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Programming as Theory Building

Peter Naur

Peter Naur's classic 1985 essay "Programming as Theory Building" argues that a program is not its source code. A program is a shared mental construct (he uses the word theory) that lives in the minds of the people who work on it. If you lose the people, you lose the program. The code is merely a written representation of the program, and it's lossy, so you can't reconstruct

Raspberry Pi on Internet via reverse SSH tunnel

HackerNews discussed this with many alternative solutions: https://news.ycombinator.com/item?id=24893615

I already have my own domain name: mydomain.com. I wanted to be able to run some webapps on my Raspberry Pi 4B running perpetually at home in headless mode (just needs 5W power and wireless internet). I wanted to be able to access these apps from public Internet. Dynamic DNS wasn't an option because my ISP blocks all incoming traffic. ngrok would work but the free plan is too restrictive.

I bought a cheap 2GB RAM, 20GB disk VM + a 25GB volume on Hetzner for about 4 EUR/month. Hetzner gave me a static IP for it. I haven't purchased a floating IP yet.

Foreward

This document was originally written several years ago. At the time I was working as an execution core verification engineer at Arm. The following points are coloured heavily by working in and around the execution cores of various processors. Apply a pinch of salt; points contain varying degrees of opinion.

It is still my opinion that RISC-V could be much better designed; though I will also say that if I was building a 32 or 64-bit CPU today I'd likely implement the architecture to benefit from the existing tooling.

Mostly based upon the RISC-V ISA spec v2.0. Some updates have been made for v2.2

Original Foreword: Some Opinion

The RISC-V ISA has pursued minimalism to a fault. There is a large emphasis on minimizing instruction count, normalizing encoding, etc. This pursuit of minimalism has resulted in false orthogonalities (such as reusing the same instruction for branches, calls and returns) and a requirement for superfluous instructions which impacts code density both in terms of size and

Recon and Attack Vectors from My Logs

This document contains excerpts from my web server logs collected over a period of 7 years that shows various kinds of recon and attack vectors.

There were a total of 37.2 million lines of logs out of which 1.1 million unique HTTP requests (Method + URI) were found.

$ sed 's/^.* - - \[.*\] "\(.*\) HTTP\/.*" .*/\1/' access.log &gt; requests.txt

	<!DOCTYPE html>
	<html lang="en">
	<head>
	<meta charset="utf-8" />
	<meta name="viewport" content="width=device-width, initial-scale=1" />
	<title>scratch</title>
	<style>
	body {
	font-family: Hack, Menlo, Monaco, 'Droid Sans Mono', 'Courier New', monospace;
	white-space: pre;

	""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
	" VIM SETTINGS
	""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""

	" TURNS LINE NUMBERING ON
	set nu

	" TRIGGER `autoread` WHEN FILES CHANGES ON DISK
	set autoread
	autocmd FocusGained,BufEnter,CursorHold,CursorHoldI * if mode() != 'c' \| checktime \| endif

	# Stick this in your home directory and point your Global Git config at it by running:
	#
	# $ git config --global core.attributesfile ~/.gitattributes
	#
	# See https://tekin.co.uk/2020/10/better-git-diff-output-for-ruby-python-elixir-and-more for more details

	*.c diff=cpp
	*.h diff=cpp
	*.c++ diff=cpp
	*.h++ diff=cpp

	#!/bin/bash
	###
	### my-script — does one thing well
	###
	### Usage:
	### my-script <input> <output>
	###
	### Options:
	### <input> Input file to read.
	### <output> Output file to write. Use '-' for stdout.

	I was drawn to programming, science, technology and science fiction
	ever since I was a little kid. I can't say it's because I wanted to
	make the world a better place. Not really. I was simply drawn to it
	because I was drawn to it. Writing programs was fun. Figuring out how
	nature works was fascinating. Science fiction felt like a grand
	adventure.

	Then I started a software company and poured every ounce of energy
	into it. It failed. That hurt, but that part is ok. I made a lot of
	mistakes and learned from them. This experience made me much, much