OSDK can be used to create a new kernel project or a new library project. A kernel project defines the entry point of the kernel and can be run with QEMU. A library project can provide certain OS functionalities and be imported by other OSes.
## Creating a new kernel project
Creating a new kernel project is simple. You only need to execute the following command:
```bash
cargo osdk new --kernel myos
```
## Creating a new library project
Creating a new library project requires just one command:
```bash
cargo osdk new mylib
```
## Generated files
Next, we will introduce the contents of the generated project in detail. If you don't wish to delve into the details, you can skip the following sections.
### Overview
The generated directory for both the kernel project and library project contains the following contents:
```text
myos/
src/
lib.rs
Cargo.toml
OSDK.toml
rust-toolchain.toml
```
### `src/lib.rs`
#### Kernel project
The `src/lib.rs` file contains the code for a simple kernel. The function marked with the `#[aster_main]` macro is considered the kernel entry point by OSDK. The kernel will print `Hello world from the guest kernel!` to the console and then abort.
There is also a code snippet that demonstrates how to write kernel mode unit tests. It follows a similar code pattern as user mode unit tests. The test module is marked with the `#[cfg(ktest)]` macro, and each test case is marked with `#[ktest]`.
```rust
#![no_std]
#![no_main]
#![forbid(unsafe_code)]
#[macro_use]
extern crate ktest;
use aster_frame::prelude::*;
#[aster_main]
fn kernel_main() -> ! {
println!("Hello world from guest kernel!");
abort();
}
#[cfg(ktest)]
mod tests {
#[ktest]
fn it_works() {
let memory_regions = aster_frame::boot::memory_regions();
assert!(!memory_regions.is_empty());
}
}
```
#### Library project
The `src/lib.rs` of library project only contains a simple kernel mode unit test.
```rust
#![no_std]
#[macro_use]
extern crate ktest;
extern crate aster_frame;
#[cfg(ktest)]
mod tests {
#[ktest]
fn it_works() {
let memory_regions = aster_frame::boot::memory_regions();
assert!(!memory_regions.is_empty());
}
}
```
### `Cargo.toml`
The `Cargo.toml` file is the Rust project manifest. In addition to the contents of a normal Rust project, OSDK will add the dependencies of the Asterinas framework to the file. The dependency version may change over time.
```toml
[dependencies.aster_frame]
git = "https://github.com/asterinas/asterinas"
branch = "main"
[dependencies.ktest]
git = "https://github.com/asterinas/asterinas"
branch = "main"
```
### `OSDK.toml`
The `OSDK.toml` file is a manifest that defines the exact behavior of OSDK. By default, it contains the following contents. It includes settings on how to start QEMU to run a kernel. The meaning of each key can be found in the [manifest documentation](../reference/manifest.md). Please avoid changing the default settings unless you know what you are doing.
```toml
[boot]
ovmf = "/usr/share/OVMF"
[qemu]
machine = "q35"
args = [
"--no-reboot",
"-m 2G",
"-nographic",
"-serial chardev:mux",
"-monitor chardev:mux",
"-chardev stdio,id=mux,mux=on,signal=off",
"-display none",
"-device isa-debug-exit,iobase=0xf4,iosize=0x04",
]
```
### `rust-toolchain.toml`
The Rust toolchain for the kernel. It aligns with the toolchain of the Asterinas framework.
