[kernel] Give processes and threads self handles

It was not consistent how processes got handles to themselves or their
threads, ending up with double entries. Now make such handles automatic
and expose them with new self_handle() methods.

src/kernel/objects/process.cpp

@@ -21,13 +21,16 @@ process::process() :
 	m_state {state::running}
 {
 	s_processes.append(this);
+
+	j6_handle_t self = add_handle(this);
+	kassert(self == self_handle(), "Process self-handle is not 0");
 }
 
 // The "kernel process"-only constructor
 process::process(page_table *kpml4) :
 	kobject {kobject::type::process},
 	m_space {kpml4},
-	m_next_handle {0},
+	m_next_handle {self_handle()+1},
 	m_state {state::running}
 {
 }
@@ -120,6 +123,7 @@ process::thread_exited(thread *th)
 	kassert(&th->m_parent == this, "Process got thread_exited for non-child!");
 	uint32_t status = th->m_return_code;
 	m_threads.remove_swap(th);
+	remove_handle(th->self_handle());
 	delete th;
 
 	if (m_threads.count() == 0) {

src/kernel/objects/process.h

@@ -68,6 +68,9 @@ public:
 	/// \returns  True if this thread ending has ended the process
 	bool thread_exited(thread *th);
 
+	/// Get the handle for this process to refer to itself
+	inline j6_handle_t self_handle() const { return 0; }
+
 	/// Get the process object that owns kernel threads and the
 	/// kernel address space
 	static process & kernel_process();

src/kernel/objects/thread.cpp

@@ -26,6 +26,8 @@ thread::thread(process &parent, uint8_t pri, uintptr_t rsp0) :
 		setup_kernel_stack();
 	else
 		m_tcb.rsp0 = rsp0;
+
+	m_self_handle = parent.add_handle(this);
 }
 
 thread::~thread()

src/kernel/objects/thread.h

@@ -141,6 +141,9 @@ public:
 	/// \arg rip  The address to return to, must be user space
 	void add_thunk_user(uintptr_t rip);
 
+	/// Get the handle representing this thread to its process
+	j6_handle_t self_handle() const { return m_self_handle; }
+
 	/// Create the kernel idle thread
 	/// \arg kernel The process object that owns kernel tasks
 	/// \arg pri    The idle thread priority value
@@ -175,4 +178,6 @@ private:
 	uint64_t m_wait_data;
 	j6_status_t m_wait_result;
 	j6_koid_t m_wait_obj;
+
+	j6_handle_t m_self_handle;
 };