DWARFDebugFrame.cpp revision 0b821eff4c9c8d3b7ac872691bc453337ad3d03a 
1//===-- DWARFDebugFrame.h - Parsing of .debug_frame -------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9
10#include "DWARFDebugFrame.h"
11#include "llvm/ADT/SmallString.h"
12#include "llvm/Support/DataTypes.h"
13#include "llvm/Support/Dwarf.h"
14#include "llvm/Support/Format.h"
15
16using namespace llvm;
17using namespace dwarf;
18
19
20/// \brief Abstract frame entry defining the common interface concrete
21/// entries implement.
22class llvm::FrameEntry {
23public:
24  enum FrameKind {FK_CIE, FK_FDE};
25  FrameEntry(FrameKind K, DataExtractor D, uint64_t Offset, uint64_t Length)
26    : Kind(K), Data(D), Offset(Offset), Length(Length) {}
27
28  virtual ~FrameEntry() {
29  }
30
31  FrameKind getKind() const { return Kind; }
32
33  virtual void dumpHeader(raw_ostream &OS) const = 0;
34
35protected:
36  const FrameKind Kind;
37
38  /// \brief The data stream holding the section from which the entry was
39  /// parsed.
40  DataExtractor Data;
41
42  /// \brief Offset of this entry in the section.
43  uint64_t Offset;
44
45  /// \brief Entry length as specified in DWARF.
46  uint64_t Length;
47};
48
49
50/// \brief DWARF Common Information Entry (CIE)
51class CIE : public FrameEntry {
52public:
53  // CIEs (and FDEs) are simply container classes, so the only sensible way to
54  // create them is by providing the full parsed contents in the constructor.
55  CIE(DataExtractor D, uint64_t Offset, uint64_t Length, uint8_t Version,
56      SmallString<8> Augmentation, uint64_t CodeAlignmentFactor,
57      int64_t DataAlignmentFactor, uint64_t ReturnAddressRegister)
58   : FrameEntry(FK_CIE, D, Offset, Length), Version(Version),
59     Augmentation(Augmentation), CodeAlignmentFactor(CodeAlignmentFactor),
60     DataAlignmentFactor(DataAlignmentFactor),
61     ReturnAddressRegister(ReturnAddressRegister) {}
62
63  ~CIE() {
64  }
65
66  void dumpHeader(raw_ostream &OS) const {
67    OS << format("%08x %08x %08x CIE",
68                 (uint32_t)Offset, (uint32_t)Length, DW_CIE_ID)
69       << "\n";
70    OS << format("  Version:               %d\n", Version);
71    OS << "  Augmentation:          \"" << Augmentation << "\"\n";
72    OS << format("  Code alignment factor: %u\n", (uint32_t)CodeAlignmentFactor);
73    OS << format("  Data alignment factor: %d\n", (int32_t)DataAlignmentFactor);
74    OS << format("  Return address column: %d\n", (int32_t)ReturnAddressRegister);
75    OS << "\n";
76  }
77
78  static bool classof(const FrameEntry *FE) {
79    return FE->getKind() == FK_CIE;
80  }
81
82private:
83  /// The following fields are defined in section 6.4.1 of the DWARF standard v3
84  uint8_t Version;
85  SmallString<8> Augmentation;
86  uint64_t CodeAlignmentFactor;
87  int64_t DataAlignmentFactor;
88  uint64_t ReturnAddressRegister;
89};
90
91
92/// \brief DWARF Frame Description Entry (FDE)
93class FDE : public FrameEntry {
94public:
95  // Each FDE has a CIE it's "linked to". Our FDE contains is constructed with
96  // an offset to the CIE (provided by parsing the FDE header). The CIE itself
97  // is obtained lazily once it's actually required.
98  FDE(DataExtractor D, uint64_t Offset, uint64_t Length,
99      int64_t LinkedCIEOffset, uint64_t InitialLocation, uint64_t AddressRange)
100   : FrameEntry(FK_FDE, D, Offset, Length), LinkedCIEOffset(LinkedCIEOffset),
101     InitialLocation(InitialLocation), AddressRange(AddressRange),
102     LinkedCIE(NULL) {}
103
104  ~FDE() {
105  }
106
107  void dumpHeader(raw_ostream &OS) const {
108    OS << format("%08x %08x %08x FDE ",
109                 (uint32_t)Offset, (uint32_t)Length, (int32_t)LinkedCIEOffset);
110    OS << format("cie=%08x pc=%08x...%08x\n",
111                 (int32_t)LinkedCIEOffset,
112                 (uint32_t)InitialLocation,
113                 (uint32_t)InitialLocation + (uint32_t)AddressRange);
114    OS << "\n";
115    if (LinkedCIE) {
116      OS << format("%p\n", LinkedCIE);
117    }
118  }
119
120  static bool classof(const FrameEntry *FE) {
121    return FE->getKind() == FK_FDE;
122  }
123private:
124
125  /// The following fields are defined in section 6.4.1 of the DWARF standard v3
126  uint64_t LinkedCIEOffset;
127  uint64_t InitialLocation;
128  uint64_t AddressRange;
129  CIE *LinkedCIE;
130};
131
132
133DWARFDebugFrame::DWARFDebugFrame() {
134}
135
136
137DWARFDebugFrame::~DWARFDebugFrame() {
138  for (EntryVector::iterator I = Entries.begin(), E = Entries.end();
139       I != E; ++I) {
140    delete *I;
141  }
142}
143
144
145static void LLVM_ATTRIBUTE_UNUSED dumpDataAux(DataExtractor Data,
146                                              uint32_t Offset, int Length) {
147  errs() << "DUMP: ";
148  for (int i = 0; i < Length; ++i) {
149    uint8_t c = Data.getU8(&Offset);
150    errs().write_hex(c); errs() << " ";
151  }
152  errs() << "\n";
153}
154
155
156void DWARFDebugFrame::parse(DataExtractor Data) {
157  uint32_t Offset = 0;
158
159  while (Data.isValidOffset(Offset)) {
160    uint32_t StartOffset = Offset;
161
162    bool IsDWARF64 = false;
163    uint64_t Length = Data.getU32(&Offset);
164    uint64_t Id;
165
166    if (Length == UINT32_MAX) {
167      // DWARF-64 is distinguished by the first 32 bits of the initial length
168      // field being 0xffffffff. Then, the next 64 bits are the actual entry
169      // length.
170      IsDWARF64 = true;
171      Length = Data.getU64(&Offset);
172    }
173
174    // At this point, Offset points to the next field after Length.
175    // Length is the structure size excluding itself. Compute an offset one
176    // past the end of the structure (needed to know how many instructions to
177    // read).
178    // TODO: For honest DWARF64 support, DataExtractor will have to treat
179    //       offset_ptr as uint64_t*
180    uint32_t EndStructureOffset = Offset + static_cast<uint32_t>(Length);
181
182    // The Id field's size depends on the DWARF format
183    Id = Data.getUnsigned(&Offset, IsDWARF64 ? 8 : 4);
184    bool IsCIE = ((IsDWARF64 && Id == DW64_CIE_ID) || Id == DW_CIE_ID);
185
186    if (IsCIE) {
187      // Note: this is specifically DWARFv3 CIE header structure. It was
188      // changed in DWARFv4.
189      uint8_t Version = Data.getU8(&Offset);
190      const char *Augmentation = Data.getCStr(&Offset);
191      uint64_t CodeAlignmentFactor = Data.getULEB128(&Offset);
192      int64_t DataAlignmentFactor = Data.getSLEB128(&Offset);
193      uint64_t ReturnAddressRegister = Data.getULEB128(&Offset);
194
195      CIE *NewCIE = new CIE(Data, StartOffset, Length, Version,
196                            StringRef(Augmentation), CodeAlignmentFactor,
197                            DataAlignmentFactor, ReturnAddressRegister);
198      Entries.push_back(NewCIE);
199    } else {
200      // FDE
201      uint64_t CIEPointer = Id;
202      uint64_t InitialLocation = Data.getAddress(&Offset);
203      uint64_t AddressRange = Data.getAddress(&Offset);
204
205      FDE *NewFDE = new FDE(Data, StartOffset, Length, CIEPointer,
206                            InitialLocation, AddressRange);
207      Entries.push_back(NewFDE);
208    }
209
210    Offset = EndStructureOffset;
211  }
212}
213
214
215void DWARFDebugFrame::dump(raw_ostream &OS) const {
216  OS << "\n";
217  for (EntryVector::const_iterator I = Entries.begin(), E = Entries.end();
218       I != E; ++I) {
219    (*I)->dumpHeader(OS);
220  }
221}
222
223