DWARFDebugFrame.cpp revision 2e402d5b5f2fce8bfe29509cc771b9919946003b 
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", Offset, Length, DW_CIE_ID) << "\n";
68    OS << format("  Version:               %d\n", Version);
69    OS << "  Augmentation:          \"" << Augmentation << "\"\n";
70    OS << format("  Code alignment factor: %u\n", CodeAlignmentFactor);
71    OS << format("  Data alignment factor: %d\n", DataAlignmentFactor);
72    OS << format("  Return address column: %d\n", ReturnAddressRegister);
73    OS << "\n";
74  }
75
76  static bool classof(const FrameEntry *FE) {
77    return FE->getKind() == FK_CIE;
78  }
79
80private:
81  /// The following fields are defined in section 6.4.1 of the DWARF standard v3
82  uint8_t Version;
83  SmallString<8> Augmentation;
84  uint64_t CodeAlignmentFactor;
85  int64_t DataAlignmentFactor;
86  uint64_t ReturnAddressRegister;
87};
88
89
90/// \brief DWARF Frame Description Entry (FDE)
91class FDE : public FrameEntry {
92public:
93  // Each FDE has a CIE it's "linked to". Our FDE contains is constructed with
94  // an offset to the CIE (provided by parsing the FDE header). The CIE itself
95  // is obtained lazily once it's actually required.
96  FDE(DataExtractor D, uint64_t Offset, uint64_t Length,
97      int64_t LinkedCIEOffset, uint64_t InitialLocation, uint64_t AddressRange)
98   : FrameEntry(FK_FDE, D, Offset, Length), LinkedCIEOffset(LinkedCIEOffset),
99     InitialLocation(InitialLocation), AddressRange(AddressRange),
100     LinkedCIE(NULL) {}
101
102  ~FDE() {
103  }
104
105  void dumpHeader(raw_ostream &OS) const {
106    OS << format("%08x %08x %08x FDE ", Offset, Length, LinkedCIEOffset);
107    OS << format("cie=%08x pc=%08x...%08x\n",
108                 LinkedCIEOffset, InitialLocation,
109                 InitialLocation + AddressRange);
110    OS << "\n";
111    if (LinkedCIE) {
112      OS << format("%p\n", LinkedCIE);
113    }
114  }
115
116  static bool classof(const FrameEntry *FE) {
117    return FE->getKind() == FK_FDE;
118  }
119private:
120
121  /// The following fields are defined in section 6.4.1 of the DWARF standard v3
122  uint64_t LinkedCIEOffset;
123  uint64_t InitialLocation;
124  uint64_t AddressRange;
125  CIE *LinkedCIE;
126};
127
128
129DWARFDebugFrame::DWARFDebugFrame() {
130}
131
132
133DWARFDebugFrame::~DWARFDebugFrame() {
134  for (EntryVector::iterator I = Entries.begin(), E = Entries.end();
135       I != E; ++I) {
136    delete *I;
137  }
138}
139
140
141static void LLVM_ATTRIBUTE_UNUSED dumpDataAux(DataExtractor Data,
142                                              uint32_t Offset, int Length) {
143  errs() << "DUMP: ";
144  for (int i = 0; i < Length; ++i) {
145    uint8_t c = Data.getU8(&Offset);
146    errs().write_hex(c); errs() << " ";
147  }
148  errs() << "\n";
149}
150
151
152void DWARFDebugFrame::parse(DataExtractor Data) {
153  uint32_t Offset = 0;
154
155  while (Data.isValidOffset(Offset)) {
156    uint32_t StartOffset = Offset;
157
158    bool IsDWARF64 = false;
159    uint64_t Length = Data.getU32(&Offset);
160    uint64_t Id;
161
162    if (Length == UINT32_MAX) {
163      // DWARF-64 is distinguished by the first 32 bits of the initial length
164      // field being 0xffffffff. Then, the next 64 bits are the actual entry
165      // length.
166      IsDWARF64 = true;
167      Length = Data.getU64(&Offset);
168    }
169
170    // At this point, Offset points to the next field after Length.
171    // Length is the structure size excluding itself. Compute an offset one
172    // past the end of the structure (needed to know how many instructions to
173    // read).
174    // TODO: For honest DWARF64 support, DataExtractor will have to treat
175    //       offset_ptr as uint64_t*
176    uint32_t EndStructureOffset = Offset + static_cast<uint32_t>(Length);
177
178    // The Id field's size depends on the DWARF format
179    Id = Data.getUnsigned(&Offset, IsDWARF64 ? 8 : 4);
180    bool IsCIE = ((IsDWARF64 && Id == DW64_CIE_ID) || Id == DW_CIE_ID);
181
182    if (IsCIE) {
183      // Note: this is specifically DWARFv3 CIE header structure. It was
184      // changed in DWARFv4.
185      uint8_t Version = Data.getU8(&Offset);
186      const char *Augmentation = Data.getCStr(&Offset);
187      uint64_t CodeAlignmentFactor = Data.getULEB128(&Offset);
188      int64_t DataAlignmentFactor = Data.getSLEB128(&Offset);
189      uint64_t ReturnAddressRegister = Data.getULEB128(&Offset);
190
191      CIE *NewCIE = new CIE(Data, StartOffset, Length, Version,
192                            StringRef(Augmentation), CodeAlignmentFactor,
193                            DataAlignmentFactor, ReturnAddressRegister);
194      Entries.push_back(NewCIE);
195    } else {
196      // FDE
197      uint64_t CIEPointer = Id;
198      uint64_t InitialLocation = Data.getAddress(&Offset);
199      uint64_t AddressRange = Data.getAddress(&Offset);
200
201      FDE *NewFDE = new FDE(Data, StartOffset, Length, CIEPointer,
202                            InitialLocation, AddressRange);
203      Entries.push_back(NewFDE);
204    }
205
206    Offset = EndStructureOffset;
207  }
208}
209
210
211void DWARFDebugFrame::dump(raw_ostream &OS) const {
212  OS << "\n";
213  for (EntryVector::const_iterator I = Entries.begin(), E = Entries.end();
214       I != E; ++I) {
215    (*I)->dumpHeader(OS);
216  }
217}
218
219