linux-kernel - Re: [PATCH v2 00/19] Implement DWARF modversions

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Message-ID: <20420395-28ed-4579-84e1-4f7e7641363e@suse.com>
Date: Mon, 2 Sep 2024 11:57:11 +0200
From: Petr Pavlu <petr.pavlu@...e.com>
To: Sami Tolvanen <samitolvanen@...gle.com>,
 Masahiro Yamada <masahiroy@...nel.org>
Cc: Luis Chamberlain <mcgrof@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Matthew Maurer <mmaurer@...gle.com>, Alex Gaynor <alex.gaynor@...il.com>,
 Wedson Almeida Filho <wedsonaf@...il.com>, Gary Guo <gary@...yguo.net>,
 Petr Pavlu <petr.pavlu@...e.com>, Neal Gompa <neal@...pa.dev>,
 Hector Martin <marcan@...can.st>, Janne Grunau <j@...nau.net>,
 Asahi Linux <asahi@...ts.linux.dev>, linux-kbuild@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org,
 rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v2 00/19] Implement DWARF modversions

On 8/29/24 00:53, Sami Tolvanen wrote:
> On Wed, Aug 28, 2024 at 04:04:09PM +0900, Masahiro Yamada wrote:
>> On Fri, Aug 16, 2024 at 2:39 AM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>>> - Added a --symtypes flag for generating a genksyms-style
>>>   symtypes output based on Petr's feedback, and refactored
>>>   symbol version calculations to be based on symtypes instead
>>>   of raw --dump-dies output.
>>
>>
>>
>> I do not know if this is worthwhile.
> 
> Greg, Petr, do you want to comment on the usefulness of the symtypes
> output? I was under the impression it was a useful tool for figuring
> out exactly what caused the versions to change?

Right, the symtypes data is useful if distributions wish to maintain
stable kABI for their kernels. The data can be compressed/consolidated
and stored together with the source code for the distribution kernel,
serving as a reference kABI. Later, when the kernel is updated and CRCs
of some symbols change, the reference can be compared with the new
symtypes data to understand what has actually changed.

The previous discussion was under v1 of the series:
https://lore.kernel.org/linux-modules/0b2697fd-7ab4-469f-83a6-ec9ebc701ba0@suse.com/t/#u

-- 
Cheers,
Petr