[RFC PATCH 0/5] Kernel Rust out-of-tree module support

[RFC PATCH 0/5] Kernel Rust out-of-tree module support

[Yoann Congal]

As followup of Harish Sadineni's RFC series "Enable rust support for
linux kernel" [0] (and to increase its test coverage), this series add
support for out-of-tree kernel module written in Rust as well as
associated test.

[0]: https://lists.openembedded.org/g/openembedded-core/message/226560

Yoann Congal (5):
  kernel.bbclass: Export artifacts needed for out-of-tree Rust
    compilation
  module.bbclass: Prepare out-of-tree rust module compilation
  meta-skeleton: Add rust-out-of-tree-module recipe
  rust-out-of-tree-module: Add myself as maintainer
  runtime_test: Add rust-out-of-tree selftest

 .../rust-out-of-tree-module_git.bb             | 18 ++++++++++++++++++
 meta/classes-recipe/kernel.bbclass             | 18 ++++++++++++++++++
 meta/classes-recipe/module.bbclass             |  8 ++++++++
 meta/conf/distro/include/maintainers.inc       |  1 +
 meta/lib/oeqa/selftest/cases/runtime_test.py   |  9 ++++++++-
 5 files changed, 53 insertions(+), 1 deletion(-)
 create mode 100644 meta-skeleton/recipes-kernel/rust-out-of-tree-module/rust-out-of-tree-module_git.bb

[RFC PATCH 1/5] kernel.bbclass: Export artifacts needed for out-of-tree Rust compilation

[Yoann Congal]

From: Yoann Congal <yoann.congal@smile.fr>

Publish artifacts from kernel compilation to allow out-of-tree Rust
compilation:
* scripts/target.json: target definition: architecture, ABI, compiler
  options, ...
* rust/: the crates compiled by the kernel available to
  out-of-tree-modules

Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
---
 meta/classes-recipe/kernel.bbclass | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/meta/classes-recipe/kernel.bbclass b/meta/classes-recipe/kernel.bbclass
index 003a155e794..a9a25b9819a 100644
--- a/meta/classes-recipe/kernel.bbclass
+++ b/meta/classes-recipe/kernel.bbclass
@@ -631,6 +631,24 @@ do_shared_workdir () {
 		cp -r scripts/gcc-plugins ${kerneldir}/scripts
 	fi
 
+    if ${@bb.utils.contains("DISTRO_FEATURES", "rust-kernel", "true", "false", d)}; then
+        # Copy target.json file needed for out-of-tree rust modules
+        if [ -e scripts/target.json ]; then
+            bbnote "Copying scripts/target.json"
+            mkdir -p ${kerneldir}/scripts
+            cp scripts/target.json ${kerneldir}/scripts
+        else
+            bbwarn "scripts/target.json not found in compiled kernel. Out-of-tree rust modules will fail to build."
+        fi
+
+        # Copy rust/ needed by out-of-tree module (firstly for the core rust crate)
+        if [ -e rust/ ]; then
+            bbnote "Copying rust/"
+            cp -r rust ${kerneldir}/
+        else
+            bbwarn "rust/ not found in compiled kernel. Out-of-tree rust modules will fail to build."
+        fi
+    fi
 }
 
 # We don't need to stage anything, not the modules/firmware since those would clash with linux-firmware

[RFC PATCH 2/5] module.bbclass: Prepare out-of-tree rust module compilation

[Yoann Congal]

From: Yoann Congal <yoann.congal@smile.fr>

Conditioned to the "rust-linux" DISTRO_FEATURES:
* Add dependency to rust-native
* Remap ${S} in compiled output to avoid buildpath errors

Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
---
 meta/classes-recipe/module.bbclass | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/meta/classes-recipe/module.bbclass b/meta/classes-recipe/module.bbclass
index 4948e995c5d..7dbd4194d17 100644
--- a/meta/classes-recipe/module.bbclass
+++ b/meta/classes-recipe/module.bbclass
@@ -87,3 +87,11 @@ EXPORT_FUNCTIONS do_compile do_install
 KERNEL_MODULES_META_PACKAGE = "${PN}"
 FILES:${PN} = ""
 ALLOW_EMPTY:${PN} = "1"
+
+# Rust module support
+DEPENDS += "${@bb.utils.contains('DISTRO_FEATURES', 'rust-kernel', 'rust-native', '', d)}"
+
+RUST_DEBUG_REMAP ?= "--remap-path-prefix=${S}=${TARGET_DBGSRC_DIR}"
+KRUSTFLAGS:append = " ${RUST_DEBUG_REMAP}"
+EXTRA_OEMAKE:append = " ${@bb.utils.contains('DISTRO_FEATURES', 'rust-kernel', \
+                                             ' KRUSTFLAGS="${KRUSTFLAGS}"', '',d)}"

[RFC PATCH 3/5] meta-skeleton: Add rust-out-of-tree-module recipe

[Yoann Congal]

From: Yoann Congal <yoann.congal@smile.fr>

Basic template for an out-of-tree Linux kernel module written in Rust.

Mainly to test Rust integration into the kernel.

Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
---
 .../rust-out-of-tree-module_git.bb             | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 meta-skeleton/recipes-kernel/rust-out-of-tree-module/rust-out-of-tree-module_git.bb

diff --git a/meta-skeleton/recipes-kernel/rust-out-of-tree-module/rust-out-of-tree-module_git.bb b/meta-skeleton/recipes-kernel/rust-out-of-tree-module/rust-out-of-tree-module_git.bb
new file mode 100644
index 00000000000..642fa80319a
--- /dev/null
+++ b/meta-skeleton/recipes-kernel/rust-out-of-tree-module/rust-out-of-tree-module_git.bb
@@ -0,0 +1,18 @@
+SUMMARY = "Basic template for an out-of-tree Linux kernel module written in Rust"
+HOMEPAGE = "https://github.com/Rust-for-Linux/rust-out-of-tree-module"
+
+LICENSE = "GPL-2.0-only"
+LIC_FILES_CHKSUM = "file://LICENSE;md5=b234ee4d69f5fce4486a80fdaf4a4263"
+
+inherit module features_check
+REQUIRED_DISTRO_FEATURES = "rust-kernel"
+
+SRC_URI = "git://github.com/Rust-for-Linux/rust-out-of-tree-module.git;protocol=https;branch=main"
+SRCREV = "00b5a8ee2bf53532d115004d7636b61a54f49802" 
+UPSTREAM_CHECK_COMMITS = "1"
+
+EXTRA_OEMAKE += "KDIR=${STAGING_KERNEL_DIR}"
+
+# The inherit of module.bbclass will automatically name module packages with
+# "kernel-module-" prefix as required by the oe-core build environment.
+RPROVIDES:${PN} += "kernel-module-rust-out-of-tree"

[RFC PATCH 4/5] rust-out-of-tree-module: Add myself as maintainer

[Yoann Congal]

From: Yoann Congal <yoann.congal@smile.fr>

Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
---
 meta/conf/distro/include/maintainers.inc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/meta/conf/distro/include/maintainers.inc b/meta/conf/distro/include/maintainers.inc
index 6c3174cbb72..7204a5e5992 100644
--- a/meta/conf/distro/include/maintainers.inc
+++ b/meta/conf/distro/include/maintainers.inc
@@ -774,6 +774,7 @@ RECIPE_MAINTAINER:pn-ruby = "Ross Burton <ross.burton@arm.com>"
 RECIPE_MAINTAINER:pn-run-postinsts = "Ross Burton <ross.burton@arm.com>"
 RECIPE_MAINTAINER:pn-rust = "Randy MacLeod <Randy.MacLeod@windriver.com>"
 RECIPE_MAINTAINER:pn-rust-cross-canadian-${TRANSLATED_TARGET_ARCH} = "Randy MacLeod <Randy.MacLeod@windriver.com>"
+RECIPE_MAINTAINER:pn-rust-out-of-tree-module = "Yoann Congal <yoann.congal@smile.fr>"
 RECIPE_MAINTAINER:pn-rxvt-unicode = "Unassigned <unassigned@yoctoproject.org>"
 RECIPE_MAINTAINER:pn-sassc = "Simone Weiß <simone.p.weiss@posteo.com>"
 RECIPE_MAINTAINER:pn-sato-screenshot = "Ross Burton <ross.burton@arm.com>"

[RFC PATCH 5/5] runtime_test: Add rust-out-of-tree selftest

[Yoann Congal]

From: Yoann Congal <yoann.congal@smile.fr>

This new case tests that the rust-out-of-tree-module recipe compiles and
run properly: check that the dmesg output is as expected.

Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
---
 meta/lib/oeqa/selftest/cases/runtime_test.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/meta/lib/oeqa/selftest/cases/runtime_test.py b/meta/lib/oeqa/selftest/cases/runtime_test.py
index 66cb112a7c1..a6f75c1e29f 100644
--- a/meta/lib/oeqa/selftest/cases/runtime_test.py
+++ b/meta/lib/oeqa/selftest/cases/runtime_test.py
@@ -493,7 +493,7 @@ class RustKernel(OESelftestTestCase):
             import textwrap
             self.write_config(textwrap.dedent("""
                 DISTRO_FEATURES:append = ' rust-kernel'
-                CORE_IMAGE_EXTRA_INSTALL += "kernel-module-rust-minimal"
+                CORE_IMAGE_EXTRA_INSTALL += "kernel-module-rust-minimal kernel-module-rust-out-of-tree"
             """))
             bitbake(self.image)
 
@@ -505,3 +505,10 @@ class RustKernel(OESelftestTestCase):
                 self.logger.debug(f"rust_minimal dmesg output:\n" + textwrap.indent(output, "  "))
                 self.assertIn("Rust minimal sample", output, "Kernel Rust sample expected output not found in dmesg")
 
+                qemu.run_serial("dmesg -c > /dev/null")
+                status, _ = qemu.run_serial("modprobe rust_out_of_tree")
+                self.assertEqual(status, 1, "Loading rust_out_of_tree module failed!")
+                _, output = qemu.run_serial("dmesg")
+                self.logger.debug(f"rust_out_of_tree dmesg output:\n" + textwrap.indent(output, "  "))
+                self.assertIn("Rust out-of-tree sample", output, "Out-of-tree Rust sample expected output not found in dmesg")
+

Re: [OE-core] [RFC PATCH 0/5] Kernel Rust out-of-tree module support

[Mathieu Dubois-Briand]

On Wed Nov 19, 2025 at 8:55 PM CET, Yoann Congal via lists.openembedded.org wrote:
> As followup of Harish Sadineni's RFC series "Enable rust support for
> linux kernel" [0] (and to increase its test coverage), this series add
> support for out-of-tree kernel module written in Rust as well as
> associated test.
>
> [0]: https://lists.openembedded.org/g/openembedded-core/message/226560
>
> Yoann Congal (5):
>   kernel.bbclass: Export artifacts needed for out-of-tree Rust
>     compilation
>   module.bbclass: Prepare out-of-tree rust module compilation
>   meta-skeleton: Add rust-out-of-tree-module recipe
>   rust-out-of-tree-module: Add myself as maintainer
>   runtime_test: Add rust-out-of-tree selftest
>
>  .../rust-out-of-tree-module_git.bb             | 18 ++++++++++++++++++
>  meta/classes-recipe/kernel.bbclass             | 18 ++++++++++++++++++
>  meta/classes-recipe/module.bbclass             |  8 ++++++++
>  meta/conf/distro/include/maintainers.inc       |  1 +
>  meta/lib/oeqa/selftest/cases/runtime_test.py   |  9 ++++++++-
>  5 files changed, 53 insertions(+), 1 deletion(-)
>  create mode 100644 meta-skeleton/recipes-kernel/rust-out-of-tree-module/rust-out-of-tree-module_git.bb

Hi Yoann,

I ran a few RFC series on the autobuilder, and I suspect this one of
these two issues, during oe-selftests.

First issues:

2025-11-29 08:23:13,186 - oe-selftest - INFO - 2: 6/31 214/648 (110.21s) (0 failed) (distrodata.Distrodata.test_maintainers)
2025-11-29 08:23:13,186 - oe-selftest - INFO - testtools.testresult.real._StringException: Traceback (most recent call last):
  File "/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/layers/openembedded-core/meta/lib/oeqa/selftest/cases/distrodata.py", line 115, in test_maintainers
    self.fail("""
  File "/usr/lib/python3.12/unittest/case.py", line 715, in fail
    raise self.failureException(msg)
AssertionError:
Unable to find recipes for the following entries in maintainers.inc:
rust-out-of-tree-module

I saw you added something, but for some reason the test is not happy.

Second issues:

ERROR: core-image-minimal-1.0-r0 do_rootfs: Could not invoke dnf. Command '/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/recipe-sysroot-native/usr/bin/dnf -v --rpmverbosity=info -y -c /srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/rootfs/etc/dnf/dnf.conf --setopt=reposdir=/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/rootfs/etc/yum.repos.d --installroot=/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/rootfs --setopt=logdir=/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/temp --repofrompath=oe-repo,/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/oe-rootfs-repo --nogpgcheck install kernel-module-rust-minimal kernel-module-rust-out-of-tree packagegroup-core-boot run-postinsts ssh-pregen-hostkeys' returned 1:
...
No match for argument: kernel-module-rust-out-of-tree
Error: Unable to find a match: kernel-module-rust-out-of-tree
kernel-module-rust-out-of-tree is neither a recipe nor a generated package.

https://autobuilder.yoctoproject.org/valkyrie/#/builders/23/builds/2915
https://autobuilder.yoctoproject.org/valkyrie/#/builders/35/builds/2777
https://autobuilder.yoctoproject.org/valkyrie/#/builders/48/builds/2672

Thanks,
Mathieu

-- 
Mathieu Dubois-Briand, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

Re: [OE-core] [RFC PATCH 0/5] Kernel Rust out-of-tree module support

[Yoann Congal]

Le 01/12/2025 à 10:48, Mathieu Dubois-Briand a écrit :
> On Wed Nov 19, 2025 at 8:55 PM CET, Yoann Congal via lists.openembedded.org wrote:
>> As followup of Harish Sadineni's RFC series "Enable rust support for
>> linux kernel" [0] (and to increase its test coverage), this series add
>> support for out-of-tree kernel module written in Rust as well as
>> associated test.
>>
>> [0]: https://lists.openembedded.org/g/openembedded-core/message/226560
>>
>> Yoann Congal (5):
>>   kernel.bbclass: Export artifacts needed for out-of-tree Rust
>>     compilation
>>   module.bbclass: Prepare out-of-tree rust module compilation
>>   meta-skeleton: Add rust-out-of-tree-module recipe
>>   rust-out-of-tree-module: Add myself as maintainer
>>   runtime_test: Add rust-out-of-tree selftest
>>
>>  .../rust-out-of-tree-module_git.bb             | 18 ++++++++++++++++++
>>  meta/classes-recipe/kernel.bbclass             | 18 ++++++++++++++++++
>>  meta/classes-recipe/module.bbclass             |  8 ++++++++
>>  meta/conf/distro/include/maintainers.inc       |  1 +
>>  meta/lib/oeqa/selftest/cases/runtime_test.py   |  9 ++++++++-
>>  5 files changed, 53 insertions(+), 1 deletion(-)
>>  create mode 100644 meta-skeleton/recipes-kernel/rust-out-of-tree-module/rust-out-of-tree-module_git.bb
> 
> Hi Yoann,
> 
> I ran a few RFC series on the autobuilder, and I suspect this one of
> these two issues, during oe-selftests.
> 
> First issues:
> 
> 2025-11-29 08:23:13,186 - oe-selftest - INFO - 2: 6/31 214/648 (110.21s) (0 failed) (distrodata.Distrodata.test_maintainers)
> 2025-11-29 08:23:13,186 - oe-selftest - INFO - testtools.testresult.real._StringException: Traceback (most recent call last):
>   File "/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/layers/openembedded-core/meta/lib/oeqa/selftest/cases/distrodata.py", line 115, in test_maintainers
>     self.fail("""
>   File "/usr/lib/python3.12/unittest/case.py", line 715, in fail
>     raise self.failureException(msg)
> AssertionError:
> Unable to find recipes for the following entries in maintainers.inc:
> rust-out-of-tree-module
> 
> I saw you added something, but for some reason the test is not happy.
> 
> Second issues:
> 
> ERROR: core-image-minimal-1.0-r0 do_rootfs: Could not invoke dnf. Command '/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/recipe-sysroot-native/usr/bin/dnf -v --rpmverbosity=info -y -c /srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/rootfs/etc/dnf/dnf.conf --setopt=reposdir=/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/rootfs/etc/yum.repos.d --installroot=/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/rootfs --setopt=logdir=/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/temp --repofrompath=oe-repo,/srv/pokybuild/yocto-worker/oe-selftest-armhost/build/build-st-179319/tmp/work/qemuarm64-poky-linux/core-image-minimal/1.0/oe-rootfs-repo --nogpgcheck install kernel-module-rust-minimal kernel-module-rust-out-of-tree packagegroup-core-boot run-postinsts ssh-pregen-hostkeys' returned 1:
> ...
> No match for argument: kernel-module-rust-out-of-tree
> Error: Unable to find a match: kernel-module-rust-out-of-tree
> kernel-module-rust-out-of-tree is neither a recipe nor a generated package.
> 
> https://autobuilder.yoctoproject.org/valkyrie/#/builders/23/builds/2915
> https://autobuilder.yoctoproject.org/valkyrie/#/builders/35/builds/2777
> https://autobuilder.yoctoproject.org/valkyrie/#/builders/48/builds/2672

It appears that meta-skeleton:
* is not covered by maintainers.inc
* is not included by default during this selftest (I had it in my local
  config)

I will fix these in v2.

Thanks!

> Thanks,
> Mathieu
> 

-- 
Yoann Congal
Smile ECS