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 - 2018, 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 #include "acnamesp.h"
  60
  61 #define _COMPONENT          ACPI_PARSER
  62         ACPI_MODULE_NAME    ("psparse")
  63
  64
  65 /*******************************************************************************
  66  *
  67  * FUNCTION:    AcpiPsGetOpcodeSize
  68  *
  69  * PARAMETERS:  Opcode          - An AML opcode
  70  *
  71  * RETURN:      Size of the opcode, in bytes (1 or 2)
  72  *
  73  * DESCRIPTION: Get the size of the current opcode.
  74  *
  75  ******************************************************************************/
  76
  77 UINT32
  78 AcpiPsGetOpcodeSize (
  79     UINT32                  Opcode)
  80 {
  81
  82     /* Extended (2-byte) opcode if > 255 */
  83
  84     if (Opcode > 0x00FF)
  85     {
  86         return (2);
  87     }
  88
  89     /* Otherwise, just a single byte opcode */
  90
  91     return (1);
  92 }
  93
  94
  95 /*******************************************************************************
  96  *
  97  * FUNCTION:    AcpiPsPeekOpcode
  98  *
  99  * PARAMETERS:  ParserState         - A parser state object
 100  *
 101  * RETURN:      Next AML opcode
 102  *
 103  * DESCRIPTION: Get next AML opcode (without incrementing AML pointer)
 104  *
 105  ******************************************************************************/
 106
 107 UINT16
 108 AcpiPsPeekOpcode (
 109     ACPI_PARSE_STATE        *ParserState)
 110 {
 111     UINT8                   *Aml;
 112     UINT16                  Opcode;
 113
 114
 115     Aml = ParserState->Aml;
 116     Opcode = (UINT16) ACPI_GET8 (Aml);
 117
 118     if (Opcode == AML_EXTENDED_PREFIX)
 119     {
 120         /* Extended opcode, get the second opcode byte */
 121
 122         Aml++;
 123         Opcode = (UINT16) ((Opcode << 8) | ACPI_GET8 (Aml));
 124     }
 125
 126     return (Opcode);
 127 }
 128
 129
 130 /*******************************************************************************
 131  *
 132  * FUNCTION:    AcpiPsCompleteThisOp
 133  *
 134  * PARAMETERS:  WalkState       - Current State
 135  *              Op              - Op to complete
 136  *
 137  * RETURN:      Status
 138  *
 139  * DESCRIPTION: Perform any cleanup at the completion of an Op.
 140  *
 141  ******************************************************************************/
 142
 143 ACPI_STATUS
 144 AcpiPsCompleteThisOp (
 145     ACPI_WALK_STATE         *WalkState,
 146     ACPI_PARSE_OBJECT       *Op)
 147 {
 148     ACPI_PARSE_OBJECT       *Prev;
 149     ACPI_PARSE_OBJECT       *Next;
 150     const ACPI_OPCODE_INFO  *ParentInfo;
 151     ACPI_PARSE_OBJECT       *ReplacementOp = NULL;
 152     ACPI_STATUS             Status = AE_OK;
 153
 154
 155     ACPI_FUNCTION_TRACE_PTR (PsCompleteThisOp, Op);
 156
 157
 158     /* Check for null Op, can happen if AML code is corrupt */
 159
 160     if (!Op)
 161     {
 162         return_ACPI_STATUS (AE_OK);  /* OK for now */
 163     }
 164
 165     AcpiExStopTraceOpcode (Op, WalkState);
 166
 167     /* Delete this op and the subtree below it if asked to */
 168
 169     if (((WalkState->ParseFlags & ACPI_PARSE_TREE_MASK) != ACPI_PARSE_DELETE_TREE) ||
 170          (WalkState->OpInfo->Class == AML_CLASS_ARGUMENT))
 171     {
 172         return_ACPI_STATUS (AE_OK);
 173     }
 174
 175     /* Make sure that we only delete this subtree */
 176
 177     if (Op->Common.Parent)
 178     {
 179         Prev = Op->Common.Parent->Common.Value.Arg;
 180         if (!Prev)
 181         {
 182             /* Nothing more to do */
 183
 184             goto Cleanup;
 185         }
 186
 187         /*
 188          * Check if we need to replace the operator and its subtree
 189          * with a return value op (placeholder op)
 190          */
 191         ParentInfo = AcpiPsGetOpcodeInfo (Op->Common.Parent->Common.AmlOpcode);
 192
 193         switch (ParentInfo->Class)
 194         {
 195         case AML_CLASS_CONTROL:
 196
 197             break;
 198
 199         case AML_CLASS_CREATE:
 200             /*
 201              * These opcodes contain TermArg operands. The current
 202              * op must be replaced by a placeholder return op
 203              */
 204             ReplacementOp = AcpiPsAllocOp (
 205                 AML_INT_RETURN_VALUE_OP, Op->Common.Aml);
 206             if (!ReplacementOp)
 207             {
 208                 Status = AE_NO_MEMORY;
 209             }
 210             break;
 211
 212         case AML_CLASS_NAMED_OBJECT:
 213             /*
 214              * These opcodes contain TermArg operands. The current
 215              * op must be replaced by a placeholder return op
 216              */
 217             if ((Op->Common.Parent->Common.AmlOpcode == AML_REGION_OP)       ||
 218                 (Op->Common.Parent->Common.AmlOpcode == AML_DATA_REGION_OP)  ||
 219                 (Op->Common.Parent->Common.AmlOpcode == AML_BUFFER_OP)       ||
 220                 (Op->Common.Parent->Common.AmlOpcode == AML_PACKAGE_OP)      ||
 221                 (Op->Common.Parent->Common.AmlOpcode == AML_BANK_FIELD_OP)   ||
 222                 (Op->Common.Parent->Common.AmlOpcode == AML_VARIABLE_PACKAGE_OP))
 223             {
 224                 ReplacementOp = AcpiPsAllocOp (
 225                     AML_INT_RETURN_VALUE_OP, Op->Common.Aml);
 226                 if (!ReplacementOp)
 227                 {
 228                     Status = AE_NO_MEMORY;
 229                 }
 230             }
 231             else if ((Op->Common.Parent->Common.AmlOpcode == AML_NAME_OP) &&
 232                      (WalkState->PassNumber <= ACPI_IMODE_LOAD_PASS2))
 233             {
 234                 if ((Op->Common.AmlOpcode == AML_BUFFER_OP) ||
 235                     (Op->Common.AmlOpcode == AML_PACKAGE_OP) ||
 236                     (Op->Common.AmlOpcode == AML_VARIABLE_PACKAGE_OP))
 237                 {
 238                     ReplacementOp = AcpiPsAllocOp (Op->Common.AmlOpcode,
 239                         Op->Common.Aml);
 240                     if (!ReplacementOp)
 241                     {
 242                         Status = AE_NO_MEMORY;
 243                     }
 244                     else
 245                     {
 246                         ReplacementOp->Named.Data = Op->Named.Data;
 247                         ReplacementOp->Named.Length = Op->Named.Length;
 248                     }
 249                 }
 250             }
 251             break;
 252
 253         default:
 254
 255             ReplacementOp = AcpiPsAllocOp (
 256                 AML_INT_RETURN_VALUE_OP, Op->Common.Aml);
 257             if (!ReplacementOp)
 258             {
 259                 Status = AE_NO_MEMORY;
 260             }
 261         }
 262
 263         /* We must unlink this op from the parent tree */
 264
 265         if (Prev == Op)
 266         {
 267             /* This op is the first in the list */
 268
 269             if (ReplacementOp)
 270             {
 271                 ReplacementOp->Common.Parent = Op->Common.Parent;
 272                 ReplacementOp->Common.Value.Arg = NULL;
 273                 ReplacementOp->Common.Node = Op->Common.Node;
 274                 Op->Common.Parent->Common.Value.Arg = ReplacementOp;
 275                 ReplacementOp->Common.Next = Op->Common.Next;
 276             }
 277             else
 278             {
 279                 Op->Common.Parent->Common.Value.Arg = Op->Common.Next;
 280             }
 281         }
 282
 283         /* Search the parent list */
 284
 285         else while (Prev)
 286         {
 287             /* Traverse all siblings in the parent's argument list */
 288
 289             Next = Prev->Common.Next;
 290             if (Next == Op)
 291             {
 292                 if (ReplacementOp)
 293                 {
 294                     ReplacementOp->Common.Parent = Op->Common.Parent;
 295                     ReplacementOp->Common.Value.Arg = NULL;
 296                     ReplacementOp->Common.Node = Op->Common.Node;
 297                     Prev->Common.Next = ReplacementOp;
 298                     ReplacementOp->Common.Next = Op->Common.Next;
 299                     Next = NULL;
 300                 }
 301                 else
 302                 {
 303                     Prev->Common.Next = Op->Common.Next;
 304                     Next = NULL;
 305                 }
 306             }
 307             Prev = Next;
 308         }
 309     }
 310
 311
 312 Cleanup:
 313
 314     /* Now we can actually delete the subtree rooted at Op */
 315
 316     AcpiPsDeleteParseTree (Op);
 317     return_ACPI_STATUS (Status);
 318 }
 319
 320
 321 /*******************************************************************************
 322  *
 323  * FUNCTION:    AcpiPsNextParseState
 324  *
 325  * PARAMETERS:  WalkState           - Current state
 326  *              Op                  - Current parse op
 327  *              CallbackStatus      - Status from previous operation
 328  *
 329  * RETURN:      Status
 330  *
 331  * DESCRIPTION: Update the parser state based upon the return exception from
 332  *              the parser callback.
 333  *
 334  ******************************************************************************/
 335
 336 ACPI_STATUS
 337 AcpiPsNextParseState (
 338     ACPI_WALK_STATE         *WalkState,
 339     ACPI_PARSE_OBJECT       *Op,
 340     ACPI_STATUS             CallbackStatus)
 341 {
 342     ACPI_PARSE_STATE        *ParserState = &WalkState->ParserState;
 343     ACPI_STATUS             Status = AE_CTRL_PENDING;
 344
 345
 346     ACPI_FUNCTION_TRACE_PTR (PsNextParseState, Op);
 347
 348
 349     switch (CallbackStatus)
 350     {
 351     case AE_CTRL_TERMINATE:
 352         /*
 353          * A control method was terminated via a RETURN statement.
 354          * The walk of this method is complete.
 355          */
 356         ParserState->Aml = ParserState->AmlEnd;
 357         Status = AE_CTRL_TERMINATE;
 358         break;
 359
 360     case AE_CTRL_BREAK:
 361
 362         ParserState->Aml = WalkState->AmlLastWhile;
 363         WalkState->ControlState->Common.Value = FALSE;
 364         Status = AE_CTRL_BREAK;
 365         break;
 366
 367     case AE_CTRL_CONTINUE:
 368
 369         ParserState->Aml = WalkState->AmlLastWhile;
 370         Status = AE_CTRL_CONTINUE;
 371         break;
 372
 373     case AE_CTRL_PENDING:
 374
 375         ParserState->Aml = WalkState->AmlLastWhile;
 376         break;
 377
 378 #if 0
 379     case AE_CTRL_SKIP:
 380
 381         ParserState->Aml = ParserState->Scope->ParseScope.PkgEnd;
 382         Status = AE_OK;
 383         break;
 384 #endif
 385
 386     case AE_CTRL_TRUE:
 387         /*
 388          * Predicate of an IF was true, and we are at the matching ELSE.
 389          * Just close out this package
 390          */
 391         ParserState->Aml = AcpiPsGetNextPackageEnd (ParserState);
 392         Status = AE_CTRL_PENDING;
 393         break;
 394
 395     case AE_CTRL_FALSE:
 396         /*
 397          * Either an IF/WHILE Predicate was false or we encountered a BREAK
 398          * opcode. In both cases, we do not execute the rest of the
 399          * package;  We simply close out the parent (finishing the walk of
 400          * this branch of the tree) and continue execution at the parent
 401          * level.
 402          */
 403         ParserState->Aml = ParserState->Scope->ParseScope.PkgEnd;
 404
 405         /* In the case of a BREAK, just force a predicate (if any) to FALSE */
 406
 407         WalkState->ControlState->Common.Value = FALSE;
 408         Status = AE_CTRL_END;
 409         break;
 410
 411     case AE_CTRL_TRANSFER:
 412
 413         /* A method call (invocation) -- transfer control */
 414
 415         Status = AE_CTRL_TRANSFER;
 416         WalkState->PrevOp = Op;
 417         WalkState->MethodCallOp = Op;
 418         WalkState->MethodCallNode = (Op->Common.Value.Arg)->Common.Node;
 419
 420         /* Will return value (if any) be used by the caller? */
 421
 422         WalkState->ReturnUsed = AcpiDsIsResultUsed (Op, WalkState);
 423         break;
 424
 425     default:
 426
 427         Status = CallbackStatus;
 428         if ((CallbackStatus & AE_CODE_MASK) == AE_CODE_CONTROL)
 429         {
 430             Status = AE_OK;
 431         }
 432         break;
 433     }
 434
 435     return_ACPI_STATUS (Status);
 436 }
 437
 438
 439 /*******************************************************************************
 440  *
 441  * FUNCTION:    AcpiPsParseAml
 442  *
 443  * PARAMETERS:  WalkState       - Current state
 444  *
 445  *
 446  * RETURN:      Status
 447  *
 448  * DESCRIPTION: Parse raw AML and return a tree of ops
 449  *
 450  ******************************************************************************/
 451
 452 ACPI_STATUS
 453 AcpiPsParseAml (
 454     ACPI_WALK_STATE         *WalkState)
 455 {
 456     ACPI_STATUS             Status;
 457     ACPI_THREAD_STATE       *Thread;
 458     ACPI_THREAD_STATE       *PrevWalkList = AcpiGbl_CurrentWalkList;
 459     ACPI_WALK_STATE         *PreviousWalkState;
 460
 461
 462     ACPI_FUNCTION_TRACE (PsParseAml);
 463
 464     ACPI_DEBUG_PRINT ((ACPI_DB_PARSE,
 465         "Entered with WalkState=%p Aml=%p size=%X\n",
 466         WalkState, WalkState->ParserState.Aml,
 467         WalkState->ParserState.AmlSize));
 468
 469     if (!WalkState->ParserState.Aml)
 470     {
 471         return_ACPI_STATUS (AE_BAD_ADDRESS);
 472     }
 473
 474     /* Create and initialize a new thread state */
 475
 476     Thread = AcpiUtCreateThreadState ();
 477     if (!Thread)
 478     {
 479         if (WalkState->MethodDesc)
 480         {
 481             /* Executing a control method - additional cleanup */
 482
 483             AcpiDsTerminateControlMethod (WalkState->MethodDesc, WalkState);
 484         }
 485
 486         AcpiDsDeleteWalkState (WalkState);
 487         return_ACPI_STATUS (AE_NO_MEMORY);
 488     }
 489
 490     WalkState->Thread = Thread;
 491
 492     /*
 493      * If executing a method, the starting SyncLevel is this method's
 494      * SyncLevel
 495      */
 496     if (WalkState->MethodDesc)
 497     {
 498         WalkState->Thread->CurrentSyncLevel =
 499             WalkState->MethodDesc->Method.SyncLevel;
 500     }
 501
 502     AcpiDsPushWalkState (WalkState, Thread);
 503
 504     /*
 505      * This global allows the AML debugger to get a handle to the currently
 506      * executing control method.
 507      */
 508     AcpiGbl_CurrentWalkList = Thread;
 509
 510     /*
 511      * Execute the walk loop as long as there is a valid Walk State. This
 512      * handles nested control method invocations without recursion.
 513      */
 514     ACPI_DEBUG_PRINT ((ACPI_DB_PARSE, "State=%p\n", WalkState));
 515
 516     Status = AE_OK;
 517     while (WalkState)
 518     {
 519         if (ACPI_SUCCESS (Status))
 520         {
 521             /*
 522              * The ParseLoop executes AML until the method terminates
 523              * or calls another method.
 524              */
 525             Status = AcpiPsParseLoop (WalkState);
 526         }
 527
 528         ACPI_DEBUG_PRINT ((ACPI_DB_PARSE,
 529             "Completed one call to walk loop, %s State=%p\n",
 530             AcpiFormatException (Status), WalkState));
 531
 532         if (Status == AE_CTRL_TRANSFER)
 533         {
 534             /*
 535              * A method call was detected.
 536              * Transfer control to the called control method
 537              */
 538             Status = AcpiDsCallControlMethod (Thread, WalkState, NULL);
 539             if (ACPI_FAILURE (Status))
 540             {
 541                 Status = AcpiDsMethodError (Status, WalkState);
 542             }
 543
 544             /*
 545              * If the transfer to the new method method call worked
 546              *, a new walk state was created -- get it
 547              */
 548             WalkState = AcpiDsGetCurrentWalkState (Thread);
 549             continue;
 550         }
 551         else if (Status == AE_CTRL_TERMINATE)
 552         {
 553             Status = AE_OK;
 554         }
 555         else if ((Status != AE_OK) && (WalkState->MethodDesc))
 556         {
 557             /* Either the method parse or actual execution failed */
 558
 559             AcpiExExitInterpreter ();
 560             if (Status == AE_ABORT_METHOD)
 561             {
 562                 AcpiNsPrintNodePathname (
 563                     WalkState->MethodNode, "Method aborted:");
 564                 AcpiOsPrintf ("\n");
 565             }
 566             else
 567             {
 568                 ACPI_ERROR_METHOD ("Method parse/execution failed",
 569                     WalkState->MethodNode, NULL, Status);
 570             }
 571             AcpiExEnterInterpreter ();
 572
 573             /* Check for possible multi-thread reentrancy problem */
 574
 575             if ((Status == AE_ALREADY_EXISTS) &&
 576                 (!(WalkState->MethodDesc->Method.InfoFlags &
 577                     ACPI_METHOD_SERIALIZED)))
 578             {
 579                 /*
 580                  * Method is not serialized and tried to create an object
 581                  * twice. The probable cause is that the method cannot
 582                  * handle reentrancy. Mark as "pending serialized" now, and
 583                  * then mark "serialized" when the last thread exits.
 584                  */
 585                 WalkState->MethodDesc->Method.InfoFlags |=
 586                     ACPI_METHOD_SERIALIZED_PENDING;
 587             }
 588         }
 589
 590         /* We are done with this walk, move on to the parent if any */
 591
 592         WalkState = AcpiDsPopWalkState (Thread);
 593
 594         /* Reset the current scope to the beginning of scope stack */
 595
 596         AcpiDsScopeStackClear (WalkState);
 597
 598         /*
 599          * If we just returned from the execution of a control method or if we
 600          * encountered an error during the method parse phase, there's lots of
 601          * cleanup to do
 602          */
 603         if (((WalkState->ParseFlags & ACPI_PARSE_MODE_MASK) ==
 604             ACPI_PARSE_EXECUTE &&
 605             !(WalkState->ParseFlags & ACPI_PARSE_MODULE_LEVEL)) ||
 606             (ACPI_FAILURE (Status)))
 607         {
 608             AcpiDsTerminateControlMethod (WalkState->MethodDesc, WalkState);
 609         }
 610
 611         /* Delete this walk state and all linked control states */
 612
 613         AcpiPsCleanupScope (&WalkState->ParserState);
 614         PreviousWalkState = WalkState;
 615
 616         ACPI_DEBUG_PRINT ((ACPI_DB_PARSE,
 617             "ReturnValue=%p, ImplicitValue=%p State=%p\n",
 618             WalkState->ReturnDesc, WalkState->ImplicitReturnObj, WalkState));
 619
 620         /* Check if we have restarted a preempted walk */
 621
 622         WalkState = AcpiDsGetCurrentWalkState (Thread);
 623         if (WalkState)
 624         {
 625             if (ACPI_SUCCESS (Status))
 626             {
 627                 /*
 628                  * There is another walk state, restart it.
 629                  * If the method return value is not used by the parent,
 630                  * The object is deleted
 631                  */
 632                 if (!PreviousWalkState->ReturnDesc)
 633                 {
 634                     /*
 635                      * In slack mode execution, if there is no return value
 636                      * we should implicitly return zero (0) as a default value.
 637                      */
 638                     if (AcpiGbl_EnableInterpreterSlack &&
 639                         !PreviousWalkState->ImplicitReturnObj)
 640                     {
 641                         PreviousWalkState->ImplicitReturnObj =
 642                             AcpiUtCreateIntegerObject ((UINT64) 0);
 643                         if (!PreviousWalkState->ImplicitReturnObj)
 644                         {
 645                             return_ACPI_STATUS (AE_NO_MEMORY);
 646                         }
 647                     }
 648
 649                     /* Restart the calling control method */
 650
 651                     Status = AcpiDsRestartControlMethod (WalkState,
 652                         PreviousWalkState->ImplicitReturnObj);
 653                 }
 654                 else
 655                 {
 656                     /*
 657                      * We have a valid return value, delete any implicit
 658                      * return value.
 659                      */
 660                     AcpiDsClearImplicitReturn (PreviousWalkState);
 661
 662                     Status = AcpiDsRestartControlMethod (WalkState,
 663                         PreviousWalkState->ReturnDesc);
 664                 }
 665                 if (ACPI_SUCCESS (Status))
 666                 {
 667                     WalkState->WalkType |= ACPI_WALK_METHOD_RESTART;
 668                 }
 669             }
 670             else
 671             {
 672                 /* On error, delete any return object or implicit return */
 673
 674                 AcpiUtRemoveReference (PreviousWalkState->ReturnDesc);
 675                 AcpiDsClearImplicitReturn (PreviousWalkState);
 676             }
 677         }
 678
 679         /*
 680          * Just completed a 1st-level method, save the final internal return
 681          * value (if any)
 682          */
 683         else if (PreviousWalkState->CallerReturnDesc)
 684         {
 685             if (PreviousWalkState->ImplicitReturnObj)
 686             {
 687                 *(PreviousWalkState->CallerReturnDesc) =
 688                     PreviousWalkState->ImplicitReturnObj;
 689             }
 690             else
 691             {
 692                  /* NULL if no return value */
 693
 694                 *(PreviousWalkState->CallerReturnDesc) =
 695                     PreviousWalkState->ReturnDesc;
 696             }
 697         }
 698         else
 699         {
 700             if (PreviousWalkState->ReturnDesc)
 701             {
 702                 /* Caller doesn't want it, must delete it */
 703
 704                 AcpiUtRemoveReference (PreviousWalkState->ReturnDesc);
 705             }
 706             if (PreviousWalkState->ImplicitReturnObj)
 707             {
 708                 /* Caller doesn't want it, must delete it */
 709
 710                 AcpiUtRemoveReference (PreviousWalkState->ImplicitReturnObj);
 711             }
 712         }
 713
 714         AcpiDsDeleteWalkState (PreviousWalkState);
 715     }
 716
 717     /* Normal exit */
 718
 719     AcpiExReleaseAllMutexes (Thread);
 720     AcpiUtDeleteGenericState (ACPI_CAST_PTR (ACPI_GENERIC_STATE, Thread));
 721     AcpiGbl_CurrentWalkList = PrevWalkList;
 722     return_ACPI_STATUS (Status);
 723 }