netdev - Re: bpf: LLVM BTF inner map struct type def missing

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Message-ID: <aINvq2iqUJkNBvZT@gmail.com>
Date: Fri, 25 Jul 2025 13:51:07 +0200
From: Mahe Tardy <mahe.tardy@...il.com>
To: Yonghong Song <yhs@...a.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>
Subject: Re: bpf: LLVM BTF inner map struct type def missing

On Tue, Jul 22, 2025 at 11:02:58PM +0000, Yonghong Song wrote:
> > If you think it's reasonable to fix, I would be interested looking into
> > this.
> 
> Looks like this may be something we want to fix as people starts or already uses
> nested maps. So yes, please go ahead to look into this.

Here is my proposal patch https://github.com/llvm/llvm-project/pull/150608.
The idea is to visit inner maps as we visit the global maps during BTF
generation. Unfortunately, for that, I had to add a boolean arg to some
functions, I hope it's okay.

> 
> FYI, the llvm patch https://github.com/llvm/llvm-project/pull/141719/ tried to solve
> nested struct definition issue (similar to here). In that case, a type_tag is the
> indicator which allows further type generation. The patch listed llvm source
> locations you likely need to touch.

Thank you, it was very useful to have this pointer!

> 
> > 
> > [^1]: https://github.com/cilium/ebpf/discussions/1658#discussioncomment-12491339