long strncpy_from_user(char *dst, const char __user *src, long count);
long __strncpy_from_user(char *dst, const char __user *src, long count);
long strnlen_user(const char __user *str, long n);
+long __strnlen_user(const char __user *str, long n);
long strlen_user(const char __user *str);
unsigned long clear_user(void __user *mem, unsigned long len);
unsigned long __clear_user(void __user *mem, unsigned long len);