On Wed, Feb 5, 2025 at 6:55 PM Yafang Shao <laoar.shao@xxxxxxxxx> wrote: [...] > > I think we should first understand why the trampoline is not > > freed. > > IIUC, the fexit works as follows, > > bpf_trampoline > + __bpf_tramp_enter > + percpu_ref_get(&tr->pcref); > > + call do_exit() > > + __bpf_tramp_exit > + percpu_ref_put(&tr->pcref); > > Since do_exit() never returns, the refcnt of the trampoline image is > never decremented, preventing it from being freed. Thanks for the explanation. In this case, I think it makes sense to disallow attaching fexit programs on __noreturn functions. I am not sure what is the best solution for it though. Thanks, Song > > > > > We could either add functions annotated as "__noreturn" to the deny > > > list for fexit as follows, or we could explore a more generic > > > solution, such as embedding the "noreturn" information into the BTF > > > and extracting it when attaching fexit. > > > > I personally don't think this is really necessary. It is good to have. > > But a reasonable user should not expect noreturn function to > > generate fexit events.
