lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp

//===-- RuntimeDyld.h - 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 "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Twine.h"
#include "llvm/ExecutionEngine/RuntimeDyld.h"
#include "llvm/Object/MachOObject.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/Memory.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/system_error.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
using namespace llvm::object;

// Empty out-of-line virtual destructor as the key function.
RTDyldMemoryManager::~RTDyldMemoryManager() {}

namespace llvm {
class RuntimeDyldImpl {
  unsigned CPUType;
  unsigned CPUSubtype;

  // The MemoryManager to load objects into.
  RTDyldMemoryManager *MemMgr;


  // For each function, we have a MemoryBlock of it's instruction data.
  StringMap<sys::MemoryBlock> Functions;

  // Master symbol table. As modules are loaded and external symbols are
  // resolved, their addresses are stored here.
  StringMap<uint64_t> SymbolTable;

  // FIXME: Should have multiple data blocks, one for each loaded chunk of
  //        compiled code.
//  sys::MemoryBlock Data;

  bool HasError;
  std::string ErrorStr;

  // Set the error state and record an error string.
  bool Error(const Twine &Msg) {
    ErrorStr = Msg.str();
    HasError = true;
    return true;
  }

  void extractFunction(StringRef Name, uint8_t *StartAddress,
                       uint8_t *EndAddress);
  bool resolveRelocation(uint32_t BaseSection, macho::RelocationEntry RE,
                         SmallVectorImpl<void *> &SectionBases,
                         SmallVectorImpl<StringRef> &SymbolNames);
  bool resolveX86_64Relocation(intptr_t Address, intptr_t Value, bool isPCRel,
                               unsigned Type, unsigned Size);
  bool resolveARMRelocation(intptr_t Address, intptr_t Value, bool isPCRel,
                            unsigned Type, unsigned Size);

  bool loadSegment32(const MachOObject *Obj,
                     const MachOObject::LoadCommandInfo *SegmentLCI,
                     const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC);
  bool loadSegment64(const MachOObject *Obj,
                     const MachOObject::LoadCommandInfo *SegmentLCI,
                     const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC);

public:
  RuntimeDyldImpl(RTDyldMemoryManager *mm) : MemMgr(mm), HasError(false) {}

  bool loadObject(MemoryBuffer *InputBuffer);

  void *getSymbolAddress(StringRef Name) {
    // FIXME: Just look up as a function for now. Overly simple of course.
    // Work in progress.
    return Functions.lookup(Name).base();
  }

  // Is the linker in an error state?
  bool hasError() { return HasError; }

  // Mark the error condition as handled and continue.
  void clearError() { HasError = false; }

  // Get the error message.
  StringRef getErrorString() { return ErrorStr; }
};

void RuntimeDyldImpl::extractFunction(StringRef Name, uint8_t *StartAddress,
                                      uint8_t *EndAddress) {
  // Allocate memory for the function via the memory manager.
  uintptr_t Size = EndAddress - StartAddress + 1;
  uint8_t *Mem = MemMgr->startFunctionBody(Name.data(), Size);
  assert(Size >= (uint64_t)(EndAddress - StartAddress + 1) &&
         "Memory manager failed to allocate enough memory!");
  // Copy the function payload into the memory block.
  memcpy(Mem, StartAddress, EndAddress - StartAddress + 1);
  MemMgr->endFunctionBody(Name.data(), Mem, Mem + Size);
  // Remember where we put it.
  Functions[Name] = sys::MemoryBlock(Mem, Size);
  DEBUG(dbgs() << "    allocated to " << Mem << "\n");
}

bool RuntimeDyldImpl::
resolveRelocation(uint32_t BaseSection, macho::RelocationEntry RE,
                  SmallVectorImpl<void *> &SectionBases,
                  SmallVectorImpl<StringRef> &SymbolNames) {
  // struct relocation_info {
  //   int32_t r_address;
  //   uint32_t r_symbolnum:24,
  //            r_pcrel:1,
  //            r_length:2,
  //            r_extern:1,
  //            r_type:4;
  // };
  uint32_t SymbolNum = RE.Word1 & 0xffffff; // 24-bit value
  bool isPCRel = (RE.Word1 >> 24) & 1;
  unsigned Log2Size = (RE.Word1 >> 25) & 3;
  bool isExtern = (RE.Word1 >> 27) & 1;
  unsigned Type = (RE.Word1 >> 28) & 0xf;
  if (RE.Word0 & macho::RF_Scattered)
    return Error("NOT YET IMPLEMENTED: scattered relocations.");

  // The address requiring a relocation.
  intptr_t Address = (intptr_t)SectionBases[BaseSection] + RE.Word0;

  // Figure out the target address of the relocation. If isExtern is true,
  // this relocation references the symbol table, otherwise it references
  // a section in the same object, numbered from 1 through NumSections
  // (SectionBases is [0, NumSections-1]).
  intptr_t Value;
  if (isExtern) {
    StringRef Name = SymbolNames[SymbolNum];
    if (SymbolTable.lookup(Name)) {
      // The symbol is in our symbol table, so we can resolve it directly.
      Value = (intptr_t)SymbolTable[Name];
    } else {
      return Error("NOT YET IMPLEMENTED: relocations to pre-compiled code.");
    }
    DEBUG(dbgs() << "Resolve relocation(" << Type << ") from '" << Name
                 << "' to " << format("0x%x", Address) << ".\n");
  } else {
    // For non-external relocations, the SymbolNum is actual a section number
    // as described above.
    Value = (intptr_t)SectionBases[SymbolNum - 1];
  }

  unsigned Size = 1 << Log2Size;
  switch (CPUType) {
  default: assert(0 && "Unsupported CPU type!");
  case mach::CTM_x86_64:
    return resolveX86_64Relocation(Address, Value, isPCRel, Type, Size);
  case mach::CTM_ARM:
    return resolveARMRelocation(Address, Value, isPCRel, Type, Size);
  }
  llvm_unreachable("");
}

bool RuntimeDyldImpl::resolveX86_64Relocation(intptr_t Address, intptr_t Value,
                                              bool isPCRel, unsigned Type,
                                              unsigned Size) {
  // 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 -= Address + 4;

  switch(Type) {
  default:
    llvm_unreachable("Invalid relocation type!");
  case macho::RIT_X86_64_Unsigned:
  case macho::RIT_X86_64_Branch: {
    // 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*)Address;
    for (unsigned i = 0; i < Size; ++i) {
      *p++ = (uint8_t)Value;
      Value >>= 8;
    }
    return false;
  }
  case macho::RIT_X86_64_Signed:
  case macho::RIT_X86_64_GOTLoad:
  case macho::RIT_X86_64_GOT:
  case macho::RIT_X86_64_Subtractor:
  case macho::RIT_X86_64_Signed1:
  case macho::RIT_X86_64_Signed2:
  case macho::RIT_X86_64_Signed4:
  case macho::RIT_X86_64_TLV:
    return Error("Relocation type not implemented yet!");
  }
  return false;
}

bool RuntimeDyldImpl::resolveARMRelocation(intptr_t Address, intptr_t Value,
                                           bool isPCRel, unsigned Type,
                                           unsigned Size) {
  // If the relocation is PC-relative, the value to be encoded is the
  // pointer difference.
  if (isPCRel) {
    Value -= Address;
    // 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:
  case macho::RIT_Vanilla: {
    llvm_unreachable("Invalid relocation type!");
    // 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*)Address;
    for (unsigned i = 0; i < Size; ++i) {
      *p++ = (uint8_t)Value;
      Value >>= 8;
    }
    break;
  }
  case macho::RIT_Pair:
  case macho::RIT_Difference:
  case macho::RIT_ARM_LocalDifference:
  case macho::RIT_ARM_PreboundLazyPointer:
  case macho::RIT_ARM_Branch24Bit: {
    // 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*)Address;
    // 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::RIT_ARM_ThumbBranch22Bit:
  case macho::RIT_ARM_ThumbBranch32Bit:
  case macho::RIT_ARM_Half:
  case macho::RIT_ARM_HalfDifference:
    return Error("Relocation type not implemented yet!");
  }
  return false;
}

bool RuntimeDyldImpl::
loadSegment32(const MachOObject *Obj,
              const MachOObject::LoadCommandInfo *SegmentLCI,
              const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
  InMemoryStruct<macho::SegmentLoadCommand> Segment32LC;
  Obj->ReadSegmentLoadCommand(*SegmentLCI, Segment32LC);
  if (!Segment32LC)
    return Error("unable to load segment load command");

  for (unsigned SectNum = 0; SectNum != Segment32LC->NumSections; ++SectNum) {
    InMemoryStruct<macho::Section> Sect;
    Obj->ReadSection(*SegmentLCI, SectNum, Sect);
    if (!Sect)
      return Error("unable to load section: '" + Twine(SectNum) + "'");

    // FIXME: Improve check.
    if (Sect->Flags != 0x80000400)
      return Error("unsupported section type!");

    // Address and names of symbols in the section.
    typedef std::pair<uint64_t, StringRef> SymbolEntry;
    SmallVector<SymbolEntry, 32> Symbols;
    for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
      InMemoryStruct<macho::SymbolTableEntry> STE;
      Obj->ReadSymbolTableEntry(SymtabLC->SymbolTableOffset, i, STE);
      if (!STE)
        return Error("unable to read symbol: '" + Twine(i) + "'");
      if (STE->SectionIndex > Segment32LC->NumSections)
        return Error("invalid section index for symbol: '" + Twine(i) + "'");

      // Just skip symbols not defined in this section.
      if ((unsigned)STE->SectionIndex - 1 != SectNum)
        continue;

      // Get the symbol name.
      StringRef Name = Obj->getStringAtIndex(STE->StringIndex);

      // FIXME: Check the symbol type and flags.
      if (STE->Type != 0xF)  // external, defined in this section.
        return Error("unexpected symbol type!");
      if (STE->Flags != 0x0)
        return Error("unexpected symbol type!");

      uint64_t BaseAddress = Sect->Address;
      uint64_t Address = BaseAddress + STE->Value;

      // Remember the symbol.
      Symbols.push_back(SymbolEntry(Address, Name));

      DEBUG(dbgs() << "Function sym: '" << Name << "' @ " << Address << "\n");
    }
    // Sort the symbols by address, just in case they didn't come in that
    // way.
    array_pod_sort(Symbols.begin(), Symbols.end());

    // Extract the function data.
    uint8_t *Base = (uint8_t*)Obj->getData(Segment32LC->FileOffset,
                                           Segment32LC->FileSize).data();
    for (unsigned i = 0, e = Symbols.size() - 1; i != e; ++i) {
      uint64_t StartOffset = Symbols[i].first;
      uint64_t EndOffset = Symbols[i + 1].first - 1;
      DEBUG(dbgs() << "Extracting function: " << Symbols[i].second
                   << " from [" << StartOffset << ", " << EndOffset << "]\n");
      extractFunction(Symbols[i].second, Base + StartOffset, Base + EndOffset);
    }
    // The last symbol we do after since the end address is calculated
    // differently because there is no next symbol to reference.
    uint64_t StartOffset = Symbols[Symbols.size() - 1].first;
    uint64_t EndOffset = Sect->Size - 1;
    DEBUG(dbgs() << "Extracting function: " << Symbols[Symbols.size()-1].second
                 << " from [" << StartOffset << ", " << EndOffset << "]\n");
    extractFunction(Symbols[Symbols.size()-1].second,
                    Base + StartOffset, Base + EndOffset);
  }

  return false;
}


bool RuntimeDyldImpl::
loadSegment64(const MachOObject *Obj,
              const MachOObject::LoadCommandInfo *SegmentLCI,
              const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
  InMemoryStruct<macho::Segment64LoadCommand> Segment64LC;
  Obj->ReadSegment64LoadCommand(*SegmentLCI, Segment64LC);
  if (!Segment64LC)
    return Error("unable to load segment load command");

  for (unsigned SectNum = 0; SectNum != Segment64LC->NumSections; ++SectNum) {
    InMemoryStruct<macho::Section64> Sect;
    Obj->ReadSection64(*SegmentLCI, SectNum, Sect);
    if (!Sect)
      return Error("unable to load section: '" + Twine(SectNum) + "'");

    // FIXME: Improve check.
    if (Sect->Flags != 0x80000400)
      return Error("unsupported section type!");

    // Address and names of symbols in the section.
    typedef std::pair<uint64_t, StringRef> SymbolEntry;
    SmallVector<SymbolEntry, 64> Symbols;
    for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
      InMemoryStruct<macho::Symbol64TableEntry> STE;
      Obj->ReadSymbol64TableEntry(SymtabLC->SymbolTableOffset, i, STE);
      if (!STE)
        return Error("unable to read symbol: '" + Twine(i) + "'");
      if (STE->SectionIndex > Segment64LC->NumSections)
        return Error("invalid section index for symbol: '" + Twine(i) + "'");

      // Just skip symbols not defined in this section.
      if ((unsigned)STE->SectionIndex - 1 != SectNum)
        continue;

      // Get the symbol name.
      StringRef Name = Obj->getStringAtIndex(STE->StringIndex);

      // FIXME: Check the symbol type and flags.
      if (STE->Type != 0xF)  // external, defined in this section.
        return Error("unexpected symbol type!");
      if (STE->Flags != 0x0)
        return Error("unexpected symbol type!");

      uint64_t BaseAddress = Sect->Address;
      uint64_t Address = BaseAddress + STE->Value;

      // Remember the symbol.
      Symbols.push_back(SymbolEntry(Address, Name));

      DEBUG(dbgs() << "Function sym: '" << Name << "' @ " << Address << "\n");
    }
    // Sort the symbols by address, just in case they didn't come in that
    // way.
    array_pod_sort(Symbols.begin(), Symbols.end());

    // Extract the function data.
    uint8_t *Base = (uint8_t*)Obj->getData(Segment64LC->FileOffset,
                                           Segment64LC->FileSize).data();
    for (unsigned i = 0, e = Symbols.size() - 1; i != e; ++i) {
      uint64_t StartOffset = Symbols[i].first;
      uint64_t EndOffset = Symbols[i + 1].first - 1;
      DEBUG(dbgs() << "Extracting function: " << Symbols[i].second
                   << " from [" << StartOffset << ", " << EndOffset << "]\n");
      extractFunction(Symbols[i].second, Base + StartOffset, Base + EndOffset);
    }
    // The last symbol we do after since the end address is calculated
    // differently because there is no next symbol to reference.
    uint64_t StartOffset = Symbols[Symbols.size() - 1].first;
    uint64_t EndOffset = Sect->Size - 1;
    DEBUG(dbgs() << "Extracting function: " << Symbols[Symbols.size()-1].second
                 << " from [" << StartOffset << ", " << EndOffset << "]\n");
    extractFunction(Symbols[Symbols.size()-1].second,
                    Base + StartOffset, Base + EndOffset);
  }

  return false;
}

bool RuntimeDyldImpl::loadObject(MemoryBuffer *InputBuffer) {
  // If the linker is in an error state, don't do anything.
  if (hasError())
    return true;
  // Load the Mach-O wrapper object.
  std::string ErrorStr;
  OwningPtr<MachOObject> Obj(
    MachOObject::LoadFromBuffer(InputBuffer, &ErrorStr));
  if (!Obj)
    return Error("unable to load object: '" + ErrorStr + "'");

  // Get the CPU type information from the header.
  const macho::Header &Header = Obj->getHeader();

  // FIXME: Error checking that the loaded object is compatible with
  //        the system we're running on.
  CPUType = Header.CPUType;
  CPUSubtype = Header.CPUSubtype;

  // Validate that the load commands match what we expect.
  const MachOObject::LoadCommandInfo *SegmentLCI = 0, *SymtabLCI = 0,
    *DysymtabLCI = 0;
  for (unsigned i = 0; i != Header.NumLoadCommands; ++i) {
    const MachOObject::LoadCommandInfo &LCI = Obj->getLoadCommandInfo(i);
    switch (LCI.Command.Type) {
    case macho::LCT_Segment:
    case macho::LCT_Segment64:
      if (SegmentLCI)
        return Error("unexpected input object (multiple segments)");
      SegmentLCI = &LCI;
      break;
    case macho::LCT_Symtab:
      if (SymtabLCI)
        return Error("unexpected input object (multiple symbol tables)");
      SymtabLCI = &LCI;
      break;
    case macho::LCT_Dysymtab:
      if (DysymtabLCI)
        return Error("unexpected input object (multiple symbol tables)");
      DysymtabLCI = &LCI;
      break;
    default:
      return Error("unexpected input object (unexpected load command");
    }
  }

  if (!SymtabLCI)
    return Error("no symbol table found in object");
  if (!SegmentLCI)
    return Error("no symbol table found in object");

  // Read and register the symbol table data.
  InMemoryStruct<macho::SymtabLoadCommand> SymtabLC;
  Obj->ReadSymtabLoadCommand(*SymtabLCI, SymtabLC);
  if (!SymtabLC)
    return Error("unable to load symbol table load command");
  Obj->RegisterStringTable(*SymtabLC);

  // Read the dynamic link-edit information, if present (not present in static
  // objects).
  if (DysymtabLCI) {
    InMemoryStruct<macho::DysymtabLoadCommand> DysymtabLC;
    Obj->ReadDysymtabLoadCommand(*DysymtabLCI, DysymtabLC);
    if (!DysymtabLC)
      return Error("unable to load dynamic link-exit load command");

    // FIXME: We don't support anything interesting yet.
//    if (DysymtabLC->LocalSymbolsIndex != 0)
//      return Error("NOT YET IMPLEMENTED: local symbol entries");
//    if (DysymtabLC->ExternalSymbolsIndex != 0)
//      return Error("NOT YET IMPLEMENTED: non-external symbol entries");
//    if (DysymtabLC->UndefinedSymbolsIndex != SymtabLC->NumSymbolTableEntries)
//      return Error("NOT YET IMPLEMENTED: undefined symbol entries");
  }

  // Load the segment load command.
  if (SegmentLCI->Command.Type == macho::LCT_Segment) {
    if (loadSegment32(Obj.get(), SegmentLCI, SymtabLC))
      return true;
  } else {
    if (loadSegment64(Obj.get(), SegmentLCI, SymtabLC))
      return true;
  }

  return false;
}


//===----------------------------------------------------------------------===//
// RuntimeDyld class implementation
RuntimeDyld::RuntimeDyld(RTDyldMemoryManager *MM) {
  Dyld = new RuntimeDyldImpl(MM);
}

RuntimeDyld::~RuntimeDyld() {
  delete Dyld;
}

bool RuntimeDyld::loadObject(MemoryBuffer *InputBuffer) {
  return Dyld->loadObject(InputBuffer);
}

void *RuntimeDyld::getSymbolAddress(StringRef Name) {
  return Dyld->getSymbolAddress(Name);
}

StringRef RuntimeDyld::getErrorString() {
  return Dyld->getErrorString();
}

} // end namespace llvm