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/include/kernel/Process.h

@@ -38,11 +38,13 @@ namespace Kernel
 		};
 
 	public:
+		static Process* create_kernel();
 		static Process* create_kernel(entry_t, void*);
 		static BAN::ErrorOr<Process*> create_userspace(const Credentials&, BAN::StringView);
 		~Process();
 		void cleanup_function();
 
+		void register_to_scheduler();
 		void exit(int status, int signal);
 
 		static void for_each_process(const BAN::Function<BAN::Iteration(Process&)>& callback);
@@ -138,7 +140,6 @@ namespace Kernel
 	private:
 		Process(const Credentials&, pid_t pid, pid_t parent, pid_t sid, pid_t pgrp);
 		static Process* create_process(const Credentials&, pid_t parent, pid_t sid = 0, pid_t pgrp = 0);
-		static void register_process(Process*);
 
 		// Load an elf file to virtual address space of the current page table
 		static BAN::ErrorOr<BAN::UniqPtr<LibELF::ELF>> load_elf_for_exec(const Credentials&, BAN::StringView file_path, const BAN::String& cwd);

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();
 	}