Kernel Development

Kernel development is much more strict than application development. In this guide, we present some implicit rules that you should follow when writing kernel code.

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Execution Flow

Once the kernel is booted, it will behaves like an event handler: it waits for events (e.g. system calls, interrupts, and exceptions), saves the current thread's state, does the necessary job, and resumes a thread.

Single Kernel Stack Design

Unlike traditional operating systems, Starina kernel uses a single stack per CPU, instead of having a dedicated stack for each thread. This design resembles how async Rust works - we need a separate state machine to resume the thread's execution later. In kernel, we don't use async/await syntax, but we use ThreadState to represent the state of a thread.

APIs

In kernel, we use some std alternatives that are more suitable for kernel:

libstd equivalent	Kernel alternative	Remarks
Arc	crate::refcount::SharedRef
Mutex	crate::spinlock::SpinLock
thread_local	CpuVar	A CPU-local variable, which is similar to thread_local in the userspace.

Rules

• Avoid panics. If you use unwrap, describe why you think it never fails.
• Handle allocation failures in collections (e.g. Vec). Use try_reserve before adding a new element to a collection.