221 results for "":
In the bowels of glibc
Good morning, and welcome back to “how many executables can we run with our custom dynamic loader before things get really out of control”.
In Part 13, we “implemented” thread-local storage. I’m using scare quotes because, well, we spent most of the article blabbering about Addressing Memory Through The Ages, And Other Fun Tidbits.
But that was then, and this is now, which is, uh, nine months later. Not only am I wiser and more productive, I’m also finally done updating all the previous thirteen parts of this series to fix some inconsistencies, upgrade crate versions, and redo all the diagrams as SVG.
What's in a Linux executable?
Executables have been fascinating to me ever since I discovered, as a kid,
that they were just files. If you renamed a .exe to something else, you
could open it in notepad! And if you renamed something else to a .exe,
you’d get a neat error dialog.
Clearly, something was different about these files. Seen from notepad, they were mostly gibberish, but there had to be order in that chaos. 12-year-old me knew that, although he didn’t quite know how or where to dig to make sense of it all.
Crafting ARP packets to find a remote host's MAC address
Alright. ALRIGHT. I know, we’re all excited, but let’s think about what we’re doing again.
So we’ve managed to look at real network traffic and parse it completely. We’ve also taken some ICMP packets, parsed them, and then serialized them right back and we got the exact same result.
So I know what you’re thinking - let’s just move our way down the stack again - stuff that ICMP packet in an IP packet, then in an Ethernet frame, and then serialize the whole thing.
Proc macro support in rust-analyzer for nightly rustc versions
I don’t mean to complain. Doing software engineering for a living is a situation of extreme privilege. But there’s something to be said about how alienating it can be at times.
Once, just once, I want to be able to answer someone’s “what are you working on?” question with “see that house? it wasn’t there last year. I built that”.
Instead for now, I have to answer with: “well you see… support for proc macros was broken in rust-analyzer for folks who used a nightly rustc toolchain, due to incompatibilities in the bridge (which is an unstable interface in the first place), and it’s bound to stay broken for the foreseeable future, not specifically because of technical challenges, but mostly because of human and organizational challenges, and I think I’ve found a way forward that will benefit everyone.”
Day 5 (Advent of Code 2022)
Part 1
The day 5 challenge actually looks fun!
Our input looks like this:
[D]
[N] [C]
[Z] [M] [P]
1 2 3
move 1 from 2 to 1
move 3 from 1 to 3
move 2 from 2 to 1
move 1 from 1 to 2
Which is a visual representation of stacks, and so, for once, we have some serious parsing to do, and that means I finally have a good reason to bust out the nom crate.
Day 13 (Advent of Code 2020)
In the Day 13 problem, we’re trying to take the bus.
Our input looks like this:
939
7,13,x,x,59,x,31,19
The first line indicates the earliest minute we can leave from the bus terminal, and the second line indicates the “identifier” of the buses that are active.
Each bus departs every “bus ID” minutes - bus 7 leaves at minute 0, minute 7, minute 14, minute 21, etc. The question is: which bus can we take first (apparently they either all go to the same destination, or we don’t really care where we’re going), and how long do we have to wait for it?
*andfall
Welp, I did it again - I released an album: it’s named *andfall, a play on the word “landfall”, and I wrote it in one week-end, for @McFunkyPants’ entry in the Ludum Dare 33 game jam.
It’s my first solo album, the previous ones were collaborations with @bigsylvain and @geckojsc. It feels a bit weird to release an album alone - there’s nobody to blame for the flaws, and nobody to praise for the good parts!
Windows dynamic libraries, calling conventions, and transmute
So, how does ping.exe actually send a ping? It seems unrealistic that
ping.exe itself implements all the protocols involved in sending a ping.
So it must be calling some sort of library. Also, since it ends up
talking to the outside world via a NIC (network interface controller),
the kernel is probably involved at some point.
In reading files the hard way - part 2, we learned about dynamic libraries (like libc), and the Linux kernel, and how syscalls allowed us to ask the Linux kernel to do our bidding. For this series, we’re going to have to look at the Windows equivalents.
Request coalescing in async Rust
As the popular saying goes, there are only two hard problems in computer science: caching, off-by-one errors, and getting a Rust job that isn’t cryptocurrency-related.
Today, we’ll discuss caching! Or rather, we’ll discuss… “request coalescing”, or “request deduplication”, or “single-flighting” - there’s many names for that concept, which we’ll get into fairly soon.
And then there were fewer bugs
Intro
This deals with rock internals, so fasten your seatbelts and expect many weird things along the way. I’m not necessarily proud of the state of the implementation, I’m just rolling with it and trying to improve it gradually rather than throw everything away.
An error out of nowhere
While working on my current game, John Q. Adamant, I was looking to extract a class into another module - this is routine refactoring and shouldn’t be too hard.