text: /*
   * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
   *
   * SPDX-License-Identifier: BSD-2-Clause
   */
  
  #include <AK/ScopedValueRollback.h>
  #include <AK/String.h>
  #include <AK/Vector.h>
  #include <alloca.h>
  #include <assert.h>
  #include <bits/pthread_integration.h>
  #include <errno.h>
  #include <fcntl.h>
  #include <getopt.h>
  #include <grp.h>
  #include <pwd.h>
  #include <stdarg.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/ioctl.h>
  #include <sys/mman.h>
  #include <sys/select.h>
  #include <sys/types.h>
  #include <syscall.h>
  #include <termios.h>
  #include <time.h>
  #include <unistd.h>
  
  extern "C" {
  
  #ifdef NO_TLS
  static int s_cached_tid = 0;
  #else
  static __thread int s_cached_tid = 0;
  #endif
  
  static int s_cached_pid = 0;
  
  int lchown(const char* pathname, uid_t uid, gid_t gid)
  {
      if (!pathname) {
          errno = EFAULT;
          return -1;
      }
      Syscall::SC_chown_params params { { pathname, strlen(pathname) }, uid, gid, AT_FDCWD, false };
      int rc = syscall(SC_chown, &params);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int chown(const char* pathname, uid_t uid, gid_t gid)
  {
      if (!pathname) {
          errno = EFAULT;
          return -1;
      }
      Syscall::SC_chown_params params { { pathname, strlen(pathname) }, uid, gid, AT_FDCWD, true };
      int rc = syscall(SC_chown, &params);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int fchown(int fd, uid_t uid, gid_t gid)
  {
      int rc = syscall(SC_fchown, fd, uid, gid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int fchownat(int fd, const char* pathname, uid_t uid, gid_t gid, int flags)
  {
      if (!pathname) {
          errno = EFAULT;
          return -1;
      }
      Syscall::SC_chown_params params { { pathname, strlen(pathname) }, uid, gid, fd, !(flags & AT_SYMLINK_NOFOLLOW) };
      int rc = syscall(SC_chown, &params);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  pid_t fork()
  {
      __pthread_fork_prepare();
  
      int rc = syscall(SC_fork);
      if (rc == 0) {
          s_cached_tid = 0;
          s_cached_pid = 0;
          __pthread_fork_child();
      } else if (rc != -1) {
          __pthread_fork_parent();
      }
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  pid_t vfork()
  {
      return fork();
  }
  
  int execv(const char* path, char* const argv[])
  {
      return execve(path, argv, environ);
  }
  
  int execve(const char* filename, char* const argv[], char* const envp[])
  {
      size_t arg_count = 0;
      for (size_t i = 0; argv[i]; ++i)
          ++arg_count;
  
      size_t env_count = 0;
      for (size_t i = 0; envp[i]; ++i)
          ++env_count;
  
      auto copy_strings = [&](auto& vec, size_t count, auto& output) {
          output.length = count;
          for (size_t i = 0; vec[i]; ++i) {
              output.strings[i].characters = vec[i];
              output.strings[i].length = strlen(vec[i]);
          }
      };
  
      Syscall::SC_execve_params params;
      params.arguments.strings = (Syscall::StringArgument*)alloca(arg_count * sizeof(Syscall::StringArgument));
      params.environment.strings = (Syscall::StringArgument*)alloca(env_count * sizeof(Syscall::StringArgument));
  
      params.path = { filename, strlen(filename) };
      copy_strings(argv, arg_count, params.arguments);
      copy_strings(envp, env_count, params.environment);
  
      int rc = syscall(SC_execve, &params);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int execvpe(const char* filename, char* const argv[], char* const envp[])
  {
      if (strchr(filename, '/'))
          return execve(filename, argv, envp);
  
      ScopedValueRollback errno_rollback(errno);
      String path = getenv("PATH");
      if (path.is_empty())
          path = "/bin:/usr/bin";
      auto parts = path.split(':');
      for (auto& part : parts) {
          auto candidate = String::formatted("{}/{}", part, filename);
          int rc = execve(candidate.characters(), argv, envp);
          if (rc < 0 && errno != ENOENT) {
              errno_rollback.set_override_rollback_value(errno);
              dbgln("execvpe() failed on attempt ({}) with {}", candidate, strerror(errno));
              return rc;
          }
      }
      errno_rollback.set_override_rollback_value(ENOENT);
      dbgln("execvpe() leaving :(");
      return -1;
  }
  
  int execvp(const char* filename, char* const argv[])
  {
      int rc = execvpe(filename, argv, environ);
      int saved_errno = errno;
      dbgln("execvp({}, ...) about to return {} with errno={}", filename, rc, saved_errno);
      errno = saved_errno;
      return rc;
  }
  
  int execl(const char* filename, const char* arg0, ...)
  {
      Vector<const char*, 16> args;
      args.append(arg0);
  
      va_list ap;
      va_start(ap, arg0);
      for (;;) {
          const char* arg = va_arg(ap, const char*);
          if (!arg)
              break;
          args.append(arg);
      }
      va_end(ap);
      args.append(nullptr);
      return execve(filename, const_cast<char* const*>(args.data()), environ);
  }
  
  int execle(char const* filename, char const* arg0, ...)
  {
      Vector<char const*> args;
      args.append(arg0);
  
      va_list ap;
      va_start(ap, arg0);
      char const* arg;
      do {
          arg = va_arg(ap, char const*);
          args.append(arg);
      } while (arg);
  
      auto argv = const_cast<char* const*>(args.data());
      auto envp = const_cast<char* const*>(va_arg(ap, char* const*));
      va_end(ap);
  
      return execve(filename, argv, envp);
  }
  
  int execlp(const char* filename, const char* arg0, ...)
  {
      Vector<const char*, 16> args;
      args.append(arg0);
  
      va_list ap;
      va_start(ap, arg0);
      for (;;) {
          const char* arg = va_arg(ap, const char*);
          if (!arg)
              break;
          args.append(arg);
      }
      va_end(ap);
      args.append(nullptr);
      return execvpe(filename, const_cast<char* const*>(args.data()), environ);
  }
  
  uid_t geteuid()
  {
      return syscall(SC_geteuid);
  }
  
  gid_t getegid()
  {
      return syscall(SC_getegid);
  }
  
  uid_t getuid()
  {
      return syscall(SC_getuid);
  }
  
  gid_t getgid()
  {
      return syscall(SC_getgid);
  }
  
  pid_t getpid()
  {
      int cached_pid = s_cached_pid;
      if (!cached_pid) {
          cached_pid = syscall(SC_getpid);
          s_cached_pid = cached_pid;
      }
      return cached_pid;
  }
  
  pid_t getppid()
  {
      return syscall(SC_getppid);
  }
  
  int getresuid(uid_t* ruid, uid_t* euid, uid_t* suid)
  {
      return syscall(SC_getresuid, ruid, euid, suid);
  }
  
  int getresgid(gid_t* rgid, gid_t* egid, gid_t* sgid)
  {
      return syscall(SC_getresgid, rgid, egid, sgid);
  }
  
  pid_t getsid(pid_t pid)
  {
      int rc = syscall(SC_getsid, pid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  pid_t setsid()
  {
      int rc = syscall(SC_setsid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  pid_t tcgetpgrp(int fd)
  {
      pid_t pgrp;
      int rc = ioctl(fd, TIOCGPGRP, &pgrp);
      if (rc < 0)
          return rc;
      return pgrp;
  }
  
  int tcsetpgrp(int fd, pid_t pgid)
  {
      return ioctl(fd, TIOCSPGRP, pgid);
  }
  
  int setpgid(pid_t pid, pid_t pgid)
  {
      int rc = syscall(SC_setpgid, pid, pgid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  pid_t getpgid(pid_t pid)
  {
      int rc = syscall(SC_getpgid, pid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  pid_t getpgrp()
  {
      int rc = syscall(SC_getpgrp);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  ssize_t read(int fd, void* buf, size_t count)
  {
      int rc = syscall(SC_read, fd, buf, count);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  ssize_t pread(int fd, void* buf, size_t count, off_t offset)
  {
      int rc = syscall(SC_pread, fd, buf, count, &offset);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  ssize_t write(int fd, const void* buf, size_t count)
  {
      int rc = syscall(SC_write, fd, buf, count);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  ssize_t pwrite(int fd, const void* buf, size_t count, off_t offset)
  {
      // FIXME: This is not thread safe and should be implemented in the kernel instead.
      off_t old_offset = lseek(fd, 0, SEEK_CUR);
      lseek(fd, offset, SEEK_SET);
      ssize_t nwritten = write(fd, buf, count);
      lseek(fd, old_offset, SEEK_SET);
      return nwritten;
  }
  
  int ttyname_r(int fd, char* buffer, size_t size)
  {
      int rc = syscall(SC_ttyname, fd, buffer, size);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  static char ttyname_buf[32];
  char* ttyname(int fd)
  {
      if (ttyname_r(fd, ttyname_buf, sizeof(ttyname_buf)) < 0)
          return nullptr;
      return ttyname_buf;
  }
  
  int close(int fd)
  {
      int rc = syscall(SC_close, fd);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int chdir(const char* path)
  {
      if (!path) {
          errno = EFAULT;
          return -1;
      }
      int rc = syscall(SC_chdir, path, strlen(path));
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int fchdir(int fd)
  {
      int rc = syscall(SC_fchdir, fd);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  char* getcwd(char* buffer, size_t size)
  {
      if (buffer && size == 0) {
          // POSIX requires that we set errno to EINVAL here, but in our syscall it makes sense to
          // allow "probing" the Kernel with a zero-sized buffer, and it does not return -EINVAL.
          // So we have to inject EINVAL here.
          errno = EINVAL;
          return nullptr;
      }
  
      bool self_allocated = false;
      if (!buffer) {
          size = size ? size : 64;
          buffer = (char*)malloc(size);
          self_allocated = true;
      }
  
      int rc = syscall(SC_getcwd, buffer, size);
      if (rc < 0) {
          if (self_allocated)
              free(buffer);
          errno = -rc;
          return nullptr;
      }
  
      size_t actual_size = static_cast<size_t>(rc);
      if (actual_size <= size) {
          return buffer;
      }
  
      // If we get here, the current directory path was silently truncated.
  
      if (!self_allocated) {
          // In this case, POSIX causes information loss: the caller cannot learn about the ideal
          // buffer size. This is the reason we went with silently truncation instead.
          errno = ERANGE;
          return nullptr;
      }
  
      // Try again.
      free(buffer);
      size = actual_size;
      buffer = (char*)malloc(size);
      rc = syscall(SC_getcwd, buffer, size);
      if (rc < 0) {
          // Can only happen if we lose a race. Let's pretend we lost the race in the first place.
          free(buffer);
          errno = -rc;
          return nullptr;
      }
  
      actual_size = static_cast<size_t>(rc);
      if (actual_size < size) {
          // If we're here, then cwd has become longer while we were looking at it. (Race with another thread?)
          // There's not much we can do, unless we want to loop endlessly
          // in this case. Let's leave it up to the caller whether to loop.
          free(buffer);
          errno = EAGAIN;
          return nullptr;
      }
  
      return buffer;
  }
  
  char* getwd(char* buf)
  {
      if (buf == nullptr) {
          errno = EINVAL;
          return nullptr;
      }
      auto* p = getcwd(buf, PATH_MAX);
      if (errno == ERANGE) {
          // POSIX quirk
          errno = ENAMETOOLONG;
      }
      return p;
  }
  
  unsigned int sleep(unsigned int seconds)
  {
      struct timespec ts = { seconds, 0 };
      if (clock_nanosleep(CLOCK_MONOTONIC_COARSE, 0, &ts, nullptr) < 0)
          return ts.tv_sec;
      return 0;
  }
  
  int usleep(useconds_t usec)
  {
      struct timespec ts = { (long)(usec / 1000000), (long)(usec % 1000000) * 1000 };
      return clock_nanosleep(CLOCK_MONOTONIC_COARSE, 0, &ts, nullptr);
  }
  
  int gethostname(char* buffer, size_t size)
  {
      int rc = syscall(SC_gethostname, buffer, size);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int sethostname(const char* hostname, ssize_t size)
  {
      int rc = syscall(SC_sethostname, hostname, size);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  ssize_t readlink(const char* path, char* buffer, size_t size)
  {
      Syscall::SC_readlink_params params { { path, strlen(path) }, { buffer, size } };
      int rc = syscall(SC_readlink, &params);
      // Return the number of bytes placed in the buffer, not the full path size.
      __RETURN_WITH_ERRNO(rc, min((size_t)rc, size), -1);
  }
  
  off_t lseek(int fd, off_t offset, int whence)
  {
      int rc = syscall(SC_lseek, fd, &offset, whence);
      __RETURN_WITH_ERRNO(rc, offset, -1);
  }
  
  int link(const char* old_path, const char* new_path)
  {
      if (!old_path || !new_path) {
          errno = EFAULT;
          return -1;
      }
      Syscall::SC_link_params params { { old_path, strlen(old_path) }, { new_path, strlen(new_path) } };
      int rc = syscall(SC_link, &params);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int unlink(const char* pathname)
  {
      int rc = syscall(SC_unlink, pathname, strlen(pathname));
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int symlink(const char* target, const char* linkpath)
  {
      if (!target || !linkpath) {
          errno = EFAULT;
          return -1;
      }
      Syscall::SC_symlink_params params { { target, strlen(target) }, { linkpath, strlen(linkpath) } };
      int rc = syscall(SC_symlink, &params);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int rmdir(const char* pathname)
  {
      if (!pathname) {
          errno = EFAULT;
          return -1;
      }
      int rc = syscall(SC_rmdir, pathname, strlen(pathname));
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int isatty(int fd)
  {
      return fcntl(fd, F_ISTTY);
  }
  
  int dup(int old_fd)
  {
      return fcntl(old_fd, F_DUPFD, 0);
  }
  
  int dup2(int old_fd, int new_fd)
  {
      int rc = syscall(SC_dup2, old_fd, new_fd);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int setgroups(size_t size, const gid_t* list)
  {
      int rc = syscall(SC_setgroups, size, list);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int getgroups(int size, gid_t list[])
  {
      int rc = syscall(SC_getgroups, size, list);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int pipe(int pipefd[2])
  {
      return pipe2(pipefd, 0);
  }
  
  int pipe2(int pipefd[2], int flags)
  {
      int rc = syscall(SC_pipe, pipefd, flags);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  unsigned int alarm(unsigned int seconds)
  {
      return syscall(SC_alarm, seconds);
  }
  
  int seteuid(uid_t euid)
  {
      int rc = syscall(SC_seteuid, euid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int setegid(gid_t egid)
  {
      int rc = syscall(SC_setegid, egid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int setuid(uid_t uid)
  {
      int rc = syscall(SC_setuid, uid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int setgid(gid_t gid)
  {
      int rc = syscall(SC_setgid, gid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int setreuid(uid_t ruid, uid_t euid)
  {
      int rc = syscall(SC_setreuid, ruid, euid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int setresuid(uid_t ruid, uid_t euid, uid_t suid)
  {
      int rc = syscall(SC_setresuid, ruid, euid, suid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int setresgid(gid_t rgid, gid_t egid, gid_t sgid)
  {
      int rc = syscall(SC_setresgid, rgid, egid, sgid);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int access(const char* pathname, int mode)
  {
      if (!pathname) {
          errno = EFAULT;
          return -1;
      }
      int rc = syscall(SC_access, pathname, strlen(pathname), mode);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int mknod(const char* pathname, mode_t mode, dev_t dev)
  {
      if (!pathname) {
          errno = EFAULT;
          return -1;
      }
      Syscall::SC_mknod_params params { { pathname, strlen(pathname) }, mode, dev };
      int rc = syscall(SC_mknod, &params);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  long fpathconf([[maybe_unused]] int fd, int name)
  {
      switch (name) {
      case _PC_NAME_MAX:
          return NAME_MAX;
      case _PC_PATH_MAX:
          return PATH_MAX;
      case _PC_VDISABLE:
          return _POSIX_VDISABLE;
      case _PC_LINK_MAX:
          return LINK_MAX;
      }
  
      VERIFY_NOT_REACHED();
  }
  
  long pathconf([[maybe_unused]] const char* path, int name)
  {
      switch (name) {
      case _PC_NAME_MAX:
          return NAME_MAX;
      case _PC_PATH_MAX:
          return PATH_MAX;
      case _PC_PIPE_BUF:
          return PIPE_BUF;
      case _PC_LINK_MAX:
          return LINK_MAX;
      }
  
      VERIFY_NOT_REACHED();
  }
  
  void _exit(int status)
  {
      syscall(SC_exit, status);
      VERIFY_NOT_REACHED();
  }
  
  void sync()
  {
      syscall(SC_sync);
  }
  
  static String getlogin_buffer;
  
  char* getlogin()
  {
      if (getlogin_buffer.is_null()) {
          if (auto* passwd = getpwuid(getuid())) {
              getlogin_buffer = String(passwd->pw_name);
          }
          endpwent();
      }
      return const_cast<char*>(getlogin_buffer.characters());
  }
  
  int ftruncate(int fd, off_t length)
  {
      int rc = syscall(SC_ftruncate, fd, &length);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int truncate(const char* path, off_t length)
  {
      int fd = open(path, O_RDWR | O_CREAT, 0666);
      if (fd < 0)
          return fd;
      int rc = ftruncate(fd, length);
      int saved_errno = errno;
      if (int close_rc = close(fd); close_rc < 0)
          return close_rc;
      errno = saved_errno;
      return rc;
  }
  
  int gettid()
  {
      int cached_tid = s_cached_tid;
      if (!cached_tid) {
          cached_tid = syscall(SC_gettid);
          s_cached_tid = cached_tid;
      }
      return cached_tid;
  }
  
  int sysbeep()
  {
      int rc = syscall(SC_beep);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int fsync(int fd)
  {
      int rc = syscall(SC_fsync, fd);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int mount(int source_fd, const char* target, const char* fs_type, int flags)
  {
      if (!target || !fs_type) {
          errno = EFAULT;
          return -1;
      }
  
      Syscall::SC_mount_params params {
          { target, strlen(target) },
          { fs_type, strlen(fs_type) },
          source_fd,
          flags
      };
      int rc = syscall(SC_mount, &params);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int umount(const char* mountpoint)
  {
      int rc = syscall(SC_umount, mountpoint, strlen(mountpoint));
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  void dump_backtrace()
  {
      syscall(SC_dump_backtrace);
  }
  
  int get_process_name(char* buffer, int buffer_size)
  {
      int rc = syscall(SC_get_process_name, buffer, buffer_size);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int set_process_name(const char* name, size_t name_length)
  {
      int rc = syscall(SC_set_process_name, name, name_length);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int pledge(const char* promises, const char* execpromises)
  {
      Syscall::SC_pledge_params params {
          { promises, promises ? strlen(promises) : 0 },
          { execpromises, execpromises ? strlen(execpromises) : 0 }
      };
      int rc = syscall(SC_pledge, &params);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int unveil(const char* path, const char* permissions)
  {
      Syscall::SC_unveil_params params {
          { path, path ? strlen(path) : 0 },
          { permissions, permissions ? strlen(permissions) : 0 }
      };
      int rc = syscall(SC_unveil, &params);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  char* getpass(const char* prompt)
  {
      dbgln("FIXME: getpass('{}')", prompt);
      TODO();
  }
  
  long sysconf(int name)
  {
      int rc = syscall(SC_sysconf, name);
      __RETURN_WITH_ERRNO(rc, rc, -1);
  }
  
  int getpagesize()
  {
      return PAGE_SIZE;
  }
  
  int pause()
  {
      return select(0, nullptr, nullptr, nullptr, nullptr);
  }
  
  int chroot(const char* path)
  {
      dbgln("FIXME: chroot(\"{}\")", path);
      return -1;
  }
  }
  