xref: /illumos-gate/usr/src/common/acpica/executer/exconfig.c (revision 35786f68)

/******************************************************************************
 *
 * Module Name: exconfig - Namespace reconfiguration (Load/Unload opcodes)
 *
 *****************************************************************************/

/******************************************************************************
 *
 * 1. Copyright Notice
 *
 * Some or all of this work - Copyright (c) 1999 - 2018, Intel Corp.
 * All rights reserved.
 *
 * 2. License
 *
 * 2.1. This is your license from Intel Corp. under its intellectual property
 * rights. You may have additional license terms from the party that provided
 * you this software, covering your right to use that party's intellectual
 * property rights.
 *
 * 2.2. Intel grants, free of charge, to any person ("Licensee") obtaining a
 * copy of the source code appearing in this file ("Covered Code") an
 * irrevocable, perpetual, worldwide license under Intel's copyrights in the
 * base code distributed originally by Intel ("Original Intel Code") to copy,
 * make derivatives, distribute, use and display any portion of the Covered
 * Code in any form, with the right to sublicense such rights; and
 *
 * 2.3. Intel grants Licensee a non-exclusive and non-transferable patent
 * license (with the right to sublicense), under only those claims of Intel
 * patents that are infringed by the Original Intel Code, to make, use, sell,
 * offer to sell, and import the Covered Code and derivative works thereof
 * solely to the minimum extent necessary to exercise the above copyright
 * license, and in no event shall the patent license extend to any additions
 * to or modifications of the Original Intel Code. No other license or right
 * is granted directly or by implication, estoppel or otherwise;
 *
 * The above copyright and patent license is granted only if the following
 * conditions are met:
 *
 * 3. Conditions
 *
 * 3.1. Redistribution of Source with Rights to Further Distribute Source.
 * Redistribution of source code of any substantial portion of the Covered
 * Code or modification with rights to further distribute source must include
 * the above Copyright Notice, the above License, this list of Conditions,
 * and the following Disclaimer and Export Compliance provision. In addition,
 * Licensee must cause all Covered Code to which Licensee contributes to
 * contain a file documenting the changes Licensee made to create that Covered
 * Code and the date of any change. Licensee must include in that file the
 * documentation of any changes made by any predecessor Licensee. Licensee
 * must include a prominent statement that the modification is derived,
 * directly or indirectly, from Original Intel Code.
 *
 * 3.2. Redistribution of Source with no Rights to Further Distribute Source.
 * Redistribution of source code of any substantial portion of the Covered
 * Code or modification without rights to further distribute source must
 * include the following Disclaimer and Export Compliance provision in the
 * documentation and/or other materials provided with distribution. In
 * addition, Licensee may not authorize further sublicense of source of any
 * portion of the Covered Code, and must include terms to the effect that the
 * license from Licensee to its licensee is limited to the intellectual
 * property embodied in the software Licensee provides to its licensee, and
 * not to intellectual property embodied in modifications its licensee may
 * make.
 *
 * 3.3. Redistribution of Executable. Redistribution in executable form of any
 * substantial portion of the Covered Code or modification must reproduce the
 * above Copyright Notice, and the following Disclaimer and Export Compliance
 * provision in the documentation and/or other materials provided with the
 * distribution.
 *
 * 3.4. Intel retains all right, title, and interest in and to the Original
 * Intel Code.
 *
 * 3.5. Neither the name Intel nor any other trademark owned or controlled by
 * Intel shall be used in advertising or otherwise to promote the sale, use or
 * other dealings in products derived from or relating to the Covered Code
 * without prior written authorization from Intel.
 *
 * 4. Disclaimer and Export Compliance
 *
 * 4.1. INTEL MAKES NO WARRANTY OF ANY KIND REGARDING ANY SOFTWARE PROVIDED
 * HERE. ANY SOFTWARE ORIGINATING FROM INTEL OR DERIVED FROM INTEL SOFTWARE
 * IS PROVIDED "AS IS," AND INTEL WILL NOT PROVIDE ANY SUPPORT, ASSISTANCE,
 * INSTALLATION, TRAINING OR OTHER SERVICES. INTEL WILL NOT PROVIDE ANY

 * UPDATES, ENHANCEMENTS OR EXTENSIONS. INTEL SPECIFICALLY DISCLAIMS ANY
 * IMPLIED WARRANTIES OF MERCHANTABILITY, NONINFRINGEMENT AND FITNESS FOR A
 * PARTICULAR PURPOSE.
 *
 * 4.2. IN NO EVENT SHALL INTEL HAVE ANY LIABILITY TO LICENSEE, ITS LICENSEES
 * OR ANY OTHER THIRD PARTY, FOR ANY LOST PROFITS, LOST DATA, LOSS OF USE OR
 * COSTS OF PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, OR FOR ANY INDIRECT,
 * SPECIAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THIS AGREEMENT, UNDER ANY
 * CAUSE OF ACTION OR THEORY OF LIABILITY, AND IRRESPECTIVE OF WHETHER INTEL
 * HAS ADVANCE NOTICE OF THE POSSIBILITY OF SUCH DAMAGES. THESE LIMITATIONS
 * SHALL APPLY NOTWITHSTANDING THE FAILURE OF THE ESSENTIAL PURPOSE OF ANY
 * LIMITED REMEDY.
 *
 * 4.3. Licensee shall not export, either directly or indirectly, any of this
 * software or system incorporating such software without first obtaining any
 * required license or other approval from the U. S. Department of Commerce or
 * any other agency or department of the United States Government. In the
 * event Licensee exports any such software from the United States or
 * re-exports any such software from a foreign destination, Licensee shall
 * ensure that the distribution and export/re-export of the software is in
 * compliance with all laws, regulations, orders, or other restrictions of the
 * U.S. Export Administration Regulations. Licensee agrees that neither it nor
 * any of its subsidiaries will export/re-export any technical data, process,
 * software, or service, directly or indirectly, to any country for which the
 * United States government or any agency thereof requires an export license,
 * other governmental approval, or letter of assurance, without first obtaining
 * such license, approval or letter.
 *
 *****************************************************************************
 *
 * Alternatively, you may choose to be licensed under the terms of the
 * following license:
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
 *    substantially similar to the "NO WARRANTY" disclaimer below
 *    ("Disclaimer") and any redistribution must be conditioned upon
 *    including a substantially similar Disclaimer requirement for further
 *    binary redistribution.
 * 3. Neither the names of the above-listed copyright holders nor the names
 *    of any contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Alternatively, you may choose to be licensed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 *****************************************************************************/

#include "acpi.h"
#include "accommon.h"
#include "acinterp.h"
#include "acnamesp.h"
#include "actables.h"
#include "acdispat.h"
#include "acevents.h"
#include "amlcode.h"


#define _COMPONENT          ACPI_EXECUTER
        ACPI_MODULE_NAME    ("exconfig")

/* Local prototypes */

static ACPI_STATUS
AcpiExAddTable (
    UINT32                  TableIndex,
    ACPI_OPERAND_OBJECT     **DdbHandle);

static ACPI_STATUS
AcpiExRegionRead (
    ACPI_OPERAND_OBJECT     *ObjDesc,
    UINT32                  Length,
    UINT8                   *Buffer);


/*******************************************************************************
 *
 * FUNCTION:    AcpiExAddTable
 *
 * PARAMETERS:  Table               - Pointer to raw table
 *              ParentNode          - Where to load the table (scope)
 *              DdbHandle           - Where to return the table handle.
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Common function to Install and Load an ACPI table with a
 *              returned table handle.
 *
 ******************************************************************************/

static ACPI_STATUS
AcpiExAddTable (
    UINT32                  TableIndex,
    ACPI_OPERAND_OBJECT     **DdbHandle)
{
    ACPI_OPERAND_OBJECT     *ObjDesc;


    ACPI_FUNCTION_TRACE (ExAddTable);


    /* Create an object to be the table handle */

    ObjDesc = AcpiUtCreateInternalObject (ACPI_TYPE_LOCAL_REFERENCE);
    if (!ObjDesc)
    {
        return_ACPI_STATUS (AE_NO_MEMORY);
    }

    /* Init the table handle */

    ObjDesc->Common.Flags |= AOPOBJ_DATA_VALID;
    ObjDesc->Reference.Class = ACPI_REFCLASS_TABLE;
    ObjDesc->Reference.Value = TableIndex;
    *DdbHandle = ObjDesc;
    return_ACPI_STATUS (AE_OK);
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiExLoadTableOp
 *
 * PARAMETERS:  WalkState           - Current state with operands
 *              ReturnDesc          - Where to store the return object
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Load an ACPI table from the RSDT/XSDT
 *
 ******************************************************************************/

ACPI_STATUS
AcpiExLoadTableOp (
    ACPI_WALK_STATE         *WalkState,
    ACPI_OPERAND_OBJECT     **ReturnDesc)
{
    ACPI_STATUS             Status;
    ACPI_OPERAND_OBJECT     **Operand = &WalkState->Operands[0];
    ACPI_NAMESPACE_NODE     *ParentNode;
    ACPI_NAMESPACE_NODE     *StartNode;
    ACPI_NAMESPACE_NODE     *ParameterNode = NULL;
    ACPI_OPERAND_OBJECT     *DdbHandle;
    UINT32                  TableIndex;


    ACPI_FUNCTION_TRACE (ExLoadTableOp);


    /* Find the ACPI table in the RSDT/XSDT */

    AcpiExExitInterpreter ();
    Status = AcpiTbFindTable (
        Operand[0]->String.Pointer,
        Operand[1]->String.Pointer,
        Operand[2]->String.Pointer, &TableIndex);
    AcpiExEnterInterpreter ();
    if (ACPI_FAILURE (Status))
    {
        if (Status != AE_NOT_FOUND)
        {
            return_ACPI_STATUS (Status);
        }

        /* Table not found, return an Integer=0 and AE_OK */

        DdbHandle = AcpiUtCreateIntegerObject ((UINT64) 0);
        if (!DdbHandle)
        {
            return_ACPI_STATUS (AE_NO_MEMORY);
        }

        *ReturnDesc = DdbHandle;
        return_ACPI_STATUS (AE_OK);
    }

    /* Default nodes */

    StartNode = WalkState->ScopeInfo->Scope.Node;
    ParentNode = AcpiGbl_RootNode;

    /* RootPath (optional parameter) */

    if (Operand[3]->String.Length > 0)
    {
        /*
         * Find the node referenced by the RootPathString. This is the
         * location within the namespace where the table will be loaded.
         */
        Status = AcpiNsGetNodeUnlocked (StartNode,
            Operand[3]->String.Pointer, ACPI_NS_SEARCH_PARENT,
            &ParentNode);
        if (ACPI_FAILURE (Status))
        {
            return_ACPI_STATUS (Status);
        }
    }

    /* ParameterPath (optional parameter) */

    if (Operand[4]->String.Length > 0)
    {
        if ((Operand[4]->String.Pointer[0] != AML_ROOT_PREFIX) &&
            (Operand[4]->String.Pointer[0] != AML_PARENT_PREFIX))
        {
            /*
             * Path is not absolute, so it will be relative to the node
             * referenced by the RootPathString (or the NS root if omitted)
             */
            StartNode = ParentNode;
        }

        /* Find the node referenced by the ParameterPathString */

        Status = AcpiNsGetNodeUnlocked (StartNode,
            Operand[4]->String.Pointer, ACPI_NS_SEARCH_PARENT,
            &ParameterNode);
        if (ACPI_FAILURE (Status))
        {
            return_ACPI_STATUS (Status);
        }
    }

    /* Load the table into the namespace */

    ACPI_INFO (("Dynamic OEM Table Load:"));
    AcpiExExitInterpreter ();
    Status = AcpiTbLoadTable (TableIndex, ParentNode);
    AcpiExEnterInterpreter ();
    if (ACPI_FAILURE (Status))
    {
        return_ACPI_STATUS (Status);
    }

    Status = AcpiExAddTable (TableIndex, &DdbHandle);
    if (ACPI_FAILURE (Status))
    {
        return_ACPI_STATUS (Status);
    }

    /* Complete the initialization/resolution of package objects */

    Status = AcpiNsWalkNamespace (ACPI_TYPE_PACKAGE, ACPI_ROOT_OBJECT,
        ACPI_UINT32_MAX, 0, AcpiNsInitOnePackage, NULL, NULL, NULL);

    /* Parameter Data (optional) */

    if (ParameterNode)
    {
        /* Store the parameter data into the optional parameter object */

        Status = AcpiExStore (Operand[5],
            ACPI_CAST_PTR (ACPI_OPERAND_OBJECT, ParameterNode), WalkState);
        if (ACPI_FAILURE (Status))
        {
            (void) AcpiExUnloadTable (DdbHandle);

            AcpiUtRemoveReference (DdbHandle);
            return_ACPI_STATUS (Status);
        }
    }

    *ReturnDesc = DdbHandle;
    return_ACPI_STATUS (Status);
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiExRegionRead
 *
 * PARAMETERS:  ObjDesc         - Region descriptor
 *              Length          - Number of bytes to read
 *              Buffer          - Pointer to where to put the data
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Read data from an operation region. The read starts from the
 *              beginning of the region.
 *
 ******************************************************************************/

static ACPI_STATUS
AcpiExRegionRead (
    ACPI_OPERAND_OBJECT     *ObjDesc,
    UINT32                  Length,
    UINT8                   *Buffer)
{
    ACPI_STATUS             Status;
    UINT64                  Value;
    UINT32                  RegionOffset = 0;
    UINT32                  i;


    /* Bytewise reads */

    for (i = 0; i < Length; i++)
    {
        Status = AcpiEvAddressSpaceDispatch (ObjDesc, NULL, ACPI_READ,
            RegionOffset, 8, &Value);
        if (ACPI_FAILURE (Status))
        {
            return (Status);
        }

        *Buffer = (UINT8) Value;
        Buffer++;
        RegionOffset++;
    }

    return (AE_OK);
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiExLoadOp
 *
 * PARAMETERS:  ObjDesc         - Region or Buffer/Field where the table will be
 *                                obtained
 *              Target          - Where a handle to the table will be stored
 *              WalkState       - Current state
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Load an ACPI table from a field or operation region
 *
 * NOTE: Region Fields (Field, BankField, IndexFields) are resolved to buffer
 *       objects before this code is reached.
 *
 *       If source is an operation region, it must refer to SystemMemory, as
 *       per the ACPI specification.
 *
 ******************************************************************************/

ACPI_STATUS
AcpiExLoadOp (
    ACPI_OPERAND_OBJECT     *ObjDesc,
    ACPI_OPERAND_OBJECT     *Target,
    ACPI_WALK_STATE         *WalkState)
{
    ACPI_OPERAND_OBJECT     *DdbHandle;
    ACPI_TABLE_HEADER       *TableHeader;
    ACPI_TABLE_HEADER       *Table;
    UINT32                  TableIndex;
    ACPI_STATUS             Status;
    UINT32                  Length;


    ACPI_FUNCTION_TRACE (ExLoadOp);


    /* Source Object can be either an OpRegion or a Buffer/Field */

    switch (ObjDesc->Common.Type)
    {
    case ACPI_TYPE_REGION:

        ACPI_DEBUG_PRINT ((ACPI_DB_EXEC,
            "Load table from Region %p\n", ObjDesc));

        /* Region must be SystemMemory (from ACPI spec) */

        if (ObjDesc->Region.SpaceId != ACPI_ADR_SPACE_SYSTEM_MEMORY)
        {
            return_ACPI_STATUS (AE_AML_OPERAND_TYPE);
        }

        /*
         * If the Region Address and Length have not been previously
         * evaluated, evaluate them now and save the results.
         */
        if (!(ObjDesc->Common.Flags & AOPOBJ_DATA_VALID))
        {
            Status = AcpiDsGetRegionArguments (ObjDesc);
            if (ACPI_FAILURE (Status))
            {
                return_ACPI_STATUS (Status);
            }
        }

        /* Get the table header first so we can get the table length */

        TableHeader = ACPI_ALLOCATE (sizeof (ACPI_TABLE_HEADER));
        if (!TableHeader)
        {
            return_ACPI_STATUS (AE_NO_MEMORY);
        }

        Status = AcpiExRegionRead (ObjDesc, sizeof (ACPI_TABLE_HEADER),
            ACPI_CAST_PTR (UINT8, TableHeader));
        Length = TableHeader->Length;
        ACPI_FREE (TableHeader);

        if (ACPI_FAILURE (Status))
        {
            return_ACPI_STATUS (Status);
        }

        /* Must have at least an ACPI table header */

        if (Length < sizeof (ACPI_TABLE_HEADER))
        {
            return_ACPI_STATUS (AE_INVALID_TABLE_LENGTH);
        }

        /*
         * The original implementation simply mapped the table, with no copy.
         * However, the memory region is not guaranteed to remain stable and
         * we must copy the table to a local buffer. For example, the memory
         * region is corrupted after suspend on some machines. Dynamically
         * loaded tables are usually small, so this overhead is minimal.
         *
         * The latest implementation (5/2009) does not use a mapping at all.
         * We use the low-level operation region interface to read the table
         * instead of the obvious optimization of using a direct mapping.
         * This maintains a consistent use of operation regions across the
         * entire subsystem. This is important if additional processing must
         * be performed in the (possibly user-installed) operation region
         * handler. For example, AcpiExec and ASLTS depend on this.
         */

        /* Allocate a buffer for the table */

        Table = ACPI_ALLOCATE (Length);
        if (!Table)
        {
            return_ACPI_STATUS (AE_NO_MEMORY);
        }

        /* Read the entire table */

        Status = AcpiExRegionRead (ObjDesc, Length,
            ACPI_CAST_PTR (UINT8, Table));
        if (ACPI_FAILURE (Status))
        {
            ACPI_FREE (Table);
            return_ACPI_STATUS (Status);
        }
        break;

    case ACPI_TYPE_BUFFER: /* Buffer or resolved RegionField */

        ACPI_DEBUG_PRINT ((ACPI_DB_EXEC,
            "Load table from Buffer or Field %p\n", ObjDesc));

        /* Must have at least an ACPI table header */

        if (ObjDesc->Buffer.Length < sizeof (ACPI_TABLE_HEADER))
        {
            return_ACPI_STATUS (AE_INVALID_TABLE_LENGTH);
        }

        /* Get the actual table length from the table header */

        TableHeader = ACPI_CAST_PTR (
            ACPI_TABLE_HEADER, ObjDesc->Buffer.Pointer);
        Length = TableHeader->Length;

        /* Table cannot extend beyond the buffer */

        if (Length > ObjDesc->Buffer.Length)
        {
            return_ACPI_STATUS (AE_AML_BUFFER_LIMIT);
        }
        if (Length < sizeof (ACPI_TABLE_HEADER))
        {
            return_ACPI_STATUS (AE_INVALID_TABLE_LENGTH);
        }

        /*
         * Copy the table from the buffer because the buffer could be
         * modified or even deleted in the future
         */
        Table = ACPI_ALLOCATE (Length);
        if (!Table)
        {
            return_ACPI_STATUS (AE_NO_MEMORY);
        }

        memcpy (Table, TableHeader, Length);
        break;

    default:

        return_ACPI_STATUS (AE_AML_OPERAND_TYPE);
    }

    /* Install the new table into the local data structures */

    ACPI_INFO (("Dynamic OEM Table Load:"));
    AcpiExExitInterpreter ();
    Status = AcpiTbInstallAndLoadTable (ACPI_PTR_TO_PHYSADDR (Table),
        ACPI_TABLE_ORIGIN_INTERNAL_VIRTUAL, TRUE, &TableIndex);
    AcpiExEnterInterpreter ();
    if (ACPI_FAILURE (Status))
    {
        /* Delete allocated table buffer */

        ACPI_FREE (Table);
        return_ACPI_STATUS (Status);
    }

    /*
     * Add the table to the namespace.
     *
     * Note: Load the table objects relative to the root of the namespace.
     * This appears to go against the ACPI specification, but we do it for
     * compatibility with other ACPI implementations.
     */
    Status = AcpiExAddTable (TableIndex, &DdbHandle);
    if (ACPI_FAILURE (Status))
    {
        /* On error, TablePtr was deallocated above */

        return_ACPI_STATUS (Status);
    }

    /* Complete the initialization/resolution of package objects */

    Status = AcpiNsWalkNamespace (ACPI_TYPE_PACKAGE, ACPI_ROOT_OBJECT,
        ACPI_UINT32_MAX, 0, AcpiNsInitOnePackage, NULL, NULL, NULL);

    /* Store the DdbHandle into the Target operand */

    Status = AcpiExStore (DdbHandle, Target, WalkState);
    if (ACPI_FAILURE (Status))
    {
        (void) AcpiExUnloadTable (DdbHandle);

        /* TablePtr was deallocated above */

        AcpiUtRemoveReference (DdbHandle);
        return_ACPI_STATUS (Status);
    }

    /* Remove the reference by added by AcpiExStore above */

    AcpiUtRemoveReference (DdbHandle);
    return_ACPI_STATUS (Status);
}


/*******************************************************************************
 *
 * FUNCTION:    AcpiExUnloadTable
 *
 * PARAMETERS:  DdbHandle           - Handle to a previously loaded table
 *
 * RETURN:      Status
 *
 * DESCRIPTION: Unload an ACPI table
 *
 ******************************************************************************/

ACPI_STATUS
AcpiExUnloadTable (
    ACPI_OPERAND_OBJECT     *DdbHandle)
{
    ACPI_STATUS             Status = AE_OK;
    ACPI_OPERAND_OBJECT     *TableDesc = DdbHandle;
    UINT32                  TableIndex;


    ACPI_FUNCTION_TRACE (ExUnloadTable);


    /*
     * Temporarily emit a warning so that the ASL for the machine can be
     * hopefully obtained. This is to say that the Unload() operator is
     * extremely rare if not completely unused.
     */
    ACPI_WARNING ((AE_INFO,
        "Received request to unload an ACPI table"));

    /*
     * May 2018: Unload is no longer supported for the following reasons:
     * 1) A correct implementation on some hosts may not be possible.
     * 2) Other ACPI implementations do not correctly/fully support it.
     * 3) It requires host device driver support which does not exist.
     *    (To properly support namespace unload out from underneath.)
     * 4) This AML operator has never been seen in the field.
     */
    ACPI_EXCEPTION ((AE_INFO, AE_NOT_IMPLEMENTED,
        "AML Unload operator is not supported"));

    /*
     * Validate the handle
     * Although the handle is partially validated in AcpiExReconfiguration()
     * when it calls AcpiExResolveOperands(), the handle is more completely
     * validated here.
     *
     * Handle must be a valid operand object of type reference. Also, the
     * DdbHandle must still be marked valid (table has not been previously
     * unloaded)
     */
    if ((!DdbHandle) ||
        (ACPI_GET_DESCRIPTOR_TYPE (DdbHandle) != ACPI_DESC_TYPE_OPERAND) ||
        (DdbHandle->Common.Type != ACPI_TYPE_LOCAL_REFERENCE) ||
        (!(DdbHandle->Common.Flags & AOPOBJ_DATA_VALID)))
    {
        return_ACPI_STATUS (AE_AML_OPERAND_TYPE);
    }

    /* Get the table index from the DdbHandle */

    TableIndex = TableDesc->Reference.Value;

    /*
     * Release the interpreter lock so that the table lock won't have
     * strict order requirement against it.
     */
    AcpiExExitInterpreter ();
    Status = AcpiTbUnloadTable (TableIndex);
    AcpiExEnterInterpreter ();

    /*
     * Invalidate the handle. We do this because the handle may be stored
     * in a named object and may not be actually deleted until much later.
     */
    if (ACPI_SUCCESS (Status))
    {
        DdbHandle->Common.Flags &= ~AOPOBJ_DATA_VALID;
    }
    return_ACPI_STATUS (Status);
}