[d33]

My idea is to avoid context switching like in VDSO, but with a generalized solution that would allow this sort of behavior for all system calls. Could you point me to any write-ups about exception-less syscalls?

[anonymousDan]

See the FlexSC paper at the bottom here: https://www.usenix.org/conference/osdi10/flexsc-flexible-sys... or more recently SCONE in the context of Intel SGX: https://www.usenix.org/conference/osdi16/technical-sessions/...