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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, branches to the authenticated address, with a hint that this instruction is a subroutine return.
Key A is used for RETAA, and key B is used for RETAB.
If the authentication passes, the PE continues execution at the target of the branch. If the authentication fails, a Translation fault is generated.
The authenticated address is not written back to 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 | 1 | 1 | 1 | 1 | 1 |
Z | op | A | Rn | Rm |
boolean use_key_a = (M == '0');
if !integer n =UInt(Rn);
BranchType branch_type;
integer m = UInt(Rm);
boolean pac = (A == '1');
boolean use_key_a = (M == '0');
boolean source_is_sp = ((Z == '1') && (m == 31));
if !pac && m != 0 then
UNDEFINED;
elsif pac && !HavePACExt() then
UNDEFINED;
case op of
when '00' branch_type = BranchType_INDIR;
when '01' branch_type = BranchType_INDCALL;
when '10' branch_type = BranchType_RET;
otherwise UNDEFINED;
if pac then
if Z == '0' && m != 31 then
UNDEFINED;
if branch_type == BranchType_RET() then
UNDEFINED;then
if n != 31 then UNDEFINED;
n = 30;
source_is_sp = TRUE;
bits(64) target = X[30];
bits(64) modifier =[n];
if pac then
bits(64) modifier = if source_is_sp then SP[];
if use_key_a then
target =[] else X[m];
if use_key_a then
target = AuthIA(target, modifier);
else
target = AuthIB(target, modifier);(target, modifier);
if branch_type ==
BranchToBranchType_INDCALL(target,then X[30] = PC[] + 4;
// Value in BTypeNext will be used to set PSTATE.BTYPE
case branch_type of
when BranchType_INDIR // BR, BRAA, BRAB, BRAAZ, BRABZ
if InGuardedPage then
if n == 16 || n == 17 then
BTypeNext = '01';
else
BTypeNext = '11';
else
BTypeNext = '01';
when BranchType_INDCALL // BLR, BLRAA, BLRAB, BLRAAZ, BLRABZ
BTypeNext = '10';
when BranchType_RET // RET, RETAA, RETAB
BTypeNext = '00';
BranchTo);(target, branch_type);
Internal version only: isa v30.44, AdvSIMD v27.08, pseudocode v8.5-2019-06_rc2-5-g22901f2, sve v2019-06_rc4
; Build timestamp: 2019-06-26T22:3004
Copyright © 2010-2019 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.
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