On Tue, Jul 28, 2020 at 04:35:16PM -0700, Andrii Nakryiko wrote:
SNIP
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index bae557ff2da8..c981e258fed3 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -1306,6 +1306,8 @@ int btf_struct_access(struct bpf_verifier_log *log,
> > const struct btf_type *t, int off, int size,
> > enum bpf_access_type atype,
> > u32 *next_btf_id);
> > +bool btf_struct_ids_match(struct bpf_verifier_log *log,
> > + int off, u32 id, u32 mid);
> > int btf_resolve_helper_id(struct bpf_verifier_log *log,
> > const struct bpf_func_proto *fn, int);
> >
> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > index 1ab5fd5bf992..562d4453fad3 100644
> > --- a/kernel/bpf/btf.c
> > +++ b/kernel/bpf/btf.c
> > @@ -4140,6 +4140,35 @@ int btf_struct_access(struct bpf_verifier_log *log,
> > return -EINVAL;
> > }
> >
> > +bool btf_struct_ids_match(struct bpf_verifier_log *log,
> > + int off, u32 id, u32 mid)
> > +{
> > + const struct btf_type *type;
> > + u32 nid;
> > + int err;
> > +
>
> mid and nid are terrible names, especially as an input argument name.
> mid == need_type_id? nid == cur_type_id or something along those
> lines?
'mid' was for matching id, 'nid' for nested id ;-)
need_type_id/cur_type_id sound good
>
> > + do {
> > + type = btf_type_by_id(btf_vmlinux, id);
> > + if (!type)
> > + return false;
> > + err = btf_struct_walk(log, type, off, 1, &nid);
> > + if (err < 0)
> > + return false;
> > +
> > + /* We found nested struct object. If it matches
> > + * the requested ID, we're done. Otherwise let's
> > + * continue the search with offset 0 in the new
> > + * type.
> > + */
> > + if (err == walk_struct && mid == nid)
> > + return true;
> > + off = 0;
> > + id = nid;
> > + } while (err == walk_struct);
>
> This seems like a slightly more obvious control flow:
>
> again:
>
> ...
>
> if (err != walk_struct)
> return false;
ok, and perhaps use in here the switch(err) as in the previous patch?
thanks,
jirka
>
> if (mid != nid) {
> off = 0;
> id = nid;
> goto again;
> }
>
> return true;
>
> > +
> > + return false;
> > +}
> > +
> > int btf_resolve_helper_id(struct bpf_verifier_log *log,
> > const struct bpf_func_proto *fn, int arg)
> > {
>
> [...]
>
