Why OSDK

OSDK is designed to elevate the development experience for Rust OS developers to the ease and convenience typically associated with Rust application development. Imagine crafting operating systems with the same simplicity as applications! This is important to Asterinas as we believe that the project’s success is intricately tied to the productivity and happiness of its developers. So the OSDK is here to upgrade your dev experience.

老實說，編寫作業系統內核非常困難。即便使用了對作業系統開發者來說具有劃時代意義的 Rust 語言，挑戰依然巨大。這背後有許多原因。

首先，從零開始編寫一個新內核非常困難。應用程式開發者視為理所當然的一切都消失了：沒有堆疊（stack）、沒有堆積（heap）、沒有執行緒，甚至連標準 I/O 都沒有。你只能獨自面對 Rust 的 no_std 世界。你必須親自動手處理電腦架構中最底層、最容易出錯且最繁瑣的細節，來實現這些基礎的程式設計原語（primitive）。這是一個不斷學習、實作，並祈禱一切都能順利運作的過程。這也意味著對於新的作業系統創作者來說，進入門檻非常高。

Second, it is hard to reuse OS-related libraries/crates across projects. Think about it: most applications share a common groundwork, like libc, Rust’s std library, or an SDK. This isn’t the case with kernels - they lack this shared starting point, forcing each one to craft its own set of tools from the ground up. Take device drivers, for example. They often need DMA-capable buffers for chatting with hardware, but since every kernel has its own DMA API flavor, a driver for one kernel is pretty much a no-go for another. This means that for each new kernel out there, developers find themselves having to ‘reinvent the wheel’ for many core components that are standard in other kernels.

Third, it is hard to do unit tests for OS functionalities. Unit testing plays a crucial role in ensuring code quality, but when you’re dealing with a monolithic kernel like Linux, it’s like a spaghetti bowl of intertwined parts. Trying to isolate one part for testing? Forget about it. You’d have to boot the whole kernel just to test a slice of it. Loadable kernel modules are no exception: you can’t test them without plugging them into a live kernel. This monolithic approach to unit testing is slow and unproductive as it performs the job of unit tests at a price of integration tests. Regardless of the kernel architecture, Rust’s built-in unit testing facility is not suited for kernel development, leaving each kernel to hack together their own testing frameworks.

Last, it is hard to avoid writing unsafe Rust in a Rust kernel. Rust brings safety… well, at least for Rust applications, where you can pretty much stay in the wonderland of safe Rust all the way through. But for a Rust kernel, one cannot help but use unsafe Rust. This is because, among other reasons, low-level operations (e.g., managing page tables, doing context switching, handling interrupts, and interacting with devices) have to be expressed with unsafe Rust features (like executing assembly code or dereferencing raw pointers). The misuse of unsafe Rust could lead to various safety and security issues, as reported by RustSec Advisory Database. Despite having a whole book to document “the Dark Arts of Unsafe Rust”, unsafe Rust is still tricky to use correctly, even among seasoned Rust developers.