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

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Message-ID:
 <PH0PR15MB56391FD0639B8A5AF5FE2443CA59A@PH0PR15MB5639.namprd15.prod.outlook.com>
Date: Fri, 25 Jul 2025 17:40:34 +0000
From: Yonghong Song <yhs@...a.com>
To: Mahe Tardy <mahe.tardy@...il.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

>> ________________________________________
>> From: Mahe Tardy <mahe.tardy@...il.com>
>> Sent: Friday, July 25, 2025 4:51 AM
>> To: Yonghong Song
>> Cc: netdev@...r.kernel.org; Alexei Starovoitov; Daniel Borkmann
>> 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.

Sure. Will take a look. Thanks!

>> 
>> >
>> > 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