On Wed, Aug 7, 2019 at 12:30 PM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Tue, Aug 06, 2019 at 10:37:54PM -0700, Andrii Nakryiko wrote:
> > Simplify code by relying on newly added BTF helper functions.
> >
> > Signed-off-by: Andrii Nakryiko <andriin@xxxxxx>
> ..
> >
> > - for (i = 0, vsi = (struct btf_var_secinfo *)(t + 1);
> > - i < vars; i++, vsi++) {
> > + for (i = 0, vsi = (void *)btf_var_secinfos(t); i < vars; i++, vsi++) {
>
> > + struct btf_member *m = (void *)btf_members(t);
> ...
> > case BTF_KIND_ENUM: {
> > - struct btf_enum *m = (struct btf_enum *)(t + 1);
> > - __u16 vlen = BTF_INFO_VLEN(t->info);
> > + struct btf_enum *m = (void *)btf_enum(t);
> > + __u16 vlen = btf_vlen(t);
> ...
> > case BTF_KIND_FUNC_PROTO: {
> > - struct btf_param *m = (struct btf_param *)(t + 1);
> > - __u16 vlen = BTF_INFO_VLEN(t->info);
> > + struct btf_param *m = (void *)btf_params(t);
> > + __u16 vlen = btf_vlen(t);
>
> So all of these 'void *' type hacks are only to drop const-ness ?
Yes.
> May be the helpers shouldn't be taking const then?
>
Probably not, because then we'll have much wider-spread problem of
casting const pointers into non-const when passing btf_type into
helpers.
I think const as a default is the right choice, because normally BTF
is immutable and btf__type_by_id is returning const pointer, etc.
That's typical and expected use-case. btf_dedup and BTF sanitization +
datasec size setting pieces are an exception that have to modify BTF
types in place before passing it to user.
So realistically I think we can just leave it as (void *), or I can do
explicit non-const type casts, or we can just not use helpers for
mutable cases. Do you have a preference?
