Re: [OE-core] [PATCH v5 00/15] Enable rust support for linux kernel

[Paul Barker <paul@pbarker.dev>]

[-- Attachment #1: Type: text/plain, Size: 7146 bytes --]

On Thu, 2026-01-29 at 08:38 -0800, Sadineni, Harish via
lists.openembedded.org wrote:
> From: Harish Sadineni <Harish.Sadineni@windriver.com>
> 
> v5:
> - Regression in autobuilder with v4 series is due to applying v4 series together with following patch 
>   "llvm: enable LLVMgold.so build by adding binutils dependency"(https://lists.openembedded.org/g/openembedded-core/message/229387)
>   is fixed by droping Alistair Francis's patch(https://lists.openembedded.org/g/openembedded-core/message/229091).
> - Updated patch "rust: install Rust library sources for 'make rustavailable' support" to install 
>   rust standard library sources for rust-native. 
> 
> v4:
> - Resolved patchtest failures.
> 
> v3:
> - Removed the DISTRO_FEATURES dependency for installing Rust library sources in the Rust recipe,
> - Extended support for on target rust kernel module developmet by installing Rust library sources and
>   introduced packaging of the Rust standard library sources in a dedicated ${PN}-src-lib package.
> - Integrated Alistair Francis's patch(https://lists.openembedded.org/g/openembedded-core/message/229091)
>   that uses the Rust bootstrap tool to install Rust library sources for rust-native.
> - Dropped the patch that added rust-kernel to native/nativesdk feature filters in bitbake.conf.
> - Updated flags in the make-mod-scripts recipe to fix build failures when building Rust out-of-tree
>   module recipes.
> - Dropped the bindgen-cli patch extending BBCLASSEXTEND to include
>   nativesdk, as it has been merged into oe-core.
> 
> v2:
> - Combined [PATCH 05/16][0] & [PATCH 06/16][1] from v1.
> - Updated commit message and added in code comments for patch "[PATCH 09/15] kernel-devsrc: copying
>   rust-kernel source to $kerneldir/build"
> 
> [0] https://lists.openembedded.org/g/openembedded-core/message/228559
> [1] https://lists.openembedded.org/g/openembedded-core/message/228560
> 
> v1:
> The previous series was RFC v4, "Enable Rust support for Linux kernel"
> (https://lists.openembedded.org/g/openembedded-core/message/226623).
> 
> In addition, Yoann Congal posted RFC v2, "Kernel Rust out-of-tree module support"
> (https://lists.openembedded.org/g/openembedded-core/message/227281), which builds on top of RFC v4.
> 
> The current patch series is a unified version that combines both efforts.
> Compared to the earlier series, the main changes are:
> 
> -Kernel configuration fragments have been moved to yocto-kernel-cache.
> -The kernel fragments have been removed from SRC_URI and from the files
>  directory previously stored underrecipes-kernel/linux/files.
> -Updated the "[PATCH 11/16] selftest/cases/runtime_test: Add test for Linux Rust sample"
>  by appending KERNEL_EXTRA_FEATURES:append = 'features/kernel-sample/kernel-rust-sample.scc'
>  instead of adding this directly in the linux-yocto recipe.
> 
> 
> This patch series introduces Rust support into the linux-yocto kernel recipe and
> related build infrastructure in the Yocto Project. The goal is to enable building
> the Linux kernel with Rust components and provide support for building kernel module
> which is written in rust and also provide support to build rust kernel modules in sdk.
> 
> And this series adds test for Linux Rust sample and also added support
> for out-of-tree kernel module written in Rust as well as associated test.
> 
> Summary of patches:
> 
> - Patch 01: Add required dependencies ('clang-native', 'rust-native','bindgen-cli-native') to the kernel to support Rust binding generation.
> - Patch 02: Install the Rust standard library source ('library/') for  native,target and sdk.
> - Patch 03: Updated `kernel-yocto.bbclass` to invoke `make rustavailable` during 'do_kernel_configme', ensuring Rust readiness.
> - Patch 04: Add kernel configuration support for Rust (via 'kernel-rust.scc'), enabling the Rust build options in kernel config.
> - Patch 05: Fixed buildpaths errors when rust is enabled for kernel by appending --remap-path-prefix to RUST_DEBUG_REMAP
> - Patch 06: split `HOSTCC` flag to align with to linux-yocto and fix build issue with make-mod-scripts recipe.
> - Patch 07: Disabling ccache when rust-kernel is enabled for linux-yocto.
> - Patch 08: Copy Rust kernel sources into kernel-devsrc build directory which will be required while running 'make prepare' in sdk.
> - Patch 09: Added oe-selftest case for the Linux Rust sample.
> - patch 10: Copying include/config/auto.conf in STAGING_KERNEL_BUILDDIR
> - patch 11: Export artifacts needed for out-of-tree Rust compilation
> - patch 12: Prepare out-of-tree rust module compilation
> - patch 13: Added rust-out-of-tree-module recipe in meta-skeleton layer
> - Patch 14: Fixed buildpaths errors for rust-out-of-tree-module recipe by appending --remap-path-prefix to RUST_DEBUG_REMAP
> - patch 15: Added rust-out-of-tree selftest
> 
> Patches have been build-tested successfully on:
> - qemuarm64
> - qemux86-64
> 
> Benchmark test-result for x86-64:
> +-------------------------------+------------+-----------+-----------+-----------+
> > DISTRO_FEATURES               |   real     |   user    |    sys    |  FS usage |
> +-------------------------------+------------+-----------+-----------+-----------+
> > rust-kernel (enabled)         | 46m1.720s  | 0m28.864s | 0m3.696s  |   58 GB   |
> > rust-kernel (disabled)        | 30m1.053s  | 0m20.091s | 0m2.748s  |   33 GB   |
> +-------------------------------+------------+-----------+-----------+-----------+

We discussed these patches on Monday and have some feedback on the
design. Things are nearly correct, we do want to ensure that the user
experience is good before merging this though as people will quickly
start to depend on it.

We think it would be better if Rust support was controlled by
KERNEL_FEATURES instead of DISTRO_FEATURES. This option now only impacts
the kernel and any kernel module recipes. It also may need to change
depending on MACHINE which makes it not a good fit for DISTRO_FEATURES -
e.g. one BSP may use an older LTS kernel with no required Rust code and
a different BSP may use a newer kernel and need a driver written in Rust
for the board to function.

We should add a new module-rust.bbclass instead of extending
module.bbclass with conditional logic. This can be included by any
modules which use Rust and handle any common setup. It can also check
for the presence of required files (scripts/target.json & rust/*) in the
kernel's shared workdir, and perhaps the kernel config so that we can
give a sensible error message if they are missing. This means that
module-rust.bbclass doesn't need to check KERNEL_FEATURES for
rust-kernel, it can just look at the shared workdir (probably in
do_configure) to make sure that we're ready to build a Rust module.

If we can't use KERNEL_FEATURES, then perhaps a new KERNEL_RUST_SUPPORT
variable would work. In either case, this should only be checked in the
kernel recipe itself.

Bruce - what do you think about KERNEL_FEATURES being used in this way?

Best regards,

-- 
Paul Barker


[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 252 bytes --]