On 7/29/21 10:34 PM, Andrii Nakryiko wrote:

Add new BPF helper, bpf_get_attach_cookie(), which can be used by BPF programs
to get access to a user-provided bpf_cookie value, specified during BPF
program attachment (BPF link creation) time.

Naming is hard, though. With the concept being named "BPF cookie", I've
considered calling the helper:
   - bpf_get_cookie() -- seems too unspecific and easily mistaken with socket
     cookie;
   - bpf_get_bpf_cookie() -- too much tautology;
   - bpf_get_link_cookie() -- would be ok, but while we create a BPF link to
     attach BPF program to BPF hook, it's still an "attachment" and the
     bpf_cookie is associated with BPF program attachment to a hook, not a BPF
     link itself. Technically, we could support bpf_cookie with old-style
     cgroup programs.So I ultimately rejected it in favor of
     bpf_get_attach_cookie().

Currently all perf_event-backed BPF program types support
bpf_get_attach_cookie() helper. Follow-up patches will add support for
fentry/fexit programs as well.

While at it, mark bpf_tracing_func_proto() as static to make it obvious that
it's only used from within the kernel/trace/bpf_trace.c.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Acked-by: Yonghong Song <redacted>