Re: [PATCH v3 1/1] RISC-V: enable building 64-bit kernels with rust support

[Gary Guo]

On Tue,  9 Apr 2024 18:25:16 +0100
Conor Dooley <conor@xxxxxxxxxx> wrote:

> From: Miguel Ojeda <ojeda@xxxxxxxxxx>
> 
> The rust modules work on 64-bit RISC-V, with no twiddling required.
> Select HAVE_RUST and provide the required flags to kbuild so that the
> modules can be used. The Makefile and Kconfig changes are lifted from
> work done by Miguel in the Rust-for-Linux tree, hence his authorship.
> Following the rabbit hole, the Makefile changes originated in a script,
> created based on config files originally added by Gary, hence his
> co-authorship.

Thanks for sending the patch!

> 32-bit is broken in core rust code, so support is limited to 64-bit:
> ld.lld: error: undefined symbol: __udivdi3

I wouldn't call the core rust code broken :)

The missing symbol here should be easily stubbed by changing the
redirect-intrinsics in rust/Makefile and adding a stub in
compiler_builtins.rs. Although we probably instead of panicking, want
to redirect the division to kernel division routine (IIRC the division
is used for formatting integers, which is a legit use of division).

> 
> As 64-bit RISC-V is now supported, add it to the arch support table.
> 
> Co-developed-by: Gary Guo <gary@xxxxxxxxxxx>
> Signed-off-by: Gary Guo <gary@xxxxxxxxxxx>
> Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
> Co-developed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> ---
>  Documentation/rust/arch-support.rst | 1 +
>  arch/riscv/Kconfig                  | 1 +
>  arch/riscv/Makefile                 | 7 +++++++
>  scripts/generate_rust_target.rs     | 6 ++++++
>  4 files changed, 15 insertions(+)