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      1 //===-- SymbolizableObjectFile.cpp ----------------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // Implementation of SymbolizableObjectFile class.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "SymbolizableObjectFile.h"
     15 #include "llvm/Object/SymbolSize.h"
     16 #include "llvm/Support/DataExtractor.h"
     17 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
     18 
     19 namespace llvm {
     20 namespace symbolize {
     21 
     22 using namespace object;
     23 
     24 static DILineInfoSpecifier
     25 getDILineInfoSpecifier(FunctionNameKind FNKind) {
     26   return DILineInfoSpecifier(
     27       DILineInfoSpecifier::FileLineInfoKind::AbsoluteFilePath, FNKind);
     28 }
     29 
     30 ErrorOr<std::unique_ptr<SymbolizableObjectFile>>
     31 SymbolizableObjectFile::create(object::ObjectFile *Obj,
     32                                std::unique_ptr<DIContext> DICtx) {
     33   std::unique_ptr<SymbolizableObjectFile> res(
     34       new SymbolizableObjectFile(Obj, std::move(DICtx)));
     35   std::unique_ptr<DataExtractor> OpdExtractor;
     36   uint64_t OpdAddress = 0;
     37   // Find the .opd (function descriptor) section if any, for big-endian
     38   // PowerPC64 ELF.
     39   if (Obj->getArch() == Triple::ppc64) {
     40     for (section_iterator Section : Obj->sections()) {
     41       StringRef Name;
     42       StringRef Data;
     43       if (auto EC = Section->getName(Name))
     44         return EC;
     45       if (Name == ".opd") {
     46         if (auto EC = Section->getContents(Data))
     47           return EC;
     48         OpdExtractor.reset(new DataExtractor(Data, Obj->isLittleEndian(),
     49                                              Obj->getBytesInAddress()));
     50         OpdAddress = Section->getAddress();
     51         break;
     52       }
     53     }
     54   }
     55   std::vector<std::pair<SymbolRef, uint64_t>> Symbols =
     56       computeSymbolSizes(*Obj);
     57   for (auto &P : Symbols)
     58     res->addSymbol(P.first, P.second, OpdExtractor.get(), OpdAddress);
     59 
     60   // If this is a COFF object and we didn't find any symbols, try the export
     61   // table.
     62   if (Symbols.empty()) {
     63     if (auto *CoffObj = dyn_cast<COFFObjectFile>(Obj))
     64       if (auto EC = res->addCoffExportSymbols(CoffObj))
     65         return EC;
     66   }
     67   return std::move(res);
     68 }
     69 
     70 SymbolizableObjectFile::SymbolizableObjectFile(ObjectFile *Obj,
     71                                                std::unique_ptr<DIContext> DICtx)
     72     : Module(Obj), DebugInfoContext(std::move(DICtx)) {}
     73 
     74 namespace {
     75 struct OffsetNamePair {
     76   uint32_t Offset;
     77   StringRef Name;
     78   bool operator<(const OffsetNamePair &R) const {
     79     return Offset < R.Offset;
     80   }
     81 };
     82 }
     83 
     84 std::error_code SymbolizableObjectFile::addCoffExportSymbols(
     85     const COFFObjectFile *CoffObj) {
     86   // Get all export names and offsets.
     87   std::vector<OffsetNamePair> ExportSyms;
     88   for (const ExportDirectoryEntryRef &Ref : CoffObj->export_directories()) {
     89     StringRef Name;
     90     uint32_t Offset;
     91     if (auto EC = Ref.getSymbolName(Name))
     92       return EC;
     93     if (auto EC = Ref.getExportRVA(Offset))
     94       return EC;
     95     ExportSyms.push_back(OffsetNamePair{Offset, Name});
     96   }
     97   if (ExportSyms.empty())
     98     return std::error_code();
     99 
    100   // Sort by ascending offset.
    101   array_pod_sort(ExportSyms.begin(), ExportSyms.end());
    102 
    103   // Approximate the symbol sizes by assuming they run to the next symbol.
    104   // FIXME: This assumes all exports are functions.
    105   uint64_t ImageBase = CoffObj->getImageBase();
    106   for (auto I = ExportSyms.begin(), E = ExportSyms.end(); I != E; ++I) {
    107     OffsetNamePair &Export = *I;
    108     // FIXME: The last export has a one byte size now.
    109     uint32_t NextOffset = I != E ? I->Offset : Export.Offset + 1;
    110     uint64_t SymbolStart = ImageBase + Export.Offset;
    111     uint64_t SymbolSize = NextOffset - Export.Offset;
    112     SymbolDesc SD = {SymbolStart, SymbolSize};
    113     Functions.insert(std::make_pair(SD, Export.Name));
    114   }
    115   return std::error_code();
    116 }
    117 
    118 std::error_code SymbolizableObjectFile::addSymbol(const SymbolRef &Symbol,
    119                                                   uint64_t SymbolSize,
    120                                                   DataExtractor *OpdExtractor,
    121                                                   uint64_t OpdAddress) {
    122   SymbolRef::Type SymbolType = Symbol.getType();
    123   if (SymbolType != SymbolRef::ST_Function && SymbolType != SymbolRef::ST_Data)
    124     return std::error_code();
    125   ErrorOr<uint64_t> SymbolAddressOrErr = Symbol.getAddress();
    126   if (auto EC = SymbolAddressOrErr.getError())
    127     return EC;
    128   uint64_t SymbolAddress = *SymbolAddressOrErr;
    129   if (OpdExtractor) {
    130     // For big-endian PowerPC64 ELF, symbols in the .opd section refer to
    131     // function descriptors. The first word of the descriptor is a pointer to
    132     // the function's code.
    133     // For the purposes of symbolization, pretend the symbol's address is that
    134     // of the function's code, not the descriptor.
    135     uint64_t OpdOffset = SymbolAddress - OpdAddress;
    136     uint32_t OpdOffset32 = OpdOffset;
    137     if (OpdOffset == OpdOffset32 &&
    138         OpdExtractor->isValidOffsetForAddress(OpdOffset32))
    139       SymbolAddress = OpdExtractor->getAddress(&OpdOffset32);
    140   }
    141   ErrorOr<StringRef> SymbolNameOrErr = Symbol.getName();
    142   if (auto EC = SymbolNameOrErr.getError())
    143     return EC;
    144   StringRef SymbolName = *SymbolNameOrErr;
    145   // Mach-O symbol table names have leading underscore, skip it.
    146   if (Module->isMachO() && SymbolName.size() > 0 && SymbolName[0] == '_')
    147     SymbolName = SymbolName.drop_front();
    148   // FIXME: If a function has alias, there are two entries in symbol table
    149   // with same address size. Make sure we choose the correct one.
    150   auto &M = SymbolType == SymbolRef::ST_Function ? Functions : Objects;
    151   SymbolDesc SD = { SymbolAddress, SymbolSize };
    152   M.insert(std::make_pair(SD, SymbolName));
    153   return std::error_code();
    154 }
    155 
    156 // Return true if this is a 32-bit x86 PE COFF module.
    157 bool SymbolizableObjectFile::isWin32Module() const {
    158   auto *CoffObject = dyn_cast<COFFObjectFile>(Module);
    159   return CoffObject && CoffObject->getMachine() == COFF::IMAGE_FILE_MACHINE_I386;
    160 }
    161 
    162 uint64_t SymbolizableObjectFile::getModulePreferredBase() const {
    163   if (auto *CoffObject = dyn_cast<COFFObjectFile>(Module))
    164     return CoffObject->getImageBase();
    165   return 0;
    166 }
    167 
    168 bool SymbolizableObjectFile::getNameFromSymbolTable(SymbolRef::Type Type,
    169                                                     uint64_t Address,
    170                                                     std::string &Name,
    171                                                     uint64_t &Addr,
    172                                                     uint64_t &Size) const {
    173   const auto &SymbolMap = Type == SymbolRef::ST_Function ? Functions : Objects;
    174   if (SymbolMap.empty())
    175     return false;
    176   SymbolDesc SD = { Address, Address };
    177   auto SymbolIterator = SymbolMap.upper_bound(SD);
    178   if (SymbolIterator == SymbolMap.begin())
    179     return false;
    180   --SymbolIterator;
    181   if (SymbolIterator->first.Size != 0 &&
    182       SymbolIterator->first.Addr + SymbolIterator->first.Size <= Address)
    183     return false;
    184   Name = SymbolIterator->second.str();
    185   Addr = SymbolIterator->first.Addr;
    186   Size = SymbolIterator->first.Size;
    187   return true;
    188 }
    189 
    190 bool SymbolizableObjectFile::shouldOverrideWithSymbolTable(
    191     FunctionNameKind FNKind, bool UseSymbolTable) const {
    192   // When DWARF is used with -gline-tables-only / -gmlt, the symbol table gives
    193   // better answers for linkage names than the DIContext. Otherwise, we are
    194   // probably using PEs and PDBs, and we shouldn't do the override. PE files
    195   // generally only contain the names of exported symbols.
    196   return FNKind == FunctionNameKind::LinkageName && UseSymbolTable &&
    197          isa<DWARFContext>(DebugInfoContext.get());
    198 }
    199 
    200 DILineInfo SymbolizableObjectFile::symbolizeCode(uint64_t ModuleOffset,
    201                                                  FunctionNameKind FNKind,
    202                                                  bool UseSymbolTable) const {
    203   DILineInfo LineInfo;
    204   if (DebugInfoContext) {
    205     LineInfo = DebugInfoContext->getLineInfoForAddress(
    206         ModuleOffset, getDILineInfoSpecifier(FNKind));
    207   }
    208   // Override function name from symbol table if necessary.
    209   if (shouldOverrideWithSymbolTable(FNKind, UseSymbolTable)) {
    210     std::string FunctionName;
    211     uint64_t Start, Size;
    212     if (getNameFromSymbolTable(SymbolRef::ST_Function, ModuleOffset,
    213                                FunctionName, Start, Size)) {
    214       LineInfo.FunctionName = FunctionName;
    215     }
    216   }
    217   return LineInfo;
    218 }
    219 
    220 DIInliningInfo SymbolizableObjectFile::symbolizeInlinedCode(
    221     uint64_t ModuleOffset, FunctionNameKind FNKind, bool UseSymbolTable) const {
    222   DIInliningInfo InlinedContext;
    223 
    224   if (DebugInfoContext)
    225     InlinedContext = DebugInfoContext->getInliningInfoForAddress(
    226         ModuleOffset, getDILineInfoSpecifier(FNKind));
    227   // Make sure there is at least one frame in context.
    228   if (InlinedContext.getNumberOfFrames() == 0)
    229     InlinedContext.addFrame(DILineInfo());
    230 
    231   // Override the function name in lower frame with name from symbol table.
    232   if (shouldOverrideWithSymbolTable(FNKind, UseSymbolTable)) {
    233     std::string FunctionName;
    234     uint64_t Start, Size;
    235     if (getNameFromSymbolTable(SymbolRef::ST_Function, ModuleOffset,
    236                                FunctionName, Start, Size)) {
    237       InlinedContext.getMutableFrame(InlinedContext.getNumberOfFrames() - 1)
    238           ->FunctionName = FunctionName;
    239     }
    240   }
    241 
    242   return InlinedContext;
    243 }
    244 
    245 DIGlobal SymbolizableObjectFile::symbolizeData(uint64_t ModuleOffset) const {
    246   DIGlobal Res;
    247   getNameFromSymbolTable(SymbolRef::ST_Data, ModuleOffset, Res.Name, Res.Start,
    248                          Res.Size);
    249   return Res;
    250 }
    251 
    252 }  // namespace symbolize
    253 }  // namespace llvm
    254 
    255