Re: [PATCH v4 bpf-next 2/3] libbpf: support custom SEC() handlers

[Alan Maguire <alan.maguire@oracle.com>]

On Thu, 24 Feb 2022, Andrii Nakryiko wrote:

> Allow registering and unregistering custom handlers for BPF program.
> This allows user applications and libraries to plug into libbpf's
> declarative SEC() definition handling logic. This allows to offload
> complex and intricate custom logic into external libraries, but still
> provide a great user experience.
> 
> One such example is USDT handling library, which has a lot of code and
> complexity which doesn't make sense to put into libbpf directly, but it
> would be really great for users to be able to specify BPF programs with
> something like SEC("usdt/<path-to-binary>:<usdt_provider>:<usdt_name>")
> and have correct BPF program type set (BPF_PROGRAM_TYPE_KPROBE, as it is
> uprobe) and even support BPF skeleton's auto-attach logic.
> 
> In some cases, it might be even good idea to override libbpf's default
> handling, like for SEC("perf_event") programs. With custom library, it's
> possible to extend logic to support specifying perf event specification
> right there in SEC() definition without burdening libbpf with lots of
> custom logic or extra library dependecies (e.g., libpfm4). With current
> patch it's possible to override libbpf's SEC("perf_event") handling and
> specify a completely custom ones.
> 
> Further, it's possible to specify a generic fallback handling for any
> SEC() that doesn't match any other custom or standard libbpf handlers.
> This allows to accommodate whatever legacy use cases there might be, if
> necessary.
> 
> See doc comments for libbpf_register_prog_handler() and
> libbpf_unregister_prog_handler() for detailed semantics.
> 
> This patch also bumps libbpf development version to v0.8 and adds new
> APIs there.
> 
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Reviewed-by: Alan Maguire <alan.maguire@oracle.com>

also if you need it, for the series

Tested-by: Alan Maguire <alan.maguire@oracle.com>

Thanks!