Base Instructions | SIMD&FP Instructions | SVE Instructions | SME Instructions | Index by Encoding | Shared Pseudocode | Proprietary Notice

## RETAA, RETAB

Return from subroutine, with pointer authentication. This instruction authenticates the address that is held in LR, using SP as the modifier and the specified key, and branches to the authenticated address, with a hint that this instruction is a subroutine return.

Key A is used for RETAA. Key B is used for RETAB.

If the authentication passes, the PE continues execution at the target of the branch. For information on behavior if the authentication fails, see Faulting on pointer authentication.

The authenticated address is not written back to LR.

If FEAT_PAuth_LR is implemented and PSTATE.PACM is 1, then RETAA and RETAB include a second modifier that is in X16.

### Integer
(FEAT_PAuth)

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
1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | M | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1
| Z |  | op | op2 |  | A |  | Rn | Rm

#### RETAA (M == 0)

RETAA

#### RETAB (M == 1)

RETAB

if !IsFeatureImplemented(FEAT_PAuth) then UNDEFINED; boolean use_key_a = (M == '0'); boolean auth_then_branch = TRUE;

### Operation

GCSInstruction inst_type; bits(64) target = X[30, 64]; bits(64) modifier = SP[]; bits(64) modifier2; boolean use_modifier2 = FALSE; if IsFeatureImplemented(FEAT_PAuth_LR) && PSTATE.PACM == '1' then modifier2 = X[16, 64]; use_modifier2 = TRUE; if use_key_a then if use_modifier2 && IsFeatureImplemented(FEAT_PAuth_LR) then target = AuthIA2(target, modifier, modifier2, auth_then_branch); else target = AuthIA(target, modifier, auth_then_branch); else if use_modifier2 && IsFeatureImplemented(FEAT_PAuth_LR) then target = AuthIB2(target, modifier, modifier2, auth_then_branch); else target = AuthIB(target, modifier, auth_then_branch); if IsFeatureImplemented(FEAT_GCS) && GCSPCREnabled(PSTATE.EL) then inst_type = if use_key_a then GCSInstType_PRETAA else GCSInstType_PRETAB; target = LoadCheckGCSRecord(target, inst_type); SetCurrentGCSPointer(GetCurrentGCSPointer() + 8); // Value in BTypeNext will be used to set PSTATE.BTYPE BTypeNext = '00'; boolean branch_conditional = FALSE; BranchTo(target, BranchType_RET, branch_conditional);

Base Instructions | SIMD&FP Instructions | SVE Instructions | SME Instructions | Index by Encoding | Shared Pseudocode | Proprietary Notice

Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

Copyright © 2010-2024 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.