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/******************************************************************************

 *

 * Module Name: psparse - Parser top level AML parse routines

 *

 *****************************************************************************/

/******************************************************************************

 *

 * 1. Copyright Notice

 *

 * Some or all of this work - Copyright (c) 1999 - 2010, 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.

 *

 *****************************************************************************/

/*

 * Parse the AML and build an operation tree as most interpreters,

 * like Perl, do.  Parsing is done by hand rather than with a YACC

 * generated parser to tightly constrain stack and dynamic memory

 * usage.  At the same time, parsing is kept flexible and the code

 * fairly compact by parsing based on a list of AML opcode

 * templates in AmlOpInfo[]

 */

#include "acpi.h"

#include "accommon.h"

#include "acparser.h"

#include "acdispat.h"

#include "amlcode.h"

#include "acnamesp.h"

#include "acinterp.h"

#define _COMPONENT          ACPI_PARSER

        ACPI_MODULE_NAME    ("psparse")

/*******************************************************************************

 *

 * FUNCTION:    AcpiPsGetOpcodeSize

 *

 * PARAMETERS:  Opcode          - An AML opcode

 *

 * RETURN:      Size of the opcode, in bytes (1 or 2)

 *

 * DESCRIPTION: Get the size of the current opcode.

 *

 ******************************************************************************/

UINT32

AcpiPsGetOpcodeSize (

    UINT32                  Opcode)

{

    /* Extended (2-byte) opcode if > 255 */

    if (Opcode > 0x00FF)

    {

        return (2);

    }

    /* Otherwise, just a single byte opcode */

    return (1);

}

/*******************************************************************************

 *

 * FUNCTION:    AcpiPsPeekOpcode

 *

 * PARAMETERS:  ParserState         - A parser state object

 *

 * RETURN:      Next AML opcode

 *

 * DESCRIPTION: Get next AML opcode (without incrementing AML pointer)

 *

 ******************************************************************************/

UINT16

AcpiPsPeekOpcode (

    ACPI_PARSE_STATE        *ParserState)

{

    UINT8                   *Aml;

    UINT16                  Opcode;

    Aml = ParserState->Aml;

    Opcode = (UINT16) ACPI_GET8 (Aml);

    if (Opcode == AML_EXTENDED_OP_PREFIX)

    {

        /* Extended opcode, get the second opcode byte */

        Aml++;

        Opcode = (UINT16) ((Opcode << 8) | ACPI_GET8 (Aml));

    }

    return (Opcode);

}

/*******************************************************************************

 *

 * FUNCTION:    AcpiPsCompleteThisOp

 *

 * PARAMETERS:  WalkState       - Current State

 *              Op              - Op to complete

 *

 * RETURN:      Status

 *

 * DESCRIPTION: Perform any cleanup at the completion of an Op.

 *

 ******************************************************************************/

ACPI_STATUS

AcpiPsCompleteThisOp (

    ACPI_WALK_STATE         *WalkState,

    ACPI_PARSE_OBJECT       *Op)

{

    ACPI_PARSE_OBJECT       *Prev;

    ACPI_PARSE_OBJECT       *Next;

    const ACPI_OPCODE_INFO  *ParentInfo;

    ACPI_PARSE_OBJECT       *ReplacementOp = NULL;

    ACPI_STATUS             Status = AE_OK;

    ACPI_FUNCTION_TRACE_PTR (PsCompleteThisOp, Op);

    /* Check for null Op, can happen if AML code is corrupt */

    if (!Op)

    {

        return_ACPI_STATUS (AE_OK);  /* OK for now */

    }

    /* Delete this op and the subtree below it if asked to */

    if (((WalkState->ParseFlags & ACPI_PARSE_TREE_MASK) != ACPI_PARSE_DELETE_TREE) ||

         (WalkState->OpInfo->Class == AML_CLASS_ARGUMENT))

    {

        return_ACPI_STATUS (AE_OK);

    }

    /* Make sure that we only delete this subtree */

    if (Op->Common.Parent)

    {

        Prev = Op->Common.Parent->Common.Value.Arg;

        if (!Prev)

        {

            /* Nothing more to do */

            goto Cleanup;

        }

        /*

         * Check if we need to replace the operator and its subtree

         * with a return value op (placeholder op)

         */

        ParentInfo = AcpiPsGetOpcodeInfo (Op->Common.Parent->Common.AmlOpcode);

        switch (ParentInfo->Class)

        {

        case AML_CLASS_CONTROL:

            break;

        case AML_CLASS_CREATE:

            /*

             * These opcodes contain TermArg operands.  The current

             * op must be replaced by a placeholder return op

             */

            ReplacementOp = AcpiPsAllocOp (AML_INT_RETURN_VALUE_OP);

            if (!ReplacementOp)

            {

                Status = AE_NO_MEMORY;

            }

            break;

        case AML_CLASS_NAMED_OBJECT:

            /*

             * These opcodes contain TermArg operands.  The current

             * op must be replaced by a placeholder return op

             */

            if ((Op->Common.Parent->Common.AmlOpcode == AML_REGION_OP)       ||

                (Op->Common.Parent->Common.AmlOpcode == AML_DATA_REGION_OP)  ||

                (Op->Common.Parent->Common.AmlOpcode == AML_BUFFER_OP)       ||

                (Op->Common.Parent->Common.AmlOpcode == AML_PACKAGE_OP)      ||

                (Op->Common.Parent->Common.AmlOpcode == AML_BANK_FIELD_OP)   ||

                (Op->Common.Parent->Common.AmlOpcode == AML_VAR_PACKAGE_OP))

            {

                ReplacementOp = AcpiPsAllocOp (AML_INT_RETURN_VALUE_OP);

                if (!ReplacementOp)

                {

                    Status = AE_NO_MEMORY;

                }

            }

            else if ((Op->Common.Parent->Common.AmlOpcode == AML_NAME_OP) &&

                     (WalkState->PassNumber <= ACPI_IMODE_LOAD_PASS2))

            {

                if ((Op->Common.AmlOpcode == AML_BUFFER_OP) ||

                    (Op->Common.AmlOpcode == AML_PACKAGE_OP) ||

                    (Op->Common.AmlOpcode == AML_VAR_PACKAGE_OP))

                {

                    ReplacementOp = AcpiPsAllocOp (Op->Common.AmlOpcode);

                    if (!ReplacementOp)

                    {

                        Status = AE_NO_MEMORY;

                    }

                    else

                    {

                        ReplacementOp->Named.Data = Op->Named.Data;

                        ReplacementOp->Named.Length = Op->Named.Length;

                    }

                }

            }

            break;

        default:

            ReplacementOp = AcpiPsAllocOp (AML_INT_RETURN_VALUE_OP);

            if (!ReplacementOp)

            {

                Status = AE_NO_MEMORY;

            }

        }

        /* We must unlink this op from the parent tree */

        if (Prev == Op)

        {

            /* This op is the first in the list */

            if (ReplacementOp)

            {

                ReplacementOp->Common.Parent        = Op->Common.Parent;

                ReplacementOp->Common.Value.Arg     = NULL;

                ReplacementOp->Common.Node          = Op->Common.Node;

                Op->Common.Parent->Common.Value.Arg = ReplacementOp;

                ReplacementOp->Common.Next          = Op->Common.Next;

            }

            else

            {

                Op->Common.Parent->Common.Value.Arg = Op->Common.Next;

            }

        }

        /* Search the parent list */

        else while (Prev)

        {

            /* Traverse all siblings in the parent's argument list */

            Next = Prev->Common.Next;

            if (Next == Op)

            {

                if (ReplacementOp)

                {

                    ReplacementOp->Common.Parent    = Op->Common.Parent;

                    ReplacementOp->Common.Value.Arg = NULL;

                    ReplacementOp->Common.Node      = Op->Common.Node;

                    Prev->Common.Next               = ReplacementOp;

                    ReplacementOp->Common.Next      = Op->Common.Next;

                    Next = NULL;

                }

                else

                {

                    Prev->Common.Next = Op->Common.Next;

                    Next = NULL;

                }

            }

            Prev = Next;

        }

    }

Cleanup:

    /* Now we can actually delete the subtree rooted at Op */

    AcpiPsDeleteParseTree (Op);

    return_ACPI_STATUS (Status);

}

/*******************************************************************************

 *

 * FUNCTION:    AcpiPsNextParseState

 *

 * PARAMETERS:  WalkState           - Current state

 *              Op                  - Current parse op

 *              CallbackStatus      - Status from previous operation

 *

 * RETURN:      Status

 *

 * DESCRIPTION: Update the parser state based upon the return exception from

 *              the parser callback.

 *

 ******************************************************************************/

ACPI_STATUS

AcpiPsNextParseState (

    ACPI_WALK_STATE         *WalkState,

    ACPI_PARSE_OBJECT       *Op,

    ACPI_STATUS             CallbackStatus)

{

    ACPI_PARSE_STATE        *ParserState = &WalkState->ParserState;

    ACPI_STATUS             Status = AE_CTRL_PENDING;

    ACPI_FUNCTION_TRACE_PTR (PsNextParseState, Op);

    switch (CallbackStatus)

    {

    case AE_CTRL_TERMINATE:

        /*

         * A control method was terminated via a RETURN statement.

         * The walk of this method is complete.

         */

        ParserState->Aml = ParserState->AmlEnd;

        Status = AE_CTRL_TERMINATE;

        break;

    case AE_CTRL_BREAK:

        ParserState->Aml = WalkState->AmlLastWhile;

        WalkState->ControlState->Common.Value = FALSE;

        Status = AE_CTRL_BREAK;

        break;

    case AE_CTRL_CONTINUE:

        ParserState->Aml = WalkState->AmlLastWhile;

        Status = AE_CTRL_CONTINUE;

        break;

    case AE_CTRL_PENDING:

        ParserState->Aml = WalkState->AmlLastWhile;

        break;

#if 0

    case AE_CTRL_SKIP:

        ParserState->Aml = ParserState->Scope->ParseScope.PkgEnd;

        Status = AE_OK;

        break;

#endif

    case AE_CTRL_TRUE:

        /*

         * Predicate of an IF was true, and we are at the matching ELSE.

         * Just close out this package

         */

        ParserState->Aml = AcpiPsGetNextPackageEnd (ParserState);

        Status = AE_CTRL_PENDING;

        break;

    case AE_CTRL_FALSE:

        /*

         * Either an IF/WHILE Predicate was false or we encountered a BREAK

         * opcode.  In both cases, we do not execute the rest of the

         * package;  We simply close out the parent (finishing the walk of

         * this branch of the tree) and continue execution at the parent

         * level.

         */

        ParserState->Aml = ParserState->Scope->ParseScope.PkgEnd;

        /* In the case of a BREAK, just force a predicate (if any) to FALSE */

        WalkState->ControlState->Common.Value = FALSE;

        Status = AE_CTRL_END;

        break;

    case AE_CTRL_TRANSFER:

        /* A method call (invocation) -- transfer control */

        Status = AE_CTRL_TRANSFER;

        WalkState->PrevOp = Op;

        WalkState->MethodCallOp = Op;

        WalkState->MethodCallNode = (Op->Common.Value.Arg)->Common.Node;

        /* Will return value (if any) be used by the caller? */

        WalkState->ReturnUsed = AcpiDsIsResultUsed (Op, WalkState);

        break;

    default:

        Status = CallbackStatus;

        if ((CallbackStatus & AE_CODE_MASK) == AE_CODE_CONTROL)

        {

            Status = AE_OK;

        }

        break;

    }

    return_ACPI_STATUS (Status);

}

/*******************************************************************************

 *

 * FUNCTION:    AcpiPsParseAml

 *

 * PARAMETERS:  WalkState       - Current state

 *

 *

 * RETURN:      Status

 *

 * DESCRIPTION: Parse raw AML and return a tree of ops

 *

 ******************************************************************************/

ACPI_STATUS

AcpiPsParseAml (

    ACPI_WALK_STATE         *WalkState)

{

    ACPI_STATUS             Status;

    ACPI_THREAD_STATE       *Thread;

    ACPI_THREAD_STATE       *PrevWalkList = AcpiGbl_CurrentWalkList;

    ACPI_WALK_STATE         *PreviousWalkState;

    ACPI_FUNCTION_TRACE (PsParseAml);

    ACPI_DEBUG_PRINT ((ACPI_DB_PARSE,

        "Entered with WalkState=%p Aml=%p size=%X\n",

        WalkState, WalkState->ParserState.Aml,

        WalkState->ParserState.AmlSize));

    if (!WalkState->ParserState.Aml)

    {

        return_ACPI_STATUS (AE_NULL_OBJECT);

    }

    /* Create and initialize a new thread state */

    Thread = AcpiUtCreateThreadState ();

    if (!Thread)

    {

        if (WalkState->MethodDesc)

        {

            /* Executing a control method - additional cleanup */

            AcpiDsTerminateControlMethod (WalkState->MethodDesc, WalkState);

        }

        AcpiDsDeleteWalkState (WalkState);

        return_ACPI_STATUS (AE_NO_MEMORY);

    }

    WalkState->Thread = Thread;

    /*

     * If executing a method, the starting SyncLevel is this method's

     * SyncLevel

     */

    if (WalkState->MethodDesc)

    {

        WalkState->Thread->CurrentSyncLevel = WalkState->MethodDesc->Method.SyncLevel;

    }

    AcpiDsPushWalkState (WalkState, Thread);

    /*

     * This global allows the AML debugger to get a handle to the currently

     * executing control method.

     */

    AcpiGbl_CurrentWalkList = Thread;

    /*

     * Execute the walk loop as long as there is a valid Walk State.  This

     * handles nested control method invocations without recursion.

     */

    ACPI_DEBUG_PRINT ((ACPI_DB_PARSE, "State=%p\n", WalkState));

    Status = AE_OK;

    while (WalkState)

    {

        if (ACPI_SUCCESS (Status))

        {

            /*

             * The ParseLoop executes AML until the method terminates

             * or calls another method.

             */

            Status = AcpiPsParseLoop (WalkState);

        }

        ACPI_DEBUG_PRINT ((ACPI_DB_PARSE,

            "Completed one call to walk loop, %s State=%p\n",

            AcpiFormatException (Status), WalkState));

        if (Status == AE_CTRL_TRANSFER)

        {

            /*

             * A method call was detected.

             * Transfer control to the called control method

             */

            Status = AcpiDsCallControlMethod (Thread, WalkState, NULL);

            if (ACPI_FAILURE (Status))

            {

                Status = AcpiDsMethodError (Status, WalkState);

            }

            /*

             * If the transfer to the new method method call worked, a new walk

             * state was created -- get it

             */

            WalkState = AcpiDsGetCurrentWalkState (Thread);

            continue;

        }

        else if (Status == AE_CTRL_TERMINATE)

        {

            Status = AE_OK;

        }

        else if ((Status != AE_OK) && (WalkState->MethodDesc))

        {

            /* Either the method parse or actual execution failed */

            ACPI_ERROR_METHOD ("Method parse/execution failed",

                WalkState->MethodNode, NULL, Status);

            /* Check for possible multi-thread reentrancy problem */

            if ((Status == AE_ALREADY_EXISTS) &&

                (!WalkState->MethodDesc->Method.Mutex))

            {

                ACPI_INFO ((AE_INFO,

                    "Marking method %4.4s as Serialized because of AE_ALREADY_EXISTS error",

                    WalkState->MethodNode->Name.Ascii));

                /*

                 * Method tried to create an object twice. The probable cause is

                 * that the method cannot handle reentrancy.

                 *

                 * The method is marked NotSerialized, but it tried to create

                 * a named object, causing the second thread entrance to fail.

                 * Workaround this problem by marking the method permanently

                 * as Serialized.

                 */

                WalkState->MethodDesc->Method.MethodFlags |= AML_METHOD_SERIALIZED;

                WalkState->MethodDesc->Method.SyncLevel = 0;

            }

        }

        /* We are done with this walk, move on to the parent if any */

        WalkState = AcpiDsPopWalkState (Thread);

        /* Reset the current scope to the beginning of scope stack */

        AcpiDsScopeStackClear (WalkState);

        /*

         * If we just returned from the execution of a control method or if we

         * encountered an error during the method parse phase, there's lots of

         * cleanup to do

         */

        if (((WalkState->ParseFlags & ACPI_PARSE_MODE_MASK) == ACPI_PARSE_EXECUTE) ||

            (ACPI_FAILURE (Status)))

        {

            AcpiDsTerminateControlMethod (WalkState->MethodDesc, WalkState);

        }

        /* Delete this walk state and all linked control states */

        AcpiPsCleanupScope (&WalkState->ParserState);

        PreviousWalkState = WalkState;

        ACPI_DEBUG_PRINT ((ACPI_DB_PARSE,

            "ReturnValue=%p, ImplicitValue=%p State=%p\n",

            WalkState->ReturnDesc, WalkState->ImplicitReturnObj, WalkState));

        /* Check if we have restarted a preempted walk */

        WalkState = AcpiDsGetCurrentWalkState (Thread);

        if (WalkState)

        {

            if (ACPI_SUCCESS (Status))

            {

                /*

                 * There is another walk state, restart it.

                 * If the method return value is not used by the parent,

                 * The object is deleted

                 */

                if (!PreviousWalkState->ReturnDesc)

                {

                    /*

                     * In slack mode execution, if there is no return value

                     * we should implicitly return zero (0) as a default value.

                     */

                    if (AcpiGbl_EnableInterpreterSlack &&

                        !PreviousWalkState->ImplicitReturnObj)

                    {

                        PreviousWalkState->ImplicitReturnObj =

                            AcpiUtCreateIntegerObject ((UINT64) 0);

                        if (!PreviousWalkState->ImplicitReturnObj)

                        {

                            return_ACPI_STATUS (AE_NO_MEMORY);

                        }

                    }

                    /* Restart the calling control method */

                    Status = AcpiDsRestartControlMethod (WalkState,

                                PreviousWalkState->ImplicitReturnObj);

                }

                else

                {

                    /*

                     * We have a valid return value, delete any implicit

                     * return value.

                     */

                    AcpiDsClearImplicitReturn (PreviousWalkState);

                    Status = AcpiDsRestartControlMethod (WalkState,

                                PreviousWalkState->ReturnDesc);

                }

                if (ACPI_SUCCESS (Status))

                {

                    WalkState->WalkType |= ACPI_WALK_METHOD_RESTART;

                }

            }

            else

            {

                /* On error, delete any return object or implicit return */

                AcpiUtRemoveReference (PreviousWalkState->ReturnDesc);

                AcpiDsClearImplicitReturn (PreviousWalkState);

            }

        }

        /*

         * Just completed a 1st-level method, save the final internal return

         * value (if any)

         */

        else if (PreviousWalkState->CallerReturnDesc)

        {

            if (PreviousWalkState->ImplicitReturnObj)

            {

                *(PreviousWalkState->CallerReturnDesc) =

                    PreviousWalkState->ImplicitReturnObj;

            }

            else

            {

                 /* NULL if no return value */

                *(PreviousWalkState->CallerReturnDesc) =

                    PreviousWalkState->ReturnDesc;

            }

        }

        else

        {

            if (PreviousWalkState->ReturnDesc)

            {

                /* Caller doesn't want it, must delete it */

                AcpiUtRemoveReference (PreviousWalkState->ReturnDesc);

            }

            if (PreviousWalkState->ImplicitReturnObj)

            {

                /* Caller doesn't want it, must delete it */

                AcpiUtRemoveReference (PreviousWalkState->ImplicitReturnObj);

            }

        }

        AcpiDsDeleteWalkState (PreviousWalkState);

    }

    /* Normal exit */

    AcpiExReleaseAllMutexes (Thread);

    AcpiUtDeleteGenericState (ACPI_CAST_PTR (ACPI_GENERIC_STATE, Thread));

    AcpiGbl_CurrentWalkList = PrevWalkList;

    return_ACPI_STATUS (Status);

}