You're in the clear with the syscall numbers, at least. Linux treats them as part of the stable public API for each platform. If they want to update a syscall,

You're in the clear with the syscall numbers, at least. Linux treats them as part of the stable public API for each platform. If they want to update a syscall, they have to make a new version with its own number, and keep the old version around for as long as x86-64 is supported.