Split vmas had no objects. Now fixed.

When sys_munmap() splits a vma, the new vma had no copy of the objects
in the original vma. Now we fixed that using a vma_copy_links() function
which can also be used as part of fork().

tasks/mm0/include/vm_area.h

@@ -252,6 +252,7 @@ static inline void task_add_vma(struct tcb *task, struct vm_area *vma)
 /* Main page fault entry point */
 int page_fault_handler(struct tcb *faulty_task, fault_kdata_t *fkdata);
 
+int vma_copy_links(struct vm_area *new_vma, struct vm_area *vma);
 int vma_drop_merge_delete(struct vm_area *vma, struct vm_obj_link *link);
 int vma_drop_merge_delete_all(struct vm_area *vma);
 

tasks/mm0/src/fault.c

@@ -262,6 +262,32 @@ struct page *copy_to_new_page(struct page *orig)
 }
 
 
+/* Copy all mapped object link stack from vma to new vma */
+int vma_copy_links(struct vm_area *new_vma, struct vm_area *vma)
+{
+	struct vm_obj_link *vmo_link, *new_link;
+
+	/* Get the first object on the vma */
+	BUG_ON(list_empty(&vma->vm_obj_list));
+	vmo_link = list_entry(vma->vm_obj_list.next,
+			      struct vm_obj_link, list);
+	do {
+		/* Create a new link */
+		new_link = vm_objlink_create();
+
+		/* Link object with new link */
+		vm_link_object(new_link, vmo_link->obj);
+
+		/* Add the new link to vma in object order */
+		list_add_tail(&new_link->list, &new_vma->vm_obj_list);
+
+	/* Continue traversing links, doing the same copying */
+	} while((vmo_link = vma_next_link(&vmo_link->list,
+					  &vma->vm_obj_list)));
+
+	return 0;
+}
+
 /*
  * Determine if an object is deletable.
  *

tasks/mm0/src/munmap.c

@@ -8,7 +8,7 @@
 #include <l4/api/errno.h>
 #include <l4/lib/math.h>
 #include <l4lib/arch/syslib.h>
-
+#include <vm_area.h>
 
 /* This splits a vma, splitter region must be in the *middle* of original vma */
 int vma_split(struct vm_area *vma, struct tcb *task,
@@ -33,6 +33,13 @@ int vma_split(struct vm_area *vma, struct tcb *task,
 	vma->pfn_end = pfn_start;
 	new->flags = vma->flags;
 
+	/*
+	 * Copy the object links of original vma to new vma. A split like this
+	 * increases the map count of mapped object(s) since now 2 vmas on the
+	 * same task maps the same object(s).
+	 */
+	vma_copy_links(new, vma);
+
 	/* Add new one next to original vma */
 	list_add_tail(&new->list, &vma->list);
 

tasks/mm0/src/task.c

@@ -129,7 +129,6 @@ int tcb_destroy(struct tcb *task)
 int copy_vmas(struct tcb *to, struct tcb *from)
 {
 	struct vm_area *vma, *new_vma;
-	struct vm_obj_link *vmo_link, *new_link;
 
 	list_for_each_entry(vma, &from->vm_area_head->list, list) {
 
@@ -137,23 +136,8 @@ int copy_vmas(struct tcb *to, struct tcb *from)
 		new_vma = vma_new(vma->pfn_start, vma->pfn_end - vma->pfn_start,
 				  vma->flags, vma->file_offset);
 
-		/* Get the first object on the vma */
+		/* Copy all object links */
-		BUG_ON(list_empty(&vma->vm_obj_list));
+		vma_copy_links(new_vma, vma);
-		vmo_link = list_entry(vma->vm_obj_list.next,
-				      struct vm_obj_link, list);
-		do {
-			/* Create a new link */
-			new_link = vm_objlink_create();
-
-			/* Link object with new link */
-			vm_link_object(new_link, vmo_link->obj);
-
-			/* Add the new link to vma in object order */
-			list_add_tail(&new_link->list, &new_vma->vm_obj_list);
-
-		/* Continue traversing links, doing the same copying */
-		} while((vmo_link = vma_next_link(&vmo_link->list,
-						  &vma->vm_obj_list)));
 
 		/* All link copying is finished, now add the new vma to task */
 		task_add_vma(to, new_vma);