Philipp Oppermann's blog
This blog series creates a small operating system in the Rust programming language. Each post is a small tutorial and includes all needed code, so you can follow along if you like. The source code is also available in the corresponding Github repository.
Latest post: Paging Implementation
This post explores unit testing in no_std executables using Rust's built-in test framework. We will adjust our code so that cargo test works and add some basic unit tests to our VGA buffer module.
To complete the testing picture we implement a basic integration test framework, which allows us to run tests on the target system. The idea is to run tests inside QEMU and report the results back to the host through the serial port.
read more…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.
read more…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.
read more…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.
read more…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.
read more…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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