描述These system calls are not implemented in the Linux 2.4 kernel.
返回值These system calls always return -1 and set errno to ENOSYS.
注意Note that ftime(3), profil(3) and ulimit(3) are implemented as library functions.
Some system calls, like alloc_hugepages(2), free_hugepages(2), ioperm(2), iopl(2), and vm86(2) only exist on certain architectures.
Some system calls, like ipc(2), create_module(2), init_module(2), anddelete_module(2) only exist when the Linux kernel was built with support for them.