Index: kernel/generic/src/mm/as.c
===================================================================
--- kernel/generic/src/mm/as.c	(revision 7f11dc6ba31c85d4b1daa9c4ebd4d6f99082a87c)
+++ kernel/generic/src/mm/as.c	(revision 46577995860f76c247274a43eb6f67b944f0d3a8)
@@ -111,5 +111,5 @@
 as_t *AS_KERNEL = NULL;
 
-NO_TRACE static int as_constructor(void *obj, unsigned int flags)
+NO_TRACE static errno_t as_constructor(void *obj, unsigned int flags)
 {
 	as_t *as = (as_t *) obj;
@@ -760,5 +760,5 @@
  *
  */
-int as_area_resize(as_t *as, uintptr_t address, size_t size, unsigned int flags)
+errno_t as_area_resize(as_t *as, uintptr_t address, size_t size, unsigned int flags)
 {
 	if (!IS_ALIGNED(address, PAGE_SIZE))
@@ -969,5 +969,5 @@
  *
  */
-int as_area_destroy(as_t *as, uintptr_t address)
+errno_t as_area_destroy(as_t *as, uintptr_t address)
 {
 	mutex_lock(&as->lock);
@@ -1085,5 +1085,5 @@
  *
  */
-int as_area_share(as_t *src_as, uintptr_t src_base, size_t acc_size,
+errno_t as_area_share(as_t *src_as, uintptr_t src_base, size_t acc_size,
     as_t *dst_as, unsigned int dst_flags_mask, uintptr_t *dst_base,
     uintptr_t bound)
@@ -1248,5 +1248,5 @@
  *
  */
-int as_area_change_flags(as_t *as, unsigned int flags, uintptr_t address)
+errno_t as_area_change_flags(as_t *as, unsigned int flags, uintptr_t address)
 {
 	/* Flags for the new memory mapping */
@@ -2208,17 +2208,17 @@
 }
 
-sysarg_t sys_as_area_resize(uintptr_t address, size_t size, unsigned int flags)
-{
-	return (sysarg_t) as_area_resize(AS, address, size, 0);
-}
-
-sysarg_t sys_as_area_change_flags(uintptr_t address, unsigned int flags)
-{
-	return (sysarg_t) as_area_change_flags(AS, flags, address);
-}
-
-sysarg_t sys_as_area_destroy(uintptr_t address)
-{
-	return (sysarg_t) as_area_destroy(AS, address);
+sys_errno_t sys_as_area_resize(uintptr_t address, size_t size, unsigned int flags)
+{
+	return (sys_errno_t) as_area_resize(AS, address, size, 0);
+}
+
+sys_errno_t sys_as_area_change_flags(uintptr_t address, unsigned int flags)
+{
+	return (sys_errno_t) as_area_change_flags(AS, flags, address);
+}
+
+sys_errno_t sys_as_area_destroy(uintptr_t address)
+{
+	return (sys_errno_t) as_area_destroy(AS, address);
 }
 
Index: kernel/generic/src/mm/backend_user.c
===================================================================
--- kernel/generic/src/mm/backend_user.c	(revision 7f11dc6ba31c85d4b1daa9c4ebd4d6f99082a87c)
+++ kernel/generic/src/mm/backend_user.c	(revision 46577995860f76c247274a43eb6f67b944f0d3a8)
@@ -126,5 +126,5 @@
 	IPC_SET_ARG5(data, pager_info->id3);
 
-	int rc = ipc_req_internal(pager_info->pager, &data, (sysarg_t) true);
+	errno_t rc = ipc_req_internal(pager_info->pager, &data, (sysarg_t) true);
 
 	if (rc != EOK) {
Index: kernel/generic/src/mm/page.c
===================================================================
--- kernel/generic/src/mm/page.c	(revision 7f11dc6ba31c85d4b1daa9c4ebd4d6f99082a87c)
+++ kernel/generic/src/mm/page.c	(revision 46577995860f76c247274a43eb6f67b944f0d3a8)
@@ -190,5 +190,5 @@
 }
 
-int page_find_mapping(uintptr_t virt, uintptr_t *phys)
+errno_t page_find_mapping(uintptr_t virt, uintptr_t *phys)
 {
 	page_table_lock(AS, true);
@@ -215,13 +215,13 @@
  *
  */
-sysarg_t sys_page_find_mapping(uintptr_t virt, uintptr_t *phys_ptr)
+sys_errno_t sys_page_find_mapping(uintptr_t virt, uintptr_t *phys_ptr)
 {
 	uintptr_t phys;
-	int rc = page_find_mapping(virt, &phys);
+	errno_t rc = page_find_mapping(virt, &phys);
 	if (rc != EOK)
 		return rc;
 	
 	rc = copy_to_uspace(phys_ptr, &phys, sizeof(phys));
-	return (sysarg_t) rc;
+	return (sys_errno_t) rc;
 }
 
Index: kernel/generic/src/mm/slab.c
===================================================================
--- kernel/generic/src/mm/slab.c	(revision 7f11dc6ba31c85d4b1daa9c4ebd4d6f99082a87c)
+++ kernel/generic/src/mm/slab.c	(revision 46577995860f76c247274a43eb6f67b944f0d3a8)
@@ -608,5 +608,5 @@
  */
 NO_TRACE static void _slab_cache_create(slab_cache_t *cache, const char *name,
-    size_t size, size_t align, int (*constructor)(void *obj,
+    size_t size, size_t align, errno_t (*constructor)(void *obj,
     unsigned int kmflag), size_t (*destructor)(void *obj), unsigned int flags)
 {
@@ -662,5 +662,5 @@
  */
 slab_cache_t *slab_cache_create(const char *name, size_t size, size_t align,
-    int (*constructor)(void *obj, unsigned int kmflag),
+    errno_t (*constructor)(void *obj, unsigned int kmflag),
     size_t (*destructor)(void *obj), unsigned int flags)
 {