Kernel: Create the time page region before initializing the timers

We were unconditionally trying to update it in the interrupt, which
would depend on the timer interrupt not being received too soon after
the timers are initialized (before the time page was initialized),
which was the case when using HPET timers via the ACPI tables, but not
when using the PIT when ACPI was disabled.

Kernel/Time/TimeManagement.cpp

@@ -152,8 +152,6 @@ UNMAP_AFTER_INIT void TimeManagement::initialize(u32 cpu)
                 s_the->set_system_timer(*apic_timer);
             }
         }
-
-        s_the->m_time_page_region = MM.allocate_kernel_region(PAGE_SIZE, "Time page"sv, Memory::Region::Access::ReadWrite, AllocationStrategy::AllocateNow).release_value();
     } else {
         VERIFY(s_the.is_initialized());
         if (auto* apic_timer = APIC::the().get_timer()) {
@@ -183,6 +181,7 @@ time_t TimeManagement::boot_time() const
 }
 
 UNMAP_AFTER_INIT TimeManagement::TimeManagement()
+    : m_time_page_region(MM.allocate_kernel_region(PAGE_SIZE, "Time page"sv, Memory::Region::Access::ReadWrite, AllocationStrategy::AllocateNow).release_value_but_fixme_should_propagate_errors())
 {
     bool probe_non_legacy_hardware_timers = !(kernel_command_line().is_legacy_time_enabled());
     if (ACPI::is_enabled()) {
@@ -436,16 +435,16 @@ bool TimeManagement::disable_profile_timer()
 
 void TimeManagement::update_time_page()
 {
-    auto* page = time_page();
-    u32 update_iteration = AK::atomic_fetch_add(&page->update2, 1u, AK::MemoryOrder::memory_order_acquire);
-    page->clocks[CLOCK_REALTIME_COARSE] = m_epoch_time;
-    page->clocks[CLOCK_MONOTONIC_COARSE] = monotonic_time(TimePrecision::Coarse).to_timespec();
-    AK::atomic_store(&page->update1, update_iteration + 1u, AK::MemoryOrder::memory_order_release);
+    auto& page = time_page();
+    u32 update_iteration = AK::atomic_fetch_add(&page.update2, 1u, AK::MemoryOrder::memory_order_acquire);
+    page.clocks[CLOCK_REALTIME_COARSE] = m_epoch_time;
+    page.clocks[CLOCK_MONOTONIC_COARSE] = monotonic_time(TimePrecision::Coarse).to_timespec();
+    AK::atomic_store(&page.update1, update_iteration + 1u, AK::MemoryOrder::memory_order_release);
 }
 
-TimePage* TimeManagement::time_page()
+TimePage& TimeManagement::time_page()
 {
-    return static_cast<TimePage*>((void*)m_time_page_region->vaddr().as_ptr());
+    return *static_cast<TimePage*>((void*)m_time_page_region->vaddr().as_ptr());
 }
 
 Memory::VMObject& TimeManagement::time_page_vmobject()

Kernel/Time/TimeManagement.h

@@ -76,7 +76,7 @@ public:
     Memory::VMObject& time_page_vmobject();
 
 private:
-    TimePage* time_page();
+    TimePage& time_page();
     void update_time_page();
 
     bool probe_and_set_legacy_hardware_timers();
@@ -108,7 +108,7 @@ private:
     Atomic<u32> m_profile_enable_count { 0 };
     RefPtr<HardwareTimerBase> m_profile_timer;
 
-    OwnPtr<Memory::Region> m_time_page_region;
+    NonnullOwnPtr<Memory::Region> m_time_page_region;
 };
 
 }