Re: [PATCH, RFC] Add public function syscall_no_errno

[Askar Safin <safinaskar@zohomail.com>]

 ---- On Wed, 07 Feb 2024 05:57:49 +0400  Mike Frysinger  wrote --- 
 > sounds like you want this project:
 > https://chromium.googlesource.com/linux-syscall-support/

This project has exactly the problem I'm talking abort! Exactly problem
I'm trying to fix using syscall_no_errno!

linux-syscall-support always unconditionally checks syscall result and sets
errno based on it:

https://chromium.googlesource.com/linux-syscall-support/+/ed31caa60f20a4f6569883b2d752ef7522de51e0/linux_syscall_support.h#2175

You can verify that this happens in all code paths by carefully reading the
source. Fortunately, the project doesn't provide "getuid" at all. I think
this is because authors aware of the problem.

Also, the project is simply buggy. Look at this (my!) commit:

https://chromium.googlesource.com/linux-syscall-support/+/e1e7b0ad8ee99a875b272c8e33e308472e897660

If I didn't notice this bug and didn't fix it, the bug would stay forever!

So, after my expirence with this project I conclude: I don't trust such projects. I. e. small
project claiming to support performing direct syscalls. I don't trust C libraries
for this purpose and I don't trust Rust libraries for this purpose.
The only libraries I trust are glibc and musl. But both don't export
anything like syscall_no_errno. And this is what I'm trying
to change.

I'm aware of existance of "nolibc" project inside Linux source tree.
But (based on my expirence with linux-syscall-support) I don't trust it,
either.

But... well, I *will* trust some of these projects if I carefully read sources.

So, yes, I can fix problem for me personally: just carefully read sources of
linux-syscall-support and use it! Or some similar C or Rust library.

Moreover: my task is even simpler! The only architectures I want to support
in my project are x86_64 and i386. So I can simply copy needed assembly
from glibc sources and all will be done!

But I'm not trying to fix the problem for me personally. I want to fix it
for everyone! I want anyone to be able just to use universally available
trusted function from glibc. Without the need for assembly or
third party projects such as linux-syscall-support.

glibc already provides "syscall", thus it should provide "syscall_no_errno", too!


Askar Safin
https://types.pl/@safinaskar