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# GCSPUSHX, Guarded Control Stack Push exception return record

The GCSPUSHX characteristics are:

## Purpose

Decrements the current Guarded Control Stack Pointer register by the size of a Guarded Control Stack exception return record and stores a Guarded Control Stack exception return record to the Guarded Control Stack.

## Configuration

This instruction is present only when FEAT_GCS is implemented. Otherwise, direct accesses to GCSPUSHX are UNDEFINED.

## Attributes

GCSPUSHX is a 64-bit System instruction.

## Field descriptions

This instruction has no applicable fields.

The value in the register specified by <Xt> is ignored.

## Executing GCSPUSHX

Rt should be encoded as 0b11111. If the Rt field is not set to 0b11111, it is CONSTRAINED UNPREDICTABLE whether:

- The instruction is UNDEFINED.

- The instruction behaves as if the Rt field is set to 0b11111.

Accesses to this instruction use the following encodings in the System instruction encoding space:

#### GCSPUSHX

op0 | op1 | CRn | CRm | op2
--- | --- | --- | --- | ---
0b01 | 0b000 | 0b0111 | 0b0111 | 0b100

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if IsFeatureImplemented(FEAT_GCS) && GetCurrentEXLOCKEN() && !Halted() && PSTATE.EXLOCK == '0' then EXLOCKException(); elsif EL2Enabled() && IsFeatureImplemented(FEAT_FGT) && (!HaveEL(EL3) || SCR_EL3.FGTEn == '1') && HFGITR_EL2.nGCSEPP == '0' then AArch64.SystemAccessTrap(EL2, 0x18); else GCSPUSHX(); elsif PSTATE.EL == EL2 then if IsFeatureImplemented(FEAT_GCS) && GetCurrentEXLOCKEN() && !Halted() && PSTATE.EXLOCK == '0' then EXLOCKException(); else GCSPUSHX(); elsif PSTATE.EL == EL3 then if IsFeatureImplemented(FEAT_GCS) && GetCurrentEXLOCKEN() && !Halted() && PSTATE.EXLOCK == '0' then EXLOCKException(); else GCSPUSHX();

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26/03/2024 09:49; 67c0ae5282a7629ba0ea0ba7267b43cd4f7939f6

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