witch_t *naviJul 24, 2025
https://stackoverflow.com/questions/33051108/how-to-get-around-the-linux-too-many-arguments-limit/33278482

> I have to pass 256Kb of text as an argument to the "aws sqs"

what, uhhh, what

> MAX_ARG_STRLEN is defined as 32 times the page size in linux/include/uapi/linux/binfmts.h:
> The default page size is 4 KB so you cannot pass arguments longer than 128 KB.
> I modified linux/include/uapi/linux/binfmts.h to #define MAX_ARG_STRLEN (PAGE_SIZE * 64), recompiled my kernel and now your code produces

casually patching the kernel to send a quarter megabyte as a *single* argument oh my god i'm laughing hard
Show threadkloenkJul 24, 2025
@navi well in the early rust for Linux days we hit this limit with the passing kconfig options to rustc. Fun times
Show threadLaurent BercotJul 24, 2025

@kloenk @navi Back when 128 kB was the limit for argv+envp, Google was hitting it too because they passed all the configuration for their whole software stack on the command line as --long-option=value switches.

Their solution? Compress the command line. So every binary started by ungzipping argv[1] and parsing it to get the configuration.

The person explaining this to me saw my horrified face, and said with the perfect Hide The Pain Harold smile: "a series of individually completely rational and reasonable decisions led to this." and I have been thinking a lot about it since.

Show threadThe Cat CollectiveJul 24, 2025
@ska @kloenk @navi What the hell did I just read oh my god, that is TERRIFYING. Yet that is also so ingenious that I don't know how to feel about it

-James
Show threadLaurent BercotJul 24, 2025
@thecatcollective @navi @kloenk "Brilliant and cursed" applies to way too much software, and I want the exact opposite of that - I want things that work dumbly, simply, elegantly, and that can be understood by mere mortals.
Show threadkloenkJul 24, 2025
@ska @thecatcollective @navi isn’t technically a OS not being able to be written with C as the C spec defines some required things as UB? So yes that would be nice but sometimes fear we might need new abstraction for some of those types of software we have
Show threadThe Cat CollectiveJul 24, 2025
@kloenk Excuse the beginner question, but: If operating systems are not to be written in C due to the C spec defining some stuff as UB, how do kernels get away with it?

As far as I know, something being defined as UB means it may work, it may not work, it may do unintended stuff, but then how do they get around this?

-James
Show threadJohnJul 25, 2025

@thecatcollective @kloenk operating systems commonly use features that are provided by the specific compiler(s) that they're developed with, but that are not part of the C language standard. OSes also commonly have small pieces of low level functionality implemented directly in assembly language for their target platforms.

See, for example, https://maskray.me/blog/2024-05-12-exploring-gnu-extensions-in-linux-kernel

Show threadThe Cat Collective
@jpab @kloenk We will take a look at this, thank you!

-James
Jul 25, 2025 at 5:09pmWeb