[LSF/MM/BPF TOPIC] multi kprobe updates

[Jiri Olsa <olsajiri@gmail.com>]

There's few ongoing kprobe multi features that I'd like to give an update
about and discuss.

- Support to execute bpf program for both entry and return probes. This
  way we don't need to create 2 links when we need to run bpf program on
  entry/return probes of the same function, first rfc posted [0].

- In addition to above feature introduce shared 'session' data between
  entry and exit probe accessible from bpf program, originally discussed
  in [1].

- Allow to use per program re-entry checks instead of current hard coded
  per cpu re-entry check, or just change to per program check directly.

- There's ongoing development of patchset moving fprobe implementation
  from function tracer on top of fgraph tracer by Masami Hiramatsu [2].
  As kprobe multi link is implemented via fprobe I'd like to give an
  update what this change means for kprobe multi link.


[0] https://lore.kernel.org/bpf/20240207153550.856536-1-jolsa@kernel.org/
[1] https://lore.kernel.org/bpf/CAEf4Bzb6sPXAtDVke=CtCXev0mxhfgEG_O-xUA-e9-8NnbBtJQ@mail.gmail.com/
[2] https://lore.kernel.org/bpf/170723204881.502590.11906735097521170661.stgit@devnote2/