GCSSTTR
Guarded Control Stack store register (unprivileged)
This instruction stores a
doubleword from a register to memory. The address that
is used for the store is calculated from a base register.
Explicit Memory effects produced by the instruction behave as if the instruction was
executed at EL0 if the Effective value of
PSTATE.UAO is 0 and either:
The instruction is executed at EL1 and the Effective value of HCR_EL2.{NV1, NV} is not {1, 1}.
The instruction is executed at EL2 when the Effective value
of HCR_EL2().{E2H, TGE} is '11'.
Otherwise, the Explicit Memory effects operate with the restrictions determined by
the Exception level at which the instruction is executed.
1
1
0
1
1
0
0
1
0
0
0
1
1
1
1
1
0
0
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1
GCSSTTR <Xt>, [<Xn|SP>]
if !IsFeatureImplemented(FEAT_GCS) then EndOfDecode(Decode_UNDEF); end;
let t : integer{} = UInt(Rt);
let n : integer{} = UInt(Rn);
<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.
var address : bits(64);
let effective_el : bits(2) = if AArch64_IsUnprivAccessPriv() then PSTATE.EL else EL0;
if effective_el == PSTATE.EL then
CheckGCSSTREnabled();
end;
let privileged : boolean = effective_el != EL0;
let accdesc : AccessDescriptor = CreateAccDescGCS(MemOp_STORE, privileged);
if n == 31 then
CheckSPAlignment();
address = SP{64}();
else
address = X{64}(n);
end;
Mem{64}(address, accdesc) = X{64}(t);
2026-03-26 20:27:25
2026-03_rel