Re: [OE-core] [RFC PATCH 6/7] linux-yocto: enable Rust support in kernel configuration

[Randy MacLeod <randy.macleod@windriver.com>]

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On 2025-10-23 7:25 a.m., Sadineni, Harish via lists.openembedded.org wrote:
> From: Harish Sadineni<Harish.Sadineni@windriver.com>
>
> Add initial support for building the Linux kernel with Rust enabled:
>
> - Introduce `rust.cfg` to set Rust-related kernel config options, including:
>    - `CONFIG_RUST`, `CONFIG_HAVE_RUST`, and `CONFIG_RUST_IS_AVAILABLE`
>    - Rust sample modules and developer checks (overflow/debug assertions)
>    - Disable BTF and module versioning for compatibility
>
> - Add `rust.scc` to include `rust.cfg` via `kconf` in the kernel feature stack
>
> - Update `linux-yocto_${PV}.bb` to:
>    - Append `rust.scc` to `SRC_URI` and `KERNEL_FEATURES`
>    - Suppress `buildpaths` QA warning due to Rust path inclusion during builds
>
> Signed-off-by: Harish Sadineni<Harish.Sadineni@windriver.com>
> ---
>   meta/recipes-kernel/linux/files/rust.cfg      | 20 +++++++++++++++++++
>   meta/recipes-kernel/linux/files/rust.scc      |  1 +
This is fine for an RFC but at some point, when Bruce asks for an 
non-RFC version,
I expect that you will need to move this to the yocto-kenrel-cache, 
perhaps under:

https://git.yoctoproject.org/yocto-kernel-cache/tree/cfg

Take a look at the yocto-kernel-cache repo and docs:
https://docs.yoctoproject.org/kernel-dev/advanced.html
if you haven't already.

>   meta/recipes-kernel/linux/linux-yocto_6.16.bb |  4 ++++
>   3 files changed, 25 insertions(+)
>   create mode 100644 meta/recipes-kernel/linux/files/rust.cfg
>   create mode 100644 meta/recipes-kernel/linux/files/rust.scc
>
> diff --git a/meta/recipes-kernel/linux/files/rust.cfg b/meta/recipes-kernel/linux/files/rust.cfg
> new file mode 100644
> index 0000000000..293438e8e0
> --- /dev/null
> +++ b/meta/recipes-kernel/linux/files/rust.cfg
> @@ -0,0 +1,20 @@
> +CONFIG_RUST=y
> +CONFIG_SAMPLES_RUST=y
> +CONFIG_SAMPLE_RUST_MINIMAL=y
> +CONFIG_SAMPLE_RUST_PRINT=y
> +CONFIG_SAMPLE_RUST_HOSTPROGS=y
> +CONFIG_RUST_DEBUG_ASSERTIONS=y
> +CONFIG_RUST_OVERFLOW_CHECKS=y
> +CONFIG_RUST_BUILD_ASSERT_ALLOW=y
> +# Disable module versioning
> +CONFIG_MODVERSIONS=n
> +
> +# Disable BTF debug info
> +CONFIG_DEBUG_INFO_BTF=n
> +
> +# Rust availability
> +CONFIG_RUST_IS_AVAILABLE=y
> +
> +# Indicate Rust support present
> +CONFIG_HAVE_RUST=y


You'll have to review this list to divide it up into:
   1. a minimal rust.cfg and perhaps
   2. a rust-samples.cfg
   3. a rust-debug.cfg  if that's really what 
CONFIG_RUST_DEBUG_ASSERTIONS and friends are doing: 
https://cateee.net/lkddb/web-lkddb/RUST_DEBUG_ASSERTIONS.html Also, 
you'll need to explain and justify each option or set of options more 
clearly in the commit log.


As Bruce said, the next steps are:
1. Rust being optional and off by default 2. Rust binary / prebuilt 
components to minimize the overhead and dependencies of rust and related 
tools on the kernel.

Anyway, this is a super start and I understand you have a v2 almost 
ready that makes kenrel rust-support be optional so send that now and 
we'll see what the next step after that is.


Thanks,

../Randy

> +
> diff --git a/meta/recipes-kernel/linux/files/rust.scc b/meta/recipes-kernel/linux/files/rust.scc
> new file mode 100644
> index 0000000000..4686d9ce5e
> --- /dev/null
> +++ b/meta/recipes-kernel/linux/files/rust.scc
> @@ -0,0 +1 @@
> +kconf hardware rust.cfg
> diff --git a/meta/recipes-kernel/linux/linux-yocto_6.16.bb b/meta/recipes-kernel/linux/linux-yocto_6.16.bb
> index 2188c7fed2..fda964e78d 100644
> --- a/meta/recipes-kernel/linux/linux-yocto_6.16.bb
> +++ b/meta/recipes-kernel/linux/linux-yocto_6.16.bb
> @@ -77,3 +77,7 @@ KERNEL_FEATURES:append:powerpc64le = " arch/powerpc/powerpc-debug.scc"
>   # Check again during next major version upgrade
>   KERNEL_FEATURES:remove:riscv32 = "features/debug/debug-kernel.scc"
>   INSANE_SKIP:kernel-vmlinux:qemuppc64 = "textrel"
> +INSANE_SKIP:kernel-vmlinux = "buildpaths"
> +INSANE_SKIP:kernel-dbg = "buildpaths"
> +SRC_URI +="file://rust.scc"
> +KERNEL_FEATURES += "rust.scc"
>
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# Randy MacLeod
# Wind River Linux

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