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