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.
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.
This instruction provides a hint that this is a subroutine return.
If FEAT_PAuth_LR is implemented and PSTATE.PACM is 1, then
RETAA and RETAB include a second modifier that is in X16.
1
1
0
1
0
1
1
0
0
1
0
1
1
1
1
1
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
0
RETAA
1
RETAB
if !IsFeatureImplemented(FEAT_PAuth) then EndOfDecode(Decode_UNDEF); end;
let use_key_a : boolean = (M == '0');
let auth_then_branch : boolean = TRUE;
var inst_type : GCSInstruction;
var target : bits(64) = X{}(30);
let modifier : bits(64) = SP{}();
var modifier2 : bits(64);
var use_modifier2 : boolean = FALSE;
if IsFeatureImplemented(FEAT_PAuth_LR) && PSTATE.PACM == '1' then
modifier2 = X{64}(16);
use_modifier2 = TRUE;
end;
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);
end;
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);
end;
end;
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);
end;
// Value in BTypeNext will be used to set PSTATE.BTYPE
BTypeNext = '00';
let branch_conditional : boolean = FALSE;
BranchTo{64}(target, BranchType_RET, branch_conditional);
2026-03-26 20:27:25
2026-03_rel