//===- llvm/Support/Unix/Program.cpp -----------------------------*- C++ -*-===//

//

// 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 file implements the Unix specific portion of the Program class.

//

//===----------------------------------------------------------------------===//

//===----------------------------------------------------------------------===//

//=== WARNING: Implementation here must contain only generic UNIX code that

//===          is guaranteed to work on *all* UNIX variants.

//===----------------------------------------------------------------------===//

#include "Unix.h"

#include "llvm/ADT/StringExtras.h"

#include "llvm/Config/config.h"

#include "llvm/Support/Compiler.h"

#include "llvm/Support/Errc.h"

#include "llvm/Support/FileSystem.h"

#include "llvm/Support/Path.h"

#include "llvm/Support/StringSaver.h"

#include "llvm/Support/raw_ostream.h"

#if HAVE_SYS_STAT_H

#include <sys/stat.h>

#endif

#if HAVE_SYS_RESOURCE_H

#include <sys/resource.h>

#endif

#if HAVE_SIGNAL_H

#include <signal.h>

#endif

#if HAVE_FCNTL_H

#include <fcntl.h>

#endif

#if HAVE_UNISTD_H

#include <unistd.h>

#endif

#ifdef HAVE_POSIX_SPAWN

#include <spawn.h>

#if defined(__APPLE__)

#include <TargetConditionals.h>

#endif

#if defined(__APPLE__) && !(defined(TARGET_OS_IPHONE) && TARGET_OS_IPHONE)

#define USE_NSGETENVIRON 1

#else

#define USE_NSGETENVIRON 0

#endif

#if !USE_NSGETENVIRON

  extern char **environ;

#else

#include <crt_externs.h> // _NSGetEnviron

#endif

#endif

namespace llvm {

using namespace sys;

ProcessInfo::ProcessInfo() : Pid(0), ReturnCode(0) {}

ErrorOr<std::string> sys::findProgramByName(StringRef Name,

                                            ArrayRef<StringRef> Paths) {

  assert(!Name.empty() && "Must have a name!");

  // Use the given path verbatim if it contains any slashes; this matches

  // the behavior of sh(1) and friends.

  if (Name.find('/') != StringRef::npos) return std::string(Name);

  SmallVector<StringRef, 16> EnvironmentPaths;

  if (Paths.empty())

    if (const char *PathEnv = std::getenv("PATH")) {

      SplitString(PathEnv, EnvironmentPaths, ":");

      Paths = EnvironmentPaths;

    }

  for (auto Path : Paths) {

    if (Path.empty())

      continue;

    // Check to see if this first directory contains the executable...

    SmallString<128> FilePath(Path);

    sys::path::append(FilePath, Name);

    if (sys::fs::can_execute(FilePath.c_str()))

      return std::string(FilePath.str());  // Found the executable!

  }

  return errc::no_such_file_or_directory;

}

static bool RedirectIO(Optional<StringRef> Path, int FD, std::string* ErrMsg) {

  if (!Path) // Noop

    return false;

  std::string File;

  if (Path->empty())

    // Redirect empty paths to /dev/null

    File = "/dev/null";

  else

    File = std::string(*Path);

  // Open the file

  int InFD = open(File.c_str(), FD == 0 ? O_RDONLY : O_WRONLY|O_CREAT, 0666);

  if (InFD == -1) {

    MakeErrMsg(ErrMsg, "Cannot open file '" + File + "' for "

              + (FD == 0 ? "input" : "output"));

    return true;

  }

  // Install it as the requested FD

  if (dup2(InFD, FD) == -1) {

    MakeErrMsg(ErrMsg, "Cannot dup2");

    close(InFD);

    return true;

  }

  close(InFD);      // Close the original FD

  return false;

}

#ifdef HAVE_POSIX_SPAWN

static bool RedirectIO_PS(const std::string *Path, int FD, std::string *ErrMsg,

                          posix_spawn_file_actions_t *FileActions) {

  if (!Path) // Noop

    return false;

  const char *File;

  if (Path->empty())

    // Redirect empty paths to /dev/null

    File = "/dev/null";

  else

    File = Path->c_str();

  if (int Err = posix_spawn_file_actions_addopen(

          FileActions, FD, File,

          FD == 0 ? O_RDONLY : O_WRONLY | O_CREAT, 0666))

    return MakeErrMsg(ErrMsg, "Cannot posix_spawn_file_actions_addopen", Err);

  return false;

}

#endif

static void TimeOutHandler(int Sig) {

}

static void SetMemoryLimits(unsigned size) {

#if HAVE_SYS_RESOURCE_H && HAVE_GETRLIMIT && HAVE_SETRLIMIT

  struct rlimit r;

  __typeof__ (r.rlim_cur) limit = (__typeof__ (r.rlim_cur)) (size) * 1048576;

  // Heap size

  getrlimit (RLIMIT_DATA, &r);

  r.rlim_cur = limit;

  setrlimit (RLIMIT_DATA, &r);

#ifdef RLIMIT_RSS

  // Resident set size.

  getrlimit (RLIMIT_RSS, &r);

  r.rlim_cur = limit;

  setrlimit (RLIMIT_RSS, &r);

#endif

#endif

}

}

static std::vector<const char *>

toNullTerminatedCStringArray(ArrayRef<StringRef> Strings, StringSaver &Saver) {

  std::vector<const char *> Result;

  for (StringRef S : Strings)

    Result.push_back(Saver.save(S).data());

  Result.push_back(nullptr);

  return Result;

}

static bool Execute(ProcessInfo &PI, StringRef Program,

                    ArrayRef<StringRef> Args, Optional<ArrayRef<StringRef>> Env,

                    ArrayRef<Optional<StringRef>> Redirects,

                    unsigned MemoryLimit, std::string *ErrMsg) {

  if (!llvm::sys::fs::exists(Program)) {

    if (ErrMsg)

      *ErrMsg = std::string("Executable \"") + Program.str() +

                std::string("\" doesn't exist!");

    return false;

  }

  BumpPtrAllocator Allocator;

  StringSaver Saver(Allocator);

  std::vector<const char *> ArgVector, EnvVector;

  const char **Argv = nullptr;

  const char **Envp = nullptr;

  ArgVector = toNullTerminatedCStringArray(Args, Saver);

  Argv = ArgVector.data();

  if (Env) {

    EnvVector = toNullTerminatedCStringArray(*Env, Saver);

    Envp = EnvVector.data();

  }

  // If this OS has posix_spawn and there is no memory limit being implied, use

  // posix_spawn.  It is more efficient than fork/exec.

#ifdef HAVE_POSIX_SPAWN

  if (MemoryLimit == 0) {

    posix_spawn_file_actions_t FileActionsStore;

    posix_spawn_file_actions_t *FileActions = nullptr;

    // If we call posix_spawn_file_actions_addopen we have to make sure the

    // c strings we pass to it stay alive until the call to posix_spawn,

    // so we copy any StringRefs into this variable.

    std::string RedirectsStorage[3];

    if (!Redirects.empty()) {

      assert(Redirects.size() == 3);

      std::string *RedirectsStr[3] = {nullptr, nullptr, nullptr};

      for (int I = 0; I < 3; ++I) {

        if (Redirects[I]) {

          RedirectsStorage[I] = std::string(*Redirects[I]);

          RedirectsStr[I] = &RedirectsStorage[I];

        }

      }

      FileActions = &FileActionsStore;

      posix_spawn_file_actions_init(FileActions);

      // Redirect stdin/stdout.

      if (RedirectIO_PS(RedirectsStr[0], 0, ErrMsg, FileActions) ||

          RedirectIO_PS(RedirectsStr[1], 1, ErrMsg, FileActions))

        return false;

      if (!Redirects[1] || !Redirects[2] || *Redirects[1] != *Redirects[2]) {

        // Just redirect stderr

        if (RedirectIO_PS(RedirectsStr[2], 2, ErrMsg, FileActions))

          return false;

      } else {

        // If stdout and stderr should go to the same place, redirect stderr

        // to the FD already open for stdout.

        if (int Err = posix_spawn_file_actions_adddup2(FileActions, 1, 2))

          return !MakeErrMsg(ErrMsg, "Can't redirect stderr to stdout", Err);

      }

    }

    if (!Envp)

#if !USE_NSGETENVIRON

      Envp = const_cast<const char **>(environ);

#else

      // environ is missing in dylibs.

      Envp = const_cast<const char **>(*_NSGetEnviron());

#endif

    constexpr int maxRetries = 8;

    int retries = 0;

    pid_t PID;

    int Err;

    do {

      PID = 0; // Make Valgrind happy.

      Err = posix_spawn(&PID, Program.str().c_str(), FileActions,

                        /*attrp*/ nullptr, const_cast<char **>(Argv),

                        const_cast<char **>(Envp));

    } while (Err == EINTR && ++retries < maxRetries);

    if (FileActions)

      posix_spawn_file_actions_destroy(FileActions);

    if (Err)

     return !MakeErrMsg(ErrMsg, "posix_spawn failed", Err);

    PI.Pid = PID;

    PI.Process = PID;

    return true;

  }

#endif

  // Create a child process.

  int child = fork();

  switch (child) {

    // An error occurred:  Return to the caller.

    case -1:

      MakeErrMsg(ErrMsg, "Couldn't fork");

      return false;

    // Child process: Execute the program.

    case 0: {

      // Redirect file descriptors...

      if (!Redirects.empty()) {

        // Redirect stdin

        if (RedirectIO(Redirects[0], 0, ErrMsg)) { return false; }

        // Redirect stdout

        if (RedirectIO(Redirects[1], 1, ErrMsg)) { return false; }

        if (Redirects[1] && Redirects[2] && *Redirects[1] == *Redirects[2]) {

          // If stdout and stderr should go to the same place, redirect stderr

          // to the FD already open for stdout.

          if (-1 == dup2(1,2)) {

            MakeErrMsg(ErrMsg, "Can't redirect stderr to stdout");

            return false;

          }

        } else {

          // Just redirect stderr

          if (RedirectIO(Redirects[2], 2, ErrMsg)) { return false; }

        }

      }

      // Set memory limits

      if (MemoryLimit!=0) {

        SetMemoryLimits(MemoryLimit);

      }

      // Execute!

      std::string PathStr = std::string(Program);

      if (Envp != nullptr)

        execve(PathStr.c_str(), const_cast<char **>(Argv),

               const_cast<char **>(Envp));

      else

        execv(PathStr.c_str(), const_cast<char **>(Argv));

      // If the execve() failed, we should exit. Follow Unix protocol and

      // return 127 if the executable was not found, and 126 otherwise.

      // Use _exit rather than exit so that atexit functions and static

      // object destructors cloned from the parent process aren't

      // redundantly run, and so that any data buffered in stdio buffers

      // cloned from the parent aren't redundantly written out.

      _exit(errno == ENOENT ? 127 : 126);

    }

    // Parent process: Break out of the switch to do our processing.

    default:

      break;

  }

  PI.Pid = child;

  PI.Process = child;

  return true;

}

namespace llvm {

ProcessInfo sys::Wait(const ProcessInfo &PI, unsigned SecondsToWait,

                      bool WaitUntilTerminates, std::string *ErrMsg) {

  struct sigaction Act, Old;

  assert(PI.Pid && "invalid pid to wait on, process not started?");

  int WaitPidOptions = 0;

  pid_t ChildPid = PI.Pid;

  if (WaitUntilTerminates) {

    SecondsToWait = 0;

  } else if (SecondsToWait) {

    // Install a timeout handler.  The handler itself does nothing, but the

    // simple fact of having a handler at all causes the wait below to return

    // with EINTR, unlike if we used SIG_IGN.

    memset(&Act, 0, sizeof(Act));

    Act.sa_handler = TimeOutHandler;

    sigemptyset(&Act.sa_mask);

    sigaction(SIGALRM, &Act, &Old);

    alarm(SecondsToWait);

  } else if (SecondsToWait == 0)

    WaitPidOptions = WNOHANG;

  // Parent process: Wait for the child process to terminate.

  int status;

  ProcessInfo WaitResult;

  do {

    WaitResult.Pid = waitpid(ChildPid, &status, WaitPidOptions);

  } while (WaitUntilTerminates && WaitResult.Pid == -1 && errno == EINTR);

  if (WaitResult.Pid != PI.Pid) {

    if (WaitResult.Pid == 0) {

      // Non-blocking wait.

      return WaitResult;

    } else {

      if (SecondsToWait && errno == EINTR) {

        // Kill the child.

        kill(PI.Pid, SIGKILL);

        // Turn off the alarm and restore the signal handler

        alarm(0);

        sigaction(SIGALRM, &Old, nullptr);

        // Wait for child to die

        if (wait(&status) != ChildPid)

          MakeErrMsg(ErrMsg, "Child timed out but wouldn't die");

        else

          MakeErrMsg(ErrMsg, "Child timed out", 0);

        WaitResult.ReturnCode = -2; // Timeout detected

        return WaitResult;

      } else if (errno != EINTR) {

        MakeErrMsg(ErrMsg, "Error waiting for child process");

        WaitResult.ReturnCode = -1;

        return WaitResult;

      }

    }

  }

  // We exited normally without timeout, so turn off the timer.

  if (SecondsToWait && !WaitUntilTerminates) {

    alarm(0);

    sigaction(SIGALRM, &Old, nullptr);

  }

  // Return the proper exit status. Detect error conditions

  // so we can return -1 for them and set ErrMsg informatively.

  int result = 0;

  if (WIFEXITED(status)) {

    result = WEXITSTATUS(status);

    WaitResult.ReturnCode = result;

    if (result == 127) {

      if (ErrMsg)

        *ErrMsg = llvm::sys::StrError(ENOENT);

      WaitResult.ReturnCode = -1;

      return WaitResult;

    }

    if (result == 126) {

      if (ErrMsg)

        *ErrMsg = "Program could not be executed";

      WaitResult.ReturnCode = -1;

      return WaitResult;

    }

  } else if (WIFSIGNALED(status)) {

    if (ErrMsg) {

      *ErrMsg = strsignal(WTERMSIG(status));

#ifdef WCOREDUMP

      if (WCOREDUMP(status))

        *ErrMsg += " (core dumped)";

#endif

    }

    // Return a special value to indicate that the process received an unhandled

    // signal during execution as opposed to failing to execute.

    WaitResult.ReturnCode = -2;

  }

  return WaitResult;

}

std::error_code sys::ChangeStdinToBinary() {

  // Do nothing, as Unix doesn't differentiate between text and binary.

  return std::error_code();

}

std::error_code sys::ChangeStdoutToBinary() {

  // Do nothing, as Unix doesn't differentiate between text and binary.

  return std::error_code();

}

std::error_code

llvm::sys::writeFileWithEncoding(StringRef FileName, StringRef Contents,

                                 WindowsEncodingMethod Encoding /*unused*/) {

  std::error_code EC;

  llvm::raw_fd_ostream OS(FileName, EC, llvm::sys::fs::OpenFlags::OF_Text);

  if (EC)

    return EC;

  OS << Contents;

  if (OS.has_error())

    return make_error_code(errc::io_error);

  return EC;

}

bool llvm::sys::commandLineFitsWithinSystemLimits(StringRef Program,

                                                  ArrayRef<StringRef> Args) {

  static long ArgMax = sysconf(_SC_ARG_MAX);

  // POSIX requires that _POSIX_ARG_MAX is 4096, which is the lowest possible

  // value for ARG_MAX on a POSIX compliant system.

  static long ArgMin = _POSIX_ARG_MAX;

  // This the same baseline used by xargs.

  long EffectiveArgMax = 128 * 1024;

  if (EffectiveArgMax > ArgMax)

    EffectiveArgMax = ArgMax;

  else if (EffectiveArgMax < ArgMin)

    EffectiveArgMax = ArgMin;

  // System says no practical limit.

  if (ArgMax == -1)

    return true;

  // Conservatively account for space required by environment variables.

  long HalfArgMax = EffectiveArgMax / 2;

  size_t ArgLength = Program.size() + 1;

  for (StringRef Arg : Args) {

    // Ensure that we do not exceed the MAX_ARG_STRLEN constant on Linux, which

    // does not have a constant unlike what the man pages would have you

    // believe. Since this limit is pretty high, perform the check

    // unconditionally rather than trying to be aggressive and limiting it to

    // Linux only.

    if (Arg.size() >= (32 * 4096))

      return false;

    ArgLength += Arg.size() + 1;

    if (ArgLength > size_t(HalfArgMax)) {

      return false;

    }

  }

  return true;

}

}