1 //===-- DWARFDebugFrame.h - Parsing of .debug_frame -------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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/ErrorHandling.h"
15 #include "llvm/Support/Format.h"
16 #include "llvm/Support/raw_ostream.h"
21 using namespace dwarf;
24 /// \brief Abstract frame entry defining the common interface concrete
25 /// entries implement.
26 class llvm::FrameEntry {
28 enum FrameKind {FK_CIE, FK_FDE};
29 FrameEntry(FrameKind K, uint64_t Offset, uint64_t Length)
30 : Kind(K), Offset(Offset), Length(Length) {}
32 virtual ~FrameEntry() {
35 FrameKind getKind() const { return Kind; }
36 virtual uint64_t getOffset() const { return Offset; }
38 /// \brief Parse and store a sequence of CFI instructions from Data,
39 /// starting at *Offset and ending at EndOffset. If everything
40 /// goes well, *Offset should be equal to EndOffset when this method
41 /// returns. Otherwise, an error occurred.
42 virtual void parseInstructions(DataExtractor Data, uint32_t *Offset,
45 /// \brief Dump the entry header to the given output stream.
46 virtual void dumpHeader(raw_ostream &OS) const = 0;
48 /// \brief Dump the entry's instructions to the given output stream.
49 virtual void dumpInstructions(raw_ostream &OS) const;
54 /// \brief Offset of this entry in the section.
57 /// \brief Entry length as specified in DWARF.
60 /// An entry may contain CFI instructions. An instruction consists of an
61 /// opcode and an optional sequence of operands.
62 typedef std::vector<uint64_t> Operands;
64 Instruction(uint8_t Opcode)
72 std::vector<Instruction> Instructions;
74 /// Convenience methods to add a new instruction with the given opcode and
75 /// operands to the Instructions vector.
76 void addInstruction(uint8_t Opcode) {
77 Instructions.push_back(Instruction(Opcode));
80 void addInstruction(uint8_t Opcode, uint64_t Operand1) {
81 Instructions.push_back(Instruction(Opcode));
82 Instructions.back().Ops.push_back(Operand1);
85 void addInstruction(uint8_t Opcode, uint64_t Operand1, uint64_t Operand2) {
86 Instructions.push_back(Instruction(Opcode));
87 Instructions.back().Ops.push_back(Operand1);
88 Instructions.back().Ops.push_back(Operand2);
93 // See DWARF standard v3, section 7.23
94 const uint8_t DWARF_CFI_PRIMARY_OPCODE_MASK = 0xc0;
95 const uint8_t DWARF_CFI_PRIMARY_OPERAND_MASK = 0x3f;
97 void FrameEntry::parseInstructions(DataExtractor Data, uint32_t *Offset,
99 while (*Offset < EndOffset) {
100 uint8_t Opcode = Data.getU8(Offset);
101 // Some instructions have a primary opcode encoded in the top bits.
102 uint8_t Primary = Opcode & DWARF_CFI_PRIMARY_OPCODE_MASK;
105 // If it's a primary opcode, the first operand is encoded in the bottom
106 // bits of the opcode itself.
107 uint64_t Op1 = Opcode & DWARF_CFI_PRIMARY_OPERAND_MASK;
109 default: llvm_unreachable("Impossible primary CFI opcode");
110 case DW_CFA_advance_loc:
112 addInstruction(Primary, Op1);
115 addInstruction(Primary, Op1, Data.getULEB128(Offset));
119 // Extended opcode - its value is Opcode itself.
121 default: llvm_unreachable("Invalid extended CFI opcode");
123 case DW_CFA_remember_state:
124 case DW_CFA_restore_state:
125 case DW_CFA_GNU_window_save:
127 addInstruction(Opcode);
131 addInstruction(Opcode, Data.getAddress(Offset));
133 case DW_CFA_advance_loc1:
134 // Operands: 1-byte delta
135 addInstruction(Opcode, Data.getU8(Offset));
137 case DW_CFA_advance_loc2:
138 // Operands: 2-byte delta
139 addInstruction(Opcode, Data.getU16(Offset));
141 case DW_CFA_advance_loc4:
142 // Operands: 4-byte delta
143 addInstruction(Opcode, Data.getU32(Offset));
145 case DW_CFA_restore_extended:
146 case DW_CFA_undefined:
147 case DW_CFA_same_value:
148 case DW_CFA_def_cfa_register:
149 case DW_CFA_def_cfa_offset:
151 addInstruction(Opcode, Data.getULEB128(Offset));
153 case DW_CFA_def_cfa_offset_sf:
155 addInstruction(Opcode, Data.getSLEB128(Offset));
157 case DW_CFA_offset_extended:
158 case DW_CFA_register:
160 case DW_CFA_val_offset:
161 // Operands: ULEB128, ULEB128
162 addInstruction(Opcode, Data.getULEB128(Offset),
163 Data.getULEB128(Offset));
165 case DW_CFA_offset_extended_sf:
166 case DW_CFA_def_cfa_sf:
167 case DW_CFA_val_offset_sf:
168 // Operands: ULEB128, SLEB128
169 addInstruction(Opcode, Data.getULEB128(Offset),
170 Data.getSLEB128(Offset));
172 case DW_CFA_def_cfa_expression:
173 case DW_CFA_expression:
174 case DW_CFA_val_expression:
175 // TODO: implement this
176 report_fatal_error("Values with expressions not implemented yet!");
183 void FrameEntry::dumpInstructions(raw_ostream &OS) const {
184 // TODO: at the moment only instruction names are dumped. Expand this to
185 // dump operands as well.
186 for (const auto &Instr : Instructions) {
187 uint8_t Opcode = Instr.Opcode;
188 if (Opcode & DWARF_CFI_PRIMARY_OPCODE_MASK)
189 Opcode &= DWARF_CFI_PRIMARY_OPCODE_MASK;
190 OS << " " << CallFrameString(Opcode) << ":\n";
196 /// \brief DWARF Common Information Entry (CIE)
197 class CIE : public FrameEntry {
199 // CIEs (and FDEs) are simply container classes, so the only sensible way to
200 // create them is by providing the full parsed contents in the constructor.
201 CIE(uint64_t Offset, uint64_t Length, uint8_t Version,
202 SmallString<8> Augmentation, uint64_t CodeAlignmentFactor,
203 int64_t DataAlignmentFactor, uint64_t ReturnAddressRegister)
204 : FrameEntry(FK_CIE, Offset, Length), Version(Version),
205 Augmentation(Augmentation), CodeAlignmentFactor(CodeAlignmentFactor),
206 DataAlignmentFactor(DataAlignmentFactor),
207 ReturnAddressRegister(ReturnAddressRegister) {}
212 void dumpHeader(raw_ostream &OS) const override {
213 OS << format("%08x %08x %08x CIE",
214 (uint32_t)Offset, (uint32_t)Length, DW_CIE_ID)
216 OS << format(" Version: %d\n", Version);
217 OS << " Augmentation: \"" << Augmentation << "\"\n";
218 OS << format(" Code alignment factor: %u\n",
219 (uint32_t)CodeAlignmentFactor);
220 OS << format(" Data alignment factor: %d\n",
221 (int32_t)DataAlignmentFactor);
222 OS << format(" Return address column: %d\n",
223 (int32_t)ReturnAddressRegister);
227 static bool classof(const FrameEntry *FE) {
228 return FE->getKind() == FK_CIE;
232 /// The following fields are defined in section 6.4.1 of the DWARF standard v3
234 SmallString<8> Augmentation;
235 uint64_t CodeAlignmentFactor;
236 int64_t DataAlignmentFactor;
237 uint64_t ReturnAddressRegister;
241 /// \brief DWARF Frame Description Entry (FDE)
242 class FDE : public FrameEntry {
244 // Each FDE has a CIE it's "linked to". Our FDE contains is constructed with
245 // an offset to the CIE (provided by parsing the FDE header). The CIE itself
246 // is obtained lazily once it's actually required.
247 FDE(uint64_t Offset, uint64_t Length, int64_t LinkedCIEOffset,
248 uint64_t InitialLocation, uint64_t AddressRange)
249 : FrameEntry(FK_FDE, Offset, Length), LinkedCIEOffset(LinkedCIEOffset),
250 InitialLocation(InitialLocation), AddressRange(AddressRange),
251 LinkedCIE(nullptr) {}
256 void dumpHeader(raw_ostream &OS) const override {
257 OS << format("%08x %08x %08x FDE ",
258 (uint32_t)Offset, (uint32_t)Length, (int32_t)LinkedCIEOffset);
259 OS << format("cie=%08x pc=%08x...%08x\n",
260 (int32_t)LinkedCIEOffset,
261 (uint32_t)InitialLocation,
262 (uint32_t)InitialLocation + (uint32_t)AddressRange);
264 OS << format("%p\n", LinkedCIE);
268 static bool classof(const FrameEntry *FE) {
269 return FE->getKind() == FK_FDE;
273 /// The following fields are defined in section 6.4.1 of the DWARF standard v3
274 uint64_t LinkedCIEOffset;
275 uint64_t InitialLocation;
276 uint64_t AddressRange;
279 } // end anonymous namespace
282 DWARFDebugFrame::DWARFDebugFrame() {
285 DWARFDebugFrame::~DWARFDebugFrame() {
288 static void LLVM_ATTRIBUTE_UNUSED dumpDataAux(DataExtractor Data,
289 uint32_t Offset, int Length) {
291 for (int i = 0; i < Length; ++i) {
292 uint8_t c = Data.getU8(&Offset);
293 errs().write_hex(c); errs() << " ";
299 void DWARFDebugFrame::parse(DataExtractor Data) {
302 while (Data.isValidOffset(Offset)) {
303 uint32_t StartOffset = Offset;
305 bool IsDWARF64 = false;
306 uint64_t Length = Data.getU32(&Offset);
309 if (Length == UINT32_MAX) {
310 // DWARF-64 is distinguished by the first 32 bits of the initial length
311 // field being 0xffffffff. Then, the next 64 bits are the actual entry
314 Length = Data.getU64(&Offset);
317 // At this point, Offset points to the next field after Length.
318 // Length is the structure size excluding itself. Compute an offset one
319 // past the end of the structure (needed to know how many instructions to
321 // TODO: For honest DWARF64 support, DataExtractor will have to treat
322 // offset_ptr as uint64_t*
323 uint32_t EndStructureOffset = Offset + static_cast<uint32_t>(Length);
325 // The Id field's size depends on the DWARF format
326 Id = Data.getUnsigned(&Offset, IsDWARF64 ? 8 : 4);
327 bool IsCIE = ((IsDWARF64 && Id == DW64_CIE_ID) || Id == DW_CIE_ID);
330 // Note: this is specifically DWARFv3 CIE header structure. It was
331 // changed in DWARFv4. We currently don't support reading DWARFv4
332 // here because LLVM itself does not emit it (and LLDB doesn't
333 // support it either).
334 uint8_t Version = Data.getU8(&Offset);
335 const char *Augmentation = Data.getCStr(&Offset);
336 uint64_t CodeAlignmentFactor = Data.getULEB128(&Offset);
337 int64_t DataAlignmentFactor = Data.getSLEB128(&Offset);
338 uint64_t ReturnAddressRegister = Data.getULEB128(&Offset);
340 Entries.emplace_back(new CIE(StartOffset, Length, Version,
341 StringRef(Augmentation), CodeAlignmentFactor,
342 DataAlignmentFactor, ReturnAddressRegister));
345 uint64_t CIEPointer = Id;
346 uint64_t InitialLocation = Data.getAddress(&Offset);
347 uint64_t AddressRange = Data.getAddress(&Offset);
349 Entries.emplace_back(new FDE(StartOffset, Length, CIEPointer,
350 InitialLocation, AddressRange));
353 Entries.back()->parseInstructions(Data, &Offset, EndStructureOffset);
355 if (Offset != EndStructureOffset) {
357 raw_string_ostream OS(Str);
358 OS << format("Parsing entry instructions at %lx failed", StartOffset);
359 report_fatal_error(Str);
365 void DWARFDebugFrame::dump(raw_ostream &OS) const {
367 for (const auto &Entry : Entries) {
368 Entry->dumpHeader(OS);
369 Entry->dumpInstructions(OS);