On Tue, 2024-01-02 at 11:00 -0800, Andrii Nakryiko wrote:
[...]
> +static int clone_func_btf_info(struct btf *btf, int orig_fn_id, struct bpf_program *prog)
> +{
[...]
> + /* clone FUNC first, btf__add_func() enforces
> + * non-empty name, so use entry program's name as
> + * a placeholder, which we replace immediately
> + */
> + fn_id = btf__add_func(btf, prog->name, btf_func_linkage(fn_t), fn_t->type);
Nit: Why not call this function near the end, when fn_proto_id is available?
Thus avoiding need to "guess" fn_t->type.
[...]
> +static int bpf_program_fixup_func_info(struct bpf_object *obj, struct bpf_program *prog)
> +{
[...]
> + for (i = 1, n = btf__type_cnt(btf); i < n; i++) {
[...]
> +
> + /* clone fn/fn_proto, unless we already did it for another arg */
> + if (func_rec->type_id == orig_fn_id) {
> + int fn_id;
> +
> + fn_id = clone_func_btf_info(btf, orig_fn_id, prog);
> + if (fn_id < 0) {
> + err = fn_id;
> + goto err_out;
> + }
> +
> + /* point func_info record to a cloned FUNC type */
> + func_rec->type_id = fn_id;
Would it be helpful to add a log here, saying that BTF for function
so and so is changed before load?
> + }
> +
> + /* create PTR -> STRUCT type chain to mark PTR_TO_CTX argument;
> + * we do it just once per main BPF program, as all global
> + * funcs share the same program type, so need only PTR ->
> + * STRUCT type chain
> + */
> + if (ptr_id == 0) {
> + struct_id = btf__add_struct(btf, ctx_name, 0);
Nit: Maybe try looking up existing id for type ctx_name first?
> + ptr_id = btf__add_ptr(btf, struct_id);
> + if (ptr_id < 0 || struct_id < 0) {
> + err = -EINVAL;
> + goto err_out;
> + }
> + }
> +
[...]
