I have seen this technique being used to implement syscalls for processes running on intel SGX [0]. In that cases, it makes even more sense because exiting SGX,

I have seen this technique being used to implement syscalls for processes running on intel SGX [0]. In that cases, it makes even more sense because exiting SGX, making a syscall and then reentering SGX is a lot of overhead for a single syscall, while writing to shared memory is doable without exiting the SGX environment. [0]: https://www.usenix.org/system/files/conference/osdi16/osdi16-arnautov.pdf https://www.usenix.org/system/files/conference/osdi16/osdi16...