Since the only way a program like that would be interacting with the environment via a side channel, it'd be equivalent to not running the code at all.

As a result, you can disable all syscalls for your program with one simple request: 'exit()'

Printing hello world is a syscall - you need that to write to STDOUT .

There are alternative to syscall. For example, writing to shared memory. Shared memory as IPC is hard. And you need some syscall to set the memory up.. .