On Thu, Nov 24, 2022 at 7:16 AM Benjamin Tissoires
<benjamin.tissoires@xxxxxxxxxx> wrote:
>
> So we can then build light skeletons with loaders in any language.
>
It would be useful to include an example generated JSON. Other than
that the overall idea makes sense. Kind of machine-friendly "BPF
object schema" to allow automation.
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
> ---
> tools/bpf/bpftool/gen.c | 95 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 95 insertions(+)
>
> diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
> index cf8b4e525c88..818a5209b3ac 100644
> --- a/tools/bpf/bpftool/gen.c
> +++ b/tools/bpf/bpftool/gen.c
> @@ -904,6 +904,96 @@ codegen_progs_skeleton(struct bpf_object *obj, size_t prog_cnt, bool populate_li
> }
> }
>
> +static int gen_json(struct bpf_object *obj, const char *obj_name, size_t file_sz, uint8_t *obj_data)
> +{
> + struct bpf_program *prog;
> + struct bpf_map *map;
> + char ident[256];
> +
> + jsonw_start_object(json_wtr); /* root object */
> +
> + jsonw_string_field(json_wtr, "name", obj_name);
> +
> + jsonw_bool_field(json_wtr, "use_loader", use_loader);
> +
> + /* print all maps */
> + jsonw_name(json_wtr, "maps");
> + jsonw_start_array(json_wtr);
> + bpf_object__for_each_map(map, obj) {
> + if (!get_map_ident(map, ident, sizeof(ident))) {
> + p_err("ignoring unrecognized internal map '%s'...",
> + bpf_map__name(map));
> + continue;
> + }
> +
> + jsonw_start_object(json_wtr); /* map object */
> + jsonw_string_field(json_wtr, "ident", ident);
> + jsonw_string_field(json_wtr, "name", bpf_map__name(map));
> +
> + /* print mmap data value */
> + if (is_internal_mmapable_map(map, ident, sizeof(ident))) {
> + const void *mmap_data = NULL;
> + size_t mmap_size = 0;
> +
> + mmap_data = bpf_map__initial_value(map, &mmap_size);
> +
> + jsonw_uint_field(json_wtr, "size", mmap_size);
> + jsonw_uint_field(json_wtr, "mmap_sz", bpf_map_mmap_sz(map));
> + jsonw_name(json_wtr, "data");
> + print_hex_data_json((uint8_t *)mmap_data, mmap_size);
> +
> + }
> + jsonw_end_object(json_wtr); /* map object */
> + }
> + jsonw_end_array(json_wtr);
> +
> + /* print all progs */
> + jsonw_name(json_wtr, "progs");
> + jsonw_start_array(json_wtr);
> + bpf_object__for_each_program(prog, obj) {
> + jsonw_start_object(json_wtr); /* prog object */
> + jsonw_string_field(json_wtr, "name", bpf_program__name(prog));
> + jsonw_string_field(json_wtr, "sec", bpf_program__section_name(prog));
> + jsonw_end_object(json_wtr); /* prog object */
> + }
> + jsonw_end_array(json_wtr);
> +
> + /* print object data */
> + if (use_loader) {
> + DECLARE_LIBBPF_OPTS(gen_loader_opts, opts);
> + int err = 0;
> +
> + err = bpf_object__gen_loader(obj, &opts);
> + if (err)
> + return err;
> +
> + err = bpf_object__load(obj);
> + if (err) {
> + p_err("failed to load object file");
> + return err;
> + }
> + /* If there was no error during load then gen_loader_opts
> + * are populated with the loader program.
> + */
> +
> + jsonw_uint_field(json_wtr, "data_sz", opts.data_sz);
> + jsonw_name(json_wtr, "data");
> + print_hex_data_json((uint8_t *)opts.data, opts.data_sz);
> +
> + jsonw_uint_field(json_wtr, "insns_sz", opts.insns_sz);
> + jsonw_name(json_wtr, "insns");
> + print_hex_data_json((uint8_t *)opts.insns, opts.insns_sz);
> +
> + } else {
> + jsonw_name(json_wtr, "data");
> + print_hex_data_json(obj_data, file_sz);
> + }
> +
> + jsonw_end_object(json_wtr); /* root object */
> +
> + return 0;
> +}
> +
> static int do_skeleton(int argc, char **argv)
> {
> char header_guard[MAX_OBJ_NAME_LEN + sizeof("__SKEL_H__")];
> @@ -986,6 +1076,11 @@ static int do_skeleton(int argc, char **argv)
> goto out;
> }
>
> + if (json_output) {
> + err = gen_json(obj, obj_name, file_sz, (uint8_t *)obj_data);
> + goto out;
> + }
> +
> bpf_object__for_each_map(map, obj) {
> if (!get_map_ident(map, ident, sizeof(ident))) {
> p_err("ignoring unrecognized internal map '%s'...",
> --
> 2.38.1
>
