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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, 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.

Integer
(Armv8.3)

313029282726252423222120191817161514131211109876543210
110101100101111100001M1111111111
ZopARnRm

RETAA (M == 0)

RETAA

RETAB (M == 1)

RETAB

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;

Operation

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

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