vm: replace vm-region with address-space

address-space is a non-recursive data structure, which contains a flat list of vm_areas representing
mapped vm-objects.

userspace programs can no longer create sub-address-spaces. instead, they can reserve portions of
the address space, and use that reserved space to create mappings.

arch/x86_64/pmap.c

@@ -1,3 +1,4 @@
+#include <kernel/address-space.h>
 #include <kernel/compiler.h>
 #include <kernel/libc/stdio.h>
 #include <kernel/memblock.h>
@@ -7,7 +8,6 @@
 #include <kernel/task.h>
 #include <kernel/types.h>
 #include <kernel/vm-object.h>
-#include <kernel/vm-region.h>
 #include <kernel/vm.h>
 #include <mango/status.h>
 
@@ -363,12 +363,20 @@ kern_status_t pmap_handle_fault(
 	}
 
 	struct task *task = current_task();
-	struct vm_region *space = task->t_address_space;
+	if (!task) {
+		return KERN_FATAL_ERROR;
+	}
+
+	struct address_space *space = task->t_address_space;
+	if (!space) {
+		return KERN_FATAL_ERROR;
+	}
 
 	unsigned long lock_flags;
-	vm_region_lock_irqsave(space, &lock_flags);
-	kern_status_t status = vm_region_demand_map(space, fault_addr, flags);
-	vm_region_unlock_irqrestore(space, lock_flags);
+	address_space_lock_irqsave(space, &lock_flags);
+	kern_status_t status
+		= address_space_demand_map(space, fault_addr, flags);
+	address_space_unlock_irqrestore(space, lock_flags);
 
 	return status;
 }