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/DebugInfo/DWARF/DWARFContext.h" 15 #include "llvm/DebugInfo/DWARF/DWARFExpression.h" 16 #include "llvm/Object/ObjectFile.h" 17 #include "llvm/Support/Endian.h" 18 #include <memory> 19 #include <vector> 20 21 namespace llvm { 22 namespace dwarfutil { 23 24 // ObjFileAddressMap allows to check whether specified DIE referencing 25 // dead addresses. It uses tombstone values to determine dead addresses. 26 // The concrete values of tombstone constants were discussed in 27 // https://reviews.llvm.org/D81784 and https://reviews.llvm.org/D84825. 28 // So we use following values as indicators of dead addresses: 29 // 30 // bfd: (LowPC == 0) or (LowPC == 1 and HighPC == 1 and DWARF v4 (or less)) 31 // or ([LowPC, HighPC] is not inside address ranges of .text sections). 32 // 33 // maxpc: (LowPC == -1) or (LowPC == -2 and DWARF v4 (or less)) 34 // That value is assumed to be compatible with 35 // http://www.dwarfstd.org/ShowIssue.php?issue=200609.1 36 // 37 // exec: [LowPC, HighPC] is not inside address ranges of .text sections 38 // 39 // universal: maxpc and bfd 40 class ObjFileAddressMap : public AddressesMap { 41 public: 42 ObjFileAddressMap(DWARFContext &Context, const Options &Options, 43 object::ObjectFile &ObjFile) 44 : Opts(Options) { 45 // Remember addresses of existing text sections. 46 for (const object::SectionRef &Sect : ObjFile.sections()) { 47 if (!Sect.isText()) 48 continue; 49 const uint64_t Size = Sect.getSize(); 50 if (Size == 0) 51 continue; 52 const uint64_t StartAddr = Sect.getAddress(); 53 TextAddressRanges.insert({StartAddr, StartAddr + Size}); 54 } 55 56 // Check CU address ranges for tombstone value. 57 for (std::unique_ptr<DWARFUnit> &CU : Context.compile_units()) { 58 Expected<llvm::DWARFAddressRangesVector> ARanges = 59 CU->getUnitDIE().getAddressRanges(); 60 if (ARanges) { 61 for (auto &Range : *ARanges) { 62 if (!isDeadAddressRange(Range.LowPC, Range.HighPC, CU->getVersion(), 63 Options.Tombstone, CU->getAddressByteSize())) 64 DWARFAddressRanges.insert({Range.LowPC, Range.HighPC}, 0); 65 } 66 } 67 } 68 } 69 70 // should be renamed into has valid address ranges 71 bool hasValidRelocs() override { return !DWARFAddressRanges.empty(); } 72 73 bool isLiveSubprogram(const DWARFDie &DIE, 74 CompileUnit::DIEInfo &Info) override { 75 assert((DIE.getTag() == dwarf::DW_TAG_subprogram || 76 DIE.getTag() == dwarf::DW_TAG_label) && 77 "Wrong type of input die"); 78 79 if (std::optional<uint64_t> LowPC = 80 dwarf::toAddress(DIE.find(dwarf::DW_AT_low_pc))) { 81 if (!isDeadAddress(*LowPC, DIE.getDwarfUnit()->getVersion(), 82 Opts.Tombstone, 83 DIE.getDwarfUnit()->getAddressByteSize())) { 84 Info.AddrAdjust = 0; 85 Info.InDebugMap = true; 86 return true; 87 } 88 } 89 90 return false; 91 } 92 93 bool isLiveVariable(const DWARFDie &DIE, 94 CompileUnit::DIEInfo &Info) override { 95 assert((DIE.getTag() == dwarf::DW_TAG_variable || 96 DIE.getTag() == dwarf::DW_TAG_constant) && 97 "Wrong type of input die"); 98 99 if (Expected<DWARFLocationExpressionsVector> Loc = 100 DIE.getLocations(dwarf::DW_AT_location)) { 101 DWARFUnit *U = DIE.getDwarfUnit(); 102 for (const auto &Entry : *Loc) { 103 DataExtractor Data(toStringRef(Entry.Expr), 104 U->getContext().isLittleEndian(), 0); 105 DWARFExpression Expression(Data, U->getAddressByteSize(), 106 U->getFormParams().Format); 107 bool HasLiveAddresses = 108 any_of(Expression, [&](const DWARFExpression::Operation &Op) { 109 // TODO: add handling of dwarf::DW_OP_addrx 110 return !Op.isError() && 111 (Op.getCode() == dwarf::DW_OP_addr && 112 !isDeadAddress(Op.getRawOperand(0), U->getVersion(), 113 Opts.Tombstone, 114 DIE.getDwarfUnit()->getAddressByteSize())); 115 }); 116 117 if (HasLiveAddresses) { 118 Info.AddrAdjust = 0; 119 Info.InDebugMap = true; 120 return true; 121 } 122 } 123 } else { 124 // FIXME: missing DW_AT_location is OK here, but other errors should be 125 // reported to the user. 126 consumeError(Loc.takeError()); 127 } 128 129 return false; 130 } 131 132 bool applyValidRelocs(MutableArrayRef<char>, uint64_t, bool) override { 133 // no need to apply relocations to the linked binary. 134 return false; 135 } 136 137 RangesTy &getValidAddressRanges() override { return DWARFAddressRanges; }; 138 139 void clear() override { DWARFAddressRanges.clear(); } 140 141 protected: 142 // returns true if specified address range is inside address ranges 143 // of executable sections. 144 bool isInsideExecutableSectionsAddressRange(uint64_t LowPC, 145 std::optional<uint64_t> HighPC) { 146 std::optional<AddressRange> Range = 147 TextAddressRanges.getRangeThatContains(LowPC); 148 149 if (HighPC) 150 return Range.has_value() && Range->end() >= *HighPC; 151 152 return Range.has_value(); 153 } 154 155 uint64_t isBFDDeadAddressRange(uint64_t LowPC, std::optional<uint64_t> HighPC, 156 uint16_t Version) { 157 if (LowPC == 0) 158 return true; 159 160 if ((Version <= 4) && HighPC && (LowPC == 1 && *HighPC == 1)) 161 return true; 162 163 return !isInsideExecutableSectionsAddressRange(LowPC, HighPC); 164 } 165 166 uint64_t isMAXPCDeadAddressRange(uint64_t LowPC, 167 std::optional<uint64_t> HighPC, 168 uint16_t Version, uint8_t AddressByteSize) { 169 if (Version <= 4 && HighPC) { 170 if (LowPC == (dwarf::computeTombstoneAddress(AddressByteSize) - 1)) 171 return true; 172 } else if (LowPC == dwarf::computeTombstoneAddress(AddressByteSize)) 173 return true; 174 175 if (!isInsideExecutableSectionsAddressRange(LowPC, HighPC)) 176 warning("Address referencing invalid text section is not marked with " 177 "tombstone value"); 178 179 return false; 180 } 181 182 bool isDeadAddressRange(uint64_t LowPC, std::optional<uint64_t> HighPC, 183 uint16_t Version, TombstoneKind Tombstone, 184 uint8_t AddressByteSize) { 185 switch (Tombstone) { 186 case TombstoneKind::BFD: 187 return isBFDDeadAddressRange(LowPC, HighPC, Version); 188 case TombstoneKind::MaxPC: 189 return isMAXPCDeadAddressRange(LowPC, HighPC, Version, AddressByteSize); 190 case TombstoneKind::Universal: 191 return isBFDDeadAddressRange(LowPC, HighPC, Version) || 192 isMAXPCDeadAddressRange(LowPC, HighPC, Version, AddressByteSize); 193 case TombstoneKind::Exec: 194 return !isInsideExecutableSectionsAddressRange(LowPC, HighPC); 195 } 196 197 llvm_unreachable("Unknown tombstone value"); 198 } 199 200 bool isDeadAddress(uint64_t LowPC, uint16_t Version, TombstoneKind Tombstone, 201 uint8_t AddressByteSize) { 202 return isDeadAddressRange(LowPC, std::nullopt, Version, Tombstone, 203 AddressByteSize); 204 } 205 206 private: 207 RangesTy DWARFAddressRanges; 208 AddressRanges TextAddressRanges; 209 const Options &Opts; 210 }; 211 212 static bool knownByDWARFUtil(StringRef SecName) { 213 return llvm::StringSwitch<bool>(SecName) 214 .Case(".debug_info", true) 215 .Case(".debug_types", true) 216 .Case(".debug_abbrev", true) 217 .Case(".debug_loc", true) 218 .Case(".debug_loclists", true) 219 .Case(".debug_frame", true) 220 .Case(".debug_aranges", true) 221 .Case(".debug_ranges", true) 222 .Case(".debug_rnglists", true) 223 .Case(".debug_line", true) 224 .Case(".debug_line_str", true) 225 .Case(".debug_addr", true) 226 .Case(".debug_macro", true) 227 .Case(".debug_macinfo", true) 228 .Case(".debug_str", true) 229 .Case(".debug_str_offsets", true) 230 .Case(".debug_pubnames", true) 231 .Case(".debug_pubtypes", true) 232 .Case(".debug_names", true) 233 .Default(false); 234 } 235 236 static std::optional<DwarfLinkerAccelTableKind> 237 getAcceleratorTableKind(StringRef SecName) { 238 return llvm::StringSwitch<std::optional<DwarfLinkerAccelTableKind>>(SecName) 239 .Case(".debug_pubnames", DwarfLinkerAccelTableKind::Pub) 240 .Case(".debug_pubtypes", DwarfLinkerAccelTableKind::Pub) 241 .Case(".debug_names", DwarfLinkerAccelTableKind::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 Error linkDebugInfo(object::ObjectFile &File, const Options &Options, 288 raw_pwrite_stream &OutStream) { 289 290 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 output streamer. 310 DwarfStreamer OutStreamer(OutputFileType::Object, OutStream, nullptr, 311 ReportWarn, ReportWarn); 312 Triple TargetTriple = File.makeTriple(); 313 if (!OutStreamer.init(TargetTriple, formatv("cannot create a stream for {0}", 314 TargetTriple.getTriple()) 315 .str())) 316 return createStringError(std::errc::invalid_argument, ""); 317 318 std::unique_ptr<DWARFContext> Context = DWARFContext::create(File); 319 320 // Create DWARF linker. 321 DWARFLinker DebugInfoLinker(&OutStreamer, DwarfLinkerClient::LLD); 322 323 DebugInfoLinker.setEstimatedObjfilesAmount(1); 324 DebugInfoLinker.setErrorHandler(ReportErr); 325 DebugInfoLinker.setWarningHandler(ReportWarn); 326 DebugInfoLinker.setNumThreads(Options.NumThreads); 327 DebugInfoLinker.setNoODR(!Options.DoODRDeduplication); 328 DebugInfoLinker.setVerbosity(Options.Verbose); 329 DebugInfoLinker.setUpdate(!Options.DoGarbageCollection); 330 331 std::vector<std::unique_ptr<DWARFFile>> ObjectsForLinking(1); 332 std::vector<std::unique_ptr<AddressesMap>> AddresssMapForLinking(1); 333 std::vector<std::string> EmptyWarnings; 334 335 // Add object files to the DWARFLinker. 336 AddresssMapForLinking[0] = 337 std::make_unique<ObjFileAddressMap>(*Context, Options, File); 338 339 ObjectsForLinking[0] = std::make_unique<DWARFFile>( 340 File.getFileName(), &*Context, AddresssMapForLinking[0].get(), 341 EmptyWarnings); 342 343 uint16_t MaxDWARFVersion = 0; 344 std::function<void(const DWARFUnit &Unit)> OnCUDieLoaded = 345 [&MaxDWARFVersion](const DWARFUnit &Unit) { 346 MaxDWARFVersion = std::max(Unit.getVersion(), MaxDWARFVersion); 347 }; 348 349 for (size_t I = 0; I < ObjectsForLinking.size(); I++) 350 DebugInfoLinker.addObjectFile(*ObjectsForLinking[I], nullptr, 351 OnCUDieLoaded); 352 353 // If we haven't seen any CUs, pick an arbitrary valid Dwarf version anyway. 354 if (MaxDWARFVersion == 0) 355 MaxDWARFVersion = 3; 356 357 if (Error Err = DebugInfoLinker.setTargetDWARFVersion(MaxDWARFVersion)) 358 return Err; 359 360 SmallVector<DwarfLinkerAccelTableKind> AccelTables; 361 362 switch (Options.AccelTableKind) { 363 case DwarfUtilAccelKind::None: 364 // Nothing to do. 365 break; 366 case DwarfUtilAccelKind::DWARF: 367 // use .debug_names for all DWARF versions. 368 AccelTables.push_back(DwarfLinkerAccelTableKind::DebugNames); 369 break; 370 } 371 372 // Add accelerator tables to DWARFLinker. 373 for (DwarfLinkerAccelTableKind Table : AccelTables) 374 DebugInfoLinker.addAccelTableKind(Table); 375 376 SmallVector<StringRef> AccelTableNamesToReplace; 377 SmallVector<StringRef> AccelTableNamesToDelete; 378 379 // Unknown debug sections or non-requested accelerator sections would be 380 // removed. Display warning for such sections. 381 for (SectionName Sec : Context->getDWARFObj().getSectionNames()) { 382 if (isDebugSection(Sec.Name)) { 383 std::optional<DwarfLinkerAccelTableKind> SrcAccelTableKind = 384 getAcceleratorTableKind(Sec.Name); 385 386 if (SrcAccelTableKind) { 387 assert(knownByDWARFUtil(Sec.Name)); 388 389 if (Options.AccelTableKind == DwarfUtilAccelKind::None) 390 AccelTableNamesToDelete.push_back(Sec.Name); 391 else if (std::find(AccelTables.begin(), AccelTables.end(), 392 *SrcAccelTableKind) == AccelTables.end()) 393 AccelTableNamesToReplace.push_back(Sec.Name); 394 } else if (!knownByDWARFUtil(Sec.Name)) { 395 assert(!SrcAccelTableKind); 396 warning( 397 formatv("'{0}' is not currently supported: section will be skipped", 398 Sec.Name), 399 Options.InputFileName); 400 } 401 } 402 } 403 404 // Display message for the replaced accelerator tables. 405 if (!AccelTableNamesToReplace.empty()) 406 warning(getMessageForReplacedAcceleratorTables(AccelTableNamesToReplace, 407 Options.AccelTableKind), 408 Options.InputFileName); 409 410 // Display message for the removed accelerator tables. 411 if (!AccelTableNamesToDelete.empty()) 412 warning(getMessageForDeletedAcceleratorTables(AccelTableNamesToDelete), 413 Options.InputFileName); 414 415 // Link debug info. 416 if (Error Err = DebugInfoLinker.link()) 417 return Err; 418 419 OutStreamer.finish(); 420 return Error::success(); 421 } 422 423 } // end of namespace dwarfutil 424 } // end of namespace llvm 425