tools: bpftool: support pretty print with kind_flag set

The following example shows map pretty print with structures
which include bitfield members.

  enum A { A1, A2, A3, A4, A5 };
  typedef enum A ___A;
  struct tmp_t {
       char a1:4;
       int  a2:4;
       int  :4;
       __u32 a3:4;
       int b;
       ___A b1:4;
       enum A b2:4;
  };
  struct bpf_map_def SEC("maps") tmpmap = {
       .type = BPF_MAP_TYPE_ARRAY,
       .key_size = sizeof(__u32),
       .value_size = sizeof(struct tmp_t),
       .max_entries = 1,
  };
  BPF_ANNOTATE_KV_PAIR(tmpmap, int, struct tmp_t);

and the following map update in the bpf program:

  key = 0;
  struct tmp_t t = {};
  t.a1 = 2;
  t.a2 = 4;
  t.a3 = 6;
  t.b = 7;
  t.b1 = 8;
  t.b2 = 10;
  bpf_map_update_elem(&tmpmap, &key, &t, 0);

With this patch, I am able to print out the map values
correctly with this patch:
bpftool map dump id 187
  [{
        "key": 0,
        "value": {
            "a1": 0x2,
            "a2": 0x4,
            "a3": 0x6,
            "b": 7,
            "b1": 0x8,
            "b2": 0xa
        }
    }
  ]

Previously, if a function prototype argument has a typedef
type, the prototype is not printed since
function __btf_dumper_type_only() bailed out with error
if the type is a typedef. This commit corrected this
behavior by printing out typedef properly.

The following example shows forward type and
typedef type can be properly printed in function prototype
with modified test_btf_haskv.c.

  struct t;
  union  u;

  __attribute__((noinline))
  static int test_long_fname_1(struct dummy_tracepoint_args *arg,
                               struct t *p1, union u *p2,
                               __u32 unused)
  ...
  int _dummy_tracepoint(struct dummy_tracepoint_args *arg) {
    return test_long_fname_1(arg, 0, 0, 0);
  }

  $ bpftool p d xlated id 24
  ...
  int test_long_fname_1(struct dummy_tracepoint_args * arg,
                        struct t * p1, union u * p2,
                        __u32 unused)
  ...

Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c
index 06e3d2b..3f0629e 100644 (file)
--- a/tools/bpf/bpftool/btf_dumper.c
+++ b/tools/bpf/bpftool/btf_dumper.c
@@ -193,6 +193,7 @@ static int btf_dumper_struct(const struct btf_dumper *d, __u32 type_id,
        const struct btf_type *t;
        struct btf_member *m;
        const void *data_off;
+       int kind_flag;
        int ret = 0;
        int i, vlen;
 
@@ -200,18 +201,32 @@ static int btf_dumper_struct(const struct btf_dumper *d, __u32 type_id,
        if (!t)
                return -EINVAL;
 
+       kind_flag = BTF_INFO_KFLAG(t->info);
        vlen = BTF_INFO_VLEN(t->info);
        jsonw_start_object(d->jw);
        m = (struct btf_member *)(t + 1);
 
        for (i = 0; i < vlen; i++) {
-               data_off = data + BITS_ROUNDDOWN_BYTES(m[i].offset);
+               __u32 bit_offset = m[i].offset;
+               __u32 bitfield_size = 0;
+
+               if (kind_flag) {
+                       bitfield_size = BTF_MEMBER_BITFIELD_SIZE(bit_offset);
+                       bit_offset = BTF_MEMBER_BIT_OFFSET(bit_offset);
+               }
+
                jsonw_name(d->jw, btf__name_by_offset(d->btf, m[i].name_off));
-               ret = btf_dumper_do_type(d, m[i].type,
-                                        BITS_PER_BYTE_MASKED(m[i].offset),
-                                        data_off);
-               if (ret)
-                       break;
+               if (bitfield_size) {
+                       btf_dumper_bitfield(bitfield_size, bit_offset,
+                                           data, d->jw, d->is_plain_text);
+               } else {
+                       data_off = data + BITS_ROUNDDOWN_BYTES(bit_offset);
+                       ret = btf_dumper_do_type(d, m[i].type,
+                                                BITS_PER_BYTE_MASKED(bit_offset),
+                                                data_off);
+                       if (ret)
+                               break;
+               }
        }
 
        jsonw_end_object(d->jw);
@@ -298,6 +313,7 @@ static int __btf_dumper_type_only(const struct btf *btf, __u32 type_id,
 
        switch (BTF_INFO_KIND(t->info)) {
        case BTF_KIND_INT:
+       case BTF_KIND_TYPEDEF:
                BTF_PRINT_ARG("%s ", btf__name_by_offset(btf, t->name_off));
                break;
        case BTF_KIND_STRUCT:
@@ -321,10 +337,11 @@ static int __btf_dumper_type_only(const struct btf *btf, __u32 type_id,
                BTF_PRINT_TYPE(t->type);
                BTF_PRINT_ARG("* ");
                break;
-       case BTF_KIND_UNKN:
        case BTF_KIND_FWD:
-       case BTF_KIND_TYPEDEF:
-               return -1;
+               BTF_PRINT_ARG("%s %s ",
+                             BTF_INFO_KFLAG(t->info) ? "union" : "struct",
+                             btf__name_by_offset(btf, t->name_off));
+               break;
        case BTF_KIND_VOLATILE:
                BTF_PRINT_ARG("volatile ");
                BTF_PRINT_TYPE(t->type);
@@ -348,6 +365,7 @@ static int __btf_dumper_type_only(const struct btf *btf, __u32 type_id,
                if (pos == -1)
                        return -1;
                break;
+       case BTF_KIND_UNKN:
        default:
                return -1;
        }