I've rebased Adhemerval's glibc patches for this and put them here:
https://git.zx2c4.com/glibc/log/?h=vdso
If you're running systemd, you may want to whitelist the syscall in
order to make use of it:
https://github.com/seccomp/libseccomp/pull/395
https://github.com/systemd/systemd/pull/25519