xref: /netbsd-src/external/apache2/llvm/dist/llvm/tools/llvm-jitlink/llvm-jitlink.cpp (revision 82d56013d7b633d116a93943de88e08335357a7c)

//===- llvm-jitlink.cpp -- Command line interface/tester for llvm-jitlink -===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This utility provides a simple command line interface to the llvm jitlink
// library, which makes relocatable object files executable in memory. Its
// primary function is as a testing utility for the jitlink library.
//
//===----------------------------------------------------------------------===//

#include "llvm-jitlink.h"

#include "llvm/BinaryFormat/Magic.h"
#include "llvm/ExecutionEngine/Orc/DebugObjectManagerPlugin.h"
#include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
#include "llvm/ExecutionEngine/Orc/TPCDebugObjectRegistrar.h"
#include "llvm/ExecutionEngine/Orc/TPCDynamicLibrarySearchGenerator.h"
#include "llvm/ExecutionEngine/Orc/TPCEHFrameRegistrar.h"
#include "llvm/ExecutionEngine/Orc/TargetProcess/JITLoaderGDB.h"
#include "llvm/ExecutionEngine/Orc/TargetProcess/RegisterEHFrames.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDisassembler/MCDisassembler.h"
#include "llvm/MC/MCInstPrinter.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCTargetOptions.h"
#include "llvm/Object/COFF.h"
#include "llvm/Object/MachO.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/InitLLVM.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/Timer.h"

#include <cstring>
#include <list>
#include <string>

#ifdef LLVM_ON_UNIX
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>
#endif // LLVM_ON_UNIX

#define DEBUG_TYPE "llvm_jitlink"

using namespace llvm;
using namespace llvm::jitlink;
using namespace llvm::orc;

static cl::list<std::string> InputFiles(cl::Positional, cl::OneOrMore,
                                        cl::desc("input files"));

static cl::opt<bool> NoExec("noexec", cl::desc("Do not execute loaded code"),
                            cl::init(false));

static cl::list<std::string>
    CheckFiles("check", cl::desc("File containing verifier checks"),
               cl::ZeroOrMore);

static cl::opt<std::string>
    CheckName("check-name", cl::desc("Name of checks to match against"),
              cl::init("jitlink-check"));

static cl::opt<std::string>
    EntryPointName("entry", cl::desc("Symbol to call as main entry point"),
                   cl::init(""));

static cl::list<std::string> JITLinkDylibs(
    "jld", cl::desc("Specifies the JITDylib to be used for any subsequent "
                    "input file arguments"));

static cl::list<std::string>
    Dylibs("dlopen", cl::desc("Dynamic libraries to load before linking"),
           cl::ZeroOrMore);

static cl::list<std::string> InputArgv("args", cl::Positional,
                                       cl::desc("<program arguments>..."),
                                       cl::ZeroOrMore, cl::PositionalEatsArgs);

static cl::opt<bool>
    NoProcessSymbols("no-process-syms",
                     cl::desc("Do not resolve to llvm-jitlink process symbols"),
                     cl::init(false));

static cl::list<std::string> AbsoluteDefs(
    "define-abs",
    cl::desc("Inject absolute symbol definitions (syntax: <name>=<addr>)"),
    cl::ZeroOrMore);

static cl::list<std::string> TestHarnesses("harness", cl::Positional,
                                           cl::desc("Test harness files"),
                                           cl::ZeroOrMore,
                                           cl::PositionalEatsArgs);

static cl::opt<bool> ShowInitialExecutionSessionState(
    "show-init-es",
    cl::desc("Print ExecutionSession state before resolving entry point"),
    cl::init(false));

static cl::opt<bool> ShowAddrs(
    "show-addrs",
    cl::desc("Print registered symbol, section, got and stub addresses"),
    cl::init(false));

static cl::opt<bool> ShowLinkGraph(
    "show-graph",
    cl::desc("Print the link graph after fixups have been applied"),
    cl::init(false));

static cl::opt<bool> ShowSizes(
    "show-sizes",
    cl::desc("Show sizes pre- and post-dead stripping, and allocations"),
    cl::init(false));

static cl::opt<bool> ShowTimes("show-times",
                               cl::desc("Show times for llvm-jitlink phases"),
                               cl::init(false));

static cl::opt<std::string> SlabAllocateSizeString(
    "slab-allocate",
    cl::desc("Allocate from a slab of the given size "
             "(allowable suffixes: Kb, Mb, Gb. default = "
             "Kb)"),
    cl::init(""));

static cl::opt<uint64_t> SlabAddress(
    "slab-address",
    cl::desc("Set slab target address (requires -slab-allocate and -noexec)"),
    cl::init(~0ULL));

static cl::opt<bool> ShowRelocatedSectionContents(
    "show-relocated-section-contents",
    cl::desc("show section contents after fixups have been applied"),
    cl::init(false));

static cl::opt<bool> PhonyExternals(
    "phony-externals",
    cl::desc("resolve all otherwise unresolved externals to null"),
    cl::init(false));

static cl::opt<std::string> OutOfProcessExecutor(
    "oop-executor", cl::desc("Launch an out-of-process executor to run code"),
    cl::ValueOptional);

static cl::opt<std::string> OutOfProcessExecutorConnect(
    "oop-executor-connect",
    cl::desc("Connect to an out-of-process executor via TCP"));

ExitOnError ExitOnErr;

LLVM_ATTRIBUTE_USED void linkComponents() {
  errs() << (void *)&llvm_orc_registerEHFrameSectionWrapper
         << (void *)&llvm_orc_deregisterEHFrameSectionWrapper
         << (void *)&llvm_orc_registerJITLoaderGDBWrapper;
}

namespace llvm {

static raw_ostream &
operator<<(raw_ostream &OS, const Session::MemoryRegionInfo &MRI) {
  return OS << "target addr = "
            << format("0x%016" PRIx64, MRI.getTargetAddress())
            << ", content: " << (const void *)MRI.getContent().data() << " -- "
            << (const void *)(MRI.getContent().data() + MRI.getContent().size())
            << " (" << MRI.getContent().size() << " bytes)";
}

static raw_ostream &
operator<<(raw_ostream &OS, const Session::SymbolInfoMap &SIM) {
  OS << "Symbols:\n";
  for (auto &SKV : SIM)
    OS << "  \"" << SKV.first() << "\" " << SKV.second << "\n";
  return OS;
}

static raw_ostream &
operator<<(raw_ostream &OS, const Session::FileInfo &FI) {
  for (auto &SIKV : FI.SectionInfos)
    OS << "  Section \"" << SIKV.first() << "\": " << SIKV.second << "\n";
  for (auto &GOTKV : FI.GOTEntryInfos)
    OS << "  GOT \"" << GOTKV.first() << "\": " << GOTKV.second << "\n";
  for (auto &StubKV : FI.StubInfos)
    OS << "  Stub \"" << StubKV.first() << "\": " << StubKV.second << "\n";
  return OS;
}

static raw_ostream &
operator<<(raw_ostream &OS, const Session::FileInfoMap &FIM) {
  for (auto &FIKV : FIM)
    OS << "File \"" << FIKV.first() << "\":\n" << FIKV.second;
  return OS;
}

static Error applyHarnessPromotions(Session &S, LinkGraph &G) {

  // If this graph is part of the test harness there's nothing to do.
  if (S.HarnessFiles.empty() || S.HarnessFiles.count(G.getName()))
    return Error::success();

  LLVM_DEBUG(dbgs() << "Appling promotions to graph " << G.getName() << "\n");

  // If this graph is part of the test then promote any symbols referenced by
  // the harness to default scope, remove all symbols that clash with harness
  // definitions.
  std::vector<Symbol *> DefinitionsToRemove;
  for (auto *Sym : G.defined_symbols()) {

    if (!Sym->hasName())
      continue;

    if (Sym->getLinkage() == Linkage::Weak) {
      if (!S.CanonicalWeakDefs.count(Sym->getName()) ||
          S.CanonicalWeakDefs[Sym->getName()] != G.getName()) {
        LLVM_DEBUG({
          dbgs() << "  Externalizing weak symbol " << Sym->getName() << "\n";
        });
        DefinitionsToRemove.push_back(Sym);
      } else {
        LLVM_DEBUG({
          dbgs() << "  Making weak symbol " << Sym->getName() << " strong\n";
        });
        if (S.HarnessExternals.count(Sym->getName()))
          Sym->setScope(Scope::Default);
        else
          Sym->setScope(Scope::Hidden);
        Sym->setLinkage(Linkage::Strong);
      }
    } else if (S.HarnessExternals.count(Sym->getName())) {
      LLVM_DEBUG(dbgs() << "  Promoting " << Sym->getName() << "\n");
      Sym->setScope(Scope::Default);
      Sym->setLive(true);
      continue;
    } else if (S.HarnessDefinitions.count(Sym->getName())) {
      LLVM_DEBUG(dbgs() << "  Externalizing " << Sym->getName() << "\n");
      DefinitionsToRemove.push_back(Sym);
    }
  }

  for (auto *Sym : DefinitionsToRemove)
    G.makeExternal(*Sym);

  return Error::success();
}

static uint64_t computeTotalBlockSizes(LinkGraph &G) {
  uint64_t TotalSize = 0;
  for (auto *B : G.blocks())
    TotalSize += B->getSize();
  return TotalSize;
}

static void dumpSectionContents(raw_ostream &OS, LinkGraph &G) {
  constexpr JITTargetAddress DumpWidth = 16;
  static_assert(isPowerOf2_64(DumpWidth), "DumpWidth must be a power of two");

  // Put sections in address order.
  std::vector<Section *> Sections;
  for (auto &S : G.sections())
    Sections.push_back(&S);

  llvm::sort(Sections, [](const Section *LHS, const Section *RHS) {
    if (llvm::empty(LHS->symbols()) && llvm::empty(RHS->symbols()))
      return false;
    if (llvm::empty(LHS->symbols()))
      return false;
    if (llvm::empty(RHS->symbols()))
      return true;
    SectionRange LHSRange(*LHS);
    SectionRange RHSRange(*RHS);
    return LHSRange.getStart() < RHSRange.getStart();
  });

  for (auto *S : Sections) {
    OS << S->getName() << " content:";
    if (llvm::empty(S->symbols())) {
      OS << "\n  section empty\n";
      continue;
    }

    // Sort symbols into order, then render.
    std::vector<Symbol *> Syms(S->symbols().begin(), S->symbols().end());
    llvm::sort(Syms, [](const Symbol *LHS, const Symbol *RHS) {
      return LHS->getAddress() < RHS->getAddress();
    });

    JITTargetAddress NextAddr = Syms.front()->getAddress() & ~(DumpWidth - 1);
    for (auto *Sym : Syms) {
      bool IsZeroFill = Sym->getBlock().isZeroFill();
      JITTargetAddress SymStart = Sym->getAddress();
      JITTargetAddress SymSize = Sym->getSize();
      JITTargetAddress SymEnd = SymStart + SymSize;
      const uint8_t *SymData = IsZeroFill ? nullptr
                                          : reinterpret_cast<const uint8_t *>(
                                                Sym->getSymbolContent().data());

      // Pad any space before the symbol starts.
      while (NextAddr != SymStart) {
        if (NextAddr % DumpWidth == 0)
          OS << formatv("\n{0:x16}:", NextAddr);
        OS << "   ";
        ++NextAddr;
      }

      // Render the symbol content.
      while (NextAddr != SymEnd) {
        if (NextAddr % DumpWidth == 0)
          OS << formatv("\n{0:x16}:", NextAddr);
        if (IsZeroFill)
          OS << " 00";
        else
          OS << formatv(" {0:x-2}", SymData[NextAddr - SymStart]);
        ++NextAddr;
      }
    }
    OS << "\n";
  }
}

class JITLinkSlabAllocator final : public JITLinkMemoryManager {
public:
  static Expected<std::unique_ptr<JITLinkSlabAllocator>>
  Create(uint64_t SlabSize) {
    Error Err = Error::success();
    std::unique_ptr<JITLinkSlabAllocator> Allocator(
        new JITLinkSlabAllocator(SlabSize, Err));
    if (Err)
      return std::move(Err);
    return std::move(Allocator);
  }

  Expected<std::unique_ptr<JITLinkMemoryManager::Allocation>>
  allocate(const JITLinkDylib *JD, const SegmentsRequestMap &Request) override {

    using AllocationMap = DenseMap<unsigned, sys::MemoryBlock>;

    // Local class for allocation.
    class IPMMAlloc : public Allocation {
    public:
      IPMMAlloc(JITLinkSlabAllocator &Parent, AllocationMap SegBlocks)
          : Parent(Parent), SegBlocks(std::move(SegBlocks)) {}
      MutableArrayRef<char> getWorkingMemory(ProtectionFlags Seg) override {
        assert(SegBlocks.count(Seg) && "No allocation for segment");
        return {static_cast<char *>(SegBlocks[Seg].base()),
                SegBlocks[Seg].allocatedSize()};
      }
      JITTargetAddress getTargetMemory(ProtectionFlags Seg) override {
        assert(SegBlocks.count(Seg) && "No allocation for segment");
        return pointerToJITTargetAddress(SegBlocks[Seg].base()) +
               Parent.TargetDelta;
      }
      void finalizeAsync(FinalizeContinuation OnFinalize) override {
        OnFinalize(applyProtections());
      }
      Error deallocate() override {
        for (auto &KV : SegBlocks)
          if (auto EC = sys::Memory::releaseMappedMemory(KV.second))
            return errorCodeToError(EC);
        return Error::success();
      }

    private:
      Error applyProtections() {
        for (auto &KV : SegBlocks) {
          auto &Prot = KV.first;
          auto &Block = KV.second;
          if (auto EC = sys::Memory::protectMappedMemory(Block, Prot))
            return errorCodeToError(EC);
          if (Prot & sys::Memory::MF_EXEC)
            sys::Memory::InvalidateInstructionCache(Block.base(),
                                                    Block.allocatedSize());
        }
        return Error::success();
      }

      JITLinkSlabAllocator &Parent;
      AllocationMap SegBlocks;
    };

    AllocationMap Blocks;

    for (auto &KV : Request) {
      auto &Seg = KV.second;

      if (Seg.getAlignment() > PageSize)
        return make_error<StringError>("Cannot request higher than page "
                                       "alignment",
                                       inconvertibleErrorCode());

      if (PageSize % Seg.getAlignment() != 0)
        return make_error<StringError>("Page size is not a multiple of "
                                       "alignment",
                                       inconvertibleErrorCode());

      uint64_t ZeroFillStart = Seg.getContentSize();
      uint64_t SegmentSize = ZeroFillStart + Seg.getZeroFillSize();

      // Round segment size up to page boundary.
      SegmentSize = (SegmentSize + PageSize - 1) & ~(PageSize - 1);

      // Take segment bytes from the front of the slab.
      void *SlabBase = SlabRemaining.base();
      uint64_t SlabRemainingSize = SlabRemaining.allocatedSize();

      if (SegmentSize > SlabRemainingSize)
        return make_error<StringError>("Slab allocator out of memory",
                                       inconvertibleErrorCode());

      sys::MemoryBlock SegMem(SlabBase, SegmentSize);
      SlabRemaining =
          sys::MemoryBlock(reinterpret_cast<char *>(SlabBase) + SegmentSize,
                           SlabRemainingSize - SegmentSize);

      // Zero out the zero-fill memory.
      memset(static_cast<char *>(SegMem.base()) + ZeroFillStart, 0,
             Seg.getZeroFillSize());

      // Record the block for this segment.
      Blocks[KV.first] = std::move(SegMem);
    }
    return std::unique_ptr<InProcessMemoryManager::Allocation>(
        new IPMMAlloc(*this, std::move(Blocks)));
  }

private:
  JITLinkSlabAllocator(uint64_t SlabSize, Error &Err) {
    ErrorAsOutParameter _(&Err);

    PageSize = sys::Process::getPageSizeEstimate();

    if (!isPowerOf2_64(PageSize)) {
      Err = make_error<StringError>("Page size is not a power of 2",
                                    inconvertibleErrorCode());
      return;
    }

    // Round slab request up to page size.
    SlabSize = (SlabSize + PageSize - 1) & ~(PageSize - 1);

    const sys::Memory::ProtectionFlags ReadWrite =
        static_cast<sys::Memory::ProtectionFlags>(sys::Memory::MF_READ |
                                                  sys::Memory::MF_WRITE);

    std::error_code EC;
    SlabRemaining =
        sys::Memory::allocateMappedMemory(SlabSize, nullptr, ReadWrite, EC);

    if (EC) {
      Err = errorCodeToError(EC);
      return;
    }

    // Calculate the target address delta to link as-if slab were at
    // SlabAddress.
    if (SlabAddress != ~0ULL)
      TargetDelta =
          SlabAddress - pointerToJITTargetAddress(SlabRemaining.base());
  }

  sys::MemoryBlock SlabRemaining;
  uint64_t PageSize = 0;
  int64_t TargetDelta = 0;
};

Expected<uint64_t> getSlabAllocSize(StringRef SizeString) {
  SizeString = SizeString.trim();

  uint64_t Units = 1024;

  if (SizeString.endswith_lower("kb"))
    SizeString = SizeString.drop_back(2).rtrim();
  else if (SizeString.endswith_lower("mb")) {
    Units = 1024 * 1024;
    SizeString = SizeString.drop_back(2).rtrim();
  } else if (SizeString.endswith_lower("gb")) {
    Units = 1024 * 1024 * 1024;
    SizeString = SizeString.drop_back(2).rtrim();
  }

  uint64_t SlabSize = 0;
  if (SizeString.getAsInteger(10, SlabSize))
    return make_error<StringError>("Invalid numeric format for slab size",
                                   inconvertibleErrorCode());

  return SlabSize * Units;
}

static std::unique_ptr<JITLinkMemoryManager> createMemoryManager() {
  if (!SlabAllocateSizeString.empty()) {
    auto SlabSize = ExitOnErr(getSlabAllocSize(SlabAllocateSizeString));
    return ExitOnErr(JITLinkSlabAllocator::Create(SlabSize));
  }
  return std::make_unique<InProcessMemoryManager>();
}

LLVMJITLinkObjectLinkingLayer::LLVMJITLinkObjectLinkingLayer(
    Session &S, JITLinkMemoryManager &MemMgr)
    : ObjectLinkingLayer(S.ES, MemMgr), S(S) {}

Error LLVMJITLinkObjectLinkingLayer::add(ResourceTrackerSP RT,
                                         std::unique_ptr<MemoryBuffer> O) {

  if (S.HarnessFiles.empty() || S.HarnessFiles.count(O->getBufferIdentifier()))
    return ObjectLinkingLayer::add(std::move(RT), std::move(O));

  // Use getObjectSymbolInfo to compute the init symbol, but ignore
  // the symbols field. We'll handle that manually to include promotion.
  auto ObjSymInfo =
      getObjectSymbolInfo(getExecutionSession(), O->getMemBufferRef());

  if (!ObjSymInfo)
    return ObjSymInfo.takeError();

  auto &InitSymbol = ObjSymInfo->second;

  // If creating an object file was going to fail it would have happened above,
  // so we can 'cantFail' this.
  auto Obj =
      cantFail(object::ObjectFile::createObjectFile(O->getMemBufferRef()));

  SymbolFlagsMap SymbolFlags;

  // The init symbol must be included in the SymbolFlags map if present.
  if (InitSymbol)
    SymbolFlags[InitSymbol] = JITSymbolFlags::MaterializationSideEffectsOnly;

  for (auto &Sym : Obj->symbols()) {
    Expected<uint32_t> SymFlagsOrErr = Sym.getFlags();
    if (!SymFlagsOrErr)
      // TODO: Test this error.
      return SymFlagsOrErr.takeError();

    // Skip symbols not defined in this object file.
    if ((*SymFlagsOrErr & object::BasicSymbolRef::SF_Undefined))
      continue;

    auto Name = Sym.getName();
    if (!Name)
      return Name.takeError();

    // Skip symbols that have type SF_File.
    if (auto SymType = Sym.getType()) {
      if (*SymType == object::SymbolRef::ST_File)
        continue;
    } else
      return SymType.takeError();

    auto SymFlags = JITSymbolFlags::fromObjectSymbol(Sym);
    if (!SymFlags)
      return SymFlags.takeError();

    if (SymFlags->isWeak()) {
      // If this is a weak symbol that's not defined in the harness then we
      // need to either mark it as strong (if this is the first definition
      // that we've seen) or discard it.
      if (S.HarnessDefinitions.count(*Name) || S.CanonicalWeakDefs.count(*Name))
        continue;
      S.CanonicalWeakDefs[*Name] = O->getBufferIdentifier();
      *SymFlags &= ~JITSymbolFlags::Weak;
      if (!S.HarnessExternals.count(*Name))
        *SymFlags &= ~JITSymbolFlags::Exported;
    } else if (S.HarnessExternals.count(*Name)) {
      *SymFlags |= JITSymbolFlags::Exported;
    } else if (S.HarnessDefinitions.count(*Name) ||
               !(*SymFlagsOrErr & object::BasicSymbolRef::SF_Global))
      continue;

    auto InternedName = S.ES.intern(*Name);
    SymbolFlags[InternedName] = std::move(*SymFlags);
  }

  auto MU = std::make_unique<BasicObjectLayerMaterializationUnit>(
      *this, std::move(O), std::move(SymbolFlags), std::move(InitSymbol));

  auto &JD = RT->getJITDylib();
  return JD.define(std::move(MU), std::move(RT));
}

Expected<std::unique_ptr<TargetProcessControl>>
LLVMJITLinkRemoteTargetProcessControl::LaunchExecutor() {
#ifndef LLVM_ON_UNIX
  // FIXME: Add support for Windows.
  return make_error<StringError>("-" + OutOfProcessExecutor.ArgStr +
                                     " not supported on non-unix platforms",
                                 inconvertibleErrorCode());
#else

  shared::registerStringError<LLVMJITLinkChannel>();

  constexpr int ReadEnd = 0;
  constexpr int WriteEnd = 1;

  // Pipe FDs.
  int ToExecutor[2];
  int FromExecutor[2];

  pid_t ChildPID;

  // Create pipes to/from the executor..
  if (pipe(ToExecutor) != 0 || pipe(FromExecutor) != 0)
    return make_error<StringError>("Unable to create pipe for executor",
                                   inconvertibleErrorCode());

  ChildPID = fork();

  if (ChildPID == 0) {
    // In the child...

    // Close the parent ends of the pipes
    close(ToExecutor[WriteEnd]);
    close(FromExecutor[ReadEnd]);

    // Execute the child process.
    std::unique_ptr<char[]> ExecutorPath, FDSpecifier;
    {
      ExecutorPath = std::make_unique<char[]>(OutOfProcessExecutor.size() + 1);
      strcpy(ExecutorPath.get(), OutOfProcessExecutor.data());

      std::string FDSpecifierStr("filedescs=");
      FDSpecifierStr += utostr(ToExecutor[ReadEnd]);
      FDSpecifierStr += ',';
      FDSpecifierStr += utostr(FromExecutor[WriteEnd]);
      FDSpecifier = std::make_unique<char[]>(FDSpecifierStr.size() + 1);
      strcpy(FDSpecifier.get(), FDSpecifierStr.c_str());
    }

    char *const Args[] = {ExecutorPath.get(), FDSpecifier.get(), nullptr};
    int RC = execvp(ExecutorPath.get(), Args);
    if (RC != 0) {
      errs() << "unable to launch out-of-process executor \""
             << ExecutorPath.get() << "\"\n";
      exit(1);
    }
  }
  // else we're the parent...

  // Close the child ends of the pipes
  close(ToExecutor[ReadEnd]);
  close(FromExecutor[WriteEnd]);

  // Return an RPC channel connected to our end of the pipes.
  auto SSP = std::make_shared<SymbolStringPool>();
  auto Channel = std::make_unique<shared::FDRawByteChannel>(
      FromExecutor[ReadEnd], ToExecutor[WriteEnd]);
  auto Endpoint = std::make_unique<LLVMJITLinkRPCEndpoint>(*Channel, true);

  auto ReportError = [](Error Err) {
    logAllUnhandledErrors(std::move(Err), errs(), "");
  };

  Error Err = Error::success();
  std::unique_ptr<LLVMJITLinkRemoteTargetProcessControl> RTPC(
      new LLVMJITLinkRemoteTargetProcessControl(
          std::move(SSP), std::move(Channel), std::move(Endpoint),
          std::move(ReportError), Err));
  if (Err)
    return std::move(Err);
  return std::move(RTPC);
#endif
}

#ifdef LLVM_ON_UNIX
static Error createTCPSocketError(Twine Details) {
  return make_error<StringError>(
      formatv("Failed to connect TCP socket '{0}': {1}",
              OutOfProcessExecutorConnect, Details),
      inconvertibleErrorCode());
}

static Expected<int> connectTCPSocket(std::string Host, std::string PortStr) {
  addrinfo *AI;
  addrinfo Hints{};
  Hints.ai_family = AF_INET;
  Hints.ai_socktype = SOCK_STREAM;
  Hints.ai_flags = AI_NUMERICSERV;

  if (int EC = getaddrinfo(Host.c_str(), PortStr.c_str(), &Hints, &AI))
    return createTCPSocketError("Address resolution failed (" +
                                StringRef(gai_strerror(EC)) + ")");

  // Cycle through the returned addrinfo structures and connect to the first
  // reachable endpoint.
  int SockFD;
  addrinfo *Server;
  for (Server = AI; Server != nullptr; Server = Server->ai_next) {
    // socket might fail, e.g. if the address family is not supported. Skip to
    // the next addrinfo structure in such a case.
    if ((SockFD = socket(AI->ai_family, AI->ai_socktype, AI->ai_protocol)) < 0)
      continue;

    // If connect returns null, we exit the loop with a working socket.
    if (connect(SockFD, Server->ai_addr, Server->ai_addrlen) == 0)
      break;

    close(SockFD);
  }
  freeaddrinfo(AI);

  // If we reached the end of the loop without connecting to a valid endpoint,
  // dump the last error that was logged in socket() or connect().
  if (Server == nullptr)
    return createTCPSocketError(std::strerror(errno));

  return SockFD;
}
#endif

Expected<std::unique_ptr<TargetProcessControl>>
LLVMJITLinkRemoteTargetProcessControl::ConnectToExecutor() {
#ifndef LLVM_ON_UNIX
  // FIXME: Add TCP support for Windows.
  return make_error<StringError>("-" + OutOfProcessExecutorConnect.ArgStr +
                                     " not supported on non-unix platforms",
                                 inconvertibleErrorCode());
#else

  shared::registerStringError<LLVMJITLinkChannel>();

  StringRef Host, PortStr;
  std::tie(Host, PortStr) = StringRef(OutOfProcessExecutorConnect).split(':');
  if (Host.empty())
    return createTCPSocketError("Host name for -" +
                                OutOfProcessExecutorConnect.ArgStr +
                                " can not be empty");
  if (PortStr.empty())
    return createTCPSocketError("Port number in -" +
                                OutOfProcessExecutorConnect.ArgStr +
                                " can not be empty");
  int Port = 0;
  if (PortStr.getAsInteger(10, Port))
    return createTCPSocketError("Port number '" + PortStr +
                                "' is not a valid integer");

  Expected<int> SockFD = connectTCPSocket(Host.str(), PortStr.str());
  if (!SockFD)
    return SockFD.takeError();

  auto SSP = std::make_shared<SymbolStringPool>();
  auto Channel = std::make_unique<shared::FDRawByteChannel>(*SockFD, *SockFD);
  auto Endpoint = std::make_unique<LLVMJITLinkRPCEndpoint>(*Channel, true);

  auto ReportError = [](Error Err) {
    logAllUnhandledErrors(std::move(Err), errs(), "");
  };

  Error Err = Error::success();
  std::unique_ptr<LLVMJITLinkRemoteTargetProcessControl> RTPC(
      new LLVMJITLinkRemoteTargetProcessControl(
          std::move(SSP), std::move(Channel), std::move(Endpoint),
          std::move(ReportError), Err));
  if (Err)
    return std::move(Err);
  return std::move(RTPC);
#endif
}

Error LLVMJITLinkRemoteTargetProcessControl::disconnect() {
  std::promise<MSVCPError> P;
  auto F = P.get_future();
  auto Err = closeConnection([&](Error Err) -> Error {
    P.set_value(std::move(Err));
    Finished = true;
    return Error::success();
  });
  ListenerThread.join();
  return joinErrors(std::move(Err), F.get());
}

class PhonyExternalsGenerator : public DefinitionGenerator {
public:
  Error tryToGenerate(LookupState &LS, LookupKind K, JITDylib &JD,
                      JITDylibLookupFlags JDLookupFlags,
                      const SymbolLookupSet &LookupSet) override {
    SymbolMap PhonySymbols;
    for (auto &KV : LookupSet)
      PhonySymbols[KV.first] = JITEvaluatedSymbol(0, JITSymbolFlags::Exported);
    return JD.define(absoluteSymbols(std::move(PhonySymbols)));
  }
};

Expected<std::unique_ptr<Session>> Session::Create(Triple TT) {

  auto PageSize = sys::Process::getPageSize();
  if (!PageSize)
    return PageSize.takeError();

  /// If -oop-executor is passed then launch the executor.
  std::unique_ptr<TargetProcessControl> TPC;
  if (OutOfProcessExecutor.getNumOccurrences()) {
    if (auto RTPC = LLVMJITLinkRemoteTargetProcessControl::LaunchExecutor())
      TPC = std::move(*RTPC);
    else
      return RTPC.takeError();
  } else if (OutOfProcessExecutorConnect.getNumOccurrences()) {
    if (auto RTPC = LLVMJITLinkRemoteTargetProcessControl::ConnectToExecutor())
      TPC = std::move(*RTPC);
    else
      return RTPC.takeError();
  } else
    TPC = std::make_unique<SelfTargetProcessControl>(
        std::make_shared<SymbolStringPool>(), std::move(TT), *PageSize,
        createMemoryManager());

  Error Err = Error::success();
  std::unique_ptr<Session> S(new Session(std::move(TPC), Err));
  if (Err)
    return std::move(Err);
  return std::move(S);
}

Session::~Session() {
  if (auto Err = ES.endSession())
    ES.reportError(std::move(Err));
}

// FIXME: Move to createJITDylib if/when we start using Platform support in
// llvm-jitlink.
Session::Session(std::unique_ptr<TargetProcessControl> TPC, Error &Err)
    : TPC(std::move(TPC)), ObjLayer(*this, this->TPC->getMemMgr()) {

  /// Local ObjectLinkingLayer::Plugin class to forward modifyPassConfig to the
  /// Session.
  class JITLinkSessionPlugin : public ObjectLinkingLayer::Plugin {
  public:
    JITLinkSessionPlugin(Session &S) : S(S) {}
    void modifyPassConfig(MaterializationResponsibility &MR, LinkGraph &G,
                          PassConfiguration &PassConfig) override {
      S.modifyPassConfig(G.getTargetTriple(), PassConfig);
    }

    Error notifyFailed(MaterializationResponsibility &MR) override {
      return Error::success();
    }
    Error notifyRemovingResources(ResourceKey K) override {
      return Error::success();
    }
    void notifyTransferringResources(ResourceKey DstKey,
                                     ResourceKey SrcKey) override {}

  private:
    Session &S;
  };

  ErrorAsOutParameter _(&Err);

  if (auto MainJDOrErr = ES.createJITDylib("main"))
    MainJD = &*MainJDOrErr;
  else {
    Err = MainJDOrErr.takeError();
    return;
  }

  if (!NoExec && !this->TPC->getTargetTriple().isOSWindows()) {
    ObjLayer.addPlugin(std::make_unique<EHFrameRegistrationPlugin>(
        ES, ExitOnErr(TPCEHFrameRegistrar::Create(*this->TPC))));
    ObjLayer.addPlugin(std::make_unique<DebugObjectManagerPlugin>(
        ES, ExitOnErr(createJITLoaderGDBRegistrar(*this->TPC))));
  }

  ObjLayer.addPlugin(std::make_unique<JITLinkSessionPlugin>(*this));

  // Process any harness files.
  for (auto &HarnessFile : TestHarnesses) {
    HarnessFiles.insert(HarnessFile);

    auto ObjBuffer =
        ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(HarnessFile)));

    auto ObjSymbolInfo =
        ExitOnErr(getObjectSymbolInfo(ES, ObjBuffer->getMemBufferRef()));

    for (auto &KV : ObjSymbolInfo.first)
      HarnessDefinitions.insert(*KV.first);

    auto Obj = ExitOnErr(
        object::ObjectFile::createObjectFile(ObjBuffer->getMemBufferRef()));

    for (auto &Sym : Obj->symbols()) {
      uint32_t SymFlags = ExitOnErr(Sym.getFlags());
      auto Name = ExitOnErr(Sym.getName());

      if (Name.empty())
        continue;

      if (SymFlags & object::BasicSymbolRef::SF_Undefined)
        HarnessExternals.insert(Name);
    }
  }

  // If a name is defined by some harness file then it's a definition, not an
  // external.
  for (auto &DefName : HarnessDefinitions)
    HarnessExternals.erase(DefName.getKey());
}

void Session::dumpSessionInfo(raw_ostream &OS) {
  OS << "Registered addresses:\n" << SymbolInfos << FileInfos;
}

void Session::modifyPassConfig(const Triple &TT,
                               PassConfiguration &PassConfig) {
  if (!CheckFiles.empty())
    PassConfig.PostFixupPasses.push_back([this](LinkGraph &G) {
      if (TPC->getTargetTriple().getObjectFormat() == Triple::ELF)
        return registerELFGraphInfo(*this, G);

      if (TPC->getTargetTriple().getObjectFormat() == Triple::MachO)
        return registerMachOGraphInfo(*this, G);

      return make_error<StringError>("Unsupported object format for GOT/stub "
                                     "registration",
                                     inconvertibleErrorCode());
    });

  if (ShowLinkGraph)
    PassConfig.PostFixupPasses.push_back([](LinkGraph &G) -> Error {
      outs() << "Link graph \"" << G.getName() << "\" post-fixup:\n";
      G.dump(outs());
      return Error::success();
    });

  PassConfig.PrePrunePasses.push_back(
      [this](LinkGraph &G) { return applyHarnessPromotions(*this, G); });

  if (ShowSizes) {
    PassConfig.PrePrunePasses.push_back([this](LinkGraph &G) -> Error {
      SizeBeforePruning += computeTotalBlockSizes(G);
      return Error::success();
    });
    PassConfig.PostFixupPasses.push_back([this](LinkGraph &G) -> Error {
      SizeAfterFixups += computeTotalBlockSizes(G);
      return Error::success();
    });
  }

  if (ShowRelocatedSectionContents)
    PassConfig.PostFixupPasses.push_back([](LinkGraph &G) -> Error {
      outs() << "Relocated section contents for " << G.getName() << ":\n";
      dumpSectionContents(outs(), G);
      return Error::success();
    });
}

Expected<Session::FileInfo &> Session::findFileInfo(StringRef FileName) {
  auto FileInfoItr = FileInfos.find(FileName);
  if (FileInfoItr == FileInfos.end())
    return make_error<StringError>("file \"" + FileName + "\" not recognized",
                                   inconvertibleErrorCode());
  return FileInfoItr->second;
}

Expected<Session::MemoryRegionInfo &>
Session::findSectionInfo(StringRef FileName, StringRef SectionName) {
  auto FI = findFileInfo(FileName);
  if (!FI)
    return FI.takeError();
  auto SecInfoItr = FI->SectionInfos.find(SectionName);
  if (SecInfoItr == FI->SectionInfos.end())
    return make_error<StringError>("no section \"" + SectionName +
                                       "\" registered for file \"" + FileName +
                                       "\"",
                                   inconvertibleErrorCode());
  return SecInfoItr->second;
}

Expected<Session::MemoryRegionInfo &>
Session::findStubInfo(StringRef FileName, StringRef TargetName) {
  auto FI = findFileInfo(FileName);
  if (!FI)
    return FI.takeError();
  auto StubInfoItr = FI->StubInfos.find(TargetName);
  if (StubInfoItr == FI->StubInfos.end())
    return make_error<StringError>("no stub for \"" + TargetName +
                                       "\" registered for file \"" + FileName +
                                       "\"",
                                   inconvertibleErrorCode());
  return StubInfoItr->second;
}

Expected<Session::MemoryRegionInfo &>
Session::findGOTEntryInfo(StringRef FileName, StringRef TargetName) {
  auto FI = findFileInfo(FileName);
  if (!FI)
    return FI.takeError();
  auto GOTInfoItr = FI->GOTEntryInfos.find(TargetName);
  if (GOTInfoItr == FI->GOTEntryInfos.end())
    return make_error<StringError>("no GOT entry for \"" + TargetName +
                                       "\" registered for file \"" + FileName +
                                       "\"",
                                   inconvertibleErrorCode());
  return GOTInfoItr->second;
}

bool Session::isSymbolRegistered(StringRef SymbolName) {
  return SymbolInfos.count(SymbolName);
}

Expected<Session::MemoryRegionInfo &>
Session::findSymbolInfo(StringRef SymbolName, Twine ErrorMsgStem) {
  auto SymInfoItr = SymbolInfos.find(SymbolName);
  if (SymInfoItr == SymbolInfos.end())
    return make_error<StringError>(ErrorMsgStem + ": symbol " + SymbolName +
                                       " not found",
                                   inconvertibleErrorCode());
  return SymInfoItr->second;
}

} // end namespace llvm

static Triple getFirstFileTriple() {
  static Triple FirstTT = []() {
    assert(!InputFiles.empty() && "InputFiles can not be empty");
    for (auto InputFile : InputFiles) {
      auto ObjBuffer =
          ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(InputFile)));
      switch (identify_magic(ObjBuffer->getBuffer())) {
      case file_magic::elf_relocatable:
      case file_magic::macho_object:
      case file_magic::coff_object: {
        auto Obj = ExitOnErr(
            object::ObjectFile::createObjectFile(ObjBuffer->getMemBufferRef()));
        return Obj->makeTriple();
      }
      default:
        break;
      }
    }
    return Triple();
  }();

  return FirstTT;
}

static Error sanitizeArguments(const Triple &TT, const char *ArgV0) {
  // Set the entry point name if not specified.
  if (EntryPointName.empty()) {
    if (TT.getObjectFormat() == Triple::MachO)
      EntryPointName = "_main";
    else
      EntryPointName = "main";
  }

  // -noexec and --args should not be used together.
  if (NoExec && !InputArgv.empty())
    outs() << "Warning: --args passed to -noexec run will be ignored.\n";

  // If -slab-address is passed, require -slab-allocate and -noexec
  if (SlabAddress != ~0ULL) {
    if (SlabAllocateSizeString == "" || !NoExec)
      return make_error<StringError>(
          "-slab-address requires -slab-allocate and -noexec",
          inconvertibleErrorCode());
  }

  // Only one of -oop-executor and -oop-executor-connect can be used.
  if (!!OutOfProcessExecutor.getNumOccurrences() &&
      !!OutOfProcessExecutorConnect.getNumOccurrences())
    return make_error<StringError>(
        "Only one of -" + OutOfProcessExecutor.ArgStr + " and -" +
            OutOfProcessExecutorConnect.ArgStr + " can be specified",
        inconvertibleErrorCode());

  // If -oop-executor was used but no value was specified then use a sensible
  // default.
  if (!!OutOfProcessExecutor.getNumOccurrences() &&
      OutOfProcessExecutor.empty()) {
    SmallString<256> OOPExecutorPath(sys::fs::getMainExecutable(
        ArgV0, reinterpret_cast<void *>(&sanitizeArguments)));
    sys::path::remove_filename(OOPExecutorPath);
    if (OOPExecutorPath.back() != '/')
      OOPExecutorPath += '/';
    OOPExecutorPath += "llvm-jitlink-executor";
    OutOfProcessExecutor = OOPExecutorPath.str().str();
  }

  return Error::success();
}

static Error loadProcessSymbols(Session &S) {
  auto FilterMainEntryPoint =
      [EPName = S.ES.intern(EntryPointName)](SymbolStringPtr Name) {
        return Name != EPName;
      };
  S.MainJD->addGenerator(
      ExitOnErr(orc::TPCDynamicLibrarySearchGenerator::GetForTargetProcess(
          *S.TPC, std::move(FilterMainEntryPoint))));

  return Error::success();
}

static Error loadDylibs(Session &S) {
  for (const auto &Dylib : Dylibs) {
    auto G = orc::TPCDynamicLibrarySearchGenerator::Load(*S.TPC, Dylib.c_str());
    if (!G)
      return G.takeError();
    S.MainJD->addGenerator(std::move(*G));
  }

  return Error::success();
}

static void addPhonyExternalsGenerator(Session &S) {
  S.MainJD->addGenerator(std::make_unique<PhonyExternalsGenerator>());
}

static Error loadObjects(Session &S) {
  std::map<unsigned, JITDylib *> IdxToJLD;

  // First, set up JITDylibs.
  LLVM_DEBUG(dbgs() << "Creating JITDylibs...\n");
  {
    // Create a "main" JITLinkDylib.
    IdxToJLD[0] = S.MainJD;
    S.JDSearchOrder.push_back(S.MainJD);
    LLVM_DEBUG(dbgs() << "  0: " << S.MainJD->getName() << "\n");

    // Add any extra JITLinkDylibs from the command line.
    std::string JDNamePrefix("lib");
    for (auto JLDItr = JITLinkDylibs.begin(), JLDEnd = JITLinkDylibs.end();
         JLDItr != JLDEnd; ++JLDItr) {
      auto JD = S.ES.createJITDylib(JDNamePrefix + *JLDItr);
      if (!JD)
        return JD.takeError();
      unsigned JDIdx =
          JITLinkDylibs.getPosition(JLDItr - JITLinkDylibs.begin());
      IdxToJLD[JDIdx] = &*JD;
      S.JDSearchOrder.push_back(&*JD);
      LLVM_DEBUG(dbgs() << "  " << JDIdx << ": " << JD->getName() << "\n");
    }

    // Set every dylib to link against every other, in command line order.
    for (auto *JD : S.JDSearchOrder) {
      auto LookupFlags = JITDylibLookupFlags::MatchExportedSymbolsOnly;
      JITDylibSearchOrder LinkOrder;
      for (auto *JD2 : S.JDSearchOrder) {
        if (JD2 == JD)
          continue;
        LinkOrder.push_back(std::make_pair(JD2, LookupFlags));
      }
      JD->setLinkOrder(std::move(LinkOrder));
    }
  }

  LLVM_DEBUG(dbgs() << "Adding test harness objects...\n");
  for (auto HarnessFile : TestHarnesses) {
    LLVM_DEBUG(dbgs() << "  " << HarnessFile << "\n");
    auto ObjBuffer =
        ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(HarnessFile)));
    ExitOnErr(S.ObjLayer.add(*S.MainJD, std::move(ObjBuffer)));
  }

  // Load each object into the corresponding JITDylib..
  LLVM_DEBUG(dbgs() << "Adding objects...\n");
  for (auto InputFileItr = InputFiles.begin(), InputFileEnd = InputFiles.end();
       InputFileItr != InputFileEnd; ++InputFileItr) {
    unsigned InputFileArgIdx =
        InputFiles.getPosition(InputFileItr - InputFiles.begin());
    const std::string &InputFile = *InputFileItr;
    auto &JD = *std::prev(IdxToJLD.lower_bound(InputFileArgIdx))->second;
    LLVM_DEBUG(dbgs() << "  " << InputFileArgIdx << ": \"" << InputFile
                      << "\" to " << JD.getName() << "\n";);
    auto ObjBuffer =
        ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(InputFile)));

    auto Magic = identify_magic(ObjBuffer->getBuffer());
    if (Magic == file_magic::archive ||
        Magic == file_magic::macho_universal_binary)
      JD.addGenerator(ExitOnErr(StaticLibraryDefinitionGenerator::Load(
          S.ObjLayer, InputFile.c_str(), S.TPC->getTargetTriple())));
    else
      ExitOnErr(S.ObjLayer.add(JD, std::move(ObjBuffer)));
  }

  // Define absolute symbols.
  LLVM_DEBUG(dbgs() << "Defining absolute symbols...\n");
  for (auto AbsDefItr = AbsoluteDefs.begin(), AbsDefEnd = AbsoluteDefs.end();
       AbsDefItr != AbsDefEnd; ++AbsDefItr) {
    unsigned AbsDefArgIdx =
      AbsoluteDefs.getPosition(AbsDefItr - AbsoluteDefs.begin());
    auto &JD = *std::prev(IdxToJLD.lower_bound(AbsDefArgIdx))->second;

    StringRef AbsDefStmt = *AbsDefItr;
    size_t EqIdx = AbsDefStmt.find_first_of('=');
    if (EqIdx == StringRef::npos)
      return make_error<StringError>("Invalid absolute define \"" + AbsDefStmt +
                                     "\". Syntax: <name>=<addr>",
                                     inconvertibleErrorCode());
    StringRef Name = AbsDefStmt.substr(0, EqIdx).trim();
    StringRef AddrStr = AbsDefStmt.substr(EqIdx + 1).trim();

    uint64_t Addr;
    if (AddrStr.getAsInteger(0, Addr))
      return make_error<StringError>("Invalid address expression \"" + AddrStr +
                                     "\" in absolute define \"" + AbsDefStmt +
                                     "\"",
                                     inconvertibleErrorCode());
    JITEvaluatedSymbol AbsDef(Addr, JITSymbolFlags::Exported);
    if (auto Err = JD.define(absoluteSymbols({{S.ES.intern(Name), AbsDef}})))
      return Err;

    // Register the absolute symbol with the session symbol infos.
    S.SymbolInfos[Name] = {ArrayRef<char>(), Addr};
  }

  LLVM_DEBUG({
    dbgs() << "Dylib search order is [ ";
    for (auto *JD : S.JDSearchOrder)
      dbgs() << JD->getName() << " ";
    dbgs() << "]\n";
  });

  return Error::success();
}

static Error runChecks(Session &S) {

  auto TripleName = S.TPC->getTargetTriple().str();
  std::string ErrorStr;
  const Target *TheTarget = TargetRegistry::lookupTarget(TripleName, ErrorStr);
  if (!TheTarget)
    ExitOnErr(make_error<StringError>("Error accessing target '" + TripleName +
                                          "': " + ErrorStr,
                                      inconvertibleErrorCode()));

  std::unique_ptr<MCSubtargetInfo> STI(
      TheTarget->createMCSubtargetInfo(TripleName, "", ""));
  if (!STI)
    ExitOnErr(
        make_error<StringError>("Unable to create subtarget for " + TripleName,
                                inconvertibleErrorCode()));

  std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TripleName));
  if (!MRI)
    ExitOnErr(make_error<StringError>("Unable to create target register info "
                                      "for " +
                                          TripleName,
                                      inconvertibleErrorCode()));

  MCTargetOptions MCOptions;
  std::unique_ptr<MCAsmInfo> MAI(
      TheTarget->createMCAsmInfo(*MRI, TripleName, MCOptions));
  if (!MAI)
    ExitOnErr(make_error<StringError>("Unable to create target asm info " +
                                          TripleName,
                                      inconvertibleErrorCode()));

  MCContext Ctx(Triple(TripleName), MAI.get(), MRI.get(), STI.get());

  std::unique_ptr<MCDisassembler> Disassembler(
      TheTarget->createMCDisassembler(*STI, Ctx));
  if (!Disassembler)
    ExitOnErr(make_error<StringError>("Unable to create disassembler for " +
                                          TripleName,
                                      inconvertibleErrorCode()));

  std::unique_ptr<MCInstrInfo> MII(TheTarget->createMCInstrInfo());

  std::unique_ptr<MCInstPrinter> InstPrinter(
      TheTarget->createMCInstPrinter(Triple(TripleName), 0, *MAI, *MII, *MRI));

  auto IsSymbolValid = [&S](StringRef Symbol) {
    return S.isSymbolRegistered(Symbol);
  };

  auto GetSymbolInfo = [&S](StringRef Symbol) {
    return S.findSymbolInfo(Symbol, "Can not get symbol info");
  };

  auto GetSectionInfo = [&S](StringRef FileName, StringRef SectionName) {
    return S.findSectionInfo(FileName, SectionName);
  };

  auto GetStubInfo = [&S](StringRef FileName, StringRef SectionName) {
    return S.findStubInfo(FileName, SectionName);
  };

  auto GetGOTInfo = [&S](StringRef FileName, StringRef SectionName) {
    return S.findGOTEntryInfo(FileName, SectionName);
  };

  RuntimeDyldChecker Checker(
      IsSymbolValid, GetSymbolInfo, GetSectionInfo, GetStubInfo, GetGOTInfo,
      S.TPC->getTargetTriple().isLittleEndian() ? support::little
                                                : support::big,
      Disassembler.get(), InstPrinter.get(), dbgs());

  std::string CheckLineStart = "# " + CheckName + ":";
  for (auto &CheckFile : CheckFiles) {
    auto CheckerFileBuf =
        ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(CheckFile)));
    if (!Checker.checkAllRulesInBuffer(CheckLineStart, &*CheckerFileBuf))
      ExitOnErr(make_error<StringError>(
          "Some checks in " + CheckFile + " failed", inconvertibleErrorCode()));
  }

  return Error::success();
}

static void dumpSessionStats(Session &S) {
  if (ShowSizes)
    outs() << "Total size of all blocks before pruning: " << S.SizeBeforePruning
           << "\nTotal size of all blocks after fixups: " << S.SizeAfterFixups
           << "\n";
}

static Expected<JITEvaluatedSymbol> getMainEntryPoint(Session &S) {
  return S.ES.lookup(S.JDSearchOrder, EntryPointName);
}

namespace {
struct JITLinkTimers {
  TimerGroup JITLinkTG{"llvm-jitlink timers", "timers for llvm-jitlink phases"};
  Timer LoadObjectsTimer{"load", "time to load/add object files", JITLinkTG};
  Timer LinkTimer{"link", "time to link object files", JITLinkTG};
  Timer RunTimer{"run", "time to execute jitlink'd code", JITLinkTG};
};
} // namespace

int main(int argc, char *argv[]) {
  InitLLVM X(argc, argv);

  InitializeAllTargetInfos();
  InitializeAllTargetMCs();
  InitializeAllDisassemblers();

  cl::ParseCommandLineOptions(argc, argv, "llvm jitlink tool");
  ExitOnErr.setBanner(std::string(argv[0]) + ": ");

  /// If timers are enabled, create a JITLinkTimers instance.
  std::unique_ptr<JITLinkTimers> Timers =
      ShowTimes ? std::make_unique<JITLinkTimers>() : nullptr;

  ExitOnErr(sanitizeArguments(getFirstFileTriple(), argv[0]));

  auto S = ExitOnErr(Session::Create(getFirstFileTriple()));

  {
    TimeRegion TR(Timers ? &Timers->LoadObjectsTimer : nullptr);
    ExitOnErr(loadObjects(*S));
  }

  if (!NoProcessSymbols)
    ExitOnErr(loadProcessSymbols(*S));
  ExitOnErr(loadDylibs(*S));

  if (PhonyExternals)
    addPhonyExternalsGenerator(*S);


  if (ShowInitialExecutionSessionState)
    S->ES.dump(outs());

  JITEvaluatedSymbol EntryPoint = 0;
  {
    TimeRegion TR(Timers ? &Timers->LinkTimer : nullptr);
    EntryPoint = ExitOnErr(getMainEntryPoint(*S));
  }

  if (ShowAddrs)
    S->dumpSessionInfo(outs());

  ExitOnErr(runChecks(*S));

  dumpSessionStats(*S);

  if (NoExec)
    return 0;

  int Result = 0;
  {
    TimeRegion TR(Timers ? &Timers->RunTimer : nullptr);
    Result = ExitOnErr(S->TPC->runAsMain(EntryPoint.getAddress(), InputArgv));
  }

  ExitOnErr(S->ES.endSession());
  ExitOnErr(S->TPC->disconnect());

  return Result;
}