On Fri, Dec 6, 2024 at 9:29 AM Eduard Zingerman <eddyz87@xxxxxxxxx> wrote: > > On Fri, 2024-12-06 at 08:08 -0800, Andrii Nakryiko wrote: > > [...] > > > The tags would be that generalizable side effect declaration approach, > > so seems worth it to set a uniform approach. > > > > > Please take a look at the patch, the change for check_cfg() is 32 lines. > > > > I did, actually. And I already explained what I don't like about it: > > eagerness. check_cfg() is not the right place for this, if we want to > > support dead code elimination and BPF CO-RE-based feature gating. > > Which your patches clearly violate, so I don't like them, sorry. > > > > We made this eagerness mistake with global subprogs verification > > previously, and had to switch it to lazy on-demand global subprog > > validation. I think we should preserve this lazy approach going > > forward. > > In this context tags have same detection power as current changes for check_cfg(), You keep ignoring the eagerness issue. I can't decide whether you think *it makes no difference* (I disagree, but whatever), or you *see no difference* (in which case let me know and I can explain with some simple example). > it is not possible to remove tag using dead code elimination. That's not the point of the tag to be dynamically adjustable. It's the opposite. It's something that the user declares upfront, and this is being enforced by the verifier (to prevent user errors, for example). If the user wants to have a "dynamic tag", they can have two global subprogs, one with and one without the tag, and pick which one should be called through, e.g., .rodata feature flag variable. I.e., make this decision outside of global subprog itself. > So I really don't see any advantages in the context of this particular issue. See also my reply to Alexei, and keep in mind freplace scenario, as one of the things your approach can't support. > > [...] >
