Eliminating Data Races in Firefox – A Technical Report
We successfully deployed ThreadSanitizer in the Firefox project to eliminate data races in our remaining C/C++ components. In the process, we found several impactful bugs and can safely say that data races are often underestimated in terms of their impact on program correctness. We recommend that all multithreaded C/C++ projects adopt the ThreadSanitizer tool to enhance code quality.
The multi-generational LRU
One of the key tasks assigned to the memory-management subsystem is to optimize the system’s use of the available memory; that means pushing out pages containing unused data so that they can be put to better use elsewhere. Predicting which pages will be accessed in the near future is a tricky task, and the kernel has evolved a number of mechanisms designed to improve its chances of guessing right. But the kernel not only often gets it wrong, it also can expend a lot of CPU time to make the incorrect choice. The multi-generational LRU patch set posted by Yu Zhao is an attempt to improve that situation.
The end of TenFourFox and what I've learned from it
Porting Firefox to Apple Silicon
Even with all the pieces in place, quite a bit of work to do.
The release of Apple Silicon-based Macs at the end of last year generated a flurry of news coverage and some surprises at the machine’s performance. This post details some background information on the experience of porting Firefox to run natively on these CPUs.
We’ll start with some background on the Mac transition and give an overview of Firefox internals that needed to know about the new architecture, before moving on to the concept of Universal Binaries.
We’ll then explain how DRM/EME works on the new platform, talk about our experience with macOS Big Sur, and discuss various updater problems we had to deal with. We’ll conclude with the release and an overview of various other improvements that are in the pipeline.
Windows Timer Resolution: The Great Rule Change
The behavior of the Windows scheduler changed significantly in Windows 10 2004, in a way that will break a few applications, and there appears to have been no announcement, and the documentation has not been updated. This isn’t the first time this has happened, but this change seems bigger than last time.
The short version is that calls to timeBeginPeriod from one process now affect other processes less than they used to, but there is still an effect.
Zig's New Relationship with LLVM
In the early days, Zig was but a thin frontend in front of LLVM. This was instrumental for getting started quickly and filling in gaps of Andrew’s knowledge as a compiler developer. Now, the training wheels of the bicycle are coming off, and LLVM is transitioning into an optional component.
The move to a self-hosted compiler for Zig has similar advantages for the core contributors, but it also makes LLVM an optional dependency, increases compilation speed (instead of losing it), and adds an amazing feature for debug builds of your code: incremental compilation with in-place binary patching, another unique Zig feature.
Modernizing the OpenBSD console
At the beginning were text mode consoles. Traditionally, *BSD and Linux on i386 and amd64 used text mode consoles which by default provided 25 rows of 80 columns, the “80x25 mode”. This mode uses a 8x16 font stored in the VGA BIOS (which can be slightly different across vendors).
Make system(3) and popen(3) use posix_spawn(3) internally
After 1 week of reading POSIX and writing code, 2 weeks of coding and another 1.5 weeks of bugfixes I have successfully implemented posix_spawn in usage in system(3) and popen(3) internally.
Improving Chromium's browser compatibility in 2020
It is clear that it is still painful to develop a website or web app that works reliably across browsers.
Installation images renamed from .fs to .img
There are some UEFI direct-from-internet bootloaders that require the name *.img. So this makes things more convenient for those, while keeping it consistant in all architectures.
Five Years of Rust
With all that’s going on in the world you’d be forgiven for forgetting that as of today, it has been five years since we released 1.0 in 2015! Rust has changed a lot these past five years, so we wanted reflect back on all of our contributors’ work since the stabilization of the language.
New Crypto in Go 1.14
Go 1.14 is out and with it come a few nice updates to crypto/tls!
Recent and future pattern matching improvements
Much of writing software revolves around checking if some data has some shape (“pattern“), extracting information from it, and then reacting if there was a match. To facilitate this, many modern languages, Rust included, support what is known as “pattern matching”.
Avoiding gaps in IOMMU protection at boot
But setting things up in the OS isn’t sufficient. If an attacker is able to trigger arbitrary DMA before the OS has started then they can tamper with the system firmware or your bootloader and modify the kernel before it even starts running. So ideally you want your firmware to set up the IOMMU before it even enables any external devices, and newer firmware should actually do this automatically. It sounds like the problem is solved.
The Linux CSPRNG Is Now Good!
Oceans of ink and hours on stage have been spent to convince the world that the best random number generator is /dev/urandom, the kernel one. And it is, and it’s always been. However, an uncomfortable truth was that the Linux CSPRNG really could have been better than it was. Userspace CSPRNGs couldn’t be better than the kernel one, so our advice was still valid, but that space for improvement always frustrated me.
Good news everyone! In recent years, the Linux CSPRNG got a number of great incremental improvements, and I can now say in good conscience that it’s not only the best, it’s also good.
e2k19 Hackathon Report: Stefan Sperling on GoT and wireless
All about the new ML Super Resolution feature in Pixelmator Pro
To create the ML Super Resolution feature, we used a convolutional neural network. This type of deep neural network reduces raster images and their complex inter-pixel dependencies into a form that is easier to process (i.e. requires less computation) without losing important features (edges, patterns, colors, textures, gradients, and so on). The ML Super Resolution network includes 29 convolutional layers which scan the image and create an over-100-channel-deep version of it that contains a range of identified features. This is then upscaled, post-processed and turned back into a raster image. Below is a simplified representation of the neural network.
Not quite all about it, and there’s better references for the technique, but neat to see this trickle down to entry level photo editing.
Real hardware breakthroughs, and focusing on rustc
After the addition of the NVMe driver a couple months ago, I have been running Redox OS permanently (from an install to disk) on a System76 Galago Pro (galp3-c), with System76 Open Firmware as well as the un-announced, in-development, GPLv3 System76 EC firmware . This particular hardware has full support for the keyboard, touchpad, storage, and ethernet, making it easy to use with Redox.
Building Redox OS on Redox OS has always been one of the highest priorities of the project. Rustc seems to be only a few months of work away, after which I can begin to improve the system while running on it permanently, at least on one machine. With Redox OS being a microkernel, it is possible that even the driver level could be recompiled and respawned without downtime, making it incredibly fast to develop for. With this in place, I would work more efficiently on porting more software and tackling more hardware support issues, such as filling in the USB stack and adding graphics drivers.
Async-await on stable Rust!
On this coming Thursday, November 7, async-await syntax hits stable Rust, as part of the 1.39.0 release. This work has been a long time in development -- the key ideas for zero-cost futures, for example, were first proposed by Aaron Turon and Alex Crichton in 2016! -- and we are very proud of the end result. We believe that Async I/O is going to be an increasingly important part of Rust’s story.
Vulkan Progress Report #5
Another month, another Vulkan progress report! October was a busy month, as most of it was split between working on the new Global Illumination system and Godotcon/GIC in Poland. Despite this, strong progress was made and the new GI system seems pretty much complete.
Godot 3.0 introduced GIProbes. They provide Global Illumination to scenes. They were, however, pretty limited. Only static geometry could provide GI and dynamic objects were ignored. Added to this, changes in light settings had significant frames of delay. Added to a not so great performance and quality, the feature was barely usable as is.
For Godot 4.0, GIProbes will see several significant changes, which will be outlined as follows: