Index

GCSSTTR

Guarded Control Stack unprivileged Store stores a doubleword from a register to memory. The address that is used for the store is calculated from a base register.

Memory accesses made 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 memory access operates with the restrictions determined by the Exception level at which the instruction is executed.

Integer
(FEAT_GCS)

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

GCSSTTR <Xt>, [<Xn|SP>]

if !IsFeatureImplemented(FEAT_GCS) then UNDEFINED;
integer n = UInt(Rn);
integer t = UInt(Rt);

Assembler Symbols

<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.

Operation

bits(64) address;
bits(64) data;

bits(2) effective_el = if AArch64.IsUnprivAccessPriv() then PSTATE.EL else EL0;

if effective_el == PSTATE.EL then
    CheckGCSSTREnabled();

AccessDescriptor accdesc = CreateAccDescGCS(effective_el, MemOp_STORE);

if n == 31 then
    CheckSPAlignment();
    address = SP[];
else
    address = X[n, 64];

data = X[t, 64];
Mem[address, 8, accdesc] = data;