1 //===- SymbolizableObjectFile.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 // Implementation of SymbolizableObjectFile class. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "SymbolizableObjectFile.h" 14 #include "llvm/ADT/STLExtras.h" 15 #include "llvm/ADT/Triple.h" 16 #include "llvm/BinaryFormat/COFF.h" 17 #include "llvm/DebugInfo/DWARF/DWARFContext.h" 18 #include "llvm/Object/COFF.h" 19 #include "llvm/Object/ELFObjectFile.h" 20 #include "llvm/Object/ObjectFile.h" 21 #include "llvm/Object/SymbolSize.h" 22 #include "llvm/Support/Casting.h" 23 #include "llvm/Support/DataExtractor.h" 24 #include <algorithm> 25 26 using namespace llvm; 27 using namespace object; 28 using namespace symbolize; 29 30 Expected<std::unique_ptr<SymbolizableObjectFile>> 31 SymbolizableObjectFile::create(const object::ObjectFile *Obj, 32 std::unique_ptr<DIContext> DICtx, 33 bool UntagAddresses) { 34 assert(DICtx); 35 std::unique_ptr<SymbolizableObjectFile> res( 36 new SymbolizableObjectFile(Obj, std::move(DICtx), UntagAddresses)); 37 std::unique_ptr<DataExtractor> OpdExtractor; 38 uint64_t OpdAddress = 0; 39 // Find the .opd (function descriptor) section if any, for big-endian 40 // PowerPC64 ELF. 41 if (Obj->getArch() == Triple::ppc64) { 42 for (section_iterator Section : Obj->sections()) { 43 Expected<StringRef> NameOrErr = Section->getName(); 44 if (!NameOrErr) 45 return NameOrErr.takeError(); 46 47 if (*NameOrErr == ".opd") { 48 Expected<StringRef> E = Section->getContents(); 49 if (!E) 50 return E.takeError(); 51 OpdExtractor.reset(new DataExtractor(*E, Obj->isLittleEndian(), 52 Obj->getBytesInAddress())); 53 OpdAddress = Section->getAddress(); 54 break; 55 } 56 } 57 } 58 std::vector<std::pair<SymbolRef, uint64_t>> Symbols = 59 computeSymbolSizes(*Obj); 60 for (auto &P : Symbols) 61 if (Error E = 62 res->addSymbol(P.first, P.second, OpdExtractor.get(), OpdAddress)) 63 return std::move(E); 64 65 // If this is a COFF object and we didn't find any symbols, try the export 66 // table. 67 if (Symbols.empty()) { 68 if (auto *CoffObj = dyn_cast<COFFObjectFile>(Obj)) 69 if (Error E = res->addCoffExportSymbols(CoffObj)) 70 return std::move(E); 71 } 72 73 std::vector<SymbolDesc> &SS = res->Symbols; 74 // Sort by (Addr,Size,Name). If several SymbolDescs share the same Addr, 75 // pick the one with the largest Size. This helps us avoid symbols with no 76 // size information (Size=0). 77 llvm::stable_sort(SS); 78 auto I = SS.begin(), E = SS.end(), J = SS.begin(); 79 while (I != E) { 80 auto OI = I; 81 while (++I != E && OI->Addr == I->Addr) { 82 } 83 *J++ = I[-1]; 84 } 85 SS.erase(J, SS.end()); 86 87 return std::move(res); 88 } 89 90 SymbolizableObjectFile::SymbolizableObjectFile(const ObjectFile *Obj, 91 std::unique_ptr<DIContext> DICtx, 92 bool UntagAddresses) 93 : Module(Obj), DebugInfoContext(std::move(DICtx)), 94 UntagAddresses(UntagAddresses) {} 95 96 namespace { 97 98 struct OffsetNamePair { 99 uint32_t Offset; 100 StringRef Name; 101 102 bool operator<(const OffsetNamePair &R) const { 103 return Offset < R.Offset; 104 } 105 }; 106 107 } // end anonymous namespace 108 109 Error SymbolizableObjectFile::addCoffExportSymbols( 110 const COFFObjectFile *CoffObj) { 111 // Get all export names and offsets. 112 std::vector<OffsetNamePair> ExportSyms; 113 for (const ExportDirectoryEntryRef &Ref : CoffObj->export_directories()) { 114 StringRef Name; 115 uint32_t Offset; 116 if (auto EC = Ref.getSymbolName(Name)) 117 return EC; 118 if (auto EC = Ref.getExportRVA(Offset)) 119 return EC; 120 ExportSyms.push_back(OffsetNamePair{Offset, Name}); 121 } 122 if (ExportSyms.empty()) 123 return Error::success(); 124 125 // Sort by ascending offset. 126 array_pod_sort(ExportSyms.begin(), ExportSyms.end()); 127 128 // Approximate the symbol sizes by assuming they run to the next symbol. 129 // FIXME: This assumes all exports are functions. 130 uint64_t ImageBase = CoffObj->getImageBase(); 131 for (auto I = ExportSyms.begin(), E = ExportSyms.end(); I != E; ++I) { 132 OffsetNamePair &Export = *I; 133 // FIXME: The last export has a one byte size now. 134 uint32_t NextOffset = I != E ? I->Offset : Export.Offset + 1; 135 uint64_t SymbolStart = ImageBase + Export.Offset; 136 uint64_t SymbolSize = NextOffset - Export.Offset; 137 Symbols.push_back({SymbolStart, SymbolSize, Export.Name, 0}); 138 } 139 return Error::success(); 140 } 141 142 Error SymbolizableObjectFile::addSymbol(const SymbolRef &Symbol, 143 uint64_t SymbolSize, 144 DataExtractor *OpdExtractor, 145 uint64_t OpdAddress) { 146 // Avoid adding symbols from an unknown/undefined section. 147 const ObjectFile &Obj = *Symbol.getObject(); 148 Expected<StringRef> SymbolNameOrErr = Symbol.getName(); 149 if (!SymbolNameOrErr) 150 return SymbolNameOrErr.takeError(); 151 StringRef SymbolName = *SymbolNameOrErr; 152 153 uint32_t ELFSymIdx = 154 Obj.isELF() ? ELFSymbolRef(Symbol).getRawDataRefImpl().d.b : 0; 155 Expected<section_iterator> Sec = Symbol.getSection(); 156 if (!Sec || Obj.section_end() == *Sec) { 157 if (Obj.isELF()) { 158 // Store the (index, filename) pair for a file symbol. 159 ELFSymbolRef ESym(Symbol); 160 if (ESym.getELFType() == ELF::STT_FILE) 161 FileSymbols.emplace_back(ELFSymIdx, SymbolName); 162 } 163 return Error::success(); 164 } 165 166 Expected<SymbolRef::Type> SymbolTypeOrErr = Symbol.getType(); 167 if (!SymbolTypeOrErr) 168 return SymbolTypeOrErr.takeError(); 169 SymbolRef::Type SymbolType = *SymbolTypeOrErr; 170 if (Obj.isELF()) { 171 // Allow function and data symbols. Additionally allow STT_NONE, which are 172 // common for functions defined in assembly. 173 uint8_t Type = ELFSymbolRef(Symbol).getELFType(); 174 if (Type != ELF::STT_NOTYPE && Type != ELF::STT_FUNC && 175 Type != ELF::STT_OBJECT && Type != ELF::STT_GNU_IFUNC) 176 return Error::success(); 177 // Some STT_NOTYPE symbols are not desired. This excludes STT_SECTION and 178 // ARM mapping symbols. 179 uint32_t Flags = cantFail(Symbol.getFlags()); 180 if (Flags & SymbolRef::SF_FormatSpecific) 181 return Error::success(); 182 } else if (SymbolType != SymbolRef::ST_Function && 183 SymbolType != SymbolRef::ST_Data) { 184 return Error::success(); 185 } 186 187 Expected<uint64_t> SymbolAddressOrErr = Symbol.getAddress(); 188 if (!SymbolAddressOrErr) 189 return SymbolAddressOrErr.takeError(); 190 uint64_t SymbolAddress = *SymbolAddressOrErr; 191 if (UntagAddresses) { 192 // For kernel addresses, bits 56-63 need to be set, so we sign extend bit 55 193 // into bits 56-63 instead of masking them out. 194 SymbolAddress &= (1ull << 56) - 1; 195 SymbolAddress = (int64_t(SymbolAddress) << 8) >> 8; 196 } 197 if (OpdExtractor) { 198 // For big-endian PowerPC64 ELF, symbols in the .opd section refer to 199 // function descriptors. The first word of the descriptor is a pointer to 200 // the function's code. 201 // For the purposes of symbolization, pretend the symbol's address is that 202 // of the function's code, not the descriptor. 203 uint64_t OpdOffset = SymbolAddress - OpdAddress; 204 if (OpdExtractor->isValidOffsetForAddress(OpdOffset)) 205 SymbolAddress = OpdExtractor->getAddress(&OpdOffset); 206 } 207 // Mach-O symbol table names have leading underscore, skip it. 208 if (Module->isMachO() && !SymbolName.empty() && SymbolName[0] == '_') 209 SymbolName = SymbolName.drop_front(); 210 211 if (Obj.isELF() && ELFSymbolRef(Symbol).getBinding() != ELF::STB_LOCAL) 212 ELFSymIdx = 0; 213 Symbols.push_back({SymbolAddress, SymbolSize, SymbolName, ELFSymIdx}); 214 return Error::success(); 215 } 216 217 // Return true if this is a 32-bit x86 PE COFF module. 218 bool SymbolizableObjectFile::isWin32Module() const { 219 auto *CoffObject = dyn_cast<COFFObjectFile>(Module); 220 return CoffObject && CoffObject->getMachine() == COFF::IMAGE_FILE_MACHINE_I386; 221 } 222 223 uint64_t SymbolizableObjectFile::getModulePreferredBase() const { 224 if (auto *CoffObject = dyn_cast<COFFObjectFile>(Module)) 225 return CoffObject->getImageBase(); 226 return 0; 227 } 228 229 bool SymbolizableObjectFile::getNameFromSymbolTable( 230 uint64_t Address, std::string &Name, uint64_t &Addr, uint64_t &Size, 231 std::string &FileName) const { 232 SymbolDesc SD{Address, UINT64_C(-1), StringRef(), 0}; 233 auto SymbolIterator = llvm::upper_bound(Symbols, SD); 234 if (SymbolIterator == Symbols.begin()) 235 return false; 236 --SymbolIterator; 237 if (SymbolIterator->Size != 0 && 238 SymbolIterator->Addr + SymbolIterator->Size <= Address) 239 return false; 240 Name = SymbolIterator->Name.str(); 241 Addr = SymbolIterator->Addr; 242 Size = SymbolIterator->Size; 243 244 if (SymbolIterator->ELFLocalSymIdx != 0) { 245 // If this is an ELF local symbol, find the STT_FILE symbol preceding 246 // SymbolIterator to get the filename. The ELF spec requires the STT_FILE 247 // symbol (if present) precedes the other STB_LOCAL symbols for the file. 248 assert(Module->isELF()); 249 auto It = llvm::upper_bound( 250 FileSymbols, 251 std::make_pair(SymbolIterator->ELFLocalSymIdx, StringRef())); 252 if (It != FileSymbols.begin()) 253 FileName = It[-1].second.str(); 254 } 255 return true; 256 } 257 258 bool SymbolizableObjectFile::shouldOverrideWithSymbolTable( 259 FunctionNameKind FNKind, bool UseSymbolTable) const { 260 // When DWARF is used with -gline-tables-only / -gmlt, the symbol table gives 261 // better answers for linkage names than the DIContext. Otherwise, we are 262 // probably using PEs and PDBs, and we shouldn't do the override. PE files 263 // generally only contain the names of exported symbols. 264 return FNKind == FunctionNameKind::LinkageName && UseSymbolTable && 265 isa<DWARFContext>(DebugInfoContext.get()); 266 } 267 268 DILineInfo 269 SymbolizableObjectFile::symbolizeCode(object::SectionedAddress ModuleOffset, 270 DILineInfoSpecifier LineInfoSpecifier, 271 bool UseSymbolTable) const { 272 if (ModuleOffset.SectionIndex == object::SectionedAddress::UndefSection) 273 ModuleOffset.SectionIndex = 274 getModuleSectionIndexForAddress(ModuleOffset.Address); 275 DILineInfo LineInfo = 276 DebugInfoContext->getLineInfoForAddress(ModuleOffset, LineInfoSpecifier); 277 278 // Override function name from symbol table if necessary. 279 if (shouldOverrideWithSymbolTable(LineInfoSpecifier.FNKind, UseSymbolTable)) { 280 std::string FunctionName, FileName; 281 uint64_t Start, Size; 282 if (getNameFromSymbolTable(ModuleOffset.Address, FunctionName, Start, Size, 283 FileName)) { 284 LineInfo.FunctionName = FunctionName; 285 LineInfo.StartAddress = Start; 286 if (LineInfo.FileName == DILineInfo::BadString && !FileName.empty()) 287 LineInfo.FileName = FileName; 288 } 289 } 290 return LineInfo; 291 } 292 293 DIInliningInfo SymbolizableObjectFile::symbolizeInlinedCode( 294 object::SectionedAddress ModuleOffset, 295 DILineInfoSpecifier LineInfoSpecifier, bool UseSymbolTable) const { 296 if (ModuleOffset.SectionIndex == object::SectionedAddress::UndefSection) 297 ModuleOffset.SectionIndex = 298 getModuleSectionIndexForAddress(ModuleOffset.Address); 299 DIInliningInfo InlinedContext = DebugInfoContext->getInliningInfoForAddress( 300 ModuleOffset, LineInfoSpecifier); 301 302 // Make sure there is at least one frame in context. 303 if (InlinedContext.getNumberOfFrames() == 0) 304 InlinedContext.addFrame(DILineInfo()); 305 306 // Override the function name in lower frame with name from symbol table. 307 if (shouldOverrideWithSymbolTable(LineInfoSpecifier.FNKind, UseSymbolTable)) { 308 std::string FunctionName, FileName; 309 uint64_t Start, Size; 310 if (getNameFromSymbolTable(ModuleOffset.Address, FunctionName, Start, Size, 311 FileName)) { 312 DILineInfo *LI = InlinedContext.getMutableFrame( 313 InlinedContext.getNumberOfFrames() - 1); 314 LI->FunctionName = FunctionName; 315 LI->StartAddress = Start; 316 if (LI->FileName == DILineInfo::BadString && !FileName.empty()) 317 LI->FileName = FileName; 318 } 319 } 320 321 return InlinedContext; 322 } 323 324 DIGlobal SymbolizableObjectFile::symbolizeData( 325 object::SectionedAddress ModuleOffset) const { 326 DIGlobal Res; 327 std::string FileName; 328 getNameFromSymbolTable(ModuleOffset.Address, Res.Name, Res.Start, Res.Size, 329 FileName); 330 return Res; 331 } 332 333 std::vector<DILocal> SymbolizableObjectFile::symbolizeFrame( 334 object::SectionedAddress ModuleOffset) const { 335 if (ModuleOffset.SectionIndex == object::SectionedAddress::UndefSection) 336 ModuleOffset.SectionIndex = 337 getModuleSectionIndexForAddress(ModuleOffset.Address); 338 return DebugInfoContext->getLocalsForAddress(ModuleOffset); 339 } 340 341 /// Search for the first occurence of specified Address in ObjectFile. 342 uint64_t SymbolizableObjectFile::getModuleSectionIndexForAddress( 343 uint64_t Address) const { 344 345 for (SectionRef Sec : Module->sections()) { 346 if (!Sec.isText() || Sec.isVirtual()) 347 continue; 348 349 if (Address >= Sec.getAddress() && 350 Address < Sec.getAddress() + Sec.getSize()) 351 return Sec.getIndex(); 352 } 353 354 return object::SectionedAddress::UndefSection; 355 } 356