Kernel: Create CriticalScope and fix kmalloc

This disables interrupts for the current scope and restores them
after the scope. This is used in kmalloc, since scheduler might
call into kmalloc/kfree, but deadlock if some thread is currently
trying to allocate. This allows us to use kmalloc in Scheduler.

kernel/include/kernel/CriticalScope.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <BAN/NoCopyMove.h>
+
+#include <stddef.h>
+
+namespace Kernel
+{
+
+	class CriticalScope
+	{
+		BAN_NON_COPYABLE(CriticalScope);
+		BAN_NON_MOVABLE(CriticalScope);
+	
+	public:
+		CriticalScope()
+		{
+			asm volatile("pushf; cli; pop %0" : "=r"(m_flags) :: "memory");
+		}
+
+		~CriticalScope()
+		{
+			asm volatile("push %0; popf" :: "rm"(m_flags) : "memory", "cc");
+		}
+
+	private:
+		size_t m_flags;
+	};
+
+}

kernel/include/kernel/InterruptController.h

@@ -18,6 +18,4 @@ public:
 	static InterruptController& get();
 };
 
-uintptr_t disable_interrupts_and_get_flags();
-void restore_flags(uintptr_t);
 bool interrupts_enabled();