Re: [PATCH v13 0/5] Extended MODVERSIONS Support

Masahiro Yamada
2025-01-10T17:38:47Z

On Sat, Jan 4, 2025 at 2:37 AM Matthew Maurer <mmaurer@google.com> wrote:
>
> This patch series is intended for use alongside the Implement DWARF
> modversions series [1] to enable RUST and MODVERSIONS at the same
> time.
>
> Elsewhere, we've seen a desire for long symbol name support for LTO
> symbol names [2], and the previous series came up [3] as a possible
> solution rather than hashing, which some have objected [4] to.
>
> This series adds a MODVERSIONS format which uses a section per column.
> This avoids userspace tools breaking if we need to make a similar change
> to the format in the future - we would do so by adding a new section,
> rather than editing the struct definition. In the new format, the name
> section is formatted as a concatenated sequence of NUL-terminated
> strings, which allows for arbitrary length names.
>
> Emitting the extended format is guarded by CONFIG_EXTENDED_MODVERSIONS,
> but the kernel always knows how to validate both the original and
> extended formats.
>
> Emitting the existing format is now guarded by CONFIG_BASIC_MODVERSIONS,
> but it is enabled by default when MODVERSIONS is enabled and must be
> explicitly disabled by the user.
>
> Disabling CONFIG_BASIC_MODVERSIONS may cause some userspace tools to be
> unable to retrieve CRCs until they are patched to understand the new
> location. Even with CONFIG_BASIC_MODVERSIONS enabled, those tools will
> be unable to read the CRCs for long symbols until they are updated to
> read the new format. This is not expected to interfere with normal
> operation, as the primary use for CRCs embedded in the module is
> load-time verification by the kernel. Recording and monitoring of CRCs
> is typically done through Module.symvers.
>
> Selecting RUST and MODVERSIONS is now possible if GENDWARFKSYMS is
> selected, and will implicitly select EXTENDED_MODVERSIONS.
>
> This series depends upon DWARF-based versions [1] and Masahiro's u32
> fixup patch [5].
>
> [1] https://lore.kernel.org/lkml/20241219210736.2990838-20-samitolvanen@google.com/
> [2] https://lore.kernel.org/lkml/20240605032120.3179157-1-song@kernel.org/
> [3] https://lore.kernel.org/lkml/ZoxbEEsK40ASi1cY@bombadil.infradead.org/
> [4] https://lore.kernel.org/lkml/0b2697fd-7ab4-469f-83a6-ec9ebc701ba0@suse.com/
> [5] https://lore.kernel.org/linux-kbuild/20241228154603.2234284-1-masahiroy@kernel.org
>
> Changes in v13:
> - Fixed up missed s32 usage (Thanks Sami).

Applied to linux-kbuild.
Thanks.

--
Best Regards
Masahiro Yamada