On Sat, Jan 4, 2025 at 2:37 AM Matthew Maurer [off-list ref] 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/ (local)
[2] https://lore.kernel.org/lkml/20240605032120.3179157-1-song@kernel.org/ (local)
[3] https://lore.kernel.org/lkml/ZoxbEEsK40ASi1cY@bombadil.infradead.org/ (local)
[4] https://lore.kernel.org/lkml/0b2697fd-7ab4-469f-83a6-ec9ebc701ba0@suse.com/ (local)
[5] https://lore.kernel.org/linux-kbuild/20241228154603.2234284-1-masahiroy@kernel.org (local)

Changes in v13:
- Fixed up missed s32 usage (Thanks Sami).

Applied to linux-kbuild.
Thanks.




-- 
Best Regards
Masahiro Yamada