Re: [PATCHv6 bpf] bpf: Move iterator functions into special init section

[Daniel Borkmann <daniel@iogearbox.net>]

On 11/10/20 4:40 PM, Jiri Olsa wrote:
> With upcoming changes to pahole, that change the way how and
> which kernel functions are stored in BTF data, we need a way
> to recognize iterator functions.
> 
> Iterator functions need to be in BTF data, but have no real
> body and are currently placed in .init.text section, so they
> are freed after kernel init and are filtered out of BTF data
> because of that.
> 
> The solution is to place these functions under new section:
>    .init.bpf.preserve_type
> 
> And add 2 new symbols to mark that area:
>    __init_bpf_preserve_type_begin
>    __init_bpf_preserve_type_end
> 
> The code in pahole responsible for picking up the functions will
> be able to recognize functions from this section and add them to
> the BTF data and filter out all other .init.text functions.
> 
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Suggested-by: Yonghong Song <yhs@fb.com>
> Signed-off-by: Jiri Olsa <jolsa@redhat.com>

LGTM, applied, thanks! Also added a reference to the pahole commit
to the commit log so that this info doesn't get lost in the void
plus carried over prior Acks given nothing changed logically in the
patch.

P.s.: I've been wondering whether we also need to align the begin/end
symbols via ALIGN_FUNCTION() in case ld might realign to a different
boundary on later passes but this seems neither the case for .init.text
right now, likely since it doesn't matter for kallsyms data in our
particular case.