Getting Linux Process List Without Forking Using Just A Bash Script

July 29, 2024 by Maya Posch 16 Comments

The ps command is extremely useful when you want to get some quick information on active system processes (hence the name), especially followed by piping it into grep and kin for some filtering. One gotcha is of course that ps doesn’t run in the current shell process, but is forked off into its own process, so what if everything goes wrong and you absolutely need to run ps aux on a system that is completely and utterly out of fresh process IDs to hand out? In that scenario, you fortunately can write a shell script that does the same, but all within the same shell, as [Isabella Bosia] did, with a Bash shell script.

The how and why is mostly covered in the shell script itself, using detailed comments. Initially the hope was to just read out and parse the contents of /proc/<pid>/status, but that doesn’t have details like CPU%. The result is a bit more parsing to get the desired result, as well as a significant amount of cussing in the comments. Even if it’s not entirely practical, as the odds of ending up on a system with zero free PIDs are probably between zero and NaN, but as an ‘entertaining’ job interview question and example of all the fun things one can do with shell scripting it’s definitely highly recommended.

A 64-bit X86 Bootloader From Scratch

July 14, 2024 by Al Williams 20 Comments

For most people, you turn on your computer, and it starts the operating system. However, the reality is much more complex as [Thasso] discovered. Even modern x86 chips start in 16-bit real mode and there is a bit of fancy footwork required to shift to modern protected mode with full 64-bit support. Want to see how? [Thasso] shows us the ropes.

Nowadays, it is handy to develop such things because you don’t have to use real hardware. An emulator like QEMU will suffice. If you know assembly language, the process is surprisingly simple, although there is a lot of nuance and subtlety. The biggest task is setting up appropriate paging tables to control the memory mapping. In real mode, segments have access to fixed 64 K blocks of memory unless you use some tricks. But in protected mode, segments define blocks of memory that can be very small or cover the entire address space. These segments define areas of memory even though it is possible to set segments to cover all memory and — sort of — ignore them. You still have to define them for the switch to protected mode.

In the bad old days, you had more reason to worry about this if you were writing a DOS Extender or using some tricks to get access to more memory. But still good to know if you are rolling your own operating system. Why do the processors still boot into real mode? Good question.

Ask Hackaday: Has Firefox Finally Gone Too Far?

July 14, 2024 by Jenny List 119 Comments

In a world where so much of our lives depend on the use of online services, the web browser used to access those services becomes of crucial importance. It becomes a question of whether we trust the huge corporate interests which control this software with such access to our daily lives, and it is vital that the browser world remains a playing field with many players in the game.

The mantle has traditionally fallen upon Mozilla’s Firefox browser to represent freedom from corporate ownership, but over the last couple of years even they have edged away from their open source ethos and morphed into an advertising company that happens to have a browser. We’re asking you: can we still trust Mozilla’s Firefox, when the latest version turns on ad measurement by default?

Such has been the dominance of Google’s Chromium in the browser world, that it becomes difficult to find alternatives which aren’t based on it. We can see the attraction for developers, instead of pursuing the extremely hard task of developing a new browser engine, just use one off-the-shelf upon which someone else has already done the work. As a result, once you have discounted browsers such as the venerable Netsurf or Dillo which are cool as heck but relatively useless for modern websites, the choices quickly descend into the esoteric. There are Ladybird and Servo which are both promising but still too rough around the edges for everyday use, so what’s left? Probably LibreWolf represents the best option, a version of Firefox with a focus on privacy and security.

We’re interested in your views on this topic, because we know you’ll have a lot to say about it. Meanwhile if you’re a Firefox user who’s upgraded to version 128 and you’re not sure what to do, don’t panic. Find the settings page, go to “Privacy and Security”, and un-check the “Website Advertising Preferences” checkbox.

Ticketmaster SafeTix Reverse-Engineered

July 11, 2024 by Alexander Rowsell 49 Comments

Ticketmaster is having a rough time lately. Recently, a hacker named [Conduition] managed to reverse-engineer their new “safe” electronic ticket system. Of course, they also had the recent breach where more than half a billion accounts had personal and financial data leaked without any indication of whether or not the data was fully encrypted. But we’re going to focus on the former, as it’s more technically interesting.

Ticketmaster’s stated goals for the new SafeTix system — which requires the use of a smartphone app — was to reduce fraud and ticket scalping. Essentially, you purchase a ticket using their app, and some data is downloaded to your phone which generates a rotating barcode every 15 seconds. When [Conduition] arrived at the venue, cell and WiFi service was totally swamped by everyone trying to load their barcode tickets. After many worried minutes (and presumably a few choice words) [Conduition] managed to get a cell signal long enough to update the barcode, and was able to enter, albeit with a large contingent of similarly annoyed fans trying to enter with their legally purchased tickets.

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C Compiler Exists Entirely In Vim

July 7, 2024 by Donald Papp 36 Comments

8cc.vim is a C compiler that exists as pure Vimscript. Is it small? It sure is! How about fast? Absolutely not! Efficient? Also no. But does it work and is it neat? You betcha!

Ever typed :wq to write the buffer and exit in Vim? When you do that, you’re using Vimscript. Whenever one enters command mode : in Vim, one is in fact using a live Vimscript interpreter. That’s the space in which this project exists and does its magic. Given enough time, anyway.

Vimscript itself was created by [Bram Moolenaar] in 1991. The idea was to execute batches of vim commands programmatically. It’s been used for a variety of purposes since then.

8cc is a lightweight C compiler that has been supplanted by chibicc, but that doesn’t matter much because as author [rhysd] admits, this is really just a fun concept project more than anything. It may take twenty minutes or more to compile “hello world”, but doing it entirely from within Vim is a trip.

Custom Microcode Compiler, Made In Google Sheets

July 7, 2024 by Donald Papp 12 Comments

When homebrewing a CPU, one has to deal with microcode. Microcode is the low-level nuts and bolts of how, precisely, a CPU executes instructions (like opcodes) and performs functions such as updating the cycle counter or handling interrupt requests. To make this task easier, [Bob Alexander] created a microcode compiler built in Google Sheets to help with his own homebrew work, but it’s flexible and configurable enough to be useful to others, as well.

A CPU’s microcode usually lives in read-only memory, and writing the microcode is only one step in the journey. [Bob]’s tool compiles his microcode into files that can be burned into memory (multiple EEPROM chips, in [Bob]’s case) or used as a Verilog program in the case of implementing the CPU in an FPGA. It’s configurable enough to be adapted for other homebrew CPU projects, though one would of course have to re-write the microcode portion.

A read-only version of the spreadsheet makes for some fun browsing, and if it piques your interest enough to get a copy of your own complete with the compiler script, you can do that here. It uses Google Sheets, and writes the output files into one’s Google Drive.

This kind of low-level project really highlights the finer points of just how the hard work of digital computing gets done. A good example is the Gigatron which implemented a RISC CPU using only microcode, memory, and logic gates in the late 70s. We’ve even seen custom microcode used to aid complex debugging.

A Second OctoPrint Plugin Has Been Falsifying Stats

July 4, 2024 by Tom Nardi 34 Comments

The ongoing story of bogus analytical data being submitted to the public OctoPrint usage statistics has taken a surprising turn with the news that a second plugin was being artificially pushed up the charts. At least this time, the developer of the plugin has admitted to doing the deed personally.

Just to recap, last week OctoPrint creator [Gina Häußge] found that somebody had been generating fictitious OctoPrint usage stats since 2022 in an effort to make the OctoEverywhere plugin appear to be more popular than it actually was. It was a clever attempt, and if it wasn’t for the fact that the fake data was reporting itself to be from a significantly out of date build of OctoPrint, there’s no telling how long it would have continued. When the developers of the plugin were confronted, they claimed it was an overzealous user operating under their own initiative, and denied any knowledge that the stats were being manipulated in their favor.

Presumably it was around this time that Obico creator [Kenneth Jiang] started sweating bullets. It turns out he’d been doing the same thing, for just about as long. When [Gina] contacted him about the suspicious data she was seeing regarding his plugin, he owned up to falsifying the data and published what strikes us as a fairly contrite apology on the Obico blog. While this doesn’t absolve him of making a very poor decision, we respect that he didn’t try to shift the blame elsewhere.

That said, there’s at least one part of his version of events that doesn’t quite pass the sniff test for us. According to [Kenneth], he first wrote the script that generated the fake data back in 2022 because he suspected (correctly, it turns out) that the developers of OctoEverywhere were doing something similar. But after that, he says he didn’t realize the script was still running until [Gina] confronted him about it.

Now admittedly, we’re not professional programmers here at Hackaday. But we’ve written enough code to be suspicious when somebody claims a script they whipped up on a lark was able to run unattended for two years and never once crashed or otherwise bailed out. We won’t even begin to speculate where said script could have been running since 2022 without anyone noticing…

But we won’t dwell on the minutiae here. [Gina] has once again purged the garbage data from the OctoPrint stats, and hopefully things are finally starting to reflect reality. We know she was already angry about the earlier attempts to manipulate the stats, so she’s got to be seething right about now. But as we said before, these unfortunate incidents are ultimately just bumps in the road. We don’t need any stat tracker to know that the community as a whole greatly appreciates the incredible work she’s put into OctoPrint.