content: rust for kernel module

content/posts/rust_for_kernel_module.md

@@ -0,0 +1,104 @@
+---
+title: "Rust for Kernel Module"
+date: 2024-09-27T11:24:03-05:00
+draft: false
+toc: false
+images:
+tags:
+  - kernel
+  - rust
+---
+
+## Outline
+
+- about kernel module
+- add a new module in `rust`
+
+## About Kernel Module
+
+### Lifetime of kernel module
+
+- init when being `loaded`
+- register to the certain `subsystem`
+
+- when receive some action from an `actor`
+- subsystem perform a `callback` to the module
+- then returns
+
+......
+
+- when `unload`
+- unregister to `subsystem`
+
+### What we're going to build
+
+some `/dev/scull0`, `/dev/scull1`, ...
+that are **readable** and **writeable**
+**TODO**
+
+### Development workflow
+
+- do some change to kernel src
+- boot with `qemu` with `busybox`, resources can be found [Debug Linux Kernel](./debug_linux_kernel.md) & [Rust for Linux](./rust_for_linux.md)
+- and debug it through remote `gdb`
+
+## Add a New Module
+
+### modify Kconfig and Makefile
+
+- add the `Kconfig` at `linux/samples/rust/Kconfig` for our new module:
+
+```Kconfig
+config SAMPLE_RUST_SCULL
+	tristate "Scull module"
+	help
+	  This option builds the Rust scull module sample.
+
+	  To compile this as a module, choose M here:
+	  the module will be called rust_scull.
+
+	  If unsure, say N.
+```
+
+- add the compile command for our new module at `linux/samples/rust/Makefile`:
+
+```Makefile
+obj-$(CONFIG_SAMPLE_RUST_SCULL)			+= rust_scull.o
+```
+
+- create the file
+
+```bash
+touch linux/samples/rust/rust_scull.rs
+```
+
+- enable this in `menuconfig`
+- then it should compiles
+- remember to use `make LLVM=1 rust-analyzer` to generate index for lsp
+
+### Edit our module
+
+in `linux/samples/rust/rust_scull.rs`
+
+```rust
+//! Scull module in Rust
+
+use kernel::prelude::*;
+
+module! {
+    type: Scull,
+    name: "scull",
+    license: "GPL",
+}
+
+struct Scull;
+
+impl kernel::Module for Scull {
+    fn init(_module: &'static ThisModule) -> kernel::error::Result<Self> {
+	    pr_info!("Hello World\n");
+        Ok(Scull)
+    }
+}
+```
+
+now it can be compiled, you can see the hello world from our module by `dmesg`