Rust out-of-tree module

This is a basic template for an out-of-tree Linux kernel module written in Rust.

Please note that:

• The Rust support is experimental.

• The kernel that the module is built against needs to be Rust-enabled (CONFIG_RUST=y).

• The kernel tree (KDIR) requires the Rust metadata to be available. These are generated during the kernel build, but may not be available for installed/distributed kernels (the scripts that install/distribute kernel headers etc. for the different package systems and Linux distributions are not updated to take into account Rust support yet).

• All Rust symbols are EXPORT_SYMBOL_GPL.

Example:

$ make KDIR=.../linux-with-rust-support LLVM=1
make -C .../linux-with-rust-support M=$PWD
make[1]: Entering directory '.../linux-with-rust-support'
  RUSTC [M] .../rust-out-of-tree-module/rust_out_of_tree.o
  MODPOST .../rust-out-of-tree-module/Module.symvers
  CC [M]  .../rust-out-of-tree-module/rust_out_of_tree.mod.o
  LD [M]  .../rust-out-of-tree-module/rust_out_of_tree.ko
make[1]: Leaving directory '.../linux-with-rust-support'

Example dmesg when insmod:

[   18.718387] rust_out_of_tree: loading out-of-tree module taints kernel.
[   18.720848] rust_out_of_tree: Rust out-of-tree sample (init)
[   18.721391] rust_out_of_tree: PASS! rust_oft_pinned_data.rusty_number 2023 @0xffff888001c57d30 is pinned!
[   18.722393] rust_out_of_tree: rust_oft_pinned_data.rusty_number @0xffff888001c57d30 is initially: 2023
[   18.723249] rust_out_of_tree: Updated Rusty Number @ 0xffff888001c57d30 to 20232023
[   18.723943] rust_out_of_tree: PASS! rust_oft_unpinned_data.rusty_number 3202 @0xffffc9000008f8dc is moved to unpinned_rusty_number_moved @0xffffc9000008f964!
[   18.725194] rust_out_of_tree: rust_oft_unpinned_data.rusty_number @0xffffc9000008f964 is initially: 3202
[   18.726038] rust_out_of_tree: Updated Rusty Number @ 0xffffc9000008f964 to 32023202

Example dmesg when rmmod:

[   24.066984] rust_out_of_tree: My numbers are [72, 108, 200]
[   24.068931] rust_out_of_tree: My pinned number is 20232023
[   24.069916] rust_out_of_tree: My unpinned number is 32023202
[   24.070436] rust_out_of_tree: Rust out-of-tree sample (exit)

For details about the Rust support, see https://rust-for-linux.com.

For details about out-of-tree modules, see https://docs.kernel.org/kbuild/modules.html.

rust-analyzer

Rust for Linux (with https://lore.kernel.org/rust-for-linux/20230121052507.885734-1-varmavinaym@gmail.com/ applied) supports building a rust-project.json configuration for rust-analyzer, including for out-of-tree modules:

make -C .../linux-with-rust-support M=$PWD rust-analyzer