AUTIA, AUTIA1716, AUTIASP, AUTIAZ, AUTIZA

Authenticate instruction address, using key A

This instruction authenticates an instruction address, using a modifier and key A.

If the authentication passes, the upper bits of the address are restored to enable subsequent use of the address. For information on behavior if the authentication fails, see Faulting on pointer authentication.

The address is:

  • In the general-purpose register that is specified by <Xd> for AUTIA and AUTIZA.
  • In X17, for AUTIA1716.
  • In X30, for AUTIASP and AUTIAZ.

    • The modifier is:

  • In the general-purpose register or stack pointer that is specified by <Xn|SP> for AUTIA.
  • The value zero, for AUTIZA and AUTIAZ.
  • In X16, for AUTIA1716.
  • In SP, for AUTIASP.

    • If FEAT_PAuth_LR is implemented and PSTATE.PACM is 1, then AUTIA1716 and AUTIASP include a second modifier that is:

  • In X15, for AUTIA1716.
  • In X16, for AUTIASP.

    • Encoding: Integer

    Variants: FEAT_PAuth (ARMv8.3)

    313029282726252423222120191817161514131211109876543210
    110110101100000100100
    sfSopcode2ZRnRd

    AUTIA (Z == 0)

    AUTIA <Xd>, <Xn|SP>

    AUTIZA (Z == 1 && Rn == 11111)

    AUTIZA <Xd>

    Decoding algorithm

    if !IsFeatureImplemented(FEAT_PAuth) then EndOfDecode(Decode_UNDEF);
if Z == '1' && Rn != '11111' then EndOfDecode(Decode_UNDEF);
constant boolean autia1716 = FALSE;
constant integer d = UInt(Rd);
constant integer n = UInt(Rn);
constant boolean auth_combined = FALSE;

constant boolean source_is_sp = Z == '0' && n == 31;

    Encoding: System

    Variants: FEAT_PAuth (ARMv8.3)

    313029282726252423222120191817161514131211109876543210
    1101010100000011001000x110x11111
    CRmop2

    AUTIA1716 (CRm == 0001 && op2 == 100)

    AUTIA1716

    AUTIASP (CRm == 0011 && op2 == 101)

    AUTIASP

    AUTIAZ (CRm == 0011 && op2 == 100)

    AUTIAZ

    Decoding algorithm

    if !IsFeatureImplemented(FEAT_PAuth) then EndOfDecode(Decode_NOP);
integer d;
integer n;
boolean source_is_sp = FALSE;
boolean autia1716 = FALSE;
constant boolean auth_combined = FALSE;

case CRm:op2 of
    when '0011 100' // AUTIAZ
        d = 30;
        n = 31;
    when '0011 101' // AUTIASP
        d = 30;
        source_is_sp = TRUE;
    when '0001 100' // AUTIA1716
        d = 17;
        n = 16;
        autia1716 = TRUE;

    Operation

    if source_is_sp then
    if IsFeatureImplemented(FEAT_PAuth_LR) && PSTATE.PACM == '1' then
        X[d, 64] = AuthIA2(X[d, 64], SP[64], X[16, 64], auth_combined);
    else
        X[d, 64] = AuthIA(X[d, 64], SP[64], auth_combined);
else
    if IsFeatureImplemented(FEAT_PAuth_LR) && PSTATE.PACM == '1' && autia1716 then
        X[d, 64] = AuthIA2(X[d, 64], X[n, 64], X[15, 64], auth_combined);
    else
        X[d, 64] = AuthIA(X[d, 64], X[n, 64], auth_combined);

    Explanations

    <Xd>: Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field.
    <Xn|SP>: Is the 64-bit name of the general-purpose source register or stack pointer, encoded in the "Rn" field.