bpf: Show target_{obj,btf}_id in tracing link fdinfo

The target_btf_id can help us understand which kernel function is
linked by a tracing prog. The target_btf_id and target_obj_id have
already been exposed to userspace, so we just need to show them.

The result as follows,

$ cat /proc/10673/fdinfo/10
pos:    0
flags:  02000000
mnt_id: 15
ino:    2094
link_type:      tracing
link_id:        2
prog_tag:       a04f5eef06a7f555
prog_id:        13
attach_type:    24
target_obj_id:  1
target_btf_id:  13964

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230517103126.68372-2-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 909c112ef537819ca79d3bff4a89db3342eb17b1..b2621089904ba89818ff9dda20597d3bcbc7beb7 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2968,10 +2968,17 @@ static void bpf_tracing_link_show_fdinfo(const struct bpf_link *link,
 {
        struct bpf_tracing_link *tr_link =
                container_of(link, struct bpf_tracing_link, link.link);
+       u32 target_btf_id, target_obj_id;
 
+       bpf_trampoline_unpack_key(tr_link->trampoline->key,
+                                 &target_obj_id, &target_btf_id);
        seq_printf(seq,
-                  "attach_type:\t%d\n",
-                  tr_link->attach_type);
+                  "attach_type:\t%d\n"
+                  "target_obj_id:\t%u\n"
+                  "target_btf_id:\t%u\n",
+                  tr_link->attach_type,
+                  target_obj_id,
+                  target_btf_id);
 }
 
 static int bpf_tracing_link_fill_link_info(const struct bpf_link *link,