1 //=== DebugInfoLinker.cpp -------------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #include "DebugInfoLinker.h" 10 #include "Error.h" 11 #include "llvm/ADT/StringSwitch.h" 12 #include "llvm/DWARFLinker/DWARFLinker.h" 13 #include "llvm/DWARFLinker/DWARFStreamer.h" 14 #include "llvm/DWARFLinkerParallel/DWARFLinker.h" 15 #include "llvm/DebugInfo/DWARF/DWARFContext.h" 16 #include "llvm/DebugInfo/DWARF/DWARFExpression.h" 17 #include "llvm/Object/ObjectFile.h" 18 #include "llvm/Support/Endian.h" 19 #include <memory> 20 #include <vector> 21 22 namespace llvm { 23 namespace dwarfutil { 24 25 // ObjFileAddressMap allows to check whether specified DIE referencing 26 // dead addresses. It uses tombstone values to determine dead addresses. 27 // The concrete values of tombstone constants were discussed in 28 // https://reviews.llvm.org/D81784 and https://reviews.llvm.org/D84825. 29 // So we use following values as indicators of dead addresses: 30 // 31 // bfd: (LowPC == 0) or (LowPC == 1 and HighPC == 1 and DWARF v4 (or less)) 32 // or ([LowPC, HighPC] is not inside address ranges of .text sections). 33 // 34 // maxpc: (LowPC == -1) or (LowPC == -2 and DWARF v4 (or less)) 35 // That value is assumed to be compatible with 36 // http://www.dwarfstd.org/ShowIssue.php?issue=200609.1 37 // 38 // exec: [LowPC, HighPC] is not inside address ranges of .text sections 39 // 40 // universal: maxpc and bfd 41 template <typename AddressMapBase> 42 class ObjFileAddressMap : public AddressMapBase { 43 public: 44 ObjFileAddressMap(DWARFContext &Context, const Options &Options, 45 object::ObjectFile &ObjFile) 46 : Opts(Options) { 47 // Remember addresses of existing text sections. 48 for (const object::SectionRef &Sect : ObjFile.sections()) { 49 if (!Sect.isText()) 50 continue; 51 const uint64_t Size = Sect.getSize(); 52 if (Size == 0) 53 continue; 54 const uint64_t StartAddr = Sect.getAddress(); 55 TextAddressRanges.insert({StartAddr, StartAddr + Size}); 56 } 57 58 // Check CU address ranges for tombstone value. 59 for (std::unique_ptr<DWARFUnit> &CU : Context.compile_units()) { 60 Expected<llvm::DWARFAddressRangesVector> ARanges = 61 CU->getUnitDIE().getAddressRanges(); 62 if (!ARanges) { 63 llvm::consumeError(ARanges.takeError()); 64 continue; 65 } 66 67 for (auto &Range : *ARanges) { 68 if (!isDeadAddressRange(Range.LowPC, Range.HighPC, CU->getVersion(), 69 Options.Tombstone, CU->getAddressByteSize())) { 70 HasValidAddressRanges = true; 71 break; 72 } 73 } 74 75 if (HasValidAddressRanges) 76 break; 77 } 78 } 79 80 // should be renamed into has valid address ranges 81 bool hasValidRelocs() override { return HasValidAddressRanges; } 82 83 std::optional<int64_t> 84 getSubprogramRelocAdjustment(const DWARFDie &DIE) override { 85 assert((DIE.getTag() == dwarf::DW_TAG_subprogram || 86 DIE.getTag() == dwarf::DW_TAG_label) && 87 "Wrong type of input die"); 88 89 if (std::optional<uint64_t> LowPC = 90 dwarf::toAddress(DIE.find(dwarf::DW_AT_low_pc))) { 91 if (!isDeadAddress(*LowPC, DIE.getDwarfUnit()->getVersion(), 92 Opts.Tombstone, 93 DIE.getDwarfUnit()->getAddressByteSize())) 94 // Relocation value for the linked binary is 0. 95 return 0; 96 } 97 98 return std::nullopt; 99 } 100 101 std::optional<int64_t> getExprOpAddressRelocAdjustment( 102 DWARFUnit &U, const DWARFExpression::Operation &Op, uint64_t StartOffset, 103 uint64_t EndOffset) override { 104 switch (Op.getCode()) { 105 default: { 106 assert(false && "Specified operation does not have address operand"); 107 } break; 108 case dwarf::DW_OP_const4u: 109 case dwarf::DW_OP_const8u: 110 case dwarf::DW_OP_const4s: 111 case dwarf::DW_OP_const8s: 112 case dwarf::DW_OP_addr: { 113 if (!isDeadAddress(Op.getRawOperand(0), U.getVersion(), Opts.Tombstone, 114 U.getAddressByteSize())) 115 // Relocation value for the linked binary is 0. 116 return 0; 117 } break; 118 case dwarf::DW_OP_constx: 119 case dwarf::DW_OP_addrx: { 120 if (std::optional<object::SectionedAddress> Address = 121 U.getAddrOffsetSectionItem(Op.getRawOperand(0))) { 122 if (!isDeadAddress(Address->Address, U.getVersion(), Opts.Tombstone, 123 U.getAddressByteSize())) 124 // Relocation value for the linked binary is 0. 125 return 0; 126 } 127 } break; 128 } 129 130 return std::nullopt; 131 } 132 133 bool applyValidRelocs(MutableArrayRef<char>, uint64_t, bool) override { 134 // no need to apply relocations to the linked binary. 135 return false; 136 } 137 138 void clear() override {} 139 140 protected: 141 // returns true if specified address range is inside address ranges 142 // of executable sections. 143 bool isInsideExecutableSectionsAddressRange(uint64_t LowPC, 144 std::optional<uint64_t> HighPC) { 145 std::optional<AddressRange> Range = 146 TextAddressRanges.getRangeThatContains(LowPC); 147 148 if (HighPC) 149 return Range.has_value() && Range->end() >= *HighPC; 150 151 return Range.has_value(); 152 } 153 154 uint64_t isBFDDeadAddressRange(uint64_t LowPC, std::optional<uint64_t> HighPC, 155 uint16_t Version) { 156 if (LowPC == 0) 157 return true; 158 159 if ((Version <= 4) && HighPC && (LowPC == 1 && *HighPC == 1)) 160 return true; 161 162 return !isInsideExecutableSectionsAddressRange(LowPC, HighPC); 163 } 164 165 uint64_t isMAXPCDeadAddressRange(uint64_t LowPC, 166 std::optional<uint64_t> HighPC, 167 uint16_t Version, uint8_t AddressByteSize) { 168 if (Version <= 4 && HighPC) { 169 if (LowPC == (dwarf::computeTombstoneAddress(AddressByteSize) - 1)) 170 return true; 171 } else if (LowPC == dwarf::computeTombstoneAddress(AddressByteSize)) 172 return true; 173 174 if (!isInsideExecutableSectionsAddressRange(LowPC, HighPC)) 175 warning("Address referencing invalid text section is not marked with " 176 "tombstone value"); 177 178 return false; 179 } 180 181 bool isDeadAddressRange(uint64_t LowPC, std::optional<uint64_t> HighPC, 182 uint16_t Version, TombstoneKind Tombstone, 183 uint8_t AddressByteSize) { 184 switch (Tombstone) { 185 case TombstoneKind::BFD: 186 return isBFDDeadAddressRange(LowPC, HighPC, Version); 187 case TombstoneKind::MaxPC: 188 return isMAXPCDeadAddressRange(LowPC, HighPC, Version, AddressByteSize); 189 case TombstoneKind::Universal: 190 return isBFDDeadAddressRange(LowPC, HighPC, Version) || 191 isMAXPCDeadAddressRange(LowPC, HighPC, Version, AddressByteSize); 192 case TombstoneKind::Exec: 193 return !isInsideExecutableSectionsAddressRange(LowPC, HighPC); 194 } 195 196 llvm_unreachable("Unknown tombstone value"); 197 } 198 199 bool isDeadAddress(uint64_t LowPC, uint16_t Version, TombstoneKind Tombstone, 200 uint8_t AddressByteSize) { 201 return isDeadAddressRange(LowPC, std::nullopt, Version, Tombstone, 202 AddressByteSize); 203 } 204 205 private: 206 AddressRanges TextAddressRanges; 207 const Options &Opts; 208 bool HasValidAddressRanges = false; 209 }; 210 211 static bool knownByDWARFUtil(StringRef SecName) { 212 return llvm::StringSwitch<bool>(SecName) 213 .Case(".debug_info", true) 214 .Case(".debug_types", true) 215 .Case(".debug_abbrev", true) 216 .Case(".debug_loc", true) 217 .Case(".debug_loclists", true) 218 .Case(".debug_frame", true) 219 .Case(".debug_aranges", true) 220 .Case(".debug_ranges", true) 221 .Case(".debug_rnglists", true) 222 .Case(".debug_line", true) 223 .Case(".debug_line_str", true) 224 .Case(".debug_addr", true) 225 .Case(".debug_macro", true) 226 .Case(".debug_macinfo", true) 227 .Case(".debug_str", true) 228 .Case(".debug_str_offsets", true) 229 .Case(".debug_pubnames", true) 230 .Case(".debug_pubtypes", true) 231 .Case(".debug_names", true) 232 .Default(false); 233 } 234 235 template <typename AccelTableKind> 236 static std::optional<AccelTableKind> 237 getAcceleratorTableKind(StringRef SecName) { 238 return llvm::StringSwitch<std::optional<AccelTableKind>>(SecName) 239 .Case(".debug_pubnames", AccelTableKind::Pub) 240 .Case(".debug_pubtypes", AccelTableKind::Pub) 241 .Case(".debug_names", AccelTableKind::DebugNames) 242 .Default(std::nullopt); 243 } 244 245 static std::string getMessageForReplacedAcceleratorTables( 246 SmallVector<StringRef> &AccelTableNamesToReplace, 247 DwarfUtilAccelKind TargetTable) { 248 std::string Message; 249 250 Message += "'"; 251 for (StringRef Name : AccelTableNamesToReplace) { 252 if (Message.size() > 1) 253 Message += ", "; 254 Message += Name; 255 } 256 257 Message += "' will be replaced with requested "; 258 259 switch (TargetTable) { 260 case DwarfUtilAccelKind::DWARF: 261 Message += ".debug_names table"; 262 break; 263 264 default: 265 assert(false); 266 } 267 268 return Message; 269 } 270 271 static std::string getMessageForDeletedAcceleratorTables( 272 SmallVector<StringRef> &AccelTableNamesToReplace) { 273 std::string Message; 274 275 Message += "'"; 276 for (StringRef Name : AccelTableNamesToReplace) { 277 if (Message.size() > 1) 278 Message += ", "; 279 Message += Name; 280 } 281 282 Message += "' will be deleted as no accelerator tables are requested"; 283 284 return Message; 285 } 286 287 template <typename Linker, typename OutDwarfFile, typename AddressMapBase> 288 Error linkDebugInfoImpl(object::ObjectFile &File, const Options &Options, 289 raw_pwrite_stream &OutStream) { 290 auto ReportWarn = [&](const Twine &Message, StringRef Context, 291 const DWARFDie *Die) { 292 warning(Message, Context); 293 294 if (!Options.Verbose || !Die) 295 return; 296 297 DIDumpOptions DumpOpts; 298 DumpOpts.ChildRecurseDepth = 0; 299 DumpOpts.Verbose = Options.Verbose; 300 301 WithColor::note() << " in DIE:\n"; 302 Die->dump(errs(), /*Indent=*/6, DumpOpts); 303 }; 304 auto ReportErr = [&](const Twine &Message, StringRef Context, 305 const DWARFDie *) { 306 WithColor::error(errs(), Context) << Message << '\n'; 307 }; 308 309 // Create DWARF linker. 310 std::unique_ptr<Linker> DebugInfoLinker = 311 Linker::createLinker(ReportErr, ReportWarn); 312 313 Triple TargetTriple = File.makeTriple(); 314 if (Error Err = DebugInfoLinker->createEmitter( 315 TargetTriple, Linker::OutputFileType::Object, OutStream)) 316 return Err; 317 318 DebugInfoLinker->setEstimatedObjfilesAmount(1); 319 DebugInfoLinker->setNumThreads(Options.NumThreads); 320 DebugInfoLinker->setNoODR(!Options.DoODRDeduplication); 321 DebugInfoLinker->setVerbosity(Options.Verbose); 322 DebugInfoLinker->setUpdateIndexTablesOnly(!Options.DoGarbageCollection); 323 324 std::vector<std::unique_ptr<OutDwarfFile>> ObjectsForLinking(1); 325 std::vector<std::string> EmptyWarnings; 326 327 // Add object files to the DWARFLinker. 328 std::unique_ptr<DWARFContext> Context = DWARFContext::create(File); 329 std::unique_ptr<ObjFileAddressMap<AddressMapBase>> AddressesMap( 330 std::make_unique<ObjFileAddressMap<AddressMapBase>>(*Context, Options, 331 File)); 332 333 ObjectsForLinking[0] = 334 std::make_unique<OutDwarfFile>(File.getFileName(), std::move(Context), 335 std::move(AddressesMap), EmptyWarnings); 336 337 uint16_t MaxDWARFVersion = 0; 338 std::function<void(const DWARFUnit &Unit)> OnCUDieLoaded = 339 [&MaxDWARFVersion](const DWARFUnit &Unit) { 340 MaxDWARFVersion = std::max(Unit.getVersion(), MaxDWARFVersion); 341 }; 342 343 for (size_t I = 0; I < ObjectsForLinking.size(); I++) 344 DebugInfoLinker->addObjectFile(*ObjectsForLinking[I], nullptr, 345 OnCUDieLoaded); 346 347 // If we haven't seen any CUs, pick an arbitrary valid Dwarf version anyway. 348 if (MaxDWARFVersion == 0) 349 MaxDWARFVersion = 3; 350 351 if (Error Err = DebugInfoLinker->setTargetDWARFVersion(MaxDWARFVersion)) 352 return Err; 353 354 SmallVector<typename Linker::AccelTableKind> AccelTables; 355 356 switch (Options.AccelTableKind) { 357 case DwarfUtilAccelKind::None: 358 // Nothing to do. 359 break; 360 case DwarfUtilAccelKind::DWARF: 361 // use .debug_names for all DWARF versions. 362 AccelTables.push_back(Linker::AccelTableKind::DebugNames); 363 break; 364 } 365 366 // Add accelerator tables to DWARFLinker. 367 for (typename Linker::AccelTableKind Table : AccelTables) 368 DebugInfoLinker->addAccelTableKind(Table); 369 370 for (std::unique_ptr<OutDwarfFile> &CurFile : ObjectsForLinking) { 371 SmallVector<StringRef> AccelTableNamesToReplace; 372 SmallVector<StringRef> AccelTableNamesToDelete; 373 374 // Unknown debug sections or non-requested accelerator sections would be 375 // removed. Display warning for such sections. 376 for (SectionName Sec : CurFile->Dwarf->getDWARFObj().getSectionNames()) { 377 if (isDebugSection(Sec.Name)) { 378 std::optional<typename Linker::AccelTableKind> SrcAccelTableKind = 379 getAcceleratorTableKind<typename Linker::AccelTableKind>(Sec.Name); 380 381 if (SrcAccelTableKind) { 382 assert(knownByDWARFUtil(Sec.Name)); 383 384 if (Options.AccelTableKind == DwarfUtilAccelKind::None) 385 AccelTableNamesToDelete.push_back(Sec.Name); 386 else if (!llvm::is_contained(AccelTables, *SrcAccelTableKind)) 387 AccelTableNamesToReplace.push_back(Sec.Name); 388 } else if (!knownByDWARFUtil(Sec.Name)) { 389 assert(!SrcAccelTableKind); 390 warning( 391 formatv( 392 "'{0}' is not currently supported: section will be skipped", 393 Sec.Name), 394 Options.InputFileName); 395 } 396 } 397 } 398 399 // Display message for the replaced accelerator tables. 400 if (!AccelTableNamesToReplace.empty()) 401 warning(getMessageForReplacedAcceleratorTables(AccelTableNamesToReplace, 402 Options.AccelTableKind), 403 Options.InputFileName); 404 405 // Display message for the removed accelerator tables. 406 if (!AccelTableNamesToDelete.empty()) 407 warning(getMessageForDeletedAcceleratorTables(AccelTableNamesToDelete), 408 Options.InputFileName); 409 } 410 411 // Link debug info. 412 if (Error Err = DebugInfoLinker->link()) 413 return Err; 414 415 DebugInfoLinker->getEmitter()->finish(); 416 return Error::success(); 417 } 418 419 Error linkDebugInfo(object::ObjectFile &File, const Options &Options, 420 raw_pwrite_stream &OutStream) { 421 if (Options.UseLLVMDWARFLinker) 422 return linkDebugInfoImpl<dwarflinker_parallel::DWARFLinker, 423 dwarflinker_parallel::DWARFFile, 424 dwarflinker_parallel::AddressesMap>(File, Options, 425 OutStream); 426 else 427 return linkDebugInfoImpl<DWARFLinker, DWARFFile, AddressesMap>( 428 File, Options, OutStream); 429 } 430 431 } // end of namespace dwarfutil 432 } // end of namespace llvm 433