Re: [PATCH dwarves v4 2/2] pahole: Inject kfunc decl tags into BTF

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

On 13/03/2024 03:17, Daniel Xu wrote:
> Hi Alan,
> 
> On Wed, Feb 28, 2024 at 05:57:01PM -0700, Daniel Xu wrote:
>> Hi Alan,
>>
>> On Thu, Feb 08, 2024 at 10:00:15AM +0000, Alan Maguire wrote:
>>> On 04/02/2024 18:40, Daniel Xu wrote:
> 
> [...]
> 
>>>
>>> Then all you'd need to do is iterate over BTF functions, using
>>> btf_encoder__find_function() to get a function and associated ELF info
>>> by name.
>>
>> Didn't know about this, thanks. I'll take a look at if the patch can use
>> the existing function metadata. That should get rid of
>> btf_encoder__collect_btf_funcs() if it works.
> 
> I experimented with this a bit and I'm not sure if it's a good approach.
> 
> Here are the two commits:
> 
>         https://pastes.dxuuu.xyz/xo9jwk
>         https://pastes.dxuuu.xyz/xmzew5
> 
> Basically my approach was to fan-in all the function info collected by
> the different threads. I don't think it'll work cuz some of the data
> (the name in particular) in struct elf_function belongs to the thread's
> struct btf_encoder instance. Which is all freed by btf_encoder__delete()
> before btf_encoder__encode().
> 
> It could probably be fixed, but doesn't seem very clean to me. So I
> think it'll be better to keep the code as-is. Unless you were thinking
> something different.
> 

Thanks for trying! We may end up revisiting the freeing of ELF
function/variable info in the future if we add address information from
symbols into BTF, but since that's not there yet, it makes sense to do
your collection separately.

Alan