# GETSEC[CAPABILITIES] — Report the SMX Capabilities

Opcode | Instruction | Description
--- | --- | ---
NP 0F 37 (EAX = 0) | GETSEC[CAPABILITIES] | Report the SMX capabilities. The capabilities index is input in EBX with the result returned in EAX.

## Description ¶

The GETSEC[CAPABILITIES] function returns a bit vector of supported GETSEC leaf functions. The CAPABILITIES leaf of GETSEC is selected with EAX set to 0 at entry. EBX is used as the selector for returning the bit vector field in EAX. GETSEC[CAPABILITIES] may be executed at all privilege levels, but the CR4.SMXE bit must be set or an undefined opcode exception (#UD) is returned.

With EBX = 0 upon execution of GETSEC[CAPABILITIES], EAX returns the a bit vector representing status on the presence of a Intel® TXT-capable chipset and the first 30 available GETSEC leaf functions. The format of the returned bit vector is provided in Table 7-3.

If bit 0 is set to 1, then an Intel® TXT-capable chipset has been sampled present by the processor. If bits in the range of 1-30 are set, then the corresponding GETSEC leaf function is available. If the bit value at a given bit index is 0, then the GETSEC leaf function corresponding to that index is unsupported and attempted execution results in a #UD.

Bit 31 of EAX indicates if further leaf indexes are supported. If the Extended Leafs bit 31 is set, then additional leaf functions are accessed by repeating GETSEC[CAPABILITIES] with EBX incremented by one. When the most significant bit of EAX is not set, then additional GETSEC leaf functions are not supported; indexing EBX to a higher value results in EAX returning zero.

Field | Bit position | Description
--- | --- | ---
Chipset Present | 0 | Intel® TXT-capable chipset is present.
Undefined | 1 | Reserved
ENTERACCS | 2 | GETSEC[ENTERACCS] is available.
EXITAC | 3 | GETSEC[EXITAC] is available.
SENTER | 4 | GETSEC[SENTER] is available.
SEXIT | 5 | GETSEC[SEXIT] is available.
PARAMETERS | 6 | GETSEC[PARAMETERS] is available.
SMCTRL | 7 | GETSEC[SMCTRL] is available.
WAKEUP | 8 | GETSEC[WAKEUP] is available.
Undefined | 30:9 | Reserved
Extended Leafs | 31 | Reserved for extended information reporting of GETSEC capabilities.

Table 7-3. GETSEC Capability Result Encoding (EBX = 0)

## Operation ¶

    IF (CR4.SMXE=0)
        THEN #UD;
    ELSIF (in VMX non-root operation)
        THEN VM Exit (reason=”GETSEC instruction”);
    IF (EBX=0) THEN
            BitVector := 0;
            IF (TXT chipset present)
                BitVector[Chipset present] := 1;
            IF (ENTERACCS Available)
                THEN BitVector[ENTERACCS] := 1;
            IF (EXITAC Available)
                THEN BitVector[EXITAC] := 1;
            IF (SENTER Available)
                THEN BitVector[SENTER] := 1;
            IF (SEXIT Available)
                THEN BitVector[SEXIT] := 1;
            IF (PARAMETERS Available)
                THEN BitVector[PARAMETERS] := 1;
            IF (SMCTRL Available)
                THEN BitVector[SMCTRL] := 1;
            IF (WAKEUP Available)
                THEN BitVector[WAKEUP] := 1;
            EAX := BitVector;
    ELSE
        EAX := 0;
    END;;

## Flags Affected ¶

None.

## Use of Prefixes ¶

LOCK Causes #UD.

REP* Cause #UD (includes REPNE/REPNZ and REP/REPE/REPZ).

Operand size Causes #UD.

NP 66/F2/F3 prefixes are not allowed.

Segmentoverrides Ignored.

Address size Ignored.

REX Ignored.

## Protected Mode Exceptions ¶

#UD | If CR4.SMXE = 0.

## Real-Address Mode Exceptions ¶

#UD | If CR4.SMXE = 0.

## Virtual-8086 Mode Exceptions ¶

#UD | If CR4.SMXE = 0.

## Compatibility Mode Exceptions ¶

#UD | If CR4.SMXE = 0.

## 64-Bit Mode Exceptions ¶

#UD | If CR4.SMXE = 0.

## VM-exit Condition ¶

Reason (GETSEC) If in VMX non-root operation.