On Tue, Mar 1, 2022 at 6:49 PM Delyan Kratunov <delyank@xxxxxx> wrote:
>
> In symmetry with bpf_object__open_skeleton(),
> bpf_object__open_subskeleton() performs the actual walking and linking
> of symbols described by bpf_sym_skeleton objects.
>
> Signed-off-by: Delyan Kratunov <delyank@xxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 76 ++++++++++++++++++++++++++++++++++++++++
> tools/lib/bpf/libbpf.h | 21 +++++++++++
> tools/lib/bpf/libbpf.map | 2 ++
> 3 files changed, 99 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index d20ae8f225ee..e6c27f4b9dea 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -11748,6 +11748,82 @@ int bpf_object__open_skeleton(struct bpf_object_skeleton *s,
> return 0;
> }
>
> +int bpf_object__open_subskeleton(struct bpf_object_subskeleton *s)
> +{
> + int i, len, map_type_id, sym_idx;
> + const char *var_name;
> + struct bpf_map *map;
> + struct btf *btf;
> + const struct btf_type *map_type, *var_type;
> + const struct bpf_sym_skeleton *sym;
> + struct btf_var_secinfo *var;
> + struct bpf_map *last_map = NULL;
> + const struct btf_type *last_map_type = NULL;
> +
> + if (!s->obj)
> + return libbpf_err(-EINVAL);
> +
> + btf = bpf_object__btf(s->obj);
> + if (!btf)
> + return libbpf_err(errno);
-errno
> +
> + for (sym_idx = 0; sym_idx < s->sym_cnt; sym_idx++) {
> + sym = &s->syms[sym_idx];
> + if (last_map && (strcmp(sym->section, bpf_map__section_name(last_map)) == 0)) {
see above about having struct bpf_map ** instead of sym->section
> + map = last_map;
> + map_type = last_map_type;
> + } else {
> + map = bpf_object__find_map_by_name(s->obj, sym->section);
> + if (!map) {
> + pr_warn("Could not find map for section %1$s, symbol %2$s",
> + sym->section, s->syms[i].name);
> + return libbpf_err(-EINVAL);
> + }
> + map_type_id = btf__find_by_name_kind(btf, sym->section, BTF_KIND_DATASEC);
bpf_map__btf_value_type_id() ?
> + if (map_type_id < 0) {
> + pr_warn("Could not find map type in btf for section %1$s (due to symbol %2$s)",
> + sym->section, sym->name);
> + return libbpf_err(-EINVAL);
> + }
> + map_type = btf__type_by_id(btf, map_type_id);
> + }
> +
[...]
> +
> +void bpf_object__destroy_subskeleton(struct bpf_object_subskeleton *s)
> +{
> + if (!s)
> + return;
> + if (s->syms)
> + free(s->syms);
no need to check s->syms, free handles NULL just fine
> + free(s);
> +}
> +
> int bpf_object__load_skeleton(struct bpf_object_skeleton *s)
> {
> int i, err;
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 7b66794f1c0a..915d59c31ad5 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -1291,6 +1291,27 @@ LIBBPF_API int bpf_object__attach_skeleton(struct bpf_object_skeleton *s);
> LIBBPF_API void bpf_object__detach_skeleton(struct bpf_object_skeleton *s);
> LIBBPF_API void bpf_object__destroy_skeleton(struct bpf_object_skeleton *s);
>
> +struct bpf_sym_skeleton {
I tried to get used to this "sym" terminology for a bit, but it still
feels off. From user's perspective all this are variables. Any
objections to use "var" terminology?
> + const char *name;
> + const char *section;
what if we store a pointer to struct bpf_map * instead, that way we
won't need to search, we'll just have a pointer ready
> + void **addr;
> +};
> +
> +struct bpf_object_subskeleton {
> + size_t sz; /* size of this struct, for forward/backward compatibility */
> +
> + const struct bpf_object *obj;
> +
> + int sym_cnt;
> + int sym_skel_sz;
> + struct bpf_sym_skeleton *syms;
as mentioned in previous patch, let's also record maps and prog, it is
important and needed from the very beginning
> +};
> +
> +LIBBPF_API int
> +bpf_object__open_subskeleton(struct bpf_object_subskeleton *s);
> +LIBBPF_API void
> +bpf_object__destroy_subskeleton(struct bpf_object_subskeleton *s);
> +
> struct gen_loader_opts {
> size_t sz; /* size of this struct, for forward/backward compatiblity */
> const char *data;
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index 5c85d297d955..81a1d0259866 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -443,4 +443,6 @@ LIBBPF_0.7.0 {
> LIBBPF_0.8.0 {
> global:
> bpf_map__section_name;
> + bpf_object__open_subskeleton;
> + bpf_object__destroy_subskeleton;
indentation looks off here... global should be indented with one tab,
and then APIs with two tabs
> } LIBBPF_0.7.0;
> --
> 2.34.1
