On Wed, Oct 23, 2024 at 02:31:30AM +0000, Matthew Maurer wrote:
> From: Sami Tolvanen <samitolva...@google.com>
> 
> Previously, two things stopped Rust from using MODVERSIONS:
> 1. Rust symbols are occasionally too long to be represented in the
>    original versions table
> 2. Rust types cannot be properly hashed by the existing genksyms
>    approach because:
>       * Looking up type definitions in Rust is more complex than C
>       * Type layout is potentially dependent on the compiler in Rust,
>         not just the source type declaration.
> 
> CONFIG_EXTENDED_MODVERSIONS addresses the first point, and
> CONFIG_GENDWARFKSYMS the second. If Rust wants to use MODVERSIONS, allow
> it to do so by selecting both features.
> 
> Signed-off-by: Sami Tolvanen <samitolva...@google.com>
> Co-developed-by: Matthew Maurer <mmau...@google.com>
> Signed-off-by: Matthew Maurer <mmau...@google.com>
> ---
>  init/Kconfig  |  3 ++-
>  rust/Makefile | 32 ++++++++++++++++++++++++++++++--
>  2 files changed, 32 insertions(+), 3 deletions(-)
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index 
> 530a382ee0feb391b4717abdba3672e584a462d0..f5cce579f29b2ed89e97f8075a3bf70e32e71ad0
>  100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1942,7 +1942,8 @@ config RUST
>       bool "Rust support"
>       depends on HAVE_RUST
>       depends on RUST_IS_AVAILABLE
> -     depends on !MODVERSIONS
> +     select EXTENDED_MODVERSIONS if MODVERSIONS
> +     depends on (GENDWARFKSYMS || !MODVERSIONS)

Nit: `depends on !MODVERSIONS || GENDWARFKSYMS` would match the
convention used below.

> +cmd_gendwarfksyms = $(if $(skip_gendwarfksyms),, \
> +     $(call rust_exports,$@,"%s\n",$$3) | \
> +     scripts/gendwarfksyms/gendwarfksyms \
> +             $(if $(KBUILD_SYMTYPES), --symtypes $(@:.o=.symtypes),) \
> +             $@ >> $(dot-target).cmd)

Note that Petr suggested adding a KBUILD_ flag for passing the
--stable parameter to gendwarfksyms, which I think would be useful,
so once I send out v5 of that series, we'll have to update this to
also use the parameter when processing Rust objects:

https://lore.kernel.org/linux-modules/8017c328-f039-46c3-b472-f203cd6e2...@suse.com/

Sami

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