feat: scheduling, usermode, shell

kernel/src/Timekeeping/ApicTimer.cpp

@@ -10,6 +10,7 @@
 #include <Io/IoPort.hpp>
 #include <Terminal/Terminal.hpp>
 #include <CppLib/Stream.hpp>
+#include <Sched/Scheduler.hpp>
 
 using namespace Kt;
 
@@ -34,9 +35,15 @@ namespace Timekeeping {
     static volatile uint64_t g_tickCount = 0;
     static uint32_t g_ticksPerMs = 0;
 
-    // Timer IRQ handler: increment tick count
+    static bool g_schedEnabled = false;
+
+    // Timer IRQ handler: increment tick count and drive scheduler
     static void TimerHandler(uint8_t) {
         g_tickCount = g_tickCount + 1;
+
+        if (g_schedEnabled) {
+            Sched::Tick();
+        }
     }
 
     // Use PIT channel 2 to create a precise delay for calibration.
@@ -128,10 +135,14 @@ namespace Timekeeping {
         return g_tickCount;  // 1 tick = 1 ms at 1000 Hz
     }
 
+    void EnableSchedulerTick() {
+        g_schedEnabled = true;
+    }
+
     void Sleep(uint64_t ms) {
         uint64_t target = g_tickCount + ms;
         while (g_tickCount < target) {
             asm volatile("hlt");
         }
     }
-};
+};

kernel/src/Timekeeping/ApicTimer.hpp

@@ -17,6 +17,9 @@ namespace Timekeeping {
     // Get elapsed milliseconds since timer initialization
     uint64_t GetMilliseconds();
 
+    // Enable scheduler tick (called after scheduler is initialized)
+    void EnableSchedulerTick();
+
     // Busy-wait sleep for the given number of milliseconds
     void Sleep(uint64_t ms);
-};
+};