[kernel] Use kernel proc space as kernel space

As mentioned in the last commit, with processes owning spaces, there was
a weird extra space in the "kernel" process that owns the kernel
threads. Now we use that space as the global kernel space, and don't
create a separate one.

src/kernel/objects/process.cpp

@@ -1,29 +1,48 @@
 #include "j6/signals.h"
 #include "kutil/assert.h"
+#include "kutil/no_construct.h"
 #include "cpu.h"
 #include "objects/process.h"
 #include "objects/thread.h"
 #include "page_manager.h"
 
+// This object is initialized _before_ global constructors are called,
+// so we don't want it to have a global constructor at all, lest it
+// overwrite the previous initialization.
+static kutil::no_construct<process> __g_kernel_process_storage;
+process &g_kernel_process = __g_kernel_process_storage.value;
+
+
 kutil::vector<process*> process::s_processes;
 
 process::process() :
-	kobject(kobject::type::process),
-	m_next_handle(0),
-	m_state(state::running)
+	kobject {kobject::type::process},
+	m_next_handle {0},
+	m_state {state::running}
 {
 	s_processes.append(this);
 }
 
+process::process(page_table *kpml4) :
+	kobject {kobject::type::process},
+	m_space {kpml4},
+	m_next_handle {0},
+	m_state {state::running}
+{
+}
+
 process::~process()
 {
 	s_processes.remove_swap(this);
 }
 
-process &
-process::current()
+process & process::current() { return *bsp_cpu_data.p; }
+process & process::kernel_process() { return g_kernel_process; }
+
+process *
+process::create_kernel_process(page_table *pml4)
 {
-	return *bsp_cpu_data.p;
+	return new (&g_kernel_process) process {pml4};
 }
 
 void

src/kernel/objects/process.h

@@ -63,12 +63,19 @@ public:
 	/// \returns  True if this thread ending has ended the process
 	bool thread_exited(thread *th);
 
+	/// Get the process object that owns kernel threads and the
+	/// kernel address space
+	static process & kernel_process();
+
 	/// 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);
+	/// \arg pml4 The kernel-only pml4
+	/// \returns  The kernel process object
+	static process * create_kernel_process(page_table *pml4);
 
 private:
+	// This constructor is called by create_kernel_process
+	process(page_table *kpml4);
+
 	uint32_t m_return_code;
 
 	vm_space m_space;