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/ErrorHandling.h" 15#include "llvm/Support/Format.h" 16#include "llvm/Support/raw_ostream.h" 17#include <string> 18#include <vector> 19 20using namespace llvm; 21using namespace dwarf; 22 23 24/// \brief Abstract frame entry defining the common interface concrete 25/// entries implement. 26class llvm::FrameEntry { 27public: 28 enum FrameKind {FK_CIE, FK_FDE}; 29 FrameEntry(FrameKind K, uint64_t Offset, uint64_t Length) 30 : Kind(K), Offset(Offset), Length(Length) {} 31 32 virtual ~FrameEntry() { 33 } 34 35 FrameKind getKind() const { return Kind; } 36 virtual uint64_t getOffset() const { return Offset; } 37 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, 43 uint32_t EndOffset); 44 45 /// \brief Dump the entry header to the given output stream. 46 virtual void dumpHeader(raw_ostream &OS) const = 0; 47 48 /// \brief Dump the entry's instructions to the given output stream. 49 virtual void dumpInstructions(raw_ostream &OS) const; 50 51protected: 52 const FrameKind Kind; 53 54 /// \brief Offset of this entry in the section. 55 uint64_t Offset; 56 57 /// \brief Entry length as specified in DWARF. 58 uint64_t Length; 59 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; 63 struct Instruction { 64 Instruction(uint8_t Opcode) 65 : Opcode(Opcode) 66 {} 67 68 uint8_t Opcode; 69 Operands Ops; 70 }; 71 72 std::vector<Instruction> Instructions; 73 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)); 78 } 79 80 void addInstruction(uint8_t Opcode, uint64_t Operand1) { 81 Instructions.push_back(Instruction(Opcode)); 82 Instructions.back().Ops.push_back(Operand1); 83 } 84 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); 89 } 90}; 91 92 93// See DWARF standard v3, section 7.23 94const uint8_t DWARF_CFI_PRIMARY_OPCODE_MASK = 0xc0; 95const uint8_t DWARF_CFI_PRIMARY_OPERAND_MASK = 0x3f; 96 97void FrameEntry::parseInstructions(DataExtractor Data, uint32_t *Offset, 98 uint32_t EndOffset) { 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; 103 104 if (Primary) { 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; 108 switch (Primary) { 109 default: llvm_unreachable("Impossible primary CFI opcode"); 110 case DW_CFA_advance_loc: 111 case DW_CFA_restore: 112 addInstruction(Primary, Op1); 113 break; 114 case DW_CFA_offset: 115 addInstruction(Primary, Op1, Data.getULEB128(Offset)); 116 break; 117 } 118 } else { 119 // Extended opcode - its value is Opcode itself. 120 switch (Opcode) { 121 default: llvm_unreachable("Invalid extended CFI opcode"); 122 case DW_CFA_nop: 123 case DW_CFA_remember_state: 124 case DW_CFA_restore_state: 125 case DW_CFA_GNU_window_save: 126 // No operands 127 addInstruction(Opcode); 128 break; 129 case DW_CFA_set_loc: 130 // Operands: Address 131 addInstruction(Opcode, Data.getAddress(Offset)); 132 break; 133 case DW_CFA_advance_loc1: 134 // Operands: 1-byte delta 135 addInstruction(Opcode, Data.getU8(Offset)); 136 break; 137 case DW_CFA_advance_loc2: 138 // Operands: 2-byte delta 139 addInstruction(Opcode, Data.getU16(Offset)); 140 break; 141 case DW_CFA_advance_loc4: 142 // Operands: 4-byte delta 143 addInstruction(Opcode, Data.getU32(Offset)); 144 break; 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: 150 // Operands: ULEB128 151 addInstruction(Opcode, Data.getULEB128(Offset)); 152 break; 153 case DW_CFA_def_cfa_offset_sf: 154 // Operands: SLEB128 155 addInstruction(Opcode, Data.getSLEB128(Offset)); 156 break; 157 case DW_CFA_offset_extended: 158 case DW_CFA_register: 159 case DW_CFA_def_cfa: 160 case DW_CFA_val_offset: 161 // Operands: ULEB128, ULEB128 162 addInstruction(Opcode, Data.getULEB128(Offset), 163 Data.getULEB128(Offset)); 164 break; 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)); 171 break; 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!"); 177 } 178 } 179 } 180} 181 182 183void 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"; 191 } 192} 193 194 195namespace { 196/// \brief DWARF Common Information Entry (CIE) 197class CIE : public FrameEntry { 198public: 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) {} 208 209 ~CIE() { 210 } 211 212 void dumpHeader(raw_ostream &OS) const override { 213 OS << format("%08x %08x %08x CIE", 214 (uint32_t)Offset, (uint32_t)Length, DW_CIE_ID) 215 << "\n"; 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); 224 OS << "\n"; 225 } 226 227 static bool classof(const FrameEntry *FE) { 228 return FE->getKind() == FK_CIE; 229 } 230 231private: 232 /// The following fields are defined in section 6.4.1 of the DWARF standard v3 233 uint8_t Version; 234 SmallString<8> Augmentation; 235 uint64_t CodeAlignmentFactor; 236 int64_t DataAlignmentFactor; 237 uint64_t ReturnAddressRegister; 238}; 239 240 241/// \brief DWARF Frame Description Entry (FDE) 242class FDE : public FrameEntry { 243public: 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) {} 252 253 ~FDE() { 254 } 255 256 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); 263 if (LinkedCIE) { 264 OS << format("%p\n", LinkedCIE); 265 } 266 } 267 268 static bool classof(const FrameEntry *FE) { 269 return FE->getKind() == FK_FDE; 270 } 271 272private: 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; 277 CIE *LinkedCIE; 278}; 279} // end anonymous namespace 280 281 282DWARFDebugFrame::DWARFDebugFrame() { 283} 284 285DWARFDebugFrame::~DWARFDebugFrame() { 286} 287 288static void LLVM_ATTRIBUTE_UNUSED dumpDataAux(DataExtractor Data, 289 uint32_t Offset, int Length) { 290 errs() << "DUMP: "; 291 for (int i = 0; i < Length; ++i) { 292 uint8_t c = Data.getU8(&Offset); 293 errs().write_hex(c); errs() << " "; 294 } 295 errs() << "\n"; 296} 297 298 299void DWARFDebugFrame::parse(DataExtractor Data) { 300 uint32_t Offset = 0; 301 302 while (Data.isValidOffset(Offset)) { 303 uint32_t StartOffset = Offset; 304 305 bool IsDWARF64 = false; 306 uint64_t Length = Data.getU32(&Offset); 307 uint64_t Id; 308 309 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 312 // length. 313 IsDWARF64 = true; 314 Length = Data.getU64(&Offset); 315 } 316 317 // 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 320 // read). 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); 324 325 // 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); 328 329 if (IsCIE) { 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); 339 340 Entries.emplace_back(new CIE(StartOffset, Length, Version, 341 StringRef(Augmentation), CodeAlignmentFactor, 342 DataAlignmentFactor, ReturnAddressRegister)); 343 } else { 344 // FDE 345 uint64_t CIEPointer = Id; 346 uint64_t InitialLocation = Data.getAddress(&Offset); 347 uint64_t AddressRange = Data.getAddress(&Offset); 348 349 Entries.emplace_back(new FDE(StartOffset, Length, CIEPointer, 350 InitialLocation, AddressRange)); 351 } 352 353 Entries.back()->parseInstructions(Data, &Offset, EndStructureOffset); 354 355 if (Offset != EndStructureOffset) { 356 std::string Str; 357 raw_string_ostream OS(Str); 358 OS << format("Parsing entry instructions at %lx failed", StartOffset); 359 report_fatal_error(Str); 360 } 361 } 362} 363 364 365void DWARFDebugFrame::dump(raw_ostream &OS) const { 366 OS << "\n"; 367 for (const auto &Entry : Entries) { 368 Entry->dumpHeader(OS); 369 Entry->dumpInstructions(OS); 370 OS << "\n"; 371 } 372} 373 374