__NR_madvise
__SYSCALL(__NR_madvise, sys_madvise)
__SYSCALL(__NR_madvise, sys_madvise)
ASSERT_EQ(syscall(__NR_madvise, ptr_p, page_size, MADV_GUARD_INSTALL), 0);
sret = syscall(__NR_madvise, start, len, types);