The helpers are in http://elixir.free-electrons.com/linux/v4.15-rc3/source/kernel/bpf/helpers.c http://elixir.free-electrons.com/linux/v4.15-rc3/source/kern....

The helpers are in http://elixir.free-electrons.com/linux/v4.15-rc3/source/kernel/bpf/helpers.c http://elixir.free-electrons.com/linux/v4.15-rc3/source/kern.... See the field gpl_only. For the list of which helpers are available in which hooks, the code needs to be read, to find things like: http://elixir.free-electrons.com/linux/v4.15-rc3/source/net/core/filter.c#L3357 http://elixir.free-electrons.com/linux/v4.15-rc3/source/net/.... Unfortunately, I don't believe the high level list of which hooks have gpl helpers is published, so reading the code is the best method currently.