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 <AK/String.h>
  #include <AK/StringBuilder.h>
  #include <AK/StringView.h>
  #include <Kernel/Process.h>
  #include <Kernel/VM/MemoryManager.h>
  #include <Kernel/VM/PageDirectory.h>
  
  namespace Kernel {
  
  int Process::sys$create_thread(void* (*entry)(void*), Userspace<const Syscall::SC_create_thread_params*> user_params)
  {
      REQUIRE_PROMISE(thread);
  
      Syscall::SC_create_thread_params params;
      if (!copy_from_user(&params, user_params))
          return -EFAULT;
  
      unsigned detach_state = params.m_detach_state;
      int schedule_priority = params.m_schedule_priority;
      unsigned stack_size = params.m_stack_size;
  
      auto user_stack_address = (u8*)params.m_stack_location + stack_size;
  
      if (!MM.validate_user_stack(*this, VirtualAddress(user_stack_address - 4)))
          return -EFAULT;
  
      // FIXME: return EAGAIN if Thread::all_threads().size() is greater than PTHREAD_THREADS_MAX
  
      int requested_thread_priority = schedule_priority;
      if (requested_thread_priority < THREAD_PRIORITY_MIN || requested_thread_priority > THREAD_PRIORITY_MAX)
          return -EINVAL;
  
      bool is_thread_joinable = (0 == detach_state);
  
      // FIXME: Do something with guard pages?
  
      auto* thread = new Thread(*this);
  
      // We know this thread is not the main_thread,
      // So give it a unique name until the user calls $set_thread_name on it
      // length + 4 to give space for our extra junk at the end
      StringBuilder builder(m_name.length() + 4);
      builder.append(m_name);
      builder.appendf("[%d]", thread->tid().value());
      thread->set_name(builder.to_string());
  
      if (!is_thread_joinable)
          thread->detach();
  
      auto& tss = thread->tss();
      tss.eip = (FlatPtr)entry;
      tss.eflags = 0x0202;
      tss.cr3 = page_directory().cr3();
      tss.esp = (u32)user_stack_address;
  
      auto tsr_result = thread->make_thread_specific_region({});
      if (tsr_result.is_error())
          return tsr_result.error();
  
      ScopedSpinLock lock(g_scheduler_lock);
      thread->set_priority(requested_thread_priority);
      thread->set_state(Thread::State::Runnable);
      return thread->tid().value();
  }
  
  void Process::sys$exit_thread(Userspace<void*> exit_value)
  {
      REQUIRE_PROMISE(thread);
      cli();
      auto current_thread = Thread::current();
      current_thread->m_exit_value = reinterpret_cast<void*>(exit_value.ptr());
      current_thread->set_should_die();
      big_lock().force_unlock_if_locked();
      current_thread->die_if_needed();
      ASSERT_NOT_REACHED();
  }
  
  int Process::sys$detach_thread(pid_t tid)
  {
      REQUIRE_PROMISE(thread);
      auto thread = Thread::from_tid(tid);
      if (!thread || thread->pid() != pid())
          return -ESRCH;
  
      if (!thread->is_joinable())
          return -EINVAL;
  
      thread->detach();
      return 0;
  }
  
  int Process::sys$join_thread(pid_t tid, Userspace<void**> exit_value)
  {
      REQUIRE_PROMISE(thread);
  
      auto thread = Thread::from_tid(tid);
      if (!thread || thread->pid() != pid())
          return -ESRCH;
  
      auto current_thread = Thread::current();
      if (thread == current_thread)
          return -EDEADLK;
  
      void* joinee_exit_value = nullptr;
  
      // NOTE: pthread_join() cannot be interrupted by signals. Only by death.
      for (;;) {
          KResult try_join_result(KSuccess);
          auto result = current_thread->block<Thread::JoinBlocker>(nullptr, *thread, try_join_result, joinee_exit_value);
          if (result == Thread::BlockResult::NotBlocked) {
              if (try_join_result.is_error())
                  return try_join_result.error();
              break;
          }
          if (result == Thread::BlockResult::InterruptedByDeath)
              break;
      }
  
      if (exit_value && !copy_to_user(exit_value, &joinee_exit_value))
          return -EFAULT;
      return 0;
  }
  
  int Process::sys$set_thread_name(pid_t tid, Userspace<const char*> user_name, size_t user_name_length)
  {
      REQUIRE_PROMISE(thread);
      auto name = copy_string_from_user(user_name, user_name_length);
      if (name.is_null())
          return -EFAULT;
  
      const size_t max_thread_name_size = 64;
      if (name.length() > max_thread_name_size)
          return -EINVAL;
  
      auto thread = Thread::from_tid(tid);
      if (!thread || thread->pid() != pid())
          return -ESRCH;
  
      thread->set_name(move(name));
      return 0;
  }
  
  int Process::sys$get_thread_name(pid_t tid, Userspace<char*> buffer, size_t buffer_size)
  {
      REQUIRE_PROMISE(thread);
      if (buffer_size == 0)
          return -EINVAL;
  
      auto thread = Thread::from_tid(tid);
      if (!thread || thread->pid() != pid())
          return -ESRCH;
  
      // We must make a temporary copy here to avoid a race with sys$set_thread_name
      auto thread_name = thread->name();
      if (thread_name.length() + 1 > (size_t)buffer_size)
          return -ENAMETOOLONG;
  
      if (!copy_to_user(buffer, thread_name.characters(), thread_name.length() + 1))
          return -EFAULT;
      return 0;
  }
  
  int Process::sys$gettid()
  {
      REQUIRE_PROMISE(stdio);
      return Thread::current()->tid().value();
  }
  
  }
  