Kernel: Modify TimeManagement::current_time(..) API so it can't fail. (…

…SerenityOS#6869)

The fact that current_time can "fail" makes its use a bit awkward.
All callers in the Kernel are trusted besides syscalls, so assert
that they never get there, and make sure all current callers perform
validation of the clock_id with TimeManagement::is_valid_clock_id().

I have fuzzed this change locally for a bit to make sure I didn't
miss any obvious regression.

Kernel/Syscalls/alarm.cpp

@@ -25,7 +25,7 @@ KResultOr<unsigned> Process::sys$alarm(unsigned seconds)
  }
 
  if (seconds > 0) {
- auto deadline = TimeManagement::the().current_time(CLOCK_REALTIME_COARSE).value();
+ auto deadline = TimeManagement::the().current_time(CLOCK_REALTIME_COARSE);
  deadline = deadline + Time::from_seconds(seconds);
  m_alarm_timer = TimerQueue::the().add_timer_without_id(CLOCK_REALTIME_COARSE, deadline, [this]() {
  [[maybe_unused]] auto rc = send_signal(SIGALRM, nullptr);

Kernel/Syscalls/clock.cpp

@@ -14,13 +14,13 @@ KResultOr<int> Process::sys$clock_gettime(clockid_t clock_id, Userspace<timespec
 {
  REQUIRE_PROMISE(stdio);
 
- auto time = TimeManagement::the().current_time(clock_id);
- if (time.is_error())
- return time.error();
+ if (!TimeManagement::is_valid_clock_id(clock_id))
+ return EINVAL;
 
- auto ts = time.value().to_timespec();
+ auto ts = TimeManagement::the().current_time(clock_id).to_timespec();
  if (!copy_to_user(user_ts, &ts))
  return EFAULT;
+
  return 0;
 }
 

Kernel/ThreadBlockers.cpp

@@ -23,7 +23,7 @@ Thread::BlockTimeout::BlockTimeout(bool is_absolute, const Time* time, const Tim
  m_time = *time;
  m_should_block = true;
  }
- m_start_time = start_time ? *start_time : TimeManagement::the().current_time(clock_id).value();
+ m_start_time = start_time ? *start_time : TimeManagement::the().current_time(clock_id);
  if (!is_absolute)
  m_time += m_start_time;
 }
@@ -326,7 +326,7 @@ void Thread::SleepBlocker::calculate_remaining()
 {
  if (!m_remaining)
  return;
- auto time_now = TimeManagement::the().current_time(m_deadline.clock_id()).value();
+ auto time_now = TimeManagement::the().current_time(m_deadline.clock_id());
  if (time_now < m_deadline.absolute_time())
  *m_remaining = m_deadline.absolute_time() - time_now;
  else

Kernel/Time/TimeManagement.cpp

@@ -44,7 +44,7 @@ bool TimeManagement::is_valid_clock_id(clockid_t clock_id)
  };
 }
 
-KResultOr<Time> TimeManagement::current_time(clockid_t clock_id) const
+Time TimeManagement::current_time(clockid_t clock_id) const
 {
  switch (clock_id) {
  case CLOCK_MONOTONIC:
@@ -58,7 +58,8 @@ KResultOr<Time> TimeManagement::current_time(clockid_t clock_id) const
  case CLOCK_REALTIME_COARSE:
  return epoch_time(TimePrecision::Coarse);
  default:
- return KResult(EINVAL);
+ // Syscall entrypoint is missing a is_valid_clock_id(..) check?
+ VERIFY_NOT_REACHED();
  }
 }
 

Kernel/Time/TimeManagement.h

@@ -34,7 +34,7 @@ class TimeManagement {
  static TimeManagement& the();
 
  static bool is_valid_clock_id(clockid_t);
- KResultOr<Time> current_time(clockid_t) const;
+ Time current_time(clockid_t) const;
  Time monotonic_time(TimePrecision = TimePrecision::Coarse) const;
  Time monotonic_time_raw() const
  {

Kernel/TimerQueue.cpp

@@ -44,7 +44,7 @@ Time Timer::now(bool is_firing) const
  break;
  }
  }
- return TimeManagement::the().current_time(clock_id).value();
+ return TimeManagement::the().current_time(clock_id);
 }
 
 TimerQueue& TimerQueue::the()
@@ -59,7 +59,7 @@ UNMAP_AFTER_INIT TimerQueue::TimerQueue()
 
 RefPtr<Timer> TimerQueue::add_timer_without_id(clockid_t clock_id, const Time& deadline, Function<void()>&& callback)
 {
- if (deadline <= TimeManagement::the().current_time(clock_id).value())
+ if (deadline <= TimeManagement::the().current_time(clock_id))
  return {};
 
  // Because timer handlers can execute on any processor and there is
@@ -117,7 +117,7 @@ void TimerQueue::add_timer_locked(NonnullRefPtr<Timer> timer)
 
 TimerId TimerQueue::add_timer(clockid_t clock_id, const Time& deadline, Function<void()>&& callback)
 {
- auto expires = TimeManagement::the().current_time(clock_id).value();
+ auto expires = TimeManagement::the().current_time(clock_id);
  expires = expires + deadline;
  return add_timer(adopt_ref(*new Timer(clock_id, expires, move(callback))));
 }