summaryrefslogtreecommitdiffstats
path: root/EmbeddedPkg/GdbStub/GdbStub.c
blob: 213038ad08c93f04a8a46472c8d1b8fb453db526 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
/** @file
  UEFI driver that implements a GDB stub

  Note: Any code in the path of the Serial IO output can not call DEBUG as will
  will blow out the stack. Serial IO calls DEBUG, debug calls Serail IO, ...


  Copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>

  This program and the accompanying materials
  are licensed and made available under the terms and conditions of the BSD License
  which accompanies this distribution.  The full text of the license may be found at
  http://opensource.org/licenses/bsd-license.php

  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/

#include <GdbStubInternal.h>
#include <Protocol/DebugPort.h>


UINTN     gMaxProcessorIndex = 0;

//
// Buffers for basic gdb communication
//
CHAR8 gInBuffer[MAX_BUF_SIZE];
CHAR8 gOutBuffer[MAX_BUF_SIZE];

// Assume gdb does a "qXfer:libraries:read::offset,length" when it connects so we can default
// this value to FALSE. Since gdb can reconnect its self a global default is not good enough
BOOLEAN   gSymbolTableUpdate = FALSE;
EFI_EVENT gEvent;
VOID      *gGdbSymbolEventHandlerRegistration = NULL;

//
// Globals for returning XML from qXfer:libraries:read packet
//
UINTN                             gPacketqXferLibraryOffset = 0;
UINTN                             gEfiDebugImageTableEntry = 0;
EFI_DEBUG_IMAGE_INFO_TABLE_HEADER *gDebugImageTableHeader = NULL;
EFI_DEBUG_IMAGE_INFO              *gDebugTable = NULL;
CHAR8                             gXferLibraryBuffer[2000];

GLOBAL_REMOVE_IF_UNREFERENCED CONST CHAR8 mHexToStr[] = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};


VOID
EFIAPI
GdbSymbolEventHandler (
  IN  EFI_EVENT       Event,
  IN  VOID            *Context
  )
{
}


/**
  The user Entry Point for Application. The user code starts with this function
  as the real entry point for the image goes into a library that calls this
  function.

  @param[in] ImageHandle    The firmware allocated handle for the EFI image.
  @param[in] SystemTable    A pointer to the EFI System Table.

  @retval EFI_SUCCESS       The entry point is executed successfully.
  @retval other             Some error occurs when executing this entry point.

**/
EFI_STATUS
EFIAPI
GdbStubEntry (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
{
  EFI_STATUS                  Status;
  EFI_DEBUG_SUPPORT_PROTOCOL  *DebugSupport;
  UINTN                       HandleCount;
  EFI_HANDLE                  *Handles;
  UINTN                       Index;
  UINTN                       Processor;
  BOOLEAN                     IsaSupported;

  Status = EfiGetSystemConfigurationTable (&gEfiDebugImageInfoTableGuid, (VOID **)&gDebugImageTableHeader);
  if (EFI_ERROR (Status)) {
    gDebugImageTableHeader = NULL;
  }

  Status = gBS->LocateHandleBuffer (
                  ByProtocol,
                  &gEfiDebugSupportProtocolGuid,
                  NULL,
                  &HandleCount,
                  &Handles
                  );
  if (EFI_ERROR (Status)) {
    DEBUG ((EFI_D_ERROR, "Debug Support Protocol not found\n"));

    return Status;
  }

  DebugSupport = NULL;
  IsaSupported = FALSE;
  do {
    HandleCount--;
    Status = gBS->HandleProtocol (
                    Handles[HandleCount],
                    &gEfiDebugSupportProtocolGuid,
                    (VOID **) &DebugSupport
                    );
    if (!EFI_ERROR (Status)) {
      if (CheckIsa (DebugSupport->Isa)) {
        // We found what we are looking for so break out of the loop
        IsaSupported = TRUE;
        break;
      }
    }
  } while (HandleCount > 0);
  FreePool (Handles);

  if (!IsaSupported) {
    DEBUG ((EFI_D_ERROR, "Debug Support Protocol does not support our ISA\n"));

    return EFI_NOT_FOUND;
  }

  Status = DebugSupport->GetMaximumProcessorIndex (DebugSupport, &gMaxProcessorIndex);
  ASSERT_EFI_ERROR (Status);

  DEBUG ((EFI_D_INFO, "Debug Support Protocol ISA %x\n", DebugSupport->Isa));
  DEBUG ((EFI_D_INFO, "Debug Support Protocol Processor Index %d\n", gMaxProcessorIndex));

  // Call processor-specific init routine
  InitializeProcessor ();

  for (Processor = 0; Processor <= gMaxProcessorIndex; Processor++) {
    for (Index = 0; Index < MaxEfiException (); Index++) {
      Status = DebugSupport->RegisterExceptionCallback (DebugSupport, Processor,  GdbExceptionHandler, gExceptionType[Index].Exception);
      ASSERT_EFI_ERROR (Status);
    }
    //
    // Current edk2 DebugPort is not interrupt context safe so we can not use it
    //
    Status = DebugSupport->RegisterPeriodicCallback (DebugSupport, Processor, GdbPeriodicCallBack);
    ASSERT_EFI_ERROR (Status);
  }

  //
  // This even fires every time an image is added. This allows the stub to know when gdb needs
  // to update the symbol table.
  //
  Status = gBS->CreateEvent (
                  EVT_NOTIFY_SIGNAL,
                  TPL_CALLBACK,
                  GdbSymbolEventHandler,
                  NULL,
                  &gEvent
                  );
  ASSERT_EFI_ERROR (Status);

  //
  // Register for protocol notifications on this event
  //
  Status = gBS->RegisterProtocolNotify (
                  &gEfiLoadedImageProtocolGuid,
                  gEvent,
                  &gGdbSymbolEventHandlerRegistration
                  );
  ASSERT_EFI_ERROR (Status);


 if (PcdGetBool (PcdGdbSerial)) {
   GdbInitializeSerialConsole ();
 }

  return EFI_SUCCESS;
}

/**
 Transfer length bytes of input buffer, starting at Address, to memory.

 @param     length                  the number of the bytes to be transferred/written
 @param     *address                the start address of the transferring/writing the memory
 @param     *new_data               the new data to be written to memory
 **/

VOID
TransferFromInBufToMem (
  IN    UINTN                       Length,
  IN    unsigned char               *Address,
  IN    CHAR8                       *NewData
  )
{
  CHAR8 c1;
  CHAR8 c2;

  while (Length-- > 0) {
    c1 = (CHAR8)HexCharToInt (*NewData++);
    c2 = (CHAR8)HexCharToInt (*NewData++);

    if ((c1 < 0) || (c2 < 0)) {
      Print ((CHAR16 *)L"Bad message from write to memory..\n");
      SendError (GDB_EBADMEMDATA);
      return;
    }
    *Address++ = (UINT8)((c1 << 4) + c2);
  }

  SendSuccess();
}


/**
 Transfer Length bytes of memory starting at Address to an output buffer, OutBuffer. This function will finally send the buffer
 as a packet.

 @param     Length                  the number of the bytes to be transferred/read
 @param     *address                pointer to the start address of the transferring/reading the memory
 **/

VOID
TransferFromMemToOutBufAndSend (
  IN    UINTN                       Length,
  IN    unsigned char               *Address
  )
{
  // there are Length bytes and every byte is represented as 2 hex chars
  CHAR8   OutBuffer[MAX_BUF_SIZE];
  CHAR8   *OutBufPtr;             // pointer to the output buffer
  CHAR8   Char;

  if (ValidateAddress(Address) == FALSE) {
    SendError(14);
    return;
  }

  OutBufPtr = OutBuffer;
  while (Length > 0) {

    Char = mHexToStr[*Address >> 4];
    if ((Char >= 'A') && (Char <= 'F')) {
      Char = Char - 'A' + 'a';
    }
    *OutBufPtr++ = Char;

    Char = mHexToStr[*Address & 0x0f];
    if ((Char >= 'A') && (Char <= 'F')) {
      Char = Char - 'A' + 'a';
    }
    *OutBufPtr++ = Char;

    Address++;
    Length--;
  }

  *OutBufPtr = '\0' ;  // the end of the buffer
  SendPacket (OutBuffer);
}



/**
  Send a GDB Remote Serial Protocol Packet

  $PacketData#checksum PacketData is passed in and this function adds the packet prefix '$',
  the packet teminating character '#' and the two digit checksum.

  If an ack '+' is not sent resend the packet, but timeout eventually so we don't end up
  in an infinit loop. This is so if you unplug the debugger code just keeps running

  @param PacketData   Payload data for the packet


  @retval             Number of bytes of packet data sent.

**/
UINTN
SendPacket (
  IN  CHAR8 *PacketData
  )
{
  UINT8 CheckSum;
  UINTN Timeout;
  CHAR8 *Ptr;
  CHAR8 TestChar;
  UINTN Count;

  Timeout = PcdGet32 (PcdGdbMaxPacketRetryCount);

  Count = 0;
  do {

    Ptr = PacketData;

    if (Timeout-- == 0) {
      // Only try a finite number of times so we don't get stuck in the loop
      return Count;
    }

    // Packet prefix
    GdbPutChar ('$');

    for (CheckSum = 0, Count =0 ; *Ptr != '\0'; Ptr++, Count++) {
      GdbPutChar (*Ptr);
      CheckSum = CheckSum + *Ptr;
    }

    // Packet terminating character and checksum
    GdbPutChar ('#');
    GdbPutChar (mHexToStr[CheckSum >> 4]);
    GdbPutChar (mHexToStr[CheckSum & 0x0F]);

    TestChar =  GdbGetChar ();
  } while (TestChar != '+');

  return Count;
}

/**
  Receive a GDB Remote Serial Protocol Packet

  $PacketData#checksum PacketData is passed in and this function adds the packet prefix '$',
  the packet teminating character '#' and the two digit checksum.

  If host re-starts sending a packet without ending the previous packet, only the last valid packet is proccessed.
  (In other words, if received packet is '$12345$12345$123456#checksum', only '$123456#checksum' will be processed.)

  If an ack '+' is not sent resend the packet

  @param PacketData   Payload data for the packet

  @retval             Number of bytes of packet data received.

**/
UINTN
ReceivePacket (
  OUT  CHAR8 *PacketData,
  IN   UINTN PacketDataSize
 )
{
  UINT8 CheckSum;
  UINTN Index;
  CHAR8 Char;
  CHAR8 SumString[3];
  CHAR8 TestChar;

  ZeroMem (PacketData, PacketDataSize);

  for (;;) {
      // wait for the start of a packet
    TestChar = GdbGetChar ();
    while (TestChar != '$') {
      TestChar = GdbGetChar ();
    };

  retry:
    for (Index = 0, CheckSum = 0; Index < (PacketDataSize - 1); Index++) {
      Char = GdbGetChar ();
      if (Char == '$') {
        goto retry;
      }
      if (Char == '#') {
        break;
      }

      PacketData[Index] = Char;
      CheckSum = CheckSum + Char;
    }
    PacketData[Index] = '\0';

    if (Index == PacketDataSize) {
      continue;
    }

    SumString[0] = GdbGetChar ();
    SumString[1] = GdbGetChar ();
    SumString[2] = '\0';

    if (AsciiStrHexToUintn (SumString) == CheckSum) {
      // Ack: Success
      GdbPutChar ('+');

      // Null terminate the callers string
      PacketData[Index] = '\0';
      return Index;
    } else {
      // Ack: Failure
      GdbPutChar ('-');
    }
  }

  //return 0;
}


/**
 Empties the given buffer
 @param   Buf          pointer to the first element in buffer to be emptied
 **/
VOID
EmptyBuffer (
  IN  CHAR8           *Buf
  )
{
  *Buf = '\0';
}


/**
 Converts an 8-bit Hex Char into a INTN.

 @param   Char the hex character to be converted into UINTN
 @retval  a INTN, from 0 to 15, that corressponds to Char
 -1 if Char is not a hex character
 **/
INTN
HexCharToInt (
  IN  CHAR8           Char
  )
{
  if ((Char >= 'A') && (Char <= 'F')) {
    return Char - 'A' + 10;
  } else if ((Char >= 'a') && (Char <= 'f')) {
    return Char - 'a' + 10;
  } else if ((Char >= '0') && (Char <= '9')) {
    return Char - '0';
  } else { // if not a hex value, return a negative value
    return -1;
  }
}

  // 'E' + the biggest error number is 255, so its 2 hex digits + buffer end
CHAR8 *gError = "E__";

/** 'E NN'
 Send an error with the given error number after converting to hex.
 The error number is put into the buffer in hex. '255' is the biggest errno we can send.
 ex: 162 will be sent as A2.

 @param   errno           the error number that will be sent
 **/
VOID
EFIAPI
SendError (
  IN  UINT8              ErrorNum
  )
{
  //
  // Replace _, or old data, with current errno
  //
  gError[1] = mHexToStr [ErrorNum >> 4];
  gError[2] = mHexToStr [ErrorNum & 0x0f];

  SendPacket (gError); // send buffer
}



/**
 Send 'OK' when the function is done executing successfully.
 **/
VOID
EFIAPI
SendSuccess (
  VOID
  )
{
  SendPacket ("OK"); // send buffer
}


/**
 Send empty packet to specify that particular command/functionality is not supported.
 **/
VOID
EFIAPI
SendNotSupported (
  VOID
  )
{
  SendPacket ("");
}


/**
 Send the T signal with the given exception type (in gdb order) and possibly with n:r pairs related to the watchpoints

 @param  SystemContext        Register content at time of the exception
 @param  GdbExceptionType     GDB exception type
 **/
VOID
GdbSendTSignal (
  IN  EFI_SYSTEM_CONTEXT  SystemContext,
  IN  UINT8               GdbExceptionType
  )
{
  CHAR8 TSignalBuffer[128];
  CHAR8 *TSignalPtr;
  UINTN BreakpointDetected;
  BREAK_TYPE BreakType;
  UINTN DataAddress;
  CHAR8 *WatchStrPtr = NULL;
  UINTN RegSize;

  TSignalPtr = &TSignalBuffer[0];

  //Construct TSignal packet
  *TSignalPtr++ = 'T';

  //
  // replace _, or previous value, with Exception type
  //
  *TSignalPtr++ = mHexToStr [GdbExceptionType >> 4];
  *TSignalPtr++ = mHexToStr [GdbExceptionType & 0x0f];

  if (GdbExceptionType == GDB_SIGTRAP) {
    if (gSymbolTableUpdate) {
      //
      // We can only send back on reason code. So if the flag is set it means the breakpoint is from our event handler
      //
      WatchStrPtr = "library:;";
      while (*WatchStrPtr != '\0') {
        *TSignalPtr++ = *WatchStrPtr++;
      }
      gSymbolTableUpdate = FALSE;
    } else {


      //
      // possible n:r pairs
      //

      //Retrieve the breakpoint number
      BreakpointDetected = GetBreakpointDetected (SystemContext);

      //Figure out if the exception is happend due to watch, rwatch or awatch.
      BreakType = GetBreakpointType (SystemContext, BreakpointDetected);

      //INFO: rwatch is not supported due to the way IA32 debug registers work
      if ((BreakType == DataWrite) || (BreakType == DataRead) || (BreakType == DataReadWrite)) {

        //Construct n:r pair
        DataAddress = GetBreakpointDataAddress (SystemContext, BreakpointDetected);

        //Assign appropriate buffer to print particular watchpoint type
        if (BreakType == DataWrite) {
          WatchStrPtr = "watch";
        } else if (BreakType == DataRead) {
          WatchStrPtr = "rwatch";
        } else if (BreakType == DataReadWrite) {
          WatchStrPtr = "awatch";
        }

        while (*WatchStrPtr != '\0') {
          *TSignalPtr++ = *WatchStrPtr++;
        }

        *TSignalPtr++ = ':';

        //Set up series of bytes in big-endian byte order. "awatch" won't work with little-endian byte order.
        RegSize = REG_SIZE;
        while (RegSize > 0) {
          RegSize = RegSize-4;
          *TSignalPtr++ = mHexToStr[(UINT8)(DataAddress >> RegSize) & 0xf];
        }

        //Always end n:r pair with ';'
        *TSignalPtr++ = ';';
      }
    }
  }

  *TSignalPtr = '\0';

  SendPacket (TSignalBuffer);
}


/**
 Translates the EFI mapping to GDB mapping

 @param   EFIExceptionType    EFI Exception that is being processed
 @retval  UINTN that corresponds to EFIExceptionType's GDB exception type number
 **/
UINT8
ConvertEFItoGDBtype (
  IN  EFI_EXCEPTION_TYPE      EFIExceptionType
  )
{
  UINTN Index;

  for (Index = 0; Index < MaxEfiException () ; Index++) {
    if (gExceptionType[Index].Exception == EFIExceptionType) {
      return gExceptionType[Index].SignalNo;
    }
  }
  return GDB_SIGTRAP; // this is a GDB trap
}


/** "m addr,length"
 Find the Length of the area to read and the start addres. Finally, pass them to
 another function, TransferFromMemToOutBufAndSend, that will read from that memory space and
 send it as a packet.
 **/

VOID
EFIAPI
ReadFromMemory (
  CHAR8 *PacketData
  )
{
  UINTN Address;
  UINTN Length;
  CHAR8 AddressBuffer[MAX_ADDR_SIZE]; // the buffer that will hold the address in hex chars
  CHAR8 *AddrBufPtr; // pointer to the address buffer
  CHAR8 *InBufPtr; /// pointer to the input buffer

  AddrBufPtr = AddressBuffer;
  InBufPtr = &PacketData[1];
  while (*InBufPtr != ',') {
    *AddrBufPtr++ = *InBufPtr++;
  }
  *AddrBufPtr = '\0';

  InBufPtr++; // this skips ',' in the buffer

  /* Error checking */
  if (AsciiStrLen (AddressBuffer) >= MAX_ADDR_SIZE) {
    Print((CHAR16 *)L"Address is too long\n");
    SendError (GDB_EBADMEMADDRBUFSIZE);
    return;
  }

  // 2 = 'm' + ','
  if (AsciiStrLen (PacketData) - AsciiStrLen (AddressBuffer) - 2 >= MAX_LENGTH_SIZE) {
    Print((CHAR16 *)L"Length is too long\n");
    SendError (GDB_EBADMEMLENGTH);
    return;
  }

  Address = AsciiStrHexToUintn (AddressBuffer);
  Length = AsciiStrHexToUintn (InBufPtr);

  TransferFromMemToOutBufAndSend (Length, (unsigned char *)Address);
}


/** "M addr,length :XX..."
 Find the Length of the area in bytes to write and the start addres. Finally, pass them to
 another function, TransferFromInBufToMem, that will write to that memory space the info in
 the input buffer.
 **/
VOID
EFIAPI
WriteToMemory (
  IN CHAR8 *PacketData
  )
{
  UINTN Address;
  UINTN Length;
  UINTN MessageLength;
  CHAR8 AddressBuffer[MAX_ADDR_SIZE]; // the buffer that will hold the Address in hex chars
  CHAR8 LengthBuffer[MAX_LENGTH_SIZE]; // the buffer that will hold the Length in hex chars
  CHAR8 *AddrBufPtr; // pointer to the Address buffer
  CHAR8 *LengthBufPtr; // pointer to the Length buffer
  CHAR8 *InBufPtr; /// pointer to the input buffer

  AddrBufPtr = AddressBuffer;
  LengthBufPtr = LengthBuffer;
  InBufPtr = &PacketData[1];

  while (*InBufPtr != ',') {
    *AddrBufPtr++ = *InBufPtr++;
  }
  *AddrBufPtr = '\0';

  InBufPtr++; // this skips ',' in the buffer

  while (*InBufPtr != ':') {
    *LengthBufPtr++ = *InBufPtr++;
  }
  *LengthBufPtr = '\0';

  InBufPtr++; // this skips ':' in the buffer

  Address = AsciiStrHexToUintn (AddressBuffer);
  Length = AsciiStrHexToUintn (LengthBuffer);

  /* Error checking */

  //Check if Address is not too long.
  if (AsciiStrLen (AddressBuffer) >= MAX_ADDR_SIZE) {
    Print ((CHAR16 *)L"Address too long..\n");
    SendError (GDB_EBADMEMADDRBUFSIZE);
    return;
  }

  //Check if message length is not too long
  if (AsciiStrLen (LengthBuffer) >= MAX_LENGTH_SIZE) {
    Print ((CHAR16 *)L"Length too long..\n");
    SendError (GDB_EBADMEMLENGBUFSIZE);
    return;
  }

  // Check if Message is not too long/short.
  // 3 = 'M' + ',' + ':'
  MessageLength = (AsciiStrLen (PacketData) - AsciiStrLen (AddressBuffer) - AsciiStrLen (LengthBuffer) - 3);
  if (MessageLength != (2*Length)) {
    //Message too long/short. New data is not the right size.
    SendError (GDB_EBADMEMDATASIZE);
    return;
  }
  TransferFromInBufToMem (Length, (unsigned char *)Address, InBufPtr);
}

/**
  Parses breakpoint packet data and captures Breakpoint type, Address and length.
  In case of an error, function returns particular error code. Returning 0 meaning
  no error.

  @param  PacketData  Pointer to the payload data for the packet.
  @param  Type        Breakpoint type
  @param  Address     Breakpoint address
  @param  Length      Breakpoint length in Bytes (1 byte, 2 byte, 4 byte)

  @retval 1           Success
  @retval {other}     Particular error code

**/
UINTN
ParseBreakpointPacket (
  IN  CHAR8 *PacketData,
  OUT UINTN *Type,
  OUT UINTN *Address,
  OUT UINTN *Length
  )
{
  CHAR8 AddressBuffer[MAX_ADDR_SIZE];
  CHAR8 *AddressBufferPtr;
  CHAR8 *PacketDataPtr;

  PacketDataPtr = &PacketData[1];
  AddressBufferPtr = AddressBuffer;

  *Type = AsciiStrHexToUintn (PacketDataPtr);

  //Breakpoint/watchpoint type should be between 0 to 4
  if (*Type > 4) {
    Print ((CHAR16 *)L"Type is invalid\n");
    return 22; //EINVAL: Invalid argument.
  }

  //Skip ',' in the buffer.
  while (*PacketDataPtr++ != ',');

  //Parse Address information
  while (*PacketDataPtr != ',') {
    *AddressBufferPtr++ = *PacketDataPtr++;
  }
  *AddressBufferPtr = '\0';

  //Check if Address is not too long.
  if (AsciiStrLen (AddressBuffer) >= MAX_ADDR_SIZE) {
    Print ((CHAR16 *)L"Address too long..\n");
    return 40; //EMSGSIZE: Message size too long.
  }

  *Address = AsciiStrHexToUintn (AddressBuffer);

  PacketDataPtr++; //This skips , in the buffer

  //Parse Length information
  *Length = AsciiStrHexToUintn (PacketDataPtr);

  //Length should be 1, 2 or 4 bytes
  if (*Length > 4) {
    Print ((CHAR16 *)L"Length is invalid\n");
    return 22; //EINVAL: Invalid argument
  }

  return 0; //0 = No error
}

UINTN
gXferObjectReadResponse (
  IN  CHAR8         Type,
  IN  CHAR8         *Str
  )
{
  CHAR8   *OutBufPtr;             // pointer to the output buffer
  CHAR8   Char;
  UINTN   Count;

  // Response starts with 'm' or 'l' if it is the end
  OutBufPtr = gOutBuffer;
  *OutBufPtr++ = Type;
  Count = 1;

  // Binary data encoding
  OutBufPtr = gOutBuffer;
  while (*Str != '\0') {
    Char = *Str++;
    if ((Char == 0x7d) || (Char == 0x23) || (Char == 0x24) || (Char == 0x2a)) {
      // escape character
      *OutBufPtr++ = 0x7d;

      Char ^= 0x20;
    }
    *OutBufPtr++ = Char;
    Count++;
  }

  *OutBufPtr = '\0' ;  // the end of the buffer
  SendPacket (gOutBuffer);

  return Count;
}


/**
  Note: This should be a library function.  In the Apple case you have to add
  the size of the PE/COFF header into the starting address to make things work
  right as there is no way to pad the Mach-O for the size of the PE/COFF header.


  Returns a pointer to the PDB file name for a PE/COFF image that has been
  loaded into system memory with the PE/COFF Loader Library functions.

  Returns the PDB file name for the PE/COFF image specified by Pe32Data.  If
  the PE/COFF image specified by Pe32Data is not a valid, then NULL is
  returned.  If the PE/COFF image specified by Pe32Data does not contain a
  debug directory entry, then NULL is returned.  If the debug directory entry
  in the PE/COFF image specified by Pe32Data does not contain a PDB file name,
  then NULL is returned.
  If Pe32Data is NULL, then ASSERT().

  @param  Pe32Data   Pointer to the PE/COFF image that is loaded in system
                     memory.
  @param  DebugBase  Address that the debugger would use as the base of the image

  @return The PDB file name for the PE/COFF image specified by Pe32Data or NULL
          if it cannot be retrieved. DebugBase is only valid if PDB file name is
          valid.

**/
VOID *
EFIAPI
PeCoffLoaderGetDebuggerInfo (
  IN VOID     *Pe32Data,
  OUT VOID    **DebugBase
  )
{
  EFI_IMAGE_DOS_HEADER                  *DosHdr;
  EFI_IMAGE_OPTIONAL_HEADER_PTR_UNION   Hdr;
  EFI_IMAGE_DATA_DIRECTORY              *DirectoryEntry;
  EFI_IMAGE_DEBUG_DIRECTORY_ENTRY       *DebugEntry;
  UINTN                                 DirCount;
  VOID                                  *CodeViewEntryPointer;
  INTN                                  TEImageAdjust;
  UINT32                                NumberOfRvaAndSizes;
  UINT16                                Magic;
  UINTN                                 SizeOfHeaders;

  ASSERT (Pe32Data   != NULL);

  TEImageAdjust       = 0;
  DirectoryEntry      = NULL;
  DebugEntry          = NULL;
  NumberOfRvaAndSizes = 0;
  SizeOfHeaders       = 0;

  DosHdr = (EFI_IMAGE_DOS_HEADER *)Pe32Data;
  if (DosHdr->e_magic == EFI_IMAGE_DOS_SIGNATURE) {
    //
    // DOS image header is present, so read the PE header after the DOS image header.
    //
    Hdr.Pe32 = (EFI_IMAGE_NT_HEADERS32 *)((UINTN) Pe32Data + (UINTN) ((DosHdr->e_lfanew) & 0x0ffff));
  } else {
    //
    // DOS image header is not present, so PE header is at the image base.
    //
    Hdr.Pe32 = (EFI_IMAGE_NT_HEADERS32 *)Pe32Data;
  }

  if (Hdr.Te->Signature == EFI_TE_IMAGE_HEADER_SIGNATURE) {
    if (Hdr.Te->DataDirectory[EFI_TE_IMAGE_DIRECTORY_ENTRY_DEBUG].VirtualAddress != 0) {
      DirectoryEntry  = &Hdr.Te->DataDirectory[EFI_TE_IMAGE_DIRECTORY_ENTRY_DEBUG];
      TEImageAdjust   = sizeof (EFI_TE_IMAGE_HEADER) - Hdr.Te->StrippedSize;
      DebugEntry = (EFI_IMAGE_DEBUG_DIRECTORY_ENTRY *)((UINTN) Hdr.Te +
                    Hdr.Te->DataDirectory[EFI_TE_IMAGE_DIRECTORY_ENTRY_DEBUG].VirtualAddress +
                    TEImageAdjust);
    }
    SizeOfHeaders = sizeof (EFI_TE_IMAGE_HEADER) + (UINTN)Hdr.Te->BaseOfCode - (UINTN)Hdr.Te->StrippedSize;

    // __APPLE__ check this math...
    *DebugBase = ((CHAR8 *)Pe32Data) -  TEImageAdjust;
  } else if (Hdr.Pe32->Signature == EFI_IMAGE_NT_SIGNATURE) {

    *DebugBase = Pe32Data;


    //
    // NOTE: We use Machine field to identify PE32/PE32+, instead of Magic.
    //       It is due to backward-compatibility, for some system might
    //       generate PE32+ image with PE32 Magic.
    //
    switch (Hdr.Pe32->FileHeader.Machine) {
    case EFI_IMAGE_MACHINE_IA32:
      //
      // Assume PE32 image with IA32 Machine field.
      //
      Magic = EFI_IMAGE_NT_OPTIONAL_HDR32_MAGIC;
      break;
    case EFI_IMAGE_MACHINE_X64:
    case EFI_IMAGE_MACHINE_IA64:
      //
      // Assume PE32+ image with X64 or IPF Machine field
      //
      Magic = EFI_IMAGE_NT_OPTIONAL_HDR64_MAGIC;
      break;
    default:
      //
      // For unknow Machine field, use Magic in optional Header
      //
      Magic = Hdr.Pe32->OptionalHeader.Magic;
    }

    if (Magic == EFI_IMAGE_NT_OPTIONAL_HDR32_MAGIC) {
      //
      // Use PE32 offset get Debug Directory Entry
      //
      SizeOfHeaders = Hdr.Pe32->OptionalHeader.SizeOfHeaders;
      NumberOfRvaAndSizes = Hdr.Pe32->OptionalHeader.NumberOfRvaAndSizes;
      DirectoryEntry = (EFI_IMAGE_DATA_DIRECTORY *)&(Hdr.Pe32->OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_DEBUG]);
      DebugEntry     = (EFI_IMAGE_DEBUG_DIRECTORY_ENTRY *) ((UINTN) Pe32Data + DirectoryEntry->VirtualAddress);
    } else if (Hdr.Pe32->OptionalHeader.Magic == EFI_IMAGE_NT_OPTIONAL_HDR64_MAGIC) {
      //
      // Use PE32+ offset get Debug Directory Entry
      //
      SizeOfHeaders = Hdr.Pe32Plus->OptionalHeader.SizeOfHeaders;
      NumberOfRvaAndSizes = Hdr.Pe32Plus->OptionalHeader.NumberOfRvaAndSizes;
      DirectoryEntry = (EFI_IMAGE_DATA_DIRECTORY *)&(Hdr.Pe32Plus->OptionalHeader.DataDirectory[EFI_IMAGE_DIRECTORY_ENTRY_DEBUG]);
      DebugEntry     = (EFI_IMAGE_DEBUG_DIRECTORY_ENTRY *) ((UINTN) Pe32Data + DirectoryEntry->VirtualAddress);
    }

    if (NumberOfRvaAndSizes <= EFI_IMAGE_DIRECTORY_ENTRY_DEBUG) {
      DirectoryEntry = NULL;
      DebugEntry = NULL;
    }
  } else {
    return NULL;
  }

  if (DebugEntry == NULL || DirectoryEntry == NULL) {
    return NULL;
  }

  for (DirCount = 0; DirCount < DirectoryEntry->Size; DirCount += sizeof (EFI_IMAGE_DEBUG_DIRECTORY_ENTRY), DebugEntry++) {
    if (DebugEntry->Type == EFI_IMAGE_DEBUG_TYPE_CODEVIEW) {
      if (DebugEntry->SizeOfData > 0) {
        CodeViewEntryPointer = (VOID *) ((UINTN) DebugEntry->RVA + ((UINTN)Pe32Data) + (UINTN)TEImageAdjust);
        switch (* (UINT32 *) CodeViewEntryPointer) {
        case CODEVIEW_SIGNATURE_NB10:
          return (VOID *) ((CHAR8 *)CodeViewEntryPointer + sizeof (EFI_IMAGE_DEBUG_CODEVIEW_NB10_ENTRY));
        case CODEVIEW_SIGNATURE_RSDS:
          return (VOID *) ((CHAR8 *)CodeViewEntryPointer + sizeof (EFI_IMAGE_DEBUG_CODEVIEW_RSDS_ENTRY));
        case CODEVIEW_SIGNATURE_MTOC:
          *DebugBase = (VOID *)(UINTN)((UINTN)DebugBase - SizeOfHeaders);
          return (VOID *) ((CHAR8 *)CodeViewEntryPointer + sizeof (EFI_IMAGE_DEBUG_CODEVIEW_MTOC_ENTRY));
        default:
          break;
        }
      }
    }
  }

  (void)SizeOfHeaders;
  return NULL;
}


/**
  Process "qXfer:object:read:annex:offset,length" request.

  Returns an XML document that contains loaded libraries. In our case it is
  information in the EFI Debug Image Table converted into an XML document.

  GDB will call with an arbitrary length (it can't know the real length and
  will reply with chunks of XML that are easy for us to deal with. Gdb will
  keep calling until we say we are done. XML doc looks like:

  <library-list>
    <library name="/a/a/c/d.dSYM"><segment address="0x10000000"/></library>
    <library name="/a/m/e/e.pdb"><segment address="0x20000000"/></library>
    <library name="/a/l/f/f.dll"><segment address="0x30000000"/></library>
  </library-list>

  Since we can not allocate memory in interrupt context this module has
  assumptions about how it will get called:
  1) Length will generally be max remote packet size (big enough)
  2) First Offset of an XML document read needs to be 0
  3) This code will return back small chunks of the XML document on every read.
     Each subsequent call will ask for the next available part of the document.

  Note: The only variable size element in the XML is:
  "  <library name=\"%s\"><segment address=\"%p\"/></library>\n" and it is
  based on the file path and name of the symbol file. If the symbol file name
  is bigger than the max gdb remote packet size we could update this code
  to respond back in chunks.

 @param Offset  offset into special data area
 @param Length  number of bytes to read starting at Offset

 **/
VOID
QxferLibrary (
  IN  UINTN   Offset,
  IN  UINTN   Length
  )
{
  VOID                              *LoadAddress;
  CHAR8                             *Pdb;
  UINTN                             Size;

  if (Offset != gPacketqXferLibraryOffset) {
    SendError (GDB_EINVALIDARG);
    Print (L"\nqXferLibrary (%d, %d) != %d\n", Offset, Length, gPacketqXferLibraryOffset);

    // Force a retry from the beginning
    gPacketqXferLibraryOffset = 0;

    return;
  }

  if (Offset == 0) {
    gPacketqXferLibraryOffset += gXferObjectReadResponse ('m', "<library-list>\n");

    // The owner of the table may have had to ralloc it so grab a fresh copy every time
    // we assume qXferLibrary will get called over and over again until the entire XML table is
    // returned in a tight loop. Since we are in the debugger the table should not get updated
    gDebugTable = gDebugImageTableHeader->EfiDebugImageInfoTable;
    gEfiDebugImageTableEntry = 0;
    return;
  }

  if (gDebugTable != NULL) {
    for (; gEfiDebugImageTableEntry < gDebugImageTableHeader->TableSize; gEfiDebugImageTableEntry++, gDebugTable++) {
      if (gDebugTable->NormalImage != NULL) {
        if ((gDebugTable->NormalImage->ImageInfoType == EFI_DEBUG_IMAGE_INFO_TYPE_NORMAL) &&
            (gDebugTable->NormalImage->LoadedImageProtocolInstance != NULL)) {
          Pdb = PeCoffLoaderGetDebuggerInfo (
                 gDebugTable->NormalImage->LoadedImageProtocolInstance->ImageBase,
                 &LoadAddress
                 );
          if (Pdb != NULL) {
            Size = AsciiSPrint (
                    gXferLibraryBuffer,
                    sizeof (gXferLibraryBuffer),
                    "  <library name=\"%a\"><segment address=\"0x%p\"/></library>\n",
                    Pdb,
                    LoadAddress
                    );
            if ((Size != 0) && (Size != (sizeof (gXferLibraryBuffer) - 1))) {
              gPacketqXferLibraryOffset += gXferObjectReadResponse ('m', gXferLibraryBuffer);

              // Update loop variables so we are in the right place when we get back
              gEfiDebugImageTableEntry++;
              gDebugTable++;
              return;
            } else {
              // We could handle <library> entires larger than sizeof (gXferLibraryBuffer) here if
              // needed by breaking up into N packets
              // "<library name=\"%s
              // the rest of the string (as many packets as required
              // \"><segment address=\"%d\"/></library> (fixed size)
              //
              // But right now we just skip any entry that is too big
            }
          }
        }
      }
    }
  }


  gXferObjectReadResponse ('l', "</library-list>\n");
  gPacketqXferLibraryOffset = 0;
  return;
}


/**
 Exception Hanldler for GDB. It will be called for all exceptions
 registered via the gExceptionType[] array.

 @param ExceptionType     Exception that is being processed
 @param SystemContext     Register content at time of the exception
 **/
VOID
EFIAPI
GdbExceptionHandler (
  IN  EFI_EXCEPTION_TYPE        ExceptionType,
  IN OUT EFI_SYSTEM_CONTEXT     SystemContext
  )
{
  UINT8   GdbExceptionType;
  CHAR8   *Ptr;


  if (ValidateException (ExceptionType, SystemContext) == FALSE) {
    return;
  }

  RemoveSingleStep (SystemContext);

  GdbExceptionType = ConvertEFItoGDBtype (ExceptionType);
  GdbSendTSignal (SystemContext, GdbExceptionType);

  for( ; ; ) {
    ReceivePacket (gInBuffer, MAX_BUF_SIZE);

    switch (gInBuffer[0]) {
      case '?':
        GdbSendTSignal (SystemContext, GdbExceptionType);
        break;

      case 'c':
        ContinueAtAddress (SystemContext, gInBuffer);
        return;

      case 'g':
        ReadGeneralRegisters (SystemContext);
        break;

      case 'G':
        WriteGeneralRegisters (SystemContext, gInBuffer);
        break;

      case 'H':
        //Return "OK" packet since we don't have more than one thread.
        SendSuccess ();
        break;

      case 'm':
        ReadFromMemory (gInBuffer);
        break;

      case 'M':
        WriteToMemory (gInBuffer);
        break;

      case 'P':
        WriteNthRegister (SystemContext, gInBuffer);
        break;

      //
      // Still debugging this code. Not used in Darwin
      //
      case 'q':
        // General Query Packets
        if (AsciiStrnCmp (gInBuffer, "qSupported", 10) == 0) {
          // return what we currently support, we don't parse what gdb suports
          AsciiSPrint (gOutBuffer, MAX_BUF_SIZE, "qXfer:libraries:read+;PacketSize=%d", MAX_BUF_SIZE);
          SendPacket (gOutBuffer);
        } else if (AsciiStrnCmp (gInBuffer, "qXfer:libraries:read::", 22) == 0) {
          // ‘qXfer:libraries:read::offset,length
          // gInBuffer[22] is offset string, ++Ptr is length string’
          for (Ptr = &gInBuffer[22]; *Ptr != ','; Ptr++);

          // Not sure if multi-radix support is required. Currently only support decimal
          QxferLibrary (AsciiStrHexToUintn (&gInBuffer[22]), AsciiStrHexToUintn (++Ptr));
        } if (AsciiStrnCmp (gInBuffer, "qOffsets", 10) == 0) {
          AsciiSPrint (gOutBuffer, MAX_BUF_SIZE, "Text=1000;Data=f000;Bss=f000");
          SendPacket (gOutBuffer);
        } else {
          //Send empty packet
          SendNotSupported ();
        }
        break;

      case 's':
        SingleStep (SystemContext, gInBuffer);
        return;

      case 'z':
        RemoveBreakPoint (SystemContext, gInBuffer);
        break;

      case 'Z':
        InsertBreakPoint (SystemContext, gInBuffer);
        break;

      default:
        //Send empty packet
        SendNotSupported ();
        break;
    }
  }
}


/**
 Periodic callback for GDB. This function is used to catch a ctrl-c or other
 break in type command from GDB.

 @param SystemContext     Register content at time of the call
 **/
VOID
EFIAPI
GdbPeriodicCallBack (
  IN OUT EFI_SYSTEM_CONTEXT     SystemContext
  )
{
  //
  // gCtrlCBreakFlag may have been set from a previous F response package
  // and we set the global as we need to process it at a point where we
  // can update the system context. If we are in the middle of processing
  // a F Packet it is not safe to read the GDB serial stream so we need
  // to skip it on this check
  //
  if (!gCtrlCBreakFlag && !gProcessingFPacket) {
    //
    // Ctrl-C was not pending so grab any pending characters and see if they
    // are a Ctrl-c (0x03). If so set the Ctrl-C global.
    //
    while (TRUE) {
      if (!GdbIsCharAvailable ()) {
        //
        // No characters are pending so exit the loop
        //
        break;
      }

      if (GdbGetChar () == 0x03) {
        gCtrlCBreakFlag = TRUE;
        //
        // We have a ctrl-c so exit the loop
        //
        break;
      }
    }
  }

  if (gCtrlCBreakFlag) {
    //
    // Update the context to force a single step trap when we exit the GDB
    // stub. This will transfer control to GdbExceptionHandler () and let
    // us break into the program. We don't want to break into the GDB stub.
    //
    AddSingleStep (SystemContext);
    gCtrlCBreakFlag = FALSE;
  }
}