[kernel] Create process kernel object

Re-implent the concept of processes as separate from threads, and as a
kobject API object. Also improve scheduler::prune which was doing some
unnecessary iterations.

src/kernel/objects/process.h

@@ -0,0 +1,46 @@
+#pragma once
+/// \file process.h
+/// Definition of process kobject types
+
+#include "objects/kobject.h"
+#include "page_table.h"
+
+class process :
+	public kobject
+{
+public:
+	/// Constructor.
+	/// \args pml4  Root of the process' page tables
+	process(page_table *pml4);
+
+	/// Destructor.
+	virtual ~process();
+
+	/// Terminate this process.
+	/// \arg code   The return code to exit with.
+	void exit(unsigned code);
+
+	/// Update internal bookkeeping about threads.
+	void update();
+
+	/// Get the process' page table root
+	page_table * pml4() { return m_pml4; }
+
+	/// Create a new thread in this process
+	/// \args priority  The new thread's scheduling priority
+	/// \returns        The newly created thread object
+	thread * create_thread(uint8_t priorty);
+
+	/// Inform the process of an exited thread
+	/// \args th  The thread which has exited
+	/// \returns  True if this thread ending has ended the process
+	bool thread_exited(thread *th);
+
+private:
+	uint32_t m_return_code;
+
+	page_table *m_pml4;
+	kutil::vector<thread*> m_threads;
+
+	static kutil::vector<process*> s_processes;
+};