Hey internet! So, someone broke into some of my accounts.

I’m taking entire responsibility for this - there’s the part where I fucked up, and if I didn’t fuck up, then none of this would’ve happened.

But there’s also the part where a series of design decisions from various vendors combined into the perfect storm for me.

And we’re going to talk about both! Separately! And calmly.

In Part 11, we spent some time clarifying mechanisms we had previously glossed over: how variables and functions from other ELF objects were accessed at runtime.

We saw that doing so “proper” required the cooperation of the compiler, the assembler, the linker, and the dynamic loader. We also learned that the mechanism for functions was actually quite complicated! And sorta clever!

So!

I have no shortage of ongoing writing projects - I still need to edit and publish the final parts of making our own executable packer, and I’ve recently announced I was working on a Rust book/series. Those are still both on the table.

Buuut… I’m also looking at other things. My best writing happens when I’m learning about something at the same time I’m writing about it. So for example, the Rust book is a bit harder to write, because I’m mostly trying to distill knowledge I’ve already absorbed (for the most part).

Let’s play a game: your objective is to guess a word, but you can only ask yes or no questions. You should also aim to ask as few questions as possible.

You might have played a variant of this game before, guessing famous actors or musicians. You’d usually ask questions like “Are they alive?”, or “Have they won an Oscar”? And that would allow you to narrow down the possibilities, until you finally resort to a list of direct guesses (“Is it Amy Adams?”) or simply give up.

Disclaimer:

At the time of this writing, I benefit from the fly.io “Employee Free Tier”. I don’t pay for side projects hosted there “within reasonable limits”. The project discussed here qualifies for that.

Why you might want a remote dev environment

Fearmongering aside — and Cthulhu knows there’s been a bunch, since this unfortunate tweet — there’s a bunch of reasons to want a remote dev environment.

In our last article, we managed to load and execute a PIE (position-independent executable) compiled from the following code:

; in `samples/hello-pie.asm` global _start section .text _start: mov rdi, 1 ; stdout fd lea rsi, [rel msg] mov rdx, 9 ; 8 chars + newline mov rax, 1 ; write syscall , , "hi there", 10

Day 2, Day 2! Woo!

The Advent of Code 2020, Day 2 problem talks about passwords. Sounds familiar.

Basically, our input looks like this:

1-3 a: abcde 1-3 b: cdefg 2-9 c: ccccccccc

Each line contains a “password policy” and a “password”. For the first line, the policy is that the password must contain between 1 and 3 (inclusive) times the letter “a”.