bpf: Add bpf_get_attach_cookie() BPF helper to access bpf_cookie value

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>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210815070609.987780-7-andrii@kernel.org

1 files changed, 0 insertions, 3 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 83c3cc5e90df..f4c16f19f83e 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2102,9 +2102,6 @@ extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
 extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
 extern const struct bpf_func_proto bpf_sk_getsockopt_proto;
 
-const struct bpf_func_proto *bpf_tracing_func_proto(
-	enum bpf_func_id func_id, const struct bpf_prog *prog);
-
 const struct bpf_func_proto *tracing_prog_func_proto(
   enum bpf_func_id func_id, const struct bpf_prog *prog);