Serhii Ivanov s3rj1k

Create Alpine Linux unified kernel image with netboot

This explains how to create an Alpine Linux unified kernel image (UKI) with netboot.

For this we need:

a kernel
an initramfs image
a modloop image (a squashfs image with the kernel modules for the kernel)
the ukify tool from systemd

QEMU on Apple Silicon with Vulkan support

The following is taken from https://gist.github.com/akihikodaki/87df4149e7ca87f18dc56807ec5a1bc5 with modifications to introduce Vulkan support. Since we need custom patches to QEMU, virglrenderer, MoltenVK, and libepoxy, the provided script will pull the right refs and build everything with the right params. Feel free to inspect the script to find the source for all the modifications. We are actively working to upstream everything so please do not build anything long-term with these patches.

Testing

Prerequisites

Xcode (relatively recent version)
Vulkan SDK for macOS (Make sure to select "System Global Installation" during Select Components.)

Native Secure Enclave backed ssh keys on MacOS

It turns out that MacOS Tahoe can generate and use secure-enclave backed SSH keys! This replaces projects like https://github.com/maxgoedjen/secretive

There is a shared library /usr/lib/ssh-keychain.dylib that traditionally has been used to add smartcard support to ssh by implementing PKCS11Provider interface. However since recently it also implements SecurityKeyProivder which supports loading keys directly from the secure enclave! SecurityKeyProvider is what is normally used to talk to FIDO2 devices (e.g. libfido2 can be used to talk to your Yubikey). However you can now use it to talk to your Secure Enclave instead!

What you NEED to Know Before Touching a Video File

Hanging out in subtitling and video re-editing communities, I see my fair share of novice video editors and video encoders, and see plenty of them make the classic beginner mistakes when it comes to working with videos. A man can only read "Use Handbrake to convert your mkv to an mp4 :)" so many times before losing it, so I am writing this article to channel the resulting psychic damage into something productive.

If you are new to working with videos (or, let's face it, even if you aren't), please read through this guide to avoid making mistakes that can cost you lots of time, computing power, storage space, or video quality.

C Speed Optimization Checklist

This is a list of general-purpose optimizations for C programs, from the most impactful to the tiniest low-level micro-optimizations to squeeze out every last bit of performance. It is meant to be read top-down as a checklist, with each item being a potential optimization to consider. Everything is in order of speed gain.

Algorithm && Data Structures

Choose the best algorithm and data structure for the problem at hand by evaluating:

time complexity

What is an "arena" in memory allocation?

I first leanred about "arena" when I was trying to understand the internal of [glibc malloc][glibc-alloc] around 2010, but I [later realized][trend] the concept is narrowly defined [in][arena1] [other][arena2] [context][arena3]. This blog post explains the difference in definition and the limitations in the so-called "arena allocators" we use today.

Background: why is malloc needed?

Every atomic object has a timeline (TL) of writes:
- A write is either a store or a read-modify-write (RMW): it read latest write & pushed new one.
- A write is either tagged Relaxed, Release, or SeqCst.
- A read observes some write on the timeline:
  - On the same thread, future reads can't go backwards on the timeline.
  - A read is either tagged Relaxed, Acquire, or SeqCst.
  - RMWs can also be tagged Acquire (or AcqRel). If so, the Acquire refers to the "read" portion of "RMW".
Each thread has its own view of the world:

Shared write timelines but each thread could be reading at different points.

	CC ?= clang
	CFLAGS = -std=c23 -Wall -Werror

	run: clean abuse
	@./abuse

	abuse:
	@$(CC) $(CFLAGS) -I. -o abuse abuse.c

	clean:

	"""
	The most atomic way to train and run inference for a GPT in pure, dependency-free Python.
	This file is the complete algorithm.
	Everything else is just efficiency.

	@karpathy
	"""

	import os # os.path.exists
	import math # math.log, math.exp

	// defer.h
	// john@crashoverride.com
	// © 2025 Crash Override, Inc.
	// Licensed under the BSD 3-Clause license

	#pragma once
	#include <stdint.h>

	typedef struct n00b_defer_ll_t n00b_defer_ll_t;