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 - 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 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 #include "acnamesp.h"
  60
  61 #define _COMPONENT          ACPI_PARSER
  62 ACPI_MODULE_NAME("psparse")
  63
  64 /*******************************************************************************
  65  *
  66  * FUNCTION:    acpi_ps_get_opcode_size
  67  *
  68  * PARAMETERS:  opcode          - An AML opcode
  69  *
  70  * RETURN:      Size of the opcode, in bytes (1 or 2)
  71  *
  72  * DESCRIPTION: Get the size of the current opcode.
  73  *
  74  ******************************************************************************/
  75 u32 acpi_ps_get_opcode_size(u32 opcode)
  76 {
  77
  78         /* Extended (2-byte) opcode if > 255 */
  79
  80         if (opcode > 0x00FF) {
  81                 return (2);
  82         }
  83
  84         /* Otherwise, just a single byte opcode */
  85
  86         return (1);
  87 }
  88
  89 /*******************************************************************************
  90  *
  91  * FUNCTION:    acpi_ps_peek_opcode
  92  *
  93  * PARAMETERS:  parser_state        - A parser state object
  94  *
  95  * RETURN:      Next AML opcode
  96  *
  97  * DESCRIPTION: Get next AML opcode (without incrementing AML pointer)
  98  *
  99  ******************************************************************************/
 100
 101 u16 acpi_ps_peek_opcode(struct acpi_parse_state * parser_state)
 102 {
 103         u8 *aml;
 104         u16 opcode;
 105
 106         aml = parser_state->aml;
 107         opcode = (u16) ACPI_GET8(aml);
 108
 109         if (opcode == AML_EXTENDED_PREFIX) {
 110
 111                 /* Extended opcode, get the second opcode byte */
 112
 113                 aml++;
 114                 opcode = (u16) ((opcode << 8) | ACPI_GET8(aml));
 115         }
 116
 117         return (opcode);
 118 }
 119
 120 /*******************************************************************************
 121  *
 122  * FUNCTION:    acpi_ps_complete_this_op
 123  *
 124  * PARAMETERS:  walk_state      - Current State
 125  *              op              - Op to complete
 126  *
 127  * RETURN:      Status
 128  *
 129  * DESCRIPTION: Perform any cleanup at the completion of an Op.
 130  *
 131  ******************************************************************************/
 132
 133 acpi_status
 134 acpi_ps_complete_this_op(struct acpi_walk_state *walk_state,
 135                          union acpi_parse_object *op)
 136 {
 137         union acpi_parse_object *prev;
 138         union acpi_parse_object *next;
 139         const struct acpi_opcode_info *parent_info;
 140         union acpi_parse_object *replacement_op = NULL;
 141         acpi_status status = AE_OK;
 142
 143         ACPI_FUNCTION_TRACE_PTR(ps_complete_this_op, op);
 144
 145         /* Check for null Op, can happen if AML code is corrupt */
 146
 147         if (!op) {
 148                 return_ACPI_STATUS(AE_OK);      /* OK for now */
 149         }
 150
 151         acpi_ex_stop_trace_opcode(op, walk_state);
 152
 153         /* Delete this op and the subtree below it if asked to */
 154
 155         if (((walk_state->parse_flags & ACPI_PARSE_TREE_MASK) !=
 156              ACPI_PARSE_DELETE_TREE)
 157             || (walk_state->op_info->class == AML_CLASS_ARGUMENT)) {
 158                 return_ACPI_STATUS(AE_OK);
 159         }
 160
 161         /* Make sure that we only delete this subtree */
 162
 163         if (op->common.parent) {
 164                 prev = op->common.parent->common.value.arg;
 165                 if (!prev) {
 166
 167                         /* Nothing more to do */
 168
 169                         goto cleanup;
 170                 }
 171
 172                 /*
 173                  * Check if we need to replace the operator and its subtree
 174                  * with a return value op (placeholder op)
 175                  */
 176                 parent_info =
 177                     acpi_ps_get_opcode_info(op->common.parent->common.
 178                                             aml_opcode);
 179
 180                 switch (parent_info->class) {
 181                 case AML_CLASS_CONTROL:
 182
 183                         break;
 184
 185                 case AML_CLASS_CREATE:
 186                         /*
 187                          * These opcodes contain term_arg operands. The current
 188                          * op must be replaced by a placeholder return op
 189                          */
 190                         replacement_op =
 191                             acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP,
 192                                              op->common.aml);
 193                         if (!replacement_op) {
 194                                 status = AE_NO_MEMORY;
 195                         }
 196                         break;
 197
 198                 case AML_CLASS_NAMED_OBJECT:
 199                         /*
 200                          * These opcodes contain term_arg operands. The current
 201                          * op must be replaced by a placeholder return op
 202                          */
 203                         if ((op->common.parent->common.aml_opcode ==
 204                              AML_REGION_OP)
 205                             || (op->common.parent->common.aml_opcode ==
 206                                 AML_DATA_REGION_OP)
 207                             || (op->common.parent->common.aml_opcode ==
 208                                 AML_BUFFER_OP)
 209                             || (op->common.parent->common.aml_opcode ==
 210                                 AML_PACKAGE_OP)
 211                             || (op->common.parent->common.aml_opcode ==
 212                                 AML_BANK_FIELD_OP)
 213                             || (op->common.parent->common.aml_opcode ==
 214                                 AML_VARIABLE_PACKAGE_OP)) {
 215                                 replacement_op =
 216                                     acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP,
 217                                                      op->common.aml);
 218                                 if (!replacement_op) {
 219                                         status = AE_NO_MEMORY;
 220                                 }
 221                         } else
 222                             if ((op->common.parent->common.aml_opcode ==
 223                                  AML_NAME_OP)
 224                                 && (walk_state->pass_number <=
 225                                     ACPI_IMODE_LOAD_PASS2)) {
 226                                 if ((op->common.aml_opcode == AML_BUFFER_OP)
 227                                     || (op->common.aml_opcode == AML_PACKAGE_OP)
 228                                     || (op->common.aml_opcode ==
 229                                         AML_VARIABLE_PACKAGE_OP)) {
 230                                         replacement_op =
 231                                             acpi_ps_alloc_op(op->common.
 232                                                              aml_opcode,
 233                                                              op->common.aml);
 234                                         if (!replacement_op) {
 235                                                 status = AE_NO_MEMORY;
 236                                         } else {
 237                                                 replacement_op->named.data =
 238                                                     op->named.data;
 239                                                 replacement_op->named.length =
 240                                                     op->named.length;
 241                                         }
 242                                 }
 243                         }
 244                         break;
 245
 246                 default:
 247
 248                         replacement_op =
 249                             acpi_ps_alloc_op(AML_INT_RETURN_VALUE_OP,
 250                                              op->common.aml);
 251                         if (!replacement_op) {
 252                                 status = AE_NO_MEMORY;
 253                         }
 254                 }
 255
 256                 /* We must unlink this op from the parent tree */
 257
 258                 if (prev == op) {
 259
 260                         /* This op is the first in the list */
 261
 262                         if (replacement_op) {
 263                                 replacement_op->common.parent =
 264                                     op->common.parent;
 265                                 replacement_op->common.value.arg = NULL;
 266                                 replacement_op->common.node = op->common.node;
 267                                 op->common.parent->common.value.arg =
 268                                     replacement_op;
 269                                 replacement_op->common.next = op->common.next;
 270                         } else {
 271                                 op->common.parent->common.value.arg =
 272                                     op->common.next;
 273                         }
 274                 }
 275
 276                 /* Search the parent list */
 277
 278                 else
 279                         while (prev) {
 280
 281                                 /* Traverse all siblings in the parent's argument list */
 282
 283                                 next = prev->common.next;
 284                                 if (next == op) {
 285                                         if (replacement_op) {
 286                                                 replacement_op->common.parent =
 287                                                     op->common.parent;
 288                                                 replacement_op->common.value.
 289                                                     arg = NULL;
 290                                                 replacement_op->common.node =
 291                                                     op->common.node;
 292                                                 prev->common.next =
 293                                                     replacement_op;
 294                                                 replacement_op->common.next =
 295                                                     op->common.next;
 296                                                 next = NULL;
 297                                         } else {
 298                                                 prev->common.next =
 299                                                     op->common.next;
 300                                                 next = NULL;
 301                                         }
 302                                 }
 303                                 prev = next;
 304                         }
 305         }
 306
 307 cleanup:
 308
 309         /* Now we can actually delete the subtree rooted at Op */
 310
 311         acpi_ps_delete_parse_tree(op);
 312         return_ACPI_STATUS(status);
 313 }
 314
 315 /*******************************************************************************
 316  *
 317  * FUNCTION:    acpi_ps_next_parse_state
 318  *
 319  * PARAMETERS:  walk_state          - Current state
 320  *              op                  - Current parse op
 321  *              callback_status     - Status from previous operation
 322  *
 323  * RETURN:      Status
 324  *
 325  * DESCRIPTION: Update the parser state based upon the return exception from
 326  *              the parser callback.
 327  *
 328  ******************************************************************************/
 329
 330 acpi_status
 331 acpi_ps_next_parse_state(struct acpi_walk_state *walk_state,
 332                          union acpi_parse_object *op,
 333                          acpi_status callback_status)
 334 {
 335         struct acpi_parse_state *parser_state = &walk_state->parser_state;
 336         acpi_status status = AE_CTRL_PENDING;
 337
 338         ACPI_FUNCTION_TRACE_PTR(ps_next_parse_state, op);
 339
 340         switch (callback_status) {
 341         case AE_CTRL_TERMINATE:
 342                 /*
 343                  * A control method was terminated via a RETURN statement.
 344                  * The walk of this method is complete.
 345                  */
 346                 parser_state->aml = parser_state->aml_end;
 347                 status = AE_CTRL_TERMINATE;
 348                 break;
 349
 350         case AE_CTRL_BREAK:
 351
 352                 parser_state->aml = walk_state->aml_last_while;
 353                 walk_state->control_state->common.value = FALSE;
 354                 status = AE_CTRL_BREAK;
 355                 break;
 356
 357         case AE_CTRL_CONTINUE:
 358
 359                 parser_state->aml = walk_state->aml_last_while;
 360                 status = AE_CTRL_CONTINUE;
 361                 break;
 362
 363         case AE_CTRL_PENDING:
 364
 365                 parser_state->aml = walk_state->aml_last_while;
 366                 break;
 367
 368 #if 0
 369         case AE_CTRL_SKIP:
 370
 371                 parser_state->aml = parser_state->scope->parse_scope.pkg_end;
 372                 status = AE_OK;
 373                 break;
 374 #endif
 375
 376         case AE_CTRL_TRUE:
 377                 /*
 378                  * Predicate of an IF was true, and we are at the matching ELSE.
 379                  * Just close out this package
 380                  */
 381                 parser_state->aml = acpi_ps_get_next_package_end(parser_state);
 382                 status = AE_CTRL_PENDING;
 383                 break;
 384
 385         case AE_CTRL_FALSE:
 386                 /*
 387                  * Either an IF/WHILE Predicate was false or we encountered a BREAK
 388                  * opcode. In both cases, we do not execute the rest of the
 389                  * package;  We simply close out the parent (finishing the walk of
 390                  * this branch of the tree) and continue execution at the parent
 391                  * level.
 392                  */
 393                 parser_state->aml = parser_state->scope->parse_scope.pkg_end;
 394
 395                 /* In the case of a BREAK, just force a predicate (if any) to FALSE */
 396
 397                 walk_state->control_state->common.value = FALSE;
 398                 status = AE_CTRL_END;
 399                 break;
 400
 401         case AE_CTRL_TRANSFER:
 402
 403                 /* A method call (invocation) -- transfer control */
 404
 405                 status = AE_CTRL_TRANSFER;
 406                 walk_state->prev_op = op;
 407                 walk_state->method_call_op = op;
 408                 walk_state->method_call_node =
 409                     (op->common.value.arg)->common.node;
 410
 411                 /* Will return value (if any) be used by the caller? */
 412
 413                 walk_state->return_used =
 414                     acpi_ds_is_result_used(op, walk_state);
 415                 break;
 416
 417         default:
 418
 419                 status = callback_status;
 420                 if ((callback_status & AE_CODE_MASK) == AE_CODE_CONTROL) {
 421                         status = AE_OK;
 422                 }
 423                 break;
 424         }
 425
 426         return_ACPI_STATUS(status);
 427 }
 428
 429 /*******************************************************************************
 430  *
 431  * FUNCTION:    acpi_ps_parse_aml
 432  *
 433  * PARAMETERS:  walk_state      - Current state
 434  *
 435  *
 436  * RETURN:      Status
 437  *
 438  * DESCRIPTION: Parse raw AML and return a tree of ops
 439  *
 440  ******************************************************************************/
 441
 442 acpi_status acpi_ps_parse_aml(struct acpi_walk_state *walk_state)
 443 {
 444         acpi_status status;
 445         struct acpi_thread_state *thread;
 446         struct acpi_thread_state *prev_walk_list = acpi_gbl_current_walk_list;
 447         struct acpi_walk_state *previous_walk_state;
 448
 449         ACPI_FUNCTION_TRACE(ps_parse_aml);
 450
 451         ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 452                           "Entered with WalkState=%p Aml=%p size=%X\n",
 453                           walk_state, walk_state->parser_state.aml,
 454                           walk_state->parser_state.aml_size));
 455
 456         if (!walk_state->parser_state.aml) {
 457                 return_ACPI_STATUS(AE_NULL_OBJECT);
 458         }
 459
 460         /* Create and initialize a new thread state */
 461
 462         thread = acpi_ut_create_thread_state();
 463         if (!thread) {
 464                 if (walk_state->method_desc) {
 465
 466                         /* Executing a control method - additional cleanup */
 467
 468                         acpi_ds_terminate_control_method(walk_state->
 469                                                          method_desc,
 470                                                          walk_state);
 471                 }
 472
 473                 acpi_ds_delete_walk_state(walk_state);
 474                 return_ACPI_STATUS(AE_NO_MEMORY);
 475         }
 476
 477         walk_state->thread = thread;
 478
 479         /*
 480          * If executing a method, the starting sync_level is this method's
 481          * sync_level
 482          */
 483         if (walk_state->method_desc) {
 484                 walk_state->thread->current_sync_level =
 485                     walk_state->method_desc->method.sync_level;
 486         }
 487
 488         acpi_ds_push_walk_state(walk_state, thread);
 489
 490         /*
 491          * This global allows the AML debugger to get a handle to the currently
 492          * executing control method.
 493          */
 494         acpi_gbl_current_walk_list = thread;
 495
 496         /*
 497          * Execute the walk loop as long as there is a valid Walk State. This
 498          * handles nested control method invocations without recursion.
 499          */
 500         ACPI_DEBUG_PRINT((ACPI_DB_PARSE, "State=%p\n", walk_state));
 501
 502         status = AE_OK;
 503         while (walk_state) {
 504                 if (ACPI_SUCCESS(status)) {
 505                         /*
 506                          * The parse_loop executes AML until the method terminates
 507                          * or calls another method.
 508                          */
 509                         status = acpi_ps_parse_loop(walk_state);
 510                 }
 511
 512                 ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 513                                   "Completed one call to walk loop, %s State=%p\n",
 514                                   acpi_format_exception(status), walk_state));
 515
 516                 if (status == AE_CTRL_TRANSFER) {
 517                         /*
 518                          * A method call was detected.
 519                          * Transfer control to the called control method
 520                          */
 521                         status =
 522                             acpi_ds_call_control_method(thread, walk_state,
 523                                                         NULL);
 524                         if (ACPI_FAILURE(status)) {
 525                                 status =
 526                                     acpi_ds_method_error(status, walk_state);
 527                         }
 528
 529                         /*
 530                          * If the transfer to the new method method call worked
 531                          *, a new walk state was created -- get it
 532                          */
 533                         walk_state = acpi_ds_get_current_walk_state(thread);
 534                         continue;
 535                 } else if (status == AE_CTRL_TERMINATE) {
 536                         status = AE_OK;
 537                 } else if ((status != AE_OK) && (walk_state->method_desc)) {
 538
 539                         /* Either the method parse or actual execution failed */
 540
 541                         acpi_ex_exit_interpreter();
 542                         if (status == AE_ABORT_METHOD) {
 543                                 acpi_ns_print_node_pathname(walk_state->
 544                                                             method_node,
 545                                                             "Method aborted:");
 546                                 acpi_os_printf("\n");
 547                         } else {
 548                                 ACPI_ERROR_METHOD
 549                                     ("Method parse/execution failed",
 550                                      walk_state->method_node, NULL, status);
 551                         }
 552                         acpi_ex_enter_interpreter();
 553
 554                         /* Check for possible multi-thread reentrancy problem */
 555
 556                         if ((status == AE_ALREADY_EXISTS) &&
 557                             (!(walk_state->method_desc->method.info_flags &
 558                                ACPI_METHOD_SERIALIZED))) {
 559                                 /*
 560                                  * Method is not serialized and tried to create an object
 561                                  * twice. The probable cause is that the method cannot
 562                                  * handle reentrancy. Mark as "pending serialized" now, and
 563                                  * then mark "serialized" when the last thread exits.
 564                                  */
 565                                 walk_state->method_desc->method.info_flags |=
 566                                     ACPI_METHOD_SERIALIZED_PENDING;
 567                         }
 568                 }
 569
 570                 /* We are done with this walk, move on to the parent if any */
 571
 572                 walk_state = acpi_ds_pop_walk_state(thread);
 573
 574                 /* Reset the current scope to the beginning of scope stack */
 575
 576                 acpi_ds_scope_stack_clear(walk_state);
 577
 578                 /*
 579                  * If we just returned from the execution of a control method or if we
 580                  * encountered an error during the method parse phase, there's lots of
 581                  * cleanup to do
 582                  */
 583                 if (((walk_state->parse_flags & ACPI_PARSE_MODE_MASK) ==
 584                      ACPI_PARSE_EXECUTE &&
 585                      !(walk_state->parse_flags & ACPI_PARSE_MODULE_LEVEL)) ||
 586                     (ACPI_FAILURE(status))) {
 587                         acpi_ds_terminate_control_method(walk_state->
 588                                                          method_desc,
 589                                                          walk_state);
 590                 }
 591
 592                 /* Delete this walk state and all linked control states */
 593
 594                 acpi_ps_cleanup_scope(&walk_state->parser_state);
 595                 previous_walk_state = walk_state;
 596
 597                 ACPI_DEBUG_PRINT((ACPI_DB_PARSE,
 598                                   "ReturnValue=%p, ImplicitValue=%p State=%p\n",
 599                                   walk_state->return_desc,
 600                                   walk_state->implicit_return_obj, walk_state));
 601
 602                 /* Check if we have restarted a preempted walk */
 603
 604                 walk_state = acpi_ds_get_current_walk_state(thread);
 605                 if (walk_state) {
 606                         if (ACPI_SUCCESS(status)) {
 607                                 /*
 608                                  * There is another walk state, restart it.
 609                                  * If the method return value is not used by the parent,
 610                                  * The object is deleted
 611                                  */
 612                                 if (!previous_walk_state->return_desc) {
 613                                         /*
 614                                          * In slack mode execution, if there is no return value
 615                                          * we should implicitly return zero (0) as a default value.
 616                                          */
 617                                         if (acpi_gbl_enable_interpreter_slack &&
 618                                             !previous_walk_state->
 619                                             implicit_return_obj) {
 620                                                 previous_walk_state->
 621                                                     implicit_return_obj =
 622                                                     acpi_ut_create_integer_object
 623                                                     ((u64) 0);
 624                                                 if (!previous_walk_state->
 625                                                     implicit_return_obj) {
 626                                                         return_ACPI_STATUS
 627                                                             (AE_NO_MEMORY);
 628                                                 }
 629                                         }
 630
 631                                         /* Restart the calling control method */
 632
 633                                         status =
 634                                             acpi_ds_restart_control_method
 635                                             (walk_state,
 636                                              previous_walk_state->
 637                                              implicit_return_obj);
 638                                 } else {
 639                                         /*
 640                                          * We have a valid return value, delete any implicit
 641                                          * return value.
 642                                          */
 643                                         acpi_ds_clear_implicit_return
 644                                             (previous_walk_state);
 645
 646                                         status =
 647                                             acpi_ds_restart_control_method
 648                                             (walk_state,
 649                                              previous_walk_state->return_desc);
 650                                 }
 651                                 if (ACPI_SUCCESS(status)) {
 652                                         walk_state->walk_type |=
 653                                             ACPI_WALK_METHOD_RESTART;
 654                                 }
 655                         } else {
 656                                 /* On error, delete any return object or implicit return */
 657
 658                                 acpi_ut_remove_reference(previous_walk_state->
 659                                                          return_desc);
 660                                 acpi_ds_clear_implicit_return
 661                                     (previous_walk_state);
 662                         }
 663                 }
 664
 665                 /*
 666                  * Just completed a 1st-level method, save the final internal return
 667                  * value (if any)
 668                  */
 669                 else if (previous_walk_state->caller_return_desc) {
 670                         if (previous_walk_state->implicit_return_obj) {
 671                                 *(previous_walk_state->caller_return_desc) =
 672                                     previous_walk_state->implicit_return_obj;
 673                         } else {
 674                                 /* NULL if no return value */
 675
 676                                 *(previous_walk_state->caller_return_desc) =
 677                                     previous_walk_state->return_desc;
 678                         }
 679                 } else {
 680                         if (previous_walk_state->return_desc) {
 681
 682                                 /* Caller doesn't want it, must delete it */
 683
 684                                 acpi_ut_remove_reference(previous_walk_state->
 685                                                          return_desc);
 686                         }
 687                         if (previous_walk_state->implicit_return_obj) {
 688
 689                                 /* Caller doesn't want it, must delete it */
 690
 691                                 acpi_ut_remove_reference(previous_walk_state->
 692                                                          implicit_return_obj);
 693                         }
 694                 }
 695
 696                 acpi_ds_delete_walk_state(previous_walk_state);
 697         }
 698
 699         /* Normal exit */
 700
 701         acpi_ex_release_all_mutexes(thread);
 702         acpi_ut_delete_generic_state(ACPI_CAST_PTR
 703                                      (union acpi_generic_state, thread));
 704         acpi_gbl_current_walk_list = prev_walk_list;
 705         return_ACPI_STATUS(status);
 706 }