// SPDX-License-Identifier: MIT
/*
$info$
tags: Bin|FEXLoader
desc: Glues the ELF loader, FEXCore and LinuxSyscalls to launch an elf under fex
$end_info$
*/

#include "AOT/AOTGenerator.h"
#include "Common/ArgumentLoader.h"
#include "Common/FEXServerClient.h"
#include "Common/Config.h"
#include "ELFCodeLoader.h"
#include "VDSO_Emulation.h"
#include "LinuxSyscalls/LinuxAllocator.h"
#include "LinuxSyscalls/Syscalls.h"
#include "LinuxSyscalls/Utils/Threads.h"
#include "LinuxSyscalls/x32/Syscalls.h"
#include "LinuxSyscalls/x64/Syscalls.h"
#include "LinuxSyscalls/SignalDelegator.h"
#include "Linux/Utils/ELFContainer.h"

#include <FEXCore/Config/Config.h>
#include <FEXCore/Core/Context.h>
#include <FEXCore/Core/CoreState.h>
#include <FEXCore/Utils/Allocator.h>
#include <FEXCore/Utils/LogManager.h>
#include <FEXCore/Utils/Telemetry.h>
#include <FEXCore/Utils/Threads.h>
#include <FEXCore/Utils/Profiler.h>
#include <FEXCore/fextl/fmt.h>
#include <FEXCore/fextl/memory.h>
#include <FEXCore/fextl/sstream.h>
#include <FEXCore/fextl/string.h>
#include <FEXCore/fextl/vector.h>
#include <FEXHeaderUtils/Filesystem.h>

#include <atomic>
#include <cerrno>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <elf.h>
#include <fcntl.h>
#include <mutex>
#include <queue>
#include <set>
#include <sys/auxv.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/select.h>
#include <system_error>
#include <thread>
#include <unistd.h>
#include <utility>

#include <sys/sysinfo.h>
#include <sys/signal.h>

namespace {
static bool SilentLog;
static int OutputFD {STDERR_FILENO};
static bool ExecutedWithFD {false};

void MsgHandler(LogMan::DebugLevels Level, char const *Message) {
  if (SilentLog) {
    return;
  }

  const auto Output = fextl::fmt::format("[{}] {}\n", LogMan::DebugLevelStr(Level), Message);
  write(OutputFD, Output.c_str(), Output.size());
  fsync(OutputFD);
}

void AssertHandler(char const *Message) {
  if (SilentLog) {
    return;
  }

  const auto Output = fextl::fmt::format("[ASSERT] {}\n", Message);
  write(OutputFD, Output.c_str(), Output.size());
  fsync(OutputFD);
}

} // Anonymous namespace

namespace FEXServerLogging {
  int FEXServerFD{};
  void MsgHandler(LogMan::DebugLevels Level, char const *Message) {
    FEXServerClient::MsgHandler(FEXServerFD, Level, Message);
  }

  void AssertHandler(char const *Message) {
    FEXServerClient::AssertHandler(FEXServerFD, Message);
  }
}

namespace AOTIR {
  class AOTIRWriterFD final : public FEXCore::Context::AOTIRWriter {
    public:
      AOTIRWriterFD(const fextl::string &Path) {
        // Create and truncate if exists.
        constexpr int USER_PERMS = S_IRWXU | S_IRWXG | S_IRWXO;
        FD = open(Path.c_str(), O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC, USER_PERMS);
      }

      operator bool() const {
        return FD != -1;
      }

      void Write(const void* Data, size_t Size) override {
        write(FD, Data, Size);
      }

      size_t Offset() override {
        return lseek(FD, 0, SEEK_CUR);
      }

      void Close() override {
        if (FD != -1) {
          close(FD);
          FD = -1;
        }
      }

      virtual ~AOTIRWriterFD() {
        Close();
      }
    private:
      int FD{-1};
  };
}

void InterpreterHandler(fextl::string *Filename, fextl::string const &RootFS, fextl::vector<fextl::string> *args) {
  // Open the Filename to determine if it is a shebang file.
  int FD = open(Filename->c_str(), O_RDONLY | O_CLOEXEC);
  if (FD == -1) {
    return;
  }

  std::array<char, 257> Header;
  const auto ChunkSize = 257l;
  const auto ReadSize = pread(FD, &Header.at(0), ChunkSize, 0);

  const auto Data = std::span<char>(Header.data(), ReadSize);

  // Is the file large enough for shebang
  if (ReadSize <= 2) {
    close(FD);
    return;
  }

  // Handle shebang files
  if (Data[0] == '#' &&
      Data[1] == '!') {
    fextl::string InterpreterLine {
        Data.begin() + 2, // strip off "#!" prefix
        std::find(Data.begin(), Data.end(), '\n')
    };
    fextl::vector<fextl::string> ShebangArguments{};

    // Shebang line can have a single argument
    fextl::istringstream InterpreterSS(InterpreterLine);
    fextl::string Argument;
    while (std::getline(InterpreterSS, Argument, ' ')) {
      if (Argument.empty()) {
        continue;
      }
      ShebangArguments.push_back(std::move(Argument));
    }

    // Executable argument
    fextl::string &ShebangProgram = ShebangArguments[0];

    // If the filename is absolute then prepend the rootfs
    // If it is relative then don't append the rootfs
    if (ShebangProgram[0] == '/') {
      ShebangProgram = RootFS + ShebangProgram;
    }
    *Filename = ShebangProgram;

    // Insert all the arguments at the start
    args->insert(args->begin(), ShebangArguments.begin(), ShebangArguments.end());
  }
  close(FD);
}

void RootFSRedirect(fextl::string *Filename, fextl::string const &RootFS) {
  auto RootFSLink = ELFCodeLoader::ResolveRootfsFile(*Filename, RootFS);

  if (FHU::Filesystem::Exists(RootFSLink)) {
    *Filename = RootFSLink;
  }
}

bool RanAsInterpreter(const char *Program) {
  return ExecutedWithFD || FEXLOADER_AS_INTERPRETER;
}

bool IsInterpreterInstalled() {
  // The interpreter is installed if both the binfmt_misc handlers are available
  // Or if we were originally executed with FD. Which means the interpreter is installed

  return ExecutedWithFD ||
         (access("/proc/sys/fs/binfmt_misc/FEX-x86", F_OK) == 0 &&
          access("/proc/sys/fs/binfmt_misc/FEX-x86_64", F_OK) == 0);
}

namespace FEX::TSO {
  void SetupTSOEmulation(FEXCore::Context::Context *CTX) {
    // We need to check if these are defined or not. This is a very fresh feature.
#ifndef PR_GET_MEM_MODEL
#define PR_GET_MEM_MODEL 0x6d4d444c
#endif
#ifndef PR_SET_MEM_MODEL
#define PR_SET_MEM_MODEL 0x4d4d444c
#endif
#ifndef PR_SET_MEM_MODEL_DEFAULT
#define PR_SET_MEM_MODEL_DEFAULT 0
#endif
#ifndef PR_SET_MEM_MODEL_TSO
#define PR_SET_MEM_MODEL_TSO 1
#endif
    // Check to see if this is supported.
    auto Result = prctl(PR_GET_MEM_MODEL, 0, 0, 0, 0);
    if (Result == -1) {
      // Unsupported, early exit.
      return;
    }

    FEX_CONFIG_OPT(TSOEnabled, TSOENABLED);

    if (!TSOEnabled()) {
      // TSO emulation isn't even enabled, early exit.
      return;
    }

    if (Result == PR_SET_MEM_MODEL_DEFAULT) {
      // Try to set the TSO mode if we are currently default.
      Result = prctl(PR_SET_MEM_MODEL, PR_SET_MEM_MODEL_TSO, 0, 0, 0);
      if (Result == 0) {
        // TSO mode successfully enabled. Tell the context to disable TSO emulation through atomics.
        // This flag gets inherited on thread creation, so FEX only needs to set it at the start.
        CTX->SetHardwareTSOSupport(true);
      }
    }
  }
}

int main(int argc, char **argv, char **const envp) {
  auto SBRKPointer = FEXCore::Allocator::DisableSBRKAllocations();
  FEXCore::Allocator::GLIBCScopedFault GLIBFaultScope;
  const bool IsInterpreter = RanAsInterpreter(argv[0]);

  ExecutedWithFD = getauxval(AT_EXECFD) != 0;
  const char* FEXFD = getenv("FEX_EXECVEFD");
  const std::string_view FEXFDView = FEXFD ? std::string_view{FEXFD} : std::string_view{};

  LogMan::Throw::InstallHandler(AssertHandler);
  LogMan::Msg::InstallHandler(MsgHandler);

  auto Program = FEX::Config::LoadConfig(
    IsInterpreter,
    true,
    argc, argv, envp,
    ExecutedWithFD,
    FEXFDView);

  if (Program.ProgramPath.empty() && !FEXFD) {
    // Early exit if we weren't passed an argument
    return 0;
  }

  auto Args = FEX::ArgLoader::Get();
  auto ParsedArgs = FEX::ArgLoader::GetParsedArgs();

  // Reload the meta layer
  FEXCore::Config::ReloadMetaLayer();
  FEXCore::Config::Set(FEXCore::Config::CONFIG_IS_INTERPRETER, IsInterpreter ? "1" : "0");
  FEXCore::Config::Set(FEXCore::Config::CONFIG_INTERPRETER_INSTALLED, IsInterpreterInstalled() ? "1" : "0");

  // Early check for process stall
  // Doesn't use CONFIG_ROOTFS and we don't want it to spin up a squashfs instance
  FEX_CONFIG_OPT(StallProcess, STALLPROCESS);
  if (StallProcess) {
    while (1) {
      // Stall this process out forever
      select(0, nullptr, nullptr, nullptr, nullptr);
    }
  }

  // Ensure FEXServer is setup before config options try to pull CONFIG_ROOTFS
  if (!FEXServerClient::SetupClient(argv[0])) {
    LogMan::Msg::EFmt("FEXServerClient: Failure to setup client");
    return -1;
  }

  FEX_CONFIG_OPT(SilentLog, SILENTLOG);
  FEX_CONFIG_OPT(AOTIRCapture, AOTIRCAPTURE);
  FEX_CONFIG_OPT(AOTIRGenerate, AOTIRGENERATE);
  FEX_CONFIG_OPT(AOTIRLoad, AOTIRLOAD);
  FEX_CONFIG_OPT(OutputLog, OUTPUTLOG);
  FEX_CONFIG_OPT(LDPath, ROOTFS);
  FEX_CONFIG_OPT(Environment, ENV);
  FEX_CONFIG_OPT(HostEnvironment, HOSTENV);
  ::SilentLog = SilentLog();

  if (::SilentLog) {
    LogMan::Throw::UnInstallHandlers();
    LogMan::Msg::UnInstallHandlers();
  }
  else {
    auto LogFile = OutputLog();
    // If stderr or stdout then we need to dup the FD
    // In some cases some applications will close stderr and stdout
    // then redirect the FD to either a log OR some cases just not use
    // stderr/stdout and the FD will be reused for regular FD ops.
    //
    // We want to maintain the original output location otherwise we
    // can run in to problems of writing to some file
    if (LogFile == "stderr") {
      OutputFD = dup(STDERR_FILENO);
    }
    else if (LogFile == "stdout") {
      OutputFD = dup(STDOUT_FILENO);
    }
    else if (LogFile == "server") {
      LogMan::Throw::UnInstallHandlers();
      LogMan::Msg::UnInstallHandlers();

      FEXServerLogging::FEXServerFD = FEXServerClient::RequestLogFD(FEXServerClient::GetServerFD());
      if (FEXServerLogging::FEXServerFD != -1) {
        LogMan::Throw::InstallHandler(FEXServerLogging::AssertHandler);
        LogMan::Msg::InstallHandler(FEXServerLogging::MsgHandler);
      }
    }
    else if (!LogFile.empty()) {
      OutputFD = open(LogFile.c_str(), O_CREAT | O_CLOEXEC | O_WRONLY);
    }
  }

  FEXCore::Profiler::Init();
  FEXCore::Telemetry::Initialize();

  RootFSRedirect(&Program.ProgramPath, LDPath());
  InterpreterHandler(&Program.ProgramPath, LDPath(), &Args);

  if (!ExecutedWithFD && !FEXFD && !FHU::Filesystem::Exists(Program.ProgramPath)) {
    // Early exit if the program passed in doesn't exist
    // Will prevent a crash later
    fextl::fmt::print(stderr, "{}: command not found\n", Program.ProgramPath);
    return -ENOEXEC;
  }

  uint32_t KernelVersion = FEX::HLE::SyscallHandler::CalculateHostKernelVersion();
  if (KernelVersion < FEX::HLE::SyscallHandler::KernelVersion(4, 17)) {
    // We require 4.17 minimum for MAP_FIXED_NOREPLACE
    LogMan::Msg::EFmt("FEXLoader requires kernel 4.17 minimum. Expect problems.");
  }

  // Before we go any further, set all of our host environment variables that the config has provided
  for (auto &HostEnv : HostEnvironment.All()) {
    // We are going to keep these alive in memory.
    // No need to split the string with setenv
    putenv(HostEnv.data());
  }

  ELFCodeLoader Loader{Program.ProgramPath, FEXFDView, LDPath(), Args, ParsedArgs, envp, &Environment};

  if (!Loader.ELFWasLoaded()) {
    // Loader couldn't load this program for some reason
    fextl::fmt::print(stderr, "Invalid or Unsupported elf file.\n");
#ifdef _M_ARM_64
    fextl::fmt::print(stderr, "This is likely due to a misconfigured x86-64 RootFS\n");
    fextl::fmt::print(stderr, "Current RootFS path set to '{}'\n", LDPath());
    if (LDPath().empty() ||
        FHU::Filesystem::Exists(LDPath()) == false) {
      fextl::fmt::print(stderr, "RootFS path doesn't exist. This is required on AArch64 hosts\n");
      fextl::fmt::print(stderr, "Use FEXRootFSFetcher to download a RootFS\n");
    }
#endif
    return -ENOEXEC;
  }

  if (ExecutedWithFD) {
    // Don't need to canonicalize Program.ProgramPath, Config loader will have resolved this already.
    FEXCore::Config::EraseSet(FEXCore::Config::CONFIG_APP_FILENAME, Program.ProgramPath);
    FEXCore::Config::EraseSet(FEXCore::Config::CONFIG_APP_CONFIG_NAME, Program.ProgramName);
  }
  else if (FEXFD) {
    // Anonymous program.
    FEXCore::Config::EraseSet(FEXCore::Config::CONFIG_APP_FILENAME, "<Anonymous>");
    FEXCore::Config::EraseSet(FEXCore::Config::CONFIG_APP_CONFIG_NAME, "<Anonymous>");
  }
  else {
    {
      char ExistsTempPath[PATH_MAX];
      char *RealPath = realpath(Program.ProgramPath.c_str(), ExistsTempPath);
      if (RealPath) {
        FEXCore::Config::EraseSet(FEXCore::Config::CONFIG_APP_FILENAME, fextl::string(RealPath));
      }
    }
    FEXCore::Config::EraseSet(FEXCore::Config::CONFIG_APP_CONFIG_NAME, Program.ProgramName);
  }

  // Setup Thread handlers, so FEXCore can create threads.
  FEX::LinuxEmulation::Threads::SetupThreadHandlers();

  FEXCore::Config::EraseSet(FEXCore::Config::CONFIG_IS64BIT_MODE, Loader.Is64BitMode() ? "1" : "0");

  fextl::unique_ptr<FEX::HLE::MemAllocator> Allocator;
  fextl::vector<FEXCore::Allocator::MemoryRegion> Base48Bit;

  if (Loader.Is64BitMode()) {
    // Destroy the 48th bit if it exists
    Base48Bit = FEXCore::Allocator::Steal48BitVA();
  } else {
    FEX_CONFIG_OPT(Use32BitAllocator, FORCE32BITALLOCATOR);
    if (KernelVersion < FEX::HLE::SyscallHandler::KernelVersion(4, 17)) {
      Use32BitAllocator = true;
    }

    // Setup our userspace allocator
    if (!Use32BitAllocator &&
        KernelVersion >= FEX::HLE::SyscallHandler::KernelVersion(4, 17)) {
      FEXCore::Allocator::SetupHooks();
    }

    if (Use32BitAllocator) {
      Allocator = FEX::HLE::Create32BitAllocator();
    }
    else {
      Allocator = FEX::HLE::CreatePassthroughAllocator();
    }
  }

  // System allocator is now system allocator or FEX
  FEXCore::Context::InitializeStaticTables(Loader.Is64BitMode() ? FEXCore::Context::MODE_64BIT : FEXCore::Context::MODE_32BIT);

  auto CTX = FEXCore::Context::Context::CreateNewContext();
  CTX->InitializeContext();

  // Setup TSO hardware emulation immediately after initializing the context.
  FEX::TSO::SetupTSOEmulation(CTX.get());

  auto SignalDelegation = FEX::HLE::CreateSignalDelegator(CTX.get(), Program.ProgramName);

  auto SyscallHandler = Loader.Is64BitMode() ? FEX::HLE::x64::CreateHandler(CTX.get(), SignalDelegation.get())
                                             : FEX::HLE::x32::CreateHandler(CTX.get(), SignalDelegation.get(), std::move(Allocator));

  {
    // Load VDSO in to memory prior to mapping our ELFs.
    void* VDSOBase = FEX::VDSO::LoadVDSOThunks(Loader.Is64BitMode(), SyscallHandler.get());
    Loader.SetVDSOBase(VDSOBase);
    Loader.CalculateHWCaps(CTX.get());

    if (!Loader.MapMemory(SyscallHandler.get())) {
      // failed to map
      LogMan::Msg::EFmt("Failed to map %d-bit elf file.", Loader.Is64BitMode() ? 64 : 32);
      return -ENOEXEC;
    }
  }

  SyscallHandler->SetCodeLoader(&Loader);

  auto BRKInfo = Loader.GetBRKInfo();

  SyscallHandler->DefaultProgramBreak(BRKInfo.Base, BRKInfo.Size);

  CTX->SetSignalDelegator(SignalDelegation.get());
  CTX->SetSyscallHandler(SyscallHandler.get());
  CTX->InitCore(Loader.DefaultRIP(), Loader.GetStackPointer());

  // Pass in our VDSO thunks
  CTX->AppendThunkDefinitions(FEX::VDSO::GetVDSOThunkDefinitions());
  SignalDelegation->SetVDSOSigReturn();

  FEXCore::Context::ExitReason ShutdownReason = FEXCore::Context::ExitReason::EXIT_SHUTDOWN;

  // There might already be an exit handler, leave it installed
  if(!CTX->GetExitHandler()) {
    CTX->SetExitHandler([&](uint64_t thread, FEXCore::Context::ExitReason reason) {
      if (reason != FEXCore::Context::ExitReason::EXIT_DEBUG) {
        ShutdownReason = reason;
        CTX->Stop();
      }
    });
  }

  const bool AOTEnabled = AOTIRLoad() || AOTIRCapture() || AOTIRGenerate();
  if (AOTEnabled) {
    LogMan::Msg::IFmt("Warning: AOTIR is experimental, and might lead to crashes. "
                      "Capture doesn't work with programs that fork.");

    CTX->SetAOTIRLoader([](const fextl::string &fileid) -> int {
      const auto filepath = fextl::fmt::format("{}/aotir/{}.aotir", FEXCore::Config::GetDataDirectory(), fileid);
      return open(filepath.c_str(), O_RDONLY);
    });

    CTX->SetAOTIRWriter([](const fextl::string& fileid) -> fextl::unique_ptr<AOTIR::AOTIRWriterFD> {
      const auto filepath = fextl::fmt::format("{}/aotir/{}.aotir.tmp", FEXCore::Config::GetDataDirectory(), fileid);
      auto AOTWrite = fextl::make_unique<AOTIR::AOTIRWriterFD>(filepath);
      if (*AOTWrite) {
        LogMan::Msg::IFmt("AOTIR: Storing {}", fileid);
      } else {
        LogMan::Msg::IFmt("AOTIR: Failed to store {}", fileid);
      }
      return AOTWrite;
    });

    CTX->SetAOTIRRenamer([](const fextl::string& fileid) -> void {
      const auto TmpFilepath = fextl::fmt::format("{}/aotir/{}.aotir.tmp", FEXCore::Config::GetDataDirectory(), fileid);
      const auto NewFilepath = fextl::fmt::format("{}/aotir/{}.aotir", FEXCore::Config::GetDataDirectory(), fileid);

      // Rename the temporary file to atomically update the file
      if (!FHU::Filesystem::RenameFile(TmpFilepath, NewFilepath)) {
        LogMan::Msg::IFmt("Couldn't rename aotir");
      }
    });
  }

  if (AOTIRGenerate()) {
    for(auto &Section: Loader.Sections) {
      FEX::AOT::AOTGenSection(CTX.get(), Section);
    }
  } else {
    CTX->RunUntilExit();
  }

  if (AOTEnabled) {
    if (FHU::Filesystem::CreateDirectories(fextl::fmt::format("{}/aotir", FEXCore::Config::GetDataDirectory()))) {
      CTX->WriteFilesWithCode([](const fextl::string& fileid, const fextl::string& filename) {
        const auto filepath = fextl::fmt::format("{}/aotir/{}.path", FEXCore::Config::GetDataDirectory(), fileid);
        int fd = open(filepath.c_str(), O_CREAT | O_EXCL | O_WRONLY, 0644);
        if (fd != -1) {
          write(fd, filename.c_str(), filename.size());
          close(fd);
        }
      });
    }

    if (AOTIRCapture() || AOTIRGenerate()) {
      CTX->FinalizeAOTIRCache();
      LogMan::Msg::IFmt("AOTIR Cache Stored");
    }
  }

  auto ProgramStatus = CTX->GetProgramStatus();

  SyscallHandler.reset();
  SignalDelegation.reset();

  FEX::LinuxEmulation::Threads::Shutdown();

  Loader.FreeSections();

  FEXCore::Config::Shutdown();

  LogMan::Throw::UnInstallHandlers();
  LogMan::Msg::UnInstallHandlers();

  FEXCore::Allocator::ClearHooks();
  FEXCore::Allocator::ReclaimMemoryRegion(Base48Bit);
  // Allocator is now original system allocator
  FEXCore::Telemetry::Shutdown(Program.ProgramName);
  FEXCore::Profiler::Shutdown();

  FEXCore::Allocator::ReenableSBRKAllocations(SBRKPointer);

  if (ShutdownReason == FEXCore::Context::ExitReason::EXIT_SHUTDOWN) {
    return ProgramStatus;
  }
  else {
    return -64 | ShutdownReason;
  }
}