kernel: Rework the entire time system to use modular clocks

kernel/CMakeLists.txt

@@ -19,13 +19,12 @@ set(SOURCES
     src/memory/SharedMemory.cpp
     src/boot/Init.cpp
     src/arch/Serial.cpp
-    src/arch/Timer.cpp
     src/arch/PCI.cpp
     src/lib/Mutex.cpp
     src/thread/Thread.cpp
     src/thread/ThreadImage.cpp
     src/thread/Scheduler.cpp
-    src/thread/Timer.cpp
+    src/thread/Clock.cpp
     src/sys/Syscall.cpp
     src/sys/exit.cpp
     src/sys/clock_gettime.cpp
@@ -93,7 +92,7 @@ if("${LUNA_ARCH}" MATCHES "x86_64")
         src/arch/x86_64/Serial.cpp
         src/arch/x86_64/MMU.cpp
         src/arch/x86_64/CPU.cpp
-        src/arch/x86_64/Timer.cpp
+        src/arch/x86_64/Clock.cpp
         src/arch/x86_64/Thread.cpp
         src/arch/x86_64/PCI.cpp
         src/arch/x86_64/Keyboard.cpp

kernel/src/Log.cpp

@@ -1,7 +1,7 @@
 #include "Log.h"
 #include "arch/CPU.h"
 #include "arch/Serial.h"
-#include "arch/Timer.h"
+#include "thread/Clock.h"
 #include "video/TextConsole.h"
 #include <luna/Format.h>
 #include <luna/SourceLocation.h>
@@ -35,9 +35,10 @@ static void log_serial(LogLevel level, const char* format, va_list origin)
                    "\x1b[0m ",
                    ansi_color_codes_per_log_level[(int)level], log_level_letters[(int)level]);
 
-    auto* time = Timer::monotonic_clock();
+    struct timespec time;
+    g_monotonic_clock.get_time(time);
 
-    Serial::printf("%4zu.%.3zu ", time->tv_sec, time->tv_nsec / 1'000'000);
+    Serial::printf("%4zu.%.3zu ", time.tv_sec, time.tv_nsec / 1'000'000);
 
     // NOTE: We do this manually because of a lack of vprintf() in both Serial and TextConsole.
     cstyle_format(

kernel/src/arch/Timer.cpp

@@ -1,91 +0,0 @@
-#include "arch/Timer.h"
-#include "Log.h"
-#include "arch/Serial.h"
-#include "boot/bootboot.h"
-#include <luna/TypeTraits.h>
-
-static struct timespec s_monotonic_clock = { 0, 0 };
-static struct timespec s_realtime_clock;
-
-static inline constexpr bool isleap(u32 year)
-{
-    return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
-}
-
-static constexpr u32 make_yday(u32 year, u32 month)
-{
-    constexpr u16 upto[12] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
-
-    u32 yd = upto[month - 1];
-    if (month > 2 && isleap(year)) yd++;
-    return yd;
-}
-
-// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_16
-static constexpr u64 broken_down_to_unix(u64 year, u64 yday, u64 hour, u64 min, u64 sec)
-{
-    return sec + min * 60 + hour * 3600 + yday * 86400 + (year - 70) * 31536000 + ((year - 69) / 4) * 86400 -
-           ((year - 1) / 100) * 86400 + ((year + 299) / 400) * 86400;
-}
-
-// The bootloader encodes the date and time in Binary-Coded Decimal (BCD), which represents decimal digits using
-// hexadecimal digits. For example, BCD 0x22 is 22 in decimal.
-// https://gitlab.com/bztsrc/bootboot/-/blob/master/bootboot_spec_1st_ed.pdf, page 15.
-static inline constexpr u32 bcd_number_to_decimal(u32 num)
-{
-    return ((num >> 4) * 10) + (num & 0xf);
-}
-
-static u64 bootloader_time_to_unix(const u8 boottime[8])
-{
-    const u32 year = bcd_number_to_decimal(boottime[0]) * 100 + bcd_number_to_decimal(boottime[1]);
-    const u32 month = bcd_number_to_decimal(boottime[2]);
-    const u32 day = bcd_number_to_decimal(boottime[3]);
-    const u32 hour = bcd_number_to_decimal(boottime[4]);
-    const u32 minute = bcd_number_to_decimal(boottime[5]);
-    const u32 second = bcd_number_to_decimal(boottime[6]);
-    // "The last byte can store 1/100th second precision, but in lack of support on most platforms, it is 0x00".
-    // Therefore, let's not rely on it.
-    kinfoln("Current time: %.2d/%.2d/%d %.2d:%.2d:%.2d UTC", day, month, year, hour, minute, second);
-    return broken_down_to_unix(year - 1900, make_yday(year, month) + (day - 1), hour, minute, second);
-}
-
-extern const BOOTBOOT bootboot;
-
-namespace Timer
-{
-    static struct timespec s_interval = { .tv_sec = 0, .tv_nsec = ARCH_TIMER_RESOLUTION * 1000 };
-
-    void tick()
-    {
-        timespecadd(&s_monotonic_clock, &s_interval, &s_monotonic_clock);
-        timespecadd(&s_realtime_clock, &s_interval, &s_realtime_clock);
-    }
-
-    usize ticks_ms()
-    {
-        return (s_monotonic_clock.tv_sec * 1000) + (s_monotonic_clock.tv_nsec / 1'000'000);
-    }
-
-    struct timespec* monotonic_clock()
-    {
-        return &s_monotonic_clock;
-    }
-
-    struct timespec* realtime_clock()
-    {
-        return &s_realtime_clock;
-    }
-
-    void init()
-    {
-        s_realtime_clock.tv_sec = bootloader_time_to_unix(bootboot.datetime);
-        s_realtime_clock.tv_nsec = 0;
-        arch_init();
-    }
-}
-
-bool should_invoke_scheduler()
-{
-    return (s_realtime_clock.tv_nsec % 1'000'000) == 0;
-}

kernel/src/arch/Timer.h

@@ -1,29 +0,0 @@
-#pragma once
-#include <bits/timespec.h>
-#include <luna/Types.h>
-
-#ifdef ARCH_X86_64
-#include "arch/x86_64/Timer.h"
-#else
-#error "Unknown architecture."
-#endif
-
-static const usize MS_PER_SECOND = 1000;
-static const usize US_PER_SECOND = MS_PER_SECOND * 1000;
-static const usize NS_PER_SECOND = US_PER_SECOND * 1000;
-
-namespace Timer
-{
-    void tick();
-
-    usize ticks_ms();
-
-    struct timespec* monotonic_clock();
-
-    struct timespec* realtime_clock();
-
-    void arch_init();
-    void init();
-}
-
-bool should_invoke_scheduler();

kernel/src/arch/x86_64/CPU.cpp

@@ -3,13 +3,13 @@
 #include "Symbols.h"
 #include "api/Mouse.h"
 #include "arch/Keyboard.h"
-#include "arch/Timer.h"
 #include "arch/x86_64/CPU.h"
 #include "arch/x86_64/IO.h"
 #include "fs/devices/KeyboardDevice.h"
 #include "fs/devices/MouseDevice.h"
 #include "memory/MemoryManager.h"
 #include "sys/Syscall.h"
+#include "thread/Clock.h"
 #include "thread/Scheduler.h"
 #include "video/TextConsole.h"
 #include <bits/signal.h>
@@ -164,9 +164,17 @@ void io_thread()
     }
 }
 
+static bool should_invoke_scheduler()
+{
+    struct timespec time;
+    g_realtime_clock.get_time(time);
+    return (time.tv_nsec % 1'000'000) == 0;
+}
+
 static void timer_interrupt(Registers* regs, void*)
 {
-    Timer::tick();
+    g_realtime_clock.tick();
+    g_monotonic_clock.tick();
     if (should_invoke_scheduler()) Scheduler::invoke(regs);
 }
 

kernel/src/arch/x86_64/Clock.cpp

@@ -1,15 +1,24 @@
-#include "arch/Timer.h"
+#include "thread/Clock.h"
 #include "arch/x86_64/IO.h"
 
+// Every timer tick is equivalent to 250 microseconds.
+// FIXME: Change ARCH_TIMER_RESOLUTION to use nanoseconds.
+const usize ARCH_TIMER_RESOLUTION = 250;
+
 #define PIT_CHANNEL_0 0x40
 
 const u64 base_frequency = 1193182;
 
-void Timer::arch_init()
+void Clock::arch_init()
 {
     constexpr u16 divisor = (u16)(base_frequency / ((1000 / ARCH_TIMER_RESOLUTION) * 1000));
     static_assert(divisor >= 100, "ARCH_TIMER_RESOLUTION is too low");
     IO::outb(PIT_CHANNEL_0, (u8)(divisor & 0xFF));
     IO::outb(0x80, 0); // short delay
     IO::outb(PIT_CHANNEL_0, (u8)((divisor & 0xFF00) >> 8));
+
+    long resolution = ARCH_TIMER_RESOLUTION * 1000;
+
+    g_realtime_clock.set_resolution(resolution);
+    g_monotonic_clock.set_resolution(resolution);
 }

kernel/src/arch/x86_64/Timer.h

@@ -1,6 +0,0 @@
-#pragma once
-#include <luna/Types.h>
-
-// Every timer tick is equivalent to 250 microseconds.
-// FIXME: Change ARCH_TIMER_RESOLUTION to use nanoseconds.
-const usize ARCH_TIMER_RESOLUTION = 250;

kernel/src/arch/x86_64/disk/ATA.cpp

@@ -2,10 +2,10 @@
 #include "Log.h"
 #include "arch/CPU.h"
 #include "arch/Serial.h"
-#include "arch/Timer.h"
 #include "arch/x86_64/IO.h"
 #include "fs/MBR.h"
 #include "memory/MemoryManager.h"
+#include "thread/Clock.h"
 #include "thread/Scheduler.h"
 #include <luna/Alignment.h>
 #include <luna/Buffer.h>
@@ -34,6 +34,13 @@ static usize copy_ata_string(char* out, u16* in, usize size)
     return size;
 }
 
+static u64 ticks_ms()
+{
+    struct timespec time;
+    g_monotonic_clock.get_time(time);
+    return time.tv_sec * 1000 + time.tv_nsec / 1'000'000;
+}
+
 namespace ATA
 {
     Result<void> Controller::scan()
@@ -199,24 +206,24 @@ namespace ATA
 
     bool Channel::wait_for_reg_set(Register reg, u8 value, u64 timeout)
     {
-        u64 begin = Timer::ticks_ms();
+        u64 begin = ticks_ms();
         while (true)
         {
             u8 reg_value = reg == Register::Status ? read_control(ControlRegister::AltStatus) : read_register(reg);
             if (reg_value & value) return true;
-            if ((Timer::ticks_ms() - begin) >= timeout) return false;
+            if ((ticks_ms() - begin) >= timeout) return false;
             kernel_sleep(1);
         }
     }
 
     bool Channel::wait_for_reg_clear(Register reg, u8 value, u64 timeout)
     {
-        u64 begin = Timer::ticks_ms();
+        u64 begin = ticks_ms();
         while (true)
         {
             u8 reg_value = reg == Register::Status ? read_control(ControlRegister::AltStatus) : read_register(reg);
             if ((reg_value & value) == 0) return true;
-            if ((Timer::ticks_ms() - begin) >= timeout) return false;
+            if ((ticks_ms() - begin) >= timeout) return false;
             kernel_sleep(1);
         }
     }

kernel/src/fs/VFS.h

@@ -1,5 +1,5 @@
 #pragma once
-#include "arch/Timer.h"
+#include "thread/Clock.h"
 #include <bits/makedev.h>
 #include <bits/timespec.h>
 #include <luna/SharedPtr.h>
@@ -163,7 +163,7 @@ namespace VFS
         virtual Result<void> set_metadata(const InodeMetadata& metadata)
         {
             m_metadata = metadata;
-            m_metadata.ctime = *Timer::realtime_clock();
+            g_realtime_clock.get_time(m_metadata.ctime);
             return {};
         }
 

kernel/src/fs/devpts/FileSystem.cpp

@@ -1,5 +1,4 @@
 #include "fs/devpts/FileSystem.h"
-#include "arch/Timer.h"
 #include "fs/devices/DeviceRegistry.h"
 #include "fs/devpts/Inode.h"
 #include <luna/Alloc.h>
@@ -22,7 +21,9 @@ namespace DevPTS
         root->set_fs(*fs, {});
         root->set_inode_number();
         root->m_metadata.mode = 0755;
-        root->m_metadata.atime = root->m_metadata.ctime = root->m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(root->m_metadata.ctime);
+        g_realtime_clock.get_time(root->m_metadata.atime);
+        g_realtime_clock.get_time(root->m_metadata.mtime);
         fs->set_root(root);
 
         TRY(g_devpts_instances.try_append(fs.ptr()));

kernel/src/fs/devpts/Inode.cpp

@@ -43,7 +43,7 @@ namespace DevPTS
 
         inode->did_link();
 
-        m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(m_metadata.mtime);
 
         return {};
     }
@@ -61,7 +61,7 @@ namespace DevPTS
 
         inode->did_unlink();
 
-        m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(m_metadata.mtime);
 
         return {};
     }

kernel/src/fs/tmpfs/FileSystem.cpp

@@ -1,7 +1,7 @@
 #include "fs/tmpfs/FileSystem.h"
-#include "arch/Timer.h"
 #include "fs/devices/DeviceRegistry.h"
 #include "fs/tmpfs/Inode.h"
+#include "thread/Clock.h"
 #include <luna/Alloc.h>
 #include <luna/CString.h>
 #include <luna/Ignore.h>
@@ -27,7 +27,9 @@ namespace TmpFS
         inode->set_fs(*this, {});
         inode->set_inode_number(m_next_inode_number++, {});
         inode->m_metadata.mode = mode;
-        inode->m_metadata.atime = inode->m_metadata.ctime = inode->m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(inode->m_metadata.mtime);
+        g_realtime_clock.get_time(inode->m_metadata.atime);
+        g_realtime_clock.get_time(inode->m_metadata.ctime);
         return (SharedPtr<VFS::Inode>)inode;
     }
 
@@ -37,7 +39,9 @@ namespace TmpFS
         inode->set_fs(*this, {});
         TRY(inode->set_link(link, {}));
         inode->set_inode_number(m_next_inode_number++, {});
-        inode->m_metadata.atime = inode->m_metadata.ctime = inode->m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(inode->m_metadata.mtime);
+        g_realtime_clock.get_time(inode->m_metadata.atime);
+        g_realtime_clock.get_time(inode->m_metadata.ctime);
         return (SharedPtr<VFS::Inode>)inode;
     }
 
@@ -52,7 +56,9 @@ namespace TmpFS
         inode->set_fs(*this, {});
         inode->set_inode_number(m_next_inode_number++, {});
         inode->m_metadata.mode = mode;
-        inode->m_metadata.atime = inode->m_metadata.ctime = inode->m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(inode->m_metadata.mtime);
+        g_realtime_clock.get_time(inode->m_metadata.atime);
+        g_realtime_clock.get_time(inode->m_metadata.ctime);
 
         return (SharedPtr<VFS::Inode>)inode;
     }
@@ -69,7 +75,9 @@ namespace TmpFS
         // device ID atm.
         inode->set_device_id(luna_dev_makedev(major, minor), {});
         inode->m_metadata.mode = mode;
-        inode->m_metadata.atime = inode->m_metadata.ctime = inode->m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(inode->m_metadata.mtime);
+        g_realtime_clock.get_time(inode->m_metadata.atime);
+        g_realtime_clock.get_time(inode->m_metadata.ctime);
         inode->m_metadata.size = device->size();
 
         return (SharedPtr<VFS::Inode>)inode;

kernel/src/fs/tmpfs/Inode.cpp

@@ -45,7 +45,7 @@ namespace TmpFS
 
         inode->did_link();
 
-        m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(m_metadata.mtime);
 
         return {};
     }
@@ -63,7 +63,7 @@ namespace TmpFS
 
         inode->did_unlink();
 
-        m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(m_metadata.mtime);
 
         return {};
     }
@@ -118,7 +118,7 @@ namespace TmpFS
 
         m_metadata.size = m_data_buffer.size();
 
-        m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(m_metadata.mtime);
 
         return length;
     }
@@ -133,7 +133,7 @@ namespace TmpFS
 
         m_metadata.size = m_data_buffer.size();
 
-        m_metadata.mtime = *Timer::realtime_clock();
+        g_realtime_clock.get_time(m_metadata.mtime);
 
         return {};
     }

kernel/src/main.cpp

@@ -1,7 +1,6 @@
 #include "Log.h"
 #include "Symbols.h"
 #include "arch/CPU.h"
-#include "arch/Timer.h"
 #include "binfmt/BinaryFormat.h"
 #include "boot/Init.h"
 #include "config.h"
@@ -11,6 +10,7 @@
 #include "fs/devices/PTYMultiplexer.h"
 #include "fs/tmpfs/FileSystem.h"
 #include "memory/MemoryManager.h"
+#include "thread/Clock.h"
 #include "thread/Scheduler.h"
 #include <luna/Units.h>
 
@@ -96,7 +96,7 @@ extern "C" [[noreturn]] void _start()
     Init::check_magic();
     Init::early_init();
 
-    Timer::init();
+    Clock::init();
 
     Thread::init();
     Scheduler::init();

kernel/src/sys/alarm.cpp

@@ -2,6 +2,7 @@
 #include "sys/Syscall.h"
 #include "thread/Scheduler.h"
 #include "thread/Timer.h"
+#include <luna/Common.h>
 
 Result<u64> sys_alarm(Registers*, SyscallArgs args)
 {
@@ -11,19 +12,24 @@ Result<u64> sys_alarm(Registers*, SyscallArgs args)
 
     TRY(check_pledge(current, Promise::p_stdio));
 
-    u64 ticks_left = current->timer ? current->timer->ticks_left() : 0;
+    Clock* clock = nullptr;
+
+    u64 ticks_left = current->timer ? current->timer->clock->ticks_left(current->timer) : 0;
 
     if (current->timer)
     {
-        if (current->timer->delta_ticks > 0) Scheduler::remove_from_timer_queue(current->timer);
+        clock = current->timer->clock;
+        if (clock) clock->remove_from_timer_queue(current->timer);
     }
     else
-        current->timer = TRY(make<Scheduler::Timer>());
+        current->timer = TRY(make<Timer>());
 
-    current->timer->total_ticks = seconds * 1000;
+    if (!clock) clock = &g_realtime_clock;
+
+    current->timer->total_ticks = ceil_div((static_cast<long>(seconds) * 1'000'000'000), clock->resolution());
     current->timer->thread = current;
 
-    Scheduler::add_to_timer_queue(current->timer);
+    clock->add_to_timer_queue(current->timer);
 
-    return ticks_left * 1000;
+    return (ticks_left * clock->resolution()) / 1'000'000'000;
 }

kernel/src/sys/clock_gettime.cpp

@@ -1,7 +1,7 @@
 #include "Pledge.h"
-#include "arch/Timer.h"
 #include "memory/MemoryManager.h"
 #include "sys/Syscall.h"
+#include "thread/Clock.h"
 #include "thread/Scheduler.h"
 #include <bits/clockid.h>
 #include <bits/timespec.h>
@@ -15,18 +15,24 @@ Result<u64> sys_clock_gettime(Registers*, SyscallArgs args)
 
     TRY(check_pledge(current, Promise::p_stdio));
 
+    Clock* clock;
+
     switch (id)
     {
     case CLOCK_MONOTONIC: {
-        if (!MemoryManager::copy_to_user_typed(ts, Timer::monotonic_clock())) return err(EFAULT);
+        clock = &g_monotonic_clock;
         break;
     }
     case CLOCK_REALTIME: {
-        if (!MemoryManager::copy_to_user_typed(ts, Timer::realtime_clock())) return err(EFAULT);
+        clock = &g_realtime_clock;
         break;
     }
     default: return err(EINVAL);
     }
 
+    struct timespec time;
+    clock->get_time(time);
+    if (!MemoryManager::copy_to_user_typed(ts, &time)) return err(EFAULT);
+
     return 0;
 }

kernel/src/sys/file.cpp

@@ -318,7 +318,7 @@ Result<u64> sys_utimensat(Registers*, SyscallArgs args)
     auto metadata = inode->metadata();
     if (ktimes[0].tv_nsec != UTIME_OMIT)
     {
-        if (ktimes[0].tv_nsec == UTIME_NOW) metadata.atime = *Timer::realtime_clock();
+        if (ktimes[0].tv_nsec == UTIME_NOW) g_realtime_clock.get_time(metadata.atime);
         else
         {
             if (ktimes[0].tv_nsec < 0 || ktimes[0].tv_nsec > 999'999'999) return err(EINVAL);
@@ -327,7 +327,7 @@ Result<u64> sys_utimensat(Registers*, SyscallArgs args)
     }
     if (ktimes[1].tv_nsec != UTIME_OMIT)
     {
-        if (ktimes[1].tv_nsec == UTIME_NOW) metadata.mtime = *Timer::realtime_clock();
+        if (ktimes[1].tv_nsec == UTIME_NOW) g_realtime_clock.get_time(metadata.mtime);
         else
         {
             if (ktimes[1].tv_nsec < 0 || ktimes[1].tv_nsec > 999'999'999) return err(EINVAL);

kernel/src/thread/Clock.cpp

@@ -0,0 +1,161 @@
+#include "thread/Clock.h"
+#include "Log.h"
+#include "arch/Serial.h"
+#include "boot/bootboot.h"
+#include "thread/Thread.h"
+
+Clock g_realtime_clock;
+Clock g_monotonic_clock;
+
+static inline constexpr bool isleap(u32 year)
+{
+    return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
+}
+
+static constexpr u32 make_yday(u32 year, u32 month)
+{
+    constexpr u16 upto[12] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };
+
+    u32 yd = upto[month - 1];
+    if (month > 2 && isleap(year)) yd++;
+    return yd;
+}
+
+// https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_16
+static constexpr u64 broken_down_to_unix(u64 year, u64 yday, u64 hour, u64 min, u64 sec)
+{
+    return sec + min * 60 + hour * 3600 + yday * 86400 + (year - 70) * 31536000 + ((year - 69) / 4) * 86400 -
+           ((year - 1) / 100) * 86400 + ((year + 299) / 400) * 86400;
+}
+
+// The bootloader encodes the date and time in Binary-Coded Decimal (BCD), which represents decimal digits using
+// hexadecimal digits. For example, BCD 0x22 is 22 in decimal.
+// https://gitlab.com/bztsrc/bootboot/-/blob/master/bootboot_spec_1st_ed.pdf, page 15.
+static inline constexpr u32 bcd_number_to_decimal(u32 num)
+{
+    return ((num >> 4) * 10) + (num & 0xf);
+}
+
+static u64 bootloader_time_to_unix(const u8 boottime[8])
+{
+    const u32 year = bcd_number_to_decimal(boottime[0]) * 100 + bcd_number_to_decimal(boottime[1]);
+    const u32 month = bcd_number_to_decimal(boottime[2]);
+    const u32 day = bcd_number_to_decimal(boottime[3]);
+    const u32 hour = bcd_number_to_decimal(boottime[4]);
+    const u32 minute = bcd_number_to_decimal(boottime[5]);
+    const u32 second = bcd_number_to_decimal(boottime[6]);
+    // "The last byte can store 1/100th second precision, but in lack of support on most platforms, it is 0x00".
+    // Therefore, let's not rely on it.
+    kinfoln("Current time: %.2d/%.2d/%d %.2d:%.2d:%.2d UTC", day, month, year, hour, minute, second);
+    return broken_down_to_unix(year - 1900, make_yday(year, month) + (day - 1), hour, minute, second);
+}
+
+extern const BOOTBOOT bootboot;
+
+void Clock::init()
+{
+    struct timespec time = { .tv_sec = (time_t)bootloader_time_to_unix(bootboot.datetime), .tv_nsec = 0 };
+    g_realtime_clock.update(time);
+    arch_init();
+}
+
+void Clock::set_resolution(long resolution)
+{
+    m_resolution = resolution;
+}
+
+void Clock::update(const struct timespec& time)
+{
+    m_time = time;
+}
+
+void Clock::add_to_timer_queue(Timer* timer)
+{
+    check(timer->clock == nullptr);
+
+    timer->delta_ticks = timer->total_ticks;
+
+    for (auto* t : m_timer_queue)
+    {
+        if (timer->delta_ticks <= t->delta_ticks)
+        {
+            t->delta_ticks -= timer->delta_ticks;
+            m_timer_queue.add_before(t, timer);
+            return;
+        }
+        timer->delta_ticks -= t->delta_ticks;
+    }
+
+    m_timer_queue.append(timer);
+
+    timer->clock = this;
+}
+
+void Clock::remove_from_timer_queue(Timer* timer)
+{
+    check(timer->clock == this);
+
+    auto maybe_next = m_timer_queue.next(timer);
+    if (maybe_next.has_value())
+    {
+        auto next = maybe_next.value();
+        next->delta_ticks += timer->delta_ticks;
+    }
+    m_timer_queue.remove(timer);
+
+    timer->clock = nullptr;
+}
+
+void Clock::tick()
+{
+    struct timespec interval = { .tv_sec = 0, .tv_nsec = m_resolution };
+
+    timespecadd(&m_time, &interval, &m_time);
+
+    auto maybe_first = m_timer_queue.first();
+    if (!maybe_first.has_value()) return;
+
+    auto first = *maybe_first;
+    first->delta_ticks--;
+
+    LinkedList<Timer> timers_to_be_restarted;
+
+    m_timer_queue.delayed_for_each([&](Timer* t) {
+        if (t->delta_ticks == 0)
+        {
+            this->m_timer_queue.remove(t);
+            t->clock = nullptr;
+            t->thread->send_signal(t->signo);
+            if (t->restart) timers_to_be_restarted.append(t);
+            return true;
+        }
+
+        return false;
+    });
+
+    timers_to_be_restarted.consume([this](Timer* t) { add_to_timer_queue(t); });
+}
+
+void Clock::get_time(struct timespec& out)
+{
+    out = m_time;
+}
+
+long Clock::resolution()
+{
+    return m_resolution;
+}
+
+u64 Clock::ticks_left(Timer* timer)
+{
+    check(timer->clock == this);
+
+    u64 total = 0;
+    if (timer->delta_ticks == 0) return 0;
+    for (auto* t : m_timer_queue)
+    {
+        total += t->delta_ticks;
+        if (t == timer) break;
+    }
+    return total;
+}

kernel/src/thread/Clock.h

@@ -0,0 +1,36 @@
+#pragma once
+#include "thread/Timer.h"
+#include <bits/timespec.h>
+
+struct Clock
+{
+    static void init();
+    static void arch_init();
+
+    void set_resolution(long resolution);
+
+    void update(const struct timespec& time);
+
+    void tick();
+
+    void add_to_timer_queue(Timer* timer);
+    void remove_from_timer_queue(Timer* timer);
+
+    void get_time(struct timespec& out);
+    long resolution();
+
+    u64 ticks_left(Timer* timer);
+
+  private:
+    struct timespec m_time
+    {
+        .tv_sec = 0, .tv_nsec = 0
+    };
+
+    long m_resolution = 1'000'000'000;
+
+    LinkedList<Timer> m_timer_queue;
+};
+
+extern Clock g_realtime_clock;
+extern Clock g_monotonic_clock;

kernel/src/thread/Scheduler.cpp

@@ -219,7 +219,7 @@ namespace Scheduler
 
         if (thread->timer)
         {
-            Scheduler::remove_from_timer_queue(thread->timer);
+            thread->timer->clock->remove_from_timer_queue(thread->timer);
             delete thread->timer;
         }
 
@@ -300,8 +300,6 @@ namespace Scheduler
     {
         CPU::disable_interrupts();
 
-        tick_queue();
-
         if (is_in_kernel(regs)) g_current->kernel_ticks_self++;
         else
             g_current->user_ticks_self++;

kernel/src/thread/Thread.h

@@ -19,10 +19,7 @@
 #error "Unknown architecture."
 #endif
 
-namespace Scheduler
-{
 class Timer;
-}
 
 enum class ThreadState
 {
@@ -101,7 +98,7 @@ struct Thread : public LinkedListNode<Thread>
 
     mode_t umask { 0 };
 
-    Scheduler::Timer* timer { nullptr };
+    Timer* timer { nullptr };
 
     StaticString<128> cmdline;
 

kernel/src/thread/Timer.cpp

@@ -1,73 +0,0 @@
-#include "thread/Timer.h"
-#include "Log.h"
-
-static LinkedList<Scheduler::Timer> g_timer_queue;
-
-namespace Scheduler
-{
-    void add_to_timer_queue(Timer* timer)
-    {
-        timer->delta_ticks = timer->total_ticks;
-
-        for (auto* t : g_timer_queue)
-        {
-            if (timer->delta_ticks <= t->delta_ticks)
-            {
-                t->delta_ticks -= timer->delta_ticks;
-                g_timer_queue.add_before(t, timer);
-                return;
-            }
-            timer->delta_ticks -= t->delta_ticks;
-        }
-
-        g_timer_queue.append(timer);
-    }
-
-    void remove_from_timer_queue(Timer* timer)
-    {
-        auto maybe_next = g_timer_queue.next(timer);
-        if (maybe_next.has_value())
-        {
-            auto next = maybe_next.value();
-            next->delta_ticks += timer->delta_ticks;
-        }
-        g_timer_queue.remove(timer);
-    }
-
-    void tick_queue()
-    {
-        auto maybe_first = g_timer_queue.first();
-        if (!maybe_first.has_value()) return;
-
-        auto first = *maybe_first;
-        first->delta_ticks--;
-
-        LinkedList<Scheduler::Timer> timers_to_be_restarted;
-
-        g_timer_queue.delayed_for_each([&](Timer* t) {
-            if (t->delta_ticks == 0)
-            {
-                g_timer_queue.remove(t);
-                t->thread->send_signal(t->signo);
-                if (t->restart) timers_to_be_restarted.append(t);
-                return true;
-            }
-
-            return false;
-        });
-
-        timers_to_be_restarted.consume([](Timer* t) { add_to_timer_queue(t); });
-    }
-
-    u64 Timer::ticks_left()
-    {
-        u64 total = 0;
-        if (delta_ticks == 0) return 0;
-        for (auto* t : g_timer_queue)
-        {
-            total += t->delta_ticks;
-            if (t == this) break;
-        }
-        return total;
-    }
-}

kernel/src/thread/Timer.h

@@ -1,9 +1,10 @@
 #pragma once
-#include "thread/Thread.h"
+#include <bits/signal.h>
 #include <luna/LinkedList.h>
 
-namespace Scheduler
+struct Thread;
-{
+struct Clock;
+
 class Timer : public LinkedListNode<Timer>
 {
   public:
@@ -13,11 +14,5 @@ namespace Scheduler
     int signo { SIGALRM };
     bool restart { false };
 
-        u64 ticks_left();
+    Clock* clock;
 };
-
-    void add_to_timer_queue(Timer* timer);
-    void remove_from_timer_queue(Timer* timer);
-
-    void tick_queue();
-}