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Kernel: Modify TimeManagement::current_time(..) API so it can't fail. (#6869)

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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.
This commit is contained in:
Brian Gianforcaro 2021-05-05 16:51:06 +00:00 committed by GitHub
parent 64b4e3f34b
commit 11306d7121
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GPG Key ID: 4AEE18F83AFDEB23
Notes: sideshowbarker 2024-07-18 18:41:23 +09:00 
Author: https://github.com/bgianfo
Commit: https://github.com/SerenityOS/serenity/commit/11306d7121f
Pull-request: https://github.com/SerenityOS/serenity/pull/6869
6 changed files with 14 additions and 13 deletions
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2
Kernel/Syscalls/alarm.cpp
View File

@ -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);

8
Kernel/Syscalls/clock.cpp
View File

@ -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;
}

4
Kernel/ThreadBlockers.cpp
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@ -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

5
Kernel/Time/TimeManagement.cpp
View File

@ -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();
}
}

2
Kernel/Time/TimeManagement.h
View File

@ -34,7 +34,7 @@ public:
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
{

6
Kernel/TimerQueue.cpp
View File

@ -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))));
}