feat(scheduler): working scheduler

Kernel/Source/OS/Panic.c

@@ -93,11 +93,11 @@ __attribute__((noreturn)) void OSPanicException(ExceptionsContext* frame) {
     PrintSeparator();
     OSLog("Registers:\n");
     PrintSeparator();
-    OSLog("x0 = 0x%X; x1 = 0x%X\n", frame->x0, frame->x1);
-    OSLog("x2 = 0x%X; x3 = 0x%X\n", frame->x2, frame->x3);
-    OSLog("x4 = 0x%X; x5 = 0x%X\n", frame->x4, frame->x5);
-    OSLog("x6 = 0x%X; x7 = 0x%X\n", frame->x6, frame->x7);
-    OSLog("x8 = 0x%X; x9 = 0x%X\n", frame->x8, frame->x9);
+    OSLog("x0  = 0x%X; x1  = 0x%X\n", frame->x0, frame->x1);
+    OSLog("x2  = 0x%X; x3  = 0x%X\n", frame->x2, frame->x3);
+    OSLog("x4  = 0x%X; x5  = 0x%X\n", frame->x4, frame->x5);
+    OSLog("x6  = 0x%X; x7  = 0x%X\n", frame->x6, frame->x7);
+    OSLog("x8  = 0x%X; x9  = 0x%X\n", frame->x8, frame->x9);
     OSLog("x10 = 0x%X; x11 = 0x%X\n", frame->x10, frame->x11);
     OSLog("x12 = 0x%X; x13 = 0x%X\n", frame->x12, frame->x13);
     OSLog("x14 = 0x%X; x15 = 0x%X\n", frame->x14, frame->x15);
@@ -107,8 +107,8 @@ __attribute__((noreturn)) void OSPanicException(ExceptionsContext* frame) {
     OSLog("x22 = 0x%X; x23 = 0x%X\n", frame->x22, frame->x23);
     OSLog("x24 = 0x%X; x25 = 0x%X\n", frame->x24, frame->x25);
     OSLog("x26 = 0x%X; x27 = 0x%X\n", frame->x26, frame->x27);
-    OSLog("\t\tx28 = 0x%X\n", frame->x28);
-    OSLog("FP = 0x%X; LR = 0x%X\n", frame->x29, frame->x30);
+    OSLog("\t  x28 = 0x%X\n", frame->x28);
+    OSLog("FP  = 0x%X; LR  = 0x%X\n", frame->x29, frame->x30);
 
     DrawPanicFooter();
     Halt();

Kernel/Source/OS/Scheduler.c

@@ -0,0 +1,116 @@
+#include <OS/Scheduler.h>
+#include <OS/Panic.h>
+#include <Arch/Exceptions.h>
+#include <Arch/CPU.h>
+#include <VM/VMM.h>
+#include <VM/Heap.h>
+#include <Lib/Align.h>
+#include <Lib/String.h>
+
+OSTask* gOSSchedulerCurrentTask = nullptr;
+UInt32 gOSSchedulerNextProcessID = 1;
+
+static OSProcess sOSSchedulerKernelProcess;
+
+void SchedulerInitialize() {
+    sOSSchedulerKernelProcess.id = 0;
+    sOSSchedulerKernelProcess.state = OSTaskStateRunning;
+    sOSSchedulerKernelProcess.l0Table = gVMKernelL0Table;
+    StringCopy(sOSSchedulerKernelProcess.name, "kernel");
+
+    OSTask* kernelTask = (OSTask*)HeapAllocate(sizeof(OSTask));
+    if (!kernelTask) OSPanic("Failed to allocate kernel task");
+
+    MemorySet(kernelTask, 0, sizeof(OSTask));
+    kernelTask->id = 0;
+    kernelTask->process = &sOSSchedulerKernelProcess;
+    kernelTask->sleepTicks = 0;
+    kernelTask->next = kernelTask;
+    kernelTask->state = OSTaskStateRunning;
+    kernelTask->waitingForProcessId = -1;
+
+    gOSSchedulerCurrentTask = kernelTask;
+}
+
+OSTask* SchedulerSpawn(void(*entryPoint)(), OSProcess* owner, Boolean isUser, Address fixedUserStackAddress) {
+    OSTask* task = (OSTask*)HeapAllocate(sizeof(OSTask));
+    Pointer stackBase = nullptr;
+    if (!task) goto cleanup;
+
+    if (!owner) owner = &sOSSchedulerKernelProcess;
+    Size stackSize = kOSSchedulerTaskStackSize;
+    stackBase = HeapAllocate(stackSize);
+    if (!stackBase) goto cleanup;
+
+    Address stackPointer = (Address)stackBase + stackSize;
+    stackPointer -= sizeof(ExceptionsContext);
+    stackPointer = AlignDown64(stackPointer, 16);
+    ExceptionsContext* context = (ExceptionsContext*)stackPointer;
+    MemorySet(context, 0, sizeof(ExceptionsContext));
+    context->elr_el1 = (Address)entryPoint;
+
+    if (isUser) {
+        context->spsr_el1 = 0x00000000; // El0t (M[3:0] = 0b0000) allow interrupts
+        context->sp_el0 = fixedUserStackAddress;
+    } else {
+        context->spsr_el1 = 0x00000005; // El1h (M[3:0] = 0b0101) allow interrupts
+    }
+
+    task->stackPointer = stackPointer;
+    task->process = owner;
+    task->id = owner->id;
+    task->sleepTicks = 0;
+    task->kernelStackBase = stackBase;
+    task->kernelStackTop = (Address)stackBase + stackSize;
+    task->state = OSTaskStateRunning;
+    task->waitingForProcessId = -1;
+
+    task->next = gOSSchedulerCurrentTask->next;
+    gOSSchedulerCurrentTask->next = task;
+
+    return task;
+cleanup:
+    if (task) HeapFree(task);
+    if (stackBase) HeapFree(stackBase);
+    return nullptr;
+}
+
+Address SchedulerNext(Address stackPointer) {
+    if (!gOSSchedulerCurrentTask) return stackPointer;
+
+    gOSSchedulerCurrentTask->stackPointer = stackPointer;
+    OSTask* taskIterator = gOSSchedulerCurrentTask->next;
+
+    do {
+        if (taskIterator->sleepTicks > 0) taskIterator->sleepTicks--;
+        taskIterator = taskIterator->next;
+    } while (taskIterator != gOSSchedulerCurrentTask->next);
+    
+    if (gOSSchedulerCurrentTask->sleepTicks > 0) gOSSchedulerCurrentTask->sleepTicks--;
+
+    OSTask* nextTask = gOSSchedulerCurrentTask->next;
+    loop {
+        if (nextTask->state == OSTaskStateSleeping && nextTask->sleepTicks == 0) nextTask->state = OSTaskStateRunning;
+        if (nextTask->state == OSTaskStateRunning) break;
+        nextTask = nextTask->next;
+
+        if (nextTask == gOSSchedulerCurrentTask) {
+            if (gOSSchedulerCurrentTask->state == OSTaskStateRunning) break;
+            OSPanic("No running tasks");
+        }
+    }
+
+    if (nextTask->process->l0Table != gOSSchedulerCurrentTask->process->l0Table) {
+        Address physicalL0Table = VMHHDMToPhys((Address)nextTask->process->l0Table);
+        CPUSwitchAddressSpace(physicalL0Table);
+    }
+    gOSSchedulerCurrentTask = nextTask;
+    
+    return gOSSchedulerCurrentTask->stackPointer;
+}
+
+void SchedulerYield(UInt64 ticks) {
+    gOSSchedulerCurrentTask->sleepTicks = ticks;
+    gOSSchedulerCurrentTask->state = OSTaskStateSleeping;
+    CPUException(kOSSchedulerExceptionNumber);
+}