PACIB, PACIB1716, PACIBSP, PACIBZ, PACIZB

Pointer Authentication Code for instruction address, using key B

This instruction calculates and inserts a Pointer Authentication Code for an instruction address, using a modifier and key B.

The address is:

• In the general-purpose register that is specified by <Xd> for PACIB and PACIZB.
• In X17, for PACIB1716.
• In X30, for PACIBSP and PACIBZ.

The modifier is:

• In the general-purpose register or stack pointer that is specified by <Xn|SP> for PACIB.
• The value zero, for PACIZB and PACIBZ.
• In X16, for PACIB1716.
• In SP, for PACIBSP.

If FEAT_PAuth_LR is implemented and PSTATE.PACM is 1, then PACIB1716 and PACIBSP include a second modifier that is:

• In X15, for PACIB1716.
• The value of PC, for PACIBSP.

A PACIBSP instruction has an implicit BTI instruction. The implicit BTI instruction of a PACIBSP instruction is always compatible with PSTATE.BTYPE == 0b01 and PSTATE.BTYPE == 0b10. Controls in SCTLR_ELx configure whether the implicit BTI instruction of a PACIBSP instruction is compatible with PSTATE.BTYPE == 0b11. For more information, see PSTATE.BTYPE.

It has encodings from 2 classes: Integer and System

Integer
(FEAT_PAuth)

Decode for all variants of this encoding

if !IsFeatureImplemented(FEAT_PAuth) then EndOfDecode(Decode_UNDEF); end; var source_is_sp : boolean = FALSE; let pacib1716 : boolean = FALSE; let d : integer = UInt(Rd); let n : integer = UInt(Rn); if Z == '0' then // PACIB if n == 31 then source_is_sp = TRUE; end; else // PACIZB if n != 31 then EndOfDecode(Decode_UNDEF); end; end;

System
(FEAT_PAuth)

Decode for all variants of this encoding

if !IsFeatureImplemented(FEAT_PAuth) then EndOfDecode(Decode_NOP); end; var d : integer; var n : integer; var source_is_sp : boolean = FALSE; var pacib1716 : boolean = FALSE; case CRm::op2 of when '0011 010' => // PACIBZ d = 30; n = 31; when '0011 011' => // PACIBSP d = 30; source_is_sp = TRUE; if IsFeatureImplemented(FEAT_BTI) then // Check for branch target compatibility between PSTATE.BTYPE // and implicit branch target of PACIBSP instruction. let pacinst : PACInstType = PACIxSP; SetBTypeCompatible(BTypeCompatible_PAC(pacinst)); end; when '0001 010' => // PACIB1716 d = 17; n = 16; pacib1716 = TRUE; end;