Writing an OS in Rust

Philipp Oppermann's blog

Writing an OS in Rust


Latest post: Async/Await

A Freestanding Rust Binary

The first step in creating our own operating system kernel is to create a Rust executable that does not link the standard library. This makes it possible to run Rust code on the bare metal without an underlying operating system.

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A Minimal Rust Kernel

In this post we create a minimal 64-bit Rust kernel for the x86 architecture. We build upon the freestanding Rust binary from the previous post to create a bootable disk image, that prints something to the screen.

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VGA Text Mode

The VGA text mode is a simple way to print text to the screen. In this post, we create an interface that makes its usage safe and simple, by encapsulating all unsafety in a separate module. We also implement support for Rust's formatting macros.

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This post explores unit and integration testing in no_std executables. We will use Rust's support for custom test frameworks to execute test functions inside our kernel. To report the results out of QEMU, we will use different features of QEMU and the bootimage tool.

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CPU Exceptions

CPU exceptions occur in various erroneous situations, for example when accessing an invalid memory address or when dividing by zero. To react to them we have to set up an interrupt descriptor table that provides handler functions. At the end of this post, our kernel will be able to catch breakpoint exceptions and to resume normal execution afterwards.

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Double Faults

This post explores the double fault exception in detail, which occurs when the CPU fails to invoke an exception handler. By handling this exception we avoid fatal triple faults that cause a system reset. To prevent triple faults in all cases we also set up an Interrupt Stack Table to catch double faults on a separate kernel stack.

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Hardware Interrupts

In this post we set up the programmable interrupt controller to correctly forward hardware interrupts to the CPU. To handle these interrupts we add new entries to our interrupt descriptor table, just like we did for our exception handlers. We will learn how to get periodic timer interrupts and how to get input from the keyboard.

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Introduction to Paging

This post introduces paging, a very common memory management scheme that we will also use for our operating system. It explains why memory isolation is needed, how segmentation works, what virtual memory is, and how paging solves memory fragmentation issues. It also explores the layout of multilevel page tables on the x86_64 architecture.

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Paging Implementation

This post shows how to implement paging support in our kernel. It first explores different techniques to make the physical page table frames accessible to the kernel and discusses their respective advantages and drawbacks. It then implements an address translation function and a function to create a new mapping.

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Heap Allocation

This post adds support for heap allocation to our kernel. First, it gives an introduction to dynamic memory and shows how the borrow checker prevents common allocation errors. It then implements the basic allocation interface of Rust, creates a heap memory region, and sets up an allocator crate. At the end of this post all the allocation and collection types of the built-in alloc crate will be available to our kernel.

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Allocator Designs

This post explains how to implement heap allocators from scratch. It presents and discusses different allocator designs, including bump allocation, linked list allocation, and fixed-size block allocation. For each of the three designs, we will create a basic implementation that can be used for our kernel.

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In this post we explore cooperative multitasking and the async/await feature of Rust. We take a detailed look how async/await works in Rust, including the design of the Future trait, the state machine transformation, and pinning. We then add basic support for async/await to our kernel by creating an asynchronous keyboard task and a basic executor.

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Status Updates

These posts give a regular overview of the most important changes to the blog and the tools and libraries behind the scenes.

First Edition

You are currently viewing the second edition of “Writing an OS in Rust”. The first edition is very different in many aspects, for example it builds upon the GRUB bootloader instead of using the `bootloader` crate. In case you're interested in it, it is still available. Note that the first edition is no longer updated and might contain outdated information. read the first edition »

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