Updating bpf syscall: What kernel version should a PR be compatible with?

[Quentin Monnet]

Hello,

I use bpf() system call, that receives frequent updates in Linux
kernel, and I would like to submit a pull request on GitHub in order
to support the recent commands, map types, etc. for this syscall in
strace (i.e., I want to update patch [1]).

My question is: what is the *maximum* kernel version that would be
acceptable to compile strace on, if I submit a pull request now? Did I
miss a list of supported kernels somewhere?

I ask because my patch [2] adds updates for BPF commands that landed
in kernel 4.4, 4.8 or… _will_ land in 4.10. This means that  the
associated <linux/bpf.h> header must be available on the host or unit
tests will fail to compile. Adding #ifdef guards might be a solution,
but I am not sure this is clean enough (practically, most BPF features
would need their own #ifdef).

So I'd like to submit, but I don't want to propose something that
would break things, could someone please tell me how I should proceed?

Best regards,
Quentin Monnet

[1] https://github.com/strace/strace/commit/ddb53dd142ea6702afbc1ff238840969183a709d
[2] https://github.com/qmonnet/strace/commit/5232624b18fb002db11f3adf733bbef56b780d89