RuntimeDyldMachO.cpp   [plain text]

//===-- RuntimeDyldMachO.cpp - Run-time dynamic linker for MC-JIT -*- C++ -*-=//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Implementation of the MC-JIT runtime dynamic linker.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "dyld"
#include "RuntimeDyldMachO.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
using namespace llvm;
using namespace llvm::object;

namespace llvm {

static unsigned char *processFDE(unsigned char *P, intptr_t DeltaForText, intptr_t DeltaForEH) {
  uint32_t Length = *((uint32_t*)P);
  P += 4;
  unsigned char *Ret = P + Length;
  uint32_t Offset = *((uint32_t*)P);
  if (Offset == 0) // is a CIE
    return Ret;

  P += 4;
  intptr_t FDELocation = *((intptr_t*)P);
  intptr_t NewLocation = FDELocation - DeltaForText;
  *((intptr_t*)P) = NewLocation;
  P += sizeof(intptr_t);

  // Skip the FDE address range
  P += sizeof(intptr_t);

  uint8_t Augmentationsize = *P;
  P += 1;
  if (Augmentationsize != 0) {
    intptr_t LSDA = *((intptr_t*)P);
    intptr_t NewLSDA = LSDA - DeltaForEH;
    *((intptr_t*)P) = NewLSDA;
  }

  return Ret;
}

static intptr_t computeDelta(SectionEntry *A, SectionEntry *B) {
  intptr_t ObjDistance = A->ObjAddress  - B->ObjAddress;
  intptr_t MemDistance = A->LoadAddress - B->LoadAddress;
  return ObjDistance - MemDistance;
}

void RuntimeDyldMachO::registerEHFrames() {

  if (!MemMgr)
    return;
  for (int i = 0, e = UnregisteredEHFrameSections.size(); i != e; ++i) {
    EHFrameRelatedSections &SectionInfo = UnregisteredEHFrameSections[i];
    if (SectionInfo.EHFrameSID == RTDYLD_INVALID_SECTION_ID ||
        SectionInfo.TextSID == RTDYLD_INVALID_SECTION_ID)
      continue;
    SectionEntry *Text = &Sections[SectionInfo.TextSID];
    SectionEntry *EHFrame = &Sections[SectionInfo.EHFrameSID];
    SectionEntry *ExceptTab = NULL;
    if (SectionInfo.ExceptTabSID != RTDYLD_INVALID_SECTION_ID)
      ExceptTab = &Sections[SectionInfo.ExceptTabSID];

    intptr_t DeltaForText = computeDelta(Text, EHFrame);
    intptr_t DeltaForEH = 0;
    if (ExceptTab)
      DeltaForEH = computeDelta(ExceptTab, EHFrame);

    unsigned char *P = EHFrame->Address;
    unsigned char *End = P + EHFrame->Size;
    do  {
      P = processFDE(P, DeltaForText, DeltaForEH);
    } while(P != End);

    MemMgr->registerEHFrames(EHFrame->Address,
                             EHFrame->LoadAddress,
                             EHFrame->Size);
  }
  UnregisteredEHFrameSections.clear();
}

void RuntimeDyldMachO::finalizeLoad(ObjectImage &ObjImg,
                                    ObjSectionToIDMap &SectionMap) {
  unsigned EHFrameSID = RTDYLD_INVALID_SECTION_ID;
  unsigned TextSID = RTDYLD_INVALID_SECTION_ID;
  unsigned ExceptTabSID = RTDYLD_INVALID_SECTION_ID;
  for (auto const &i : SectionMap) {
    const SectionRef &Section = i.first;
    StringRef Name;
    Section.getName(Name);
    if (Name == "__eh_frame")
      EHFrameSID = i.second;
    else if (Name == "__text")
      TextSID = i.second;
    else if (Name == "__gcc_except_tab")
      ExceptTabSID = i.second;
    else if (Name == "__jump_table")
      populateJumpTable(cast<MachOObjectFile>(*ObjImg.getObjectFile()),
                        Section, i.second);
    else if (Name == "__pointers")
      populatePointersSection(cast<MachOObjectFile>(*ObjImg.getObjectFile()),
                              Section, i.second);
  }
  UnregisteredEHFrameSections.push_back(
    EHFrameRelatedSections(EHFrameSID, TextSID, ExceptTabSID));

  assert(MemMgr && "No memory manager!");
  // Allocate the GOT if necessary
  size_t NumGOTEntries = GOTMgr.GOTEntries.size();
  if (!NumGOTEntries)
    return;

  // Allocate memory for the section
  size_t GOTEntrySize = getGOTEntrySize();
  SID GOTSectionID = Sections.size();
  size_t TotalSize = NumGOTEntries * GOTEntrySize;
  uint8_t *GOTAddr = MemMgr->allocateDataSection(TotalSize, GOTEntrySize,
                                                 GOTSectionID, "__got", true);
  if (!GOTAddr)
    report_fatal_error("Unable to allocate memory for GOT!");

  Sections.push_back(SectionEntry("__got", GOTAddr, TotalSize, 0));
  uint64_t Offset = 0;
  for (auto const &GOTEntry : GOTMgr.GOTEntries) {
    RelocationEntry RE(GOTSectionID, Offset, MachO::ARM64_RELOC_UNSIGNED,
                       GOTEntry.Addend, /*IsPCRel=*/false, /*Size=*/3);
    if (GOTEntry.SymbolName)
      addRelocationForSymbol(RE, GOTEntry.SymbolName);
    else
      addRelocationForSection(RE, GOTEntry.SectionID);
    Offset += getGOTEntrySize();
  }
  GOTMgr.commit(GOTSectionID);
}

// The target location for the relocation is described by RE.SectionID and
// RE.Offset.  RE.SectionID can be used to find the SectionEntry.  Each
// SectionEntry has three members describing its location.
// SectionEntry::Address is the address at which the section has been loaded
// into memory in the current (host) process.  SectionEntry::LoadAddress is the
// address that the section will have in the target process.
// SectionEntry::ObjAddress is the address of the bits for this section in the
// original emitted object image (also in the current address space).
//
// Relocations will be applied as if the section were loaded at
// SectionEntry::LoadAddress, but they will be applied at an address based
// on SectionEntry::Address.  SectionEntry::ObjAddress will be used to refer to
// Target memory contents if they are required for value calculations.
//
// The Value parameter here is the load address of the symbol for the
// relocation to be applied.  For relocations which refer to symbols in the
// current object Value will be the LoadAddress of the section in which
// the symbol resides (RE.Addend provides additional information about the
// symbol location).  For external symbols, Value will be the address of the
// symbol in the target address space.
void RuntimeDyldMachO::resolveRelocation(const RelocationEntry &RE,
                                         uint64_t Value) {
  const SectionEntry &Section = Sections[RE.SectionID];
  return resolveRelocation(Section, RE.Offset, Value, RE.RelType, RE.Addend,
                           RE.IsPCRel, RE.Size, RE.Sections.SectionA,
                           RE.Sections.SectionB);
}

void RuntimeDyldMachO::resolveRelocation(const SectionEntry &Section,
                                         uint64_t Offset,
                                         uint64_t Value,
                                         uint32_t Type,
                                         int64_t Addend,
                                         bool IsPCRel,
                                         unsigned LogSize,
                                         unsigned SectionAID,
                                         unsigned SectionBID) {
  uint8_t *LocalAddress = Section.Address + Offset;
  uint64_t FinalAddress = Section.LoadAddress + Offset;
  unsigned MachoType = Type;
  unsigned Size = 1 << LogSize;

  DEBUG(dbgs() << "resolveRelocation LocalAddress: "
        << format("%p", LocalAddress)
        << " FinalAddress: " << format("%p", FinalAddress)
        << " Value: " << format("%p", Value)
        << " Addend: " << Addend
        << " isPCRel: " << IsPCRel
        << " MachoType: " << MachoType
        << " Size: " << Size << "\n"
        << "Section A: " << SectionAID << "\n"
        << "Section B: " << SectionBID
        << "\n");

  // This just dispatches to the proper target specific routine.
  switch (Arch) {
  default: llvm_unreachable("Unsupported CPU type!");
  case Triple::x86_64:
    resolveX86_64Relocation(LocalAddress,
                            FinalAddress,
                            (uintptr_t)Value,
                            IsPCRel,
                            MachoType,
                            Size,
                            Addend);
    break;
  case Triple::x86:
    resolveI386Relocation(LocalAddress,
                          FinalAddress,
                          (uintptr_t)Value,
                          IsPCRel,
                          MachoType,
                          Size,
                          Addend,
                          SectionAID,
                          SectionBID);
    break;
  case Triple::arm:    // Fall through.
  case Triple::thumb:
    resolveARMRelocation(LocalAddress,
                         FinalAddress,
                         (uintptr_t)Value,
                         IsPCRel,
                         MachoType,
                         Size,
                         Addend);
    break;
  case Triple::arm64:
    resolveARM64Relocation(LocalAddress,
                           FinalAddress,
                           (uintptr_t)Value,
                           IsPCRel,
                           MachoType,
                           Size,
                           Addend);
    break;
  }
}

bool RuntimeDyldMachO::resolveI386Relocation(uint8_t *LocalAddress,
                                             uint64_t FinalAddress,
                                             uint64_t Value,
                                             bool IsPCRel,
                                             unsigned Type,
                                             unsigned Size,
                                             int64_t Addend,
                                             unsigned SectionAID,
                                             unsigned SectionBID) {
  if (IsPCRel)
    Value -= FinalAddress + 4; // see resolveX86_64Relocation

  switch (Type) {
  default:
    llvm_unreachable("Invalid relocation type!");
  case MachO::GENERIC_RELOC_VANILLA: {
    uint8_t *p = LocalAddress;
    uint64_t ValueToWrite = Value + Addend;
    for (unsigned i = 0; i < Size; ++i) {
      *p++ = (uint8_t)(ValueToWrite & 0xff);
      ValueToWrite >>= 8;
    }
    return false;
  }
  case MachO::GENERIC_RELOC_SECTDIFF:
  case MachO::GENERIC_RELOC_LOCAL_SECTDIFF: {
    uint64_t SectionABase = Sections[SectionAID].LoadAddress;
    uint64_t SectionBBase = Sections[SectionBID].LoadAddress;
    assert((Value == SectionABase || Value == SectionBBase) &&
           "Unexpected SECDIFF relocation value.");
    Value = SectionABase - SectionBBase + Addend;
    uint8_t *p = LocalAddress;
    uint64_t ValueToWrite = SectionABase - SectionBBase + Addend;
    for (unsigned i = 0; i < Size; ++i) {
      *p++ = (uint8_t)(ValueToWrite & 0xff);
      ValueToWrite >>= 8;
    }
  }
  case MachO::GENERIC_RELOC_PB_LA_PTR:
    return Error("Relocation type not implemented yet!");
  }
}

bool RuntimeDyldMachO::resolveX86_64Relocation(uint8_t *LocalAddress,
                                               uint64_t FinalAddress,
                                               uint64_t Value,
                                               bool IsPCRel,
                                               unsigned Type,
                                               unsigned Size,
                                               int64_t Addend) {
  // If the relocation is PC-relative, the value to be encoded is the
  // pointer difference.
  if (IsPCRel)
    // FIXME: It seems this value needs to be adjusted by 4 for an effective PC
    // address. Is that expected? Only for branches, perhaps?
    Value -= FinalAddress + 4;

  switch(Type) {
  default:
    llvm_unreachable("Invalid relocation type!");
  case MachO::X86_64_RELOC_SIGNED_1:
  case MachO::X86_64_RELOC_SIGNED_2:
  case MachO::X86_64_RELOC_SIGNED_4:
  case MachO::X86_64_RELOC_SIGNED:
  case MachO::X86_64_RELOC_UNSIGNED:
  case MachO::X86_64_RELOC_BRANCH: {
    Value += Addend;
    // Mask in the target value a byte at a time (we don't have an alignment
    // guarantee for the target address, so this is safest).
    uint8_t *p = (uint8_t*)LocalAddress;
    for (unsigned i = 0; i < Size; ++i) {
      *p++ = (uint8_t)Value;
      Value >>= 8;
    }
    return false;
  }
  case MachO::X86_64_RELOC_GOT_LOAD:
  case MachO::X86_64_RELOC_GOT:
  case MachO::X86_64_RELOC_SUBTRACTOR:
  case MachO::X86_64_RELOC_TLV:
    return Error("Relocation type not implemented yet!");
  }
}

bool RuntimeDyldMachO::resolveARMRelocation(uint8_t *LocalAddress,
                                            uint64_t FinalAddress,
                                            uint64_t Value,
                                            bool IsPCRel,
                                            unsigned Type,
                                            unsigned Size,
                                            int64_t Addend) {
  // If the relocation is PC-relative, the value to be encoded is the
  // pointer difference.
  if (IsPCRel) {
    Value -= FinalAddress;
    // ARM PCRel relocations have an effective-PC offset of two instructions
    // (four bytes in Thumb mode, 8 bytes in ARM mode).
    // FIXME: For now, assume ARM mode.
    Value -= 8;
  }

  switch(Type) {
  default:
    llvm_unreachable("Invalid relocation type!");
  case MachO::ARM_RELOC_VANILLA: {
    // Mask in the target value a byte at a time (we don't have an alignment
    // guarantee for the target address, so this is safest).
    uint8_t *p = (uint8_t*)LocalAddress;
    for (unsigned i = 0; i < Size; ++i) {
      *p++ = (uint8_t)Value;
      Value >>= 8;
    }
    break;
  }
  case MachO::ARM_RELOC_BR24: {
    // Mask the value into the target address. We know instructions are
    // 32-bit aligned, so we can do it all at once.
    uint32_t *p = (uint32_t*)LocalAddress;
    // The low two bits of the value are not encoded.
    Value >>= 2;
    // Mask the value to 24 bits.
    Value &= 0xffffff;
    // FIXME: If the destination is a Thumb function (and the instruction
    // is a non-predicated BL instruction), we need to change it to a BLX
    // instruction instead.

    // Insert the value into the instruction.
    *p = (*p & ~0xffffff) | Value;
    break;
  }
  case MachO::ARM_THUMB_RELOC_BR22:
  case MachO::ARM_THUMB_32BIT_BRANCH:
  case MachO::ARM_RELOC_HALF:
  case MachO::ARM_RELOC_HALF_SECTDIFF:
  case MachO::ARM_RELOC_PAIR:
  case MachO::ARM_RELOC_SECTDIFF:
  case MachO::ARM_RELOC_LOCAL_SECTDIFF:
  case MachO::ARM_RELOC_PB_LA_PTR:
    return Error("Relocation type not implemented yet!");
  }
  return false;
}

bool RuntimeDyldMachO::resolveARM64Relocation(uint8_t *LocalAddress,
                                              uint64_t FinalAddress,
                                              uint64_t RelocVal,
                                              bool IsPCRel,
                                              unsigned Type,
                                              unsigned Size,
                                              int64_t Addend) {
  switch(Type) {
  default:
    llvm_unreachable("Invalid relocation type!");
  case MachO::ARM64_RELOC_UNSIGNED: {
    assert(!IsPCRel && "PCRel and ARM64_RELOC_UNSIGNED not supported");
    // Mask in the target value a byte at a time (we don't have an alignment
    // guarantee for the target address, so this is safest).
    if (Size < 4)
      llvm_unreachable("Invalid size for ARM64_RELOC_UNSIGNED");

    RelocVal += Addend;
    uint8_t *p = (uint8_t*)LocalAddress;
    for (unsigned i = 0; i < Size; ++i) {
      *p++ = (uint8_t)RelocVal;
      RelocVal >>= 8;
    }
    break;
  }
  case MachO::ARM64_RELOC_BRANCH26: {
    assert(IsPCRel && "not PCRel and ARM64_RELOC_BRANCH26 not supported");
    // Mask the value into the target address. We know instructions are
    // 32-bit aligned, so we can do it all at once.
    uint32_t *p = (uint32_t*)LocalAddress;
    // Check if the addend is encoded in the instruction.
    uint32_t EncodedAddend = *p & 0x03FFFFFF;
    if (EncodedAddend != 0 ) {
      if (Addend == 0)
        llvm_unreachable("branch26 instruction has embedded addend.");
      else
        llvm_unreachable("branch26 instruction has embedded addend and" \
                         "ARM64_RELOC_ADDEND.");
    }
    // Check if branch is in range.
    uint64_t PCRelVal = RelocVal - FinalAddress + Addend;
    assert(isInt<26>(PCRelVal) && "Branch target out of range!");
    // Insert the value into the instruction.
    *p = (*p & 0xFC000000) | ((uint32_t)(PCRelVal >> 2) & 0x03FFFFFF);
    break;
  }
  case MachO::ARM64_RELOC_GOT_LOAD_PAGE21:
    // Replace the targte address with the addres of the GOT entry that holds
    // this target address. Also correct for the addend that will be added
    // later on.
    RelocVal = findGOTEntry(RelocVal + Addend) - Addend;
    // Fall through to ARM64_RELOC_PAGE21.
  case MachO::ARM64_RELOC_PAGE21: {
    assert(IsPCRel && "not PCRel and ARM64_RELOC_PAGE21 not supported");
    // Mask the value into the target address. We know instructions are
    // 32-bit aligned, so we can do it all at once.
    uint32_t *p = (uint32_t*)LocalAddress;
    // Check if the addend is encoded in the instruction.
    uint32_t EncodedAddend = ((*p & 0x60000000) >> 29) |
                             ((*p & 0x01FFFFE0) >> 3);
    if (EncodedAddend != 0) {
      if (Addend == 0)
        llvm_unreachable("adrp instruction has embedded addend.");
      else
        llvm_unreachable("adrp instruction has embedded addend and" \
                         "ARM64_RELOC_ADDEND.");
    }
    // Adjust for PC-relative relocation and offset.
    uint64_t PCRelVal = ((RelocVal + Addend) & (-4096)) -
                         (FinalAddress & (-4096));
    // Check that the value fits into 21 bits (+ 12 lower bits).
    assert(isInt<33>(PCRelVal) && "Invalid page reloc value!");
    // Insert the value into the instruction.
    uint32_t ImmLoValue = (uint32_t)(PCRelVal << 17) & 0x60000000;
    uint32_t ImmHiValue = (uint32_t)(PCRelVal >>  9) & 0x00FFFFE0;
    *p = (*p & 0x9F00001F) | ImmHiValue | ImmLoValue;
    break;
  }
  case MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12:
    // Replace the targte address with the addres of the GOT entry that holds
    // this target address. Also correct for the addend that will be added
    // later on.
    RelocVal = findGOTEntry(RelocVal + Addend) - Addend;
    // Fall through to ARM64_RELOC_PAGEOFF12.
  case MachO::ARM64_RELOC_PAGEOFF12: {
    assert(!IsPCRel && "PCRel and ARM64_RELOC_PAGEOFF21 not supported");
    // Mask the value into the target address. We know instructions are
    // 32-bit aligned, so we can do it all at once.
    uint32_t *p = (uint32_t*)LocalAddress;
    // Check if the addend is encoded in the instruction.
    uint32_t EncodedAddend = *p & 0x003FFC00;
    if (EncodedAddend != 0) {
      if (Addend == 0)
        llvm_unreachable("adrp instruction has embedded addend.");
      else
        llvm_unreachable("adrp instruction has embedded addend and" \
                         "ARM64_RELOC_ADDEND.");
    }
    // Add the offset from the symbol.
    RelocVal += Addend;
    // Mask out the page address and only use the lower 12 bits.
    RelocVal &= 0xFFF;
    // Check which instruction we are updating to obtain the implicit shift
    // factor from LDR/STR instructions.
    if (*p & 0x08000000) {
      uint32_t ImplicitShift = ((*p >> 30) & 0x3);
      switch (ImplicitShift) {
      case 0:
        // Check if this a vector op.
        if ((*p & 0x04800000) == 0x04800000) {
          ImplicitShift = 4;
          assert(((RelocVal & 0xF) == 0) &&
                 "128-bit LDR/STR not 16-byte aligned.");
        }
        break;
      case 1:
        assert(((RelocVal & 0x1) == 0) && "16-bit LDR/STR not 2-byte aligned.");
      case 2:
        assert(((RelocVal & 0x3) == 0) && "32-bit LDR/STR not 4-byte aligned.");
      case 3:
        assert(((RelocVal & 0x7) == 0) && "64-bit LDR/STR not 8-byte aligned.");
      }
      // Compensate for implicit shift.
      RelocVal >>= ImplicitShift;
    }
    // Insert the value into the instruction.
    *p = (*p & 0xFFC003FF) | ((uint32_t)(RelocVal << 10) & 0x003FFC00);
    break;
  }
  case MachO::ARM64_RELOC_SUBTRACTOR:
  case MachO::ARM64_RELOC_POINTER_TO_GOT:
  case MachO::ARM64_RELOC_TLVP_LOAD_PAGE21:
  case MachO::ARM64_RELOC_TLVP_LOAD_PAGEOFF12:
    llvm_unreachable("Relocation type not implemented yet!");
    return Error("Relocation type not implemented yet!");
  case MachO::ARM64_RELOC_ADDEND:
    llvm_unreachable("ARM64_RELOC_ADDEND should have been handeled by " \
                     "processRelocationRef!");
  }
  return false;
}

void RuntimeDyldMachO::populateJumpTable(MachOObjectFile &Obj,
                                         const SectionRef &JTSection,
                                         unsigned JTSectionID) {
  assert(!Obj.is64Bit() &&
         "__jump_table section not supported in 64-bit MachO.");

  MachO::dysymtab_command DySymTabCmd = Obj.getDysymtabLoadCommand();
  MachO::section Sec32 = Obj.getSection(JTSection.getRawDataRefImpl());
  uint32_t JTSectionSize = Sec32.size;
  unsigned FirstIndirectSymbol = Sec32.reserved1;
  unsigned JTEntrySize = Sec32.reserved2;
  unsigned NumJTEntries = JTSectionSize / JTEntrySize;
  uint8_t* JTSectionAddr = getSectionAddress(JTSectionID);
  unsigned JTEntryOffset = 0;

  assert((JTSectionSize % JTEntrySize) == 0 &&
         "Jump-table section does not contain a whole number of stubs?");

  for (unsigned i = 0; i < NumJTEntries; ++i) {
    unsigned SymbolIndex =
      Obj.getIndirectSymbolTableEntry(DySymTabCmd, FirstIndirectSymbol + i);
    symbol_iterator SI = Obj.getSymbolByIndex(SymbolIndex);
    StringRef IndirectSymbolName;
    SI->getName(IndirectSymbolName);
    uint8_t* JTEntryAddr = JTSectionAddr + JTEntryOffset;
    createStubFunction(JTEntryAddr);
    RelocationEntry RE(JTSectionID, JTEntryOffset + 1,
                       MachO::GENERIC_RELOC_VANILLA, 0, true, 2);
    addRelocationForSymbol(RE, IndirectSymbolName);
    JTEntryOffset += JTEntrySize;
  }
}

void RuntimeDyldMachO::populatePointersSection(MachOObjectFile &Obj,
                                               const SectionRef &PTSection,
                                               unsigned PTSectionID) {
  assert(!Obj.is64Bit() &&
         "__pointers section not supported in 64-bit MachO.");

  MachO::dysymtab_command DySymTabCmd = Obj.getDysymtabLoadCommand();
  MachO::section Sec32 = Obj.getSection(PTSection.getRawDataRefImpl());
  uint32_t PTSectionSize = Sec32.size;
  unsigned FirstIndirectSymbol = Sec32.reserved1;
  const unsigned PTEntrySize = 4;
  unsigned NumPTEntries = PTSectionSize / PTEntrySize;
  unsigned PTEntryOffset = 0;

  assert((PTSectionSize % PTEntrySize) == 0 &&
         "Pointers section does not contain a whole number of stubs?");

  for (unsigned i = 0; i < NumPTEntries; ++i) {
    unsigned SymbolIndex =
      Obj.getIndirectSymbolTableEntry(DySymTabCmd, FirstIndirectSymbol + i);
    symbol_iterator SI = Obj.getSymbolByIndex(SymbolIndex);
    StringRef IndirectSymbolName;
    SI->getName(IndirectSymbolName);
    RelocationEntry RE(PTSectionID, PTEntryOffset,
                       MachO::GENERIC_RELOC_VANILLA, 0, false, 2);
    addRelocationForSymbol(RE, IndirectSymbolName);
    PTEntryOffset += PTEntrySize;
  }
}


section_iterator getSectionByAddress(const MachOObjectFile &Obj,
                                     uint64_t Addr) {
  section_iterator SI = Obj.section_begin();
  section_iterator SE = Obj.section_end();

  for (; SI != SE; ++SI) {
    uint64_t SAddr, SSize;
    SI->getAddress(SAddr);
    SI->getSize(SSize);
    if ((Addr >= SAddr) && (Addr < SAddr + SSize))
      return SI;
  }

  return SE;
}

relocation_iterator RuntimeDyldMachO::processSECTDIFFRelocation(
                                            unsigned SectionID,
                                            relocation_iterator RelI,
                                            ObjectImage &Obj,
                                            ObjSectionToIDMap &ObjSectionToID) {
  const MachOObjectFile *MachO =
    static_cast<const MachOObjectFile*>(Obj.getObjectFile());
  MachO::any_relocation_info RE =
    MachO->getRelocation(RelI->getRawDataRefImpl());

  SectionEntry &Section = Sections[SectionID];
  uint32_t RelocType = MachO->getAnyRelocationType(RE);
  bool IsPCRel = MachO->getAnyRelocationPCRel(RE);
  unsigned Size = MachO->getAnyRelocationLength(RE);
  uint64_t Offset;
  RelI->getOffset(Offset);
  uint8_t *LocalAddress = Section.Address + Offset;
  unsigned NumBytes = 1 << Size;
  int64_t Addend = 0;
  memcpy(&Addend, LocalAddress, NumBytes);

  ++RelI;
  MachO::any_relocation_info RE2 =
    MachO->getRelocation(RelI->getRawDataRefImpl());

  uint32_t AddrA = MachO->getScatteredRelocationValue(RE);
  section_iterator SAI = getSectionByAddress(*MachO, AddrA);
  assert(SAI != MachO->section_end() && "Can't find section for address A");
  uint64_t SectionABase;
  SAI->getAddress(SectionABase);
  uint64_t SectionAOffset = AddrA - SectionABase;
  SectionRef SectionA = *SAI;
  bool IsCode;
  SectionA.isText(IsCode);
  uint32_t SectionAID = findOrEmitSection(Obj, SectionA, IsCode,
                                          ObjSectionToID);

  uint32_t AddrB = MachO->getScatteredRelocationValue(RE2);
  section_iterator SBI = getSectionByAddress(*MachO, AddrB);
  assert(SBI != MachO->section_end() && "Can't find seciton for address B");
  uint64_t SectionBBase;
  SBI->getAddress(SectionBBase);
  uint64_t SectionBOffset = AddrB - SectionBBase;
  SectionRef SectionB = *SBI;
  uint32_t SectionBID = findOrEmitSection(Obj, SectionB, IsCode,
                                          ObjSectionToID);

  if (Addend != AddrA - AddrB)
    Error("Unexpected SECTDIFF relocation addend.");

  RelocationEntry R(SectionID, Offset, RelocType, 0,
                    SectionAID, SectionAOffset, SectionBID, SectionBOffset,
                    IsPCRel, Size);

  addRelocationForSection(R, SectionAID);
  addRelocationForSection(R, SectionBID);

  return RelI;
}

relocation_iterator
RuntimeDyldMachO::processRelocationRef(unsigned SectionID,
                                       const section_iterator &SI,
                                       relocation_iterator RelI,
                                       ObjectImage &Obj,
                                       ObjSectionToIDMap &ObjSectionToID,
                                       const SymbolTableMap &Symbols,
                                       StubMap &Stubs) {
  const ObjectFile *OF = Obj.getObjectFile();
  const MachOObjectFile *MachO = static_cast<const MachOObjectFile*>(OF);
  MachO::any_relocation_info RE =
    MachO->getRelocation(RelI->getRawDataRefImpl());
  int64_t RelocAddendValue = 0;
  bool HasRelocAddendValue = false;

  uint32_t RelocType = MachO->getAnyRelocationType(RE);
  if (Arch == Triple::arm64) {
    // ARM64_RELOC_ADDEND provides the offset (addend) that will be used by the
    // next relocation entry. Save the value and advance to the next relocation
    // entry.
    if (RelocType == MachO::ARM64_RELOC_ADDEND) {
      assert(!MachO->getPlainRelocationExternal(RE));
      assert(!MachO->getAnyRelocationPCRel(RE));
      assert(MachO->getAnyRelocationLength(RE) == 2);
      uint64_t RawAddend = MachO->getPlainRelocationSymbolNum(RE);
      // Sign-extend the 24-bit to 64-bit.
      RelocAddendValue = RawAddend << 40;
      RelocAddendValue >>= 40;
      HasRelocAddendValue = true;

      // Get the next entry.
      RE = MachO->getRelocation((++RelI)->getRawDataRefImpl());
      RelocType = MachO->getAnyRelocationType(RE);
      assert(RelocType == MachO::ARM64_RELOC_BRANCH26 ||
             RelocType == MachO::ARM64_RELOC_PAGE21 ||
             RelocType == MachO::ARM64_RELOC_PAGEOFF12);

    } else if (RelocType == MachO::ARM64_RELOC_BRANCH26 ||
               RelocType == MachO::ARM64_RELOC_PAGE21 ||
               RelocType == MachO::ARM64_RELOC_PAGEOFF12 ||
               RelocType == MachO::ARM64_RELOC_GOT_LOAD_PAGE21 ||
               RelocType == MachO::ARM64_RELOC_GOT_LOAD_PAGEOFF12) {
      RelocAddendValue = 0;
      HasRelocAddendValue = true;
    }
  }

  // FIXME: Properly handle scattered relocations.
  //        For now, optimistically skip these: they can often be ignored, as
  //        the static linker will already have applied the relocation, and it
  //        only needs to be reapplied if symbols move relative to one another.
  //        Note: This will fail horribly where the relocations *do* need to be
  //        applied, but that was already the case.
  if (MachO->isRelocationScattered(RE)) {
    if (Arch == Triple::x86 &&
        (RelocType == MachO::GENERIC_RELOC_SECTDIFF ||
         RelocType == MachO::GENERIC_RELOC_LOCAL_SECTDIFF))
      return processSECTDIFFRelocation(SectionID, RelI, Obj, ObjSectionToID);

    return ++RelI;
  }

  RelocationValueRef RelocVal;
  SectionEntry &Section = Sections[SectionID];

  bool isExtern = MachO->getPlainRelocationExternal(RE);
  bool IsPCRel = MachO->getAnyRelocationPCRel(RE);
  unsigned Size = MachO->getAnyRelocationLength(RE);
  uint64_t Offset;
  RelI->getOffset(Offset);
  uint8_t *LocalAddress = Section.Address + Offset;
  unsigned NumBytes = 1 << Size;
  int64_t Addend = 0;
  if (HasRelocAddendValue)
    Addend = RelocAddendValue;
  else
    memcpy(&Addend, LocalAddress, NumBytes);

  // If this is an ARM BR24 reloc, decode the addend. <rdar://problem/17750739>
  if (Arch == Triple::arm && (RelocType & 0xf) == MachO::ARM_RELOC_BR24) {
    Addend &= 0x00ffffff;
    Addend = SignExtend32<26>(Addend << 2);
  }

  if (isExtern) {
    // Obtain the symbol name which is referenced in the relocation
    symbol_iterator Symbol = RelI->getSymbol();
    StringRef TargetName;
    Symbol->getName(TargetName);
    // First search for the symbol in the local symbol table
    SymbolTableMap::const_iterator lsi = Symbols.find(TargetName.data());
    if (lsi != Symbols.end()) {
      RelocVal.SectionID = lsi->second.first;
      RelocVal.Addend = lsi->second.second + Addend;
    } else {
      // Search for the symbol in the global symbol table
      SymbolTableMap::const_iterator gsi = GlobalSymbolTable.find(TargetName.data());
      if (gsi != GlobalSymbolTable.end()) {
        RelocVal.SectionID = gsi->second.first;
        RelocVal.Addend = gsi->second.second + Addend;
      } else {
        RelocVal.SymbolName = TargetName.data();
        RelocVal.Addend = Addend;
      }
    }

    // Fix up ARM PC-rel extern references. <rdar://problem/17750739>
    if (IsPCRel && Arch == Triple::arm &&
        (RelocType & 0xf) == MachO::ARM_RELOC_BR24) {
      uint64_t SectionBaseAddr = 0;
      SI->getAddress(SectionBaseAddr);
      RelocVal.Addend += SectionBaseAddr + Offset + 8;
    }

  } else {
    SectionRef Sec = MachO->getRelocationSection(RE);
    bool IsCode = false;
    Sec.isText(IsCode);
    RelocVal.SectionID = findOrEmitSection(Obj, Sec, IsCode, ObjSectionToID);
    uint64_t Addr;
    Sec.getAddress(Addr);
    RelocVal.Addend = Addend - Addr;
    if (IsPCRel) {
      RelocVal.Addend += Offset + NumBytes;

      if (Arch == Triple::x86) {
        // On i386 we need to account for the base address of the section.
        uint64_t SectionBaseAddr = 0;
        SI->getAddress(SectionBaseAddr);
        RelocVal.Addend += SectionBaseAddr;
      }
    }
  }

  if (Arch == Triple::x86_64 && (RelocType == MachO::X86_64_RELOC_GOT ||
                                 RelocType == MachO::X86_64_RELOC_GOT_LOAD)) {
    assert(IsPCRel);
    assert(Size == 2);

    // FIXME: Teach the generic code above not to prematurely conflate
    //        relocation addends and symbol offsets.
    RelocVal.Addend -= Addend;
    StubMap::const_iterator i = Stubs.find(RelocVal);
    uint8_t *Addr;
    if (i != Stubs.end()) {
      Addr = Section.Address + i->second;
    } else {
      Stubs[RelocVal] = Section.StubOffset;
      uint8_t *GOTEntry = Section.Address + Section.StubOffset;
      RelocationEntry GOTRE(SectionID, Section.StubOffset,
                            MachO::X86_64_RELOC_UNSIGNED, RelocVal.Addend, false,
                            3);
      if (RelocVal.SymbolName)
        addRelocationForSymbol(GOTRE, RelocVal.SymbolName);
      else
        addRelocationForSection(GOTRE, RelocVal.SectionID);
      Section.StubOffset += 8;
      Addr = GOTEntry;
    }
    resolveRelocation(Section, Offset, (uint64_t)Addr,
                      MachO::X86_64_RELOC_UNSIGNED, Addend, true, 2);
  } else if (Arch == Triple::arm &&
             (RelocType & 0xf) == MachO::ARM_RELOC_BR24) {
    // This is an ARM branch relocation, need to use a stub function.

    //  Look up for existing stub.
    StubMap::const_iterator i = Stubs.find(RelocVal);
    if (i != Stubs.end())
      resolveRelocation(Section, Offset,
                        (uint64_t)Section.Address + i->second,
                        RelocType, 0, IsPCRel, Size);
    else {
      // Create a new stub function.
      Stubs[RelocVal] = Section.StubOffset;
      uint8_t *StubTargetAddr = createStubFunction(Section.Address +
                                                   Section.StubOffset);
      RelocationEntry RE(SectionID, StubTargetAddr - Section.Address,
                         MachO::GENERIC_RELOC_VANILLA, RelocVal.Addend, false,
                         2);
      if (RelocVal.SymbolName)
        addRelocationForSymbol(RE, RelocVal.SymbolName);
      else
        addRelocationForSection(RE, RelocVal.SectionID);
      resolveRelocation(Section, Offset,
                        (uint64_t)Section.Address + Section.StubOffset,
                        RelocType, 0, IsPCRel, Size);
      Section.StubOffset += getMaxStubSize();
    }
  } else {
    if (Arch == Triple::arm64 &&
        RelocType == MachO::ARM64_RELOC_GOT_LOAD_PAGE21)
      GOTMgr.insert(RelocVal);

    RelocationEntry RE(SectionID, Offset, RelocType, RelocVal.Addend,
                       IsPCRel, Size);
    if (RelocVal.SymbolName)
      addRelocationForSymbol(RE, RelocVal.SymbolName);
    else
      addRelocationForSection(RE, RelocVal.SectionID);
  }
  return ++RelI;
}

void RuntimeDyldMachO::updateGOTEntries(StringRef Name, uint64_t Addr) {
  for (auto &G : GOTMgr) {
    auto result = G.find(Name);
    if (result.second) {
      size_t Index = result.first;
      G.Entries[Index].Offset = Addr;
      G.insert(Addr, Index);
    }
  }
}

size_t RuntimeDyldMachO::getGOTEntrySize() {
  size_t Result = 0;
  switch (Arch) {
  default: llvm_unreachable("Unsupported CPU type!");
  case Triple::x86_64:
  case Triple::aarch64:
  case Triple::arm64:
  case Triple::ppc64:
  case Triple::ppc64le:
  case Triple::systemz:
    Result = sizeof(uint64_t);
    break;
  case Triple::x86:
  case Triple::arm:
  case Triple::thumb:
  case Triple::mips:
  case Triple::mipsel:
    Result = sizeof(uint32_t);
    break;
  }
  return Result;
}

uint64_t RuntimeDyldMachO::findGOTEntry(uint64_t Addr) {
  size_t EntrySize = getGOTEntrySize();
  for (auto &G : GOTMgr) {
    auto result = G.find(Addr);
    if (result.second)
      return getSectionLoadAddress(G.SectionID) + (result.first * EntrySize);

    // Slow path - scan the vector.
    for (unsigned i = 0, e = G.size(); i != e; ++i) {
      RelocationValueRef const &RelocVal = G.Entries[i];
      uint64_t EntryAddress = getSectionLoadAddress(RelocVal.SectionID) +
                              RelocVal.Addend;
      if (EntryAddress == Addr) {
        // Cache the entry for future lookups.
        G.insert(Addr, i);
        return getSectionLoadAddress(G.SectionID) + (i * EntrySize);
      }
    }
  }
  llvm_unreachable("Unable to find requested GOT entry.");
  return 0;
}

bool RuntimeDyldMachO::isCompatibleFormat(
        const ObjectBuffer *InputBuffer) const {
  if (InputBuffer->getBufferSize() < 4)
    return false;
  StringRef Magic(InputBuffer->getBufferStart(), 4);
  if (Magic == "\xFE\xED\xFA\xCE") return true;
  if (Magic == "\xCE\xFA\xED\xFE") return true;
  if (Magic == "\xFE\xED\xFA\xCF") return true;
  if (Magic == "\xCF\xFA\xED\xFE") return true;
  return false;
}

bool RuntimeDyldMachO::isCompatibleFile(
        const object::ObjectFile *Obj) const {
  return Obj->isMachO();
}

} // end namespace llvm