minibase VS liblinux

I remember simple use cases for clone() such as spawning child processes with just enough shared resources to execve(). I remember reading a lot of old emails from Torvalds about it, can't find them anymore.

I used to value portability but now I believe in using Linux everywhere and for everything. I like OpenBSD too but Linux is the stable one you can build anything on. What I wanted to eventually accomplish is a 100% freestanding Linux user space with no libraries at all. Maybe boot straight into the program I want to use, just like we can pass init=/usr/bin/bash in the kernel command line. How far could this go? Using nothing but system calls it's actually possible to get a framebuffer and use software renderering to draw some graphics. I'm guessing pretty far.

By starting from scratch like this it's possible to fix all the historical problems with our systems. For example, I think it's unacceptable when libraries keep global state. This can't be fixed without getting rid of libc and its buffers and caches and errno. Removing this cruft would actually simplify a threads implementation. And then there's completely insane stuff that should be dropped like .init and .fini sections:

https://blogs.oracle.com/solaris/init-and-fini-processing-wh...

A similar statically-linked user space project I found years ago:

https://github.com/arsv/minibase

> libc isn't really getting in the way here.

For the standard set of system calls, the libc is pretty great. For Linux-specific features, it could take years for glibc to gain support. Perhaps it's gotten better since then, perhaps it still takes years. I don't know.

Years ago I read about the tale of the getrandom system call and the quest to get glibc to support it:

https://lwn.net/Articles/711013/

A kernel hacker wrote in an email:

> maybe the kernel developers should support a libinux.a library that would allow us to bypass glibc when they are being non-helpful

That made a lot of sense to me. I took that concept and kind of ran with it. Started a liblinux project, essentially a libc with nothing but the thinnest possible system call wrappers. Researched quite a bit about glibc's attitude towards Linux to justify it:

https://github.com/matheusmoreira/liblinux#why

Eventually I discovered Linux was already doing the same thing with their own nolibc.h file which they were already using in their own tools. It was a single file back then, by now it's become a sprawling directory full of code:

https://github.com/torvalds/linux/tree/master/tools/include/...

Even asked Greg Kroah-Hartman on reddit about it once:

https://old.reddit.com/r/linux/comments/fx5e4v/im_greg_kroah...

Since the kernel was developing their own awesome headers, I decided to drop liblinux and start lone instead. :)

It gives you access to 100% of Linux's system calls. It eliminates a lot of global state. It gets rid of a lot of legacy libc crap.

Years ago I wrote a fairly referenced rationale in my liblinux project:

https://github.com/matheusmoreira/liblinux/blob/master/READM...

> Now, do I think it would make total sense for syscall wrappers and NSS to be split into their own libs (or dbus interfaces maybe) with stable ABIs to enable other libc's, absolutely!

I worked on this a few years ago: liblinux.

https://github.com/matheusmoreira/liblinux

I'm not developing it anymore though because I found out the Linux kernel itself has a superior nolibc library:

https://github.com/torvalds/linux/tree/master/tools/include/...

It used to be a single header but it looks like they've recently organized it into a proper project!

I wonder if it will become some kind of official kernel library at some point. I asked Greg Kroah-Hartman about this and he mentioned there was once a klibc:

https://old.reddit.com/r/linux/comments/fx5e4v/im_greg_kroah...

> This is something the BSD's got absolutely right.

BSDs, every other operating system really, force us to use the bundled C libraries and the C ABI. I think Linux's approach is better. It has a language-agnostic system call binary interface: it's just a simple calling convention and the system call instruction.

The right place for system call support is the compiler. We should have system_call keywords that cause it to emit code in the aforementioned calling convention. With this single keyword, it's possible to do program literally anything on Linux. Wrappers for every specific system call should be part of every language's standard library with language-specific types and semantics.

I'm not using this stuff professionally, it's just my own home lab's virtual machines with little services implemented as freestanding C programs. Not doing anything fancy right now, much of it was just to see if I could do it.

I've seen other people commenting here on HN saying they're using the same approach so it's defenitely not my invention.

I published some of my work in the form of a liblinux that I use to make system calls:

https://github.com/matheusmoreira/liblinux

I'm not developing it anymore though because I found out the kernel itself has a nolibc library:

https://github.com/torvalds/linux/tree/master/tools/include/...

It used to be a single header but it looks like they've organized it into a proper project.

That's awesome. I didn't know about rwildcard until now. Is it part of GMSL? I searched for rwildcard on gmsl.sourceforge.io but didn't find it.

I think my function is needlessly complicated compared to rwildcard. Here's my code:

https://github.com/matheusmoreira/liblinux/blob/modular-buil...

https://github.com/matheusmoreira/liblinux/blob/modular-buil...

The file? and directory? functions were inspired by GMSL.

I wrote a general recursion function. It takes a function to apply to lists and a function to compute whether an element is a base case.

The recursive file system traversal function applies a directory globbing function to the list of paths and has file? as base case.

The find function filters out any items not matching a given predicate function. It was my intention to provide predicates like C_file? and header_file? but I stopped developing that project before that happened.

I think rwildcard is probably simpler and more efficient!