PACIA, PACIA1716, PACIASP, PACIAZ, PACIZA

Pointer Authentication Code for Instruction address, using key A. This instruction computes and inserts a pointer authentication code for an instruction address, using a modifier and key A.

The address is:

• In the general-purpose register that is specified by <Xd> for PACIA and PACIZA.
• In X17, for PACIA1716.
• In X30, for PACIASP and PACIAZ.

The modifier is:

• In the general-purpose register or stack pointer that is specified by <Xn|SP> for PACIA.
• The value zero, for PACIZA and PACIAZ.
• In X16, for PACIA1716.
• In SP, for PACIASP.

If FEAT_PAuth_LR is implemented and PSTATE.PACM is 1, then PACIA1716 and PACIASP include a second modifier that is:

• In X15, for PACIA1716.
• The value of PC, for PACIASP.

A PACIASP instruction has an implicit BTI instruction. The implicit BTI instruction of a PACIASP instruction is always compatible with PSTATE.BTYPE == 0b01 and PSTATE.BTYPE == 0b10. Controls in SCTLR_ELx configure whether the implicit BTI instruction of a PACIASP 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)

if !IsFeatureImplemented(FEAT_PAuth) then UNDEFINED; boolean source_is_sp = FALSE; boolean pacia1716 = FALSE; integer d = UInt(Rd); integer n = UInt(Rn); if Z == '0' then // PACIA if n == 31 then source_is_sp = TRUE; else // PACIZA if n != 31 then UNDEFINED;

System
(FEAT_PAuth)

if !IsFeatureImplemented(FEAT_PAuth) then EndOfInstruction(); // Instruction executes as NOP integer d; integer n; boolean source_is_sp = FALSE; boolean pacia1716 = FALSE; case CRm:op2 of when '0011 000' // PACIAZ d = 30; n = 31; when '0011 001' // PACIASP d = 30; source_is_sp = TRUE; if IsFeatureImplemented(FEAT_BTI) then // Check for branch target compatibility between PSTATE.BTYPE // and implicit branch target of PACIASP instruction. SetBTypeCompatible(BTypeCompatible_PACIXSP()); when '0001 000' // PACIA1716 d = 17; n = 16; pacia1716 = TRUE; when '0001 010' SEE "PACIB"; when '0001 100' SEE "AUTIA"; when '0001 110' SEE "AUTIB"; when '0011 01x' SEE "PACIB"; when '0011 10x' SEE "AUTIA"; when '0011 11x' SEE "AUTIB"; when '0000 111' SEE "XPACLRI"; otherwise SEE "HINT";