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:
Otherwise, the Explicit Memory effects operate with the restrictions determined by the Exception level at which the instruction is executed.
| 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 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | Rn | Rt | ||||||||
| opc | |||||||||||||||||||||||||||||||
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_rel 2026-03-26 20:48:11
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