Kernel: MMU::get() is now MMU::kernel

MMU is can now be locked with RecursiveSpinLock.

Scheduler now has get_current_tid() that works before the Scheduler
is initialized. This allows RecursiveSpinLock usage early on.

kernel/include/kernel/Memory/MMU.h

@@ -1,6 +1,7 @@
 #pragma once
 
-#include <kernel/Memory/Heap.h>
+#include <kernel/Memory/Types.h>
+#include <kernel/SpinLock.h>
 
 namespace Kernel
 {
@@ -18,7 +19,7 @@ namespace Kernel
 
 	public:
 		static void initialize();
-		static MMU& get();
+		static MMU& kernel();
 
 		static MMU& current();
 
@@ -44,12 +45,16 @@ namespace Kernel
 
 		void load();
 
+		void lock() const { m_lock.lock(); }
+		void unlock() const { m_lock.unlock(); }
+
 	private:
 		uint64_t get_page_data(vaddr_t) const;
 		void initialize_kernel();
 
 	private:
-		uint64_t* m_highest_paging_struct;
+		uint64_t*					m_highest_paging_struct { nullptr };
+		mutable RecursiveSpinLock	m_lock;
 	};
 
 }

kernel/include/kernel/Process.h

@@ -68,7 +68,7 @@ namespace Kernel
 
 		static Process& current() { return Thread::current().process(); }
 
-		MMU& mmu() { return m_mmu ? *m_mmu : MMU::get(); }
+		MMU& mmu() { return m_mmu ? *m_mmu : MMU::kernel(); }
 
 	private:
 		Process(pid_t);

kernel/include/kernel/Scheduler.h

@@ -26,6 +26,7 @@ namespace Kernel
 		void unblock_threads(Semaphore*);
 
 		Thread& current_thread();
+		static pid_t current_tid();
 
 	private:
 		Scheduler() = default;

kernel/include/kernel/Thread.h

@@ -49,6 +49,8 @@ namespace Kernel
 		uintptr_t interrupt_stack_size() const { return m_interrupt_stack_size; }
 
 		static Thread& current() ;
+		static pid_t current_tid();
+
 		Process& process();
 		bool has_process() const { return m_process; }