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