bpftool: Display cookie for kprobe multi link

Displaying cookies for kprobe multi link, in plain mode:

  # bpftool link
  ...
  1397: kprobe_multi  prog 47532
          kretprobe.multi  func_cnt 3
          addr             cookie           func [module]
          ffffffff82b370c0 3                bpf_fentry_test1
          ffffffff82b39780 1                bpf_fentry_test2
          ffffffff82b397a0 2                bpf_fentry_test3

And in json mode:

  # bpftool link -j | jq
  ...
    {
      "id": 1397,
      "type": "kprobe_multi",
      "prog_id": 47532,
      "retprobe": true,
      "func_cnt": 3,
      "missed": 0,
      "funcs": [
        {
          "addr": 18446744071607382208,
          "func": "bpf_fentry_test1",
          "module": null,
          "cookie": 3
        },
        {
          "addr": 18446744071607392128,
          "func": "bpf_fentry_test2",
          "module": null,
          "cookie": 1
        },
        {
          "addr": 18446744071607392160,
          "func": "bpf_fentry_test3",
          "module": null,
          "cookie": 2
        }
      ]
    }

Cookie is attached to specific address, and because we sort addresses
before printing, we need to sort cookies the same way, hence adding
the struct addr_cookie to keep and sort them together.

Also adding missing dd.sym_count check to show_kprobe_multi_json.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240119110505.400573-9-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

src/link.c

@@ -249,33 +249,65 @@ static int get_prog_info(int prog_id, struct bpf_prog_info *info)
 	return err;
 }
 
-static int cmp_u64(const void *A, const void *B)
+struct addr_cookie {
+	__u64 addr;
+	__u64 cookie;
+};
+
+static int cmp_addr_cookie(const void *A, const void *B)
+{
+	const struct addr_cookie *a = A, *b = B;
+
+	if (a->addr == b->addr)
+		return 0;
+	return a->addr < b->addr ? -1 : 1;
+}
+
+static struct addr_cookie *
+get_addr_cookie_array(__u64 *addrs, __u64 *cookies, __u32 count)
 {
-	const __u64 *a = A, *b = B;
+	struct addr_cookie *data;
+	__u32 i;
 
-	return *a - *b;
+	data = calloc(count, sizeof(data[0]));
+	if (!data) {
+		p_err("mem alloc failed");
+		return NULL;
+	}
+	for (i = 0; i < count; i++) {
+		data[i].addr = addrs[i];
+		data[i].cookie = cookies[i];
+	}
+	qsort(data, count, sizeof(data[0]), cmp_addr_cookie);
+	return data;
 }
 
 static void
 show_kprobe_multi_json(struct bpf_link_info *info, json_writer_t *wtr)
 {
+	struct addr_cookie *data;
 	__u32 i, j = 0;
-	__u64 *addrs;
 
 	jsonw_bool_field(json_wtr, "retprobe",
 			 info->kprobe_multi.flags & BPF_F_KPROBE_MULTI_RETURN);
 	jsonw_uint_field(json_wtr, "func_cnt", info->kprobe_multi.count);
 	jsonw_uint_field(json_wtr, "missed", info->kprobe_multi.missed);
 	jsonw_name(json_wtr, "funcs");
 	jsonw_start_array(json_wtr);
-	addrs = u64_to_ptr(info->kprobe_multi.addrs);
-	qsort(addrs, info->kprobe_multi.count, sizeof(addrs[0]), cmp_u64);
+	data = get_addr_cookie_array(u64_to_ptr(info->kprobe_multi.addrs),
+				     u64_to_ptr(info->kprobe_multi.cookies),
+				     info->kprobe_multi.count);
+	if (!data)
+		return;
 
 	/* Load it once for all. */
 	if (!dd.sym_count)
 		kernel_syms_load(&dd);
+	if (!dd.sym_count)
+		goto error;
+
 	for (i = 0; i < dd.sym_count; i++) {
-		if (dd.sym_mapping[i].address != addrs[j])
+		if (dd.sym_mapping[i].address != data[j].addr)
 			continue;
 		jsonw_start_object(json_wtr);
 		jsonw_uint_field(json_wtr, "addr", dd.sym_mapping[i].address);
@@ -287,11 +319,14 @@ show_kprobe_multi_json(struct bpf_link_info *info, json_writer_t *wtr)
 		} else {
 			jsonw_string_field(json_wtr, "module", dd.sym_mapping[i].module);
 		}
+		jsonw_uint_field(json_wtr, "cookie", data[j].cookie);
 		jsonw_end_object(json_wtr);
 		if (j++ == info->kprobe_multi.count)
 			break;
 	}
 	jsonw_end_array(json_wtr);
+error:
+	free(data);
 }
 
 static __u64 *u64_to_arr(__u64 val)
@@ -675,8 +710,8 @@ void netfilter_dump_plain(const struct bpf_link_info *info)
 
 static void show_kprobe_multi_plain(struct bpf_link_info *info)
 {
+	struct addr_cookie *data;
 	__u32 i, j = 0;
-	__u64 *addrs;
 
 	if (!info->kprobe_multi.count)
 		return;
@@ -688,21 +723,24 @@ static void show_kprobe_multi_plain(struct bpf_link_info *info)
 	printf("func_cnt %u  ", info->kprobe_multi.count);
 	if (info->kprobe_multi.missed)
 		printf("missed %llu  ", info->kprobe_multi.missed);
-	addrs = (__u64 *)u64_to_ptr(info->kprobe_multi.addrs);
-	qsort(addrs, info->kprobe_multi.count, sizeof(__u64), cmp_u64);
+	data = get_addr_cookie_array(u64_to_ptr(info->kprobe_multi.addrs),
+				     u64_to_ptr(info->kprobe_multi.cookies),
+				     info->kprobe_multi.count);
+	if (!data)
+		return;
 
 	/* Load it once for all. */
 	if (!dd.sym_count)
 		kernel_syms_load(&dd);
 	if (!dd.sym_count)
-		return;
+		goto error;
 
-	printf("\n\t%-16s %s", "addr", "func [module]");
+	printf("\n\t%-16s %-16s %s", "addr", "cookie", "func [module]");
 	for (i = 0; i < dd.sym_count; i++) {
-		if (dd.sym_mapping[i].address != addrs[j])
+		if (dd.sym_mapping[i].address != data[j].addr)
 			continue;
-		printf("\n\t%016lx %s",
-		       dd.sym_mapping[i].address, dd.sym_mapping[i].name);
+		printf("\n\t%016lx %-16llx %s",
+		       dd.sym_mapping[i].address, data[j].cookie, dd.sym_mapping[i].name);
 		if (dd.sym_mapping[i].module[0] != '\0')
 			printf(" [%s]  ", dd.sym_mapping[i].module);
 		else
@@ -711,6 +749,8 @@ static void show_kprobe_multi_plain(struct bpf_link_info *info)
 		if (j++ == info->kprobe_multi.count)
 			break;
 	}
+error:
+	free(data);
 }
 
 static void show_uprobe_multi_plain(struct bpf_link_info *info)
@@ -966,6 +1006,14 @@ static int do_show_link(int fd)
 				return -ENOMEM;
 			}
 			info.kprobe_multi.addrs = ptr_to_u64(addrs);
+			cookies = calloc(count, sizeof(__u64));
+			if (!cookies) {
+				p_err("mem alloc failed");
+				free(addrs);
+				close(fd);
+				return -ENOMEM;
+			}
+			info.kprobe_multi.cookies = ptr_to_u64(cookies);
 			goto again;
 		}
 	}