[kernel] Add userspace threading

Implement the syscalls necessary for threads to create other threads in
their same process. This involved rearranging a number of syscalls, as
well as implementing object_wait and a basic implementation of a
process' list of handles.

src/kernel/objects/process.h

@@ -9,6 +9,12 @@ class process :
 	public kobject
 {
 public:
+	/// Top of memory area where thread stacks are allocated
+	constexpr static uintptr_t stacks_top = 0x0000800000000000;
+
+	/// Size of userspace thread stacks
+	constexpr static size_t stack_size = 0x4000;
+
 	/// Constructor.
 	/// \args pml4  Root of the process' page tables
 	process(page_table *pml4);
@@ -28,19 +34,44 @@ public:
 
 	/// Create a new thread in this process
 	/// \args priority  The new thread's scheduling priority
+	/// \args user      If true, create a userspace stack for this thread
 	/// \returns        The newly created thread object
-	thread * create_thread(uint8_t priorty);
+	thread * create_thread(uint8_t priorty, bool user = true);
+
+	/// Start tracking an object with a handle.
+	/// \args obj  The object this handle refers to
+	/// \returns   The new handle for this object
+	j6_handle_t add_handle(kobject *obj);
+
+	/// Stop tracking an object with a handle.
+	/// \args handle The handle that refers to the object
+	/// \returns     True if the handle was removed
+	bool remove_handle(j6_handle_t handle);
+
+	/// Lookup an object for a handle
+	/// \args handle The handle to the object
+	/// \returns     Pointer to the object, or null if not found
+	kobject * lookup_handle(j6_handle_t handle);
 
 	/// 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);
 
+	/// Create the special kernel process that owns kernel tasks
+	/// \arg pml4     The kernel-only pml4
+	/// \arg idle_rsp The idle thread's rsp
+	static process * create_kernel_process(page_table *pml4, uintptr_t idle_rsp);
+
 private:
 	uint32_t m_return_code;
 
 	page_table *m_pml4;
 	kutil::vector<thread*> m_threads;
+	kutil::vector<kobject*> m_handles;
+
+	enum class state : uint8_t { running, exited };
+	state m_state;
 
 	static kutil::vector<process*> s_processes;
 };