[PATCH v3 09/16] kernel-devsrc: copying rust-kernel source to $kerneldir/build

[Harish.Sadineni@windriver.com]

From: Harish Sadineni <Harish.Sadineni@windriver.com>

When CONFIG_RUST is enabled, running 'make prepare' in the  target & SDK
fails because the Rust kernel infrastructure is incomplete in the staged
kernel sources.

The Rust build system requires a wider set of interdependent sources
during make prepare, including bindgen inputs, C helper sources,
generated headers, and other support files. These are all located under
the kernel rust/ directory.

To ensure make prepare succeeds and to support building Rust-based
kernel modules from the  target & SDK, copy the full rust/ directory
(of size 2.5MB) into $kerneldir/build when the rust-kernel distro feature
is enabled.

Additionally, when Rust support is enabled, 'make prepare' generates
.rmeta files (crate metadata in a custom binary format) and shared
objects (.so) that are required for compiling Rust kernel modules.

Signed-off-by: Harish Sadineni <Harish.Sadineni@windriver.com>
---
 meta/recipes-kernel/linux/kernel-devsrc.bb | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/meta/recipes-kernel/linux/kernel-devsrc.bb b/meta/recipes-kernel/linux/kernel-devsrc.bb
index 23a9093ede..07f082132b 100644
--- a/meta/recipes-kernel/linux/kernel-devsrc.bb
+++ b/meta/recipes-kernel/linux/kernel-devsrc.bb
@@ -139,6 +139,15 @@ do_install() {
         cd ${S}
 
         cp -a scripts $kerneldir/build
+        
+        # In sdk, when CONFIG_RUST is enabled, `make prepare` requires the full Rust
+        # kernel infrastructure. The Rust build system pulls in bindgen inputs, C helpers,
+        # generated headers, and generate crate metadata (.rmeta), and shared objects 
+        # needed for building Rust kernel modules. Copy the entire rust/ directory (of size 2.5MB)
+        # to avoid failures with 'make prepare'.
+        if ${@bb.utils.contains('DISTRO_FEATURES', 'rust-kernel', 'true', 'false', d)}; then
+            cp -a rust ${kerneldir}/build
+        fi
 
         # for v6.1+ (otherwise we are missing multiple default targets)
         cp -a --parents Kbuild $kerneldir/build 2>/dev/null || :
-- 
2.49.0