xref: /netbsd-src/sys/external/bsd/acpica/dist/compiler/dtutils.c (revision 122b5006ee1bd67145794b4cde92f4fe4781a5ec)
1 /******************************************************************************
2  *
3  * Module Name: dtutils.c - Utility routines for the data table compiler
4  *
5  *****************************************************************************/
6 
7 /*
8  * Copyright (C) 2000 - 2021, Intel Corp.
9  * All rights reserved.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  * 1. Redistributions of source code must retain the above copyright
15  *    notice, this list of conditions, and the following disclaimer,
16  *    without modification.
17  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
18  *    substantially similar to the "NO WARRANTY" disclaimer below
19  *    ("Disclaimer") and any redistribution must be conditioned upon
20  *    including a substantially similar Disclaimer requirement for further
21  *    binary redistribution.
22  * 3. Neither the names of the above-listed copyright holders nor the names
23  *    of any contributors may be used to endorse or promote products derived
24  *    from this software without specific prior written permission.
25  *
26  * Alternatively, this software may be distributed under the terms of the
27  * GNU General Public License ("GPL") version 2 as published by the Free
28  * Software Foundation.
29  *
30  * NO WARRANTY
31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
32  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
33  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
34  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
35  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
40  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
41  * POSSIBILITY OF SUCH DAMAGES.
42  */
43 
44 #include "aslcompiler.h"
45 #include "actables.h"
46 
47 #define _COMPONENT          DT_COMPILER
48         ACPI_MODULE_NAME    ("dtutils")
49 
50 /* Local prototypes */
51 
52 static void
53 DtSum (
54     DT_SUBTABLE             *Subtable,
55     void                    *Context,
56     void                    *ReturnValue);
57 
58 
59 /******************************************************************************
60  *
61  * FUNCTION:    DtError
62  *
63  * PARAMETERS:  Level               - Seriousness (Warning/error, etc.)
64  *              MessageId           - Index into global message buffer
65  *              Op                  - Parse node where error happened
66  *              ExtraMessage        - additional error message
67  *
68  * RETURN:      None
69  *
70  * DESCRIPTION: Common error interface for data table compiler
71  *
72  *****************************************************************************/
73 
74 void
75 DtError (
76     UINT8                   Level,
77     UINT16                  MessageId,
78     DT_FIELD                *FieldObject,
79     char                    *ExtraMessage)
80 {
81     UINT32                  Line = 0;
82 
83 
84     /* Field object could be NULL */
85 
86     if (FieldObject)
87     {
88         Line = FieldObject->Line;
89     }
90 
91     /* Check if user wants to ignore this exception */
92 
93     if (AslIsExceptionIgnored (AslGbl_Files[ASL_FILE_INPUT].Filename,
94         Line, Level, MessageId))
95     {
96         return;
97     }
98 
99     if (FieldObject)
100     {
101         AslCommonError (Level, MessageId,
102             FieldObject->Line,
103             FieldObject->Line,
104             FieldObject->ByteOffset,
105             FieldObject->Column,
106             AslGbl_Files[ASL_FILE_INPUT].Filename, ExtraMessage);
107     }
108     else
109     {
110         AslCommonError (Level, MessageId, 0,
111             0, 0, 0, 0, ExtraMessage);
112     }
113 }
114 
115 
116 /******************************************************************************
117  *
118  * FUNCTION:    DtNameError
119  *
120  * PARAMETERS:  Level               - Seriousness (Warning/error, etc.)
121  *              MessageId           - Index into global message buffer
122  *              Op                  - Parse node where error happened
123  *              ExtraMessage        - additional error message
124  *
125  * RETURN:      None
126  *
127  * DESCRIPTION: Error interface for named objects
128  *
129  *****************************************************************************/
130 
131 void
132 DtNameError (
133     UINT8                   Level,
134     UINT16                  MessageId,
135     DT_FIELD                *FieldObject,
136     char                    *ExtraMessage)
137 {
138 
139     switch (Level)
140     {
141     case ASL_WARNING2:
142     case ASL_WARNING3:
143 
144         if (AslGbl_WarningLevel < Level)
145         {
146             return;
147         }
148         break;
149 
150     default:
151 
152         break;
153     }
154 
155     if (FieldObject)
156     {
157         AslCommonError (Level, MessageId,
158             FieldObject->Line,
159             FieldObject->Line,
160             FieldObject->ByteOffset,
161             FieldObject->NameColumn,
162             AslGbl_Files[ASL_FILE_INPUT].Filename, ExtraMessage);
163     }
164     else
165     {
166         AslCommonError (Level, MessageId, 0,
167             0, 0, 0, 0, ExtraMessage);
168     }
169 }
170 
171 
172 /*******************************************************************************
173  *
174  * FUNCTION:    DtFatal
175  *
176  * PARAMETERS:  None
177  *
178  * RETURN:      None
179  *
180  * DESCRIPTION: Dump the error log and abort the compiler. Used for serious
181  *              compile or I/O errors
182  *
183  ******************************************************************************/
184 
185 void
186 DtFatal (
187     UINT16                  MessageId,
188     DT_FIELD                *FieldObject,
189     char                    *ExtraMessage)
190 {
191 
192     DtError (ASL_ERROR, MessageId, FieldObject, ExtraMessage);
193 
194 /*
195  * TBD: remove this entire function, DtFatal
196  *
197  * We cannot abort the compiler on error, because we may be compiling a
198  * list of files. We must move on to the next file.
199  */
200 #ifdef __OBSOLETE
201     CmCleanupAndExit ();
202     exit (1);
203 #endif
204 }
205 
206 
207 /*******************************************************************************
208  *
209  * FUNCTION:    DtDoConstant
210  *
211  * PARAMETERS:  String              - Only hex constants are supported,
212  *                                    regardless of whether the 0x prefix
213  *                                    is used
214  *
215  * RETURN:      Converted Integer
216  *
217  * DESCRIPTION: Convert a string to an integer, with overflow/error checking.
218  *
219  ******************************************************************************/
220 
221 UINT64
222 DtDoConstant (
223     char                    *String)
224 {
225     UINT64                  ConvertedInteger;
226 
227 
228     /*
229      * TBD: The ImplicitStrtoul64 function does not report overflow
230      * conditions. The input string is simply truncated. If it is
231      * desired to report overflow to the table compiler, this should
232      * somehow be added here. Note: integers that are prefixed with 0x
233      * or not are both hex integers.
234      */
235     ConvertedInteger = AcpiUtImplicitStrtoul64 (String);
236     return (ConvertedInteger);
237 }
238 
239 /******************************************************************************
240  *
241  * FUNCTION:    DtGetFieldValue
242  *
243  * PARAMETERS:  Field               - Current field list pointer
244  *
245  * RETURN:      Field value
246  *
247  * DESCRIPTION: Get field value
248  *
249  *****************************************************************************/
250 
251 char *
252 DtGetFieldValue (
253     DT_FIELD                *Field)
254 {
255     if (!Field)
256     {
257         return (NULL);
258     }
259 
260     return (Field->Value);
261 }
262 
263 
264 /******************************************************************************
265  *
266  * FUNCTION:    DtGetFieldType
267  *
268  * PARAMETERS:  Info                - Data table info
269  *
270  * RETURN:      Field type
271  *
272  * DESCRIPTION: Get field type
273  *
274  *****************************************************************************/
275 
276 UINT8
277 DtGetFieldType (
278     ACPI_DMTABLE_INFO       *Info)
279 {
280     UINT8                   Type;
281 
282 
283     /* DT_FLAG means that this is the start of a block of flag bits */
284     /* TBD - we can make these a separate opcode later */
285 
286     if (Info->Flags & DT_FLAG)
287     {
288         return (DT_FIELD_TYPE_FLAGS_INTEGER);
289     }
290 
291     /* Type is based upon the opcode for this field in the info table */
292 
293     switch (Info->Opcode)
294     {
295     case ACPI_DMT_FLAG0:
296     case ACPI_DMT_FLAG1:
297     case ACPI_DMT_FLAG2:
298     case ACPI_DMT_FLAG3:
299     case ACPI_DMT_FLAG4:
300     case ACPI_DMT_FLAG5:
301     case ACPI_DMT_FLAG6:
302     case ACPI_DMT_FLAG7:
303     case ACPI_DMT_FLAGS0:
304     case ACPI_DMT_FLAGS1:
305     case ACPI_DMT_FLAGS2:
306     case ACPI_DMT_FLAGS4:
307     case ACPI_DMT_FLAGS4_0:
308     case ACPI_DMT_FLAGS4_4:
309     case ACPI_DMT_FLAGS4_8:
310     case ACPI_DMT_FLAGS4_12:
311     case ACPI_DMT_FLAGS16_16:
312 
313         Type = DT_FIELD_TYPE_FLAG;
314         break;
315 
316     case ACPI_DMT_NAME4:
317     case ACPI_DMT_SIG:
318     case ACPI_DMT_NAME6:
319     case ACPI_DMT_NAME8:
320     case ACPI_DMT_STRING:
321     case ACPI_DMT_IVRS_UNTERMINATED_STRING:
322 
323         Type = DT_FIELD_TYPE_STRING;
324         break;
325 
326     case ACPI_DMT_BUFFER:
327     case ACPI_DMT_RAW_BUFFER:
328     case ACPI_DMT_BUF7:
329     case ACPI_DMT_BUF10:
330     case ACPI_DMT_BUF12:
331     case ACPI_DMT_BUF16:
332     case ACPI_DMT_BUF128:
333     case ACPI_DMT_PCI_PATH:
334     case ACPI_DMT_PMTT_VENDOR:
335 
336         Type = DT_FIELD_TYPE_BUFFER;
337         break;
338 
339     case ACPI_DMT_GAS:
340     case ACPI_DMT_HESTNTFY:
341     case ACPI_DMT_IORTMEM:
342 
343         Type = DT_FIELD_TYPE_INLINE_SUBTABLE;
344         break;
345 
346     case ACPI_DMT_UNICODE:
347     case ACPI_DMT_WPBT_UNICODE:
348 
349         Type = DT_FIELD_TYPE_UNICODE;
350         break;
351 
352     case ACPI_DMT_UUID:
353 
354         Type = DT_FIELD_TYPE_UUID;
355         break;
356 
357     case ACPI_DMT_DEVICE_PATH:
358 
359         Type = DT_FIELD_TYPE_DEVICE_PATH;
360         break;
361 
362     case ACPI_DMT_LABEL:
363 
364         Type = DT_FIELD_TYPE_LABEL;
365         break;
366 
367     default:
368 
369         Type = DT_FIELD_TYPE_INTEGER;
370         break;
371     }
372 
373     return (Type);
374 }
375 
376 
377 /******************************************************************************
378  *
379  * FUNCTION:    DtGetBufferLength
380  *
381  * PARAMETERS:  Buffer              - List of integers,
382  *                                    for example "10 3A 4F 2E"
383  *
384  * RETURN:      Count of integer
385  *
386  * DESCRIPTION: Get length of bytes needed to store the integers
387  *
388  *****************************************************************************/
389 
390 UINT32
391 DtGetBufferLength (
392     char                    *Buffer)
393 {
394     UINT32                  ByteLength = 0;
395 
396 
397     while (*Buffer)
398     {
399         if (*Buffer == ' ')
400         {
401             ByteLength++;
402 
403             while (*Buffer == ' ')
404             {
405                 Buffer++;
406             }
407         }
408 
409         Buffer++;
410     }
411 
412     return (++ByteLength);
413 }
414 
415 
416 /******************************************************************************
417  *
418  * FUNCTION:    DtGetFieldLength
419  *
420  * PARAMETERS:  Field               - Current field
421  *              Info                - Data table info
422  *
423  * RETURN:      Field length
424  *
425  * DESCRIPTION: Get length of bytes needed to compile the field
426  *
427  * Note: This function must remain in sync with AcpiDmDumpTable.
428  *
429  *****************************************************************************/
430 
431 UINT32
432 DtGetFieldLength (
433     DT_FIELD                *Field,
434     ACPI_DMTABLE_INFO       *Info)
435 {
436     UINT32                  ByteLength = 0;
437     char                    *Value;
438 
439 
440     /* Length is based upon the opcode for this field in the info table */
441 
442     switch (Info->Opcode)
443     {
444     case ACPI_DMT_FLAG0:
445     case ACPI_DMT_FLAG1:
446     case ACPI_DMT_FLAG2:
447     case ACPI_DMT_FLAG3:
448     case ACPI_DMT_FLAG4:
449     case ACPI_DMT_FLAG5:
450     case ACPI_DMT_FLAG6:
451     case ACPI_DMT_FLAG7:
452     case ACPI_DMT_FLAGS0:
453     case ACPI_DMT_FLAGS1:
454     case ACPI_DMT_FLAGS2:
455     case ACPI_DMT_FLAGS4:
456     case ACPI_DMT_FLAGS4_0:
457     case ACPI_DMT_FLAGS4_4:
458     case ACPI_DMT_FLAGS4_8:
459     case ACPI_DMT_FLAGS4_12:
460     case ACPI_DMT_FLAGS16_16:
461     case ACPI_DMT_LABEL:
462     case ACPI_DMT_EXTRA_TEXT:
463 
464         ByteLength = 0;
465         break;
466 
467     case ACPI_DMT_UINT8:
468     case ACPI_DMT_CHKSUM:
469     case ACPI_DMT_SPACEID:
470     case ACPI_DMT_ACCWIDTH:
471     case ACPI_DMT_CEDT:
472     case ACPI_DMT_IVRS:
473     case ACPI_DMT_IVRS_DE:
474     case ACPI_DMT_GTDT:
475     case ACPI_DMT_MADT:
476     case ACPI_DMT_NHLT1:
477     case ACPI_DMT_NHLT1a:
478     case ACPI_DMT_PCCT:
479     case ACPI_DMT_PMTT:
480     case ACPI_DMT_PPTT:
481     case ACPI_DMT_RGRT:
482     case ACPI_DMT_SDEV:
483     case ACPI_DMT_SRAT:
484     case ACPI_DMT_AEST:
485     case ACPI_DMT_AEST_RES:
486     case ACPI_DMT_AEST_XFACE:
487     case ACPI_DMT_AEST_XRUPT:
488     case ACPI_DMT_ASF:
489     case ACPI_DMT_HESTNTYP:
490     case ACPI_DMT_FADTPM:
491     case ACPI_DMT_EINJACT:
492     case ACPI_DMT_EINJINST:
493     case ACPI_DMT_ERSTACT:
494     case ACPI_DMT_ERSTINST:
495     case ACPI_DMT_DMAR_SCOPE:
496     case ACPI_DMT_VIOT:
497 
498         ByteLength = 1;
499         break;
500 
501     case ACPI_DMT_UINT16:
502     case ACPI_DMT_DMAR:
503     case ACPI_DMT_HEST:
504     case ACPI_DMT_HMAT:
505     case ACPI_DMT_NFIT:
506     case ACPI_DMT_PCI_PATH:
507     case ACPI_DMT_PHAT:
508 
509         ByteLength = 2;
510         break;
511 
512     case ACPI_DMT_UINT24:
513 
514         ByteLength = 3;
515         break;
516 
517     case ACPI_DMT_UINT32:
518     case ACPI_DMT_AEST_CACHE:
519     case ACPI_DMT_AEST_GIC:
520     case ACPI_DMT_NAME4:
521     case ACPI_DMT_SIG:
522     case ACPI_DMT_LPIT:
523     case ACPI_DMT_TPM2:
524 
525         ByteLength = 4;
526         break;
527 
528     case ACPI_DMT_UINT40:
529 
530         ByteLength = 5;
531         break;
532 
533     case ACPI_DMT_UINT48:
534     case ACPI_DMT_NAME6:
535 
536         ByteLength = 6;
537         break;
538 
539     case ACPI_DMT_UINT56:
540     case ACPI_DMT_BUF7:
541 
542         ByteLength = 7;
543         break;
544 
545     case ACPI_DMT_UINT64:
546     case ACPI_DMT_NAME8:
547 
548         ByteLength = 8;
549         break;
550 
551     case ACPI_DMT_STRING:
552 
553         Value = DtGetFieldValue (Field);
554         if (Value)
555         {
556             ByteLength = strlen (Value) + 1;
557         }
558         else
559         {   /* At this point, this is a fatal error */
560 
561             snprintf (AslGbl_MsgBuffer, sizeof(AslGbl_MsgBuffer), "Expected \"%s\"", Info->Name);
562             DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, AslGbl_MsgBuffer);
563             return (0);
564         }
565         break;
566 
567     case ACPI_DMT_IVRS_UNTERMINATED_STRING:
568 
569         Value = DtGetFieldValue (Field);
570         if (Value)
571         {
572             ByteLength = strlen (Value);
573         }
574         else
575         {   /* At this point, this is a fatal error */
576 
577             sprintf (AslGbl_MsgBuffer, "Expected \"%s\"", Info->Name);
578             DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, AslGbl_MsgBuffer);
579             return (0);
580         }
581         break;
582 
583     case ACPI_DMT_GAS:
584 
585         ByteLength = sizeof (ACPI_GENERIC_ADDRESS);
586         break;
587 
588     case ACPI_DMT_HESTNTFY:
589 
590         ByteLength = sizeof (ACPI_HEST_NOTIFY);
591         break;
592 
593     case ACPI_DMT_IORTMEM:
594 
595         ByteLength = sizeof (ACPI_IORT_MEMORY_ACCESS);
596         break;
597 
598     case ACPI_DMT_BUFFER:
599     case ACPI_DMT_RAW_BUFFER:
600     case ACPI_DMT_PMTT_VENDOR:
601 
602         Value = DtGetFieldValue (Field);
603         if (Value)
604         {
605             ByteLength = DtGetBufferLength (Value);
606         }
607         else
608         {   /* At this point, this is a fatal error */
609 
610             snprintf (AslGbl_MsgBuffer, sizeof(AslGbl_MsgBuffer), "Expected \"%s\"", Info->Name);
611             DtFatal (ASL_MSG_COMPILER_INTERNAL, NULL, AslGbl_MsgBuffer);
612             return (0);
613         }
614         break;
615 
616     case ACPI_DMT_BUF10:
617 
618         ByteLength = 10;
619         break;
620 
621     case ACPI_DMT_BUF12:
622 
623         ByteLength = 12;
624         break;
625 
626     case ACPI_DMT_BUF16:
627     case ACPI_DMT_UUID:
628 
629         ByteLength = 16;
630         break;
631 
632     case ACPI_DMT_BUF128:
633 
634         ByteLength = 128;
635         break;
636 
637     case ACPI_DMT_UNICODE:
638     case ACPI_DMT_WPBT_UNICODE:
639 
640         Value = DtGetFieldValue (Field);
641 
642         /* TBD: error if Value is NULL? (as below?) */
643 
644         ByteLength = (strlen (Value) + 1) * sizeof (UINT16);
645         break;
646 
647     default:
648 
649         DtFatal (ASL_MSG_COMPILER_INTERNAL, Field, "Invalid table opcode");
650         return (0);
651     }
652 
653     return (ByteLength);
654 }
655 
656 
657 /******************************************************************************
658  *
659  * FUNCTION:    DtSum
660  *
661  * PARAMETERS:  DT_WALK_CALLBACK:
662  *              Subtable            - Subtable
663  *              Context             - Unused
664  *              ReturnValue         - Store the checksum of subtable
665  *
666  * RETURN:      Status
667  *
668  * DESCRIPTION: Get the checksum of subtable
669  *
670  *****************************************************************************/
671 
672 static void
673 DtSum (
674     DT_SUBTABLE             *Subtable,
675     void                    *Context,
676     void                    *ReturnValue)
677 {
678     UINT8                   Checksum;
679     UINT8                   *Sum = ReturnValue;
680 
681 
682     Checksum = AcpiTbChecksum (Subtable->Buffer, Subtable->Length);
683     *Sum = (UINT8) (*Sum + Checksum);
684 }
685 
686 
687 /******************************************************************************
688  *
689  * FUNCTION:    DtSetTableChecksum
690  *
691  * PARAMETERS:  ChecksumPointer     - Where to return the checksum
692  *
693  * RETURN:      None
694  *
695  * DESCRIPTION: Set checksum of the whole data table into the checksum field
696  *
697  *****************************************************************************/
698 
699 void
700 DtSetTableChecksum (
701     UINT8                   *ChecksumPointer)
702 {
703     UINT8                   Checksum = 0;
704     UINT8                   OldSum;
705 
706 
707     DtWalkTableTree (AslGbl_RootTable, DtSum, NULL, &Checksum);
708 
709     OldSum = *ChecksumPointer;
710     Checksum = (UINT8) (Checksum - OldSum);
711 
712     /* Compute the final checksum */
713 
714     Checksum = (UINT8) (0 - Checksum);
715     *ChecksumPointer = Checksum;
716 }
717 
718 
719 /******************************************************************************
720  *
721  * FUNCTION:    DtSetTableLength
722  *
723  * PARAMETERS:  None
724  *
725  * RETURN:      None
726  *
727  * DESCRIPTION: Walk the subtables and set all the length fields
728  *
729  *****************************************************************************/
730 
731 void
732 DtSetTableLength (
733     void)
734 {
735     DT_SUBTABLE             *ParentTable;
736     DT_SUBTABLE             *ChildTable;
737 
738 
739     ParentTable = AslGbl_RootTable;
740     ChildTable = NULL;
741 
742     if (!ParentTable)
743     {
744         return;
745     }
746 
747     DtSetSubtableLength (ParentTable);
748 
749     while (1)
750     {
751         ChildTable = DtGetNextSubtable (ParentTable, ChildTable);
752         if (ChildTable)
753         {
754             if (ChildTable->LengthField)
755             {
756                 DtSetSubtableLength (ChildTable);
757             }
758 
759             if (ChildTable->Child)
760             {
761                 ParentTable = ChildTable;
762                 ChildTable = NULL;
763             }
764             else
765             {
766                 ParentTable->TotalLength += ChildTable->TotalLength;
767                 if (ParentTable->LengthField)
768                 {
769                     DtSetSubtableLength (ParentTable);
770                 }
771             }
772         }
773         else
774         {
775             ChildTable = ParentTable;
776 
777             if (ChildTable == AslGbl_RootTable)
778             {
779                 break;
780             }
781 
782             ParentTable = DtGetParentSubtable (ParentTable);
783 
784             ParentTable->TotalLength += ChildTable->TotalLength;
785             if (ParentTable->LengthField)
786             {
787                 DtSetSubtableLength (ParentTable);
788             }
789         }
790     }
791 }
792 
793 
794 /******************************************************************************
795  *
796  * FUNCTION:    DtWalkTableTree
797  *
798  * PARAMETERS:  StartTable          - Subtable in the tree where walking begins
799  *              UserFunction        - Called during the walk
800  *              Context             - Passed to user function
801  *              ReturnValue         - The return value of UserFunction
802  *
803  * RETURN:      None
804  *
805  * DESCRIPTION: Performs a depth-first walk of the subtable tree
806  *
807  *****************************************************************************/
808 
809 void
810 DtWalkTableTree (
811     DT_SUBTABLE             *StartTable,
812     DT_WALK_CALLBACK        UserFunction,
813     void                    *Context,
814     void                    *ReturnValue)
815 {
816     DT_SUBTABLE             *ParentTable;
817     DT_SUBTABLE             *ChildTable;
818 
819 
820     ParentTable = StartTable;
821     ChildTable = NULL;
822 
823     if (!ParentTable)
824     {
825         return;
826     }
827 
828     UserFunction (ParentTable, Context, ReturnValue);
829 
830     while (1)
831     {
832         ChildTable = DtGetNextSubtable (ParentTable, ChildTable);
833         if (ChildTable)
834         {
835             UserFunction (ChildTable, Context, ReturnValue);
836 
837             if (ChildTable->Child)
838             {
839                 ParentTable = ChildTable;
840                 ChildTable = NULL;
841             }
842         }
843         else
844         {
845             ChildTable = ParentTable;
846             if (ChildTable == AslGbl_RootTable)
847             {
848                 break;
849             }
850 
851             ParentTable = DtGetParentSubtable (ParentTable);
852 
853             if (ChildTable->Peer == StartTable)
854             {
855                 break;
856             }
857         }
858     }
859 }
860