linux-kernel - Re: [PATCH v5 00/16] Extended MODVERSIONS Support

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Message-ID: <CAEg-Je_Fn=OWdhJn0xnNd4dT5wZNKz6XkOAHvDu-pkkhirEwgg@mail.gmail.com>
Date: Sat, 28 Sep 2024 17:35:15 -0400
From: Neal Gompa <neal@...pa.dev>
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, 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

On Wed, Sep 25, 2024 at 7:39 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)
>
> v4: https://lore.kernel.org/asahi/20240924212024.540574-1-mmaurer@google.com/
> - Fix incorrect dot munging in PPC
>
> v3: https://lore.kernel.org/lkml/87le0w2hop.fsf@mail.lhotse/T/
> - Split up the module verification refactor into smaller patches, per
>   Greg K-H's suggestion.
>
> v2: https://lore.kernel.org/all/20231118025748.2778044-1-mmaurer@google.com/
> - Add loading/verification refactor before modifying, per Luis's request
>
> v1: https://lore.kernel.org/rust-for-linux/20231115185858.2110875-1-mmaurer@google.com/
>
> Matthew Maurer (16):
>   module: Take const arg in validate_section_offset
>   module: Factor out elf_validity_ehdr
>   module: Factor out elf_validity_cache_sechdrs
>   module: Factor out elf_validity_cache_secstrings
>   module: Factor out elf_validity_cache_index_info
>   module: Factor out elf_validity_cache_index_mod
>   module: Factor out elf_validity_cache_index_sym
>   module: Factor out elf_validity_cache_index_str
>   module: Group section index calculations together
>   module: Factor out elf_validity_cache_strtab
>   module: Additional validation in elf_validity_cache_strtab
>   module: Reformat struct for code style
>   export_report: Rehabilitate script
>   modules: Support extended MODVERSIONS info
>   modpost: Produce extended modversion information
>   export_report: Use new version info format
>
>  arch/powerpc/kernel/module_64.c |  23 +-
>  kernel/module/internal.h        |  18 +-
>  kernel/module/main.c            | 647 ++++++++++++++++++++++++--------
>  kernel/module/version.c         |  45 +++
>  scripts/export_report.pl        |  17 +-
>  scripts/mod/modpost.c           |  39 +-
>  6 files changed, 628 insertions(+), 161 deletions(-)
>
> --
> 2.46.1.824.gd892dcdcdd-goog
>
>

The series looks straightforward and reasonable to me.

Acked-by: Neal Gompa <neal@...pa.dev>



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