autia

Authenticate Instruction Address (Key A)

AUTIA <Xd>, <Xn>

Authenticates an instruction address signed with Key A.

Details

Authenticates a 64-bit instruction address in Xd using Key A and a modifier in Xn. The instruction performs cryptographic verification of the pointer authentication code (PAC) embedded in Xd. If authentication fails, the result is corrupted (set to an invalid address). This instruction is AArch64-only and requires ARMv8.3-A or later with PAC extension enabled; it does not affect condition flags.

Pseudocode Operation

Xd ← AuthIA(Xd, Xn)

Example

AUTIA x0, x1

Encoding

Binary Layout
1
1
0
11010110
00001
00
0
100
Rn
Rd
 
Format Data Processing
Opcode 0xDAC11000
Extension PAC (Security)

Operands

  • Xd
    Destination 64-bit integer register
  • Xn
    Modifier

Reference (Arm A64 ISA)

Instruction Forms

Encoding Instruction ISA Bit pattern
0xDAC11000 AUTIA <Xd>, <Xn|SP> A64 1 | 1 | 0 | 11010110 | 00001 | 00 | 0 | 100 | Rn | Rd

Description

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

Operation

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