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

## RETAASPPC, RETABSPPC (register)

Return from subroutine, with enhanced pointer authentication return (register). This instruction authenticates the address that is held in LR, using SP as the first modifier, the value in the specified register as the second 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 RETAASPPC. Key B is used for RETABSPPC.

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.

### Integer
(FEAT_PAuth_LR)

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 | != 11111
| opc | op2 |  |  | Rn | Rm

#### RETAASPPC (M == 0)

RETAASPPC <Xm>

#### RETABSPPC (M == 1)

RETABSPPC <Xm>

if !IsFeatureImplemented(FEAT_PAuth_LR) then UNDEFINED; integer m = UInt(Rm); boolean use_key_a = M == '0'; boolean auth_then_branch = TRUE;

### Assembler Symbols

<Xm> | Is the 64-bit name of the general-purpose source register, encoded in the "Rm" field.

### Operation

GCSInstruction inst_type; bits(64) target = X[30, 64]; bits(64) modifier = SP[]; bits(64) modifier2 = X[m, 64]; if use_key_a then target = AuthIA2(target, modifier, modifier2, auth_then_branch); else target = AuthIB2(target, modifier, modifier2, 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

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