linux-kernel - Re: [PATCH v8 00/18] Implement DWARF modversions

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Message-ID: <CAK7LNAT6QcJokDPS2gcuFJwTRRpTeUrr4Px9Pex=JaG0E3AGzg@mail.gmail.com>
Date: Sat, 11 Jan 2025 02:36:51 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
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>, Gary Guo <gary@...yguo.net>, 
	Petr Pavlu <petr.pavlu@...e.com>, Daniel Gomez <da.gomez@...sung.com>, Neal Gompa <neal@...pa.dev>, 
	Hector Martin <marcan@...can.st>, Janne Grunau <j@...nau.net>, Miroslav Benes <mbenes@...e.cz>, 
	Asahi Linux <asahi@...ts.linux.dev>, Sedat Dilek <sedat.dilek@...il.com>, 
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-modules@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v8 00/18] Implement DWARF modversions

On Sat, Jan 4, 2025 at 5:45 AM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> Hi,
>
> Here's v8 of the DWARF modversions series. The main motivation is
> modversions support for Rust, which is important for distributions
> like Android that are about to ship Rust kernel modules. Per Luis'
> request [1], v2 dropped the Rust specific bits from the series and
> instead added the feature as an option for the entire kernel to
> make it easier to evaluate the benefits of this approach, and to
> get better test coverage. Matt is addressing Rust modversion_info
> compatibility issues in a separate patch set [2] that depends on
> this series, and actually allows modversions to be enabled with
> Rust.
>
> Short background: Unlike C, Rust source code doesn't have sufficient
> information about the final ABI, as the compiler has considerable
> freedom in adjusting structure layout, for example, which makes
> using a source code parser like genksyms a non-starter. Based on
> earlier feedback, this series uses DWARF debugging information for
> computing versions. DWARF is an established and a relatively stable
> format, which includes all the necessary ABI details, and adding a
> CONFIG_DEBUG_INFO dependency for Rust symbol versioning seems like a
> reasonable trade-off as most distributions already enable it.
>
> The first 15 patches add gendwarfksyms, a tool for computing symbol
> versions from DWARF. When passed a list of exported symbols and
> object files, the tool generates an expanded type string for each
> symbol and computes symbol versions. gendwarfksyms is written in C,
> uses libdw to process DWARF, and zlib for CRC32. Patch 16 ensures
> that debugging information is present where we need it, patch 17
> adds gendwarfksyms as an alternative to genksyms, and the last patch
> adds documentation.
>
> v8 is based on 6.13-rc5, and for your convenience, the series is
> also available here:
>
> https://github.com/samitolvanen/linux/commits/gendwarfksyms-v8
>
> If you also want to test the series with actual Rust modules, this
> branch adds v13 of Matt's modversion_info series:
>
> https://github.com/samitolvanen/linux/commits/rustmodversions-v8
>
> Sami
>
>
> [1] https://lore.kernel.org/lkml/ZnIZEtkkQWEIGf9n@bombadil.infradead.org/
> [2] https://lore.kernel.org/lkml/20250103-extended-modversions-v13-0-35d87c65ee04@google.com/
>

Applied to linux-kbuild.
Thanks.


-- 
Best Regards
Masahiro Yamada