Re: [PATCH dwarves] pahole: Inject kfunc decl tags into BTF

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

On 21/12/2023 17:05, Alexei Starovoitov wrote:
> On Thu, Dec 21, 2023 at 12:35 AM Jiri Olsa <olsajiri@gmail.com> wrote:
>> you need to pick up only 'BTF_ID(func, ...)' IDs that belongs to SET8 lists,
>> which are bounded by __BTF_ID__set8__<name> symbols, which also provide size
> 
> +1
> 
>>>
>>> Maybe we need a codemod from:
>>>
>>>         BTF_ID(func, ...
>>>
>>> to:
>>>
>>>         BTF_ID(kfunc, ...
>>
>> I think it's better to keep just 'func' and not to do anything special for
>> kfuncs in resolve_btfids logic to keep it simple
>>
>> also it's going to be already in pahole so if we want to make a fix in future
>> you need to change pahole, resolve_btfids and possibly also kernel
> 
> I still don't understand why you guys want to add it to vmlinux BTF.
> The kernel has no use in this additional data.
> It already knows about all kfuncs.
> This extra memory is a waste of space from kernel pov.
> Unless I am missing something.
> 
> imo this logic belongs in bpftool only.
> It can dump vmlinux BTF and emit __ksym protos into vmlinux.h
> 

If the goal is to have bpftool detect all kfuncs, would having a BPF
kfunc iterator that bpftool could use to iterate over registered kfuncs
work perhaps?