Linux

🤔 What’s a syscall, anyway? Image credits: Mike Norris via Pexels Every time your program reads a file, writes to a socket, or allocates memory, at some point it has to ask the kernel to actually do it. That ask is a syscall, the narrow, well defined boundary where userspace code crosses into the kernel. write(), read(), open(), mmap(), these aren’t just library functions, they’re the entire vocabulary your program has for talking to the outside world. Everything else, fwrite, Python’s file.write(), std::fs::File, is just a wrapper around this same handful of kernel entry points. ...

🧭 Where we left off Welcome back to our ongoing series on measuring test coverage for binary programs! In part 1 we used Go’s built-in -cover flag — clean and accurate, but only works if you own the source and can recompile. In part 2 we used valgrind and gdb to trace gzip without touching its source. In part 3 we explored Intel PIN, a proper dynamic binary instrumentation framework — powerful, but it came with a ~100MB proprietary C++ SDK and was limited to x86_64. ...

📦 That new package smell We’ve all been there: you see a shiny new app on GitHub and you want to “unwrap” it immediately. But in the traditional Linux world, opening a package often feels like opening a box of glitter in your living room—before you know it, dependencies are scattered everywhere, and you’re still finding weird library versions in /usr/lib three months later. This is why I’ve started reaching for the Flatpak. It’s like an unboxing experience where the box stays a box. You get all the “goodies” inside, but the mess stays contained. Let’s see what happens when we tear off the shrink-wrap. ...

👋 Intro If you have ever spent time hardening Linux applications, you probably know the frustration of the all-or-nothing permission model. In the standard Linux environment, once a process starts running, it usually has far more filesystem access than it actually needs. While we have tools like seccomp, chroot, or heavy-duty modules like SELinux and AppArmor, they often feel too complex for simple, application-level sandboxing. Landlock changes this. Since its merge into the Linux kernel in version 5.13, it has become a game-changer for developers. It allows a process to restrict itself without requiring root privileges, moving security away from global system policies and directly into your application code. ...