 is used to describe the concatenation of APIBKeyHi_EL1: APIBKeyLo_EL1.

## Configuration

This register is present only when FEAT_PAuth is implemented. Otherwise, direct accesses to APIBKeyLo_EL1 are UNDEFINED.

## Attributes

APIBKeyLo_EL1 is a 64-bit register.

## Field descriptions

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
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
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

#### Bits [63:0]

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

The reset behavior of this field is:

- On a Warm reset, this field resets to an architecturally UNKNOWN value.

## Accessing APIBKeyLo_EL1

Accesses to this register use the following encodings in the System register encoding space:

#### MRS <Xt>, APIBKeyLo_EL1

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b000 | 0b0010 | 0b0001 | 0b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.APK == '0' then UNDEFINED; elsif EL2Enabled() && HCR_EL2.APK == '0' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGRTR_EL2.APIBKey == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && SCR_EL3.APK == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else X[t, 64] = APIBKeyLo_EL1; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.APK == '0' then UNDEFINED; elsif HaveEL(EL3) && SCR_EL3.APK == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else X[t, 64] = APIBKeyLo_EL1; elsif PSTATE.EL == EL3 then X[t, 64] = APIBKeyLo_EL1;

#### MSR APIBKeyLo_EL1, <Xt>

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b11 | 0b000 | 0b0010 | 0b0001 | 0b010

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.APK == '0' then UNDEFINED; elsif EL2Enabled() && HCR_EL2.APK == '0' then AArch64.SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGWTR_EL2.APIBKey == '1' then AArch64.SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && SCR_EL3.APK == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else APIBKeyLo_EL1 = X[t, 64]; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && SCR_EL3.APK == '0' then UNDEFINED; elsif HaveEL(EL3) && SCR_EL3.APK == '0' then if EL3SDDUndef() then UNDEFINED; else AArch64.SystemAccessTrap(EL3, 0x18); else APIBKeyLo_EL1 = X[t, 64]; elsif PSTATE.EL == EL3 then APIBKeyLo_EL1 = X[t, 64];

AArch32 Registers | AArch64 Registers | AArch32 Instructions | AArch64 Instructions | Index by Encoding | External Registers | External Registers by Offset | Registers by Functional Group | Proprietary Notice

26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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