drivers/acpi/acpica/psparse.c

   1 /******************************************************************************
   2  *
   3  * Module Name: psparse - Parser top level AML parse routines
   4  *
   5  *****************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2012, 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 aml_op_info[]
  51  */
  52
  53 #include <acpi/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  * FUNCTION:    acpi_ps_get_opcode_size
  66  *
  67  * PARAMETERS:  Opcode          - An AML opcode
  68  *
  69  * RETURN:      Size of the opcode, in bytes (1 or 2)
  70  *
  71  * DESCRIPTION: Get the size of the current opcode.
  72  *
  73  ******************************************************************************/
  74 u32 acpi_ps_get_opcode_size(u32 opcode)
  75 {
  76
  77         /* Extended (2-byte) opcode if > 255 */
  78
  79         if (opcode > 0x00FF) {
  80                 return (2);
  81         }
  82
  83         /* Otherwise, just a single byte opcode */
  84
  85         return (1);
  86 }
  87
  88 /*******************************************************************************
  89  *
  90  * FUNCTION:    acpi_ps_peek_opcode
  91  *
  92  * PARAMETERS:  parser_state        - A parser state object
  93  *
  94  * RETURN:      Next AML opcode
  95  *
  96  * DESCRIPTION: Get next AML opcode (without incrementing AML pointer)
  97  *
  98  ******************************************************************************/
  99
 100 u16 acpi_ps_peek_opcode(struct acpi_parse_state * parser_state)
 101 {
 102         u8 *aml;
 103         u16 opcode;
 104
 105         aml = parser_state->aml;
 106         opcode = (u16) ACPI_GET8(aml);
 107
 108         if (opcode == AML_EXTENDED_OP_PREFIX) {
 109
 110                 /* Extended opcode, get the second opcode byte */
 111
 112                 aml++;
 113                 opcode = (u16) ((opcode << 8) | ACPI_GET8(aml));
 114         }
 115
 116         return (opcode);
 117 }
 118
 119 /*******************************************************************************
 120  *
 121  * FUNCTION:    acpi_ps_complete_this_op
 122  *
 123  * PARAMETERS:  walk_state      - Current State
 124  *              Op              - Op to complete
 125  *
 126  * RETURN:      Status
 127  *
 128  * DESCRIPTION: Perform any cleanup at the completion of an Op.
 129  *
 130  ******************************************************************************/
 131
 132 acpi_status
 133 acpi_ps_complete_this_op(struct acpi_walk_state * walk_state,
 134                          union acpi_parse_object * op)
 135 {
 136         union acpi_parse_object *prev;
 137         union acpi_parse_object *next;
 138         const struct acpi_opcode_info *parent_info;
 139         union acpi_parse_object *replacement_op = NULL;
 140         acpi_status status = AE_OK;
 141
 142         ACPI_FUNCTION_TRACE_PTR(ps_complete_this_op, op);
 143
 144         /* Check for null Op, can happen if AML code is corrupt */
 145
 146         if (!op) {
 147                 return_ACPI_STATUS(AE_OK);      /* OK for now */
 148         }
 149
 150         /* Delete this op and the subtree below it if asked to */
 151
 152         if (((walk_state->parse_flags & ACPI_PARSE_TREE_MASK) !=
 153              ACPI_PARSE_DELETE_TREE)
 154             || (walk_state->op_info->class == AML_CLASS_ARGUMENT)) {
 155                 return_ACPI_STATUS(AE_OK);
 156         }
 157
 158         /* Make sure that we only delete this subtree */
 159
 160         if (op->common.parent) {
 161                 prev = op->common.parent->common.value.arg;
 162                 if (!prev) {
 163
 164                         /* Nothing more to do */
 165
 166                         goto cleanup;
 167                 }
 168
 169                 /*
 170                  * Check if we need to replace the operator and its subtree
 171                  * with a return value op (placeholder op)
 172                  */
 173                 parent_info =
 174                     acpi_ps_get_opcode_info(op->common.parent->common.
 175                                             aml_opcode);
 176
 177                 switch (parent_info->class) {
 178                 case AML_CLASS_CONTROL:
 179                         break;
 180
 181                 case AML_CLASS_CREATE:
 182
 183                         /*
 184                          * These opcodes contain term_arg operands. The current
 185                          * op must be replaced by a placeholder return op
 186                          */
 187                         replacement_op =
 188                             acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP);
 189                         if (!replacement_op) {
 190                                 status = AE_NO_MEMORY;
 191                         }
 192                         break;
 193
 194                 case AML_CLASS_NAMED_OBJECT:
 195
 196                         /*
 197                          * These opcodes contain term_arg operands. The current
 198                          * op must be replaced by a placeholder return op
 199                          */
 200                         if ((op->common.parent->common.aml_opcode ==
 201                              AML_REGION_OP)
 202                             || (op->common.parent->common.aml_opcode ==
 203                                 AML_DATA_REGION_OP)
 204                             || (op->common.parent->common.aml_opcode ==
 205                                 AML_BUFFER_OP)
 206                             || (op->common.parent->common.aml_opcode ==
 207                                 AML_PACKAGE_OP)
 208                             || (op->common.parent->common.aml_opcode ==
 209                                 AML_BANK_FIELD_OP)
 210                             || (op->common.parent->common.aml_opcode ==
 211                                 AML_VAR_PACKAGE_OP)) {
 212                                 replacement_op =
 213                                     acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP);
 214                                 if (!replacement_op) {
 215                                         status = AE_NO_MEMORY;
 216                                 }
 217                         } else
 218                             if ((op->common.parent->common.aml_opcode ==
 219                                  AML_NAME_OP)
 220                                 && (walk_state->pass_number <=
 221                                     ACPI_IMODE_LOAD_PASS2)) {
 222                                 if ((op->common.aml_opcode == AML_BUFFER_OP)
 223                                     || (op->common.aml_opcode == AML_PACKAGE_OP)
 224                                     || (op->common.aml_opcode ==
 225                                         AML_VAR_PACKAGE_OP)) {
 226                                         replacement_op =
 227                                             acpi_ps_alloc_op(op->common.
 228                                                              aml_opcode);
 229                                         if (!replacement_op) {
 230                                                 status = AE_NO_MEMORY;
 231                                         } else {
 232                                                 replacement_op->named.data =
 233                                                     op->named.data;
 234                                                 replacement_op->named.length =
 235                                                     op->named.length;
 236                                         }
 237                                 }
 238                         }
 239                         break;
 240
 241                 default:
 242
 243                         replacement_op =
 244                             acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP);
 245                         if (!replacement_op) {
 246                                 status = AE_NO_MEMORY;
 247                         }
 248                 }
 249
 250                 /* We must unlink this op from the parent tree */
 251
 252                 if (prev == op) {
 253
 254                         /* This op is the first in the list */
 255
 256                         if (replacement_op) {
 257                                 replacement_op->common.parent =
 258                                     op->common.parent;
 259                                 replacement_op->common.value.arg = NULL;
 260                                 replacement_op->common.node = op->common.node;
 261                                 op->common.parent->common.value.arg =
 262                                     replacement_op;
 263                                 replacement_op->common.next = op->common.next;
 264                         } else {
 265                                 op->common.parent->common.value.arg =
 266                                     op->common.next;
 267                         }
 268                 }
 269
 270                 /* Search the parent list */
 271
 272                 else
 273                         while (prev) {
 274
 275                                 /* Traverse all siblings in the parent's argument list */
 276
 277                                 next = prev->common.next;
 278                                 if (next == op) {
 279                                         if (replacement_op) {
 280                                                 replacement_op->common.parent =
 281                                                     op->common.parent;
 282                                                 replacement_op->common.value.
 283                                                     arg = NULL;
 284                                                 replacement_op->common.node =
 285                                                     op->common.node;
 286                                                 prev->common.next =
 287                                                     replacement_op;
 288                                                 replacement_op->common.next =
 289                                                     op->common.next;
 290                                                 next = NULL;
 291                                         } else {
 292                                                 prev->common.next =
 293                                                     op->common.next;
 294                                                 next = NULL;
 295                                         }
 296                                 }
 297                                 prev = next;
 298                         }
 299         }
 300
 301       cleanup:
 302
 303         /* Now we can actually delete the subtree rooted at Op */
 304
 305         acpi_ps_delete_parse_tree(op);
 306         return_ACPI_STATUS(status);
 307 }
 308
 309 /*******************************************************************************
 310  *
 311  * FUNCTION:    acpi_ps_next_parse_state
 312  *
 313  * PARAMETERS:  walk_state          - Current state
 314  *              Op                  - Current parse op
 315  *              callback_status     - Status from previous operation
 316  *
 317  * RETURN:      Status
 318  *
 319  * DESCRIPTION: Update the parser state based upon the return exception from
 320  *              the parser callback.
 321  *
 322  ******************************************************************************/
 323
 324 acpi_status
 325 acpi_ps_next_parse_state(struct acpi_walk_state *walk_state,
 326                          union acpi_parse_object *op,
 327                          acpi_status callback_status)
 328 {
 329         struct acpi_parse_state *parser_state = &walk_state->parser_state;
 330         acpi_status status = AE_CTRL_PENDING;
 331
 332         ACPI_FUNCTION_TRACE_PTR(ps_next_parse_state, op);
 333
 334         switch (callback_status) {
 335         case AE_CTRL_TERMINATE:
 336                 /*
 337                  * A control method was terminated via a RETURN statement.
 338                  * The walk of this method is complete.
 339                  */
 340                 parser_state->aml = parser_state->aml_end;
 341                 status = AE_CTRL_TERMINATE;
 342                 break;
 343
 344         case AE_CTRL_BREAK:
 345
 346                 parser_state->aml = walk_state->aml_last_while;
 347                 walk_state->control_state->common.value = FALSE;
 348                 status = AE_CTRL_BREAK;
 349                 break;
 350
 351         case AE_CTRL_CONTINUE:
 352
 353                 parser_state->aml = walk_state->aml_last_while;
 354                 status = AE_CTRL_CONTINUE;
 355                 break;
 356
 357         case AE_CTRL_PENDING:
 358
 359                 parser_state->aml = walk_state->aml_last_while;
 360                 break;
 361
 362 #if 0
 363         case AE_CTRL_SKIP:
 364
 365                 parser_state->aml = parser_state->scope->parse_scope.pkg_end;
 366                 status = AE_OK;
 367                 break;
 368 #endif
 369
 370         case AE_CTRL_TRUE:
 371                 /*
 372                  * Predicate of an IF was true, and we are at the matching ELSE.
 373                  * Just close out this package
 374                  */
 375                 parser_state->aml = acpi_ps_get_next_package_end(parser_state);
 376                 status = AE_CTRL_PENDING;
 377                 break;
 378
 379         case AE_CTRL_FALSE:
 380                 /*
 381                  * Either an IF/WHILE Predicate was false or we encountered a BREAK
 382                  * opcode.  In both cases, we do not execute the rest of the
 383                  * package;  We simply close out the parent (finishing the walk of
 384                  * this branch of the tree) and continue execution at the parent
 385                  * level.
 386                  */
 387                 parser_state->aml = parser_state->scope->parse_scope.pkg_end;
 388
 389                 /* In the case of a BREAK, just force a predicate (if any) to FALSE */
 390
 391                 walk_state->control_state->common.value = FALSE;
 392                 status = AE_CTRL_END;
 393                 break;
 394
 395         case AE_CTRL_TRANSFER:
 396
 397                 /* A method call (invocation) -- transfer control */
 398
 399                 status = AE_CTRL_TRANSFER;
 400                 walk_state->prev_op = op;
 401                 walk_state->method_call_op = op;
 402                 walk_state->method_call_node =
 403                     (op->common.value.arg)->common.node;
 404
 405                 /* Will return value (if any) be used by the caller? */
 406
 407                 walk_state->return_used =
 408                     acpi_ds_is_result_used(op, walk_state);
 409                 break;
 410
 411         default:
 412
 413                 status = callback_status;
 414                 if ((callback_status & AE_CODE_MASK) == AE_CODE_CONTROL) {
 415                         status = AE_OK;
 416                 }
 417                 break;
 418         }
 419
 420         return_ACPI_STATUS(status);
 421 }
 422
 423 /*******************************************************************************
 424  *
 425  * FUNCTION:    acpi_ps_parse_aml
 426  *
 427  * PARAMETERS:  walk_state      - Current state
 428  *
 429  *
 430  * RETURN:      Status
 431  *
 432  * DESCRIPTION: Parse raw AML and return a tree of ops
 433  *
 434  ******************************************************************************/
 435
 436 acpi_status acpi_ps_parse_aml(struct acpi_walk_state *walk_state)
 437 {
 438         acpi_status status;
 439         struct acpi_thread_state *thread;
 440         struct acpi_thread_state *prev_walk_list = acpi_gbl_current_walk_list;
 441         struct acpi_walk_state *previous_walk_state;
 442
 443         ACPI_FUNCTION_TRACE(ps_parse_aml);
 444
 445         ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 446                           "Entered with WalkState=%p Aml=%p size=%X\n",
 447                           walk_state, walk_state->parser_state.aml,
 448                           walk_state->parser_state.aml_size));
 449
 450         if (!walk_state->parser_state.aml) {
 451                 return_ACPI_STATUS(AE_NULL_OBJECT);
 452         }
 453
 454         /* Create and initialize a new thread state */
 455
 456         thread = acpi_ut_create_thread_state();
 457         if (!thread) {
 458                 if (walk_state->method_desc) {
 459
 460                         /* Executing a control method - additional cleanup */
 461
 462                         acpi_ds_terminate_control_method(
 463                                 walk_state->method_desc, walk_state);
 464                 }
 465
 466                 acpi_ds_delete_walk_state(walk_state);
 467                 return_ACPI_STATUS(AE_NO_MEMORY);
 468         }
 469
 470         walk_state->thread = thread;
 471
 472         /*
 473          * If executing a method, the starting sync_level is this method's
 474          * sync_level
 475          */
 476         if (walk_state->method_desc) {
 477                 walk_state->thread->current_sync_level =
 478                     walk_state->method_desc->method.sync_level;
 479         }
 480
 481         acpi_ds_push_walk_state(walk_state, thread);
 482
 483         /*
 484          * This global allows the AML debugger to get a handle to the currently
 485          * executing control method.
 486          */
 487         acpi_gbl_current_walk_list = thread;
 488
 489         /*
 490          * Execute the walk loop as long as there is a valid Walk State.  This
 491          * handles nested control method invocations without recursion.
 492          */
 493         ACPI_DEBUG_PRINT((ACPI_DB_PARSE, "State=%p\n", walk_state));
 494
 495         status = AE_OK;
 496         while (walk_state) {
 497                 if (ACPI_SUCCESS(status)) {
 498                         /*
 499                          * The parse_loop executes AML until the method terminates
 500                          * or calls another method.
 501                          */
 502                         status = acpi_ps_parse_loop(walk_state);
 503                 }
 504
 505                 ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 506                                   "Completed one call to walk loop, %s State=%p\n",
 507                                   acpi_format_exception(status), walk_state));
 508
 509                 if (status == AE_CTRL_TRANSFER) {
 510                         /*
 511                          * A method call was detected.
 512                          * Transfer control to the called control method
 513                          */
 514                         status =
 515                             acpi_ds_call_control_method(thread, walk_state,
 516                                                         NULL);
 517                         if (ACPI_FAILURE(status)) {
 518                                 status =
 519                                     acpi_ds_method_error(status, walk_state);
 520                         }
 521
 522                         /*
 523                          * If the transfer to the new method method call worked, a new walk
 524                          * state was created -- get it
 525                          */
 526                         walk_state = acpi_ds_get_current_walk_state(thread);
 527                         continue;
 528                 } else if (status == AE_CTRL_TERMINATE) {
 529                         status = AE_OK;
 530                 } else if ((status != AE_OK) && (walk_state->method_desc)) {
 531
 532                         /* Either the method parse or actual execution failed */
 533
 534                         ACPI_ERROR_METHOD("Method parse/execution failed",
 535                                           walk_state->method_node, NULL,
 536                                           status);
 537
 538                         /* Check for possible multi-thread reentrancy problem */
 539
 540                         if ((status == AE_ALREADY_EXISTS) &&
 541                             (!(walk_state->method_desc->method.
 542                                info_flags & ACPI_METHOD_SERIALIZED))) {
 543                                 /*
 544                                  * Method is not serialized and tried to create an object
 545                                  * twice. The probable cause is that the method cannot
 546                                  * handle reentrancy. Mark as "pending serialized" now, and
 547                                  * then mark "serialized" when the last thread exits.
 548                                  */
 549                                 walk_state->method_desc->method.info_flags |=
 550                                     ACPI_METHOD_SERIALIZED_PENDING;
 551                         }
 552                 }
 553
 554                 /* We are done with this walk, move on to the parent if any */
 555
 556                 walk_state = acpi_ds_pop_walk_state(thread);
 557
 558                 /* Reset the current scope to the beginning of scope stack */
 559
 560                 acpi_ds_scope_stack_clear(walk_state);
 561
 562                 /*
 563                  * If we just returned from the execution of a control method or if we
 564                  * encountered an error during the method parse phase, there's lots of
 565                  * cleanup to do
 566                  */
 567                 if (((walk_state->parse_flags & ACPI_PARSE_MODE_MASK) ==
 568                      ACPI_PARSE_EXECUTE) || (ACPI_FAILURE(status))) {
 569                         acpi_ds_terminate_control_method(walk_state->
 570                                                          method_desc,
 571                                                          walk_state);
 572                 }
 573
 574                 /* Delete this walk state and all linked control states */
 575
 576                 acpi_ps_cleanup_scope(&walk_state->parser_state);
 577                 previous_walk_state = walk_state;
 578
 579                 ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 580                                   "ReturnValue=%p, ImplicitValue=%p State=%p\n",
 581                                   walk_state->return_desc,
 582                                   walk_state->implicit_return_obj, walk_state));
 583
 584                 /* Check if we have restarted a preempted walk */
 585
 586                 walk_state = acpi_ds_get_current_walk_state(thread);
 587                 if (walk_state) {
 588                         if (ACPI_SUCCESS(status)) {
 589                                 /*
 590                                  * There is another walk state, restart it.
 591                                  * If the method return value is not used by the parent,
 592                                  * The object is deleted
 593                                  */
 594                                 if (!previous_walk_state->return_desc) {
 595                                         /*
 596                                          * In slack mode execution, if there is no return value
 597                                          * we should implicitly return zero (0) as a default value.
 598                                          */
 599                                         if (acpi_gbl_enable_interpreter_slack &&
 600                                             !previous_walk_state->
 601                                             implicit_return_obj) {
 602                                                 previous_walk_state->
 603                                                     implicit_return_obj =
 604                                                     acpi_ut_create_integer_object
 605                                                     ((u64) 0);
 606                                                 if (!previous_walk_state->
 607                                                     implicit_return_obj) {
 608                                                         return_ACPI_STATUS
 609                                                             (AE_NO_MEMORY);
 610                                                 }
 611                                         }
 612
 613                                         /* Restart the calling control method */
 614
 615                                         status =
 616                                             acpi_ds_restart_control_method
 617                                             (walk_state,
 618                                              previous_walk_state->
 619                                              implicit_return_obj);
 620                                 } else {
 621                                         /*
 622                                          * We have a valid return value, delete any implicit
 623                                          * return value.
 624                                          */
 625                                         acpi_ds_clear_implicit_return
 626                                             (previous_walk_state);
 627
 628                                         status =
 629                                             acpi_ds_restart_control_method
 630                                             (walk_state,
 631                                              previous_walk_state->return_desc);
 632                                 }
 633                                 if (ACPI_SUCCESS(status)) {
 634                                         walk_state->walk_type |=
 635                                             ACPI_WALK_METHOD_RESTART;
 636                                 }
 637                         } else {
 638                                 /* On error, delete any return object or implicit return */
 639
 640                                 acpi_ut_remove_reference(previous_walk_state->
 641                                                          return_desc);
 642                                 acpi_ds_clear_implicit_return
 643                                     (previous_walk_state);
 644                         }
 645                 }
 646
 647                 /*
 648                  * Just completed a 1st-level method, save the final internal return
 649                  * value (if any)
 650                  */
 651                 else if (previous_walk_state->caller_return_desc) {
 652                         if (previous_walk_state->implicit_return_obj) {
 653                                 *(previous_walk_state->caller_return_desc) =
 654                                     previous_walk_state->implicit_return_obj;
 655                         } else {
 656                                 /* NULL if no return value */
 657
 658                                 *(previous_walk_state->caller_return_desc) =
 659                                     previous_walk_state->return_desc;
 660                         }
 661                 } else {
 662                         if (previous_walk_state->return_desc) {
 663
 664                                 /* Caller doesn't want it, must delete it */
 665
 666                                 acpi_ut_remove_reference(previous_walk_state->
 667                                                          return_desc);
 668                         }
 669                         if (previous_walk_state->implicit_return_obj) {
 670
 671                                 /* Caller doesn't want it, must delete it */
 672
 673                                 acpi_ut_remove_reference(previous_walk_state->
 674                                                          implicit_return_obj);
 675                         }
 676                 }
 677
 678                 acpi_ds_delete_walk_state(previous_walk_state);
 679         }
 680
 681         /* Normal exit */
 682
 683         acpi_ex_release_all_mutexes(thread);
 684         acpi_ut_delete_generic_state(ACPI_CAST_PTR
 685                                      (union acpi_generic_state, thread));
 686         acpi_gbl_current_walk_list = prev_walk_list;
 687         return_ACPI_STATUS(status);
 688 }