While on a hike with colleagues, one asked a thought provoking question: Should the United States Post Service (USPS) operate as an Internet Service Provider (ISP)? This post is an opinion piece playing with that idea; here are my thoughts. It’s far from a hot take, and has been discussed before. Ar...

If you’re new to the Arm ecosystem, consider this a quick primer on terms you likely have seen before but might have questions about. The Arm architecture is a family of Reduced Instruction Set Architectures (RISC) with simple addressing modes. Data processing is done on register operands otherwise ...

The Open Source software development model is a powerful approach to collaboratively iterating on a shared solution to a common problem. Rather than competitors duplicating effort to come up with multiple suboptimal solutions, they can collaborate together to build something greater. Forking is the ...

A maximal length sequence of branch-free code that terminates with a branch or jump is referred to as a basic block. A basic block that branches to another forms an edge in the Control Flow Graph (CFG). The initial basic block starting an edge is the predecessor; it precedes and is succeeded by the ...

Unless work is done per architecture to implement HAVE_ARCH_VMAP_STACK / CONFIG_VMAP_STACK, the Linux kernel defaults to two pages worth of stack per thread. Note: on many contemporary systems the page size is 4KiB, but this is actually configurable for many architectures. The trade offs probably re...

“War stories” in programming are entertaining tales of truly evil bugs that kept you up at night. Inspired by posts like My Hardest Bug Ever, Debugging an evil Go runtime bug, and others from /r/TalesFromDebugging, I wanted to share with you one of my favorites from recent memory. Recent work has gi...

“War stories” in programming are entertaining tales of truly evil bugs that kept you up at night. Inspired by posts like My Hardest Bug Ever, Debugging an evil Go runtime bug, and others from /r/TalesFromDebugging, I wanted to share with you one of my favorites from recent memory. Recent work has gi...

TL;DR Prefer f(void) in C to potentially save a 2B instruction per function call when targeting x86_64 as a micro-optimization. -Wstrict-prototypes can help. Doesn’t matter for C++. The Problem While messing around with some C code in godbolt Compiler Explorer, I kept noticing a particular funny cas...

TL;DR Prefer f(void) in C to potentially save a 2B instruction per function call when targeting x86_64 as a micro-optimization. -Wstrict-prototypes can help. Doesn’t matter for C++. The Problem While messing around with some C code in godbolt Compiler Explorer, I kept noticing a particular funny cas...

Support for a long awaited GNU C extension, asm goto, is in the midst of landing in Clang and LLVM. We want to make sure that we release a high quality implementation, so it’s important to test the new patches on real code and not just small test cases. When we hit compiler bugs in large source file...

Support for a long awaited GNU C extension, asm goto, is in the midst of landing in Clang and LLVM. We want to make sure that we release a high quality implementation, so it’s important to test the new patches on real code and not just small test cases. When we hit compiler bugs in large source file...

Typically, when we modify a program, we’d like to run it to verify our changes. Before booting a compiled Linux kernel image on actual hardware, it can save us time and potential headache to do a quick boot in a virtual machine like QEMU as a sanity check. If your kernel boots in QEMU, it’s not a gu...

Typically, when we modify a program, we’d like to run it to verify our changes. Before booting a compiled Linux kernel image on actual hardware, it can save us time and potential headache to do a quick boot in a virtual machine like QEMU as a sanity check. If your kernel boots in QEMU, it’s not a gu...

ccache, the compiler cache, is a fantastic way to speed up build times for C and C++ code that I previously recommended. Recently, I was playing around with trying to get it to speed up my Linux kernel builds, but wasn’t seeing any benefit. Usually when this happens with ccache, there’s something no...

ccache, the compiler cache, is a fantastic way to speed up build times for C and C++ code that I previously recommended. Recently, I was playing around with trying to get it to speed up my Linux kernel builds, but wasn’t seeing any benefit. Usually when this happens with ccache, there’s something no...

A blog post from a few years ago that really stuck with me was Martin Olsson’s Browser Engines 2015: Commit Rates and Active Developer Counts, where he shows information about the number of authors and commits to popular web browsers. The graphs and analysis had interesting takeaways like showing th...

A blog post from a few years ago that really stuck with me was Martin Olsson’s Browser Engines 2015: Commit Rates and Active Developer Counts, where he shows information about the number of authors and commits to popular web browsers. The graphs and analysis had interesting takeaways like showing th...

Clang-Tidy is a linter from the LLVM ecosystem. I wanted to try to run it on the Linux kernel to see what kind of bugs it would find. The false positive rate seems pretty high (a persistent bane to static analysis), but some patching in both the tooling and the source can likely help bring this rate...

Clang-Tidy is a linter from the LLVM ecosystem. I wanted to try to run it on the Linux kernel to see what kind of bugs it would find. The false positive rate seems pretty high (a persistent bane to static analysis), but some patching in both the tooling and the source can likely help bring this rate...

After working on the Linux kernel for Nexus and Pixel phones for nearly a year, and messing around with the excellent Eudyptula challenge, I finally wanted to take a crack at submitting patches upstream to the Linux kernel. This post is woefully inadequate compared to the existing documentation, whi...

After working on the Linux kernel for Nexus and Pixel phones for nearly a year, and messing around with the excellent Eudyptula challenge, I finally wanted to take a crack at submitting patches upstream to the Linux kernel. This post is woefully inadequate compared to the existing documentation, whi...

This is the second post in a series on memory segmentation. It covers working with static and dynamic libraries in Linux and OSX. Make sure to check out the first on object files and symbols. Let’s say we wanted to reuse some of the code from our previous project in our next one. We could continue t...

This is the second post in a series on memory segmentation. It covers working with static and dynamic libraries in Linux and OSX. Make sure to check out the first on object files and symbols. Let’s say we wanted to reuse some of the code from our previous project in our next one. We could continue t...

What was supposed to be one blog post about memory segmentation turned into what will be a series of posts. As the first in the series, we cover the extreme basics of object files and symbols. In follow up posts, I plan to talk about static libraries, dynamic libraries, dynamic linkage, memory segme...

What was supposed to be one blog post about memory segmentation turned into what will be a series of posts. As the first in the series, we cover the extreme basics of object files and symbols. In follow up posts, I plan to talk about static libraries, dynamic libraries, dynamic linkage, memory segme...