Re: [RFC] Linux system call builtins

[Paul Floyd <paulf@free.fr>]

On 08-04-24 09:19, Matheus Afonso Martins Moreira via Gcc wrote:

>    + It's becoming common
> 
>          Despite being specific to the Linux kernel,
>          support for it is showing up in other systems.
>          FreeBSD implements limited support[4] for Linux ABIs.
>          Windows Subsystem for Linux started out[5] similarly,
>          as an implementation of this system call ABI.
>          Apparently it's becoming something of a lingua franca.
>          Maybe one day Linux programs will actually become
>          portable by virtue of this stable binary interface.

I don't really buy your portability argument.

FreeBSD implements this as a syscall (two actually).
syscall 0:
int syscall(int number, ...);
syscall 198:
int __syscall(int64_t number, ...);

(I've never seen the second one used in anger, it's supposed to be for 
systems that have unusual argument padding).

The argument shuffling gets done in the kernel, not libc. In fact 
FreeBSD 15 just moved all syscall wrappers to a separate library, 
libsys, so it's there now.

Over in OpenBSD they are going to removing 'syscall' from libc.

https://lwn.net/Articles/949078/

 From what I've seen it has also been removed by Apple.

Whilst you aren't proposing the same thing, I see systems making it more 
difficult for code to make syscalls, not easier.

I also think that this could be misleading. There are sometimes subtle 
differences between the syscall interface and the interface exported by 
libc.

A+
Paul