reactos/drivers/bus/acpi/acpica/parser/psparse.c

   1 /******************************************************************************
   2  *
   3  * Module Name: psparse - Parser top level AML parse routines
   4  *
   5  *****************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2017, Intel Corp.
   9  * All rights reserved.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions, and the following disclaimer,
  16  *    without modification.
  17  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
  18  *    substantially similar to the "NO WARRANTY" disclaimer below
  19  *    ("Disclaimer") and any redistribution must be conditioned upon
  20  *    including a substantially similar Disclaimer requirement for further
  21  *    binary redistribution.
  22  * 3. Neither the names of the above-listed copyright holders nor the names
  23  *    of any contributors may be used to endorse or promote products derived
  24  *    from this software without specific prior written permission.
  25  *
  26  * Alternatively, this software may be distributed under the terms of the
  27  * GNU General Public License ("GPL") version 2 as published by the Free
  28  * Software Foundation.
  29  *
  30  * NO WARRANTY
  31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  32  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  33  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
  34  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  35  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  40  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  41  * POSSIBILITY OF SUCH DAMAGES.
  42  */
  43
  44 /*
  45  * Parse the AML and build an operation tree as most interpreters,
  46  * like Perl, do. Parsing is done by hand rather than with a YACC
  47  * generated parser to tightly constrain stack and dynamic memory
  48  * usage. At the same time, parsing is kept flexible and the code
  49  * fairly compact by parsing based on a list of AML opcode
  50  * templates in AmlOpInfo[]
  51  */
  52
  53 #include "acpi.h"
  54 #include "accommon.h"
  55 #include "acparser.h"
  56 #include "acdispat.h"
  57 #include "amlcode.h"
  58 #include "acinterp.h"
  59
  60 #define _COMPONENT          ACPI_PARSER
  61         ACPI_MODULE_NAME    ("psparse")
  62
  63
  64 /*******************************************************************************
  65  *
  66  * FUNCTION:    AcpiPsGetOpcodeSize
  67  *
  68  * PARAMETERS:  Opcode          - An AML opcode
  69  *
  70  * RETURN:      Size of the opcode, in bytes (1 or 2)
  71  *
  72  * DESCRIPTION: Get the size of the current opcode.
  73  *
  74  ******************************************************************************/
  75
  76 UINT32
  77 AcpiPsGetOpcodeSize (
  78     UINT32                  Opcode)
  79 {
  80
  81     /* Extended (2-byte) opcode if > 255 */
  82
  83     if (Opcode > 0x00FF)
  84     {
  85         return (2);
  86     }
  87
  88     /* Otherwise, just a single byte opcode */
  89
  90     return (1);
  91 }
  92
  93
  94 /*******************************************************************************
  95  *
  96  * FUNCTION:    AcpiPsPeekOpcode
  97  *
  98  * PARAMETERS:  ParserState         - A parser state object
  99  *
 100  * RETURN:      Next AML opcode
 101  *
 102  * DESCRIPTION: Get next AML opcode (without incrementing AML pointer)
 103  *
 104  ******************************************************************************/
 105
 106 UINT16
 107 AcpiPsPeekOpcode (
 108     ACPI_PARSE_STATE        *ParserState)
 109 {
 110     UINT8                   *Aml;
 111     UINT16                  Opcode;
 112
 113
 114     Aml = ParserState->Aml;
 115     Opcode = (UINT16) ACPI_GET8 (Aml);
 116
 117     if (Opcode == AML_EXTENDED_OP_PREFIX)
 118     {
 119         /* Extended opcode, get the second opcode byte */
 120
 121         Aml++;
 122         Opcode = (UINT16) ((Opcode << 8) | ACPI_GET8 (Aml));
 123     }
 124
 125     return (Opcode);
 126 }
 127
 128
 129 /*******************************************************************************
 130  *
 131  * FUNCTION:    AcpiPsCompleteThisOp
 132  *
 133  * PARAMETERS:  WalkState       - Current State
 134  *              Op              - Op to complete
 135  *
 136  * RETURN:      Status
 137  *
 138  * DESCRIPTION: Perform any cleanup at the completion of an Op.
 139  *
 140  ******************************************************************************/
 141
 142 ACPI_STATUS
 143 AcpiPsCompleteThisOp (
 144     ACPI_WALK_STATE         *WalkState,
 145     ACPI_PARSE_OBJECT       *Op)
 146 {
 147     ACPI_PARSE_OBJECT       *Prev;
 148     ACPI_PARSE_OBJECT       *Next;
 149     const ACPI_OPCODE_INFO  *ParentInfo;
 150     ACPI_PARSE_OBJECT       *ReplacementOp = NULL;
 151     ACPI_STATUS             Status = AE_OK;
 152
 153
 154     ACPI_FUNCTION_TRACE_PTR (PsCompleteThisOp, Op);
 155
 156
 157     /* Check for null Op, can happen if AML code is corrupt */
 158
 159     if (!Op)
 160     {
 161         return_ACPI_STATUS (AE_OK);  /* OK for now */
 162     }
 163
 164     AcpiExStopTraceOpcode (Op, WalkState);
 165
 166     /* Delete this op and the subtree below it if asked to */
 167
 168     if (((WalkState->ParseFlags & ACPI_PARSE_TREE_MASK) != ACPI_PARSE_DELETE_TREE) ||
 169          (WalkState->OpInfo->Class == AML_CLASS_ARGUMENT))
 170     {
 171         return_ACPI_STATUS (AE_OK);
 172     }
 173
 174     /* Make sure that we only delete this subtree */
 175
 176     if (Op->Common.Parent)
 177     {
 178         Prev = Op->Common.Parent->Common.Value.Arg;
 179         if (!Prev)
 180         {
 181             /* Nothing more to do */
 182
 183             goto Cleanup;
 184         }
 185
 186         /*
 187          * Check if we need to replace the operator and its subtree
 188          * with a return value op (placeholder op)
 189          */
 190         ParentInfo = AcpiPsGetOpcodeInfo (Op->Common.Parent->Common.AmlOpcode);
 191
 192         switch (ParentInfo->Class)
 193         {
 194         case AML_CLASS_CONTROL:
 195
 196             break;
 197
 198         case AML_CLASS_CREATE:
 199             /*
 200              * These opcodes contain TermArg operands. The current
 201              * op must be replaced by a placeholder return op
 202              */
 203             ReplacementOp = AcpiPsAllocOp (
 204                 AML_INT_RETURN_VALUE_OP, Op->Common.Aml);
 205             if (!ReplacementOp)
 206             {
 207                 Status = AE_NO_MEMORY;
 208             }
 209             break;
 210
 211         case AML_CLASS_NAMED_OBJECT:
 212             /*
 213              * These opcodes contain TermArg operands. The current
 214              * op must be replaced by a placeholder return op
 215              */
 216             if ((Op->Common.Parent->Common.AmlOpcode == AML_REGION_OP)       ||
 217                 (Op->Common.Parent->Common.AmlOpcode == AML_DATA_REGION_OP)  ||
 218                 (Op->Common.Parent->Common.AmlOpcode == AML_BUFFER_OP)       ||
 219                 (Op->Common.Parent->Common.AmlOpcode == AML_PACKAGE_OP)      ||
 220                 (Op->Common.Parent->Common.AmlOpcode == AML_BANK_FIELD_OP)   ||
 221                 (Op->Common.Parent->Common.AmlOpcode == AML_VAR_PACKAGE_OP))
 222             {
 223                 ReplacementOp = AcpiPsAllocOp (
 224                     AML_INT_RETURN_VALUE_OP, Op->Common.Aml);
 225                 if (!ReplacementOp)
 226                 {
 227                     Status = AE_NO_MEMORY;
 228                 }
 229             }
 230             else if ((Op->Common.Parent->Common.AmlOpcode == AML_NAME_OP) &&
 231                      (WalkState->PassNumber <= ACPI_IMODE_LOAD_PASS2))
 232             {
 233                 if ((Op->Common.AmlOpcode == AML_BUFFER_OP) ||
 234                     (Op->Common.AmlOpcode == AML_PACKAGE_OP) ||
 235                     (Op->Common.AmlOpcode == AML_VAR_PACKAGE_OP))
 236                 {
 237                     ReplacementOp = AcpiPsAllocOp (Op->Common.AmlOpcode,
 238                         Op->Common.Aml);
 239                     if (!ReplacementOp)
 240                     {
 241                         Status = AE_NO_MEMORY;
 242                     }
 243                     else
 244                     {
 245                         ReplacementOp->Named.Data = Op->Named.Data;
 246                         ReplacementOp->Named.Length = Op->Named.Length;
 247                     }
 248                 }
 249             }
 250             break;
 251
 252         default:
 253
 254             ReplacementOp = AcpiPsAllocOp (
 255                 AML_INT_RETURN_VALUE_OP, Op->Common.Aml);
 256             if (!ReplacementOp)
 257             {
 258                 Status = AE_NO_MEMORY;
 259             }
 260         }
 261
 262         /* We must unlink this op from the parent tree */
 263
 264         if (Prev == Op)
 265         {
 266             /* This op is the first in the list */
 267
 268             if (ReplacementOp)
 269             {
 270                 ReplacementOp->Common.Parent = Op->Common.Parent;
 271                 ReplacementOp->Common.Value.Arg = NULL;
 272                 ReplacementOp->Common.Node = Op->Common.Node;
 273                 Op->Common.Parent->Common.Value.Arg = ReplacementOp;
 274                 ReplacementOp->Common.Next = Op->Common.Next;
 275             }
 276             else
 277             {
 278                 Op->Common.Parent->Common.Value.Arg = Op->Common.Next;
 279             }
 280         }
 281
 282         /* Search the parent list */
 283
 284         else while (Prev)
 285         {
 286             /* Traverse all siblings in the parent's argument list */
 287
 288             Next = Prev->Common.Next;
 289             if (Next == Op)
 290             {
 291                 if (ReplacementOp)
 292                 {
 293                     ReplacementOp->Common.Parent = Op->Common.Parent;
 294                     ReplacementOp->Common.Value.Arg = NULL;
 295                     ReplacementOp->Common.Node = Op->Common.Node;
 296                     Prev->Common.Next = ReplacementOp;
 297                     ReplacementOp->Common.Next = Op->Common.Next;
 298                     Next = NULL;
 299                 }
 300                 else
 301                 {
 302                     Prev->Common.Next = Op->Common.Next;
 303                     Next = NULL;
 304                 }
 305             }
 306             Prev = Next;
 307         }
 308     }
 309
 310
 311 Cleanup:
 312
 313     /* Now we can actually delete the subtree rooted at Op */
 314
 315     AcpiPsDeleteParseTree (Op);
 316     return_ACPI_STATUS (Status);
 317 }
 318
 319
 320 /*******************************************************************************
 321  *
 322  * FUNCTION:    AcpiPsNextParseState
 323  *
 324  * PARAMETERS:  WalkState           - Current state
 325  *              Op                  - Current parse op
 326  *              CallbackStatus      - Status from previous operation
 327  *
 328  * RETURN:      Status
 329  *
 330  * DESCRIPTION: Update the parser state based upon the return exception from
 331  *              the parser callback.
 332  *
 333  ******************************************************************************/
 334
 335 ACPI_STATUS
 336 AcpiPsNextParseState (
 337     ACPI_WALK_STATE         *WalkState,
 338     ACPI_PARSE_OBJECT       *Op,
 339     ACPI_STATUS             CallbackStatus)
 340 {
 341     ACPI_PARSE_STATE        *ParserState = &WalkState->ParserState;
 342     ACPI_STATUS             Status = AE_CTRL_PENDING;
 343
 344
 345     ACPI_FUNCTION_TRACE_PTR (PsNextParseState, Op);
 346
 347
 348     switch (CallbackStatus)
 349     {
 350     case AE_CTRL_TERMINATE:
 351         /*
 352          * A control method was terminated via a RETURN statement.
 353          * The walk of this method is complete.
 354          */
 355         ParserState->Aml = ParserState->AmlEnd;
 356         Status = AE_CTRL_TERMINATE;
 357         break;
 358
 359     case AE_CTRL_BREAK:
 360
 361         ParserState->Aml = WalkState->AmlLastWhile;
 362         WalkState->ControlState->Common.Value = FALSE;
 363         Status = AE_CTRL_BREAK;
 364         break;
 365
 366     case AE_CTRL_CONTINUE:
 367
 368         ParserState->Aml = WalkState->AmlLastWhile;
 369         Status = AE_CTRL_CONTINUE;
 370         break;
 371
 372     case AE_CTRL_PENDING:
 373
 374         ParserState->Aml = WalkState->AmlLastWhile;
 375         break;
 376
 377 #if 0
 378     case AE_CTRL_SKIP:
 379
 380         ParserState->Aml = ParserState->Scope->ParseScope.PkgEnd;
 381         Status = AE_OK;
 382         break;
 383 #endif
 384
 385     case AE_CTRL_TRUE:
 386         /*
 387          * Predicate of an IF was true, and we are at the matching ELSE.
 388          * Just close out this package
 389          */
 390         ParserState->Aml = AcpiPsGetNextPackageEnd (ParserState);
 391         Status = AE_CTRL_PENDING;
 392         break;
 393
 394     case AE_CTRL_FALSE:
 395         /*
 396          * Either an IF/WHILE Predicate was false or we encountered a BREAK
 397          * opcode. In both cases, we do not execute the rest of the
 398          * package;  We simply close out the parent (finishing the walk of
 399          * this branch of the tree) and continue execution at the parent
 400          * level.
 401          */
 402         ParserState->Aml = ParserState->Scope->ParseScope.PkgEnd;
 403
 404         /* In the case of a BREAK, just force a predicate (if any) to FALSE */
 405
 406         WalkState->ControlState->Common.Value = FALSE;
 407         Status = AE_CTRL_END;
 408         break;
 409
 410     case AE_CTRL_TRANSFER:
 411
 412         /* A method call (invocation) -- transfer control */
 413
 414         Status = AE_CTRL_TRANSFER;
 415         WalkState->PrevOp = Op;
 416         WalkState->MethodCallOp = Op;
 417         WalkState->MethodCallNode = (Op->Common.Value.Arg)->Common.Node;
 418
 419         /* Will return value (if any) be used by the caller? */
 420
 421         WalkState->ReturnUsed = AcpiDsIsResultUsed (Op, WalkState);
 422         break;
 423
 424     default:
 425
 426         Status = CallbackStatus;
 427         if ((CallbackStatus & AE_CODE_MASK) == AE_CODE_CONTROL)
 428         {
 429             Status = AE_OK;
 430         }
 431         break;
 432     }
 433
 434     return_ACPI_STATUS (Status);
 435 }
 436
 437
 438 /*******************************************************************************
 439  *
 440  * FUNCTION:    AcpiPsParseAml
 441  *
 442  * PARAMETERS:  WalkState       - Current state
 443  *
 444  *
 445  * RETURN:      Status
 446  *
 447  * DESCRIPTION: Parse raw AML and return a tree of ops
 448  *
 449  ******************************************************************************/
 450
 451 ACPI_STATUS
 452 AcpiPsParseAml (
 453     ACPI_WALK_STATE         *WalkState)
 454 {
 455     ACPI_STATUS             Status;
 456     ACPI_THREAD_STATE       *Thread;
 457     ACPI_THREAD_STATE       *PrevWalkList = AcpiGbl_CurrentWalkList;
 458     ACPI_WALK_STATE         *PreviousWalkState;
 459
 460
 461     ACPI_FUNCTION_TRACE (PsParseAml);
 462
 463     ACPI_DEBUG_PRINT ((ACPI_DB_PARSE,
 464         "Entered with WalkState=%p Aml=%p size=%X\n",
 465         WalkState, WalkState->ParserState.Aml,
 466         WalkState->ParserState.AmlSize));
 467
 468     if (!WalkState->ParserState.Aml)
 469     {
 470         return_ACPI_STATUS (AE_NULL_OBJECT);
 471     }
 472
 473     /* Create and initialize a new thread state */
 474
 475     Thread = AcpiUtCreateThreadState ();
 476     if (!Thread)
 477     {
 478         if (WalkState->MethodDesc)
 479         {
 480             /* Executing a control method - additional cleanup */
 481
 482             AcpiDsTerminateControlMethod (WalkState->MethodDesc, WalkState);
 483         }
 484
 485         AcpiDsDeleteWalkState (WalkState);
 486         return_ACPI_STATUS (AE_NO_MEMORY);
 487     }
 488
 489     WalkState->Thread = Thread;
 490
 491     /*
 492      * If executing a method, the starting SyncLevel is this method's
 493      * SyncLevel
 494      */
 495     if (WalkState->MethodDesc)
 496     {
 497         WalkState->Thread->CurrentSyncLevel =
 498             WalkState->MethodDesc->Method.SyncLevel;
 499     }
 500
 501     AcpiDsPushWalkState (WalkState, Thread);
 502
 503     /*
 504      * This global allows the AML debugger to get a handle to the currently
 505      * executing control method.
 506      */
 507     AcpiGbl_CurrentWalkList = Thread;
 508
 509     /*
 510      * Execute the walk loop as long as there is a valid Walk State. This
 511      * handles nested control method invocations without recursion.
 512      */
 513     ACPI_DEBUG_PRINT ((ACPI_DB_PARSE, "State=%p\n", WalkState));
 514
 515     Status = AE_OK;
 516     while (WalkState)
 517     {
 518         if (ACPI_SUCCESS (Status))
 519         {
 520             /*
 521              * The ParseLoop executes AML until the method terminates
 522              * or calls another method.
 523              */
 524             Status = AcpiPsParseLoop (WalkState);
 525         }
 526
 527         ACPI_DEBUG_PRINT ((ACPI_DB_PARSE,
 528             "Completed one call to walk loop, %s State=%p\n",
 529             AcpiFormatException (Status), WalkState));
 530
 531         if (Status == AE_CTRL_TRANSFER)
 532         {
 533             /*
 534              * A method call was detected.
 535              * Transfer control to the called control method
 536              */
 537             Status = AcpiDsCallControlMethod (Thread, WalkState, NULL);
 538             if (ACPI_FAILURE (Status))
 539             {
 540                 Status = AcpiDsMethodError (Status, WalkState);
 541             }
 542
 543             /*
 544              * If the transfer to the new method method call worked
 545              *, a new walk state was created -- get it
 546              */
 547             WalkState = AcpiDsGetCurrentWalkState (Thread);
 548             continue;
 549         }
 550         else if (Status == AE_CTRL_TERMINATE)
 551         {
 552             Status = AE_OK;
 553         }
 554         else if ((Status != AE_OK) && (WalkState->MethodDesc))
 555         {
 556             /* Either the method parse or actual execution failed */
 557
 558             AcpiExExitInterpreter ();
 559             ACPI_ERROR_METHOD ("Method parse/execution failed",
 560                 WalkState->MethodNode, NULL, Status);
 561             AcpiExEnterInterpreter ();
 562
 563             /* Check for possible multi-thread reentrancy problem */
 564
 565             if ((Status == AE_ALREADY_EXISTS) &&
 566                 (!(WalkState->MethodDesc->Method.InfoFlags &
 567                     ACPI_METHOD_SERIALIZED)))
 568             {
 569                 /*
 570                  * Method is not serialized and tried to create an object
 571                  * twice. The probable cause is that the method cannot
 572                  * handle reentrancy. Mark as "pending serialized" now, and
 573                  * then mark "serialized" when the last thread exits.
 574                  */
 575                 WalkState->MethodDesc->Method.InfoFlags |=
 576                     ACPI_METHOD_SERIALIZED_PENDING;
 577             }
 578         }
 579
 580         /* We are done with this walk, move on to the parent if any */
 581
 582         WalkState = AcpiDsPopWalkState (Thread);
 583
 584         /* Reset the current scope to the beginning of scope stack */
 585
 586         AcpiDsScopeStackClear (WalkState);
 587
 588         /*
 589          * If we just returned from the execution of a control method or if we
 590          * encountered an error during the method parse phase, there's lots of
 591          * cleanup to do
 592          */
 593         if (((WalkState->ParseFlags & ACPI_PARSE_MODE_MASK) ==
 594             ACPI_PARSE_EXECUTE &&
 595             !(WalkState->ParseFlags & ACPI_PARSE_MODULE_LEVEL)) ||
 596             (ACPI_FAILURE (Status)))
 597         {
 598             AcpiDsTerminateControlMethod (WalkState->MethodDesc, WalkState);
 599         }
 600
 601         /* Delete this walk state and all linked control states */
 602
 603         AcpiPsCleanupScope (&WalkState->ParserState);
 604         PreviousWalkState = WalkState;
 605
 606         ACPI_DEBUG_PRINT ((ACPI_DB_PARSE,
 607             "ReturnValue=%p, ImplicitValue=%p State=%p\n",
 608             WalkState->ReturnDesc, WalkState->ImplicitReturnObj, WalkState));
 609
 610         /* Check if we have restarted a preempted walk */
 611
 612         WalkState = AcpiDsGetCurrentWalkState (Thread);
 613         if (WalkState)
 614         {
 615             if (ACPI_SUCCESS (Status))
 616             {
 617                 /*
 618                  * There is another walk state, restart it.
 619                  * If the method return value is not used by the parent,
 620                  * The object is deleted
 621                  */
 622                 if (!PreviousWalkState->ReturnDesc)
 623                 {
 624                     /*
 625                      * In slack mode execution, if there is no return value
 626                      * we should implicitly return zero (0) as a default value.
 627                      */
 628                     if (AcpiGbl_EnableInterpreterSlack &&
 629                         !PreviousWalkState->ImplicitReturnObj)
 630                     {
 631                         PreviousWalkState->ImplicitReturnObj =
 632                             AcpiUtCreateIntegerObject ((UINT64) 0);
 633                         if (!PreviousWalkState->ImplicitReturnObj)
 634                         {
 635                             return_ACPI_STATUS (AE_NO_MEMORY);
 636                         }
 637                     }
 638
 639                     /* Restart the calling control method */
 640
 641                     Status = AcpiDsRestartControlMethod (WalkState,
 642                         PreviousWalkState->ImplicitReturnObj);
 643                 }
 644                 else
 645                 {
 646                     /*
 647                      * We have a valid return value, delete any implicit
 648                      * return value.
 649                      */
 650                     AcpiDsClearImplicitReturn (PreviousWalkState);
 651
 652                     Status = AcpiDsRestartControlMethod (WalkState,
 653                         PreviousWalkState->ReturnDesc);
 654                 }
 655                 if (ACPI_SUCCESS (Status))
 656                 {
 657                     WalkState->WalkType |= ACPI_WALK_METHOD_RESTART;
 658                 }
 659             }
 660             else
 661             {
 662                 /* On error, delete any return object or implicit return */
 663
 664                 AcpiUtRemoveReference (PreviousWalkState->ReturnDesc);
 665                 AcpiDsClearImplicitReturn (PreviousWalkState);
 666             }
 667         }
 668
 669         /*
 670          * Just completed a 1st-level method, save the final internal return
 671          * value (if any)
 672          */
 673         else if (PreviousWalkState->CallerReturnDesc)
 674         {
 675             if (PreviousWalkState->ImplicitReturnObj)
 676             {
 677                 *(PreviousWalkState->CallerReturnDesc) =
 678                     PreviousWalkState->ImplicitReturnObj;
 679             }
 680             else
 681             {
 682                  /* NULL if no return value */
 683
 684                 *(PreviousWalkState->CallerReturnDesc) =
 685                     PreviousWalkState->ReturnDesc;
 686             }
 687         }
 688         else
 689         {
 690             if (PreviousWalkState->ReturnDesc)
 691             {
 692                 /* Caller doesn't want it, must delete it */
 693
 694                 AcpiUtRemoveReference (PreviousWalkState->ReturnDesc);
 695             }
 696             if (PreviousWalkState->ImplicitReturnObj)
 697             {
 698                 /* Caller doesn't want it, must delete it */
 699
 700                 AcpiUtRemoveReference (PreviousWalkState->ImplicitReturnObj);
 701             }
 702         }
 703
 704         AcpiDsDeleteWalkState (PreviousWalkState);
 705     }
 706
 707     /* Normal exit */
 708
 709     AcpiExReleaseAllMutexes (Thread);
 710     AcpiUtDeleteGenericState (ACPI_CAST_PTR (ACPI_GENERIC_STATE, Thread));
 711     AcpiGbl_CurrentWalkList = PrevWalkList;
 712     return_ACPI_STATUS (Status);
 713 }