llvm/lib/DebugInfo/Symbolize/SymbolizableObjectFile.cpp

   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 }