> On Nov 9, 2023, at 11:50 AM, Jose Marchesi <jose.march...@oracle.com> wrote: > >> >> On Thu, Nov 09, 2023 at 03:49:49PM +0000, Qing Zhao wrote: >>> Is it reasonable to add one option to disable the “counted_by” attribute? >>> (then no insertion of the new .ACCESS_WITH_SIZE into IL). >>> >>> The major reason is: some users might want to ignore all the “counted_by” >>> attribute added in the source code, >>> We need to provide them a way to disable this feature. >> >> -D'counted_by(x)=' >> and/or >> -D'__counted_by__(x)=' >> ? > > The insertion of .ACCESS_WITH_SIZE collides with the BPF CO-RE > preserve_access_index implementation. > > I don't think this will be a problem in practice (the BPF program can > define counted_by to the empty string as Jakub suggests) but we ought to > at least detect when a data structure featuring a counted_by FMA is > accessed with access index preservation (either attribute or builtin) > and either error out or warning out and try to accomodate by turning the > .ACCESS_WTIH_INDEX back to plain accesses. We can do either with BPF > specific backend code.
Yes, I agree that handling this in BPF backend code might be a better approach since this is really a BPF CO-RE specific issue. For the counted_by implementation, I will keep the current design. But I will add this identified BPF CO-RE issue into the proposal as a known issue for record purpose. Thanks a lot for raising this issue and the possible solutions. Qing
