bpf: Add support for tracing multi link

Adding new link to allow to attach program to multiple function
BTF IDs. The link is represented by struct bpf_tracing_multi_link.

To configure the link, new fields are added to bpf_attr::link_create
to pass array of BTF IDs;

  struct {
    __aligned_u64 ids;
    __u32         cnt;
  } tracing_multi;

Each BTF ID represents function (BTF_KIND_FUNC) that the link will
attach bpf program to.

We use previously added bpf_trampoline_multi_attach/detach functions
to attach/detach the link.

The linkinfo/fdinfo callbacks will be implemented in following changes.

Note this is supported only for archs (x86_64) with ftrace direct and
have single ops support.

  CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS &&
  CONFIG_HAVE_SINGLE_FTRACE_DIRECT_OPS

Note using sort_r (instead of plain sort) in check_dup_ids, because we
will use the swap callback in following changes.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-14-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index d49338c44014..308c76b57d13 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -787,6 +787,7 @@ int bpf_get_perf_event_info(const struct perf_event *event, u32 *prog_id,
 			    unsigned long *missed);
 int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);
 int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog);
+int bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr);
 #else
 static inline unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
 {
@@ -844,6 +845,11 @@ bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
 {
 	return -EOPNOTSUPP;
 }
+static inline int
+bpf_tracing_multi_attach(struct bpf_prog *prog, const union bpf_attr *attr)
+{
+	return -EOPNOTSUPP;
+}
 #endif
 
 enum {