RETAASPPC, RETABSPPC -- A64

Return from subroutine, with enhanced pointer authentication using an immediate offset

This instruction authenticates the address that is held in LR, using SP as the first modifier, the specified immediate subtracted from PC as the second modifier, and the specified key, and branches to the authenticated address, with a hint that this instruction is a subroutine return.

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.

Integer
(FEAT_PAuth_LR)

Decode for all variants of this encoding

if !IsFeatureImplemented(FEAT_PAuth_LR) then EndOfDecode(Decode_UNDEF); constant boolean use_key_a = opc<0> == '0'; constant bits(64) offset = ZeroExtend(imm16:'00', 64); constant boolean auth_then_branch = TRUE;

Assembler Symbols

<label>

Is the program label whose address is to be calculated. Its negative offset from the address of this instruction, a multiple of 4 in the range -262140 to 0, is encoded as an unsigned value in the "imm16" field as <label>/4.

Operation

GCSInstruction inst_type; bits(64) target = X[30, 64]; constant bits(64) modifier = SP[64]; constant bits(64) modifier2 = PC64 - offset; 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'; constant boolean branch_conditional = FALSE; BranchTo(target, BranchType_RET, branch_conditional);

Internal version only: aarchmrs v2024-12_rel, pseudocode v2024-12_rel ; Build timestamp: 2024-12-15T22:18