Message-ID: <CABCJKudA=EvCE7vv44VDMqHjFv+5vyJ1ZfqG+TSPc49vtmT9RA@mail.gmail.com>
Date: Thu, 26 Sep 2024 22:53:46 +0000
From: Sami Tolvanen <samitolvanen@...gle.com>
To: Matthew Maurer <mmaurer@...gle.com>
Cc: masahiroy@...nel.org, ndesaulniers@...gle.com, ojeda@...nel.org, 
	gary@...yguo.net, mcgrof@...nel.org, Alex Gaynor <alex.gaynor@...il.com>, 
	rust-for-linux@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	linux-kernel@...r.kernel.org, neal@...pa.dev, marcan@...can.st, j@...nau.net, 
	asahi@...ts.linux.dev, linux-modules@...r.kernel.org, 
	Boqun Feng <boqun.feng@...il.com>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>
Subject: Re: [PATCH v5 00/16] Extended MODVERSIONS Support

Hi Matt,

On Wed, Sep 25, 2024 at 11:39 PM Matthew Maurer <mmaurer@...gle.com> wrote:
>
> This patch series is intended for use alongside the Implement
> MODVERSIONS for RUST [1] series as a replacement for the symbol name
> hashing approach used there 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.
>
> Currently, this series emits both the extended format and the current
> format on all modules, and prefers the extended format when checking if
> present. I'm open to various other policies via Kconfig knobs, but this
> seemed like a good initial default.
>
> The refactor to MODVERSIONS is prefixed to this series as result of an
> explicit request [5] by Luis in response to the original patchset.
>
> If you are testing this patch alongside RUST by manually removing the
> !MODVERSIONS restriction (this series doesn't remove it, because the
> CRCs don't mean what we'd want them to yet, we need the DWARF patch for
> that) and have kernel hardening enabled, you may need the CPU
> Mitigations [6] series. Without it, the foo.mod.o file produced by the
> C compiler will reference __x86_return_thunk, but foo.o will not.
> This means that the version table will not contain a version for
> __x86_return_thunk, but foo.ko will reference it, which will result
> in a version check failure.
>
> [1] https://lore.kernel.org/all/20240617175818.58219-17-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/lkml/ZVZNh%2FPA5HiVRkeb@bombadil.infradead.org/
> [6] https://lore.kernel.org/all/20240725183325.122827-1-ojeda@kernel.org/
>
> Changes in v5:
> - Addresses Sami's comments from v3 that I missed in v4 (missing early
>   return, extra parens)

v5 looks good to me, thank you for fixing these issues. I tested this
with my latest Rust modversions patches [1] and everything seems to
work for me (on x86_64, arm64, and riscv64 w/ clang).  For the series:

Reviewed-by: Sami Tolvanen <samitolvanen@...gle.com>
Tested-by: Sami Tolvanen <samitolvanen@...gle.com>

[1] https://github.com/samitolvanen/linux/commits/rustmodversions-v3

Sami

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