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      1 //===-- RuntimeDyldMachO.cpp - Run-time dynamic linker for MC-JIT -*- C++ -*-=//
      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 the MC-JIT runtime dynamic linker.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "RuntimeDyldMachO.h"
     15 #include "Targets/RuntimeDyldMachOAArch64.h"
     16 #include "Targets/RuntimeDyldMachOARM.h"
     17 #include "Targets/RuntimeDyldMachOI386.h"
     18 #include "Targets/RuntimeDyldMachOX86_64.h"
     19 #include "llvm/ADT/STLExtras.h"
     20 #include "llvm/ADT/StringRef.h"
     21 
     22 using namespace llvm;
     23 using namespace llvm::object;
     24 
     25 #define DEBUG_TYPE "dyld"
     26 
     27 namespace {
     28 
     29 class LoadedMachOObjectInfo final
     30     : public RuntimeDyld::LoadedObjectInfoHelper<LoadedMachOObjectInfo> {
     31 public:
     32   LoadedMachOObjectInfo(RuntimeDyldImpl &RTDyld,
     33                         ObjSectionToIDMap ObjSecToIDMap)
     34       : LoadedObjectInfoHelper(RTDyld, std::move(ObjSecToIDMap)) {}
     35 
     36   OwningBinary<ObjectFile>
     37   getObjectForDebug(const ObjectFile &Obj) const override {
     38     return OwningBinary<ObjectFile>();
     39   }
     40 };
     41 
     42 }
     43 
     44 namespace llvm {
     45 
     46 int64_t RuntimeDyldMachO::memcpyAddend(const RelocationEntry &RE) const {
     47   unsigned NumBytes = 1 << RE.Size;
     48   uint8_t *Src = Sections[RE.SectionID].getAddress() + RE.Offset;
     49 
     50   return static_cast<int64_t>(readBytesUnaligned(Src, NumBytes));
     51 }
     52 
     53 Expected<relocation_iterator>
     54 RuntimeDyldMachO::processScatteredVANILLA(
     55                           unsigned SectionID, relocation_iterator RelI,
     56                           const ObjectFile &BaseObjT,
     57                           RuntimeDyldMachO::ObjSectionToIDMap &ObjSectionToID) {
     58   const MachOObjectFile &Obj =
     59     static_cast<const MachOObjectFile&>(BaseObjT);
     60   MachO::any_relocation_info RE =
     61     Obj.getRelocation(RelI->getRawDataRefImpl());
     62 
     63   SectionEntry &Section = Sections[SectionID];
     64   uint32_t RelocType = Obj.getAnyRelocationType(RE);
     65   bool IsPCRel = Obj.getAnyRelocationPCRel(RE);
     66   unsigned Size = Obj.getAnyRelocationLength(RE);
     67   uint64_t Offset = RelI->getOffset();
     68   uint8_t *LocalAddress = Section.getAddressWithOffset(Offset);
     69   unsigned NumBytes = 1 << Size;
     70   int64_t Addend = readBytesUnaligned(LocalAddress, NumBytes);
     71 
     72   unsigned SymbolBaseAddr = Obj.getScatteredRelocationValue(RE);
     73   section_iterator TargetSI = getSectionByAddress(Obj, SymbolBaseAddr);
     74   assert(TargetSI != Obj.section_end() && "Can't find section for symbol");
     75   uint64_t SectionBaseAddr = TargetSI->getAddress();
     76   SectionRef TargetSection = *TargetSI;
     77   bool IsCode = TargetSection.isText();
     78   uint32_t TargetSectionID = ~0U;
     79   if (auto TargetSectionIDOrErr =
     80         findOrEmitSection(Obj, TargetSection, IsCode, ObjSectionToID))
     81     TargetSectionID = *TargetSectionIDOrErr;
     82   else
     83     return TargetSectionIDOrErr.takeError();
     84 
     85   Addend -= SectionBaseAddr;
     86   RelocationEntry R(SectionID, Offset, RelocType, Addend, IsPCRel, Size);
     87 
     88   addRelocationForSection(R, TargetSectionID);
     89 
     90   return ++RelI;
     91 }
     92 
     93 
     94 Expected<RelocationValueRef>
     95 RuntimeDyldMachO::getRelocationValueRef(
     96     const ObjectFile &BaseTObj, const relocation_iterator &RI,
     97     const RelocationEntry &RE, ObjSectionToIDMap &ObjSectionToID) {
     98 
     99   const MachOObjectFile &Obj =
    100       static_cast<const MachOObjectFile &>(BaseTObj);
    101   MachO::any_relocation_info RelInfo =
    102       Obj.getRelocation(RI->getRawDataRefImpl());
    103   RelocationValueRef Value;
    104 
    105   bool IsExternal = Obj.getPlainRelocationExternal(RelInfo);
    106   if (IsExternal) {
    107     symbol_iterator Symbol = RI->getSymbol();
    108     StringRef TargetName;
    109     if (auto TargetNameOrErr = Symbol->getName())
    110       TargetName = *TargetNameOrErr;
    111     else
    112       return TargetNameOrErr.takeError();
    113     RTDyldSymbolTable::const_iterator SI =
    114       GlobalSymbolTable.find(TargetName.data());
    115     if (SI != GlobalSymbolTable.end()) {
    116       const auto &SymInfo = SI->second;
    117       Value.SectionID = SymInfo.getSectionID();
    118       Value.Offset = SymInfo.getOffset() + RE.Addend;
    119     } else {
    120       Value.SymbolName = TargetName.data();
    121       Value.Offset = RE.Addend;
    122     }
    123   } else {
    124     SectionRef Sec = Obj.getAnyRelocationSection(RelInfo);
    125     bool IsCode = Sec.isText();
    126     if (auto SectionIDOrErr = findOrEmitSection(Obj, Sec, IsCode,
    127                                                 ObjSectionToID))
    128       Value.SectionID = *SectionIDOrErr;
    129     else
    130       return SectionIDOrErr.takeError();
    131     uint64_t Addr = Sec.getAddress();
    132     Value.Offset = RE.Addend - Addr;
    133   }
    134 
    135   return Value;
    136 }
    137 
    138 void RuntimeDyldMachO::makeValueAddendPCRel(RelocationValueRef &Value,
    139                                             const relocation_iterator &RI,
    140                                             unsigned OffsetToNextPC) {
    141   auto &O = *cast<MachOObjectFile>(RI->getObject());
    142   section_iterator SecI = O.getRelocationRelocatedSection(RI);
    143   Value.Offset += RI->getOffset() + OffsetToNextPC + SecI->getAddress();
    144 }
    145 
    146 void RuntimeDyldMachO::dumpRelocationToResolve(const RelocationEntry &RE,
    147                                                uint64_t Value) const {
    148   const SectionEntry &Section = Sections[RE.SectionID];
    149   uint8_t *LocalAddress = Section.getAddress() + RE.Offset;
    150   uint64_t FinalAddress = Section.getLoadAddress() + RE.Offset;
    151 
    152   dbgs() << "resolveRelocation Section: " << RE.SectionID
    153          << " LocalAddress: " << format("%p", LocalAddress)
    154          << " FinalAddress: " << format("0x%016" PRIx64, FinalAddress)
    155          << " Value: " << format("0x%016" PRIx64, Value) << " Addend: " << RE.Addend
    156          << " isPCRel: " << RE.IsPCRel << " MachoType: " << RE.RelType
    157          << " Size: " << (1 << RE.Size) << "\n";
    158 }
    159 
    160 section_iterator
    161 RuntimeDyldMachO::getSectionByAddress(const MachOObjectFile &Obj,
    162                                       uint64_t Addr) {
    163   section_iterator SI = Obj.section_begin();
    164   section_iterator SE = Obj.section_end();
    165 
    166   for (; SI != SE; ++SI) {
    167     uint64_t SAddr = SI->getAddress();
    168     uint64_t SSize = SI->getSize();
    169     if ((Addr >= SAddr) && (Addr < SAddr + SSize))
    170       return SI;
    171   }
    172 
    173   return SE;
    174 }
    175 
    176 
    177 // Populate __pointers section.
    178 Error RuntimeDyldMachO::populateIndirectSymbolPointersSection(
    179                                                     const MachOObjectFile &Obj,
    180                                                     const SectionRef &PTSection,
    181                                                     unsigned PTSectionID) {
    182   assert(!Obj.is64Bit() &&
    183          "Pointer table section not supported in 64-bit MachO.");
    184 
    185   MachO::dysymtab_command DySymTabCmd = Obj.getDysymtabLoadCommand();
    186   MachO::section Sec32 = Obj.getSection(PTSection.getRawDataRefImpl());
    187   uint32_t PTSectionSize = Sec32.size;
    188   unsigned FirstIndirectSymbol = Sec32.reserved1;
    189   const unsigned PTEntrySize = 4;
    190   unsigned NumPTEntries = PTSectionSize / PTEntrySize;
    191   unsigned PTEntryOffset = 0;
    192 
    193   assert((PTSectionSize % PTEntrySize) == 0 &&
    194          "Pointers section does not contain a whole number of stubs?");
    195 
    196   DEBUG(dbgs() << "Populating pointer table section "
    197                << Sections[PTSectionID].getName() << ", Section ID "
    198                << PTSectionID << ", " << NumPTEntries << " entries, "
    199                << PTEntrySize << " bytes each:\n");
    200 
    201   for (unsigned i = 0; i < NumPTEntries; ++i) {
    202     unsigned SymbolIndex =
    203       Obj.getIndirectSymbolTableEntry(DySymTabCmd, FirstIndirectSymbol + i);
    204     symbol_iterator SI = Obj.getSymbolByIndex(SymbolIndex);
    205     StringRef IndirectSymbolName;
    206     if (auto IndirectSymbolNameOrErr = SI->getName())
    207       IndirectSymbolName = *IndirectSymbolNameOrErr;
    208     else
    209       return IndirectSymbolNameOrErr.takeError();
    210     DEBUG(dbgs() << "  " << IndirectSymbolName << ": index " << SymbolIndex
    211           << ", PT offset: " << PTEntryOffset << "\n");
    212     RelocationEntry RE(PTSectionID, PTEntryOffset,
    213                        MachO::GENERIC_RELOC_VANILLA, 0, false, 2);
    214     addRelocationForSymbol(RE, IndirectSymbolName);
    215     PTEntryOffset += PTEntrySize;
    216   }
    217   return Error::success();
    218 }
    219 
    220 bool RuntimeDyldMachO::isCompatibleFile(const object::ObjectFile &Obj) const {
    221   return Obj.isMachO();
    222 }
    223 
    224 template <typename Impl>
    225 Error
    226 RuntimeDyldMachOCRTPBase<Impl>::finalizeLoad(const ObjectFile &Obj,
    227                                              ObjSectionToIDMap &SectionMap) {
    228   unsigned EHFrameSID = RTDYLD_INVALID_SECTION_ID;
    229   unsigned TextSID = RTDYLD_INVALID_SECTION_ID;
    230   unsigned ExceptTabSID = RTDYLD_INVALID_SECTION_ID;
    231 
    232   for (const auto &Section : Obj.sections()) {
    233     StringRef Name;
    234     Section.getName(Name);
    235 
    236     // Force emission of the __text, __eh_frame, and __gcc_except_tab sections
    237     // if they're present. Otherwise call down to the impl to handle other
    238     // sections that have already been emitted.
    239     if (Name == "__text") {
    240       if (auto TextSIDOrErr = findOrEmitSection(Obj, Section, true, SectionMap))
    241         TextSID = *TextSIDOrErr;
    242       else
    243         return TextSIDOrErr.takeError();
    244     } else if (Name == "__eh_frame") {
    245       if (auto EHFrameSIDOrErr = findOrEmitSection(Obj, Section, false,
    246                                                    SectionMap))
    247         EHFrameSID = *EHFrameSIDOrErr;
    248       else
    249         return EHFrameSIDOrErr.takeError();
    250     } else if (Name == "__gcc_except_tab") {
    251       if (auto ExceptTabSIDOrErr = findOrEmitSection(Obj, Section, true,
    252                                                      SectionMap))
    253         ExceptTabSID = *ExceptTabSIDOrErr;
    254       else
    255         return ExceptTabSIDOrErr.takeError();
    256     } else {
    257       auto I = SectionMap.find(Section);
    258       if (I != SectionMap.end())
    259         if (auto Err = impl().finalizeSection(Obj, I->second, Section))
    260           return Err;
    261     }
    262   }
    263   UnregisteredEHFrameSections.push_back(
    264     EHFrameRelatedSections(EHFrameSID, TextSID, ExceptTabSID));
    265 
    266   return Error::success();
    267 }
    268 
    269 template <typename Impl>
    270 unsigned char *RuntimeDyldMachOCRTPBase<Impl>::processFDE(uint8_t *P,
    271                                                           int64_t DeltaForText,
    272                                                           int64_t DeltaForEH) {
    273   typedef typename Impl::TargetPtrT TargetPtrT;
    274 
    275   DEBUG(dbgs() << "Processing FDE: Delta for text: " << DeltaForText
    276                << ", Delta for EH: " << DeltaForEH << "\n");
    277   uint32_t Length = readBytesUnaligned(P, 4);
    278   P += 4;
    279   uint8_t *Ret = P + Length;
    280   uint32_t Offset = readBytesUnaligned(P, 4);
    281   if (Offset == 0) // is a CIE
    282     return Ret;
    283 
    284   P += 4;
    285   TargetPtrT FDELocation = readBytesUnaligned(P, sizeof(TargetPtrT));
    286   TargetPtrT NewLocation = FDELocation - DeltaForText;
    287   writeBytesUnaligned(NewLocation, P, sizeof(TargetPtrT));
    288 
    289   P += sizeof(TargetPtrT);
    290 
    291   // Skip the FDE address range
    292   P += sizeof(TargetPtrT);
    293 
    294   uint8_t Augmentationsize = *P;
    295   P += 1;
    296   if (Augmentationsize != 0) {
    297     TargetPtrT LSDA = readBytesUnaligned(P, sizeof(TargetPtrT));
    298     TargetPtrT NewLSDA = LSDA - DeltaForEH;
    299     writeBytesUnaligned(NewLSDA, P, sizeof(TargetPtrT));
    300   }
    301 
    302   return Ret;
    303 }
    304 
    305 static int64_t computeDelta(SectionEntry *A, SectionEntry *B) {
    306   int64_t ObjDistance = static_cast<int64_t>(A->getObjAddress()) -
    307                         static_cast<int64_t>(B->getObjAddress());
    308   int64_t MemDistance = A->getLoadAddress() - B->getLoadAddress();
    309   return ObjDistance - MemDistance;
    310 }
    311 
    312 template <typename Impl>
    313 void RuntimeDyldMachOCRTPBase<Impl>::registerEHFrames() {
    314 
    315   for (int i = 0, e = UnregisteredEHFrameSections.size(); i != e; ++i) {
    316     EHFrameRelatedSections &SectionInfo = UnregisteredEHFrameSections[i];
    317     if (SectionInfo.EHFrameSID == RTDYLD_INVALID_SECTION_ID ||
    318         SectionInfo.TextSID == RTDYLD_INVALID_SECTION_ID)
    319       continue;
    320     SectionEntry *Text = &Sections[SectionInfo.TextSID];
    321     SectionEntry *EHFrame = &Sections[SectionInfo.EHFrameSID];
    322     SectionEntry *ExceptTab = nullptr;
    323     if (SectionInfo.ExceptTabSID != RTDYLD_INVALID_SECTION_ID)
    324       ExceptTab = &Sections[SectionInfo.ExceptTabSID];
    325 
    326     int64_t DeltaForText = computeDelta(Text, EHFrame);
    327     int64_t DeltaForEH = 0;
    328     if (ExceptTab)
    329       DeltaForEH = computeDelta(ExceptTab, EHFrame);
    330 
    331     uint8_t *P = EHFrame->getAddress();
    332     uint8_t *End = P + EHFrame->getSize();
    333     while (P != End) {
    334       P = processFDE(P, DeltaForText, DeltaForEH);
    335     }
    336 
    337     MemMgr.registerEHFrames(EHFrame->getAddress(), EHFrame->getLoadAddress(),
    338                             EHFrame->getSize());
    339   }
    340   UnregisteredEHFrameSections.clear();
    341 }
    342 
    343 std::unique_ptr<RuntimeDyldMachO>
    344 RuntimeDyldMachO::create(Triple::ArchType Arch,
    345                          RuntimeDyld::MemoryManager &MemMgr,
    346                          RuntimeDyld::SymbolResolver &Resolver) {
    347   switch (Arch) {
    348   default:
    349     llvm_unreachable("Unsupported target for RuntimeDyldMachO.");
    350     break;
    351   case Triple::arm:
    352     return make_unique<RuntimeDyldMachOARM>(MemMgr, Resolver);
    353   case Triple::aarch64:
    354     return make_unique<RuntimeDyldMachOAArch64>(MemMgr, Resolver);
    355   case Triple::x86:
    356     return make_unique<RuntimeDyldMachOI386>(MemMgr, Resolver);
    357   case Triple::x86_64:
    358     return make_unique<RuntimeDyldMachOX86_64>(MemMgr, Resolver);
    359   }
    360 }
    361 
    362 std::unique_ptr<RuntimeDyld::LoadedObjectInfo>
    363 RuntimeDyldMachO::loadObject(const object::ObjectFile &O) {
    364   if (auto ObjSectionToIDOrErr = loadObjectImpl(O))
    365     return llvm::make_unique<LoadedMachOObjectInfo>(*this,
    366                                                     *ObjSectionToIDOrErr);
    367   else {
    368     HasError = true;
    369     raw_string_ostream ErrStream(ErrorStr);
    370     logAllUnhandledErrors(ObjSectionToIDOrErr.takeError(), ErrStream, "");
    371     return nullptr;
    372   }
    373 }
    374 
    375 } // end namespace llvm
    376