On Fri, Dec 17, 2021 at 07:20:24AM +0530, Kumar Kartikeya Dwivedi wrote:
>
> +/* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
> +static bool __btf_type_is_scalar_struct(struct bpf_verifier_log *log,
> + const struct btf *btf,
> + const struct btf_type *t, int rec)
> +{
> + const struct btf_type *member_type;
> + const struct btf_member *member;
> + u16 i;
> +
> + if (rec == 4) {
> + bpf_log(log, "max struct nesting depth 4 exceeded\n");
> + return false;
> + }
As Matteo found out that saves stack with gcc only,
so I moved this check few lines below, just before recursive call.
> + if (is_kfunc) {
> + /* Permit pointer to mem, but only when argument
> + * type is pointer to scalar, or struct composed
> + * (recursively) of scalars.
> + */
> + if (!btf_type_is_scalar(ref_t) && !__btf_type_is_scalar_struct(log, btf, ref_t, 0)) {
... and reformatted this line to fit screen width.
... and applied.
Please add individual selftest for this feature
(not tied into refcnted kfuncs and CT).
