diff --git a/tasks/mm0/src/mmap.c b/tasks/mm0/src/mmap.c
index ce8abf0..c4c61d4 100644
--- a/tasks/mm0/src/mmap.c
+++ b/tasks/mm0/src/mmap.c
@@ -444,6 +444,35 @@ unsigned long find_unmapped_area(unsigned long npages, struct tcb *task)
 	return 0;
 }
 
+/* Validate an address that is a possible candidate for an mmap() region */
+int mmap_address_validate(unsigned long map_address, unsigned int vm_flags)
+{
+	if (map_address == 0)
+		return 0;
+
+	/* Private mappings can only go in task address space */
+	if (vm_flags & VMA_PRIVATE) {
+		if (map_address >= USER_AREA_START ||
+	    	    map_address < USER_AREA_END) {
+			return 1;
+		} else
+			return 0;
+	/*
+	 * Shared mappings can *also* go in the utcb address space,
+	 * taking in account that utcb's are shared mappings done
+	 * by individual tasks.
+	 */
+	} else if (vm_flags & VMA_SHARED) {
+		if ((map_address >= UTCB_AREA_START &&
+		     map_address < UTCB_AREA_END) ||
+		    (map_address >= USER_AREA_START &&
+	    	     map_address < USER_AREA_END))
+			return 1;
+		else
+			return 0;
+	} else
+		BUG();
+}
 /*
  * Maps the given file with given flags at the given page offset to the given
  * task's address space at the specified virtual memory address and length.
@@ -487,8 +516,7 @@ int do_mmap(struct vm_file *mapfile, unsigned long file_offset, struct tcb *task
 	}
 
 	/* Check invalid map address */
-	if (map_address == 0 || map_address < USER_AREA_START ||
-	    map_address >= USER_AREA_END) {
+	if (!mmap_address_validate(map_address, flags)) {
 
 		/* Get new map address for region of this size */
 		if ((int)(map_address =
diff --git a/tasks/mm0/src/task.c b/tasks/mm0/src/task.c
index eb68cac..cbdc78e 100644
--- a/tasks/mm0/src/task.c
+++ b/tasks/mm0/src/task.c
@@ -285,7 +285,7 @@ int start_boot_task(struct vm_file *file, struct task_ids *ids)
 	       task->utcb_address);
 	if ((err = do_mmap(0, 0, task, task->utcb_address,
 			   VM_READ | VM_WRITE | VMA_SHARED | VMA_ANONYMOUS,
-			   DEFAULT_UTCB_SIZE) < 0)) {
+			   __pfn(DEFAULT_UTCB_SIZE)) < 0)) {
 		printf("do_mmap: Mapping utcb failed with %d.\n", err);
 		goto error;
 	}
@@ -318,6 +318,7 @@ int start_boot_tasks(struct initdata *initdata)
 	struct task_ids ids;
 	int total = 0;
 
+	INIT_LIST_HEAD(&tcb_head.list);
 	do {
 		file = 0;
 		list_for_each_entry_safe(file, n, &initdata->boot_file_list,