Load register, with pointer authentication
This instruction authenticates an address from a base register using a modifier of zero and the specified key, adds an immediate offset to the authenticated address, and loads a 64-bit doubleword from memory at this resulting address into a register.
Key A is used for LDRAA. Key B is used for LDRAB.
If the authentication passes, the PE behaves the same as for an LDR instruction. For information on behavior if the authentication fails, see Faulting on pointer authentication.
The authenticated address is not written back to the base register, unless the pre-indexed variant of the instruction is used. In this case, the address that is written back to the base register does not include the pointer authentication code.
For information about addressing modes, see Load/Store addressing modes.
| 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 | 1 | 1 | 1 | 0 | 0 | 0 | M | S | 1 | imm9 | W | 1 | Rn | Rt | ||||||||||||||||
| size | VR | ||||||||||||||||||||||||||||||
if !IsFeatureImplemented(FEAT_PAuth) then EndOfDecode(Decode_UNDEF); end; let t : integer = UInt(Rt); let n : integer = UInt(Rn); var wback : boolean = W == '1'; let use_key_a : boolean = M == '0'; let S10 : bits(10) = S::imm9; let offset : bits(64) = LSL(SignExtend{64}(S10), 3); let nontemporal : boolean = FALSE; let tagchecked : boolean = wback || n != 31; var wb_unknown : boolean = FALSE; if wback && n == t && n != 31 then let c : Constraint = ConstrainUnpredictable(Unpredictable_WBOVERLAPLD); assert c IN {Constraint_WBSUPPRESS, Constraint_UNKNOWN, Constraint_UNDEF, Constraint_NOP}; case c of when Constraint_WBSUPPRESS => wback = FALSE; // writeback is suppressed when Constraint_UNKNOWN => wb_unknown = TRUE; // writeback is UNKNOWN when Constraint_UNDEF => EndOfDecode(Decode_UNDEF); when Constraint_NOP => EndOfDecode(Decode_NOP); end; end;
| <Xt> |
Is the 64-bit name of the general-purpose register to be transferred, encoded in the "Rt" field. |
| <Xn|SP> |
Is the 64-bit name of the general-purpose base register or stack pointer, encoded in the "Rn" field. |
| <simm> |
Is the optional signed immediate byte offset, a multiple of 8 in the range -4096 to 4088, defaulting to 0 and encoded in the "S:imm9" field as <simm>/8. |
var address : bits(64); let privileged : boolean = PSTATE.EL != EL0; let auth_then_branch : boolean = TRUE; let accdesc : AccessDescriptor = CreateAccDescGPR(MemOp_LOAD, nontemporal, privileged, tagchecked, t); if n == 31 then address = SP{64}(); else address = X{64}(n); end; if use_key_a then address = AuthDA(address, X{64}(31), auth_then_branch); else address = AuthDB(address, X{64}(31), auth_then_branch); end; if n == 31 then CheckSPAlignment(); end; address = AddressAdd(address, offset, accdesc); X{64}(t) = Mem{64}(address, accdesc); if wback then if wb_unknown then address = ARBITRARY : bits(64); end; if n == 31 then SP{64}() = address; else X{64}(n) = address; end; end;
This instruction is a data-independent-time instruction as described in About PSTATE.DIT.
2026-03_rel 2026-03-26 20:48:11
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