out of tree kernel module build is somehow broken

[fneddy]

out of tree kernel module build is somehow broken

the problem

it seems that out of tree kernel module is not behaving as expected (or as I expect it). if i

• download the newest vanilla stable source,
• extract it,
• enable rust,
• compile the kernel,
• try to build an out of tree rust module against it

it fails. I need to go back to the kernel source dir and redo the make AFTER i called once an out of tree kernel module build so the core crate is found.

steps to reproduce

1. download and extract newest stable kernel

   > curl ...
   > tar xfk linux.tar.xz 

2. compile kernel

   > export LLVM=1
   > cd $KDIR
   > time make clean
   > time make mrproper
   > time make defconfig
   > time make rust.config
   > time make all -j $(($(nproc)-1))

3. try to compile the out of tree kernel module

   
   > cd $MODULE_DIR
   > make -C $KDIR M=$PWD

error[E0463]: can't find crate for core | = note: the target target may not be installed = help: consider downloading the target with rustup target add target = help: consider building the standard library from source with cargo build -Zbuild-std

....

now if redo the `make all` in `KDIR` **AFTER** i triggered the out of tree module build everything works as expected and i can now build out of tree kernel modules.

cd $KDIR time make all -j $(($(nproc)-1)) cd $MODULE_DIR make -C $KDIR M=$PWD

this happens independent if export LLVM=1 or unset LLVM=1 is called before build.

[fneddy]

nevermind ... did this in a script and PWD was NOT in my module_dir ...

[ojeda]

No worries -- thanks for reporting!