Scheduler: Set the user_task field in a Task at creation time

We were previously looking at its segment registers to see if they were user-like, but this method is bad.
What is the task was executing a system call?

So now, we store that value at creation time.

kernel/include/thread/Task.h

@@ -36,6 +36,8 @@ struct Task
     char floating_region[512] __attribute__((aligned(16)));
     bool floating_saved = false;
 
+    bool user_task = true;
+
     bool is_user_task();
 
     ELFImage* image = nullptr;

kernel/src/thread/Scheduler.cpp

@@ -41,6 +41,7 @@ void Scheduler::init()
     idle_task.regs.ss = 0x10;
     idle_task.regs.rflags = (1 << 21) | (1 << 9);
     idle_task.task_sleep = 1000;
+    idle_task.user_task = false;
     idle_task.state = idle_task.Idle;
 
     base_task = new Task;
@@ -51,6 +52,7 @@ void Scheduler::init()
     sched_current_task->next_task = sched_current_task;
     sched_current_task->prev_task = sched_current_task;
     sched_current_task->state = sched_current_task->Running;
+    sched_current_task->user_task = false;
     task_num++;
     // the other registers will be saved next task switch
 
@@ -61,6 +63,7 @@ void Scheduler::add_kernel_task(void (*task)(void))
 {
     Task* new_task = new Task;
     ASSERT(new_task);
+    new_task->user_task = false;
     new_task->id = free_tid++;
     new_task->regs.rip = (uint64_t)task;
     new_task->allocated_stack =
@@ -88,6 +91,7 @@ void Scheduler::add_user_task(void* task)
 {
     Task* new_task = new Task;
     ASSERT(new_task);
+    new_task->user_task = true;
     new_task->id = free_tid++;
     new_task->regs.rip = (uint64_t)task;
     new_task->allocated_stack = (uint64_t)MemoryManager::get_pages(
@@ -124,6 +128,7 @@ void Scheduler::load_user_task(const char* filename)
         delete new_task;
         return;
     }
+    new_task->user_task = true;
     new_task->regs.rip = image->entry;
     new_task->image = image;
     new_task->allocated_stack = (uint64_t)MemoryManager::get_pages(

kernel/src/thread/Task.cpp

@@ -25,5 +25,5 @@ void task_restore_floating(Task& task)
 
 bool Task::is_user_task()
 {
-    return (regs.cs & 3) > 0;
+    return user_task;
 }