Index: kernel/generic/src/mm/backend_phys.c
===================================================================
--- kernel/generic/src/mm/backend_phys.c	(revision 01029fc7e46acbe4cd80f0a678a085d214882028)
+++ kernel/generic/src/mm/backend_phys.c	(revision db71e2af5cdfe169de296e6f39b3e5eda7a966f6)
@@ -111,5 +111,5 @@
  *
  * @param area Pointer to the address space area.
- * @param addr Faulting virtual address.
+ * @param upage Faulting virtual page.
  * @param access Access mode that caused the fault (i.e. read/write/exec).
  *
@@ -117,5 +117,5 @@
  * serviced).
  */
-int phys_page_fault(as_area_t *area, uintptr_t addr, pf_access_t access)
+int phys_page_fault(as_area_t *area, uintptr_t upage, pf_access_t access)
 {
 	uintptr_t base = area->backend_data.base;
@@ -123,13 +123,14 @@
 	ASSERT(page_table_locked(AS));
 	ASSERT(mutex_locked(&area->lock));
+	ASSERT(IS_ALIGNED(upage, PAGE_SIZE));
 
 	if (!as_area_check_access(area, access))
 		return AS_PF_FAULT;
 
-	ASSERT(addr - area->base < area->backend_data.frames * FRAME_SIZE);
-	page_mapping_insert(AS, addr, base + (addr - area->base),
+	ASSERT(upage - area->base < area->backend_data.frames * FRAME_SIZE);
+	page_mapping_insert(AS, upage, base + (upage - area->base),
 	    as_area_get_flags(area));
 	
-	if (!used_space_insert(area, ALIGN_DOWN(addr, PAGE_SIZE), 1))
+	if (!used_space_insert(area, upage, 1))
 		panic("Cannot insert used space.");