On Mon, Feb 26, 2024 at 5:04 PM Kui-Feng Lee <thinker.li@xxxxxxxxx> wrote:
>
> For a struct_ops map, btf_value_type_id is the type ID of it's struct
> type. This value is required by bpftool to generate skeleton including
> pointers of shadow types. The code generator gets the type ID from
> bpf_map__btf_vaule_type_id() in order to get the type information of the
> struct type of a map.
>
> Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index ef8fd20f33ca..465b50235a01 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -1229,6 +1229,7 @@ static int init_struct_ops_maps(struct bpf_object *obj, const char *sec_name,
> map->name = strdup(var_name);
> if (!map->name)
> return -ENOMEM;
> + map->btf_value_type_id = type_id;
>
this part is good
> map->def.type = BPF_MAP_TYPE_STRUCT_OPS;
> map->def.key_size = sizeof(int);
> @@ -4818,7 +4819,9 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
> if (obj->btf && btf__fd(obj->btf) >= 0) {
> create_attr.btf_fd = btf__fd(obj->btf);
> create_attr.btf_key_type_id = map->btf_key_type_id;
> - create_attr.btf_value_type_id = map->btf_value_type_id;
> + create_attr.btf_value_type_id =
> + def->type != BPF_MAP_TYPE_STRUCT_OPS ?
> + map->btf_value_type_id : 0;
but here I think it's cleaner to reset create_attr.btf_value_type_id
to zero a bit lower, see that we have special logic for
PERF_EVENT_ARRAY, CGROUP_ARRAY and a bunch more maps. Just add a case
for BPF_MAP_TYPE_STRUCT_OPS that will clear
create_attr.btf_value_type_id only (keeping btf_fd and
map->btf_value_Type_id intact)
> }
>
> if (bpf_map_type__is_map_in_map(def->type)) {
> --
> 2.34.1
>
