On Sat, Jun 5, 2021 at 4:11 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: > > Adding support to attach multiple functions to tracing program > by using the link_create/link_update interface. > > Adding multi_btf_ids/multi_btf_ids_cnt pair to link_create struct > API, that define array of functions btf ids that will be attached > to prog_fd. > > The prog_fd needs to be multi prog tracing program (BPF_F_MULTI_FUNC). > > The new link_create interface creates new BPF_LINK_TYPE_TRACING_MULTI > link type, which creates separate bpf_trampoline and registers it > as direct function for all specified btf ids. > > The new bpf_trampoline is out of scope (bpf_trampoline_lookup) of > standard trampolines, so all registered functions need to be free > of direct functions, otherwise the link fails. Overall the api makes sense to me. The restriction of multi vs non-multi is too severe though. The multi trampoline can serve normal fentry/fexit too. If ip is moved to the end (instead of start) the trampoline will be able to call into multi and normal fentry/fexit progs. Right?
