Re: [PATCH v2] bpf: restore the ebpf program ID for BPF_AUDIT_UNLOAD and PERF_BPF_EVENT_PROG_UNLOAD

> - tstamp_type_access:1; /* Accessed __sk_buff->tstamp_type */ > + tstamp_type_access:1, /* Accessed __sk_buff->tstamp_type */ > + valid_id:1; /* Is bpf_prog::aux::__id valid? */ > enum bpf_prog_type type; /* Type of BPF program */ > enum bpf_attach_type expected_attach_type; /* For some prog types */ > u32 len; /* Number of filter blocks */ > @@ -1688,6 +1689,12 @@ void bpf_prog_inc(struct bpf_prog *prog); > struct bpf_prog * __must_check bpf_prog_inc_not_zero(struct bpf_prog *prog); > void bpf_prog_put(struct bpf_prog *prog); > > +static inline u32 bpf_prog_get_id(const struct bpf_prog *prog) > +{ > + if (WARN(!prog->valid_id, "Attempting to use an invalid eBPF program")) > + return 0; > + return prog->aux->__id; > +} I'm still missing why we need to have this WARN and have a check at all. IIUC, we're actually too eager in resetting the id to 0, and need to keep that stale id around at least for perf/audit. Why not have a flag only to protect against double-idr_remove bpf_prog_free_id and keep the rest as is? Which places are we concerned about that used to report id=0 but now would report stale id?