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 - 2016, 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         acpi_ex_stop_trace_opcode(op, walk_state);
 151
 152         /* Delete this op and the subtree below it if asked to */
 153
 154         if (((walk_state->parse_flags & ACPI_PARSE_TREE_MASK) !=
 155              ACPI_PARSE_DELETE_TREE)
 156             || (walk_state->op_info->class == AML_CLASS_ARGUMENT)) {
 157                 return_ACPI_STATUS(AE_OK);
 158         }
 159
 160         /* Make sure that we only delete this subtree */
 161
 162         if (op->common.parent) {
 163                 prev = op->common.parent->common.value.arg;
 164                 if (!prev) {
 165
 166                         /* Nothing more to do */
 167
 168                         goto cleanup;
 169                 }
 170
 171                 /*
 172                  * Check if we need to replace the operator and its subtree
 173                  * with a return value op (placeholder op)
 174                  */
 175                 parent_info =
 176                     acpi_ps_get_opcode_info(op->common.parent->common.
 177                                             aml_opcode);
 178
 179                 switch (parent_info->class) {
 180                 case AML_CLASS_CONTROL:
 181
 182                         break;
 183
 184                 case AML_CLASS_CREATE:
 185                         /*
 186                          * These opcodes contain term_arg operands. The current
 187                          * op must be replaced by a placeholder return op
 188                          */
 189                         replacement_op =
 190                             acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP,
 191                                              op->common.aml);
 192                         if (!replacement_op) {
 193                                 status = AE_NO_MEMORY;
 194                         }
 195                         break;
 196
 197                 case AML_CLASS_NAMED_OBJECT:
 198                         /*
 199                          * These opcodes contain term_arg operands. The current
 200                          * op must be replaced by a placeholder return op
 201                          */
 202                         if ((op->common.parent->common.aml_opcode ==
 203                              AML_REGION_OP)
 204                             || (op->common.parent->common.aml_opcode ==
 205                                 AML_DATA_REGION_OP)
 206                             || (op->common.parent->common.aml_opcode ==
 207                                 AML_BUFFER_OP)
 208                             || (op->common.parent->common.aml_opcode ==
 209                                 AML_PACKAGE_OP)
 210                             || (op->common.parent->common.aml_opcode ==
 211                                 AML_BANK_FIELD_OP)
 212                             || (op->common.parent->common.aml_opcode ==
 213                                 AML_VAR_PACKAGE_OP)) {
 214                                 replacement_op =
 215                                     acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP,
 216                                                      op->common.aml);
 217                                 if (!replacement_op) {
 218                                         status = AE_NO_MEMORY;
 219                                 }
 220                         } else
 221                             if ((op->common.parent->common.aml_opcode ==
 222                                  AML_NAME_OP)
 223                                 && (walk_state->pass_number <=
 224                                     ACPI_IMODE_LOAD_PASS2)) {
 225                                 if ((op->common.aml_opcode == AML_BUFFER_OP)
 226                                     || (op->common.aml_opcode == AML_PACKAGE_OP)
 227                                     || (op->common.aml_opcode ==
 228                                         AML_VAR_PACKAGE_OP)) {
 229                                         replacement_op =
 230                                             acpi_ps_alloc_op(op->common.
 231                                                              aml_opcode,
 232                                                              op->common.aml);
 233                                         if (!replacement_op) {
 234                                                 status = AE_NO_MEMORY;
 235                                         } else {
 236                                                 replacement_op->named.data =
 237                                                     op->named.data;
 238                                                 replacement_op->named.length =
 239                                                     op->named.length;
 240                                         }
 241                                 }
 242                         }
 243                         break;
 244
 245                 default:
 246
 247                         replacement_op =
 248                             acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP,
 249                                              op->common.aml);
 250                         if (!replacement_op) {
 251                                 status = AE_NO_MEMORY;
 252                         }
 253                 }
 254
 255                 /* We must unlink this op from the parent tree */
 256
 257                 if (prev == op) {
 258
 259                         /* This op is the first in the list */
 260
 261                         if (replacement_op) {
 262                                 replacement_op->common.parent =
 263                                     op->common.parent;
 264                                 replacement_op->common.value.arg = NULL;
 265                                 replacement_op->common.node = op->common.node;
 266                                 op->common.parent->common.value.arg =
 267                                     replacement_op;
 268                                 replacement_op->common.next = op->common.next;
 269                         } else {
 270                                 op->common.parent->common.value.arg =
 271                                     op->common.next;
 272                         }
 273                 }
 274
 275                 /* Search the parent list */
 276
 277                 else
 278                         while (prev) {
 279
 280                                 /* Traverse all siblings in the parent's argument list */
 281
 282                                 next = prev->common.next;
 283                                 if (next == op) {
 284                                         if (replacement_op) {
 285                                                 replacement_op->common.parent =
 286                                                     op->common.parent;
 287                                                 replacement_op->common.value.
 288                                                     arg = NULL;
 289                                                 replacement_op->common.node =
 290                                                     op->common.node;
 291                                                 prev->common.next =
 292                                                     replacement_op;
 293                                                 replacement_op->common.next =
 294                                                     op->common.next;
 295                                                 next = NULL;
 296                                         } else {
 297                                                 prev->common.next =
 298                                                     op->common.next;
 299                                                 next = NULL;
 300                                         }
 301                                 }
 302                                 prev = next;
 303                         }
 304         }
 305
 306 cleanup:
 307
 308         /* Now we can actually delete the subtree rooted at Op */
 309
 310         acpi_ps_delete_parse_tree(op);
 311         return_ACPI_STATUS(status);
 312 }
 313
 314 /*******************************************************************************
 315  *
 316  * FUNCTION:    acpi_ps_next_parse_state
 317  *
 318  * PARAMETERS:  walk_state          - Current state
 319  *              op                  - Current parse op
 320  *              callback_status     - Status from previous operation
 321  *
 322  * RETURN:      Status
 323  *
 324  * DESCRIPTION: Update the parser state based upon the return exception from
 325  *              the parser callback.
 326  *
 327  ******************************************************************************/
 328
 329 acpi_status
 330 acpi_ps_next_parse_state(struct acpi_walk_state *walk_state,
 331                          union acpi_parse_object *op,
 332                          acpi_status callback_status)
 333 {
 334         struct acpi_parse_state *parser_state = &walk_state->parser_state;
 335         acpi_status status = AE_CTRL_PENDING;
 336
 337         ACPI_FUNCTION_TRACE_PTR(ps_next_parse_state, op);
 338
 339         switch (callback_status) {
 340         case AE_CTRL_TERMINATE:
 341                 /*
 342                  * A control method was terminated via a RETURN statement.
 343                  * The walk of this method is complete.
 344                  */
 345                 parser_state->aml = parser_state->aml_end;
 346                 status = AE_CTRL_TERMINATE;
 347                 break;
 348
 349         case AE_CTRL_BREAK:
 350
 351                 parser_state->aml = walk_state->aml_last_while;
 352                 walk_state->control_state->common.value = FALSE;
 353                 status = AE_CTRL_BREAK;
 354                 break;
 355
 356         case AE_CTRL_CONTINUE:
 357
 358                 parser_state->aml = walk_state->aml_last_while;
 359                 status = AE_CTRL_CONTINUE;
 360                 break;
 361
 362         case AE_CTRL_PENDING:
 363
 364                 parser_state->aml = walk_state->aml_last_while;
 365                 break;
 366
 367 #if 0
 368         case AE_CTRL_SKIP:
 369
 370                 parser_state->aml = parser_state->scope->parse_scope.pkg_end;
 371                 status = AE_OK;
 372                 break;
 373 #endif
 374
 375         case AE_CTRL_TRUE:
 376                 /*
 377                  * Predicate of an IF was true, and we are at the matching ELSE.
 378                  * Just close out this package
 379                  */
 380                 parser_state->aml = acpi_ps_get_next_package_end(parser_state);
 381                 status = AE_CTRL_PENDING;
 382                 break;
 383
 384         case AE_CTRL_FALSE:
 385                 /*
 386                  * Either an IF/WHILE Predicate was false or we encountered a BREAK
 387                  * opcode. In both cases, we do not execute the rest of the
 388                  * package;  We simply close out the parent (finishing the walk of
 389                  * this branch of the tree) and continue execution at the parent
 390                  * level.
 391                  */
 392                 parser_state->aml = parser_state->scope->parse_scope.pkg_end;
 393
 394                 /* In the case of a BREAK, just force a predicate (if any) to FALSE */
 395
 396                 walk_state->control_state->common.value = FALSE;
 397                 status = AE_CTRL_END;
 398                 break;
 399
 400         case AE_CTRL_TRANSFER:
 401
 402                 /* A method call (invocation) -- transfer control */
 403
 404                 status = AE_CTRL_TRANSFER;
 405                 walk_state->prev_op = op;
 406                 walk_state->method_call_op = op;
 407                 walk_state->method_call_node =
 408                     (op->common.value.arg)->common.node;
 409
 410                 /* Will return value (if any) be used by the caller? */
 411
 412                 walk_state->return_used =
 413                     acpi_ds_is_result_used(op, walk_state);
 414                 break;
 415
 416         default:
 417
 418                 status = callback_status;
 419                 if ((callback_status & AE_CODE_MASK) == AE_CODE_CONTROL) {
 420                         status = AE_OK;
 421                 }
 422                 break;
 423         }
 424
 425         return_ACPI_STATUS(status);
 426 }
 427
 428 /*******************************************************************************
 429  *
 430  * FUNCTION:    acpi_ps_parse_aml
 431  *
 432  * PARAMETERS:  walk_state      - Current state
 433  *
 434  *
 435  * RETURN:      Status
 436  *
 437  * DESCRIPTION: Parse raw AML and return a tree of ops
 438  *
 439  ******************************************************************************/
 440
 441 acpi_status acpi_ps_parse_aml(struct acpi_walk_state *walk_state)
 442 {
 443         acpi_status status;
 444         struct acpi_thread_state *thread;
 445         struct acpi_thread_state *prev_walk_list = acpi_gbl_current_walk_list;
 446         struct acpi_walk_state *previous_walk_state;
 447
 448         ACPI_FUNCTION_TRACE(ps_parse_aml);
 449
 450         ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 451                           "Entered with WalkState=%p Aml=%p size=%X\n",
 452                           walk_state, walk_state->parser_state.aml,
 453                           walk_state->parser_state.aml_size));
 454
 455         if (!walk_state->parser_state.aml) {
 456                 return_ACPI_STATUS(AE_NULL_OBJECT);
 457         }
 458
 459         /* Create and initialize a new thread state */
 460
 461         thread = acpi_ut_create_thread_state();
 462         if (!thread) {
 463                 if (walk_state->method_desc) {
 464
 465                         /* Executing a control method - additional cleanup */
 466
 467                         acpi_ds_terminate_control_method(walk_state->
 468                                                          method_desc,
 469                                                          walk_state);
 470                 }
 471
 472                 acpi_ds_delete_walk_state(walk_state);
 473                 return_ACPI_STATUS(AE_NO_MEMORY);
 474         }
 475
 476         walk_state->thread = thread;
 477
 478         /*
 479          * If executing a method, the starting sync_level is this method's
 480          * sync_level
 481          */
 482         if (walk_state->method_desc) {
 483                 walk_state->thread->current_sync_level =
 484                     walk_state->method_desc->method.sync_level;
 485         }
 486
 487         acpi_ds_push_walk_state(walk_state, thread);
 488
 489         /*
 490          * This global allows the AML debugger to get a handle to the currently
 491          * executing control method.
 492          */
 493         acpi_gbl_current_walk_list = thread;
 494
 495         /*
 496          * Execute the walk loop as long as there is a valid Walk State. This
 497          * handles nested control method invocations without recursion.
 498          */
 499         ACPI_DEBUG_PRINT((ACPI_DB_PARSE, "State=%p\n", walk_state));
 500
 501         status = AE_OK;
 502         while (walk_state) {
 503                 if (ACPI_SUCCESS(status)) {
 504                         /*
 505                          * The parse_loop executes AML until the method terminates
 506                          * or calls another method.
 507                          */
 508                         status = acpi_ps_parse_loop(walk_state);
 509                 }
 510
 511                 ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 512                                   "Completed one call to walk loop, %s State=%p\n",
 513                                   acpi_format_exception(status), walk_state));
 514
 515                 if (status == AE_CTRL_TRANSFER) {
 516                         /*
 517                          * A method call was detected.
 518                          * Transfer control to the called control method
 519                          */
 520                         status =
 521                             acpi_ds_call_control_method(thread, walk_state,
 522                                                         NULL);
 523                         if (ACPI_FAILURE(status)) {
 524                                 status =
 525                                     acpi_ds_method_error(status, walk_state);
 526                         }
 527
 528                         /*
 529                          * If the transfer to the new method method call worked
 530                          *, a new walk state was created -- get it
 531                          */
 532                         walk_state = acpi_ds_get_current_walk_state(thread);
 533                         continue;
 534                 } else if (status == AE_CTRL_TERMINATE) {
 535                         status = AE_OK;
 536                 } else if ((status != AE_OK) && (walk_state->method_desc)) {
 537
 538                         /* Either the method parse or actual execution failed */
 539
 540                         acpi_ex_exit_interpreter();
 541                         ACPI_ERROR_METHOD("Method parse/execution failed",
 542                                           walk_state->method_node, NULL,
 543                                           status);
 544                         acpi_ex_enter_interpreter();
 545
 546                         /* Check for possible multi-thread reentrancy problem */
 547
 548                         if ((status == AE_ALREADY_EXISTS) &&
 549                             (!(walk_state->method_desc->method.info_flags &
 550                                ACPI_METHOD_SERIALIZED))) {
 551                                 /*
 552                                  * Method is not serialized and tried to create an object
 553                                  * twice. The probable cause is that the method cannot
 554                                  * handle reentrancy. Mark as "pending serialized" now, and
 555                                  * then mark "serialized" when the last thread exits.
 556                                  */
 557                                 walk_state->method_desc->method.info_flags |=
 558                                     ACPI_METHOD_SERIALIZED_PENDING;
 559                         }
 560                 }
 561
 562                 /* We are done with this walk, move on to the parent if any */
 563
 564                 walk_state = acpi_ds_pop_walk_state(thread);
 565
 566                 /* Reset the current scope to the beginning of scope stack */
 567
 568                 acpi_ds_scope_stack_clear(walk_state);
 569
 570                 /*
 571                  * If we just returned from the execution of a control method or if we
 572                  * encountered an error during the method parse phase, there's lots of
 573                  * cleanup to do
 574                  */
 575                 if (((walk_state->parse_flags & ACPI_PARSE_MODE_MASK) ==
 576                      ACPI_PARSE_EXECUTE &&
 577                      !(walk_state->parse_flags & ACPI_PARSE_MODULE_LEVEL)) ||
 578                     (ACPI_FAILURE(status))) {
 579                         acpi_ds_terminate_control_method(walk_state->
 580                                                          method_desc,
 581                                                          walk_state);
 582                 }
 583
 584                 /* Delete this walk state and all linked control states */
 585
 586                 acpi_ps_cleanup_scope(&walk_state->parser_state);
 587                 previous_walk_state = walk_state;
 588
 589                 ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 590                                   "ReturnValue=%p, ImplicitValue=%p State=%p\n",
 591                                   walk_state->return_desc,
 592                                   walk_state->implicit_return_obj, walk_state));
 593
 594                 /* Check if we have restarted a preempted walk */
 595
 596                 walk_state = acpi_ds_get_current_walk_state(thread);
 597                 if (walk_state) {
 598                         if (ACPI_SUCCESS(status)) {
 599                                 /*
 600                                  * There is another walk state, restart it.
 601                                  * If the method return value is not used by the parent,
 602                                  * The object is deleted
 603                                  */
 604                                 if (!previous_walk_state->return_desc) {
 605                                         /*
 606                                          * In slack mode execution, if there is no return value
 607                                          * we should implicitly return zero (0) as a default value.
 608                                          */
 609                                         if (acpi_gbl_enable_interpreter_slack &&
 610                                             !previous_walk_state->
 611                                             implicit_return_obj) {
 612                                                 previous_walk_state->
 613                                                     implicit_return_obj =
 614                                                     acpi_ut_create_integer_object
 615                                                     ((u64) 0);
 616                                                 if (!previous_walk_state->
 617                                                     implicit_return_obj) {
 618                                                         return_ACPI_STATUS
 619                                                             (AE_NO_MEMORY);
 620                                                 }
 621                                         }
 622
 623                                         /* Restart the calling control method */
 624
 625                                         status =
 626                                             acpi_ds_restart_control_method
 627                                             (walk_state,
 628                                              previous_walk_state->
 629                                              implicit_return_obj);
 630                                 } else {
 631                                         /*
 632                                          * We have a valid return value, delete any implicit
 633                                          * return value.
 634                                          */
 635                                         acpi_ds_clear_implicit_return
 636                                             (previous_walk_state);
 637
 638                                         status =
 639                                             acpi_ds_restart_control_method
 640                                             (walk_state,
 641                                              previous_walk_state->return_desc);
 642                                 }
 643                                 if (ACPI_SUCCESS(status)) {
 644                                         walk_state->walk_type |=
 645                                             ACPI_WALK_METHOD_RESTART;
 646                                 }
 647                         } else {
 648                                 /* On error, delete any return object or implicit return */
 649
 650                                 acpi_ut_remove_reference(previous_walk_state->
 651                                                          return_desc);
 652                                 acpi_ds_clear_implicit_return
 653                                     (previous_walk_state);
 654                         }
 655                 }
 656
 657                 /*
 658                  * Just completed a 1st-level method, save the final internal return
 659                  * value (if any)
 660                  */
 661                 else if (previous_walk_state->caller_return_desc) {
 662                         if (previous_walk_state->implicit_return_obj) {
 663                                 *(previous_walk_state->caller_return_desc) =
 664                                     previous_walk_state->implicit_return_obj;
 665                         } else {
 666                                 /* NULL if no return value */
 667
 668                                 *(previous_walk_state->caller_return_desc) =
 669                                     previous_walk_state->return_desc;
 670                         }
 671                 } else {
 672                         if (previous_walk_state->return_desc) {
 673
 674                                 /* Caller doesn't want it, must delete it */
 675
 676                                 acpi_ut_remove_reference(previous_walk_state->
 677                                                          return_desc);
 678                         }
 679                         if (previous_walk_state->implicit_return_obj) {
 680
 681                                 /* Caller doesn't want it, must delete it */
 682
 683                                 acpi_ut_remove_reference(previous_walk_state->
 684                                                          implicit_return_obj);
 685                         }
 686                 }
 687
 688                 acpi_ds_delete_walk_state(previous_walk_state);
 689         }
 690
 691         /* Normal exit */
 692
 693         acpi_ex_release_all_mutexes(thread);
 694         acpi_ut_delete_generic_state(ACPI_CAST_PTR
 695                                      (union acpi_generic_state, thread));
 696         acpi_gbl_current_walk_list = prev_walk_list;
 697         return_ACPI_STATUS(status);
 698 }