On Tue, Mar 15, 2022 at 3:15 PM Delyan Kratunov <delyank@xxxxxx> wrote:
>
> In symmetry with bpf_object__open_skeleton(),
> bpf_object__open_subskeleton() performs the actual walking and linking
> of maps, progs, and globals described by bpf_*_skeleton objects.
>
> Signed-off-by: Delyan Kratunov <delyank@xxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 136 +++++++++++++++++++++++++++++++++------
> tools/lib/bpf/libbpf.h | 29 +++++++++
> tools/lib/bpf/libbpf.map | 2 +
> 3 files changed, 146 insertions(+), 21 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index e98a8381aad8..dac905171aaf 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -11812,6 +11812,49 @@ int libbpf_num_possible_cpus(void)
> return tmp_cpus;
> }
>
[...]
> +int bpf_object__open_subskeleton(struct bpf_object_subskeleton *s)
> +{
> + int err, len, var_idx, i;
> + const char *var_name;
> + const struct bpf_map *map;
> + struct btf *btf;
> + __u32 map_type_id;
> + const struct btf_type *map_type, *var_type;
> + const struct bpf_var_skeleton *var_skel;
> + struct btf_var_secinfo *var;
> +
> + if (!s->obj)
> + return libbpf_err(-EINVAL);
> +
> + btf = bpf_object__btf(s->obj);
> + if (!btf)
> + return libbpf_err(-errno);
can you please add an error message here that subskeletons expect
bpf_object to have BTF? Might be very confusing to users to understand
what's wrong if this happens
> +
> + err = populate_skeleton_maps(s->obj, s->maps, s->map_cnt);
> + if (err) {
> + pr_warn("failed to populate subskeleton maps: %d\n", err);
> + return libbpf_err(err);
> }
>
> - for (i = 0; i < s->prog_cnt; i++) {
> - struct bpf_program **prog = s->progs[i].prog;
> - const char *name = s->progs[i].name;
> + err = populate_skeleton_progs(s->obj, s->progs, s->prog_cnt);
> + if (err) {
> + pr_warn("failed to populate subskeleton maps: %d\n", err);
> + return libbpf_err(err);
> + }
>
> - *prog = bpf_object__find_program_by_name(obj, name);
> - if (!*prog) {
> - pr_warn("failed to find skeleton program '%s'\n", name);
> - return libbpf_err(-ESRCH);
> + for (var_idx = 0; var_idx < s->var_cnt; var_idx++) {
> + var_skel = &s->vars[var_idx];
> + map = *var_skel->map;
> + map_type_id = bpf_map__btf_value_type_id(map);
> + map_type = btf__type_by_id(btf, map_type_id);
> +
> + if (!btf_is_datasec(map_type)) {
> + pr_warn("Type for map '%1$s' is not a datasec: %2$s",
> + bpf_map__name(map),
> + __btf_kind_str(btf_kind(map_type)));
nit: other messages in this function start with lower case, let's keep
it consistent. But I think this is very unlikely error, so I think it
would be fine without pr_warn() altogether (missing BTF above seems
more probable)
> + return libbpf_err(-EINVAL);
> }
> - }
>
> + len = btf_vlen(map_type);
> + var = btf_var_secinfos(map_type);
> + for (i = 0; i < len; i++, var++) {
> + var_type = btf__type_by_id(btf, var->type);
> + var_name = btf__name_by_offset(btf, var_type->name_off);
> + if (strcmp(var_name, var_skel->name) == 0) {
> + *var_skel->addr = map->mmaped + var->offset;
> + break;
> + }
> + }
> + }
> return 0;
> }
>
[...]
