liblinux VS termux-packages

> 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!

usbredirect, USB drives/disks, Termux, termux-usb, QEMU, and Alpine Linux in action in April 2024 on an Android 11 phone that is not rooted --> Update-6, Update-7, Update-8, Update-9, Update-10 at https://github.com/termux/termux-packages/issues/19635

"USB Network Redirection protocol description version 0.7 (19 May 2014)": https://gitlab.freedesktop.org/spice/usbredir/-/blob/main/do... (gitlab.freedesktop.org/spice/usbredir/-/blob/main/docs/usb-redirection-protocol.md)

"How to use Spice "Open remote computing"" Hans de Goede "@ T-DOSE 2011, Eindhoven": https://www.youtube.com/watch?v=e1fC3GOTHOY (www.youtube.com/watch?v=e1fC3GOTHOY)

Phone (not rooted) running Android 11 and Termux doing superuser/root operations on a USB flash drive connected to the phone, for example "cryptsetup luksFormat /dev/sda1" and "mkfs.ext4 /dev/mapper/v1" --> Update-6 through Update-8 and "Connecting a USB device to QEMU using termux, termux-usb, usbredirect" at https://github.com/termux/termux-packages/issues/19635 (see also Update-9, Update-10, Update-11).

Done on a phone that is not rooted running Termux, termux-usb, usbredirect, and QEMU --> "cryptsetup luksFormat /dev/sda1" and "cryptsetup luksOpen /dev/sda1 v1" and "mkfs.ext4 /dev/mapper/v1" and "mount /dev/mapper/v1 /root/1" where "/dev/sda1" is a partition on a USB flash drive ("dev/sda") plugged in the phone: https://github.com/termux/termux-packages/issues/19635 (github.com/termux/termux-packages/issues/19635'cryptsetup)

Yes. Even without enabling root, you can install Termux[1] and have a full Linux cli environment with ssh.

> don't understand not more people want to access their DCIM folder via sshfs

I agree. I sync my camera folder with Syncthing[1], so as soon as I take a photo it is available on my laptop.

1: https://termux.dev/

As usual don't forget that Android/Linux isn't GNU/Linux,

https://github.com/termux/termux-packages/wiki/Termux-and-An...

https://developer.android.com/ndk/guides/stable_apis

https://android.googlesource.com/platform/bionic/+/master/an...

With this, I was able to cross compile lone for x86_64 from within the Termux environment of my aarch64 smartphone. All I had to do was obtain the Linux user space API headers for x86_64.

I made a Termux package request for multiplatform Linux UAPI headers specifically so I could cross compile lone but unfortunately it was rejected.

https://github.com/termux/termux-packages/issues/16069

I wonder how far you could get with the git client in termux. I got vim running at one point.

[1] https://termux.dev/

[2] https://packages.termux.dev/apt/termux-main/pool/main/g/git/

Crystal can be installed with just pkg install crystal. If you have Docker, you could also clone the build environment and try building Crystal locally with scripts/run-docker.sh scripts/build-package.sh -I -a aarch64 crystal.