aboutsummaryrefslogtreecommitdiff
path: root/src/processor/stackwalker_arm_unittest.cc
blob: 8a0fd5e95b15d8b4fab3c390fba831076b9f4c6a (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
// Copyright (c) 2010, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// Original author: Jim Blandy <jimb@mozilla.com> <jimb@red-bean.com>

// stackwalker_arm_unittest.cc: Unit tests for StackwalkerARM class.

#include <string.h>
#include <string>
#include <vector>

#include "breakpad_googletest_includes.h"
#include "common/test_assembler.h"
#include "common/using_std_string.h"
#include "google_breakpad/common/minidump_format.h"
#include "google_breakpad/processor/basic_source_line_resolver.h"
#include "google_breakpad/processor/call_stack.h"
#include "google_breakpad/processor/code_module.h"
#include "google_breakpad/processor/source_line_resolver_interface.h"
#include "google_breakpad/processor/stack_frame_cpu.h"
#include "processor/stackwalker_unittest_utils.h"
#include "processor/stackwalker_arm.h"
#include "processor/windows_frame_info.h"

using google_breakpad::BasicSourceLineResolver;
using google_breakpad::CallStack;
using google_breakpad::CodeModule;
using google_breakpad::StackFrameSymbolizer;
using google_breakpad::StackFrame;
using google_breakpad::StackFrameARM;
using google_breakpad::Stackwalker;
using google_breakpad::StackwalkerARM;
using google_breakpad::SystemInfo;
using google_breakpad::WindowsFrameInfo;
using google_breakpad::test_assembler::kLittleEndian;
using google_breakpad::test_assembler::Label;
using google_breakpad::test_assembler::Section;
using std::vector;
using testing::_;
using testing::AnyNumber;
using testing::Return;
using testing::SetArgumentPointee;
using testing::Test;

class StackwalkerARMFixture {
 public:
  StackwalkerARMFixture()
    : stack_section(kLittleEndian),
      // Give the two modules reasonable standard locations and names
      // for tests to play with.
      module1(0x40000000, 0x10000, "module1", "version1"),
      module2(0x50000000, 0x10000, "module2", "version2") {
    // Identify the system as a Linux system.
    system_info.os = "Linux";
    system_info.os_short = "linux";
    system_info.os_version = "Lugubrious Labrador";
    system_info.cpu = "arm";
    system_info.cpu_info = "";

    // Put distinctive values in the raw CPU context.
    BrandContext(&raw_context);

    // Create some modules with some stock debugging information.
    modules.Add(&module1);
    modules.Add(&module2);

    // By default, none of the modules have symbol info; call
    // SetModuleSymbols to override this.
    EXPECT_CALL(supplier, GetCStringSymbolData(_, _, _, _, _))
      .WillRepeatedly(Return(MockSymbolSupplier::NOT_FOUND));

    // Avoid GMOCK WARNING "Uninteresting mock function call - returning
    // directly" for FreeSymbolData().
    EXPECT_CALL(supplier, FreeSymbolData(_)).Times(AnyNumber());

    // Reset max_frames_scanned since it's static.
    Stackwalker::set_max_frames_scanned(1024);
  }

  // Set the Breakpad symbol information that supplier should return for
  // MODULE to INFO.
  void SetModuleSymbols(MockCodeModule *module, const string &info) {
    size_t buffer_size;
    char *buffer = supplier.CopySymbolDataAndOwnTheCopy(info, &buffer_size);
    EXPECT_CALL(supplier, GetCStringSymbolData(module, &system_info, _, _, _))
      .WillRepeatedly(DoAll(SetArgumentPointee<3>(buffer),
                            SetArgumentPointee<4>(buffer_size),
                            Return(MockSymbolSupplier::FOUND)));
  }

  // Populate stack_region with the contents of stack_section. Use
  // stack_section.start() as the region's starting address.
  void RegionFromSection() {
    string contents;
    ASSERT_TRUE(stack_section.GetContents(&contents));
    stack_region.Init(stack_section.start().Value(), contents);
  }

  // Fill RAW_CONTEXT with pseudo-random data, for round-trip checking.
  void BrandContext(MDRawContextARM *raw_context) {
    uint8_t x = 173;
    for (size_t i = 0; i < sizeof(*raw_context); i++)
      reinterpret_cast<uint8_t *>(raw_context)[i] = (x += 17);
  }

  SystemInfo system_info;
  MDRawContextARM raw_context;
  Section stack_section;
  MockMemoryRegion stack_region;
  MockCodeModule module1;
  MockCodeModule module2;
  MockCodeModules modules;
  MockSymbolSupplier supplier;
  BasicSourceLineResolver resolver;
  CallStack call_stack;
  const vector<StackFrame *> *frames;
};

class SanityCheck: public StackwalkerARMFixture, public Test { };

TEST_F(SanityCheck, NoResolver) {
  // Since we have no call frame information, and all unwinding
  // requires call frame information, the stack walk will end after
  // the first frame.
  StackFrameSymbolizer frame_symbolizer(NULL, NULL);
  StackwalkerARM walker(&system_info, &raw_context, -1, &stack_region, &modules,
                        &frame_symbolizer);
  // This should succeed even without a resolver or supplier.
  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(0U, modules_without_symbols.size());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(1U, frames->size());
  StackFrameARM *frame = static_cast<StackFrameARM *>(frames->at(0));
  // Check that the values from the original raw context made it
  // through to the context in the stack frame.
  EXPECT_EQ(0, memcmp(&raw_context, &frame->context, sizeof(raw_context)));
}

class GetContextFrame: public StackwalkerARMFixture, public Test { };

TEST_F(GetContextFrame, Simple) {
  // Since we have no call frame information, and all unwinding
  // requires call frame information, the stack walk will end after
  // the first frame.
  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
  StackwalkerARM walker(&system_info, &raw_context, -1, &stack_region, &modules,
                        &frame_symbolizer);
  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(0U, modules_without_symbols.size());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(1U, frames->size());
  StackFrameARM *frame = static_cast<StackFrameARM *>(frames->at(0));
  // Check that the values from the original raw context made it
  // through to the context in the stack frame.
  EXPECT_EQ(0, memcmp(&raw_context, &frame->context, sizeof(raw_context)));
}

// The stackwalker should be able to produce the context frame even
// without stack memory present.
TEST_F(GetContextFrame, NoStackMemory) {
  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
  StackwalkerARM walker(&system_info, &raw_context, -1, NULL, &modules,
                        &frame_symbolizer);
  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(0U, modules_without_symbols.size());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(1U, frames->size());
  StackFrameARM *frame = static_cast<StackFrameARM *>(frames->at(0));
  // Check that the values from the original raw context made it
  // through to the context in the stack frame.
  EXPECT_EQ(0, memcmp(&raw_context, &frame->context, sizeof(raw_context)));
}

class GetCallerFrame: public StackwalkerARMFixture, public Test { };

TEST_F(GetCallerFrame, ScanWithoutSymbols) {
  // When the stack walker resorts to scanning the stack,
  // only addresses located within loaded modules are
  // considered valid return addresses.
  // Force scanning through three frames to ensure that the
  // stack pointer is set properly in scan-recovered frames.
  stack_section.start() = 0x80000000;
  uint32_t return_address1 = 0x50000100;
  uint32_t return_address2 = 0x50000900;
  Label frame1_sp, frame2_sp;
  stack_section
    // frame 0
    .Append(16, 0)                      // space

    .D32(0x40090000)                    // junk that's not
    .D32(0x60000000)                    // a return address

    .D32(return_address1)               // actual return address
    // frame 1
    .Mark(&frame1_sp)
    .Append(16, 0)                      // space

    .D32(0xF0000000)                    // more junk
    .D32(0x0000000D)

    .D32(return_address2)               // actual return address
    // frame 2
    .Mark(&frame2_sp)
    .Append(32, 0);                     // end of stack
  RegionFromSection();

  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40005510;
  raw_context.iregs[MD_CONTEXT_ARM_REG_SP] = stack_section.start().Value();

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
  StackwalkerARM walker(&system_info, &raw_context, -1, &stack_region, &modules,
                        &frame_symbolizer);
  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(2U, modules_without_symbols.size());
  ASSERT_EQ("module1", modules_without_symbols[0]->debug_file());
  ASSERT_EQ("module2", modules_without_symbols[1]->debug_file());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(3U, frames->size());

  StackFrameARM *frame0 = static_cast<StackFrameARM *>(frames->at(0));
  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);
  ASSERT_EQ(StackFrameARM::CONTEXT_VALID_ALL, frame0->context_validity);
  EXPECT_EQ(0, memcmp(&raw_context, &frame0->context, sizeof(raw_context)));

  StackFrameARM *frame1 = static_cast<StackFrameARM *>(frames->at(1));
  EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame1->trust);
  ASSERT_EQ((StackFrameARM::CONTEXT_VALID_PC |
             StackFrameARM::CONTEXT_VALID_SP),
            frame1->context_validity);
  EXPECT_EQ(return_address1, frame1->context.iregs[MD_CONTEXT_ARM_REG_PC]);
  EXPECT_EQ(frame1_sp.Value(), frame1->context.iregs[MD_CONTEXT_ARM_REG_SP]);

  StackFrameARM *frame2 = static_cast<StackFrameARM *>(frames->at(2));
  EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame2->trust);
  ASSERT_EQ((StackFrameARM::CONTEXT_VALID_PC |
             StackFrameARM::CONTEXT_VALID_SP),
            frame2->context_validity);
  EXPECT_EQ(return_address2, frame2->context.iregs[MD_CONTEXT_ARM_REG_PC]);
  EXPECT_EQ(frame2_sp.Value(), frame2->context.iregs[MD_CONTEXT_ARM_REG_SP]);
}

TEST_F(GetCallerFrame, ScanWithFunctionSymbols) {
  // During stack scanning, if a potential return address
  // is located within a loaded module that has symbols,
  // it is only considered a valid return address if it
  // lies within a function's bounds.
  stack_section.start() = 0x80000000;
  uint32_t return_address = 0x50000200;
  Label frame1_sp;

  stack_section
    // frame 0
    .Append(16, 0)                      // space

    .D32(0x40090000)                    // junk that's not
    .D32(0x60000000)                    // a return address

    .D32(0x40001000)                    // a couple of plausible addresses
    .D32(0x5000F000)                    // that are not within functions

    .D32(return_address)                // actual return address
    // frame 1
    .Mark(&frame1_sp)
    .Append(32, 0);                     // end of stack
  RegionFromSection();

  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40000200;
  raw_context.iregs[MD_CONTEXT_ARM_REG_SP] = stack_section.start().Value();

  SetModuleSymbols(&module1,
                   // The youngest frame's function.
                   "FUNC 100 400 10 monotreme\n");
  SetModuleSymbols(&module2,
                   // The calling frame's function.
                   "FUNC 100 400 10 marsupial\n");

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
  StackwalkerARM walker(&system_info, &raw_context, -1, &stack_region, &modules,
                        &frame_symbolizer);
  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(0U, modules_without_symbols.size());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(2U, frames->size());

  StackFrameARM *frame0 = static_cast<StackFrameARM *>(frames->at(0));
  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);
  ASSERT_EQ(StackFrameARM::CONTEXT_VALID_ALL, frame0->context_validity);
  EXPECT_EQ(0, memcmp(&raw_context, &frame0->context, sizeof(raw_context)));
  EXPECT_EQ("monotreme", frame0->function_name);
  EXPECT_EQ(0x40000100U, frame0->function_base);

  StackFrameARM *frame1 = static_cast<StackFrameARM *>(frames->at(1));
  EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame1->trust);
  ASSERT_EQ((StackFrameARM::CONTEXT_VALID_PC |
             StackFrameARM::CONTEXT_VALID_SP),
            frame1->context_validity);
  EXPECT_EQ(return_address, frame1->context.iregs[MD_CONTEXT_ARM_REG_PC]);
  EXPECT_EQ(frame1_sp.Value(), frame1->context.iregs[MD_CONTEXT_ARM_REG_SP]);
  EXPECT_EQ("marsupial", frame1->function_name);
  EXPECT_EQ(0x50000100U, frame1->function_base);
}

TEST_F(GetCallerFrame, ScanFirstFrame) {
  // If the stackwalker resorts to stack scanning, it will scan much
  // farther to find the caller of the context frame.
  stack_section.start() = 0x80000000;
  uint32_t return_address1 = 0x50000100;
  uint32_t return_address2 = 0x50000900;
  Label frame1_sp, frame2_sp;
  stack_section
    // frame 0
    .Append(32, 0)                      // space

    .D32(0x40090000)                    // junk that's not
    .D32(0x60000000)                    // a return address

    .Append(96, 0)                      // more space

    .D32(return_address1)               // actual return address
    // frame 1
    .Mark(&frame1_sp)
    .Append(32, 0)                      // space

    .D32(0xF0000000)                    // more junk
    .D32(0x0000000D)

    .Append(136, 0)                     // more space

    .D32(return_address2)               // actual return address
                                        // (won't be found)
    // frame 2
    .Mark(&frame2_sp)
    .Append(32, 0);                     // end of stack
  RegionFromSection();

  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40005510;
  raw_context.iregs[MD_CONTEXT_ARM_REG_SP] = stack_section.start().Value();

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
  StackwalkerARM walker(&system_info, &raw_context, -1, &stack_region, &modules,
                        &frame_symbolizer);
  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(2U, modules_without_symbols.size());
  ASSERT_EQ("module1", modules_without_symbols[0]->debug_file());
  ASSERT_EQ("module2", modules_without_symbols[1]->debug_file());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(2U, frames->size());

  StackFrameARM *frame0 = static_cast<StackFrameARM *>(frames->at(0));
  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);
  ASSERT_EQ(StackFrameARM::CONTEXT_VALID_ALL, frame0->context_validity);
  EXPECT_EQ(0, memcmp(&raw_context, &frame0->context, sizeof(raw_context)));

  StackFrameARM *frame1 = static_cast<StackFrameARM *>(frames->at(1));
  EXPECT_EQ(StackFrame::FRAME_TRUST_SCAN, frame1->trust);
  ASSERT_EQ((StackFrameARM::CONTEXT_VALID_PC |
             StackFrameARM::CONTEXT_VALID_SP),
            frame1->context_validity);
  EXPECT_EQ(return_address1, frame1->context.iregs[MD_CONTEXT_ARM_REG_PC]);
  EXPECT_EQ(frame1_sp.Value(), frame1->context.iregs[MD_CONTEXT_ARM_REG_SP]);
}

// Test that set_max_frames_scanned prevents using stack scanning
// to find caller frames.
TEST_F(GetCallerFrame, ScanningNotAllowed) {
  // When the stack walker resorts to scanning the stack,
  // only addresses located within loaded modules are
  // considered valid return addresses.
  stack_section.start() = 0x80000000;
  uint32_t return_address1 = 0x50000100;
  uint32_t return_address2 = 0x50000900;
  Label frame1_sp, frame2_sp;
  stack_section
    // frame 0
    .Append(16, 0)                      // space

    .D32(0x40090000)                    // junk that's not
    .D32(0x60000000)                    // a return address

    .D32(return_address1)               // actual return address
    // frame 1
    .Mark(&frame1_sp)
    .Append(16, 0)                      // space

    .D32(0xF0000000)                    // more junk
    .D32(0x0000000D)

    .D32(return_address2)               // actual return address
    // frame 2
    .Mark(&frame2_sp)
    .Append(32, 0);                     // end of stack
  RegionFromSection();

  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40005510;
  raw_context.iregs[MD_CONTEXT_ARM_REG_SP] = stack_section.start().Value();

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
  StackwalkerARM walker(&system_info, &raw_context, -1, &stack_region, &modules,
                        &frame_symbolizer);
  Stackwalker::set_max_frames_scanned(0);

  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(1U, modules_without_symbols.size());
  ASSERT_EQ("module1", modules_without_symbols[0]->debug_file());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(1U, frames->size());

  StackFrameARM *frame0 = static_cast<StackFrameARM *>(frames->at(0));
  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);
  ASSERT_EQ(StackFrameARM::CONTEXT_VALID_ALL, frame0->context_validity);
  EXPECT_EQ(0, memcmp(&raw_context, &frame0->context, sizeof(raw_context)));
}

struct CFIFixture: public StackwalkerARMFixture {
  CFIFixture() {
    // Provide a bunch of STACK CFI records; we'll walk to the caller
    // from every point in this series, expecting to find the same set
    // of register values.
    SetModuleSymbols(&module1,
                     // The youngest frame's function.
                     "FUNC 4000 1000 10 enchiridion\n"
                     // Initially, nothing has been pushed on the stack,
                     // and the return address is still in the link register.
                     "STACK CFI INIT 4000 100 .cfa: sp .ra: lr\n"
                     // Push r4, the frame pointer, and the link register.
                     "STACK CFI 4001 .cfa: sp 12 + r4: .cfa 12 - ^"
                     " r11: .cfa 8 - ^ .ra: .cfa 4 - ^\n"
                     // Save r4..r7 in r0..r3: verify that we populate
                     // the youngest frame with all the values we have.
                     "STACK CFI 4002 r4: r0 r5: r1 r6: r2 r7: r3\n"
                     // Restore r4..r7. Save the non-callee-saves register r1.
                     "STACK CFI 4003 .cfa: sp 16 + r1: .cfa 16 - ^"
                     " r4: r4 r5: r5 r6: r6 r7: r7\n"
                     // Move the .cfa back four bytes, to point at the return
                     // address, and restore the sp explicitly.
                     "STACK CFI 4005 .cfa: sp 12 + r1: .cfa 12 - ^"
                     " r11: .cfa 4 - ^ .ra: .cfa ^ sp: .cfa 4 +\n"
                     // Recover the PC explicitly from a new stack slot;
                     // provide garbage for the .ra.
                     "STACK CFI 4006 .cfa: sp 16 + pc: .cfa 16 - ^\n"

                     // The calling function.
                     "FUNC 5000 1000 10 epictetus\n"
                     // Mark it as end of stack.
                     "STACK CFI INIT 5000 1000 .cfa: 0 .ra: 0\n"

                     // A function whose CFI makes the stack pointer
                     // go backwards.
                     "FUNC 6000 1000 20 palinal\n"
                     "STACK CFI INIT 6000 1000 .cfa: sp 4 - .ra: lr\n"

                     // A function with CFI expressions that can't be
                     // evaluated.
                     "FUNC 7000 1000 20 rhetorical\n"
                     "STACK CFI INIT 7000 1000 .cfa: moot .ra: ambiguous\n");

    // Provide some distinctive values for the caller's registers.
    expected.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40005510;
    expected.iregs[MD_CONTEXT_ARM_REG_SP] = 0x80000000;
    expected.iregs[4] = 0xb5d55e68;
    expected.iregs[5] = 0xebd134f3;
    expected.iregs[6] = 0xa31e74bc;
    expected.iregs[7] = 0x2dcb16b3;
    expected.iregs[8] = 0x2ada2137;
    expected.iregs[9] = 0xbbbb557d;
    expected.iregs[10] = 0x48bf8ca7;
    expected.iregs[MD_CONTEXT_ARM_REG_FP] = 0x8112e110;

    // Expect CFI to recover all callee-saves registers. Since CFI is the
    // only stack frame construction technique we have, aside from the
    // context frame itself, there's no way for us to have a set of valid
    // registers smaller than this.
    expected_validity = (StackFrameARM::CONTEXT_VALID_PC |
                         StackFrameARM::CONTEXT_VALID_SP |
                         StackFrameARM::CONTEXT_VALID_R4 |
                         StackFrameARM::CONTEXT_VALID_R5 |
                         StackFrameARM::CONTEXT_VALID_R6 |
                         StackFrameARM::CONTEXT_VALID_R7 |
                         StackFrameARM::CONTEXT_VALID_R8 |
                         StackFrameARM::CONTEXT_VALID_R9 |
                         StackFrameARM::CONTEXT_VALID_R10 |
                         StackFrameARM::CONTEXT_VALID_FP);

    // By default, context frames provide all registers, as normal.
    context_frame_validity = StackFrameARM::CONTEXT_VALID_ALL;

    // By default, registers are unchanged.
    raw_context = expected;
  }

  // Walk the stack, using stack_section as the contents of the stack
  // and raw_context as the current register values. (Set the stack
  // pointer to the stack's starting address.) Expect two stack
  // frames; in the older frame, expect the callee-saves registers to
  // have values matching those in 'expected'.
  void CheckWalk() {
    RegionFromSection();
    raw_context.iregs[MD_CONTEXT_ARM_REG_SP] = stack_section.start().Value();

    StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
    StackwalkerARM walker(&system_info, &raw_context, -1, &stack_region,
                          &modules, &frame_symbolizer);
    walker.SetContextFrameValidity(context_frame_validity);
    vector<const CodeModule*> modules_without_symbols;
    vector<const CodeModule*> modules_with_corrupt_symbols;
    ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                            &modules_with_corrupt_symbols));
    ASSERT_EQ(0U, modules_without_symbols.size());
    ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
    frames = call_stack.frames();
    ASSERT_EQ(2U, frames->size());

    StackFrameARM *frame0 = static_cast<StackFrameARM *>(frames->at(0));
    EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);
    ASSERT_EQ(context_frame_validity, frame0->context_validity);
    EXPECT_EQ("enchiridion", frame0->function_name);
    EXPECT_EQ(0x40004000U, frame0->function_base);

    StackFrameARM *frame1 = static_cast<StackFrameARM *>(frames->at(1));
    EXPECT_EQ(StackFrame::FRAME_TRUST_CFI, frame1->trust);
    ASSERT_EQ(expected_validity, frame1->context_validity);
    if (expected_validity & StackFrameARM::CONTEXT_VALID_R1)
      EXPECT_EQ(expected.iregs[1], frame1->context.iregs[1]);
    if (expected_validity & StackFrameARM::CONTEXT_VALID_R4)
      EXPECT_EQ(expected.iregs[4], frame1->context.iregs[4]);
    if (expected_validity & StackFrameARM::CONTEXT_VALID_R5)
      EXPECT_EQ(expected.iregs[5], frame1->context.iregs[5]);
    if (expected_validity & StackFrameARM::CONTEXT_VALID_R6)
      EXPECT_EQ(expected.iregs[6], frame1->context.iregs[6]);
    if (expected_validity & StackFrameARM::CONTEXT_VALID_R7)
      EXPECT_EQ(expected.iregs[7], frame1->context.iregs[7]);
    if (expected_validity & StackFrameARM::CONTEXT_VALID_R8)
      EXPECT_EQ(expected.iregs[8], frame1->context.iregs[8]);
    if (expected_validity & StackFrameARM::CONTEXT_VALID_R9)
      EXPECT_EQ(expected.iregs[9], frame1->context.iregs[9]);
    if (expected_validity & StackFrameARM::CONTEXT_VALID_R10)
      EXPECT_EQ(expected.iregs[10], frame1->context.iregs[10]);
    if (expected_validity & StackFrameARM::CONTEXT_VALID_FP)
      EXPECT_EQ(expected.iregs[MD_CONTEXT_ARM_REG_FP],
                frame1->context.iregs[MD_CONTEXT_ARM_REG_FP]);

    // We would never have gotten a frame in the first place if the SP
    // and PC weren't valid or ->instruction weren't set.
    EXPECT_EQ(expected.iregs[MD_CONTEXT_ARM_REG_SP],
              frame1->context.iregs[MD_CONTEXT_ARM_REG_SP]);
    EXPECT_EQ(expected.iregs[MD_CONTEXT_ARM_REG_PC],
              frame1->context.iregs[MD_CONTEXT_ARM_REG_PC]);
    EXPECT_EQ(expected.iregs[MD_CONTEXT_ARM_REG_PC],
              frame1->instruction + 2);
    EXPECT_EQ("epictetus", frame1->function_name);
  }

  // The values we expect to find for the caller's registers.
  MDRawContextARM expected;

  // The validity mask for expected.
  int expected_validity;

  // The validity mask to impose on the context frame.
  int context_frame_validity;
};

class CFI: public CFIFixture, public Test { };

TEST_F(CFI, At4000) {
  stack_section.start() = expected.iregs[MD_CONTEXT_ARM_REG_SP];
  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40004000;
  raw_context.iregs[MD_CONTEXT_ARM_REG_LR] = 0x40005510;
  CheckWalk();
}

TEST_F(CFI, At4001) {
  Label frame1_sp = expected.iregs[MD_CONTEXT_ARM_REG_SP];
  stack_section
    .D32(0xb5d55e68)            // saved r4
    .D32(0x8112e110)            // saved fp
    .D32(0x40005510)            // return address
    .Mark(&frame1_sp);          // This effectively sets stack_section.start().
  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40004001;
  raw_context.iregs[4] = 0x635adc9f;                     // distinct callee r4
  raw_context.iregs[MD_CONTEXT_ARM_REG_FP] = 0xbe145fc4; // distinct callee fp
  CheckWalk();
}

// As above, but unwind from a context that has only the PC and SP.
TEST_F(CFI, At4001LimitedValidity) {
  context_frame_validity =
    StackFrameARM::CONTEXT_VALID_PC | StackFrameARM::CONTEXT_VALID_SP;
  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40004001;
  raw_context.iregs[MD_CONTEXT_ARM_REG_FP] = 0xbe145fc4; // distinct callee fp
  Label frame1_sp = expected.iregs[MD_CONTEXT_ARM_REG_SP];
  stack_section
    .D32(0xb5d55e68)            // saved r4
    .D32(0x8112e110)            // saved fp
    .D32(0x40005510)            // return address
    .Mark(&frame1_sp);          // This effectively sets stack_section.start().
  expected_validity = (StackFrameARM::CONTEXT_VALID_PC
                       | StackFrameARM::CONTEXT_VALID_SP
                       | StackFrameARM::CONTEXT_VALID_FP
                       | StackFrameARM::CONTEXT_VALID_R4);
  CheckWalk();
}

TEST_F(CFI, At4002) {
  Label frame1_sp = expected.iregs[MD_CONTEXT_ARM_REG_SP];
  stack_section
    .D32(0xfb81ff3d)            // no longer saved r4
    .D32(0x8112e110)            // saved fp
    .D32(0x40005510)            // return address
    .Mark(&frame1_sp);          // This effectively sets stack_section.start().
  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40004002;
  raw_context.iregs[0] = 0xb5d55e68;  // saved r4
  raw_context.iregs[1] = 0xebd134f3;  // saved r5
  raw_context.iregs[2] = 0xa31e74bc;  // saved r6
  raw_context.iregs[3] = 0x2dcb16b3;  // saved r7
  raw_context.iregs[4] = 0xfdd35466;  // distinct callee r4
  raw_context.iregs[5] = 0xf18c946c;  // distinct callee r5
  raw_context.iregs[6] = 0xac2079e8;  // distinct callee r6
  raw_context.iregs[7] = 0xa449829f;  // distinct callee r7
  raw_context.iregs[MD_CONTEXT_ARM_REG_FP] = 0xbe145fc4; // distinct callee fp
  CheckWalk();
}

TEST_F(CFI, At4003) {
  Label frame1_sp = expected.iregs[MD_CONTEXT_ARM_REG_SP];
  stack_section
    .D32(0x48c8dd5a)            // saved r1 (even though it's not callee-saves)
    .D32(0xcb78040e)            // no longer saved r4
    .D32(0x8112e110)            // saved fp
    .D32(0x40005510)            // return address
    .Mark(&frame1_sp);          // This effectively sets stack_section.start().
  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40004003;
  raw_context.iregs[1] = 0xfb756319;                     // distinct callee r1
  raw_context.iregs[MD_CONTEXT_ARM_REG_FP] = 0x0a2857ea; // distinct callee fp
  expected.iregs[1] = 0x48c8dd5a;    // caller's r1
  expected_validity |= StackFrameARM::CONTEXT_VALID_R1;
  CheckWalk();
}

// We have no new rule at module offset 0x4004, so the results here should
// be the same as those at module offset 0x4003.
TEST_F(CFI, At4004) {
  Label frame1_sp = expected.iregs[MD_CONTEXT_ARM_REG_SP];
  stack_section
    .D32(0x48c8dd5a)            // saved r1 (even though it's not callee-saves)
    .D32(0xcb78040e)            // no longer saved r4
    .D32(0x8112e110)            // saved fp
    .D32(0x40005510)            // return address
    .Mark(&frame1_sp);          // This effectively sets stack_section.start().
  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40004004;
  raw_context.iregs[1] = 0xfb756319; // distinct callee r1
  expected.iregs[1] = 0x48c8dd5a; // caller's r1
  expected_validity |= StackFrameARM::CONTEXT_VALID_R1;
  CheckWalk();
}

// Here we move the .cfa, but provide an explicit rule to recover the SP,
// so again there should be no change in the registers recovered.
TEST_F(CFI, At4005) {
  Label frame1_sp = expected.iregs[MD_CONTEXT_ARM_REG_SP];
  stack_section
    .D32(0x48c8dd5a)            // saved r1 (even though it's not callee-saves)
    .D32(0xf013f841)            // no longer saved r4
    .D32(0x8112e110)            // saved fp
    .D32(0x40005510)            // return address
    .Mark(&frame1_sp);          // This effectively sets stack_section.start().
  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40004005;
  raw_context.iregs[1] = 0xfb756319; // distinct callee r1
  expected.iregs[1] = 0x48c8dd5a; // caller's r1
  expected_validity |= StackFrameARM::CONTEXT_VALID_R1;
  CheckWalk();
}

// Here we provide an explicit rule for the PC, and have the saved .ra be
// bogus.
TEST_F(CFI, At4006) {
  Label frame1_sp = expected.iregs[MD_CONTEXT_ARM_REG_SP];
  stack_section
    .D32(0x40005510)            // saved pc
    .D32(0x48c8dd5a)            // saved r1 (even though it's not callee-saves)
    .D32(0xf013f841)            // no longer saved r4
    .D32(0x8112e110)            // saved fp
    .D32(0xf8d15783)            // .ra rule recovers this, which is garbage
    .Mark(&frame1_sp);          // This effectively sets stack_section.start().
  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40004006;
  raw_context.iregs[1] = 0xfb756319; // callee's r1, different from caller's
  expected.iregs[1] = 0x48c8dd5a; // caller's r1
  expected_validity |= StackFrameARM::CONTEXT_VALID_R1;
  CheckWalk();
}

// Check that we reject rules that would cause the stack pointer to
// move in the wrong direction.
TEST_F(CFI, RejectBackwards) {
  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40006000;
  raw_context.iregs[MD_CONTEXT_ARM_REG_SP] = 0x80000000;
  raw_context.iregs[MD_CONTEXT_ARM_REG_LR] = 0x40005510;
  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
  StackwalkerARM walker(&system_info, &raw_context, -1, &stack_region, &modules,
                        &frame_symbolizer);
  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(0U, modules_without_symbols.size());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(1U, frames->size());
}

// Check that we reject rules whose expressions' evaluation fails.
TEST_F(CFI, RejectBadExpressions) {
  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40007000;
  raw_context.iregs[MD_CONTEXT_ARM_REG_SP] = 0x80000000;
  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
  StackwalkerARM walker(&system_info, &raw_context, -1, &stack_region, &modules,
                        &frame_symbolizer);
  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(0U, modules_without_symbols.size());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(1U, frames->size());
}

class StackwalkerARMFixtureIOS : public StackwalkerARMFixture {
 public:
  StackwalkerARMFixtureIOS() {
    system_info.os = "iOS";
    system_info.os_short = "ios";
  }
};

class GetFramesByFramePointer: public StackwalkerARMFixtureIOS, public Test { };

TEST_F(GetFramesByFramePointer, OnlyFramePointer) {
  stack_section.start() = 0x80000000;
  uint32_t return_address1 = 0x50000100;
  uint32_t return_address2 = 0x50000900;
  Label frame1_sp, frame2_sp;
  Label frame1_fp, frame2_fp;
  stack_section
    // frame 0
    .Append(32, 0)           // Whatever values on the stack.
    .D32(0x0000000D)         // junk that's not
    .D32(0xF0000000)         // a return address.

    .Mark(&frame1_fp)        // Next fp will point to the next value.
    .D32(frame2_fp)          // Save current frame pointer.
    .D32(return_address2)    // Save current link register.
    .Mark(&frame1_sp)

    // frame 1
    .Append(32, 0)           // Whatever values on the stack.
    .D32(0x0000000D)         // junk that's not
    .D32(0xF0000000)         // a return address.

    .Mark(&frame2_fp)
    .D32(0)
    .D32(0)
    .Mark(&frame2_sp)

    // frame 2
    .Append(32, 0)           // Whatever values on the stack.
    .D32(0x0000000D)         // junk that's not
    .D32(0xF0000000);        // a return address.
  RegionFromSection();


  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x40005510;
  raw_context.iregs[MD_CONTEXT_ARM_REG_LR] = return_address1;
  raw_context.iregs[MD_CONTEXT_ARM_REG_IOS_FP] = frame1_fp.Value();
  raw_context.iregs[MD_CONTEXT_ARM_REG_SP] = stack_section.start().Value();

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
  StackwalkerARM walker(&system_info, &raw_context, MD_CONTEXT_ARM_REG_IOS_FP,
                        &stack_region, &modules, &frame_symbolizer);

  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(2U, modules_without_symbols.size());
  ASSERT_EQ("module1", modules_without_symbols[0]->debug_file());
  ASSERT_EQ("module2", modules_without_symbols[1]->debug_file());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(3U, frames->size());

  StackFrameARM *frame0 = static_cast<StackFrameARM *>(frames->at(0));
  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);
  ASSERT_EQ(StackFrameARM::CONTEXT_VALID_ALL, frame0->context_validity);
  EXPECT_EQ(0, memcmp(&raw_context, &frame0->context, sizeof(raw_context)));

  StackFrameARM *frame1 = static_cast<StackFrameARM *>(frames->at(1));
  EXPECT_EQ(StackFrame::FRAME_TRUST_FP, frame1->trust);
  ASSERT_EQ((StackFrameARM::CONTEXT_VALID_PC |
             StackFrameARM::CONTEXT_VALID_LR |
             StackFrameARM::RegisterValidFlag(MD_CONTEXT_ARM_REG_IOS_FP) |
             StackFrameARM::CONTEXT_VALID_SP),
            frame1->context_validity);
  EXPECT_EQ(return_address1, frame1->context.iregs[MD_CONTEXT_ARM_REG_PC]);
  EXPECT_EQ(return_address2, frame1->context.iregs[MD_CONTEXT_ARM_REG_LR]);
  EXPECT_EQ(frame1_sp.Value(), frame1->context.iregs[MD_CONTEXT_ARM_REG_SP]);
  EXPECT_EQ(frame2_fp.Value(),
            frame1->context.iregs[MD_CONTEXT_ARM_REG_IOS_FP]);

  StackFrameARM *frame2 = static_cast<StackFrameARM *>(frames->at(2));
  EXPECT_EQ(StackFrame::FRAME_TRUST_FP, frame2->trust);
  ASSERT_EQ((StackFrameARM::CONTEXT_VALID_PC |
             StackFrameARM::CONTEXT_VALID_LR |
             StackFrameARM::RegisterValidFlag(MD_CONTEXT_ARM_REG_IOS_FP) |
             StackFrameARM::CONTEXT_VALID_SP),
            frame2->context_validity);
  EXPECT_EQ(return_address2, frame2->context.iregs[MD_CONTEXT_ARM_REG_PC]);
  EXPECT_EQ(0U, frame2->context.iregs[MD_CONTEXT_ARM_REG_LR]);
  EXPECT_EQ(frame2_sp.Value(), frame2->context.iregs[MD_CONTEXT_ARM_REG_SP]);
  EXPECT_EQ(0U, frame2->context.iregs[MD_CONTEXT_ARM_REG_IOS_FP]);
}

TEST_F(GetFramesByFramePointer, FramePointerAndCFI) {
  // Provide the standatd STACK CFI records that is obtained when exmining an
  // executable produced by XCode.
  SetModuleSymbols(&module1,
                     // Adding a function in CFI.
                     "FUNC 4000 1000 10 enchiridion\n"

                     "STACK CFI INIT 4000 100 .cfa: sp 0 + .ra: lr\n"
                     "STACK CFI 4001 .cfa: sp 8 + .ra: .cfa -4 + ^"
                     " r7: .cfa -8 + ^\n"
                     "STACK CFI 4002 .cfa: r7 8 +\n"
                  );

  stack_section.start() = 0x80000000;
  uint32_t return_address1 = 0x40004010;
  uint32_t return_address2 = 0x50000900;
  Label frame1_sp, frame2_sp;
  Label frame1_fp, frame2_fp;
  stack_section
    // frame 0
    .Append(32, 0)           // Whatever values on the stack.
    .D32(0x0000000D)         // junk that's not
    .D32(0xF0000000)         // a return address.

    .Mark(&frame1_fp)        // Next fp will point to the next value.
    .D32(frame2_fp)          // Save current frame pointer.
    .D32(return_address2)    // Save current link register.
    .Mark(&frame1_sp)

    // frame 1
    .Append(32, 0)           // Whatever values on the stack.
    .D32(0x0000000D)         // junk that's not
    .D32(0xF0000000)         // a return address.

    .Mark(&frame2_fp)
    .D32(0)
    .D32(0)
    .Mark(&frame2_sp)

    // frame 2
    .Append(32, 0)           // Whatever values on the stack.
    .D32(0x0000000D)         // junk that's not
    .D32(0xF0000000);        // a return address.
  RegionFromSection();


  raw_context.iregs[MD_CONTEXT_ARM_REG_PC] = 0x50000400;
  raw_context.iregs[MD_CONTEXT_ARM_REG_LR] = return_address1;
  raw_context.iregs[MD_CONTEXT_ARM_REG_IOS_FP] = frame1_fp.Value();
  raw_context.iregs[MD_CONTEXT_ARM_REG_SP] = stack_section.start().Value();

  StackFrameSymbolizer frame_symbolizer(&supplier, &resolver);
  StackwalkerARM walker(&system_info, &raw_context, MD_CONTEXT_ARM_REG_IOS_FP,
                        &stack_region, &modules, &frame_symbolizer);

  vector<const CodeModule*> modules_without_symbols;
  vector<const CodeModule*> modules_with_corrupt_symbols;
  ASSERT_TRUE(walker.Walk(&call_stack, &modules_without_symbols,
                          &modules_with_corrupt_symbols));
  ASSERT_EQ(1U, modules_without_symbols.size());
  ASSERT_EQ("module2", modules_without_symbols[0]->debug_file());
  ASSERT_EQ(0U, modules_with_corrupt_symbols.size());
  frames = call_stack.frames();
  ASSERT_EQ(3U, frames->size());

  StackFrameARM *frame0 = static_cast<StackFrameARM *>(frames->at(0));
  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);
  ASSERT_EQ(StackFrameARM::CONTEXT_VALID_ALL, frame0->context_validity);
  EXPECT_EQ(0, memcmp(&raw_context, &frame0->context, sizeof(raw_context)));

  StackFrameARM *frame1 = static_cast<StackFrameARM *>(frames->at(1));
  EXPECT_EQ(StackFrame::FRAME_TRUST_FP, frame1->trust);
  ASSERT_EQ((StackFrameARM::CONTEXT_VALID_PC |
             StackFrameARM::CONTEXT_VALID_LR |
             StackFrameARM::RegisterValidFlag(MD_CONTEXT_ARM_REG_IOS_FP) |
             StackFrameARM::CONTEXT_VALID_SP),
            frame1->context_validity);
  EXPECT_EQ(return_address1, frame1->context.iregs[MD_CONTEXT_ARM_REG_PC]);
  EXPECT_EQ(return_address2, frame1->context.iregs[MD_CONTEXT_ARM_REG_LR]);
  EXPECT_EQ(frame1_sp.Value(), frame1->context.iregs[MD_CONTEXT_ARM_REG_SP]);
  EXPECT_EQ(frame2_fp.Value(),
            frame1->context.iregs[MD_CONTEXT_ARM_REG_IOS_FP]);
  EXPECT_EQ("enchiridion", frame1->function_name);
  EXPECT_EQ(0x40004000U, frame1->function_base);


  StackFrameARM *frame2 = static_cast<StackFrameARM *>(frames->at(2));
  EXPECT_EQ(StackFrame::FRAME_TRUST_CFI, frame2->trust);
  ASSERT_EQ((StackFrameARM::CONTEXT_VALID_PC |
             StackFrameARM::CONTEXT_VALID_LR |
             StackFrameARM::RegisterValidFlag(MD_CONTEXT_ARM_REG_IOS_FP) |
             StackFrameARM::CONTEXT_VALID_SP),
            frame2->context_validity);
  EXPECT_EQ(return_address2, frame2->context.iregs[MD_CONTEXT_ARM_REG_PC]);
  EXPECT_EQ(0U, frame2->context.iregs[MD_CONTEXT_ARM_REG_LR]);
  EXPECT_EQ(frame2_sp.Value(), frame2->context.iregs[MD_CONTEXT_ARM_REG_SP]);
  EXPECT_EQ(0U, frame2->context.iregs[MD_CONTEXT_ARM_REG_IOS_FP]);
}