bpf: pass whole link instead of prog when triggering raw tracepoint

Instead of passing prog as an argument to bpf_trace_runX() helpers, that
are called from tracepoint triggering calls, store BPF link itself
(struct bpf_raw_tp_link for raw tracepoints). This will allow to pass
extra information like BPF cookie into raw tracepoint registration.

Instead of replacing `struct bpf_prog *prog = __data;` with
corresponding `struct bpf_raw_tp_link *link = __data;` assignment in
`__bpf_trace_##call` I just passed `__data` through into underlying
bpf_trace_runX() call. This works well because we implicitly cast `void *`,
and it also avoids naming clashes with arguments coming from
tracepoint's "proto" list. We could have run into the same problem with
"prog", we just happened to not have a tracepoint that has "prog" input
argument. We are less lucky with "link", as there are tracepoints using
"link" argument name already. So instead of trying to avoid naming
conflicts, let's just remove intermediate local variable. It doesn't
hurt readibility, it's either way a bit of a maze of calls and macros,
that requires careful reading.

Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Message-ID: <20240319233852.1977493-3-andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 2 insertions, 7 deletions

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index ae2ff73bde7e..1cb4c3809af4 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3469,17 +3469,12 @@ out_put_prog:
 	return err;
 }
 
-struct bpf_raw_tp_link {
-	struct bpf_link link;
-	struct bpf_raw_event_map *btp;
-};
-
 static void bpf_raw_tp_link_release(struct bpf_link *link)
 {
 	struct bpf_raw_tp_link *raw_tp =
 		container_of(link, struct bpf_raw_tp_link, link);
 
-	bpf_probe_unregister(raw_tp->btp, raw_tp->link.prog);
+	bpf_probe_unregister(raw_tp->btp, raw_tp);
 	bpf_put_raw_tracepoint(raw_tp->btp);
 }
 
@@ -3833,7 +3828,7 @@ static int bpf_raw_tp_link_attach(struct bpf_prog *prog,
 		goto out_put_btp;
 	}
 
-	err = bpf_probe_register(link->btp, prog);
+	err = bpf_probe_register(link->btp, link);
 	if (err) {
 		bpf_link_cleanup(&link_primer);
 		goto out_put_btp;