LDRAA, LDRAB
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.
If PSTATE.DIT is 1, the timing of this instruction is insensitive to the value of the data being loaded or stored.
1
1
1
1
1
0
0
0
1
1
0
0
LDRAA <Xt>, [<Xn|SP>{, #<simm>}]
0
1
LDRAA <Xt>, [<Xn|SP>{, #<simm>}]!
1
0
LDRAB <Xt>, [<Xn|SP>{, #<simm>}]
1
1
LDRAB <Xt>, [<Xn|SP>{, #<simm>}]!
if !IsFeatureImplemented(FEAT_PAuth) then UNDEFINED;
constant integer t = UInt(Rt);
constant integer n = UInt(Rn);
boolean wback = W == '1';
constant boolean use_key_a = M == '0';
constant bits(10) S10 = S:imm9;
constant bits(64) offset = LSL(SignExtend(S10, 64), 3);
constant boolean nontemporal = FALSE;
constant boolean tagchecked = wback || n != 31;
<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.
bits(64) address;
constant boolean privileged = PSTATE.EL != EL0;
boolean wb_unknown = FALSE;
constant boolean auth_then_branch = TRUE;
constant AccessDescriptor accdesc = CreateAccDescGPR(MemOp_LOAD, nontemporal, privileged,
tagchecked);
if wback && n == t && n != 31 then
constant Constraint c = 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 UNDEFINED;
when Constraint_NOP ExecuteAsNOP();
if n == 31 then
address = SP[];
else
address = X[n, 64];
if use_key_a then
address = AuthDA(address, X[31, 64], auth_then_branch);
else
address = AuthDB(address, X[31, 64], auth_then_branch);
if n == 31 then
CheckSPAlignment();
address = AddressAdd(address, offset, accdesc);
X[t, 64] = Mem[address, 8, accdesc];
if wback then
if wb_unknown then
address = bits(64) UNKNOWN;
if n == 31 then
SP[] = address;
else
X[n, 64] = address;