Kernel: Allow creationg of empty processes and manual registration

You can now create kernel processes without any threads, add the
needed threads and only then register the process and its threads
to the scheduler.

kernel/kernel/Process.cpp

@@ -78,22 +78,29 @@ namespace Kernel
 		return process;
 	}
 
-	void Process::register_process(Process* process)
+	void Process::register_to_scheduler()
 	{
 		s_process_lock.lock();
-		MUST(s_processes.push_back(process));
+		MUST(s_processes.push_back(this));
 		s_process_lock.unlock();
-		for (auto* thread : process->m_threads)
+		for (auto* thread : m_threads)
 			MUST(Scheduler::get().add_thread(thread));
 	}
 
+	Process* Process::create_kernel()
+	{
+		auto* process = create_process({ 0, 0, 0, 0 }, 0);
+		MUST(process->m_working_directory.push_back('/'));
+		return process;
+	}
+
 	Process* Process::create_kernel(entry_t entry, void* data)
 	{
 		auto* process = create_process({ 0, 0, 0, 0 }, 0);
 		MUST(process->m_working_directory.push_back('/'));
 		auto* thread = MUST(Thread::create_kernel(entry, data, process));
 		process->add_thread(thread);
-		register_process(process);
+		process->register_to_scheduler();
 		return process;
 	}
 
@@ -146,7 +153,7 @@ namespace Kernel
 
 		auto* thread = MUST(Thread::create_userspace(process));
 		process->add_thread(thread);
-		register_process(process);
+		process->register_to_scheduler();
 		return process;
 	}
 
@@ -353,8 +360,7 @@ namespace Kernel
 		// FIXME: this should be able to fail
 		Thread* thread = MUST(Thread::current().clone(forked, rsp, rip));
 		forked->add_thread(thread);
-		
-		register_process(forked);
+		forked->register_to_scheduler();
 
 		return forked->pid();
 	}