bpf: Add multi uprobe link

Adding new multi uprobe link that allows to attach bpf program
to multiple uprobes.

Uprobes to attach are specified via new link_create uprobe_multi
union:

  struct {
    __aligned_u64   path;
    __aligned_u64   offsets;
    __aligned_u64   ref_ctr_offsets;
    __u32           cnt;
    __u32           flags;
  } uprobe_multi;

Uprobes are defined for single binary specified in path and multiple
calling sites specified in offsets array with optional reference
counters specified in ref_ctr_offsets array. All specified arrays
have length of 'cnt'.

The 'flags' supports single bit for now that marks the uprobe as
return probe.

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20230809083440.3209381-4-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/include/uapi/linux/bpf.h

@@ -1039,6 +1039,7 @@ enum bpf_attach_type {
 	BPF_NETFILTER,
 	BPF_TCX_INGRESS,
 	BPF_TCX_EGRESS,
+	BPF_TRACE_UPROBE_MULTI,
 	__MAX_BPF_ATTACH_TYPE
 };
 
@@ -1057,6 +1058,7 @@ enum bpf_link_type {
 	BPF_LINK_TYPE_STRUCT_OPS = 9,
 	BPF_LINK_TYPE_NETFILTER = 10,
 	BPF_LINK_TYPE_TCX = 11,
+	BPF_LINK_TYPE_UPROBE_MULTI = 12,
 	MAX_BPF_LINK_TYPE,
 };
 
@@ -1190,6 +1192,13 @@ enum {
 	BPF_F_KPROBE_MULTI_RETURN = (1U << 0)
 };
 
+/* link_create.uprobe_multi.flags used in LINK_CREATE command for
+ * BPF_TRACE_UPROBE_MULTI attach type to create return probe.
+ */
+enum {
+	BPF_F_UPROBE_MULTI_RETURN = (1U << 0)
+};
+
 /* link_create.netfilter.flags used in LINK_CREATE command for
  * BPF_PROG_TYPE_NETFILTER to enable IP packet defragmentation.
  */
@@ -1626,6 +1635,13 @@ union bpf_attr {
 				};
 				__u64		expected_revision;
 			} tcx;
+			struct {
+				__aligned_u64	path;
+				__aligned_u64	offsets;
+				__aligned_u64	ref_ctr_offsets;
+				__u32		cnt;
+				__u32		flags;
+			} uprobe_multi;
 		};
 	} link_create;