On 01/05/2024 18:43, Eduard Zingerman wrote:
> On Wed, 2024-05-01 at 18:29 +0100, Alan Maguire wrote:
>
> [...]
>
>>>> +/* Check if a member of a split BTF struct/union refers to a base BTF
>>>> + * struct/union. Members can be const/restrict/volatile/typedef
>>>> + * reference types, but if a pointer is encountered, type is no longer
>>>> + * considered embedded.
>>>> + */
>>>> +static int btf_find_embedded_composite_type_ids(__u32 *id, void *ctx)
>>>> +{
>>>> + struct btf_distill *dist = ctx;
>>>> + const struct btf_type *t;
>>>> + __u32 next_id = *id;
>>>> +
>>>> + do {
>>>> + if (next_id == 0)
>>>> + return 0;
>>>> + t = btf_type_by_id(dist->pipe.src, next_id);
>>>> + switch (btf_kind(t)) {
>>>> + case BTF_KIND_CONST:
>>>> + case BTF_KIND_RESTRICT:
>>>> + case BTF_KIND_VOLATILE:
>>>> + case BTF_KIND_TYPEDEF:
>>>
>>> I think BTF_KIND_TYPE_TAG is missing.
>>>
>>
>> It's implicit in the default clause; I can't see a case for having a
>> split BTF type tag base BTF types, but I might be missing something
>> there. I can make all the unexpected types explicit if that would be
>> clearer?
>
> I mean, this skips a series of modifiers, e.g.:
>
> struct buz {
> // next_id will get to 'struct bar' eventually
> const volatile struct bar foo;
> }
>
> Now, it is legal to have this chain like below:
>
> struct buz {
> const volatile __type_tag("quux") struct bar foo;
> }
>
> In which case the traversal does not have to stop.
> Am I confused?
>
no, sorry, I was! You're absolutely right, BTF_KIND_TYPE_TAG needs to be
accounted for here. Thanks for catching this!
> (Note: at the moment type tags are only applied to pointers but that
> would change in the future, I have a stalled LLVM change for this).
>
> [...]
