text: /*
   * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice, this
   *    list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   */
  
  #include <Kernel/Process.h>
  #include <Kernel/TTY/TTY.h>
  
  namespace Kernel {
  
  pid_t Process::sys$getsid(pid_t pid)
  {
      REQUIRE_PROMISE(proc);
      if (pid == 0)
          return m_sid;
      ScopedSpinLock lock(g_processes_lock);
      auto* process = Process::from_pid(pid);
      if (!process)
          return -ESRCH;
      if (m_sid != process->m_sid)
          return -EPERM;
      return process->m_sid;
  }
  
  pid_t Process::sys$setsid()
  {
      REQUIRE_PROMISE(proc);
      InterruptDisabler disabler;
      bool found_process_with_same_pgid_as_my_pid = false;
      Process::for_each_in_pgrp(pid(), [&](auto&) {
          found_process_with_same_pgid_as_my_pid = true;
          return IterationDecision::Break;
      });
      if (found_process_with_same_pgid_as_my_pid)
          return -EPERM;
      m_sid = m_pid;
      m_pgid = m_pid;
      m_tty = nullptr;
      return m_sid;
  }
  
  pid_t Process::sys$getpgid(pid_t pid)
  {
      REQUIRE_PROMISE(proc);
      if (pid == 0)
          return m_pgid;
      ScopedSpinLock lock(g_processes_lock); // FIXME: Use a ProcessHandle
      auto* process = Process::from_pid(pid);
      if (!process)
          return -ESRCH;
      return process->m_pgid;
  }
  
  pid_t Process::sys$getpgrp()
  {
      REQUIRE_PROMISE(stdio);
      return m_pgid;
  }
  
  static pid_t get_sid_from_pgid(pid_t pgid)
  {
      ScopedSpinLock lock(g_processes_lock);
      auto* group_leader = Process::from_pid(pgid);
      if (!group_leader)
          return -1;
      return group_leader->sid();
  }
  
  int Process::sys$setpgid(pid_t specified_pid, pid_t specified_pgid)
  {
      REQUIRE_PROMISE(proc);
      ScopedSpinLock lock(g_processes_lock); // FIXME: Use a ProcessHandle
      pid_t pid = specified_pid ? specified_pid : m_pid;
      if (specified_pgid < 0) {
          // The value of the pgid argument is less than 0, or is not a value supported by the implementation.
          return -EINVAL;
      }
      auto* process = Process::from_pid(pid);
      if (!process)
          return -ESRCH;
      if (process != this && process->ppid() != m_pid) {
          // The value of the pid argument does not match the process ID
          // of the calling process or of a child process of the calling process.
          return -ESRCH;
      }
      if (process->pid() == process->sid()) {
          // The process indicated by the pid argument is a session leader.
          return -EPERM;
      }
      if (process->ppid() == m_pid && process->sid() != sid()) {
          // The value of the pid argument matches the process ID of a child
          // process of the calling process and the child process is not in
          // the same session as the calling process.
          return -EPERM;
      }
  
      pid_t new_pgid = specified_pgid ? specified_pgid : process->m_pid;
      pid_t current_sid = get_sid_from_pgid(process->m_pgid);
      pid_t new_sid = get_sid_from_pgid(new_pgid);
      if (current_sid != new_sid) {
          // Can't move a process between sessions.
          return -EPERM;
      }
      // FIXME: There are more EPERM conditions to check for here..
      process->m_pgid = new_pgid;
      return 0;
  }
  
  }
  