Re: [PATCH bpf-next 3/3] bpftool: Display ref_ctr_offset for uprobe link info

[Jiri Olsa <olsajiri@gmail.com>]

On Wed, May 07, 2025 at 10:56:35AM +0200, Jiri Olsa wrote:
> On Tue, May 06, 2025 at 03:33:33PM -0700, Andrii Nakryiko wrote:
> > On Tue, May 6, 2025 at 6:58 AM Jiri Olsa <jolsa@kernel.org> wrote:
> > >
> > > Adding support to display ref_ctr_offset in link output, like:
> > >
> > >   # bpftool link
> > >   ...
> > >   42: perf_event  prog 174
> > >           uprobe /proc/self/exe+0x102f13  cookie 3735928559  ref_ctr_offset 50500538
> > 
> > let's use hex for ref_ctr_offset?
> 
> I had that, then I saw cookie was dec ;-) either way is fine for me
> 
> > 
> > and also, why do we have bpf_cookie and cookie emitted? Are they different?
> 
> hum, right.. so there's bpf_cookie retrieval from perf_link through the
> task_file iterator:
> 
>   cbdaf71f7e65 bpftool: Add bpf_cookie to link output
> 
> I guess it was added before we decided to have bpf_link_info.perf_event
> interface, which seems easier to me

we could drop the bpf_cookie with attached patch, but should we worry
about loosing 'bpf_cookie' tag from json output (there will be just
'cookie' tag now with the same value)

jirka


---
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 9eb764fe4cc8..ca8923425637 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -104,9 +104,7 @@ struct obj_ref {
 
 struct obj_refs {
 	int ref_cnt;
-	bool has_bpf_cookie;
 	struct obj_ref *refs;
-	__u64 bpf_cookie;
 };
 
 struct btf;
diff --git a/tools/bpf/bpftool/pids.c b/tools/bpf/bpftool/pids.c
index 23f488cf1740..e81518dfc835 100644
--- a/tools/bpf/bpftool/pids.c
+++ b/tools/bpf/bpftool/pids.c
@@ -80,8 +80,6 @@ static void add_ref(struct hashmap *map, struct pid_iter_entry *e)
 	memcpy(ref->comm, e->comm, sizeof(ref->comm));
 	ref->comm[sizeof(ref->comm) - 1] = '\0';
 	refs->ref_cnt = 1;
-	refs->has_bpf_cookie = e->has_bpf_cookie;
-	refs->bpf_cookie = e->bpf_cookie;
 
 	err = hashmap__append(map, e->id, refs);
 	if (err)
@@ -214,9 +212,6 @@ void emit_obj_refs_json(struct hashmap *map, __u32 id,
 		if (refs->ref_cnt == 0)
 			break;
 
-		if (refs->has_bpf_cookie)
-			jsonw_lluint_field(json_writer, "bpf_cookie", refs->bpf_cookie);
-
 		jsonw_name(json_writer, "pids");
 		jsonw_start_array(json_writer);
 		for (i = 0; i < refs->ref_cnt; i++) {
@@ -246,9 +241,6 @@ void emit_obj_refs_plain(struct hashmap *map, __u32 id, const char *prefix)
 		if (refs->ref_cnt == 0)
 			break;
 
-		if (refs->has_bpf_cookie)
-			printf("\n\tbpf_cookie %llu", (unsigned long long) refs->bpf_cookie);
-
 		printf("%s", prefix);
 		for (i = 0; i < refs->ref_cnt; i++) {
 			struct obj_ref *ref = &refs->refs[i];
diff --git a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
index 948dde25034e..ea6d54f43425 100644
--- a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
+++ b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
@@ -15,19 +15,6 @@ enum bpf_obj_type {
 	BPF_OBJ_BTF,
 };
 
-struct bpf_perf_link___local {
-	struct bpf_link link;
-	struct file *perf_file;
-} __attribute__((preserve_access_index));
-
-struct perf_event___local {
-	u64 bpf_cookie;
-} __attribute__((preserve_access_index));
-
-enum bpf_link_type___local {
-	BPF_LINK_TYPE_PERF_EVENT___local = 7,
-};
-
 extern const void bpf_link_fops __ksym;
 extern const void bpf_link_fops_poll __ksym __weak;
 extern const void bpf_map_fops __ksym;
@@ -52,17 +39,6 @@ static __always_inline __u32 get_obj_id(void *ent, enum bpf_obj_type type)
 	}
 }
 
-/* could be used only with BPF_LINK_TYPE_PERF_EVENT links */
-static __u64 get_bpf_cookie(struct bpf_link *link)
-{
-	struct bpf_perf_link___local *perf_link;
-	struct perf_event___local *event;
-
-	perf_link = container_of(link, struct bpf_perf_link___local, link);
-	event = BPF_CORE_READ(perf_link, perf_file, private_data);
-	return BPF_CORE_READ(event, bpf_cookie);
-}
-
 SEC("iter/task_file")
 int iter(struct bpf_iter__task_file *ctx)
 {
@@ -102,18 +78,6 @@ int iter(struct bpf_iter__task_file *ctx)
 	e.pid = task->tgid;
 	e.id = get_obj_id(file->private_data, obj_type);
 
-	if (obj_type == BPF_OBJ_LINK &&
-	    bpf_core_enum_value_exists(enum bpf_link_type___local,
-				       BPF_LINK_TYPE_PERF_EVENT___local)) {
-		struct bpf_link *link = (struct bpf_link *) file->private_data;
-
-		if (BPF_CORE_READ(link, type) == bpf_core_enum_value(enum bpf_link_type___local,
-								     BPF_LINK_TYPE_PERF_EVENT___local)) {
-			e.has_bpf_cookie = true;
-			e.bpf_cookie = get_bpf_cookie(link);
-		}
-	}
-
 	bpf_probe_read_kernel_str(&e.comm, sizeof(e.comm),
 				  task->group_leader->comm);
 	bpf_seq_write(ctx->meta->seq, &e, sizeof(e));
diff --git a/tools/bpf/bpftool/skeleton/pid_iter.h b/tools/bpf/bpftool/skeleton/pid_iter.h
index bbb570d4cca6..5692cf257adb 100644
--- a/tools/bpf/bpftool/skeleton/pid_iter.h
+++ b/tools/bpf/bpftool/skeleton/pid_iter.h
@@ -6,8 +6,6 @@
 struct pid_iter_entry {
 	__u32 id;
 	int pid;
-	__u64 bpf_cookie;
-	bool has_bpf_cookie;
 	char comm[16];
 };