text: /*
   * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
   *
   * SPDX-License-Identifier: BSD-2-Clause
   */
  
  #include <AK/Variant.h>
  #include <Kernel/Debug.h>
  #include <Kernel/Process.h>
  
  namespace Kernel {
  
  ErrorOr<siginfo_t> Process::do_waitid(Variant<Empty, NonnullRefPtr<Process>, NonnullRefPtr<ProcessGroup>> waitee, int options)
  {
      ErrorOr<siginfo_t> result = siginfo_t {};
      if (Thread::current()->block<Thread::WaitBlocker>({}, options, move(waitee), result).was_interrupted())
          return EINTR;
      VERIFY(!result.is_error() || (options & WNOHANG));
      return result;
  }
  
  ErrorOr<FlatPtr> Process::sys$waitid(Userspace<Syscall::SC_waitid_params const*> user_params)
  {
      VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this)
      TRY(require_promise(Pledge::proc));
      auto params = TRY(copy_typed_from_user(user_params));
  
      Variant<Empty, NonnullRefPtr<Process>, NonnullRefPtr<ProcessGroup>> waitee;
      switch (params.idtype) {
      case P_ALL:
          break;
      case P_PID: {
          auto waitee_process = Process::from_pid(params.id);
          if (!waitee_process)
              return ECHILD;
          bool waitee_is_child = waitee_process->ppid() == Process::current().pid();
          bool waitee_is_our_tracee = waitee_process->has_tracee_thread(Process::current().pid());
          if (!waitee_is_child && !waitee_is_our_tracee)
              return ECHILD;
          waitee = waitee_process.release_nonnull();
          break;
      }
      case P_PGID: {
          auto waitee_group = ProcessGroup::from_pgid(params.id);
          if (!waitee_group) {
              return ECHILD;
          }
          waitee = waitee_group.release_nonnull();
          break;
      }
      default:
          return EINVAL;
      }
  
      dbgln_if(PROCESS_DEBUG, "sys$waitid({}, {}, {}, {})", params.idtype, params.id, params.infop, params.options);
  
      auto siginfo = TRY(do_waitid(move(waitee), params.options));
      TRY(copy_to_user(params.infop, &siginfo));
      return 0;
  }
  
  }
  