Index: kernel/generic/src/proc/program.c
===================================================================
--- kernel/generic/src/proc/program.c	(revision cde999aca79219e8751af76502001a86d411d176)
+++ kernel/generic/src/proc/program.c	(revision 3b47db687606b55f2694aaa5c4c6db563b5b61eb)
@@ -69,5 +69,5 @@
  *
  */
-int program_create(as_t *as, uintptr_t entry_addr, char *name, program_t *prg)
+errno_t program_create(as_t *as, uintptr_t entry_addr, char *name, program_t *prg)
 {
 	prg->loader_status = EE_OK;
@@ -137,5 +137,5 @@
  *
  */
-int program_create_from_image(void *image_addr, char *name, program_t *prg)
+errno_t program_create_from_image(void *image_addr, char *name, program_t *prg)
 {
 	as_t *as = as_create(0);
@@ -174,5 +174,5 @@
  *
  */
-int program_create_loader(program_t *prg, char *name)
+errno_t program_create_loader(program_t *prg, char *name)
 {
 	as_t *as = as_create(0);
@@ -225,5 +225,5 @@
  *
  */
-sysarg_t sys_program_spawn_loader(char *uspace_name, size_t name_len)
+sys_errno_t sys_program_spawn_loader(char *uspace_name, size_t name_len)
 {
 	/* Cap length of name and copy it from userspace. */
@@ -232,7 +232,7 @@
 	
 	char namebuf[TASK_NAME_BUFLEN];
-	int rc = copy_from_uspace(namebuf, uspace_name, name_len);
+	errno_t rc = copy_from_uspace(namebuf, uspace_name, name_len);
 	if (rc != 0)
-		return (sysarg_t) rc;
+		return (sys_errno_t) rc;
 	
 	namebuf[name_len] = 0;
Index: kernel/generic/src/proc/task.c
===================================================================
--- kernel/generic/src/proc/task.c	(revision cde999aca79219e8751af76502001a86d411d176)
+++ kernel/generic/src/proc/task.c	(revision 3b47db687606b55f2694aaa5c4c6db563b5b61eb)
@@ -83,5 +83,5 @@
 /* Forward declarations. */
 static void task_kill_internal(task_t *);
-static int tsk_constructor(void *, unsigned int);
+static errno_t tsk_constructor(void *, unsigned int);
 static size_t tsk_destructor(void *obj);
 
@@ -158,9 +158,9 @@
 }
 
-int tsk_constructor(void *obj, unsigned int kmflags)
+errno_t tsk_constructor(void *obj, unsigned int kmflags)
 {
 	task_t *task = (task_t *) obj;
 
-	int rc = caps_task_alloc(task);
+	errno_t rc = caps_task_alloc(task);
 	if (rc != EOK)
 		return rc;
@@ -246,5 +246,5 @@
 	    (container_check(ipc_phone_0->task->container, task->container))) {
 		cap_handle_t phone_handle;
-		int rc = phone_alloc(task, &phone_handle);
+		errno_t rc = phone_alloc(task, &phone_handle);
 		if (rc != EOK) {
 			task->as = NULL;
@@ -345,5 +345,5 @@
  *
  */
-sysarg_t sys_task_get_id(sysarg64_t *uspace_taskid)
+sys_errno_t sys_task_get_id(sysarg64_t *uspace_taskid)
 {
 	/*
@@ -351,5 +351,5 @@
 	 * the lifespan of the task.
 	 */
-	return (sysarg_t) copy_to_uspace(uspace_taskid, &TASK->taskid,
+	return (sys_errno_t) copy_to_uspace(uspace_taskid, &TASK->taskid,
 	    sizeof(TASK->taskid));
 }
@@ -385,5 +385,5 @@
  *
  */
-sysarg_t sys_task_set_name(const char *uspace_name, size_t name_len)
+sys_errno_t sys_task_set_name(const char *uspace_name, size_t name_len)
 {
 	char namebuf[TASK_NAME_BUFLEN];
@@ -393,7 +393,7 @@
 		name_len = TASK_NAME_BUFLEN - 1;
 	
-	int rc = copy_from_uspace(namebuf, uspace_name, name_len);
+	errno_t rc = copy_from_uspace(namebuf, uspace_name, name_len);
 	if (rc != 0)
-		return (sysarg_t) rc;
+		return (sys_errno_t) rc;
 	
 	namebuf[name_len] = '\0';
@@ -426,12 +426,12 @@
  *
  */
-sysarg_t sys_task_kill(task_id_t *uspace_taskid)
+sys_errno_t sys_task_kill(task_id_t *uspace_taskid)
 {
 	task_id_t taskid;
-	int rc = copy_from_uspace(&taskid, uspace_taskid, sizeof(taskid));
+	errno_t rc = copy_from_uspace(&taskid, uspace_taskid, sizeof(taskid));
 	if (rc != 0)
-		return (sysarg_t) rc;
-	
-	return (sysarg_t) task_kill(taskid);
+		return (sys_errno_t) rc;
+	
+	return (sys_errno_t) task_kill(taskid);
 }
 
@@ -539,5 +539,5 @@
  *
  */
-int task_kill(task_id_t id)
+errno_t task_kill(task_id_t id)
 {
 	if (id == 1)
@@ -596,5 +596,5 @@
  *
  */
-sysarg_t sys_task_exit(sysarg_t notify)
+sys_errno_t sys_task_exit(sysarg_t notify)
 {
 	task_kill_self(notify);
Index: kernel/generic/src/proc/thread.c
===================================================================
--- kernel/generic/src/proc/thread.c	(revision cde999aca79219e8751af76502001a86d411d176)
+++ kernel/generic/src/proc/thread.c	(revision 3b47db687606b55f2694aaa5c4c6db563b5b61eb)
@@ -153,5 +153,5 @@
  *
  */
-static int thr_constructor(void *obj, unsigned int kmflags)
+static errno_t thr_constructor(void *obj, unsigned int kmflags)
 {
 	thread_t *thread = (thread_t *) obj;
@@ -639,5 +639,5 @@
  *
  */
-int thread_join_timeout(thread_t *thread, uint32_t usec, unsigned int flags)
+errno_t thread_join_timeout(thread_t *thread, uint32_t usec, unsigned int flags)
 {
 	if (thread == THREAD)
@@ -930,5 +930,5 @@
  *
  */
-sysarg_t sys_thread_create(uspace_arg_t *uspace_uarg, char *uspace_name,
+sys_errno_t sys_thread_create(uspace_arg_t *uspace_uarg, char *uspace_name,
     size_t name_len, thread_id_t *uspace_thread_id)
 {
@@ -937,7 +937,7 @@
 	
 	char namebuf[THREAD_NAME_BUFLEN];
-	int rc = copy_from_uspace(namebuf, uspace_name, name_len);
+	errno_t rc = copy_from_uspace(namebuf, uspace_name, name_len);
 	if (rc != 0)
-		return (sysarg_t) rc;
+		return (sys_errno_t) rc;
 	
 	namebuf[name_len] = 0;
@@ -953,5 +953,5 @@
 	if (rc != 0) {
 		free(kernel_uarg);
-		return (sysarg_t) rc;
+		return (sys_errno_t) rc;
 	}
 	
@@ -977,5 +977,5 @@
 				free(kernel_uarg);
 				
-				return (sysarg_t) rc;
+				return (sys_errno_t) rc;
 			 }
 		}
@@ -999,5 +999,5 @@
 		free(kernel_uarg);
 	
-	return (sysarg_t) ENOMEM;
+	return (sys_errno_t) ENOMEM;
 }
 
@@ -1005,5 +1005,5 @@
  *
  */
-sysarg_t sys_thread_exit(int uspace_status)
+sys_errno_t sys_thread_exit(int uspace_status)
 {
 	thread_exit();
@@ -1018,5 +1018,5 @@
  *
  */
-sysarg_t sys_thread_get_id(thread_id_t *uspace_thread_id)
+sys_errno_t sys_thread_get_id(thread_id_t *uspace_thread_id)
 {
 	/*
@@ -1025,10 +1025,10 @@
 	 *
 	 */
-	return (sysarg_t) copy_to_uspace(uspace_thread_id, &THREAD->tid,
+	return (sys_errno_t) copy_to_uspace(uspace_thread_id, &THREAD->tid,
 	    sizeof(THREAD->tid));
 }
 
 /** Syscall wrapper for sleeping. */
-sysarg_t sys_thread_usleep(uint32_t usec)
+sys_errno_t sys_thread_usleep(uint32_t usec)
 {
 	thread_usleep(usec);
@@ -1036,5 +1036,5 @@
 }
 
-sysarg_t sys_thread_udelay(uint32_t usec)
+sys_errno_t sys_thread_udelay(uint32_t usec)
 {
 	delay(usec);