Re: [PATCH bpf-next v2 4/8] bpftool: Skip __bpf_relocatable on verifier-rewritten context types

[Ihor Solodrai <ihor.solodrai@linux.dev>]

On 10/27/26 11:06 AM, Andrii Nakryiko wrote:
> On Fri, Oct 23, 2026 at 3:27 PM Ihor Solodrai <ihor.solodrai@linux.dev> wrote:
>>
>> 
>> [...]
>> +
>> +/*
>> + * Anonymous records within types that need static offsets must not start
>> + * CO-RE access chains. Named records, typedefs and pointer targets are
>> + * separate types.
>> + */
>> +static void btf_c_mark_no_pai(const struct btf *btf, __u32 id, unsigned long *no_pai)
> 
> mark_static_offset to keep terminology consistent?
> 
>> +{
>> +       const struct btf_type *t = btf__type_by_id(btf, id);
>> +       const struct btf_member *m = btf_members(t);
>> +       __u32 i;
>> +
>> +       __set_bit(id, no_pai);
>> +       for (i = 0; i < btf_vlen(t); i++, m++) {
>> +               const struct btf_type *mt;
>> +               __u32 mid = m->type;
>> +
>> +               mt = btf__type_by_id(btf, mid);
>> +               while (btf_is_array(mt) || btf_is_mod(mt)) {
>> +                       mid = btf_is_array(mt) ? btf_array(mt)->type : mt->type;
>> +                       mt = btf__type_by_id(btf, mid);
>> +               }
>> +               if (btf_is_composite(mt) && !mt->name_off && !test_bit(mid, no_pai))
>> +                       btf_c_mark_no_pai(btf, mid, no_pai);
>> +       }
>> +}
>> +
>>  static int btf_c_annotate_records(struct btf *btf)
>>  {
>>         __u32 i, cnt = btf__type_cnt(btf);
>> +       unsigned long *no_pai;
>>         int err;
>>
>> +       no_pai = bitmap_zalloc(cnt);
> 
> this will cause problems for github mirror that won't have access to
> linux-internal include/linux/bitmap.h, 

Good point, haven't thought of that.


> ...I'd just open-code a simple
> bitmap or use bool array for simplicity, memory usage increase doesn't
> really matter here
> 
>> +       if (!no_pai)
>> +               return -ENOMEM;
>> +
>> +       for (i = 1; i < cnt; i++) {
>> +               if (btf_c_needs_static_offset(btf, btf__type_by_id(btf, i)))
>> +                       btf_c_mark_no_pai(btf, i, no_pai);
>> +       }
>> +
>>         for (i = 1; i < cnt; i++) {
>>                 const struct btf_type *t = btf__type_by_id(btf, i);
>>
>>                 if (!btf_is_composite(t))
>>                         continue;
>> +               if (test_bit(i, no_pai))
>> +                       continue;
>>                 err = btf__add_decl_attr(btf, "__bpf_relocatable", i, -1);
>>                 if (err < 0)
>> -                       return err;
>> +                       goto out;
>>         }
>>
>> -       return 0;
>> +       err = 0;
>> +out:
>> +       bitmap_free(no_pai);
>> +       return err;
>>  }
>>
>>  static int dump_btf_c(struct btf *btf,
>> --
>> 2.56.0
>>