MachOUtils.cpp   [plain text]

//===-- MachOUtils.h - Mach-o specific helpers for dsymutil  --------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "MachOUtils.h"
#include "BinaryHolder.h"
#include "DebugMap.h"
#include "dsymutil.h"
#include "NonRelocatableStringpool.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Object/MachO.h"
#include "llvm/Support/FileUtilities.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/raw_ostream.h"

namespace llvm {
namespace dsymutil {
namespace MachOUtils {

std::string getArchName(StringRef Arch) {
  if (Arch.startswith("thumb"))
    return (llvm::Twine("arm") + Arch.drop_front(5)).str();
  return Arch;
}

static bool runLipo(StringRef SDKPath, SmallVectorImpl<const char *> &Args) {
  auto Path = sys::findProgramByName("lipo", makeArrayRef(SDKPath));
  if (!Path)
    Path = sys::findProgramByName("lipo");

  if (!Path) {
    errs() << "error: lipo: " << Path.getError().message() << "\n";
    return false;
  }

  std::string ErrMsg;
  int result =
      sys::ExecuteAndWait(*Path, Args.data(), nullptr, nullptr, 0, 0, &ErrMsg);
  if (result) {
    errs() << "error: lipo: " << ErrMsg << "\n";
    return false;
  }

  return true;
}

bool generateUniversalBinary(SmallVectorImpl<ArchAndFilename> &ArchFiles,
                             StringRef OutputFileName,
                             const LinkOptions &Options, StringRef SDKPath) {
  // No need to merge one file into a universal fat binary. First, try
  // to move it (rename) to the final location. If that fails because
  // of cross-device link issues then copy and delete.
  if (ArchFiles.size() == 1) {
    StringRef From(ArchFiles.front().Path);
    // Nothing to do for stdout.
    if (From == "-")
      return true;
    if (sys::fs::rename(From, OutputFileName)) {
      if (std::error_code EC = sys::fs::copy_file(From, OutputFileName)) {
        errs() << "error: while copying " << From << " to " << OutputFileName
               << ": " << EC.message() << "\n";
        return false;
      }
      sys::fs::remove(From);
    }
    return true;
  }

  SmallVector<const char *, 8> Args;
  Args.push_back("lipo");
  Args.push_back("-create");

  for (auto &Thin : ArchFiles)
    Args.push_back(Thin.Path.c_str());

  // Align segments to match dsymutil-classic alignment
  for (auto &Thin : ArchFiles) {
    Thin.Arch = getArchName(Thin.Arch);
    Args.push_back("-segalign");
    Args.push_back(Thin.Arch.c_str());
    Args.push_back("20");
  }

  Args.push_back("-output");
  Args.push_back(OutputFileName.data());
  Args.push_back(nullptr);

  if (Options.Verbose) {
    outs() << "Running lipo\n";
    for (auto Arg : Args)
      outs() << ' ' << ((Arg == nullptr) ? "\n" : Arg);
  }

  return Options.NoOutput ? true : runLipo(SDKPath, Args);
}

// Return a MachO::segment_command_64 that holds the same values as
// the passed MachO::segment_command. We do that to avoid having to
// duplicat the logic for 32bits and 64bits segments.
struct MachO::segment_command_64 adaptFrom32bits(MachO::segment_command Seg) {
  MachO::segment_command_64 Seg64;
  Seg64.cmd = Seg.cmd;
  Seg64.cmdsize = Seg.cmdsize;
  memcpy(Seg64.segname, Seg.segname, sizeof(Seg.segname));
  Seg64.vmaddr = Seg.vmaddr;
  Seg64.vmsize = Seg.vmsize;
  Seg64.fileoff = Seg.fileoff;
  Seg64.filesize = Seg.filesize;
  Seg64.maxprot = Seg.maxprot;
  Seg64.initprot = Seg.initprot;
  Seg64.nsects = Seg.nsects;
  Seg64.flags = Seg.flags;
  return Seg64;
}

// Iterate on all \a Obj segments, and apply \a Handler to them.
template <typename FunctionTy>
static void iterateOnSegments(const object::MachOObjectFile &Obj,
                              FunctionTy Handler) {
  for (const auto &LCI : Obj.load_commands()) {
    MachO::segment_command_64 Segment;
    if (LCI.C.cmd == MachO::LC_SEGMENT)
      Segment = adaptFrom32bits(Obj.getSegmentLoadCommand(LCI));
    else if (LCI.C.cmd == MachO::LC_SEGMENT_64)
      Segment = Obj.getSegment64LoadCommand(LCI);
    else
      continue;

    Handler(Segment);
  }
}

// Transfer the symbols described by \a NList to \a NewSymtab which is
// just the raw contents of the symbol table for the dSYM companion file.
// \returns whether the symbol was tranfered or not.
template <typename NListTy>
static bool transferSymbol(NListTy NList, bool IsLittleEndian,
                           StringRef Strings, SmallVectorImpl<char> &NewSymtab,
                           NonRelocatableStringpool &NewStrings,
                           bool &InDebugNote) {
  // Do not transfer undefined symbols, we want real addresses.
  if ((NList.n_type & MachO::N_TYPE) == MachO::N_UNDF)
    return false;

  StringRef Name = StringRef(Strings.begin() + NList.n_strx);
  if (InDebugNote) {
    InDebugNote =
        (NList.n_type != MachO::N_SO) || (!Name.empty() && Name[0] != '\0');
    return false;
  } else if (NList.n_type == MachO::N_SO) {
    InDebugNote = true;
    return false;
  }

  // FIXME: The + 1 is here to mimic dsymutil-classic that has 2 empty
  // strings at the start of the generated string table (There is
  // corresponding code in the string table emission).
  NList.n_strx = NewStrings.getStringOffset(Name) + 1;
  if (IsLittleEndian != sys::IsLittleEndianHost)
    MachO::swapStruct(NList);

  NewSymtab.append(reinterpret_cast<char *>(&NList),
                   reinterpret_cast<char *>(&NList + 1));
  return true;
}

// Wrapper around transferSymbol to transfer all of \a Obj symbols
// to \a NewSymtab. This function does not write in the output file.
// \returns the number of symbols in \a NewSymtab.
static unsigned transferSymbols(const object::MachOObjectFile &Obj,
                                SmallVectorImpl<char> &NewSymtab,
                                NonRelocatableStringpool &NewStrings) {
  unsigned Syms = 0;
  StringRef Strings = Obj.getStringTableData();
  bool IsLittleEndian = Obj.isLittleEndian();
  bool InDebugNote = false;

  if (Obj.is64Bit()) {
    for (const object::SymbolRef &Symbol : Obj.symbols()) {
      object::DataRefImpl DRI = Symbol.getRawDataRefImpl();
      if (transferSymbol(Obj.getSymbol64TableEntry(DRI), IsLittleEndian,
                         Strings, NewSymtab, NewStrings, InDebugNote))
        ++Syms;
    }
  } else {
    for (const object::SymbolRef &Symbol : Obj.symbols()) {
      object::DataRefImpl DRI = Symbol.getRawDataRefImpl();
      if (transferSymbol(Obj.getSymbolTableEntry(DRI), IsLittleEndian, Strings,
                         NewSymtab, NewStrings, InDebugNote))
        ++Syms;
    }
  }
  return Syms;
}

static MachO::section
getSection(const object::MachOObjectFile &Obj,
           const MachO::segment_command &Seg,
           const object::MachOObjectFile::LoadCommandInfo &LCI, unsigned Idx) {
  return Obj.getSection(LCI, Idx);
}

static MachO::section_64
getSection(const object::MachOObjectFile &Obj,
           const MachO::segment_command_64 &Seg,
           const object::MachOObjectFile::LoadCommandInfo &LCI, unsigned Idx) {
  return Obj.getSection64(LCI, Idx);
}

// Transfer \a Segment from \a Obj to the output file. This calls into \a Writer
// to write these load commands directly in the output file at the current
// position.
// The function also tries to find a hole in the address map to fit the __DWARF
// segment of \a DwarfSegmentSize size. \a EndAddress is updated to point at the
// highest segment address.
// When the __LINKEDIT segment is transfered, its offset and size are set resp.
// to \a LinkeditOffset and \a LinkeditSize.
template <typename SegmentTy>
static void transferSegmentAndSections(
    const object::MachOObjectFile::LoadCommandInfo &LCI, SegmentTy Segment,
    const object::MachOObjectFile &Obj, MCObjectWriter &Writer,
    uint64_t LinkeditOffset, uint64_t LinkeditSize, uint64_t DwarfSegmentSize,
    uint64_t &GapForDwarf, uint64_t &EndAddress) {
  if (StringRef("__DWARF") == Segment.segname)
    return;

  Segment.fileoff = Segment.filesize = 0;

  if (StringRef("__LINKEDIT") == Segment.segname) {
    Segment.fileoff = LinkeditOffset;
    Segment.filesize = LinkeditSize;
  }

  // Check if the end address of the last segment and our current
  // start address leave a sufficient gap to store the __DWARF
  // segment.
  uint64_t PrevEndAddress = EndAddress;
  EndAddress = RoundUpToAlignment(EndAddress, 0x1000);
  if (GapForDwarf == UINT64_MAX && Segment.vmaddr > EndAddress &&
      Segment.vmaddr - EndAddress >= DwarfSegmentSize)
    GapForDwarf = EndAddress;

  // The segments are not necessarily sorted by their vmaddr.
  EndAddress =
      std::max<uint64_t>(PrevEndAddress, Segment.vmaddr + Segment.vmsize);
  unsigned nsects = Segment.nsects;
  if (Obj.isLittleEndian() != sys::IsLittleEndianHost)
    MachO::swapStruct(Segment);
  Writer.writeBytes(
      StringRef(reinterpret_cast<char *>(&Segment), sizeof(Segment)));
  for (unsigned i = 0; i < nsects; ++i) {
    auto Sect = getSection(Obj, Segment, LCI, i);
    Sect.offset = Sect.reloff = Sect.nreloc = 0;
    if (Obj.isLittleEndian() != sys::IsLittleEndianHost)
      MachO::swapStruct(Sect);
    Writer.writeBytes(StringRef(reinterpret_cast<char *>(&Sect), sizeof(Sect)));
  }
}

// Write the __DWARF segment load command to the output file.
static void createDwarfSegment(uint64_t VMAddr, uint64_t FileOffset,
                               uint64_t FileSize, unsigned NumSections,
                               MCAsmLayout &Layout, MachObjectWriter &Writer) {
  Writer.writeSegmentLoadCommand("__DWARF", NumSections, VMAddr,
                                 RoundUpToAlignment(FileSize, 0x1000),
                                 FileOffset, FileSize, /* MaxProt */ 7,
                                 /* InitProt =*/3);

  for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
    MCSection *Sec = Layout.getSectionOrder()[i];
    if (Sec->begin() == Sec->end() || !Layout.getSectionFileSize(Sec))
      continue;

    unsigned Align = Sec->getAlignment();
    if (Align > 1) {
      VMAddr = RoundUpToAlignment(VMAddr, Align);
      FileOffset = RoundUpToAlignment(FileOffset, Align);
    }
    Writer.writeSection(Layout, *Sec, VMAddr, FileOffset, 0, 0, 0);

    FileOffset += Layout.getSectionAddressSize(Sec);
    VMAddr += Layout.getSectionAddressSize(Sec);
  }
}

static bool isExecutable(const object::MachOObjectFile &Obj) {
  if (Obj.is64Bit())
    return Obj.getHeader64().filetype != MachO::MH_OBJECT;
  else
    return Obj.getHeader().filetype != MachO::MH_OBJECT;
}

static bool hasLinkEditSegment(const object::MachOObjectFile &Obj) {
  bool HasLinkEditSegment = false;
  iterateOnSegments(Obj, [&](const MachO::segment_command_64 &Segment) {
    if (StringRef("__LINKEDIT") == Segment.segname)
      HasLinkEditSegment = true;
  });
  return HasLinkEditSegment;
}

static unsigned segmentLoadCommandSize(bool Is64Bit, unsigned NumSections) {
  if (Is64Bit)
    return sizeof(MachO::segment_command_64) +
           NumSections * sizeof(MachO::section_64);

  return sizeof(MachO::segment_command) + NumSections * sizeof(MachO::section);
}

// Stream a dSYM companion binary file corresponding to the binary referenced
// by \a DM to \a OutFile. The passed \a MS MCStreamer is setup to write to
// \a OutFile and it must be using a MachObjectWriter object to do so.
bool generateDsymCompanion(const DebugMap &DM,
                           std::function<StringRef(StringRef)> Translator,
                           MCStreamer &MS, raw_fd_ostream &OutFile) {
  auto &ObjectStreamer = static_cast<MCObjectStreamer &>(MS);
  MCAssembler &MCAsm = ObjectStreamer.getAssembler();
  auto &Writer = static_cast<MachObjectWriter &>(MCAsm.getWriter());
  MCAsmLayout Layout(MCAsm);

  MCAsm.layout(Layout);

  BinaryHolder InputBinaryHolder(false);
  auto ErrOrObjs = InputBinaryHolder.GetObjectFiles(DM.getBinaryPath());
  if (auto Error = ErrOrObjs.getError())
    return error(Twine("opening ") + DM.getBinaryPath() + ": " +
                     Error.message(),
                 "output file streaming");

  auto ErrOrInputBinary =
      InputBinaryHolder.GetAs<object::MachOObjectFile>(DM.getTriple());
  if (auto Error = ErrOrInputBinary.getError())
    return error(Twine("opening ") + DM.getBinaryPath() + ": " +
                     Error.message(),
                 "output file streaming");
  auto &InputBinary = *ErrOrInputBinary;

  bool Is64Bit = Writer.is64Bit();
  MachO::symtab_command SymtabCmd = InputBinary.getSymtabLoadCommand();

  // Get UUID.
  MachO::uuid_command UUIDCmd;
  memset(&UUIDCmd, 0, sizeof(UUIDCmd));
  UUIDCmd.cmd = MachO::LC_UUID;
  UUIDCmd.cmdsize = sizeof(MachO::uuid_command);
  for (auto &LCI : InputBinary.load_commands()) {
    if (LCI.C.cmd == MachO::LC_UUID) {
      UUIDCmd = InputBinary.getUuidCommand(LCI);
      break;
    }
  }

  // Compute the number of load commands we will need.
  unsigned LoadCommandSize = 0;
  unsigned NumLoadCommands = 0;
  // We will copy the UUID if there is one.
  if (UUIDCmd.cmd != 0) {
    ++NumLoadCommands;
    LoadCommandSize += sizeof(MachO::uuid_command);
  }

  // If we have a valid symtab to copy, do it.
  bool ShouldEmitSymtab =
      isExecutable(InputBinary) && hasLinkEditSegment(InputBinary);
  if (ShouldEmitSymtab) {
    LoadCommandSize += sizeof(MachO::symtab_command);
    ++NumLoadCommands;
  }

  unsigned HeaderSize =
      Is64Bit ? sizeof(MachO::mach_header_64) : sizeof(MachO::mach_header);
  // We will copy every segment that isn't __DWARF.
  iterateOnSegments(InputBinary, [&](const MachO::segment_command_64 &Segment) {
    if (StringRef("__DWARF") == Segment.segname)
      return;

    ++NumLoadCommands;
    LoadCommandSize += segmentLoadCommandSize(Is64Bit, Segment.nsects);
  });

  // We will add our own brand new __DWARF segment if we have debug
  // info.
  unsigned NumDwarfSections = 0;
  uint64_t DwarfSegmentSize = 0;

  for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
    MCSection *Sec = Layout.getSectionOrder()[i];
    if (Sec->begin() == Sec->end())
      continue;

    if (uint64_t Size = Layout.getSectionFileSize(Sec)) {
      DwarfSegmentSize =
          RoundUpToAlignment(DwarfSegmentSize, Sec->getAlignment());
      DwarfSegmentSize += Size;
      ++NumDwarfSections;
    }
  }

  if (NumDwarfSections) {
    ++NumLoadCommands;
    LoadCommandSize += segmentLoadCommandSize(Is64Bit, NumDwarfSections);
  }

  SmallString<0> NewSymtab;
  NonRelocatableStringpool NewStrings(Translator);
  unsigned NListSize = Is64Bit ? sizeof(MachO::nlist_64) : sizeof(MachO::nlist);
  unsigned NumSyms = 0;
  uint64_t NewStringsSize = 0;
  if (ShouldEmitSymtab) {
    NewSymtab.reserve(SymtabCmd.nsyms * NListSize / 2);
    NumSyms = transferSymbols(InputBinary, NewSymtab, NewStrings);
    NewStringsSize = NewStrings.getSize() + 1;
  }

  uint64_t SymtabStart = LoadCommandSize;
  SymtabStart += HeaderSize;
  SymtabStart = RoundUpToAlignment(SymtabStart, 0x1000);

  // We gathered all the information we need, start emitting the output file.
  Writer.writeHeader(MachO::MH_DSYM, NumLoadCommands, LoadCommandSize, false);

  // Write the load commands.
  assert(OutFile.tell() == HeaderSize);
  if (UUIDCmd.cmd != 0) {
    Writer.write32(UUIDCmd.cmd);
    Writer.write32(UUIDCmd.cmdsize);
    Writer.writeBytes(
        StringRef(reinterpret_cast<const char *>(UUIDCmd.uuid), 16));
    assert(OutFile.tell() == HeaderSize + sizeof(UUIDCmd));
  }

  assert(SymtabCmd.cmd && "No symbol table.");
  uint64_t StringStart = SymtabStart + NumSyms * NListSize;
  if (ShouldEmitSymtab)
    Writer.writeSymtabLoadCommand(SymtabStart, NumSyms, StringStart,
                                  NewStringsSize);

  uint64_t DwarfSegmentStart = StringStart + NewStringsSize;
  DwarfSegmentStart = RoundUpToAlignment(DwarfSegmentStart, 0x1000);

  // Write the load commands for the segments and sections we 'import' from
  // the original binary.
  uint64_t EndAddress = 0;
  uint64_t GapForDwarf = UINT64_MAX;
  for (auto &LCI : InputBinary.load_commands()) {
    if (LCI.C.cmd == MachO::LC_SEGMENT)
      transferSegmentAndSections(LCI, InputBinary.getSegmentLoadCommand(LCI),
                                 InputBinary, Writer, SymtabStart,
                                 StringStart + NewStringsSize - SymtabStart,
                                 DwarfSegmentSize, GapForDwarf, EndAddress);
    else if (LCI.C.cmd == MachO::LC_SEGMENT_64)
      transferSegmentAndSections(LCI, InputBinary.getSegment64LoadCommand(LCI),
                                 InputBinary, Writer, SymtabStart,
                                 StringStart + NewStringsSize - SymtabStart,
                                 DwarfSegmentSize, GapForDwarf, EndAddress);
  }

  uint64_t DwarfVMAddr = RoundUpToAlignment(EndAddress, 0x1000);
  uint64_t DwarfVMMax = Is64Bit ? UINT64_MAX : UINT32_MAX;
  if (DwarfVMAddr + DwarfSegmentSize > DwarfVMMax ||
      DwarfVMAddr + DwarfSegmentSize < DwarfVMAddr /* Overflow */) {
    // There is no room for the __DWARF segment at the end of the
    // address space. Look trhough segments to find a gap.
    DwarfVMAddr = GapForDwarf;
    if (DwarfVMAddr == UINT64_MAX)
      warn("not enough VM space for the __DWARF segment.",
           "output file streaming");
  }

  // Write the load command for the __DWARF segment.
  createDwarfSegment(DwarfVMAddr, DwarfSegmentStart, DwarfSegmentSize,
                     NumDwarfSections, Layout, Writer);

  assert(OutFile.tell() == LoadCommandSize + HeaderSize);
  Writer.WriteZeros(SymtabStart - (LoadCommandSize + HeaderSize));
  assert(OutFile.tell() == SymtabStart);

  // Transfer symbols.
  if (ShouldEmitSymtab) {
    Writer.writeBytes(NewSymtab.str());
    assert(OutFile.tell() == StringStart);

    // Transfer string table.
    // FIXME: The NonRelocatableStringpool starts with an empty string, but
    // dsymutil-classic starts the reconstructed string table with 2 of these.
    // Reproduce that behavior for now (there is corresponding code in
    // transferSymbol).
    Writer.WriteZeros(1);
    std::vector<DwarfStringPoolEntryRef> Entries = NewStrings.getEntries();
    for (auto Entry : Entries) {
      if (Entry.getIndex() == -1U)
        break;
      Writer.writeBytes(
        StringRef(Entry.getString().data(), Entry.getString().size() + 1));
    }
  }

  assert(OutFile.tell() == StringStart + NewStringsSize);

  // Pad till the Dwarf segment start.
  Writer.WriteZeros(DwarfSegmentStart - (StringStart + NewStringsSize));
  assert(OutFile.tell() == DwarfSegmentStart);

  // Emit the Dwarf sections contents.
  for (const MCSection &Sec : MCAsm) {
    if (Sec.begin() == Sec.end())
      continue;

    uint64_t Pos = OutFile.tell();
    Writer.WriteZeros(RoundUpToAlignment(Pos, Sec.getAlignment()) - Pos);
    MCAsm.writeSectionData(&Sec, Layout);
  }

  return true;
}
}
}
}