[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.cpp

@@ -0,0 +1,78 @@
+#include "j6/signals.h"
+#include "kutil/assert.h"
+#include "objects/process.h"
+#include "objects/thread.h"
+#include "page_manager.h"
+
+kutil::vector<process*> process::s_processes;
+
+process::process(page_table *pml4) :
+	kobject(kobject::type::process),
+	m_pml4(pml4)
+{
+	s_processes.append(this);
+}
+
+process::~process()
+{
+	s_processes.remove_swap(this);
+}
+
+void
+process::exit(unsigned code)
+{
+	for (auto *thread : m_threads) {
+		thread->exit(code);
+	}
+	m_return_code = code;
+	page_manager::get()->delete_process_map(m_pml4);
+	assert_signal(j6_signal_process_exit);
+}
+
+void
+process::update()
+{
+	kassert(m_threads.count() > 0, "process::update with zero threads!");
+
+	size_t i = 0;
+	uint32_t status = 0;
+	while (i < m_threads.count()) {
+		thread *th = m_threads[i];
+		if (th->has_state(thread::state::exited)) {
+			status = th->m_return_code;
+			m_threads.remove_swap_at(i);
+			continue;
+		}
+		i++;
+	}
+
+	if (m_threads.count() == 0) {
+		// TODO: What really is the return code in this case?
+		exit(status);
+	}
+}
+
+thread *
+process::create_thread(uint8_t priority)
+{
+	thread *th = new thread(*this, priority);
+	kassert(th, "Failed to create thread!");
+	m_threads.append(th);
+	return th;
+}
+
+bool
+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);
+	delete th;
+
+	if (m_threads.count() == 0) {
+		exit(status);
+		return true;
+	}
+
+	return false;
+}