bpf: enhance BPF_OBJ_GET_INFO_BY_FD decoder

* bpf.c (print_bpf_map_info): Print only those fields that are
present in the structure, as it has been growing over time.
(print_bpf_prog_info): Likewise.  Print map_ids field as an array
of uint32_t instead of uint64_t; print "name" field.

Co-Authored-by: Dmitry V. Levin <ldv@altlinux.org>

diff --git a/bpf.c b/bpf.c
index ec5e18a63b795e89543c517df623ef1d24f45a4b..0a1b58c3f4097f784c9d9c983fab73c799dfd809 100644 (file)
--- a/bpf.c
+++ b/bpf.c
@@ -459,12 +459,27 @@ print_bpf_map_info(struct tcb * const tcp, uint32_t bpf_fd,
        PRINT_FIELD_U(", ", info, value_size);
        PRINT_FIELD_U(", ", info, max_entries);
        PRINT_FIELD_FLAGS(", ", info, map_flags, bpf_map_flags, "BPF_F_???");
+
+       /*
+        * "name" field was introduced by Linux commit v4.15-rc1~84^2~605^2~3.
+        */
+       if (len <= offsetof(struct bpf_map_info_struct, name))
+               goto print_bpf_map_info_end;
        PRINT_FIELD_CSTRING(", ", info, name);
+
+       /*
+        * ifindex, netns_dev, and netns_ino fields were introduced
+        * by Linux commit v4.16-rc1~123^2~109^2~5^2~4.
+        */
+       if (len <= offsetof(struct bpf_map_info_struct, ifindex))
+               goto print_bpf_map_info_end;
        PRINT_FIELD_IFINDEX(", ", info, ifindex);
        PRINT_FIELD_DEV(", ", info, netns_dev);
        PRINT_FIELD_U(", ", info, netns_ino);
 
        decode_attr_extra_data(tcp, info_buf, size, bpf_map_info_struct_size);
+
+print_bpf_map_info_end:
        tprints("}");
 }
 
@@ -510,6 +525,12 @@ print_bpf_prog_info(struct tcb * const tcp, uint32_t bpf_fd,
        print_ebpf_prog(tcp, info.xlated_prog_insns, info.xlated_prog_len / 8,
                        !!saved->xlated_prog_len);
 
+       /*
+        * load_time, created_by_uid, nr_map_ids, map_ids, and name fields
+        * were introduced by Linux commit v4.15-rc1~84^2~605^2~4.
+        */
+       if (len <= offsetof(struct bpf_prog_info_struct, load_time))
+               goto print_bpf_prog_info_end;
        PRINT_FIELD_U(", ", info, load_time);
        PRINT_FIELD_UID(", ", info, created_by_uid);
 
@@ -522,13 +543,23 @@ print_bpf_prog_info(struct tcb * const tcp, uint32_t bpf_fd,
        print_big_u64_addr(info.map_ids);
        print_array(tcp, info.map_ids, info.nr_map_ids,
                    &map_id_buf, sizeof(map_id_buf),
-                   tfetch_mem, print_uint64_array_member, 0);
+                   tfetch_mem, print_uint32_array_member, 0);
+
+       PRINT_FIELD_CSTRING(", ", info, name);
 
+       /*
+        * ifindex, netns_dev, and netns_ino fields were introduced
+        * by Linux commit v4.16-rc1~123^2~227^2~5^2~2.
+        */
+       if (len <= offsetof(struct bpf_prog_info_struct, ifindex))
+               goto print_bpf_prog_info_end;
        PRINT_FIELD_IFINDEX(", ", info, ifindex);
        PRINT_FIELD_DEV(", ", info, netns_dev);
        PRINT_FIELD_U(", ", info, netns_ino);
 
        decode_attr_extra_data(tcp, info_buf, size, bpf_prog_info_struct_size);
+
+print_bpf_prog_info_end:
        tprints("}");
 }