1 /******************************************************************************
2 *
3 * Module Name: psparse - Parser top level AML parse routines
4 *
5 *****************************************************************************/
6
7 /*
8 * Copyright (C) 2000 - 2022, 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 MERCHANTABILITY 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
AcpiPsGetOpcodeSize(UINT32 Opcode)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
AcpiPsPeekOpcode(ACPI_PARSE_STATE * ParserState)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
AcpiPsCompleteThisOp(ACPI_WALK_STATE * WalkState,ACPI_PARSE_OBJECT * Op)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
AcpiPsNextParseState(ACPI_WALK_STATE * WalkState,ACPI_PARSE_OBJECT * Op,ACPI_STATUS CallbackStatus)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 (ACPI_CNTL_EXCEPTION (CallbackStatus))
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
AcpiPsParseAml(ACPI_WALK_STATE * WalkState)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 (WalkState->MethodPathname && WalkState->MethodIsNested)
533 {
534 /* Optional object evaluation log */
535
536 ACPI_DEBUG_PRINT_RAW ((ACPI_DB_EVALUATION, "%-26s: %*s%s\n",
537 " Exit nested method",
538 (WalkState->MethodNestingDepth + 1) * 3, " ",
539 &WalkState->MethodPathname[1]));
540
541 ACPI_FREE (WalkState->MethodPathname);
542 WalkState->MethodIsNested = FALSE;
543 }
544 if (Status == AE_CTRL_TRANSFER)
545 {
546 /*
547 * A method call was detected.
548 * Transfer control to the called control method
549 */
550 Status = AcpiDsCallControlMethod (Thread, WalkState, NULL);
551 if (ACPI_FAILURE (Status))
552 {
553 Status = AcpiDsMethodError (Status, WalkState);
554 }
555
556 /*
557 * If the transfer to the new method method call worked,
558 * a new walk state was created -- get it
559 */
560 WalkState = AcpiDsGetCurrentWalkState (Thread);
561 continue;
562 }
563 else if (Status == AE_CTRL_TERMINATE)
564 {
565 Status = AE_OK;
566 }
567 else if ((Status != AE_OK) && (WalkState->MethodDesc))
568 {
569 /* Either the method parse or actual execution failed */
570
571 AcpiExExitInterpreter ();
572 if (Status == AE_ABORT_METHOD)
573 {
574 AcpiNsPrintNodePathname (
575 WalkState->MethodNode, "Aborting method");
576 AcpiOsPrintf ("\n");
577 }
578 else
579 {
580 ACPI_ERROR_METHOD ("Aborting method",
581 WalkState->MethodNode, NULL, Status);
582 }
583 AcpiExEnterInterpreter ();
584
585 /* Check for possible multi-thread reentrancy problem */
586
587 if ((Status == AE_ALREADY_EXISTS) &&
588 (!(WalkState->MethodDesc->Method.InfoFlags &
589 ACPI_METHOD_SERIALIZED)))
590 {
591 /*
592 * Method is not serialized and tried to create an object
593 * twice. The probable cause is that the method cannot
594 * handle reentrancy. Mark as "pending serialized" now, and
595 * then mark "serialized" when the last thread exits.
596 */
597 WalkState->MethodDesc->Method.InfoFlags |=
598 ACPI_METHOD_SERIALIZED_PENDING;
599 }
600 }
601
602 /* We are done with this walk, move on to the parent if any */
603
604 WalkState = AcpiDsPopWalkState (Thread);
605
606 /* Reset the current scope to the beginning of scope stack */
607
608 AcpiDsScopeStackClear (WalkState);
609
610 /*
611 * If we just returned from the execution of a control method or if we
612 * encountered an error during the method parse phase, there's lots of
613 * cleanup to do
614 */
615 if (((WalkState->ParseFlags & ACPI_PARSE_MODE_MASK) ==
616 ACPI_PARSE_EXECUTE &&
617 !(WalkState->ParseFlags & ACPI_PARSE_MODULE_LEVEL)) ||
618 (ACPI_FAILURE (Status)))
619 {
620 AcpiDsTerminateControlMethod (WalkState->MethodDesc, WalkState);
621 }
622
623 /* Delete this walk state and all linked control states */
624
625 AcpiPsCleanupScope (&WalkState->ParserState);
626 PreviousWalkState = WalkState;
627
628 ACPI_DEBUG_PRINT ((ACPI_DB_PARSE,
629 "ReturnValue=%p, ImplicitValue=%p State=%p\n",
630 WalkState->ReturnDesc, WalkState->ImplicitReturnObj, WalkState));
631
632 /* Check if we have restarted a preempted walk */
633
634 WalkState = AcpiDsGetCurrentWalkState (Thread);
635 if (WalkState)
636 {
637 if (ACPI_SUCCESS (Status))
638 {
639 /*
640 * There is another walk state, restart it.
641 * If the method return value is not used by the parent,
642 * The object is deleted
643 */
644 if (!PreviousWalkState->ReturnDesc)
645 {
646 /*
647 * In slack mode execution, if there is no return value
648 * we should implicitly return zero (0) as a default value.
649 */
650 if (AcpiGbl_EnableInterpreterSlack &&
651 !PreviousWalkState->ImplicitReturnObj)
652 {
653 PreviousWalkState->ImplicitReturnObj =
654 AcpiUtCreateIntegerObject ((UINT64) 0);
655 if (!PreviousWalkState->ImplicitReturnObj)
656 {
657 return_ACPI_STATUS (AE_NO_MEMORY);
658 }
659 }
660
661 /* Restart the calling control method */
662
663 Status = AcpiDsRestartControlMethod (WalkState,
664 PreviousWalkState->ImplicitReturnObj);
665 }
666 else
667 {
668 /*
669 * We have a valid return value, delete any implicit
670 * return value.
671 */
672 AcpiDsClearImplicitReturn (PreviousWalkState);
673
674 Status = AcpiDsRestartControlMethod (WalkState,
675 PreviousWalkState->ReturnDesc);
676 }
677 if (ACPI_SUCCESS (Status))
678 {
679 WalkState->WalkType |= ACPI_WALK_METHOD_RESTART;
680 }
681 }
682 else
683 {
684 /* On error, delete any return object or implicit return */
685
686 AcpiUtRemoveReference (PreviousWalkState->ReturnDesc);
687 AcpiDsClearImplicitReturn (PreviousWalkState);
688 }
689 }
690
691 /*
692 * Just completed a 1st-level method, save the final internal return
693 * value (if any)
694 */
695 else if (PreviousWalkState->CallerReturnDesc)
696 {
697 if (PreviousWalkState->ImplicitReturnObj)
698 {
699 *(PreviousWalkState->CallerReturnDesc) =
700 PreviousWalkState->ImplicitReturnObj;
701 }
702 else
703 {
704 /* NULL if no return value */
705
706 *(PreviousWalkState->CallerReturnDesc) =
707 PreviousWalkState->ReturnDesc;
708 }
709 }
710 else
711 {
712 if (PreviousWalkState->ReturnDesc)
713 {
714 /* Caller doesn't want it, must delete it */
715
716 AcpiUtRemoveReference (PreviousWalkState->ReturnDesc);
717 }
718 if (PreviousWalkState->ImplicitReturnObj)
719 {
720 /* Caller doesn't want it, must delete it */
721
722 AcpiUtRemoveReference (PreviousWalkState->ImplicitReturnObj);
723 }
724 }
725
726 AcpiDsDeleteWalkState (PreviousWalkState);
727 }
728
729 /* Normal exit */
730
731 AcpiExReleaseAllMutexes (Thread);
732 AcpiUtDeleteGenericState (ACPI_CAST_PTR (ACPI_GENERIC_STATE, Thread));
733 AcpiGbl_CurrentWalkList = PrevWalkList;
734 return_ACPI_STATUS (Status);
735 }
736